Relation of the radial nerve to the anterior capsule of the elbow: Anatomy with correlation to arthroscopy

Purpose: To determine the location and proximity of the radial nerve to the anterior capsule and to delineate and describe the anatomy of the brachialis as it relates to the radial nerve and anterior capsule. Methods: Arthroscopy was performed on 24 cadavers using only a standard anteromedial portal. A Beath pin was placed laterally, entering the joint at the most lateral edge of the radiocapitellar joint space, and a suture was placed through the pin and into the joint for reference during the dissection. The second phase was to perform open anatomic dissections. Results: We found that in all specimens the radial nerve coursed longitudinally medial to the capitellum. The brachialis muscle was found to lie between the radial nerve and the joint capsule at the joint line and all proximal levels. Only at the most distal aspect of the joint line (corresponding to the level of the radial neck) did the nerve run in direct contact with the capsule in 11 specimens (55%). The brachialis muscle thickness was 4 mm or greater at the joint line and at all proximal measurement points. Conclusions: We found that the radial nerve is more medially located than previously thought. At the level of the radiocapitellar joint line, the radial nerve runs medial to the capitellum. The brachialis muscle lies between the radial nerve and the joint capsule at the level of the joint line and proximally. Clinical Relevance: Arthroscopic capsular release laterally should be performed at the level of the joint line or above. The most dangerous area for capsular resection is distally over the radial head/neck, where 50% of our specimens had no brachialis protecting the nerve.