A New Approach to the Measurement of Pelvic Asymmetry: Proposed Methods and Reliability

Three-Dimensional CT-Based Limb Length Evaluation Is Highly Dependent on Anatomical Landmark Selection and Pelvic Asymmetry

Background

Pelvic skeletal asymmetry can result in rotational differences and morphologic bony prominence variance between the left and right hemipelvis. When selecting bony reference points for modern computed tomography-based robotic total hip arthroplasty planning, it is unclear which bony landmarks are the most reliable and accurate, especially in the presence of significant pelvic asymmetry.

Methods

A retrospective study was conducted utilizing a database of computed tomography scans. Multiple bony landmarks in the pelvis and femur were selected for comparison, with the aim of measuring pelvic asymmetry. Specifically, the study measured the average difference in lateral offset between the left and right hemipelvis caused by pelvic asymmetry. Landmarks were also compared to determine the impact of pelvic asymmetry on hip length, femur length, and limb length discrepancies. Furthermore, a scenario was simulated in the software whereby a total hip replacement was inserted, potentially changing the hip length. The impact of pelvic reference point selection on the measurement of this simulated change in hip length was examined.

Results

This study population showed widespread pelvic asymmetry. The anatomical landmarks of the opposite side cannot be relied upon for predicting the anatomy of the affected side. The center of rotation axis is more reliable than the inferior obturator foramen axis for hip length discrepancy due to pelvic asymmetry (P < .05).

Conclusions

Current computer-assisted surgery THR software reports measurements of global offset and hip length that do not consider pelvic asymmetry. Surgeons are not given confidence ranges to represent the potential impact of asymmetry on the global offset and hip length values. Surgeons following these numbers to guide implant position may incur implant placement error should significant pelvic asymmetry be present in a given patient.

Asymmetry of the pelvis in Polish young adults

Introduction

Symmetry is one of the criteria of correct body posture in upright position. The spatial positioning of the pelvic girdle is crucial to it. Functional and structural asymmetries within the lumbo-pelvic-hip complex can have a significant influence on the structure and functions of many human body organs and systems. The aim of the study was to present the results of inclinometer measurements of selected landmarks of the pelvic girdle in young adults aged 19-29.

Methods

The analysis of occurrence of spatial pelvic asymmetry was based on the authors' original, clinical classification and the significance of the body mass and height for the analyzed asymmetries. The inclinometer measurements of the selected landmarks of the pelvic girdle were performed in a sample consisting of 300 young individuals. Then, the occurrences of the spatial asymmetry of the pelvis were analyzed based on the authors' own clinical classification using alignment symmetry of the iliac crests, the anterior superior iliac spines and the trochanters major as a criterion. All study subjects with asymmetry <1 degree were treated as those with a symmetrical pelvis.

Results

The significance of gender, body mass and height for the analyzed asymmetries was assessed. Symmetric positioning of the iliac crests was observed in only 32% of the respondents. The iliac crest depression on the left side was more frequently observed - in 41% of the respondents. This occurred more often in women (44%) than in men (38%). In the group of women, the rotated pelvis was the most often observed (39.4%) asymmetry, while for men, it was the oblique pelvis (40%). More detailed analysis by pelvic asymmetry subtypes showed their statistical differentiation between women and men (p    <     0.0001). Analysis of moderate rotation of the pelvis for men, were reported slightly higher values but these differences were not statistically significant (p = 0.253). Women, in turn, showed slightly higher mean values but here too, the differences were not statistically significant (p = 0.245).

Discussion

Asymmetries in the pelvis area are common; they were observed in less than three-quarters of the examined population. Oblique pelvis was found in less than a quarter of women and in more than one-third men with the predominant structural asymmetries. Rotated pelvis was observed in more than one-third of women and men with dominating functional asymmetries. There were no linear correlations between the body mass and height, and the angle of asymmetries.

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.

Pelvic Sagittal Torsion Caused by Induced Leg Length Discrepancy: Geometrical Illusion May Influence Measures Based on Superior-iliac Spines Positions

OBJECTIVE

To investigate whether a common measure of sagittal pelvic torsion based on the superior iliac spines behave similarly to predictions of a rigid (non-torsioned) plane, when leg length discrepancies (LLD) are induced.

METHOD

Twenty-four young asymptomatic participants were subjected to pelvic posture measurements that use the anterior-superior iliac spines (ASISs) and posterior-superior iliac spines (PSISs) as references, while standing on level ground and with a one-, two- and three-centimeter lifts under the left foot. A special caliper with digital inclinometers was used. The following angles were measured: angles of the right and left PSIS-to-ASIS lines; right-left relative angle (RLRA), as the angle between the right and left PSIS-to-ASIS lines, which is a traditional lateral-view measure intended to detect sagittal torsions; angle of the inter-ASISs line; angle of the inter-PSISs line; anterior-posterior relative angle (APRA), as the angle between the inter-ASISs and inter-PSISs lines. According to trigonometric predictions based on the geometry given by the lines linking the superior iliac spines (i.e. a trapezoid plane), a pure lateral tilt of the pelvis, without interinnominate sagittal motion, would change RLRA in a specific direction and would not change APRA.

RESULTS

Repeated-measures ANOVAs revealed that RLRA (p<0.001) and right and left PSIS-to-ASIS angles (p≤0.001) changed, and APRA did not change (p=0.33), as predicted.

CONCLUSIONS

At least part of the sagittal torsion detected by measures that assume the PSIS-to-ASIS angles as the sagittal angles of the innominates is due to pelvic geometry and not to the occurrence of actual torsion, when LLDs are induced.

The association between pelvic asymmetry and non-specific chronic low back pain as assessed by the global postural system

BACKGROUND

Empirical evidence that demonstrates the relationship between pelvic asymmetry and non-specific chronic low back pain (NCLBP) is currently lacking.

OBJECTIVE

To establish the reliability of the Global Postural System (GPS) in assessing pelvic asymmetry and identify the association between pelvic asymmetry parameters and the occurrence of NCLBP in young adults.

DESIGN

A cross-sectional, regression study.

METHODS

People who were aged between 18 and 30 and were diagnosed with NCLBP were recruited. Healthy individuals who were matched for age, sex, and education level were recruited as controls. Global Postural System (GPS) was employed to assess pelvic asymmetry. Prior to exploring the association, the reliability of GPS was assessed by the ICC (2, k) for interrater reliability, ICC (3, k) for intra-rater reliability, standard error and minimal detectable difference. Bivariate correlation analysis and logistic regression analysis were used to determine the relationship between pelvic asymmetry and the occurrence of NCLBP.

RESULTS

Twenty-eight healthy participants and 28 people with NCLBP were recruited. Moderate to excellent ICCs were observed for the inter-rater and intra-rater reliability of most postural parameters. The bivariate correlation analysis indicated that age, body mass index and pelvic asymmetry parameters were related to the occurrence of NCLBP. Pelvic angle asymmetry (odds ratio = 1.17), and asymmetry of the distance between the posterior superior iliac spine and the floor (odds ratio = 1.21) were associated with NCLBP.

LIMITATIONS

This study did not explore the causal relationship between pelvic asymmetry in the sagittal plane/pelvic asymmetry in the transverse plane and the occurrence of NCLBP. The interpretation of the results may not be generalized beyond the sample population.

CONCLUSIONS

The GPS is a reliable method to assess pelvic asymmetry in a clinical setting. Two pelvic parameters were associated with the presence of NLBP. Measurement of pelvic asymmetry may assist in the early identification of potential occurrence of NCLBP but further work is required.