[Correction of kyphotic deformity of the cervical spine in ankylosing spondylitis using pedicle subtraction osteotomy of the seventh cervical vertebra].

PURPOSE OF THE STUDY The aim of the study is to present the technique of pedicle subtraction osteotomy (PSO) of the seventh cervical vertebra (C7) for correction of rigid kyphotic deformity of the cervicothoracic junction (C/Th) in patients with severe ankylosing spondylitis (AS).. MATERIAL AND METHODS The PSO technique for correction of rigid deformity of the C/Th spine was used in five patients with the aim to restore their ability of horizontal vision. The follow-up in all patients lasted two years at least. Clinical assessment of treatment results was based on the patients' neurological status and their satisfaction with the correction achieved. Improvement in a vertical 2) line of sight was evaluated using the angle measured between the forehead-chin line and the vertical (FCv angle) in a lateral view photograph of the standing patient. The achieved correction of kyphotic deformity was assessed by comparing the pre-operative Cobb's angle between the second cervical and the fourth thoracic vertebra with the post-operative one. RESULTS The average operative time was 4 hours (range, 3.5 to 5 h). The average blood loss was 1600 ml (range, 800 to 2100 ml). On the average, the FCv angle was reduced by 45.2° and Cobb's angle was corrected) by 54.6°. All patients were satisfied with the degree of correction achieved and reported alleviation of neck pain. none of the patients showed any significant loss of correction or neurological deterioration at two-year follow-up. DISCUSSION The theoretical and technical principles of corrective osteotomy at the C7 level performed for rigid kyphotic deformity of the spine at the C/Th junction are presented in our group of patients. Our results give support to the superiority of instrumented PSO used currently over the previous techniques. In accordance with the relevant literature data, attention is drawn to a relatively higher risk of this procedure in comparison with corrective surgery performed at the other spinal levels. CONCLUSIONS Corrective osteotomy of a rigid kyphotic deformity at the C/Th spine level in AS patients involves a complex reconstructive surgical procedure. The PSO technique reduces the risk of injury to the visceral structures ventral to the spine, and provides optimal conditions for bone healing at the site of vertebral body resection. If the patient heals well, a successful PSO procedure will markedly improve the quality of his/her life.