Consider prone transpsoas approach in complex, revision cases for safety, efficiency
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During the past decade, lateral lumbar interbody fusion has increasingly gained popularity as a minimally invasive surgical approach.
Lateral lumbar interbody fusion (LLIF) allows the surgeon to achieve indirect decompression, reliable lumbar fusion, restoration of disc height and correction of deformity.
Moreover, the lateral approach allows for the placement of a transapophyseal interbody device, thus providing enhanced segmental stability and less subsidence. Despite these advantages, the LLIF approach has several limitations, namely limited lordotic correction at the fused motion segment, approach-related neurologic deficits and typical staging of the procedure to reposition the patient when supplemental direct decompression or posterior fixation is necessary.
Recently, Luiz Pimenta, MD, PhD, and colleagues described a lateral-access variant called the prone transpsoas (PTP) technique, a novel approach to lateral lumbar fusion that places the patient in the prone position, obviating the need to reposition the patient during surgery (single position surgery). This approach provides the benefit of shortened operative time, therefore decreasing the patient’s time under anesthesia and increasing the potential for swifter recovery and a shortened hospital stay. Furthermore, previous studies have suggested prone positioning with the hips and legs extended may allow for benefits such as increased segmental lordosis and associated posterior migration of the lumbar plexus. Perhaps the most novel aspect of the PTP technique is the ability to access the posterior and anterior columns simultaneously, which can be a difference-maker in complex deformity or revision surgery.
Position, imaging
The patient is positioned prone over a Jackson-type operating table with the hips and legs extended. Specialized bolsters allow the abdomen to hang freely and the ability to perform coronal rotation of the pelvis to enhance access. After induction of general anesthesia, neuromonitoring is commenced and the patient’s back and flank on the side of the approach are prepped and draped, allowing for access to both the posterior and lateral aspects (Figure 1). Using fluoroscopy, orthogonal radiographs are obtained to identify the operative level and planned incision site and to ensure perfect orthogonal rotation of the vertebrae in relation to the horizontal plane. The incision is made slightly more posterior than is done with lateral-position lateral access procedures and should span from the posterior margin of the foramen to the posterior third of the disc space, approximately 2 cm to 3 cm.
Source: Matthew W. Colman, MD.
Retroperitoneal access is gained by blunt dissection through the abdominal wall and using a finger or smooth blunt retractor to sweep retroperitoneal contents away from the wall. The psoas is digitally palpated and initial dilators are placed down the posterior surface of the surgeon’s finger. Transpsoas passage is gained under triggered electromyography and fluoroscopic guidance to dock the initial dilator directly orthogonal to the vertebral column in line with the disc space. Sequential dilation is then performed followed by the placement of a rigid, monobloc retractor system mounted directly to the patient positioners. The retractor system is then gently opened preferentially anteriorly, away from the lumbar plexus, to facilitate discectomy and device placement. Orthogonal radiographs ensure perfect positioning of the rigid retractor and, although not frequently necessary, disc shims may be used to anchor the retractor further. The table is rotated 20° to 30° to facilitate surgeon comfort/visualization (Figure 2).
Discectomy, endplate preparation
The surgeon proceeds with discectomy, endplate preparation and lateral device implantation using the retractor trajectory as a guide. This technique is differentiated from standard lateral access because the posterior stage may be performed simultaneously, before or after the lateral approach. At minimum, this facilitates efficient single-stage surgery, but it may also facilitate simultaneous direct decompression, posterior facet osteotomy and other maneuvers to enhance sagittal balance. Additionally, it facilitates other scenarios, such as difficult revision operations where a posterior-anterior-posterior strategy might otherwise be employed. Complex revision surgery where simultaneous posterior and lateral access allows extraction of failed implants and safe, single-position reconstruction of the spine can be performed with this technique (Figures 3, 4).
The PTP approach to lateral lumbar fusion addresses several of the intrinsic flaws of the traditional LLIF technique, improving on an already paradigm-changing procedure by making it simpler, safer and more flexible. Most notably, this approach provides the potential for improved segmental lordotic correction due to the effect of gravity and lordotic patient positioning, as well as greater operative workflow and efficiency, therefore negating the need for a two-staged procedure. Additionally, many cases requiring direct open decompression are not currently performed using lateral surgery because an all-posterior transforaminal lumbar interbody fusion-type approach is deemed to be more efficient. The PTP approach allows the surgeon to leverage the unique benefits of lateral surgery and still perform traditional open or complex posterior surgery in the same stage.
Despite the reported advantages of the PTP approach, there is likely a learning curve, particularly among surgeons who are less experienced with the nuances of the LLIF procedure. Excellent 3D spatial awareness is required to ensure the surgeon can troubleshoot problems, such as retractor malpositioning in the prone position. It is also important that the retractor system be rigid and directly mounted to the patient positioners to minimize the risk of retractor migration. Furthermore, the PTP LLIF approach may pose a challenge in obese patients where soft tissue sag may make the standard lateral approach more feasible. Overall, while larger-scale longitudinal studies are warranted to elucidate differences among techniques, the current limited literature on this topic has shown PTP LLIF is an innovative and safe technique with the potential for improved operating room efficiencies and outcomes.
- References:
- Ahlquist S, et al. Spine J. 2018;doi:10.1016/ j.spinee.2018.03.014.
- Gandhi S, et al. Prone Trans-psoas lumbar corpectomy: Simultaneous posterior and lateral lumbar access for difficult clinical scenarios. J Neurosurg Spine; Accepted December 2020.
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- For more information:
- Matthew W. Colman, MD, is an orthopedic spine and musculoskeletal oncology surgeon and associate professor at Rush University Medical Center and Midwest Orthopedics at Rush; and
- Athan Zavras is a clinical research fellow in orthopedic spine surgery and musculoskeletal oncology at Midwest Orthopaedics at Rush. They can be reached at 1611 W. Harrison St., Suite 300, Chicago, IL 60612; Colman’s email: matthew.colman@rushortho.com. Zavras’s email: athan.zavras@rushortho.com.
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