Graphic analysis of femoral growth in young children with Perthes' disease

Ellipsoidal Process of the Femoral Head in Legg-Calvé-Perthes Disease: Effect of Prophylactic Hemiepiphysiodesis

PURPOSE

Legg-Calvé-Perthes disease (LCPD) often causes the residual deformity, typically appearing as an ellipsoidal shape. In some cases, this ovalization is related to the asymmetric growth of the femoral head physis, which presents a growth-inhibiting necrotic area in the anterosuperior quadrant. The objective of the present study is to evaluate the effectiveness of selective hemiepiphysiodesis of the healthy physis in the posteroinferior quadrant as a means of disrupting femoral head ovalization in cases of LCPD with the previous onset of ovalization.

METHODS

We performed a prospective study of 39 LCPD hips operated on consecutively by selective hemiepiphysiodesis of the posteroinferior portion of the head during the reossification phase.Surgical indication was based on a progressive increase in the ellipsoidal index (EI), the presence of a double epiphyseal nucleus of reossification, physeal narrowing, and physeal angulation. Hemiepiphysiodesis was performed at the mean patient age of 8.8 years (SD 1.5) and a mean of 4.7 years (SD 1.4) following disease onset.

RESULTS

Preoperative EI was 1.80 (SD 0.2), which was reduced to 1.72 (SD 0.2) postoperatively (P > 0.05). Physeal angulation increased from 50° preoperatively (SD 9.3) to 54.29° (SD 9.7) at the end of growth (P > 0.05). The final result according to the Stulberg classification revealed 20 class-II cases, 16 class III, and 3 class IV, and SDS was 25.97 (SD 9.95), range: 9.36-51.67.

CONCLUSION

As revealed by the EI, the ellipsoidal process may be stopped by selective hemiepiphysiodesis in the posteroinferior quadrant of the femoral head.

LEVEL OF EVIDENCE

II.

Computer-assisted design model to evaluate the outcome of combined osteotomies in Legg-Calvé-Perthes disease

OBJECTIVE

The current study aims to conduct a quantitative dynamic analysis of hip morphology using a computer-assisted design (CAD) model to evaluate the combined pelvic and femoral osteotomies in the treatment of Legg-Calvé-Perthes disease (LCPD).

MATERIALS AND METHODS

CAD models of patients with unilateral LCPD treated by combined pelvic and proximal femoral osteotomies were established based on the data of CT scan, on which morphological parameters were measured. Shape difference analysis of normal hips was adopted to locate the most apparent displacement and the main strain on the surface of the proximal femur.

RESULTS

Fifteen patients were included, and the mean age of receiving operation was 6.63 years old. There were 10 hips rated as Herring type C, and the rest were type B. Compared with the normal side, the affected hip joints have a longer distance between femoral head and acetabular sphere. The difference of coverage area of the femoral head surface and femoral head volume between the affected and normal sides was bigger compared with the preoperative model, respectively. The changes in the acetabular radius and the area of the surface were not apparent, pre-, and post-operatively. The displacement was mainly on superior and lateral superior portions of the femoral head where the stresses were concentrated.

CONCLUSION

Combined pelvic and femoral osteotomies could effectively improve the superior and superior-posterior area of acetabulum containment with increased femoral head volume. CAD model and shape difference analysis can provide a better understanding of deformations of LCPD and more information for surgical planning and evaluation of treatment outcomes.

Ellipsoidal process of the femoral head in Legg-Calvé-Perthes disease. Part I

Legg-Calvé-Perthes disease (LCPD) often produces a residual deformity, typically consistent with coxa magna, coxa plana, and ellipsoidal shape. Depending on the degree of asphericity and flatness, this morphology was classified by Stulberg in stages III and IV. Thus far, few studies have investigated physeal injury as an etiological cause or evaluated its progressive profile throughout Waldenström's reossification stage and the remodelling stage. In this study, we analysed the ellipsoidal process of the femoral head. This was a retrospective control case study involving 83 unoperated hips with LCPD and Stulberg stages III and IV outcome. The data were compared with those obtained for 49 healthy contralateral hips (control). The Ellipsoidal Index, the presence of a double epiphyseal reossification nucleus, physeal narrowing, intraphyseal angle, epiphyseal height, diameter of the head, and Reimer's Index were determined. Measurements were performed at four-time points: the year the reossification stage was initiated, the final growth stage, and two equally spaced time points in between. The Ellipsoidal Index gradually increased throughout the course of the disease from 1.6 in the initial reossification stage to 2.0 at the end of growth. In the control cases, this value was consistently 1.4. More ellipsoidal deformity was observed in Stulberg stage IV versus Stulberg stage III patients (P < 0.05). Moreover, there was a direct link between a high Ellipsoidal Index and the appearance of a double reossification nucleus, a physeal narrowing in the area underlying the anterosuperior nucleus, intraphyseal angle. Reimer's Index showed a gradual extrusion from baseline to the end of growth (26.1 versus 31.8, respectively; P < 0.05). The ellipsoidal process of the femoral head occurs gradually throughout the reossification and remodelling stages. This was linked to the appearance of a double epiphyseal nucleus, gradual extrusion, an angulated physis appearance, an asymmetrical narrowing of the physis and a high Ellipsoidal Index, which may be indicative of poor prognosis. Levels of Evidence for Primary Research Question: Level III, case-control study.

Legg-Calvé-Perthes' disease. Congruent aspherity caused by physeal injury

INTRODUCTION

Perthes disease often produces a congruent nonspherical coxa. The most widely accepted cause is initial bone collapse, but some authors refer to physeal injury as the cause of this deformity. We analyze this elliptical process in cases of congruent nonspherical Perthes.

METHODS

Retrospective case-control study of 49 unilateral class III-IV Perthes cases that were not operated on. Results were compared with 49 healthy contralateral hips. The following radiological variables were determined both in AP and lateral projection, and at 4 points in time of the disease: ovalization index (OI), arthrotrochanteric distance, intraphysial angle, physeal narrowing, presence of double epiphyseal reosification nucleus, physeal length and Reimers index.

RESULTS

The initial OI was 1.7 in the early reosification phase and final OI was 2.07 at physeal closure. The OI in the control cases was invariably 1.4. There was a direct relation between a high index and the initial appearance of a double epiphyseal ossification nucleus, asymmetric physeal effacement and the increase of the intraphyseal angle in both radiographic projections.

CONCLUSIONS

The elliptical process of the femoral head occurs progressively throughout the disease and not only during bone collapse. It starts in the reosification phase and ends when growth stops. The initial risk signs found were the appearance of the double nucleus of reosification, the progressive angulation of the physis and the progressive increase in the rate of ovalization.

3-dimensional metrics of proximal femoral shape deformities in Legg-Calvé-Perthes disease and slipped capital femoral epiphysis

Legg-Calvé-Perthes disease (LCPD) and slipped capital femoral epiphysis (SCFE) are two common pediatric hip disorders that affect the 3-dimensional shape and function of the proximal femur. This study applied the principles of continuum mechanics to statistical shape modeling (SSM) and determined 3-D metrics for the evaluation of shape deformations in normal growth, LCPD, and SCFE. CT scans were obtained from 32 patients with asymptomatic, LCPD, and SCFE hips ((0.5-0.9 mm)² in-plane resolution, 0.63 mm slice thickness). SSM was performed on segmented proximal femoral surfaces, and shape deformations were described by surface displacement, strain, and growth plate angle metrics. Asymptomatic normal femurs underwent coordinated, growth-associated surface displacements and anisotropic strains that were site-specific and highest at the greater trochanter. After size- and age-based shape adjustment, LCPD femurs exhibited large displacements and surface strains in the femoral head and neck, with associated changes in femoral head growth plate angles. Mild SCFE femurs had contracted femoral neck surfaces, and surface displacements in all regions tended to increase with severity of slip. The results of this paper provide new 3-D metrics for characterizing the shape and biomechanics of the proximal femur. Statement of Clinical Significance: Quantitative 3-D metrics of shape may be useful for understanding and monitoring disease progression, identifying target regions for shape modulation therapies, and objectively evaluating the success of such therapies. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:1526-1535, 2018.

Visualization and analysis of the deforming piglet femur and hip following experimentally induced avascular necrosis of the femoral head

Childhood avascular necrosis (AVN) of the femoral head leads to its progressive deformation and compensatory changes of the adjacent acetabulum. To simulate this disease for laboratory study, we used an AVN model of the hip in a skeletally immature piglet. The 3-D visualization and analysis of this piglet's deforming femur and hip form the basis for this paper. In particular, the data for this analysis were generated via serial CT images of bilateral femurs and acetabula of a piglet at regular time intervals following experimental unilateral induction of femoral head AVN. The contralateral femur and acetabulum served as the control. We applied a shape analysis technique that effectively captured not only the temporal shape changes of the femurs and acetabula, but also their codependencies. The resulting computational framework not only confirmed the widely accepted deformational changes of the femoral head following AVN; it also revealed the underappreciated compensatory changes of the surrounding acetabulum. The 3-D visualization of these dynamically changing structures provided a visual understanding of the shape changes associated with the AVN and control models. By quantitatively mapping the deformation trajectory of these shapes over time, we created an objective tool for clinical decision making.

High prevalence of acetabular retroversion in both affected and unaffected hips after Legg-Calvé-Perthes disease

BACKGROUND

Acetabular retroversion is observed in hips after various pediatric hip diseases. This study sought to examine the frequency of acetabular retroversion in both affected and unaffected hips after Legg-Calvé-Perthes disease and its correlation with the prominence of the ischial spine.

METHODS

We retrospectively investigated the version and morphological features of the acetabulum using pelvic radiographs after Legg-Calvé-Perthes disease (107 affected hips treated non-operatively and 72 unaffected hips from the contralateral side). The diagnosis of acetabular retroversion was made based on the presence of a positive cross-over sign on anteroposterior pelvic radiographs. The correlation between the presence of a positive cross-over sign and modified Stulberg classes, the onset age of Legg-Calvé-Perthes disease, radiographic parameters for acetabular dysplasia and the prominence of the ischial spine were examined.

RESULTS

The prevalence of a positive cross-over sign was 49.5 % (45 of 91 hips) in affected hips and 45.8 % (33 of 72 hips) in unaffected hips. Hips with a positive cross-over sign were significantly coexistent bilaterally. The prevalence of prominence of the ischial spine in the positive cross-over sign group was 71.4 % in the affected side and 81.8 % in the unaffected side, indicating a significant correlation between the cross-over sign and the prominence of the ischial spine in both affected and unaffected hips. The positive cross-over sign did not have any correlation with the parameters for acetabular dysplasia and the onset age, however, had a significant correlation with the severity of the femoral head deformity.

CONCLUSIONS

High prevalence of acetabular retroversion in both affected and unaffected hips after Legg-Calvé-Perthes disease was demonstrated. Symmetric acetabular deformity and the coexistence of prominence of the ischial spine suggested the effects of the Legg-Calvé-Perthes disease lesions on the skeletal development of the whole pelvis. Further follow-up is needed to clarify the pathological significance of acetabular retroversion after Legg-Calvé-Perthes disease.

The proximal femoral growth plate in Perthes disease

We hypothesized the extent of involvement of the proximal femoral growth plate in Perthes disease determined the final radiographic outcome after containment by shelf acetabuloplasty. We retrospectively evaluated the extent of growth plate involvement using a modified version of the method described by Yasuda and Tamura. In our modification, we used only the epiphyseal border for measurements, which was clearly visible as a thin white line, unlike Yasuda and Tamura who used the metaphyseal and epiphyseal borders. We could not clearly demarcate the metaphyseal border in the radiographs of our patient population between 1944 and 1998, which consisted of 69 patients who had surgery at a mean age of 9 years (range, 6.0-14.1 years). From these measurements, we formulated an index termed "growth plate involvement." Radiographic results were classified as described by Stulberg et al A growth plate involvement index less than 0.25 resulted in a good radiographic outcome. We found 93.2% sensitivity and 100% specificity in predicting Stulberg's outcomes. The growth plate involvement index is a reliable and reproducible measurement method and may be used prospectively as a useful prognostic factor to predict radiographic outcomes after containment acetabuloplasty.

Lateral acetabular growth stimulation following a labral support procedure in Legg-Calve-Perthes disease

BACKGROUND

The main goal of containment treatment in cases of Legg-Calvé-Perthes disease is to prevent hip deformity, which leads to arthritis in adulthood. Recently, the shelf arthroplasty (the labral support procedure) has been proposed as a method of containment. The purpose of the present study was to evaluate growth stimulation of the acetabulum in patients with unilateral Legg-Calvé-Perthes disease by measuring acetabular depth and height following treatment with the labral support procedure. Uninvolved, contralateral hips and hips that were treated with proximal femoral varus osteotomy were used to compare growth.

METHODS

Sixty-five consecutive patients with unilateral Legg-Calvé-Perthes disease that had been treated with the labral support procedure (forty-nine) or a proximal femoral varus osteotomy (sixteen) were evaluated on the basis of radiographic and clinical data that had been obtained at the time of surgery as well as at one, three, and five years after surgery. Acetabular dimensions (depth, height, and total depth with shelf) were measured and, to eliminate radiographic magnification error, the data were expressed in ratios between the involved and uninvolved sides.

RESULTS

Preoperatively, both surgical groups were comparable. Acetabular depth indexes at the time of surgery were not different between the groups (p = 0.46). At one, three, and five years postoperatively, the mean depth indexes in the labral support group were significantly higher than those in the proximal femoral varus osteotomy group (F = 5.417, p = 0.001), and trend analysis showed a significant quadratic effect over time in the labral support procedure group (F = 13.132, p = 0.001). The acetabular height indexes at the time of surgery were not different between groups and showed 11% to 13% acetabular overgrowth. The acetabular height indexes in both groups remained unchanged at the time of follow-up (F = 2.82, p = 0.1). The total depth index showed decreasing linear trend values over the period studied (F = 35.115, p = 0.001).

CONCLUSIONS

Overgrowth of the acetabulum occurs naturally and early in the course of Legg-Calvé-Perthes disease and is more pronounced in terms of height. The labral support procedure induces additional lateral growth of the true acetabulum (excluding the shelf) for three years following surgery, whereas a proximal femoral varus osteotomy does not. Thus, beneficial effects of the labral support procedure are lateral acetabular growth stimulation, prevention of subluxation, and shelf resolution after femoral epiphyseal reossification.

LEVEL OF EVIDENCE

Therapeutic Level III. See Instructions to Authors for a complete description of levels of evidence.