Effect of gap size on gliding resistance after flexor tendon repair

Background: Gap formation is a common complication after flexor tendon repair and is associated with adhesion formation, tendon rupture, and decreased strength. The purpose of this study was to investigate the effect of gap formation on tendon gliding resistance after flexor tendon repair in a human cadaver model. Methods: Twelve index, middle, and ring fingers from four adult human cadaveric hands were used. Gliding resistance versus excursion between the flexor digitorum profundus tendon and the A2 pulley was first measured in intact tendons. After full laceration, each tendon was repaired with the Pennington suture technique and the gliding resistance was measured again. Then, the repaired tendon (a 0-mm gap) was stretched to form a 1-mm gap, and gliding resistance was remeasured. A magnified video image was used to monitor gap size. This process was repeated to evaluate gap sizes of 2, 3, and 4 mm at the repair site. Peak gliding resistance was determined, and the peak gliding resistance was compared among the groups. Results: No significant difference in peak gliding resistance was detected between repaired tendons without a gap and tendons with a 1-mm gap. Repaired tendons with a 2-mm gap could pass through the A2 pulley; however, peak gliding resistance was significantly higher than that for tendons with a 0 or a 1-mm gap (p < 0.05). When the gap reached ≥3 mm, all tendons caught at the A2 pulley edge, causing a dramatically increased peak gliding resistance. Conclusions: The presence of a 2-mm gap after flexor tendon repair significantly increased tendon peak gliding resistance (p < 0.05), while a gap of ≥3 mm further increased peak gliding resistance because of catching at the pulley edge. Clinical Relevance: This study suggests that a large gap (≥3 mm) that develops after repair of the flexor digitorum profundus tendon may increase the risk of triggering (catching) at the pulley edge, which may predispose the tendon to rupture, limitation of motion, or adhesion formation during postoperative rehabilitation. Therefore, we believe that minimizing gap formation is an important consideration in flexor tendon repair.