The carpal stretch test at the scapholunate joint.

Abstract

The purpose of this study was to evaluate the principle of the carpal stretch test. Eleven upper extremities from 6 fresh cadaver specimens and 40 normal wrists from 20 volunteers were used in this study. Changes in intercarpal distances (carpal interval ratio of the radioscaphoid, radiolunate, and lunocapitate joints) and step-off deformities at the scapholunate joint seen on the posteroanterior view of an x-ray film were analyzed with and without the carpal stretch test. In the cadaver wrists, the dorsal capsulotomy and radioscapholunate ligament (stage 1), the palmar half of the scapholunate interosseous ligament (stage 2), the dorsal half of the scapholunate interosseous ligament (stage 3), and the radioscaphocapitate ligament (stage 4) were sequentially sectioned. The carpal stretch test was completed in each stage. Each carpal interval ratio increased as each stage was added. Step-off deformities at the scapholunate joint were seen in 6 of 11 wrists in stage 2 and in 10 wrists in stages 3 and 4 with the carpal stretch test. In the normal wrists, neither gender nor wrist laxity (Garcia's criteria) not influenced the results of the carpal stretch test. The carpal stretch test may be helpful in identifying occult and/or dynamic scapholunate dissociation.