Background: Surgical interventions are commonly advocated for correcting kyphotic deformities and relieving severe back pain in ankylosing spondylitis (AS) patients. The aim of this study was to evaluate the clinical outcome of osteotomy performed through the gap of a pathological fracture for the treatment of kyphosis in ankylosing spondylitis and to introduce the key points of this novel surgical approach. Methods: From January 1, 2010, to December 31, 2014, 13 consecutive AS patients who were treated with osteotomy through the fracture gap were retrospectively reviewed. Patients underwent the radiographic assessment of sagittal balance parameters. Visual analog scale (VAS) scores were used to assess improvement in back pain. Results: The average follow-up time was 2 years and 1 month. The median operation time was 280 min (range, 220-460 min). The mean blood loss was 1100 mL (range, 820-1300 mL). No major acute complications such as death or complete paralysis occurred. There were no neurologic complications or cerebrospinal fluid leaks in any patient. One patient had postoperative wound infection, which subsided after a switch of antibiotics. The global kyphosis Cobb angle of patients decreased from the preoperative 55.8 degrees +/- 11.0 degrees to 23.2 degrees +/- 6.7 degrees (P < 0.001) after surgery. The C7 plumb line was used to assess global balance; its relationship with the posterosuperior corner of the sacrum decreased from 166 +/- 37 mm to 111 +/- 20 mm (P < 0.001). The thoracolumbar kyphosis Cobb angle decreased from 51.0 degrees +/- 9.9 degrees to 21.6 degrees +/- 11.0 degrees (P < 0.001). VAS scores for back pain decreased from 7.2 +/- 1.2 to 2.1 +/- 1.1 (P < 0.001). Lumbar lordosis increased from 5.7 degrees +/- 23.2 degrees to 10.5 degrees +/- 29.2 degrees (P = 0.001). Conclusions: Osteotomy through the pathological fracture gap is a safe and effective surgical procedure for kyphosis correction and improvement of back pain in AS patients with pathological fractures. A significant kyphosis correction and improvement of back pain can be achieved with this surgical procedure.