Research Fellow Johns Hopkins School of Medicine Baltimore, Maryland, United States
Introduction: Tethered spinal cord occurs in a total of 0.25 per thousand births. Treatment includes conservative management, detethering, vertebrectomy and fusion etc. Complications of surgery include retethering, spasticity, scoliosis and neurological dysfunction. Surgical modalities of treatment is limited by lack of a robust ex-vivo model for a tethered spinal cord. In this experiment, we aim to replicate a tethered spinal cord in a cadaveric spine.
Methods: A cadaver with no prior spine surgeries was placed prone on a Jackson table. Incision was made from T10 up to the sacrum. Dissection was carried out to expose spinous processes and laminas. Wide laminectomies were performed from T10 to L5 with a partial sacrectomy. A durotomy was performed beginning at T10 up to S2. Borders of the dura was tied using suture to the paraspinal muscles. Using suture material, the conus medullaris was tied off while the other end of the thread was passed over a pulley system attached to the table and tied to a Newton Force meter. Care was taken to ensure the thread was parallel to the surface of the table, was not in contact with surrounding structures and was kept in alignment with the spinal cord. The Newton force meter was fixed to a stereotactic frame. Tension was induced by gradually extending the stereotactic frame and applying tension to the suture material in increments. Quantitative measurement of force was obtained by the Newton force meter. B mode ultrasound was used to measure the spinal cord diameter across the various levels of tension and longitudinal 'stretch' of the cord.
Results: The initial diameter of the spinal cord at 0 g of force was 0.75cm. Tethering was induced by extending the stereotactic frame up to 250 g (2.45 N) of force on the Newton force meter. At >250g of force, tissue integrity was lost causing disruption of the suture tie at the conus. At maximum tension (250g/2.45N), spinal cord diameter was 0.68 cm. Spinal cord was longitudinally displaced for a total of 0.3 cm.
Conclusion : Cadaveric model of tethered spinal cord can prove useful in surgical treatment research.
