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1 Original article 222 Legg Calvé Perthes disease in patients under 5 years of age does not always result in a good outcome. Personal experience and meta-analysis of the literature Kristof Fabry, Guy Fabry and Pierre Moens This study attempted to analyze objectively the longstanding impression that children under 5 years of age, who have Legg Calvé Perthes disease, generally do well. Thirty patients, with 36 hips and onset of disease prior to their fifth birthday were reviewed at skeletal maturity. More than 50% of the hips were classified in Catterall group 3 or 4, and Herring group C. The end evaluation by the Stulberg classification showed 44.5% good, 22.2% fair and 33.3% poor results. By the Mose rating the results were respectively 27.8% good, 30.6% fair and 41.6% poor. A meta-analysis of the literature showed a very broad spectrum of results, leading to the conclusion, first, that comparison is difficult and, second, that young age is not a free ticket to a good result. J Pediatr Orthop B 12: c 2003 Lippincott Williams & Wilkins. Journal of Pediatric Orthopaedics B 2003, 12: Keywords: Legg Calvé Perthes disease under 5 years, end results in LCP, meta-analysis of literature in LCP Department of Orthopaedic Surgery, University Hospital Pellenberg, Lubbeek, Pellenberg, Belgium. Correspondence and requests for reprints to G. Fabry, Department of Orthopaedic Surgery, U.Z. Pellenberg, Weligerveld 1, Lubbeek (Pellenberg), Belgium. Tel: ; fax: Introduction The degree of femoral head involvement and age of onset of disease have been identified as the variables with the greatest effect on outcome of Perthes disease. Children with minimal involvement or earlier onset of Perthes disease have been noted to have a better prognosis than children with larger involvement of the femoral head or later onset of disease. However, our impression from following Legg Calvé Perthes in the orthopedic department of the University Hospital in Pellenberg was that many of these children with onset of disease at under 5 years of age healed with very poor roentgenographic result. Hence, we set up this study to check this impression and compare with the literature. Materials and methods The medical records of all patients with Perthes disease presenting to the University Hospital of Pellenberg between 1976 and 1992 were retrieved. We selected those who had their onset of disease prior to their fifth birthday. The onset of disease was defined as the onset of first radiological changes on the anteroposterior and frog-leg roentgenograms of the hips. Fiftythree patients were identified, presenting 61 hips affected with Legg Calvé Perthes disease. Nineteen of these patients were not skeletally mature at time of follow-up, four of them were skeletally mature but were lost for follow-up. The skeletal maturation was determined by the Oxford method on the pelvic roentgenogram [1]. Thirty patients could therefore be retained for final review: 26 boys and four girls presenting 36 hips (24 unilateral and six bilateral cases). Their mean age at the beginning of the disease was 3 years and 8 months (between 17 months and 5 years of age). The mean follow-up period was 12 years and 10 months (between 7 years and 1 month and 22 years and 5 months). The average age at follow-up was 17 years and 5 months (Table 1). The roentgenograms of all patients were classified (1) with respect to epiphyseal involvement using Catterall s method [2], (2) by the lateral pillar classification of Herring [3] and (3) by the appearance and extent of a subchondral fracture (Salter Thompson) [4]. The end results were evaluated roentgenographically using the Stulberg classification [5]. The study by Stulberg showed that after 30 years osteoarthritis developed in 0% in the first three Stulberg groups and in respectively 40 and 86% in groups IV and V. After 40 years osteoarthritis was seen in 0, 16, 58, 75 and 78% respectively. Based on these figures, we can accept Stulberg I and II as a good result, III as fair and IV and V as poor. For better comparison with other studies the hips were also rated according to Mose s concentric circles method [6]: hips were rated as good if there was complete sphericity of the femoral head on both projections. Hips were rated fair if the femoral head deviated up to 2 mm in sphericity. Loss of sphericity of more than 2 mm X c 2003 Lippincott Williams & Wilkins DOI: /01.bpb f7

2 Legg Calvé Perthes disease in patients Fabry et al. 223 Table 1 Characteristics of the study group Number of patients Number of hips Female/male ratio Average age at beginning Average age at final follow-up /26 3 years 8 months 17 years 6 months Table 2 Catterall classification with Stulberg and Mose rating per group Catterall classification Number of hips Stulberg classification Mose I II III IV V G F P 1 3 (8%) (28%) (19%) (44%) % 22.2% 33.3% 27.8% 30.6% 41.6% Table 3 Herring classification with Stulberg and Mose rating per group Herring classification Number of hips Stulberg classification Mose I II III IV V G F P Herring A 12 (33%) Herring B 5 (14%) Herring C 19 (53%) on either roentgenographic projection resulted in a poor result. Eight patients underwent a surgical treatment: three shelf acetabuloplasties (two combined with an epiphysiodesis of the greater trochanter), two valgization extension osteotomies, one varization derotation osteotomy and one epiphysiodesis of the greater trochanter. Fifteen patients received a conservative treatment with an abduction-brace for years, most of the time preceded by 1 or 2 weeks of skin traction. Seven patients did not receive any treatment at all. Because of the disparity of the treatment methods and the small number of patients in some treatment method groups, no further conclusions will be drawn from these variables. Results All of the 36 hips could be classified by the Catterall criteria: 13 hips were grouped into Catterall classes 1 and 2 (mild forms), 23 were in classes 3 and 4 (severe forms). All three hips of the Catterall 1 group ended up in Stulberg I and were rated as good according to Mose. The Catterall 2 group (ten hips) ended in eight Stulberg I, one Stulberg II and one Stulberg IV and respectively seven good, two fair and one poor according to Mose. In the third group of Catterall (seven hips) there was one Stulberg II, two Stulberg III, and four Stulberg IV, and three fair and four poor Mose ratings. In the fourth group of Catterall (sixteen hips) we found three Stulberg II, six Stulberg III and seven Stulberg IV, and six fair and ten poor Mose ratings. As percentages this translates to, according to the Stulberg classification, 44% good, 22% fair and 33% poor results and, according to Mose s rating, 28% good, 31% fair and 42% poor (Table 2). The classification by Herring was distributed as follows: In the Herring A group (12 hips) 11 reached a Stulberg I, and one a Stulberg II, and 10 good and two fair Mose ratings. In the Herring B group (five hips) there were two Stulberg III and three Stulberg IV, and one fair and four poor Mose ratings. In the Herring C group (19 hips) there were four Stulberg II, six Stulberg III and nine Stulberg IV, and eight fair and 11 poor Mose ratings (Table 3). In 16 of the 36 hips we identified a subchondral fracture. The distribution by Salter Thompson in our group of patients was as follows: All four hips in the Salter A group ended up in Stulberg I and a good Mose rating. In the Salter B group there were two Stulberg I, four Stulberg III, six Stulberg IV, and two good, one fair and nine poor Mose ratings (Table 4). The overall results, according to the Stulberg classification, showed 44.5% good, 22.2% fair and 33.3% poor results. The Mose rating is more severe and does not allow any deformity. The overall results are, therefore, worse: 27.8% good, 30.6% fair and 41.6% poor. Univariate analysis showed a positive correlation between the Catterall and Herring classifications, and the Stulberg

3 224 Journal of Pediatric Orthopaedics B 2003, Vol 12 No 3 Table 4 Salter Thompson classification with Stulberg and Mose rating per group Salter Thompson classification Number of hips Stulberg classification Mose I II III IV V G F P Salter A Salter B classification with correlation coefficients of and 0.723, respectively. Also, we found a positive correlation between the Catterall and Herring classification and the outcome according to Mose with correlation coefficients of and 0.606, respectively (Spearman real correlation, P < 0.01). No significant correlation was found between the age of onset and the outcome variables (Stulberg and Mose). Literature review The generally accepted view is that if the patient is 5 or 6 years old or younger at the onset of the disease he or she is likely to have a better result than the child who is older. Several reports support this conclusion; others are more critical. In the original study by Catterall [2] in which the different groups were presented, the author studied 97 hips, of which 35 were of patients under 4 years of age. Forty-three percent presented with a fair or poor result. Sixteen hips were in the Catterall groups 3 and 4, of which 81% show a fair or poor result at follow-up. The author used head shape and function as evaluation methods. In Broder s series [7] fair and poor results were seen in 45% of cases overall, but only 19% in patients under the age of 5 years at the onset of disease. The hips were evaluated according to the Heyman Herndon comprehensive quotient. The analogous figures in Eaton s series [8] were 36 and 0% respectively. The author used a personal rating system based on femoral head shape. Evan s figures showed 31 and 13% respectively. The rating was clinical and based on femoral head shape [9]. While the study by Katz [10] showed 22 and 11% poor results overall and in the under age 4 years group respectively. Fair and poor results together, however, were seen in 58% of hips under the age of 4 years. The evaluation was done according to Mose s concentric rings method. Gossling stated that 96% of his patients with poor results were 6 or more years old. This evaluation was also according to Mose [11]. Heyman and Herndon [12] stated that the only factor of real prognostic significance was age at onset of disease. For poor results Moller [13] gave an average age at onset of 12 years while for good results the average age was 6 years or younger. Evaluation was done according to femoral head shape and function. Salter and Thompson [4,14] stated that with patients who have the onset of disease at 4 years or younger treatment is not required because the results are good, even in the presence of significant head deformity at the end of the disease. Sundt [15] stated that the younger the child the better the prognosis. Skaggs and Tolo [16] stated that most cases older than 8 years of age at the beginning of the disease do badly. The threshold being between 6 and 8 years of age. A study by Ratliff [17,18] showed good results in children younger than 5 years of age. The evaluation was clinical and based on head shape. The study comprised, however, only 10 patients. O Hara et al. [19] showed good results in children younger than 5 years and bad results in children older than 6 years of age. The evaluation was done by the Mose method after a follow-up of years. Danielsson and Hernborg [20] stated in a follow-up study after 33 years, based on the grade of osteoarthritis, that functional problems tend to be greater when the child is older at the beginning of the disease. The dividing age was 8 years. After a follow-up study of 47.7 years, MacAndrew and Weinstein [21], found better results in children younger than 8 years of age at the beginning of the disease, stating that the dividing age between good and bad results is 8 years. For evaluation they used the Iowa hip rating system. Grasemann et al. [22] showed that after a follow-up of 7 years 16 out of 20 hips in children younger than 6 years of age presented with a Stulberg I or II classification. Weinstein [23] stated that not so much the age at onset of the disease is important, but more so the age at onset of healing. The importance of age, however, comes second to the extent of deformity. In their overall age study with a follow-up of 32 years and 2 months (61 hips between 2 years and 5 months and 15 years old at onset) Ippolito et al. [24] found a statistically significant correlation between age at diagnosis and

4 Legg Calvé Perthes disease in patients Fabry et al. 225 Stulberg classification. They did not, however, find an age borderline between good and bad prognosis, nor an influence that the degree of involvement of the femur head at onset might have at any given age on long-term prognosis. In their group of patients younger than 5 years at onset of the disease (12 hips) two were in Catterall s group 1, one in group 2, one in group 3 and eight in group 4. No one ended up in Stulberg III, IV or V. The investigators found a statistical correlation between the four groups of the Catterall classification and the first two Stulberg classes (P < 0.002) [24]. Ralston [25] found no correlation of results with the age of onset. Urban [26] found 43% poor results in patients under 5 years of age. Snyder [27] studied 31 hips in patients with onset under 5 years of age and found that 10 of 31 had poor results, and that this proportion was greater in untreated children. He also stated that there was no correlation between radiographic signs and function. Some hips tended to improve in sphericity over the period from early healing to final follow-up [27]. Schoenecker et al. [28] made a roentgenographic review of 109 patients with unilateral Perthes disease under 6 years of age; 24% of his patients in Catterall group three or four had a poor result at final follow-up (grouped according to the modified Mose rating). He concluded that, despite the early onset of the disease, patients with involvement of greater than half the femoral head are at risk for poor radiographic results. The average age at final follow-up in his study, however, was only 12 years and 6 months, clearly not an age of skeletal maturity. In 73 patients with 81 affected hips Ismail and Macnicol [29] compared the prognostic value of the Catterall grouping, the Salter Thompson grading, the arthrographic shape of the femoral head, and the Herring lateral pillar grouping during the fragmentation stage of Perthes disease. The Herring grade and arthrographic sphericity proved to be the best predictors of final outcome. In Herring group B, the age of the child and the sphericity of the femoral head influenced the end result. If the child was less than 7 years old at the onset of symptoms the prognosis was invariably good. None of the hips in Herring group C had a normal appearance at maturity and the outcome was not significantly influenced by the age at onset or the arthrographic appearance [29]. Kelly et al. [30] stated that children older than 6 years of age at the beginning of the disease were prone to have a fair result, but those older than 8 years a poor result. They also found poor results in children under the age of 6 years when they were not treated. One conclusion of their study was to treat all children regardless of age. The evaluation was done using the Mose rating. In a previous study from this department Dekelver and Fabry [31] found, according to Mose, in children under the age of 5 years, 50% good results, 28.5% fair and 21.5% poor. A majority of the hips were in Catterall groups 3 and 4. The follow-up was, however, only 6 years and 8 months. From the same department, Mukherjee and Fabry [32] studied 116 hips, of which 55 were younger than 5 years of age at the time of presentation. The evaluation was done according to Mose, the epiphyseal quotient and the centre edge angle. Of the hips under 5 years of age, 27.27% showed a moderate or poor result, compared with 40.99% in children older than 5 years and 34.48% overall. This difference was, however, not statistically significant. Again more than half of the hips under 5 years were in Catterall groups 3 and 4. The follow-up was, however, only 6 years and several hips were not skeletally mature. The methods of evaluation used in these studies, both at diagnosis and at follow-up are not uniform and reproducible, which makes comparison of results very difficult. The number of patients in the younger age group is sometimes small and statistics are usually lacking. Only the studies by MacAndrew and Weinstein [21], Ippolito et al. [24], Snyder [27], Schoenecker et al. [28] and Mukherjee and Fabry [32] contain a statistical evaluation. Discussion How do these results compare with those of the present study? Table 5 shows the results of different studies, which are more or less comparable with the present one, that is to say with an end evaluation by the Stulberg or Mose method. We considered only the severe cases (Catterall 3 and 4), as the less affected cases present in the majority with a good result. A first important observation is the high percentage of severe cases, from 54 to 86%, 68.5% on average. This compares with the average of 63.5% severe cases in the older age group ( > 5 years) in the studies by Ippolito et al. [24], Kelly et al. [30], Dekelver and Fabry [31] and Mukherjee and Fabry [32]. Catterall s study showed 46% of severe cases in the group under the age of 4 years, and 30% in the older age group [2]. A first conclusion that can be drawn is that hips affected by Legg Calvé Perthes in children in the younger age group, are not protected from severe involvement. In

5 226 Journal of Pediatric Orthopaedics B 2003, Vol 12 No 3 Table 5 Outcome of severe cases in seven studies, compared with the present study Study Number of severe cases Outcome according to Stulberg Outcome according to Mose Present study I II III IV V Good Fair Poor (patients < 5 years) Catterall 3: n = 36 Catterall 4: 16 (64%) Ippolito et al. [24] I II III IV V (patients < 5 years) Catterall 3: n = 12 Catterall 4: 8 (75%) Schoenecker et al. [28] Good Poor (patients < 6 years) Catterall 3: n = 109 Catterall 4: 32 (54%) 23 9 Kelly et al. [30] Good Fair Poor (patients < 5 years, all treated) Catterall 3: n = 31 Catterall 4: 4 (77%) Dekelver and Fabry [31] Good Fair Poor (patients < 5 years) Catterall 3: n = 28 Catterall 4: 8 (86%) Katz [10] Good Fair Poor (patients < 4 years) 88 hips under 4 years of age, specific number of n = 88 severe cases not known. Graseman et al. [22] I II III IV V (patients < 6 years ) n =20 Mukherjee and Fabry [32] (patients < 5 years) n =55 20 hips under 6 years of age, specific number of severe cases not known Evaluation according to Mose, epiphyseal index and centre edge angle Excellent Good Fair Poor Caterall 3: Caterall 4: 6 (55%) three studies [24,30,31] the percentage of severe cases is even remarkably high. Table 5 also compares the end results, either by Stulberg classification or by Mose s method. Invariably, the results in the present study are worse than in the other considered studies: 83% of the severe cases end up in Stulberg III or IV, compared with 0% for Ippolito et al. [24] and 2% for Graseman et al. [22]. As regards the Mose classification, the results are 100% either fair or poor in the present study, as compared with 24% for Schoenecker et al. [28], 0% for Kelly et al. [30], 58% for Katz [10], 38% for Dekelver and Fabry [31] and 37% for Mukherjee and Fabry [32]. It should, however, be mentioned that the Mose method has not always been applied in its original form by all authors. In the present study the original Mose method was used, which is more rigorous than some modified methods. Objective comparison with other studies is not possible because of different final evaluation methods, absence of exact numbers and omission to mention the severity of the cases. Different studies [4,11 13,15,16,18] mainly state that good results are usually seen in the younger age group and bad results in the older, putting the threshold age between 6 and 8 years. Accompanying figures are difficult to interpret, in order to make some form of statistical analysis. The studies, in which some form of mathematical calculations could be made can be divided in two groups. One group [7 9,22,24] showed poor or fair and poor results (this division is not always clear) in less than 20% of cases (from 0 to 19%). The study by Katz [15] showed 11% poor results, but 58% fair and poor results. A second group [26 28,31,32] mentions poor or fair and poor results in 24 to 50%. Finally, two studies [25,32] found no statistical correlation between age and results. Concerning the lateral pillar classification 53% of our patients belonged to Herring group C. This matches with

6 Legg Calvé Perthes disease in patients Fabry et al. 227 Table 6 Comparison of the outcome of Herring C patients between the present study and Herring and colleagues study Study Number of severe cases (Herring C) Outcome according to Stulberg I II III IV V Present Herring (patients < 9 years) [3] the percentage of group C found by Herring et al. [12] in their original paper: 46% of group C patients in a patient group of 78 with onset of disease under 9 years of age, while 33% of group C patients in a group of 15 with onset of disease after their ninth birthday. In group C 12 of the 36 patients reached a Stulberg II result, 19 a Stulberg III and only five a Stulberg IV [3]. Our study showed a higher prevalence of Stulberg IV (Table 6). Conclusion It will become clear to the reader that a meta-analysis of the literature in matters of age correlation with end results in Legg Calvé Perthes disease is a difficult task. Furthermore, taking into account that Stulberg s radiographic parameters of sphericity, shortened femoral neck, and steepness of the acetabulum are poorly defined and lack intra-rater reliability [33] and that Mose s rating system is often modified and differently applied, thus generating better results, a comparison of studies, even using these methods, can hardly be objective. We think, however, that we have clearly shown that there is no unanimity on the long-stated correlation of good results with young age. This study and also a few others, which clearly make the distinction between mild and severe cases, show the much greater importance of degree of involvement as a prognostic factor, than age at presentation. In conclusion, we can probably say that a younger age increases the possibility of a better result, over an older age; certainly disease onset after 9 years of age, almost invariably means a poor result. Young age, however, is certainly not a free ticket to a good result, especially in the severe cases, which make up more than half of the affected hips. References 1 Acheson RM. The Oxford method of assessing skeletal maturity. Clin Orthop 1957; 10: Catterall A. The natural history of Perthes disease. J Bone Joint Surg (Br) 1971; 53-B: Herring JA, Neustadt JB, Williams JJ, Early JS, Browne RH. The lateral pillar classification of Legg Calvé Perthes disease. J Pediatr Orthop 1992; 13: Salter RB, Thompson GH. Legg Calvé Perthes disease: the prognostic significance of the subchondral fracture and a two-group classification of the femoral head involvement. J Bone Joint Surg (Am) 1984; 66-A: Stulberg SD, Cooperman DR, Wallensten R. The natural history of Legg Calvé Perthes disease. J Bone Joint Surg (Am) 1981; 63-A: Mose K. Methods of measuring in Legg Calvé Perthes disease with special regard to the prognosis. Clin Orthop 1980; 150: Broder H. 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7 228 Journal of Pediatric Orthopaedics B 2003, Vol 12 No 3 31 Dekelver L, Fabry G. Legg Calvé Perthes follow-up study. Arch Orthop Trauma Surg. 1982; 100: Mukherjee A, Fabry G. Evaluation of the prognostic indices in Legg Calvé Perthes disease: statistical analysis of 116 hips. J Pediatric Orthop 1990; 10: Neyt JG, Weinstein SL, Spatt KF, et al. Stulberg classification system for evaluation of Legg Calvé Perthes disease: Intra-rater and inter-rater reliability. J Bone and Joint Surg 1999; 81: