# Biomechanical Investigations of a New Model Graft Attachment to Distal Phalanx in Two-Stage Flexor Tendon Reconstruction

## TL;DR

A new method for attaching tendon grafts to the finger's distal phalanx was tested and found to be strong enough for active rehabilitation.

## Contribution

A new biomechanical model for tendon graft attachment in two-stage flexor tendon reconstruction was tested and validated.

## Key findings

- The mean rupture strength of the new connection was 44.53 N, exceeding the 20 N needed for active rehabilitation.
- Elongation at 20 N was minimal (4.28 mm), ensuring effective motion transmission.

## Abstract

Background/Objectives: In two-stage flexor tendon reconstruction, a biomechanically strong connection between the tendon graft, the motor unit, and the distal phalanx of the finger is essential to enable active rehabilitation after surgery. However, the available literature contains few biomechanical studies concerning the strength of this connection. In this study, we tested a new model of this connection involving suturing the tendon graft to the phalanx using an anchor and to the flexor digitorum profundus stump with a three-level continuous suture (palmaris longus—flexor digitorum profundus—anchor (PL-FDP-A)). Methods: For this study, we used eight fingers from patients with injuries that were unsuitable for replantation, as well as eight palmaris longus tendons harvested from cadavers. Eight specimens simulating the PL-FDP-A connections were prepared and tested on a tensile testing machine. The elongation of the specimens under a 20 N load (the minimum for active loading) and the force at rupture were assessed. Results: The mean rupture strength was 44.53 N (SD 16.27, min. 16.50, max. 64.60), with elongation at 20 N of 4.28 mm (SD 2.65, min. 1.49, max. 9.14). Conclusions: Based on our findings, we recommend the PL-FDP-A connection for use in two-stage flexor tendon reconstruction due to (1) rupture values which significantly exceeded the force required for active rehabilitation, and (2) minimal elongation at 20 N, so that motion transmission was not impaired.