Left-Right Weight-Bearing: Short Term Measurement Precision and Effects of Weight-Bearing

ASTUDY INVESTIGATING THE LONG-TERM EFFECTS ON FUNCTION, BONE MINERAL DENSITY AND LEAN TISSUE MASS POST TOTAL KNEE REPLACEMENT IN A FEMALE POSTMENOPAUSAL POPULATION

SJ Hopkins*[1], CW Smith[1], AD Toms[2], M Brown[2],JRWelsman[3], KM Knapp[1]<BR>[1]College of Engineering, Mathematics and Physical Sciences, University of Exeter, UK; [2]Princess Elizabeth Orthopaedic Centre, Royal Devon and Exeter Hospital, UK; [3]College of Life and Environmental Sciences, University of Exeter, UK

Introduction:Disuse osteopenia is a known consequence of reduced weight-bearing on lower limbs.Osteoarthritis (OA) commonly necessitates joint replacement with limited mobility for a variable period post surgery. Although OA isgenerally associated with higher levels of BMD, a significantincrease in hip fracture incidencein the year following total knee replacement (TKR) has been demonstrated;however the extent of disuse-related bone loss at the hip following TKR and its potential contribution to post-surgical fracture risk has notbeen reported.

Material and Methods:This study investigated long-term changes in DXA BMD at the neck of femur(NOF) and total hip (TH),(GE Lunar Prodigy),and leg lean tissue mass (LLTM)in a population of 11 postmenopausal females following TKR compared to 45 postmenopausal controls. Relative ipsilateral/contralateral weight-bearing, lower limb function, 3 day pedometer readingsand fallswere also recorded.Measurements were obtained at pre-surgery baseline, and six months post surgery.

Discussion: No significant differences were demonstrated between groupsat baselinebilaterally in LLTM or BMD at the NOF and TH.Significant losses in ipsilateralhip BMD and bilateral LLTM are demonstrated in the TKR group 6 months post surgery.

Conclusion: Significant impairment in function and weight-bearing persisted in the TKR group 6 months post operatively alongside significant deficits in bilateral muscle mass and ipsilateral NOF and TH BMD. Falls incidence was not significantly higher in the TKR group suggesting that disuse-related reduction in hip BMD and LLTMmay contribute to increased hip fracture incidence following TKR.