Although the cause of osteoarthritis of the TM joint is probably multifactorial, instability
secondary to degeneration of the POL has been implicated. Indeed, the forces experienced at the normal TM joint with grip and pinch are not only magnified severalfold [2,3], but appear to be concentrated in the palmar aspect of the joint. The observation that ligament reconstruction of the painful TM joint is successful treatment for Eaton Stage I disease reflects the importance of the POL and DRL in providing stability to the joint [7,9] and in limiting dorsal translation of the metacar-pal, which normally occurs with dynamic pinch activity.
The precise role of thumb metacarpal extension osteotomy for the hypermobile TM joint is no longer ill-defined. Biomechanical and clinical data validate the rationale and favorable outcome. The precise mechanism for pain relief is not known, but it is probably a combination of load transfer and diminished laxity. Because extension osteotomy shifts mechanical loading at the TM joint more dorsally and redirects force vectors, fixed subluxation or multidirectional instability contraindicate the procedure. Indeed, a preopera-tive TM stress test is meant to provoke pain related to POL incompetence only. More global instability may reflect a greater degree of capsu-loligamentous injury, and may necessitate ligament reconstruction .
In summary, pre- and postoperative subjective and objective assessment has allowed a comprehensive analysis of outcome following a 30° extension osteotomy of the thumb metacarpal . Excellent pain relief and improved grip and pinch strength compare favorably with those published following ligament reconstruction [10,11]. For Eaton Stage I disease of the TM joint, this procedure appears to be an efficacious alternative to ligament reconstruction. Further, it has been the author's personal observation that this procedure provides more reliable pain relief than TM arthroscopy, synovec-tomy, and capsular shrinkage.
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