Muscle functional MRI analysis of trunk muscle recruitment during extension exercises in asymptomatic individuals.

The present study examined the activity levels of the thoracic and lumbar extensor muscles during different extension exercise modalities in healthy individuals. Therefore, 14 subjects performed four different types of extension exercises in prone position: dynamic trunk extension, dynamic-static trunk extension, dynamic leg extension, and dynamic-static leg extension. Pre- and post-exercise muscle functional magnetic resonance imaging scans from the latissimus dorsi, the thoracic and lumbar parts of the longissimus, iliocostalis, and multifidus were performed. Differences in water relaxation values (T2-relaxation) before and after exercise were calculated (T2-shift) as a measure of muscle activity and compared between extension modalities. Linear mixed-model analysis revealed higher lumbar extensor activity during trunk extension compared with leg extension (T2-shift of 5.01 ms and 3.55 ms, respectively) and during the dynamic-static exercise performance compared with the dynamic exercise performance (T2-shift of 4.77 ms and 3.55 ms, respectively). No significant differences in the thoracic extensor activity between the exercises could be demonstrated. During all extension exercises, the latissimus dorsi was the least activated compared with the paraspinal muscles. While all extension exercises are equivalent effective to train the thoracic muscles, trunk extension exercises performed in a dynamic-static way are the most appropriate to enhance lumbar muscle strength.

The functional coupling of the deep abdominal and paraspinal muscles: the effects of simulated paraspinal muscle contraction on force transfer to the middle and posterior layer of the thoracolumbar fascia.

The thoracolumbar fascia (TLF) consists of aponeurotic and fascial layers that interweave the paraspinal and abdominal muscles into a complex matrix stabilizing the lumbosacral spine. To better understand low back pain, it is essential to appreciate how these muscles cooperate to influence lumbopelvic stability. This study tested the following hypotheses: (i) pressure within the TLF's paraspinal muscular compartment (PMC) alters load transfer between the TLF's posterior and middle layers (PLF and MLF); and (ii) with increased tension of the common tendon of the transversus abdominis (CTrA) and internal oblique muscles and incremental PMC pressure, fascial tension is primarily transferred to the PLF. In cadaveric axial sections, paraspinal muscles were replaced with inflatable tubes to simulate paraspinal muscle contraction. At each inflation increment, tension was created in the CTrA to simulate contraction of the deep abdominal muscles. Fluoroscopic images and load cells captured changes in the size, shape and tension of the PMC due to inflation, with and without tension to the CTrA. In the absence of PMC pressure, increasing tension on the CTrA resulted in anterior and lateral movement of the PMC. PMC inflation in the absence of tension to the CTrA resulted in a small increase in the PMC perimeter and a larger posterior displacement. Combining PMC inflation and tension to the CTrA resulted in an incremental increase in PLF tension without significantly altering tension in the MLF. Paraspinal muscle contraction leads to posterior displacement of the PLF. When expansion is combined with abdominal muscle contraction, the CTrA and internal oblique transfers tension almost exclusively to the PLF, thereby girdling the paraspinal muscles. The lateral border of the PMC is restrained from displacement to maintain integrity. Posterior movement of the PMC represents an increase of the PLF extension moment arm. Dysfunctional paraspinal muscles would reduce the posterior displacement of the PLF and increase the compliance of the lateral border. The resulting change in PMC geometry could diminish any effects of increased tension of the CTrA. This study reveals a co-dependent mechanism involving balanced tension between deep abdominal and lumbar spinal muscles, which are linked through the aponeurotic components of the TLF. This implies the existence of a point of equal tension between the paraspinal muscles and the transversus abdominis and internal oblique muscles, acting through the CTrA.

The sacroiliac joint: an overview of its anatomy, function and potential clinical implications.

This article focuses on the (functional) anatomy and biomechanics of the pelvic girdle and specifically the sacroiliac joints (SIJs). The SIJs are essential for effective load transfer between the spine and legs. The sacrum, pelvis and spine, and the connections to the arms, legs and head, are functionally interrelated through muscular, fascial and ligamentous interconnections. A historical overview is presented on pelvic and especially SIJ research, followed by a general functional anatomical overview of the pelvis. In specific sections, the development and maturation of the SIJ is discussed, and a description of the bony anatomy and sexual morphism of the pelvis and SIJ is debated. The literature on the SIJ ligaments and innervation is discussed, followed by a section on the pathology of the SIJ. Pelvic movement studies are investigated and biomechanical models for SIJ stability analyzed, including examples of insufficient versus excessive sacroiliac force closure.

A description of the lumbar interfascial triangle and its relation with the lateral raphe: anatomical constituents of load transfer through the lateral margin of the thoracolumbar fascia.

Movement and stability of the lumbosacral region is contingent on the balance of forces distributed through the myofascial planes associated with the thoracolumbar fascia (TLF). This structure is located at the common intersection of several extremity muscles (e.g. latissimus dorsi and gluteus maximus), as well as hypaxial (e.g. ventral trunk muscles) and epaxial (paraspinal) muscles. The mechanical properties of the fascial constituents establish the parameters guiding the dynamic interaction of muscle groups that stabilize the lumbosacral spine. Understanding the construction of this complex myofascial junction is fundamental to biomechanical analysis and implementation of effective rehabilitation in individuals with low back and pelvic girdle pain. Therefore, the main objectives of this study were to describe the anatomy of the lateral margin of the TLF, and specifically the interface between the fascial sheath surrounding the paraspinal muscles and the aponeurosis of the transversus abdominis (TA) and internal oblique (IO) muscles. The lateral margin of the TLF was exposed via serial reduction dissections from anterior and posterior approaches. Axial sections (cadaveric and magnetic resonance imaging) were examined to characterize the region between the TA and IO aponeurosis and the paraspinal muscles. It is confirmed that the paraspinal muscles are enveloped by a continuous paraspinal retinacular sheath (PRS), formed by the deep lamina of the posterior layer of the TLF. The PRS extends from the spinous process to transverse process, and is distinct from both the superficial lamina of the posterior layer and middle layer of the TLF. As the aponeurosis approaches the lateral border of the PRS, it appears to separate into two distinct laminae, which join the anterior and posterior walls of the PRS. This configuration creates a previously undescribed fat-filled lumbar interfascial triangle situated along the lateral border of the paraspinal muscles from the 12th rib to the iliac crest. This triangle results in the unification of different fascial sheaths along the lateral border of the TLF, creating a ridged-union of dense connective tissue that has been termed the lateral raphe (Spine, 9,1984, 163). This triangle may function in the distribution of laterally mediated tension to balance different viscoelastic moduli, along either the middle or posterior layers of the TLF.

The thoracolumbar fascia: anatomy, function and clinical considerations.

In this overview, new and existent material on the organization and composition of the thoracolumbar fascia (TLF) will be evaluated in respect to its anatomy, innervation biomechanics and clinical relevance. The integration of the passive connective tissues of the TLF and active muscular structures surrounding this structure are discussed, and the relevance of their mutual interactions in relation to low back and pelvic pain reviewed. The TLF is a girdling structure consisting of several aponeurotic and fascial layers that separates the paraspinal muscles from the muscles of the posterior abdominal wall. The superficial lamina of the posterior layer of the TLF (PLF) is dominated by the aponeuroses of the latissimus dorsi and the serratus posterior inferior. The deeper lamina of the PLF forms an encapsulating retinacular sheath around the paraspinal muscles. The middle layer of the TLF (MLF) appears to derive from an intermuscular septum that developmentally separates the epaxial from the hypaxial musculature. This septum forms during the fifth and sixth weeks of gestation. The paraspinal retinacular sheath (PRS) is in a key position to act as a 'hydraulic amplifier', assisting the paraspinal muscles in supporting the lumbosacral spine. This sheath forms a lumbar interfascial triangle (LIFT) with the MLF and PLF. Along the lateral border of the PRS, a raphe forms where the sheath meets the aponeurosis of the transversus abdominis. This lateral raphe is a thickened complex of dense connective tissue marked by the presence of the LIFT, and represents the junction of the hypaxial myofascial compartment (the abdominal muscles) with the paraspinal sheath of the epaxial muscles. The lateral raphe is in a position to distribute tension from the surrounding hypaxial and extremity muscles into the layers of the TLF. At the base of the lumbar spine all of the layers of the TLF fuse together into a thick composite that attaches firmly to the posterior superior iliac spine and the sacrotuberous ligament. This thoracolumbar composite (TLC) is in a position to assist in maintaining the integrity of the lower lumbar spine and the sacroiliac joint. The three-dimensional structure of the TLF and its caudally positioned composite will be analyzed in light of recent studies concerning the cellular organization of fascia, as well as its innervation. Finally, the concept of a TLC will be used to reassess biomechanical models of lumbopelvic stability, static posture and movement.

Stabilization of the sacroiliac joint in vivo: verification of muscular contribution to force closure of the pelvis.

A model of sacroiliac joint (SIJ) function postulates that SIJ shear is prevented by friction, dynamically influenced by muscle force and ligament tension. Thus, SIJ stability can be accommodated to specific loading situations. The purpose of this study was to examine, in vivo, whether muscles contribute to force closure of the SIJ. SIJ stiffness was measured using a verified method combining color Doppler imaging with induced oscillation of the ilium relative to the sacrum in six healthy women. SIJ stiffness was measured both in a relaxed situation and during isometric voluntary contractions (electromyographically recorded). The biceps femoris, gluteus maximus, erector spinae, and contralateral latissimus dorsi were included in this study. Results were statistically analyzed. The study showed that SIJ stiffness significantly increased when the individual muscles were activated. This held especially true for activation of the erector spinae, the biceps femoris and the gluteus maximus muscles. During some tests significant co-contraction of other muscles occurred. The finding that SIJ stiffness increased even with slight muscle activity supports the notion that effectiveness of load transfer from spine to legs is improved when muscle forces actively compress the SIJ, preventing shear. When joints are manually tested, the influence of muscle activation patterns must be considered, since both inter- and intra-tester reliability of the test can be affected by muscle activity. In this respect, the relation between emotional states, muscle activity and joint stiffness deserves further exploration.

Reliability and validity of the active straight leg raise test in posterior pelvic pain since pregnancy.

STUDY DESIGN: A cross-sectional analysis was performed in a group of women meeting strict criteria for posterior pelvic pain since pregnancy (PPPP). The scores on the Active Straight Leg Raise Test (ASLR test) were compared with the scores of healthy controls. OBJECTIVES: To develop a new diagnostic instrument for use in patients with PPPP. The objectives of the present study were to assess the validity and reliability of the ASLR test. SUMMARY OF BACKGROUND DATA: Various diagnostic tools are used to diagnose PPPP, but there is still a need for simple tests with high reliability, sensitivity, and specificity. METHODS: Reliability of the ASLR test was assessed in a group of 50 women with lumbopelvic pain of various etiologies and various degrees of severity. Sensitivity was assessed in 200 patients with PPPP and specificity in 50 healthy women. Sensitivity and specificity of the ASLR test were compared with the posterior pelvic pain provocation test (PPPP test). RESULTS: The test-retest reliability measured with Pearson's correlation coefficient between the two ASLR scores 1 week apart was 0.87. The intraclass correlation coefficient (ICC) was 0.83. Pearson's correlation coefficient between the scores of the patient and the scores of a blinded assessor was 0.78; the ICC was 0.77. In the patient group, the ASLR score ranged from 0-10; in the control group it ranged from 0-2. The best balance between specificity and sensitivity was found when scores 1-10 are designated as positive and zero as negative. With this cut-off point sensitivity of the test was 0.87 and specificity was 0.94. The sensitivity of the ASLR test is higher than the sensitivity of the PPPP test; an advantage of the ASLR test is the simplicity of measuring the score. CONCLUSION: The ASLR test is a suitable diagnostic instrument to discriminate between patients who are disabled by PPPP and healthy subjects. The test is easy to perform; reliability, sensitivity, and specificity are high. It seems that the integrity of the function to transfer loads between the lumbosacral spine and legs is tested by the ASLR test.

Exercise treatment for sacroiliac pain.

The reciprocal relationship of the latissimus dorsi on one side and the gluteus maximus on the other side has been demonstrated anatomically. To demonstrate this relationship by muscle action, electromyographic studies were performed in 15 healthy individuals. This formed the baseline for evaluation of 5 symptomatic patients with sacroiliac dysfunction. Abnormal hyperactivity of the gluteus muscle on the involved side and increased activity of the latissimus on the contralateral side was contrasted with the normal function of the healthy individuals. All patients in the rotary strengthening exercise program improved in strength and return of myoelectric activity to more normal patterns.

A radiostereometric analysis of movements of the sacroiliac joints during the standing hip flexion test.

STUDY DESIGN: The standing hip flexion test was evaluated by using a radiostereometric analysis. OBJECTIVES: To evaluate whether the commonly used standing hip flexion test reflects movement in the sacroiliac joints, or whether the increased load of one sacroiliac joint also reduces the mobility of the other sacroiliac joint according to the theory of form and form closure in the sacroiliac joints. SUMMARY OF BACKGROUND DATA: The standing hip flexion test, used frequently to analyze sacroiliac joint mobility, is advocated as a test for study of normal or impaired motion in the sacroiliac joint. METHODS: In this study, 22 patients considered to have sacroiliac pain were analyzed with radiostereometric analysis when standing and when performing the standing hip flexion test on the right and left sides. RESULTS: Very small movements were registered in the sacroiliac joints. When provoking one side, the rotations were small on both sides. CONCLUSIONS: The small movements registered support the theory of form and force closure in the sacroiliac joints. The self-locking mechanism that goes into effect when the pelvis is loaded in a one-leg standing position probably obstructs the movements in the sacroiliac joints. Therefore, the standing hip flexion test cannot be recommended as a diagnostic tool for evaluating joint motion in the sacroiliac joints.

A radiostereometric analysis of the movements of the sacroiliac joints in the reciprocal straddle position.

STUDY DESIGN: A Radiostereometric analysis of the reciprocal straddle position. OBJECTIVES: To evaluate the magnitude of rotation in the sacroiliac joints in the reciprocal straddle position. SUMMARY OF BACKGROUND DATA: The reciprocal straddle position has been objectified in different studies, using different techniques, to show a sacroiliac motion between 5 degrees and 36 degrees. Previous studies with radiostereometric analysis during different provocations reported much smaller movements. METHODS: Six women with posterior pelvic pain of long duration after pregnancy (n = 5) and sacroiliitis (n = 1) underwent radiostereometric analysis in the sustained reciprocal straddle position. RESULTS: A reciprocal movement could be demonstrated in the sacroiliac joints in the reciprocal straddle position. However, the movements were 10 times smaller than reported in earlier studies of the reciprocal straddle position. CONCLUSIONS: It was possible to demonstrate reciprocal movements of the sacroiliac joints in the straddle position. However, the radiostereometric analysis technique showed the movements to be small, as reported in other mobility studies.

Upper limb tension tests as tools in the diagnosis of nerve and plexus lesions. Anatomical and biomechanical aspects.

OBJECTIVE: To analyse the validity of nerve tension tests used in the diagnosis of nerve (root) and plexus lesions of the upper extremity. DESIGN: In six arms of embalmed human bodies, in situ measurements were performed to assess the effect of nerve tension tests on the median, ulnar and radial nerves and the cords of the brachial plexus. BACKGROUND: In clinical practice it is useful to have fast, easy and cheap tests for the diagnosis of nerve (root) lesions of the upper extremity, analogous to Lasègue's Straight Leg Raising test.Methods. The Upper Limb Tension Tests for the median, ulnar and radial nerves, as well as the Upper Limb Tension Tests combined with contralateral rotation and lateral bend of the cervical spine (Upper Limb Tension Test+) were used to generate tension to these nerves. Buckle force transducers were used to assess tensile forces in the nerves and in the medial, lateral and posterior cords of the brachial plexus. RESULTS: Nerve tension introduced in the distal part of the median, ulnar and radial nerves was transmitted upward to the cords of the brachial plexus. Exclusively the median nerve Upper Limb Tension Test and Upper Limb Tension Test+ turned out to be sensitive and specific tension tests. Mechanical tension caused by the Upper Limb Tension Test+ was not significantly higher than that caused by the Upper Limb Tension Tests. The Upper Limb Tension Tests cannot be used to selectively stress cervical nerve roots. The findings justify investigation of exclusively the median nerve Upper Limb Tension Test and Upper Limb Tension Test+ on their clinical validity. RELEVANCE: Before nerve tension tests for the median, ulnar and radial nerves can be introduced to clinical practice it is necessary to assess their validity quantitatively.

The active straight leg raising test and mobility of the pelvic joints.

Objective signs to assess impairment in patients who are disabled by peripartum pelvic girdle pain hardly exist. The purpose of this study was to develop a clinical test to quantify and qualify disability in these patients. The study examined the relationship between impaired active straight leg raising (ASLR) and mobility of pelvic joints in patients with peripartum pelvic girdle pain, focusing on (1) the reduction of impairment of ASLR when the patient was wearing a pelvic belt, and (2) motions between the pubic bones measured by X-ray examination when the patient was standing on one leg, alternating left and right. Twenty-one non-pregnant patients with peripartum pelvic girdle pain in whom pain and impairment of ASLR were mainly located on one side were selected. ASLR was performed in the supine position, first without a pelvic belt and then with a belt. The influence of the belt on the ability to actively raise the leg was assessed by the patient. Mobility of the pelvic joints was radiographically visualized by means of the Chamberlain method. Assessment was blinded. Ability to perform ASLR was improved by a pelvic belt in 20 of the 21 patients (binomial two-tailed P = 0.0000). When the patient was standing on one leg, alternating the symptomatic side and the reference side, a significant difference between the two sides was observed with respect to the size of the radiographically visualized steps between the pubic bones (binomial two-tailed P = 0.01). The step at the symptomatic side was on average larger when the leg at that side was hanging down than when the patient was standing on the leg at that side. Impairment of ASLR correlates strongly with mobility of the pelvic joints in patients with peripartum pelvic girdle pain. The ASLR test could be a suitable instrument to quantify and qualify disability in diseases related to mobility of the pelvic joints. Further studies are needed to assess the relationship with clinical parameters, sensitivity, specificity and responsiveness in various categories of patients. In contrast with the opinion of Chamberlain, that a radiographically visualized step between the pubic bones is caused by cranial shift of the pubic bone at the side of the standing leg, it is concluded that the step is caused by caudal shift of the pubic bone at the side of the leg hanging down. The caudal shift is caused by an anterior rotation of the hip bone about a horizontal axis near the sacroiliac joint.

Insufficient lumbopelvic stability: a clinical, anatomical and biomechanical approach to 'a-specific' low back pain.

SUMMARY. A clinical, anatomical and biomechanical model is introduced based on the concept that under postural load specific ligament and muscle forces are necessary to intrinsically stabilize the pelvis. Since load transfer from spine to pelvis passes through the sacroiliac (SI) joints, effective stabilization of these joints is essential. The stabilization of the SI joint can be increased in two ways. Firstly, by interlocking of the ridges and grooves on the joint surfaces (form closure); secondly, by compressive forces of structures like muscles, ligaments and fascia (force closure). Muscle weakness and insufficient tension of ligaments can lead to diminished compression, influencing load transfer negatively. Continuous strain of pelvic ligaments can be a consequence leading to pain. For treatment purposes stabilization techniques followed by specific muscle strengthening procedures are indicated. When there is a loss of force closure, for instance in peripartum pelvic instability, application of a pelvic belt can be advised. Copyright 1998 Harcourt Publishers Ltd.

Understanding peripartum pelvic pain. Implications of a patient survey.

STUDY DESIGN: An analysis was made of the self-reported medical histories of patients with peripartum pelvic pain. OBJECTIVES: To compile an inventory of the disabilities of patients with peripartum pelvic pain, analyze factors associated with the risk for development of the disease, and to formulate a hypothesis on pathogenesis and specific preventive and therapeutic measures. SUMMARY OF BACKGROUND DATA: Pregnancy is an important risk factor for development of chronic low back pain. Understanding the pathogenesis of pelvic and low back pain during pregnancy and delivery could be useful in understanding and managing nonspecific low back pain. METHODS: By means of a questionnaire, background data were collected among patients of the Dutch Association for Patients With Pelvic Complaints in Relation to Symphysiolysis. Results were compared with the general population. Subgroups were compared with each other. RESULTS: Peripartum pelvic pain seriously interferes with many activities of daily living such us standing, walking, sitting, and all other activities in which the pelvis is involved. Most patients experience a relapse around menstruation and during a subsequent pregnancy. Occurrence of peripartum pelvic pain was associated with twin pregnancy, first pregnancy, higher age at first pregnancy, larger weight of the baby, forceps or vacuum extraction, fundus expression, and a flexed position of the woman during childbirth; a negative association was observed with cesarean section. CONCLUSIONS: It is hypothesized that peripartum pelvic pain is caused by strain of ligaments in the pelvis and lower spine resulting from a combination of damage to ligaments (recently or in the past), hormonal effects, muscle weakness, and the weight of the fetus.

The function of the long dorsal sacroiliac ligament: its implication for understanding low back pain.

STUDY DESIGN: In embalmed human bodies the tension of the long dorsal sacroiliac ligament was measured during incremental loading of anatomical structures that are biomechanically relevant. OBJECTIVES: To assess the function of the long dorsal sacroiliac ligament. SUMMARY OF BACKGROUND DATA: In many patients with aspecific low back pain or peripartum pelvic pain, pain is experienced in the region in which the long dorsal sacroiliac ligament is located. It is not well known that the ligament can be easily palpated in the area directly caudal to the posterior superior iliac spine. Data on the functional and clinical importance of this ligament are lacking. METHODS: A dissection study was performed on the sacral and lumbar regions. The tension of the long dorsal sacroiliac ligament (n = 12) was tested under loading. Tension was measured with a buckle transducer. Several structures, including the erector spinae muscle, the posterior layer of the thoracolumbar fascia, the sarcotuberous ligament, and the sacrum, were incrementally loaded (with forces of 0-50 newtons). The sacrum was loaded in two directions, causing nutation (ventral rotation of the sacrum relative to the iliac bones) and counternutation (the reverse). RESULTS: Forced nutation in the sacroiliac joints diminished the tension and forced counternutation increased the tension. Tension in the long dorsal sacroiliac ligament increased during loading of the ipsilateral sacrotuberous ligament and erector spinae muscle. The tension decreased during traction to the gluteus maximus muscle. Tension also decreased during traction to the ipsilateral and contralateral posterior layer of the thoracolumbar fascia in a direction simulating contraction of the latissimus dorsi muscle. CONCLUSIONS: The long dorsal sacroiliac ligament has close anatomical relations with the erector spinae muscle, the posterior layer of the thoracolumbar fascia, and a specific part of the sacrotuberous ligament (tuberoiliac ligament). Functionally, it is an important link between legs, spine, and arms. The ligament is tensed when the sacroiliac joints are counternutated and slackened when nutated. The reverse holds for the sacrotuberous ligament. Slackening of the long dorsal sacroiliac ligament can be counterbalanced by both the sacrotuberous ligament and the erector muscle. Pain localized within the boundaries of the long ligament could indicate among other things a spinal condition with sustained counternutation of the sacroiliac joints. In diagnosing patients with aspecific low back pain or peripartum pelvic pain, the long dorsal sacroiliac ligament should not be neglected. Even in cases of arthrodesis of the sacroiliac joints, tension in the long ligament can still be altered by different structures.

The use of color Doppler imaging for the assessment of sacroiliac joint stiffness: a study on embalmed human pelvises.

PURPOSE: The validity and reproducibility of an instrumented dynamic examination method to measure sacroiliac (SI) joint stiffness was tested in vitro. METHODS: Four embalmed human female pelvises were excitated by a pelvic vibrator. A color Doppler imaging (CDI) scanner was used to image the amplitude of vibrations at different sites of the pelvis. Vibrations were applied to the anterior superior iliac spines unilaterally and were received by CDI all over the ipsilateral SI region. Three different stability conditions were created in the SI joints: no intervention, screwed and ligaments cut. Test results were quantified by taking the minimum threshold levels of the bones. The relative difference of vibration intensity between ipsilateral ilium and sacrum at each stability condition is accepted as the stiffness level for the SI joint. RESULTS: Statistics showed high reproducibility and significant differences between the stability conditions. Dynamic testing based on the use of vibrations provides visible and quantifiable intra- and inter-individual differences between SI joint stiffnesses. CONCLUSIONS: This new method is objective and reproducible. Future in vivo application is promising since there are no technical and safety restrictions.

The measurements of sacroiliac joint stiffness with colour Doppler imaging: a study on healthy subjects.

RATIONALE AND OBJECTIVES: Primary peripartum pelvic and low back pain is a common complaint of females. The etiologic relation between pain and pelvic stability has been shown in previous studies, but at present there is no objective clinical testing method to evaluate pelvic stability. METHODS: In this study, a dynamic measurement method using sonoelasticity to assess the sacroiliac joint (SI) stiffness was tested in vivo in 14 healthy female volunteers. With the subjects in supine position vibrations were unilaterally applied to the anterior iliac spine. The vibrations were registered by a Colour Doppler Imaging (CDI) transducer over the ipsilateral SI joint. Since the threshold level of the apparatus has a direct relation with the power of the vibrations, the intensity of the vibrations (sonoelasticity) on the sacrum and ilium was measured indirectly in threshold units. The differences between the threshold values were accepted as the power loss of vibrations through the SI joint. One-way analysis of variance-test and T-test for paired samples were applied on the measurement results (P < 0.05). RESULTS: Statistically, the results showed a satisfactory intraindividual reproducibility and inter-individual variability. There was no significant difference between the data derived from the left SI joint and right SI joint. CONCLUSIONS: Based on the promising results on healthy female volunteers, this method will be specifically used in future studies on patients with peripartum pelvic pain.

Why leg crossing? The influence of common postures on abdominal muscle activity.

STUDY DESIGN: Abdominal muscle activity is recorded in the supine position, unconstrained standing, and in the sitting position on an office chair with the use of backrest and armrests, with and without crossed legs. OBJECTIVES: To assess the role of oblique abdominal muscles in relation to the stability of lumbar spine and pelvis in commonly adopted unconstrained postures. SUMMARY OF BACKGROUND DATA: Cross-legged sitting is very common for men and women. No solid evidence exists for either a beneficial or a detrimental effect of this posture. No electromyographic study deals with the activity of abdominal muscles in this commonly adopted unconstrained posture. METHODS: In healthy subjects, electromyographic activity of the rectus abdomini and external and internal oblique abdominals was recorded bilaterally during commonly adopted unconstrained postures. RESULTS: The activity of the internal oblique muscle was significantly higher in the sitting position than in supine position. For the external and internal oblique abdominals, the activity was significantly higher in the standing position than in the sitting position. When sitting, the activity of the oblique abdominals is significantly lowered by crossing the legs in the preferred way (either upper legs cross or ankle on knee). In contrast, the activity of the rectus abdominis is not significantly altered by leg crossing. CONCLUSIONS: From these remarkable findings, we conclude that leg crossing is physiologically valuable. It should be studied whether leg crossing can be implemented in the design of the workplace.

Peripheral nerve tension due to joint motion. A comparison between embalmed and unembalmed human bodies.

Various joint positions of the upper extremity were used to study the tensile forces on the median nerve. To analyse the effect of embalmment, tensile forces were measured in situ in unembalmed and embalmed human bodies. A positive correlation was found between tensile force data from unembalmed and embalmed nerves. This finding justifies, for comparative studies, the use of embalmed human bodies, although the absolute tensile forces are higher. RELEVANCE: In daily activities or during certain operations positions of the upper extremity vary, hence creating tensile forces of different magnitude on peripheral nerves. Tensile forces are also applied in the diagnosis of nerve (root) lesions of the upper extremity. To analyse these tensile forces, in-situ experiments on unembalmed human bodies, though problematic, are supposed to be the most realistic approach. In this study it has been shown that in comparative studies on peripheral nerve tension, data obtained from embalmed human bodies can be used.