Second-generation cementless THA prosthesis shows good results at 9 years

No acetabular components produced complete radiolucencies and only three components were revised for radiographic loosening.

A second-generation circumferentially, proximally porous-coated femoral component shows good clinical results at 9 years mean follow-up for noncemented total hip arthroplasty, according to a study by researchers in New Mexico.

Jonathan W. Surdam, MD, and colleagues at New Mexico Orthopaedics, Albuquerque, reviewed their results implanting the Multilock [Zimmer] femoral component and either the Harris-Galante II [Zimmer] or the Trilogy [Zimmer] acetabular components in 258 hips of 231 patients. All procedures were performed from 1990 to 1996. Patients averaged 53 years of age at the time of surgery, according to the study.

The data analysis included 237 hips for 211 patients with minimum 5 years follow-up. Five patients had died and 16 were lost before completing 5-year follow-up examinations.

At the most recent follow-up, the researchers found that the average Harris Hip Score had improved to 89 points from 50 points preoperatively. Of the 237 hips, 166 (70%) had excellent results, 50 (21%) had good results, five (2%) had fair results and 16 (7%) had poor results, according to the study.

The Harris activity level also improved, from 9.21 preoperatively to 12.94 at final follow-up, the authors noted.

Intraoperative complications occurred in 10 hips (4.2%) and included nine nondisplaced femoral neck fractures, which were managed with cerclage wire or cable. Investigators also identified one periprosthetic femur fracture postoperatively and managed it with 12 weeks of modified weight-bearing.

In addition, 26 patients (11%) experienced dislocations postoperatively, which surgeons initially treated with closed reduction and 12 weeks of bracing. Recurrent dislocations occurred in nine patients (4%), which required surgical revision of the cup, head and liner in four patients and an exchange of the head and liner in five patients, according to the study.

Overall, 20 patients required 21 reoperations (9%), five of which were due to wear and osteolysis. These five cases were treated with liner and head exchange and with grafting of periacetabular or trochanteric osteolytic lesions. Another two patients were resected due to sepsis, three patients were revised due to acetabular loosening with osteolysis, and two patients were revised due to aseptic loosening, the authors reported.

Complete radiographic follow-up was available at 5 years for 226 stems. Overall, 197 stems (87%) were in neutral alignment, 24 (11%) were varus and five (2%) were valgus.

Surgeons identified an incomplete bone pedestal in 53 stems (23%) and 125 stems (55%) showed proximal remodeling. Surgeons also found osteolysis around 16 femoral components (7%) and found acetabular radiolucencies in 20 hips (8.4%), according to the study.

No acetabular components showed a complete radiolucent line, and only three components were revised for radiographic loosening, the authors noted.

Using any either revision or radiographic loosening as the end point, the researchers found a 92% Kaplan-Meier survivorship rate at 10 years. "When femoral component revision for aseptic loosening or radiographic loosening was used as the end point, survivorship at 10 years was 98%," the authors wrote.

Survivorship increased to 99% at 10 years when using acetabular revision for aseptic or radiographic loosening as the end point, they noted.

For more information:
Surdam JW, Archibeck MJ, Schultz SC Jr, et al. A second-generation cementless total hip arthroplasty, mean 9-year results. J Arthroplasty. 2007;22:204-209.