Skeletal muscle fiber characteristics of the lumbar multifidus muscle in patients undergoing microdiscectomy for unilateral lumbar disc herniation

Abstract

Background context Because of its role in spinal stability there is an increased interest in the role of the Lumbar Multifidus muscle in low back pain research. Degenerative changes of the Lumbar Multifidus muscle are observed to be different in various low back pathologies, which may influence long-term disability and pain. Whether a change in muscle characteristics can be observed in the Lumbar Multifidus muscle following LDH in humans remains unknown.

Aim The aim of the study is to compare side-to-side Lumbar Multifidus muscle fiber characteristics in unilateral LDH patients, and compare both sides to a healthy control group.

Methods Muscle biopsy samples were obtained from 30 patients scheduled for microdiscectomy for unilateral disc herniation and 10 healthy controls. Biopsies were taken from the Lumbar Multifidus muscle at the level of surgery (n=15 L4-L5, n=14 L5-S1) at both the herniated (injured) and non-herniated (uninjured) side in the patient group. In healthy controls a muscle biopsy sample was taken from the right Lumbar Multifidus muscle at level L4-L5.

Results No significant differences were observed for type I or type II muscle fiber size and/or type distribution between groups. The proportion of muscle fibers with centrally located myonuclei was higher in the patients (injured side: 7.6±1.2 %, uninjured side: 8.6±1.3 %) compared with the healthy controls (1.9±2.0 %). Various indices of type I and type II muscle fiber capillarization were substantially greater (ranging from +22 to +281%) in LDH patients compared with controls. Both pro-and anti-inflammatory cell content was significantly higher in the LDH patient group compared with controls. No differences were observed between the injured and uninjured side within the LDH patients.

Conclusion This study shows clear differences in Lumbar Multifidus muscle fiber characteristics between LDH patients, irrespective of injured or uninjured side, and healthy controls.