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XLIF: Single Position Lateral Versus Prone Lateral

Extreme lateral lumbar interbody fusion (XLIF) is a newer technique in spinal surgery that has the advantage of insertion of a larger cage leading to less subsidence and greater lumbar lordosis restoration. The single-position (SP) XLIF focuses on inserting percutaneous pedicle screws (PPS) in the lateral position without the need to “flip” the patient to a prone position to save operative time. Traditionally, the dual position (DP) XLIF involved a time-consuming process of modifying the patient positioning, in turn, “flipping” the patient to assist with the insertion of pedicle screws.[1] This predisposed patients to heavier anesthesia doses and increased operative time and required expertise in modifying the patient position. In the present article, we discuss the benefits and potential drawbacks of SP XLIF.

Why Single Position?

The SP technique has the potential to reduce blood loss, operative time, and length of hospital stay while achieving the singular unified goal of lateral interbody fusion.[1] In a systematic review by Guiroy et al, patients who underwent an SP approach were found to have reduced operative time, estimated blood loss, length of hospital stay, and fluoroscopic radiation dosage compared to patients who underwent a dual position approach.[1,2] Similarly, in a study by Ziino et al, repositioning, re-prep, and re-drape while transitioning to a prone position in DP increased the overall operating room time by 44 minutes as compared to SP.[3] In terms of postoperative complications, the reduced operative and occupancy time have been linked to decreased incidence of ileus, peritoneal injury, and ipsilateral muscle injury in patients with SP procedures.[4] Another advantage of SP is the ability to minimize the incidence of increased intraocular pressure, cortical blindness, and subconjunctival hemorrhage as compared to the DP procedure.[3] In terms of radiological outcomes, Blizzard et al reported that the pedicle screw accuracy rates in their SP group were equivalent to those of the DP group, which made SP a feasible option for lateral interbody fusion.[5] This evidence further strengthens the advent of SP lateral fusion as the preferred surgical treatment approach for various spinal pathologies.[6]

Characteristics of SP XLIF

In addition to the numerous benefits of the SP approach for patients and surgeons, this approach has recently gained popularity due to its efficacy in operation. There are currently two options for SP: XLIF in lateral decubitus position (std-XLIF) and XLIF in prone single-position (pro-XLIF).

Std-XLIF is now the default option for SP due to its clinical data and experience. It involves conventional XLIF and pedicle screw insertion with a lateral position. In particular, the lateral decubitus position stabilizes patients’ spine firmly, providing surgeons with a safe procedure, including the approach to the intervertebral space and cage placement in XLIF. However, there are some difficulties with screw placement in the lateral position. One issue is the difficulty of setting up the radiographic and instrument handling in the lateral position. During the PPS procedure in the lateral position, the fluoroscopic arm may be in the way and care must be taken to keep the operative field clean. Additionally, screw insertion on the “down” side, which is the right side in the right-side-down lateral position, requires particular attention. In patients with a high BMI and when inserting the L5 or S1 PPS, the instrument needs to be angled largely under the patient. Utilizing navigation, patient positioning and robotic arms are key to solving these problems. Navigation provides a more comfortable procedure compared to a procedure with a C-arm, as there is no C-arm to barricade the surgical area. Regarding patients’ position, a slightly more forward-leaning posture than the lateral decubitus position for cage placement can make it easier to handle the instruments during screw insertion. Furthermore, a recent study reported that use of a robotic arm could improve the feasibility of PPS in lateral decubitus position.[7] With such ingenuity and surgical proficiency, std-XLIF can be an effective tool to minimize the invasion.

Performing both XLIF and PPS insertion in the prone position, as in pro-XLIF, may be advantageous to many spine surgeons who are familiar with this position. It allows surgeons to insert PPS as normally as in the original version and to directly access the posterior spinal column and decompression if required. However, cage insertion in a prone position becomes unfamiliar contrary to the std-XLIF. The different points of prone-lateral XLIF were exposures and stabilization of the spine. Maintaining visual access to the surgical site in a sitting position can be challenging. An additional point of concern is the location of the nerve and organs, but previous studies have revealed that the iliopsoas muscle and the femoral nerve are typically more posteriorly located at the L4-5 disc space in the prone position compared to in the lateral decubitus position, which allows for a larger safe zone.[8,9] Regarding spine stabilization, it is possible to see where the spine is more mobile in the pro-XLIF surgical field than in the std-XLIF field, but again, navigation can help.

Pro-XLIF offers several advantages over conventional lateral single position for adjacent segmental disorders (ASD). Due to problems such as rod connection to the previous surgical site, it has been difficult to achieve additional surgery for ASD using XLIF in the lateral position, requiring flipping the position. Pro-XLIF can make it simple, as every surgical procedure, including posterior dissection, can be achieved in one position. Furthermore, this position has been reported to be advantageous for obtaining lumbar lordosis.[9] It is an effective approach in terms of lordosis acquisition and can be an effective means of preventing long-term malalignment, even in cases of adjacent intervertebral disorders in which there is a risk of developing flatback.

Most surgeons, including those in spine and urology specialties, find that surgeries in the lateral decubitus position are more comfortable. Moreover, this position also offers advantages in certain scenarios, such as when a urethral tract injury requires salvage procedures. If accidental urethral tract injury occurs in the prone position, flipping to the lateral decubitus or the supine position may be required. In the cases of vascular injury, flipping is mandatory for the additional procedure by vascular surgeons, but changing position from lateral decubitus would be easier than from prone to supine. Each institution needs to establish a consensus for salvage procedures and flipping in cases of intraoperative complications for both pro-XLIF and std-XLIF.

Clinical Outcomes of std-XLIF vs proXLIF

When considering surgical techniques for patients, it is important to weigh the benefits and drawbacks of each approach.

Regarding pro-XLIF, a cadaveric feasibility study and early experiences revealed its safety and reproducibility,[10-12] and preliminary clinical results showed comparable clinical results to std-XLIF.[13] Furthermore, prone-lateral LLIF was safely performed in the early analysis of the surgery for ASD.[14] Based on these results, the pro-XLIF is safe enough for clinical application. However, the analysis for the surgical complications is lacking because the number of patients analyzed remains limited.

A CT-based assessment study found that the accuracy of PPS in the lateral position was lower than that in the prone position with higher breach rates (14.1% vs 7.2%), but none of them resulted in clinical sequelae.[7] However, another report suggested that the accuracy of PPS in both positions may be comparable.15 It appears that proficiency in the technique, rather than the position itself, will be the key factor in achieving accurate PPS placement. Short-term postoperative outcomes are generally equivalent for both procedures if performed safely, but no large-scale studies have been conducted to date. Further studies are needed to understand the impact on long-term results and complication rates resulting from differences in lumbar lordosis acquisition due to body position.

Summary and Future

In summary, XLIF allows the insertion of a larger interbody cage that has the advantages of greater lordosis restoration and less subsidence. Traditionally, XLIF used to be done in the lateral position followed by an intraoperative flip to the prone position for the insertion of pedicle screws. SP XLIF evolved mainly to avoid intraoperative repositioning and thus decrease the operative time. The recent addition to the realm of XLIF has been prone to lateral surgery. XLIF in the prone position provides the advantages of a familiar position in PPS for spine surgeons, increased lumbar lordosis due to positioning, simultaneous posterior access for decompression/osteotomies, and possibly a more posterior location of the femoral nerve. Although there have been various studies demonstrating the benefits of SP XLIF establishing it as a surgical option, there are fewer data available on the safety and efficacy of pro-XLIF, mainly because it is a relatively new surgery. In our experience, pro-XLIF has demonstrated similar outcomes as std-XLIF with a favorable side-effect profile. Future research with a larger sample size and longer follow-up is required to assess long-term outcomes and compare prone lateral with single-position lateral procedures.

References

1. Guiroy A, Carazzo C, Camino-Willhuber G, et al. Single-position surgery versus lateral-then-prone-position circumferential lumbar interbody fusion: a systematic literature review. World Neurosurg. 2021;151:e379-e386.

2. 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;21:810-820.

3. Ziino C, Konopka JA, Ajiboye RM, Ledesma JB, Koltsov JCB, Cheng I. Single position versus lateral-then-prone positioning for lateral interbody fusion and pedicle screw fixation. J Spine Surg. 2018;4:717-724.

4. Ouchida J, Kanemura T, Satake K, Nakashima H, Ishikawa Y, Imagama S. Simultaneous single-position lateral interbody fusion and percutaneous pedicle screw fixation using O-arm-based navigation reduces the occupancy time of the operating room. Eur Spine J. 2020;29:1277-1286.

5. Blizzard DJ, Thomas JA. MIS single-position lateral and oblique lateral lumbar interbody fusion and bilateral pedicle screw fixation: feasibility and perioperative results. Spine (Phila Pa 1976). 2018;43:440-446.

6. Hiyama A, Katoh H, Sakai D, Sato M, Tanaka M, Watanabe M. Comparison of radiological changes after single-position versus dual-position for lateral interbody fusion and pedicle screw fixation. BMC Musculoskelet Disord. 2019;20:601.

7. Fayed I, Tai A, Triano MJ, et al. Lateral versus prone robot-assisted percutaneous pedicle screw placement: a CT-based comparative assessment of accuracy. J Neurosurg Spine. 2022;37(1):4-12.

8. Alluri R, Clark N, Sheha E, et al. Location of the femoral nerve in the lateral decubitus versus prone position. Global Spine J. 2021:21925682211049170.

9. Amaral R, Daher MT, Pratali R, et al. The effect of patient position on psoas morphology and in lumbar lordosis. World Neurosurg. 2021;153:e131-e140.

10. Godzik J, Ohiorhenuan IE, Xu DS, et al. Single-position prone lateral approach: cadaveric feasibility study and early clinical experience. Neurosurg Focus. 2020;49:E15. doi:10.3171/2020.6.FOCUS20359

11. North RY, Strong MJ, Yee TJ, Kashlan ON, Oppenlander ME, Park P. Navigation and robotic-assisted single-position prone lateral lumbar interbody fusion: technique, feasibility, safety, and case series. World Neurosurg. 2021;152:221-230.e1.

12. Farber SH, Naeem K, Bhargava M, Porter RW. Single-position prone lateral transpsoas approach: early experience and outcomes. J Neurosurg Spine. 2021:1-8.

13. Lamartina C, Berjano P. Prone single-position extreme lateral interbody fusion (Pro-XLIF): preliminary results. Eur Spine J. 2020;29:6-13.

14. Wang TY, Mehta VA, Sankey EW, et al. Single-position prone transpsoas fusion for the treatment of lumbar adjacent segment disease: early experience of twenty-four cases across three tertiary medical centers. Eur Spine J. 2022;31:2255-2261.

15. Hiyama A, Katoh H, Sakai D, Sato M, Tanaka M, Watanabe M. Accuracy of percutaneous pedicle screw placement after single-position versus dual-position insertion for lateral interbody fusion and pedicle screw fixation using fluoroscopy. Asian Spine J. 2022;16:20-27.

Nishtha Singh, MBBS

Tomoyuki Asada, MD

Sumedha Singh, MBBS, MD

Pratyush Shahi, MBBS, MS (Ortho)

Sheeraz Qureshi, MD, MBA

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