The development and validation of a more discriminating functional hip score for research

Background: Total hip arthroplasty (THA) is a commonly performed procedure with increasing frequency in the young adult. While most available outcome measures can document postoperative improvement in pain and function, they do not measure the ability to perform high-demand activities.

Questions/purposes: We present and validate a user-friendly discriminating hip scoring system (the functional hip score) for use in younger, "high-demand" patients undergoing hip arthroplasty surgery.

Methods: We studied 38 subjects without any hip symptoms and 72 patients undergoing THA for osteoarthritis of the hip. Preprocedure and postprocedure scores were collected in the latter cohort of patients. SF-36 and WOMAC scores were used to validate our functional scoring system. The functional hip score was tested for internal consistency, reliability, and criterion validity.

Results: The functional hip score had high test-retest reliability, internal consistency, and criterion validity. This can be used to measure functional outcome in the younger high-demand adult patient undergoing THA.

Conclusion: Our discriminating functional hip score can reliably measure improvement in hip function in the younger high-demand adult. Current scoring systems have ceiling effects and are unable to differentiate a high performing hip replacement from the routine hip replacement. The use of functional tasks that are measured objectively allows better documentation of improvement in hip function.