The effect of fatty infiltration, revision surgery, and sex on lumbar multifidus passive mechanical properties

Purpose Previous research has demonstrated increased stiffness in the multifidus muscle compared to other paraspinal muscles at fiber bundle level. We aimed compare single and passive mechanical properties of muscle: (1) 40 patients undergoing primary versus revision surgery (2) with mild severe fatty infiltration. Methods The degree infiltration was graded using patients' spine magnetic resonance images. Average across three tests were between (N = 30) 10) status, levels, sexes, age from stress–strain excised intraoperative biopsies. Results At level, elastic modulus unaffected by or status. Female sex (p 0.001) younger 0.04) associated lower modulus. which includes connective tissue around fibers, 0.01) 0.06) Primary also a moderate, but non-significant effect for 0.10). Conclusions Our results demonstrate that female is driver reduced multifidus, while severity level individuals lumbar pathology.