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Long-Term Outcomes Comparing Patients With Carpometacarpal Arthroplasty And Metacarpophalangeal Fusion, Carpometacarpal Arthroplasty And The Unoperated Side
Carissa C Dock, BS1; Rebecca Stone McGaver, MS, ATC2; Clare McCarthy, MD3
1University of Minnesota Medical School, Minneapolis, MN; 2Twin Cities Orthopedices, Edina, MN; 3Twin Cities Orthopedics, Edina, MN

Hypothesis Patients with carpometacarpal (CMC) arthritis often present with metacarpophalangeal (MP) hyperextension and/or thenar atrophy concomitantly. This study hypothesizes that an MP fusion done at the time of CMC arthroplasty for patients with MP hyperextension greater than 30, moderate to severe thenar atrophy, or MP arthritis will have greater pinch strength long-term when compared with the unoperated side or those who had a CMC arthroplasty alone.
Methods: Retrospective review of long-term results from patients who had undergone either a CMC arthroplasty (consisting of trapezial excision, abductor pollicis longus suspension sling, and cadaveric fascia lata graft interposition) or a CMC arthroplasty and MP fusion (with Stryker EZ clip staples and trapezial bone graft) done by the senior author were recorded. The Quick Disabilities of the Arm, Shoulder, and Hand Score (QuickDASH), Visual Analog Scale (VAS), surgical satisfaction, and an average of three pinch readings from each thumb were measured on the Baseline pinch gauge (30-pound capacity) and recorded. Statistical analysis included paired sample t-tests to determine significant differences between groups. Significance was set at p<0.05.

Results: Ninety patients (68 females) had 113 operated thumbs: 53 CMC arthroplasties and 60 CMC/MP fusions. The average age was 67.3 years. The average length of follow up was 71.0 months (range 1 year to 16.9 years). CMC/MP fusion pinch strength (12.7lbs) was significantly stronger than patients who had a CMC arthroplasty alone, 10.9lbs (p=0.01). When comparing pinch strength values of those with a CMC arthroplasty and the unoperated side there was no significant difference 10.9lbs. vs 10.8lbs. (p=0.46). When CMC/MP fusions were compared with unoperated thumbs, there was a significant difference in pinch strength 12.7lbs. vs 10.8lbs (p=0.01). In a paired analysis of eighteen patients who had a CMC arthroplasty on one hand and a CMC/MP fusion on their other hand, the CMC/MP fusion was significantly stronger than the CMC arthroplasty alone 10.5lbs vs. 12.3lbs (p=0.03). Quick DASH, VAS, and patient satisfaction revealed similar values in both the CMC (11.8 and 0.60 and 100%) and CMC/MP (10.8 and 0.53 and 98.3%) groups respectively.
Summary Points:

  • Long-term results demonstrate a significantly stronger pinch in those patients who have a CMC/MP fusion than those who underwent a CMC arthroplasty alone.
  • CMC/MP fusions were also stronger than the unoperated side.
  • The MP fusion adds strength to thumbs by restoring the functional mechanics at the MP joint and this strength was maintained long-term.

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