Biomechanical analysis of four-strand extensor tendon repair techniques

Abstract

Experience with flexor tendon repairs has suggested the superiority of the augmented Becker (MGH) technique for strength, toughness, and gap resistance. In an effort to apply these findings to the extensor tendons, 3 four-strand extensor tendon repair techniques were biomechanically tested in fresh human cadaver limbs: modified Bunnell, modified Krackow-Thomas, and MGH. Repairs were performed in Verdan's zone VI. Repaired tendons were distracted at constant speed until rupture. Tendon load and tendon distraction were continuously monitored. Benchmark values for load were measured as fingers were pulled from full metacarpophalangeal (MP) joint flexion to full extension, to 1-mm gap formation at the tenorrhaphy, and to complete rupture of the repair. The MGH repair proved significantly more resistant to gap formation (stronger and tougher) than the Bunnell and Krackow-Thomas repairs (p < .02). No differences were seen between groups in repair performance at MP joint extension and at complete rupture. This study suggests that the MGH technique has superior gap resistance to the other four-strand methods tested for extensor tendon repair in Verdan's zone VI. The MGH repair is recommended for extensor tendon repairs in zone VI when early postoperative motion regimens are considered.