Elbow arthroscopy has been most commonly performed in medium to large breed dogs but has also been reported in small dogs (Hans et al. 2016) and in cats (Staiger and Beale 2005). Elbow joint arthroscopy is indicated when there is front leg lameness with elbow pain, crepitus, joint capsule distension, joint thickening or swelling, reduced range of joint motion, or when there are radiographic changes compatible with medial coronoid process disease (MCPD or FCP), osteochondritis dissecans (OCD), ununited anconeal process (UAP), intra‐articular fractures, or any visible degenerative changes. Significant MCPD can be present in the radiographically normal joint so even very subtle radiographic changes compatible with MCPD are a definite indication for arthroscopy. Pain on palpation of the craniomedial aspect of the elbow joint over the medial coronoid process, pain with full flexion of the elbow joint, or pain with internal or external rotation of the antebrachium is strongly suggestive of MCPD. Absence of pain does not rule out the disease. Localized swelling in the craniomedial aspect of the joint over the medial coronoid process can also be helpful in establishing an indication for arthroscopy. Crepitus is not commonly detected with MCPD and is more likely to be found when there is UAP. Joint capsule distension or joint capsule thickening is nonspecific and can be seen with any of the disease conditions that occur in the elbow joint but is a clear indication for arthroscopy. Generalized swelling or thickening of the joint is also nonspecific, is an indication for arthroscopy, and typically is suggestive of severe joint disease, especially if combined with reduced range of joint motion. Joints with reduced range of motion and swelling may require a more aggressive multiport approach to the joint for treatment of the originating pathology and for removal of multiple secondary osteophytes. It is not important to differentiate between MCPD and OCD of the elbow joint before arthroscopy as patient positioning and portal placement are the same for both conditions. Unless radiographs are normal, CT or MRI is not needed to establish an indication for arthroscopy. CT is recommended before arthroscopy to improve definition of the pathology that is present and is especially important if there is severe joint pathology with multiple large osteophytes. The CT findings are used to help define the location of osteophytes or arthroliths that need to be removed. Information gained from a CT is very beneficial in planning the arthroscopic procedure. When fragmented medial coronoid process first entered our index of suspicion when evaluating front leg lameness with radiographic changes in the elbow open surgical exploration was used as a diagnostic technique. Arthroscopy was first used by the author as a diagnostic technique to avoid open surgery just to make a diagnosis. Arthroscopy has contributed significantly to our knowledge of the multitude of changes seen with elbow dysplasia. With time and experience, arthroscopy became part of our treatment protocol. Arthroscopy has replaced open surgery as the procedure of choice for diagnosis and management of all forms of elbow dysplasia and provides superior results to other options (Barthélémy et al. 2014; Evans et al. 2008; Galindo‐Zamora et al. 2014). Although there is disagreement with this conclusion there is too much variation in results, case selection, experience, small numbers, and evaluation methods to indicate that arthroscopy is not indicated (Burton et al. 2011; Dempsey et al. 2019). The patient is typically placed in dorsal recumbency for elbow arthroscopy whether for bilateral or unilateral procedures. For bilateral procedures, the legs are clipped, suspended (Figure 2.2a and b), prepared, and draped to allow free manipulation of the leg and access to all sides of the elbow joint or joints. For unilateral procedures, the contralateral limb is retracted caudally out of the way and is tied to the surgery table. For unilateral MCPD, OCD, UAP, and multiport joint debridement procedures, two monitors are recommended, one at each end of the table (Figure 2.5), or the monitor can be placed across the table from the surgeon with the assistant standing on the cranial side of the surgeon (Figure 2.6). The monitor is placed at the head of the table for bilateral MCPD and OCD procedures with the assistant and surgeon on the same side of the table with the assistant standing on the cranial side of the surgeon between the monitor and the surgeon (Figure 2.4). Arthroscopy for bilateral UAP can be done with one monitor at the foot of the table (Figure 2.3) but is best done with two monitors, one at the head of the table and one at the foot of the table (Figure 2.5). MCPD is commonly associated with UAP and evaluation of the medial coronoid process with appropriate treatment is an important portion of arthroscopic management for UAP. The reported combination of these two pathologies is 16% (Meyer‐Lindenberg and Fehr 2006) but the authors’ experience suggests that the incidence of this combination is closer to 100%. An operative procedure in the craniomedial portion of the joint and in the caudal joint compartment are required for UAP management so without two monitors one of the procedures is performed working with the telescope pointing away from the monitor. This dramatically increases the difficulty of the procedure. Alternatives are to move the monitor between the different parts of the procedure or to perform unilateral procedures with the monitor placed across the table from the surgeon. Complete joint debridement with removal of multiple osteophytes through multiple telescope and operative portals are performed as unilateral procedures with the monitor placed across the table, at the head of the table, or preferably with two monitors. Use of two monitors allows the patient to be rolled from side to side and allows access to the medial aspect of the joint, the lateral aspect of the joint and for placement of caudal compartment portals. The most common telescope portal for the elbow joint is the medial portal (Figure 4.1) (Jardel et al. 2010; Tatarunas and Matera 2006; Van Ryssen et al. 1993). This portal is located directly distal or distal and caudal to the tip of the medial epicondyle of the humerus. The difference in this description does not change the portal position but the difference is based on the landmarks used to define portal location. If the shaft of the humerus is used for alignment, the portal is directly distal to the tip of the epicondyle but if the outside contour of the limb is used for alignment the portal is distal and caudal to the tip of the epicondyle. Descriptions of the location of this portal using the outside of the limb commonly use measured distances, like 1–1.5 cm, caudal to the epicondyle but variability in dog size makes this unhelpful. Comparison of palpation with distance based on radiographs of the patient can be used if palpation by itself is not enough to locate the correct site for portal placement. This portal site is located by palpating the tip of the epicondyle then sliding distally, in alignment with the humoral shaft, until the distal (caudal) margin of the superficial digital flexor muscle is palpated. Telescope insertion is facilitated by internal rotation (pronation) and abduction of the antebrachium to open the medial aspect of the joint. In thin dogs, the medial margin of the articular surface of the semilunar notch can be palpated as the antebrachium is internally and externally rotated opening and closing the medial aspect of the joint. The ulnar nerve can be palpated on the medial aspect of the elbow joint immediately caudal to the telescope portal site (Figure 4.1). The nerve is palpated before starting portal placement. A 20‐gauge 1.5″ hypodermic needle is placed into the joint at the telescope portal site to confirm accurate placement, joint fluid is aspirated, and the joint is distended with sterile saline. The ulnar nerve is palpated again at this point to confirm that the portal is being placed at a safe location. The needle can be removed or left in place, a stab incision is made into the joint with a no. 11 scalpel blade aligned parallel to the muscle fibers, and the telescope cannula is placed into the joint using the blunt obturator. Figure 4.1 Portal sites on the medial aspect of the elbow joint. The three portals shown are the medial telescope portal (asterisk), the craniomedial operative portal(square), and the caudomedial egress portal(X). The ulnar nerve is seen as the white band running along the caudal aspect of the humerus and then curving to run distally along the caudal margin of the ulna. The median nerve is the white band running obliquely across the medial surface of the humerus to run parallel to the medial collateral ligament of the elbow. The medial telescope portal is distal to the medial epicondyle of the humerus in a direct line with the axis of the bone represented by the straight line. The craniomedial operative portal is directly over the medial coronoid process, cranial and slightly proximal to the medial telescope portal, and is caudal to the medial collateral ligament. The caudomedial portal is commonly used for an egress portal but is also used for an operative portal for UAP removal. Source: Modified from Freeman (1999). © John Wiley & Sons. A variation of the medial telescope portal, the caudomedial telescope portal places it caudal to the ulnar nerve (Figure 4.2). The same technique is used except that the location is at the caudal margin of the medial supracondylar ridge. The primary indication for this portal is for removing medial humeral condylar ridge OCD lesions. These lesions are typically directly under the normal medial telescope portal making maintaining a visual field difficult. This proximity to the lesion also increases the difficulty for manipulation of instrumentation to remove the fragments and to debride the bed of the lesion. This more caudally placed portal decreases the difficulty of this procedure. Figure 4.2 The modified medial or caudomedial telescope portal (asterisk) placed caudal rather than cranial to the ulnar nerve. Anatomic structures are the same as seen in Figure 4.1. Source: Modified from Freeman (1999). © John Wiley & Sons. The craniolateral telescope portal (Figure 4.3) was the original telescope portal used by the author for the elbow joint but has been replaced by the medial portal and is no longer commonly used. Primary indications for this portal are for access to the elbow joint when the patient is in lateral recumbency with the joint to be examined on the uppermost side, for complete debridement of the elbow joint using multiple portals, for removal of coronoid process fragments that escape into the cranial compartment, and for arthroscopy‐assisted lateral humeral condyle fracture repair. This portal is at the intersection of the cranial margin of the radial head and the cranial aspect of the capitulum. The notch produced by this intersection can be palpated before joint capsule distension. When the joint is distended the joint capsule protrudes at this point to make a small bump and the telescope is inserted through this joint capsule prominence. If there is adequate joint distension due to the disease process, a 20‐gauge 1″ hypodermic needle is inserted at the portal site, joint fluid is aspirated, and the joint is distended with saline. A stab incision is made with a no. 11 scalpel blade and the telescope cannula is inserted using the blunt obturator. If there is inadequate joint distension secondary to elbow disease, a 20‐gauge 1.5″–2″ hypodermic needle is placed into the caudal joint compartment and the joint is distended with saline to allow portal placement. This portal can be difficult to place because there is a tendency for the blunt obturator of the telescope cannula to slip off the joint capsule and slide across the cranial aspect of the humeral condyle without entering the joint. This can be corrected by extending the stab incision through the joint capsule or using the sharp trocar for joint entry. Structures of the cranial compartment of the joint, including the medial coronoid process, can be evaluated with this portal by passing the telescope medially across the cranial aspect of the humoral condyle (Figure 4.4). Figure 4.3 The craniolateral telescope portal site (asterisk) on the lateral aspect of the elbow joint. This portal is placed at the junction of the cranial margin of the radial head and the cranial surface of the lateral ridge of the humoral condyle. The portal is cranial to the lateral collateral ligament of the elbow joint seen as the band of tissue running from the lateral epicondyle of the humerus across the joint and splitting to insert on both the radius and ulna. The white stripe running cranial to the humerus and elbow joint is the deep branch of the radial nerve. This craniolateral telescope portal is also used as an operative portal for access to the cranial compartment of the joint. Source: Modified from Freeman (1999). © John Wiley & Sons. A lateral operative portal can be placed directly over the lateral coronoid process of the ulna. The caudolateral portal is commonly used as an egress portal but the same site is used for caudolateral operative or telescope portals. This caudolateral portal is placed caudal to the caudal margin of the supracondylar ridge of the humerus and proximal to the olecranon into the olecranon fossa. Figure 4.4 From the craniolateral telescope portal structures of the cranial compartment can be examined by passing the telescope medially across the cranial aspect of the humoral condyle. Source: Modified from Freeman (1999). © 1999, Elsevier. Caudal telescope portals are placed into the caudal joint compartment by insertion into the olecranon fossa either medial or lateral to the triceps tendon. These portals allow visualization of the anconeal process and the olecranon fossa. The caudal portal on the lateral side can also provide access to the lateral coronoid process. Primary application of these portals is for removal of anconeal process osteophytes that interfere with joint extension as part of complete multiport joint debridement. The caudal portal on the lateral side can also be used when combined with a lateral operative portal for removal of lateral coronoid process pathology that cannot be accessed using the medial telescope portal. UAP fragment removal is generally performed using the medial telescope portal with a caudal operative portal on the medial side. Medial and lateral caudal portals can also be used for UAP removal and to evaluate the caudal compartment for any residual loose debris after the UAP fragment has been removed. The craniomedial operative portal site can be used as a telescope portal site for visualization of radial head osteophytes, humeral condyle fractures, and MCPD fragments that have escaped into the cranial compartment of the joint. This site is used as a telescope portal site after it has been used as an operative portal site and the transfer can be done with a switching stick or the telescope cannula can be passed through the portal with the blunt obturator. Access to the cranial compartment of the joint through the standard medial telescope portal is facilitated by subtotal coronoidectomy. Figure 4.5 Instruments passed through the medial telescope portal and the craniomedial operative portal provide excellent access and triangulation for medial coronoid process revision. Source: Modified from Freeman (1999). © 1999, Elsevier. Figure 4.6 A 20‐gauge hypodermic needle seen in the craniomedial joint compartment in preparation for craniomedial operative portal placement. The telescope is looking craniolaterally from the medial portal with dorsal up and medial to the left. The medial ridge of the humeral condyle is seen to the upper left, medial coronoid process fills the bottom of the image, the medial collateral ligament is the vertical band of tissue in the center, a small portion of radial head is to the left, and intraarticular fat covered with mild synovial reaction is to the right. The visible cartilage surfaces are normal and no coronoid process abnormality is present. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 4.7 The tip of a no.11 scalpel blade seen in the craniomedial joint compartment, next to a previously placed needle, making a craniomedial operative portal incision. Proximal is up and medial is to the left with the telescope looking craniolaterally from a medial portal. Medial humeral condyle ridge is seen to the upper right, and medial coronoid process with grade III chondromalacia fills the bottom of the image. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 4.8 A curved mosquito hemostat placed through the craniomedial operative portal incision is being used to enlarge the portal and establish a tissue tract. This is the same elbow as the previous figure with the same telescope position and orientation. In addition to the structures described in the previous image a small portion of radial head is seen to the far right and medial collateral ligament is the vertical band in the upper center background. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Access to the lateral coronoid process of the ulna and lateral ridge of the humeral condyle can be attained by entering the lateral aspect of the joint distal to the epicondyle using landmarks similar the medal telescope portal but on the lateral side. This operative portal can be combined with a craniolateral or caudolateral telescope portal or can also be used with a medial telescope portal for procedures requiring limited manipulations. Uses of this portal are for removal of lateral coronoid process pathology and for removal of medial coronoid process fragments or OCD fragments that escape into the lateral joint space. This portal can also be used as a telescope portal. An operative portal can also be established at the craniolateral telescope portal site (Figure 4.3). This operative portal is used for removal of coronoid process fragments that escape into the cranial compartment of the joint and for removal of dorsal radial head osteophytes as part of a multiport elbow debridement procedure. This portal is usually placed from inside the joint using a craniomedial operative portal cannula and a switching stick. Caudal compartment operative portals are placed either medial or lateral to the triceps tendon at the same locations as described for the caudal telescope portals. They are used for debridement of anconeal process osteophytes as part of multiport complete joint debridement combined with a caudal telescope portal. For this application, the operative portal is placed at the caudal portal site not used by the telescope. A caudal operative portal on the medial side is used for removal of UAP fragments combined with a medial telescope portal. The operative portal for UAP removal is more accurately a mini‐arthrotomy than a portal because it needs to be large enough for removal of the UAP fragment in one piece. The most common egress portal sites for the elbow joint are caudal portals on the medial or lateral sides with the egress cannula positioned into the olecranon fossa (Figures 4.1 and 4.2). The craniomedial operative portal site (Figures 4.1 and 4.2) can be used as an egress portal site during caudal joint compartment debridement or during UAP removal. For these procedures, the craniomedial site is used as an operative portal for managing medial coronoid process pathology and is then converted into an egress portal simply by placing an egress cannula into the already established operative portal site. Any of the elbow joint operative portal sites can also be used for outflow either with an egress cannula, with outflow around operative instruments, or through an operative cannula. The ulnar nerve is within millimeters of the medial telescope portal of the elbow joint (Jardel et al. 2010). The ulnar nerve courses along the cranial border of the medial head of the triceps continuing on the medial aspect of the humerus immediately caudal to the point of the medial epicondyle to cross the medial aspect of the elbow joint. After crossing the elbow joint, the ulnar nerve courses distally on the caudomedial antebrachium between the humeral head of the superficial digital flexor muscle and the ulnar head of the flexor carpi ulnaris muscle (Figure 4.1). The nerve can be palpated as it crosses the medial epicondyle, allowing location of the nerve at the time of portal site selection and placement. Errors made in attempting to enter the elbow joint are to place the portal too far caudally directly over the nerve for the standard telescope portal or to be too far distally and to slide away from the joint on the medial surface of the ulna. The ulnar nerve is at risk when these errors occur. The ulnar nerve is also within millimeters of the modified medial telescope portal of the elbow joint. This portal is placed caudal to the ulnar nerve distal to the epicondyle and caudal to the axis of the humeral shaft using palpation of the ulnar nerve as a landmark (Figure 4.2). The possible errors in placing this portal are reversed from the standard medial telescope portal with placement of this portal too far cranially or too far dorsally increasing the risk of ulnar nerve damage. The median nerve is at risk with placement of the craniomedial operative portal of the elbow joint (Jardel et al. 2010). The median nerve crosses the medial extent of the flexor surface of the elbow joint, deep to the craniomedial flexor muscles, near the medial collateral ligament (Figure 4.1). This is close to the operative portal, within millimeters, but because the location of this portal is accurately established by intra‐articular observation of needle placement little risk is involved. Keeping this portal caudal to the medial collateral ligament, the standard position of the portal, minimizes the chance for damage to this nerve. The craniolateral telescope portal is close to the radial nerve. The deep branch of the radial nerve crosses the flexor surface of the elbow joint, cranial and medial to this portal, and deep to the extensor muscles (Figure 4.3). Correct placement of this portal is into the protrusion of the distended craniolateral joint capsule at the junction of the articular surfaces of the capitulum and the radial head. There is little risk for radial nerve damage when the portal is properly placed at this location in adequate distension of the joint before portal placement or cranial displacement of the insertion site can cause the cannula to slide medially on the cranial surface of the joint capsule. The radial nerve is at risk when this occurs. When first entering the elbow through the standard medial telescope portal, anatomic structures are identified that allow orientation within the joint. Maintaining the antebrachium in an internally rotated position with the medial aspect of the joint opened is essential for examination of the elbow joint. The medial coronoid process of the ulna, the radial head, the medial ridge of the humoral condyle, and the medial collateral ligament (Figure 4.9) are used for orientation. Other structures that can be used are the articulation between the ulna and the caudal margin of the radial head (Figure 4.10), the concave ridge of the semilunar notch with the convex surface of the humeral condyle, and the anconeal process (Figure 4.11). Once orientation is established, the joint is examined in a systematic manner to insure evaluation of all the important structures of the joint. Starting in the craniomedial portion of the joint with the telescope oriented cranially the medial coronoid process, medial aspect of the radial head, medial collateral ligament, and the medial ridge of the humeral condyle are evaluated (Figure 4.9). The telescope is swept caudolaterally to see the radial head (Figure 4.12) and continuing in this direction the lateral portion of the radial head articulating with the lateral ridge of the humeral condyle (Figure 4.13) and the radial notch of the ulna (Figure 4.14a). With application of additional rotational and abduction force, rotation of the telescope to face the 30° angle of view distally, and deeper insertion of the telescope, the lateral coronoid process can be seen in most elbows (Figure 4.14b). In this image, the caudal portion of the radial head, articulation of the radial head with lateral coronoid process, and the lateral ridge of the humeral condyle are also seen. There is extensive variation in the normal appearance of the lateral coronoid process from a thin projection with a narrow but well‐defined articulation with the humeral condyle (Figure 4.15) to wide and blunt with a large articular surface with the humeral condyle (Figure 4.16) or small and irregular with no articulation with the humeral condyle (Figure 4.17). Continued caudal angulation of the telescope exposes the semilunar notch and lateral ridge of the humeral condyle (Figure 4.18). The central portion of the semilunar notch with the base of the anconeal process and central portion of the articular surface of the trochlea of the humerus are seen when the telescope is pointed more caudally (Figure 4.19). When the telescope is pointed caudally, the anconeal process is seen with the caudal trochlea of the humeral condyle (Figure 4.20). With flexion of the joint, the tip of the anconeal process is visible (Figure 4.21) and in some joints, the telescope can be passed into the caudal compartment of the joint from the medial telescope portal (Figure 4.22). Figure 4.9 Normal structures in the elbow joint used for orientation from the medial telescope portal with the telescope angled craniolaterally are the medial coronoid process seen filling the bottom of the image, the radial head visible to the right, the convex medial ridge of the humeral condyle across the top, the medial collateral ligament of the elbow seen at the left of the image with identifiable ligamentous bands, and irregular fat covered with mildly increased vascularity in the center of the picture. Proximal, or dorsal, is up in the image and cranial is to the left. Cartilage surfaces in this image are all normal. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 4.10 Normal structures of the elbow joint seen from the craniomedial telescope portal with the telescope directed laterally. The convex surface of the lateral ridge of the humeral condyle fills the upper right half of the image, the concave ridge of the semilunar notch is seen in the lower right of the picture tapering to the cranial margin of the joint surface, the caudal margin of the radial head is visible in the upper left, articulation between the radial head and the radial notch of the ulna is present in the left center, and the base of the lateral coronoid process is visible extending beyond the semilunar notch. Proximal, or dorsal, is up in the picture and cranial is to the left. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 4.11 The tip of the anconeal process is seen filling the image and articulating with the caudal trochlear sulcus of the humoral condyle articular surface seen extending from the lower right, up to the upper right, across the top, and to the upper left. The telescope is looking caudally from a medial telescope portal. Dorsal is to the upper right and medial is to the left. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 4.12 From the initial position seen in Figure 4.9 the telescope in this picture is angled more laterally to visualize the radial head. The antebrachium has been returned to an unstressed attitude with neutral rotation allowing the radial head to be in a normal position relative to the ulna. The humeral condyle articular surface is seen extending across the top of the picture, the ulnar articular surface at the base of the medial coronoid process fills the bottom foreground of the image, and the articular surface of the radial head is seen in the center background. A small area of villus synovial reaction is seen in the far left of the image in this otherwise normal appearing joint. Dorsal, or proximal is up on the image and medial is to the left. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 4.13 With continued movement of the visual field caudally the lateral surface of the radial head is visible across the bottom of this image with the lateral ridge of the humeral condyle at the top of the image, and with a narrow view of the craniolateral joint space in the background. Proximal is up on this image and cranial is to the left with the telescope looking laterally from a medial portal. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 4.14 (a) In this image, cranial is to the right, dorsal is up, and the telescope is looking laterally. Continuing to move the telescope angle laterally and caudally, the lateral portion of the radial head is visible articulating with the lateral ridge of the humeral condyle and the radial notch of the ulna. The medial ridge of the humeral condyle is to the upper right, the radial head is to the upper right, with the ulnar articular surface filling the lower foreground. The articulation between the caudal margin of the radial head and the radial notch of the ulna is seen as a cleft between the two bones curving across the center of the picture. The lateral coronoid process of the ulna is partially visible extending into the lower left of the image. Note that the level of the radial and ulnar articular surfaces are aligned in this normal joint. (b) The lateral coronoid process is exposed in this elbow with application of additional rotational and abduction force, rotation of the 30° angle of the telescope view to face distally, and with deeper insertion of the telescope. The lateral coronoid process is seen in the center of the image. Also visible are the caudal margin of the radial head to the right, the lateral ridge of the humeral condyle across the top of the image, and the articulation of the radial head with the ulna to the right of the lateral coronoid process. The lateral joint space and joint capsule are visible beyond the tip of the lateral coronoid process. Cranial is to the right and proximal is up with the telescope looking laterally. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Orientation when using the craniolateral telescope portal uses the cranial or dorsal aspect of the radial head (Figure 4.23), cranial articular surface of the humeral condyle (Figures 4.23 and 4.24), the cranial tip of the medial coronoid process (Figures 4.24 and 4.25), and attachment of joint capsule to the distal humerus (Figure 4.26). The cranial compartment of the joint can also be accessed for examination through the medial telescope portal after removal of the medial coronoid process or through a craniomedial operative portal. Access through the medial telescope portal is easier after a subtotal medial coronoidectomy has been performed. From the medial telescope portal, the arthroscope is passed through the space lateral to the medial collateral ligament (Figure 4.27). The dorsal aspect of the radial head and the cranial surface of the humeral condyle (Figure 4.28) are used for landmarks. Figure 4.15 A thin lateral coronoid process with a narrow well‐defined cartilage surface articulating with the humeral condyle. A small portion of radial head is seen to the far right, the lateral coronoid process is in the center with articulation of the radial head with the radial notch of the ulna seen as the dark curved cleft between the two bones, lateral ridge of the humeral condyle fills the upper image, with the ridge of the semilunar notch across the bottom. There is normal alignment of the two articular surfaces. Proximal is up, cranial is to the right, and the telescope is looking laterally from a medial portal. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 4.16 A large lateral coronoid process with a wide articular surface is seen in the center of the image in contact with the lateral ridge of the humeral condyle that fills the upper right of the picture. A small portion of the caudal margin of the radial head is visible in the upper left, with articulation of the two bones seen as a dark line, and the ridge of the semilunar notch is in the foreground running from the left to the lower right of the image. Dorsal is to the upper right and cranial is to the upper left. Again note the alignment of the radial head and ulnar articular surfaces in this normal joint. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 4.17 A small irregular lateral coronoid process with no appreciable surface articulating with the humeral condyle. Proximal, or dorsal, is up on this image with cranial to the right and the telescope os looking laterally from a medial portal. The lateral ridge of the humeral condyle fills the upper image with radial head to the right and ulna across the bottom of the image. Without an articular surface on the lateral coronoid process alignment of the radial head and ulna is not appreciated. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 4.18 The top of the ridge of the semilunar notch is seen in the foreground at the bottom of this image with the lateral ridge of the humeral condyle filling the top of the picture. A small portion of the caudal margin of the radial head is to the far left with the lateral coronoid process seen in the center background. Dorsal is up and cranial is to the left with the telescope looking laterally from a medial portal. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 4.19 The central portion of the semilunar notch is seen at the bottom of this figure with the base of the anconeal process sweeping up to the left and the lateral ridge of the humeral condyle filling the upper right. Proximal is to the upper right, caudal is to the lower left, distal is down, and the telescope is looking caudolaterally from a medial portal. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 4.20 The caudal end of the semilunar notch is visible with the anconeal process on the left and the caudal extent of the humeral condyle to the right. Proximal is to the right, distal is down, medial is to the upper left, and the telescope is looking caudolaterally from a medial portal. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 4.21 The tip of the anconeal process is seen in the center of the picture with the joint fully flexed. Proximal or dorsal is up with distal down to the left and medial is to the right. The needle tip on the right is in the medial side of the caudal joint compartment. The telescope is looking caudally from a medial portal. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 4.22 In some patients the telescope can be extended into the caudal joint compartment of the elbow from the medial telescope portal. The medial margin of the anconeal process is visible on the left side of the image with the lateral articular surface of the medial wall of the olecranon fossa on the upper right transitioning into medial joint capsule in the lower right. Proximal is up and medial is to the right. The tip of a 20‐gauge needle is seen penetrating through the medial joint capsule into the caudal joint compartment. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 4.23 Normal structures of the cranial compartment of the elbow seen from the craniolateral telescope portal with the telescope looking medially. Cranial is to the right and dorsal or proximal is up. The dorsal or cranial margin of the radial head is seen at the bottom of the picture with the cranial surface of the humeral condyle filling the top of the picture. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. The caudal portals use the tip of the anconeal process and the caudal articular surfaces of the humeral trochlea for orientation (Figures 4.29 and 4.30). From the caudal portals, the soft tissue membrane of the supratrochlear foramen is seen (Figure 4.31). The telescope can be passed through the supratrochlear foramen (Figure 4.32) to visualize the cranial joint space (Figure 4.33). Figure 4.24 Moving the telescope further medially from the previous figure exposes the articular surface of the radial head across the bottom of the figure with the tip of the medial coronoid process slightly to the left in the background, craniomedial joint capsule in the background on the right, and the cranial surface of the medial ridge of the humeral condyle across the top. Proximal is up and cranial is to the right with the telescope looking medially. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 4.25 The tip of the medial coronoid process is seen in the left center of the image with the telescope advanced from the position in the previous figure. A small portion of the craniomedial margin of the radial head is visible at the bottom of the picture with the cranial surface of the medial ridge of the humeral condyle filling the top and the craniomedial joint capsule is to the right. Proximal is up with cranial to the right and the telescope is looking medially from a craniolateral portal. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Examination of the caudomedial joint space medial to the epiphysis of the humerus is needed to evaluate for injury of the origin of the extensor muscles of the carpus. This area is examined from the medial telescope portal by directing the telescope tip caudally and medially to enter the joint space medial to the bone and deep to the muscles. The reflection of the joint capsule at the proximal extent of the joint space with the tendon origin of the flexor muscles (Figure 4.34) and continuation of the tendon across the caudal margin of the supratrochlear ridge (Figure 4.35) are seen in this joint space. Figure 4.26 The craniomedial joint space seen from the craniolateral telescope portal with the telescope view shifted proximally bringing the dorsal margin of the humeral condylar articular surface into view on the left. The cranial joint capsule is seen coming off the humerus in the upper left, arching over the top of the image, and extending down the right side of the image. There is a mild villus synovial reaction present in this joint seen as strands of tissue floating in the irrigation liquid. Dorsal or proximal is up and cranial is to the right. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 4.27 Visual access to the cranial compartment of the joint from the medial telescope portal is through the space lateral to the medial collateral ligament and medial to both the radial head and medial humeral condyle. In some patients the telescope can be inserted through this space into the cranial joint space, but this typically requires removal of the medial coronoid process. The medial margin of the humeral condyle is seen in the upper left of the picture with the radial head in the lower left, the medial coronoid process in the lower right, and the medial collateral ligament on the right. The cranial joint capsule is seen in the central background. Proximal is to the upper left and cranial is to the right with the telescope looking craniolaterally from a medial portal. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 4.28 Insertion of the telescope into the cranial joint compartment from the medial telescope portal provides an oblique view of the cranial joint. The dorsal margin of the radial head is visible at the bottom of the picture, the cranial joint surface of the humeral condyle is in the upper left, and the joint capsule is seen from the right side of the image across the center to the left extent. There is mild villus reaction in the lower part of the joint capsule. Dorsal is up and cranial is to the right. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 4.29 The caudal surface of the tip of the anconeal process at the bottom and the caudal articular surface of the humeral trochlea across the top are visualized looking cranially from a caudal telescope portal. The slight vascular pattern along the margin of the anconeal process is secondary to mild joint disease. Dorsal or proximal is up. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. The pars nudosa is a normal area without articular cartilage on the ulnar articular surface. This cartilage defect has a wide range of appearance and size including small shallow areas containing fat (Figure 4.36), deeper areas lined with periosteum (Figure 4.37), and large irregular areas (Figure 4.38). Figure 4.30 The tip of the anconeal process is projecting across the middle of the picture with its tip on the right seen from an oblique angle through a caudal telescope portal. The soft tissue membrane of the supratrochlear foramen is seen on the right above the tip of the anconeal process. This membrane can be complete or incomplete as is seen in this view with an opening into the cranial joint. Proximal or dorsal is up and cranial is to the right. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 4.31 Normal fat in the caudal joint compartment on the caudal surface of a complete soft tissue membrane across the supratrochlear foramen. The telescope is looking cranially from a caudal portal. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. The ligament of the radial head extends from its attachment on the base of the medial surface of the medial coronoid process around the radial head to attach to the lateral surface of the proximal ulna. The medial portion of this ligament can be seen medial and cranial to the medial collateral ligament with the telescope directed cranially and medially from the medial telescope portal (Figure 4.39). Figure 4.32 The supratrochlear foramen visualized with the telescope looking cranially from a caudal portal. The soft tissue membrane of the supratrochlear foramen was complete but has been penetrated with the telescope to create an opening and providing access to the cranial compartment of the joint. Proximal is up. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 4.33 The dorsal or proximal margin of the cranial surface of the humeral condyle as seen with the telescope passed through the perforation in the supratrochlear foramen membrane seen in the previous figure. The humeral condyle articular cartilage margin is visible in the bottom center of the picture with a white ridge of joint capsule coursing from the lower right up over the top of the image. Distended joint capsule is also seen in the background to the left of the articular cartilage and ridge of joint capsule. Cranial is to the left with proximal up. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 4.34 The caudomedial joint space seen with the telescope directed caudally and medially from the medial telescope portal. The joint capsule refection is at the top of the image coming off the bone on the right and the joint capsule covering the origin of the flexor muscles is on the left. Proximal is up and medial is to the left. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 4.35 The caudomedial joint space seen with distal angulation from the image in the previous figure. The medial surface of the epiphysis of the humerus is on the right and the tendons of origin of the flexor muscles is on the left. Proximal is up and medial is to the left. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 4.36 A small pars nudosa at approximately the middle of the semilunar notch containing a small quantity of fat. The lateral ridge of the humeral condyle fills the top of the image and the ulna extends across the bottom. Proximal or dorsal is up and cranial is to the right. The telescope is looking laterally from a medial portal. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 4.37 A small deep pars nudosa of the ulnar articular surface. The lateral ridge of the humeral condyle fills the top of the image and the ulna extends across the bottom. Proximal or dorsal is up and cranial is to the left. The telescope is looking laterally from a medial portal. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Intra‐articular fat is a common finding and is seen in many areas of the elbow joint (Figures 4.6, 4.9, 4.22, 4.27, 4.31–4.33, and 4.36). Figure 4.38 A large pars nudosa occupying a significant portion of the ulnar articular surface centered at the cranial end of the ridge of the semilunar notch. A small portion of the lateral ridge of the humeral condyle is to the upper right, a small portion of the caudal margin of the radial head is to the upper left, and the ulna fills the remainder of the image. Proximal is up and cranial is to the left with the telescope looking laterally from a medial portal. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 4.39 The medial end of the ligament of the radial head seen cranial and medial to the medial collateral ligament with the telescope directed cranially from a medial portal. The medial collateral ligament is seen on the right with craniomedial margin of the tip of the medial coronoid process seen in the lower right, and the ligament of the radial head is seen traversing obliquely across the upper left of the picture. Dorsal is up and medial is to the left. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. This entity has gone through a series of names over the past 30 years in an attempt to more accurately refer to a combination of abnormalities of the elbow joint. First called elbow dysplasia, then fragmented coronoid process (FCP), elbow incongruity, medial coronoid process disease (MCPD), medial coronoid process pathology (MCPP), and medial compartment syndrome (MCS). None of these names are any better suited than the others and none accurately describe the variation of underlying pathology. The first name, elbow dysplasia, is as good as any of the more recent monikers and more accurately describes our lack of understanding of this elbow joint pathology. The term elbow dysplasia when first used included ununited anconeal process and any degenerative changes seen on radiographs without other specific diagnoses, as they had not been defined at that time. With the addition of diagnoses including OCD, abnormal formation of the medial coronoid process, and abnormal interaction of the ulna with the radial head and humeral condyle, the term elbow dysplasia encompasses this spectrum of diseases but with more variation allowed. Many theories have been discussed and published concerning the underlying etiology of elbow dysplasia. The more that is said, the more that is published, and the more elbow cases that are done the less is understood about the elbow. None of the current theories seem to cover all the changes that are seen. There are many interacting factors that come from multiple abnormalities that do not yet have answers. The need to keep looking and continue to question all the presented theories is definitely still present and will continue until we have a complete understanding of this disease. In addition to pathology associated with interaction of the humeral condyle with the radial head and ulnar articular surface, there may also be pathology involving articulation of the articular circumference of the radial head with the radial notch of the ulna. If these two surfaces are not congruent then abnormal forces occur with subsequent fragmentation of the axial or lateral aspect of the medial coronoid process. Many medial coronoid process fragments fit this concept as an etiology. But this is not the only etiology. I do not have the answers. Most of the theories presented look only at the adult elbow joint. The relationships of the involved bones during growth have not been studied and consideration needs to be given to possible changes during growth. In thinking about the changes seen in some elbow joints, it is evident that the relationship of radial and ulnar length, specifically the relationship of the weight‐bearing surfaces of the radial head to the semilunar notch, may not be the same during all phases of growth as it is in the adult dog. This could account for changes in both the coronoid process and the anconeal process. This could also account for an abnormal medial coronoid process with cartilage loss that sits below the level of the radial head. Or is the pathology in the humeral condyle from abnormal circumference or varus–valgus angulation. The remaining questions far overshadow the current answers. A complete discussion of the history, theories, and pathophysiology of elbow dysplasia is beyond the scope of this work. The focus of this book is aimed at the applications, procedures, and techniques of arthroscopy. Those interested in gaining further knowledge on the abnormalities of the elbow need to pursue this in other publications. The comments in the previous paragraphs are the opinions of the author developed with 37 years of experience performing elbow arthroscopy, reading many of the publications on elbow disease, independent discussions with other surgeons, and group discussions with other surgeons at meetings. Elbow dysplasia is the most common indication for, and diagnosis achieved with arthroscopy of the elbow joint. Arthroscopy of the elbow joint is indicated with front leg lameness in medium to large breed dogs when there is elbow joint pain, swelling, thickening, reduced range of motion, or there are any radiographic changes present in the elbow joint. Medial coronoid process changes are diagnosed primarily in young dogs but have been seen as an acute onset lameness in dogs as old as nine years. Definitive differentiation of the etiology of radiographic change is not necessary before arthroscopy as arthroscopy will allow determination of the diagnosis. The most common conditions seen in the elbow joint, medial coronoid process disease, ununited anconeal process, and OCD, are approached through the same medial telescope portal. Elbow CT is a very important addition to understanding the changes in individual elbows (Botazzoli et al. 2008; Coppieters et al. 2016a, b; Eljack and Böttcher 2015; Griffon et al. 2018; Groth et al. 2009; Kramer et al. 2006; Krotscheck et al. 2014; Lau et al. 2015; Moores et al. 2008; Skinner et al. 2015; Villamonte‐Chevalier et al. 2015; Wagner et al. 2007) but is not needed for arthroscopy to be indicated and performed. Elbow dysplasia is commonly a bilateral disease process and bilateral elbow arthroscopy is routinely recommended even in the presence of unilateral presentation. Unilateral presentation does not necessarily indicate unilateral involvement but may only indicate that the presenting elbow is more painful than the nonclinical elbow. In many cases, it seems that more benefit is achieved with arthroscopy for the asymptomatic joint than for the joint of presentation because it is treated at an earlier stage with less joint damage. It is also far easier for the patient and more economical for the client to perform a bilateral procedure than two independent unilateral procedures. There are many open surgical procedures applied to the elbow joint for management of elbow dysplasia. Various forms of elbow osteotomy with or without fixation are the most common of these procedures. The primary humeral procedure is sliding humeral osteotomy. Open intraarticular procedures are also included in this list. It is the authors’ opinion that there is no science that supports any of these open surgical procedures providing any better long‐term results than arthroscopy by itself. These open surgeries are unnecessarily invasive, traumatic, and painful. They also require prolonged recovery and induce the risk for failure of the osteotomy to heal. For these reasons, it is the authors’ opinion that these open surgeries are not indicated. In line with Noel Fitzpatrick’s statement in an elbow dysplasia session at a recent ACVS Symposium, “There is nothing we can do to prevent progression of degenerative joint disease of the elbow joint.” If we believe in this statement and it probably is true, then all we are doing is pain management. The list of open surgeries, especially those involving osteotomies, cause pain for a significant period of time and there is no science to support that long‐term pain is reduced more than with arthroscopy alone. Arthroscopy for elbow dysplasia is performed through a medial telescope portal and a craniomedial operative portal (Figure 4.1). An additional caudomedial operative portal is required when there is an ununited anconeal process and is at the site shown for the egress portal (Figure 4.1). Egress is typically through the operative portal. An egress portal can be placed in the caudal compartment of the joint if needed but is seldom required. Medial coronoid process disease is typically easily visible, but some lesions are subtle and are not easily seen on initial examination of the joint. There is an extensive variety of pathology that can be present with a wide presentation of lesion severity. The wide variation of lesions that are seen also indicates that this is not a single disease process but is a variety of different abnormalities producing a wide range of distinctly different lesions. Figure 4.40 A small free medial coronoid process fragment on the lateral margin of the medial coronoid process is seen as a bright white area slightly to the left of center on the image. Cartilage is present on the free fragment with full thickness cartilage loss on both the fixed portion of the coronoid process and on the medial ridge of the humeral condyle. The full thickness cartilage loss with exposed eburnated bone represents Grade V chondromalacia. The humeral condyle is visible across the top of the figure with normal cartilage at the far left and exposed bone with a pink color from the cartilage margin to the right side of picture. The medial coronoid process fills the lower right as exposed bone with no cartilage other than on the free fragment. The radial head is seen to the left of the medial coronoid process with an indistinct margin between the two bones. There is cartilage on most of the radial head but a small area to the right of the free fragment is exposed radial head bone. Dorsal, or proximal, is up on the picture with medial to the right, cranial to the upper right, and the telescope is looking craniolaterally from a medial portal. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 4.41 (a) A medium size free medial coronoid process fragment with normal cartilage on the fragment, normal cartilage on the fixed portion of the medial coronoid process, and normal cartilage on the medial ridge of the humeral condyle. In this image proximal, or dorsal, is up with medial to the left and the telescope is looking craniolaterally from a medial portal. The free fragment fills the center of the figure with a clear fracture line, fixed medial coronoid process is to the left and bottom, radial head is to the right, and humeral condyle is to the upper right. (b) A medium size loose medial coronoid process fragment is seen in the center of the image with normal cartilage on the fragment. The fixed portion of the medial coronoid process is to the right and across the bottom of the figure with a small area of full thickness cartilage loss (Grade IV chondromalacia) below the fragment plus irregular cartilage (Grade II chondromalacia) to the right. The humeral condyle extends across the top of the picture with an area of partial thickness cartilage erosion is seen in the upper center on the medial ridge of the humoral condyle (Grade III chondromalacia). Dorsal, or proximal, is up on the picture with medial to the right and the telescope is looking cranially from a medial portal. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 4.42 A large free medial coronoid process fragment on the lateral margin of the medial coronoid process extending across the midlevel of the image with Grade I chondromalacia, cartilage swelling, on the free fragment. Normal cartilage is present on the fixed portion of the medial coronoid process seen across the bottom of the image and on the medial ridge of the humeral condyle at the top. Dorsal, or proximal, is up on the picture with medial to the right and the telescope is looking craniolaterally from a medial portal. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 4.43 A massive free medial coronoid process fragment extending across the midlevel of the image (The largest seen by the author) comprising the entire lateral margin of the medial coronoid process with Grade II chondromalacia on the free fragment. Full thickness cartilage loss (Grade V chondromalacia) is seen both on the fixed portion of the medial coronoid process at the bottom of the figure and on the medial ridge of the humeral condyle where it contacts the fixed portion of the medial coronoid process at the top. The humeral condyle cartilage loss is where it contacts the fixed portion of the medial coronoid process but not where it contacts the free fragment. The needle seen entering the right side of the image was placed in preparation for creation of a craniomedial operative portal. Dorsal, or proximal, is up on the picture with medial to the right and the telescope is looking craniolaterally from a medial portal. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 4.44 Three, two distinct and one indistinct, small free medial coronoid process fragments at the base of the lateral margin of the medial coronoid process in an elbow with full thickness cartilage loss on the medial ridge of the humeral condyle and on an area of the base of the fixed portion of the medial coronoid process. The free fragments are covered with cartilage but are too small to accurately assess the degree of chondromalacia. The medial ridge of the humeral condyle across the top of the image and fixed portion of the medial coronoid process across the bottom both show Grade V chondromalacia. Dorsal, or proximal, is up on the picture with medial to the left and the telescope is looking craniolaterally from a medial portal. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 4.45 Two large free medial coronoid process fragments comprising the complete lateral margin of the medial coronoid process are seen filling the midlevel of the image with normal cartilage on the arthrolith to the left and irregular cartilage (Grade II chondromalacia) on the one to the right. Full thickness cartilage loss exposing bone (Grade IV chondromalacia) is seen on the on the medial ridge of the humeral condyle at the top and a small area of full thickness cartilage wear (Grade IV chondromalacia) is seen on the fixed portion of the base of the medial coronoid process at the lower right. Dorsal, or proximal, is up on the picture with medial to the left and the telescope is looking craniolaterally from a medial portal. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 4.46 A small free medial coronoid process fragment with normal cartilage on the free fragment in the center of the image, on the humeral condyle at the top, and on the fixed portion of the medial coronoid process to the left and bottom of the image. There is a clear line of demarcation between the fragment and fixed bone. Dorsal, or proximal, is up on the picture with medial to the left and the telescope is looking craniolaterally from a medial portal. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 4.47 Two free medial coronoid process fragments on the lateral margin of the medial coronoid process with normal cartilage on the medial ridge of the humeral condyle at the top, on the fixed portion of the medial coronoid process across the bottom, and on the free fragments in the center. The left or caudal fragment has a clear line of demarcation with the right fragment being less clearly defined. Palpation confirmed that both fragments were easily movable and were loose or free fragments. Dorsal, or proximal, is up on the picture with medial to the left and the telescope is looking craniolaterally from a medial portal. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 4.48 A very small fixed medial coronoid process fragment on the lateral margin of the medial coronoid process to the left of center seen as a subtle semicircle line in the cartilage. The fragment did not move with joint manipulation or palpation using a probe. There is normal cartilage on all visible joint surfaces including the humeral condyle to the upper right, the medial margin of the radial head to the right of radial‐ulnar articulation below the humeral condyle, and on the medial coronoid process seen obliquely across the lower left. Dorsal, or proximal, is up on the picture with medial to the left and the telescope is looking craniolaterally from a medial portal. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 4.49 A medium sized fixed coronoid process fragment on the lateral margin of the medial coronoid process to the right of center with normal cartilage on its articular surface and a clear line of demarcation in the cartilage. Two small areas of Grade II chondromalacia are seen on the lateral margin of the fragment with one at its midpoint and one at the caudal end. Normal cartilage is present on the medial ridge of the humeral condyle across the top, on the radial head to the left, and on the fixed portion of the medial coronoid process to the bottom and far right. Dorsal, or proximal, is up on the picture with medial to the right and the telescope is looking craniolaterally from a medial portal. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 4.50 A large, fixed fragment on the lateral margin of the medial coronoid process with normal cartilage on all visible joint surfaces. A subtle line is visible in the cartilage defining the margin of the fragment. Humeral condyle is at the top, radial head to the left, with the medial coronoid process filling the lower right, and the fixed fragment situated obliquely across the center of the image. Dorsal, or proximal, is up on the picture with medial to the right and the telescope is looking craniolaterally from a medial portal. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Cartilage pathology is not related to free fragment size as small lesions are seen with extensive cartilage loss (Figure 4.40) and large fragments occur with minimal or no cartilage damage (Figure 4.50). Medial coronoid process fragments most commonly arise from the lateral side of the medial coronoid process occurring at any position along that margin, cranially (Figures 4.41, 4.46, 4.53), in the middle (Figures 4.40, 4.48–4.50), at the base (Figure 4.44), or can be the entire lateral margin of the process (Figures 4.42, 4.43, 4.45, 4.47, 4.51, 4.52). Fragments can also arise from other parts of the medial coronoid process including the apex (Figure 4.62) and uncommonly the medial margin (Figure 4.63). Figure 4.51 A multipart fixed fragment on the lateral margin of the medial coronoid process with normal cartilage on all joint surfaces. Dorsal, or proximal, is up on the picture with medial to the left and the telescope is looking craniolaterally from a medial portal. The medial ridge of the humeral condyle is seen across the top of the image with a small portion of lateral humeral condyle ridge to the far right, medial coronoid process is to the lower left and the radial head is seen to the right of the coronoid process. The caudal fixed fragment has a clear cartilage line defining its margin and separation from the cranial fixed fragment but the cartilage line defining the lateral margin of the cranial fragment is less clear. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 4.52 Fixed and free medial coronoid process fragments in the same elbow joint with the free fragment concentrically positioned in the fixed fragment. The free fragment is seen in the center of the image to the left of the tip of the needle with the fixed fragment below and to the right of the free fragment with a clear line of demarcation. Normal cartilage is present on the humeral condyle across the top and on the radial head in the background to the left. Grade II chondromalacia is present on the fixed portion of the medial coronoid process at the bottom and lower right. Dorsal, or proximal, is up on the picture with medial to the right and the telescope is looking craniolaterally from a medial portal. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 4.53 A free medial coronoid process fragment in the contralateral elbow joint in the dog with a fixed fragment in the joint shown in Figure 4.48. Dorsal, or proximal, is up on the picture with medial to the left and the telescope is looking craniolaterally from a medial portal. Humeral condyle is seen across the top, the fixed portion of the medial coronoid process is to the lower left and bottom, the radial head is in the background to the right, and the free fragment is to the left of center. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 4.54 A fixed medial coronoid process fragment with an indistinct linear margin of Grade II chondromalacia running obliquely from the lower left to the right of the image. Humeral condyle is to the upper left, radial head to the left, medial coronoid process to the lower right, and reactive cranial compartment synovium in the background of the upper center of the picture. Dorsal, or proximal, is up on the picture with medial to the right and the telescope is looking craniolaterally from a medial portal. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 4.55 Distinct linear mineralization of cartilage defining the margin of a fixed medial coronoid process fragment seen running horizontally across the lower portion of the image as a raised irregular band with slightly yellow coloration compared to the surrounding normal cartilage. Dorsal, or proximal, is up on the picture with medial to the right and the telescope is looking craniolaterally from a medial portal. Radial head fills the top of the image, the medial coronoid process fills the bottom, and the fixed fragment is on the lateral margin of the coronoid process above the line of demarcation. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 4.56 A medial coronoid process with a fixed fragment that is completely hidden with normal cartilage. The only visible indication of pathology is a small area of Grade I chondromalacia on the lateral margin of the medial coronoid process seen as a slightly irregular and lighter colored tissue. In this patient a fissure line was visible on CT and was exposed when the overlying cartilage was removed. Humeral condyle is to the upper right, medial coronoid process fills the lower left, radial head is between these two bones in the background, and medial collateral ligament is to the upper left. Dorsal, or proximal, is up on the picture with medial to the left and the telescope is looking craniolaterally from a medial portal. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 4.57 Grade III chondromalacia on the medial coronoid process obscuring the margin of a fixed medial coronoid process fragment. Dorsal, or proximal, is up on the picture with medial to the right and the telescope is looking craniolaterally from a medial portal. Humeral condyle is to the upper left with normal cartilage, medial coronoid process fills the lower right of the image with an irregular cartilage surface becoming more severe towards the upper left along its lateral margin, and a small portion of radial head is visible to the far left. A fissure line was defined with CT and the margin of the fixed fragment is seen after cartilage removal. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 4.58 Another example of Grade III chondromalacia on the medial coronoid process obscuring the margin of a fixed medial coronoid process fragment. Dorsal, or proximal, is up on the picture with medial to the right and the telescope is looking craniolaterally from a medial portal. Humeral condyle is at the top with medial coronoid process filling the bottom of the image. Normal cartilage is present on the humeral condyle and on the medial portion of the medial coronoid process articular surface with progressively worsening chondromalacia from the medial normal cartilage to the lateral margin of the process. Cartilage removal revealed a demarcation line in the bone that corresponded with the transition from normal cartilage to chondromalacia. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 4.59 The margin or fissure line defining a fixed medial coronoid process fragment on the lateral margin of the medial coronoid process is seen as a white line in the exposed bone because of the Grade V chondromalacia. Dorsal, or proximal, is up on the picture with medial to the right and the telescope is looking craniolaterally from a medial portal. Humeral condyle with exposed bone is to the upper left, exposed bone of the medial coronoid process fills the lower right, the fixed fragment is to the upper left of the exposed medial coronoid process, Grade IV chondromalacia on the radial head is in the background to the left, and the separation of radius and ulna is seen as a band if frayed irregular white cartilage running from the top to the lower left of the image. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 4.60 A fissure line with residual cartilage defining the margin of a fixed medial coronoid process fragment exposed by complete loss of cartilage on both sides of the fissure line. The humeral condyle fills the top of the image with exposed bone to the left and a feathered cartilage margin running obliquely across the articular surface with thinned worn cartilage containing glaciation groves to the right. The medial coronoid process fills the bottom of the figure with the demarcation or fissure line seen as the white band running obliquely from right to lower left. Dorsal, or proximal, is up on the picture with medial to the left and the telescope is looking craniolaterally from a medial portal. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 4.61 A fissure line defining the margin of a fixed medial coronoid process exposed by removal of overlying cartilage using an arthroscopic shaver with a burr. The fragment was fixed prior to removal of cartilage and bone. The fragment became loose during the shaving procedure as can be seen by the open fissure line. Dorsal, or proximal, is up on the picture with medial to the right and the telescope is looking craniolaterally from a medial portal. The shaver burr was inserted through a craniomedial operative portal. The fissure line is seen as a narrow dark line extending from the shaver burr down with a slight curve to the left. Bone to the right is the medial fixed portion of the medial coronoid process and whiter bone to the left of the fissure represents the fragment. Debris created by the shaver obscures the lateral margin of the fragment and structures to the left. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 4.62 A free fragment at the cranial tip of the medial coronoid process. Dorsal, or proximal, is up on the picture with medial to the left and the telescope is looking cranially from a medial portal. The free fragment is the irregular tissue in the center of the image. Humeral condyle is to the upper right, the fixed portion of the medial coronoid process is at the bottom, radial head is to the far right, and the medial collateral ligament is indistinct in the background to the upper left. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Chondromalacia involving the medial coronoid process can be minimal with low‐grade minor changes involving small areas of the joint surface to full thickness cartilage loss with eburnation of exposed bone over an extensive area of the ulnar articular surface. Table 3.1 defines the modified Outerbridge chondromalacia grading system (Griffon 2012; Outerbridge 1961) used in these descriptions. Medial coronoid process disease is uncommonly seen with normal cartilage on all structures within the joint (Figures 4.41, 4.46–4.48, 4.50, and 4.51). More commonly there is damage to cartilage on the fixed portion of the medial coronoid process with the grade of chondromalacia seen on free medial coronoid process fragments typically being much less than that seen on the fixed portion of the medial coronoid process (Figures 4.40–4.45). Small Grade I lesions on the fixed portion of the medial coronoid process are seen showing blistering (Figure 4.64), softening (Figure 4.65), or swelling (Figure 4.56). Grade II lesions are seen as small areas with fibrillation (Figure 4.66), fissures (Figure 4.67), or loss of cartilage thickness (Figure 4.68). Larger lesions with deeper cartilage involvement represent Grade III chondromalacia with fibrillation (Figure 4.58), fissures, uniform loss of cartilage thickness (Figure 4.69), or loss of cartilage thickness with a moth‐eaten appearance (Figure 4.57). Grade IV chondromalacia signifies full thickness cartilage damage with exposed bone (Figure 4.70) seen as uniform loss of cartilage thickness (Figure 4.45) or irregular moth‐eaten cartilage loss (Figure 4.71). Grade V chondromalacia is seen on the fixed portion of the medial coronoid process as complete loss of cartilage and smooth exposed and eburnated bone with feathered cartilage margins (Figures 4.40, 4.44, and 4.60). Figure 4.63 An unusual free fragment originating from the medial margin of the medial coronoid process. Dorsal, or proximal, is up on the picture with medial to the right and the telescope is looking cranially from a medial portal. The fragment fills the center of the image with humeral condyle across the top, the fixed portion of the medial coronoid process to the left, and the bone defect where the fragment originated is seen at the bottom of the picture filled with hyperemic villus synovial reactive tissue. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 4.64 A cartilage blister, Grade I chondromalacia, on the lateral margin of the medial coronoid process representing subtle medial coronoid process pathology. The telescope is looking craniolaterally from a medial portal with proximal, or dorsal, up on the image and medial is to the left. The bright white areas are mineralized cartilage. The medial coronoid process is to the lower left with the radial head to the upper right and cranial joint capsule with villus synovial reaction is to the upper left. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 4.65 A band of soft cartilage seen as a narrow band of slightly darker tissue on the lateral margin of the medial coronoid process, Grade I chondromalacia, is another example of subtle medial coronoid process pathology. The telescope is looking cranially from a medial portal with proximal, or dorsal, up on the image and medial is to the right. Humeral condyle extends across the top of the image with medial coronoid process across the bottom, radial head is to the left between the two bones, and reactive synovium is to the right. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Chondromalacia also commonly occurs on the humoral condyle with all Grades being seen. Minor or Grade I chondromalacia appears as swelling (Figure 4.72), blisters (Figure 4.73), or softening (Figure 4.74). Small partial thickness, Grade II chondromalacia, including erosions (Figure 4.75), partial thickness wear lesions (Figure 4.76), fibrillation (Figure 4.77), or moth‐eaten cartilage (Figure 4.78). Grade III chondromalacia lesions have the same range of appearance as Grade II lesions but are larger and deeper but do not penetrate to bone. Erosions (Figure 4.79), wear lesions as single grooves (Figure 4.80) or widespread cartilage damage (Figure 4.81), cartilage fibrillation (Figures 4.80 and 4.82), moth‐eaten cartilage (Figure 4.83), and cartilage fissures (Figure 4.84) are all representative of Grade III chondromalacia. Progression to exposed bone is termed Grade IV chondromalacia and is also expressed as erosions (Figures 4.45 and 4.85), wear lesions (Figure 4.86), cartilage fibrillation (Figure 4.87), and moth‐eaten cartilage (Figure 4.88). Extensive full thickness lesions with eburnation of exposed bone are given the category of Grade V chondromalacia. This grade was added to the original four Outerbridge grades as part of the “Modified” grading system (Griffon 2012) and is specifically suited to categorizing elbow pathology. Full thickness wear lesions are commonly seen on the medial ridge of the humeral condyle (Figures 4.40, 4.43, 4.44, and 4.60) and chondromalacia occasionally extends laterally onto the trochlea of the humeral condyle as Grade II (Figure 4.89), Grade III (Figure 4.90), Grade IV (Figure 4.91), and Grade V (Figure 4.92) lesions. Figure 4.66 A small area of cartilage fibrillation, Grade II chondromalacia, on the base of the lateral margin of the medial coronoid process in an elbow with a small fixed medial coronoid process fragment. The telescope is looking craniolaterally from a medial portal with proximal, or dorsal, up on the image and medial is to the right. Humeral condyle is to the upper left, ulnar articular surface fills the lower right of the image with radial head in the background. The radial‐ulnar articulation runs from the upper right to the lower left and the area of chondromalacia is the slightly fuzzy margin of the ulna where it articulates with the radial head. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 4.67 Grade II chondromalacia on the lateral margin of the medial coronoid process represented by fissure lines and fibrillation. The telescope is looking craniolaterally from a medial portal with proximal, or dorsal, up on the image and medial is to the right. The medial coronoid process fills the lower right of the image with radial head in the background and humeral condyle across the top. The area of chondromalacia is seen as irregular tissue on the near side of the radial‐ulnar articulation running from the upper right to the lower left. An area of humeral condyle chondromalacia is also present at the upper right of the image but the severity cannot be determined in this picture. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 4.68 An area of loss of cartilage thickness at the tip of the medial coronoid process representing Grade II chondromalacia. The medial coronoid process fills the bottom of the image with its cranial margin running horizontally across the upper center to the right edge of the picture, the lateral margin runs from the upper center down to the lower left, humeral condyle is to the upper left, joint capsule is to the upper right, and the radial head is to the left seen between the humeral condyle and the lateral margin of the medial coronoid process. The area of chondromalacia is the slightly darker triangle of cartilage formed by the two visible sides of the medial coronoid process and with its base running as a straight line from the right to the lower left. The telescope is looking craniolaterally from a medial portal with proximal, or dorsal, up on the image and medial is to the right. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 4.69 Uniform loss of cartilage thickness over a large area of the fixed portion of the medial coronoid process, Grade III chondromalacia, fills the lower left of the image. The small area of full thickness cartilage loss near the center of the image is iatrogenic. The large free medial coronoid process fragment is seen beyond the lateral margin of the medial coronoid process is covered with swollen cartilage demonstrating Grade I chondromalacia. A small portion of humeral condyle is visible to the upper right above the coronoid process fragment. The telescope is looking craniolaterally from a medial portal with proximal, or dorsal, up on the image and medial is to the left. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 4.70 Grade IV chondromalacia on the tip of the fixed portion of the medial coronoid process showing pink exposed bone extending across the bottom of the image. A coronoid process fragment covered with more normal cartilage, Grade II chondromalacia, is seen to the right of the exposed bone without a visible fragment margin. Palpation with a probe determined that this was a free fragment. The telescope is looking craniolaterally from a medial portal with proximal, or dorsal, up on the image and medial is to the left. A small portion of humeral condyle is to the upper right, medial collateral ligament is the vertical band of smooth white tissue just to the right of center between the humeral condyle and the coronoid process, and craniolateral joint capsule is the fuzzy tissue with visible blood vessels to the upper left. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 4.71 Grade IV chondromalacia on the fixed portion of the medial coronoid process appearing as moth‐eaten cartilage with small areas of exposed bone. The medial coronoid process fills the lower left of the image, an area of humeral condyle is to the upper right, a short segment of medial collateral ligament is seen in the upper center, and a small bit of radial head is to the far right. The needle visible in the image is positioned to locate the appropriate site for operative portal placement. A small coronoid process fragment is present behind the middle of the needle with the needle obscuring the fragment from the medial coronoid process. The telescope is looking craniolaterally from a medial portal with proximal, or dorsal, up on the image and medial is to the left. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 4.72 Irregular swelling, Grade I chondromalacia, of cartilage on the trochlea of the humeral condyle. Grade II chondromalacia is seen as roughened cartilage on the medial margin of the radial head and on the lateral margin of the base of the medial coronoid process. The telescope is looking craniolaterally from a medial portal with proximal, or dorsal, up on the image and medial is to the right. Humeral condyle extends across the top of the figure with its medial ridge to the right, the lateral ridge to the lower left, and the valley of the trochlea in the center. Medial coronoid process is to the lower right with radial head seen between the two other bones. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 4.73 Grade I chondromalacia of cartilage on the humeral trochlea demonstrated as a single blister. The telescope is looking craniolaterally from a medial portal with proximal, or dorsal, up on the image and medial is to the left. The humeral condyle is to the upper right, radial head is below the humerus behind the needle, and a small portion of ulna is visible to the lower left. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 4.74 Soft cartilage on the trochlea of the humeral condyle with subtle variation in cartilage coloration seen as another presentation of Grade I chondromalacia. The telescope is looking craniolaterally from a medial portal with proximal, or dorsal, up on the image and medial is to the right. Humeral condyle fills most of the image with reactive synovium to the lower right. Source: Timothy C. McCarthy. © John Wiley & Sons Inc.
4
Arthroscopy of the Elbow Joint
4.1 Patient Preparation, Positioning, and Operating Room Setup
4.2 Portal Sites and Portal Placement
4.2.1 Telescope Portals (Medial, Craniolateral, Caudomedial, and Caudal)
4.2.2 Operative Portals (Craniomedial, Lateral, Craniolateral, and Caudal)
The craniomedial operative portal (Figures 4.1 and 4.2) is the most common operative portal for the elbow joint and is used for medial coronoid process disease management and for removal of OCD lesions of the medial humeral condylar ridge. This site is caudal to the medial collateral ligament and is located cranial and slightly proximal to the telescope portal. This site is directly over the medial coronoid process of the ulna providing excellent access and triangulation for fragment removal and coronoid process revision (Figure 4.5). The portal site is located with a 20‐gauge 1.0″ or 1.5″ needle, accurate placement is confirmed by visualizing the needle inside the joint with the telescope (Figure 4.6) (Video 2.2), a stab incision is made with a no. 11 scalpel blade parallel to the needle and aligned to pass between, not across, the muscle fibers (Figure 4.7), and a curved mosquito hemostat is used to dissect a portal tract into the joint (Figure 4.8) (Video 2.2). Operative cannulas are difficult to maintain at this portal site because of the small joint space and short distance of the bone from the joint capsule.
4.2.3 Egress Portals
4.3 Nerves of Concern with Elbow Joint Arthroscopy
4.4 Examination Protocol and Normal Arthroscopic Anatomy
4.5 Diseases of the Elbow Diagnosed and Managed with Arthroscopy
4.5.1 Elbow Dysplasia
There is a wide range in size of free medial coronoid process fragments from small (Figure 4.40), to medium (Figure 4.41a and b), large (Figure 4.42), massive (Figure 4.43), and there can be multiple fragments of various sizes (Figures 4.44 and 4.45). Small coronoid process fragments with no other pathology are seen in only a small percentage of cases (Video 4.1). In these cases, normal cartilage is present on the free fragment, the fixed portion of the medial coronoid process, and on the medial ridge of the humeral condyle (Figure 4.46). Small free fragments are also seen with all grades of cartilage damage (Video 4.2). Classic larger free coronoid process fragments (Figure 4.42) and multiple fragments (Figure 4.47) are also occasionally seen with normal cartilage surfaces (Videos 4.3 and 4.4). Medial coronoid process fragments are most commonly free or loose movable bone as shown in the previous figures, but “fixed” fragments are not uncommon (Video 4.5). Many fragments are obviously loose, but the status of other fragments is only determined by palpation for movement (Video 4.6). Fixed fragments have the same range of size from small (Figure 4.48), medium (Figure 4.49), to large (Figure 4.50), and multiple (Figure 4.51) as do free fragments. Free and fixed fragments can be present in the same joint (Figure 4.52) (Video 4.7) or fixed fragments present in one joint (Figure 4.47) with a free fragment in the contralateral joint (Figure 4.53). The margins of fixed fragments can be clearly seen in some patients as a linear cartilage defect with no cartilage damage other than this linear defect (Figures 4.48–4.51), as indistinct linear chondromalacia (Figure 4.54), or as distinct linear cartilage mineralization (Figure 4.55). In other cases, there may be no visible margin with overlying normal cartilage (Figure 4.56), there may be no visible margin because the margin is obscured by chondromalacia (Figures 4.57 and 4.58), or the margin can be seen when there is Grade V chondromalacia and a fissure line is visible in the exposed bone (Figures 4.59 and 4.60). Fixed fragments that are hidden by normal cartilage or chondromalacia are best diagnosed with preoperative CT studies that define fissure lines. The hidden fissure lines can also be found by removal of the overlying cartilage (Figure 4.61).
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
