Abstract
Introduction: The search for a gold standard uncemented hip prosthesis with long term results matching cemented Charnley implants continues. It has been suggested that biological fixation would reduce the incidence of aseptic loosening caused by cement and polyethylene particles. The ABG (Howmedica) is a titanium alloy stem with an anatomic design and a modular head option of vitallium or ceramic. The cup is hemispherical and is fully coated with hydroxyapatite while the stem is proximally coated for metaphyseal fixation. We present a prospective series of 100 Consecutive patients with an immediate term follow up.
Methods: 100 patients who had an ABG prosthesis inserted between 1991 & 1996 were included in the study. All patients were operated upon by the senior author or under his direct supervision. Patients underwent a preoperative assessment including a detailed history, measurement of range of motion, Postel Merle D’Aubigne scoring and ADL assessment. Clinical and radiological review was Conducted at 3 months, 6 months, 1 year and then at yearly intervals. At each visit Patients were questioned regarding the presence of any thigh pain and Complications. All patients were clinically evaluated, Postel Merle D’Aubigne Score was obtained and ADL status assessed. AP and lateral radiographs were Taken and studied. Polyethylene wear was measured by using the Livermore Method. The Kaplan- Meier method was used to explore the survival pattern of the implants.
Results: The mean age of the patients was 52 years (range 23–72). Follow up ranged from 3 To 8 years (mean 5 years ). The mean preoperative Postel Merle D’Aubigne score Was 7 ( range 0–14) and mean score at final follow-up was 17.7(range 15–18).
Only 4 patients complained of thigh pain and most had dramatic and lasting improvement of the ADL status. Complications included 3 dislocations and 2 Superficial infections. Non progressive lucencies were noted in 6 stems and 2 cups. No stems were loose and one patient had a loose cup and is awaiting surgery. A high rate of superior polethylene wear of 0.2mm/year was identified in a Number of patients yet the survivorship was 99% after an average 5 year follow up.
Conclusion: Our results demonstrate the efficacy and excellent medium term outcome of the ABG prosthesis. A higher rate of complications in the first 2 years reiterates the lesson that every surgeon has to complete a learning curve before being technically comfortable with a new prosthesis. Of concern was the high rate of superior polyethylene wear although this did not effect the survivorship.
The abstracts were prepared by Mr Ray Moran. Correspondence should be addressed to him at the Irish Orthopaedic Association, Secretariat, c/o Cappagh Orthopaedic Hospital, Finglas, Dublin
