Risk Factors Contributing to Early Implant Fracture in Silicone Metacarpophalangeal Joint Arthroplasty for Patients With Rheumatoid Arthritis

Purpose: To identify the risk factors associated with early implant fracture of silicone metacarpophalangeal (MCP) joint arthroplasty using the volar hinge silicone implant for patients with rheumatoid arthritis. Methods: We retrospectively reviewed 113 fingers of 31 hands that underwent MCP joint arthroplasty between 2008 and 2014, with a minimum follow-up of 3 years,. An implant fracture within 3 years after surgery was regarded as an early implant fracture. Patient records were reviewed for potential risk factors of age, affected fingers, ulnar drift angle, and range of motion of the MCP joint before surgery and 1 year after surgery. Candidate risk factors were compared at the level of the digit and at the patient level. Results: With fracture of the implants as the end point, Kaplan–Meier estimated survival rate was 74.3% at 3 years and 67.9% at 5 years. Early implant fracture was detected in 29 fingers. Bivariate analyses showed significant associations between early implant fracture and MCP joint arc of motion before surgery, MCP joint flexion range 1 year after surgery, and MCP joint arc of motion 1 year after surgery. Multiple logistic regression analysis showed that increased MCP joint flexion range 1 year after surgery was an independent risk factor for early implant fracture. Conclusions: Increasing MCP joint flexion range was associated with increased fractures of the implants. We propose that the MCP joint flexion range should be restricted to less than 60° in postoperative rehabilitation; it is necessary to educate the patient to permanently avoid excessive flexion of the MCP joint. Type of study/level of evidence: Therapeutic IV.