Cementless fixation is the current preferred method for acetabular reconstruction in total hip arthroplasty (THA). Despite promising long-term results among several designs, theoretic concerns regarding the high modulus of elasticity, low friction against bone and low volumetric porosity of contemporary cementless cups have spurred the introduction of novel porous surfaces that are designed to improve osseointegration and decrease aseptic loosening. Although several novel surfaces have been introduced into clinical use over the past decade, very little literature regarding their clinical and radiographic performance exists. The current study investigates the performance of one such novel surface, Tritanium (Stryker, Mahwah, NJ).
We prospectively evaluated 121 consecutive THAs performed in 94 patients by a single arthroplasty surgeon using the Tritanium Primary Acetabular Component (Stryker, Mahwah, NJ). 109 hips (90.1%) had adequate clinical and radiological follow-up for analysis. Clinical parameters recorded included implant survivorship, Harris Hip Scores, WOMAC and SF-12. Furthermore, radiographs at the 6-week, 1 year and most recent clinical visit were evaluated by two blinded observers for implant position, evidence of radiolucency, sclerosis and component migration.
At an average of 3.88+1.71 years, implant survivorship was 98.1% with two hips requiring revision for aseptic loosening. Radiographs revealed that at one year postoperatively, 35.5% of hips demonstrated radiolucencies and sclerotic changes in two or more DeLee zones, with half of these (17.3%) involving all three zones. These proportions subsequently increased (37.2% and 18.4% respectively) on radiographs taken at a minimum of two years postoperatively. Hips with radiolucencies in three zones exhibited significantly lower Harris Hip Scores at two years compared to non-radiolucent hips (p=0.016). Age, gender, BMI, preoperative function and cup position did not differ between patients with and without radiolucencies. Observable bone-implant gaps on six-week radiographs were not found to be correlated with the later presence of radiolucencies.
Despite adequate implant survivorship, we found that over one third of hips implanted with a Tritanium coated primary shell exhibit radiographic signs of fibrous ingrowth that appear to increase in prevalence over time and lead to poorer clinical function. We advocate that patients that have received this implant be followed closely for evidence of clinical deterioration and component loosening.