Cyclic Testing of a Modified Pull-Out Suture Repair Technique for Flexor Digitorum Profundus Avulsion in a Turkey Foot Model

Abstract

Background: Numerous repair techniques have been described for closed flexor digitorum profundus (FDP) avulsion. One option is a pull-out suture tied over the nail plate (Bunnell repair). We modified the Bunnell repair by incorporating a portion of the distal interphalangeal (DIP) joint volar plate into the repair to improve strength and reduce gapping. The aim of this study is to compare gap formation and load to failure between the Bunnell repair and our modification in a turkey foot model. Methods: Twenty-four fresh-frozen cadaveric turkey feet were divided into two repair groups namely the conventional Bunnell pull-out suture technique and the modified Bunnell pull-out suture technique, incorporating the middle-third of the DIP joint volar plate into the repair. Both repairs were carried out with 3-0 prolene suture and underwent ex-vivo cyclic loading at 2-12 n in a sinusoidal wave for 100 cycles to simulate a passive range of motion (ROM) protocol. Subsequently, specimens were loaded to failure at 12 mm/minute. Gap formation and load to failure were measured. Results: No repair ruptures occurred during cyclical testing. Mean gap formation was 9.2 mm (±1.49) in the Bunnell repair, and 3.5 mm (±1.19) in the modified Bunnell repair (p < 0.0001). The mean load to failure for the Bunnell repair was 35.4 n compared to 45 n for the modified repair (p = 0.0017). Conclusions: Gap formation was reduced and load to failure increased by augmenting the Bunnell pull-out suture repair with the central portion of the DIP joint volar plate.