Diastematomyelia is a congenital condition where the spinal cord is split by a bony or cartilaginous septum. Neurological signs and symptoms arise when this septum tethers the spinal cord. Surgical detethering often improves symptoms; however, recurrent tethering of the cord is increasingly recognised as a long-term complication. In order to prevent retethering many techniques have been used, including early patient mobilisation and sectioning of the cord. Dorsal expansile duroplasty, using synthetic grafts, is a commonly used technique to prevent recurrent dorsal tethering. We present a 31-year-old woman with recurrent ventral tethering of the cord where we used expanded polytetrafluoroethylene (Gore Preclude MVP Dura Substitute; WL Gore and Associates, Flagstaff, AZ, USA) to cover the ventral dural surface, separating the cord from its dural site of tethering. This technique may be useful to prevent ventral retethering in diastematomyelia.