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Thoracic Curvature Shape and Thoracic Kyphotic Angle in Elder Women without Vertebral Compression Fracture: Biomechanical Implications 2013

Category General Spine Jacob Enterkin, MD
Walter Bartynski,MD
Jayesh Madrecha, BS
Kalliopi Petropoulou, MD
Sara Bartynski, BS
Timothy Amrhein, MD
Purpose The thoracic kyphotic angle (TKA) is known to increase with age. A subset of elder patients (≥65yo) is recognized with an increased TKA without evidence of a vertebral compression fracture (VCF) but with bimodal TKA distribution noted, potentially increasing vertebral body stress. 1 Exaggerated thoracic kyphosis is known to affect spine loads and balance in the elderly. 2 The purpose of this study is to evaluate the thoracic curvature shape and TKA in elder women without compression fracture to better characterize potential biomechanical impact of TKA increase. Materials & Methods Ninety six elder women (≥65yo) were identified without evidence of vertebral compression fracture/wedge deformity on digital lateral chest X-ray. The TKA (Cobb angle) was measured utilizing available PACS software (Stentor) from the T1-T2 level to the T12-L1 level based on endplate visualization. The shape of the thoracic curvature was classified into four distinct recognizable subgroups: 1) gentile-uniform curvature, 2) dominant-upper-thoracic curvature (between T1 and T5), 3) dominant-middle-thoracic curvature (between T4 and T8), and dominant-lower-thoracic curvature (between T8 and T12). Thoracic curve shapes and associated average TKAs were compared. Results Gentile-uniform shape was noted in 63 of 96 (65%, Figure 1A) patients with dominant middle-thoracic curvature seen in 19 of 96 (20%, Figure 1B), dominant upper-thoracic curvature in 12 of 96 (13%) and dominant lower-thoracic curvature in 2 of 96 (2%). A difference in TKA was noted between the observed curve shapes. Average TKA was greatest in patients with dominant middle-thoracic curvature (48°) with lower TKA in patients with gentile-thoracic curvature (44°) and dominant lower-thoracic curvature (41°). Surprisingly, average TKA was only 30° degrees in patients with dominant upper-thoracic curvature. Bimodal distribution was noted in the dataset when all curve shapes were combined, Bimodal distribution was noted in the patients with gentile-uniform curve shape with an average upper mode TKA of 51 degrees, further suggesting a subgroup at risk even with gentile curvature. Conclusion Distinct differences in thoracic curvature shape and average TKA are noted in elder women without evidence of compression fracture. Dominant focal middle-thoracic curvature and those with high TKA gentile curvature might have important implications in the development of thoraco-lumbar junction VCF and balance stability. TKA and thoracic curve shape are likely important to consider when developing biomechanical load models of the  thoracic spine. References
  1. Bartynski WS, Heller MT, Grahovac SZ, et al.: Severe thoracic kyphosis in the older patient in the absence of vertebral fracture: association of extreme curve with age, AJNR Am J Neuroradiol 2005, 26:2077-2085
  2. Briggs AM, van Dieen JH, Wrigley TV, et al.: Thoracic kyphosis affects spinal loads and trunk muscle force, Phys Ther 2007, 87:595-607