Abstract
There is an increasing interest amongst surgeons and demand from patients for hip resurfacing. One concern regarding resurfacing is the incidence of femoral neck fracture post operatively. McMinn and Treacy report an incidence of 0.4% in their series, our finding was of an incidence of over four times as high (1.9%). We looked at our database of hip resurfacings and tried to identify the risk factors for fracture.
We identified 11 fractures and compared these with 22 controls selected by choosing the cases performed by the surgeon immediately before and after the fracture case. We analysed their medical notes and x-rays. Statistical analysis was performed using a package in ™Excel. The implants were either Birmingham Hip (Midland Medical Technologies) or Cormet (Corin) resurfacings.
No statistically significant correlation was found for sex, age or body mass index. We found that fracture was twice as likely in the presence of possible or probable osteopenia. We did not find that fracture was more likely to occur in patients with a previous diagnosis of Perthes, DDH, SUFE and avascular necrosis (AVN).
We found patients with a superior overhang of the femoral component on the neck did not risk fracture, however we could not demonstrate that notching in itself increased the risk of fracture.
There was no correlation with neck-shaft and stem-shaft angle or neck lengthening and offset and subsequent neck fracture.
In 13 bilateral cases there was fracture in 3 (incidence 23%). Apart from one fracture that occurred at 18 weeks post-operatively all the others occurred before eight weeks. Five fractures occurred in patients who subsequently on histological analysis were found to have avascular necrosis.
We conclude that bilateral surgery is probably unwise. That a superior overhang seems to protect against fracture as long as this is not at the expense of creating an inferior notch. Finally, we find AVN in a number of retrieved heads, what is the true incidence of AVN and does the approach adopted cause the avascular process and if so why do we see so few fractures?
The abstracts were prepared by Mr Peter Kay, Editorial Secretary. Correspondence should be addressed to British Hip Society, The Hip Centre, Wrightington Hospital, Appley Bridge, Wigan, Lancashire WN6 9EP.
