Results with 98 Endo-Modell rotating hinge prostheses for primary knee arthroplasty

Rotating hinge knee prostheses have been developed as an advancement of the fixed hinge models. Some authors suggest that this type of prosthesis is associated with a greater risk of aseptic loosening because of the increased stresses to the bone-prosthesis interface; therefore, they are scarcely used as primary implants. The current authors evaluated of a series of 98 rotating hinge knee arthroplasties Endo-Modell (Waldemar LINK GmbH and Co, Hamburg, Germany) implanted for knee osteoarthritis. The Hospital for Special Surgery Knee Score and the Knee Society Score were used for the clinical and radiographic evaluation. Log-rank or Wilcoxon tests were used to test the statistical significances, and the Kaplan-Maier method was used to calculate the implant survival probability. After a medium follow-up of approximately 174 months, the clinical scores showed a statistically significant improvement from the pre- to postoperative period. The complication rate was high, and the cumulative implants survival rate was 88.7% at 1 year, 85.9% at 5 years, 79.8% at 10 years, and 75.8% at 15 years. The Endo-Modell rotating hinge implants demonstrated no significant risk of aseptic loosening, and the hinge was not a primary cause of failure. However, the overall failure rate was higher than that of unhinged implants; therefore, this prosthesis is recommended for cases of instability and revision rather than primary knee arthroplasty.