Radiologic features of dropped head syndrome in the overall sagittal alignment of the spine.

PURPOSE: Dropped head syndrome (DHS) is a rare clinical entity which is defined as a chin-on-chest deformity in the standing or sitting position, resulting from sagittal imbalance of the cervical region. The purpose of the present study was to clarify the radiologic features of DHS in the overall sagittal alignment of the spine. We also investigated the changes in sagittal alignment after correction surgery for DHS.

METHODS: Twenty DHS patients [1 male and 19 female, with an average age of 78.9 years (range 59-88)] with a main complaint of horizontal gaze disorder were enrolled in this study. Spino-pelvic lateral radiographs in the free-standing clavicle position were taken of all patients. Parameters such as sagittal vertical axis (SVA), C2-7 angle, clivo-axial angle (CAA), C2-7 SVA, T1 slope, thoracic kyphosis (TK), lumbar lordosis (LL), pelvic incidence (PI), sacral slope (SS), and pelvic tilt (PT) were measured, and the radiologic features of DHS in the overall sagittal alignment of the spino-pelvis were investigated. Eight patients underwent correction surgery, and the parameter changes between pre- and post-operative radiographs were also examined.

RESULTS: DHS appeared to have two distinct types: SVA+ and SVA-. Seven of 20 cases were SVA+, and 13 were SVA-. The radiologic parameters in which we found statistically significant differences between the groups were: 80.2 ± 68 and -44.5 ± 40 (SVA), 42.1 ± 16.8 and 18.4 ± 11.4 (T1 slope), and 21.1 ± 19.2 and 44.2 ± 19.8 (LL) in SVA+ and SVA-, respectively. After surgical intervention, T1 slope and LL appeared to approach normal in the SVA- group, because compensation at downward spine was no longer necessary. In SVA+ group, although the patients gained horizontal gaze after surgery, abnormality of the sagittal alignment in the whole spine remained, because compensation in the thoracic and lumbar spine was still insufficient.

CONCLUSIONS: The present study has indicated that radiologic feature of DHS in the sagittal alignment of the overall spino-pelvis can be categorized into two types: SVA+ and SVA-.