We have now had a century of recognition of “An Obscure Affliction of the Hip Joint” as Dr Legg titled his paper in 1910.1 In these 100 years, many aspects of the disorder have been studied, and yet much remains in the realm of mystery, opinion, and bias, especially in relationship to treatment decisions. In this brief report, I would like to first review and list some of the elements of our understanding of the disease that have been discovered over these 100 years. I will then summarize some of the evidence-based information that deals with treatment of the child with this hip disorder.
HISTORY OF OUR KNOWLEDGE BASE
Knowledge of the Disease
The initial bit of understanding that led to the identification of the disorder was that it was not tuberculosis. This was a direct result of the availability of x-ray with radiographs showing that the affected children lacked the typical changes of tuberculosis. In addition, there was noted a very atypical clinical picture with a benign course of the disease compared with tuberculosis. Almost immediately the discoverers presumed a vascular etiology, a theory, which is maintained today.2,3
Over the decades, our understanding of etiology has expanded. Evidence exists to support an arterial infarction, possibly several such infarctions, whereas somewhat contradictory evidence also supports a venous congestion etiology.4 Findings of delayed bone age, shorter stature than controls, and minor radiographic findings in the contralateral hip have suggested that this disorder is a generalized abnormality affecting susceptible individuals.5–7 Finally, trauma to the immature hip may also be an accessory etiologic factor.8,9 Ongoing research is evaluating the role of systemic coagulopathy and environmental factors such as passive exposure to tobacco smoke.10–12
Radiographic studies have identified the stages of progression of the disease (Waldenstrom), classification systems have been developed (Legg, Waldenstrom, Goff, Catterall, Mose, Salter-Thompson, Lateral Pillar, bone scan, and magnetic resonance imaging scan).
Legg, Calve, and Perthes each began treating patients by methods common to the management of tuberculosis of the hip. These included traction, bed rest, and relief of weight-bearing with a caliper brace.13 Later Legg and Waldenstrom both were quoted as stating that “no treatment should be applied.”13 In the 1950s, a number of institutions used enforced, bed rest with abduction splinting, often with several years of in-patient management. Snyder slings often followed for more years. Petrie casting, abduction bracing both with and without allowing ambulation followed. Varus femoral osteotomy,14 Salter pelvic osteotomy, shelf arthroplasty, Chiari osteotomy, and cheilectomy have all had a period of popularity in management.
THE EVIDENCE BASE FOR TREATMENT EFFICACY
In 1994, I published a review of the literature regarding treatment of Legg-Calve-Perthes disease.15 In the summary of that review, I concluded that “most of the reported studies have simply lacked the controls necessary to allow valid scientific conclusions to be drawn.” This was said to emphasize that Perthes is a remarkably variable disease, and objective studies must consider the known variables before concluding that one treatment is better than another. These variables include (1) the age at onset of disease, (2) the stage of disease at which treatment is applied, (3) a reliable classification of disease severity, and (4) the exact method of treatment. An example of the need for treatment detail would be interpreting results from a study of brace treatment without measuring brace compliance or hip position within the brace.
The lack of scientific basis for treatment of this disorder became evident to a number of members of the Pediatric Orthopedic Study Group after a debate at the 1982 meeting of that organization. Our discussions led to the formation of the Legg Perthes Study Group, which included 39 pediatric orthopedists from the US, Canada, and New Zealand. The study was termed a “best effort” study in which each surgeon used the same treatment method for every patient included. The observed groups were Atlanta brace treatment, range of motion protocol, no treatment, femoral osteotomy, and Salter osteotomy. Patients were between 6 and 11 years old at onset, were treated in the initial or early fragmentation stage of disease, and were followed-up to maturity.
Wiig et al16 in 2008 reported a multicenter study from Norway using a similar “best effort” protocol, with physiotherapy, orthosis, and femoral osteotomy as the treatment options. Patients of all ages were included.
Rosenfeld et al17 reviewed a 50-year series of mostly untreated patients with onset of Legg Perthes before the sixth birthday. The results of these level II studies and one level IV study provide valid bases for this discussion of treatment choices.
Age at onset is usually known and stage of disease at treatment can be determined. Classification of severity is more difficult. The Catterall classification was proposed in 1971 and used exclusively for many years.18 In 198019 and 1986,20 Hardcastle et al and Christensen et al reported that the classification could not be reliably reproduced by orthopedists. In the early days of our multicenter study, the investigators reviewed many radiographs on a number of occasions and could not reach satisfactory agreement on the Catterall classification.
We then studied radiographs of patients at maturity, comparing the resulting head deformity to the radiographic findings in the early stages. We found a reproducible classification based on the changes in the lateral portion of the femoral head, which we termed the lateral pillar.21 Before concluding this study, we again validated the classification after adding a borderline classification.22 The lateral pillar classification with categories A, B, B/C border, and C has proved to be both reproducible and of prognostic value.23–28
The major drawback to the lateral pillar classification is that it can only be determined when lucent areas become evident in the early fragmentation stage of the femoral head. In our study, treatment, including surgical procedures, was begun before fragmentation stage. Later, results were stratified by lateral pillar classification. An ideal classification would be one, which could be applied at the earliest stage. We and others are now comparing magnetic resonance imaging studies in the initial stage with later femoral head changes to find correlations, which may be of prognostic value.
The Mose and Stulberg classifications are widely used for end result radiographic analysis. Our techniques for using these are described in detail in our study report.29
FACTORS OTHER THAN TREATMENT RELATED TO OUTCOME
Age at Onset
In our multicenter study, in all treatment groups, age was correlated with Stulberg outcome. Of those under 8 at onset, 59% had a Stulberg II result whereas of the over 8 patients, 39% had Stulberg II outcome. In the Wiig et al study, 57% of patients under 6 had Stulberg I to II results, whereas 38% of those over 6 had that outcome (There was no breakdown of results relative to age 8 at onset in this study).
The lateral pillar classification was strongly associated with outcome in both studies. In our study, a Stulberg I, II outcome was found in 100% of lateral pillar A hips, 62% of lateral pillar B hips, 28% of B/C border hips, and in only 13% of lateral pillar C hips. We were unable to use the Catterall classification because of lack of agreement among study members.
In Wiig et al study, Stulberg I to II outcome occurred in 70% of lateral pillar A hips, 51% of lateral pillar B hips, and 30% of C hips. They found that 84% of Catterall 1 and 2 hips had a Stulberg I to II outcome, whereas 44% of Catterall 3, 4 hips had Stulberg I to II outcomes.
In our study, we found no significant differences between the 3 nonoperative methods, bracing, no treatment, and range of motion, and combined these for analysis. The 2 surgical groups, femoral osteotomy and Salter osteotomy were also similar in outcome and were combined. We did not find a significant difference in outcome between the treatment groups in patients under age 8 at onset. In those over 8, we found that surgical treatment was significantly associated with better outcome in lateral pillar groups B and B/C border. We found no association between treatment method and outcome in the lateral pillar C group at any age. In lateral pillar B group over age 8, there were 73% Stulberg I to II results in the operative group compared with 44% in the nonoperative group. In group C, there were 7% Stulberg I to II results in the nonoperative group and none in the operative group. These data support a significant improvement in outcome in patients over age 8 at onset who have lateral pillar B and B/C involvement when they are treated with either osteotomy compared with nonoperative treatment.
In the Wiig et al study, in patients over 6 with more than 50% head involvement (Catterall groups 3, 4), Stulberg I to II results were present in 33% of the physiotherapy patients, 20% of the brace treated patients, and 43% of the osteotomy patients. The authors concluded that treatment with femoral osteotomy improved outcome for patients over age 6 with Catterall 3 or 4 classification.
PATIENTS UNDER AGE 6 AT ONSET
Our group reviewed radiographs of all patients treated at Texas Scottish Rite Hospital for Children with onset of Legg-Calve-Perthes before their sixth birthday.17 We studied 188 hips. The average age was 4.6 years at onset. One hundred fourteen or 68% had no active treatment, whereas the others had braces. All of the lateral pillar A hips had a Stulberg I to II outcome and 94% of the lateral pillar B hips had that result. Fifty-five percent of the B/C border hips and 48% of the C hips had a Stulberg I to II result. Those treated with braces had similar outcomes to those not treated.
An odds ratio table was created, which indicates that most of the hips destined for nonspherical outcome are those in children between 4 and 6 at onset with lateral pillar C classification (Table 1).
Wiig et al also studied patients under 6 at onset. Total 57% of patients under age 6 had a Stulberg I to II result. There were no differences in outcome between the various treatment methods in these younger patients.
From our multicenter study we have evidence at level 2, which shows significant correlations between surgical procedures, especially varus producing proximal femoral osteotomy, and improved outcome for hips in the lateral pillar B and B/C border categories, in patients over age 8 at onset. In our study, we were not able to show an effect in patients less than 8 years of age at onset, whereas Wiig et al showed efficacy in those more than 6 at onset. We could see no evidence of efficacy in hips categorized as lateral pillar C.
The strongest message I see in these results is that the lateral pillar B hips in children less than 8 at onset have a good prognosis there was no trend of improvement with higher levels of treatment. Hopefully this will spare many children from unneeded treatment.
The second message is that we must, in well-designed, controlled studies, explore new methods that will alter outcome for the lateral pillar C group. I would emphasize the need for level 1 and 2 studies and would discourage small series of radical methods. The disorder itself is so variable that little is learned from haphazard reports.
In addition, we clearly need valid animal studies, which can be an avenue to test biologic approaches with bisphosphonates, bone morphogenic proteins, and newer agents, which may alter the pathophysiology of the disorder. Nothing will substitute for the basic science of understanding of the causative factors, the nature of the vascular events, the intricate events of bone and cartilage damage, particle removal, and eventual repair. Hopefully, the next decade will exceed the previous century in furthering our understanding and management of this disorder.
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