Thoracic Curvature Shape and Thoracic Kyphotic Angle In Elder Women without Vertebral Compression Fracture

Exaggerated thoracic kyphosis increases spinal loading leading to functional limitations and increased risk of vertebral compression fracture (VCF). The purpose of this study is to evaluate Thoracic Kyphotic Angle (TKA) and thoracic curvature shape in elder women without VCF or vertebral deformity to better characterize the potential biomechanical implications.

The TKA was assessed via the Cobb angle measurement technique on digital lateral chest radiographs in 96 elder females without evidence of vertebral compression deformity or fracture. Focus on elder women was chosen due to their higher incidence of VCF and earlier bone loss as compared to men. Thoracic curvature shape was further classified in these patients into four distinct recognizable subgroups based on the normal uniform shape of the thoracic curvature to include: 1) uniform-gentle curvature along with 3 supplemental focal curve shapes 2) focal-upper-thoracic, 3) focal-middle-thoracic, and 4) focal-lower-thoracic curvatures superimposed on the patient's normal uniform kyphosis. Focal curves were assessed for upper/lower limits, central axis and disc degenerative features. Thoracic curvature shapes and corresponding TKA's were compared.

Uniform-gentle curve shape was most commonly identified (66%). Less frequent identification of focal-middle (20%), focal-upper (13%) and focal-lower-thoracic (2%) curvature shapes primarily related to anterior greater than posterior disc degeneration superimposed on the patient's natural uniform curve. Bi-modal distribution of TKA was present in the overall population and in the uniform-gentle curvature subgroup. Average TKA was greatest in patients with focal-middle-thoracic curvature (48°) with hyper-kyphosis present in 79% of these patients. Average TKA was also elevated in patients with uniform-gentle curvature (44°) with hyper-kyphosis identified in 2/3 of these patients. Average TKA was low in patients with focal-upper curvature shape (30°).

Distinct differences in thoracic curvature shape and TKA exist in elder women without VCF/deformity. Exaggerated thoracic kyphosis either with uniform curvature or uniform curve augmented by focal (in particular mid-thoracic) features may augment biomechanical loading on the thoracic spine.