The Effect of Wrist Position on Tendon Loads Following Pulley Sectioning and Operative Reconstruction
Nina Suh, MD, FRCSC1; Brett A Byers, MD FRCSC2; Mohammad Haddara, BEng3; Louis Ferreira, PhD Peng2; (1)Roth|MacFarlane Hand and Upper Limb Centre, University of Western Ontario, Roth|MacFarlane Hand and Upper Limb Centre, Canada, London, ON, Canada, (2)St. Joseph's Health Care London, London, ON, Canada, (3)Western University, London, ON, Canada
Background: Isolated flexor tendon pulley ruptures often require surgical reconstruction to prevent tendon bowstringing. Post-operative rehabilitation is imperative and must balance potential rupture of the pulley reconstruction with aggressive therapy and tendon adhesion formation from overly cautious protocols. Using tendon loads as a proxy for pulley strain, we sought to identify the optimal wrist position for rehabilitation after pulley reconstruction.
Methods: Fourteen digits, comprised of the index, long and ring fingers, were tested from 5 cadaveric specimens. Active (tendon-driven) finger flexion was simulated using a validated cadaveric motion simulator, utilizing servo-motors to generate motion through closed-loop control of tendon excursion and finger range of motion. FDP tendon loads were measured sequentially with native intact pulleys, A2 and A4 pulleys sectioned, and finally with reconstructed A2 and A4 flexor tendon pulleys. Each pulley condition was tested in wrist neutral, and 30 degrees of wrist flexion and extension. Using the simulator to measure FDP tendon load, the effects of wrist position on sectioned and reconstructed A2 and A4 pulleys were analyzed using repeated-measures ANOVA.
Results: With the wrist in neutral, FDP tendon loads were 8.5N, 6.2N, and 7.8N with pulleys intact, sectioned, and reconstructed, respectively. With a flexed wrist, the loads were 8.5N, 4.7N, and 5.4N. When the wrist was extended, the loads were 8.7N, 5.2N, and 6.7N. With pulleys reconstructed, the wrist position had a significant effect on tendon load (p=0.030). The flexed wrist position resulted in a 31% reduction of FDP load compared to the neutral wrist position (p=0.010). Wrist extension also produced an apparent reduction, though not statistically significant.
Conclusion: The in-vitro finger motion simulator detected a significant decrease in FDP tendon loads caused by sectioning of A2 and A4 pulleys. Reconstructing the pulleys largely restored FDP loads to within no significant difference of the intact state, which supports the decision to reconstruct. Placing the wrist in 30 degrees of flexion decreased tension in the reconstructed FDP tendon compared to a neutral wrist. These results may suggest that rehabilitation of surgically reconstructed flexor tendon pulleys should be carried out with the wrist flexed in order to reduce strain on pulley reconstructions.
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