Computational Biomechanics of the Lumbar Spine: A Study of Lower Back Pain (LBP) Based on Muscle Strength

Abstract

Chronic Low Back Pain afflicts a large number of people worldwide. The lower spine is comprised of lumbar vertebrae with intervertebral discs, and a fused sacrum that articulates with the iliac bones. The whole assembly is stabilized by large synergistic and antagonist groups of muscles. A dysfunction or abnormality in any of these structures could lead to instability and disturbed load distribution that could lead to pain. Gluteus maximus is the largest muscle in the human body contributing to the stability of the pelvis, hip and knee during gait and other activities. The present study is focused on determining effects of variation in strength of the gluteus maximus on the compressive load exerted on the sacroiliac joint. Additionally, the effects on pelvic tilt, hip and knee loads, and angles with the change in gluteus maximus strength were also explored. Our results for a single gait cycle showed maximum anterior pelvic tilt with an atrophied and hypertrophied gluteus maximus as 0.2308 and 0.1900 radians respectively as compared to a maximum anterior pelvic tilt of 0.1994 in the unaltered model. This indicates a noticeable variation in pelvic tilt based on varying strength of the gluteus maximus while there were small changes in the hip and knee loads. It was also observed that the hamstrings play a compensatory role in stabilizing the knee and the hip with minimal changes in their angles and loading for the same gait cycle.