The Relationship Between the Clavicular Tilt Angle and Sagittal Spinal Alignment Associated With Hyperkyphosis Posture.

Introduction Hyperkyphosis is a deformity of the spine's forward curvature in the sagittal alignment, and its indices include the sagittal vertical axis (SVA), thoracic kyphosis (TK), and lumbar lordosis angle (LLA). These indices are difficult to evaluate in patients who cannot maintain a standing position. Therefore, we sought to determine whether the mean clavicular tilt angle, which can be evaluated regardless of the patient's posture, can be used as an indicator of hyperkyphosis. We hypothesized that the mean clavicular tilt angle would correlate with established sagittal spinal alignment parameters and could serve as a reliable surrogate indicator of hyperkyphosis in patients unable to stand. Hyperkyphosis can be evaluated using the indices that require standing or sitting. However, no studies have attempted to evaluate hyperkyphosis regardless of the patient's posture. Methods This retrospective study analyzed 106 patients (aged ≥65 years) who underwent surgery for lumbar spinal canal stenosis at our hospital between March 2023 and July 2024. All patients had both a plane radiography of the frontal plane including the clavicle and a plane radiography of the entire spine in the sagittal plane from the cervical spine to the pelvis taken before surgery. The mean clavicular tilt angle was measured using two methods: the conventional method and a newly devised method. The new method modifies the angle reference point to enhance applicability in cases with extreme postural deformities. The correlation between the clavicular tilt angle and SVA, TK, and LLA was examined for each method. Results A positive correlation (r = 0.343, p < 0.05) was found between the mean clavicular tilt angle and TK using the conventional method. A positive correlation (r = 0.562, p < 0.05) was found between the mean clavicular tilt angle and SVA using the new method, and a negative correlation (r = -0.437, p < 0.05) was found between the mean clavicular tilt angle and LLA using the new method, indicating moderate to strong correlations with spinal alignment parameters. Conclusions This study suggests that the mean clavicular tilt angle may be a useful indicator of hyperkyphosis. In particular, the new measurement method may serve as a practical tool for evaluating hyperkyphosis in frail or immobile populations. However, being a single-center retrospective study, these findings require validation through larger prospective studies.