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Abnormal Bone Quality in Adolescent Idiopathic Scoliosis: A Case-Control Study on 635 Subjects and 269 Normal Controls With Bone Densitometry and Quantitative Ultrasound

Lam, Tsz Ping FHKAM (Ortho Surg)*; Hung, Vivian Wing Yin MPhil*; Yeung, Hiu Yan PhD*; Tse, Yee Kit MPhil; Chu, Winnie Chiu Wing MD; Ng, Bobby Kin Wah FHKAM (Ortho Surg)*; Lee, Kwong Man PhD*; Qin, Ling PhD*; Cheng, Jack Chun Yiu MD*

doi: 10.1097/BRS.0b013e3181ebab39
Deformity

Study Design. A case-control study comparing bone quality in Adolescent Idiopathic Scoliosis (AIS) with normal controls.

Objective. To evaluate bone quality with quantitative ultrasound (QUS) in AIS and normal controls so as to detect any derangement in bone quality among AIS subjects.

Summary of Background Data. AIS is characterized by complex spinal deformities. Despite its high prevalence and clinical impact in adolescents, etiology of AIS remains unknown but one possible mechanism is related to derangement of bony mechanical stability, as quantified by bone mineral density (BMD) and bone quality. AIS is known for its association with osteopenia, but little is known about the bone quality in AIS. With technological advancement, QUS can provide objective measurement of bone quality. In this study, we sought to compare bone quality in AIS with normal controls using QUS in addition to the conventional BMD measurement.

Methods. Six hundred thirty-five AIS girls and 269 age-matched normal girls were investigated. Broadband ultrasound attenuation (BUA), velocity of sound (VOS), and stiffness index (SI) were measured over the nondominant calcaneus using QUS. The results were correlated with anthropometric measurement, radiologic assessment, and BMD of both hips.

Results. The z-score of BMD at the femoral neck of AIS subjects (−0.47 ± 0.97) was significantly lower than that of normal controls (−0.12 ± 1.01, P < 0.001). Crude comparison showed that BUA, VOS, and SI of AIS group were 3.8% (P < 0.01), 0.5% (P = 0.042), and 6.9% (P < 0.01) lower than controls, respectively. After controlling confounding from maturity, body weight, body height, and BMD with multiple linear regression analysis for both mild (Cobb's angle ≤ 25°) and severe (Cobb's angle > 25°) curves, BUA and SI were found to be statistically significantly lower in AIS as compared with controls (P < 0.05).

Conclusion. In addition to higher prevalence of osteopenia, AIS patients were also found to have deranged bone quality. These might contribute to the etiopathogenesis of spinal deformities in AIS.

We evaluated bone quality in AIS with quantitative ultrasound (QUS) and compared with normal controls. After controlling confounding from maturity, body height, body weight, and BMD, broadband ultrasound attenuation (BUA) and stiffness index (SI) were lower in AIS, indicating deranged bone quality was present and could be an important etiological factor in AIS.

* Department of Orthopaedics and Traumatology

Centre for Epidemiology and Biostatistics, School of Public Health

Department of Diagnostic Radiology and Organ Imaging, The Chinese University of Hong Kong, Shatin, NT, Hong Kong, SAR, China.

Each author certifies that his or her institution has approved the reporting of these cases, that all investigations were conducted in conformity with ethical principles of research, and that informed consent for participation in the study was obtained. Address correspondence and reprint requests to Jack Chun Yiu Cheng, MD, Department of Orthopaedics and Traumatology, 5/F, Clinical Science Building, Prince of Wales Hospital, Shatin, NT, Hong Kong SAR, China; E-mail: jackcheng@cuhk.edu.hk.

Acknowledgment date: February 17, 2010. First revision date: May 5, 2010. Second revision date: May 21, 2010. Acceptance date: May 24, 2010.

The manuscript submitted does not contain information about medical device(s)/drug(s).

No benefits in any form have been or will be received from a commercial party related directly or indirectly to the subject of this manuscript.

Supported by the Research Grants Council of the Hong Kong S.A.R., China (Project no: CUHK4498/06M).

Ethical approval was granted by the IRB of author's institute to conduct the study.

© 2011 Lippincott Williams & Wilkins, Inc.