Regional differences between superficial and deep lumbar multifidus in patients with chronic lumbar spine pathology

Jennifer Padwal,James C Hubbard,Vinko Zlomislic,Steven R Garfin,Samuel R Ward,David B Berry,Bahar Shahidi,R Todd Allen

doi:10.1186/s12891-020-03791-4

Jennifer Padwal, James C Hubbard + Show 6 more

Open Access

https://doi.org/10.1186/s12891-020-03791-4

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Abstract

BackgroundDue to its unique arrangement, the deep and superficial fibers of the multifidus may have differential roles for maintaining spine stabilization and lumbar posture; the superficial multifidus is responsible for lumbar extension and the deep multifidus for intersegmental stability. In patients with chronic lumbar spine pathology, muscle activation patterns have been shown to be attenuated or delayed in the deep, but not superficial, multifidus. This has been interpreted as pain differentially influencing the deep region. However, it is unclear if degenerative changes affecting the composition and function of the multifidus differs between the superficial and deep regions, an alternative explanation for these electrophysiological changes. Therefore, the goal of this study was to investigate macrostructural and microstructural differences between the superficial and deep regions of the multifidus muscle in patients with lumbar spine pathology.MethodsIn 16 patients undergoing lumbar spinal surgery for degenerative conditions, multifidus biopsies were acquired at two distinct locations: 1) the most superficial portion of muscle adjacent to the spinous process and 2) approximately 1 cm lateral to the spinous process and deeper at the spinolaminar border of the affected vertebral level. Structural features related to muscle function were histologically compared between these superficial and deep regions, including tissue composition, fat fraction, fiber cross sectional area, fiber type, regeneration, degeneration, vascularity and inflammation.ResultsNo significant differences in fat signal fraction, muscle area, fiber cross sectional area, muscle regeneration, muscle degeneration, or vascularization were found between the superficial and deep regions of the multifidus. Total collagen content between the two regions was the same. However, the superficial region of the multifidus was found to have less loose and more dense collagen than the deep region.ConclusionsThe results of our study did not support that the deep region of the multifidus is more degenerated in patients with lumbar spine pathology, as gross degenerative changes in muscle microstructure and macrostructure were the same in the superficial and deep regions of the multifidus. In these patients, the multifidus is not protected in order to maintain mobility and structural stability of the spine.

Highlights

Due to its unique arrangement, the deep and superficial fibers of the multifidus may have differential roles for maintaining spine stabilization and lumbar posture; the superficial multifidus is responsible for lumbar extension and the deep multifidus for intersegmental stability
In patients with low back pain (LBP) arising from degenerative lumbar conditions, the lumbar multifidus muscle is often observed to have increased fatty infiltration and atrophy compared to aged controls [1], resulting in reduced long-term function and poor prognosis [2,3,4,5]
Type II muscle fiber atrophy, an increased proportion of glycolytic compared to oxidative muscle fibers, decreased vascularity, elevated inflammatory cell count, increased numbers of centrally nucleated fibers, and muscle fiber degeneration has been observed in muscle biopsies obtained from individuals with chronic lumbar spine pathology [8,9,10,11]

Summary

Introduction

Due to its unique arrangement, the deep and superficial fibers of the multifidus may have differential roles for maintaining spine stabilization and lumbar posture; the superficial multifidus is responsible for lumbar extension and the deep multifidus for intersegmental stability. In patients with chronic lumbar spine pathology, muscle activation patterns have been shown to be attenuated or delayed in the deep, but not superficial, multifidus This has been interpreted as pain differentially influencing the deep region. As the multifidus muscle is considered to be a key stabilizer of the lumbar spine [6] – due to its ability to produce high forces over a narrow range of lengths – degenerative changes to the composition and thereby function of this muscle are thought to have profound effects on degenerative lumbar spine disease. Improvements in muscle structure are rarely observed in response to most rehabilitation programs [15,16,17,18]

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