Growth of the New Thumb Metacarpal After Pollicization for Thumb Hypoplasia.

PURPOSE: To investigate the radiographic length and width of the new thumb metacarpal in relation to the middle finger proximal phalanx; to assess the incidence of premature physeal closure of the new metacarpal; and to consider whether there is a relationship between growth characteristics and the presence of union or nonunion of the new trapezium to the retained index finger metacarpal base.

METHODS: Forty pollicizations were assessed with preoperative or immediate postoperative radiographs and follow-up radiographs to establish the growth characteristics of the new thumb metacarpal. Functional outcomes comprising grip strength, pinch strength, and range of motion were correlated with radiological findings of presence or absence of open physes and presence or absence of union of the new trapezium to the metacarpal base.

RESULTS: The new thumb metacarpal physis was open in 28 pollicizations and closed in 12. In the latter group, all physes of the hand had closed indicating skeletal maturity. The length and width indices of the new thumb metacarpal in relation to the middle finger proximal phalanx were equivalent to or greater than the perioperative growth indices. There was a reduced postoperative length ratio in those patients with nonunion of the new trapezium to the base of the metacarpal. There was no change in strength and range of motion parameters with growth other than that related to normal improvement with age.

CONCLUSIONS: We are unable to demonstrate premature physeal closure following routine pollicization. The growth of the metacarpal continues in a normal manner to skeletal maturity. A failure of union of the new trapezium to the metacarpal base may compromise growth.

TYPE OF STUDY/LEVEL OF EVIDENCE: Therapeutic IV.