Analyzing Pelvic Asymmetry by Sex and Ancestry: Insights From an Osteological Collection.

INTRODUCTION: Pelvic asymmetry has been noted in pelvic imaging, and might influence the development of various spinal pathologies, most notably scoliosis. There is a limited understanding of the relationship between pelvic asymmetry and sex and ancestry, and limited use of 3D modeling. The purpose of this study was to identify pelvic asymmetry and morphology differences between sex and ancestry utilizing 3D modeling on young adults in an osteological collection. METHODS: Thirty-three osteological pelvic specimens aged 18-25 years (average age 21.4 ± 2.0 years) were scanned to create virtual 3D models for analysis. Pelvic asymmetry and morphology were measured and compared across sex (male and female) and ancestry (European American and African American). Multivariate regression analysis was performed to examine the relationship between the variables measured. RESULTS: Multivariate regression analysis demonstrated statistically significant relationships between innominate-pelvic ring ratio and both sex (p < 0.001) and ancestry (p= 0.003) with larger ratios in male and African American specimens respectively. There was also a statistically significant relationship of greater sacral 1 coronal tilt in European American specimens (p= 0.042). There were no statistically significant differences with sex or ancestry in terms of innominate or sacral asymmetry. CONCLUSION: Although there are differences in overall pelvic shape between sex and ancestry, there is no relationship between these two variables versus pelvic asymmetry in the axial or sagittal planes in young adult osteological specimens.

Can We Estimate the Amount of Malrotation in Supracondylar Humerus Fractures After CRPP?

BACKGROUND: Acceptable amounts of malrotation after CRPP for pediatric supracondylar humerus fracture (SCHFx) have yet to be defined. This is an attempt to correlate radiographic parameters of a malrotated SCHFx with degrees of rotational malalignment to assist intraoperative assessment of reduction. METHODS: 3D models of a left distal humerus were printed, simulating a transverse SCHFx with 5, 10, 15, 20, 25, and 30 degrees of malrotation. Four different scenarios were developed: (1) lateral cortical axis of rotation, (2) medial cortical axis of rotation, (3) centroid of the humerus longitudinal axis with the medial condyle rotated posteriorly, and (4) centroid of the humerus longitudinal axis with the medial condyle rotated anteriorly. Anteroposterior and lateral fluoroscopic views were taken with a consistent image profile. Five observers measured the amount of metaphyseal overhang on the lateral view and the width of the distal humerus just proximal to the fracture to establish amount of overhang as a percentage of distal humerus width. Regression analysis established "best fit" lines for the 4 scenarios. Ten observers used the observed characteristics of each type of malrotation and "best fit" lines to estimate axis and degrees of malrotation using the same fluoroscopy of the 24 models. RESULTS: The intraclass correlation coefficient of reliability for percentage of metaphyseal overhang ranged from 0.775 to 0.987. Observers correctly predicted axis of malrotation in 76% and correctly predicted amount of malrotation in 75% of models. CONCLUSIONS: Estimation of axis of malrotation and degrees of malrotation within 5 degrees in SCHFx can be predicted in 75% of our 3D printed models.

The point of epiphyseal penetration affects rotational stability of screw fixation in slipped capital femoral epiphysis: A biomechanical study.

The epiphyseal tubercle, a posterosuperior projection of the epiphysis into the metaphysis, serves as the axis of rotation in slipped capital femoral epiphysis (SCFE) and a source of physeal stability. We hypothesized that in a biomechanical model of single screw fixation of stable SCFE, a screw passing through the epiphyseal tubercle (the axis of rotation) would confer less rotational stability than a centrally placed screw. Three femurs were selected from a sample population of 8- to 15-year-old healthy hips to represent three stages of maturation: a "young" femur with a prominent epiphyseal tubercle and decreased epiphyseal cupping around the metaphysis, a "median" femur with a subsiding tubercle, and a "mature" femur with a subsided epiphyseal tubercle and increased peripheral epiphyseal cupping. Specimens were three-dimensional printed with one of two screw trajectories: passing centrally in the epiphysis or directly through the epiphyseal tubercle. Resistance to rotational displacement was measured through stiffness and maximum torque over 30° degrees of displacement. In the "young" model, epiphyseal tubercle screw position conferred less rotational stiffness and required less maximum torque during rotational displacement when compared to a centrally placed screw (P < .001). In the "median" and "mature" models where the tubercle has subsided and is replaced by peripheral epiphyseal cupping, screw position through the tubercle was associated with equal or greater rotational stiffness and maximum torque during displacement as a centrally placed screw.

3D MRI Quantification of Femoral Head Deformity in Legg-Calvé-Perthes Disease.

The purpose of this study was to quantify femoral head deformity in patients with Legg-Calvé-Perthes disease (LCPD) using a novel three dimensional (3D) magnetic resonance imaging (MRI) reconstruction and volume based analysis. Bilateral femoral heads of 17 patients (mean age 9.9 ± 2.0 years; 12 boys, 5 girls) with LCPD were scanned 1-2 times (n = 33 LCPD heads, 20 normal heads) using a 1.5T MRI scanner. Fourteen patients had unilateral and three had bilateral LCPD with five hips in the Waldenström initial stage, 9 in the fragmentation stage, 14 in the reossification stage, and 5 in the healed stage. 3D digital reconstructions of femoral heads were created using MIMICS software. Deformity was quantified using a 3D volume ratio method based on reference hemisphere volume as well as two surface geometry methods. Intra-observer analysis showed that 97% of the LCPD femoral heads were within 10% of the original value and test shapes had 99.6% accuracy. For normal femoral heads, the volume ratios of all except one were between 95 and 98% (n = 20) of a perfect hemisphere volume. For femoral heads affected with LCPD, the volume ratios ranged from 43% to 96% of a perfect hemisphere (n = 33). The volume ratio method and the two surface geometry comparison methods had high correlation (r = 0.89 and 0.96). In summary, the 3D MRI volume ratio method allowed accurate quantification and demonstrated small changes (<10%) of the femoral head deformity in LCPD. This method may serve as a useful tool to evaluate the effects of treatment on femoral head shape. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:2051-2058, 2017.