Oral Presentation 50th International Society for the Study of the Lumbar Spine Annual Meeting 2024

The association of hip muscle strength and asymmetry with functional performance and disability in individuals with chronic low back pain (#MP-1d)

Sara R Piva 1 , Mara A Hartoyo 1 , Jaclyn M Sions 2 , Charity G Patterson 1
  1. Physical Therapy, University of Pittsburgh, Pittsburgh, PA, United States
  2. Physical Therapy, University of Delaware, Newark, Delaware, United States

INTRODUCTION

Chronic low back pain (CLBP) is difficult to diagnose and treat due to ill-defined pathology, resulting in suboptimal outcomes and exorbitant healthcare costs.1,2 Identifying factors related to clinical outcomes may inform interventions and improve case. Several studies demonstrated that weakness of hip muscles is more prevalent in persons with LBP compared to controls,3-5 but it is unclear whether weakness of hip muscles and/or hip strength asymmetry associate with physical dysfunction in CLBP. This study aimed to determine whether hip extension, abduction, external rotation and flexion strength, and asymmetry in these measures (independent variables), associate with functional performance and LBP-related disability (dependent variables), in individuals with CLBP.

METHODS

Cross-sectional secondary analysis of data from a large observational study that aims to phenotype CLBP. Muscle strength was assessed by handheld dynamometry, except for hip flexion, which used manual muscle testing. Functional performance was measured by self-selected gait speed during the 4-meter Walk Test, walking endurance during the Two-minute Walk Test, and time to stand from and return to sitting by the Five Times Sit-to-stand Test. Oswestry Disability Index (ODI) assessed LBP-related disability. Univariate correlations assessed associations between each independent and dependent variables. Multivariate analysis used linear regression models adjusted by sex, age, and body mass index (BMI). Stepwise selection was used to identify the most parsimonious set of associators. Separate models were run for each dependent variable.

RESULTS

The analysis included 515 participants with an average age of 58±17 years, 63% female, 77% white, and BMI of 32±8 kg/m2. Individuals from this cohort had worse physical function and weaker hip muscles than the general population without CLBP. Hip external rotation strength was excluded from analysis because it was highly correlated (r=0.81) with hip abduction strength. In adjusted models, hip muscle weakness associated with poor functional performance and heightened LBP-related disability. Specifically, stronger abductor, flexor, and extensor muscles (R2 change of .099, .011 and .007 respectively) associated with longer distance walked in the Two-minute Walk Test (adjusted R2 of full model = 0.42). Strong hip abductors and extensors (R2 change of .079 and .016 respectively) associated with faster gait speed (R2 adj = 0.26). Stronger hip extensors and abductors (R2 change of .14 and .014 respectively) associated with faster Five Times Sit-to-stand Test performance (R2 adj = 0.26). Stronger hip extensors and flexors (R2 change of .050 and .015 respectively) associated with less disability per the ODI (R2 adj = 0.14). Hip muscle strength asymmetry did not associate with any of the dependent variables.

 

DISCUSSION

Hip extension strength associated with all performance-based tests and was the strongest associator with the ODI and sit-to-stand performance. Hip abduction strength was associated with all three performance-based tests and was the strongest associator with both gait speed and Two-minute Walk Test distance. The hip impairments investigated in this study are modifiable factors that could be addressed to improve functional performance and LBP-related disability in CLBP. Further longitudinal investigation is necessary to determine whether targeting these impairments results in improved outcomes in this population.

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