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Bilateral Clubfeet Are Highly Correlated: A Cautionary Tale for Researchers

  • Clinical Research
  • Published:
Clinical Orthopaedics and Related Research®

An Erratum to this article was published on 03 September 2014

Abstract

Background

Congenital talipes equinovarus, or clubfoot, is a common pediatric orthopaedic condition of unknown origin. In many clubfoot clinical trials, interventions are assigned to a patient, but response to treatment is assessed separately in each foot. Trials commonly report x patients with y feet where y is greater than x (eg, 35 patients with 56 feet). However, common statistical tests assume that each data point is independent. Although data from unilateral cases of clubfoot are independent, it is unknown if each foot of patients with bilateral clubfeet are correlated.

Questions/purposes

The purpose of this study was to assess the correlation in the feet of patients with bilateral clubfeet by (1) evaluating the degree of severity between lower limbs of each patient with bilateral clubfeet at baseline; (2) determining if right and left feet of each patient responded to intervention in the same way; (3) determining the proportion of bilateral relapse; and (4) determining the proportion of right and left feet which required the same intervention to correct bilateral relapse.

Methods

We performed a chart review of the records of 33 patients with bilateral clubfeet (66 feet). Baseline severity was assessed using the Pirani score. The number of Ponseti serial casts to correct the deformity, the proportion of patients who underwent bilateral Achilles tenotomy, the proportion of bilateral relapse, and the treatment to correct bilateral relapse were examined.

Results

The degree of severity between right (Pirani score mean, 5.2; SD, 0.8) and left (Pirani score mean, 5.2; SD, 0.5) feet for each patient at baseline was highly correlated (r = 0.76, p < 0.001). Response to intervention between lower limbs was highly correlated for the number of Ponseti casts required for initial correction (right mean, 5.2, SD, 1.1; left mean, 5.2, SD, 1.3) (r = 0.89, p < 0.001) and the proportion of patients who underwent bilateral Achilles tenotomy (right, 17/18; left, 16/18) (r = 0.94, p < 0.001). In the nine patients who experienced relapse, eight experienced bilateral involvement. In all cases of bilateral relapse, the right and left foot of each patient required the same intervention to correct the relapse.

Conclusions

In patients with bilateral clubfeet, baseline severity, response to initial Ponseti treatment, Achilles tenotomy, and relapse outcomes were highly correlated in the right and left feet of each patient. Pooling clinical results of patients who present with bilateral clubfeet is statistically inappropriate, since results in two limbs of the same patient do not represent independent observations. These results support analogous work in other specialties suggesting that patients with bilateral presentations should not be analyzed as independent data points.

Level of Evidence

Level IV, therapeutic study. See the Instructions for Authors for a complete description of levels of evidence.

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References

  1. Barker SL, Macnicol MF. Seasonal distribution of idiopathic congenital talipes equinovarus in Scotland. J Pediatr Orthop B. 2002;11:129–133.

    PubMed  Google Scholar 

  2. Bryant D, Havey TC, Roberts R, Guyatt G. How many patients? How many limbs? Analysis of patients or limbs in the orthopaedic literature: a systematic review. J Bone Joint Surg Am. 2006;88:41–45.

    Article  PubMed  Google Scholar 

  3. Burns J, Ouvrier R, Estilow T, Shy R, Laura M, Eichinger K, Muntoni F, Reilly MM, Pareyson D, Acsadi G, Shy ME, Finkel RS. Symmetry of foot alignment and ankle flexibility in paediatric Charcot-Marie-Tooth disease. Clin Biomech (Bristol, Avon). 2012;27:744–747.

    Article  PubMed  PubMed Central  Google Scholar 

  4. Byron-Scott R, Sharpe P, Hasler C, Cundy P, Hirte C, Chan A, Scott H, Baghurst P, Haan E. A South Australian population-based study of congenital talipes equinovarus. Paediatr Perinat Epidemiol. 2005;19:227–237.

    Article  PubMed  CAS  Google Scholar 

  5. Campeau PM, Foulkes WD, Tischkowitz MD. Hereditary breast cancer: new genetic developments, new therapeutic avenues. Hum Genet. 2008;124:31–42.

    Article  PubMed  CAS  Google Scholar 

  6. Chung CS, Nemechek RW, Larsen IJ, Ching GH. Genetic and epidemiological studies of clubfoot in Hawaii: general and medical considerations. Hum Hered. 1969;19:321–342.

    Article  PubMed  CAS  Google Scholar 

  7. Duffy CM, Salazar JJ, Humphreys L, McDowell BC. Surgical versus Ponseti approach for the management of CTEV: a comparative study. J Pediatr Orthop. 2013;33:326–332.

    Article  PubMed  Google Scholar 

  8. Dyer PJ, Davis N. The role of the Pirani scoring system in the management of club foot by the Ponseti method. J Bone Joint Surg Br. 2006;88:1082–1084.

    Article  PubMed  CAS  Google Scholar 

  9. Ederer F. Shall we count numbers of eyes or numbers of subjects? Arch Ophthalmol. 1973;89:1–2.

    Article  PubMed  CAS  Google Scholar 

  10. Gray K, Pacey V, Gibbons P, Little D, Frost C, Burns J. Interventions for congenital talipes equinovarus (clubfoot). Cochrane Database Syst Rev. 2012;4:008602.

    PubMed  Google Scholar 

  11. Halanski MA, Davison JE, Huang JC, Walker CG, Walsh SJ, Crawford HA. Ponseti method compared with surgical treatment of clubfoot: a prospective comparison. J Bone Joint Surg Am. 2010;92:270–278.

    Article  PubMed  Google Scholar 

  12. Harvey N, Daley D, Mudge A, Sims S, Adams R. Reliability of physiotherapists using the Pirani scoring system for clubfoot. Int J Ther Rehabil. 2012;19:439–445.

    Article  Google Scholar 

  13. Menz HB. Two feet, or one person? Problems associated with statistical analysis of paired data in foot and ankle medicine. Foot. 2004;14:2–5.

    Article  Google Scholar 

  14. Pavone V, Bianca S, Grosso G, Pavone P, Mistretta A, Longo MR, Marino S, Sessa G. Congenital talipes equinovarus: an epidemiological study in Sicily. Acta Orthop. 2012;83:294–298.

    Article  PubMed  PubMed Central  Google Scholar 

  15. Ponseti IV, Morcuende J, Mosca V, Pirani S, Dietz F, Herzenberg J, Weinstein S, Penny N, Steenbeek M. Clubfoot: Ponseti Management. 2nd ed. Seattle, WA: Global-HELP Organization; 2005.

    Google Scholar 

  16. Richards BS, Faulks S, Rathjen KE, Karol LA, Johnston CE, Jones SA. A comparison of two nonoperative methods of isolated clubfoot correction: the Ponseti method and the french functional (physiotherapy) method. J Bone Joint Surg Am. 2008;90:2313–2321.

    Article  PubMed  Google Scholar 

  17. Shaheen S, Jaiballa H, Pirani S. Interobserver reliability in Pirani clubfoot severity scoring between a paediatric orthopaedic surgeon and a physiotherapy assistant. J Pediatr Orthop B. 2012;21:366–368.

    Article  PubMed  Google Scholar 

  18. Sutton AJ, Muir KR, Jones AC. Two knees or one person: data analysis strategies for paired joints or organs. Ann Rheum Dis. 1997;56:401–402.

    Article  PubMed  CAS  PubMed Central  Google Scholar 

  19. Wallander H, Hovelius L, Michaelsson K. Incidence of congenital clubfoot in Sweden. Acta Orthop. 2006;77:847–852.

    Article  PubMed  Google Scholar 

  20. Zeger S, Liang KY. Longitudinal data analysis for discrete and continuous outcomes. Biometrics. 1986;42:121–130.

    Article  PubMed  CAS  Google Scholar 

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Author information

Authors and Affiliations

  1. Physiotherapy Department, The Children’s Hospital at Westmead, Locked Bag 4001, Westmead, Sydney, NSW, 2145, Australia

    Kelly Gray B App Sc

  2. Department of Orthopaedic Surgery, The Children’s Hospital at Westmead, Sydney, NSW, Australia

    Paul Gibbons MBBS & David Little MBBS, PhD

  3. Paediatric Gait Analysis Service of NSW, The Children’s Hospital at Westmead, Sydney, NSW, Australia

    Joshua Burns PhD

  4. The University of Sydney, Sydney, NSW, Australia

    Kelly Gray B App Sc, Paul Gibbons MBBS, David Little MBBS, PhD & Joshua Burns PhD

Authors
  1. Kelly Gray B App Sc
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  2. Paul Gibbons MBBS
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  3. David Little MBBS, PhD
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  4. Joshua Burns PhD
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Corresponding author

Correspondence to Kelly Gray B App Sc.

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Each author certifies that he or she, or a member of his or her immediate family, has no funding or commercial associations (eg, consultancies, stock ownership, equity interest, patent/licensing arrangements, etc) that might pose a conflict of interest in connection with the submitted article.

All ICMJE Conflict of Interest Forms for authors and Clinical Orthopaedics and Related Research editors and board members are on file with the publication and can be viewed on request.

Each author certifies that his or her institution approved the human protocol for this investigation, that all investigations were conducted in conformity with ethical principles of research, and that informed consent for participation in the study was obtained.

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Gray, K., Gibbons, P., Little, D. et al. Bilateral Clubfeet Are Highly Correlated: A Cautionary Tale for Researchers. Clin Orthop Relat Res 472, 3517–3522 (2014). https://doi.org/10.1007/s11999-014-3776-6

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  • DOI: https://doi.org/10.1007/s11999-014-3776-6

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