Results of primary tantalum trabecular metal acetabular components

INTRODUCTION Tantalum trabecular metal (TTM) acetabular components may promote bone ingrowth and bone remodeling at the bone implant interface because of their optimal elastic modulus and three-dimensional structure that mimic cancellous bone. Frictional characteristics of this material may provide enhanced primary stability and warrant the use of these components even in cases of limited bone-implant contact. The aim of this prospective study was to assess clinical and radiographic results of primary TTM acetabular components at a mean 4-year follow-up. METHODS We assessed clinical and radiographic results of 210 primary cementless modular TTM acetabular cups implanted in 182 patients (107 males and 75 females) from 2002 to 2012 at the Departments of Orthopaedic Surgery of Federico II University of Naples and Magna Graecia University of Catanzaro. The mean age of patients was 61.3 ± 12.5 years (range 31-86). The diagnosis was primary osteoarthritis of the hip in 124 cases (59%), avascular necrosis of the femoral head in 33 (16 %), post-dysplastic hip arthritis in 21 (10 %), inflammatory arthritis in 14 (6 %), sequelae of Perthes disease in 7 (3.5 % ), sequelae of slipped capital femoral epiphysis in 4 (2%), and fracture or post-traumatic conditions in 7 (3.5 %). The mean follow-up was 49.2 ± 23 months (range 12-102). Harris Hip Score (HHS) was calculated preoperatively and at latest follow-up control. The level of pain, working ability, and satisfaction with the surgery were assessed using a visual analog scale. All patients underwent radiographic examination before surgery, immediately after surgery, and at latest follow-up. The inclination of the acetabular cup, the existence of any migration of the component, radiolucent lines and osteolytic lesions at the bone implant interface, zones of increased bone density, and heterotopic ossifications were assessed. RESULTS No patients had undergone revision. The patients' mean HHS at their latest follow-up visit (88.4 ± 8.4 points) was statistically significantly better than the preoperative mean score of 43.1 ± 15 points (p < 0.001). Pain level and the working ability recorded at latest follow-up showed an improvement with respect to preoperative values from 76/100 to 10 /100 (p < 0.001) and 45/100 to 80/100 (p < 0.001), respectively. The reported satisfaction was 89 /100. The average inclination of the acetabular component was 41.6 ± 8 degrees. No radiographic loosening or migration of these acetabular components was detected at latest follow-up. Radiolucent lines and osteolytic lesions at the bone implant interface were identified in 15 and 8 cases, respectively. However, all osteolytic lesions were already present on preoperative radiographs. Increased bone density around the cup was noted in 45 cases and heterotopic ossification in 24 cases, respectively. At the multivariate analysis, the most important negative predictors of HHS at latest follow-up were age (c = -0.3 , p < 0.001) and the inclination of the cup (c = -0.4 ; p < 0.001). CONCLUSION Primary TTM acetabular components provided satisfactory clinical and radiographic results at a mean 4-year follow-up. We observed no clinical or radiographic failures. Follow-up radiographs demonstrate effective new bone formation at the bone-implant interface.