Impact of spinal alignment and back muscle strength on shoulder range of motion in middle-aged and elderly people in a prospective cohort study

The relationship between spine and shoulder motion has not been well evaluated. The purpose of this study was to clarify the relationships among thoracic kyphosis and lumbar lordosis, spinal range of motion (ROM), spinal alignment and shoulder ROM. Evaluation of spinal alignment was prospectively conducted in 317 subjects (114 males and 203 females, the average age: 67 years) who attended a public health checkup. Shoulder ROM with an angle meter and shoulder pain were evaluated. Thoracic kyphosis angle, lumbar lordosis angle, thoracic ROM, lumbar ROM and spinal inclination angle were measured using SpinalMouse(A (R)). The relationships of these factors with grip strength, back muscle strength, physical ability, osteoporosis and body mass index were examined and multivariate logistic regression analysis was performed to identify the risk factors for limited shoulder ROM. Limited shoulder flexion was found in 35 patients (11 %) and limited abduction in 50 patients (16 %). In multivariate logistic regression analyses adjusted for age, shoulder pain and other parameters, increased thoracic kyphosis angle and increased spinal inclination angle were risk factors for limited shoulder flexion (p < 0.05). Increased thoracic kyphosis angle and weak back muscle strength were also determined as risk factors for limited shoulder abduction (p < 0.05). This study provides the first evidence that increased thoracic kyphosis, increased spinal inclination and weak back muscle strength are the risk factors for limited shoulder ROM. These results suggest that maintenance of spinal alignment and back muscle strength may be important for better shoulder ROM.