The capitohamate ligaments. A comparison of biomechanical properties

The physical attributes of the three capitohamate interosseous ligaments were tested in a computer-controlled multi-axis testing machine using 12 human cadaver specimens. After an intact test run, selected ligaments were cut in random sequence and the test repeated. The remaining ligaments were tested to failure with servohydrolic stress at 5 mm/second. In the intact joint complex, the average dorsopalmar rotational displacement was approximately 9 degrees in each direction. Under the load limit, the dorsopalmar translational displacement averaged 0.9 mm and 0.5 mm respectively, proximal-distal translational displacement averaged 0.8 mm and 0.4 mm respectively, and distractional displacement averaged 0.3 mm. Based on the sequential sectioning it was found that the dorsal ligament provided 76% (SD 14) of the rotational resistance with palmar rotation of the capitate and 44% (SD 19) of translational constraint with palmar translation of the capitate. The deep ligament provided 51% (SD 15) of the rotational resistance with dorsal rotation of the capitate and 63% (SD 24) of translational resistance with dorsal translation of the capitate. With proximal-distal translation, the dorsal ligament was the most important constraint in each direction. In resisting distraction, each of the three ligaments was equally effective. Failure testing showed the deep ligament was strongest at 289 N, followed by the palmar at 171 N and the dorsal at 133 N.