There is a growing interest in muscle characteristics of the lumbar multifidus related to low back pain, but findings between studies are inconsistent. One of the issues explaining these conflicting findings might be the use of two-dimensional measures of cross-sectional area and thickness of the lumbar multifidus in most studies, which might be a suboptimal representation of the entire muscle volume. A three-dimensional volumetric assessment, combined with standardized imaging and processing measurement protocols, is highly recommended to quantify spinal muscle morphology. Three-dimensional freehand ultrasonography is a technique with large potential for daily clinical practice. It is achieved by combining conventional two-dimensional ultrasound with a motion-tracking system, recording the position and orientation of the ultrasound transducer during acquisition, resulting in a three-dimensional reconstruction. This study investigates intra- and interprocessor reliability for the quantification of muscle volume of the lumbar multifidus based on three-dimensional freehand ultrasound and its validity, in 31 patients with low back pain and 20 healthy subjects. Two processors manually segmented the lumbar multifidus on three-dimensional freehand ultrasound images using Stradwin software following a well-defined method. We assessed the concurrent validity of the measurement of multifidus muscle volume using three-dimensional freehand ultrasound compared with magnetic resonance imaging in 10 patients with low back pain. Processing reliability and agreement were determined using intraclass correlation coefficients, Bland-Altman plots, and calculation of the standard error of measurement and minimal detectable change, while validity was defined based on correlation analysis. The processing of three-dimensional freehand ultrasound images to measure lumbar multifidus volume was reliable. Good to excellent intraclass correlation coefficients were found for intraprocessor reliability. For interprocessor reliability, the intraclass correlation coefficients were moderate to good, emphasizing the importance of processing guidelines and training. A single processor analysis is preferred in clinical studies or when small differences in muscle volume are expected. The correlation between magnetic resonance imaging and three-dimensional freehand ultrasound measurements of lumbar multifidus volume was moderate to good but with a systematically smaller multifidus volume measured on three-dimensional freehand ultrasound. These results provide opportunities for both researchers and clinicians to reliably assess muscle structure using three-dimensional freehand ultrasound in patients with low back pain and to monitor changes related to pathology or interventions. To allow implementation in both research and clinical settings, guidelines on three-dimensional freehand ultrasound processing and training were provided.

UNASSIGNED: The lumbar multifidus (LMF), as a dynamic stabilizer of the lumbar spine, may play an important role in the prevention of overuse-related back complaints.
UNASSIGNED: LMF morphology is associated with trunk stability and differs between symptomatic and asymptomatic skiers.
UNASSIGNED: Cohort study.
UNASSIGNED: Level 3.
UNASSIGNED: A total of 85 youth skiers (28 females, mean age, 14.7 ± 0.7 years; 57 males, mean age, 14.9 ± 0.5 years) underwent anthropometric assessments, an estimation of biological maturation, a magnetic resonance imaging- and ultrasound-based examination of LMF morphology, and a biomechanical quantification of deadbug bridging stabilization performance. Athletes were categorized as symptomatic if they had registered at least 1 significant overuse-related back complaint episode in the 12 months before the main examination.
UNASSIGNED: Male skiers showed a greater LMF size (ie, anatomical cross-sectional area [ACSA]) than female skiers, except for vertebral body L5, where no difference was found (8.8 ± 1.8 cm2 vs 8.3 ± 1.4 cm2, P = 0.18). Conversely, female skiers displayed longer fascicles than male skiers (5.8 ± 0.8 cm vs 5.4 ± 0.8 cm, P = 0.03). Skiers aged under 16 years (U16) skiers had greater values for LMF size and fascicle length than U15 skiers. Maturity offset was associated with L5 LMF size (R2 = 0.060, P = 0.01), fascicle length (R2 = 0.038, P = 0.04), and muscle thickness (R2 = 0.064, P = 0.02). L5 LMF size was associated with trunk stability (R2 = 0.068, P = 0.01). Asymptomatic skiers showed on average a 12.8% greater value for L5 LMF size compared with symptomatic skiers (P = 0.04).
UNASSIGNED: There are sex- and age-related differences in LMF morphology in youth competitive alpine skiers. Moreover, the ACSA at the level of the lumbar vertebral body L5 undergoes changes during biological maturation, shows a small, but significant association with trunk stability, and differs between symptomatic and asymptomatic skiers with back complaints.
UNASSIGNED: The observed association of muscle structure (ie, L5 LMF ACSA) with functional aspects (ie, trunk stabilization capacity) and clinical representation (ie, overuse-related back complaints) further highlights the important role of the multifidus muscle for training and injury prevention in youth competitive alpine skiers around the growth spurt.

BACKGROUND: Since the contribution of the lumbar multifidus(LM) is not well understood in relation to non-specific low back pain(LBP), this may limit physiotherapists in choosing the most appropriate treatment strategy.
OBJECTIVE: This study aims to compare clinical characteristics, in terms of LM function and morphology, between subacute and chronic LBP patients from a large clinical practice cohort compared to healthy controls.
METHODS: Multicenter case control study.
METHODS: Subacute and chronic LBP patients and healthy controls between 18 and 65 years of age were included. Several clinical tests were performed: primary outcomes were the LM thickness from ultrasound measurements, trunk range of motion(ROM) from 3D kinematic tests, and median frequency and root mean square values of LM by electromyography measurements. The secondary outcomes Numeric Rating Scale for Pain(NRS) and the Oswestry Disability Index(ODI) were administered. Comparisons between groups were made with ANOVA, p-values<0.05, with Tukey\'s HSD post-hoc test were considered significant.
RESULTS: A total of 161 participants were included, 50 healthy controls, 59 chronic LBP patients, and 52 subacute LBP patients. Trunk ROM and LM thickness were significantly larger in healthy controls compared to all LBP patients(p < 0.01). A lower LM thickness was found between subacute and chronic LBP patients although not significant(p = 0.11-0.97). All between-group comparisons showed no statistically significant differences in electromyography outcomes (p = 0.10-0.32). NRS showed no significant differences between LBP subgroups(p = 0.21). Chronic LBP patients showed a significant higher ODI score compared to subacute LBP patients(p = 0.03).
CONCLUSIONS: Trunk ROM and LM thickness show differences between LBP patients and healthy controls.

OBJECTIVE: To evaluate Ultrasound Imaging (USI) reliability for measurement of lumbar multifidus (LMF) muscle thickness and cross sectional area (CSA) at rest and during contraction in patients with unilateral lumbar disc herniation.
METHODS: Laboratory.
METHODS: Reliability Study.
METHODS: Thirty patients, aged 25-50 years (37.55 ± 9.55), with unilateral L4-L5 lumbar disc herniation participated in this study.
METHODS: Thickness and CSA of LMF were measured using B-mode ultrasound by two raters in prone position.
RESULTS: Same day and multiple day inter-rater and same day intra-rater reliability showed good to excellent reliability (intraclass correlation coefficients ranged from 0.70 to 0.91). Also standard error of measurement and minimal detectable change for USI reliabilities ranged from 0.06 to 0.57 and 0.16 to 1.31, respectively.
CONCLUSIONS: Reliability of USI for measurements of LMF muscle thickness and CSA was high, and consistent with previous studies conducted on reliability of USI to measure LMF dimensions in other populations.

BACKGROUND: Little is known about the activity of the abdominal internal oblique (IO) and lumbar multifidus (LM) muscles relative to kinetic chain exercises performed in a standing position.
OBJECTIVE: The purpose of this study was to identify the activity of the IO and the LM muscles during weight-bearing exercises. The authors hypothesized that IO and LM muscle activity would vary with lower body positions during the kinetic chain exercises.
METHODS: Nineteen healthy, young, active subjects volunteered to participate. The electromyographic (EMG) activity (via surface EMG) of the abdominal external oblique (EO), IO, and LM muscles on both sides and the rectus femoris and semitendinosus muscles on the dominant side was determined during rhythmical lower body twisting exercise with three lower body positions: straight leg (SL), athletic position (AP), dynamic knee extension (DE) at two exercise speeds: 150 and 90 beats per min. These were reported as % maximum voluntary contraction. Mean EO, IO, and LM muscle activities were also compared with those of common core stability exercises.
RESULTS: IO EMG activity was significantly greater in SL than that of AP (p < 0.05). In contrast, LM EMG activity was significantly greater in the DE position than that of both SL and AP positions (p < 0.05).
CONCLUSIONS: IO muscle activity could be attenuated by the contraction of lower body extensor muscles during the standing position.
METHODS: Basic Laboratory Study, Level 3b.

Lumbar multifidus muscle (LM) activation deficit has been proposed as a potential underlying mechanism responsible for recurrence episode of low back pain (LBP). The quantification of voluntary LM activation can provide a better understanding of the role of muscle activation deficit in LBP. The objective of this technical report is to propose a new approach using neuromuscular electrical stimulation (NMES) in combination with the ultrasound imaging technique (USI) to investigate the ability of individual to voluntarily activate the LM. We recruited ten participants with a recurrent LBP (rLBP) and twelve participants with no history of LBP (NoLBP). Theoretically, the superimposition of NMES on the LM during maximum voluntary isometric contraction (MVIC) should activate all motor units available in the LM. The percentage of LM activation (%LM) can be calculated by the changes of LM thickness during MVIC, divided by the changes of LM thickness during the combination of MVIC and NMES. This %LM was used to compare between groups. The individuals with rLBP had significantly lower %LM (p < 0.05) compared with the NoLBP counterpart (%LM = 72.4 and 92.9, respectively). Results demonstrate that this new approach can potentially differentiate %LM among individuals with rLBP and NoLBP. This new approach can be potentially used to 1) determine the extent of LM activation deficit, 2) identify the existence of muscle activation deficit in the LM, and 3) objectively measure the effect of the intervention designed to address the LM activation deficit.

BACKGROUND: Paravertebral compartment syndrome occurring without trauma is quite rare. We report a case of compartment syndrome that occurred after spinal exercises.
METHODS: A 23-year-old Japanese rower developed severe back pain and was unable to move 1 day after performing exercises for the spinal muscles. Initial evaluation at a nearby hospital revealed hematuria and elevated creatine phosphokinase levels. He was transferred to our hospital, where magnetic resonance imaging revealed no hematoma but confirmed edema in the paravertebral muscles. The compartment pressure measurements were elevated bilaterally. Despite his pain being severe, his creatine phosphokinase levels were expected to peak and decline; his urine output was normal; and surgery was undesirable. Therefore, we opted for conservative management. The next day, the patient\'s compartment pressure diminished, and his pain levels decreased to 2/10. After 5 days, he was able to walk without medication.
CONCLUSIONS: We present a rare case of compartment syndrome of the paravertebral muscles with good resolution following conservative management. We hope our case findings will help avoid unnecessary surgery in cases of paravertebral compartment syndrome.

New trends in ultrasound imaging are focused on exploration of morphology and muscle quality. The main goal of the study was to evaluate the first-order descriptor and echostructure of lumbar multifidus at the L4 vertebral level in athletes with and without chronic lumbopelvic pain (CLPP). A case-control study was performed in 15 semiprofessional athletes with CLPP and 15 without (healthy athletes). Lumbar multifidus echointensity and echovariation were measured for muscle quality assessment. Echostructure was used to evaluate lumbar multifidus cross-sectional area (CSA) at resting and during muscle contraction, respective differences during both phases (CSADif.), activation patterns, and thoracolumbar fasciae morphology and thickness. Significant differences with a large effect size were observed in quantitative data from CLPP and healthy athletes for left lumbar multifidus CSADif. and thoracolumbar fasciae morphology. Categorical data showed statistically significant differences with a small-to-moderate effect size for lumbar multifidus activation pattern and thoracolumbar fasciae morphology. Athletes with CLPP showed a reduced CSA difference between lumbar multifidus contraction and at resting and higher disorganization of thoracolumbar fasciae morphology compared to healthy athletes. These findings suggest the importance of dynamic exploration of the lumbar region and connective tissue in sports performance and injury prevention.

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.
CONCLUSIONS: 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.

Various factors, including spinal deformities and trunk muscle atrophy, greatly affect the fall risk among older adults with lumbar spinal stenosis (LSS). However, the etiology of falls in older adults with degenerative LSS and trunk muscle atrophy is poorly understood. We investigated the association between trunk muscle atrophy and falls in older LSS patients. This retrospective study included 99 hospitalized older adults with LSS. Participants completed self-reported fall score questionnaires and were divided into the fall risk (n = 30) and non-fall risk (n = 69) groups. The patients\' low back pain visual analog scale score, Geriatric Depression Scale score, sagittal vertical axis, L4/5 lumbar multifidus cross-sectional area ratio (LMCSAR), and center of pressure (COP) values during quiet standing were evaluated. The fall risk group had a lower L4/5 LMCSAR (p = 0.002) and increased COP excursion (p = 0.034) than the non-fall risk group. No significant differences were observed in the other measured variables between the two groups. The L4/5 LMCSAR (p < 0.001) and COP (p = 0.024) were related to fall risk and may be useful in fall risk assessment in such populations. Strategies aimed at enhancing controlled lumbar segmental motion and improving trunk muscle stability or mass may decrease the fall risk in this cohort.