Abstract
This study aimed to determine the prevalence of osteoporosis in patients awaiting hip and knee replacement for osteoarthritis and to review them two years later to determine the changes in bone density following joint replacement.
Patients aged between 65 and 80 years awaiting total hip or knee replacement were invited to participate. Lumbar spine, bilateral femoral and forearm bone mineral density (BMD) measurements were obtained using dual energy x-ray absorptiometry. BMD values were standardised using previously published T-scores and Z-scores. To assess clinical status, patients completed a questionnaire including the Western Ontario and McMaster University OA Index (WOMAC). All measurements were repeated at two-years.
Participants included 199 patients (84 hips and 115 knees) with a mean age of 72 years (SD 4.0) and were predominantly female (hips 67%, knees 50%). At baseline 46/199 (23%) patients (39 females) had evidence of osteoporosis (WHO definition) at one or more sites with the highest prevalence at the forearm (14%). At two-years 144 patients attended for review with 128 having undergone hip (56) or knee (72) replacement. At this review 39/144 (27%) patients (33 females) had evidence of osteoporosis at one or more sites with the highest prevalence at the forearm (22%). The greatest bone loss occurred at the forearm with median BMD change of minus 4% for females (25th percentile minus 7.3%, 75th percentile minus 1.9%) and minus 2.9% for males (25th percentile minus 4.6%, 75th percentile minus 1.1%). There was a significant difference in WOMAC Pain scores at follow-up between the osteo-porotic and non-osteoporotic knee patients (67 versus 81, p=0.002) indicating that osteoporotic patients had greater knee pain.
We have identified the forearm as not only the site with the highest prevalence of osteoporosis but also the greatest bone loss at follow-up. Further evaluation of forearm bone density measurements in the preopera-tive assessment and follow-up of patients awaiting joint replacement for hip and knee OA is required. Larger studies are needed to confirm our finding that the presence of osteoporosis is predictive of worse patient-reported outcomes of knee replacement.
Correspondence should be addressed to Mr Carlos Wigderowitz, Senior Lecturer, University Department of Orthopaedic and Trauma Surgery, Ninewells Hospital and Medical School, Dundee DD1 9SY.
