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Peripheral TFCC Tears Cause Ulnocarpal Instability: a Biomechanical Study
Christopher J. Dy1, Arianna Trionfo, MD2, Anna-Lena Makowski3, Edward Milne, BS4, Loren Latta, PhD, PE4, E. Anne Ouellette3
1Hospital for Special Surgery, New York, 2UMDNJ, Camden, 3Physicians For The Hand/The Hand Place, Coral Gables, FL, 4 Max Biedermann Institute for Biomechanics, Miami Beach, FL

Hypothesis:

Disruption of the peripheral the triangular fibrocartilage complex TFCC causes ulnocarpal instability. An arthroscopically-created tear of the articular disk of the TFCC will cause a significant decrease in ulnocarpal stability on mechanical testing.

Methods:

24 fresh-frozen human upper extremities with intact elbow to the hand were held with the elbow in 90° flexion, the forearm in pronation and wrist in neutral on a servo-hydraulic loading machine. A screw in the distal ulna was fixed to the loading ram and a vertical load was cycled at ¼ Hz while the vertical movement was measurement. The dorsal/volar excursion (D/VE) between two firm end points were measured on the load-displacement curve and slope of the end points wastermed ulnocarpal stiffness.

A standardized 3mm lesion of the ulnar-sided peripheral TFCC was created via a single incision with a #15 scalpel blade under direct arthroscopic visualization. The loading regimen was repeated after the TFCC lesion. Statistical analyses used were mean, standard deviation, skewness and kurtosis. Two separate paired t-tests were used to compare UC stiffness and D/VE before and after creation of the TFCC tear.

Results:

The mean stiffness was significantly decreased after creation of the tear (p=0.003). The change in D/VE after the articular disk tear was not significantly different (p=0.08), see Table 1.
n=20 specimens Mean SD Paired T-Test
Stiffness: baseline 4.86 N/mm 3.68
Stiffness: post-tear 3.14 N/mm 2.47 p=0.003*
D/VE: baseline 1.82 mm 0.63
D/VE: post-tear 2.33mm 1.38 p=08**

Table 1: *Lower stiffness indicates more stability, **Higher value of D/VE indicates more stability

Conclusions:

  • a peripheral tear of the articular disk of the TFC significantly increases instability at the ulnocarpal joint
  • biomechanical instability ensues at the ulnocarpal joint after a peripheral TFCC lesion
  • The presence of UCI after an isolated lesion of the articular disk suggests that both the distal radioulnar and ulnocarpal joints should be evaluated in treatment strategies for patients with pathology of the TFCC, even if the ulnocarpal ligaments, ulnar collateral ligament, and ECU subsheath appear unaffected on advanced imaging modalities.

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