Abstract
The need for better durability and longevity in total hip arthroplasty in high demand patients is a constant challenge. For this purpose a metal-on-metal prosthesis with improved tribology was developed. Our early results of using this system are presented.
Materials and Methods: From 1997 till present 68 Meta-sul hip arthroplasties were performed on 64 patients. 16 cases performed during 2001 were not included in the study due to short follow-up period. Of the remaining 52 cases, 39 were fully followed up (18 male and 21 female) and five were telephonically contacted. Six were lost to follow up and two died for reason not related to the THR. The average age at operation was 57y (27–77y), average height 163cm and average weight 79kg (50–180kg). 18 cases were left and 21 right sides.
4 patients had bilateral THR. There were 3 revision cases due to loosening of cemented cup and 3 post surgical hip procedures. The etiology of the hip pathology was OA in 23, AVN in 10, CDH in 3, two post surgical procedures and one Paget’s disease. The THR prosthesis system consisted of a Wagner type uncemented cup with a factory-assembled Metasul inlay. An uncemented collarless hydroxypaptite coated, Spotorno stem, with a modular 28mm head was used. Long stem was used in 3 cases and reinforcement cage in one. Additional screws (average of 3,4) were used for primary cup fixation. The anterolateral approach, laying either supine or on the side was performed. Average hospitalization time was 12 days. Full weight bearing was allowed as tolerated.
Results: The average follow-up was 30 months. Average Harris Hip Score pre-operatively was 45 (15-74) and post-operatively 75 (15–99). Subjectively, 87% of the primary cases with various etiologies were satisfied with the outcome. The majority of patients had pain-free range of motion and returned to improved daily function. One technical intra-operative complication (false route) was resolved with immediate revision. Two patients required cerclage wiring due to a femoral crack. Immediate post-operative complications included 2 cases of persistent distal peroneal nerve palsy. Three cases of anterior dislocations were reduced and did not recur. A case of positive intra-operative culture was treated successfully with 6 weeks of intravenous antibiotic therapy. Late complications included one case of cup loosening and one of a painful hip with suspected infection that required revision with a cemented prosthesis. Radiographic examination included measuring of radiolucent lines around the femoral stem according to the zones described by Gruen et al. and acetabulum as described by DeLee and Charnley. No femoral radiolucent lines were found. Seven cases revealed partial ace-tabular radiolucent lines.
Discussion: The Metasul metal-on-metal THR system was used so far with relatively satisfactory results in the early follow-up period despite the leaning curve. It is early to draw conclusions as to the superiority of this system over conventional metal-polyethylene bearing prosthesis. Long term follow-up studies are needed.
The abstracts were prepared by Orah Naor. Correspondence should be addressed to him at the Israel Orthopaedic Association, PO Box 7845, Haifa 31074, Israel.
