Wrist ligament strain during external fixation: a cadaveric study.

The purpose of this study was to evaluate the change in strain (elongation) that occurs in 2 extrinsic ligaments of the wrist (volar radioscaphocapitate and dorsal radiotriquetral) as the wrist is sequentially distracted with an external fixator. Six fresh cadaver specimens were dissected to expose the dorsal radiotriquetral and volar radioscaphocapitate ligaments. A differential variable reluctance transducer strain gauge was applied to both ligaments and the wrist was serially distracted in increments of 5 mm with an Agee WristJack (Hand Biomechanics Laboratory, Sacramento, CA). The distraction increments were measured on the WristJack. X-rays were obtained at each level of distraction. At 10 mm of WristJack distraction, the strain in both the volar radioscaphocapitate and dorsal radiotriquetral ligaments increased to greater than 20%. An increase to a 0.63 carpal height index resulted in an increase in strain of 20%. This increased strain may contribute to wrist stiffness.