Transforaminal Lumbar Interbody Fusion Technique Research Articles

Clinical Outcomes of the Transforaminal Lumbar Interbody Fusion Technique Among Patients With Low Back Pain Showing Type 1 Modic Changes on MRI

Clinical Outcomes of the Transforaminal Lumbar Interbody Fusion Technique Among Patients With Low Back Pain Showing Type 1 Modic Changes on MRI

Do TLIF and PLIF Techniques Differ in Perioperative Complications? - Comparison of Complications Rates of Two High Volume Centers.

Retrospective bicentric Cohort Study. Posterior (PLIF) and transforaminal lumbar interbody fusion (TLIF) have been clinically proven for the surgical treatment of degenerative spinal disorders. Despite many retrospective studies, the superiority of either technique has not been proven to date. In the literature, the complication rate of the conventional PLIF technique is reported to be significantly higher, but with inconsistent complication recording. In this retrospective bicentric study, a less invasive PLIF technique was compared with the conventional TLIF technique and complications were recorded using the validated SAVES V2 classification system. 1142 patients underwent PLIF (702) or TLIF (n = 440) up to 3 levels in two specialized centers. Epidemiological data, intra- and postoperative complications during hospitalization and after discharge were analyzed according to SAVES V2. The overall complication rate was 13.74%. TLIF-patients had slightly significant more complications than PLIF-patients (TLIF = 16.6%/PLIF = 11.9%, P = .0338). Accordingly, complications during revision surgeries were more frequent in the first cohort (TLIF = 20.9%/PLIF = 12.6%; P = .03252). In primary interventions, the surgical technique did not correlate with the complication rate (TLIF = 12.4%/PLIF = 11.7%). There were no significant differences regarding severity of complications. An important component of this work is the complication recording according to a uniform classification system (SAVES V2). In contrast to previous literature, we could demonstrate that there is not a significant difference between the two surgical techniques.

Evolution of the Transforaminal Lumbar Interbody Fusion (TLIF): From Open to Percutaneous to Patient-Specific.

The transforaminal lumbar interbody fusion (TLIF) has seen significant evolution since its early inception, reflecting advancements in surgical techniques, patient safety, and outcomes. Originally described as an improvement over the posterior lumbar interbody fusion (PLIF), the TLIF began as an open surgical procedure, that notably reduced the need for the extensive neural retractation that hindered the PLIF. In line with the broader practice of surgery, trending toward minimally invasive access, the TLIF was followed by the development of the minimally invasive TLIF (MIS-TLIF), a technique that further decreased tissue trauma and postoperative complications. Subsequent advancements, including Trans-Kambin's Triangle TLIF (percLIF) and transfacet LIF, have continued to refine surgical access, minimize surgical footprint, and reduce the risk of injury to the patient. The latest evolution, as we will describe it, the patient-specific TLIF, is a culmination of the aforementioned adaptations and incorporates advanced imaging and segmentation technologies into perioperative planning, allowing surgeons to tailor approaches based on individual patient anatomy and pathology. These developments signify a shift towards more precise methods in spine surgery. The ongoing evolution of the TLIF technique illustrates the dynamic nature of surgery and emphasizes the need for continued adaptation and refinement.

Biportal endoscopic transforaminal lumbar interbody fusion using a large cage for degenerative spondylolisthesis with stenosis.

Recently, biportal endoscopic transforaminal lumbar interbody fusion (TLIF) has been used to treat lumbar degenerative diseases, such as lumbar instability and spondylolisthesis. Biportal endoscopic TLIF may have the advantages of endoscopic spine approaches and minimally invasive lumbar fusion surgeries. In this biportal endoscopic TLIF, large cages similar to oblique lumbar interbody fusion (OLIF) cages have been used. Biportal endoscopic TLIF using a large cage can be successfully performed in the lower lumbar area. The author presents the surgical technique of biportal endoscopic TLIF using a large cage. The video can be found here: https://stream.cadmore.media/r10.3171/2024.1.FOCVID23231.

Comparative Analysis of Uniportal and Biportal Endoscopic Transforaminal Lumbar Interbody Fusion in Early Learning Stage: Technical Considerations and Radiological Outcomes

Objective: This study compared the clinical and radiological outcomes of uniportal endoscopic and biportal endoscopic transforaminal lumbar interbody fusion (TLIF) for lumbar degenerative disease during the early learning stage of the technique.Methods: We retrospectively analyzed patients who underwent uniportal endoscopic TLIF (n=15) and biportal endoscopic TLIF (n=19) between January and October 2021 during the first year of adoption of these techniques. Radiological parameters, including Bridewell fusion and subsidence grading, were evaluated by x-ray and computed tomography (CT) at 3-month, 6-month, and 1-year follow-up visits. Clinical outcomes were evaluated using the visual analogue scale (VAS) and the Oswestry Disability Index (ODI).Results: Uniportal endoscopic TLIF showed significantly higher frequencies of intraoperative endplate injuries (uniportal [20%] vs. biportal [0%], p=0.01) and 1-year cage subsidence (uniportal [60%] vs. biportal [26.3%], p=0.04) than biportal endoscopic TLIF. The 1-year fusion rates did not differ significantly between the 2 surgical groups (uniportal [93.3%] vs. biportal [89.5%], p=0.37). Neural complications such as postoperative dysesthesia and dural tears occurred in uniportal endoscopic TLIF. There were no significant differences in the VAS for back and leg pain or ODI.Conclusion: Complete endplate preparation under endoscopic guidance improved interbody fusion, and this procedure may be feasible in the early learning stage, regardless of the type of endoscope. Both endoscopic TLIF techniques achieved good clinical outcomes and fusion rates. However, unskilled use of the cage guide device caused endplate breakage and neural injury during uniportal endoscopic cage insertion. Uniportal endoscopic TLIF may require more experience for appropriate cage insertion.

Complex neuroimaging study of the proximal segment after rigid fixation and dynamic stabilization in patients with degenerative lumbar disease

Background. The development of the adjacent level syndrome and, as a consequence, adjacent segment degenerative disease are currently the most common complications of decompression and stabilization surgery with the development of segmental instability. The aim of the study. To conduct a comprehensive neuroimaging assessment of the proximal adjacent segment after rigid fixation and dynamic stabilization in degenerative lumbar disease. Materials and methods. We conducted a prospective multicenter study of the results of surgical treatment of 274 patients with degenerative-dystrophic diseases of the lumbar spine, who underwent monosegmental decompression and stabilization surgery using the TLIF (transforaminal lumbar interbody fusion) technique and open transpedicular rigid fixation, as well as open hemilaminectomy with stabilization of the operated segments with nitinol rods. The study included radiography, diffusion-weighted magnetic resonance imaging and computed tomography (dualenergy mode) of intervertebral discs and isolated facet degeneration of the upper adjacent level. Results and discussion. Combination of the initial proximal segment degeneration in the form of facet joints degeneration (density of cartilaginous plate – 163.5 ± 14.2 HU, density of external facet – 709.35 ± 13.6 HU, density of internal facet – 578.1 ± 12.1 HU), Pfirrmann III, IV grade degeneration of intervertebral disc and a measured diffusion coefficient of less than 1300 mm2/s cause high risks of developing adjacent segment degenerative disease, which regulates the use of monosegmental dynamic fixation with nitinol rods, or preventive rigid fixation of the adjacent segment. Conclusion. Using complex neuroimaging in the preoperative period makes it possible to predict the results of surgical treatment, take timely measures to prevent degenerative diseases of the adjacent segment, and to carry out dynamic monitoring of processes in the structures of the spinal motion segment.

Bibliometric analysis of transforaminal lumbar interbody fusion: research status, trends, and future directions.

Transforaminal lumbar interbody fusion (TLIF) is a classic surgical procedure for posterior lumbar fusion. This study aims to analyze the TLIF field by bibliometric method and comprehensively summarize the research status and trends. All TLIF-related articles were retrieved from the Web of Science. The data were analyzed using R software and SPSS to calculate corresponding indicators. Visualizations were drawn using VOSviewer and Scimago Graphica, including country, institution, journal, author, and keywords. A total of 919 articles were included. The annual publication volume of TLIF-related articles presented an exponential growth. North America, Europe, and Asia were the main sources of articles, with the USA and China being the main contributors and the USA being the global research center for TLIF. The level of the national economy was an important factor affecting TLIF-related research. The highest number of contributions in this field was made by Kern Singh among authors and by Rush University among institutions. The European Spine Journal was the most influential journal. The research focus has gradually shifted from perfecting the TLIF technique toward emphasizing the patient level. The improvement of minimally invasive techniques and how to improve clinical outcomes as well as accelerate postoperative rehabilitation of patients may be the hot spot of future research. With the advancement of medical technology and the popularization of minimally invasive concepts in recent years, TLIF and its derivative technologies have attracted increasing attention. Patient-centered minimally invasive surgery is a hot research topic in the field of TLIF currently and will continue to be so into the future.

Comparative Analysis of Open Transforaminal Lumbar Interbody Fusion and Wiltse Transforaminal Lumbar Interbody Fusion Approaches for Treating Single-Level Lumbar Spondylolisthesis: A Single-Center Retrospective Study

Background: The aim of this study is to compare the surgical outcomes of two different surgical approaches, open transforaminal lumbar interbody fusion (TLIF) and Wiltse TLIF, in the treatment of single-level lumbar spondylolisthesis and also to provide the advantages and disadvantages of each approach. Methods: This retrospective study included 600 patients with single-level lumbar spondylolisthesis who underwent fusion surgery at a single academic institution between January 2018 and December 2022. Patients were divided into two groups: traditional open TLIF (group A; 300 patients) and the Wiltse TLIF approach (group B; 300 patients). Preoperative diagnostic tests were performed on all patients. Results: The fluoroscopy time for the Wiltse TLIF group was longer, whereas the mean blood loss for the Wiltse TLIF approach was less. Both techniques resulted in significant improvements in pain relief and functional disability, with no significant difference between the two groups in terms of their pre- or post-operative (Oswestry Disability Index) ODI scores. The Wiltse TLIF technique resulted in significantly shorter hospital stays and had a lower rate of complications compared with the open TLIF technique. Conclusion: The Wiltse TLIF approach showed advantages in shorter surgical times, reduced blood loss, and shorter hospital stays, whereas the traditional open TLIF approach exhibited shorter fluoroscopy times.

Comparison of surgical outcomes of degenerative spondylolisthesis with open or minimally invasive (MIS) transforaminal lumbar interbody fusion (TLIF)

Introduction. One of the most commonly used surgical treatment methods for degenerative lumbar spondylolisthesis (DLS) is transforaminal lumbar interbody fusion (TLIF). It can be performed either with an open classic posterior midline approach or the minimally invasive (MIS) method using Wiltse paraspinal intermuscular accesses. Aim. To prospectively compare clinical and radiological outcomes of DLS treatment with open (O) or (MIS) TLIF. Materials and methods. Forty six surgically treated patients who met the study criteria were divided into two groups according to the access method used: O group – 24 patients, MIS group – 22 patients. Clinical and radiological outcomes were evaluated before and after the surgery and after the follow-up period in both groups. The clinical peri and postoperative parameters and complications, back and leg pain with the VAS scale, and the outcomes in the ODI scale were evaluated. Radiological outcomes were measured with the standing X-ray images in the AP and lateral projections, as well as MRI/CT and functional X-rays. During statistical comparisons, both groups were adjusted in terms of pre-operative and postoperative data. Results. Preoperative demographic data in both groups did not differ significantly, except for the follow–up period, which was longer for the O group (mean 33.2 months), and 19.5 months for the MIS group. Both VAS and ODI clinical outcomes improved in both groups. Patients from the MIS group achieved significantly better clinical results immediately after the procedure and in the early outcomes. After the follow–up period, no significant differences were found. In the MIS group, only blood loss and the length of the postoperative stay were significantly lower than in the O group. The X-ray doses were significantly higher in the MIS group. Postoperative X-ray parameters improved in both groups with no significant differences, except for the slip correction, which was better in the O group. Conclusions. Both TLIF methods lead to significant clinical and radiological improvement in patients with DLS. In certain aspects, MIS has advantages over the “open” TLIF technique in the surgical treatment of degenerative spondylolisthesis.

Clinical outcomes of transforaminal lumbar interbody fusion using a modified posterior spinous process-splitting approach for lumbar degenerative or isthmic spondylolisthesis: a prospective cohort study.

In the conventional posterior approach to the lumbar spine for transforaminal lumbar interbody fusion (TLIF), the paravertebral muscles are stripped from the spinous process. The authors developed a novel surgical procedure in which TLIF was performed via a modified spinous process-splitting (SPS) approach that enabled the preservation of the attachment of the paravertebral muscles to the spinous process. The SPS TLIF group comprised 52 patients with lumbar degenerative or isthmic spondylolisthesis who underwent surgery using a modified SPS TLIF technique, whereas the control group comprised 54 patients who underwent conventional TLIF. Compared with the control group, the SPS TLIF group had a significantly shorter operation time, smaller intra- and postoperative blood loss volumes, and shorter hospital stay and time to ambulation (p < 0.05). The SPS TLIF group had a lower mean visual analog scale score for back pain than the control group on both postoperative day 3 and at 2 years postoperatively (p < 0.05). Follow-up MRI showed changes in the paravertebral muscles in 46 of 54 patients (85%) in the control group and 5 of 52 patients (10%) in the SPS TLIF group (p < 0.001). This novel technique may be a useful alternative to the conventional posterior approach for TLIF.

The Use of Dual Direction Expandable Titanium Cage With Biportal Endoscopic Transforaminal Lumbar Interbody Fusion: A Technical Consideration With Preliminary Results.

Expandable cage technology has emerged for lumbar interbody fusion to restore intervertebral disc space height and alignment through a narrow surgical corridor. The purpose of this study is to present the technique of biportal endoscopic transforaminal lumbar interbody fusion (TLIF) using dual direction expandable cage and provide early clinical results. We performed the biportal endoscopic TLIF using a dual direction expandable titanium cage for height restoration and a larger footprint in 10 patients. Clinical parameters including Oswestry Disability Index (ODI), visual analogue scale (VAS), and complications were retrospectively analyzed. Also, we investigated radiologic parameters using preoperative and postoperative x-ray images. We successfully inserted dual direction expandable cages during biportal endoscopic TLIF. There was no significant subsidence or collapse of the expandable cages during the 6-month follow-up period. Lumbar lordosis and disc height were significantly increased after surgery. ODI and VAS scores were significantly improved at 6 months after surgery. In this report, we describe the first use of a dual direction expandable interbody TLIF cage that expands in both width and height in biportal endoscopic TLIF surgery. Early clinical and radiographic outcomes of this TLIF technique may be favorable in early 6-month follow-up.

A Comparison of Clinical and Radiological Outcomes between Open and Minimally Invasive Transforaminal Lumbar Interbody Fusion

Objective: To compare the clinical, radiological and functional outcomes of patients between open TLIF and minimally invasive TLIF techniques. Study Design: Prospective cohort study Place and duration: Study was conducted at department of neurosurgery Bakhtawar Amin Hospital, Multan from August 2021 to July 2022 in duration of one year. Methodology: A total of 94 patients planned for transforaminal lumbar interbody fusion (TLIF) were enrolled in study. Main variables of study were intra operative blood loss, duration of surgery, VAS score, ODI index and functional score. SPSS version 24 was used for data analysis, t-test and chi square test were applied to see association among variables. P value less than or equal 0.05 was considered as significant. Results: Oswestry disability index readings were 35.16±2.18 and 5.12±0.61 in O-TLIF and MIS-TLIF groups respectively at 3 weeks after surgery. The differences were statistically insignificant, (p&gt;0.050). Physical component summary of both the groups at different time intervals as shown better outcomes in MIS-TLIF group, no difference was found to be statistically significant except at 6 week. Mental component summary in both the groups was almost equal, (p&gt;0.050). Implications: There was no local study on comparison of open and minimally invasive technique for TLIF, our study will fulfill the local reference gap and help the surgeons for choice of better management technique in future. Conclusion: Minimally invasive surgery TLIF technique is better in immediate benefits as soft tissue injury and iatrogenic injury which is associated with better post operative pain functional recovery time. So, minimal invasive interbody fusion is a safe and reliable option for short term (blood loss, post operative pain) and long term outcomes like functional recovery. Keywords: Interbody fusion, VAS score, SF-36, ODI index, TLIF Technique

Comprehensive analysis of the results of surgical treatment of patients with degenerative diseases of the lumbar spine using rigid fixation systems

Introduction. According to the literature, the development of adjacent-level syndrome 10 years after posterior rigid stabilization is noted in 6.7–80 % of patients, of which 24 % require revision surgery.The aim: to conduct a comprehensive analysis of the results of surgical treatment of patients with degenerative diseases of the lumbar spine using rigid fixation systems.Materials and methods. A multicenter retrospective study of the results of surgical treatment of 268 patients with degenerative-dystrophic diseases of the lumbar spine, who underwent mono- or bisegmental decompression-stabilizing intervention with the implementation of the TLIF (Transforaminal Lumbar Interbody Fusion) technique and open transpedicular rigid fixation, was conducted. The study included radiography, MRI and CT (in 2-energy mode) of intervertebral discs and isolated facet degeneration of the upper adjacent level.Results and discussion. The combination of the initial degeneration of the adjacent spinal motion segment in the form of disc degeneration of grade III and higher according to Pfirrmann with threshold values of the density of the outer cartilaginous plate from 161.7 ± 18.8 to 164.8 ± 14.2 HU, the density of the outer facet – from 702.43 ± 12.3 to 713.65 ± 13.6 HU and the density of the inner facet – from 580.5 ± 11.6 to 582.1 ± 15.1 HU, as well as with signs of segmental instability of the adjacent segment can be considered as risk factors for the development of its degeneration. With the progression of degeneration of the upper intervertebral disc, revision interventions were performed within 12–60 months after surgery.Conclusion. Bisegmental stabilization with signs of initial degeneration in the intervertebral disc and facet joints in the upper segment has proven its clinical and instrumental effectiveness in the period of 36 months and reduces the risks of developing degenerative disease of the adjacent disc.

Comparison of the Susceptibility to Implant Failure in the Lateral, Posterior, and Transforaminal Lumbar Interbody Fusion: A Finite Element Analysis

There are several techniques for lumbar interbody fusion, and implant failure following lumbar interbody fusion can be troublesome. This study aimed to compare the stress in posterior implant and peri-screw vertebral bodies among lateral lumbar interbody fusion (LLIF), posterior lumbar interbody fusion (PLIF), and transforaminal lumbar interbody fusion (TLIF) and to select the technique that is least likely to cause implant failure. We created an intact L3-L5 model and simulated the LLIF, PLIF, and TLIF techniques at L4-L5 using finite element methods. All models at the lower portion of L5 were fixed and imposed a preload of 400N and a moment of 7.5 Nm on the upper portion of L3 to simulate flexion, extension, lateral bending, and axial rotation. We investigated the peak stresses and stress concentration in the posterior implant and peri-screw vertebral bodies for the LLIF, PLIF, and TLIF techniques. The extension, flexion, bending, and rotation peak stresses and stress concentration in the posterior implant, as well as the peri-screw vertebral bodies, were the lowest in LLIF, followed by PLIF and TLIF. It was found that implant failure was least likely to occur in LLIF, followed by PLIF and TLIF. Hence, surgeons should be aware of these factors when selecting an appropriate surgical technique and be careful for implant failure during postoperative follow-up.

Assessment of fusion rate with transforaminal lumbar interbody fusion in degenerative lumbar spine diseases

ObjectivesThe aim of the study was to assess the fusion rate with transforaminal lumbar interbody fusion (TLIF) in degenerative lumbar spine diseases regarding its advantages, complications, and clinical outcomes.BackgroundTLIF should offer the same benefits of circumferential fusion with higher safety than other interbody fusion methods because it avoids the direct traction to dura and nerve roots.Participants and methodsThis study included 30 patients suffering from continuous low-back pain due to degenerative lumbar spine diseases, which were treated by TLIF using PEEK banana cage supplemented by pedicle screw fixation in the Orthopedic Department of Menoufia University Hospital during November 2018 till December 2020, with follow up of at least 9 months. All patients were subjected to full history taking, clinical examination, preoperative and postoperative follow-up.ResultsAt preoperative follow-up, all the studied patients had severe Oswestry disability index (ODI). While postoperatively, on the first day all of them cannot be assessed. Also, most of the studied patients (76.67%) had improved to mild ODI after 9 months of follow-up. The ODI showed significantly linear improvement in the studied patients with the greatest improvement observed in at the 3-month follow-up.ConclusionTLIF provides good clinical and radiological outcomes in the management of degenerative lumbar spine diseases after a follow-up period of 9 months. Operative complications are less in the TLIF technique, and the risk of dural tear is diminished significantly. TLIF can save much operative time and blood loss.

Biportal Endoscopic Technique for Transforaminal Lumbar Interbody Fusion: Review of Current Research.

There are many types of minimally invasive lumbar interbody fusion procedures. Among them is the recently introduced biportal endoscopic lumbar interbody fusion surgery. Biportal endoscopic transforaminal lumbar interbody fusion (TLIF) might combine the advantages of minimally invasive TLIF and endoscopic spine approaches. However, clinical evidence in support of biportal endoscopic TLIF remains insufficient. A comprehensive review of English-language literature on biportal endoscopic lumbar interbody fusion was performed. Articles on biportal endoscopic TLIF in PubMed, the Cochrane Library, and Web of Science were searched using the terms "unilateral biportal endoscopy," "biportal endoscopic spine surgery," "transforaminal," and "lumbar interbody fusion" as well as their combinations. The clinical and radiological outcomes of biportal endoscopic TLIF were analyzed and are summarized here. The biportal endoscopic lumbar interbody fusion surgical techniques are then described. There are 3 biportal endoscopic TLIF techniques. In the available literature, the postoperative 1-year outcomes of biportal endoscopic TLIF were comparable to those of posterior lumbar interbody fusion (PLIF) and minimally invasive (MIS)-TLIF. Clinical parameters were significantly improved after biportal endoscopic TLIF. Compared to PLIF or MIS-TLIF, biportal endoscopic-TLIF may have the advantage of a faster recovery. Biportal endoscopic TLIF showed no inferiority in fusion rates compared to PLIF or MIS-TLIF. The postoperative complications were usually minor. The postoperative 1-year clinical and radiological outcomes of biportal endoscopic TLIF were favorable compared to those of PLIF and MIS-TLIF. However, long-term outcomes should be investigated through prospective, randomized controlled trials in the future. This review article outlines the most current evidence-based medicine with regard to spinal surgery with an aim to introduce a new technique.

Transforaminal Lumbar Interbody Fusion With Double Cages: 2-Dimensional Operative Video.

We provide a step-by-step technique guide for performing a transforaminal lumbar interbody fusion (TLIF) with double cages. An illustrative case was presented with detailed narration and discussion of technical nuances. Double TLIF cages create an anterior lumbar interbody fusion-sized footprint that increases the surface area for arthrodesis and force distribution while avoiding the added morbidity of an anterior approach. An appropriate TLIF technique creates lordosis through an all-posterior approach, and using a large TLIF window avoids the need for retraction of the nerve roots or thecal sac. The patient gave informed consent for the procedure and video recording. There is no identifying information in this video. Institutional review board approval was deemed unnecessary.

Transumbilical Retroperitoneal Lumbar Interbody Fusion: A Technical Note and Preliminary Case Series.

ObjectiveAnterior lumbar interbody fusion (ALIF) has advantages over posterior lumbar interbody fusion or transforaminal lumbar interbody fusion techniques in that it minimizes damage to the anatomical structure of the posterior spinal segment and enables indirect decompression of the foramen by insertion of a tall cage. However, the predominant abdominal scar tissue reduces patients’ satisfaction after ALIF. Herein, we describe the technique of transumbilical lumbar interbody fusion (TULIF) and its preliminary results in a case series. MethodsA retrospective review of 154 consecutive patients who underwent TULIF between the L2–3 and L4–5 levels was performed. After preoperatively selecting patients by evaluating the location of the umbilicus and vessel anatomy, a vertical skin incision was made on the umbilicus to minimize the abdominal scar tissue. ResultsThere were 120 single-level (110 L4–5 and 10 L3–4), 31 two-level, and 3 three-level surgeries. All patients were very satisfied with their postoperative abdominal scars, which were noticeably faint compared to those after conventional ALIF. ConclusionTULIF is a feasible, minimally invasive surgical option that can achieve both the treatment of degenerative spinal disease and satisfactory cosmesis. Although it is technically demanding, patients obtain sufficient benefits.

A Biomechanical Model for Testing Cage Subsidence in Spine Specimens with Osteopenia or Osteoporosis Under Permanent Maximum Load

Intervertebral fusions in cases of reduced bone density are a tough challenge. From a biomechanical point of view, most current studies have focused on the range of motion or have shown test setups for single-component tests. Definitive setups for biomechanical testing of the primary stability of a 360° fusion using a screw-rod system and cage on osteoporotic spine are missing. The aim of this study was to develop a test stand to provide information about the bone-implant interface under reproducible conditions. After pretesting with artificial bone, functional spine units were tested with 360° fusion in the transforaminal lumbar interbody fusion technique. The movement sequences were conducted in flexion/extension, right and left lateral bending, and right and left axial rotation on a human model with osteopenia or osteoporosis under permanent maximum load with 7.5 N-m. During the testing of human cadavers, 4 vertebrae were fully tested and were inconspicuous even after radiological and macroscopic examination. One vertebra showed a subsidence of 2 mm, and 1 vertebra had a cage collapsed into the vertebra. This setup is suitable for biomechanical testing of cyclical continuous loads on the spine with reduced bone quality or osteoporosis. The embedding method is stable and ensures a purely single-level setup with different trajectories, especially when using the cortical bone trajectory. Optical monitoring provides a very accurate indication of cage movement, which correlates with the macroscopic and radiological results.

Preoperative lordosis in L4/5 predicts segmental lordosis correction achievable by transforaminal lumbar interbody fusion.

The mean potential of lordosis restoration by transforaminal lumbar interbody fusion (TLIF) is supposed to be low in general. In contrast, clinical experience shows a wide range of segmental lordosis correction. In this study, the predictability of lordosis correction should be investigated. Prospectively collected register data were analyzed retrospectively. One hundred twenty-one consecutive patients (2014-2016) operated with single-level TLIF L4/5 (10°-lordotic cage). Segmental lordosis (L4/5) and overall lordosis (L1-S1) were measured on lumbar X-rays: preoperatively (pre), after 3-5days (post), at least 24months postoperatively (2yFU). Outcome and satisfaction of patients were assessed. Parameters were statistically compared by students t-tests (a = 0.05). In addition, predictors of correction were analyzed. Age was 60.7years, rate of 2yFU 41.3% (n = 50). Lordosis correction L4/5 was statistically significant with (post-pre) 4.9 ± 5.7° (p < 0.01), but not significant for L1-S1 (post-pre) 1.6 ± 8.0° (p = 0.3). A strong-moderate correlation of lordosis L4/5 (pre) and lordosis correction L4/5 (post-pre) was shown (r = - 0.6, p < 0,01). In a rising range of preoperative lordosis L4/5 from 15-30° the likelihood of lordosis loss increased. In 2yFU correction, L4/5 was significant with (post-pre) 5.4 ± 5.4° (p < 0.01), no significant long-term change (2yFU-postop) - 1.5 ± 4.9° (p = 0.2). No correlation (r = - 0.1) of correction and ODI. VAS-B improved by means of 2.9, VAS-L by 2.5, ODI by 19.1% (pre vs. 2yFU), each statistically significant (p < 0.01). Significant segmental relordosation can be performed by TLIF L4/5. The potential of correction strongly correlates with preoperative lordosis. Therefore, TLIF technique should be considered carefully in cases with a preoperative segmental lordosis of more than 15° and additional need of lordosation.