Use and Efficacy of Transdiscal Screws in L5-S1 Spondylolisthesis Repair

Isthmic spondylolisthesis (IS) involving L5-S1 has an incidence in the general U.S. population of approximately 4% to 8%. While the majority of patients diagnosed with L5-S1 isthmic spondylolisthesis do not go on to have symptoms from the condition, approximately 20% of individuals will, and in most cases, the symptoms will be chronic. Within this percentage of individuals with symptoms, only approximately 5% to 7% will require surgical management.¹

However, when surgery is indicated to treat IS, there is no consensus in the field on which surgical techniques and approaches provide optimal outcomes. Decompressing and fusing L5-S1 can be achieved through multiple approaches, and in most instances, the approach undertaken is driven by the surgeon’s experience and operative preferences. In particular, “High Grade” spondylolisthesis can be difficult to treat surgically, with some techniques associated with a high rate of neuropraxic injury to the adjacent nerves. 

In a recent study published in the Journal of Spine Surgery,² a team from the Department of Orthopaedic Surgery at the University of Pittsburgh outlines their technique for using transdiscal screws to achieve fixation and fusion of L5-S1, and they report clinical outcomes on a series of 13 patients to undergo surgical management for ”high grade” isthmic spondylolisthesis using the approach. The study's lead author was Stephen Chen, MD, orthopaedic surgery resident. Joon Y. Lee, MD, co-director of the Ferguson Laboratory for Spine Research, and the Orland Bethel Professor in Spine Surgery in the Department of Orthopaedic Surgery at the University of Pittsburgh School of Medicine was the study’s senior author.

Transdiscal screws, compared to the traditionally used pedicle screw, may offer mechanical advantages and improve upon fixation and decompression outcomes. However, using this approach is more complex, technically challenging, and must be confined to well-selected patients.

Study Highlights

In their paper, Drs. Chen, Lee, and colleagues review the approach they devised to using transdiscal screws, including preoperative evaluation requirements for assessing patient compatibility with the approach, necessary imaging studies including the need for intraoperative C-arm views, as well as their operative technique, highlighting the optimal angle of approach for screw fixation while avoiding the delicate foramina.

Outcomes highlighted in the study from the series of 13 cases showed good outcomes and an overall level of safety commensurate with other approaches. Of the 13 cases, 11 were primary surgical procedures, while the remaining two were revisions.

Only one case required a second procedure due to a subcutaneous seroma. Implant failures occurred in three cases, while only one case suffered a nonunion resulting from a broken screw.
Patients were followed postoperatively for a mean of 20.4 months. Within the follow-up cohort, none of the cases required a revision procedure.

"Our case series demonstrates that this approach is feasible and safe within a well-selected population and may improve long-term outcomes," says Dr. Chen. "Further research and larger case series will be required to better understand and compare outcomes between approaches for L5-S1 spondylolisthesis."

References

1. Jones TR, Rao RD. Adult Isthmic Spondylolisthesis. J Am Acad Orthop Surg. 2009 Oct; 17(10): 609-617.

2. Chen SR, Gibbs CM, Zheng A, Dalton JF, Gannon EJ, Shaw JD, Ward WT, Lee JY. Use of L5-S1 Transdiscal Screws in the Treatment of Isthmic Spondylolisthesis: A Technical Note. J Spine Surg. 2021; 7(4): 510-515.