A retrospective case-control study on the effectiveness of preoperative diffusion tensor imaging for mitigating nerve injury in extreme lateral interbody fusion surgery

Background context: Extreme lateral interbody fusion (XLIF) has been established as an effective treatment for degenerative disorders of the lumbar spine. Nevertheless, there is a potential risk of lumbar plexus damage associated with XLIF, especially during surgeries at the L4-5 segment. Diffusion tensor imaging (DTI) evaluates the directional diffusion of water molecules in tissue, providing a more intricate depiction of internal tissue microstructure compared to conventional MRI techniques. The capability of DTI sequences to elucidate the 3-dimensional interplay between lumbar nerve pathways and adjacent musculoskeletal structures, potentially reducing the incidence of nerve injury complications related to XLIF, remains to be established.

Purpose: This study evaluates the effectiveness of preoperative DTI in reducing neurological complications after XLIF surgeries at the L4-5 level, focusing on the interaction between lumbar nerves and the psoas major muscle.

Study design: Retrospective case-control study.

Patient sample: The study included 128 patients undergoing XLIF surgery for degenerative disorders at the L4-5 segment: 68 in the traditional group and 62 in the DTI group.

Outcome measures: The study assessed Visual Analogue Scale (VAS) and Oswestry Disability Index (ODI) scores, along with complication rates. It also documented psoas major muscle morphology and its correlation with nerve pathways.

Methods: A retrospective analysis of 128 patients undergoing XLIF surgery for degenerative disorders at the L4-5 segment between February 2020 and August 2022 was conducted. The cohort was divided into a traditional group (68 patients) receiving presurgery MRI scans to identify surgical entry points at the intervertebral space midpoint (Zones II-III junction) and a DTI group (62 patients) who additionally underwent preoperative DTI to customize entry points. The study evaluated VAS and ODI scores, complication rates, psoas major muscle morphology, and its interaction with nerve pathways.

Results: The traditional group uniformly chose the Zone II-III junction for entry. In contrast, the DTI group's entry points varied. Postoperative follow-up revealed significant improvements in VAS and ODI scores in both groups. However, the DTI group experienced fewer immediate postoperative complications such as thigh pain, numbness, and motor disturbances. The study also noted a ventral shift in nerve positioning in patients with elevated psoas muscles.

Conclusions: Preoperative DTI effectively maps the relationship between the psoas major muscle and lumbar nerves. Tailoring surgical entry points based on DTI results significantly reduces the risk of nerve damage in XLIF surgeries. The study underscores the importance of recognizing variability in lumbar nerve pathways due to differing psoas muscle morphologies, highlighting a higher risk of nerve injury in patients with elevated psoas muscles during XLIF procedures.