Reduction of high-grade spondylolisthesis using minimally invasive spine surgery-transforaminal lumbar interbody fusion “trial-in-situ” technique: a technical note with case series
Article information
Abstract
This retrospective case series evaluated the effectiveness of minimally invasive spine surgery-transforaminal lumbar interbody fusion (MIS-TLIF) using the “trial-in-situ” technique for reducing high-grade spondylolisthesis. The surgical management of grade ≥III spondylolisthesis has been controversial, with various methods documented in the literature, including in-situ fusion, in-situ trans-sacral delta fixation, distraction techniques, and external reduction techniques. Recently, MIS techniques have gained popularity. This study analyzed 18 cases of high-grade spondylolisthesis treated with MIS-TLIF using the “trial-in-situ” technique. The clinical outcomes were assessed using the Visual Analog Scale (VAS) and the modified Oswestry Disability Index (mODI) scores. The spinopelvic parameters and sagittal balance were also analyzed. Preoperatively, the spinopelvic parameters were deranged, with a mean pelvic tilt of 28.31°, which improved to 13.91° postoperatively. Similarly, the sacral slope improved from 45.65° to 38.01°. VAS and mODI scores improved postoperatively, indicating the effectiveness of the “trial-in-situ” technique in reducing high-grade spondylolisthesis and achieving a better sagittal profile and spinopelvic parameters. The findings indicate that MIS-TLIF using the “trial-in-situ” technique is a viable and effective method for treating high-grade spondylolisthesis.
Introduction
Spondylolisthesis, from the Greek “spondylos” (vertebrae) and “olisthesis” (slide), refers to the displacement of one vertebral body over another. High-grade spondylolisthesis occurs when slippage exceeds 50%, classified by the Meyerding scale. Degenerative spondylolisthesis, prevalent in 19.1%–43.1% of older people, mainly affects the L4–L5 level and is more common in women [1]. Isthmic spondylolisthesis, involving pars interarticularis fractures, affects 5%–7% of a younger population, predominantly men, and typically occurs at the L5–S1 level [2].
Reduction of spondylolisthesis is advocated by certain surgeons when feasible. This approach offers multiple benefits: it alleviates foraminal stenosis, enhances spinopelvic sagittal balance, and mitigates the risk of future degenerative spinal changes. However, the complexity and associated risks of reduction increase significantly in higher-grade cases or cases involving spondylolisthesis [3,4]. Surgical management of grade ≥III spondylolisthesis has been controversial, with various documented methods including in situ fusion, posterior fusion with or without reduction, combined anterior and posterior procedures, spondylectomy with reduction, and posterior interbody fusion with trans-sacral fixation. Recently, minimally invasive spine surgery-transforaminal lumbar interbody fusion (MIS-TLIF) for high-grade spondylolisthesis has gained popularity and shown promising results. Patients typically present with low backache, radiculopathy, hamstring tightness, and significant sagittal imbalance. Compensation mechanisms include increased lumbar lordosis (LL), pelvic retroversion, increased pelvic tilt (PT), and decreased sacral slope (SS), leading to a positive sagittal imbalance and the Phalen–Dickson gait. In this study, we evaluated the effectiveness of MIS-TLIF using the “trial-in-situ” technique for reducing listhesis segments and improving sagittal balance and spinopelvic parameters.
Technical Notes
Study design and participants
We retrospectively evaluated 18 cases of MIS-TLIF for high-grade spondylolisthesis (Meyerding grade III/IV) from 2016 to 2024. Isthmic (pars fracture) and degenerative cases were included. All patients experienced low back pain, unilateral or bilateral radiculopathy, and neurogenic claudication. Cases involved L5–S1 and L4–L5 levels. Radiological parameters were recorded and evaluated. Informed consent was obtained from all participants. Dynamic X-ray images of the lumbosacral spine were obtained to determine the extent of mobility. Eighteen patients underwent MIS-TLIF by the “trial-in-situ” technique. Clinical outcomes were measured using the Visual Analog Scale (VAS) and mean Oswestry Disability Index (mODI) scores at 3-, 12-, 24-, and 60-month follow-up. Changes in the slip percentage, SS, PT, LL, and Meyerding’s grade were recorded.
Surgical technique (MIS-TLIF)
The patient was positioned prone on bolsters, with one placed below the chest and another below the hip joint, which allowed the abdomen to hang freely. Pressure points were properly padded with cotton. After the induction of general anesthesia and muscle relaxation, extra cotton padding or a small pillow was added below the knees. This positioning facilitated “spontaneous reduction” of the listhesis segment. Finally, neuromonitoring leads were attached and secured to the lower limbs. An intraoperative neuromonitoring system was utilized but only for cases classified as Meyerding grade IV.
Approximately 2.5 cm from the midline, a 2.5–3.0 cm incision was marked on both sides using a 20G spinal needle and C-arm. Guidewires were placed bilaterally under fluoroscopic guidance and secured cranially and caudally. Following standards, docking was initiated on one side using serial dilators, targeting the facet joint or the lamino-pars-facet joint.
Complete ipsilateral facetectomy was performed initially by chisel and hammer to obtain bone graft for fusion and then by a high-speed drill. The exiting nerve root was identified and preserved. A standard discectomy was performed, and the end plates were prepared. A “trial” or “spacer” was inserted to distract the segments and determine the cage size. After facetectomy and discectomy for bony and soft tissue release, a trial or spacer was inserted ipsilaterally between the two endplates to achieve the desired segment distraction of the two listhetic segments (Fig. 1). On the contralateral side, facetectomy was performed, and pedicle screws were inserted through guide wires on one side only. The contralateral screws were gradually tightened, starting with the distal screw followed by the proximal screw, after the placement of the lordotic rod (Fig. 2).
Showing ‘trial-in-situ’ (blue handle) on contralateral side (A). After distraction by ‘trial,’ ipsilateral screwhead attachments or towers showing indirectly the amount of spondylolisthesis remaining (B). After tightening distal screw first (S1 in this case) followed by L5–cantilevering effect, both the screw-head attachments/towers are at same levels, indicating no listhesis remaining (C).
Showing a nice and sharp medial trajectory of pedicle screws with bi-cortical and tri-cortical purchase of L5, S1 (A, B). Postoperative incision length (C).
The trial remained in situ ipsilaterally until the contralateral screws were tightened (Fig. 1). At that point, the trial was removed, and a polyetheretherketone cage filled with autologous bone graft was inserted between the two end plates. The lordotic rods and screws on the ipsilateral side were also tightened. The distal screw was tightened initially, serving as a fulcrum. The proximal screw was gradually tightened, with the lordotic rod lifting it as a cantilever. This combination of the lordotic rod and proximal screws served as reduction screws, creating a cantilever effect that facilitated the reduction of high-grade spondylolisthesis (Fig. 3).
Pictorial diagram showing ‘near complete reduction’ with cage first technique (A). With trial-in-situ technique, because of smooth surface resulting into a ‘complete reduction’ with the help of cantilevering mechanism (B).
Primary outcomes
In this study, the average age of the patients ranged from 53 to 56 years (56.89±3.75 years), with female predominance (n=13) and body mass index (BMI) of <30 kg/m2. Most cases were classified as Meyerding grade III (n=16), with two grade IV cases. The majority (60%) were degenerative cases, whereas the remaining 40% presented with pars fractures. The latter group predominantly consisted of young and obese patients with high BMI scores. Although the average age of our cohort was 56 years, the patients had a wide age range, including a 29-year-old man with a pars fracture representing the youngest surgical case. All patients presented with low back pain and unilateral or bilateral radiculopathy. The preoperative VAS scores were 6.78±0.64 (p=0.48), and the mODI scores were at 64.39±1.72 (p=0.53), respectively. The mean operative time was 152.7 minutes, with minimal blood loss attributed to the minimally invasive technique used, averaging 81.11 mL (Table 1).
Evaluation of preoperative and postoperative parameters in trial-in-situ technique
Clinical outcomes improved significantly after surgery. Patients were free of pain and symptoms during the postoperative period. Postoperatively, the VAS and mODI scores improved significantly, with VAS scores dropping to 2.56±0.61 (p=0.29) and mODI scores improving to 15.00±1.78 (p=1.00) at 1-year follow-up (Table 1). No clinically significant differences were observed after 5 years of follow-up (VAS scores remained at 2.5±0.5, p=0.11; mODI at 16.06±1.39, p=0.33) (Table 1). However, five patients were unable to complete the full 5-year follow-up period. These patients completed 2-year follow-ups, and monitoring was continued. Radiological outcomes demonstrated significant improvements (Table 2, Fig. 4). Preoperatively, the mean PT was 28.31°, which improved to 13.91°. The SS improved from 45.64° to 38.01°. LL demonstrated an improvement from a mean of 63.62° to 51.86° postoperatively. The neurological functions remained preserved throughout the procedure, without significant nerve root or spinal cord compromise. Listhesis completely reduced in 13 cases (Table 3, Fig. 5) using the trial-in-situ technique, whereas reduction to Meyerding grade I was achieved in four cases and grade II in one case (from Meyerding grade IV).
Evaluation of post-surgical spinopelvic parameters in trial-in-situ technique
Sagittal X-ray showing severely abnormal sagittal balance and spinopelvic parameters at L4–L5 levels (A, B). Non-contrast computed tomography lumbo-sacral spine showing dramatically improved parameters (C). TK, thoracic kyphosis; SAA, sagittal acetabular anteversion; LL, lumbar lordosis; SS, sacral slope; PT, pelvic tilt; PI, pelvic incidence; PI–LL, pelvic incidence minus lumbar lordosis; tLL, target lumbar lordosis; tPT, target pelvic tilt.
Postoperative Meyerding grading reduction
High-grade spondylolisthesis at L5–S1 with abnormal preoperative sagittal balance and pelvic parameters (A). Postoperative X-ray and non-contrast computed tomography lumbo-sacral spine showing a ‘complete reduction’ and improved spinopelvic parameters at L5–S1 (B, C). LL, lumbar lordosis; SS, sacral slope; PT, pelvic tilt; PI, pelvic incidence; PI, pelvic incidence.
Discussion
Managing high-grade spondylolisthesis has been controversial, and traditional in situ fusion methods are associated with complications such as pseudarthrosis, slip progression, and cosmetic deformity [5]. Recent studies have suggested that surgical reduction for pelvic imbalance improves spinopelvic alignment and clinical outcomes [6,7]. Achieving a reduction in high-grade spondylolisthesis is challenging, particularly using open techniques such as in situ fusion [8]. The literature describes various techniques, including trans-sacral fixation via the posterior approach [9], in situ trans-sacral delta fixation [10], Jackson’s intrasacral rod technique alongside the cantilever technique [11], and distraction methods [12] for the reduction of high-grade spondylolisthesis. Notably, the cantilever and external reduction techniques [13–15], although effective, have limitations such as prolonged hospitalization and uncomfortable bed rest during the traction period.
MIS techniques, such as MIS-TLIF, show promising results for high-grade spondylolisthesis [16]. Quraishi and Rampersaud [17], Rajakumar et al. [18], and Park et al. [19] demonstrated favorable outcomes using MIS approaches, with recent advancements showcasing techniques such as “rocking” and “swing” techniques. Patel and Peshwattiwar [20] further confirmed the feasibility and safety of MIS-TLIF in high-grade spondylolisthesis (grade III) in patients with rheumatoid arthritis.
The “trial-in-situ” technique for managing high-grade spondylolisthesis offers several advantages over traditional and other minimally invasive methods. This technique allows for improved reduction and alignment, restoring spinopelvic parameters more effectively. The minimally invasive approach minimizes soft tissue damage, blood loss, and recovery time while ensuring precise guidewire placement to reduce the neural injury risk. Effective distraction with a trial or spacer promotes spontaneous segmental reduction, lowering the risk of pseudarthrosis and enhancing postoperative stability. This technique is versatile and suitable for both degenerative and isthmic spondylolisthesis and leads to significant improvements in pain and functional outcomes, as evidenced by lower VAS and mODI scores. In this study, two cases of unilateral partial foot drop due to guide wire slippage resolved completely by the 3-month follow-up. In addition, one case of paresthesia, which was likely caused by over distraction, resolved within a month. No dural tears or hardware-related complications occurred.
Limitations include the analysis of a small sample and some patients lost to follow-up, affecting long-term comparisons. Despite these limitations, MIS-TLIF trial-in-situ technique remains a promising approach for managing high-grade spondylolisthesis.
Key Points
The “trial-in-situ” technique effectively reduces high grade spondylolisthesis and improves spinopelvic alignment.
Significant postoperative improvements were observed in Visual Analog Scale, modified Oswestry Disability Index scores, and spinopelvic parameters.
The cantilever mechanism using lordotic rods enhances segment reduction with minimal invasiveness.
Most patients experienced lasting symptom relief with no major complications.
Notes
Conflict of Interest
No potential conflict of interest relevant to this article was reported.
Author Contributions
Conception and design: MK, VR. Data acquisition: MK, AJ. Analysis of data: MKG. Drafting of the manuscript: SN, VR. Critical revision: MK, VR, AJ. Supervision: MK. Final approval of the manuscript: all authors.