Abstract
Introduction: Cementless hydroxyapatite coated prosthesis are mainly selected for a relatively young and active patient population. Most clinical studies demonstrate excellent osseous integration of the HA coating and good outcome. The clinical follow-up reports of the ABG group suggest excellent results, however we observed an alarming rate of acetabular osteolysis and polyethylene wear which required revision surgery. Thus a comprehensive retrospective evaluation of all operated patients had been conducted.
Patients and Methods: 162 ABG hips were replaced in 148 patients, of them 75 patients were studied and followed-up. Mean age was 56 (range 33–71). 48 patients were women and 27 were men. 8 patients had bilateral hip replacement. Etiology of hip disease varied and included primary osteoarthritis (27 patients – 36%), congenital hip dysplasia (24 patients – 32%), osteonecrosis (12 patients – 16%), ankylosing spondylitis (5 patients – 6.6%), post traumatic arthritis (5 patients – 6.6%) and post-infectious arthrosis (2 patients – 2.6%). Postoperative follow-up period averaged 4 years (range 15–80 months).
Results: The mean postoperative Harris hip score was 89 (range 52–100). 23 patients (30%) reported of modified life activity after surgery, and the majority had resumed their previous occupations.
Complications included 3 early and one late dislocations – one patient required an early cup revision, one patient suffered a fracture of the femur during stem insertion, and 3 patients (4%) had deep vein thrombosis. There was one case of a femoral vein injury and one resolving superficial infection. No deep infections were noted.
13 patients had undergone cup revision due to severe polyethylene wear and periacetabular osteolysis. Of them 5 were diagnosed during this retrospective study and 8 were referred for revision due to clinical symptoms. Thus the revision rate of the entire operated population is 13/162 = 8.0% and 13/75 = 17.3% of the studied patients. The true loosening rate should be between these 2 figures.
In 2 patients the entire cups were removed and revised due to loosening. In 11 patients following the removal of the polyethylene inserts the metal back proved to be stable. In these cases the bone defects were filled-up with bone graft substitute, and a highly cross-linked polyethylene (22 mm head) were cemented into the metal shell. No stems needed revision.
Conclusion: In spite of a relatively high Harris Hip Score and generally good long-term follow-up a high rate of acetbular lysis and polyethylene wear were observed. This observation warrants avoiding the use of the ABG cups until further investigation is performed. A continued clinical and radiographic analysis is required for the entire operated patients. In all cases of polyethylene wear or significant osteolysis revision is indicated.
The abstracts were prepared by Orah Naor. Correspondence should be addressed to him at the Israel Orthopaedic Association, PO Box 7845, Haifa 31074, Israel.
