After total knee replacement younger patients demonstrate superior balance control compared to older patients when recovering from a forward fall.
BACKGROUND
National joint replacement registries have reported a substantial growth in younger knee osteoarthritic patients (<55years old) undergoing total knee replacement, however this younger population is generally understudied. Importantly, studies examining experimentally controlled perturbation have shown age-related differences between younger and older healthy adults, whether similar age-related differences exist among total knee replacement patients is unknown.


METHODS
A total of 59 participants, including 29 unilateral total knee replacement patients (six-months post-surgery) made up the four experimental groups: 1) younger patient (54.3 (SD 7.9) years), 2) younger control (55.2 (SD 4.0) years), 3) older patient (76.9 (SD 4.7) years), and 4) older control (77.7 (SD 4.1) years). Using a tether-release method to perturb balance and simulate a forward fall, center of mass and stepping characteristics were analyzed.


RESULTS
Younger patients recovered following the perturbation with a significantly smaller center of mass displacement compared to the older patients (14.85 (SD 0.01) v. 18.13 (SD 0.02) %ht, p=0.02); utilizing a longer (0.43 (SD 0.02) v. 0.39 (SD 0.03) m, p<0.001) and higher velocity (2.01 (SD 0.2) v. 1.59 (SD 0.2) m/s, p=0.001) recovery step. Importantly, younger patients did not differ significantly from the younger controls in center of mass displacement or recovery step characteristics (p>0.05).


CONCLUSIONS
The younger patients demonstrated superior center of mass control in response to a forward perturbation, suggesting that younger patients would be at a reduced risk of falling when recovering from a forward-directed postural perturbation compared to older patients.
Department of Kinesiology, California State University, Bakersfield, Mail Stop 22 EDUC, 9001 Stockdale Hwy, Bakersfield, CA 93311-1022, USA; Gait and Posture Neuromuscular Laboratory, California State University, Bakersfield, Mail Stop 22 EDUC, 9001 Stockdale Hwy, Bakersfield, CA 93311-1022, USA. Electronic address: bstreet1@csub.edu.
Brian D
BD
Street
School of Kinesiology and Health Science, York University, 428D HNES, 4700 Keele Street, Toronto, Ontario M3J 1P3, Canada; Orthopaedic Neuromechanics Laboratory, York University, 428D HNES, 4700 Keele Street, Toronto, Ontario M3J 1P3, Canada; Teaching and Learning, York University, 428D HNES, 4700 Keele Street, Toronto, Ontario M3J 1P3, Canada. Electronic address: whgage@yorku.ca.
William
W
Gage
D000058:Accidental Falls; D000328:Adult; D000368:Aged; D000375:Aging / Q000502:physiology*; D019645:Arthroplasty, Replacement, Knee; D005260:Female; D006801:Humans; D007717:Knee / Q000502:physiology; D007719:Knee Joint / Q000502:physiology; D008297:Male; D008875:Middle Aged; D004856:Postural Balance / Q000502:physiology*
Age-related difference; Balance recovery; Center of mass; Forward perturbation; Total knee replacement