Unilateral Legg-Calvé-Perthes Disease Research Articles

Multimodal radiomics and deep learning models for predicting early femoral head deformity in LCPD

PurposeTo develop a predictive model combining clinical, radiomic, and deep learning features based on X-ray and MRI to identify risk factors for early femoral head deformity in Legg-Calvé-Perthes disease (LCPD). MethodsThis study involved 152 patients diagnosed with early unilateral LCPD across two centers between January 2013 and December 2023, and included an independent external validation set to assess generalizability. Four machine learning methods, including logistic regression (LR), random forest (RF), support vector machine (SVM), and extreme gradient boosting (XGBoost), were employed to develop radiomics deep learning signatures. The clinical-radiomics model (Clinic + Rad), clinical-deep learning model (Clinic + DL), and clinical-radiomics-deep learning model (Clinic + Rad + DL) were developed by integrating radiomics deep learning signatures with clinical variables. The best model, integrated into a nomogram for clinical application, was evaluated using the area under the receiver operating characteristic curve (AUC). ResultsAmong the four machine learning methods, XGBoost demonstrated superior performance in our patient dataset: radiomic (Rad) model (AUC, 0.786) and deep learning (DL) model (AUC, 0.803). Clinical variables such as age at onset and JIC classification were associated with early femoral head deformity (p < 0.05). The combined model incorporating clinical, radiomic, and deep learning signatures demonstrated better predictive ability (AUC, 0.853). The nomogram can assist clinicians in effectively assessing the risk of early femoral head deformity. ConclusionThe Clinic + Rad + DL integrated model may be beneficial for prognostic assessment of early LCPD femoral head deformity, which is crucial for tailoring personalized treatment strategies for individual patients.

Demographics and risk for containment surgery in patients with unilateral Legg-Calvé-Perthes disease: a national population-based cohort study of 309 patients from the Swedish Pediatric Orthopedic Quality Register.

It is controversial as to which patients affected by Legg-Calvé-Perthes disease (LCPD) benefit from containment surgery. This population-based study based on data from a national quality registry aims to assess the incidence of LCPD and to explore which factors affect the decision for surgical intervention. This observational study involved 309 patients with unilateral LCPD reported between 2015 and 2023 to the Swedish Pediatric Orthopedic Quality Register (SPOQ). Descriptive statistics and logistic regression models were used for analysis. In 2019, the assessed incidence of LCPD in the Swedish population of 2-12-year-olds was 4.2 per 105. 238 (77%) were boys with a mean age of 6 years. At diagnosis, 55 (30%) were overweight or obese, rising to 17 patients (39%) and 16 patients (40%) at 2-year follow-up for surgically and non-surgically treated groups, respectively. At diagnosis, affected hips had reduced abduction compared with healthy hips, and their abduction remained restricted at the 2-year follow-up. Surgically treated patients had inferior abduction compared with non-surgically treated ones at diagnosis. The adjusted risk for containment surgery increased with age and in the presence of a positive Trendelenburg sign but decreased with greater hip abduction. We found a lower national yearly incidence (4.2 per 105) than previously reported in Swedish studies. A higher proportion of overweight or obese patients compared with the general Swedish population of 4-9-year-olds was identified. Increasing age, positive Trendelenburg sign, and limited hip abduction at diagnosis correlated with increased surgical intervention likelihood.

Predictors of Persistent Limp Following Proximal Femoral Varus Osteotomy for Perthes Disease.

One of the most popular containment procedures for Legg-Calvé-Perthes disease (LCPD) is proximal femur varus osteotomy (PFO). While generally successful in achieving containment, PFO can cause limb length discrepancy, abductor weakness, and (of most concern for families) a persistent limp. While many studies have focused on radiographic outcomes following containment surgery, none have analyzed predictors of this persistent limp. The aim of this study was to determine clinical, radiographic, and surgical risk factors for persistent limp 2 years after PFO in children with LCPD. A retrospective review of a prospectively collected multicenter database was conducted for patients aged 6 to 11 years at disease onset with unilateral early-stage LCPD (Waldenström I) who underwent PFO. Limp status (no, mild, and severe), age, BMI, and pain scores were obtained at initial presentation, 3-month, and 2-year postoperative visits. Preoperative and follow-up radiographs were used to measure traditional morphologic hip metrics including acetabular index (AI), lateral center-edge angle (LCEA), and femoral neck-shaft angle (NSA). Univariate analysis as well as multivariate logistic regression models were used to analyze factors associated with mild and severe limp at the 2-year visit. A total of 95 patients met the inclusion criteria, and of these 50 patients underwent concomitant greater trochanter apophysiodesis (GTA) at the time of PFO. At the 2-year visit, there were 38 patients (40%) with a mild or severe limp. Multivariate logistic regression revealed no significant radiographic factors associated with a persistent limp. However, lower 2-year BMI and undergoing GTA were associated with decreased rates of persistent limp regardless of age ( P <0.05). When stratifying by age of disease onset, apophysiodesis appeared to be protective against any severity of limp in patients aged 6 to 8 years old ( P = 0.03), but not in patients 8 years or older ( P = 0.49). Persistent limp following PFO is a frustrating problem that was seen in 40% of patients at 2 years. However, lower follow-up BMI and performing a greater trochanter apophysiodesis, particularly in patients younger than 8 years of age, correlated with a lower risk of postoperative limp.

Do Weightbearing Restrictions Cause Excess Weight Gain in Children With LEGG-Calvé-Perthes Disease?

Restricted weight bearing is commonly prescribed in Legg-Calvé-Perthes Disease (LCPD), raising concerns of causing overweight or obesity. This study utilizes prospectively collected data to address the following questions: (1) does body mass index (BMI) Z-score increase over the course of LCPD follow-up; (2) is having a BMI category of normal, overweight, or obese at baseline associated with BMI Z-score changes over the course of follow-up; and (3) is the duration of weight bearing restrictions (no restrictions, <3, 3 to <6, 6 to 9, or >9mo) associated with BMI Z-score changes. Data of 130 children aged 5 to 12 years with unilateral early-stage LCPD were extracted from an international database. Nation-specific BMI Z-scores and percentile-based weight categories were determined, and the duration of follow-up and weight bearing restrictions were calculated. Longitudinal changes in BMI Z-scores were evaluated for the 3 study questions using mixed effects linear regression models with surgery as a covariate. Sensitivity analyses were used to determine the influence of socio-cultural background (USA vs. India) for each study question. During the 35.5±15.9 months of follow-up, no statistically significant increase in BMI Z-scores was observed across the entire cohort, or following stratification by baseline weight categories or the duration of the weight bearing restriction. Sensitivity analyses indicated that patients in the USA had no change in their BMI Z-score. When stratified by weight categories, the normal weight of US children had a small increase in their BMI Z-score (0.005 per mo, 95% confidence interval: 0.0002, 0.009), but this was not seen in other BMI categories. The cohort of Indian children had a small but significant decrease in their BMI Z-score (-0.005/mo, 95% CI: -0.009, -0.0002). After stratification by weight categories, a small decrease of the BMI Z-score was observed only in the Indian overweight children (-0.016 per mo, 95% CI: -0.027, -0.005) and no other BMI category. Weightbearing restrictions over the course of follow-up for our cohort of children with early-stage LCPD were not associated with clinically meaningful increases of BMI Z-scores. Weight gain is multi-factorial and probably not caused by weight bearing restrictions alone. III Diagnostic Study.

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

ObjectiveThe 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 methodsCAD 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.ResultsFifteen 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.ConclusionCombined 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.

A Long-Term Study of Alignment Correction Following Proximal Femoral Varus Osteotomy and Pemberton Osteotomy in Children With Legg-Calvé-Perthes Disease and Developmental Dysplasia of the Hip.

Proximal femoral varus osteotomy (PFVO) is a common procedure performed in children with developmental dysplasia of the hip (DDH) and Legg–Calvé–Perthes disease (LCPD). However, the long-term effect on angular deformities of the knees and ankles following PFVO remains controversial. This study investigated the relationship between PFVO and alignment changes in the knee and ankle after the procedure. Twenty-five patients undergoing PFVO procedure with a minimum 4-year evaluation period were enrolled in the study, including 14 unilateral LCPD and 11 unilateral DDH. The standing scanogram examinations were collected before the operation, immediately following surgery, after a 1-year follow-up, after a 3-year follow-up, and at the final visit to the clinic. The radiographic parameters included leg length, femoral neck-shaft angle (FNSA), femorotibial angle (FTA), mechanical axis deviation (MAD), tibiotalar angle (TTA), and mechanical lateral distal femoral angle (mLDFA). At the final examination, FNSA demonstrated insignificant change between the operative and non-operative limbs in the DDH group. Compared with the postoperative result, FNSA significantly improved in the LCPD group (p = 0.039). Both groups did not develop statistical significance in TTA, mLDFA, MAD, and leg length discrepancy after more than a 5-year follow-up. From a biomechanical perspective that the foot passes more medial to the knee under the center of leg mass, varus knee was prone to develop. In order to correct the mechanical axis, the knee reverted to a valgus position gradually. Our study indicates that patients with LCPD or DDH receiving PFVO and Pemberton osteotomy narrow the gap of angular growth in knees and ankles between the operative and non-operative limbs after a long-term follow-up.

Predictive ability of inflammatory markers and laboratory parameters in Legg-Calvé-Perthes disease: A single-center retrospective comparative study.

Legg-Calvé-Perthes disease (LCPD) presents with chronic nature of inflammation, characterized by prolonged synovitis. So far, no single blood marker has been identified to guide clinicians in estimating the severity and prognosis. Blood neutrophil to lymphocyte ratio (NLR) or systemic immune inflammation index (SII) is a simple indicator of subclinical inflammation. This study aims to examine the predictive ability of NLR, SII, and common laboratory parameters for estimating the severity of LCPD. The pre-operative laboratory findings at the time of osteotomy and implant removal in patients with unilateral LCPD who had been treated with the Salter innominate osteotomy and followed up until skeletal maturity as well as those of age-matched control patients with idiopathic noninflammatory conditions were analyzed. The datasets of 26 or 38 LCPD patients at the time of osteotomy or implant removal, respectively, and those of 20 control patients were available for analysis. At the time of osteotomy, compared to the control group, a significantly higher mean NLR or SII and a significantly lower mean alkaline phosphatase value were observed in the LCPD group. The alkaline phosphatase levels of patients with the modified lateral pillar (LP) group-A hips were significantly lower than those with the non-LP-A hips, whereas no significant differences were observed in any of the parameters between patients with favorable LP-A or -B hips and those with unfavorable LP-B|C border or -C hips. In agreement with the conventional opinion, it may be difficult to predict a meaningful prognosis of LCPD with the use of inflammatory markers or common laboratory parameters obtained in the initial stage of the disease.

RADIOGRAPHIC STUDY OF THE MEDIAL JOINT SPACE OF THE HIP IN LEGG-CALVÉ-PERTHES DISEASE.

To evaluate medial joint space in affected and normal contralateral hips in patients with Legg-Calvé-Perthes disease (LCPD). To compare joint space, femoral head extrusion (FHE), medial space coefficient (MSC) of the hip, and femoral head width (FHW) in affected and normal hips, using 127 radiographs of patients with unilateral LCPD and considering age groups under and over six years old as well as their disease stage. No statistically significant differences were observed regarding MSC between normal and affected hips regardless of disease staging. However, medial joint distance was significantly greater in affected hips than in normal hips. In the necrosis and fragmentation phase, distance from medial space in affected hips was significantly greater than in contralateral normal hips. Comparing only affected hips, MSC and FHW showed statistically significant differences and the group > 6 yo presented higher values. Among normal hips, the group < 6 yo presented a statistically significant difference considering the MSC and FHW. No statistically significant difference was found between the medial joint space of affected and normal hips, except for early stages of the disease (necrosis and fragmentation). The isolated use of radiographic study is insufficient in LCPD and the lack of complementation with other exams, such as magnetic resonance, can delay diagnosis of and onset of treatment for the disease. Level of Evidence III, Study of Non Consecutive Patients; without Consistently Applied Reference "Gold" Standard.

Asymmetrically increased femoral version with high prevalence of moderate and severe femoral anteversion in unilateral Legg-Calvé-Perthes disease.

PurposeTo determine and stratify femoral version in Legg-Calvé-Perthes disease (LCPD), and to compare the femoral version between the LCPD hip and the contralateral unaffected hip.MethodsWe performed a retrospective review of 45 patients with unilateral LCPD who had available CT scan through the hips and knees between January 2000 and June 2017. There were 34 (76%) male cases with a mean age of 14 years (sd 4.69). Two independent readers measured femoral version on the affected and the unaffected contralateral femur. Femoral version was classified as follows: severely decreased version (< 10°); moderately decreased (10° to 14°); normal femoral version range (15° to 20°); moderately increased (21° to 25°); and severely increased version (> 25°).ResultsLCPD hips had predominantly increased femoral version (38% severely increased anteversion, 24% moderately increased anteversion), while 51% of the contralateral unaffected hips had normal femoral version (p < 0.001). LCPD hips had higher mean femoral version than the contralateral, unaffected side (mean difference = 13o; 95% confidence iterval 10o to 16o; p < 0.001). As the version of the affected hip increased, so did the discrepancy between sides. No effect of sex on the LCPD femoral version was detected (p = 0.34).ConclusionThis study included a selected group of patients with unilateral LCPD and available CT scans obtained for surgical planning. The femoral version was asymmetric, with a high proportion of excessive anteversion observed at later stages of disease in the affected hips. Future studies will be necessary to determine the pathogenesis of increased femoral version associated with LCPD.Level of EvidenceLevel IV, retrospective study.

Feasibility of Magnetic Resonance Angiography in Patients With Legg-Calvé-Perthes Disease.

The etiology of Legg-Calvé-Perthes disease (LCPD) remains unknown; however, interruption of medial circumflex femoral artery (MCFA) supply to the femoral head is the key pathogenic factor. The main purpose of this study is to determine the feasibility of using magnetic resonance angiography (MRA) to evaluate the course of the MCFA in the normal and affected hips of patients with unilateral LCPD. We analyzed 24 patients with unilateral LCPD using a time-resolved imaging of contrast kinetics magnetic resonance angiography (TRICKS-MRA). The course of the MCFA was divided into 4 segments in the coronal plane and in 3 segments in the axial plane, based on its location with respect to the femoral neck. The visibility of each segment was studied in the normal and affected sides. The segments were defined as not visible when no contrast was seen within the vessel lumen or visible when the lumen was partially or completely visualized with contrast. The statistical analysis was done using the χ2 test. TRICKS-MRA provided well-defined images of the first 2 segments of the MCFA on both the normal and affected sides of patients with LCPD (P=1). In half of the patients, the third segment was also visible using TRICKS-MRA on both sides (P=1). The fourth segment of the MCFA, which was the ascending lateral epiphyseal segment, was not visible on either side (P=0.49). No significant difference was found between the normal and affected hips in terms of visibility of the 4 segments of the MCFA using TRICKS-MRA. Anastomosis of the MCFA with the inferior gluteal artery was found in 3 hips (2 hips with LCPD and 1 normal hip). TRICKS-MRA provides well-defined images of the arterial supply to the proximal femoral epiphysis in children with LCPD, presenting a noninvasive and radiation-free alternative to conventional angiography. However, the TRICKS-MRA method used did not allow visualization of the ascending lateral epiphyseal segment of MCFA in the affected and the contralateral normal side. We believe that further advancement of this noninvasive imaging technique may open new opportunities for research aimed at evaluating the vascular supply of the femoral head in children. Level IV-case-control study.

Acetabular retroversion after triple pelvic osteotomy for Legg-Calvé-Perthes disease and its impact on the femoroacetabular impingement: a case/control study at 15 years of follow-up.

The objective of this study was to compare the effect of triple pelvic osteotomy (TPO) in Legg-Calvé-Perthes disease (LCPD) on acetabular version in a group of patients who developed a femoroacetabular impingement (FAI) and a control group without FAI. Patients who received a TPO for unilateral LCPD were retrospectively included. Patients with bilateral LCPDs, requiring TPO with femoral procedures, or with incomplete imaging were excluded. Seven patients with FAI (FAI+) and eight patients without FAI (FAI-) were evaluated at a mean follow-up of 14.8 years. The two groups were comparable in demographic data, age at diagnosis, Herring score, and BMI. We measured anatomical acetabular version on computed tomography scans, the difference (delta) of acetabular version between the operated hip and the healthy hip, the McKibbin (femoral version + acetabular version), Stulberg, and Tönnis scoring system. The two groups were not statistically different on the Stulberg and Tönnis scores. All operated hip acetabula were retroverted, FAI+: -8.41° (range, -44 to 10.5), FAI-: -3.38° (range, -37.3 to 11.5) (P = 0.61). The average delta was FAI+: 23.79° (range, 1.5-59.5), FAI-: 20.14° (range, 5-45.3) (P = 0.68). All seven patients of the FAI+ group have pathologic McKibbin index (<30°) versus only four of the FAI- group (P = 0.03). TPO induces acetabular retroversion in patients with LCPD. This retroversion, assessed in a static benchmark (anterior pelvic plane), does not in itself explain the FAI.

Diffusion-weighted MRI for outcome prediction in early Legg-Calvé-Perthes disease: Medium-term radiographic correlations

BackgroundOutcome prediction at the early sclerotic stage of Legg-Calvé-Perthes disease (LCPD) is valuable to select patients likely to benefit from early surgery. The metaphyseal apparent diffusion coefficient (ADC) ratio correlated significantly with Herring's classification of LCPD in a preliminary study of 49 MRIs, in which values greater than 1.63 were associated with poor outcomes. The objective of this study was to determine whether the femoral neck ADC ratio, with the 1.63 cut-off, determined at the initial stage of LCPD correlated with medium-term radiographic outcomes. HypothesisThe metaphyseal ADC ratio correlates significantly with medium-term radiographic outcomes of LCPD. Materials and methodsA prospective study was performed in 27 children (mean age, 13 years; range, 9.5–16 years) who underwent 49 MRIs at the sclerosis or fragmentation stage of unilateral LCPD. ADCs measured bilaterally at the femoral head and neck were used to compute the corresponding ADC ratios between the affected and unaffected sides. The patients received regular follow-up for at least 5 years. The correlation between the ADC ratios and Stulberg grade at last follow-up was assessed. ResultsAfter a mean follow-up of 6.8 years (range, 5.2–8.4 years) from the date of the first MRI, 13 hips were Stulberg 1 or 2, 13 were Stulberg 3 or 4, and 1 was Stulberg 5. The metaphyseal ADC ratio increased significantly with the Stulberg grade (p<0.01). When only MRIs obtained at the early stage of sclerosis were considered, the correlation remained significant (p=0.03). It was also significant in the subgroup of surgically treated patients (p<0.0001) but was not significant in the subgroup without surgery (p=0.51). A metaphyseal ADC ratio greater than 1.63 was associated with a worse Stulberg grade (p=0.02). Discussion/conclusionDiffusion-weighted MRI is a non-irradiating and non-invasive investigation that contributes to the management of LCPD when used in combination with morphological MRI sequences. Elevation of the femoral neck ADC is a finding of adverse prognostic significance that correlates with Herring's grade at the fragmentation stage and with Stulberg's grade at the healed stage. Early ADC elevation in the affected femoral neck can serve to select those patients most likely to benefit from early surgery before the fragmentation stage, i.e., before Herring's classification can be applied. Level of evidenceIII, prospective uncontrolled study 3.

MRI and sonography in Legg-Calvé-Perthes disease: clinical relevance of containment and influence on treatment.

:PurposeThe containment orientated treatment of Legg-Calvé-Perthes disease (LCPD) affected hip joints is broadly accepted in the literature. The prerequisite is early recognition of loss of containment. An often-used quantitative MRI containment parameter is the cartilaginous acetabulum-head-index (CAHI). Based on ultrasound (US), we analyzed the newly created ‘femoral head extrusion angle’ (HA) as a containment parameter in comparison with the CAHI in severe LCPD.MethodsIn a prospective study with 40 children (mean age 5.8 years sd 2.3) with unilateral LCPD classified as Catterall group III/IV, we measured the CAHI versus HA to assess the containment of the femoral head. HA in US was determined by the tangent from the bony acetabular rim to the cartilaginous cranio-lateral femoral head.ResultsThe HA was significantly higher in LCPD-affected hip joints (25° sd 7°) than in healthy ones (13° sd 5°; p < 0.001). Correlation analysis of all hip joints revealed a significant correlation between HA and CAHI (r = −0.69; p < 0.001). Hip joints with a low CAHI indicating loss of containment showed a higher HA in sonography.ConclusionThe results of our study suggest that the HA in US is a reliable containment parameter in severe LCPD with a HA > 22° defining a pathologic value. In comparison with the CAHI, HA measurement in ultrasound is easier than the assessment of various parameters to calculate an index. Frequent sonographical follow-up assessment in critical joints is an alternative if MRI is not available, helping to detect an impending loss of containment early enough.Level of EvidenceLevel II

Agreement of radiographic measurements and patient-reported outcome in 61 patients with Legg-Calvé-Perthes disease at mean follow-up of 28 years.

It is unclear how patient-reported outcome in patients with Legg-Calvé-Perthes disease (LCPD) is correlated with radiographic outcome. It was therefore the aim of our long-term follow-up to evaluate the agreement of patient-reported outcome measures (PROM) with radiographic outcome in patients with a history of unilateral LCPD and a femoral head involvement of more than 50%. We further investigated to what extent the functional outcome (range of motion and Trendelenburg sign) correlates with PROM and radiographic outcome. At a mean follow-up of 28 years (15-42), 61 patients were investigated clinically and by plain radiography to evaluate the sphericity deviation score, femoral head enlargement and femoral neck growth inhibition. The patients also completed questionnaires for generic measures of health-related quality-of-life (ED-5D, EQ-visual analogue scale), the joint-specific Harris hip score and the nonarthritic hip score questionnaire. The radiographic measures sphericity deviation score, femoral head enlargement and femoral neck growth inhibition were strongly correlated with the joint-specific PROMs (Harris hip score and nonarthritic hip score) but not with EQ-5D and EQ-visual analogue scale. Inferior range of flexion and abduction and a positive Trendelenburg sign were associated with an inferior patient-reported outcome. Our findings highlight the importance of supporting femoral head re-modelling and containment and balancing trochanteric and femoral neck growth in patients with LCPD. To capture the whole picture of the outcome after LCPD, future studies should include a combination of radiographic measurements and joint-specific and generic outcome scores. Level of Evidence: Level III.

Risk Factors for Femoral Head Deformity in the Early Stage of Legg-Calvé-Perthes Disease: MR Contrast Enhancement and Diffusion Indexes.

To determine whether changes in diffusion and/or contrast enhancement are of prognostic value in the early stage of Legg-Calvé-Perthes disease (LCPD). This study was approved by the institutional review board, and written informed consent was obtained from patient parents. Diffusion and contrast agent-enhanced magnetic resonance (MR) imaging studies were performed in 46 children (37 boys and nine girls; mean age, 7.5 years [age range, 3.3-11.9 years]) with unilateral LCPD at the early stage before development of extensive femoral head deformity. The degree of contrast enhancement was measured on the contrast-enhanced MR images, and the apparent diffusion coefficient (ADC) value was measured on the ADC map at various regions of interest in the proximal femur. The association of the MR imaging parameters that compared the affected side with the contralateral normal side with the femoral head deformity index value above 0.3 at 2 years was investigated. Increased diffusion in the metaphysis (P = .003) and decreased contrast enhancement in the central epiphysis (P = .034) were the significant prognostic indicators of subsequent femoral head deformation. ADC in the metaphysis 45% higher and a contrast enhancement in the central epiphysis 37% lower than those of the contralateral normal side are associated with a nonfavorable prognosis. For diffusion MR imaging, sensitivity was 83% (15 of 18), specificity was 86% (24 of 28), positive predictive value was 79% (15 of 19), negative predictive value was 89% (24 of 27), and accuracy was 85% (39 of 46). For contrast-enhanced MR imaging, sensitivity was 78% (14 of 18), specificity was 64% (18 of 28), positive predictive value was 58% (14 of 24), negative predictive value was 82% (18 of 22), and accuracy was 70% (32 of 46). Diffusion and contrast-enhanced MR imaging are potentially useful to assess risk of later development of femoral head deformity.

Extent of physeal involvement in Legg-Calvé-Perthes disease.

The growth plate involvement (GPI) index is reportedly a reliable predictor of final radiographic outcome in Legg-Calvé-Perthes disease (LCPD). We determined whether (1) the GPI index was associated with the lateral pillar classification, (2) the GPI index could predict the final radiographic outcome, and (3) the geometry of proximal femur was affected by presence of physeal involvement. We reviewed 47 patients with unilateral LCPD who were treated conservatively. The mean duration of follow-up was 9.5years (range, five to 13years). The affected hips were categorized into those with and without physeal involvement. Herring classifications were determined and the GPI indices were estimated at the stage of maximum fragmentation. The Stulberg classification, leg length discrepancy (LLD), articulotrochanteric distance (ATD) index, neck-shaft angle (NSA), neck width and height were determined at skeletal maturity. The GPI indices were lower in Herring groups A and B (p < 0.001) and Stulberg classes I and II (p = 0.002), and these values were increased in the Herring group B/C and C and Stulberg classes III, IV and V. However, the age of onset, LLD and ATD index at skeletal maturity were not associated with the GPI index. The NSA of the affected hips with physeal involvement was significantly different compared to that of unaffected hips (p < 0.001). The GPI index could be used to determine the extent of physeal involvement in LCPD, and might be considered one of the prognostic values of radiographic development in patients with LCPD who are treated conservatively.

The Sphericity Deviation Score

This study aimed to determine if a new measure of sphericity of the femoral head, the Sphericity Deviation Score (SDS), could be estimated reliably at the stage of healing of Legg-Calvé-Perthes disease (LCPD) and to determine if the SDS at the healing stage reflects the outcome at skeletal maturity. The SDS was measured with image analysis software on radiographs of 120 children with unilateral LCPD at healing of the disease and at skeletal maturity. The reproducibility of measurement was assessed. SDS values for hips in different Stulberg classes were calculated. On the basis of SDS values at healing of 82 children, a logistic regression model was developed to determine the probability of a good outcome at skeletal maturity. The validity of the model was tested on another 38 children. The SDS values at the stage of healing and at skeletal maturity were comparable. The SDS values were lowest for Stulberg Class I hips and highest for Class IV and V hips. The validated regression model showed a very high probability of a good outcome (Stulberg Class I or II) at skeletal maturity if the SDS at the stage of healing was below 10. A reliable estimate of the outcome of LCPD at skeletal maturity can be made by computing the SDS as soon as the disease heals.

Does proximal femoral varus osteotomy in Legg–Calvé–Perthes disease predispose to angular mal-alignment of the knee? A clinical and radiographic study at skeletal maturity

Though there is an impression that proximal femoral varus osteotomy (FVO) can result in a valgus deformity at the knee there is no agreement on this issue. This study was undertaken to ascertain whether a FVO predisposes to the development of genu valgum in children with Legg-Calvé-Perthes disease (LCPD). One hundred and one children with unilateral LCPD who underwent a FVO during the active stage of the disease and 32 children who were treated non-operatively were followed till skeletal maturity. The FVO was performed with a 20° varus angulation in all the patients and weight-bearing was not permitted till the stage of reconstitution. The alignment of the knee was assessed clinically at skeletal maturity. A subset of 33 operated children also had full length standing radiographs of the limbs. The mechanical axis deviation, femur-tibial angle, lateral distal femoral angle and the medial proximal tibial angle of both limbs were measured on these radiographs. The frequency of clinically appreciable mal-alignment of the knee was not greater on the affected side in patients who had undergone FVO when compared to the unaffected limb and also when compared to the affected limb in non-operated patients. The mechanical axis of the lower limb of operated children was relatively in more valgus than that of normal limbs but they fell within the normal range. This study does not support the impression that a proximal femoral osteotomy for LCPD predisposes to clinically discernable degrees of genu valgum in children who have had 20° of varus angulation at the osteotomy site and who have avoided weight-bearing for a prolonged period following surgery. Further studies are needed to clarify if genu valgum would develop if early post-operative weight-bearing is permitted. III.

Can Residual Leg Shortening Be Predicted in Patients With Legg-Calvé-Perthes’ Disease?

Although Legg-Calvé-Perthes' disease (LCPD) is frequently associated with varying degrees of femoral head deformity and leg length discrepancy (LLD), no factors that predict residual shortening have been clearly identified. We attempted to determine whether (1) the extent of femoral head involvement; (2) varus osteotomy; and (3) patient demographic characteristics are associated with LLD at skeletal maturity in patients with LCPD. We retrospectively reviewed the records of 168 skeletally mature patients with unilateral LCPD. The mean age at diagnosis was 7 years (range, 2-14 years). The extent of femoral head involvement was determined from the initial radiographs using the Herring lateral pillar and Catterall classifications. LLD was defined as shortening by ≥ 1.0 cm as measured from scanograms. The patient's sex and the treatment modalities used were also recorded. LLD ranging from 10 to 38 mm (mean, 19 mm) occurred in 93 (55%) patients and was associated with the extent of femoral head involvement. Varus osteotomy was not associated with residual shortening. The patient's age at diagnosis did not affect the LLD at skeletal maturity. The strongest predictor of LLD was a lateral pillar classification of B/C or C (odds ratio, 3.5; 95% confidence interval, 1.39-8.79). The extent of femoral head involvement, but not the patient's age at diagnosis or sex or the treatment modality, can predict the LLD at skeletal maturity in patients with unilateral LCPD.

Varus Femoral Osteotomy Improves Sphericity of the Femoral Head in Older Children With Severe Form of Legg-Calvé-Perthes Disease

In the Norwegian prospective study on Legg-Calvé-Perthes disease (LCPD), we found varus femoral osteotomy gave better femoral head sphericity at a mean of 5 years postoperative than physiotherapy in children older than 6.0 years at diagnosis with femoral head necrosis of more than 50%. That study did not include separate analyses for hips with 100% necrosis and those with a percentage of necrosis between 50% and 100%. We asked whether (1) femoral osteotomy improves femoral head sphericity at followup in all patients with more than 50% femoral head necrosis or in selected groups only and (2) there is a critical age between 6.0 and 10.0 years over which femoral osteotomy does not improve the prognosis. We treated 70 patients with unilateral LCPD, age at diagnosis of more than 6.0 years, and femoral head necrosis of more than 50% with varus femoral osteotomy between 1996 and 2000. We classified necrosis using the Catterall classification. We established a control group of 51 similar children who received physiotherapy. At the 5-year followup visit, the hips were graded according to femoral head shape: spherical, ovoid, or flat. At 5-year followup, there was no difference between the treatment groups in radiographic outcome in Catterall Group 3 hips. In Catterall Group 4 hips, femoral head sphericity was better in the osteotomy group, with flat femoral heads in 14% compared to 75% after physiotherapy. The same trend toward better head sphericity occurred when the lateral pillar classification was used. In children aged 6.0 to 10.0 years, in whom the whole femoral head is affected, femoral head sphericity 5 years after femoral osteotomy was better than that after physiotherapy.