Our findings provide scientific evidence to support the clinical situation in which the interinjection interval of 3-6 mos of botulinum toxin A at a similar dosage is used.

This study examined sequential arthroscopic sectioning of volar, interosseous, and dorsal ligaments about the scapholunate complex in cadaver wrists. We attempted to clarify the contributions of the dorsal ligamentous complex to scapholunate instability and carpal collapse. We found that after sequential sectioning of volar ligaments and the scapholunate interosseous ligament, no scapholunate diastasis or excessive scaphoid flexion occurred. After dividing the dorsal intercarpal ligament, scapholunate instability occurred without carpal collapse. With sectioning of the dorsal radiocarpal ligament from the lunate, a dorsal intercalated scapholunate instability deformity ensued. This information may be of value in comprehending the pathogenesis of scapholunate instability and carpal collapse and in devising the rationales for conservative measures and surgical intervention.In 1984, Watson and Ballet 12 identified scapholunate advanced collapse as being the most significant cause of posttraumatic arthritis in the adult wrist. Linscheid et al 4 postulated that the loss of integrity of the scapholunate interval permitted palmar flexion and dorsal subluxation of the scaphoid resulting in radioscaphoid arthritis. Simultaneously, the lunate dorsiflexes in its relationship to the capitate resulting in midcarpal incongruity and capitolunate arthritis. 4 Berger 1 elucidated the components of the scapholunate ligament and its histologic and biomechanical properties. He concluded that the dorsal component of the ligament was the thickest and provided the greatest biomechanical stability to the articulation. 1 To identify the structures that must be injured to result in radiographic evidence of ligamentous injury, sequential sectioning studies of cadaveric wrists were done. Initial evidence pointed to the role of the palmar extrinsic ligaments in stabilizing the scapholunate interval. 6 Meade et al 7 sequentially sectioned the palmar extrinsic ligaments and the palmar and dorsal components of the scapholunate ligament and concluded that radiographic instability was not produced until the scapholunate interosseous and the palmar radioscapholunate and radial collateral ligaments were sectioned. Ruby et al 8 emphasized the significance of the dorsal component of the scapholunate interosseous ligament with specific focus on its attachment to the dorsum of the lunate. Viegas et al 11 shifted attention to the dorsal ligamentous structures and postulated that the attachments of the dorsal intercarpal ligament and the dorsal radiolunotriquetral ligament to the scaphoid and lunate, respectively, additionally stabilize the interval.Our cadaveric study examined the role of the dorsal capsuloligamentous structures in preventing scapholunate instability.