Femoral canal change detected in women over time

By Lynda Williams, Senior medwireNews Reporter

Women experience a gradual expansion in femoral canal diameter with increasing age, which could impact the longevity of total hip replacement (THR), UK researchers report.

Radiographs for 949 women aged 34 to 92 years old (average age 67 years) undergoing THR at a regional orthopedic center showed a significant and positive correlation between canal diameter and age, with an average increase of 0.08 mm per year.

By contrast, there was a poor linear relationship between age and canal diameter in the 736 men aged 29 to 92 years (average age 70 years) undergoing THR, with an average increase of just 0.005 mm per year, say David Milligan (Musgrave Park Hospital, Belfast) and co-authors.

"The diameter of the femoral canal diameter of a female patient undergoing THR could be predicted to increase by 3.2 mm between the ages of 40 and 80 years, in contrast a male would be expected to experience only a 0.6 mm increase during the same period," the authors explain in Bone Joint Journal.

"This increase in the diameter of the canal with age might affect the long-term survival of the femoral component in female patients."

The team measured the femoral diaphyseal canal at its narrowest point using radiographs taken to prepare cemented custom-made femoral components for patients awaiting THR. At the isthmus, the overall mean canal diameter was 12.69 mm in the women and 13.27 mm in the men.

Canal width was significantly wider in older (70 years or older) than younger women (<60 years), by an average of 1.43 mm, but the change in diameter was gradual. "It did not occur with an abrupt transition that might be expected if it was related to the menopause," Milligan et al observe.

The team concludes: "With increasing numbers of younger patients undergoing THR it is important that we understand the implications of any expansion in the diameter of the intramedullary canal better, particularly in female patients."

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