Significance of Chin-brow Vertical Angle in Correction of Kyphotic Deformity of Ankylosing Spondylitis Patients / 대한척추외과학회지

ABSTRACT

STUDY DESIGN: Retrospective study of 34 ankylosing spondylitis patients with kyphotic deformity who performed correction osteotomy. OBJECTIVES: To assess significance of chin-brow vertical angle for planning and evaluating correction of kyphotic deformity with ankylosis of cervical spine in ankylosing spondylitis patients. SUMMARY OF LITERATURE REVIEW Accurate assessment and measurement of spinal kyphotic deformity is required when planning treatment and assessing its results. The most reliable measure of trunk deformity is the chin-brow vertical angle. MATERIALS AND METHODS: Thirty-four ankylosing spondylitis patients with cervical ankylosis who had underwent pedicle subtraction extension osteotomy for correction of kyphotic deformity were studied. The patients consisted of 32 male and 2 female patients. Mean age was 35.7 years. Most common apex of kyphosis was T12 in 11 cases. The levels of osteotomy were L1 in 3 case, L2 in 4 cases, L3 in 17 cases, and L4 in 10 cases. Radiographic assessment for sagittal balance was performed by measuring thoracic kyphosis, lumbar lordosis, and distance between the vertical line on anterosuperior point of T1 and that of S1. Chin brow-vertical angle was measured on the preoperative and postoperative clinical photo of the patients. Clinical outcomes were assessed by questionnaire measuring changes in physical function, indoor activity, outdoor activity, psychosocial activity, pain, and patient 's satisfaction with the surgery. RESULTS: Chin brow-vertical angle was 35.5 degrees preoperatively and 1.8 degrees postoperatively. Final follow-up radiograph showed an increase in lumbar lordosis from 5.5 to 43.2 degrees(an increase of 37.7 degrees) while thoracic kyphosis remain stable from 50.4 to 50.2 degrees. Sagittal imbalance significantly improved from 101.5 to12.7 mm. Decreased chin-brow vertical angle correlated negatively with correction angle while chin-brow vertical angle did not correlate with overall clinical outcome. However, the patients with chin brow vertical angle greater than 10 degrees or less than -10 degree had significantly low score concerning the item of horizontal gaze. CONCLUSIONS: The ankylosing spondylitis patient with cervical ankylosis, who had chin-brow vertical angle ranging from -10 to 10 degrees, had better horizontal gaze. Based on the results of this study, measurement of chin-brow vertical angle was recom-mended for planning correction of kyphosis and accurate evaluation of treatment outcome.