Single-position spine surgery: One position, a multitude of advantages

Prone lateral or lateral single-position technique?

In terms of learning the technique, a single-position operation may initially appear more daunting than more traditional approaches, especially when first starting out. However, based on all the points we have discussed and particularly from a safety standpoint it's better for the patient. Both the prone lateral and lateral single-position approaches come with their own learning curves.

In terms of the access, it's pretty similar in the lateral and prone lateral position but it's just that you're working at a deeper length. With the lateral approach, the vascular surgeons have to relearn how to do an ALIF in a lateral position and you as the spine surgeon have to learn how to put screws in the lateral position because you're used to having the patients prone. In particular, it’s more challenging to do an L4-5 lateral interbody fusion, as opposed to a L4-S1 ALIF.

The advantage of the prone lateral approach is that we all work in the prone position, which makes things more familiar. Putting screws in prone is easy so there's not much of a learning curve in terms of instrumentation. The learning curve is the retroperitoneal access which is challenging. This is firstly because the skin doesn't fall away as it does in the lateral position, so your blade length is 20-30 centimeters longer on average than in the lateral position and you're working in a much deeper corridor making visualization a little difficult. Secondly, the working angle is challenging; it's very ergonomically unfriendly to be working with the mallet and doing disk preparation essentially straight on. You have to rotate the bed 30 degrees, but then you're working orthogonally which means you have to be careful that you're not going too far posterior and entering the canal or too far anteriorly and accidentally releasing the anterior longitudinal ligament.

The other thing to be aware of in the prone lateral position is that you extend the hips3. This means the femoral nerve is more posterior. As a result, you think that you have more anterior access but actually you may not, because the femoral nerves are under more tension and can become stretched. We have observed anecdotally that the nerve doesn’t tolerate as much retraction time in the prone position as it does in the lateral position, especially with extended hips.

These are therefore some additional considerations when working in the prone lateral position. However, in technical terms the advantages are similar to the lateral position; there’s no flip, you can directly decompress in a position that you're used to and you can work simultaneously with other surgeons. One clear advantage of single-position lateral over prone is when doing the ALIF at L5-S1 you can get in a bigger cage. If you're doing a prone lateral and you're trying to go to L5-S1, you're basically limited to a TLIF. Therefore, you may not get the lordosis, the indirect decompression or the big cage and better biomechanical properties, but the decision ultimately comes down to the individual preference of the surgeon.

In terms of deciding to learn the prone lateral or lateral single-position technique, they both have their inherent advantages. If you want to harness the positioning lordosis or do osteotomies, it's nice to be able to do a prone lateral surgery, but for other clinical situations, it may be better to do a lateral single-position. Ideally you could learn both techniques, but single-position whatever way you do it is the way to go in terms of economic resources and efficiency.

How to get started with single-position surgery

When it comes to performing single-position surgery, our advice would be that any initial considerations should focus on the specific details of the case rather than any technical aspects. It is key to look firstly at the individual patient and at their anatomy beyond the spine. For example, examine the iliac crest and the vascular anatomy and ask is this approach favorable for this patient and have all the peripheral issues been considered? Once that is covered the technical aspects come into play.
For someone wanting to expand their skillset and learn how to perform the single-position technique, we believe the best way to move forward is by taking suitable cases and talking them through with somebody who has experience. There are a number of companies that can facilitate this. You can also go to a cadaver laboratory with an expert surgeon and work on the technique, have them teach it to you and review the indications with someone who's done hundreds of these surgeries. Finally, it is possible to attend courses that provide training on this topic.

In closing, the adoption of new techniques is always going to result in some controversy. However, we see significant advantages offered by single-position surgery, including clear safety benefits for the patient: Could it be time for you to explore single-position surgery in your center?

References:

1. Buckland AJ, Ashayeri K, Leon C, et al. Single position circumferential fusion improves operative efficiency, reduces complications and length of stay compared with traditional circumferential fusion. Spine J. 2021 May;21(5): 810-820.
2. Mills ES, Treloar J, Idowu O, et al. Single-position lumbar fusion: a systematic review and meta-analysis. Spine J. 2022 Mar;22(3):429-443.
3. Alluri R, Clark N, Sheha E, et al. Location of the Femoral Nerve in the Lateral Decubitus Versus Prone Position. Global Spine J. 2021 Oct; 21925682211049170 (Online ahead of print).