Magnetic resonance imaging evaluation of acetabular orientation in normal Chinese children

A Novel Method for Assessing the 3-dimensional Morphology of Cartilaginous Acetabulum Via Childhood Magnetic Resonance Imaging

BACKGROUND

Periarticular cartilage is abundant in children, making evaluations of 3-dimensional (D) cartilaginous acetabular morphology using x-ray or computed tomography (CT) difficult. The study aimed to visualize the 3D cartilaginous acetabular morphology in normal children and patients with pediatric developmental dysplasia of the hip (DDH).

METHODS

Magnetic resonance imaging (MRI) of 17 female children without acetabular dysplasia at 7.5 years and CT of 33 normal female adolescents with mature bones at 14.6 years were used as controls. Subjects were 26 female patients with unilateral DDH who underwent angulated Salter innominate osteotomy (A-SIO) at 5.5 years. Preoperative and postoperative MRIs were performed at 5.2 and 7.0 years, respectively. The MRI sequence was 3D-MEDIC. The medial intersection (point A) of the line connecting the centers of the bilateral femoral head and the femoral head were defined as point zero. The 3D coordinates (X, Y, Z) of the cartilaginous acetabular edge (point C) from anterior to posterior were calculated. Subsequently, a 3D scatter plot was created using 3D graph software. The subjects were divided into 6 groups, including control MRI, control CT, unaffected DDH before and after A-SIO, and affected DDH before and after A-SIO. The femoral head coverage ratio (FHCR: AC/AB) was used to quantify coverage and was compared in each group.

RESULTS

In the control MRI group, the acetabular coverage was small anteriorly, largest anterolaterally, and gradually decreased posteriorly, similar to the bony acetabulum in adolescents. In the affected DDH before A-SIO group, the coverage was significantly lower than that of the control MRI and unaffected DDH groups. After A-SIO, the morphology improved beyond the unaffected DDH and the control MRI group.

CONCLUSIONS

The global defect of the cartilaginous acetabulum in the affected DDH group was significantly improved to normal morphology after A-SIO. Evaluating the cartilaginous acetabulum using MRI was useful for assessing hip morphology in childhood.

LEVEL OF EVIDENCE

Level III-retrospective comparative study.

The Anatomical Position of Graf’s Standard Plane and Its Relationship With Pelvic Morphology: A Computed Tomography-Based Study

Objective

The Graf method is the most widely used ultrasonographic method for evaluating developmental dysplasia of the hip (DDH), and it relies on a set standard plane. However, no previous reports have discussed the detailed anatomical location of the plane. The aim of this study was to evaluate the exact anatomical position of Graf’s standard plane in the pelvis and to ascertain the correlation between this position and pelvic morphology in children without abnormal pelvic morphology.

Methods

We retrospectively assessed the pelvic CT data of 32 children (64 hips) aged three to five years without abnormal pelvic morphology and measured the pelvic winging and acetabular anteversion and coverage. We defined the coronal plane that passed through the center of the bilateral femoral head as plane A. We determined that Graf’s standard plane could be approximated by rotating plane A until the outer wall of the ilium was parallel to the sagittal plane, and we defined this as plane A′. AA′ was defined as the angle from plane A to plane A′ on the sagittal plane. The anterior rotational angle (clockwise, viewing from the right side) was measured as the positive AA′. Moreover, we measured the pelvic rotation, acetabular anteversion, and acetabular coverage and evaluated the correlation between AA′ and these morphological parameters.

Results

The average AA′ was -8.27° and AA′ had a significant correlation with acetabular anteversion (Spearman’s ρ=0.40**, p<0.01).

Conclusions

We found that Graf's standard plane, as determined by the CT scan, tilts slightly posteriorly. This information may be useful in improving the ease of ultrasonographic examination of DDH.

Anthropometric measurements of the pediatric hip using CT-based simulated anteroposterior radiographs of the pelvis

Normal anatomical variants and pathological deformities of the pediatric hip can only be differentiated after a prior definition of normal ranges for anthropometric parameters with increasing age. Aim of the present study was to provide reliable reference values of the pediatric hip morphometry, using computed tomography (CT)-based rotation-corrected summation images of the pelvis that simulate the widely available plain radiograph-based measurements, but offer the higher precision of the CT technique. This retrospective study included 85 patients (170 hips) under 15 years of age (0-15). The measured anthropometric parameters included femur head extrusion index, lateral center-edge angle, acetabular inclination, Tönnis angle, and femoral neck-shaft angle. Mean values, range, SD, P values, intra-rater, and inter-rater reliability were calculated. All measurements correlated with age. None of the measurements correlated with gender or side. Rapid growth phases were noted in all measurements at the age of 12 (14 in males and 11 in females). The inter-rater and intra-rater reliability was high (range inter/intraclass correlation coefficient 0.926-0.998 Cronbach's alpha 0.986-0.998). The present work provides age- and gender-related normative values of the classically used hip measurements as well as growth phases describing pediatric hip morphology in a broad age range. A discrepancy was noted between the values measured in the current study and the classical X-ray-based reference values in the literature especially for the Tönnis angle and LCEA values. This suggests that the rotation and inclination correction in the CT-based techniques might have the advantage of compensating for a possible overestimation in the conventional X-ray-based methods.

Role of magnetic resonance imaging in assessment of acetabular and femoral version in developmental dysplasia of the hip

Objective

To evaluate the role of magnetic resonance imaging (MRI) in the assessment of femoral and acetabular version in developmental dysplasia of the hip (DDH).

Materials and Methods

This was a cross-sectional study of 20 consecutive patients with DDH (27 dysplastic hips) who were examined with MRI. In dysplastic and normal hips (DDH and comparison groups, respectively), we evaluated the following parameters: osseous acetabular anteversion (OAA); cartilaginous acetabular anteversion (CAA); femoral anteversion; osseous Mckibbin index (OMI); cartilaginous Mckibbin index (CMI); and the thickness of the anterior and posterior acetabular cartilage.

Results

The OAA was significantly greater in the dysplastic hips. The CAA, femoral anteversion, OMI, and CMI did not differ significantly between the normal and dysplastic hips. In the DDH and comparison groups, the OAA was significantly lower than the CAA, the OMI was significantly lower than the CMI, and the posterior acetabular cartilage was significantly thicker than the anterior cartilage.

Conclusion

Our findings confirm that MRI is a valuable tool for the assessment of femoral and acetabular version in DDH. Preoperative MRI evaluation has great potential to improve the planning of pelvic and femoral osteotomies.

A longitudinal study for the prediction of the mature acetabular morphology using childhood magnetic resonance imaging

BACKGROUND

Although acetabular dysplasia is a common etiology of osteoarthritis of the hip regardless of the history of developmental dysplasia of the hip (DDH), whether or not corrective surgeries are beneficial for the childhood asymptomatic acetabular dysplasia remains controversial due to a lack of evidence. We conducted a longitudinal study to compare the cartilaginous morphology on childhood magnetic resonance imaging (MRI) and the mature hip morphology of the same patient and to assess the predictive indicators for future acetabular dysplasia.

METHODS

A total of 92 unaffected hips (47 unilateral DDH and 45 unilateral Legg-Calvé-Perthes disease) were reviewed for X-ray and MRI findings on childhood (mean age: 6.0 years) and X-ray findings from a skeletally mature age with a mean follow-up period of 15.1 years. The following parameters were measured and compared: the immature-acetabular index (AI) and center edge angle (CE) on immature X-ray; the cartilage- and bone- AI, CE, Sharp and acetabular head index (AHI) on childhood MRI; and the mature-acetabular roof obliquity (ARO), CE, Sharp and AHI on skeletally mature X-ray. The prognostic factors on childhood MRI for acetabular dysplasia, defined by a CE of <20° on skeletally mature X-ray were also assessed.

RESULTS

Positive correlations were shown between the cartilage-AI and mature-ARO (7.6°/6.3°; r = 0.44), the cartilage-CE and mature-CE (27.8°/28.0°; r = 0.62), the cartilage-Sharp and mature-Sharp (44.4°/41.8°; r = 0.52) and the cartilage-AHI and mature-AHI (78.7%/80.3%; r = 0.46). A multivariate analysis indicated cartilage-CE to be an independent predictor for acetabular dysplasia with a cut-off value of 22°. Children with a cartilage-CE <22° developed more frequently acetabular dysplasia compared to the others (52.4% vs. 1.4%).

CONCLUSIONS

Childhood MRI findings are useful for the prediction of acetabular dysplasia without a DDH history. Children with a cartilage-CE ≥23° are likely to achieve a non-dysplastic hip without the need for surgical intervention.

Development of acetabular anteversion in children with normal hips and those with developmental dysplasia of the hip: a cross-sectional study using magnetic resonance imaging

Background and purpose - Acetabular anteversion (AA) is related to hip function. Most previous studies were based on radiographic investigations that determine osseous acetabular anteversion (OAA). But children's acetabulum is mostly composed of cartilage; the cartilaginous acetabular anteversion (CAA) represents the real anteversion of the acetabulum. We measured OAA and CAA in children of various ages using MRI, and compared the developmental patterns between children with normal hips and those with developmental dysplasia of the hip (DDH).Patients and methods - The OAA and CAA were measured on MRI cross-sections of the hips in 293 children with normal hips (average age 8 years), and in 196 children with DDH (average age 34 months). Developmental patterns of OAA and CAA in children with normal hips were determined through age-based cross-sectional analysis. Differences in OAA and CAA between children with normal hips and those with DDH were compared.Results - Normal OAA increased from mean 8.7° (SD 3.2) to 12° (3.0) during the first 2 years of life and remained unchanged until 9 years of age. From 9 to 16 years, the OAA showed a minimal increase of 2°-3°. The normal CAA increased rapidly from a mean of 12° (3.1) to 15° (2.7) within the first 2 years of life, and remained constant at 15° (SD 3.4) until 16 years of age. The age-matched average OAA in the normal and DDH cases was 11° (3.2) and 15° (3.0), respectively (p < 0.001). The age-matched average CAA in normal and DDH cases was 17° (4.2) and 23° (4.5), respectively (p < 0.001). Similarly, there was a significant difference in OAA and CAA between the uninvolved hips in unilateral DDH and normal cases (p < 0.001).Interpretation - The CAA was fully formed at birth in normal children, and remained unchanged until adulthood, whereas the OAA increased with age. The OAA and CAA were both over-anteverted in DDH children. MRI evaluation is of importance in children during skeletal development when planning hip surgery.

Hip morphology in mucopolysaccharidosis type IVA through radiograph, magnetic resonance imaging and arthrogram assessment

PURPOSE

This study examined the hip morphology of paediatric patients with mucopolysaccharidosis (MPS) type IVA (MPS IVA).

METHODS

This was a retrospective chart review of 42 hips in 21 children with MPS IVA. Pelvic radiographs and magnetic resonance imaging (MRI) scans of 42 hips and arthrograms of 13 hips were analysed. The bony, cartilaginous and labral coverage of the acetabulum was determined by acetabular index (AI), centre edge angle (CEA) and femoral head coverage (FHC).

RESULTS

The mean age at the time of radiography was 66.3 ± 21.7 months. The bony, cartilaginous and labral AI in the MRI assessment were 36.3 ± 5.3, 18.3 ± 4.7 and 12.1 ± 4.6 degrees, respectively. The inter-class correlation coefficients (ICCs) for the bony AI, CEA and FHC measurements on radiographs and MRI were 0.936, 0.879 and 0.810, respectively. In the MRI assessment, labrum in 12 of 42 hips appeared as a regular triangle, and it was flat on 30/42 hips. The average arthrographic AI (AAI) was 11.1 ± 2.7 degrees. The ICCs value of AAI versus cartilaginous and labral AI on MRI indicates good agreement but higher in labral AI.

CONCLUSION

Hips in MPS IVA exhibited obvious cartilage and labrum compensation in response to abnormal ossification of bony acetabulum. Cartilage in MPS IVA hip increases the thickness in the longitudinal direction, while the labrum becomes flatten in the horizontal direction. The AAI may represent intraoperative labrum coverage. The femora-acetabular harmony is difficult to determine using radiography only, and pre-operative MRI and an intraoperative arthrogram are very important in a hip assessment in MPS IVA.

Age-related change and gender differences in pelvic morphology of healthy children

BACKGROUND

An increasing number of studies about the hip joint morphology with childhood-specific hip diseases have been reported. But there have been few reports on pelvic morphology of healthy children. The purpose of this study was to assess the pelvic morphology of healthy children in detail and clarify the age-related change and gender difference of it.

METHODS

We retrospectively assessed the pelvic morphology of 97 healthy children (3-18 years old) using their pelvic computed tomography (CT) data. Superior iliac angle (SIA), inferior iliac angle (IIA), and ischiopubic angle (IPA) as the parameters of pelvic winging, and acetabular anteversion and anterior acetabular sector angle (AASA), posterior acetabular sector angle (PASA), superior acetabular sector angle (SASA) as the parameters of acetabular coverage, are measured. Pearson's correlation coefficient was used for examining the correlation between the each measurement and the age of cases. Multiple linear regression analysis was performed to investigate the possibility of association of age and sex with each measurement.

RESULTS

In female, it was found that IIA, AASA, PASA, SASA were significantly correlated with the age of the cases. And in male, SIA, IIA, IPA, AASA, PASA were significantly correlated with the age. Multiple linear regression analysis revealed the significant difference of the distribution between males and females was observed in IIA, IPA, AVcen, PASA, and these measurements were lager for female.

CONCLUSIONS

In this study, we revealed the age-related change and gender difference of the pelvic morphology of healthy children, and this could be useful information in evaluating the hip with what appears to be an abnormal acetabular anteversion and acetabular inclination in the patients with childhood specific hip disease. Additionally, it will also help us to make operation plans pertaining to the hip.