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The Herring lateral pillar classification is widely used for the classification of Legg-Calvé-Perthes disease, but is not applied at the early stage of Legg-Calvé-Perthes disease because it is typically applied at the late fragmentation stage. The purpose of this study was to investigate the correlation between the early appearance on magnetic resonance imaging of the acetabular labrum and lateral pillar involvement in Legg-Calvé-Perthes disease.Non-contrast magnetic resonance images of 26 hips in 25 children with early-stage Legg-Calvé-Perthes disease were retrospectively reviewed. The extent of labral horizontalization was quantitatively evaluated with a new method, the labral angle, on T2*-weighted magnetic resonance images. A small labral angle indicates strong labral horizontalization. Calculation of the teardrop distance and acetabular head index on radiographs was modified for application to magnetic resonance imaging, and the extent of cartilaginous lateral subluxation (cartilaginous tear drop distance) and cartilaginous lateral extrusion (cartilaginous acetabular head index) were evaluated. The outcome measure was the lateral pillar classification.There were statistically significant correlations between the labral angle and the cartilaginous tear drop distance (p = 0.002, ɤ = -0.58) and the cartilaginous acetabular head index (p 0.001, ɤ = 0.65) on magnetic resonance images. The labral angle was small in order of groups C, B, and A, and there were significant differences between groups A and C (p 0.001) and B and C (p = 0.006).Greater labral horizontalization observed on magnetic resonance imaging at the early stage of Legg-Calvé-Perthes disease correlated with strong cartilaginous lateral subluxation and extrusion, and with increased lateral pillar collapse at the maximum fragmentation stage. Our finding suggests that a quantitative evaluation of labral horizontalization using magnetic resonance imaging in the early-stage of Legg-Calvé-Perthes disease can predict the later lateral pillar classification.

The objective screening of infant hips using ultrasonography (Graf method) is gaining favor in the diagnosis of developmental dysplasia of the hip in Japan. However, the accuracy of the Graf method is dependent on the examiner’s experience and technique. The purpose of this study was to investigate the reproducibility of acquiring ultrasonic hip images and their evaluation after examiners attended an infant hip ultrasound training course. Ultrasonic images of 70 hips of 35 newborns who were screened by ultrasonography using the Graf method, were evaluated. The images were acquired by two inexperienced examiners who attended the training course. The inter- and intra-examiner measurement errors as well as reproducibility were calculated based on the images obtained. The intra-examiner measurement error in the acquired images of the same hip was minor. The inter-examiner measurement error was also small. The intra- and inter-examiner agreements of the Graf classification were high. The intra-examiner reproducibility of the acquired ultrasonic images was substantial, and the inter-examiner reproducibility was almost perfect. Our results demonstrated that inexperienced examiners could obtain ultrasonic infant hip joint images with minor differences and high reproducibility after the training course. Our findings raise the possibility of extending the infant hip ultrasound course in Japan.

Recently, more attention has been paid to the role of the acetabular labrum. Therefore, we designed a retrospective cohort study of patients with residual hip dysplasia (RHD) who underwent magnetic resonance imaging (MRI). The objective of this study was to investigate an association between the MRI appearance of the labrum before school age and the natural history of RHD. We retrospectively investigated 45 hips of 40 patients who underwent MRI at about 3 and 4 years of age for RHD and were conservatively followed up with until 6 years of age or older. We evaluated the extent of eversion with a new method that measures the β angle (MRI β angle) using landmarks of the Graf method on MRI T2∗-weighted images. The outcome measure was the Severin classification at the final follow-up. We compared the radiographic and MRI parameters at approximately 3 and 4 years of age between the good and poor outcome groups. The Student t test or one-way analysis of variance was used to compare the quantitative variables between groups. The Chi-square test was used to perform a ratio comparison. Although there was a significant difference in the center-edge (CE) angle, there was no significant difference in the acetabular index and the ratio of the presence of femoral head necrosis and the break in Shenton line between the good and poor groups. The MRI β angle was significantly greater in the poor outcome group than in the normal and good outcome groups. The cut-off value of the MRI β angle to differentiate the good and poor outcome groups was 65°, and its specificity and sensitivity were 92% and 53%, respectively. There was labral eversion on MRI scans in patients with RHD. Acetabular development before adolescence was poorer with greater labral eversion on MRI scans. The specificity for poor acetabular development was high when the MRI β angle was 65° or more. The MRI β angle has the potential to predict acetabular development.

Paralytic hip subluxation is a common problem in children with cerebral palsy. Although surgical procedures such as soft tissue release and osteotomy have been advocated for its prevention, the exact indications of such procedures remain unclear. We attempted to evaluate preoperative radiographic parameters and identify prognostic factors in children with cerebral palsy. We retrospectively investigated 43 hips in 27 children with cerebral palsy who had undergone soft tissue release surgery for hip subluxation. We evaluated the age at the time of surgery and the radiographic parameters such as the center-edge angle (CEA), the migration percentage (MP), and the acetabular index (AI) at 3 time points: preoperation, 1 year after surgery, and at final follow-up. The outcome measure was determined by the MP value at final follow-up. Student t test was used to compare the quantitative variables between 2 groups (good vs poor outcome). Then the multiple regression analysis was applied to determine the prognostic factors upon soft tissue release surgery. Children with good outcome exhibited higher CEA (average value of -1.43° vs -13.2° in those with poor outcome), lower MP (53.9% vs 71.3%), and lower AI (28.1° vs 35.3°). Upon multiple regression analysis, we found that the age at the time of surgery, preoperative CEA, and preoperative MP did not appear to be independent prognostic factors. The only independent factor that affected prognosis after soft tissue release surgery was the preoperative AI. The preoperative AI values