Prognostic factors and outcome measures in Perthes disease

Epidemiology, natural evolution, pathogenesis, clinical spectrum, and management of Legg-Calvé-Perthes

Background

Legg-Calvé-Perthes disease is a self-limiting disorder that develops in children following interruption of the blood supply to the capital femoral epiphysis. This review outlines the current knowledge on the epidemiology, natural evolution, clinical spectrum, and management of the disease.

Methods

The literature pertaining to these aspects of the disease were studied and summarized in this review.

Results

Epidemiological studies suggest that environmental factors contribute to the causation of the disease. Incidence rates monitored over time indicate that the incidence of Legg-Calvé-Perthes disease is declining. The natural evolution followed on sequential plain radiographs enables division of the disease into Stages Ia, Ib, IIa, IIb, IIIa, IIIb, and IV. Reversible deformation of the capital occurs in Stages Ia-IIa simply on standing while irreversible deformation may occur in Stages IIb and IIIa. Treatment of Legg-Calvé-Perthes disease in Stages Ia-IIa aims to prevent the femoral head from getting deformed by containment and avoidance of weight-bearing. In Stages IIb and IIIa, treatment aims to remedy the effects of early irreversible deformation of the femoral head. In Stage IIIb and IV, treatment is directed to correcting the altered shape of the femoral head. The impression that these treatment methods are helpful is based on poor quality evidence.

Conclusion

There is an urgent need to undertake Level I studies to establish the efficacy of currently treatment.

Level of evidence

level V.

The "Discoid Epiphysis"-An Uncommon Presentation of Legg-Calvé-Perthes Disease

BACKGROUND

Among a cohort of 402 children with Legg-Calvé-Perthes disease (LCPD), 32 children presented with sclerosis and severe collapse of the entire femoral epiphysis that closely resembled a discus.This study was undertaken to identify the characteristics of children with this form of a "discoid epiphysis," compare them with typical LCPD and ascertain the radiologic outcome of their hips when the disease healed.

METHODS

Sequential radiographs of the children were studied to monitor disease evolution. Femoral epiphyseal extrusion was measured on the initial anteroposterior radiograph. Thirty-one of the 32 children were treated with a proximal femoral varus osteotomy and weight-bearing was deferred till the disease reached stage IIIb. The pattern of fragmentation of the epiphysis was noted and the Sphericity Deviation Score (SDS) was computed once the disease healed.

RESULTS

The mean age of children with a discoid epiphysis was 6.81±1.57 years at onset of symptoms while that of children with the typical presentation was 7.54±1.64 years (P<0.017). Perfusion magnetic resonance imaging scans of three children with a discoid epiphysis done in stage Ib of the disease showed that over 95% of the epiphysis was avascular. Femoral head extrusion was frequently present on the initial radiographs (mean Reimer's migration index 27.08±8.7; range: 6.4 to 42.55).In operated children with a discoid epiphysis, the disease evolved typically with fragmentation of the epiphysis followed by reconstitution. The height of the epiphysis was never restored; when the disease healed the mean epiphyseal height was 51.31±10.44% of the normal contralateral epiphysis as compared with 82.46±11.24% in children with typical LCPD (P<0.001).The SDS at healing of operated children with a discoid epiphysis was 14.95±10.86 while the SDS for operated children without a discoid epiphysis was 9.77±11.7 (P<0.019). However, the SDS of children with typical onset LCPD who had Catterall IV involvement and Herring C collapse was 15.25±15.19 (P=0.49 NS).

CONCLUSION

The outcome of treatment of children with a discoid epiphysis is comparable to that of children with typical onset LCPD with Catterall IV (whole-head involvement) and Herring C collapse of the lateral pillar. About a third of these children who undergo early surgical containment may have spherical heads when the disease heals.

Does early and aggressive management of significant extrusion of the femoral head affect the outcome of Perthes' disease with the age of onset younger than 7 years?

Background

Little literature exists regarding aggressive treatment of the extrusion in the early stage of the disease and the outcome at skeletal maturity. The purpose of the study was to evaluate the outcome of the disease with onset younger than 7 years, treated in the early stage of the disease, with aggressive management of significant extrusion (immediate containment with fixed abduction brace in children less than 5 years and varus derotation osteotomy in older children), and reached skeletal maturity.

Methods

All children with the age of onset younger than 7 years of disease during active Perthes disease were prospectively followed. Children with early stages of the disease (modified Elizabethtown classification) and reached skeletal maturity were included (68 children). The extrusion of the femur head was calculated by Reimer’s migration index on both sides. A migration difference 12 % or above was considered as “significant extrusion”. Children without significant extrusion were treated non-operatively; children with significant extrusion were treated with varus derotation osteotomy. The final radiological outcome was assessed by the Stulberg classification and sphericity deviation score (SDS). The independent “t” test and Chi-square test were done to compare the difference between the two groups.

Results

The mean age at the onset and the final follow-up was 5.7 years and 15.3 years. The frequency of significant extrusion was 57%. At the final follow-up, an excellent clinical outcome and radiological outcomes (in 88% hips) were noted. There was no significant difference in the Stulberg groups and SDS (sphericity deviation score) in both groups.

Conclusion

The outcome of the children who had the age of onset of the disease less than 7 years was good with early and aggressive management of the extrusion. The reversal of extrusion is associated with a similar result of non-operative children in this age group.

Level of evidence

III.

Reproducibility of Radiographic Measurements Made in the Active Stages of Legg-Calvé-Perthes Disease: Evaluation of a Prognostic Indicator and an Interim Outcome Measure

BACKGROUND

Deformity index (DI) and extrusion index (EI) are 2 radiographic methods currently used to quantify femoral head deformity in the active stages of Legg-Calvé-Perthes disease. This study aimed to quantify the interobserver reproducibility of the 2 methods using a large, international group of pediatric orthopaedic surgeons with diverse clinical experience.

METHODS

Radiographs of patients (age 6 to 11 y at time of diagnosis) prospectively enrolled in an international multicenter-cohort study, were measured by members of our study group. For each radiograph, the raters independently assessed EI (n=33 cases) and DI (n=32 cases), along with the rater's subjective assessment of the extent of hip deformity (ie, none, mild, moderate, or severe). Reliability analysis was conducted using intraclass correlation coefficient (ICC) and κ techniques.

RESULTS

The ICC for EI on the affected side was 0.68 (95% confidence interval: 0.57-0.79). The calculated DI ICC was 0.53 (95% confidence interval: 0.41-0.68). Subjectively, an average of 68±3.5% of surgeons agreed on the subjective description of each patient's femoral head deformity.

CONCLUSIONS

EI is measured with a reasonably high rate of correlation among surgeons from disparate backgrounds. Agreement is lower among the same group of surgeons when the more complex DI is used. DI is most useful when utilized by a small number of experienced observers in a research setting, whereas EI may have better clinical applicability.

LEVEL OF EVIDENCE

Level III-reliability study.

Effectiveness of Strontium Ranelate in the Treatment of Rat Model of Legg-Calve-Perthes Disease

BACKGROUND

Legg-Calve-Perthes disease (LCPD) causes osteonecrosis of the femoral head (ONFH) by temporarily interrupting the blood supply in children. Even with potential toward bone regeneration and revascularization in LCPD, the prognosis depends on the deformity of femoral heads, and successful rate with the current treatments varies. Antiresorptive therapy such as bisphosphonate, which maintains mechanical stability of the femoral head by inhibiting necrotic bone resorption, has proven effective in animal models. However, concerns on simultaneous decline in bone turnover rate still leave room for improvement. Strontium ranelate with dual effect on inhibiting bone resorption and accelerating bone formation is presumed to be an ideal therapy for reserving sphericity of femoral heads in LCPD.

MATERIALS AND METHODS

In this study of a rat model of ONFH, randomized groups of rats treated with strontium ranelate or normal saline are compared at different time points in analysis of radiological, histological, and bone morphometric changes. Gait analysis was also compared between the two groups.

RESULTS

The group treated with strontium ranelate recovered their normal gait earlier than the control group did. Bone density, trabecular thickness, sphericity of the femoral head, and bone regeneration potential were also preserved in the strontium ranelate group.

CONCLUSION

Strontium ranelate effectively prevented collapse of the ischemic femoral head and enhanced trabecular thickness in the rat model of LCPD. Hopefully, this preclinical experiment can improve the effectiveness of strontium ranelate treatment for pediatric ONFH.

Early outcomes of one-stage combined osteotomy in Legg-Calve´-Perthes disease

BACKGROUND

Legg-Calve´-Perthes disease (LCPD) is an idiopathic avascular necrosis of the femoral head. There are multiple approaches to the treatment of LCPD ranging from conservative management to a wide variety of surgical methods. Conservative management necessitates extreme degrees of abduction in an orthosis for a longer period of time which further jeopardize capital femoral head vascularity. Surgical containment methods are used in cases where it is desirable. Initial surgical containment methods are varus or varus-derotational osteotomy of the proximal femur or an innominate osteotomy as described by Salter and other pelvic osteotomies. The purpose of this study was to describe the early results of containment methods by one-stage combined osteotomy (femoral varus osteotomy and Salter innominate osteotomy) in patients with severe LCPD.

MATERIALS AND METHODS

23 children were operated in the age group of 4-9 years for LCPD by one-stage combined osteotomy procedure between January 2005 and June 2012. There were 19 boys and 4 girls, left hip involved in 10 cases and right in 13 cases. Preoperatively, they were classified according to Catterall, Joseph's stage and lateral pillar (LP) classification. Postoperatively, clinical results were evaluated in accordance with Ratliff classification and radiological assessment was made by Mose's index, modified Stulberg classification and Epiphyseal extrusion index.

RESULTS

Seventeen hips were Catterall group III, 6 in group IV and all had two or more "head-at-risk" signs. There were 2 patients with stage IIA, 15 were in stage IIB and 6 were in stage IIIA as classified by Joseph's stage of disease. According to LP classification, 11 patients were group B, 3 were group B/C and 9 were in group C. At an average followup of 5.4 years (range 2-9.5 years), the clinical results were good in 12, fair in 9 and poor in 2. According to Mose scale, 8 patients had good results, 13 fair results and 2 had poor results. Based on modified Stulberg classification, there were 10 patients in group A, 11 in group B and 2 in group C. The average preoperative extrusion index was 23.6% which improved postoperatively to 9.5% at latest followup.

CONCLUSIONS

The surgical treatment of LCPD with the best expected outcome is still a challenge. Advanced containment methods by one-stage combined osteotomy can be considered as an alternative treatment where femoral head subluxation or deformity which makes containment difficult or impossible by more conventional methods.

Local administration of bone morphogenetic protein-2 and bisphosphonate during non-weight-bearing treatment of ischemic osteonecrosis of the femoral head: an experimental investigation in immature pigs

BACKGROUND

Non-weight-bearing decreases the femoral head deformity but increases bone resorption without increasing bone formation in an experimental animal model of Legg-Calvé-Perthes disease. We sought to determine if local administration of bone morphogenetic protein (BMP)-2 with or without bisphosphonate can increase the bone formation during the non-weight-bearing treatment in the large animal model of Legg-Calvé-Perthes disease.

METHODS

Eighteen piglets were surgically induced with femoral head ischemia. Immediately following the surgery, all animals received an above-the-knee amputation to enforce local non-weight-bearing (NWB). One to two weeks later, six animals received local BMP-2 to the necrotic head (BMP group), six received local BMP-2 and ibandronate (BMP+IB group), and the remaining six received no treatment (NWB group). All animals were killed at eight weeks after the induction of ischemia. Radiographic, microcomputed tomography (micro-CT), and histomorphometric assessments were performed.

RESULTS

Radiographic assessment showed that the femoral heads in the NWB, BMP, and BMP+IB groups had a decrease of 20%, 14%, and 10%, respectively, in their mean epiphyseal quotient in comparison with the normal control group. Micro-CT analyses showed significantly higher femoral head bone volume in the BMP+IB group than in the BMP group (p = 0.02) and the NWB group (p < 0.001). BMP+IB and BMP groups had a significantly higher trabecular number (p < 0.01) and lower trabecular separation (p < 0.02) than the NWB group. In addition, the osteoclast number per bone surface was significantly lower in the BMP+IB group compared with the NWB group. Calcein labeling showed significantly higher bone formation in the BMP and BMP+IB groups than in the NWB group (p < 0.05). Heterotopic ossification was found in the capsule of four hips in the BMP+IB group but not in the BMP group.

CONCLUSIONS

Administration of BMP-2 with bisphosphonate best decreased bone resorption and increased new bone formation during non-weight-bearing treatment of ischemic osteonecrosis in a pig model, but heterotopic ossification is a concern.

CLINICAL RELEVANCE

This preclinical study provides new evidence that BMP-2 with bisphosphonate can effectively prevent the extreme bone loss associated with the non-weight-bearing treatment and increase new bone formation in the femoral head in this animal model of ischemic osteonecrosis.

Shelf acetabuloplasty in the treatment of severe Legg-Calvé-Perthes disease: good outcomes at midterm follow-up

The aim of the study was to retrospectively review results of operative treatment for coverage deficit of femoral head in children with severe epiphysis displacement in Legg-Calvé-Perthes (LCP) disease. The material included 23 shelf acetabuloplasty procedures for LCP disease. The average age at diagnosis was 8.1 years (range 4–12). Mean follow-up was 5.8 years (range from 2.2 to 11.2 years). Mean Reimer's index decreased statistically significantly from a mean of 32% before surgery to 10.0% at the last follow-up (P < 0.00001). The mean Wiberg center-edge angle increased also statistically significantly from a mean of 17.3° before procedure to 32.3° at the last follow-up (P < 0.00001). According to the Stulberg classification, type I was observed in 2, type II in 13, type III in 6, and type IV in 2 hips. There were no differences in the range of motion or leg length discrepancy in preoperative and postoperative standing. Partial, not significant, bone graft resorption was noted in 6 cases in the first 6–9 months after surgery. To conclude, shelf acetabuloplasty allows achieving good midterm results in the treatment of severe stages of LCP disease. The procedure improves coverage of femoral head and allows its remodelling.