METAL-ON-METAL TOTAL HIP JOINT REPLACEMENT: (A MINIMUM OF 5-YEAR FOLLOW-UP)

Abstract

Introduction: Peri-prosthetic osteolysis due to wear has been acknowledged as a major challenge to long-term survival of hip arthroplasty and this has led to a search for alternative articular bearing couples. We present our experience with metal-on-metal (Metasul^®) articulation with a minimum patient follow-up of 5 years.

Materials and methods: 193 patients (215 hips) were reviewed; 187 (209 hips) had a follow-up of ≥ 5 years. Hip scores were completed and radiographs performed at follow-up visits and data was entered prospectively into software (orthocom) designed by Sulzer Ltd.. Serial radiographs were reviewed retrospectively along with hospital notes and the database.

Results: mean age was 70 (± 7.46) years (range 47–86 years). Female: male was 143:44. Most common pre-operative diagnoses were: osteoarthritis (147) and intra-capsular hip fracture (22).

Mean pre-operative HHS was 39.7 (±15.7) and the corresponding pain score was 13.4 (±8.49). The average post-operative scores were 89.5, 87.3, 88.4 and 85.8 at 1 year, 3 years, 5 years and final follow-up respectively. The corresponding pain scores were 42.7, 41.98, 42.1 and 41.94. Implant survival for the cohort as a whole was 95.5% at 12 years (ci: 88%–100%). Survivorship for the Weber Metasul cup was 93.4% at 12 years (ci: 82.7%–100%) and for armor cup was 100% at 11 years.

Complications included: dislocations (7), periprosthetic fractures (8), deep infection- early (3) & late (3), aseptic loosening (cup) (2) & heterotopic ossification (9). There were no untoward systemic complications with regards to metal ion release.

Discussion: We believe that second generation metal-on-metal implants (Metasul^®) with improved design and better lubrication show better survival with regards to aseptic loosening and reduction in osteolysis in the medium-term. Concerns regarding metal ion and metal particle release remain theoretical but are kept under constant review.