Correction of Congenital Ring-Little Finger Metacarpal Synostosis Through Simultaneous Interpositional Allograft Bone After Split Osteotomy of the Synostosis Site and Distraction Lengthening of the Fifth Metacarpal.

PURPOSE

We attempted a technique for patients with congenital ring-little finger metacarpal synostosis involving simultaneous interpositional allograft bone after split osteotomy of the synostosis site and distraction lengthening of the fifth metacarpal along with correction of the metacarpal joint abduction contracture. The purpose of this study was to describe the surgical technique and its outcomes.

METHODS

We reviewed the medical records of children with congenital ring-little finger metacarpal synostosis treated surgically at our institute. Eight hands of six children with an average age of 5.0 (range, 1.7-9.3) years were treated by simultaneous interpositional allograft bone after split osteotomy, distraction lengthening, and tenotomy of abductor digiti minimi. We measured the metacarpal head-to-capitate area ratios from serial radiographs and analyzed them according to age. We also measured the change in the intermetacarpal angle (IMA) and metacarpal length ratio during an average of 8.1 (range, 1.4-16.8) years of follow-up. These changes were compared with changes in seven hands of five children with an average age of 8.1 (range, 1.5-15.6) years treated by the same method, but without a distraction lengthening of the fifth metacarpal and followed up for an of average 12.1 (range, 4.1-19.8) years, as a control group.

RESULTS

Abnormal metacarpal head-to-capitate area ratio before surgery was normalized in all patients within the first 2 years after surgery. The IMA change averaged 39.8°, and the metacarpal length ratio changed by 17%. The control group showed an average IMA change of 36.6° and metacarpal length ratio change of 6%.

CONCLUSIONS

Simultaneous interpositional allograft bone after split osteotomy of the synostosis site and distraction lengthening of the fifth metacarpal with correction of metacarpal joint abduction contracture can restore the radiographic parameters in congenital ring-little finger metacarpal synostosis. The normalized ossification of the fifth metacarpal head indicates that the surgical procedure is probably safe.

TYPE OF STUDY/LEVEL OF EVIDENCE: Therapeutic V.