RESUMO
Objective To investigate the effect of muscle function on structural stress in patient with lumbar disc herniation (LDH), by observing the stress changes in LDH lumbar-pelvis finite element model loaded with muscle force. Methods One normal healthy volunteer and one LDH patient were selected. Their CT data were collected to establish two corresponding normal and LDH lumbar-pelvis finite element models, and their gait data were also simultaneously collected to drive the AnyBody musculoskeletal model. The muscle force around the lumbar and pelvis as well as the hip-joint force were obtained as the loading condition. Self-loading of the normal and LDH model as well as the normal model loaded with LDH muscle forces were conducted seperately. Then the stress changes in L4 and L5 intervertebral discs and sacroiliac joints under two above loading conditions were compared. Results The stress curve of normal model loaded with LDH muscle force showed a unimodal stress curve, instead of a bimodal curve, and such trend of stress-time curve was as same as the trend of the LDH model during self-loading. But the stress difference in L4 and L5 intervertebral discs and sacroiliac joint of the normal model loaded with LDH muscle force was smaller than that in the LDH model during self-loading. Conclusions Abnormal muscle function of LDH could lead to abnormal joint stress of the intervertebral discs and sacroiliac joint. Structural imbalance itself could lead to stress imbalance, and muscle as a driving factor was an important cause of anomaly structural dynamic stress, thus leading to abnormal joint motion patterns. Therefore, attention should be paid to assessment of the imbalance of peripheral muscle function in clinical treatment of LDH.