Arthroscopy of the shoulder joint is indicated when there is front leg lameness with shoulder pain, crepitus, instability; or radiographic changes suggestive of OCD, ununited caudal glenoid ossification center, ununited supraglenoid tubercle, mineralization of the bicipital or supraspinatus tendons, intra‐articular fractures, or degenerative joint disease. Many of these conditions occur bilaterally, and arthroscopy of the contralateral joint is generally recommended. The time required to look in a normal shoulder joint with arthroscopy is minimal, typically less than five minutes, carries minimal risk of complications or increased morbidity plus it eliminates the possibility of having to perform a second procedure with the additional anesthetic episode and expense. In small animal practice, shoulder arthroscopy is commonly employed in the dog, first being reported in 1986 (Person 1986) but has also been performed in the cat (Bardet 1998). The pattern of shoulder pain may localize the disease process and reorder an index of suspicion for a specific shoulder disease but typically shoulder pain cannot be localized sufficiently to make a definitive diagnosis. Hyperextension pain is the classic finding with shoulder OCD but can also occur with ununited caudal glenoid ossification center, bicipital tendon injuries, and soft tissue injuries of the caudal, medial, and lateral structures of the shoulder. Pain on full flexion of the shoulder joint has been found to be as effective in diagnosing OCD as hyperextension and produce a pain response with many of the other conditions. Pain on palpation of the craniomedial aspect of the joint over the bicipital grove, on hyperflexion of the shoulder, while the elbow is extended, or on forced internal rotation of the shoulder are suggestive of bicipital tendon injury. Instability of the shoulder is also an indication for shoulder arthroscopy and is inconsistently detected as cranial–caudal drawer instability, medial–lateral drawer instability, or abduction instability. There is considerable variation in the degree of instability that can be defined with soft tissue injuries of the shoulder joint, the normal shoulder is not totally stable in these manipulations, and there can be bilateral involvement making comparative evaluation very difficult. Absence of detectable instability does not rule out soft tissue injury to the support structures of the shoulder joint. Radiographic changes defining shoulder pathology such as OCD, ununited caudal glenoid ossification center, ununited supraglenoid tubercle, supraspinatus or bicipital tendon mineralization, and intra‐articular fractures provide a diagnosis and confirm indication for arthroscopy. Most soft tissue injuries of the shoulder do not show radiographic changes. Increased joint fluid seen with CT, MRI, or ultrasound is sufficient information to warrant arthroscopy even if there are no other findings with these imaging techniques. A significant increase in joint fluid volume obtained by arthrocentesis is helpful in confirming joint involvement and providing additional incentive for performing arthroscopy. Many conditions involving the shoulder joint are subtle and difficult to define even with all the above techniques, and exploratory arthroscopy may be required to establish a diagnosis or to rule the shoulder out as a source of the lameness. For unilateral shoulder arthroscopy, the patient is placed in lateral recumbency with the shoulder to be examined on the upside, the monitor is placed dorsal to the patient, and the leg is suspended for preparation and draping (Figure 2.6). The surgeon and assistant stand ventral to the patient with the assistant either to the right or left of the surgeon depending on the area of most interest in the joint. To perform bilateral shoulder arthroscopy (Figures 2.3–2.5), the patient is placed in dorsal recumbency with both legs suspended for preparation and draping. Preparation and draping are done to allow the patient to be rolled from one side to the other during the procedure (Figures 2.2a,b, 3.1, and 3.2). Monitors are placed at the head and foot of the patient when procedures are planned in both cranial and caudal joint compartments and if two monitors are available (Figure 2.5). If only one monitor is available, the monitor is placed at the foot of the table for procedures performed in the caudal portion of the joint such as OCD or UCGOC (Figure 2.3) or at the head of the table for bicipital tendon evaluation and transection, and for procedures involving the medial aspect of the joint (Figure 2.4). The assistant and surgeon stand together on the side of the table away from the joint to be examined. The patient is rolled toward the surgeon to expose the first shoulder for arthroscopy (Figure 3.2). When the first shoulder procedure has been completed, the surgeon and assistant move to the other side of the table and the patient is rolled to expose the second shoulder. Bilateral procedures can be easily performed at the same time in this manner, asepsis is easily maintained, and bilateral shoulder arthroscopy is well tolerated by patients. Since OCD and UCGOC are commonly bilateral conditions, this technique is frequently employed. Figure 3.1 Preparation for bilateral shoulder arthroscopy with the legs draped to allow access to the lateral aspect of both shoulder joints when the patient is rolled from side to side. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 3.2 Patient was positioned for shoulder arthroscopy by being rolled toward the surgeon and assistant. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. A lateral portal is the most commonly employed telescope portal for shoulder arthroscopy and provides access for procedures in the caudal, cranial, and medial areas of the joint (Figures 3.3 and 3.4). This portal is placed distal to the tip of the acromion process and through the acromion portion of the deltoideus muscle. The exact distance of this portal from the tip of the acromion process varies depending on patient size and conformation. Evaluation of preoperative shoulder radiographs is very helpful in establishing the correct portal site. This portal can also be placed at the cranial margin of the acromion portion of the deltoideus muscle at an indentation that is palpable where the joint capsule is covered with only subcutaneous tissue and skin. In thin dogs, the lateral margin of the articulation of the scapula with the humerus can be palpated at this site as the joint is moved. Craniolateral or craniomedial telescope portals are used occasionally for assessment of the lateral labrum of the glenoid, for access to the medial joint space, and for access to the bicipital groove (Figure 3.5). These portals are rarely placed as the initial telescope portal and are most commonly established after examination of the joint from the lateral portal if it is determined that one of these portals is needed. This portal is placed medial (craniomedial portal) or lateral (craniolateral portal) to the origin of the bicipital tendon into the cranial compartment of the joint. This telescope portal when placed lateral to the bicipital tendon also allows access to the bicipital extension of the joint capsule. Locating the site for this portal is established using the same procedure employed for locating operative portal site placement by inserting a 20‐gauge hypodermic needle into the joint under arthroscopic guidance (Figure 3.6). Two techniques have been used to establish these portals as a telescope portal site. When the desired location has been determined, an operative cannula is inserted using visual guidance with the arthroscope, an exchange rod or switching stick is placed into the operative cannula, the operative cannula is removed, the telescope and cannula are removed from the original lateral portal, the telescope cannula is inserted at the new site over the switching stick, the switching stick is removed, and the telescope is reinserted into its cannula. Another method of establishing this portal is to visually position the tip of the telescope into the craniolateral or craniomedial portal site from inside the joint, the telescope is removed from the cannula leaving the cannula in the joint with the tip of the cannula held at the new portal site, the sharp trocar is inserted into the cannula and locked in place, the cannula is pushed through the joint capsule and overlying tissues until it exits from the skin, the trocar is removed, a switching stick is inserted into the tip of the cannula, the cannula is removed from the original portal site, the cannula is slid over the switching stick into the new portal site, the switching stick is removed, and the telescope is replaced. Figure 3.3 Arthroscopy portals on the lateral aspect of the shoulder joint. The three portals shown are the lateral (asterisk), the caudolateral (square), and the craniolateral (triangle) portals. The lateral portal site is the most common telescope portal site and is located distal to the tip of the acromion process through to the acromion body of the deltoid muscle. The caudolateral portal site is used as an operative portal for OCD and UCGOC surgery. The craniolateral portal is used as the operative portal for bicipital tendon transection, medial soft tissue injury modification, and as a telescope portal for access to the synovial sheath of the bicipital tendon. Both operative portal sites are also used as egress portals when indicated. Source: Modified from Freeman (1999). © John Wiley & Sons. Figure 3.4 Alignment of the lateral telescope portal seen on an anterior–posterior view of the shoulder joint. Source: Modified from Freeman (1999). © John Wiley & Sons. Figure 3.5 Cranial shoulder portals shown on an anterior–posterior view of the joint. Craniolateral and craniomedial telescope portals (asterisks) lateral and medial to the bicipital tendon and an operative portal over the distal extension of the synovial sheath of the bicipital tendon (square). Source: Modified from Freeman (1999). © John Wiley & Sons. Figure 3.6 A 20‐gauge hypodermic needle placed in the craniolateral portal site as seen with a telescope looking cranially from the lateral portal. Dorsal is up and cranial is to the left. The supraglenoid tubercle is seen in the upper right with the bicipital grove at the bottom and the bicipital tendon is visible crossing the picture from top to bottom. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 3.7 Arthroscopy portals are used for access to lesions in the caudal portion of the shoulder joint. The telescope is in the lateral portal and is directed caudally to allow visualization of humoral head OCD lesions, UCGOC lesions and for examination of the caudal cul‐de‐sac and caudal joint capsule. An instrument is present in the caudolateral operative portal providing triangulation with the telescope visual field. An egress needle is present at the cranial portal site. Source: Modified from Freeman (1999). © 1999, Elsevier. Figure 3.8 A 20‐gauge hypodermic needle at the caudolateral portal site as seen with the telescope looking caudomedially from the lateral portal. The location of the needle and its angle are correct for portal placement. Dorsal is up and cranial is to the right. The humeral head fills the bottom of the image, the caudal margin of the glenoid articular surface is seen at the top of the image, and the lateral margin of the OCD lesion is seen in the center with the needle touching its caudolateral margin. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 3.9 A curved mosquito hemostat in the shoulder joint at the caudolateral operative portal site as seen with the telescope looking caudomedially from the lateral portal. Dorsal is up and cranial is to the right. The tip of the hemostat is seen penetrating the caudolateral joint capsule, the caudal margin of the glenoid is at the top, the humeral head is at the bottom, and the medial joint capsule is seen in the background extending across the middle of the image. There is significant villus synovial reaction in the joint capsule typical with OCD of the shoulder joint. The caudal portion of the OCD cartilage defect is visible in the lower right of the image without the free cartilage flap. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. A craniolateral operative portal site is employed for transecting the bicipital tendon, for medial ligament and joint capsule procedures, and for removal of arthroliths in the cranial area of the joint (Figures 3.3, 3.5, and 3.10). This portal is placed medial to the greater tubercle of the humerus and lateral to the bicipital tendon. The site for this portal is determined by palpation of the greater tubercle and the bicipital groove. A 1.5″ 20‐gauge hypodermic needle is inserted at the selected site, and correct needle placement is viewed from inside the joint with the arthroscope (Figure 3.6). A skin incision is made with a no. 11 blade, and an operative cannula is placed or a tissue tract is dissected with a mosquito hemostat. Joint entry is visualized with the arthroscope from inside the joint to ensure accurate placement and prevent joint damage. Placement of an egress portal for shoulder joint procedures is optional, and egress is typically allowed through the operative portals. When an egress portal is needed for operative procedures in the caudal portion of the joint, it is placed at the same site as the craniolateral operative portal and is inserted using the same technique. Operative procedures in the cranial portion of the joint use the caudolateral operative portal site as an egress portal if one is needed. Figure 3.10 Arthroscopy to access lesions in the cranial portion of the shoulder joint uses the lateral telescope portal with the telescope directed cranially to allow visualization of the bicipital tendon, bicipital groove, medial ligaments, and cranial area of the joint. Source: Modified from Freeman (1999). © John Wiley & Sons. Nerve injury is a concern in placement of the portals for shoulder arthroscopy. Damage to nerves is the most serious complication of arthroscopy in human medicine. Nerves that are at risk when performing shoulder joint arthroscopy include the suprascapular nerve when placing the lateral telescope portal and the axillary nerve when placing the caudolateral operative portal. The suprascapular nerve courses around the cranial aspect of the scapula, across the lateral aspect of the scapular neck distal to the end of the scapular spine and lies dorsal to the margin of the glenoid (Figure 3.3). A common mistake made by beginners in small animal shoulder arthroscopy is to miss the joint when inserting the telescope cannula and slide dorsally along the lateral aspect of the scapular neck. When this happens, the suprascapular nerve is at risk. The axillary nerve is at risk when placing the caudolateral operative portal of the shoulder joint. The axillary nerve runs with the axillary artery across the caudal aspect of the shoulder joint from dorsomedial to distal and lateral around the joint capsule (Figure 3.3). This places the nerve in close proximity to the caudolateral operative portal site used for removal of OCD lesions of the humoral head and removal of ununited caudal glenoid ossification center fragments. This nerve can be damaged when there is difficulty establishing this operative portal. To place this portal safely, a skin incision is made with sharp extension through the subcutaneous tissue and superficial muscle fascia then a curved mosquito hemostat is used for blunt dissection beyond this level into the joint. The use of blunt dissection in the area of the nerve minimizes the chances of nerve damage. There are no nerves at risk with placement of the craniolateral operative portal of the shoulder joint. When first entering the shoulder joint through the lateral telescope portal, anatomic structures are identified that allow orientation within the joint. The concave glenoid articular surface and the convex humeral head articular surface (Figure 3.11), the cranial arm of the origin of the medial glenohumeral ligament (Figure 3.12), the less distinct caudal arm of the origin of the medial glenohumeral ligament (Figure 3.13), the subscapularis tendon (Figure 3.14), the medial joint space with the joint capsule (Figure 3.15), and the origin of the bicipital tendon (Figure 3.16) are all important and easily identifiable structures to use for orientation. A common mistake in starting shoulder arthroscopy is to be too deep with the tip of the telescope against the medial joint structures. Backing the telescope laterally until an image is visible will correct this problem. Once orientation is achieved, the joint is examined in a systematic manner to ensure that all important structures of the joint are seen. By directing the tip of the telescope cranially and angling the 30° view of the telescope medially, the bicipital tendon is visualized originating on the supraglenoid tubercle of the scapula (Figure 3.16). The bicipital tendon is evaluated as it traverses into the bicipital groove (Figure 3.17) and as far distally as possible (Figure 3.18). A mesotendon is present on the cranial margin of the bicipital tendon attaching the bicipital tendon to the joint capsule of the bicipital groove (Figure 3.19). The medial end of the transverse humeral ligament is identified medial to the origin of the bicipital tendon (Figure 3.20) and as it traverses across the bicipital groove cranial to the bicipital tendon (Figure 3.21). The telescope is swept medially and caudally to visualize the craniomedial joint space between the bicipital tendon and the cranial margin of the subscapularis tendon (Figure 3.22). As the telescope view is moved caudally, the articular surfaces of the scapula and humeral head are examined making sure to visualize both articular cartilage surfaces (Figures 3.11 and 3.15). Particular attention is given to articular cartilage on the caudal portion of the humeral head under the glenoid (Figure 3.23) and caudal to the glenoid (Figure 3.24), where OCD lesions are typically found. The telescope must be between the joint surfaces to see the area of interest on the humeral head (Figure 3.23). Inadequate telescope depth with the tip of the telescope lateral to the glenoid (Figure 3.25) may miss OCD lesions. The central area of the glenoid (Figure 3.11) is examined with the telescope rotated so the 30° angle is directed cranially, caudally, and dorsally. The caudal margin of the glenoid is visualized from the lateral aspect (Figure 3.25), from the caudal aspect (Figure 3.26), and from the ventral direction (Figure 3.27). Caudal movement of the telescope is continued to evaluate the caudal cul‐de‐sac of the joint (Figure 3.28). Medial structures of the joint used for orientation are examined carefully including the medial margin of the glenoid with the medial joint capsule (Figure 3.15), medial soft tissue structures of the joint with particular attention being directed at the glenohumeral ligament (Figures 3.12–3.14), the subscapularis tendon (Figure 3.14), and the craniomedial joint space (Figure 3.22) by redirecting the tip of the telescope from caudally to cranially. Examination of medial structures of the joint is facilitated by abducting the leg to open the medial aspect of the joint (Figures 3.14 and 3.29). The lateral labrum of the glenoid is visualized by retracting the telescope as far as possible without exiting the joint, angling the scope cranially, and rotating the angle of view of the telescope dorsally and laterally (Figure 3.30). Rotation of the telescope to position the viewing angle laterally allows visualization of the lateral collateral ligament of the shoulder joint (Figure 3.31). Considerable variation exists in the appearance of the origin of the bicipital tendon with some showing a well‐defined vascular pattern (Figure 3.16), or no visible vasculature (Figure 3.32), and some with an accumulation of adipose tissue attached to the origin of the tendon (Figure 3.33). Figure 3.11 Anatomic structures in the shoulder joint used for orientation from the lateral telescope portal include the concave glenoid articular surface at the top and the convex humeral head articular surface filling the bottom of the image. Dorsal is up and cranial is to the right. The telescope is looking medially from a lateral portal. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 3.12 The cranial arm of the medial glenohumeral ligament is another anatomic structure in the shoulder joint used for orientation with the telescope looking medially from the lateral portal. Dorsal is up and cranial is to the right. The cranial arm of the medial glenohumeral ligament is seen as an oblique band of bright white tissue extending across the center of the picture with subtle linear strands. The humeral head fills the bottom of the image, the medial margin of the glenoid articular surface is seen at the very top above the glenohumeral ligament, and the supraspinatus tendon is in the center background below the glenohumeral ligament. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 3.13 The less distinct caudal arm of the medial glenohumeral ligament is also an identifiable anatomic structure that can be used for orientation with the telescope looking medially from the lateral portal. Dorsal is up and cranial is to the right. The medial margin of the glenoid articular surface is at the top of the image with the medial humeral head at the bottom and the caudal arm of the glenohumeral ligament seen as a raised band of tissue crossing he medial joint from caudodorsal to cranioventral. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 3.14 The subscapularis tendon seen as an oblique band of linear strands cranial and deep to the cranial arm of the glenohumeral ligament on the medial aspect of the shoulder joint is an additional structure that can be used for orientation. The medial margin of the glenoid articular surface is at the very top, the cranial arm of the glenohumeral ligament is running in a craniodorsal to caudoventral direction at right angles to the subscapularis tendon below the glenoid, and the humeral head articular surface is visible across the bottom of the image. Dorsal is up and cranial is to the left. The telescope is looking medially from a lateral portal and the joint is abducted to open the medial joint space to allow observation of these structures. There is mild villus synovial reaction seen in this joint. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 3.15 Caudal to the subscapularis tendon and medial glenohumeral ligament orientation is established using the glenoid articular surface seen at the top of the image, the humeral head articular surface at the bottom, and the medial joint capsule seen as the slightly vascular tissue in the background running horizontally across the center. Dorsal is up and cranial is to the left. The telescope is looking medially from a lateral portal. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 3.16 Orientation is also done using the bicipital tendon. The tendon is the thick structure running obliquely across the center of this image with its origin on the supraglenoid tubercle seen in the upper right to where it disappears cranial to the bicipital groove of the humerus in the lower left. The enlargement seen at the lateral aspect of the tendon, the right side in the image, immediately adjacent to the bone is the normal typical appearance of its origin. Visible vascularity at the tendon origin is also normal. The image is obliqued putting dorsal to the upper right, lateral to the lower right, and the telescope is looking cranially from the lateral portal. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 3.17 By advancing the telescope further into the joint from its position in the previous figure the bicipital tendon is seen entering and curving into the bicipital groove. The 30 degree telescope angle is looking distally with cranial up on the image with dorsal or proximal to the left and lateral is to the right. The tendon is the tubular structure running from the bottom left across to the right and away from the telescope. A small portion of bicipital groove cartilage is seen at the bottom and cranial joint capsule extends across the top of the image. The vascular pattern seen in the joint capsule and on the cranial surface of the tendon is normal. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 3.18 Further examination of the bicipital tendon is possible in some patients from the lateral telescope portal but switching to the craniolateral portal may be required to achieve this view. The telescope is looking distally down the bicipital tendon with cranial up on the image, lateral is to the right, and medial is to the left. The tendon is seen as the tubular structure traversing distally in the bicipital groove with joint capsule arching across the top and the bicipital groove curved across the bottom of the image. The irregular white ridge of tissue on the left is the lateral labrum of glenoid and is normal. The tuft of tissue protruding from the cranial aspect of the tendon immediately distal to the labrum is fat that is normally present at the origin of the tendon. The vascular pattern seen in the joint capsule is typical for a normal joint. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 3.19 The mesotendon of the bicipital tendon is seen in this image as a pink band of tissue on the cranial surface, left side, of the tendon. Cranial is to the left, dorsal or proximal is to the upper right, distal is to the lower left, and the telescope is looking craniomedially from a craniolateral portal. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 3.20 The medial origin of the transverse humeral ligament is seen as a band of tissue in the center of the image running horizontally from the medial ridge of the proximal bicipital grove in the lower left for a short distance to disappear behind the medial margin of the bicipital tendon. The telescope is looking craniomedially from a lateral portal with craniolateral to the right, dorsal is up, and craniomedial is to the left. The origin of the bicipital tendon is on the right with the bicipital groove at the bottom, medial joint capsule to the left, and a small portion of the supraglenoid tubercle is seen at the top of the image. The irregular mildly vascular tissue at the proximal end of the bicipital tendon is normal. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 3.21 The transverse humeral ligament is seen in some patients as it traverses the bicipital groove cranial to the bicipital tendon. Cranial is up and to the right on this image with lateral to the lower right and the telescope is looking distally from a craniolateral portal. The bicipital tendon is visible traversing the picture from lower left to the right with the transverse humeral ligament seen as an indistinct white band of tissue circling the cranial aspect of the bicipital extension of the joint capsule. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 3.22 The craniomedial joint capsule is seen as a space medial to the bicipital tendon, cranial to the tendon of the subscapularis muscle, ventral to the cranial arm of the glenohumeral ligament, and craniodorsal to the articular surface of the humeral head. Cranial is to the right, dorsal is up, and the telescope is looking craniomedially from a lateral portal. The bicipital tendon is seen on the right with a small portion of the supraglenoid tubercle at the upper right, the ventral margin of the cranial arm of the medial glenohumeral ligament is coursing across the top of the image, the subscapularis tendon is seen running obliquely on the left side of the image, and the medial humeral head is visible in the lower left of the picture. There is minor villus synovial reaction along the upper portion of the cranial margin of the subscapularis tendon and the remainder of the structures are normal. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Routine examination of the joint can be completed in most patients with the joint in a neutral position but, in some cases, flexion, extension, abduction, and rotation of the joint may be required to access and assess all areas of the joint. For a complete assessment of the lateral joint capsule, lateral collateral ligament, and lateral labrum of the glenoid a cranial or craniomedial telescope portal may be required. In large breed dogs, the 4.0 mm Endocameleon facilitates examination of the lateral joint structures and the medial joint compartment with the lens angle adjusted to greater than 60°. Arthroscopes are also available with fixed angles greater than 30° that can be used for examining these areas of the joint. Figure 3.23 The caudal smooth articular surface of the humeral head under the caudomedial portion of the glenoid articular surface where OCD lesions are commonly seen. Cranial is to the right and dorsal is up on the image with the telescope positioned in the joint space between the bones and looking caudomedially from a lateral portal. The humeral head fills the lower right, the glenoid articular surface is at the top, and the caudomedial joint capsule is in the background across the center of the image. The medial margin of the glenoid is seen in the upper right extending across the picture to become the caudal margin at the far left. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 3.24 The humeral head surface caudal to the glenoid in the area where OCD lesions are also commonly seen. The caudomedial joint capsule is filling the upper half of the picture with the humeral head filling the bottom half. The vascular supply in the joint capsule is normal. Dorsal is up and cranial is to the right. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 3.25 The caudal portion of the glenoid in the upper left, the humeral head in the lower left, and the caudal joint capsule in the upper right seen with the tip of the telescope lateral to the glenoid. Dorsal is up and cranial is to the left. The telescope is looking caudomedial from a lateral portal. Viewing in this position may miss OCD lesions and the telescope is inserted further into the joint so that its tip is between the joint surfaces to ensure that an adequate area of the humeral head is examined. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 3.26 Normal caudal humeral head articular surface and caudal margin of the glenoid seen from the caudal aspect. Cranial is to the left and dorsal is up with the telescope looking caudomedially from a lateral portal and with the 30 degree angle directed cranially. The caudal margin of the glenoid is in the upper left with the humeral head filling the lower left of the image and the caudal joint capsule to the upper right. The subtle band of soft tissue irregularity following the curve of the glenoid margin is normal. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 3.27 The caudal margin of the glenoid seen from the ventral aspect with the 30‐ degree of the telescope directed dorsally. Dorsal is up and cranial is to the left with the telescope pointed caudomedially from the lateral portal. The glenoid is in the upper left, a small portion of the caudal humeral head is seen to the lower left the caudal joint capsule is filling remainder of the image. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 3.28 Normal caudal cul‐de‐sac of the shoulder joint with the caudal margin of the humeral head articular surface at the far right, attachment of the joint capsule to the humerus in the lower right, and the distended caudal joint capsule filling the left side of the image. Cranial is to the right and dorsal is up with the telescope looking caudodistally from the lateral portal and with the 30 degree angle directed medially. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 3.29 Normal medial glenohumeral ligament demonstrating the classic “Y” anatomy with the joint abducted to improve visualization. The normal medial margin of the glenoid articular surface is seen across the top and the normal humeral head articular surface is seen at the bottom of the picture. Cranial is to the left and dorsal is up with the telescope looking medially from a lateral portal. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 3.30 The cranial portion of the lateral cartilaginous labrum of the glenoid visualized by retracting the telescope, directing the tip cranially and rotating the viewing angle dorsally. The telescope is looking cranially, lateral is to the right, and dorsal is up. The lateral labrum is the rounded wide band of white tissue in the upper right of the image with the supraglenoid tubercle in the upper left, the humeral head articular surface at the bottom and the origin of the bicipital tendon in the center background. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 3.31 The lateral collateral ligament of the shoulder joint is visualized by retraction of the telescope, directing the tip cranially, and rotating the viewing angle laterally. The lateral collateral ligament is the prominent raised band of tissue filling the right side of the image, the bicipital tendon is seen on the right in the background cranial to the lateral collateral ligament, and humeral head articular surface is to the lower left. Lateral is to the right, and dorsal is up. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 3.32 A normal origin of the bicipital tendon demonstrating a typical cuff of synovial tissue around its origin with no visible vascular pattern. Cranial is to the left and dorsal is up with the telescope looking craniomedially from a lateral portal. A small portion of the supraglenoid tubercle is at the top, humoral articular surface extends across the bottom, craniomedial joint capsule is to the right, and the proximal bicipital tendon is filling the left center of the figure. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 3.33 An accumulation of adipose tissue at the origin of the bicipital tendon is a common normal finding. Cranial is to the left and dorsal is up with the telescope looking craniomedially from a lateral portal. The tip of the supraglenoid tubercle is filling the upper right with humeral head articular cartilage across the bottom and the origin of the bicipital tendon filling the center of the image. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. This is the most common indication, diagnosis, and operative procedure performed with arthroscopy in the shoulder joint (Bilmont et al. 2018; Olivieri et al. 2007; Person 1989). The classic presentation of a front leg lameness in a young large breed dog with pain on hyperextension or hyperflexion of the shoulder joint is sufficient indication for arthroscopy. Although primarily seen in large breed dogs, OCD has been reported and arthroscopy performed in small breed dogs (Bruggeman et al. 2010). Radiographs are taken to confirm a diagnosis prior to arthroscopy, but normal radiographs do not rule out OCD or eliminate the indication for arthroscopic exploration of the joint. Although radiographs have been the standard for diagnosing OCD contrast arthrography, CT, MRI, and ultrasound have also been used (Wall et al. 2014; Van Bree et al. 1993; Vandevelde et al. 2006). Bilateral shoulder arthroscopy is routinely recommended even with unilateral presentation of OCD because OCD is most commonly a bilateral disease that may only show unilateral signs. It is far easier for the patient and more economical for the client to perform a bilateral procedure rather than two unilateral procedures. Arthroscopy for OCD is performed with a lateral telescope portal and a caudolateral operative portal. Egress through the operative portal site is employed, but a craniolateral egress portal is placed if needed. This is seldom necessary. OCD lesions are typically easily visible on the caudal surface of the humoral head as a loose flap of cartilage with easily defined free margins (Figure 3.34). There are many variations of OCD lesion appearance from thick fragments containing bone (Figure 3.35) to thin cartilage flaps (Figure 3.36) and from small (Figure 3.37) to large (Figure 3.38). Thin lesions can be large (Figure 3.36) or small (Figure 3.37) and thick lesions can also be large (Figures 3.35 and 3.38) or small (Figure 3.39). The free cartilage of OCD lesions is most commonly a single smooth flap of loose cartilage (Figures 3.34–3.36, and 3.38) but also appear as irregular soft cartilage (Figure 3.40), irregular partially fragmented cartilage flaps (Figure 3.41), frayed or crushed cartilage (Figure 3.42), small frayed lesions (Figure 3.43), and fraying on the margins of OCD cartilage flaps (Figure 3.37). The wide variety of OCD lesion appearance extends to normal cartilage surface that is only found by palpation indicating a soft or movable area of cartilage (Figure 3.44), blister‐like areas of cartilage with intact cartilage margins that are large (Figure 3.45) or small (Figure 3.46), indentation of otherwise normal‐appearing cartilage (Figure 3.47), smooth (Figure 3.48) or irregular cartilage that is not raised or displaced (Figure 3.49), raised lesions with clearly visible nondisplaced margins that have a smooth (Figure 3.50) or irregular (Figure 3.51) surface, and raised margins with an intact cartilage surface at the margin (Figure 3.52). Chondromalacia (Table 3.1) appearing as small loose (Figure 3.53), small attached (Figure 3.54), or large (Figure 3.55) areas of fibrillated cartilage are a visible indication of an OCD lesion. All grades of chondromalacia are also seen in humeral head cartilage surrounding OCD lesions and on the glenoid articular surface. Figure 3.34 A classic OCD lesion on the caudal portion of the humeral head with an easily seen loose cartilage flap having a free margin. Cranial is to the left and dorsal is up in this picture. Synovial villi from the caudal joint capsule are visible on the right side of the image. Localized villus synovial reaction is common directly over the OCD lesion. The telescope is looking caudomedially from a lateral portal. Unless stated otherwise all the following images of OCD lesions showing the loose cartilage in the defect on the caudal humeral head are taken with this telescope orientation from the lateral portal. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 3.35 A thick OCD lesion containing bone is seen on the caudal portion of the humeral head. Dorsal is up and cranial is to the right. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 3.36 A thin humeral head OCD lesion on the caudal portion of the humeral head. Caudal is to the right and dorsal is up. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 3.37 An atypically small humeral head OCD lesion. The frayed margin of the cartilage in this lesion is not common. Dorsal is up and cranial is to the right. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 3.38 An atypically large humeral head OCD lesion seen filling the upper half of the figure. Dorsal is up and caudal to the left. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. The majority of OCD lesions with typical free cartilage flaps have the complete disk of loose cartilage still in the cartilage defect with no missing cartilage (Figures 3.34–3.38). Lesions are also seen with a small portion (Figure 3.56), most (Figure 3.57), or all (Figure 3.58) of the loose cartilage missing from the site of the OCD lesion. When a partially or completely empty cartilage defect is found, it means that part or all of the cartilage flap has broken‐free and has been displaced into another area of the joint. It is necessary to find these loose cartilage fragments and remove them from the joint. They are found in the caudal cul‐de‐sac as small recent fragments (Figure 3.59) or as large remodeled fragments (Figure 3.60), in the medial joint space ventrally (Figure 3.61) or medial to the glenohumeral ligament (Figure 3.62), in the craniomedial joint space (Figure 3.63), and in the bicipital extension of the joint capsule. Remodeled cartilage fragments, originating from OCD lesions, are also found free floating in the joint space as small (Figure 3.64) and large arthroliths (Figure 3.65) and small or large arthroliths lodged between the glenoid and humeral articular surfaces (Figures 3.66 and 3.67). Free cartilage pieces can be any size from submacroscopic chips that are free floating (Figure 3.68) or are imbedded in the synovium (Figure 3.69) to large osteocartilaginous arthroliths (Figures 3.60 and 3.67). Figure 3.39 A small thick humeral head OCD lesion. Grade I chondromalacia is present in the humeral head cartilage surrounding the lesion. Caudal is to the right with dorsal up. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 3.40 A small soft OCD lesion is seen with an irregular surface and a ragged margin. Grade I chondromalacia is present in the glenoid articular cartilage medial to the humeral head OCD lesion seen as an indentation. The glenoid is visible across the top of the image with medial joint capsule visible in the background and humeral head with the OCD lesion filling the bottom of the picture. Dorsal is up and caudal is to the right. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 3.41 A humeral head OCD lesion that appears to be starting to fragment with fracture lines extending cranially from its caudal margin seen as a cleft on the near or lateral side and as a fold on the far or medial side. Fraying is also seen on at the caudomedial corner of the cartilage flap. A small portion of the glenoid is seen in the upper left of the lesion and synovial villi are seen in the upper right. Caudal is to the right and dorsal is up. Figure 3.42 A frayed or crushed OCD cartilage flap indicating chronic trauma to the lesion. The tip of a 20 gauge needle is seen in the upper right of the lesion placed to establish the location for an operative portal. The caudomedial glenoid is seen across the top of the image with a caudal margin osteophyte along its caudal margin. Caudal is to the right and dorsal is up in this picture. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 3.43 A very small OCD lesion that is mostly frayed with little free intact cartilage. Dorsal is up and caudal is to the left. There are ghost villi seen as white avascular projections in the upper right of the image. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 3.44 An unusual OCD lesion in the humeral head with no visible cartilage abnormality and no visible margins on initial examination. A 2.0 mm palpation probe inserted through a caudolateral portal is being used to identify an area of soft cartilage or Grade I chondromalacia. Dorsal is up and cranial is to the left. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. The bed or cartilage defect of OCD lesions is variable in appearance due to duration of the lesion prior to examination and due to other unknown factors. The underlying bone of acute lesions can have either a viable pink smooth (Figure 3.70) or roughened (Figure 3.71) surface and can also have a smooth speckled brown and white avascular or necrotic appearance (Figures 3.58 and 3.72). With chronicity, the bone can become covered with a layer of material that appears to be fibrin (Figure 3.73) or fibrous tissue (Figure 3.74). Cartilage islands surrounded by pink viable bone (Figure 3.75) or surrounded by brown avascular bone (Figure 3.76) and cartilage covering a large area of the lesion originating from the center (Figure 3.77) or periphery (Figure 3.78). The margins of OCD lesions have a sharply defined vertical cartilage edge with vertical striations when recently formed or at the time the free cartilage flap is removed (Figure 3.70). With increasing duration, the cartilage edge becomes frayed (Figure 3.71), rounded with loss of the vertical striations (Figures 3.74, 3.75, 3.77), and chronic lesions can lose cartilage thickness at the margin developing a thin tapered edge (Figures 3.72 and 3.79). Figure 3.45 A large blister like OCD lesion on the humeral head with loose cartilage but unbroken lesion margins. In any other location this could be called Grade I chondromalacia but because it is on the caudal humeral head where OCD lesions are found penetration to subchondral bone is suspected. Manipulation with a probe confirmed that this was a full thickness loose flap of cartilage. Dorsal is up and caudal is to the left. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 3.46 A small blister like OCD lesion on the humeral head with loose cartilage and without fracture of the cartilage margins giving the appearance of Grade I chondromalacia. The loose cartilage in this patient was much larger than what is indicated by the size of the blister. Dorsal is to the upper right and caudal is to the left. The tip of a curved mosquito hemostat that has been passed through a caudolateral portal is visible in the upper left of the image. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 3.47 An OCD lesion seen as an indentation in otherwise normal appearing cartilage. In any other location this could be called Grade I chondromalacia, but manipulation revealed a full thickness loose cartilage. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 3.48 An area of smooth cartilage representing an OCD lesion that is not raised or displaced and has an indistinct margin seen as an irregular ridge of tissue running horizontally across the humeral head. The central portion of this lesion has the appearance of normal to Grade I chondromalacia with the periphery exhibiting the characteristics of Grade II chondromalacia. The telescope is looking medially from a lateral portal with dorsal up and cranial to the right. The medial portion of the glenoid is seen in the upper left with the humeral head filling the bottom, and the medial joint capsule with villus reaction is seen across the center of the image. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 3.49 An OCD lesion appearing as an irregular area of cartilage swelling that is not displaced or raised and has a poorly defined margin that could be called Grade I chondromalacia. The humeral head fills most of the image with medial joint capsule in the upper background. The telescope is looking medially from a lateral portal with dorsal up and cranial to the right. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 3.50 A smooth slightly raised OCD lesion with a non‐displaced clearly visible margin. The humeral head fills the bottom of the image with normal cartilage to the left and the loose OCD cartilage to the right. Dorsal is up and cranial is to the left with the telescope looking medially from a lateral portal. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 3.51 An irregular raised OCD lesion with a non‐displaced clearly visible margin. The humeral head fills the bottom of the image with normal cartilage to the left and the loose OCD cartilage to the right. Dorsal is up and cranial is to the left with the telescope looking medially from a lateral portal. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 3.52 A non‐displaced OCD lesion with a raised margin where the cartilage at the margin has not ruptured. Dorsal is up and the telescope is looking medially from a lateral portal with cranial to the right. Medial joint capsule with villus reaction fills the top of the image, the humeral head is at the bottom, and the OCD lesion margin is seen as a distinct ridge of cartilage. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Degenerative joint changes typically occur with chronicity of OCD, and all grades of chondromalacia are seen (Table 3.1). Typical OCD lesions are by definition Grade IV or Grade V chondromalacia, depending on the condition of the underlying bone. Atypical OCD lesions appear as all grades of chondromalacia and if seen at other sites would be diagnosed as chondromalacia and not OCD. This raises the question: Are all cartilage abnormalities on the caudal area of the humeral head OCD, are these lesions a form of subclinical OCD that does not form loose cartilage but allows chondromalacia to develop, or are some truly chondromalacia with a different pathophysiology? This question has not been answered. Table 3.1 Modified outerbridge chondromalacia grading system. Figure 3.53 A small area of raised cartilage with fibrillation is seen in the center of the picture, Grade II chondromalacia, representing an atypical humeral head OCD lesion. The glenoid articular cartilage fills the upper portion of the picture with medial glenohumeral ligament visible extending across its medial margin, a wedge of medial joint capsule is present across the middle, and the humeral head is at the bottom. The telescope is looking medially from a lateral portal with dorsal up and cranial is to the right. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 3.54 A small area of cartilage fibrillation, Grade II chondromalacia, without any loose cartilage representing an atypical humeral head OCD lesion is seen in the canter of the picture. Dorsal is up and cranial is to the right with the telescope looking medially from a lateral portal. The humeral head fills the bottom of the image with medial joint capsule filling the top of the image. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 3.55 A large loose humeral head OCD lesion cartilage fragment with fibrillation of the loose cartilage. The cartilage surface appears to be Grade III chondromalacia but is actually Grade IV chondromalacia because the lesion extends to the level of bone. Grade I chondromalacia is present in the glenoid articular cartilage opposite the humeral head lesion. Dorsal is up with cranial to the right and the telescope is looking medially from a lateral portal. The humeral head is at the bottom with the glenoid at the top. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Grade I chondromalacia at an OCD lesion site can appear as normal cartilage that is only found by palpation indicating a soft area of cartilage (Figure 3.44), as blister‐like areas of cartilage with intact cartilage margins that are large (Figure 3.45) or small (Figure 3.46), indentation of otherwise normal‐appearing cartilage (Figure 3.47), and smooth (Figure 3.48) or irregular cartilage that is not raised, lose, or displaced (Figure 3.49). Grade II chondromalacia can appear as attached areas of fibrillated cartilage (Figure 3.54) and as irregular attached cartilage (Figure 3.80) at OCD lesion sites. Grade III chondromalacia is also seen at OCD lesion sites with deeper cartilage damage covering a larger area (Figure 3.81). Chondromalacia Grades II and III are based on two criteria, the depth of cartilage damage and the size of the lesion (Table 3.1). When the two criteria are in conflict, it can be difficult to state the Grade with accuracy. An example of this (Figure 3.80) has mild cartilage damage that is clearly Grade II but covers an area that would make it a Grade III. In this case, if one parameter exceeds the Grade II criteria does this make the lesion Grade III? It can be argued that if either of the criteria is the higher grade then the lesion is that higher grade. I do not know if the answer to this question has been defined. Full‐thickness lesions, Grade IV chondromalacia, without evidence of loose cartilage at the lesion site or elsewhere in the joint are also seen at humeral head OCD lesion sites (Figure 3.82). Grade V lesions have not been seen as a primary finding but Grade V‐like lesions with large areas of exposed smooth bone are seen with displaced cartilage flaps (Figures 3.72, 3.76, and 3.79). Figure 3.56 A free OCD cartilage flap with a small portion of the loose cartilage missing from the cartilage defect. Dorsal is up and cranial is to the right with the telescope looking medially from a lateral portal. Medial joint capsule is visible in the upper background with the humeral head filling the bottom of the image and the free OCD cartilage extending across the middle. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 3.57 An OCD lesion with most of the free cartilage flap missing from the cartilage defect. Dorsal is up and cranial is to the left. The telescope is looking medially from a lateral portal. The irregular tan exposed bone of the humeral head representing the OCD cartilage defect fills the lower center of the image with the cartilage rim of the defect visible in the lower left and in the background along the medial margin the defect. The cartilage in the center of the picture extending laterally from the far cartilage margin is part of the loose cartilage that is still in its original position. This cartilage was elevated and removed. Synovial villi are seen to the upper right and partially obscure the OCD lesion. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 3.58 An OCD lesion with all of the free cartilage flap missing from the cartilage defect. A palpation probe is visible extending from a caudolateral operative portal into the medial joint. Exposed bone of the OCD defect with a smooth surface and tan coloration fills the lower portion of the image. A rim of irregular mildly frayed cartilage margin is visible along the medial margin of the defect and a small portion of the lateral cartilage margin is seen at the bottom of the picture. Villus synovial reaction is seen across the top. The telescope is looking medially from a lateral portal with dorsal up and cranial to the right. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 3.59 Small loose cartilage fragments in the caudal cul‐de‐sac of the shoulder joint in a dog with a humeral head OCD lesion that was partially missing from the primary lesion site. The fragments are seen in the bottom of the image with the caudal margin of the humeral head articular surface on the left and caudal joint capsule to the right. Dorsal is up and cranial is to the left. The telescope is looking caudally and medially from a lateral portal. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 3.60 A large loose remodeled cartilage fragment seen in the caudal cul‐de‐sac of the shoulder joint representing as a curled structure. This arthrolith represents the entire free cartilage of the OCD lesion. The telescope is looking caudomedially from a lateral portal with dorsal up and caudal to the right. A small portion of the caudomedial margin of the glenoid is visible at the very top of the picture with humeral head across the bottom. The OCD cartilage defect covered with fibrin and early cartilage regeneration is seen to the lower left with a rim of normal cartilage to the lower right of the visible humeral head. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 3.61 A free cartilage fragment originating from an OCD lesion displaced ventrally into the medial joint space of the shoulder joint. Grade II chondromalacia is visible on the humeral head cartilage. The telescope is looking medially from a lateral portal with dorsal up in the picture. Medial joint capsule fills the upper image with humeral head across the bottom and the free fragment behind, medial to, the humeral head. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 3.62 A free cartilage fragment originating from an OCD lesion is seen in the medial joint spaced displaced craniomedially and lodged between the glenohumeral ligament seen across the top of the image and the subscapularis tendon to the lower left. The humeral head is to the lower right. The loose fragment is seen as the white smooth material in the center of the image. Fragments in this location can be completely hidden behind the glenohumeral ligament. The telescope is looking medially from a lateral portal with dorsal up and cranial to the left. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 3.63 A small loose cartilage fragment originating from an OCD lesion displaced into the craniomedial joint space. The telescope is looking medially from a lateral portal with cranial to the right and dorsal up. The free cartilage fragment is seen in the center of the picture with humeral head to the lower left, medial glenohumeral ligament to the upper left, and subscapularis tendon covered with synovial reaction behind the cartilage fragment. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 3.64 A large OCD cartilage flap floating free in the joint space between the glenoid and humeral head articular surfaces. This free cartilage represents the entire OCD lesion. The glenoid articular surface is at the top with humeral head at the bottom and dorsal is up. The telescope is looking medially from a lateral portal. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 3.65 A small OCD origin arthrolith free floating in the joint space between the glenoid and humeral head articular surfaces. The OCD lesion is seen as the irregular minimally displaced cartilage in the center of the picture. The exact site of origin of this small fragment was not determined as no areas of missing cartilage were visible. The telescope is looking medially from a lateral portal with dorsal up and cranial to the left. The medial margin of the glenoid is visible to the upper left, the humeral head fills the bottom of the image, and medial joint capsule with villus reaction is seen in the background. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 3.66 OCD origin arthroliths trapped in the OCD cartilage defect between the humeral head and the glenoid articular surface. The glenoid articular cartilage fills the upper image with a small area of humeral head seen at the bottom. A 20‐gauge hypodermic needle is seen to the right entering the joint from the site for a caudolateral operative portal. The tip of the needle is on the caudal arthrolith and a second arthrolith is to the left of the first. Grade III chondromalacia is present in the glenoid articular cartilage above the trapped fragments and the humeral head cartilage defect covered with cartilage regrowth seen as an irregular white surface is below and in front of the arthroliths. The telescope is looking medially from a lateral portal with dorsal up and cranial to the left. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 3.67 A large arthrolith in the shoulder joint trapped between the glenoid and humeral head articular surfaces. This free fragment was partially mineralized and is in an inverted position so that the articular surface is down. The glenoid articular surface is at the top and the humeral head is at the bottom of the picture. The telescope is looking medially from a lateral portal and dorsal is up. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 3.68 Small free‐floating cartilage chips originating from an OCD lesion seen in the caudal cul‐de‐sac of the shoulder joint. The telescope is looking caudomedially from a lateral portal with cranial to the left and dorsal up. A portion of the humeral head is visible to the lower left with caudal joint capsule filing the remainder of the image. The free cartilage chips are seen as white areas against the hyperemic joint capsule. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 3.69 An unusual finding of cartilage chips originating from an OCD lesion that are fixed to or imbedded in the synovium. The chips are seen as indistinct white areas on the joint capsule surface. The telescope is looking caudomedially into the caudal cul‐de‐sac of the joint with a small potion of the caudal margin of the glenoid visible to the upper left. Dorsal is up and caudal is to the right. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. The presence of loose cartilage confirms a diagnosis of OCD and, in these cases, chondromalacia is secondary to the pathophysiology of OCD. The presence or absence of loose cartilage may not be able to be determined visually and manipulation with a palpation probe or other instrument may be needed to confirm a diagnosis. Figure 3.70 A irregular pink bone surface in the cartilage defect following removal of an OCD cartilage flap. The defect fills the bottom of the image with a typical sharp well attached cartilage margin seen as a white band across the far side of the defect. Medial joint capsule with villus reaction is seen across the top of the picture. Dorsal is up and cranial is to the left with the telescope looking medially from a lateral portal. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 3.71 Rough pink viable bone in the cartilage defect following removal of an OCD cartilage flap seen filling the center of the image. Small red spots of blood are seen scattered over the surface of the defect. Dorsal is up and the telescope is looking medially from a lateral portal with medial joint capsule in the upper background. A rim of cartilage is seen across the bottom and extending around to the medial margin of the defect across the middle of the picture. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Chondromalacia of all grades also occurs in the shoulder joint cartilage secondary to the original OCD pathology. Mild cartilage changes representing Grade I chondromalacia are seen in humeral head cartilage around OCD lesions (Figure 3.39) and in the glenoid articular cartilage directly opposite the OCD lesion (Figure 3.55) or peripheral to the OCD lesion (Figure 3.40). Grade II chondromalacia occurs as moderate cartilage roughening on the humeral head around OCD lesions (Figure 3.83) but can be seen in all areas of the joint as can more severe Grade III damage (Figure 3.83), full‐thickness Grade IV cartilage degeneration (Figure 3.84), and Grade V lesions (Figure 3.85). These changes are potentially due to continued release of inflammatory chemicals into the joint or due to wear from trapped cartilage or osteocartilaginous fragments between the joint surfaces. Osteophytes are commonly seen in joints with chronic lesions on either the glenoid (Figure 3.86) or humeral head margins. Figure 3.72 Smooth brown and white speckled avascular or necrotic bone in the OCD defect after removal of a free cartilage flap. The bone surface of the defect fills most of the picture with a curved hemostat and joint capsule seen in the upper background. Dorsal is up and caudal is to the right with the telescope looking medially from a lateral portal. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 3.73 An OCD cartilage defect following removal of a free cartilage flap with a layer of fibrin appearing material covering the bone of the defect. The humeral head defect fills the lower left of the image with caudal joint capsule to the upper right. Dorsal is up with caudal to the right. The telescope is looking caudomedially from a lateral portal. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 3.74 A chronic OCD cartilage defect covered with fibrous appearing tissue and islands of cartilage in a lesion with a displaced OCD cartilage flap. The arthrolith representing the OCD lesion is not visible in the picture. The humeral head is to the lower left with caudal joint capsule filling the upper right of the image. Dorsal is up with caudal to the right and the telescope is looking caudomedially from a lateral portal. Cartilage at the cranial margin of the lesion is seen as an elevated ridge to the left with islands of new cartilage seen as raised white areas in the lesion at the bottom. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 3.75 An attached island of new cartilage is seen as a raised white area in the center of the image that has formed in an OCD lesion in a shoulder joint. The displaced detached cartilage flap was found as an arthrolith and is not visible in the picture. The exposed bone of the cartilage defect appears pink and extends from the lower left to the back center of the figure. Full thickness cartilage with an irregular rounded edge surrounds the exposed bone. Small areas of blood are seen along the bone‐cartilage junction. The telescope is looking medially from a lateral portal with dorsal up. The glenoid articular surface is in the upper right of the image and the humeral head with the OCD lesion is in the lower left. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 3.76 An attached island of new cartilage is seen forming in the center of an OCD lesion after removal of the free cartilage flap. A loose cartilage fragment is seen to the upper left of the fixed island of new cartilage. Dorsal is up and caudal is to the right with the telescope looking medially from a lateral portal and the hemostat has been inserted through a caudolateral portal. A small portion of glenoid is seen in the upper left with medial joint capsule covered with villus synovial reaction between the glenoid and humeral head at the bottom. The exposed bone of the OCD defect, seen to the lower right, surrounding the cartilage island has a speckled brown avascular necrotic appearance. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Villus synovial reactions develop secondary to OCD and become progressively more significant with chronicity and severity. A small local area of synovitis is typically present early in the disease process on the caudal joint capsule, where it overlies the primary OCD lesion (Figures 3.52, 3.58, 3.70, 3.71, and 3.82). Inflammation of the synovium and villus formation develops throughout the joint with time, and examples are seen in many of the OCD figures. One area of specific interest is the synovial tissue cuff surrounding the proximal bicipital tendon and is a common area for development of this OCD‐related villus synovial reaction (Figures 3.87 and 3.88). This finding has commonly been erroneously termed bicipital tenosynovitis. Tendon injury or tendinopathy can occur at this location, but the synovial reaction can also be a nonspecific inflammatory reaction to any joint pathology even with a normal bicipital tendon. Villus synovitis secondary to OCD can be severe involving any and all areas of synovial surface in the shoulder joint (Figures 3.89–3.91). Atypical synovial reaction on intra‐articular tendons and ligaments occurs with a pannus‐like appearance (Figure 3.92a) rather than the typical villus synovial reaction. Joint capsule fibrosis is also seen with chronic OCD lesions (Figure 3.92b). Figure 3.77 A chronic OCD cartilage defect where a large area of the bone is covered with newly formed attached cartilage originating in the bed of the lesion. The 2.0 mm hook probe inserted through a caudolateral portal was used to confirm attachment of cartilage at the margin of the lesion and that the cartilage islands were fixed to bone. The telescope is looking medially from a lateral portal with dorsal up and caudal to the left. Joint capsule fills the upper half of the image with the humeral head at the bottom. The medial margin of the OCD defect is seen as a sharp cartilage layer behind the probe. There is a small amount of viable exposed bone to the right of the probe tip. The remainder of the OCD lesion between the probe tip and the bottom of the image is covered with newly formed cartilage. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Atypical cartilage lesions are seen on the humeral head in the area typical for OCD lesions without any visible loose cartilage or arthroliths (Figure 3.93). These findings could be due to atypical development of cartilage defects without a loose or free flap of cartilage or when the loose OCD cartilage has broken‐free and been completely resorbed. Chondromalacia in this area of the humeral head is also seen with no other indication that an asymptomatic typical OCD lesion occurred (Figure 3.94). This finding may be secondary to normal stresses to this part of the joint or due to a subclinical OCD lesion where the cartilage became thicker during growth but did not break loose to develop into clinical OCD.
3
Shoulder Joint
3.1 Patient Preparation, Positioning, and Operating Room Setup
3.2 Portal Sites and Portal Placement
3.2.1 Telescope Portals
3.2.2 Operative Portals
A caudolateral portal is the most common operative portal in the shoulder joint. This portal is used for removing OCD cartilage flaps, for debriding OCD cartilage defects, for removing caudal cul‐de‐sac joint mice, and for removal of UCGOC lesions (Figures 3.3 and 3.7). This portal is placed caudal and distal to the lateral telescope portal with distance depending on patient size. This is in the same location as the caudolateral surgical approach to the humoral head for open removal of OCD lesions. It is very helpful to determine the distance from the telescope portal site to the operative portal site on radiographs before surgery. Stating distances in centimeters, as is done in many publications, is of little help because of the variation in patient size. To locate this portal site, the OCD lesion is visualized with the telescope and a 1.5″ 20‐gauge hypodermic needle or a 2.5″ 20‐gauge spinal needle is directed into the joint to intersect the axis of the telescope view at the caudal margin of the shoulder joint. Correct needle placement is confirmed by intra‐articular visualization of the needle with the telescope (Figure 3.8). The needle is repositioned until it enters the joint at the correct location and is at an angle allowing access to the OCD lesion (Videos 2.1 and 3.1). If the needle angle is oblique to the joint space, access to the OCD lesion may not be possible. A short incision is made at the needle site with a no. 11 blade through skin, subcutaneous tissues, and superficial muscle fascia. A curved mosquito hemostat with the curved tip pointed cranially is used to bluntly dissect through the muscle and into the joint (Figure 3.9). The hemostat jaws are spread to create a large enough tissue tract for removal of OCD cartilage fragments. Operative cannula placement at this site is done with a stab incision made at the needle site with a no. 11 blade, and the needle is replaced with the operative cannula. This is one of the more difficult portals to place due to muscle thickness over the joint, the angle at which the joint is approached, and lac of close bony landmarks.
3.2.3 Egress Portals
3.3 Nerves of Concern with Shoulder Joint Arthroscopy
3.4 Examination Protocol and Normal Arthroscopic Anatomy
3.5 Diseases of the Shoulder Diagnosed and Managed with Arthroscopy
3.5.1 Osteochondritis Dissecans (OCD)
Grade 0
Normal cartilage
Grade I
Blisters, softening, and swelling
Grade II
Fibrillation or fissures with partial (<50%) loss of thickness involving an area less than 1.5 cm diameter
Grade III
Fissures to subchondral bone with partial (>50%) loss of thickness (or?) involving an area greater than 1.5 cm diameter
Grade IV
Full‐thickness loss of cartilage with exposed bone
Grade V
Full‐thickness loss of cartilage with exposed eburnated bone 
3.5.1.1 OCD Lesion Removal and Management
When the lesion has been identified, a needle is inserted into the joint at the operative portal site to confirm the best location for portal placement (Figure 3.8) (Videos 2.1 and 3.1). Angle of the needle is important as it needs to be aligned with the joint space to provide instrument access to the OCD lesion. Incorrect needle angle (Figure 3.95), and thus portal placement, does not allow access to the needed area of the joint making management of the OCD lesion more difficult. Once the needle is correctly placed, a skin incision is made where the needle penetrates the skin. This incision is about one centimeter long and penetrates through the skin, subcutaneous tissue, and superficial muscle fascia but no deeper. The operative portal is established using a curved mosquito hemostat to bluntly dissect through the remaining muscle, fascia, through the joint capsule (Figure 3.9), fully into the joint (Figure 3.96), and the jaws are spread (Figure 3.97) to dilate the soft tissues establishing the operative portal. OCD lesion removal is typically performed without an operative portal cannula. The tip of the curved mosquito hemostat is used to elevate and free the cartilage flap (Figure 3.98) until it is almost completely detached (Videos 3.2 and 3.3). The attached portion of the margin of the lesion is partially broken away from the normal cartilage using the closed tip of the hemostat (Figure 3.99) or by opening the hemostat and grasping the cranial margin of the loose cartilage (Figure 3.100). A small area of attachment is left intact to stabilize the free cartilage fragment. The hemostat is repositioned across the free cartilage (Figure 3.101) to include as much of the flap as possible (Figures 3.102 and 3.103) and the hemostat is elevated, retracted, or rotated to break the final attachment completely freeing the cartilage (Videos 3.2–3.5). A small point of attachment is left on the cranial or craniomedial margin of the cartilage flap to hold it in place until it is removed (Figure 3.104
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