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Curvature of modified straight stem allows implantation in narrow femoral cavities
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German researchers using a modified straight cementless hip stem with proximal-medial curvature for total hip arthroplasty in cases with narrow femoral cavities reported high stem survivorship and outcomes similar to those of a straight tapered hip design.
“Most studies … say narrow femoral bone conditions can be challenging,” Steffen Kohler, MD, said during his presentation at the SICOT XXV Triennial World Congress 2011. “The small shape of stem designs may change outcomes dramatically.”
Kohler and colleagues conducted a retrospective study of 123 total hip arthroplasties performed with a modified straight cementless proximal hip stem for narrow femora and compared the results to studies using a straight tapered stem. Of the patients, 100 hips in 92 patients were available for follow-up between February 1991 and November 1996. The learning curve was fully included. The patients had an average age of 57 years and were followed for a mean of 148 months. One-third of the patients had a preoperative diagnosis of dysplasia, one-third of patients had primary osteoarthritis and one-sixth of patients suffered aseptic femoral head necrosis or other diagnosis, according to Kohler.
One patient died of pulmonary embolism on the second postoperative day. The investigators found that femur fractures occurred within the acceptable range, according to Kohler. The team measured the dislocation rate at 1%, “which is also the standard range and also far and away what is reported from other research,” Kohler said. After the study was finished, one patient was treated for late infection and underwent a staged revision at 16.5 years.
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A patient is shown at 187 months (L) follow-up and 179 months (R) follow-up. It was the longest follow-up in this series. Images: Kohler S |
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The investigators found that the Harris Hip score improved from 28 points at baseline to 93 points at the time of last follow-up. The mean Merle D’Aubigné score was 16.7 points at last follow-up, Kohler said.
The Kaplan-Meier survival rate of the stem was 99%, with investigators finding one loose stem. They recorded high failure rates of the acetabular components of the modified device. However, Kohler noted that cup loosening and polyethylene wear did not damage the bone-implant interface of the cementless stem used in their study.
“These findings were not different to the published mid- and long-term results of the corresponding cementless straight hip stem design,” Kohler and his colleagues wrote in their study abstract. – by Renee Blisard
Reference:
- Kohler S. Results of cementless THA in indications for narrow femoral cavities. Presented at the SICOT XXV Triennial World Congress 2011. Sept. 6-9. Prague.
- Steffen Kohler, MD, can be reached at HELIOS-Klinik, Fachkrankenhaus für Orthopädie, Barbarastraße 11, 99752, Bleicherode, Germany; (03 63 38) 65-0; email: steffen.kohler@helios-kliniken.de.
- Disclosure: Kohler is a paid consultant for Aesculap AG (Tuttlingen, Germany).