The Effect of Sequential Flexor Tendon Pulley Sectioning and Reconstruction on Joint Range of Motion and Tendon Load
Nina Suh, MD, FRCSC; Brett Byers, MD FRCS(C); Mohammad Haddara, BEng; Louis Ferreira, PhD, P Eng
Western University, London, ON, Canada
Background: Injury to A2 and A4 flexor tendon pulleys are not uncommon following sharp lacerations, crush injuries, and to a lesser extent, iatrogenic injury. These defects are known to cause tendon bowstringing with subsequent range of motion (ROM) deficits of the affected finger. In response, deficient tendon pulleys are reconstructed in an effort to avoid these complications. However, it is unclear how deficient tendon pulleys and subsequent reconstructions affect actual tendon load in addition to joint ROM. The purpose of this study is to characterize the effects of sequential A2 and A4 pulley sectioning and reconstruction on joint ROM and tendon load.
Methods: A novel in-vitro finger motion simulator was designed to achieve full simulated active finger flexion and extension. The index, long, and ring fingers were used in 5 cadaveric specimens (age: 71.8±9.9 years; 3 females, 2 males), with a total of 14 digits included in the study. Our simulator controls loads and tendon excursions using closed-loop feedback control, while outcomes measures include loads, excursions, and ROM of the finger. The effects of sectioning A2 and A4 pulleys, and their reconstructions were analyzed using a 2-way repeated-measures ANOVA.
Results: With the wrist in neutral, full sectioning of both A2 and A4 pulleys reduced MCP ROM by 9.1±7.1° (p=0.016) and FDP tendon load by 2.3±1.9N (p=0.029). A flexed wrist further reduced MCP ROM by 7.4±6.3° (p=0.009) and reduced FDP tendon load by 3.6±3.5N (p=0.034) when both pulleys were cut. Reconstruction restored FDP load to within 0.5 N of the intact state (p=0.034). With the wrist extended, cutting both pulleys reduced MCP ROM by 7.2±7.3° (p=0.024), and reconstruction restored MCP ROM to within 2° of the intact state (p=0.014), while FDP tendon load was reduced by 3.5±1.7N (p<0.001). DIP and PIP ROM were not significantly altered.
Conclusion: In all wrist positions, cutting A2 and A4 pulleys reduced MCP ROM, as well as FDP tendon loads. PIP and DIP joint ROM was not significantly affected. Pulley reconstructions restored these metrics with no significant difference compared to the intact state, reinforcing their utility by not only reducing bowstringing, but by restoring natural joint biomechanics and tendon loads. The new simulator has provided additional tendon load information to compliment the state of knowledge on joint ROM in the context of pulley reconstructions.
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