Treatment of hyperextension deformity of the thumb metacarpophalangeal joint in basal joint arthritis: a novel technique based on an anatomic study.

Advanced stages of basal joint arthritis are sometimes characterized by an adduction deformity of the first metacarpal and a hyperextension deformity of the unstable metacarpophalangeal (MCP) joint. Stabilizing the MCP joint in these patients is critical to ensure a pain-free repair and efficient pinch mechanism. This study presents the anatomic basis for a novel capsulodesis technique using the volar plate that can be incorporated into any reconstructive basal joint procedure when clinically indicated. Eleven normal cadavers were dissected to expose the volar plate. The dimensions of the volar plate, relationship of the sesamoid bones to the oblique pulley, and the distance from the sesamoids to the base of the proximal phalanx were compared between specimens. The radial border of the volar plate measured 8.5 ± 1.3 mm, ulnar border 8.8 ± 1.0 mm, proximal border 7.5 ± 1.0 mm, and distal border 7.8 ± 0.6 mm. The distance between the ulnar sesamoid bone and the oblique pulley measured 12.1 ± 1.1 mm and from the radial sesamoid to the oblique pulley measured 16.6 ± 0.2 mm. The distance between the sesamoids and the base of the phalanx measured 2.2 ± 0.2 mm. The anatomic studies provide a foundation on which the surgeon can understand the complex nature of the MCP joint. This study describes a novel technique for MCP capsulodesis of the thumb in which volar plate flaps are imbricated to provide stability to the MCP joint, obviating the need for suture anchors and tendon grafts.