gms | German Medical Science

Objectives/Interrogation: Flexible hinge arthroplasty has been the most accepted and widely performed technique for the treatment of MP joints deformities in rheumatoid arthritis (RA), however, the rate of implant fracture remains considerable. The purpose of this study was to identify the risk factors that affect the early implant fracture of AVANTA silicone implant using multiple logistic regression analysis.

Methods: We performed a retrospective review of all patients with MP joint arthroplasty in RA patients between 2008 and 2012. One hundred and thirteen fingers in 31 patients with a minimum follow-up period of 3 year were included in this study. The affected joints were index 29, middle 26, ring 29 and little 27. The average age at the time of surgery was 62 (range 37-86) years and all cases were female. The apparent implant fracture or severe deformity in either the coronal or the sagittal plane by plain radiographs within three years after surgery was regarded as the early implant fracture. Patient records were reviewed for the following potential risk factors: age, affected fingers, preoperative ulnar deviation angle, MP joint ROM before surgery and one year after surgery. Univariate regression analyses by Mann-Whitney test or Kruskal-Wallis test were performed. Multiple logistic regression analysis was conducted to identify the association between early implant fracture and selected risk factors.

Results and Conclusions: The early implant fracture was detected in 29 fingers (26%). Univariate analysis showed there to be significant association between the early implant fracture and MP joint ROM before and one year after surgery, especially for flexion angle (P<0.001). Multiple logistic regression analysis showed MP joint flexion angle one year after surgery as an independent risk factor for the early implant fracture (odds ratio 1.07, p<0.01). The cut off value of MP joint flexion calculated with ROC curve was 60 degree (sensitivity 0.48, specificity 0.91). Our study suggested that postoperative flexion angle correlates with the early implant fracture of AVANTA silicone implant. The flexion angle should be limited no less than 60 degrees.