A morphological comparison of the human lumbar multifidus by chemical dissection

Five-Year Longitudinal Follow-Up of Restorative Neurostimulation Shows Durability of Effectiveness in Patients With Refractory Chronic Low Back Pain Associated With Multifidus Muscle Dysfunction

BACKGROUND

Adults with refractory, mechanical chronic low back pain associated with impaired neuromuscular control of the lumbar multifidus muscle have few treatment options that provide long-term clinical benefit. This study hypothesized that restorative neurostimulation, a rehabilitative treatment that activates the lumbar multifidus muscles to overcome underlying dysfunction, is safe and provides relevant and durable clinical benefit to patients with this specific etiology.

MATERIALS AND METHODS

In this prospective five-year longitudinal follow-up of the ReActiv8-B pivotal trial, participants (N = 204) had activity-limiting, moderate-to-severe, refractory, mechanical chronic low back pain, a positive prone instability test result indicating impaired multifidus muscle control, and no indications for spine surgery. Low back pain intensity (10-cm visual analog scale [VAS]), disability (Oswestry Disability Index), and quality of life (EuroQol's "EQ-5D-5L" index) were compared with baseline and following the intent-to-treat principle, with a supporting mixed-effects model for repeated measures that accounted for missing data.

RESULTS

At five years (n = 126), low back pain VAS had improved from 7.3 to 2.4 cm (-4.9; 95% CI, -5.3 to -4.5 cm; p < 0.0001), and 71.8% of participants had a reduction of ≥50%. The Oswestry Disability Index improved from 39.1 to 16.5 (-22.7; 95% CI, -25.4 to -20.8; p < 0.0001), and 61.1% of participants had reduction of ≥20 points. The EQ-5D-5L index improved from 0.585 to 0.807 (0.231; 95% CI, 0.195-0.267; p < 0.0001). Although the mixed-effects model attenuated completed-case results, conclusions and statistical significance were maintained. Of 52 subjects who were on opioids at baseline and had a five-year visit, 46% discontinued, and 23% decreased intake. The safety profile compared favorably with neurostimulator treatments for other types of back pain. No lead migrations were observed.

CONCLUSION

Over a five-year period, restorative neurostimulation provided clinically substantial and durable benefits with a favorable safety profile in patients with refractory chronic low back pain associated with multifidus muscle dysfunction.

CLINICAL TRIAL REGISTRATION

The Clinicaltrials.gov registration number for the study is NCT02577354; registration date: October 15, 2016; principal investigator: Christopher Gilligan, MD, Brigham and Women's Hospital, Boston, MA, USA. The study was conducted in Australia (Broadmeadow, New South Wales; Noosa Heads, Queensland; Welland, South Australia; Clayton, Victoria), Belgium (Sint-Niklaas; Wilrijk), The Netherlands (Rotterdam), UK (Leeds, London, Middlesbrough), and USA (La Jolla, CA; Santa Monica, CA; Aurora, CO; Carmel, IN; Indianapolis, IN; Kansas City, KS; Boston, MA; Royal Oak, MI; Durham, NC; Winston-Salem, NC; Cleveland, OH; Providence, RI; Spartanburg, SC; Spokane, WA; Charleston, WV).

Pictorial Essay on Ultrasound and Magnetic Resonance Imaging of Paraspinal Muscles for Myofascial Pain Syndrome

The paraspinal muscles of the cervical, thoracic, and lumbar spine are important pain generators because muscle strains or myofascial pain syndrome caused by trigger points are common during clinical practice. Ultrasonography is the most convenient imaging tool for evaluating these muscles due to its advantages, such as providing good delineation of soft tissues, easy accessibility, and zero radiation. Additionally, ultrasound can serve as a useful guiding tool for paraspinal muscle intervention to prevent inadvertent injuries to vital axial neurovascular structures. This pictorial essay presents ultrasound scanning protocols for the paraspinal and other associated muscles as well as a discussion of their clinical relevance. Axial magnetic resonance imaging has also been used to elucidate reciprocal anatomy. In conclusion, ultrasound imaging proves to be a valuable tool that facilitates the differentiation of individual paraspinal muscles. This capability significantly enhances the precision of interventions designed to address myofascial pain syndrome.

Fatty infiltration of the erector spinae at the upper lumbar spine could be a landmark for low back pain

PURPOSE

Intervertebral disc degeneration (IVDD), Modic changes, and fatty infiltration in the paraspinal muscles are possible causes of low back pain (LBP). Multifidus has been the most commonly blamed paraspinal muscle in the etiology of LBP. However, it contributes to 20% of the extensor moment on the lumbar spine. In the present study, we aimed to identify whether patients with LBP and asymptomatic subjects differed in terms of intervertebral discs, end-plates, and fatty infiltration in their paraspinal muscles.

METHODS

Consecutive women and men, who visited the spine outpatient clinics with chronic LBP and had lumbar spine MRI for their LBP without leg pain were included. Asymptomatic subjects without LBP/leg pain for the last year were recruited. Modic changes, IVDD, and fatty infiltration in the paraspinal muscles were evaluated on lumbar spine magnetic resonance imagings of the patients with LBP and age-, gender- and BMI-matched asymptomatic controls.

RESULTS

Low back pain was closely associated with fatty infiltration in the paraspinal muscles at all lumbar levels whereas it had association with severe IVDD and Modic changes at lower lumbar levels. Multifidus at the lower lumbar levels was the fattiest paraspinal muscle in both asymptomatic subjects and patients with LBP. Patients with LBP had severe fatty infiltration in the erector spinae at the upper lumbar levels.

CONCLUSION

Severe IVDD and Modic changes were more common at lower lumbar levels in patients with LBP. Both asymptomatic subjects and those with LBP had fatty multifidus at lower lumbar levels, whereas those with LBP had fatty infiltration in the erector spinae at upper lumbar levels. We suggest that fatty infiltration could have started in the multifidus. The erector spinae had greater contribution to the lumbar extension compared to the multifidus. Thus, LBP could develop when the quality of the erector spinae at the upper lumbar levels impairs due to fatty infiltration.

Understanding a mass in the paraspinal region: an anatomical approach

The paraspinal region encompasses all tissues around the spine. The regional anatomy is complex and includes the paraspinal muscles, spinal nerves, sympathetic chains, Batson's venous plexus and a rich arterial network. A wide variety of pathologies can occur in the paraspinal region, originating either from paraspinal soft tissues or the vertebral column. The most common paraspinal benign neoplasms include lipomas, fibroblastic tumours and benign peripheral nerve sheath tumours. Tumour-like masses such as haematomas, extramedullary haematopoiesis or abscesses should be considered in patients with suggestive medical histories. Malignant neoplasms are less frequent than benign processes and include liposarcomas and undifferentiated sarcomas. Secondary and primary spinal tumours may present as midline expansile soft tissue masses invading the adjacent paraspinal region. Knowledge of the anatomy of the paraspinal region is of major importance since it allows understanding of the complex locoregional tumour spread that can occur via many adipose corridors, haematogenous pathways and direct contact. Paraspinal tumours can extend into other anatomical regions, such as the retroperitoneum, pleura, posterior mediastinum, intercostal space or extradural neural axis compartment. Imaging plays a crucial role in formulating a hypothesis regarding the aetiology of the mass and tumour staging, which informs preoperative planning. Understanding the complex relationship between the different elements and the imaging features of common paraspinal masses is fundamental to achieving a correct diagnosis and adequate patient management. This review gives an overview of the anatomy of the paraspinal region and describes imaging features of the main tumours and tumour-like lesions that occur in the region.

Influence of Handgrip Strength and Paraspinal Muscles' Volume on Clinical Outcomes in the Patients With Each Sagittal Imbalance and Lumbar Spinal Stenosis

STUDY DESIGN

Cross-sectional study.

OBJECTIVE

To compare handgrip strength (HGS), paraspinal muscles' (PSM) volume, and their effects on clinical symptom severity between the patients with sagittal imbalance (SI) and symptomatic lumbar spinal stenosis (LSS).

METHODS

A total of 54 paired consecutive patients with SI and LSS were enrolled after propensity score matching. Preoperative HGS, cross-sectional area (CSA) of psoas (PS) and multifidus (MF) muscles, and patient-reported measures, including visual analog scale (VAS) for back/ leg pain, Oswestry Disability Index (ODI), and EuroQOL (EQ-5D) were compared between both groups. Within each SI and LSS group, patient-reported measures were compared between high and low HGS subgroups. The correlation of HGS and CSA of PSMs to patient-reported measures was evaluated.

RESULTS

There was no difference in HGS between 2 groups, however, the CSA of PS and MF muscles in SI group was significantly lower than those in LSS group. Patients with low HGS showed inferior results for ODI and EQ-5D, compared to those with high HGS subgroup in both SI and LSS groups. HGS and CSA of MF muscle were correlated with ODI in both groups.

CONCLUSIONS

There was no significant difference between the SI and LSS groups in HGS, however, PSMs' volume in SI group were significantly lower than those in LSS group. Therefore SI would be associated with loss of localized muscle mass in back area, rather than global skeletal muscle weakness. HGS and PSMs' volume were adversely associated with functional status in SI and LSS patients.

Facet overhang: A novel parameter in the pathophysiology of multifidus muscle atrophy

The relationship between degenerative zygapophysial joint (facet) arthropathy and multifidus muscle atrophy has not been rigorously evaluated. The purpose of this study was to determine if specific morphological features of degenerative facet arthropathy are correlated with multifidus muscle atrophy. We retrospectively reviewed medical records and imaging studies of patients with lumbar spinal stenosis. Facet overhang, bridging osteophyte formation, facet effusion, and facet angles were evaluated by univariable and multivariable regression to identify independent associations with deep and superficial parts of the multifidus total cross-sectional area (tCSA), functional cross-sectional area (fnCSA), and fatty infiltration (FI). Facet overhang was classified as severe in 50 females (53.2%) versus 56 males (36.9%) (p = 0.030). Severity of facet overhang and female sex were independently associated with smaller deep part of the multifidus tCSA and fnCSA as well as higher FI, reflecting greater atrophy of the deep region compared to total muscle mass. In comparison, severe facet overhang (p < 0.001; OR = 3.47, 95% CI = 2.13-5.66) and female sex (p < 0.001; OR = 4.19, 95% CI = 2.58-6.79) were independently associated only with higher superficial part of the multifidus FI, reflecting muscle steatosis without significant lean muscle atrophy. In patients with degenerative lumbar spinal stenosis, facet overhang is an independent risk factor for deep part of the multifidus atrophy. Bridging osteophyte formation, facet effusion, and facet angles were not independently associated with deep part of the multifidus atrophy.

Restorative Neurostimulation: A Clinical Guide for Therapy Adoption

In this review, we present a comprehensive clinical approach to restorative neurostimulation, a novel form of stimulation for refractory chronic mechanical low back pain, targeting impaired neuromuscular control and degeneration of the multifidus muscle. We focus on patient identification, technique guidance, and review of the scientific background and clinical evidence. As our understanding of back pain grows, there is clear evidence that impaired neuromuscular control and consequent degeneration of the multifidus muscle contribute to mechanical low back pain development and maintenance. We provide clinical guidance regarding an implantable restorative neurostimulation system that targets impaired neuromuscular control. Supported by results from a randomized, active-sham-controlled clinical trial with long-term follow-up, we provide clinicians with a comprehensive overview and practical clinical guidance for the adoption of this therapy modality.

Changes in Paraspinal Muscles and Facet Joints after Minimally Invasive Posterior Lumbar Interbody Fusion Using the Cortical Bone Trajectory Technique: A Prospective Study

In this prospective cohort study, we aimed to determine the surgical and adjacent segment changes in paraspinal muscles and facet joints in patients with lumbar spinal stenosis after minimally invasive posterior lumbar interbody fusion (PLIF) using the cortical bone trajectory (CBT) technique. We enrolled 30 consecutive patients who underwent the single-level CBT technique between October 2017 and October 2018. We evaluated preoperative and 1-month, 3-month, 6-month, and 1-year postoperative clinical data including Visual Analogue Scale (VAS) scores and Oswestry Disability Index (ODI). Magnetic resonance imaging (MRI) was performed a year after surgery. The erector spinae (ES) muscle area, volume, and fat infiltration (FI) on the surgical and adjacent segments were evaluated using the thresholding method, and the degree of adjacent facet joint degeneration was calculated using the Weishaupt scale. FI rate was graded using the Kjaer method. All patients underwent a 12-month follow-up. The VAS and ODI scores significantly improved after surgery in all patients. No patient showed degeneration of the adjacent facet joints (P > 0.05) during the 1-year follow-up postoperation. There was no significant difference in ES muscle volume, area, and FI on the surgical and adjacent segments (P > 0.05). The FI rate of the upper ES muscles increased postoperatively (P < 0.05); however, there were no significant changes in FI rate of the lower ES muscles. Patients with lumbar spinal stenosis could obtain satisfactory short-term clinical outcomes via minimally invasive PLIF using the CBT technique. Moreover, this technique may reduce the impact on the paravertebral muscles, especially the ES muscle, and the adjacent facet joints.

Increased Joint Mobility Is Associated With Impaired Transversus Abdominis Contraction

Mitchell, UH, Owen, PJ, Rantalainen, T, and Belavý, DL. Increased joint mobility is associated with impaired transversus abdominis contraction. J Strength Cond Res XX(X): 000-000, 2020-Increased joint mobility is a risk factor for joint injury, but muscle function may be able to compensate for it. Current evidence suggests reduced force production capacity in people with hypermobility. However, little is known about the lumbar spine. The purpose of this cross-sectional study was to assess whether there was a link between joint mobility and transverse abdominis and multifidus muscles contraction, muscles ascribed a core-stability role. Using a modified quantitative version of the Beighton scale (BOM score), we measured joint mobility of 30 middle-aged individuals without low back pain. These scores were correlated with magnetic resonance imaging-derived measures of transverse abdominis and multifidus muscle contraction during a spinal loading maneuver. The level of significance was set for p ≤ 0.05. The results showed greater joint mobility (a higher BOM score) correlated (r = 0.468; p = 0.009) with reduced transversus abdominis (TrA) shortening during contraction (i.e., less muscle shortening in people with greater joint mobility). The trunk subdomain score exhibited a correlation of 0.354 with TrA length change, but this did not reach statistical significance (p = 0.055). The subdomains of the BOM score did not correlate significantly with each other (p ≥ 0.097). No association was seen between multifidus contraction and joint mobility. The results suggest that greater general joint mobility is associated with impaired contraction of the TrA muscle. This should be considered when coaching athletes or treating patients with (functional) spinal instability. The quantitative approach we developed to measure joint mobility could be used in the future studies of global flexibility.

Inconsistent descriptions of lumbar multifidus morphology: A scoping review

Background

Lumbar multifidus (LM) is regarded as the major stabilizing muscle of the spine. The effects of exercise therapy in low back pain (LBP) are attributed to this muscle. A current literature review is warranted, however, given the complexity of LM morphology and the inconsistency of anatomical descriptions in the literature.

Methods

Scoping review of studies on LM morphology including major anatomy atlases. All relevant studies were searched in PubMed (Medline) and EMBASE until June 2019. Anatomy atlases were retrieved from multiple university libraries and online. All studies and atlases were screened for the following LM parameters: location, imaging methods, spine levels, muscle trajectory, muscle thickness, cross-sectional area, and diameter. The quality of the studies and atlases was also assessed using a five-item evaluation system.

Results

In all, 303 studies and 19 anatomy atlases were included in this review. In most studies, LM morphology was determined by MRI, ultrasound imaging, or drawings – particularly for levels L4–S1. In 153 studies, LM is described as a superficial muscle only, in 72 studies as a deep muscle only, and in 35 studies as both superficial and deep. Anatomy atlases predominantly depict LM as a deep muscle covered by the erector spinae and thoracolumbar fascia. About 42% of the studies had high quality scores, with 39% having moderate scores and 19% having low scores. The quality of figures in anatomy atlases was ranked as high in one atlas, moderate in 15 atlases, and low in 3 atlases.

Discussion

Anatomical studies of LM exhibit inconsistent findings, describing its location as superficial (50%), deep (25%), or both (12%). This is in sharp contrast to anatomy atlases, which depict LM predominantly as deep muscle. Within the limitations of the self-developed quality-assessment tool, high-quality scores were identified in a majority of studies (42%), but in only one anatomy atlas.

Conclusions

We identified a lack of standardization in the depiction and description of LM morphology. This could affect the precise understanding of its role in background and therapy in LBP patients. Standardization of research methodology on LM morphology is recommended. Anatomy atlases should be updated on LM morphology.

Balance Control in Patients with Subacute Non-Specific Low Back Pain, with and without Lumbar Instability: A Cross-Sectional Study

BACKGROUND

Patients with low back pain (LBP) have poorly coordinated neuromuscular control, which may alter the normal postural stability of the spine. Altered movement control may occur at any stage of LBP.

PURPOSE

(1) To identify differences in balance control and proprioceptive sense between subacute non-specific LBP (NSLBP) patients with and without lumbar instability (LI) and healthy subjects and (2) to investigate the correlation between factors of motor control deficits and balance.

PATIENTS AND METHODS

Thirty-six participants matched by gender, age, and body mass index (BMI) were allocated into three groups of 12: subacute NSLBP patients with LI, subacute NSLBP patients without LI, and healthy subjects. Balance, proprioceptive sense, pain, functional disability, and fear of movement were evaluated.

RESULTS

Subacute NSLBP patients with LI exhibited greater impairments in balance control, proprioceptive sense, and functional ability than patients without LI (p<0.05). Subacute NSLBP patients showed more impairments in balance control, proprioceptive sense, and fear of movement than healthy subjects (p<0.001), with the following effect sizes (partial η2) for static balance on stable and unstable surface: 0.597 and 0.560, anticipatory balance: 0.417, and dynamic balance: 0.536; proprioceptive sense: 0.676; and fear of movement: 0.379. Significant fair correlations were found between (1) static balance and proprioceptive sense, functional disability, and fear of movement; (2) functional reach test (FRT) and pain; and (3) the five times sit to stand test (FTSTS) and functional disability.

CONCLUSION

Subacute NSLBP patients with LI showed greater impairment in balance control than patients without LI. Reduced proprioceptive sense, increased pain, functional disability, and fear of movement were fairly related to impaired balance.

Association between back muscle degeneration and spinal-pelvic parameters in patients with degenerative spinal kyphosis

Background

The paraspinal and psoas muscles have been considered to be essentially important for stabilizing the spinal column, and the muscle degeneration was found to exist in degenerative spinal kyphosis (DSK) patients. However, it is still not clear the relationship between muscle degeneration and spinal-pelvic alignment. The purpose of this study was to determine the correlations between the individual muscle degeneration at each lumbar spinal level and spinal-pelvic parameters in DSK patients.

Methods

The imaging data of 32 patients with DSK were retrospectively analyzed. The fat infiltration (FI) and relative cross-sectional area of muscle (RCSA) were quantitatively measured for multifidus (MF), erector spinae (ES) and psoas (PS) at each spinal level from L1/2 to L5/S1. The correlations were analyzed between RCSA and the sagittal vertical axis (SVA), thoracic kyphosis (TK), thoracolumbar kyphosis (TLK), lumbar lordosis (LL), sacral slope (SS), pelvic tilt (PT) and pelvic incidence (PI).

Results

The FI of MF and ES at L3/4, L4/5 and L5/S1 were higher than that at L1/2 and L2/3. The FI of PS at L4/5 and L5/S1 were lower than that of L1/2, L2/3 and L3/4. The RCSA of ES and PS from L1/2 to L5/S1 gradually increased, whereas the RCSA of ES from L1/2 to S5/S1 gradually decreased. The RCSA of MF at the L1/2 level was negatively correlated SVA (r = − 0.397,p = 0.024); the RCSA at L3/4, L4/5 and L5/S1 levels were negatively correlated with TK (r = − 0.364, p = 0.04; r = − 0.38, p = 0.032; r = − 0.432, p = 0.014); the RCSA at L4/5 level was positively correlated with LL (r = 0.528, p = 0.002). The RCSA of ES at L3/4 and L4/5 levels were positively correlated with PI (r = 0.377, p = 0.037) and SS (r = 0.420, p = 0.019).

Conclusions

FI of MF and ES at lower lumbar level is higher than that at upper level, but FI of PS at upper lumbar level is higher than that at lower level. MF and ES have different roles for maintaining the sagittal spinal-pelvic balance.

Transversus abdominis and multifidus asymmetry in runners measured by MRI: a cross-sectional study

Objective

The transversus abdominis muscle (TrA) is active during running as a secondary respiratory muscle and acts, together with the multifidus, as trunk stabiliser. The purpose of this study was to determine size and symmetry of TrA and multifidus muscles at rest and with contraction in endurance runners without low back pain.

Design

Cross-sectional study.

Setting

A medical imaging centre in Melbourne, Australia.

Participants

Thirty middle-aged (43years±7) endurance-trained male (n=18) and female (n=12) runners without current or history of low back pain.

Outcome measures

MRI at rest and with the core engaged. The TrA and multifidus muscles were measured for thickness and length (TrA) and anteroposterior and mediolateral thickness (multifidus). Muscle activation was extrapolated from rest to contraction and compared with the same and contralateral side. Paired t-tests were performed to compare sides and contraction status.

Results

Left and right TrA and multifidus demonstrated similar parameters at rest (p>0.05). However, with contraction, the right TrA and multifidus (in mediolateral direction) were 9.2% (p=0.038) and 42% (p<0.001) thicker, respectively, than their counterparts on the left. There was no TrA thickness side difference with contraction in left-handed participants (p=0.985). When stratified by sex, the contracted TrA on the right side remained 8.4% thicker, but it was no longer statistically significant (p=0.134). The side difference with contraction of the TrA became less with increasing training age.

Conclusions

Right-handed long-term runners without low back pain exhibit a greater right side core muscle activation when performing an isometric contraction. This activation preference diminishes with increasing training age.

Relationships between paraspinal muscle morphology and neurocompressive conditions of the lumbar spine: a systematic review with meta-analysis

Background

Individual study results have demonstrated unclear relationships between neurocompressive disorders and paraspinal muscle morphology. This systematic review aimed to synthesize current evidence regarding the relationship lumbar neurocompressive disorders may have with lumbar paraspinal muscle morphology.

Methods

Searches were conducted in seven databases from inception through October 2017. Observational studies with control or comparison groups comparing herniations, facet degeneration, or canal stenosis to changes in imaging or biopsy-identified lumbar paraspinal muscle morphology were included. Data extraction and risk of bias assessment were performed by review author pairs independent of one another. Morphological differences between individuals with and without neurocompressive disorders were compared qualitatively, and where possible, standardised mean differences were obtained.

Results

Twenty-eight studies were included. Lumbar multifidus fiber diameter was smaller on the side of and below herniation for type I [SMD: −0.40 (95% CI = −0.70, −0.09) and type II fibers [SMD: −0.38 (95% CI = −0.69, −0.06)] compared to the unaffected side. The distribution of type I fibers was greater on the herniation side [SMD: 0.43 (95% CI = 0.03, 0.82)]. Qualitatively, two studies assessing small angular fiber frequency and fiber type groupings demonstrated increases in these parameters below the herniation level. For diagnostic imaging meta-analyses, there were no consistent differences across the various assessment types for any paraspinal muscle groups when patients with herniation served as their own control. However, qualitative synthesis of between-group comparisons reported greater multifidus and erector spinae muscle atrophy or fat infiltration among patients with disc herniation and radiculopathy in four of six studies, and increased fatty infiltration in paraspinal muscles with higher grades of facet joint degeneration in four of five studies. Conflicting outcomes and variations in study methodology precluded a clear conclusion for canal stenosis.

Conclusions

Based on mixed levels of risk of bias data, in patients with chronic radiculopathy, disc herniation and severe facet degeneration were associated with altered paraspinal muscle morphology at or below the pathology level. As the variability of study quality and heterogeneous approaches utilized to assess muscle morphology challenged comparison across studies, we provide recommendations to promote uniform measurement techniques for future studies.

Trial registration

PROSPERO 2015: CRD42015012985

Electronic supplementary material

The online version of this article (10.1186/s12891-018-2266-5) contains supplementary material, which is available to authorized users.

Muscular changes after minimally invasive versus open spinal stabilization of thoracolumbar fractures: A literature review

PURPOSE

This review addressed the question of whether minimally invasive surgery after traumatic thoracolumbar spine fractures can reduce paraspinal muscle injury, limit changes in muscular structure and function, and lead to better functional outcome. Special emphasis was given to studies using imaging techniques or electromyography to evaluate the lumbar multifidus muscle structure and function.

METHODS

The authors searched the literature in the PubMed/Medline, EMBASE, by cross-referencing and additional hand search. Included were comparative studies between conventional open and minimally invasive or percutaneous surgical approaches. Twelve studies were included.

RESULTS AND CONCLUSIONS

The literature review supports the assumption that minimally invasive surgery preserves muscles for the early post-operative period, even though the level of evidence is still low. The correlation of changes in muscular structure to pain, strength, disability, and quality of life remains ambiguous and should be addressed in further studies with a focus on the surgical approach.

Trunk motor control deficits in acute and subacute low back pain are not associated with pain or fear of movement

BACKGROUND CONTEXT

A subgroup of patients with acute to subacute low back pain (LBP) presenting with trunk movement control deficits, pain provocation with segmental testing, and segmental hypermobility have been clinically identified as having movement coordination impairments (MCIs) of the trunk. It is hypothesized that these patients have proprioceptive, postural, and movement control impairments of the trunk associated with LBP. Although trunk control impairments have been identified in patients with chronic LBP, they have not been investigated in this subgroup or closer to symptom onset.

PURPOSE

The purpose of the study was to identify trunk motor control (postural control and movement precision) impairments in a subgroup of patients with acute to subacute LBP who have been clinically identified to have MCIs and determine association of these impairments with pain and fear of movement.

STUDY DESIGN/SETTING

The study design includes observational design, university biomechanics laboratory, and clinical practice.

PATIENT SAMPLE

Thirty-three patients with acute to subacute LBP presenting with trunk MCIs and 33 healthy controls matched with gender, age, and body mass index were identified.

OUTCOME MEASURES

Self-report measures included Numeric Pain Rating Scale, Oswestry Disability Index Questionnaire, and Fear-Avoidance Beliefs Questionnaire and physiologic measures included postural control and movement precision.

METHODS

Center-of-pressure movement was measured while subjects attempted to volitionally control trunk posture and movement while sitting on a platform with a hemisphere mounted underneath. This created an unstable surface that required coordinated trunk control to maintain an upright seated posture. Postural control was tested using eyes-open and -closed balance protocols. Movement precision was tested with a dynamic control test requiring movement of the center of pressure along a discrete path. Group trunk motor control performance was compared with analysis of variance and t test. Performance association with pain and fear of movement were assessed with Pearson correlations.

RESULTS

Patients' postural control in the eyes-closed condition (p=.02) and movement precision (p=.04) were significantly impaired compared with healthy controls, with moderate-to-large group difference effect sizes. These trunk motor control impairments were not significantly associated with the patients self-reported pain characteristics and fear of movement.

CONCLUSIONS

Patients with clinical identification of trunk MCIs demonstrated decreased trunk motor control, suggesting that impairments in proprioception, motor output, or central processing occur early in the back pain episode. This information may help to guide interventions to address these specific limitations, improving delivery of care.

Inter-session reliability of the measurement of the deep and superficial layer of lumbar multifidus in young asymptomatic people and patients with low back pain using ultrasonography

STUDY DESIGN

Reliability study.

OBJECTIVE

To investigate the inter-session reliability of measuring the thickness of deep (dMF) and superficial layer of lumbar multifidus (sMF) using ultrasonography for participants with and without low back pain (LBP).

BACKGROUND

The lumbar multifidus is an important muscle in maintaining spinal stability. The dMF is considered important in maintaining tonic contraction and joint stability. Motor control impairment is also discovered in patients with LBP. However, no study to date has investigated the method of observing both the sMF and dMF through ultrasound imaging (USI).

METHODS

Twenty subjects aged 18-35 years old with LBP (N=10) and without LBP (N=10) were recruited. Every subject extended the upper trunk in prone lying with maximal isometric contraction. Simultaneously, the examiner measured the thickness of the dMF and the sMF using ultrasonography after ensuring the muscle belly was located. The participants performed three trials of isometric trunk extension in each session, with 30 min between each session. The reliability of measuring the change of thickness is represented by the intra-class correlation coefficient (ICC).

RESULTS

Through averaging three trials of measurement, the reliability of measuring the thickness of the dMF or the sMF in static or in the contracted condition, and the change of the thickness during contraction, is reliable (ICC=0.84-1.00).

CONCLUSIONS

The intra-rater inter-session reliability of measurement of the dMF and the sMF with USI has been established. This method could be applied to the qualification of the activation level of the dMF and the sMF with specific tasks.

Asymmetric degeneration of paravertebral muscles in patients with degenerative lumbar scoliosis

STUDY DESIGN

A prospective observational study.

OBJECTIVE

To evaluate the paravertebral muscle (PVM) degeneration in patients with degenerative lumbar scoliosis (DLS), using magnetic resonance imaging.

SUMMARY OF BACKGROUND DATA

Several studies have described the histological and morphological changes to the PVM in patients with chronic low back pain and lumbar radiculopathy. However, there is little knowledge about the PVM changes in patients with DLS.

METHODS

Fifty-seven patients with lumbar spinal stenosis (LSS) with DLS (DLS group) and 50 control patients with LSS without DLS (LSS group) were examined. The cross-sectional area (CSA) and percentage of fat infiltration area (%FIA) of the bilateral multifidus and longissimus muscles at the L1-S1 levels were measured using T2-weighted axial magnetic resonance imaging and computer software. A multifidus muscle biopsy and histological evaluation were performed in some patients.

RESULTS

In the DLS group, the CSA of the multifidus muscle was significantly smaller and the %FIA of both muscles was significantly higher on the concave side than on the convex side at all levels (P < 0.0001 for each). These differences were also found in the longissimus muscles at the L4-L5 and L5-S1 levels (P < 0.0001 for each). Histologically, the multifidus muscle exhibited reductions in the muscle fiber size and number of nuclei on the concave side. In the LSS group, the total CSA and %FIA did not differ significantly between the left and right sides. However, in patients with unilateral radiculopathy, the CSA of the multifidus muscle was significantly smaller (P < 0.05) and the %FIA of both muscles was significantly higher (P < 0.05) on the symptomatic side, especially at 1 level below.

CONCLUSION

This observational study with magnetic resonance imaging and histology showed that muscle degeneration was more common on the concave side in patients with DLS. Radiculopathy and spinal deformity may contribute to the PVM degeneration.

Functional morphology of the thoracolumbar transversospinal muscles

STUDY DESIGN. A qualitative and semiquantitative study of the morphology of the human thoracolumbar transversospinal (TSP) muscles. OBJECTIVE. To further define the functional morphology of the thoracolumbar TSP muscles. SUMMARY OF BACKGROUND DATA. The TSP muscle group plays an important role in vertebral function but few studies have rigorously investigated their morphology throughout the thoracolumbar region and details on the location of motor endplates (MEPs) and fiber types are sparse. METHODS. Thoracolumbar TSP muscles were examined by microdissection in five cadavers (seven sides). MEPs were identified using acetylcholinesterase histochemistry in muscles between T5 and S4 unilaterally in two cadavers. The relative proportions of type I and type II skeletal muscle fibers were determined using immunohistochemistry on whole cross sections of every TSP muscle from one side of one cadaver (T5-S4). RESULTS.TSP morphology was homogeneous and consistent throughout the thoracolumbar region. Notable differences to standard descriptions included: (1) consistent attachments between muscles; (2) no discrete cleavage planes between muscles; and (3) attachment sites over the sacrum and to lumbar zygapophysial joints. Previously undescribed small muscles were found attaching to the medial sacrum. All TSP muscles were multipennate, with fibers arranged in parallel having one MEP per muscle fiber. Muscles were highly aerobic (mean proportion of type I fibers 89%), with the proportion of type I fibers decreasing caudally. A significantly greater proportion of type I fibers were found in the midthoracic compared to the low lumbar regions. CONCLUSION. The complex morphology of the TSP muscles indicates that they would be better classified as spinotransverse muscles. They are multipennate, highly aerobic, with fibers organized in parallel, an arrangement lending itself to "fine-tuning" of vertebral movements. Understanding their morphology has implications for investigation, treatment, motor control, and biomechanics.

Clinical, biomechanical, and physiological translational interpretations of human resting myofascial tone or tension

BACKGROUND

Myofascial tissues generate integrated webs and networks of passive and active tensional forces that provide stabilizing support and that control movement in the body. Passive [central nervous system (CNS)-independent] resting myofascial tension is present in the body and provides a low-level stabilizing component to help maintain balanced postures. This property was recently called "human resting myofascial tone" (HRMT). The HRMT model evolved from electromyography (EMG) research in the 1950s that showed lumbar muscles usually to be EMG-silent in relaxed gravity-neutral upright postures.

METHODS

Biomechanical, clinical, and physiological studies were reviewed to interpret the passive stiffness properties of HRMT that help to stabilize various relaxed functions such as quiet balanced standing. Biomechanical analyses and experimental studies of the lumbar multifidus were reviewed to interpret its passive stiffness properties. The lumbar multifidus was illustrated as the major core stabilizing muscle of the spine, serving an important passive biomechanical role in the body.

RESULTS

Research into muscle physiology suggests that passive resting tension (CNS-independent) is generated in sarcomeres by the molecular elasticity of low-level cycling cross-bridges between the actomyosin filaments. In turn, tension is complexly transmitted to intimately enveloping fascial matrix fibrils and other molecular elements in connective tissue, which, collectively, constitute the myofascial unit. Postural myofascial tonus varies with age and sex. Also, individuals in the population are proposed to vary in a polymorphism of postural HRMT. A few people are expected to have outlier degrees of innate postural hypotonicity or hypertonicity. Such biomechanical variations likely predispose to greater risk of related musculoskeletal disorders, a situation that deserves greater attention in clinical practice and research. Axial myofascial hypertonicity was hypothesized to predispose to ankylosing spondylitis. This often-progressive deforming condition of vertebrae and sacroiliac joints is characterized by stiffness features and particular localization of bony lesions at entheseal sites. Such unique features imply concentrations and transmissions of excessive force, leading to tissue micro-injury and maladaptive repair reactions.

CONCLUSIONS

The HRMT model is now expanded and translated for clinical relevance to therapists. Its passive role in helping to maintain balanced postures is supported by biomechanical principles of myofascial elasticity, tension, stress, stiffness, and tensegrity. Further research is needed to determine the molecular basis of HRMT in sarcomeres, the transmission of tension by the enveloping fascial elements, and the means by which the myofascia helps to maintain efficient passive postural balance in the body. Significant deficiencies or excesses of postural HRMT may predispose to symptomatic or pathologic musculoskeletal disorders whose mechanisms are currently unexplained.