Biomechanics of the Trampoline Test in the Intact, Sectioned, and Repaired TFCC.

 Multiple techniques have been developed to detect a triangular fibrocartilage complex (TFCC) foveal detachment. One commonly used technique to evaluate TFCC integrity, the trampoline test, has had variable reliability.  The purpose of this biomechanical experiment was to evaluate the suitability of the trampoline test in detecting TFCC foveal detachments.  In each of 10 cadaver arms, TFCC displacement near the ulnar fovea was measured using a plunger with increasing incremental loads in the intact wrist, after ulnar sectioning of the TFCC, and following TFCC repair.  After the application of the eight incremental small weights, there was no significant difference in the relative displacement of the plunger between the intact case, after detachment of the ulnar aspect of the TFCC disc, and after repair (0.6 mm intact, 0.7 mm detached, and 0.7 repair). However, there were significant differences in the absolute ending point displacement referenced to the starting intact position (0.6 mm intact, 1.3 mm detached, and -0.9 mm after repair).  This study suggests that the trampoline test may not be adequate to quantify displacement (bouncing) of the TFCC disc after injury.