Effects of Limb Length Discrepancy on Functional and Health-Related Outcomes in Hip Fracture Patients

Abstract

Background: Limb length discrepancy (LLD), a common complication following hip fracture, is present when paired lower extremities are of unequal lengths. LLD consequences include chronic low-back pain, standing imbalance, nerve palsy and gait abnormalities. There is a paucity of LLD studies in older adults and no study to date has investigated LLD in hip fracture patients, a large population of older adults experiencing late life disability and decline in functional mobility. Objectives: Specific aims of this study were to: (1) Determine the reproducibility, validity and repeatability of Dual Energy X-ray Absorptiometry-Linear Pixel Count (DXA-LPC) method to measure limb length and assess for LLD in hip fracture patients, using mixed effects regression modeling; (2) Determine the prevalence and changes in LLD over the 12-months post fracture using general linear modeling; and (3) Determine the association between LLD severity and functional and health-related outcomes during 12-months post fracture using general linear modeling. Methods: Data come from the Baltimore Hip Studies 4th cohort (BHS-4; 1998-2004), a study of 180 community-dwelling women age 65+ with incident hip fractures enrolled in a RCT of an in-home exercise intervention. Three expert assessors and study PI measured limb lengths from whole-body DXA images electronically stored from BHS-4 at baseline and 2, 6, and 12 months post-fracture. Functional and health-related outcomes included the Lower Extremity Gain Scale (LEGS), Yale Physical Activity Scale (YPAS), mobility score, number of falls, and hip and general pain and assessed at each follow-up time-point. Results: Reproducibility of DXA-LPC was moderate, while validity and repeatability were both excellent. Majority (~75%) of participants experienced LLD; findings were consistent across all study time-points. Mean absolute LLD did not statistically change over time (mean=14.7mm). Adjusted results indicate a significant adverse relationship between LLD severity and number of falls (p=0.006) with nonsignificant adverse relationships with other functional outcomes. Conclusions: LLD severity contributes significantly to falls during the year following a hip fracture. Findings also indicate clinically meaningful differences in functional outcomes between LLD groups. Interventional studies should investigate shoe lift therapy efficacy and other post-operative mechanisms to minimize the impact of LLD on post-fracture functional recovery.