The role of muscle degeneration and spinal balance in the pathophysiology of lumbar spinal stenosis: Study protocol of a translational approach combining in vivo biomechanical experiments with clinical and radiological parameters.

OBJECTIVE: To describe a study protocol for investigating the functional association between posture, spinal balance, ambulatory biomechanics, paraspinal muscle fatigue, paraspinal muscle quality and symptoms in patients with symptomatic lumbar spinal stenosis (sLSS) before and 1-year after elective surgical intervention. DESIGN: Single-centre prospective, experimental, multimodal (clinical, biomechanical, radiological) study with three instances of data collection: baseline (study visit 1), 6-month follow-up (remote) and 1-year follow-up (study visit 2). Both study visits include an in vivo experiment aiming to elicit paraspinal muscle fatigue for postural assessment in a non-fatigued and fatigued state. EXPERIMENTAL PROTOCOL: At baseline and 1-year follow-up, 122 patients with sLSS will be assessed clinically, perform the back-performance scale assessment and complete several patient-reported outcome measure (PROMs) questionnaires regarding overall health, disease-related symptoms and kinesiophobia. Posture and biomechanical parameters (joint kinematics, kinetics, surface electromyography, back curvature) will be recorded using an optoelectronic system and retroreflective markers during different tasks including overground walking and movement assessments before and after a modified Biering-Sørensen test, used to elicit paraspinal muscle fatigue. Measurements of muscle size and quality and the severity of spinal stenosis will be obtained using magnetic resonance imaging (MRI) and sagittal postural alignment data from EOS radiographies. After each study visit, physical activity level will be assessed during 9 days using a wrist-worn activity monitor. In addition, physical activity level and PROMs will be assessed remotely at 6-month follow-up. CONCLUSION: The multimodal set of data obtained using the study protocol described in this paper will help to expand our current knowledge on the pathophysiology, biomechanics, and treatment outcome of degenerative sLSS. The results of this study may contribute to defining and/or altering patient treatment norms, surgery indication criteria and post-surgery rehabilitation schedules. TRIAL REGISTRATION: The protocol was approved by the regional ethics committee and has been registered at clinicaltrials.gov (NCT05523388).

Trunk muscle function and its association with functional limitations in sedentary occupation workers with and without chronic nonspecific low back pain.

BACKGROUND: The function of trunk muscles in chronic nonspecific low back pain (CNLBP) is controversially discussed, and trunk muscle function in sedentary occupation workers is poorly understood. OBJECTIVE: To investigate whether muscle function differs between sedentary occupation workers with and without CNLBP and to determine the association between functional limitations and muscle function. METHODS: This study included 32 sedentary occupation workers (16 workers with CNLBP and 16 age- and sex-matched workers without CNLBP). Group differences in isokinetic trunk flexion-extension strength, muscle cocontraction, endurance time (Biering-Sorensen test) and electromyographic muscle fatigue were assessed. The association of these parameters and Oswestry Disability Index (ODI) score were examined in the CNLBP group. RESULTS: Participants with CNLBP had lower trunk extensor (-20%) and flexor (-18%) strength and less cocontraction (-22%) than participants without CNLBP, but due to large variability in both groups these differences were not statistically significant. Trunk muscle endurance and fatigue were comparable between groups. Variance in endurance time explained 28% of variance in the ODI-score in the CNLBP group (R2= 0.277). CONCLUSIONS: In patients with CNLBP, greater functional disability was associated with lower endurance. Further evidence is necessary to elucidate whether specifically training endurance performance may be beneficial for sedentary occupation workers.