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.

Stability of the Basal Joints of the New Thumb After Pollicization for Thumb Hypoplasia.

PURPOSE: To investigate the presence or absence of union of the new trapezium to the retained metacarpal base after pollicization and to relate this to stability of the new trapezium and the new carpometacarpal joint. METHODS: Thirty-six patients (46 pollicizations) were assessed at clinical review. Mean time from surgery to review was 96 months (range, 9-260 mo). Clinical assessment measured range of motion (ROM) at the carpometacarpal joint, stability of the carpometacarpal joint, and extrinsic and intrinsic strength of both hands. Radiological review evaluated 3 parameters: bony union between the new trapezium and retained metacarpal base, stability of the new trapezium in relationship to the metacarpal base, and carpometacarpal joint stability. RESULTS: There was radiographic nonunion between the new trapezium and the retained metacarpal base in 8 (1 treated) of 46 pollicizations. Relative risk of instability of the new trapezium was 39 times more likely if nonunion was present. Nine pollicizations were unstable at the carpometacarpal joint, 8 in those with union and 1 with nonunion. Relative risk of instability was 1.4 times more likely for those with union. For patients with nonunion, ROM and grip strength variables were reduced but only grip strength reached statistical significance. In patients with carpometacarpal joint instability, ROM and grip strength variables were reduced but none of the variables reached statistical significance. CONCLUSIONS: This study suggests that when the surgeon is attempting to obtain union of the new trapezium to the retained metacarpal base, failure to do so results in a poorer thumb with a significantly increased risk of trapezial instability and decreased grip strength. There is a mildly increased risk of carpometacarpal joint instability with union, but significantly poorer function as a consequence of this has not been demonstrated. TYPE OF STUDY/LEVEL OF EVIDENCE: Therapeutic IV.