Open access Research BMJ Open: first published as 10.1136/bmjopen-2018-023604 on 17 January 2019. Downloaded from Association between spinal curvature disorders and injury: a nationwide population-based retrospective cohort study Yen-Liang Kuo,1,2,3 Chi-Hsiang Chung,4,5 Tsai-Wang Huang,6 Chang-Huei Tsao,7,8 Shan-Yueh Chang,3 Chung-Kan Peng,3 Wei-Erh Cheng,1,2 Wu-Chien Chien,5,8 Chih-Hao Shen3 To cite: Kuo Y-L, Chung C-H, ABSTRACT Strengths and limitations of this study Huang T-W, et al. Association Objectives Injury is an important issue in public health. Spinal between spinal curvature curvature disorders are deformities characterised by excessive ► This is the first nationwide population-based cohort disorders and injury: a curves of the spine. The prevalence of spinal curvature nationwide population- study to assess the associations between spinal disorders is not low, but its relationship with injury has not based retrospective curvature and injury. been studied. The aim of this study is to investigate whether cohort study. BMJ Open ► The main strengths of this study are the large pop- spinal curvature disorders increase the risk of injury. 2019;9:e023604. doi:10.1136/ ulation-based dataset and the retrospective cohort Design Population-based retrospective cohort study. bmjopen-2018-023604 design, which minimise selection bias. Setting Using data from the Taiwan National Health Insurance ► This study cohort is large enough to examine each ► Prepublication history for Research Database from 2000 to 2010. this paper is available online. risks of injury among subgroups. Participants and exposure Patients with spinal curvature To view these files, please visit ► The limitation of this study is the lack of informa- disorders were selected using codes from the International the journal online (http:// dx. doi. tion on the severity of spinal curvature disorders, Classification of Diseases, Ninth Revision, Clinical Modification. org/ 10. 1136/ bmjopen- 2018- detailed patient characteristics and injury severity. 023604). A cohort without spinal curvature was randomly frequency- matched to the spinal curvature disorders cohort at a ratio of W-CC and C-HS contributed 2:1 according to age, sex and index year. equally. Primary outcome measures The risk of injury was gravity. Kyphosis is a convex curvature of analysed using Cox’s proportional hazards regression models the spine that creates a hunchback appear- http://bmjopen.bmj.com/ Received 14 April 2018 adjusting for age, sex, comorbidities, urbanisation level and Revised 26 July 2018 ance. Lordosis refers to the inward concave Accepted 28 November 2018 socioeconomic status. curving of the cervical and lumbar regions Results A total of 20 566 patients with spinal curvature of the spine.1 2 When disorders of the spine disorders and 41 132 controls were enrolled in this study. occur, the natural curvatures of the spine are The risk of injury was 2.209 times higher (95% CI 2.118 to misaligned or exaggerated in certain areas. 2.303) in patients with spinal curvature disorders than in the Possible spinal curvature disorders include control group. The spinal curvature disorders cohort exhibited higher risk of developing injury compared with the control scoliosis, hyperkyphosis and hyperlordosis, which can be graded in severity by the Cobb on September 28, 2021 by guest. Protected copyright. group, regardless of age, sex, comorbidities, urbanisation 3 level and subgroup of spinal curvature disorders. Based on angle. Scoliosis indicates a lateral displace- 4 the subgroup analysis, the spinal curvature disorders cohort ment or curvature of the spine, which is had higher risks of unintentional injury and injury diagnoses defined by a curve in the spine with a Cobb such as fracture, dislocation, open wound, superficial injury/ angle of 10° or greater in adults.5 Hyper- contusion, crushing and injury to nerves and spinal cord kyphosis and hyperlordosis are commonly compared with the control cohort. referred to as kyphosis and lordosis by the Conclusions Patients with spinal curvature disorders have medical community. The evaluation of these © Author(s) (or their a significantly higher risk of developing injury than patients conditions is challenging due to the lack without spinal curvature disorders. Aggressive detection and employer(s)) 2019. Re-use of standardised diagnostic criteria. Gener- permitted under CC BY-NC. No management of spinal curvature disorders may be beneficial commercial re-use. See rights for injury prevention. ally, the Cobb angle of a normal thoracic and permissions. Published by spine ranges between 20° and 50° in young BMJ. people.1 6 For numbered affiliations see INTRODUCTIOn Among community-dwelling individ- end of article. The spine has a gentle curve when viewed uals ≥60 years old, the current incidence of 7–9 Correspondence to from the side and a straight appearance hyperkyphosis is between 20% and 40%. Dr Chih-Hao Shen; when viewed from the back. This structure There are multiple contributing factors to potato652@ yahoo. com. tw absorbs the stress from body movement and spinal curvature disorders, such as vertebral Kuo Y-L, et al. BMJ Open 2019;9:e023604. doi:10.1136/bmjopen-2018-023604 1 Open access BMJ Open: first published as 10.1136/bmjopen-2018-023604 on 17 January 2019. Downloaded from fractures with low bone density,10–12 short vertebral height and injury. We conducted a nationwide population-based as in Scheuermann’s disease,13 degenerative disc disease,14 cohort study to investigate whether spinal curvature disor- postural changes,15–18 muscle weakness,15 19–23 interver- ders increases the risk of injury. tebral ligament degeneration24 and systemic physical activity practice.25–28 Injury is an important issue in public health,29 espe- MATERIALS AND METHODS cially among the elderly.30 Injuries can be divided into Data sources several types according to various factors, such as injury Taiwan’s NHIRD has been built since Taiwan established diagnosis, cause of injury or intentionality of injury a universal healthcare system in 1995. This database according to the National Health Insurance Research includes the medical records of the Taiwanese popula- 31 Database (NHIRD) of Taiwan. The occurrence of injury tion of around 23.81 million, and the coverage reached influences the capacity for activity and can cause compli- 99.6% in 2016. In this study, data were collected from the 32–35 cations, economic burden and even mortality. Thus, NHIRD, and 1 000 000 people were randomly and anon- determining the modifiable risks and strategies for the ymously selected from the entire population. The disease prevention or management of injury deserves more clin- diagnosis codes in the NHIRD dossier are based on the ical attention. International Classification of Diseases, Ninth Revision, The potential relationship between spinal curvature Clinical Modification (ICD-9-CM).37 This study was disorders and injury is not precisely known. Sinaki et al approved after a complete ethical review by the Institu- demonstrated that thoracic hyperkyphosis in the context tional Review Board of National Defense Medical Center of reduced muscle strength plays an important role in Tri-Service General Hospital and the informed consent increasing body sway, gait unsteadiness and risk of falls was not necessary. in osteoporosis.23 De Groot et al suggest that patients with flexed posture (characterised by protrusion of the head Study design and sampled participants and increased thoracic kyphosis) have impaired postural This study was a retrospective cohort design. Patients control during walking and may therefore have higher were selected if they were diagnosed with spinal curvature risk of falling.36 However, no study has described the disorders with three or more outpatient visits and spinal sequential association between spine curvature disorders curvature disorders inpatients from 2 January 2000, to http://bmjopen.bmj.com/ on September 28, 2021 by guest. Protected copyright. Figure 1 The flow chart of study sample selection from Taiwan National Health Insurance Research Database. 2 Kuo Y-L, et al. BMJ Open 2019;9:e023604. doi:10.1136/bmjopen-2018-023604 Open access BMJ Open: first published as 10.1136/bmjopen-2018-023604 on 17 January 2019. Downloaded from programme or the end of 2010. Based on the definition Table 1 Demographic data for patients with and without 31 38 spinal curvature disorders of injury categories from prior studies, the causes of injury were classified as traffic injuries (ICD-9-CM Spinal curvature disorders E800–E849), poisoning (ICD-9-CM E850–E869), falls With Without (ICD-9-CM E880–E888), burns and fires (ICD-9-CM Variables n % n % P value E890–E899), drowning (ICD-9-CM E910), suffocation Total 20 566 33.33 41 132 66.67 (ICD-9-CM E911–E915), crushing/cutting/piercing Gender 0.999 (ICD-9-CM E916–E920) and other unintentional injuries (ICD-9-CM E870–E879, E900–E909, E951–E949). The Male 7279 35.39 14 558 35.39 intentionality categories of injuries include unintentional Female 13 287 64.61 26 574 64.61 (ICD-8-CM E800–R949), intentional (ICD-9-CM E950– Age group (years) 0.999 E979, E990–E999) and unknown. 20–40 3107 15.11 6529 15.87 41–64 6597 32.08 13 386 32.54 Comorbidities Baseline comorbidities include diabetes (ICD-9-CM 250), ≥65 10 862 52.82 21 217 51.58 hypertension (ICD-9-CM 401–405), ischaemic heart No of comorbidities <0.001 disease (ICD-9-CM codes 410–414), stroke (ICD-9-CM 0 12 469 60.63 19 513 47.44 430–438), chronic kidney disease (ICD-9-CM 585), liver 1 6074 29.53 12 021 29.23 cirrhosis (ICD-9-CM 570, 571, 572.1, 572.4, 573.1–573.3), ≥2 2023 9.84 9598 23.33 chronic obstructive lung disease (ICD-9-CM codes 490, Urbanisation level <0.001 491, 495 and 496) and cancer (ICD-9-CM 140–208).