‘This is not Prone Lateral, this is PTP’: Key advantages of the Prone Transpsoas (PTP) technique

Spinal Tech

The lateral interbody fusion (LIF) spine procedure was developed two decades ago and offers not only many MIS benefits, butala superior biomechanical stability and high fusion rates. Even with the well-documented benefits of LIF, many surgeons have not adopted this now traditional technique, and a majority of surgeons have found that there are some inherent challenges when the patient is in the lateral decubitus position. Not only can the position be unfamiliar to the surgeon and staff which leads to inefficiencies in preoperative setup and repositioning for posterior procedures, but literature demonstrates that the lateral decubitus position may not be ideal for achieving sagittal alignment - the greatest correlative to a long-term positive outcome.

What if there were a lateral approach that appealed to more surgeons, provided a greater ability to achieve alignment goals, and resulted in excellent patient outcomes?

Luiz Pimenta, MD, PhD, Medical Director at Instituto de Patalogia da Coluna, and William Taylor, MD, Clinical Professor of Surgery in the Division of Neurosurgery at University of California San Diego, partnered with Alphatec Spine to develop a more streamlined intuitive lateral approach, Prone Transpsoas or “PTP”. As its name suggests, PTP is a spinal fusion procedure in which the patient is positioned prone and the disc space is accessed laterally through the psoas muscle.

“Despite the advantages of lateral spinal fusion, including good corrections,low infection risk, and lower complication risk than alternative procedures, there was still reluctance by surgeons to adopt,” said Dr. Taylor. “Overcoming that reluctance became our goal and when we were looking at the lateral approach. We had to rethink and redo the entire lateral approach to make it more palatable for surgeons to adopt.”

“This is not just another lateral spine procedure,” said Dr. Pimenta. “PTP allows us to achieve better coronal and sagittal alignment by keeping the patient in a maximally efficient prone position throughout both the anterior and posterior aspects of the case. 

In this article, you will find a discussion of how the PTP procedure could spark more widespread use of the lateral approach for spinal fusion surgery.

Question: What are the benefits of PTP?

Dr. William Taylor: PTP has many benefits that range from superior surgical efficiency to powerful correction abilities in both the sagittal and coronal planes. From an efficiency standpoint, it reduces preoperative positioning time and eliminates the need for taping that is required in traditional LIF procedures. You also have the ability to perform posterior surgery simultaneously. PTP allows me to perform a LIF at L4/5 with a direct decompression while simultaneously completing a TLIF at L5/S1. 

PTP also simplifies decision-making. With patients in the lateral position you have to ask yourself: Do I put in pedicle screws? Do I flip them over to do a decompression? How can I achieve better sagittal correction? Now, all the decision- making is simplified. I can do a direct decompression without having to reposition the patient, which saves time and eliminates my reliance on indirect decompression.

Dr. Luiz Pimenta: There have been some questions about how much sagittal alignment we can restore with the traditional lateral procedure and the reality is that with PTP we have a greater ability to restore alignment and perform surgery in a more efficient fashion.
WT: When surgeons observe us performing PTP, they see the benefits right away because there is less time spent po- sitioning and/or repositioning the patient, easier access to the retroperitoneal space, less concern about neural injury, greater sagittal correction, and simultaneous anterior/posterior column access to achieve your overall alignment goals. The decision-making tree has been simplified.

Q: How has the procedure evolved?

WT: We have collectively done more than 1,000 PTP cases and learned quickly that the requirements around PTP differ greatly when compared to traditional lateral surgery. We developed each component of the procedure based on the clinical requirements for the patient in the prone position. First, the carbon-fiber patient positioning system allows for reproducible access to patients with high iliac crests, and provides patient stability throughout the procedure. Next, we focused on developing a solid low- profile two-bladed retractor that attaches directly to the patient positioner and can independently open posteriorly and anteriorly. The retractor allows the surgeon to expose just enough space to place the interbody implant. Finally, the SafeOp neuromonitoring platform not only provides information regarding nerve location, but for the first time, we can reproducibly monitor the real-time health of the lumbar plexus throughout the procedure with saphenous SSEP monitoring.

LP: The procedure comes with a full set of equipment that includes the patient positioning system, retractor, and SafeOp neuromonitoring - all of which are designed for the PTP approach. We developed the patient positioning system because in the traditional lateral approach, the table acts as a contralateral backstop while performing the procedure thereby eliminating patient movement. If you do the same surgery in the prone position, the patient could move. So, we needed a stable platform that would allow us to perform the PTP approach without the patient moving, while being able to coronally blend the patients with high crests. We also learned that the three-bladed retractor design common to traditional lateral procedures was not suited for this approach as it would easily lose its position due to its weight and lack of rigidity. We decided on a light-weight, two-bladed retractor that thoroughly maintains its position in accessing the disc space. 

Q: What pathologies have you been able to address with the procedure?

LP: One of the most frequent pathologies we see is spondylolisthesis. With PTP, we are seeing an increased ability to treat this indication through the corrective properties of the prone position. We have experience now using PTP to treat pathologies ranging from single-level degenerative disc disease to multi-level deformities. 

WT: It’s often that I have L4/5 spondylolisthesis patients. I can position them prone, which itself reduces the spondy and then use navigation to insert the pedicle screws. I can simultaneously do a PTP at L4/5 and a TLIF at L5/S1 without having to reposition the patient or worry about performing a laminectomy or decompression at L4/5. I can do the pro- cedure with all of the advantages of MIS surgery while hav- ing the patient in an ergonomically advantageous position.

Q: What is the difference between PTP and other prone lateral offerings?

LP: There are other companies trying to achieve similar results as PTP but with a lateral system they designed for the traditional lateral decubitus approach. But when patients are in a prone position, we cannot reproducibly perform surgery with a traditional lateral system. We learned that along the way and now have products specifically built from those learnings. This is not prone lateral, this is PTP. 

WT: Without the patient positioning system, even with taping and bolsters, the patient tends to slide across the table and the retractor disengages. The patient positioner keeps the patient stable with the retractor, which is anchored to the positioner. There are people who want to use the same instruments from the lateral decubitus procedure in prone, but I would caution against that. The PTP system has been specifically designed based on the learnings from over 1,000 cases and comes fully integrated as a procedural solution. 

Q: What do you see in the future for PTP?

WT: In spine, we are moving to the outpatient setting and the pandemic has given us even more reasons to make the move. The ability to perform this surgery in the outpatient setting is nice because we’ve simplified the procedure in a way that doesn’t require extra instruments, positioning, or time. The patient also experiences the advantages of minimally invasive lateral surgery with larger implants, high fusion rates and low subsidence in the outpatient setting. These all make PTP attractive. 

We are starting to use PTP on more complex cases as well, such as corpectomies and thoracic discectomies. It’s nice to be able to perform these procedures with the patient in the prone position.

We are constantly thinking about how to make PTP better. We want to grow the 20 to 30 percent of surgeons who are currently using the lateral approach because we think it’s safer and better for the patient.

This article is sponsored by Alphatec.

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