Choosing the ideal surgical approach for improved access to the L5-S1 spinal level 

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Chirag Berry

Chirag A Berry (Cincinnati, USA) is an assistant professor at the University of Cincinnati College of Medicine. Here he provides a summary of his recent publication in The Spine Journal, entitled, Inclusion of L5−S1 in oblique lumbar interbody fusion−techniques and early complications−a single-centre experience.’

Multi-level lumbar spinal fusion usually entails long periods of rehabilitation and is associated with a high risk of complications, thus creating a need for minimally invasive procedures. One such minimally invasive, versatile option is to use the oblique lumbar interbody fusion (OLIF) or anterior-to-psoas (ATP) technique. This allows for a mini-open anterolateral retroperitoneal access to the lumbar spine, with minimal risk of injury to the lumbar plexus (a concern with lateral trans-psoas approaches).

This mini-open muscle-splitting approach performed in the lateral position allows for multiple levels to be addressed with low morbidity (lesser blood loss, lower incidence of ileus, and quicker rehabilitation). However, the inclusion of L5−S1 in the OLIF approach—although optimal—can be challenging due to this area’s complex vascular anatomy. Although multiple variations of the oblique approach to L5-S1 have been described, there is no standardisation or guidance for the choice of technique.

Apprehensive of potentially catastrophic vascular injuries, surgeons may avoid the L5-S1 level entirely or address it posteriorly or with supine anterior methods, leading to increased operative times. L5-S1 is the lowermost mobile disc and has a large role in determining the overall spinal alignment. In multi-level spinal fusion, L5-S1 forms the foundation (base) of the construct. Hence, this level must be addressed with the best technique that would improve alignment and facilitate solid fusion. Using anterior/anterolateral techniques allows placement of larger and taller cages such that alignment and fusion rates are much better than posterior techniques. The oblique anterolateral approach enables multiple levels to be addressed in the same lateral position, saving operative time. To this end, comprehensive guidance on choosing the ideal OLIF technique and risks associated with L5-S1 inclusion is needed.

To assess the safety of L5−S1 inclusion in OLIF, we retrospectively studied 87 patients who underwent lumbar fusion using the OLIF approach. Of these, the L5-S1 level was included in 19 patients and excluded in 68 patients. In the L5-S1 inclusion group, the region was approached using one of three ways: left-sided intrabifurcation, left-sided prepsoas, and right-sided prepsoas. The choice of the technique was partly based on the surgeon’s experience and partly on the relationship of the left common iliac vein with the L5-S1 disc, as seen from preoperative MRI scans. A proposed “facet” line through the medial border of the left L5−S1 facet joint on an MRI axial section helped identify the orientation of the left common iliac vein, and guided the choice of approach.

Moreover, we compared the overall operative time, estimated blood loss, need for blood transfusion, duration of hospital stay, rehabilitation, and complications (both early and delayed) over six months across both groups. The operative time was significantly higher when L5-S1 was included but gradually decreased as the learning curve progressed among surgeons. However, blood loss and hospital stay did not widely vary between the two groups.

In addition, 28.7% of the patients had complications, but these were not significantly different between the L5-S1 inclusion and exclusion groups as well as between the three approaches. We also found that vascular ligation (as part of the access) was required more often in OLIF with L5-S1 inclusion, owing to the procedure’s complexity. One patient in each group sustained minor vascular injuries in the form of segmental bleeds, both at levels other than L5-S1. No major vascular injuries were reported.

Overall, our study demonstrates the safety and feasibility of three different OLIF approaches to the L5-S1 level without any significant increase in complications. However, the choice of the surgical technique must be guided by the surgeon’s experience and the patient’s vascular anatomy. The “facet line” on the preoperative MRI may guide the choice of approach. Assistance from an experienced access surgeon is considered critical for these surgeries. Additional learning curve and comfort level in working alongside large venous structures is required, especially for right-sided approaches. These approaches are relatively new but are proven to safe in experienced hands, and are recently gaining popularity due to their safety and low morbidity.

Disclosures: Chirag Berry is an unpaid consultant for 4WEB Medical Inc.


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