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Prevalence, Concordance, and Heritability of Scheuermann Kyphosis Based on a Study of Twins
Frank Damborg, MD1; Vilhelm Engell, MD1; Mikkel Andersen, MD1; Kirsten Ohm Kyvik, MD, PhD2; Karsten Thomsen, MD, DMSc1
1 Department of Orthopaedic Surgery, The Spine Section (RC), University Hospital of Odense, Soender Boulevard 29, DK-5000 Odense, Denmark. E-mail address for F. Damborg: Damborg@Dadlnet.dk
2 The Danish Twin Registry, Institute of Public Health, University of Southern Denmark, Soender Boulevard 29, DK-5000 Odense, Denmark
View Disclosures and Other Information
In support of their research for or preparation of this manuscript, one or more of the authors received grants or outside funding from the Sahva Foundation. None of the authors received payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity. No commercial entity paid or directed, or agreed to pay or direct, any benefits to any research fund, foundation, educational institution, or other charitable or nonprofit organization with which the authors are affiliated or associated.
Investigation performed at the Department of Orthopaedic Surgery, The Spine Section (RC), University Hospital of Odense, Odense, Denmark

The Journal of Bone and Joint Surgery, Incorporated
J Bone Joint Surg Am, 2006 Oct 01;88(10):2133-2136. doi: 10.2106/JBJS.E.01302
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Background: The purpose of this study was to establish a cohort of symptomatic twins with Scheuermann kyphosis to provide estimates of prevalence, concordance, odds ratio, and heritability. These estimates indicate to what extent genetic factors contribute to the etiology of this disease.

Methods: The Odense-based Danish Twin Registry is unique in that it contains data on all 73,000 twin pairs born in Denmark over the last 130 years. For the present study, all 46,418 twins born from 1931 through 1982 received a seventeen-page questionnaire, in which one question was "Have you been diagnosed with Scheuermann disease by a doctor"? The prevalence of self-reported Scheuermann disease was calculated, with the total number of answers used as the general population. Pairwise and probandwise concordance, odds ratio, tetrachoric correlations, and heritability were calculated.

Results: We found that the overall prevalence of Scheuermann disease was 2.8%, with a prevalence of 2.1% among women and 3.6% among men (p < 0.0001). The pairwise concordance for monozygotic twins was 0.19 compared with 0.07 for dizygotic twins. The probandwise concordance was 0.31 for monozygotic twins and 0.13 for dizygotic twins. The odds ratios were 32.92 and 6.25 in the monozygotic and dizygotic twins, respectively. These differences were significant (p < 0.01). Heritability was 74%.

Conclusions: In a large cohort of twins that included almost 35,000 individuals, the self-reported overall prevalence of Scheuermann disease was 2.8% and the male-to-female ratio was close to 2:1. Because the pairwise and probandwise concordance and the odds ratio were two to three times higher in monozygotic than in dizygotic twins and the heritability was high, we concluded that there is a major genetic contribution to the etiology of Scheuermann disease.

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    These activities have been planned and implemented in accordance with the Essential Areas and policies of the Accreditation Council for Continuing Medical Education (ACCME) through the joint sponsorship of the American Academy of Orthopaedic Surgeons and The Journal of Bone and Joint Surgery, Inc. The American Academy of Orthopaedic Surgeons is accredited by the ACCME to provide continuing medical education for physicians.
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