RELATIONSHIP BETWEEN MUSCLE CROSS-SECTIONAL AREA OF THE LUMBAR MULTIFIDUS MUSCLE AND TRUNK EXTENSOR STRENGTH IN PATIENTS WITH AFTER VERTEBRAL FRACTURE

S. Onoue¹, N. Maeda¹, T. Tashiro¹, S. Tsutsumi¹, M. Niitani², M. Komiya¹, Y. Urabe¹

¹Hiroshima University, Department of Sports Rehabilitation, Graduate School of Biomedical and Health Sciences, Hiroshima city, Japan, ²Niitani Clinic, Department of Orthopedic, Kure, Japan

Background: Kyphosis deformity occurs in 20%–40% of patients withvertebral fracture(Jain et al., 2020), resulting in reduced balance, lower back pain, and decreasedactivities. The main cause of kyphosis deformity is decreased trunk extensor strength, and the lumbar multifidus muscles are important for posture retention.However, there are no reports investigating the muscle morphology of the lumbar multifidus muscle in patients with vertebral fractures.

Purpose: This study aimed to measure the cross-sectional area of the lumbar multifidus muscle at each lumbar level in patients withvertebral fractureto apply prevent kyphosis deformity.

Methods: This study included 6 patients for the vertebral fracture group (age 84.5 ± 6.7 years) and 6 patients for the non-vertebral fracture group (age 81.3 ± 6.4 years). The fracture levels were the thoracic spine (Th)12 in one patient, lumbar spine (L)1 in three patients, and L2 in two patients. The cross-sectional area (CSA) of the lumbar multifidus muscle was measured using an ultrasound system (FUJIFILM, FC1). The ultrasound probe was positioned 2 cm from the spinous process and perpendicular to the spinal column to extract cross-sectional images (Hides et al., 2007). Ultrasound images were analyzed using image analysis software (Image J, National Institutes of Health) to calculate CSA of lumbar multifidus at each lumbar level. Isometric trunk extensor muscle strength was measured on three trials using a handheld dynamometer, and the average of the three measurements, normalized by body weight, was obtained.Statistical analysis was performed using either an unpaired t-test or Mann–Whitney U test to compare the CSA of lumbar multifidus muscle CSA and isometric trunk extensor strength at each lumbar level between the two groups. The significance level was set at 5%.

Results: The CSA of the lumbar multifidus muscle were L1: 1.6±0.3㎠, L2: 1.7±0.4㎠, L3: 1.9 0.6㎠, L4: 2.1±0.6㎠, and L5: 2.3±0.3㎠in the vertebral fracture group and L1: 2.2±0.6㎠, L2: 2.5±0.9㎠, L3: 2.8±0.7㎠, L4: 3.3±1.0㎠, and L5: 3.8±1.4㎠in the non-vertebral fracture group. CSA of the lumbar multifidus muscle at L1 and L2 levels did not show significant differences between two groups. On the other hand, CSA of the muscle at L3 to L5 levels were smaller in the vertebral fracture group (p＜0.05, respectively). The isometric trunk extensor strength did not differ significantly between the two groups.

Conclusions: This study revealed that the CSA of the lumbar multifidus muscles from L3 to L5 in the vertebral fracture group was smaller than that in the non-vertebral fracture group. The trunk muscles are less susceptible to age-related atrophy (Abe et al., 2014). The lumbar multifidus muscle in patients with vertebral fractures may be pathologically atrophic.

Implications: Selective training of the lumbar multifidus muscle at L3 to L5 level may be important for the prevention ofkyphosis deformityafter vertebral fracture. TheCSA of the lumbar multifidus muscles evaluation at the vertebral level can be useful information in the prevention of kyphosis deformity.

Funding acknowledgements: We have no funding acknowledgement in this study.

Keywords:
vertebral fracture
ultrasonography
lumbar multifidus muscle

Topics:
Musculoskeletal: spine
Disability & rehabilitation
Orthopaedics

Did this work require ethics approval? Yes

Institution: Niitani Clinic

Committee: The Ethical Committee for Epidemiology of Niitani Clinic

Ethics number: NCL 21001