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

Activation asymmetry of the lateral abdominal muscles in response to neurodevelopmental traction technique in children with pelvic asymmetry

Study aim: The aim of the study was to evaluate asymmetry of activation of lateral abdominal muscles (LAM) in response to neurodevelopmental traction technique in children with pelvic asymmetry.

Material and methods: Measurements of LAM activation asymmetry were performed during traction with the force of 5% body weight in two experimental conditions: 1) in neutral position, 2) in 20° posterior trunk inclination. Twenty-three healthy children with pelvic asymmetry participated in the study. To evaluate LAM activation asymmetry ultrasound technology was employed (two Mindray DP660 devices (Mindray, Shenzhen, China)). Activation asymmetry indices for each individual LAM were calculated.

Results: The magnitude of LAM activation asymmetry indexes formed a gradient, with the most profound transversus abdominis (TrA) showing the greatest asymmetry, and the most superficial obliquus externus – the smallest. The inter-muscle differences were most pronounced between the TrA and the two more superficial oblique muscles. There were no correlation between the magnitude of pelvic asymmetry and LAM activation asymmetry.

Conclusions: During the neurodevelopmental traction technique there is a difference in individual LAM activation symmetry, with deeper muscles showing greater asymmetry. The activation asymmetry of the LAM does not seem to be associated with the pelvic asymmetry. Results are similar to those recorded in earlier studies in samples where no pelvic asymmetry were subjected to analysis.

Automated ultrasound measurements of lateral abdominal muscles under controlled breathing phases

BACKGROUND AND OBJECTIVES

A breathing phase during ultrasound measurements of the lateral abdominal muscles (LAMs) are usually indirectly controlled by visual inspection of the position of the transversus abdominis (TrA) muscle. This is due to the lack of devices to directly control airflow that are connected to the ultrasound in order to automatically and simultaneously freeze ultrasound images at the programmed breathing phase. Such indirect control may be related with potential measurement error because LAMs are respiratory muscles. Thus, the aim of this study was to present a newly developed and automatic measurement procedure to directly control airflow and at the same time automatically collect ultrasound images at the programed breathing phase. Additionally, it was decided to compare LAMs measurements obtained manually by the examiner and with an external device controlling the peak phase of tidal inspiration and expiration and compare the elasticity and thickness measurements between tidal inspiration and expiration in young participants.

METHODS

The study was carried out on 10 healthy youth. The thickness and shear modulus were measured by an Aixplorer ultrasound scanner. The measurements were obtained manually by the examiner and with a newly developed external device controlling the peak phases of tidal inspiration and expiration.

RESULTS

A significant difference in external/internal oblique thickness between the expiration and inspiration phases depended on the measurement procedure. The TrA thickness was similar during inspiration and expiration. During inspiration, the TrA shear modulus was higher than during expiration, and the TrA shear modulus depended on the measurement procedure.

CONCLUSION

Although the raw LAMs thickness and external/internal oblique thickness/shear modulus data were similar, the measurement procedure may affect the interpretation of the results. The TrA shear modulus is the most vulnerable to errors related to the measurement procedure. Construction of this study device controlling airflow and automatically collecting ultrasound images at the selected breathing phase seems to be promising in future studies considering measurements of respiratory muscles in a strictly defined breathing phase.

ENHANCED ACTIVE CONTRACTION OF THE TRANSVERSUS ABDOMINIS DURING WALKING

ABSTRACT Introduction: We applied three-dimensional gait analysis to assess the effects of enhanced active contraction of the transversus abdominis (EACTA) during walking. We sought to evaluate the effect of EACTA during walking in order to improve walking quality. Methods: Thirty college students were recruited and trained to perform EACTA during walking. We examined gait parameters under different conditions, including EACTA and habitual ACTA (natural walking with mild contraction of the feedforward mechanism of ACTA, HACTA) during walking using three-dimensional gait analysis. We compared differences in gait parameters under the two walking conditions using SPSS 16.0 statistical software. Results: The following gait parameters were significantly lower under EACTA conditions than under HACTA conditions (P < 0.05): stance phase, 59.151% ± 1.903% vs. 59.825% ± 1.495%; stride time, 1.104 s ± 0.080 s vs. 1.134 s ± 0.073 s:; stance time, 0.656 s ± 0.057 s vs. 0.678 s ± 0.053 s; and swing time, 0.447 s ± 0.028 s vs. 0.454 s ± 0.031 s, respectively. Gait parameters single support phase and mean velocity were significantly higher for EACTA than for HACTA conditions (both P < 0.05). Conclusions: Overall, the results revealed that EACTA during walking can improve gait. This method is simple, and EACTA training during walking to improve gait quality in daily life could provide a positive basis for people to strengthen the transverse abdominal muscle. Level of evidence III; Retrospective comparative study .

What do we know about the biomechanics of the sacroiliac joint and of sacropelvic fixation? A literature review

The purpose of this review is to summarize the general knowledge about the biomechanics of the sacroiliac joint and sacropelvic fixation techniques. Additionally, this study aims to support biomechanical investigations in defining experimental protocols as well as numerical modeling of the sacropelvic structures. The sacroiliac joint is characterized by a large variability of shape and ranges of motion among individuals. Although the ligament network and the anatomical features strongly limit the joint movements, sacroiliac displacements and rotations are not negligible. Currently available treatments for sacroiliac joint dysfunction include physical therapy, steroid injections, Radio-frequency ablation of specific neural structures, and open or minimally invasive SIJ fusion. In long posterior construct, the most common solutions are the iliac screws and the S2 alar - iliac screws, whereas for the joint fixation alone, mini - invasive alternative system can be used. Several studies reported the clinical outcomes of the different techniques and investigated the biomechanical stability of the relative construct, but the effect of sacropelvic fixation techniques on the joint flexibility and on the stress generated into the bone is still unknown. In our opinion, more biomechanical analyses on the behavior of the sacroiliac joint may be performed in order to better predict the risk of failure or instability of the joint.

Biomechanical study of three kinds of internal fixation for the treatment of sacroiliac joint disruption using biomechanical test and finite element analysis

BACKGROUND

To compare the stability of sacroiliac joint disruption fixed with three kinds of internal fixation using both biomechanical test and finite element analysis.

METHODS

Five embalmed specimens of an adult were used. The symphysis pubis rupture and left sacroiliac joint disruption were created. The symphysis pubis was stabilized with a five-hole plate. The sacroiliac joint disruption was fixed with three kinds of internal fixation in a randomized design. Displacements of the whole specimen and shifts in the gap were recorded. Three-dimensional finite element models of the pelvis, the pelvis with symphysis pubis rupture and left sacroiliac joint disruption, and three kinds of internal fixation techniques were created and analyzed.

RESULTS

Under the vertical load, the displacements and shifts in the gap of the pelvis fixed with minimally invasive adjustable plate (MIAP) combined with one iliosacral (IS) screw were the smallest, and the average displacements of the pelvis fixed with an anterior plate were the largest one. The differences among them were significant. In finite element analysis and MIAP combined with one IS screw fixation showed relatively best fixation stability and lowest risks of implant failure than two IS screws fixation and anterior plate fixation.

CONCLUSION

The stability of sacroiliac joint disruption fixed with MIAP combined with one IS screw is better than that fixed with two IS screws and anterior plate under vertical load.

Biomechanical study of different fixation techniques for the treatment of sacroiliac joint injuries using finite element analyses and biomechanical tests

The pelvis is one of the most stressed areas of the human musculoskeletal system due to the transfer of truncal loads to the lower extremities. Sacroiliac joint injury may lead to abnormal joint mechanics and an unstable pelvis. Various fixation techniques have been evaluated and discussed. However, it may be difficult to investigate each technique due to variations in bone quality, bone anatomy, fracture pattern, and fixation location. Additionally, the finite element method is one useful technology that avoids these variations. Unfortunately, most previous studies neglected the effects of the lumbar spine and femurs when they investigated the biomechanics of pelvises. Thus, the aim of this study was to investigate the biomechanical performance of intact, injured, and treated pelvises using numerical and experimental approaches. Three-dimensional finite element models of the spine-pelvis-femur complex with and without muscles and ligaments were developed. The intact pelvis, the pelvis with sacroiliac joint injury, and three types of pelvic fixation techniques were analyzed. Concurrently, biomechanical tests were conducted to validate the numerical outcomes using artificial pelvises. Posterior iliosacral screw fixation showed relatively better fixation stability and lower risks of implant failure and pelvic breakage than sacral bar fixation and a locking compression plate fixation. The present study can help surgeons and engineers understand the biomechanics of intact, injured, and treated pelvises. Both the simulation technique and the experimental setup can be applied to investigate different pelvic injuries.