Reviewing the reliability of revised Melbourne Cerebral Palsy Hip Classification System across different medical specialties

Abstract

Objectives: The aim of this study was to measure the reliability of the expanded and revised Melbourne Cerebral Palsy Hip Classification System (r-MCPHCS) across different medical specialties.

Patients and methods: Anteroposterior pelvic radiographs of a total of 44 patients (20 males, 24 females; median 16.7 years; range, 12 to 32 years) with cerebral palsy (CP) were analyzed between January 2005 and December 2020. Four medical specialists (an orthopedic surgeon, a pediatric neurologist, a radiologist, and a physical medicine and rehabilitation specialist) were included in the study. The time gap between the first and the second assessment was at least three months. The intra- and inter-observer intraclass correlation coefficient (IntraOb. and InterOb. ICCs) were calculated. An ICC of >0.8 was considered excellent fit.

Results: The median IntraOb. ICC was found to be 0.93 (range, 0.89 to 0.97), the median InterOb. ICC was found to be 0.88 for the first assessment (A) and 0.93 for the second assessment (B). Both results were interpreted as excellent in terms of compatibility.

Conclusion: Our study results suggest that r-MCPHCS is a well-designed, reliable and reproducible scale that is easy to use among different medical specialists.

Introduction

Cerebral palsy (CP) is a heterogeneous spectrum of non-progressive diseases which occur in the developing child's brain, permanently affecting motor function and posture.[1-3] In addition to involvement in the musculoskeletal system, mental problems, communication difficulties and behavioral disorders may be observed in children with CP.[4,5] The progressive deterioration of motor functions in children with CP causes many orthopedic problems.[1,2,4,5] The severity of hip dysplasia correlates with neurological involvement and Gross Motor Function Classification System (GMFCS) level. Hip displacement is seen in around 35% of CP children; however, this rate increases to 90% from GMFCS-I to V.[4-7] The degree of displacement in children with CP covers a wide range. There may be different presentations ranging from a hip at risk for dislocation to a fully dislocated hip.[4,5] Degenerative arthritis, pain, difficulty in standing and walking, and hygiene problems are common in these patients.[1,2,4,5,8-11]

The hip joint often has a normal anatomy at birth in children with CP.[12] The hip begins to subluxate due to excessive spasticity of the adductors, flexors and hamstrings. The natural development and shape of the immature hip joint is disrupted. These forces increase anteversion and neck-shaft angles over time.[2,13]

Different treatment modalities have been proposed in children with CP according to the severity of muscle involvement and the degree of hip displacement. Some studies have suggested the use of sitting orthoses in the early period of hip displacement in CP.[14,15] Several treatment methods are recommended depending on the severity of the displacement such as botulinum toxin injections, muscle relaxation, reconstructive interventions, salvage interventions, and finally, total hip replacement.[11,16-18]

The grading of hip displacement in children with CP was first introduced with the Severin classification in 1941[19] and later with the Melbourne classification in 2009.[20] The drawbacks of the Severin classification based on the measurement of the center-edge angle were revealed by Ward et al.[21] Later, the Melbourne Cerebral Palsy Hip Classification System (MCPHCS) based on the measurement of the migration index was introduced by Robin et al.[20] The Melbourne classification, which initially consisted of six grades, was later revised and re-presented as seven grades.[20,22] The clinical applicability and reproducibility of such classifications are important.

In the present study, we aimed to examine the clinical performance and applicability of the most recent revised Melbourne Cerebral Palsy Hip Classification System (r-MCPHCS) for hip dysplasia in children with CP by measuring the intra- and inter-observer reliability among different clinicians at different time points.

Patients and Methods

This single-center, prospective study was conducted at Aydın Adnan Menderes University, Faculty of Medicine, Department of Orthopedics and Traumatology between January 2005 and December 2020. Initially, patients aged between 12 and 32 years with CP who had sufficient closure of the triradiate cartilage as assessed by the radiographs obtained from the hospital database were screened. Detailed clinical data and CP type of the patients could not be evaluated and presented due to lack of data. Finally, a total of 44 patients (20 males, 24 females; median 16.7 years; range, 12 to 32 years) with CP were included in the study. Physicians from four different medical specialties (an orthopedic surgeon, a pediatric neurologist, a radiologist, and a physical medicine and rehabilitation specialist) were included in the study for the evaluation of the radiographs. Data of the patients were retrospectively analyzed. A written informed consent was obtained from the patients and parents and/or legal guardians of the patients. The study protocol was approved by the Aydın Adnan Menderes University Faculty of Medicine Ethics Committee (date: 22.02.2022, no: 139117). The study was conducted in accordance with the principles of the Declaration of Helsinki.

Before evaluating the radiographs, all medical specialists included in the study were given a 10-min presentation about the classification to standardize the knowledge about the new classification system. In this presentation, the use of the Reimer migration index was explained in detail. The medical specialists in the study and their year of expertise in their field are as follows: orthopedic surgeon (MD I) 13 years, pediatric neurologist (MD II) 21 years, radiologist (MD III) 15 years, physical medicine and rehabilitation specialist (MD IV) 20 years. All medical specialists, excluding the pediatric neurologist, had no prior experience in pediatric orthopedics. The radiographs were enumerated and anonymized. All specialists were asked to perform the first evaluation, and grade each hip from 1 to 7 according to r-MCPHCS. After three months, the same medical specialists were asked to grade the same cases randomly for a second evaluation.

The results of the first evaluation by the medical specialists were compared with the results of the second evaluation. As there was not a homogenous number of cases in each grade in the cohort, grades were organized in groups for a more accurate statistical analysis. The results obtained were grouped into four groups as Grades 1-2, Grades 3-4, Grades 5-6, and Grade 7. The medical specialists who performed the evaluation were coded as MD-I, MD-II, MD-III, and MD-IV.

Statistical analysis

Statistical analysis was performed using the IBM SPSS version 21.0 software (IBM Corp., Armonk, NY, USA). Descriptive data were expressed in mean ± standard deviation (SD), median (min-max) or number and frequency, where applicable. The chi-square test was used to analyze whether there was a significant difference between categorical variables. The Mc-Nemar chi-square test was used to compare categorical variables in dependent groups. The intraand inter-observer intraclass correlation coefficient (IntraOb. and InterOb. ICCs) were calculated. The ICC was interpreted using established conventions for kappa (κ) where <0 is poor agreement, 0 to 0.2 is slight agreement, 0.2 to 0.4 is fair agreement, 0.4 to 0.6 is moderate agreement, 0.6 to 0.8 is substantial agreement and >0.8 is excellent agreement.[23] A p value of <0.05 was considered statistically significant.

Results

Tables I and II show the intra- and inter-observer results. The ICCs were found to be between 0.89 and 0.97, indicating excellent agreement. The ICCs were obtained by evaluating the results between the first evaluation (A) and the second evaluation (B). The agreement between the two evaluations (0.88 and 0.93) was excellent.

Figure 1. The revised and expanded Melbourne Cerebral Palsy Hip Classification System (r-MCPHCS).[23]

In Table III, the reliability of the scoring system was evaluated. A total of 70.8% of those who scored as Grades 1-2 in the first evaluation scored as Grades 1-2 in the second evaluation, 87% of those who scored as Grades 3-4 in the first evaluation scored as Grades 3-4 in the second evaluation, 92.1% of those who scored as Grades 5-6 in the first evaluation scored as Grades 5-6 in the second evaluation, and 100% of those who scored as Grade 7 in the first evaluation scored as Grade 7 in the second evaluation.

In Table IV, the compliance between the preand post-assessments was compared among the specialists. Before and after, the MD-I 84.1%, MD-II 93.2%, MD-III 84.1%, MD-IV 83.7% were found to be in compliance and no statistically significant difference was found in terms of compliance among the specialists (p=0.5).

Discussion

The MCPHCS is a classification based on the Reimer migration index. The measurements made with the migration index clearly reveal the grade of the hip.[20] Its main advantages are that it is easy to measure, widely used in the literature, and has no subjective effect.

This classification was originally developed in response to by the deficiencies of the Severin classification in which the center-edge angle was used.[19] The reliability of the classification system defined by Severin[19] and based on the measurement of the central-edge angle was evaluated by Ward et al.[21] Tuğrul et al.[24] reported that the central margin angle increased with age between the ages of 5 and 14 years. Therefore, measurements based on the central-angle may be misleading. Reimer migration index shows the quantity of femoral head dislocation away from the acetabulum as a percentage.[21,24] However, the major disadvantage is that the measurement is performed in twodimensional (2D) environment for posterolateral dislocations.[25]

In the present study, the pelvis and hip radiographs of the patients with CP were presented to senior medical specialists from various disciplines. In the literature, there are reliability studies on the sixgraded MCPHCS of Murnaghan et al.[25] However, there are no reliability studies on the r-MCPHCS, which is a revised classification consisting of seven grades.[26] In the study conducted by Murnaghan et al.,[25] the evaluations by an orthopedic surgeon and a physical medicine and rehabilitation specialist were used and the interval between evaluations was determined as one month. Unlike the study by Robin et.al.,[25] in the present study, the r-MCPHCS was used by four different specialists. In addition, the time interval between the first and second evaluation was three months instead of one month, to minimize the bias between the evaluations.

As the number of cases in each group was not equal and not homogenous, the patients were divided into four groups as Grade 1-2, 3-4, 5-6, and 7. Our intraOb. and interOb. ICC results were interpreted as excellent, similar to two previous studies. In our study, the IntraOb. ICC was found to be 0.93. This rate was reported as 0.91 in the study of Murnaghan et al.[25] and 0.88 in the study of Shrader et al.[27] Our InterOb. ICC result was 0.88 in the first evaluation and 0.93 in the second evaluation. These ratios were reported as 0.81 and 0.91 by Murnaghan et al.[25] and reported 0.85 and 0.84 by Shrader et al.[27] Taken together, the second evaluation of all medical specialists were more accurate than their first one (0.88 to 0.93) as a result of the learning effect.[25]

It should be noted that detailed subgroup analyses were not available in other studies in the literature. In the present study, the subgroup analyses were evaluated and attempted to point out the issues between grading the groups. Only 70.8% of the patients who were assessed as Grades 1-2 in the first assessment were assessed as Grades 1-2 in the second assessment. This difference was decreasing in higher grades. In the IntraOb. and InterOb. ICC subgroup analyses according to hip stage, the observers had more difficulties in the diagnosis of early-stage hip dysplasia and less difficulties in the diagnosis of severe stage hip dysplasia.

Interventions varied according to the stage of the hip in CP patients. Botulinum toxin injection, muscle releases, proximal femur osteotomies, bone reconstruction surgeries, salvage procedures, and total hip arthroplasty are some of these interventions.[28] By r-MCPHCS -Grade V, deformities are observed in the femoral head and neck and complex bone procedures are added to the soft tissue surgeries to be performed.[29] The management of the displaced hip in lower grade is simpler than displaced hip in higher grade. The present study showed that almost 30% of the Grades 1-2 cases were misgraded. This misgrading in early stages would lead to more aggressive interventions for the cases in future.

In the first classification system, patients who had Reimer migration index between 30-100 percentile were defined as Grade IV and dislocated hips (>100 percentile) were defined as Grade V. In the revised version, patients who had a migration index between 30-60 percentile were defined as Grade IV, patients between the 60-100 percentile were defined as Grade V, and completely dislocated hips (>100 percentile) were defined as Grade VI.[20] Thus, in the revised classification, the 30-100 percentile range was divided into two different categories.[26]

To the best of our knowledge, the present study is the first to review the reliability of the r-MCPHCS across different medical specialties.[30] Being reviewed by four different specialists, keeping the interval between the two evaluations longer than other studies, standardizing the knowledge about the classification for all medical specialties and having cases in each group are the main strengths of the study. On the other hand, the limitations include its retrospective data interpretation, excluding cases whom triradiate cartilage was not closed, performing the evaluation with 2D imaging modality, and not having enough and homogenous cases in all grades.

In conclusion, the revised and expanded MCPHCS classifies hip displacement in more detail than previous classification scale. Our study results suggest that r-MCPHCS is a well-designed, reliable and reproducible scale that is easy to use among different medical specialists. For early-stage lowgrade classified hips, special attention needs to be paid.

Citation: Gok M, Oner R, Ozgezmez FT, Aydin E, Tosun AF, Cullu E. Reviewing the reliability of revised Melbourne Cerebral Palsy Hip Classification System across different medical specialties. Jt Dis Relat Surg 2025;36(1):148-154. doi: 10.52312/jdrs.2025.2023.

Made substantial contributions to conception or design of the work: M.G., R.O., E.C.; Involved in drafting the work, approved the final version to be published; and investigated and resolved the agreement to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriate: M.G., R.O., E.C. All authors participated in collecting the data for the work. All authors participated in revising the manuscript.

The authors declared no conflicts of interest with respect to the authorship and/or publication of this article.

The authors received no financial support for the research and/or authorship of this article.

The data that support the findings of this study are available from the corresponding author upon reasonable request.

References

1. Hägglund G, Lauge-Pedersen H, Wagner P. Characteristics of children with hip displacement in cerebral palsy. BMC Musculoskelet Disord 2007;8:101. doi: 10.1186/1471-2474-8- 101.
2. Hägglund G, Andersson S, Düppe H, Lauge-Pedersen H, Nordmark E, Westbom L. Prevention of dislocation of the hip in children with cerebral palsy. The first ten years of a population-based prevention programme. J Bone Joint Surg [Br] 2005;87:95-101.
3. Maenner MJ, Blumberg SJ, Kogan MD, Christensen D, Yeargin-Allsopp M, Schieve LA. Prevalence of cerebral palsy and intellectual disability among children identified in two U.S. National Surveys, 2011-2013. Ann Epidemiol 2016;26:222-6. doi: 10.1016/j. annepidem.2016.01.001.
4. Bagg MR, Farber J, Miller F. Long-term follow-up of hip subluxation in cerebral palsy patients. J Pediatr Orthop 1993;13:32-6. doi: 10.1097/01241398-199301000-00007.
5. Moreau M, Drummond DS, Rogala E, Ashworth A, Porter T. Natural history of the dislocated hip in spastic cerebral palsy. Dev Med Child Neurol 1979;21:749-53. doi: 10.1111/ j.1469-8749.1979.tb01696.x.
6. Terjesen T. Development of the hip joints in unoperated children with cerebral palsy: A radiographic study of 76 patients. Acta Orthop 2006;77:125-31. doi: 10.1080/17453670610045803.
7. Soo B, Howard JJ, Boyd RN, Reid SM, Lanigan A, Wolfe R, et al. Hip displacement in cerebral palsy. J Bone Joint Surg [Am] 2006;88:121-9. doi: 10.2106/JBJS.E.00071.
8. Scrutton D, Baird G. Surveillance measures of the hips of children with bilateral cerebral palsy. Arch Dis Child 1997;76:381-4. doi: 10.1136/adc.76.4.381.
9. Graham HK, Rosenbaum P, Paneth N, Dan B, Lin JP, Damiano DL, et al. Cerebral palsy. Nat Rev Dis Primers 2016;2:15082. doi: 10.1038/nrdp.2015.82.
10. Ramstad K, Jahnsen RB, Terjesen T. Severe hip displacement reduces health-related quality of life in children with cerebral palsy. Acta Orthop 2017;88:205-10. doi: 10.1080/17453674.2016.1262685.
11. Cobanoglu M, Cullu E, Omurlu I. The effect of hip reconstruction on gross motor function levels in children with cerebral palsy. Acta Orthop Traumatol Turc 2018;52:44- 8. doi: 10.1016/j.aott.2017.11.001.
12. Beals RK. Developmental changes in the femur and acetabulum in spastic paraplegia and diplegia. Dev Med Child Neurol 1969;11:303-13. doi: 10.1111/j.1469-8749.1969. tb01437.x.
13. Hägglund G, Alriksson-Schmidt A, Lauge-Pedersen H, Rodby-Bousquet E, Wagner P, Westbom L. Prevention of dislocation of the hip in children with cerebral palsy: 20-Year results of a population-based prevention programme. Bone Joint J 2014;96-B:1546-52. doi: 10.1302/0301-620X.96B11.34385.
14. Kulkarni VA, Davids JR, Boyles AD, Cung NQ, Bagley A. Reliability and efficiency of three methods of calculating migration percentage on radiographs for hip surveillance in children with cerebral palsy. J Child Orthop 2018;12:145-51. doi: 10.1302/1863-2548.12.170189.
15. Kim BR, Yoon JA, Han HJ, Yoon YI, Lim J, Lee S, et al. Efficacy of a hip brace for hip displacement in children with cerebral palsy: A randomized clinical trial. JAMA Netw Open 2022;5:e2240383. doi: 10.1001/jamanetworkopen.2022.40383.
16. Graham HK, Boyd R, Carlin JB, Dobson F, Lowe K, Nattrass G, et al. Does botulinum toxin a combined with bracing prevent hip displacement in children with cerebral palsy and "hips at risk"? A randomized, controlled trial. J Bone Joint Surg [Am] 2008;90:23-33. doi: 10.2106/JBJS.F.01416.
17. Lee Y, Lee S, Jang J, Lim J, Ryu JS. Effect of botulinum toxin injection on the progression of hip dislocation in patients with spastic cerebral palsy: A pilot study. Toxins (Basel) 2021;13:872. doi: 10.3390/toxins13120872.
18. Rutz E, Vavken P, Camathias C, Haase C, Jünemann S, Brunner R. Long-term results and outcome predictors in one-stage hip reconstruction in children with cerebral palsy. J Bone Joint Surg [Am] 2015;97:500-6. doi: 10.2106/ JBJS.N.00676.
19. Severin, E. Contribution to knowledge of congenital dislocation of hip joint: Late results of closed reduction and arthrographic studies of recent cases. Acta Chirurgica Scandinavica 1941;84:1-142.
20. Robin J, Graham HK, Baker R, Selber P, Simpson P, Symons S, et al. A classification system for hip disease in cerebral palsy. Dev Med Child Neurol 2009;51:183-92. doi: 10.1111/j.1469-8749.2008.03129.x.
21. Ward WT, Vogt M, Grudziak JS, Tümer Y, Cook PC, Fitch RD. Severin classification system for evaluation of the results of operative treatment of congenital dislocation of the hip. A study of intraobserver and interobserver reliability. J Bone Joint Surg [Am] 1997;79:656-63. doi: 10.2106/00004623-199705000-00004.
22. Howard J, Khot A, Graham H. The hip in cerebral palsy. In: Alshryda S, editor. The pediatric and adolescent Hip: Essentials and evidence. New York: Springer International Publishing; 2019. p. 467-530.
23. Landis JR, Koch GG. The measurement of observer agreement for categorical data. Biometrics 1977;33:159-74.
24. Tuğrul Aİ, Yılmaz G, Aydın BK, Akel İ, Durgut F, Şenaran H. Center-edge angle values in healthy children between 5 and 14 years old in Turkey. Acta Orthop Traumatol Turc 2020;54:15-9. doi: 10.5152/j.aott.2020.01.451.
25. Murnaghan ML, Simpson P, Robin JG, Shore BJ, Selber P, Graham HK. The cerebral palsy hip classification is reliable: An inter- and intra-observer reliability study. J Bone Joint Surg [Br] 2010;92:436-41. doi: 10.1302/0301-620X.92B3.23105.
26. Burns F, Stewart R, Reddihough D, Scheinberg A, Ooi K, Graham HK. The cerebral palsy transition clinic: Administrative chore, clinical responsibility, or opportunity for audit and clinical research? J Child Orthop 2014;8:203- 13. doi: 10.1007/s11832-014-0569-0.
27. Shrader MW, Koenig AL, Falk M, Belthur M, Boan C. An independent assessment of reliability of the Melbourne Cerebral Palsy Hip Classification System. J Child Orthop 2017;11:334-8. doi: 10.1302/1863-2548.11.170077.
28. Howard JJ, Willoughby K, Thomason P, Shore BJ, Graham K, Rutz E. Hip surveillance and management of hip displacement in children with cerebral palsy: Clinical and ethical dilemmas. J Clin Med 2023;12:1651. doi: 10.3390/ jcm12041651.
29. Aslan A, Diril SK, Demirci D, Yorgancıgil H. Comparison of single event multilevel surgery and multiple surgical events in the lower extremities of children with spastic cerebral palsy. Eklem Hastalik Cerrahisi 2019;30:217-23. doi: 10.5606/ehc.2019.66516.
30. Atik OŞ. Writing for Joint Diseases and Related Surgery (JDRS): There is something new and interesting in this article! Jt Dis Relat Surg 2023;34:533. doi: 10.52312/ jdrs.2023.57916.