The aim of this study was to evaluate the survival of a collarless, straight, hydroxyapatite-coated femoral stem in total hip arthroplasty (THA) at a minimum follow-up of 20 years. We reviewed the results of 165 THAs using the Omnifit HA system in 138 patients, performed between August 1993 and December 1999. The mean age of the patients at the time of surgery was 46 years (20 to 77). Avascular necrosis was the most common indication for THA, followed by ankylosing spondylitis and primary osteoarthritis. The mean follow-up was 22 years (20 to 31). At 20 and 25 years, 113 THAs in 91 patients and 63 THAs in 55 patients were available for review, respectively, while others died or were lost to follow-up. Kaplan-Meier analysis was performed to evaluate the survival of the stem. Radiographs were reviewed regularly, and the stability of the stem was evaluated using the Engh classification.Aims
Methods
Uncemented femoral components have been used in total hip arthroplasties (THAs) for over three decades. Data on long-term performance of hydroxyapatite-coated femoral stems is however limited. This study reports the survivorship of a collarless, straight, hydroxyapatite-coated femoral stem (Omnifit HA, Osteonic) with a minimum of 20 years of follow-up. We reviewed the results of 165 THAs using Omnifit HA in 138 patients performed between August 1993 and December 1999. The mean age at surgery was 46 years (range 20 – 77 years). Avascular necrosis was the most common cause of THA, followed by ankylosing spondylitis and primary osteoarthritis. The mean follow-up was 22 years (range 20–31 years). At 20 and 25 years, 113 arthroplasties (91 patients) and 63 arthroplasties (55 patients) were available for follow-up respectively, while others had deceased or were lost to follow-up. Kaplan-Meier survivorship analysis was performed to evaluate the survival of the femoral component. Radiographs were reviewed at regular intervals, and implant stability was evaluated using Engh classification. Seven out of 165 stems were revised upon the latest follow-up; that included one case of aseptic loosening with revision done at 15 years, three peri-prosthetic fractures, two infections, and one recurrent dislocation. At 20 years, survivorship with revision of the femoral stem for any cause and aseptic loosening as the endpoint was 96.0% (95% CI, 92.6 – 99.5%) and 98.4% (95% CI, 96.2 – 100%) respectively. At 25 years, the corresponding survivorship rates were 94.5% (95% CI, 91.9 – 97.3%) and 98.1% (95% CI, 95.7 – 99.6%) respectively. Radiographic findings of stable bony fixation were seen in 86 stems (76.1%) and those of loosening in 4 stems (3.5%) at 20 years. All patients with radiographic signs of loosening were asymptomatic and did not require revision. The Omnifit HA femoral stem offered promising long-term survivorship into the third decade.
