Arthroscopy of the radiocarpal joint is indicated when there is front leg lameness with carpal pain, crepitus, swelling, thickening, or instability; radiographic changes showing intra‐articular fractures or degenerative joint disease. The carpal joint is a commonly recommended site for synovial biopsies to diagnose immune‐mediated polyarthritis. Carpal joint disease is commonly accompanied by significant joint swelling or thickening making localization of the involved joint easier than with more proximal joints. Radiocarpal joint arthroscopy is typically performed as a unilateral procedure. The patient is placed in dorsal or lateral recumbency with the leg to be evaluated on the upper side and with the involved leg suspended for preparation and draping. For examination in dorsal recumbency, the leg is extended caudally beside the body, and for the lateral recumbent position, the leg is placed at a normal standing angle and is rotated externally. A monitor is placed across the table from the surgeon when the lateral position is used (Figure 2.6) and at the head of the table for the dorsally recumbent position (Figure 2.4). An assistant stands caudal to the surgeon when the lateral position is used and cranial to the surgeon between the surgeon and monitor if the dorsal position is used. Dorsal recumbency is used for the occasional bilateral procedure with the legs extended caudally, the monitor at the head of the table, and the assistant standing cranial to the surgeon (Figure 2.4). If carpal fusion or other open surgical procedure is a consideration following arthroscopy, this is taken into account in positioning the patient to allow a smooth transition without repositioning or redraping. All portals for the radiocarpal joint are on the cranial or dorsal aspect of the joint (Figure 5.1). Portals are placed medial and lateral to the common digital extensor tendon with the telescope portal placed on the side of the tendon away from the area of interest. This allows placement of an operative portal directly over the lesion. The radiocarpal joint is very small and frequently there is not enough room for three portals, so an egress portal is not placed, and egress is allowed through the operative portal. If an egress portal is needed, it can be established medial or lateral to either of the other two portals. The portal sites are established by flexing the carpus and palpating the indentation of the radiocarpal joint space medial and lateral to the common digital extensor, a 20‐gauge 1″ needle is placed into the joint, joint fluid is aspirated, the joint is distended with saline, a stab incision is made with a no. 11 scalpel blade, and the telescope cannula is placed into the joint using the blunt obturator. Initial egress is allowed through the 20‐gauge needle until an operative portal is established. The portal site on the dorsal aspect of the joint not used for the telescope portal is used for an operative portal. A 20‐gauge 1″ needle is placed in the joint to accurately confirm portal site placement and a stab incision is made into the joint with a no. 11 scalpel blade. Instrumentation is passed directly into the joint without an instrument cannula. The lateral branch of the superficial radial nerve courses across the dorsal surface of the radiocarpal joint with the tendon of the extensor carpi radialis. This nerve with the cranial superficial antebrachial artery and the accessory cephalic vein lies between the two interchangeable portals (asterisk) on the dorsal aspect of the joint (Figure 5.1). At the level of the carpal joint, this nerve contains only sensory fibers. The combined neurovascular bundle is palpated and avoided when establishing these portals. Figure 5.1 Portal sites on the dorsal aspect of the radiocarpal joint. The portals shown are two interchangeable sites for telescope and operative portals (asterisks) medial and lateral to the common digital extensor tendon. Source: Modified from Freeman (1999). © 1999, Elsevier. Upon entering the radiocarpal joint orientation is established using the distal articular surface of the radius and ulna, proximal articular surface of the radial carpal bone, and the joint space looking either laterally (Figure 5.2) or medially (Figure 5.3). Space within the radiocarpal joint is limited, and examination requires careful manipulation of the joint through flexion and extension using small movements of the telescope in depth, angle, and rotation. The distal articular surfaces of the radius and ulna with the radioulnar ligament (Figure 5.2), the proximal surface of the radial carpal bone (Figures 5.2 and 5.3), the dorsal surface of the accessory carpal bone (Figure 5.4), the dorsal joint space (Figure 5.3), and the palmar ulnocarpal ligament of the joint (Figure 5.5) are examined (Warnock and Beale 2004). Transposing the telescope between the two dorsal portal locations facilitates a complete examination of the joint.
5
Radiocarpal Joint
5.1 Patient Preparation, Positioning, and Operating Room Setup
5.2 Portal Sites and Portal Placement
5.3 Nerves of Concern with Radiocarpal Joint Arthroscopy
5.4 Examination Protocol and Normal Arthroscopic Anatomy
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