Stand-alone L5-S1 transdiscal screw fixation and direct foraminal decompression as a minimally invasive fusion method in high grade isthmic spondylolisthesis: technical note and case series.

Transdiscal screw fixation with pedicle screws at the upper level has shown promising results for lumbosacral spondylolisthesis, but there are few reports of clinical use of isolated transdiscal fixation. This case series presents our technique of direct foraminal decompression for vertical foraminal stenosis and stand-alone transdiscal screw fixation with fully threaded 7.3 mm cannulated screws and grafting for grade 2-3 L5-S1 isthmic spondylolisthesis. Demographics, complications, revisions, radiographic measurements, and Visual Analog Scale (VAS) pain and Oswestry Disability Index (ODI) scores were collected. Five patients were included: two females and three males. Mean age was 81.6 (range, 69-93) years. Three patients had a prior decompression. Mean follow-up was 18 (range, 12-24) months. There were no complications or revisions. Mean pre-operative ODI was 46 (range, 26-60). Mean postoperative ODI was 26 (range, 4-51). Mean pre-operative VAS was 8 (range, 6-9), which improved to mean 6-week VAS of 3 (range, 0-8), mean 3-month VAS of 1 (range, 0-4), and mean 6-month VAS of 1 (range, 0-4). Mean 12-month VAS was 0.6 (0-3). Direct foraminal decompression and standalone transdiscal screw fixation with grafting is a safe and useful minimally invasive method of achieving fusion for patients with high-grade isthmic spondylolisthesis, relatively collapsed disc space, and acceptable sagittal balance.