Biomechanical characteristics of suture anchor implants for flexor digitorum profundus repair

Abstract

Purpose: To determine strength and failure characteristics of 2 suture anchors used to repair simulated flexor digitorum profundus avulsions during passive mobilization protocol simulation.

Methods: We simulated avulsion of the flexor digitorum profundus tendon in 30 distal phalanges from fresh-frozen human cadavers. Repair was performed with a 1.3 × 3.7 mm Micro-Mitek suture anchor (3-0 Orthocord suture) and a 2.2 × 4.0-mm Corkscrew suture anchor (2-0 FiberWire suture). All specimens were loaded cyclically from 2 to 15 N at 5 N/s for a total of 500 cycles. Samples were tested to failure at the completion of 500 cycles. Load at failure, load at first noteworthy displacement (> 2 mm), elongation of the system, gap formation at the tendon-bone interface, and the mechanism of failure were assessed.

Results: Suture failure at maximum load was the prevalent failure mechanism in both groups. No statistically significant difference in elongation of the tendon-suture complex was observed. The Corkscrew suture anchor showed a significantly superior performance in load to failure, load at first significant displacement, and gap formation at the tendon-bone interface.

Conclusions: The significantly higher load capacity at first displacement (> 2 mm) and the significance of a lower gap formation at the repair site seem to be the most relevant clinical parameters. Based on this concept, the Corkscrew anchor may be superior biomechanically to the Micro-Mitek when considering an early passive mobilization protocol.

Clinical relevance: The choice of an appropriate implant may influence the postoperative mobilization protocol and thereby improve currently reported success rates. Defining a biomechanically superior implant will provide an essential basis for further studies in flexor tendon repair research.

Keywords: Flexor digitorum profundus tendon avulsion; Jersey finger; flexor digitorum profundus tendon repair; suture anchor biomechanics; suture anchor design.