181. Spinal shortening osteotomy as a major factor to improve associated syrinx in scoliotic patient with Chiari 1 Malformation (CM-1)

Abstract

BACKGROUND CONTEXT Recently, one-stage posterior spinal correction without previous neurosurgical decompression has being used more popularly to treat scoliosis with CM-1 & syringomyelia (SM). But there is still lack of evidences to demonstrate potential influences to associated syrinx. PURPOSE To explore and identify factors that could influence the prognosis of syrinx in scoliotic patient with CM-1 & cervical SM. STUDY DESIGN/SETTING Retrospective case control study. PATIENT SAMPLE A total of 23 scoliotic patients with CM-1 & cervical SM, more than 5 years follow-up were performed after one-stage posterior spinal correction without previous neurosurgical decompression. OUTCOME MEASURES Continuity correction Chi-square and independent t test were used for comparative analysis between two groups. METHODS For the 23 patients, according to each selected MRI transverse imaging, syrinx tension ratio (STR) was calculated by STR = (trans diameter of syrinx + sagittal diameter of syrinx) / (trans diameter of cord + sagittal diameter of cord). The average STR value from C2, C4, C6 levels was used to reflect the size and tension of syrinx. STR reduction ≥ 20% was defined as a boundary of postop syrinx improvement. Based on the final follow-up (≥5 yrs), the cases were divided into two groups by cervical syrinx improvement or not. Then the preop demographics (gender, age), imaging data (apex, main scoliosis, kyphosis, deformity angular ratio, STR), surgical correction details (with/without spinal shortening osteotomy, coronal and sagittal correction rates) and final follow-up periods were compared between the two groups. RESULTS The average follow-up period of all cases was 6.2 yrs (5-9 yrs) and none experienced deterioration of neurological function. At the final follow-up, syrinx improvement was detected in 47.8% of patients (11/23) and 52.2% without improvement (12/23). Between the two groups, there were differences in age at surgery and with/without spinal shortening osteotomy in surgical process (P 0.05). CONCLUSIONS For the scoliotic patients with CM-1 & SM being treated by one-stage posterior spinal surgical correction, using spinal shortening osteotomy to reduce spinal cord tension is a major factor to influence postop associated syrinx improvement without neurosurgical decompression. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.