Treatment of primary osteoarthritis of the hip. A comparison of total joint and surface replacement arthroplasty

Of 285 total hip arthroplasties (260 patients) performed for primary osteoarthritis during a 6-year period, 135 were resurfaced using a Tharies prosthesis (total hip articular replacement with internal eccentric shells) and 150 were treated with the Trapezoidal-28 total hip replacement. From each of these two groups 100 hips (91 patients in the Tharies group and 86 in the Trapezoidal-28 group) that had been followed for 2 to 7 years were evaluated at the time of follow-up in accordance with a predetermined protocol. The patients were younger in the Tharies than in the Trapezoidal-28 group (average ages, 58 and 66 years), included more men (60 compared with 35), and were more active postoperatively. The average follow-up was 47 months for the total joint-replacement group and 38 months for the surface replacement group. At follow-up the ratings for pain, walking, and function according to the University of California at Los Angeles 10-point scale and the clinical results were identical in the two groups. Heterotopic ossification (Brooker grade III or IV) developed after 13 Trapezoidal-28 and 22 Tharies arthroplasties. Radiographs made at 6 and 12 months and at final follow-up showed that the incidence of radiolucencies about the acetabular component was higher in the resurfacing group: 57 with complete radiolucent lines after an average follow-up of 38 months compared with 36 with complete lines after an average follow-up of 47 months. There were 3 failures in the joint-replacement group: a hematogenous staphylococcal deep infection that required a Girdlestone procedure, a femoral stem fracture that required revision, and loosening of an acetabular component for which revision was performed. There was also one dislocation, successfully treated by closed reduction. Similarly, in the resurfacing group there were 3 failures: 2 loose acetabular components, revised successfully, and one loose femoral component that necessitated total joint arthroplasty. Multivariate stepwise regression analysis showed that the factors that affected the final extent and width of the acetabular radiolucencies adversely after resurfacing were: any radiolucent lines that were visible at 6 months, a high level of physical activity after arthroplasty, and a thin superior cement mantle. The final acetabular radiolucent lines after Trapezoidal-28 arthroplasty were also unfavorably affected by radiolucent lines that were visible at 6 months, but an acetabular cement mantle that was irregular in thickness was associated with better pain ratings. The status of the radiolucency at the cement-bone interface in the femora of the resurfaced group could not be evaluated radiographically. Radiographic evidence of loosening of the femoral stem after total hip replacement was associated with a higher level of physical activity. When patients from the two groups (32 pairs) were matched for age, date of surgery, postoperative activity level, and length of follow-up, the results were remarkably similar. The higher incidence of acetabular radiolucencies in the resurfacing group may be related to the higher activity level and youth of these patients compared with the total-arthroplasty group. After resurfacing stability was excellent, there was no sepsis, and femoral bone stock was preserved. Based on this study, Tharies resurfacing at worst appears to be an acceptable alternative to total hip replacement after intermediate follow-up. If these results are maintained after longer follow-up or are improved using better technique and a metal backing, resurfacing could become a preferred treatment for primary osteoarthritis.