Impacts of Flexor Pulley Sacrifice on Motion and Work in a Fresh Cadaveric Model
J. Bradford Hill, MD1, Pooyan Abbasi, MS1, Anthony F. Colon, MD1, Aviram M Giladi, MD, MS1, Kenneth R Means Jr, MD1 and Ryan D Katz, MD2, (1)The Curtis National Hand Center, Baltimore, MD, (2)Curtis Hand Center, The Curtis National Hand Center, Baltimore, MD
Introduction: Modern clinical experience challenges the early biomechnical predictions of morbidity from finger flexor pulley loss, specifically at A2 and A4. This inconsistency may be due to limitations with prior biomechanical models. Our objective was to quantify changes in range of motion and work of flexion after pulley loss in a fresh cadaver active motion model.
Methods: Nine fresh, never-frozen cadaver specimens were transected through the radiocarpal joint. All fingers were dissected via a mid-axial incision with oblique extensions into the palm, exposing the entire flexor-pulley system. The hands were mounted on a custom frame with proximal flexor digitorum profundus (FDP) tendons separated and individually connected to a computer-controlled servomotor. This allowed simulated full active flexion of the fingers. A load-cell ensured a limit force generation (25N or 50N) to achieve palm touchdown. The flexor pulleys were sequentially excised through multiple iterations/sequences and tested following each stage. The skin was sutured and the fingers were brought through a mean of five runs to calculate flexor tendon excursion in finger-to-palm touchdown and work of flexion.
Results: Of the nine hands, 33 fingers had complete testing. Three fingers were excluded during initial testing with all pulleys intact due to triggering or inability to reach palm touchdown. Three zones of pulley excision were labeled: “A1” (A1) “A2” (A2 and C1) and “A4” (A3, C2, and A4). Each of these zones had a mean length of ~22mm. Pulley excision at any single zone did not result in significant changes in flexor tendon excursion to reach palm touchdown. However, excision of any combination of two zones always resulted in significant increases in excursion for finger-to-palm touchdown [Table 1]. Significantly more excursion was required when A1 was excised with “A2” (5.4mm, p < 0.001) or “A4” (3.7mm, p < 0.01) [Figure 1]. Work of flexion was not significantly altered following any degree of pulley excision.
Conclusion: This study demonstrates that approximately 2cm of flexor pulley sacrifice, at any level, is acceptable with regard to flexor tendon excursion and work of flexion. Our results also indicate that the A1 pulley should be preserved when other pulley systems are compromised or excised.
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