Long, Tapered Femoral THA Stem Preserves Bone

A long, tapered hydroxyapatite-coated femoral stem during revision total hip arthroplasty achieves stable fixation and preserves bone stock up to five years after the procedure, according to a recently published study.

“In patients with good bone stock, this type of stem is a reasonable option because it is not only reliable, but also bone preserving,” Gwo-Chin Lee, M.D., told Orthopedics Today. “Of the three failures in this series, only one prosthesis was revised for subsidence.”

Lee and his colleagues retrospectively reviewed 23 men and 18 women who underwent revision total hip arthroplasty (THA) and received a KAR stem from DePuy Synthes. Thirty patients were revised for aseptic loosening; 10 patients were revised for infection and one patient was revised for dislocation. Twenty-three patients underwent both acetabular and femoral revision. At the time of the revision, 24 patients had Paprosky type I femurs, 14 patients had type II femurs and three patients had type IIIA femurs. The mean femoral component length was 207 millimeters, and the average femoral cross-sectional diameter was 16 millimeters. The patients’ average age was 62 and followed up around 63 months.

The patients had an average Harris Hip Score of 71 at final follow-up. About half of the patients reported mild hip pain with activity, and 12 patients reported they had no hip pain. During the follow-up, one prosthesis was revised for infection and another patient was revised for aseptic loosening at 15 months. Another patient underwent a subsequent revision for a symptomatic limb length discrepancy caused by component subsidence at final follow-up, Lee said.

Overall, the researchers deemed the implants well-fixed, with no radiolucent lines, good osteointegration and no radiographic evidence of proximal femoral resorption or stress shielding at final follow-up.

Lee noted the prosthesis was not appropriate for patients with severe bone loss.

“The KAR stem is used in Europe, but there is little experience with it in the United States,” Lee said. “It is important to realize that for many of these patients, this revision may not be their last, and maximizing residual bone stock should be considered when choosing implants. Particularly, when the most common type of hip stem currently in use is a blade-type stem, some revisions may not require the aggressive bone reaming that is required with the more traditional type of revision femoral components. This type of revision stem geometry can reliably achieve implant stability while maintaining bone stock.”

He added, “We plan to further define the indications of when to use this type of stem compared to more traditional revision stems.”