Assessing the role of hip arthrography in the treatment decision making for children with Legg-Calvé-Perthes disease

Serkan Erkuş1 , Önder Kalenderer1 , Ali Turgut1 , Tayfun Bacaksız2 , Özkan Köse3 , Kıvanç Yüksel4

1Department of Orthopaedics and Traumatology, Tepecik Training and Research Hospital İzmir, Turkey2Department of Orthopaedics and Traumatology, Akçakale State Hospital Şanlıurfa, Turkey3Department of Orthopaedics and Traumatology, Antalya Training and Research Hospital Antalya, Turkey4Department of Data Management and Biostatistics, Ege University, School of Medicine ARGEFAR, İzmir, Turkey

Introduction

The Legg-Calvé-Perthes Disease (LCPD) is a self-lim-iting, aseptic, idiopathic, and non-inflammatory avascular necrosis of the femoral head in which a lot of effort has been expended to figure out its ideal treatment algorithm, but it is still full of uncertainties (1-3). The main goals of the treatment are to prevent the deformation of the femoral head, to maintain its containment during the course of the disease, and to avoid subsequent premature degenerative osteoar-thritis of the hip (4). In addition to the demographic information (in particular age and gender) and physi-cal examination findings (hip range of motion [ROM], gait pattern, etc.), the radiological findings, including the stage of the disease, amount of necrosis, lateral column height of the head, and head-at-risk signs, are commonly used to guide the treatment in LCPD. The head-at-risk signs were first described by Catterall in 1971 to predict the prognosis of LCPD. These signs include Gage’s sign, calcification on the lateral part of epiphysis, lateral subluxation of the femoral head,

and horizontal proximal femoral physis (5). In 1982, Smith et al. added metaphyseal cyst to the original risk signs (6). The anteroposterior (AP) and Löwen-stein lateral (also known as frog-leg lateral view) hip radiographs, magnetic resonance imaging (MRI), and arthrography of the hip joint are frequently utilized imaging modalities used to obtain the aforementioned crucial radiological findings.

Hip arthrography is primarily used for the diagnosis of secondary changes such as labral pathologies, femoroac-etabular impingement, and lesions like hinge abduction (7). The presence of the hinge abduction, first described by Grossbard in 1981 as a poor prognostic factor, can result in rapid progression to hip osteoarthritis (8, 9). Al-though previous studies proposed treatment algorithms based on the standard hip radiographs (10, 11), there is not much information on how the hip arthrography modifies the treatment decision. Some authors claimed that hip arthrography could be an important method for decision making (12-15). However, Devilia et al. stated that it is unimportant to perform an arthrography when

A R T I C L E I N F O

Article history:Submitted 15 August 2019Received in revised form19 January 2020Accepted 3 April 2020

Keywords:ArthrographyHip radiographLegg-Calvé-Perthes diseaseReliabilityTreatment

ORCID iDs of the authors:S.E. 0000-0001-9635-2139;Ö.K. 0000-0002-7464-703X;A.T. 0000-0002-0429-2165;T.B. 0000-0002-8090-4370;Ö.K. 0000-0002-7679-9635;K.Y. 0000-0003-3491-0099.

530 DOI: 10.5152/j.aott.2020.19075

Research Article

Cite this article as: Erkuş S, Kalenderer Ö, Turgut A, Bacaksız T, Köse Ö, Yüksel K. Assessing the role of hip arthrography in the treatment decision making for children with Legg-Calvé-Perthes disease. Acta Orthop Traumatol Turc 2020; 54(5): 530-4

ACTA ORTHOPAEDICA e t TRAUMATOLOGICA TURCICAwww.aott.org.tr

Corresponding Author: Önder Kalenderer okalenderer@gmail.com

Content of this journal is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.

ABSTRACT

Objective: The aim of this study was to determine the role of hip arthrography in the treatment decision making for children with Legg-Calvé-Perthes disease (LCPD).

Methods: A total of 47 consecutive children with LCPD (42 boys, 5 girls; mean age=7.5 years; range=6-10 years) who underwent operative treatment were included in the study. The patient demographics, physical examination findings (pain and hip range of motion [ROM]), standard anteroposterior and Löwenstein lateral hip radiographs, and hip arthrography data were retrospective-ly collected. The arthrographies were performed immediately before the surgery under general anesthesia. The patients were staged according to the Catterall and Herring classifications and examined in terms of head-at-risk signs before the study. Four sets of patient files were established based on the aforementioned data, with each child in a randomized and blinded order. Ten consultant pediatric orthopedic surgeons randomly assessed the patient files on 4 separate occasions (Set 1 vs Set 2 and Set 3 vs Set 4), with a minimum time interval of 4 weeks. In the first and second sets, the demographic and clinical information, includ-ing the age, gender, hip ROM, and hip radiographs, were presented. In the third and fourth sets, hip arthrography was presented in addition to the data from Set 1 and Set 2. The observers were instructed to choose the best treatment options. The percent agreement (PA) and Gwet’s AC1 statistics were used to establish a relative level of agreement among the observers.

Results: The mean intra-observer reliabilities ranged from fair to moderate after adding the hip arthrography data (Gwet’s AC1 = 0.36 for Set 1 vs Set 2 and 0.42 for Set 3 vs Set 4). The mean PA was 56.6% (range = 29.8% to 78.7%) with a Gwet’s AC1 value of 0.51 (range: 0.21 to 0.77) between Set 1 and Set 3 (moderate intra-observer reliability). The decision for the treatment strategy was changed in 43.4% of the patients. For inter-observer reliability, Gwet’s AC1 was computed as 0.48 (moderate reliability). The correlation between the intra-observer reliability and stage progression was not significant (p>0.05) for any of the subgroups. Thus, there is a negative correlation with the disease progression.

Conclusion: Hip arthrography seems to have a significant role in the treatment decision making for children with LCPD, espe-cially in the advanced stages of the disease.

Level of Evidence: Level IV, Therapeutic study

the clinical findings and radiographs have provided sufficient informa-tion; however, in patients with advanced stage, when an osteotomy is planned, arthrography could be important to achieve a more congruent joint (16). Gallagher et al. reported that arthrography is not superior to the radiographs and added that it could be a superior method only for the individual patients for the diagnosis of the epiphyseal protrusion and for prognoses concerning arthritis (17). Thus, the research question of this study was whether hip arthrography changes the treatment mo-dality when combined with the standard hip radiographs in LCPD. We hypothesized that the hip arthrography will change the initial decision based on the standard hip radiographs.

The purpose of this study was to evaluate the effect of additional hip arthrography imaging on decision making by using inter- and in-tra-observer agreements.

Materials and Methods

Forty-seven patients (42 boys, 5 girls; mean age: 7.5 [range: 6 to 10] years) with LCPD, who had completed clinical and radiographic fol-low-ups and were surgically treated in our institution, were included in this study. The study was conducted with the approval of the In-stitutional Ethics Committee (Number: 2017-2/13.07) and in accor-dance with the ethical standards laid down in the 1964 Declaration of Helsinki and its later amendments.

The patients’ demographic characteristics (age, gender), physical examination findings (pain and hip ROM), standard hip joint AP, Löwenstein lateral hip radiographs, and hip arthrography data were retrospectively obtained from the hospital’s medical records and pic-ture archiving and communication system, PACS.

All imaging findings were jointly evaluated by three experienced pediatric orthopedic surgeons, and the patients were staged accord-ing to the Catterall and Herring classifications before the study. The surgeons also determined whether the patients had the head-at-risk signs. These surgeons did not participate in the study, and this infor-mation was not shared with the observers.

The hip radiographs and arthrography data of all patients were taken within a mean time interval of 2.3 (range: 1 to 4) days. The arthrogra-phy procedure was performed dynamically immediately before the surgery while the patient was under general anesthesia. The role of hip arthrography was assessed by both the patients’ clinical data and radiological findings. The imaging data were presented in at least two hip positions, particularly in the neutral AP and frog-leg positions.

Four sets of files were prepared in which the order of cases was ran-domized and blinded and were presented as slides. In the first and second sets, the clinical information, including age, sex, hip ROM, and standard AP and Löwenstein hip radiographs, were presented. In the third and fourth sets, the hip arthrography was presented in addition to the data from Set 1 and Set 2 (Table 1). The examples of the user interface typical of each case are shown in Figure 1.

Ten attending consultant pediatric orthopedic surgeons from differ-ent institutions, who had a surgical experience of at least five years in pediatric hip disorders, took part in the study. The assessments of the sets were performed in random order by each observer on 4 sep-arate occasions (assessment of Set 1 vs Set 2 and Set 3 vs Set 4), after a minimum time interval of 4 weeks. The observers were instructed to choose the best treatment modality among the options presented in Table 2.

First, in both the repeated presentations (Set 1 vs Set 2 and Set 3 vs Set 4), the intra-observer reliability was examined to investigate the stability of the choice of treatment in similar patients. Then, the number of times a different treatment modality was chosen for each set was calculated. The inter-observer reliability was subsequently

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• Treatment of Legg-Calvé-Perthes disease is still controversial.

• Patients are generally treated according to the standard hip radiographic findings.

• Hip arthrography is an imaging method help in making the decision to treat complex cases and advanced stages of the disease.

H I G H L I G H T S

Table 1. Contents of the presentations in each set

Demographic information and clinical findings

Standard hip radiographs Hip arthrography

Set 1 Yes Yes No

Set 2 Yes Yes No

Set 3 Yes Yes Yes

Set 4 Yes Yes Yes

Figure 1. Presentation of the clinical findings and radiographs of Case no: 1 from Set 1 and Case no: 16 from Set 3

computed by determining whether the response changed based on the radiography. To figure out the intra-observer reliability, Set 1 was compared with Set 3 for each observer separately in accordance to their choice from the 7 treatment options (Figure 2). All calculations were re-performed regarding the classification of the disease (i.e. Cat-terall, Herring or the presence of head-at-risk signs).

Statistical analysisIn recent literature, some statistical methods have been widely used to demonstrate the extent of agreement between two or more observ-ers on nominally scaled data. Herein, the most important challenge faced is the paradoxes of kappa (18). As it is less affected by the prev-alence and marginal probability and is a more stable agreement co-efficient than kappa, Gwet’s AC1 statistic was chosen for this study (18-20). The percent agreement (PA) and Gwet’s AC1 statistics were used to establish a relative level of agreement among the observers for the assessments. The interpretation of the data was performed

according to the Landis and Koch kappa benchmarks (<0: poor agree-ment; 0-0.20: slight agreement; 0.21-0.40: fair agreement; 0.41-0.60: moderate agreement; 0.61-0.80: substantial agreement; and 0.81-1.00: almost perfect agreement) (21).

The mean intra-observer reliability for each of the 10 observers showed normal distribution for each classification system and pres-ence of head-at-risk signs (Shapiro-Wilk test; p>0.05). The correlation between the intra-observer reliability and stage progression was ex-amined using the Pearson’s Correlation Coefficient.

Statistical analyses were performed using the R software package v.3.4.2 (The R Foundation, Vienna, Austria). The statistical signifi-cance level was set at p<0.05.

Results

The involvement was on the right side in 27 patients and on the left side in 20 patients. Of the patients, 6 (12.8%) were Catterall Stage II, 27 (57.4%) were Catterall Stage III, and 14 (29.8%) were Catterall Stage IV. According to the Herring’s classification, 15 (31.9%) pa-tients were in Group B and 32 (68.1%) were in Group C. Twenty-three patients (48.9%) had the signs of head-at-risk.

In evaluating the repeated presentations, based on the sets that in-cluded hip joint radiographies, Gwet’s AC1 was found as 0.36 (fair) for the mean intra-observer reliability of the treatment choices. Con-versely, according to the repeated presentations created by the ad-dition of hip arthrography, the mean intra-observer reliability was calculated as 0.42 (moderate) (Figure 2).

The mean PA was found as 56.6% (range: 29.8% to 78.7%) with a Gwet’s AC1 value of 0.51 (range: 0.21 to 0.77) (moderate intra-observ-er reliability) (Table 3). It was observed that the treatment strategy was changed in 43.4% of the patients. For inter-observer reliability, Gwet’s AC1 was computed as 0.48 (moderate reliability). When the disease staging systems were taken into consideration, the agreement

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Figure 2. Flow chart of the study to evaluate the mean intra-observer reliability

Table 2. Treatment options presented to the observers

No. Treatment modalities

1 Conservative treatment (observation, non-weight bearing, bracing, and/or traction)

2 Soft tissue releases (tenotomies)

3 Proximal femoral osteotomies (varus, valgus, derotational osteotomies)

4 Acetabular osteotomies (Salter’s, shelf, and triple osteotomies)

5 Combined femoral and acetabular osteotomies

6 Arthrodiastasis and/or shelf osteotomy

7 Safe dislocation and/or femoral head and neck reconstruction

Table 3. Results of the intra-observer statistical analysis

ObserversMean

1 2 3 4 5 6 7 8 9 10

Gwet’s AC1 0.26 0.74 0.37 0.75 0.55 0.52 0.77 0.65 0.29 0.21 0.51

PA (%) 36.2 76.6 44.7 76.6 59.6 57.5 78.7 68.1 38.3 29.8 56.6

PD (%) 63.8 23.4 55.3 23.4 40.4 42.6 21.3 31.9 61.7 70.2 43.4PA: percent agreement; PD: percent disagreement

of the treatment choices was also reanalyzed to understand if there was a change according to the stage of the disease. The Gwet’s AC1 values for inter-observer reliability, mean intra-observer reliability, and PA are given in Table 4. The correlation between the intra-ob-server reliability and stage progression was not statistically signifi-cant (p>0.05) for each of the subgroups (Table 4).

Discussion

The treatment of LCPD shows wide variations among the ortho-pedic surgeons, with numerous contra versions and no standard treatment protocol or algorithm being available (22). Besides the patient’s age and gender, hip ROM and findings obtained from the radiographs, MRI, and arthrography are used to determine the op-timal treatment modality for each individual case (23). In fact, the hip arthrography is not a routine imaging method used in LCPD. Because it is an invasive technique, it is used only for high-risk pa-tients, the cases in which poor prognosis is expected, and in those where treatment cannot be decided clearly. However, as per our knowledge, it is currently not known whether hip arthrography modifies the treatment choice or not.

The same physician can make different decisions at different times when evaluating the patients with similar demographic, clinical, and radiographic characteristics. In this respect, the present study was designed to evaluate the intra-observer reliability in repeated presen-tations. The mean intra-observer reliability obtained in the last two presentations (including hip arthrography) was higher than that ob-tained from the first two sets (not including arthrography). Although adding the arthrography data changed the clinical decision for 43.4% of the patients, it was seen that the physicians were more consistent in decision making (fair to moderate).

In this study, not only the inter-observer but also the intra-observer reliabilities were found to be moderate, with Gwet’s AC1 values of 0.48 and 0.51, respectively. The observers changed their treatment decisions in approximately 4 of 10 patients (PD: 43.4%). The second noteworthy finding of this study was that the agreement was worse in the advanced stages of the disease. When the analysis was per-formed after grouping the patients according to different clinical classification methods of LCPD, it was more likely that the low extent of involvement of the femoral head was substantial in deciding the type of treatment for a more stable condition (PA was 73.3% in Cat-terall Stage II, 63.3% in Herring Group B). It was interesting that we obtained closer values from the analysis regarding the head-at-risk signs. Among the subgroups, although there were negative correla-tions between the strength of the relationship and the progression of the disease stage, no statistical significance was detected because of the r-value being close to 0.00 and the p-value of >0.05 (Table 4).

In the literature, the role of hip arthrography in LCPD is contro-versial. Whereas some authors have asserted the importance of hip

arthrography in the treatment selection, others have reported that it did not make a significant contribution to decision making (12-17, 24, 25). Axer and Schiller have emphasized that the arthrography examination provides more useful information, especially in pro-trusion cases, than the standard radiographs (25). Gallagher et al. reported that arthrography had no superiority over the radiographs (17). Devalia et al. reported that arthrography was a useful method in supporting their decisions, but because it did not give any ad-ditional information, it did not cause any change in the treatment decision in any LCPD patient (16). However, the results of our study clearly demonstrated that the hip arthrography is influential in de-cision making in LCPD, and it may change the planned treatment modality.

In this study, the gold standard for treatment in LCPD has not been questioned; rather, our study was focused on whether the hip arthrog-raphy changed the treatment modality in the light of the responses given by the observers in both the presentations. The arthrography images caused changes in 43.4% of the treatment strategies among all observers. Moreover, with the addition of arthrography imaging to the evaluation of patients, it was seen that the stability of the sur-geon’s decision increased.

One of the limitations of this study was that most of our patients were in the advanced stage of LCPD, and complex patients were referred from other hospitals because our institution is a referral center for the pediatric hip disorders. Therefore, the decision-making process may be more complicated than usual, although all our observers were pe-diatric orthopedic surgeons. Second, only two static hip arthrography images were presented to the observers. However, hip arthrography is a dynamic examination under fluoroscopy, together with the as-sessment of hip ROM. Third limitation may be the possible variation in the surgical experience of the observers. The observers may have unintentionally chosen the treatment they were more experienced in, although they were instructed to choose the best treatment modal-ity. Finally, owing to the exclusion of the patients in Catterall Stage I and Herring Group A and B/C border, the study has missing data. Thus, the statistical data obtained from the analyses in accordance with the classification systems may have caused questionable results. The lack of comparison of the use of arthrography and MRI in mak-ing the decision is an important limitation of our study.

In conclusion, the hip arthrography examination in addition to stan-dard radiographs caused alteration in the treatment options, especial-ly in the advanced stages of the LCPD. Therefore, we recommend hip arthrography whenever necessary, particularly for complex cases and patients in the advanced stage of the disease. Deciding whether hip arthrography is a useful method in decision making in LCPD is a dilemma. The comparison of the treatment outcomes provided with or without hip arthrography will demonstrate the benefits of this im-aging method more clearly in future.

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Table 4. The results of inter- and intra-observer statistical analyses according to the classification of the disease. The values except inter-observer reliability were obtained by calculating the average intra-observer reliability of each of the 10 observers

Catterall classification Herring classification Head-at-risk sign

Stage II (n=6) Stage III (n=27) Stage IV (n=14) Group B (n=15) Group C (n=32) Absent (n=24) Present (n=23)

Inter-observer Gwet’s AC1 0.58 0.46 0.48 0.46 0.49 0.52 0.44

Mean intra-observer Gwet’s AC1 0.71 0.46 0.53 0.59 0.48 0.52 0.51

Mean PA (%) 73.3 52.2 57.9 63.3 53.4 56.7 56.5

Mean PD (%) 26.7 47.8 42.1 36.7 46.6 43.3 43.5

Pearson’s Correlation Coefficient r:-0.303 p:0.104 r:-0.250 p:0.287 r:-0.004 p:0.985PA: percent agreement; PD: percent disagreement

Ethics Committee Approval: Ethics committee approval was received for this study from the Ethics Committee of the Tepecik Training and Research Hospital (Number: 2 / Date: 07.13.2017).

Informed Consent: N/A.

Author Contributions: Concept - S.E., Ö.Kalenderer; Design - Ö.Kalenderer, S.E., A.T.; Supervision - Ö.Kalenderer, Ö.Köse; Materials - S.E., A.T.; Data Collection and/or Processing - S.E., A.T., K.Y.; Analysis and/or Interpretation - Ö.Kalenderer, S.E., A.T., Ö.Köse, K.Y.; Literature Search - Ö.Kalenderer, S.E., Ö.Köse; Writing Manu-script - Ö.Kalenderer, S.E., Ö.Köse; Critical Review - Ö.Kalenderer, Ö.Köse, S.E., A.T.

Conflict of Interest: The authors have no conflicts of interest to declare.

Financial Disclosure: The authors declared that this study has received no financial

support.

References

1. Kim HK, Herring JA. Legg-Calvé-Perthes Disease. In: Herring JA, ed. Tach-djian's Pediatric Orthopaedics. Ed. 5. Philadelphia, PA: Elsevier; 2014: 580-629.

2. Grasemann H, Nicolai RD, Patsalis T, Hövel M. The treatment of Legg-Calvé-Perthes disease. To contain or not to contain. Arch Orthop Trauma Surg 1997; 116: 50-4. [Crossref]

3. Herring JA. The treatment of Legg-Calvé-Perthes disease. A critical review of the literature. J Bone Joint Surg Am 1994; 76: 448-58. [Crossref]

4. Shah H. Perthes disease: Evaluation and management. Orthop Clin North Am 2014; 45: 87-97.[Crossref]

5. Catterall A. The natural history of Perthes' disease. J Bone Joint Surg Br 1971; 53: 37-53. [Crossref]

6. Smith SR, Ions GK, Gregg PJ. The radiological features of the metaphysis in Perthes disease. J Pediatr Orthop 1982; 2: 401-4. [Crossref]

7. Chaudhry S, Phillips D, Feldman D. Legg-Calvé-Perthes disease: an over-view with recent literature. Bull Hosp Jt Dis 2014; 72: 18-27.

8. Grossbard GD. Hip pain during adolescence after Perthes' disease. J Bone Joint Surg Br 1981; 63B: 572-4. [Crossref]

9. Shore BJ, Miller PE, Zaltz I, Schoenecker PL, Sankar WN. Determining hinge abduction in Legg-Calvé-Perthes disease: Can we reliably make the diagnosis? J Pediatr Orthop 2019; 39: e95-e101. [Crossref]

10. Manig M. Legg-Calvé-Perthes disease (LCPD). Principles of diagnosis and treatment. Orthopade 2013; 42: 891-902. [Crossref]

11. Nelitz M, Lippacher S, Krauspe R, Reichel H. Perthes disease: Current principles of diagnosis and treatment. Dtsch Arztebl Int 2009; 106: 517-23. [Crossref]

12. Kotnis R, Spiteri V, Little C, Theologis T, Wainwright A, Benson MK. Hip arthrography in the assessment of children with developmental dysplasia of the hip and Perthes' disease. J Pediatr Orthop B 2008; 17: 114-9. [Crossref]

13. Ishida A, Kuwajima SS, Laredo Filho J, Milani C. Salter innominate oste-otomy in the treatment of severe Legg-Calvé-Perthes disease: clinical and radiographic results in 32 patients (37 hips) at skeletal maturity. J Pediatr Orthop 2004; 24: 257-64. [Crossref]

14. Nakamura J, Kamegaya M, Saisu T, Kenmoku T, Takahashi K, Harada Y. Hip ar-thrography under general anesthesia to refine the definition of hinge abduction in Legg-Calvé-Perthes disease. J Pediatr Orthop 2008; 28: 614-8. [Crossref]

15. Yoo WJ, Choi IH, Cho TJ, Chung CY, Shin YW, Shin SJ. Shelf acetabuloplas-ty for children with Perthes' disease and reducible subluxation of the hip: prognostic factors related to hip remodeling. J Bone Joint Surg Br 2009; 91: 1383-7. [Crossref]

16. Devalia KL, Wright D, Sathyamurthy P, Prasad P, Bruce C. Role of preoper-ative arthrography in early Perthes disease as a decision-making tool. Is it really necessary? J Pediatr Orthop B 2007;16: 196-200. [Crossref]

17. Gallagher JM, Weiner DS, Cook AJ. When is arthrography indicated in Legg-Calvé-Perthes disease? J Bone Joint Surg Am 1983; 65: 900-5. [Crossref]

18. Gwet KL. Computing inter-rater reliability and its variance in the presence of high agreement. Br J Math Stat Psychol 2008; 61: 29-48. [Crossref]

19. Cicchetti DV, Feinstein AR. High agreement but low kappa: II. Resolving the paradoxes. J Clin Epidemiol 1990; 43: 551-8. [Crossref]

20. Wongpakaran N, Wongpakaran T, Wedding D, Gwet KL. A comparison of Cohen's Kappa and Gwet's AC1 when calculating inter-rater reliability co-efficients: a study conducted with personality disorder samples. BMC Med Res Methodol 2013; 13: 61. doi: 10.1186/1471-2288-13-61. [Crossref]

21. Landis JR, Koch GG. The measurement of observer agreement for categori-cal data. Biometrics 1977; 33: 159-74. [Crossref]

22. Agus H, Kalenderer Ö, Eryanlmaz G, Ozcalabi IT. Intra-observer and inter-ob-server reliability of Catterall, Herring, Salter-Thompson and Stulberg classifica-tion systems in Perthes disease. J Pediatr Orthop B 2004; 13: 166-9. [Crossref]

23. Çıtlak A, Kerimoğlu S, Baki C, Aydın H. Comparison between conservative and surgical treatment in Perthes disease. Arch Orthop Trauma Surg 2012; 132: 87-92.[Crossref]

24. Bennett JT, Stuecker R, Smith E, Winder C, Rice J. Arthrographic findings in Legg-Calvé-Perthes disease. J Pediatr Orthop B 2002; 11: 110-6. [Crossref]

25. Axer A, Schiller MG. The pathogenesis of the early deformity of the capital femoral epiphysis in Legg-Calvé-Perthes syndrome (L.C.P.S.). An arthro-graphic study. Clin Orthop Relat Res 1972; 84: 106-15. [Crossref]

Erkuş et al. / Acta Orthop Traumatol Turc 2020; 54(5): 530-4

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