The reliability of paraspinal muscles composition measurements using routine spine MRI and their association with back function

Paraspinal muscle endurance and morphology (PMEM) score: a new method for prediction of postoperative mechanical complications after lumbar fusion

BACKGROUND CONTEXT

Although the relationships between paraspinal muscles and lumbar degenerative disorders have been acknowledged, paraspinal muscle evaluation has not been incorporated into clinical therapies.

PURPOSE

We aimed to establish a novel paraspinal muscle endurance and morphology (PMEM) score to better predict mechanical complications after lumbar fusion.

STUDY DESIGN

Prospective cohort study.

PATIENT SAMPLE

A total of 212 patients undergoing posterior lumbar interbody fusion with at least 1 year of follow-up were finally included.

OUTCOME MEASURES

Mechanical complications including screw loosening, pseudarthrosis and other complications like cage subsidence, and patient-reported outcomes were evaluated at last follow-up.

METHODS

The PMEM score comprised 1 functional muscular parameter (the performance time of the endurance test) and 2 imaging muscular parameters (relative functional cross-sectional area [rFCSA] of paraspinal extensor muscles [PEM] and psoas major [PS] on magnetic resonance imaging). The score was established based on a weighted scoring system created by rounding β regression coefficients to the nearest integer in univariate logistic regression. The diagnostic performance of the PMEM score was determined by binary logistic regression model and receiver operating characteristic (ROC) curve with the area under the curve (AUC). Additionally, pairwise comparisons of ROC curves were conducted to compare the diagnostic performance of the PMEM score with conventional methods based on a single muscular parameter. Moreover, differences of mechanical complications and patient-reported outcomes among the PMEM categories were analyzed using Chi-square test with Bonferroni correction.

RESULTS

The PMEM score, calculated by adding the scores for each parameter, ranges from 0 to 5 points. Patients with higher PMEM scores exhibited higher rates of mechanical complications (p<.001). Binary logistic regression revealed that the PMEM score was an independent factor of mechanical complications (p<.001, OR=2.002). Moreover, the AUC of the PMEM score (AUC=0.756) was significantly greater than those of the conventional methods including the endurance test (AUC=0.691, Z=2.036, p<.05), PEM rFCSA (AUC=.690, Z=2.016, p<.05) and PS rFCSA (AUC=0.640, Z=2.771, p<.01). In terms of the PMEM categories, a score of 0-1 was categorized as low-risk muscular state of mechanical complications; 2-3, as moderate; and 4-5, as high-risk state. Moving from the low-risk state to the high-risk state, there was a progressive increase in the rates of mechanical complications (13.8% vs. 32.1% vs. 72.7%; p<.001), and a decrease in the rates of clinically significant improvement of patient-reported outcomes (all p<.05).

CONCLUSIONS

The PMEM score might comprehensively evaluate paraspinal muscle degeneration and exhibit greater ability in predicting mechanical complications than the conventional evaluations after lumbar fusion. Surgeons might develop individualized treatment strategy tailored to different muscle degeneration statuses reflected by the PMEM score for decreasing the risk of mechanical complications.

Inter-software and inter-threshold reliability of quantitative paraspinal muscle segmentation

PURPOSE

Changes in the cross-sectional area (CSA) and functional cross-sectional area (FCSA) of the lumbar multifidus (MF) and erector spinae muscles (ES) are factors that can contribute to low back pain. For the assessment of muscle CSA and composition there are various software and threshold methods used for tissue segmentation in quantitative analysis. However, there is currently no gold standard for software as well as muscle segmentation. This study aims to analyze the measurement error between different image processing software and different threshold methods for muscle segmentation.

METHODS

Magnetic resonance images (MRI) of 60 patients were evaluated. Muscle CSA and FCSA measurements were acquired from axial T2-weighted MRI of the MF and ES at L4/L5 and L5/S1. CSA, FCSA, and FCSA/CSA ratio were measured independently by two observers. The MRI images were measured using two different software programs (ImageJ and Amira) and with two threshold methods (Circle/Overlap method) for each software to evaluate FCSA and FCSA/CSA ratio.

RESULTS

Inter-software comparisons revealed high inter-rater reliability. However, poor inter-rater reliability were obtained with different threshold methods. CSA, FCSA, and FCSA/CSA showed excellent inter-software agreement of 0.75-0.99 regardless of the threshold segmentation method. The inter-rater reliability between the two observers ranged between 0.75 and 0.99. Comparison of the two segmentation methods revealed agreement between 0.19 and 0.84. FCSA and FCSA/CSA measured via the Overlap method were significantly higher than those measured via the Circle method (P < 0.01).

CONCLUSION

The present study showed a high degree of reliability with very good agreement between the two software programs. However, study results based on different threshold methods should not be directly compared.

Factors associated with intervertebral cage subsidence in posterior lumbar fusion

BACKGROUND

The interbody fusion apparatus is a key component of the operation and plays a key role in the postoperative efficacy. Cage subsidence is one of the common complications after lumbar fusion and internal fixation. Clinical studies on the risk factors of cage subsidence are incomplete and inaccurate, especially paravertebral muscle atrophy and intervertebral bone fusion time.

METHODS

Among the patients who underwent PLIF surgery in our hospital from January 2016 to January 2019, 30 patients with cage subsidence and 30 patients without cage subsidence were randomly selected to be included in this study. The differences between the two groups were compared, and the relevant factors of cage subsidence were explored by single factor comparison and multiple logistic regression analysis.

RESULTS

Bone mineral density (T) of the subsidence group [(- 1.84 ± 1.81) g/cm2 vs (- 0.87 ± 1.63) g/cm2, P = 0.018] was significantly lower than that of the normal group. There were 4 patients with end plate injury in the subsidence group (P = 0.038). Preoperative end plate Modic changes [I/II/III, (7/2/2) vs (2/5/8), P = 0.043] were significantly different between the two groups. In the subsidence group, preoperative rCSA of psoas major muscle [(1.43 ± 0.40) vs (1.64 ± 0.41), P = 0.043], CSA of paravertebral muscle [(4530.25 ± 776.55) mm2 vs (4964.75 ± 888.48) mm2, P = 0.047], paravertebral muscle rCSA [(3.03 ± 0.72) vs (3.84 ± 0.73), P < 0.001] and paravertebral muscle rFCSA [(2.29 ± 0.60) vs (2.89 ± 0.66), P < 0.001] were significantly lower than those in normal group. In the subsidence group, the vertebral body area [(1547.81 ± 309.89) mm2 vs (1326.48 ± 297.21) mm2, P = 0.004], the height of the immediately corrected vertebral space [(2.86 ± 1.10) mm vs (1.65 ± 1.02) mm, P = 0.020], immediately SL corrective Angle [(5.81 + 4.71)° vs (3.24 + 3.57) °, P = 0.009), postoperative PI-LL [(11.69 + 6.99)° vs (6.66 + 9.62) °, P = 0.029] and intervertebral fusion time [(5.38 ± 1.85) months vs (4.30 ± 1.49) months, P = 0.023] were significantly higher than those in the normal group. Multivariate logistic regression analysis showed that the time of intervertebral fusion (OR = 1.158, P = 0.045), the height of immediate intervertebral space correction (OR = 1.438, P = 0.038), and the Angle of immediate SL correction (OR = 1.101, P = 0.019) were the risk factors for cage subsidence. Bone mineral density (OR = 0.544, P = 0.016) and preoperative paravertebral muscle rFCSA (OR = 0.525, P = 0.048) were protective factors.

CONCLUSION

Intervertebral fusion time, correctable height of intervertebral space, excessive Angle of immediate SL correction, bone mineral density and preoperative paravertebral muscle rFCSA are risk factors for cage subsidence after PLIF.

Spinal‑pelvic sagittal imbalance and paraspinal muscle degeneration in patients with degenerative lumbar spinal stenosis: A monocentric, prospective and observational study

Degenerative lumbar spinal stenosis (DLSS) is a condition in which the body is held in a poor posture for a long period of time, resulting in a change in the stress structure of the lumbar spine that causes degenerative changes in the muscles of the spine. The sagittal balance of the spine and pelvis and the degeneration of the paravertebral muscles have been the focus of recent research. To explore the relationship between paraspinal muscle degeneration and changes in spine-pelvic sagittal parameters in patients with DLSS, 95 patients with DLSS (experimental group) and 70 healthy volunteers (control group) hospitalized in the Ordos Central Hospital between January 2020 and January 2022 were included as study subjects. All patients underwent lumbar magnetic resonance imaging and spinal X-ray using uniform criteria. The correlation between paravertebral muscle parameters and sagittal-pelvic sagittal parameters in patients with DLSS was obtained from two imaging examinations, and the data were organized and grouped in order to explore the correlation between these parameters. There was no significant difference in the general data between the two groups (P>0.05). In the L4-5 DLSS patient group, the ratio of fat infiltration in the right erector spinae (ES) muscle was negatively correlated with thoracic kyphosis (TK) (r=-0.536; P<0.05) but not significantly in the left side. The relative cross-sectional area of the left multifidus muscle (MF RCSA) was positively correlated with TK (r=0.685; r=0.615; P<0.05) but not significantly in the right side. In the L5-S1DLSS patient group, the right MF RCSA and right ES RCSA were significantly positively correlated with TK (r=0.685; r=0.615; P<0.05) but not significant in the left side. Thus, paravertebral muscle parameters were correlated with spinal-pelvic sagittal parameters in patients with DLSS.

Paraspinal Muscle Degeneration as an Independent Risk for Loss of Local Alignment in Degenerative Lumbar Scoliosis Patients After Corrective Surgery

STUDY DESIGN

Retrospective study.

OBJECTIVES

To investigate the effect of paraspinal muscle degeneration on the maintenance of local and global alignment among degenerative lumbar scoliosis (DLS) patients after corrective surgery.

METHODS

98 DLS patients with a mean follow-up period of 38.3 months after corrective surgery were included. The T1 pelvic angle (TPA), lumbar lordosis (LL), pelvic incidence were measured preoperatively, immediate postoperatively and at last follow-up. All patients were divided into LL maintenance group (n = 21) and LL loss group (n = 77). For patients with well-aligned correction (immediate postoperative TPA ≤ 20°, n = 73), they were divided into TPA maintenance group (last follow-up TPA ≤ 20°) and TPA loss group (last follow-up TPA > 20°). The relative gross cross-sectional area (rGCSA) and fat infiltration (FI) of multifidus (MF) and erector spinae (ES), and the relative functional CSA (rFCSA) of psoas major (PS) were measured at L3, L4 and L5 on preoperative magnetic resonance imaging.

RESULTS

MF rGCSA were significantly smaller in LL loss group than in LL maintenance group. Both MF rGCSA and PS rFCSA were significantly smaller and MF FI was significantly higher in TPA loss group than in TPA maintenance group. Binary logistic regression revealed that the MF rGCSA was an independent factor of LL loss; Large immediate postoperative TPA was an independent risk factor of TPA loss, but not the parameters of paraspinal muscles.

CONCLUSION

The effect of paraspinal muscles in lower lumbar segments might be mainly focused on the maintenance of local alignment rather than the global alignment.

Psoas weakness following oblique lateral interbody fusion surgery: a prospective observational study with an isokinetic dynamometer

BACKGROUND CONTEXT

Although the surgical corridor used for oblique lateral interbody fusion (OLIF) protects the intrapsoas nerves by causing minimal compression, transient weakness remains the most commonly reported postoperative complication.

PURPOSE

Using a dynamometer to evaluate how the hip flexor strength changes following OLIF.

STUDY DESIGN/SETTING

A prospective observational study.

PATIENT SAMPLE

Forty-six patients who underwent single or multi-level OLIF for lumbar spondylolisthesis.

OUTCOME MEASURES

Isokinetic dynamometer values (peak torque, total work, average power), visual analogue scale (VAS) scores for leg pain, hypoesthesia, subjective weakness of the left hip flexor muscle, Oswestry disability index, body mass index, bone mineral density, radiologic findings of the psoas muscle (cross-sectional area, Hounsfield unit (HU), fat portion grade), and psoas retraction time.

METHODS

The isokinetic muscle strength of the hip flexor was measured five times (preoperatively and postoperatively at 2 days, 1 week, 1 month, and 3 months) for both legs. The peak torque was defined as the postoperative strength of the left hip flexor muscles, and was compared to the preoperative baseline value. The strength of the left and right hip flexor muscles were also compared at each time point. For logistic regression analysis, when the peak torque was below the median value, it was defined as lower peak torque.

RESULTS

Up to 1 week after surgery, the strength of the left hip flexor muscle decreased significantly (paired difference in peak torque was 22.6%, p<.001). In the results of multivariate logistic regression analysis, diabetes (odds ratio [OR]=8.43, p=.020) and the HU of the psoas muscle (OR=0.916, p=.034) were associated with lower peak torque 1 week after surgery. From 1 month after surgery, postoperative weakness of the psoas muscle was not significant. In the questionnaire survey, subjective left hip flexion weakness was reported in 8.5% (4/47) of patients 1 week after surgery, and it remained in only 2.1% (1/47) of patients after 3 months of operation. The frequency of left anterior thigh pain and hypoesthesia decreased from 85.1% (40/47) at 1 week to 2.1% (1/47) at 3 months after surgery. The mean VAS score for left anterior thigh or groin pain decreased significantly at 1 month after surgery (PO2D: 4.04±1.84, PO1M: 1.67±1.10, p<.001).

CONCLUSIONS

Dynamometer measurement showed that psoas strength declined significantly up to 1 week after OLIF surgery. Patients with diabetes or lower HU of the psoas muscle showed delayed recovery from postoperative weakness of the psoas muscle. However, the weakness was insignificant from 1 month after surgery. At 3 months after surgery, the other psoas-related problems (left anterior thigh pain and hypoesthesia) also disappeared.

Preoperative paraspinal and psoas major muscle atrophy and paraspinal muscle fatty degeneration as factors influencing the results of surgical treatment of lumbar disc disease

INTRODUCTION

There is a growing number of publications highlighting sarcopenia and myosteatosis as poor prognosic factors for treatment results in oncological patients. The decrease in the cross-sectional area (CSA) of the multifidus muscle and muscle steatosis is associated with lumbar disc herniation and low back/limb pain. Nevertheless, no studies have analyzed the influence of the above parameters on patient satisfaction, pain decrease and return to daily activities. The aim of the study was to verify whether decreased preoperative CSA of the paraspinal and psoas major muscles and their fatty degeneration (myosteatosis) may influence the outcome of surgical treatment of lumbar disc disease (LDD).

MATERIALS AND METHODS

One hundred and one patients with LDD undergoing open microdiscectomy were enrolled in the analysis. Relative cross-sectional areas (rCSA) of the paraspinal and psoas major muscles as well as their fatty degeneration were measured. Patients were assessed according to the validated Polish versions of the EURO EQ-5D, Core Outcome Measure Index (COMI), Oswestry Disability Index (ODI) and Visual Analog Scale (VAS) 1 and 6 months postoperatively. The association between the variables was calculated using Pearson r and Spearman rank correlation. The Kruskal-Wallis test was used to compare the results between the groups with different rCSA of paraspinal and psoas major muscles and a different degree of paraspinal muscle myosteatosis.

RESULTS

Fatty degeneration of the paraspinal muscles correlated with better outcomes 1 and 6 months postoperatively according to ODI (P = 0.003 and P = 0.027, respectively). Patients with higher rCSA of the paraspinal and psoas major muscles achieved better results on the EURO EQ-5D scale (P = 0.0289 and P = 0.0089, respectively). Higher rCSA of the paraspinal and psoas major muscles did not correlate with better outcomes measured using ODI, COMI and VAS scales (P ≥ 0.072).

CONCLUSION

The degree of fatty degeneration of the paraspinal muscles correlates with better outcomes 1 and 6 months after microdiscectomy.

Paraspinal muscle imaging measurements for common spinal disorders: review and consensus-based recommendations from the ISSLS degenerative spinal phenotypes group

PURPOSE

Paraspinal muscle imaging is of growing interest related to improved phenotyping, prognosis, and treatment of common spinal disorders. We reviewed issues related to paraspinal muscle imaging measurement that contribute to inconsistent findings between studies and impede understanding.

METHODS

Three key contributors to inconsistencies among studies of paraspinal muscle imaging measurements were reviewed: failure to consider possible mechanisms underlying changes in paraspinal muscles, lack of control of confounding factors, and variations in spinal muscle imaging modalities and measurement protocols. Recommendations are provided to address these issues to improve the quality and coherence of future research.

RESULTS

Possible pathophysiological responses of paraspinal muscle to various common spinal disorders in acute or chronic phases are often overlooked, yet have important implications for the timing, distribution, and nature of changes in paraspinal muscle. These considerations, as well as adjustment for possible confounding factors, such as sex, age, and physical activity must be considered when planning and interpreting paraspinal muscle measurements in studies of spinal conditions. Adoption of standardised imaging measurement protocols for paraspinal muscle morphology and composition, considering the strengths and limitations of various imaging modalities, is critically important to interpretation and synthesis of research.

CONCLUSION

Study designs that consider physiological and pathophysiological responses of muscle, adjust for possible confounding factors, and use common, standardised measures are needed to advance knowledge of the determinants of variations or changes in paraspinal muscle and their influence on spinal health.

Imaging Evaluation of Fat Infiltration in Paraspinal Muscles on MRI: A Systematic Review with a Focus on Methodology

Purpose

Numerous studies have applied a variety of methods to assess paraspinal muscle degeneration. However, the methodological differences in imaging evaluation may lead to imprecise or inconsistent results. This article aimed to provide a pragmatic summary review of the current imaging modalities, measurement protocols, and imaging parameters in the evaluation of paraspinal muscle fat infiltration (FI) in MRI studies.

Methods

Web of Science, EMBASE, and PubMed were searched from January 2005 to March 2020 to identify studies that examined the FI of paraspinal muscles on MRI among patients with lumbar degenerative diseases.

Results

Intramyocellular lipids measured by magnetic resonance spectroscopy and FI measured by chemical‐shift MRI were both correlated to low back pain and several degenerative lumbar diseases, whereas results on the relationship between FI and degenerative lumbar pathologies using conventional MRI were conflicting. Multi‐segment measurement of FI at the lesion segment and adjacent segments could be a prognostic indicator for lumbar surgery. Most studies adopted the center of the intervertebral disc or endplate as the level of slice to evaluate the FI. Compared with visual semiquantitative assessment, quantitative parameters appeared to be precise for eliminating individual or modality differences. It has been demonstrated that fat CSA/total CSA (based on area) and muscle–fat index (based on signal intensity) as quantitative FI parameters are associated with multiple lumbar diseases and clinical outcomes after surgery.

Conclusion

Having a good command of the methodology of paraspinal muscle FI on MRI was effective for diagnosis and prognosis in clinical practice.

Age-Related Changes in Concentric and Eccentric Isokinetic Peak Torque of the Trunk Muscles in Healthy Older Versus Younger Men

This study investigated age-related changes in trunk muscle function in healthy men and the moderating effect of physical activity. Twelve older (67.3 ± 6.0 years) and 12 younger (24.7 ± 3.1 years) men performed isokinetic trunk flexion and extension tests across a range of angular velocities (15°/s-180°/s) and contractile modes (concentric and eccentric). For concentric trunk extension, mixed-effects analysis of covariance revealed a significant interaction between Angular velocity × Age group (p = .026) controlling for physical activity. Follow-up univariate analysis of covariance revealed that the younger group produced significantly greater peak torque for all concentric extension conditions. Eccentric trunk strength was somewhat preserved in the older group. Age-related changes in trunk strength were independent of physical activity. The normal loss of trunk muscle strength in older age is muscle- and contractile-mode specific. These findings provide guidance for effective intervention strategies to offset adverse health outcomes related to trunk strength loss in older adults.

Impact of appendicular and trunk skeletal muscle mass and back extensor strength on sagittal spinal alignment in Japanese women without vertebral fracture

Objectives

Progressive and generalized loss of skeletal muscle mass (SMM) and strength are characteristics of sarcopenia. However, the impact of appendicular and trunk SMM and back extensor strength (BES) on spinal sagittal alignment remains unclear. Herein, we investigate the relationship between these factors and spinal sagittal alignment.

Methods

In total, 202 women without vertebral fractures (median age, 66.9 years; interquartile range, 61.4–71.9 years) were analyzed at an orthopedic outpatient clinic. Pelvic incidence (PI), lumbar lordosis (LL), sagittal vertical axis (SVA), and pelvic tilt (PT) were measured on whole spine radiographs. Body mass index (BMI), appendicular and trunk relative SMM index, and BES were also evaluated. These measurements were compared between spinal sagittal alignment groups using the Mann–Whitney U test. Finally, the factors contributing to abnormal alignment were analyzed using multiple logistic regression analysis.

Results

BES was significantly lower in all abnormal sagittal alignment groups, as defined by PI-LL (≥ 10°), SVA (≥4 cm), and PT (≥20°) (all P < 0.001). On multivariate analysis, BES was a contributing factor for abnormal PI-LL (P < 0.001), SVA (P = 0.001), and PT (P < 0.001). Conversely, a decrease in appendicular and trunk relative SMM index did not statistically affect abnormal spinal sagittal alignment.

Conclusions

BES was associated with changes in spinal sagittal alignment; however, SMM, which is often used for diagnosing sarcopenia, did not affect spinal sagittal alignment.

Age-related degeneration of the lumbar paravertebral muscles: Systematic review and three-level meta-regression

BACKGROUND

Morphological changes of the lumbar spine muscles are not well characterised with ageing. To further the understanding of age-related degeneration of the lumbar spine musculature, normative morphological changes that occur within the paravertebral muscles must first be established.

METHODS

A systematic review and meta-regressions were conducted adhering to PRISMA guidelines. Searches for published and unpublished data were completed in June 2019.

RESULTS

Searches returned 4781 articles. 34 articles were included in the quantitative analysis. Three-level meta-analyses showed age-related atrophy (r = -0.26; 95% CI: -0.33, -0.17) and fat infiltration (r = 0.39; 95% CI: 0.28, 0.50) in the lumbar paravertebral muscles. Degenerative changes were muscle-specific and men (r = -0.32; 95% CI: -0.61, 0.01) exhibited significantly greater muscle atrophy than women (r = -0.24; 95% CI: -0.47, 0.03). Imaging modality, specifically ultrasound, also influenced age-related muscle atrophy. Measurements taken across all lumbar levels revealed the greatest fat infiltration with ageing (r = 0.58, 95% CI: 0.35, 0.74). Moderators explained a large proportion of between-study variance in true effects for muscle atrophy (72.6%) and fat infiltration (79.8%) models.

CONCLUSIONS

Lumbar paravertebral muscles undergo age-related degeneration in healthy adults with muscle, lumbar level and sex-specific responses. Future studies should use high-resolution imaging modalities to quantify muscle atrophy and fat infiltration.

Long-term Impacts of Brace Treatment for Adolescent Idiopathic Scoliosis on Body Composition, Paraspinal Muscle Morphology, and Bone Mineral Density

STUDY DESIGN

A retrospective, long-term follow-up study.

OBJECTIVE

We aimed to investigate the long-term impacts of brace treatment for adolescent idiopathic scoliosis (AIS) on the musculoskeletal system.

SUMMARY OF BACKGROUND DATA

Although full-time brace treatment is the mainstay of conservative treatment for AIS, the restrictive nature of brace treatment for lumbosacral motion might negatively affect the musculoskeletal system.

METHODS

Of 319 patients treated nonoperatively for AIS, 80 patients completed clinical and imaging examinations. Body composition, including body fat mass, lean mass, fat percent, and muscle mass, was estimated via bioelectrical impedance analysis. Bone mineral density (BMD) was measured at the lumbar spine and left hip. In 73 patients, the measurement of cross-sectional area and fatty degeneration of paraspinal muscles at the superior endplate of L4 were performed using axial T2-weighted magnetic resonance imaging. Patients were divided into the full-time brace (FB; >13 hours per day) and nonfull-time brace (NFB; observation, part-time bracing, or drop out from FB within a year) groups.

RESULTS

There were 44 patients in the FB group and 36 in the NFB group. Patients in the FB group were significantly younger at the initial visit (12.7 ± 1.3 years) and older at the final follow-up (41.5 ± 5.6 years) than those in the NFB group (14.2 ± 3.2 and 37.4 ± 7.1 years, respectively; P < 0.01). The rate of patients engaging in mild or moderate sports activity in adulthood tended to be higher in the FB group (47.7%) than in the NFB group (25%) (P = 0.11). However, there were no significant differences in body composition, paraspinal muscle morphology, and BMD between the two groups both before and after adjusting for age.

CONCLUSION

Full-time brace wearing during adolescence did not have any negative impacts on the musculoskeletal system in adulthood. This information will be helpful for improving the compliance of full-time bracing.

LEVEL OF EVIDENCE

4.

Cross-sectional area of the paraspinal muscles and its association with muscle strength among fighter pilots: a 5-year follow-up

Background

A small cross sectional area (CSA) of the paraspinal muscles may be related to low back pain among military aviators but previous studies have mainly concentrated on spinal disc degeneration. Therefore, the primary aim of the study was to investigate the changes in muscle CSA and composition of the psoas and paraspinal muscles during a 5-year follow up among Finnish Air Force (FINAF) fighter pilots.

Methods

Study population consisted of 26 volunteered FINAF male fighter pilots (age: 20.6 (±0.6) at the baseline). The magnetic resonance imaging (MRI) examinations were collected at baseline and after 5 years of follow-up. CSA and composition of the paraspinal and psoas muscles were obtained at the levels of 3–4 and 4–5 lumbar spine. Maximal isometric strength tests were only performed on one occasion at baseline.

Results

The follow-up comparisons indicated that the mean CSA of the paraspinal muscles increased (p < 0.01) by 8% at L3–4 level and 7% at L4–5 level during the 5-year period. There was no change in muscle composition during the follow-up period. The paraspinal and psoas muscles’ CSA was positively related to overall maximal isometric strength at the baseline. However, there was no association between LBP and muscle composition or CSA.

Conclusions

The paraspinal muscles’ CSA increased among FINAF fighter pilots during the first 5 years of service. This might be explained by physically demanding work and regular physical activity. However, no associations between muscle composition or CSA and low back pain (LBP) experienced were observed after the five-year follow-up.

Ultrasonography of multifidus muscle morphology and function in ice hockey players with and without low back pain

OBJECTIVES

To examine the relationship between lumbar multifidus (LM) morphology, function, echo-intensity (EI) and body composition among a group of university level ice hockey players with and without low back pain (LBP).

DESIGN

Cross-sectional study.

SETTING

University Research Centre.

PARTICIPANTS

Thirty-two hockey players (18 females, 14 males) participated in this study.

MAIN OUTCOME MEASURES

Resting LM cross-sectional area (CSA) was assessed bilaterally at the L5 level in prone and standing using ultrasound imaging. The LM thickness at rest and during contraction was evaluated in addition to LM EI. Body composition measures were acquired using dual-energy X-ray absorptiometry (DEXA) and LBP history was acquired using a self-reported questionnaire.

RESULTS

LM muscle CSA was significantly associated with body composition measurements. LM EI was strongly associated with total % body fat and significantly greater in females. Resting LM muscle CSA and thickness (prone) was significantly smaller in players with LBP 4-weeks prior. LM side-to-side asymmetry (standing) was also significantly greater in players with LBP 3-months prior.

CONCLUSION

The results provide new insights with regards to LM morphology and activation in ice hockey players and revealed specific deficits in LM morphology in athletes with LBP. LM morphology was strongly associated with body composition measurements.

Lumbar muscle volume in postmenopausal women with osteoporotic compression fractures: quantitative measurement using MRI

OBJECTIVE

To investigate the relationship between paraspinal and psoas muscle volumes and acute osteoporotic or low-bone-mass compression fractures of the lumbar spine in postmenopausal women.

METHODS

Patient data were retrieved retrospectively for postmenopausal women with L-spine magnetic resonance imaging (MRI) and dual-energy X-ray absorptiometry showing osteoporosis/low bone mass. Group 1 comprised eight women aged 60-80 years with MRI showing a single acute compression fracture. The age-matched group 2a (N = 12) and younger group 2b (N = 12) comprised of women whose MRIs showed no fractures. Cross-sectional MRIs of the paraspinal and psoas muscles and intramuscular fat volume for each muscle group were measured. Operator repeatability and reproducibility were obtained.

RESULTS

Group 1 showed significantly smaller lean muscle volume for all muscle groups at L5/S1. Intramuscular fat volume was also smaller in most muscle groups in group 1, though only reaching statistical significance at variable muscle groups and levels. Measurements show both good intrarater repeatability and interrater reproducibility of lean muscle volume estimations (intraclass correlation coefficient (ICC), 0.999 for rater A and 0.997 for rater B; Cronbach's alpha 0.995) and intramuscular fat volume estimations (ICC, 0.995 for rater A and 0.982 for rater B; Cronbach's alpha was 0.981).

CONCLUSIONS

This study provides the first quantitative evidence that compression fractures in postmenopausal women with underlying osteoporosis/low bone mass are associated with less paraspinal and psoas muscle volumes. Further longitudinal studies with larger cohorts are needed to verify this relationship.

KEY POINTS

• The risk of osteoporotic compression fractures is higher in older women with smaller paraspinal muscle volume. • Older women show smaller paraspinal muscle volume and more intramuscular fat compared to younger controls.

Paraspinal muscle hypotrophy and chronic discogenic low back pain

Study aim: Low back pain is accompanied by deconditioning of trunk muscles due to pain limiting patients’ physical activity, but so far it has not been explained whether the changes in the structure of muscles are the cause of disc disease or its result. The aim of the study was to analyze the prevalence of segmental paraspinal muscle hypotrophy in patients with chronic low back pain and sciatica. Material and methods: The study involved magnetic resonance imaging (MRI) of 40 patients: 20 women and 20 men aged from 30 to 47, mean 39.51 ± 3.73 years, with single level disc extrusion at L4-L5. The entire cross-sectional area of the par­aspinal muscles, the adipose tissue area in the paraspinal muscles and the extensor muscle tissue area at the level of L4-L5 were measured and compared with the healthy L3-L4 level. T2-weighted axial slices were used to facilitate distinguishing between the muscle and the fat tissue. Results: Fat tissue ingrowth and paravertebral muscle tissue hypotrophy at the disc extrusion level were highly statistically significant (p < 0.001) compared to the healthy level. Conclusions: 1. Ingrowth of the adipose tissue into the muscle tissue occurs only at the level of disc extrusion. 2. It seems rea­sonable to introduce strengthening exercises after the resolution of pain in order to rebuild the muscles of the spine.

Reliability of histographic analysis for paraspinal muscle degeneration in patients with unilateral back pain using magnetic resonance imaging

BACKGROUND

Mixed use of T1- or T2-weighted magnetic resonance imaging (MRI) in histographic analysis has impeded cross-reference of studies on fatty degeneration of muscles in patients with back pain.

OBJECTIVE

The current study aimed to establish the measurement reliability of histographic analysis for normal and painful paraspinal muscles between T1- and T2-weighted MRI.

METHODS

T1- and T2-weighted MRI at the L4-5 level were performed in 31 patients with unilateral back pain. Two raters conducted the histographic analysis on 2 separate occasions. Multifidus, erector spinae, and psoas major muscles were assessed on both normal and painful sides.

RESULTS

Intra- and interrater reliability of the parameters were generally excellent for both T1- (intrarater: 0.83 ± 0.13 and interrater: 0.93 ± 0.08) and T2-weighted images (intrarater: 0.93 ± 0.12 and interrater: 0.92 ± 0.12). Histogram width was fair to good for both kinds of image. Intraclass correlation coefficients were similar between painful and normal sides.

CONCLUSIONS

The evidence that most histographic analysis parameters had excellent reliability for both T1- and T2-weighted images allows for cross-reference of the results between the two kinds of image. Moreover, the results of this study support the availability of histographic analysis for assessment of fatty degeneration in patients with back pain.

Lumbar muscle structure and function in chronic versus recurrent low back pain: a cross-sectional study

BACKGROUND CONTEXT

Heterogeneity exists within the low back pain (LBP) population. Some patients recover after every pain episode, whereas others suffer daily from LBP complaints. Until now, studies rarely make a distinction between recurrent low back pain (RLBP) and chronic low back pain (CLBP), although both are characterized by a different clinical picture. Clinical experiences also indicate that heterogeneity exists within the CLBP population. Muscle degeneration, like atrophy, fat infiltration, alterations in muscle fiber type, and altered muscle activity, compromises proper biomechanics and motion of the spinal units in LBP patients. The amount of alterations in muscle structure and muscle function of the paraspinal muscles might be related to the recurrence or chronicity of LBP.

PURPOSE

The aim of this experimental study is to evaluate differences in muscle structure (cross-sectional area and lean muscle fat index) and muscle activity of the multifidus (MF) and erector spinae (ES) during trunk extension, in patients with RLBP, non-continuous CLBP, and continuous CLBP.

STUDY DESIGN AND SETTING

This cross-sectional study took place in the university hospital of Ghent, Belgium. Muscle structure characteristics and muscle activity were assessed by magnetic resonance imaging (MRI).

PATIENT SAMPLE

Fifty-five adults with non-specific LBP (24 RLBP in remission, 15 non-continuous CLBP, 16 continuous CLBP) participated in this study.

OUTCOME MEASURES

Total cross-sectional area, muscle cross-sectional area, fat cross-sectional area, lean muscle fat index, T2-rest and T2-shift were assessed.

METHODS

A T1-weighted Dixon MRI scan was used to evaluate spinal muscle cross-sectional area and fat infiltration in the lumbar MF and ES. Muscle functional MRI was used to evaluate the muscle activity of the lumbar MF and ES during a lumbar extension exercise. Before and after the exercise, a pain assessment was performed. This study was supported by grants from the Special Research Fund of Ghent University (DEF12/AOP/022) without potential conflict of interest-associated biases in the text of the paper.

RESULTS

Fat cross-sectional area and lean muscle fat index were significantly higher in MF and ES in continuous CLBP compared with non-continuous CLBP and RLBP (p<.05). No differencesbetween groups were found for total cross-sectional area and muscle cross-sectional area in MF or ES (p>.05). Also, no significant differences between groups for T2-rest were established. T2-shift, however, was significantly lower in MF and ES in RLBP compared with, respectively, non-continuous CLBP and continuous CLBP (p<.05).

CONCLUSIONS

These results indicate a higher amount of fat infiltration in the lumbar muscles, in the absence of clear atrophy, in continuous CLBP compared with RLBP. A lower metabolic activity of the lumbar muscles was seen in RLBP replicating a relative lower intensity in contractions performed by the lumbar muscles in RLBP compared with non-continuous and continuous CLBP. In conclusion, RLBP differs from continuous CLBP for both muscle structure and muscle function, whereas non-continuous CLBP seems comparable with RLBP for lumbar muscle structure and with continuous CLBP for lumbar muscle function. These results underline the differences in muscle structure and muscle function between different LBP populations.

Does lumbar paraspinal muscles improve after corrective fusion surgery in degenerative flat black?

BACKGROUND

Degenerative flat back (DFB) is characterized by sagittal imbalance resulting from the loss of lumbar lordosis (LL). Extensive degeneration and weakness of lumbar paraspinal extensor muscle (PSE) are thought to be the main cause of DFB. This study is to evaluate correlation between preoperative PSE conditions and angular severity of DFB and to evaluate correlation between preoperative PSE conditions and degree of improvement of DFB obtained by corrective surgery.

MATERIALS AND METHODS

Forty five patients with DFB who took magnetic resonance image (MRI) preoperatively and conducted simple radiography and three-dimensional gait analysis before and 6 months after corrective surgery were included. To determine the severity of PSE atrophy, the ratio between cross-sectional area of PSE and disc was calculated from L1-L2 to L4-L5 on MRI. To assess the degree of fat infiltration, the signal intensity of PSE was measured. Static parameters of spinopelvic segment were measured by simple radiography. Dynamic parameters of spinopelvic and lower limb joints were obtained by three-dimensional gait analysis.

RESULTS

In static parameters, thoracic angle was correlated with atrophy and fat infiltration of upper PSE. Thoracic angle was less improved after surgery, as atrophy of upper PSE was more severe. In dynamic parameters, thoracic angle showed correlation with upper PSE conditions, whereas lumbar angle had correlation with middle to lower PSE conditions. While thoracic kyphosis was less improved after surgery, as atrophy of upper PSE was more severe, LL was less improved, as atrophy and fat infiltration of PSE from L1-L2 to L4-L5 were more severe.

CONCLUSIONS

Severity of atrophy or fat infiltration of PSE showed correlation with degree of angular deformity in patients with DFB and with less improvement after corrective surgery. Dynamic parameters showed more prominent correlation with PSE conditions than static parameters and also showed segmental specificity between PSE and angular deformity.

Paraspinal muscle, facet joint, and disc problems: risk factors for adjacent segment degeneration after lumbar fusion

BACKGROUND CONTEXT

Adjacent segment degeneration (ASD) is one of the major complications after lumbar fusion. Several studies have evaluated the risk factors of ASD. Although the paraspinal muscles play an important role in spine stability, no study has assessed the relationship between paraspinal muscle atrophy and the incidence of ASD after lumbar fusion.

PURPOSE

In the present study, we aimed to verify the known risk factors of ASD, such as body mass index (BMI), preoperative adjacent facet joint degeneration, and disc degeneration, and to assess the relationship between paraspinal muscle atrophy and ASD.

STUDY DESIGN

This is a retrospective 1:1 pair analysis matched by age, sex, fusion level, and follow-up period.

PATIENT SAMPLE

To calculate the appropriate sample size for the study, we performed a pre-study analysis of the paraspinal muscle cross-sectional area (CSA), and estimated that at least 35 cases would be needed for each group. Among the 510 patients who underwent posterior lumbar fusion for degenerative lumbar disease between January 2009 and October 2009, a total of 50 patients with ASD after surgery were selected. Another group of 50 matched patients with degenerative lumbar disease without ASD after spinal fusion were selected as the control group. Each patient in the ASD group was matched with a control patient according to age, sex, fusion level, and follow-up period.

OUTCOME MEASURES

Radiographic measurements and demographic data were reviewed.

METHODS

The risk factors considered were higher BMI, preoperative adjacent segment disc and facet degeneration, and preoperative paraspinal muscle atrophy and fatty degeneration. The radiographic data were compared between the ASD and control groups to determine the predictive factors of ASD after posterior lumbar fusion by using logistic regression analysis. The study was not externally funded. The authors have no conflict of interest to declare.

RESULTS

Multivariate logistic regression analysis indicated that higher BMI (odds ratio [OR]: 1.353, p=.008), preoperative facet degeneration on computed tomography examination (OR: 3.075, p=.011), disc degeneration on magnetic resonance imaging (MRI) (OR: 2.783, p=.003), fatty degeneration (OR: 1.080, p=.044), and a smaller relative CSA of the paraspinal muscle preoperatively (OR: 0.083, p=.003) were significant factors for predicting the development of ASD.

CONCLUSIONS

The occurrence of radiological ASD is most likely multifactorial, and is associated with a higher BMI, preexisting facet and disc degeneration on preoperative examination, and a smaller preoperative relative CSA of the paraspinal muscle on MRI.

Evaluation of intramyocellular and extramyocellular lipids in the paraspinal muscle in patients with chronic low back pain using MR spectroscopy: preliminary results

OBJECTIVE:

To analyze the intramyocellular lipids (IMCL) and extramyocellular lipids (EMCL) in the psoas muscle (Pm) and multifidus muscle (Mm) using MR spectroscopy (MRS) in patients with chronic low back pain (CLBP) and asymptomatic volunteers.

METHODS:

This prospective study had institutional review board approval, and written informed consent was obtained from all individual participants. 20 patients with CLBP (mean age, 49.8 ± 12.5 years; age range, 28-66 years) with low back pain (LBP) duration of ≥3 months and asymptomatic volunteers (mean age, 44.0 ± 12.8 years; age range, 28-65 years) underwent MRS for the quantification of IMCL and EMCL of the right Pm and Mm in a volume of interest at the intervertebral level of L4 through L5. We compared patients with CLBP and asymptomatic volunteers for age and body mass index (BMI), IMCL and EMCL of Pm and Mm. The Mann-Whitney U-test was used for significant difference testing, with p-value <0.05 indicating statistical significance.

RESULTS:

No statistically significant differences were observed in the age and BMI of patients with CLBP and asymptomatic volunteers. There was no statistically significant difference in the EMCL and IMCL in Pm between the two groups. EMCL in Mm was not statistically significantly different; the IMCL of patients with CLBP was significantly higher than that of asymptomatic volunteers (p < 0.05).

CONCLUSION:

MRS demonstrates that IMCL in the Mm of patients with CLBP is significantly higher than that of asymptomatic volunteers. The increase of IMCL in the Mm may be a characteristic finding in CLBP.

ADVANCES IN KNOWLEDGE:

We investigated the detail of the fat content in the paraspinal muscles in patients CLBP and asymptomatic volunteers. The increase of fat content in the Mm of patients with LBP on previous studies was demonstrated to be the increase of IMCL.

New Predictive Index for Lumbar Paraspinal Muscle Degeneration Associated With Aging

STUDY DESIGN

A cross-sectional imaging study of paraspinal muscle degeneration using a new index for easy evaluation.

OBJECTIVE

To examine the natural progression of age-related changes in the lumbar paraspinal muscles and to verify the validity of our new index for evaluating paraspinal muscle degenerationSUMMARY OF BACKGROUND DATA.: Measurement of paraspinal muscle morphology is an effective method for reflecting atrophy and fat infiltration, but it is complicated to perform. Therefore, we focused on the groove between lumbar paraspinal muscles as a simple index for evaluating paraspinal muscle degeneration.

METHODS

A total of 160 subjects aged 10 to 88 years (10 male and 10 female subjects in each decade) with lumbar lordosis of more than 20° were included. Body mass index (BMI) was calculated. Sagittal T2-weighted magnetic resonance imaging (MRI) was used to measure lumbar lordosis, while axial T2-weighted MRI was used to measure cross-sectional area (CSA) and fat infiltration rate of the paraspinal muscles at the intervertebral disc level from L1 to L5. To quantify the depth of the groove between the paraspinal muscles, our own image index (lumbar indentation value (LIV): equal to the length of the bulge of the muscle to the attachment of the spinous process), also was measured. We then determined the correlation between LIV and paraspinal muscle degeneration.

RESULTS

There were no significant differences in BMI and lumbar lordosis between age groups. CSA of the paraspinal muscles tended to decrease with age, and fat infiltration rate increased with age. There was a negative correlation between CSA and fat infiltration rate at all levels (r = -0.474 to -0.634). LIV decreased significantly with age and strongly correlated with CSA at all levels (r = 0.709-0.789).

CONCLUSION

Our new index is a simple and effective parameter for evaluating paraspinal muscle degeneration associated with aging.

LEVEL OF EVIDENCE

4.

Comparison of Multi-Echo Dixon Methods with Volume Interpolated Breath-Hold Gradient Echo Magnetic Resonance Imaging in Fat-Signal Fraction Quantification of Paravertebral Muscle

Objective

To assess whether multi-echo Dixon magnetic resonance (MR) imaging with simultaneous T2* estimation and correction yields more accurate fat-signal fraction (FF) measurement of the lumbar paravertebral muscles, in comparison with non-T2*-corrected two-echo Dixon or T2*-corrected three-echo Dixon, using the FF measurements from single-voxel MR spectroscopy as the reference standard.

Materials and Methods

Sixty patients with low back pain underwent MR imaging with a 1.5T scanner. FF mapping images automatically obtained using T2*-corrected Dixon technique with two (non-T2*-corrected), three, and six echoes, were compared with images from single-voxel MR spectroscopy at the paravertebral muscles on levels L4 through L5. FFs were measured directly by two radiologists, who independently drew the region of interest on the mapping images from the three sequences.

Results

A total of 117 spectroscopic measurements were performed either bilaterally (57 of 60 subjects) or unilaterally (3 of 60 subjects). The mean spectroscopic FF was 14.3 ± 11.7% (range, 1.9-63.7%). Interobserver agreement was excellent between the two radiologists. Lin's concordance correlation between the spectroscopic findings and all the imaging-based FFs were statistically significant (p < 0.001). FFs obtained from the T2*-corrected six-echo Dixon sequences showed a significantly better concordance with the spectroscopic data, with its concordance correlation coefficient being 0.99 and 0.98 (p < 0.001), as compared with two- or three-echo methods.

Conclusion

T2*-corrected six-echo Dixon sequence would be a better option than two- or three-echo methods for noninvasive quantification of lumbar muscle fat quantification.

Do Muscle Characteristics on Lumbar Spine Magnetic Resonance Imaging or Computed Tomography Predict Future Low Back Pain, Physical Function, or Performance? A Systematic Review

OBJECTIVE

To determine whether lumbar muscle characteristics on magnetic resonance imaging (MRI) or computed tomography (CT) can inform clinicians as to the course of future low back pain (LBP), functional limitations, or physical performance, in adults with or without LBP. TYPE: Systematic review.

LITERATURE REVIEW

We searched PubMed, Embase, and CINAHL through October 2014 for articles published in English in which authors assessed lumbar muscle characteristics on conventional MRI/CT as predictors of future LBP, functional limitations, or physical performance in adults. Studies with only postsurgical subjects were excluded. Our search identified 3554 articles, of which 6 observational cohort studies were included in the final review.

METHODOLOGY

We used the Newcastle Ottawa Scale to evaluate potential bias. Data were extracted on study design, study population, sample size, participant characteristics, details of MRI/CT assessments, interventions, study outcomes, analysis methods, and study results. Because of heterogeneity between studies, we conducted a qualitative evidence synthesis.

SYNTHESIS

Among high-quality studies, there was limited evidence that, for individuals with or without LBP, greater MRI-detected multifidus cross-sectional area at L5-S1 predicted greater LBP intensity at 1-year follow-up, lesser erector spinae fat infiltration (FI) at L5-S1 predicted greater LBP intensity at 15-year follow-up, and greater erector spinae side-to-side FI asymmetry at L3-L4 predicted lower LBP frequency at 15-year follow-up; however, there was also limited evidence that all other MRI-detected paraspinal muscle characteristics examined were not predictive of LBP incidence, prevalence, frequency, or intensity at follow-up durations ranging from 1 to 15 years. There was limited evidence that greater CT-detected trunk muscle FI predicted worse physical performance in older adults at 3-year follow-up, but that trunk muscle cross-sectional area did not.

CONCLUSION

Few lumbar muscle characteristics have limited evidence for an association with future LBP and physical performance outcomes, and the vast majority have limited evidence for having no association with such outcomes.

Kyphosis and paraspinal muscle composition in older men: a cross-sectional study for the Osteoporotic Fractures in Men (MrOS) research group

Background

The prevalence of hyperkyphosis is increased in older men; however, risk factors other than age and vertebral fractures are not well established. We previously reported that poor paraspinal muscle composition contributes to more severe kyphosis in a cohort of both older men and women.

Methods

To specifically evaluate this association in older men, we conducted a cross-sectional study to evaluate the association of paraspinal muscle composition and degree of thoracic kyphosis in an analytic cohort of 475 randomly selected participants from the Osteoporotic Fractures in Men (MrOS) study with baseline abdominal quantitative computed tomography (QCT) scans and plain thoracic radiographs. Baseline abdominal QCT scans were used to obtain abdominal body composition measurements of paraspinal muscle and adipose tissue distribution. Supine lateral spine radiographs were used to measure Cobb angle of kyphosis. We examined the linear association of muscle volume, fat volume and kyphosis using loess plots. Multivariate linear models were used to investigate the association between muscle and kyphosis using total muscle volume, as well as individual components of the total muscle volume, including adipose and muscle compartments alone, controlling for age, height, vertebral fractures, and total hip bone mineral density (BMD). We examined these associations among those with no prevalent vertebral fracture and those with BMI < 30 kg/m².

Results

Among men in the analytic cohort, means (SD) were 74 (SD = 5.9) years for age, and 37.5 (SD = 11.9) degrees for Cobb angle of kyphosis. Men in the lowest tertile of total paraspinal muscle volume had greater mean Cobb angle than men in the highest tertile, although test of linear trend across tertiles did not reach statistical significance. Neither lower paraspinal skeletal muscle volume (p-trend = 0.08), or IMAT (p-trend = 0.96) was associated with greater kyphosis. Results were similar among those with no prevalent vertebral fractures. However, among men with BMI < 30 kg/m², those in the lowest tertile of paraspinal muscle volume had greater adjusted mean kyphosis (40.0, 95% CI: 37.8 – 42.1) compared to the highest tertile (36.3, 95% CI: 34.2 – 38.4).

Conclusions

These results suggest that differences in body composition may potentially influence kyphosis.

Changes of paraspinal muscles in postmenopausal osteoporotic spinal compression fractures: magnetic resonance imaging study

Background

To investigate the changes of cross sectional area (CSA) in paraspinal muscles upon magnetic resonance imaging (MRI) and bone mineral density (BMD) in postmenopausal osteoporotic spinal compression fractures.

Methods

We reviewed 81 postmenopausal women with osteoporosis, who had underwent MRI examination. The patients were divided into 51 patients who had osteoporotic spinal compression fractures (group I), and 30 patients who without fractures (group II). Group I were subdivided into IA and IB, based on whether they were younger (IA) of older (IB) than 70 years of age. We additionally measured body mass index and BMD. The CSA of multifidus, erector spinae, paraspinal muscles, psoas major (PT), and intervertebral (IV) discs were measured. The degree of fatty atrophy was estimated using three grades.

Results

The BMD and T-score of group I were significantly lower than those of group II. The CSA of erector spinae, paraspinal muscles, and PT in the group I was significantly smaller than that of group II. The CSA of paraspinal muscles in group IB were significantly smaller than those of group IA. The CSA of erector spinae, mutifidus, and PT in group IB were smaller than those of group IA, but the difference was not statistically significant. Group 1 exhibited greater fat infiltration in the paraspinal muscle than group II.

Conclusions

Postmenopausal osteoporotic spinal compression fracture is associated with profound changes of the lumbar paraspinal muscle, reduction of CSA, increased CSA of IV disc, and increased intramuscular fat infiltration.

MRI features of the psoas major muscle in patients with low back pain

PURPOSE

The purpose was to investigate the changes of the psoas major muscles (PM) cross-sectional area (CSA) and fat infiltration in the PM and to investigate the association between the morphology of the PM and expression of the degenerative changes of lumbar spine in patients with low back pain (LBP).

METHODS

T2-weighted scans for measurements of the CSA and analysis of fat infiltration were performed on 42 patients and 49 controls using a 1.5 Tesla MR system. For a quantitative analysis of fat tissue infiltration a 4-grade visual scale was used.

RESULTS

Patients had bigger CSA of the PM than controls at the levels of L3/L4 and L4/L5 intervertebral disc (P < 0.05). Patients with apparent degenerative changes of the lumbar spine had smaller CSA of the PM compared to the patients without apparent changes at the levels of L3/L4 and L4/L5 (P < 0.05). At the levels of L4/L5 and L5/S1 patients with present Modic changes in the lumbar vertebral bodies showed smaller CSA of the PM compared to the patients without Modic changes (P < 0.05). However, CSA of the PM in the patients with degenerative changes of lumbar spine and Modic changes was still bigger than the one of the controls. At all analyzed levels correlation between CSAs of the PM and fat infiltration of the lumbar paraspinal muscles was negative.

CONCLUSION

Results suggest increased activity of the PM in LBP patients but PM also remains active regardless of the presence of degenerative and Modic changes of the lumbar spine.

Correlative analysis of MRI-evident abductor hip muscle degeneration and power after minimally invasive versus conventional unilateral cementless THA

The 2 main null hypotheses of this study were: (1) the 4-year surgical trauma-related degeneration within the hip abductor muscles after a minimally invasive approach to total hip arthroplasty would be similar to that following a conventional approach; and (2) no differences in perioperative blood loss or postoperative hip pain would be observed between the minimally invasive and conventional approaches.In 40 consecutive randomly selected adult patients with unilateral primary hip osteoarthritis, a cementless Zweymüller-Plus THA (Smith & Nephew Orthopaedics, Baar, Switzerland) was implanted by a single surgeon in 1 institution during the same period. Twenty patients underwent a minimally invasive approach (group A), and 20 patients underwent a conventional anterolateral approach (group B). Four years postoperatively, the operated and contralateral nonoperated hips of 37 available patients from both groups were examined with magnetic resonance imaging to show any changes in the gluteus medius and tensor fascia latae. Simultaneously, hip abductor power was measured bilaterally in both groups. Anthropometric data, blood loss, Short Form 36 self-assessment questionnaire, visual analog pain score, and walking distance were also analyzed.The reliability of magnetic resonance imaging and hip abductor power measurements was high. No difference was found in hip abductor power on the operated side between the 2 groups, whereas hip abductor power on the nonoperated side was significantly higher in both groups. This study revealed no mechanical and functional benefits in favor of patients undergoing minimally invasive vs conventional total hip arthroplasty.

Increased intramuscular fatty infiltration without differences in lumbar muscle cross-sectional area during remission of unilateral recurrent low back pain

Lumbar muscle degeneration is a common feature in non-specific low back pain (LBP). It is hypothesized that degenerated muscles might compromise spinal stability and lead to further injury/pain. However, little is known about lumbar muscle morphometry after resolution of LBP. Therefore, this study investigated the extent of lumbar muscle atrophy and fatty infiltration in individuals who are at risk for a recurrence of LBP. Thirteen participants in remission of unilateral recurrent LBP were compared to 13 healthy controls, comparable for age, weight, length and level of physical activity. Total, lean muscle and fat cross-sectional area (CSA) of lumbar multifidus (MF), erector spinae (ES) and psoas (PS) were investigated on T1-weighted Magnetic Resonance Imaging (MRI), bilaterally and at 3 lumbar levels (L3 upper, L4 upper and L4 lower endplate). In addition, a muscle-fat-index (MFI) was calculated reflecting the amount of fatty infiltration in lean muscle tissue. No significant differences for total, lean muscle and fat CSA were found between people in remission of recurrent LBP and the control group. Conversely, MFI was increased bilaterally at the 2 lowest lumbar levels. There were no differences between the previously painful and non-painful side of the LBP group for any of the parameters. These results show a generalized increase in intramuscular fatty infiltration in lean muscle tissue in the absence of macroscopical signs of muscle degeneration after resolution of LBP. These findings reflect a decreased muscle quality, but not quantity, and might indicate a pathophysiological mechanism contributing to recurrence of LBP.

Quantitative paraspinal muscle measurements: inter-software reliability and agreement using OsiriX and ImageJ

BACKGROUND

Variations in paraspinal muscle cross-sectional area (CSA) and composition, particularly of the multifidus muscle, have been of interest with respect to risk of, and recovery from, low back pain problems. Several investigators have reported on the reliability of such muscle measurements using various protocols and image analysis programs. However, there is no standard protocol for tissue segmentation, nor has there been an investigation of reliability or agreement of measurements using different software.

OBJECTIVE

The purpose of this study was to provide a detailed muscle measurement protocol and determine the reliability and agreement of associated paraspinal muscle composition measurements obtained with 2 commonly used image analysis programs: OsiriX and ImageJ.

DESIGN

This was a measurement reliability study.

METHODS

Lumbar magnetic resonance images of 30 individuals were randomly selected from a cohort of patients with various low back conditions. Muscle CSA and composition measurements were acquired from axial T2-weighted magnetic resonance images of the multifidus muscle, the erector spinae muscle, and the 2 muscles combined at L4-L5 and S1 for each participant. All measurements were repeated twice using each software program, at least 5 days apart. The assessor was blinded to all earlier measurements.

RESULTS

The intrarater reliability and standard error of measurement (SEM) were comparable for most measurements obtained using OsiriX or ImageJ, with reliability coefficients (intraclass correlation coefficients [ICCs]) varying between .77 and .99 for OsiriX and .78 and .99 for ImageJ. There was similarly excellent agreement between muscle composition measurements using the 2 software applications (inter-software ICCs = .81-.99).

LIMITATIONS

The high degree of inter-software measurement reliability may not generalize to protocols using other commercial or custom-made software.

CONCLUSION

The proposed method to investigate paraspinal muscle CSA, composition, and side-to-side asymmetry was highly reliable, with excellent agreement between the 2 software programs.

The Relationship between Cross Sectional Area and Strength of Back Muscles in Patients with Chronic Low Back Pain

Objective

To evaluate the relationship between the cross sectional area (CSA) and isokinetic strength of the back muscles in patients with chronic low back pain.

Method

Data of twenty-eight middle-aged patients with chronic back pain were analyzed retrospectively. CSAs of both paraspinal muscles and the disc at the L4-L5 level were measured in MRI axial images and the relative CSAs (rCSA: CSA ratio of muscle and disc) were calculated. The degree of paraspinal muscle atrophy was rated qualitatively. Isokinetic strengths (peak torque, peak torque per body weight) of back flexor and extensor were measured with the isokinetic testing machine. Multiple regression analysis with backward elimination was used to evaluate relations between isokinetic strength and various factors, such as CSA or rCSA and clinical characteristics in all patients. The same analysis was repeated in the female patients.

Results

In analysis with CSA and clinical characteristics, body mass index (BMI) and CSA were significant influencing factors in the peak torque of the back flexor muscles. CSA was a significant influencing factor in the peak torque of total back muscles. In analysis with rCSA and clinical characteristics, BMI was significant in influencing the peak torque of the back flexors. In female patients, rCSA was a significant influencing factor in the peak torque per body weight of the back flexors, and age and BMI were influencing factors in the peak torque of back flexors and total back muscles.

Conclusion

In middle-aged patients with chronic low back pain, CSA and rCSA were influencing factors in the strength of total back muscles and back flexors. Also, gender and BMI were influencing factors.