Quantifying lumbar paraspinal intramuscular fat: Accuracy and reliability of automated thresholding models

Background

The reported level of lumbar paraspinal intramuscular fat (IMF) in people with low back pain (LBP) varies considerably across studies using conventional T1- and T2-weighted magnetic resonance imaging (MRI) sequences. This may be due to the different thresholding models employed to quantify IMF. In this study we investigated the accuracy and reliability of established (two-component) and novel (three-component) thresholding models to measure lumbar paraspinal IMF from T2-weighted MRI.

Methods

In this cross-sectional study, we included MRI scans from 30 people with LBP (50% female; mean (SD) age: 46.3 (15.0) years). Gaussian mixture modelling (GMM) and K-means clustering were used to quantify IMF bilaterally from the lumbar multifidus, erector spinae, and psoas major using two and three-component thresholding approaches (GMM2C; K-means2C; GMM3C; and K-means3C). Dixon fat-water MRI was used as the reference for IMF. Accuracy was measured using Bland-Altman analyses, and reliability was measured using ICC3,1. The mean absolute error between thresholding models was compared using repeated-measures ANOVA and post-hoc paired sample t-tests (α = 0.05).

Results

We found poor reliability for K-means2C (ICC3,1 ≤ 0.38), moderate to good reliability for K-means3C (ICC3,1 ≥ 0.68), moderate reliability for GMM2C (ICC3,1 ≥ 0.63) and good reliability for GMM3C (ICC3,1 ≥ 0.77). The GMM (p < .001) and three-component models (p < .001) had smaller mean absolute errors than K-means and two-component models, respectively. None of the investigated models adequately quantified IMF for psoas major (ICC3,1 ≤ 0.01).

Conclusions

The performance of automated thresholding models is strongly dependent on the choice of algorithms, number of components, and muscle assessed. Compared to Dixon MRI, the GMM performed better than K-means and three-component performed better than two-component models for quantifying lumbar multifidus and erector spinae IMF. None of the investigated models accurately quantified IMF for psoas major. Future research is needed to investigate the performance of thresholding models in a more heterogeneous clinical dataset and across different sites and vendors.

Investigating the associations between lumbar paraspinal muscle health and age, BMI, sex, physical activity, and back pain using an automated computer-vision model: A UK Biobank study

BACKGROUND CONTEXT

The role of lumbar paraspinal muscle health in back pain (BP) is not straightforward. Challenges in this field have included the lack of tools and large, heterogenous datasets to interrogate the association between muscle health and BP. Computer-vision models have been transformative in this space, enabling the automated quantification of muscle health and the processing of large datasets.

PURPOSE

To investigate the associations between lumbar paraspinal muscle health and age, sex, BMI, physical activity, and BP in a large, heterogenous dataset using an automated computer-vision model.

DESIGN

Cross-sectional study.

PATIENT SAMPLE

Participants from the UK Biobank with abdominal Dixon fat-water MRI (N=9,564) were included (41.8% women, mean [SD] age: 63.5 [7.6] years, BMI: 26.4 [4.1] kg/m2) of whom 6,953 reported no pain, 930 acute BP, and 1,681 chronic BP.

OUTCOME MEASURES

Intramuscular fat (IMF) and average cross-sectional area (aCSA) were automatically derived using a computer-vision model for the left and right lumbar multifidus (LM), erector spinae (ES), and psoas major (PM) from the L1 to L5 vertebral levels.

METHODS

Two-tailed partial Pearson correlations were generated for each muscle to assess the relationships between the muscle measures (IMF and aCSA) and age (controlling for BMI, sex, and physical activity), BMI (controlling for age, sex, and physical activity), and physical activity (controlling for age, sex, and BMI). One-way ANCOVA was used to identify sex differences in IMF and aCSA for each muscle while controlling for age, BMI, and physical activity. Similarly, one-way ANCOVA was used to identify between-group differences (no pain, acute BP, and chronic BP) for each muscle and along the superior-inferior expanse of the lumbar spine while controlling for age, BMI, sex, and physical activity (α=0.05).

RESULTS

Females had higher IMF (LM mean difference [MD]=11.1%, ES MD=10.2%, PM MD=0.3%, p<.001) and lower aCSA (LM MD=47.6 mm2, ES MD=350.0 mm2, PM MD=321.5 mm2, p<.001) for all muscles. Higher age was associated with higher IMF and lower aCSA for all muscles (r≥0.232, p<.001) except for LM and aCSA (r≤0.013, p≥.267). Higher BMI was associated with higher IMF and aCSA for all muscles (r≥0.174, p<.001). Higher physical activity was associated with lower IMF and higher aCSA for all muscles (r≥0.036, p≤.002) except for LM and aCSA (r≤0.010, p≥.405). People with chronic BP had higher IMF and lower aCSA than people with no pain (IMF MD≤1.6%, aCSA MD≤27.4 mm2, p<.001) and higher IMF compared to acute BP (IMF MD≤1.1%, p≤.044). The differences between people with BP and people with no pain were not spatially localized to the inferior lumbar levels but broadly distributed across the lumbar spine.

CONCLUSIONS

Paraspinal muscle health is associated with age, BMI, sex, and physical activity with the exception of the association between LM aCSA and age and physical activity. People with BP (chronic>acute) have higher IMF and lower aCSA than people reporting no pain. The differences were not localized but broadly distributed across the lumbar spine. When interpreting measures of paraspinal muscle health in the research or clinical setting, the associations with age, BMI, sex, and physical activity should be considered.

Identifying Patient Characteristics Associated With the Occurrence of Post Treatment Non-serious Adverse Events After Cervical Spine Manual Therapy Treatment in Patients With Neck Pain

OBJECTIVES

To compare prevalence rates of serious and non-serious adverse events after manipulation and mobilization and to identify risk factors of serious and non-serious adverse events following 4 types of manual therapy treatment in patients with neck pain.

DESIGN

A prospective cohort study in primary care manual therapy practice.

PARTICIPANTS

Patients with neck pain (N=686) provided data on adverse events after 1014 manipulation treatments, 829 mobilization treatments, 437 combined manipulation and mobilization treatments, and 891 treatments consisting of "other treatment modality".

INTERVENTIONS

Usual care manual therapy.

MAIN OUTCOME MEASURES

A chi-square test was performed to explore differences in prevalence rates. Logistic regression analysis was performed within the 4 treatment groups. A priori we defined associations between patient-characteristics and adverse events of odds ratio (OR)>2 or OR<0.5 as clinically relevant.

RESULTS

No serious adverse events, such as cervical artery dissection or stroke, were reported. With regard to non-serious adverse events, we found that these are common after manual therapy treatment: prevalence rates are ranging from 0.3% to 64.7%. We found a statistically significant difference between the 4 types of treatments, detrimental to mobilization treatment. Logistic regression analysis resulted in 3 main predictors related to non-serious adverse events after manual therapy treatment: smoking (OR ranges from 2.10 [95% confidence interval [CI] 1.37-3.11] to 3.33 [95% CI 1.83-5.93]), the presence of comorbidity (OR ranges from 2.32 [95% CI 1.22-4.44] to 3.88 [95% CI 1.62-9.26]), and female sex (OR ranges from 0.22 [95% CI 0.11-0.46] to 0.49 [95% CI 0.28-0.86]).

CONCLUSION

There is a significant difference in the occurrence of non-serious adverse events after mobilization compared with manipulation or a combination of manipulation and mobilization. Non-serious adverse events in manual therapy practice are common and are associated with smoking and the presence of comorbidity. In addition, women are more likely to report non-serious adverse events.

The introduction of advanced practice physiotherapy within Dutch primary care is a quest for possibilities, added value, and mutual trust: a qualitative study amongst advanced practice physiotherapists and general practitioners

Background

Despite the increased deployment and added value of Advanced Practitioner Physiotherapy (APP) in musculoskeletal care internationally, APP is not yet widely accepted within Dutch primary care. This may be due to specific constraints in the implementation of APP within the Dutch healthcare system. This study aimed to explore the experiences and perceptions of Advanced Practitioner Physiotherapists (APPs) and General Practitioners (GPs) with respect to implementing APP within Dutch primary care.

Methods

This explorative and interpretive qualitative study included 12 APPs and 3 GPs who were in various stages of implementing an APP care model. Semi-structured interviews were conducted between January and March 2021. The topic list was based on existing literature, the personal input of researchers, and the Constellation Approach framework. Data were analysed using a thematic inductive approach.

Results

Four main themes emerged from the data; 1) Both GPs’ trust in APP and a clear added value of APP are critical for starting implementation, 2) APPs need continuous support from GPs, 3) APPs believe that their position needs strengthening, and 4) Implementation of the APP model creates tension over ownership. These four themes highlight the perceived difficulties in gaining trust, lack of clarity over the added value of APP, ambiguity over APPs’ professional profile and positioning, a need on behalf of GPs to maintain authority, lack of reimbursement structure, and the struggle APPs face to strike a balance with current care.

Conclusion

This study demonstrates that implementing an APP model of care is challenging, in part, because the deployment of APP does not sufficiently align with the core values of GPs, while GPs appear reluctant to hand over control of elements of patient care to APPs. APPs do not appear to have ownership over the implementation, given their strong dependence on the practice, values and needs of GPs.

Trial registration

Ethical approval was obtained from the Medical Ethics Committee of VU University Medical Centre in Amsterdam; reference number 2020.17 . All participants were asked to provide written informed consent prior to participating in the study.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12913-022-07906-6.

Changes in spontaneous overt motor execution immediately after observing others' painful action: two pilot studies

Research has demonstrated that motor control is directly influenced by observation of others’ action, stimulating the mirror neuron system. In addition, there is evidence that both emotion and empathy after observing a painful stimulus affects motor cortical excitability and reaction times. Aim of the present two pilot studies is a) to test for significant influence of observing other’s painful bending of the trunk on execution of the same activity in a self-directed bending action (study 1) and to compare these results with a bending action according to a strict bending protocol (study 2). In addition to study 1, differences between Low Back Pain (LBP) patients versus healthy subjects are tested. Video footage of a (1) neutral, (2) painful, and (3) happy bending action was presented in random order. Changes in flexion–relaxation phenomenon (FRP) of back muscles were studied directly after watching the videos with surface EMG, in study 1 during a self-directed bending action in LBP patients and healthy subjects, in study 2 according to a strict bending protocol. FRP ratios were calculated by a custom-made analysis scheme tested for sufficient reliability prior to both studies. Evoked emotions were measured with an Emotional Questionnaire after each video. A Mixed Model ANOVA was used to test for the effect video and the difference between LBP and healthy subjects on the FRP-rs. Differences in evoked emotion will be tested with a Wilcoxon Signed Rank Test. In study 1, 24 healthy controls and 16 LBP patients FRP-rs were significantly influenced after observing a painful video in all subjects versus a happy and neutral video (p = 0.00). No differences were present between LBP and healthy controls. All subjects experienced more fear after observation of the painful video (p 0.05). In study 2, 6 healthy subjects followed the strict FRP bending protocol for three times after observing each video. No significant changes occurred in FRPs per video compared to FRPs of six healthy subjects carrying out the spontaneous bending activity. Observing a painful action in another person changes motor performance and increases fear in both people with and without back pain, during self-directed trunk flexion, but not during a protocolled trunk flexion.

The transverse abdominal muscle is excessively active during active straight leg raising in pregnancy-related posterior pelvic girdle pain: an observational study

BACKGROUND

Many studies suggest that impairment of motor control is the mechanical component of the pathogenesis of painful disorders in the lumbo-sacral region; however, this theory is still unproven and the results and recommendations for intervention remain questionable. The need for a force to compress both innominate bones against the sacrum is the basis for treatment of pregnancy-related pelvic girdle pain (PGP). Therefore, it is advised to use a pelvic belt and do exercises to enhance contraction of the muscles which provide this compression. However, our clinical experience is that contraction of those muscles appears to be excessive in PGP. Therefore, in patients with long-lasting pregnancy-related posterior PGP, there is a need to investigate the contraction pattern of an important muscle that provides a compressive force, i.e. the transverse abdominal muscle (TrA), during a load transfer test, such as active straight leg raising (ASLR).

METHODS

TrA thickness was measured by means of ultrasound imaging at rest and during ASLR in 43 non-pregnant women with ongoing posterior PGP that started during a pregnancy or delivery, and in 39 women of the same age group who had delivered at least once and had no current PGP (healthy controls).

RESULTS

In participants with PGP, the median TrA thickness increase with respect to rest during ipsilateral and contralateral ASLR was 31% (SD 46%) and 31% (SD 57%), respectively. In healthy controls, these values were 11% (SD 25%) and 13% (SD 22%), respectively.

CONCLUSIONS

Significant excessive contraction of the TrA is present during ASLR in patients with long-lasting pregnancy-related posterior PGP. The present findings do not support the idea that contraction of the TrA is decreased in long-lasting pregnancy-related PGP. This implies that there is no rationale for the prescription of exercises to enhance contraction of TrA in patients with long-lasting pregnancy-related PGP.

Support and preferences for intermediate health care services for back and neck pain: a survey among members of the Dutch patient association for spinal pain

RATIONALE, AIMS AND OBJECTIVES

Recent health care reforms in the Netherlands have led to the introduction of intermediate health care. Intermediate health care combines features of primary care and secondary (hospital) care. It is characterized by a task shift from hospital care to primary care. The initial experiences of medical specialists and general practitioners with intermediate health care are positive. However, the patients' perspectives regarding this reform are unknown. This study aimed to evaluate the level of support from patients with back and/or neck pain for intermediate health care services and to provide insight into their preferences how this care should be organized.

METHODS

A cross-sectional survey was conducted in which members of the patient association for spinal pain in the Netherlands completed electronic questionnaires to measure the level of support and preferred organization of intermediate health care services.

RESULTS

Questionnaires were returned by 367 patients (response rate: 51%). Respondents supported the concept of intermediate health care (numeric rating scale: 7/10). Aspects considered important for intermediate health care included knowledge and expertise of staff, multidisciplinary cooperation, patient contact time, reimbursement via health insurance, quality control of care, evidence-based treatments and electronic medical records. Although intermediate care is a health care reform, patients continued to think according to traditional primary and secondary care constitutions.

CONCLUSIONS

Patients with neck and/or back pain support the introduction of intermediate health care services and have explicit preferences regarding its organization, but may need to be better informed when intermediate care is introduced.

Risks in teaching manipulation techniques in master programmes

High Velocity Techniques (HVT) in the (high) cervical spine are part of the standard curricula of manual therapy educational programmes. Little is known about the risk or the presence of adverse events during skills training sessions. This article describes two cases of students with both being at risk for an adverse event; one with a congenital artery aberration and one with cancer in the high cervical region. Teachers and educational programme developers should take risk management into account when teaching HVT.

The influence of simulated transversus abdominis muscle force on sacroiliac joint flexibility during asymmetric moment application to the pelvis

BACKGROUND

The role of so-called local muscle system in motor control of the lower back and pelvis is a subject of ongoing debate. Prevailing beliefs in stabilizing function of this system were recently challenged. This study investigated the impact of in vitro simulated force of transversely oriented fibres of the transversus abdominis muscle (a part of the local system) on flexibility of the sacroiliac joint during asymmetric moment application to the pelvis.

METHODS

In 8 embalmed specimens an incremental moment was applied in the sagittal plane to one innominate with respect to the fixed contralateral innominate. Ranges of motion of the sacroiliac joint were recorded using the Vicon Motion Capture System. Load-deformation curves were plotted and flexibility of the sacroiliac joint was calculated separately for anterior and posterior rotations of the innominate, with and without simulated muscle force.

FINDINGS

Flexibility of the sacroiliac joint was significantly bigger during anterior rotation of the innominate, as compared to posterior rotation (Anova P<0.05). After application of simulated force of transversus abdominis, flexibility of the joint did not change both during anterior and posterior rotations of the innominate.

INTERPRETATION

A lack of a stiffening effect of simulated transversus abdominis force on the sacroiliac joint was demonstrated. Earlier hypotheses suggesting a stiffening influence of this muscle on the pelvis cannot be confirmed. Consistent with previous findings smaller flexibility of the joint recorded during posterior rotation of the innominate may be of clinical importance for physio- and manual therapists. However, major limitations of the study should be acknowledged: in vitro conditions and simulation of only solitary muscle force.

Age-related differences in muscle recruitment and reaction-time performance

Previously, we showed that prolonged reaction-time (RT) in older persons is related to increased antagonist muscle co-activation, occurring already before movement onset. Here, we studied whether a difference in temporal agonist and antagonist muscle activation exists between young and older persons during an RT-test. We studied Mm. Biceps (antagonist muscle) & Triceps (agonist muscle) Brachii activation time by sEMG in 60 young (26 ± 3 years) and 64 older (80 ± 6 years) community-dwelling subjects during a simple point-to-point RT-test (moving a finger using standardized elbow-extension from one pushbutton to another following a visual stimulus). RT was divided in pre-movement-time (PMT, time for stimulus processing) and movement-time (MT, time for motor response completion). Muscle activation time 1) following stimulus onset (PMAT) and 2) before movement onset (MAT) was calculated. PMAT for both muscles was significantly longer for the older subjects compared to the young (258 ± 53 ms versus 224 ± 37 ms, p=0.042 for Biceps and 280 ± 70 ms versus 218 ± 43 ms for Triceps, p<0.01). Longer agonist muscle PMAT was significantly related to worse PMT and RT in young (respectively r=0.76 & r=0.68, p<0.001) and elderly (respectively r=0.42 & r=0.40, p=0.001). In the older subjects we also found that the antagonist muscle activated significantly earlier than the agonist muscle (-22 ± 55 ms, p=0.003). We conclude that in older persons, besides the previously reported increased antagonist muscle co-activation, the muscle firing sequence is also profoundly altered. This is characterized by a delayed muscle activation following stimulus onset, and a significantly earlier recruitment of the antagonist muscle before movement onset.

Simulated transversus abdominis muscle force does not increase stiffness of the pubic symphysis and innominate bone: an in vitro study

BACKGROUND

The transversus abdominis muscle is thought to exert a stiffening effect on the sacroiliac joints. However, it is unknown whether this muscle is capable of increasing pubic symphysis and innominate bone stiffness during load exerted on the pelvis. The objective of this study is to investigate whether in vitro simulated force of transversely oriented fibres of the transversus abdominis increases stiffness of the pubic symphysis and innominate bone.

METHODS

In 15 embalmed specimens an incremental moment was applied in the sagittal plane to one innominate with respect to the fixated contralateral innominate. For pubic symphysis motion and innominate bone deformation load-deformation curves were plotted and slopes of adjusted linear regression lines were calculated. The slopes are considered to be a measure of pubic symphysis and innominate bone stiffness. Slopes were tested for significant differences before and after simulation of the transversus abdominis force.

FINDINGS

Stiffness of pubic symphysis and innominate bone does not change under influence of simulated force of the transversus abdominis. For pubic symphysis, the slope of the regression line hardly changes, from 0.0341mm/Nm (SD 0.0277) before transversus abdominis force simulation to 0.0342mm/Nm (SD 0.0273) during simulation. For innominate bone, the mean slope increases minimally, from 0.0368mm/Nm (SD 0.0369) to 0.0413mm/Nm (SD 0.0395), respectively.

INTERPRETATION

Simulation of the force of a single muscle - transversus abdominis - does not increase stiffness of the pubic symphysis and innominate bone. The hypothesized stiffening influence of the transversus abdominis on the pelvic ring was not confirmed in vitro.

Severity of signs and symptoms in lumbopelvic pain during pregnancy

Data on the severity of signs and symptoms of lumbopelvic pain (LPP) during pregnancy are scarce. Therefore, this cross-sectional study examines the severity of LPP and pain-related signs and symptoms. Women with an uncomplicated pregnancy of 20-30 weeks were invited to participate. They rated their pain and fatigue on a numerical rating scale, and pain location was indicated on a drawing. Disability was scored on the Quebec Back Pain Disability Scale (QBPDS) and urine incontinence on a Likert scale. Physical examination consisted of the Active Straight Leg Raise (ASLR) test, the Posterior Pelvic Pain Provocation (PPPP) test and pain score, and force during isometric bilateral hip adduction. Of all 182 participants, 60.4% reported LPP. Mean pain level was 3.6 (SD 2.2); in 20.0% of the women the score was >5. The mean score on the QBPDS was 27 (SD 16); in 20.9% the score was >40. Compared to women without LPP, women with LPP more frequently suffered back pain in the past (p<0.001), had a higher body mass index (p<0.01), more often had urinary incontinence (p<0.05), had less isometric hip adduction force (p<0.001), had more pain on isometric hip adduction (p<0.01), had a higher ASLR score (p<0.001) and more had often a positive PPPP test (p<0.001). Fatigue was not related to LPP during pregnancy. The main conclusion is that pain and disability of LPP during pregnancy can be interpreted as mild to moderate in most cases, and as severe in about 20%.

Course and prognosis of recovery for chronic non-specific low back pain: design, therapy program and baseline data of a prospective cohort study

BACKGROUND

There has been increasing focus on factors predicting the development of chronic musculoskeletal disorders. For patients already experiencing chronic non-specific low back pain it is also relevant to investigate which prognostic factors predict recovery. We present the design of a cohort study that aims to determine the course and prognostic factors for recovery in patients with chronic non-specific low back pain.

METHODS/DESIGN

All participating patients were recruited (Jan 2003-Dec 2008) from the same rehabilitation centre and were evaluated by means of (postal) questionnaires and physical examinations at baseline, during the 2-month therapy program, and at 5 and 12 months after start of therapy. The therapy protocol at the rehabilitation centre used a bio-psychosocial approach to stimulate patients to adopt adequate (movement) behaviour aimed at physical and functional recovery. The program is part of regular care and consists of 16 sessions of 3 hours each, over an 8-week period (in total 48 hours), followed by a 3-month self-management program. The primary outcomes are low back pain intensity, disability, quality of life, patient's global perceived effect of recovery, and participation in work. Baseline characteristics include information on socio-demographics, low back pain, employment status, and additional clinical items status such as fatigue, duration of activities, and fear of kinesiophobia. Prognostic variables are determined for recovery at short-term (5 months) and long-term (12 months) follow-up after start of therapy.

DISCUSSION

In a routine clinical setting it is important to provide patients suffering from chronic non-specific low back pain with adequate information about the prognosis of their complaint.

Age-related differences in pre-movement antagonist muscle co-activation and reaction-time performance

Multiple causes contribute to the prolonged reaction-times (RT) observed in elderly persons. The involvement of antagonist muscle co-activation remains unclear. Here the Mm. Biceps and Triceps Brachii activation in 64 apparently healthy elderly (80 ± 6 years) and 60 young (26 ± 3 years) subjects were studied during a simple RT-test (moving a finger using standardized elbow-extension from one pushbutton to another following a visual stimulus). RT was divided in pre-movement-time (PMT, time for stimulus processing) and movement-time (MT, time for motor response completion). RT-performance was significantly worse in elderly compared to young; the slowing was more pronounced for MT than PMT (respectively 101 ± 10 ms and 41 ± 6 ms slower, p<0.01). Elderly subjects showed significantly higher (p<0.01) antagonist muscle co-activation during the PMT-phase, which was significantly related to worse MT and RT (p<0.01). During the MT-phase, antagonist muscle co-activation was similar for both groups. It can be concluded that increased antagonist muscle co-activation in elderly persons occurs in an early phase, already before the start of the movement. These findings provide further understanding of the underlying mechanisms of age-related slowing of human motor performance.

Effects of slouching and muscle contraction on the strain of the iliolumbar ligament

The study consisted of biomechanical modelling and in vitro experiments. The objective of the study was to find a mechanical cause of acute low back pain (LBP) in everyday situations. The precise mechanism producing LBP is still under discussion. Most biomechanical studies link the concepts of stooped postures and buckling instability of the spine under high compressive load. No biomechanical model addresses situations with small or neglectable compressive spinal load. The proposed conceptual model describes strain on the iliolumbar ligaments (ILs) when slouching from standing upright. Delayed or absent recruitment of back muscles that protect against hyperkyphosis of the lumbar spine is a conditional factor. Erector spinae and multifidus muscle forces are included, representing a bifurcation in back muscle force: one part acting on the iliac bones and one part acting on the sacrum. The multifidus muscle action on the sacrum may produce nutation which can be counteracted by pelvic floor muscles, which would link back problems and pelvic floor problems. The effect of simulated muscle tension on the ILs and the L5-S1 intervertebral disc angle was measured using embalmed specimens. Forces were applied to simulate erector spinae and sacral part of multifidus tension, bilateral up to 100 N each. Strain gauge sensors registered elongation of the ILs. Explorative biomechanical model calculations show that dynamic slouching, driven by upper body weight and (as an example) rectus abdominis muscle force may produce failure load of the spinal column and the ILs. The quasi-static test on embalmed specimens showed a significant increase of IL elongation with simulated rectus abdominis muscle force. Adding erector spinae or multifidus muscle tension eased the ILs. Sudden slouching of the upright trunk may create failure risk for the spine and ILs. This loading mode may be prevented by controlling loss of lumbar lordosis with erector spinae and multifidus muscle force.

Possible harmful effects of high intra-abdominal pressure on the pelvic girdle

The present study explores the hypothesis that a high intra-abdominal pressure (IAP) loads the ligaments of the pelvic girdle to such an extent that frequent periods of high IAP might cause pain and/or interfere with recovery of patients with pelvic girdle pain (PGP). In a theoretical model the size of the load of IAP on the pelvic girdle was computed. The diameters of abdomen and pelvis needed for the calculations were measured on MRI scans; the IAP values during activities were gained from literature. In slim, healthy subjects the calculated load on the pelvic ring during activities of daily living was 26.0-52.0 N with peaks to 135 N. During straining, vigorous work or heavy exercises the load could increase to values ranging from 104 to 520 N. The load is higher in subjects with pain or fatigue, or in case of a distended abdomen. When the load on the pelvic ring induced by IAP is larger than 100 N, the force exceeds the force at which a pelvic belt relieves complaints in PGP; at 90 N, the force is larger than the force at which isometric hip adduction provokes pain in PGP. We conclude that the size of the load induced by IAP on the pelvic girdle seems to be sufficient to cause pain in patients with PGP and might interfere with recovery. It seems worthwhile to give patients with PGP instructions to reduce IAP as much as possible during activities.

Contribution of pelvic floor muscles to stiffness of the pelvic ring

STUDY DESIGN

A biomechanical study in embalmed specimens, on the relation between applied tension in the pelvic floor muscles, stiffness of the pelvic ring and generation of movement in the sacroiliac joints.

OBJECTIVE

To gain insight into the effect of tension in the pelvic floor muscles on stiffness of the pelvic ring. Background. According to a model on selfbracing pelvic floor muscles have the capacity to stiffen the sacroiliac joints. However, this capacity has not been demonstrated in vitro yet.

METHODS

In 18 embalmed specimens an incremental moment was applied to the sacroiliac joints to induce rotation of the innominate bones in the sagittal plane. After assessment of the relationship between rotation angle and moment, springs were applied to the pelvis to simulate tension in the pelvic floor muscles. During the simulated tension the measurements were repeated. Differences in stiffness before and after applying springs were tested for significance.

RESULTS

In females, simulated tension in the pelvic floor muscles stiffened the sacroiliac joints with 8.5% (P < 0.05). In males no significant changes occurred. In both sexes a backward rotation of the sacrum occurred due to simulated tension in the pelvic floor muscles (P < 0.05). The sacroiliac joints of female specimens were more mobile in comparison to male specimens (P < 0.05).

CONCLUSIONS

In females, pelvic floor muscles have the capacity to increase stiffness of the pelvic ring. In addition, these muscles can generate a backward rotation of the sacrum in both sexes.

RELEVANCE

The ability of pelvic floor muscles to increase stiffness of the pelvic ring is of importance in patients with impairment of pelvic stability, especially in pelvic pain patients. Increased activity of these pelvic floor muscles might compensate for loss of pelvic stability by stiffening the pelvic ring and restoring proper load transfer through the lumbopelvic region.

The iliolumbar ligament: its influence on stability of the sacroiliac joint

STUDY DESIGN

In human specimens the influence of the iliolumbar ligament on sacroiliac joint stability was tested during incremental moments applied to the sacroiliac joints.

OBJECTIVES

To assess whether the iliolumbar ligament is able to restrict sacroiliac joint mobility in embalmed cadavers.

BACKGROUND

Firstly, the sacroiliac joint can play an important role in non-specific low back pain; hence, its mobility and stability are of special interest. Secondly, the iliolumbar ligament is considered to be an important source of chronic low back pain. Data on a functional relation between the iliolumbar ligament and sacroiliac joint mobility are lacking.

METHODS

In 12 human specimens an incremental moment was applied to the sacroiliac joint to induce rotation in the sagittal plane. After the assessment of the relationship between rotation angle and moment in the intact situation, specific parts of the iliolumbar ligaments were transected. After each partial transection the measurements were repeated.

RESULTS

Sacroiliac joint mobility in the sagittal plane was significantly increased after a total cut of both iliolumbar ligaments. This increase was in particular due to the transection of a specific part of the iliolumbar ligament, the ventral band.

CONCLUSIONS

The main conclusions are: (a) the iliolumbar ligaments restrict sacroiliac joint sagittal mobility; (b) the ventral band of the iliolumbar ligament contributes most to this restriction.

RELEVANCE

In embalmed human cadavers, the mobility of the sacroiliac joint increases after sequential cutting of specific parts of the iliolumbar ligaments. It can be expected that severance of this ligament during surgery will lead to increase of mobility and hence loss of stability of the sacroiliac joint. As a consequence adjacent structures will be affected. This may well be a cause of pain in patients with failed back surgery.