Provisional ipsilateral expandable rod for disc space distraction in minimally invasive transforaminal lumbar interbody fusion: operative technique.

BACKGROUND Lumbar disc degeneration may be so advanced and asymmetrical that transforaminal access to the interbody space is limited. The extent of collapse may compromise the capacity to restore disc height and coronal balance in minimally invasive approaches. Although a variety of distractors are available for open approaches, currently there is no feasible distractor that is functional within a minimally invasive retractor. OBJECTIVE To describe the development of a provisional ipsilateral expandable rod for use in minimally invasive surgery for transforaminal lumbar interbody fusions to optimize access to the disc space, thereby facilitating placement of an interbody spacer. METHODS The authors report the clinical and radiographic data for 30 patients (3 open and 27 minimally invasive surgeries) with advanced degenerative disc disease in whom a provisional ipsilateral expandable rod was used to restore coronal balance and maintain disc height for interbody preparation and placement. Preoperative disc heights were measured, and the height of interbody spacer recorded. Mean restoration of disc heights was calculated. RESULTS The provisional ipsilateral expandable rod was successfully applied in both open exposures and within a minimally invasive retractor. The mean preoperative disc height was 4.9 mm (range, 1-9 mm), the mean height of the spacer inserted was 11.1 mm (range, 8-15 mm), and the mean increase in disc height was 6.2 mm (range, 5-11 mm). CONCLUSION A provisional ipsilateral expandable rod is feasible in either minimally invasive or open approaches. It has the capacity to maintain the disc height achieved by paddle distractors. This facilitates both the disc preparation and optimizes restoration of disc height and interbody spacer placement.