Morphometric analysis of the spinal cord in patients undergoing posterior vertebral column subtraction osteotomy for recurrent tethered cord syndrome

Objective: In posterior vertebral column subtraction osteotomy (PVCSO), a section of a thoracic or lumbar vertebra and the adjacent disc are resected to shorten the spinal column, aiming to permanently alleviate tension on the spinal cord in patients with recurrent tethered cord syndrome (TCS). The effects of this procedure on the spinal cord are not well characterized. This study investigated morphometric changes in the cord following PVCSO and assessed associated clinical outcomes in patients with recurrent TCS.

Methods: A retrospective review of patients with recurrent TCS undergoing PVCSO with robotic assistance at the authors' tertiary care institution between 2019 and 2023 was performed. Clinical data were recorded from electronic medical records, and morphometric measurements, including T12-L2 sagittal height, intradural diameter, and the diameters, area, eccentricity, and positioning of the spinal cord, were collected from MRI. Spinal cord dimensions including anteroposterior and lateral diameters, area, eccentricity, positioning, and intradural diameter were compared before and after surgery.

Results: Six patients were included in this study. At 6-week follow-up, all patients had improvement on lower-extremity motor function examinations, 40% had improvement on lower-extremity sensory function examinations, and 83% had improved self-reported pain. Bladder and bowel incontinence were improved in 50% and 60%, respectively. PVCSO reduced the height of the spinal column by a mean of 18.1 ± 5.2 mm. PVCSO increased the mean spinal cord anteroposterior diameter by 0.8 ± 0.5 mm at T12 (p = 0.03) and the mean area by 0.4 ± 0.3 mm2 at T12 (p = 0.03). The mean eccentricity of the spinal cord decreased by 0.15 ± 0.15 at L1 (p = 0.05), indicating that the spinal cord became more circular after surgery. No major complications were reported, although 1 patient experienced atelectasis and pulmonary embolism postoperatively.

Conclusions: This study provides novel insights into the morphometric changes induced by PVCSO and their correlation with clinical outcomes in patients with TCS. The procedure effectively increased spinal cord dimensions, alleviating tension and offering potential benefits in symptom relief. The study underscores the need for objective metrics to guide surgical decision-making and enhance the long-term success of PVCSO in the management of TCS.