Metal-to-metal Hip Surface Arthroplasty in 63 Cases A follow-up assessment

BACKGROUND: With the advanced progress of prostheses manufacture and surgical technique, early loosening of hip articulation prostheses and femoral neck fracture tend to reduce after hip surface arthroplasty. Meanwhile hip articulation activity has been improved. OBJECTIVE: To discuss the biocompatibility between the implants and the hosts in patients underwent hip surface arthroplasty and observe the functional recovery of hip articulations. DESIGN, TIME AND SETTING: Retrospective case analysis was carried out in the Department of Orthopaedics, Changhai Hospital Affiliated to the Second Military Medical University of Chinese PLA (Shanghai, China) from January 2006 to August 2007. PARTICIPANTS: Fifty-two patients with hip articulation diseases, including 25 females and 27 males, underwent sixty-three hip surface arthroplasties, and eleven cases of them were subjected to bilateral arthroplasty. Their average age was 47.6 years. METHODS: Hip resurfacing prostheses were offered by Zimmerm Company (Huntington, Indiana, USA). Hip resurfacing was performed using 4-mm-thick cement-less acetabular bone (metal acetabular cup of 3.7-mm thickness was coated with 0.3-mm plasma titanium). Acetabular cup exhibits large diameter and arch shape (165°), is coated with 0.3-mm plasma titanium and fixed with cement less. By means of posterolateral approach, acetabular prostheses were implanted to the central position of hip articulation with regards to anatomy. Acetabular prostheses were covered more than 90% area. MAIN OUTCOME MEASURES: Subsequent to the arthroplasty, biocompatibility between the implant materials and the hosts was recorded, such as dislocation and infection. Functional recovery of the patients was assessed with Harris hip score at 1, 3, 6 and 12 months after operation and annually thereafter. Radiological evaluation was conducted to record radioactive permeability in the areas of 1 mm around acetabular cup in the DeLee and Charnley zone. RESULTS: All patients were involved in the follow-up. There were no cases of dislocation, deep venous embolism, deep infection or neurovascular complications that required further treatment. The mean Harris score was 38 points before operation and significantly increased to 90 points after operation. Two patients appeared a 2-mm crevice below acetabular prostheses, which disappeared 6 months after arthroplasty. Acetabular or femoral prostheses removal, or local osteolysis was detectable. CONCLUSION: Metal-on-metal hip surface arthroplasty has excellent early effects on young and active patients. The arthroplasty potentially offers the ultimate bone preservation and better restoration of hip articulation function in patients, without specific biocompatibility.