The Effect of Metacarpophalangeal Joint Hyperextension on Outcomes in the Surgical Treatment of Carpometacarpal Joint Arthritis.

Purpose  In the surgical treatment of thumb carpometacarpal (CMC) joint arthritis, the effect of mild preoperative metacarpophalangeal (MCP) hyperextension on postoperative functional outcomes is unknown. We sought to examine outcomes after surgical treatment of CMC arthritis in patients with and without mild preexisting MCP deformity. Methods  A retrospective review was conducted to analyze the functional outcomes of patients treated for CMC arthritis at a single institution from March 1998 to May 2009. All patients were treated with one of two standard CMC arthroplasty procedures-either ligament reconstruction tendon interposition (LRTI) or a Weilby procedure-and none had additional procedures to address MCP hyperextension. Pre- and postoperative assessments included pinch and grip strength, degree of MCP hyperextension, and thumb radial and palmar abduction. A t -test was used to assume unequal variances. Results  A total of 203 patients were followed for an average of 27.3 months. Patients were divided into two groups: (1) patients without preoperative MCP hyperextension (167 patients) and (2) patients with mild but untreated preoperative MCP hyperextension (≤ 30 degrees; 36 patients). All patients underwent either a Weilby procedure (118 patients) or an LRTI; 85 patients). The main difference between techniques was the use of the abductor pollicis longus tendon as a post to secure the flexor carpi radialis (Weilby) or the use of a bone tunnel in the first metacarpal (LRTI). Analysis of the preoperative data showed no difference in the baseline parameters among both the groups, with the exception of MCP hyperextension. Postoperatively, neither the type of CMC procedure nor the presence of MCP hyperextension demonstrated any significant differences in key pinch, tip pinch, grip strength, and radial or palmar abduction of the thumb between the groups. Conclusion  There were no statistically significant differences in improvement of functional outcomes after surgery when comparing patients without preoperative MCP hyperextension to patients with untreated MCP hyperextension of less than 30 degrees. Level of Evidence  Level III, retrospective comparative study.