PaperAnatomy and biomechanics of psoas major
Abstract
The fascicular anatomy of the psoas major was determined by dissection in three cadavers. Its actions on the lumbar spine in the sagittal plane were modelled on erect, flexion, and extension radiographs of ten adult males. Calculations revealed that psoas exerts only very small moments that tend to extend the upper lumbar spine and to flex the lower lumbar spine, but at maximum contraction the psoas exerts severe compression forces on the lumbar segments, and large shear forces.
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Cited by (175)
The relationship between the psoas major muscle morphology characteristics with disability index and pain in patients with chronic nonspecific low back pain
2024, Journal of Bodywork and Movement TherapiesChronic nonspecific low back pain (CNLBP) is a common disorder in people of active ages and significantly affects their quality of life. Different structures in the lumbar area can cause LBP. The lumbar muscle disorders, including the psoas major (PM) muscles, have an essential role in LBP. Magnetic Resonance Imaging (MRI) has been introduced as a safe and useful instrument for investigating the morphological properties of skeletal muscle. In general, PM morphology changes may be one reason for the pain and disability experienced in CNLBP patients. Thus, this study aimed to assess the relationship among the PM's Cross-sectional area (CSA), medial-lateral (ML), and anterior-posterior (AP) diameters, with disability index and pain score in patients with CNLBP.
One hundred twenty patients with CNLBP (60 men and 60 women) participated in this cross-sectional study. Axial MRIs were obtained from L3/L4 and L4/L5 disc levels. Then, patients filled out Rolland Morris Disability Questionnaires, demographic data forms, and the Numeric Pain Rating Scale (NPRS). Image J software was used to analyze the images. Using Linear Regression and the Pearson test, the correlation between muscle CSA and diameters, as well as data obtained from questionnaires and NPRS, was analyzed.
Results from the statistical analysis showed no statistically significant relationship among morphological characteristics of the psoas major muscle in L3/L4 and L4/L5 disc levels with disability index and pain score (p < 0.05).
There is no significant relationship between the PM morphological characteristics and disability index and pain score. Therefore, muscle CSA and diameters are insufficient to determine the cause of CNLBP.
Lower limb postures resembling sitting and standing alter lumbar angles along the passive stiffness curve
2023, Journal of Electromyography and KinesiologyIn vivo lumbar passive stiffness is often used to assess time-dependent changes in lumbar tissues and to define the neutral zone. We tested the hypothesis that flexing the hips would alter tension in hip and spine musculature, leading to a more extended passive stiffness curve (i.e., right-shifted), without changes in lumbar stiffness. Twenty participants underwent side-lying passive testing with the lower limbs positioned in Stand, Kneel, and Sit representative postures. Moment-angle curves were constructed from the lumbar angles and the moment at L4/5 and partitioned into three zones. Partially supporting our hypothesis, lumbar stiffness within the low and transition stiffness zones was similar between the Stand and Sit. Contrary to our hypothesis, lumbar angles were significantly larger in the Sit compared to the Stand and Kneel postures at the first and second breakpoints, with average differences of 9.3° or 27.2% of passive range of motion (%PassRoM) in flexion and 5.6° or 16.6 %PassRoM in extension. Increased flexion in the Sit may be linked to increased posterior pelvic tilt and associated lower lumbar vertebrae flexion. Investigators must ensure consistent pelvis and hip positioning when measuring lumbar stiffness. Additionally, the adaptability of the neutral zone to pelvis posture, particularly between standing and sitting, should be considered in ergonomic applications.
The predictive value of psoas and paraspinal muscle parameters measured on MRI for severe cage subsidence after standalone lateral lumbar interbody fusion
2023, Spine JournalThe effect of psoas and paraspinal muscle parameters on cage subsidence after minimally invasive techniques, such as standalone lateral lumbar interbody fusion (SA-LLIF), is unknown.
This study aimed to determine whether the functional cross-sectional area (FCSA) of psoas and lumbar spine extensor muscles (multifidus and erector spinae), and psoas FCSA normalized to the vertebral body area (FCSA/VBA) differ among levels with severe cage subsidence after SA-LLIF when compared to levels without severe cage subsidence.
Retrospective single center cohort study.
Patients who underwent SA-LLIF between 2008 and 2020 for degenerative conditions using exclusively polyetheretherketone (PEEK) cages, had a lumbar magnetic resonance imaging (MRI) scan within 12 months, a lumbar computed tomography (CT) scan within 6 months prior to surgery, and a postoperative clinical and radiographic follow-up at a minimum of 6 months were included.
Severe cage subsidence.
MRI measurements included psoas and combined multifidus and erector spinae (paraspinal) FCSA and FCSA/VBA at the L3-L5 pedicles. Following manual segmentation of muscles on axial T2-weighted images using ITK-SNAP (version 3.8.0), the FCSA was calculated using a custom written program on Matlab (version R2019a, The MathWorks, Inc.) that used an automated pixel intensity threshold method to differentiate between fat and muscle. Mean volumetric bone mineral density (vBMD) at L1/2 was measured by quantitative CT. The primary endpoint was severe cage subsidence per level according to the classification by Marchi et al. Multivariable logistic regression analysis was performed using generalized linear mixed models. All analyses were stratified by biological sex.
95 patients (45.3% female) with a total of 188 operated levels were included in the analysis. The patient population was 92.6% Caucasian with a median age at surgery of 65 years. Overall subsidence (Grades 0-III) was 49.5% (53/107 levels) in men versus 58.0% (47/81 levels) in women (p=.302), and severe subsidence (Grades II-III) was 22.4% (24/107 levels) in men versus 25.9% (21/81 levels) in women (p=.608). In men, median psoas FCSA and psoas FCSA/VBA at L3 and L4 were significantly greater in the severe subsidence group when compared to the non-severe subsidence group. No such difference was observed in women. Paraspinal muscle parameters did not differ significantly between non-severe and severe subsidence groups for both sexes. In the multivariable logistic regression analysis with adjustments for vBMD and cage length, psoas FCSA at L3 (OR 1.002; p=.020) and psoas FCSA/VBA at L3 (OR 8.655; p=.029) and L4 (OR 4.273; p=.043) were found to be independent risk factors for severe cage subsidence in men.
Our study demonstrated that greater psoas FCSA at L3 and psoas FCSA/VBA at L3 and L4 were independent risk factors for severe cage subsidence in men after SA-LLIF with PEEK cages. The higher compressive forces the psoas exerts on lumbar segments as a potential stabilizer might explain these findings. Additional pedicle screw fixation might be warranted in these patients to avoid severe cage subsidence.
Morphometry of lumbar muscles in the seated posture with weight-bearing MR scans
2022, Journal of Clinical Orthopaedics and TraumaCitation Excerpt :All geometries were extracted at each level so that they can be used as a normative female-specific data. The three muscles selected are known to have practical clinical implications in patients and or in situations that involve prolonged seated postures.6,18 It is possible to extend this method to the other muscles in a future study.
Conventional imaging studies of human spine are done in a supine posture in which the axial loading of the spine is not considered. Upright images better reveal the interrelationships between the various internal structures of the spine. The objective of the current study is to determine the cross-sectional areas, radii, and angulations of the psoas, erector spinae, and multifidus muscles of the lumbar spine in the sitting posture. Ten young (mean age 31 ± 4.8 years) asymptomatic female subjects were enrolled. They were seated in an erect posture and weight-bearing T1 and T2 MRIs were obtained. Cross-sectional areas, radii, and angulations of the muscles were measured from L1-L5. Two observers repeated all the measurements for all parameters, and reliability was determined using the inter- and intra-class coefficients. The Pearson product moment correlation was used for association between levels, while level differences were used using a linear regression model. The cross-sectional areas of the psoas and multifidus muscles increased from L1 to L5 (1.9 ± 1.1 to 12.1 ± 2.5 cm2 and 1.8 ± 0.3 to 5.7 ± 1.4 cm2). The cross-sectional area of the erector spinae was greatest at the midlevel (13.9 ± 2.2 cm2) and it decreased in both directions. For the angle, the range for psoas muscles was 75–105°, erector spinae were 39–46° and multifidus was 11–19°. Correlations magnitudes were inconsistent between levels and muscle types. These quantitated data improve our understanding of the geometrical properties in the sitting posture. The weight-bearing MRI-quantified morphometrics of human lumbar spine muscles from this study can be used in biomechanical models for predicting loads on spinal joints under physiological and traumatic situations.
Psoas weakness following oblique lateral interbody fusion surgery: a prospective observational study with an isokinetic dynamometer
2022, Spine JournalAlthough 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.
Using a dynamometer to evaluate how the hip flexor strength changes following OLIF.
A prospective observational study.
Forty-six patients who underwent single or multi-level OLIF for lumbar spondylolisthesis.
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.
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.
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).
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.
Feedforward coactivation of trunk muscles during rapid shoulder movements
2022, JSES InternationalShoulder movements that involve unilateral and bilateral flexion, extension, abduction, and asymmetrical flexion-extension cause the activity of trunk muscles. There has not been a fixed consensus on the onset of deep trunk muscle activities including the psoas major (PM), quadratus lumborum (QL), transversus abdominis (TrA), and lumbar multifidus (MF) during shoulder movements. The purpose of this study was to measure the onset of electromyographic activity of the deep trunk muscles during rapid shoulder movements and clarify the coordinated activity pattern of the deep trunk muscles during 11 shoulder movements.
Thirteen men participated in this study. The onset of activity of the right deep trunk muscles (PM, QL, TrA, and MF) were measured using fine-wire electrodes, and those of the right and left deltoid (anterior, middle, and posterior) and right superficial trunk muscles (rectus abdominis, external oblique [EO], and internal oblique [IO]) were measured using surface electrodes as participants performed 6 types of unilateral, 3 types of bilateral, and 2 types of asymmetrical rapid shoulder movements. We defined feedforward activation as the onset of activity of trunk muscle before or within +50 ms onset of the deltoid muscle and feedback activation as that after +50 ms. A 1-way analysis of variance was performed to compare the onset of activity of each muscle during each shoulder movement.
The mean onset of activity of the PM (26.0 ms), QL (13.1 ms), TrA (−19.7 ms), and MF (20.4 ms) muscles demonstrated feedforward activation during left shoulder flexion. The onset of activity of the TrA (1.6-48.7 ms), rectus abdominis (−1.7 to 17.3 ms), and EO (5.6–40.8 ms) muscles demonstrated feedforward activation during left, right, and bilateral shoulder extension. The onset of activity of the PM (22.9 ms), QL (23.0 ms), TrA (18.9 ms), and EO (15.4 ms) demonstrated feedforward activation during left shoulder abduction, while that of the IO (4.4–10.9 ms) only demonstrated feedforward activation during right and bilateral shoulder abduction. The onset of activity of the TrA (−27.6 ms) and IO (−23.9 ms) demonstrated feedforward activation during left shoulder flexion-right shoulder extension, and that of the MF (33.4 ms) and EO (−17.2 ms), during left shoulder extension-right shoulder flexion.
Rapid shoulder movements occur with coordinated muscle activation of the deep trunk muscles depending on the direction of shoulder movements. Feedforward activation of single or combined deep trunk muscles may facilitate rapid shoulder movements.