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Outcomes After MCP Arthroplasty Dislocation; An Analysis of 33 Consecutive Cases
Eric R. Wagner, MD; Nathan Wanderman, MD; Steven L. Moran, MD; Marco Rizzo, MD
Mayo Clinic, Rochester, MN

Purpose: There remains a paucity of information regarding the treatment outcomes of dislocation after metacarpophalangeal (MCP) arthroplasty. The purpose of this study was to assess the outcomes of surgical and nonoperative treatment modalities for MCP arthroplasty dislocations.

Methods: Out of 816 primary MCP arthroplasties collected in a single institution's total joints registry, there were 33 (4%) dislocations that required intervention by a healthcare professional. Seventeen dislocations involved border digits, while diagnoses including osteoarthritis (n=1), inflammatory arthritis (n=30), and post-traumatic arthritis (n=2). Implants involved included pyrocarbon (n=13), silicone (n=9), and surface replacing arthroplasty (n=9). The analysis included treatment of dislocations after primary (n=25) and revision (n=8) MCP arthroplasty. Dislocation was defined as radiographic evidence of MCP prosthetic dislocation diagnosed and treated by a fellowship trained hand surgeon.

Results: Out of the 33 dislocations, the initial treatments included 3 closed reduction and splinting, 19 revision arthroplasties, 2 MCP arthrodesis, and 9 soft tissue procedures. Etiologies underlying the dislocations included implant fracture (n=5), component loosening (n=2), and soft tissue deficiency (n=26) with soft tissue laxity. Of the 3 that underwent closed reduction and splinting, 2 failed nonoperative management secondary to recurrent instability and requiring revision arthroplasty combined with stabilization procedures. Ultimately, 21 MCP joints underwent revision arthroplasty and 9 underwent soft tissue stabilization procedures. Four (44%) of those who underwent ST procedures had recurrent instability. Of the 21 revision arthroplasties, 8 (38%) had repeat instability, with 6 (29%) requiring revision surgery. There was no difference in risk of repeat instability comparing ST procedures to revision arthroplasties (p=0.21). After revision arthroplasty for dislocation, survival-free of repeat instability at 2 and 5 years was 81% and 54%, respectively, while survival free of re-revision surgery at 2 and 5-years was 78% and 69%, respectively (Figure 1 and 2). Components used in revision MCP arthroplasty included pyrocarbon (n=5), SRA (n=3) and silicone (n=13). Pyrocarbon implants (4 out of 5, p=0.02) had an increased risk of repeat instability compared to SRA (1 out of 3) or silicone implants (3 out of 13).

Conclusion: Treatment of MCP arthroplasty dislocation, while a rare event, is technically challenging, with high rates of repeat instability requiring repeat intervention.


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