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The Müller acetabular reinforcement ring--still an option in acetabular revision of Paprosky 2 defects? Longterm results after 10 years.

BACKGROUND
Aim of this study was to measure the clinical and radiological longterm outcome after acetabular revision arthroplasty (RTHA) using the Müller acetabular reinforcement ring.


MATERIAL AND METHODS
86 patients with 90 revision arthroplasties and a mean age of 68 years (41 to 84) were included. The mean follow-up was 10 years (range 7-12). The Harris Hip Score and the WOMAC Index were used to assess pain and functional outcome. Furthermore clinical examination of range of motion and radiologic examinations were performed in 34 patients.


RESULTS
The radiologic analysis reports no signs of loosening in 79%, 15% showed possibly loosening and 6% probable loosening. Definite radiologic loosening has not been detected. In the meantime 12 patients (13.3%) of 90 revision total hip arthroplasty underwent a revision of the acetabulum with change of the acetabular component which means a survival rate of 86.7% after 10 years follow-up. The mean center of rotation of the hip moved 0.15 cm (SD 0.74 cm) laterally and 0.1 cm (SD 0.97 cm) cranially based on the geometrically reconstructed center of rotation. A mean score of 58 points for the Harris Hip Score (range 14-93) indicated a poor functional outcome, while a mean value of 96 points (range 0-223) for the WOMAC Index indicated good results for functional outcome in daily living.


CONCLUSIONS
The revision arthroplasty in cases with acetabular defects using the Müller acetabular reinforcement ring shows acceptable longterm results.


LEVEL OF EVIDENCE
Level IV.