The Ideal Insertion Site for the Flexor Digitorum Profundus Tendon in Jersey Finger Repair: A Biomechanical Analysis

Most jersey finger repair techniques involve reattaching the tendon to an approximate location corresponding to the tendon's native attachment. This study aimed to determine the biomechanical effect on the distal interphalangeal joint flexion forces and range of motion when the flexor digitorum profundus (FDP) tendon attachment site on the distal phalanx is altered within its broad footprint.

We fixed 14 fresh-frozen cadaveric fingers to a wooden block with an attached pulley and weights system. A pressure mapping sensor placed under the fingertip measured the contact force and area in response to FDP tendon loading for the intact tendon and 3 repair sites along the FDP footprint. Two-way repeated-measures analysis of variance test using mixed-effect model was performed to test the influences of attachment location (intact, proximal, central, and distal) and digit (index, middle, and ring) on the outcomes.

Mean ± SD contact force under 45 N tendon loading force was 43.5 ± 7.2 N for the intact tendon, 34.6 ± 7.4 N for the proximal insertion, 38.0 ± 7.1 N for the central insertion, and 43.1 ± 6.3 N for the distal insertion. Compared with the intact tendon, the proximal group generated notably less contact force. No significant difference was detected between the intact tendon and the central or distal repairs. Comparisons among the 3 repair groups show that the distal group generated significantly higher force than the proximal group. There was no difference between contact areas across all groups.

The FDP tendon inserted at the distal edge of its footprint conferred significantly greater distal interphalangeal joint flexion force compared with the proximal insertion site and most closely resembled the intact FDP tendon.

Biomechanically, distal reattachment of the FDP most closely approximates the contact force of the native anatomy and may help guide intraoperative placement of the repair footprint.