Interobserver variability in grading Perthes' disease

Intra- and inter-observer reliability of Laredo classification system in Legg-Calvé-Perthes Disease

The purpose of the current study was to investigate intra- and inter-observer reliability of arthrographic Laredo classification system in Perthes disease. Forty-seven patients were included in this cross-sectional descriptive study. Patients' age, gender, physical findings and hip arthrographs were collected from hospital medical records. Two different sets of power point slides were prepared in which the order of cases was randomized and blinded. Observers were divided into three groups according to their surgical experience (9 residents, 10 seniors, 10 pediatric orthopedists), and they assessed two times 1 month's intervals. Statistical analysis was performed by using the SPSS v21. Inter- and intra-observer reliabilities were calculated using intra-class correlation coefficient, weighted kappa and percentage agreement. Percentage agreement of Laredo classification was about 50% for all groups (residents, seniors and pediatric orthopedists); intra-observer reliabilities were excellent, excellent and fair, respectively. Inter-observer reliability of Laredo classification for each set was found to be excellent for all groups. Length of experience did not correlated significantly with the level of intra-observer agreement. As a conclusion, our results showed that Laredo's arthrographic classification system's intra-observer reliability is at least at a fair level and inter-observer reliability is at an excellent level. We believe that this classification system is valuable for an orthopedic surgeon who deals with the treatment of Perthes disease.

Radiographic classifications in Perthes disease

Background and purpose - Different radiographic classifications have been proposed for prediction of outcome in Perthes disease. We assessed whether the modified lateral pillar classification would provide more reliable interobserver agreement and prognostic value compared with the original lateral pillar classification and the Catterall classification. Patients and methods - 42 patients (38 boys) with Perthes disease were included in the interobserver study. Their mean age at diagnosis was 6.5 (3-11) years. 5 observers classified the radiographs in 2 separate sessions according to the Catterall classification, the original and the modified lateral pillar classifications. Interobserver agreement was analysed using weighted kappa statistics. We assessed the associations between the classifications and femoral head sphericity at 5-year follow-up in 37 non-operatively treated patients in a crosstable analysis (Gamma statistics for ordinal variables, γ). Results - The original lateral pillar and Catterall classifications showed moderate interobserver agreement (kappa 0.49 and 0.43, respectively) while the modified lateral pillar classification had fair agreement (kappa 0.40). The original lateral pillar classification was strongly associated with the 5-year radiographic outcome, with a mean γ correlation coefficient of 0.75 (95% CI: 0.61-0.95) among the 5 observers. The modified lateral pillar and Catterall classifications showed moderate associations (mean γ correlation coefficient 0.55 [95% CI: 0.38-0.66] and 0.64 [95% CI: 0.57-0.72], respectively). Interpretation - The Catterall classification and the original lateral pillar classification had sufficient interobserver agreement and association to late radiographic outcome to be suitable for clinical use. Adding the borderline B/C group did not increase the interobserver agreement or prognostic value of the original lateral pillar classification.

Comparison of the results from simple radiography, from before to after Salter osteotomy, in patients with Legg-Calvé-Perthes disease

Objectives

To determine whether the clinical variables and preoperative classification of patients with Legg-Calvé-Perthes disease (LCPD) who undergo Salter osteotomy correlate with the radiographic result at the time of skeletal maturity.

Methods

In this retrospective cohort study, 47 individuals with LCPD who were treated using Salter osteotomy (1984–2004) were evaluated. The patients were evaluated according to sex, skin color, side affected and age at which osteotomy was performed. The preoperative radiographs were analyzed in accordance with the classifications of Waldenström, Catterall, Laredo and Herring. The radiographs obtained at the time of skeletal maturity were classified using the Stulberg method.

Results

The mean age at the time of surgical treatment was 82.87 months (6.9 years). The age presented a statistically significant correlation with the Stulberg grades at skeletal maturity (p < 0.001). Patients over the age of 6.12 years tended to present less favorable results. The variables of sex, skin color and side affected did not present any statistically significant correlation with the prognosis (p = 0.425; p = 0.467; p = 0.551, respectively). Only the Laredo classification presented a statistically significant correlation with the final result given by the Stulberg classification (p = 0.001). The other classifications used (Waldenström, Catterall and Herring) did not present any correlation between the time at which surgery was indicated and the postoperative result.

Conclusions

The age at which the patients underwent surgical treatment and the Laredo classification groups were the only variables that presented significant correlations with the Stulberg classification.

Interobserver and intraobserver reliability of the modified Waldenström classification system for staging of Legg-Calvé-Perthes disease

BACKGROUND

The absence of a reliable classification system for Legg-Calvé-Perthes disease has contributed to difficulty in establishing consistent management strategies and in interpreting outcome studies. The purpose of this study was to assess interobserver and intraobserver reliability of the modified Waldenström classification system among a large and diverse group of pediatric orthopaedic surgeons.

METHODS

Twenty surgeons independently completed the first two rounds of staging: two assessments of forty deidentified radiographs of patients with Legg-Calvé-Perthes disease in various stages. Ten of the twenty surgeons completed another two rounds of staging after the addition of a second pair of radiographs in sequence. Kappa values were calculated within and between each of the rounds.

RESULTS

Interobserver kappa values for the classification for surveys 1, 2, 3, and 4 were 0.81, 0.82, 0.76, and 0.80, respectively (with 0.61 to 0.80 considered substantial agreement and 0.81 to 1.0, nearly perfect agreement). Intraobserver agreement for the classification was an average of 0.88 (range, 0.77 to 0.96) between surveys 1 and 2 and an average of 0.87 (range, 0.81 to 0.94) between surveys 3 and 4.

CONCLUSIONS

The modified Waldenström classification system for staging of Legg-Calvé-Perthes disease demonstrated substantial to almost perfect agreement between and within observers across multiple rounds of study. In doing so, the results of this study provide a foundation for future validation studies, in which the classification stage will be associated with clinical outcomes.

What is the usefulness of the fragmentation pattern of the femoral head in managing Legg-Calvé-Perthes disease?

Background

Within the lateral pillar classification of the Legg-Calvé-Perthes (LCP) disease, hips seem quite variable in the pattern of fragmentation as seen in radiographs. The purpose of this study was to determine: if it is possible to reliably subdivide the lateral pillar groups into femoral head fragmentation patterns, and if such a subdivision of the lateral pillar groupings is clinically useful in managing LCP disease.

Methods

Two hundred and ninety-three anteroposterior radiographs taken at the maximal fragmentation stage (189 lateral pillar B, 57 B/C border, and 47 C hips; mean bone/chronologic age at the time of first visit, 6.2/7.9 years) and at skeletal maturity (mean age, 16.6 years) were analyzed. We distinguished 3 fragmentation patterns in each pillar group based on the region of major involvement. We tested the inter- and intraobserver reliability of our classification system and analyzed the relationships between the fragmentation patterns and the Stulberg outcomes as well as other factors such as surgical treatment and age.

Results

Inter- and intraobserver consistency in fragmentation pattern assignments was found to be substantial to excellent. A statistically significant trend (p = 0.001) in the proportion of Stulberg III or IV outcomes in comparison with Stulberg I and II was only found for the different fragmentation patterns in our lateral pillar B patients: fragmentation patterns having mainly lateral-central necrosis led to poor outcomes. No significant association was found between fragmentation patterns and Stulberg outcomes in pillar groups B/C border and C.

Conclusions

Our results are consistent with the lateral pillar classification itself. Therefore, fragmentation patterns in each lateral pillar classification did not provide clinical usefulness in the management of LCP disease.

Reliability and stability of three common classifications for Legg-Calvé-Perthes disease

BACKGROUND

To predict the course of Legg-Calvé-Perthes disease (LCPD) and select between treatment options in the early stages, it is critical to have a reliable predictive classification.

QUESTIONS/PURPOSES

We examined the reliability and stability of three common classification systems for LCPD.

METHODS

We identified 69 patients with LCPD, who had hip radiographs taken more than twice after the initial presentation with at least a 3-month interval. The Herring lateral pillar, Catterall, and Salter-Thompson classifications were evaluated in terms of reliability and stability. The inter- and intrarater reliability of the classification systems was determined by three orthopaedic surgeons using intraclass correlation coefficients (ICCs). To evaluate the stability of the classification systems, the percentage agreement and ICCs among the initial rating, rating when entering fragmentation, and final rating were used.

RESULTS

The interrater reliability was highest in Herring lateral pillar classification (ICC, 0.885) followed by the Catterall and Salter-Thompson classifications (ICC, 0.802 and 0.702, respectively). The percentage agreement and ICC between the initial and final rating were, respectively, 55% and 0.491 for the Herring classification and 48% and 0.378 for the Catterall classification.

CONCLUSIONS

Our data show the highest reliability of the classification of Herring et al. However, more than 40% of the hip radiographs at the initial presentation, and in particular, most of Herring Group A patients, were upgraded. Therefore, for patients older than 8 years old and graded as Herring Group A initially, surgeons should keep the possibility of surgical treatment in mind.

Prognostic factors and outcome measures in Perthes disease

The shape of the femoral head at the time when Perthes disease heals is the most important determinant of the risk for degenerative arthritis; hence, the shape of the femoral head and congruence of the hip are the most useful outcome measures. Although several prognostic factors that predict femoral head deformation may be identified during the course of Perthes disease, only two prognostic factors may be identified early enough to institute preventive intervention: femoral head extrusion and the age at onset of the disease. Femoral head extrusion is the only factor that may be influenced by treatment.

Long-term results of proximal femoral osteotomy in Legg-Calvé-Perthes disease

BACKGROUND

Legg-Calvé-Perthes disease is a childhood hip disorder that may result in a deformed and poorly functioning hip. The purpose of this study was to evaluate the correlation between hip deformity at skeletal maturity and degenerative osteoarthritis and to present the long-term results of proximal femoral varus derotational osteotomy in Legg-Calvé-Perthes disease.

METHODS

We analyzed the results of 40 patients (43 hips), who underwent proximal femoral varus derotational osteotomy for Legg-Calvé-Perthes disease in our institution between 1959 and 1983. All available patients underwent a single long-term follow-up examination. Hips were classified with the classification system of Stulberg. Osteoarthritis was evaluated using the Tönnis classification. The long-term outcomes were evaluated after a mean follow-up period of 33 years.

RESULTS

When examining the outcome using the Stulberg classification system, there were 8 Stulberg class I hips (19.5%), 15 Stulberg class II hips (36.6%), 8 Stulberg class III hips (19.5%), 9 Stulberg class IV hips (22%), and 1 Stulberg class V hip (2.4%). One patient, who had a bilateral Legg-Calvé-Perthes disease, underwent total hip replacement for osteoarthritis. Seven patients had poor clinical results.

CONCLUSIONS

Proximal femoral varus derotational osteotomy provides good long-term results for Legg-Calvé-Perthes disease. The Stulberg classification is a good predictor for patient outcome.

LEVEL OF EVIDENCE

Level IV, therapeutic study.

The importance of surgeons' experience on intraobserver and interobserver reliability of classifications used for Perthes disease

The objective of this study was to evaluate the percentage agreement and intraobserver and interobserver reliability for the Catterall, Salter-Thompson, Herring, and Stulberg classification systems, with special reference to the experience of surgeons. AP and frog-leg radiographs of 10 patients were evaluated by 18 reviewers with three levels of experience on two occasions. Each patient had three sets of radiographs of different stages of disease (initial stage, fragmentation phase, and healed phase). The interobserver percentage agreement rates were 28% for residents, 42% for senior surgeons, and 51% for pediatric orthopaedists for the Catterall classification in the initial stage; 63%, 46%, and 68% for the Salter-Thompson classification; 44%, 44%, and 61% for the Herring classification; and 34%, 37%, and 43% for the Stulberg classification at skeletal maturity. The Catterall, Herring, and Salter-Thompson classifications have a learning curve, and pediatric orthopaedists have better intra- and interobserver reliability. The Stulberg classification system when used at skeletal maturity consistently gave the best results for intraobserver and interobserver reliability for residents, senior surgeons, and pediatric orthopaedists. These results suggest that although the reliability of these classification systems improves with the experience of the observer, inter- and intraobserver error is generally high even among experienced pediatric orthopaedists.

Evaluation of the subchondral fracture in predicting the extent of femoral head necrosis in Perthes disease: a prospective study of 92 patients

The aim of this study was to evaluate the subchondral fracture as a predictor for the extent of femoral head necrosis in Perthes disease. Out of 392 patients, 92 (23.5%) had a detectable subchondral fracture at the time of diagnosis. There was concordance between predicted Catterall groups on the basis of the extent of the subchondral fracture and the actual Catterall groups at the time of maximal resorption in 61% of the cases, when assessed by an experienced observer. When using the extent of the subchondral fracture to predict Salter-Thompson groups, this observer obtained 89% concordance with the actual Salter-Thompson groups at the time of maximal resorption. The inter-observer agreement between the experienced and a less experienced observer regarding the presence or absence of a subchondral fracture was moderate (weighted kappa 0.59, 87% agreement). When using the extent of the subchondral fracture as a measure of femoral head involvement (Catterall groups), the inter-observer agreement was moderate (weighted kappa 0.46). Patients with detectable subchondral fracture were significantly older (mean 6.5 years) at the time of diagnosis than those without visible fracture (mean 5.2 years). The delay in diagnosis was significantly shorter in the group with subchondral fracture (mean 3.2 months) than among patients without visible fracture (mean 4.9 months). There was no significant difference with regard to sex, pain level, pain localization, or limping gait between the two groups. We conclude that the subchondral fracture is a relatively rare early sign in Perthes disease. When present, it is a useful sign when assessed by an experienced observer as its extent was in fairly good concordance with the extent of femoral head involvement at the time of maximal resorption. Awareness of this radiographic sign will aid the orthopaedic surgeon to establish diagnosis and, to some degree, to predict prognosis early in the course of the disease.

A scintigraphic classification of Legg-Calvé-Perthes disease

The onset of Legg-Calvé-Perthes (LCP) disease, avascular necrosis of the proximal femoral epiphysis, frequently is clinically undetectable for months before presentation. This traditional X-ray methods of diagnosis are insensitive for the diagnosis of early LCP as well as nonspecific for the diagnosis of advanced LCP. The X-ray may remain normal for weeks to months after the onset of LCP, and other disorders (steroid osteopathy, epiphyseal dysplasia) simulate the X-ray appearance of LCP during its later stages. Localization of bone-avid radiopharmaceuticals depends principally on bone perfusion and metabolism. Bone scintigraphy is a highly sensitive and specific means of detecting changes in bone perfusion. An understanding of the vascular anatomy of the pediatric hip and its revascularization mechanisms is essential for correlating the scintigraphic findings with the stages of healing in this disorder. Revascularization of bone can occur by recanalization of existing vessels or by neovascularization through the development of new vessels. Recanalization is a rapidly occurring process (minutes to weeks), whereas neovascularization is a prolonged process (months to years). The recanalization process has a characteristic scintigraphic pattern beginning with the visualization of a "lateral column" and is associated with a good prognosis for eventual outcome in LCP. Neovascularization also has a characteristic scintigraphic appearance ("base filling" and "mushrooming"), which is associated with a poorer prognosis because of the prolonged interval required for healing, which places the femoral head at risk for complications such as fracture, collapse, and extrusion. The scintigraphic staging classification presented here, when correlated with a modified Waldenstrom X-ray staging, readily differentiates three mechanisms of revascularization. The A (allright) track scintigraphic pattern represents the recanalization process, a process of short duration and good prognosis. The B (bad) track scintigraphic pattern represents the process of neovascularization, a process of long duration and poorer prognosis. A third process also is described in which complications of the healing process (collapse, extrusion), particularly during the reabsorptive phases of bone reconstitution when the bone is weakened, can cause conversion from track A to track B. Bone scintigraphy is useful in LCP for its ability to detect the disorder in its initial stages, thus allowing earlier treatment, and to provide prognostic information that may affect therapy.