Question:
How do hybrid and cementless total hip replacements in patients less than fifty years of age compare after a minimum of sixteen years of follow-up?
Design:
Randomized (allocation concealed), unblinded, controlled trial with a mean of 18.4 years of follow-up.
Setting:
The Joint Replacement Center of Korea, Ewha Womans University, Seoul, Korea.
Patients:
One hundred and sixty-six patients (228 hips) who were less than fifty years of age and undergoing total hip replacement. One hundred and fifty-seven patients (95%) (mean age, 45.1 years; 76% men) were available for follow-up.
Intervention:
Patients were allocated to hybrid (cemented) (n = 78) or cementless (n = 79) total hip replacement. The cemented implant (Charnley Elite or Elite-plus stem [Ortron 90], DePuy, Leeds, United Kingdom) was straight with a smooth surface and was applied using an intramedullary plug, pulsatile lavage, vacuum mixing, injection with a gun, a proximal rubber seal, and a distal centralizer on the femoral component. The cementless Profile femoral stem (DePuy) was an anatomical metaphyseal-fitting titanium stem that was inserted with a press fit determined with preoperative use of templates. During the operation, an attempt was made to fill the femoral canal with the broach and to leave little cancellous bone remaining. In both groups, a cementless Duraloc 100 or 1200 series acetabular component (DePuy, Warsaw, Indiana) was used.
Main outcome measures:
Patients were evaluated with use of the Harris hip score (range, 0 to 100, with higher scores indicating better outcome) and the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) (twenty-four item scale, with higher scores indicating worse pain, stiffness, and functional limitations). Level of activity was measured with use of the University of California, Los Angeles (UCLA) activity score (10-point scale, with higher scores indicating greater activity level). Pain was assessed with a 10-point visual analog scale. Computed tomography scans were performed to determine osteolysis. Revision rates of the acetabular and femoral components and survival of the implants were assessed.
Main results:
Patients in both the hybrid and cementless groups improved in terms of the mean Harris hip score, WOMAC score, and UCLA activity score after surgery (Table). Fewer patients in the hybrid group had thigh pain (Table). The groups did not differ in terms of acetabular or femoral osteolysis, revision, or implant survival (Table).
Conclusion:
In patients less than fifty years of age having total hip replacements, hybrid and cementless implants were similar.
This randomized trial by Kim and colleagues comparing the results of hybrid total hip replacement and cementless total hip replacement in patients less than fifty years of age demonstrates that excellent outcomes can be obtained up to eighteen years after surgery. Consistent with other studies, wear and periacetabular osteolysis were major factors in limiting the longevity of these prostheses. Both groups received a 22-mm head and minimally crosslinked polyethylene as a bearing surface, and this may explain the high annual penetration rate of 0.21 mm per year. Interestingly, the incidence of acetabular osteolysis was similar for components with and without holes for adjuvant screw fixation (35% versus 31%).
The majority of the patients in the study were men, and approximately two-thirds of the patients had osteonecrosis of the hip. These patients are probably lower-demand than younger patients with osteoarthritis. Although the results are encouraging, the components used in the study are no longer available today. At the present time, most cementless acetabular components have highly crosslinked polyethylene to reduce wear, and larger heads are used to provide increased range of motion and to reduce the dislocation rate. Time will tell if the highly crosslinked polyethylene liners used today will be associated with less wear and osteolysis. Despite the limitations of this study, the results demonstrate that excellent outcomes can be obtained with both cemented and cementless femoral components.