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Center-edge angle affects survival following fibular grafting for femoral head osteonecrosis
Hips with a center-edge angle of <30° were 10 times more likely to be converted to THA.
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Hips with a lower center-edge angle following free vascularized fibular grafting to treat femoral head osteonecrosis have a significantly higher risk of further femoral head collapse and conversion to total hip arthroplasty, a study found.
Thomas F. Roush, MD, and colleagues at Duke University Medical Center in Durham, N.C., evaluated the influence of acetabular orientation on outcomes following treatment for femoral head osteonecrosis. The researchers reviewed records for 200 hips of 160 consecutive patients with predegenerative osteonecrosis. All patients were treated with free vascularized fibular grafting at an average age of 33.6 years.
Of the 200 hips included in the study, 48 hips (24%) were converted to THA at an average 26 months postop. Additionally, 14 hips in 13 patients not converted to THA showed progression of collapse on their latest radiographic evaluation, according to the study.
The researchers found that hips that showed progressive collapse had a mean center-edge angle of Wiberg of 24° compared to 32° for hips without evidence of progression (P<.001). "Similarly, hips that were converted to total hip arthroplasty had a mean center-edge angle of 25°, whereas those that did not require additional surgery had a mean center-edge angle of 30° (P<.001)," the authors said in the study.
Among all 200 hips, the researchers found a 52% rate of conversion to THA for hips with a center-edge angle of <25° vs. a 12% conversion rate for hips with angles >25° (P<.001), according to the study.
"When compared with hips with a center-edge angle of >25°, hips with a center-edge angle of <25° were 11 times more likely to demonstrate progression of collapse and seven times more likely to undergo conversion to a total hip arthroplasty," the study authors said.
Radiographic follow-up of at least 2 years was available for 43 non-THA-converted hips. Of these, hips with a center-edge angle of <25° had a 69% rate of collapse progression, while hips with such angles >25° had only a 17% rate of progression (P<.001), according to the study.
Additionally, among these 43 hips, those with center-edge angles <30° had a 55% rate of collapse progression, compared with a 10% rate for hips with angles >30° (P<.002), the authors noted.
Among all 200 hips, those with a center-edge angle of <30° had a 45% rate conversion to THA, compared with a 6% conversion rate for hips with angles >30° (P<.001), according to the study.
"[Hips] with a center-edge angle of <30° were 11 times more likely to demonstrate progression of collapse and 10 times more likely to undergo conversion to a total hip arthroplasty," the author said.
For more information:
- Roush TF, Olson SA, Pietrobon R, et al. Influence of acetabular coverage on hip survival after free vascularized fibular grafting for femoral head osteonecrosis. J Bone Joint Surg Am. 2006:88-A:2152-2158.