Surgical correction of a chin-on-abdomen deformity due to ankylosing spinal deformity and obesity: illustrative case.

backgroundKyphotic spinal deformity is a complication of ankylosing spondylitis (AS). In rare cases, particularly in obese patients, the deformity might extend to the cervicothoracic spine, resulting in a severe "chin-on-abdomen" deformity. This condition severely impairs quality of life by affecting gaze, swallowing, and causing chronic pain. While corrective surgery is often performed for lumbar and thoracic kyphosis, cases involving global kyphotic deformities are less common. OBSERVATIONS: The authors present the case of a 66-year-old obese man with AS and a chin-on-abdomen deformity. Prone positioning for surgery was not feasible due to his body habitus. A three-stage corrective surgery was performed: a C7 extension osteotomy in a semisitting position, an L3 pedicle subtraction osteotomy in the lateral decubitus position, and a T11 vertebral column resection in the prone position. The first stage utilized a seldom-used, earlier osteotomy technique with modern instrumentation and neuromonitoring. Obesity again precluded prone positioning in the second stage, necessitating surgery in the lateral position. Postoperatively, the patient exhibited significant postural improvement, maintained over a 5-year follow-up period. LESSONS: This case underscores the importance of adaptable techniques and positioning strategies in correcting complex spinal deformities in obese patients with AS. Integrating traditional methods with modern technology is crucial for achieving successful outcomes. https://thejns.org/doi/10.3171/CASE24664.