Purpose of the study: Cementless hydroxyapatite-coated prostheses have proven their reliability, but how about their longevity? The intimate contact between the receiver bone and the prosthetic implant, due to the bone ongrowth, allows ‘union’ between the inert and living material. The purpose of this restrospective study was to evaluate the behavior of an anatomic femoral hydroxyapatite-coated stem at long-term follow-up.

Materials and Methods: One hundred and eleven total hip arthroplasties were performed with a ABG 1 HA-Coated hip prosthesis (ABG, Stryker Newbury, England) in 101 patients, by one senior operator. A posterolateral approach was done every time. Average patient age at surgery was 61, 3 years [33–83].

Results: Average follow-up was 13 years [10–17,5]. Seventy five THA were reviewed, 21 were dead and 15 were lost. Clinical outcome have been good. The average preoperative Harris hip score and Postel Merle d’Aubigné score were 56,7 and 11,8, which rose to 87,3 and 16,3 at the longest follow-up. Most patients were satisfied with the outcome, no thigh pain was deplored. There were sixteen revisions: 1 bipolar revision for loosening of both component, 14 cup revisions for osteolysis (11) and loosening (3) and 1 stem revision for periprosthetic fracture. Radiographic changes were consistent with bone remodeling. Osteointegration was achieved in 98,7%. Proximal stress-shielding was noted in 36,4%, osteolysis was developed in 66,7% focused essentially in gruen zones 1a and 7a and never below HA coating. Cancellous densifications were found to be mainly in zones 2, 6, 9 and 13 (92,7%, 94,2%, 91,3% and 85,5%), extending distally in zones 3, 5, 10 and 12 (33,3%, 31,9%, 34,8% and 39,1%). A femoral shaft hypertrophy was noted in 27,5%.

Discussion: In this serie, the global survivorship of ABG 1 THA at 13 years of follow-up was 78,7%. Acetabular cup survivorship was 80%. Failure of acetabular cup was well explained by osteolysis and high wear rate. Stem survivorship was 97,3% and the failure rate of femoral stem due to aseptic loosening was only 1,3%. Excellent results of femoral stem were due to the good osteointegration, cause of the anatomic design of the stem and the hydroxyapatite coating.

Conclusion: The results of our series have proven that anatomic cementless stem with HA coating provide a long term reliability and longevity.