Arthroscopy of the tibiotarsal joint is indicated when there is hind leg lameness with pain, crepitus, swelling, or thickening of the tibiotarsal joint supported by radiographic changes suggestive of OCD, intra‐articular fractures, degenerative joint disease, immune‐mediated arthritis, or neoplasia (Cook et al. 2001; Miller and Beale 2008). Tibiotarsal joint disease is commonly accompanied by significant joint swelling or thickening making localization of the involved joint easier than with more proximal joints. The tarsal joint is a recommended site for synovial biopsies for diagnosing immune‐mediated polyarthritis. Tibiotarsal joint arthroscopy is performed as a unilateral or bilateral procedure based on the pathology that is present. Dorsal recumbency is the most common position used for both unilateral and bilateral procedures. The legs are extended caudally and abducted or adducted for access to the medial or lateral aspects of the joint respectfully. The most common operating room arrangement is with a monitor at the head of the table (Figure 2.9). Alternative operating room setup places the monitor obliquely on either side of the table or when two monitors are used with one on each side of the table. Monitors on the sides are placed far enough cranially to be out of the way of the sterile operative field. The surgeon stands at the foot of the table and the assistant stands on the side of the table of the joint that is being examined. Tibiotarsal joint arthroscopy has been greatly improved by use of distraction (Rodriguez‐Quiros et al. 2014). The author uses a bolster under the joint to provide a fulcrum for distracting the facilitating access with the endoscope and instrumentation. For placement of plantar portals, the patient can also be placed in ventral recumbency with the leg or legs extended off the caudal end of the table. All four quadrants of the tibiotarsal joint can be entered for arthroscopy. The portal selected for entry depends on the location of joint lesions. Telescope and operative portals are interchangeable at all sites. Dorsomedial and dorsolateral portals are placed either medial or lateral to the long digital extensor tendon and the tendon of the cranial tibial muscle on the dorsal aspect of the joint immediately distal to the distal margin of the tibia (Figure 8.1). To establish a dorsal tibiotarsal telescope portal at either of these sites, a 20‐gauge 1″ needle is placed into the joint at the site of maximum joint capsule distension, joint fluid is aspirated, the joint is distended with saline, a stab incision is made with a no. 11 scalpel blade at the needle site, or on the other side of the extensor tendons if indicated, and the telescope cannula is placed into the joint using the blunt obturator. Plantaromedial or plantarolateral portals are placed at the junction of the plantar margin of the distal tibial articular surface and the plantar portion of the trochlear ridge of the talus on their respective sides of the joint (Figure 8.2). Plantar portals provide good access to plantar OCD lesions on the medial or lateral ridges of the talus and for removal of loose joint bodies from the caudal compartment of the joint. To establish a plantar tibiotarsal telescope portal, a 20‐gauge 1″ needle is placed into the joint at the site of maximum joint capsule distension, joint fluid is aspirated, the joint is distended with saline, a stab incision is made with a no. 11 scalpel blade at the needle site, and the telescope cannula is placed into the joint using the blunt obturator. Joint capsule thickening secondary to joint pathology may make initial plantar joint entry difficult. In some cases with marked joint capsule thickening, the joint is entered with a mini‐arthrotomy rather than a true telescope portal. A mini‐arthrotomy is performed by making a stab incision through the skin, subcutaneous tissues, and joint capsule with a no. 11 blade to access the joint and the incision extended as needed. The telescope cannula is placed into the joint with the telescope already in the cannula, irrigation is initiated, and the joint is examined. Figure 8.1 Portal sites on the dorsal aspect of the tibiotarsal joint. The two portals shown (asterisks) are interchangeable telescope and operative portals. They are located distal to the dorsal margin of the distal tibial articular surface and are medial or lateral to the long digital extensor tendon, the tendon of the cranial tibial muscle, and the dorsal neurovascular bundle. Source: Modified from Freeman (1999) © John Wiley & Sons. Access to OCD lesions on the plantar portion of the medial ridge of the talus, the most common indication for tibiotarsal arthroscopy, is most easily achieved through a medial operative portal placed distal to the malleolus and immediately caudal to the collateral ligament (Figure 8.2). Access to the joint is greatly facilitated by placing a bolster under the joint and opening the medial or lateral joint space by placing pressure on the tibia and metatarsal bones (Figures 8.3 and 8.4). Joint capsule thickening and limited space in the hock joint may preclude placing separate telescope portals and operative portals. In these cases, the telescope portal site is enlarged to serve as a combination portal with the telescope and instruments inserted through the same incision. On the dorsal aspect of the joint, the operative portal is established on the side of the extensor tendons not used for the telescope portal with initial needle placement for locating the portal site followed by a simple stab incision with a no. 11 blade through skin, subcutaneous tissue, and joint capsule. To place two portals in the plantar aspect of the joint, the patient is placed in ventral recumbency with an operative portal placed in the opposing corner of the joint from the telescope portal to achieve adequate access, visualization, and triangulation. Figure 8.2 Portal sites on the lateral aspect of the tibiotarsal joint. The plantarolateral, telescope portal (asterisk) is placed at the junction of the plantar margin of the distal tibial articular surface and the plantar portion of the lateral ridge of the talus. Lateral operative portals (square) are placed distal to the lateral malleolus and caudal to the collateral ligament. An egress portal or needle if needed is placed at the dorsolateral, telescope or operative portal site, shown in the previous figure. Medial portals are placed at the same respective locations on the medial aspect of the joint. Source: Modified from Freeman (1999) © John Wiley & Sons. A separate egress cannula is rarely used but if needed can be placed at any unused portal site. The very small space available in the tibiotarsal joint does not provide enough room for three cannulas, and egress is most commonly through the operative portal, through a mini‐arthrotomy incision, or a through 20‐gauge needle placed at an unused portal site. Figure 8.3 The tibiotarsal joint visualized with the telescope in the plantaromedial portal without distraction over a bolster. The tibial articular surface is to the upper left and the talar articular surface fills the lower right of the image. Dorsal is to the upper left. Source: Timothy C. McCarthy. © John Wiley &Sons Inc. Figure 8.4 The tibiotarsal joint visualized from the same telescope position with distraction over a bolster. Note the increased joint space. Dorsal or proximal is to the left as is the tibial articular surface. The talar articular surface is to the right. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. The superficial and deep fibular nerves with the cranial tibial artery, the cranial branch of the saphenous artery, and the cranial branch of the saphenous vein all cross the dorsal aspect of the tibiotarsal joint (Figure 8.1). At the level of the tibiotarsal joint, the nerves are primarily sensory but do contain fibers that supply muscles in the paw. The combined neurovascular bundle with the tendons of the cranial tibial and long digital extensor muscles are palpated on the dorsal aspect of the joint and avoided when making these portals minimizing the possibility of nerve damage. The termination of the tibial nerve with the caudal branch of the saphenous artery cross the joint caudal to the tibia and medial to the calcaneus (Figure 8.2). These structures are caudal and lateral but close to the plantaromedial telescope portal and are at risk of injury. The operative portal for OCD lesions on the caudomedial ridge of the talus is on the medial aspect of the joint away from the dorsal and plantar neurovascular structures. The tibial nerve at this level is also primarily sensory but does supply motor fibers to muscles in the paw. Visible anatomy, structures used for orientation, and examination protocol vary with the portals that are used. The tibiotarsal joint is small, normally allowing minimal joint distraction for examination and manipulation. Varus or valgus angulation of the joint over a bolster greatly facilitates examination by opening the joint space and is strongly recommended. The joint capsule is too close to the bony structures of the joint to allow retraction of the arthroscope for a wide visual field. Multiple portals may be required for complete examination and operation of tarsal joint pathology. Orientation is established upon entering the tibiotarsal joint using the concave distal articular surface of the tibia and the ridges of the convex articular surface of the talus (Figures 8.3 and 8.4). Space within the tibiotarsal joint is limited and examination requires careful manipulation of the joint through flexion and extension with varus and valgus stress over the bolster using small movements of the telescope in depth, angle, and rotation. The distal articular surface of the tibia and the proximal surface of the talus (Figures 8.3 and 8.4), the dorsal margin of the distal tibial articular surface (Figure 8.5), the lateral malleolus (Figure 8.6), and the accessible lateral (Figure 8.7), dorsal (Figure 8.8), and plantar (Figure 8.9) joint compartments are examined. The lateral head of the deep digital flexor tendon can be seen within the joint (Figure 8.10). Transferring the telescope among portal locations facilitates complete examination of the joint. Figure 8.5 The dorsal or cranial margin of the distal articular surface of the tibia is seen curving across the top of the figure and the proximal articular surface of the talus is seen filling the bottom of the image. The telescope is looking obliquely across the dorsal joint compartment from a dorsal portal. Proximal is up on the image and cranial is to the right. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 8.6 The plantar aspect of the intra‐articular portion of the lateral malleolus seen looking cranially from a plantarolateral telescope portal. Proximal is up on the image and lateral is to the left. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 8.7 The lateral joint space seen between the distal articular surface of the tibia and proximal articular surface of the talus seen with the telescope looking laterally from a plantaromedial portal. Proximal is up and caudal is to the right. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 8.8 The dorsal tibiotarsal joint compartment with the joint capsule filling the majority of the image and the dorsal articular surface of the talus on the left seen looking across the joint from a dorsal telescope portal. Proximal is up and dorsal or cranial is to the right. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 8.9 The plantar tibiotarsal joint compartment seen looking laterally from a plantaromedial telescope portal. The distended joint capsule fills the image. Proximal is up and plantar is to the right. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Tibiotarsal OCD lesions occur most commonly on the plantar aspect of the medial ridge of the talus (Figure 8.11) but can also occur on the plantar aspect of the lateral ridge and uncommonly dorsally on either the medial or lateral ridges (Figure 8.12). Plantaromedial lesions are typically very large relative to the size of the joint and contain bone (Figure 8.13) leaving large defects in the medial ridge of the talus with removal (Figure 8.14). Significant villus synovial reaction is also typically present, especially with plantar lesions, adding to the difficulty of arthroscopic procedures (Figure 8.15). Stress applied over a bolster to open the medial aspect of the joint greatly facilitates examination of this small tight joint making operative procedures much easier and more effective. The lesion is visualized as shown in Figure 8.11 but many times lesions are not easy to define because of their size (Figure 8.15), irregular margins (Figure 8.16), fragmentation of the free osteocartilaginous lesion (Figure 8.17), or villus synovial reaction (Figure 8.18). Once identified the loose fragment is elevated if needed (Figure 8.19), grasped with rongeurs (Figures 8.20 and 8.21) or grasping forceps (Figure 8.22) and removed in one piece or multiple pieces as required. Minimal debridement of the defect is employed with removal of loose fragments from the margin (Figure 8.23) and within the bed of the lesion (Figure 8.24) to produce a clean margin with a clean bed of exposed bone (Figure 8.14). Rongeurs, curettes, and graspers are used to remove larger loose cartilage and bone fragments with irrigation to remove fine debris. Since these plantaromedial OCD lesions are typically very large relative to the size of the joint and because removal leaves a significant deep defect in the ridge of the talus, extensive debridement with curettage or with a power shaver is not done. Figure 8.10 The lateral head of the deep digital flexor tendon (tendon of the flexor hallucis longus) with the telescope directed proximally up the tendon sheath from a plantaromedial portal. Source: Timothy C. McCarthy. © John Wiley & Sons Inc. Figure 8.11 A typical large plantar tibiotarsal OCD lesion on the medial ridge of the talus seen from a plantaromedial telescope portal. Proximal is to the upper right and plantar is to the bottom of the image. The free OCD fragment fills the right center of the image between the narrow portion of distal tibial articular surface seen on the far right and the exposed eburnated bone of the plantar medial ridge of the talus to the lower left. Source: Timothy C. McCarthy. © John Wiley & Sons Inc.
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Tibiotarsal Joint
8.1 Patient Preparation, Positioning, and Operating Room Setup
8.2 Portal Sites and Portal Placement
8.2.1 Telescope Portals
8.2.2 Operative Portals
8.2.3 Egress Portal
8.3 Nerves of Concern with Tibiotarsal Joint Arthroscopy
8.4 Examination Protocol and Normal Arthroscopic Anatomy
8.5 Diseases of the Tibiotarsal Joint Diagnosed and Managed with Arthroscopy
8.5.1 Osteochondritis Dissecans (OCD)
OCD is the most common arthroscopic diagnosis in the tibiotarsal joint and is the most common indication for operative arthroscopy of this joint (Cook et al. 2001). Tibiotarsal OCD can be either unilateral or bilateral. Preoperative radiographs are taken to establish a tentative diagnosis and to evaluate for bilateral disease. CT studies of the joint are highly recommended to establish a definitive diagnosis and to fully define the lesions. Bilateral arthroscopy is performed at the same time if bilateral lesions are found. Lesions on the plantar aspect of the medial ridge of the talus are approached with a plantaromedial telescope portal and a medial operative portal (Video 8.1) or through a plantaromedial mini‐arthrotomy.
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