Unilateral transforaminal lumbar interbody fusion: a review of the technique, indications and graft materials

Lateral-PLIF for spinal arthrodesis: concept, technique, results, complications, and outcomes

BACKGROUND

Posterior lumbar interbody fusion (PLIF) surgery represents an effective option to treat degenerative conditions in the lumbar spine. To reduce the drawbacks of the classical technique, we developed a variant, so-called Lateral-PLIF, which we then evaluated through a prospective consecutive series of patients.

METHODS

All adult patients treated at our institute with single or double level Lateral-PLIF for lumbar degenerative disease from January to December 2017 were prospectively collected. Exclusion criteria were patients < 18 years of age, traumatic patients, active infection, or malignancy, as well as unavailability of clinical and/or radiological follow-up data. The technique consists of insert the cages bilaterally through the transition zone between the central canal and the intervertebral foramen, just above the lateral recess. Pre- and postoperative (2 years) questionnaires and phone interviews (4 years) assessed pain and functional outcomes. Data related to the surgical procedure, postoperative complications, and radiological findings (1 year) were collected.

RESULTS

One hundred four patients were selected for the final analysis. The median age was 58 years and primary symptoms were mechanical back pain (100, 96.1%) and/or radicular pain (73, 70.2%). We found a high fusion rate (95%). A statistically significant improvement in functional outcome was also noted (ODI p < 0.001, Roland-Morris score p < 0.001). Walking distance increased from 812 m ± 543 m to 3443 m ± 712 m (p < 0.001). Complications included dural tear (6.7%), infection/wound dehiscence (4.8%), and instrument failure (1.9%) but no neurological deterioration.

CONCLUSIONS

Lateral-PLIF is a safe and effective technique for lumbar interbody fusion and may be considered for further comparative study validation with other techniques before extensive use to treat lumbar degenerative disease.

Different lumbar fusion techniques for lumbar spinal stenosis: a Bayesian network meta-analysis

OBJECTIVE

To comprehensively compare and assess the effects of different lumbar fusion techniques in patients with lumbar spinal stenosis (LSS).

METHODS

PubMed, Embase, Cochrane Library, and Web of Science databases were systematically searched up to December 24, 2022 in this network meta-analysis. Outcomes were pain (pain, low back pain, and leg pain), Japanese Orthopaedic Association (JOA), Oswestry Disability Index (ODI), complications, reoperation, and fusion. Network plots illustrated the direct and indirect comparisons of different fusion techniques for the outcomes. League tables showed the comparisons of any two fusion techniques, based on both direct and indirect evidence. The efficacy of each fusion technique for LSS was ranked by rank probabilities.

RESULTS

Totally 29 studies involving 2,379 patients were eligible. For pain, percutaneous endoscopic transforaminal lumbar interbody fusion (Endo-TLIF) was most likely to be the best technique, followed by minimally invasive transforaminal lumbar interbody fusion (MIS-TLIF), extreme lateral interbody fusion (XLIF), and transforaminal lumbar interbody fusion (TLIF). Percutaneous endoscopic posterior lumbar interbody fusion (Endo-PLIF) had the greatest likelihood to be the optimal technique for low back pain, followed sequentially by MIS-TLIF, minimally invasive posterior lumbar interbody fusion (MIS-PLIF), XLIF, Endo-TLIF, TLIF, oblique lumbar interbody fusion (OLIF), posterior lumbar interbody fusion (PLIF), and posterolateral lumbar fusion (PLF). MIS-PLIF was ranked the most effective technique concerning leg pain, followed by Endo-TLIF, MIS-TLIF, TLIF, Endo-PLIF, PLIF, OLIF, PLF, and XLIF. As regards JOA scores, Endo-TLIF had the maximum probability to be the best technique, followed by MIS-TLIF and TLIF. Endo-PLIF had the greatest likelihood to be the optimum technique for complications, followed by TLIF, MIS-TLIF, Endo-TLIF, OLIF, and XLIF.

CONCLUSION

Minimally invasive fusion techniques may be effective in the treatment of LSS, compared with traditional techniques. Minimally invasive techniques were likely non-inferior with regards to postoperative complications.

Short-term clinical efficacy and safety of unilateral biportal endoscopic transforaminal lumbar interbody fusion versus minimally invasive transforaminal lumbar interbody fusion in the treatment of lumbar degenerative diseases: a systematic review and meta-analysis

BACKGROUND

The aim of this study was to comprehensively evaluate the short-term clinical efficacy and safety of unilateral biportal endoscopic transforaminal lumbar interbody fusion (UBE-TLIF) versus minimally invasive transforaminal lumbar interbody fusion (MIS-TLIF) for the treatment of lumbar degenerative diseases by meta-analysis.

METHODS

A computer-based search of PubMed, Embase, Web of Science, Cochrane Database, China National Knowledge Infrastructure (CNKI), Wanfang Database, and Chinese Science and Technology Journal Database (VIP) was conducted from the inception of the each database to April 2023. The searched literature was then screened according to strict inclusion and exclusion criteria. The critical data were extracted and analyzed using Review Manager software5.4.1. Pooled effects were calculated on the basis of data attributes by mean difference (MD) or odds ratio (OR) with 95% confidence interval (CI). The Newcastle-Ottawa Scale was used to assess the quality of the studies.

RESULTS

A total of 13 studies and 949 patients met the inclusion criteria for this meta-analysis, 445 in the UBE-LIF group and 504 in the MIS-TLIF group. UBE-TLIF was superior to MIS-TLIF in terms of intraoperative blood flow, postoperative drainage flow, duration of hospital stay, VAS score for low back pain and ODI score, but the operative time was longer than MIS-TLIF group. There were no significant differences between the two groups in terms of total complication rate, modified Macnab grading criteria, fusion rate, VAS score of leg pain, lumbar lordosis, intervertebral disk height.

CONCLUSION

Both UBE-TLIF and MIS-TLIF are effective surgical modalities for the treatment of degenerative lumbar spine diseases. They have similar treatment outcomes, but UBE-TLIF has the advantages of less intraoperative blood loss, shorter postoperative hospital stay, and faster recovery.

TRIAL REGISTRATION

This study has been registered at INPLASY.COM (No. INPLASY202320087).

Clinical and Cost-Effectiveness of Lumbar Interbody Fusion Using Tritanium Posterolateral Cage (vs. Propensity-Matched Cohort of PEEK Cage)

Introduction

Surgical management of degenerative lumbar spine disorders is effective at improving patient pain, disability, and quality of life; however, obtaining a durable posterolateral fusion after decompression remains a challenge. Interbody fusion technologies are viable means of improving fusion rates in the lumbar spine, specifically various graft materials including autograft, structural allograft, titanium, and polyether ether ketone. This study assesses the effectiveness of Tritanium posterolateral cage in the treatment of degenerative disk disease.

Methods

Nearest-neighbor 1:1 matched control transforaminal lumbar interbody fusion with PEEK vs. Tritanium posterior lumbar (PL) cage interbody fusion patients were identified using propensity scoring from patients that underwent elective surgery for degenerative disk diseases. Line graphs were generated to compare the trajectories of improvement in patient-reported outcomes (PROs) from baseline to 3 and 12 months postoperatively. The nominal data were compared via the χ² test, while the continuous data were compared via Student's t-test.

Results

The two groups had no difference regarding either the 3- or 12-month Euro-Qol-5D (EQ-5D), numeric rating scale (NRS) leg pain, and NRS back pain; however, the Tritanium interbody cage group had better Oswestry Disability Index (ODI) scores compared to the control group of the PEEK interbody cage at both 3 and 12 months (p=0.013 and 0.048).

Conclusions

Our results indicate the Tritanium cage is an effective alternative to the previously used PEEK cage in terms of PROs, surgical safety, and radiological parameters of surgical success. The Tritanium cohort showed better ODI scores, higher fusion rates, lower subsidence, and lower indirect costs associated with surgical management, when compared to the propensity-matched PEEK cohort.

Unilateral versus Bilateral Pedicle Screw Instrumented Transforaminal Interbody Fusion in a Single Level Lumbar Spondylolisthesis

Background The study aims to assess the efficiency, safety and outcome of unilateral pedicle screw fixation with TLIF (Transforaminal lumbar interbody fusion) vs bilateral pedicle screw fixation with TLIF in cases of single level spondylolisthesis by comparing clinical, functional outcome and the complication rates. Methods We prospectively collected demographics and clinical data of the patients with surgically treated single level lumbar spondylolisthesis grade 1 (n=60) with follow up and comparison between clinical/functional outcomes and complication rates between January 2020 and January 2021 at Cairo University hospitals. We allocated the patients with the unilateral pedicle screw fixation with TLIF as group A and the patients with the bilateral pedicle screw fixation with TLIF as group B. Results Clinical outcome showed statistical significance between Group A and Group B (P-value < 0.001); Functional outcome (using Oswestry’s disability index) between group A and B also showed statistical significance (P-value < 0.001) in favor of group B. Complications in group A was higher especially cage migration in 26.7% of cases with p-value of 0.026 while it was only present in 3.3% of the group B cases. Conclusion We concluded that the bilateral approach showed a statistically significant better clinically/functional outcomes with lower rates of complication in comparison with the unilateral approach.

Hydroxyapatite/collagen composite graft for posterior lumbar interbody fusion: a comparison with local bone graft

Background

Autologous bone has been used for posterior lumbar intervertebral fusion (PLIF). However, harvesting autologous bone graft is associated with donor site complications. We previously developed a hydroxyapatite/collagen (HAp/Col) composite as an osteoconductive artificial bone, characterized by having a highly porous structure with sponge‐like elasticity. This study aims to investigate the effectiveness of HAp/Col composite with bone marrow aspirate (BMA) as a graft substitute in PLIF for the treatment of lumbar spinal diseases.

Methods

This study prospectively investigated patients who received one-level PLIF. For the interbody fusion, two titanium cages were inserted. On the one side of interbody space, HAp/Col composite incorporated with BMA filling the titanium cage was grafted. On the other side, local bone graft (LBG) harvested during decompressive laminotomy was grafted and then one-level instrumentation using pedicle screws was performed. The target levels were at L2/3 in 2 cases, L3/4 in 3 cases, L4/5 in 36 cases, and L5/S in 5 cases. We evaluated clinical symptoms and radiological outcomes of 46 patients and compared the fusion status of HAp/Col composite with that of LBG.

Results

The 1-year postoperative CT evaluation demonstrated that, in the HAp/Col, a complete fusion was observed in 38 patients (82.6%), whereas in the LBG, a complete fusion was observed in 35 patients (76.1%). There were no statistical differences between the HAp/Col and LBG. In the HAp/Col, incomplete fusion was observed in five patients (10.9%) and non-fusion in two patients (4.3%), and in the LBG, incomplete fusion was observed in nine patients (19.6%) and non-fusion in two patients (4.3%). At 2 years after the surgery, complete fusion increased to 44 patients (95.7%) in the HAp/Col and 41 patients (89.1%) in the LBG. There were no significant differences in the clinical scores for lumbar spine between patients with fusion and non-fusion.

Conclusions

The HAp/Col composite with BMA in the titanium cage can be effectively used as an alternative to conventional autologous LBG for intervertebral spinal fusion.

Trial registration University hospital Medical Information Network, UMIN000045010, July 30th, 2021, Retrospectively registered, https://www.umin.ac.jp/english/.

Effect of the short-segment internal fixation with intermediate inclined-angle polyaxial screw at the fractured vertebra on the treatment of Denis type B thoracolumbar fracture

BACKGROUND

Short-segment internal fixation with intermediate straight-forward monoaxial screws (SSIF-SFM) and long-segment internal fixation (LSIF) are the two major surgical options for thoracolumbar (TL) fracture. However, SSIF-SFM might not provide adequate support to the spine, and LSIF is unnecessarily extensive. SSIF with intermediate inclined-angle polyxial screw (SSIF-IAP) might offer an alternative solution for the treatment of TL fracture.

METHODS

A retrospective study was conducted. Sixty-nine patients (47 males and 22 females; average 34.5 years) with Denis type B TL fracture who met the criteria for inclusion were enrolled. Sagittal Cobb's angle (SCA), anterior vertebral body height (AVBH), vertebral body index (VBI), and spinal canal encroachment (SCE) were measured and assessed. Visual analogue scale (VAS) and Oswestry disability index (ODI) were also evaluated.

RESULTS

The average values of incision length, blood loss, duration of operation, and hospital stay in the SSIF-IAP group and SSIF-SFM group were significantly decreased compared with those in the LSIF group. The AVBH and VBI in the SSIF-IAP group and LSIF group were significantly improved than those in the SSIF-SFM group at 6-month and the latest follow-ups (P < 0.05). The correction losses of AVBH and VBI (calculated by the reduction of AVBH and VBI) in the SSIF-IAP group and LSIF group were also significantly decreased compared with those in the SSIF-SFM group at 6-month and the latest follow-ups (P < 0.05). There was no significant difference of SCE among the three groups postoperatively. The VAS and ODI in the SSIF-IAP group and SSIF-SFM group were significantly decreased compared with those in the LSIF group at 6-month and the latest follow-ups (P < 0.05).

CONCLUSION

Both SSIF-IAP and LSIF can improve the biomechanical stability as compared with SSIF-SFM. Moreover, SSIF-IAP was less extensive compared to LSIF. SSIF-IAP was an effective and reliable operative technique for patients with Denis type B TL fracture.

Fracture of allograft interbody spacer resulting in post-operative radiculopathy: A case report

BACKGROUND

Allograft interbody spacers are utilized during transforaminal lumbar interbody fusion (TLIF) to reestablish anterior column support and disc height. While the TLIF technique offers many improvements over previous surgical methods, instrumentation and bone graft-related complications such as spacer misplacement or migration, screw fracture or misplacement, or rod breakage continue to be reported. The objective of this manuscript is to report on a fractured allograft interbody spacer that displaced into the neural foramen and resulted in impingement on the exiting nerve root that required revision.

CASE SUMMARY

A 50-year-old male had two-level TLIF with immediate post-operative right L5 radiculopathy. Computed tomography scan demonstrated a fractured allograft interbody spacer that displaced into the right neural foramen and impinged on the exiting L5 nerve root. Revision surgery was performed to remove the broken allograft fragments from the right L5 foramen and the intact portion of the spacer was left in place. The right leg L5 radicular pain resolved. At the last follow up 12 mo after the index procedure, computed tomography scan confirmed sound interbody and posterolateral fusion.

CONCLUSION

Displacement of broken allograft interbody spacer following TLIF procedures can result in neurological sequelae that require revision. To avoid such an occurrence, the authors recommend allowing sufficient time for the reconstitution of the graft in saline prior to use to decrease brittleness, to use an impactor size that is as close as possible to the spacer size and meticulous inspection of the cortical allograft spacer for any visible imperfection prior to insertion.

Morphological changes of contralateral intervertebral foramen induced by cage insertion orientation after unilateral transforaminal lumbar interbody fusion

Background

This study was performed to investigate the morphological changes of contralateral intervertebral foramen (IVF) based on computed tomography images of patients with lumbar spinal stenosis after unilateral transforaminal lumbar interbody fusion (TLIF) and to compare the influence of different orientation of cage insertion on these changes.

Methods

This is a retrospective cohort study. Sixty-nine patients with lumbar spinal stenosis who had undergone single-level unilateral TLIF were retrospectively analyzed. The patients were divided into two groups according to the cage insertion orientation: the oblique group (o-group, 39 cases) and the transverse group (t-group, 30 cases). The morphological parameters of contralateral IVF were measured before and 6 months after the operation. Changes in these parameters were compared and analyzed between the two groups. The 6-month clinical outcomes of the two groups were also collected and analyzed.

Results

There was a significant difference in the rate of increase in the segmental angle (p < 0.01) between the two groups, the mean value of segmental angle increased by an average of 29.08% ± 14.93% in the o-group and 48.63% ± 12.01% in the t-group. Overall, the posterior disc height had a significant positive correlation with the foraminal height and area. In the o-group, however, an increase in the segmental angle resulted in a decrease in the foraminal area. No significant difference in clinical outcomes was found between the two groups.

Conclusions

Compared with oblique cage insertion, transverse cage insertion could achieve greater restoration of segmental lumbar lordosis without decreasing contralateral foraminal dimensions.

Evaluation of the discal height gain and lumbar lordosis variation obtained by the techniques of transforaminal and posterior lumbar intersomatic fusion

Objective

Evaluate the discal height and lumbar lordosis gains, comparatively, according to the two lumbar arthrodesis techniques, transforaminal lumbar interbody fusion (TLIF) and posterior lumbar interbody fusion (PLIF), used in the treatment of spinal degenerative diseases.

Methods

The present study, retrospective, was done with 60 patients who underwent decompression and 1 level lumbar arthrodesis in the Hospital Santa Casa de Misericórdia de Vitória (HSCMV), between January 2010 and December 2015. The patients were divided in two groups of 30 each, according to the utilized intersomatic arthrodesis technique: TLIF or PLIF. All patients presented pathologies at the L4-L5 level. In this study, the discal height gain and lumbar lordosis variation were evaluated by analyzing spinal radiographies of the pre and post-operatory periods from patients of the two groups, measured by the software Surgimap^®. In addition, the pain intensity in the post-operatory period was estimated by the Visual Analog Scale for Pain (VAS Pain).

Results

Both techniques presented a gain in the discal height in the post-operatory. There was no statistically significant difference between the discal height variation obtained with the PLIF technique when compared to the TLIF technique (p = 0.139). In the same way, there was no statistically significant difference in the lumbar lordosis variation between the two studied groups (p = 0.184). By the EVA Pain analysis, there was no significant difference in the pain intensity in the post-operatory period between both arthrodesis surgeries.

Conclusion

There is no difference in the discal height gain and lumbar lordosis variation, as well as in the pain intensity in the post-operatory periods, in patients who underwent 1 level intersomatic arthrodesis when comparing the PLIF and TLIF techniques.

A prospective clinical study comparing MI-TLIF with unilateral versus bilateral transpedicular fixation in low grade lumbar spondylolisthesis

BACKGROUND

Minimally invasive transforaminal lumbar interbody fusion (MI-TLIF) has become one of the standard techniques for approaching ipsilateral decompression, anterior column fusion, and posterior stabilization. This procedure is usually accompanied by the placement of bilateral transpedicular screws in the corresponding segment. The purpose of this study was to evaluate the clinical efficacy of unilateral screw fixation compared with bilateral fixation in patients diagnosed with low-grade symptomatic lumbar spondylolisthesis who underwent an MI-TLIF technique.

METHODS

A prospective and comparative study was performed in 67 patients with grade 1 symptomatic lumbar spondylolisthesis. The sample was allocated on both unilateral fixation group (n=33) and bilateral fixation group (n=34). Clinical outcomes were evaluated using Oswestry Disability Index (ODI), visual analogue scale (VAS) for leg and back pain, and Short Form 36 Health Survey (SF-36), preoperatively, and at 1, 3, 6, and 12 months postoperatively. Changes over time and differences between the groups were analyzed. Statistical analyses included: Friedman test, Student's t-test and Mann-Whitney's U. A two-tailed P value of <0.05 was considered significant.

RESULTS

During 1-year of evaluation there were no significant clinical differences between both groups.

CONCLUSIONS

Patients with grade 1 symptomatic lumbar spondylolisthesis treated with MI-TLIF with unilateral screw fixation had similar clinical results than those treated with bilateral fixation at 12 months postoperatively.

Comparison of Clinical and Radiographic Outcomes in Patients Receiving Single-Level Transforaminal Lumbar Interbody Fusion With Removal of Unilateral or Bilateral Facet Joints

STUDY DESIGN

A retrospective cohort study.

OBJECTIVE

The objective of this study is to compare the radiographic and clinical outcomes of transforaminal lumbar interbody fusion (TLIF) with bilateral facetectomy (BF) versus unilateral facetectomy (UF).

SUMMARY OF BACKGROUND DATA

BF is a surgical technique utilized with the intent of creating a greater degree of segmental lordosis than UF alone. However, the clinical benefits of this technique have not been defined. We seek to determine whether a difference exists between bilateral versus UF during TLIF by utilizing both clinical and radiographic outcome measures.

METHODS

The electronic medical records of 57 patients who underwent single-level TLIF with either a UF (n = 28) or BF (n = 29) were reviewed. Clinical outcomes were measured through Patient Health Questionnaire-9 (PHQ-9), Pain Disability Questionnaire (PDQ), EuroQol 5 Dimensions (EQ-5D) Health State, and Quality Adjusted Life Year (QALY). Radiographic parameters including disc height and sagittal balance were measured on plain radiographs at 1 year following operation.

RESULTS

All radiographic parameters showed no significant differences between the UF and BF cohorts. Segmental lordosis increased significantly in both cohorts. However, there was no significant difference in the increase of segmental lordosis between cohorts. Overall lumbar lordosis did not increase significantly in either cohort. Perioperative complications were also similar between cohorts. PDQ and EQ-5D scores improved significantly in both cohorts at 1 year postoperatively. The BF cohort showed a significantly greater improvement in both EQ-5D (0.1 ± 0.2 vs. 0.3 ± 0.2, P = 0.01) and PHQ-9 scores (-0.8 ± 4.6 vs. 4.6 ± 5.2, P = 0.03) than the UF cohort. The PDQ score improved over the minimally clinical important difference (MCID) of 26 in only the BF cohort.

CONCLUSION

The findings in the present study demonstrate that BF during single-level TLIF improves clinical outcomes to a greater degree than UF without any notable differences in perioperative complications or radiographic measurements.

LEVEL OF EVIDENCE

3.

Bilateral pedicle screw fixation provides superior biomechanical stability in transforaminal lumbar interbody fusion: a finite element study

BACKGROUND CONTEXT

Transforaminal lumbar interbody fusion (TLIF) is increasingly popular for the surgical treatment of degenerative lumbar disease. The optimal construct for segmental stability remains unknown.

PURPOSE

To compare the stability of fusion constructs using standard (C) and crescent-shaped (CC) polyetheretherketone TLIF cages with unilateral (UPS) or bilateral (BPS) posterior instrumentation.

STUDY DESIGN

Five TLIF fusion constructs were compared using finite element (FE) analysis.

METHODS

A previously validated L3-L5 FE model was modified to simulate decompression and fusion at L4-L5. This model was used to analyze the biomechanics of various unilateral and bilateral TLIF constructs. The inferior surface of the L5 vertebra remained immobilized throughout the load simulation, and a bending moment of 10 Nm was applied on the L3 vertebra to recreate flexion, extension, lateral bending, and axial rotation. Various biomechanical parameters were evaluated for intact and implanted models in all loading planes.

RESULTS

All reconstructive conditions displayed decreased motion at L4-L5. Bilateral posterior fixation conferred greater stability when compared with unilateral fixation in left lateral bending. More than 50% of intact motion remained in the left lateral bending with unilateral posterior fixation compared with less than 10% when bilateral pedicle screw fixation was used. Posterior implant stresses for unilateral fixation were six times greater in flexion and up to four times greater in left lateral bending compared with bilateral fixation. No effects on segmental stability or posterior implant stresses were found. An obliquely-placed, single standard cage generated the lowest cage-end plate stress.

CONCLUSIONS

Transforaminal lumbar interbody fusion augmentation with bilateral posterior fixation increases fusion construct stability and decreases posterior instrumentation stress. The shape or number of interbody implants does not appear to impact the segmental stability when bilateral pedicle screws are used. Increased posterior instrumentation stresses were observed in all loading modes with unilateral pedicle screw/rod fixation, which may theoretically accelerate implant loosening or increase the risk of construct failure.

Clinical and radiologic outcomes of TLIF applications with or without pedicle screw: a double center prospective pilot comparative study

STUDY DESIGN

Prospective cohort data by merging data from comparative studies.

OBJECTIVE

This study aimed to compare clinical and radiologic outcomes of the transforaminal lumbar interbody fusion (TLIF) procedure with or without pedicle screw support in stable patients with a degenerative disease.

SUMMARY OF BACKGROUND DATA

The unilateral lumbar interbody fusion technique has gained popularity in the management of many lumbar degenerative conditions requiring fusion. TLIF is routinely performed with the support of pedicle screws. The use of the TLIF procedure without pedicle screw support has not yet been reported.

METHODS

Between February 2006 and May 2009, surgical decompression and fusion was performed in patients with lumbar degenerative conditions using the TLIF technique either with (n=30, group A) or without pedicle screw support (n=30, group B). The 2 groups had similar age, sex distribution, pain level, and pain history. In this prospective study, patients were followed for a mean period of 31 months (range, 22 to 38 mo). The mean age was 45.5 years (range, 29 to 78 y), and all patients had a disease involving a single intervertebral space.

RESULTS

The female to male ratio was 19:11 and 18:12 in groups A and B, respectively. Pain and function were evaluated by the Oswestry disability index and visual analog scale. Pseudoarthrosis developed in 2 patients from group A and in 3 patients from group B. Although these 5 patients had insufficient fusion, they did show a clinical improvement. The mean duration of the operation was 110 and 73 minutes in groups A and B, respectively. The mean total amount of bleeding was 410 and 220 mL in groups A and B, respectively. Cage loosening did not occur in group A, but 1 patient in group B developed asymptomatic cage loosening limited to the endplates. Four patients in group A suffered sciatic pain because of the malposition of the screw, and 1 patient in group B had contralateral sciatic pain lasting for 2 months. The visual analog scale and Oswestry disability index scores were higher in group A than in group B 1 month after the operation (P<0.005), but the groups did not significantly differ at 3 months (P<0.89). The cost of the procedure was 3-fold higher in group A compared with group B.

CONCLUSIONS

This study showed that the TLIF procedure without pedicle screw support would be sufficient in the management of preoperatively stable patients with lumbar degenerative spinal disease requiring fusion after single-level decompression. This technique is minimally invasive, requires only unilateral intervention, allows magnetic resonance imaging during the postoperative period and is associated with less costs and complications when compared with pedicle screwing. This study represents the first prospective comparative report on this technique showing several of its advantages.

MRI of transforaminal lumbar interbody fusion: imaging appearance with and without the use of human recombinant bone morphogenetic protein-2 (rhBMP-2)

PURPOSE

To describe the vertebral endplate and intervertebral disc space MRI appearance following TLIF, with and without the use of rhBMP-2, and to determine if the appearance is concerning for discitis/osteomyelitis.

MATERIALS AND METHODS

After institutional review board approval, 116 TLIF assessments performed on 75 patients with rhBMP-2 were retrospectively and independently reviewed by five radiologists and compared to 73 TLIF assessments performed on 45 patients without rhBMP-2. MRIs were evaluated for endplate signal, disc space enhancement, disc space fluid, and abnormal paraspinal soft tissue. Endplate edema-like signal was reported when T1-weighted hypointensity, T2-weighted hyperintensity, and endplate enhancement were present. Subjective concern for discitis/osteomyelitis on MRI was graded on a five-point scale. Generalized estimating equation binomial regression model analysis was performed with findings correlated with rhBMP-2 use, TLIF level, graft type, and days between TLIF and MRI.

RESULTS

The rhBMP-2 group demonstrated endplate edema-like signal (OR 5.66; 95% CI [1.58, 20.24], p = 0.008) and disc space enhancement (OR 2.40; 95% CI [1.20, 4.80], p = 0.013) more often after adjusting for the TLIF level, graft type, and the number of days following TLIF. Both groups had a similar temporal distribution for endplate edema-like signal but disc space enhancement peaked earlier in the rhBMP-2 group. Disc space fluid was only present in the rhBMP-2 group. Neither group demonstrated abnormal paraspinal soft tissue and discitis/osteomyelitis was not considered likely in any patient.

CONCLUSIONS

Endplate edema-like signal and disc space enhancement were significantly more frequent and disc space enhancement developed more rapidly following TLIF when rhBMP-2 was utilized. The concern for discitis/osteomyelitis was similar and minimal in both groups.

Digitalized design of extraforaminal lumbar interbody fusion: a computer-based simulation and cadaveric study

Purpose

This study aims to investigate the feasibility of a novel lumbar approach named extraforaminal lumbar interbody fusion (ELIF), a newly emerging minimally invasive technique for treating degenerative lumbar disorders, using a digitalized simulation and a cadaveric study.

Methods

The ELIF surgical procedure was simulated using the Mimics surgical simulator and included dissection of the superior articular process, dilation of the vertebral foramen, and placement of pedicle screws and a cage. ELIF anatomical measures were documented using a digitalized technique and subsequently validated on fresh cadavers.

Results

The use of the Mimics allowed for the vivid simulation of ELIF surgical procedures, while the cadaveric study proved the feasibility of this novel approach. ELIF had a relatively lateral access approach that was located 8–9 cm lateral to the median line with an access depth of approximately 9 cm through the intermuscular space. Dissection of the superior articular processes could fully expose the target intervertebral discs and facilitate a more inclined placement of the pedicle screws and cage with robust enhancement.

Conclusions

According to the computer-based simulation and cadaveric study, it is feasible to perform ELIF. Further research including biomechanical study is needed to prove ELIF has a superior ability to preserve the posterior tension bands of the spinal column, with similar effects on spinal decompression, fixation, and fusion, and if it can enhance post-fusion spinal stability and expedites postoperative recovery.

Increased incidence of pseudarthrosis after unilateral instrumented transforaminal lumbar interbody fusion in patients with lumbar spondylosis: Clinical article

OBJECT

Transforaminal lumbar interbody fusion (TLIF) with segmental pedicular instrumentation is a well established procedure used to treat lumbar spondylosis with or without spondylolisthesis. Available biomechanical and clinical studies that compared unilateral and bilateral constructs have produced conflicting data regarding patient outcomes and hardware complications.

METHODS

A prospective cohort study was undertaken by a group of neurosurgeons. They prospectively enrolled 80 patients into either bilateral or unilateral pedicle screw instrumentation groups (40 patients/group). Demographic data collected for each group included sex, age, body mass index, tobacco use, and Workers' Compensation/litigation status. Operative data included segments operated on, number of levels involved, estimated blood loss, length of hospital stay, and perioperative complications. Long-term outcomes (hardware malfunction, wound dehiscence, and pseudarthrosis) were recorded. For all patients, preoperative baseline and 6-month postoperative scores for Medical Outcomes 36-Item Short Form Health Survey (SF-36) outcomes were recorded.

RESULTS

Patient follow-up times ranged from 37 to 63 months (mean 52 months). No patients were lost to follow-up. The patients who underwent unilateral pedicle screw instrumentation (unilateral cohort) were slightly younger than those who underwent bilateral pedicle screw instrumentation (bilateral cohort) (mean age 42 vs. 47 years, respectively; p = 0.02). No other significant differences were detected between cohorts with regard to demographic data, mean number of lumbar levels operated on, or distribution of the levels operated on. Estimated blood loss was higher for patients in the bilateral cohort, but length of stay was similar for patients in both cohorts. The incidence of pseudarthrosis was significantly higher among patients in the unilateral cohort (7 patients [17.5%]) than among those in the bilateral cohort (1 patient [2.5%]) (p = 0.02). Wound dehiscence occurred for 1 patient in the unilateral cohort. Reoperation was offered to 8 patients in the unilateral cohort and 1 patient in the bilateral cohort (p = 0.03). The physical component scores of the Medical Outcomes SF-36 outcomes improved significantly for all patients (p < 0.001).

CONCLUSIONS

Transforaminal lumbar interbody fusion with either unilateral or bilateral segmental pedicular instrumentation is an effective treatment for lumbar spondylosis. Because patients with unilateral constructs were 7 times more likely to experience pseudarthrosis and require reoperation, TLIF with bilateral constructs might be the biomechanically superior technique.

Lumbar spinal stenosis: who should be fused? An updated review

Lumbar spinal stenosis (LSS) is mostly caused by osteoarthritis (spondylosis). Clinically, the symptoms of patients with LSS can be categorized into two groups; regional (low back pain, stiffness, and so on) or radicular (spinal stenosis mainly presenting as neurogenic claudication). Both of these symptoms usually improve with appropriate conservative treatment, but in refractory cases, surgical intervention is occasionally indicated. In the patients who primarily complain of radiculopathy with an underlying biomechanically stable spine, a decompression surgery alone using a less invasive technique may be sufficient. Preoperatively, with the presence of indicators such as failed back surgery syndrome (revision surgery), degenerative instability, considerable essential deformity, symptomatic spondylolysis, refractory degenerative disc disease, and adjacent segment disease, lumbar fusion is probably recommended. Intraoperatively, in cases with extensive decompression associated with a wide disc space or insufficient bone stock, fusion is preferred. Instrumentation improves the fusion rate, but it is not necessarily associated with improved recovery rate and better functional outcome.

Finite element analysis of 3 posterior fixation techniques in the lumbar spine

This study compared the biomechanics of 3 fixation techniques: bilateral pedicle screw (BPS) fixation, unilateral pedicle screw (UPS) fixation, and UPS supplemented with translaminar facet screw (UPS+TLFS) fixation. The study was conducted in an L3-L5 finite element model. Three different finite element models were created by adopting different fixation techniques after removal of the left L3-L4 and L4-L5 facet joints. A 500-N compressive preload combined with 8-NM moment were applied in 3 finite element models with 3 fixation techniques during different movements. Angular displacement and stress distribution were recorded. As described in this article, the UPS model had the most variation in angular displacement, the BPS model was intermediate, and the UPS+TLFS model had the least mobility. Most of the stress accumulated on the body and tail of the pedicle screws and the connecting rods in the UPS and BPS models, but stress accumulated on the rods and the part of the facet joint pierced by the TLFS in the UPS+TLFS model. The middle part of the pedicle screw endured little stress compared with the upper and lower parts. The maximum stress on the fixation devices was highest in the UPS model. The maximum stress in the UPS+TLFS model was the lowest among the 3 models. Biomechanically, UPS+TLFS fixation is superior to either UPS fixation or BPS fixation in improving stability and reducing stress. Bilateral pedicle screw fixation is intermediate, and UPS fixation is inferior.

Biomechanical assessment of unilateral pedicle screws plus contralateral transfacetopedicular screws after transforaminal lumbar interbody fusion with two cages

OBJECTIVE

To assess the biomechanical stability of unilateral pedicle screws (UPS) plus contralateral transfacetopedicular screws (TFPS) after transforaminal lumbar interbody fusion (TLIF) with two cages.

METHODS

Range of motion (ROM) testing was performed in 28 fresh-frozen human cadaveric lumbar spine motion segments. The sequential test configurations included supplemental constructs after TLIF such as UPS, UPS plus contralateral TFPS and bilateral pedicle screws (BPS). All test specimens were fixated in the normal lordotic lignment, then mounted in a three-dimensional (3-D) motion testing machine and fixed to the load frame of a six degrees of freedom spine simulator. Each of the test constructs were subjected to three load-unload cycles in each of the physiologic planes generating flexion-extension, right-left lateral bending and right-left axial rotation load-displacement curves. Statistical analysis was performed on the ROM data. Comparison of data was performed by repeated-measures analysis of variance for independent samples followed by Bonferroni analysis for multiple comparison procedures.

RESULTS

The ROMs for UPS, BPS and UPS plus TFPS fixation after TLIF were significantly smaller than those of the intact spine in all modes. The ROM for UPS plus TFPS fixation was between the largest for UPS and the smallest for BPS. The differences between ROMs of UPS and UPS plus TFPS were significant for both lateral bending and rotation. There were no significant differences between BPS and UPS plus TFPS in any mode.

CONCLUSION

Because the UPS construct provides the least stability, especially during lateral bending and rotation, it should be used prudently. After TLIF with two cages, UPS plus TFPS provides stability comparable to that of TLIF with BPS. It is thus an acceptable option in minimally invasive surgery.

Cage migration after transforaminal lumbar interbody fusion and factors related to it

OBJECTIVE

To review and analyze cage migration and related risk factors in patients who have undergone transforaminal lumbar interbody fusion (TLIF).

METHODS

A retrospective study was conducted to review the complications of cage migration in 512 patients who had undergone a TLIF procedure from January 2010 to June 2011 in five spinal centers. In all, 263 men and 249 women with a mean age of 54.7 years were included. All patients were followed up at 3, 6 and 12 months after the procedure. The clinical outcomes were evaluated by visual analogue scores, the Oswestry disability index, plain radiography and three-dimensional CT scanning to analyze the incidence of, and risk factors related to, cage migration.

RESULTS

Cage migration was found in 6 of the 512 patients (1.17%). Significant differences were found between all pairs of centers. Different shapes and sizes of cages had different incidences of migration. Analysis showed that rectangular-shaped cages had a significantly greater incidence of cage migration (3.11%, 5/161) than did kidney-shaped cages (0.28%, 1/351; P < 0.05). Small cages had a tendency to more frequent post-operative cage migration (5.13%, 4/78) than did large cages (0.46%, 2/434; P < 0.05). Double segment TLIF cages migrated more frequently (5.75%, 5/87) than did mono-segment cages (0.24%, 1/425; P < 0.05)). Furthermore, when the adjacent endplates were of linear type, the cages migrated much more frequently (3.50%) than when they were of concave-concave type (0.27%; P < 0.05).

CONCLUSION

Cage size, shape, number of fused segments and adjacent endplate shape might be risk factors for cage migration in addition to surgical technique, disc height and bone mineral density.

Short-term outcome of transforaminal lumbar interbody fusion for lytic and degenerative spondylolisthesis

PURPOSE

To compare early outcome of transforaminal lumbar interbody fusion (TLIF) for lytic versus degenerative spondylolisthesis.

METHODS

14 women and 8 men aged 20 to 60 (mean, 36) years underwent TLIF for lytic (n=15) or degenerative (n=7) spondylolisthesis. Of the 15 patients with lytic spondylolisthesis, 9 involved L4/ L5 and 6 L5/S1. Of the 7 patients with degenerative spondylolisthesis, 3 involved L4/L5, 2 L5/S1, one L2/L3, and one L3/L4. The spondylolistheses were classified as grade II (n=15), grade III (n=4), and retrolisthesis (n=3). 11 patients with lytic and 2 with degenerative spondylolisthesis had sensory deficits (n=12), motor deficits (n=9), and diminished reflexes (n=7). Visual analogue score (VAS) for pain and the Oswestry Disability Index (ODI) of each patient were assessed at months 3, 6, and 12, and 6 monthly thereafter. Fusion status was assessed by radiologists. Comprehensive outcome of each patient was graded as excellent, good, fair, or poor.

RESULTS

The mean VAS score for low back pain improved significantly from 7.4 preoperatively to 2.1 at year 1 (p<0.001), as did the mean VAS score for leg pain from 6.7 to 1.4 (p<0.001) and the mean ODI from 67.8% to 11.8% (p<0.001). No patient had any residual neurological deficit, and all achieved radiological fusion. The comprehensive outcome was excellent in 16 patients, good in 5, and fair in one. 16 patients returned to their previous level of activity.

CONCLUSION

TLIF is a safe and effective surgical procedure for the treatment of lytic and degenerative spondylolisthesis.

Comparison of unilateral versus bilateral instrumented transforaminal lumbar interbody fusion in degenerative lumbar diseases

BACKGROUND CONTEXT

Transforaminal lumbar interbody fusion (TLIF) has become a well-established technique that is traditionally performed with bilateral pedicle screw (PS) fixation. There are only a small number of case reports of unilateral instrumented TLIF. To our knowledge, there have been few well-designed studies comparing unilateral versus bilateral instrumentation with TLIF.

PURPOSE

To compare clinical and radiographic outcomes in a selected series of patients treated with unilateral versus bilateral PS instrumented TLIF.

STUDY DESIGN

Prospective randomized study in one unit.

PATIENT SAMPLE

A total of 80 patients were enrolled in this study. Thirty-seven patients (17 men and 20 women; average age 57.1 years) were randomized to the unilateral PS group and 43 patients (18 men and 25 women; average age 58.2 years) to the bilateral PS group.

OUTCOME MEASURES

The demographic data collected from both groups were gender, age, preoperative index diagnosis, degenerated segment, and single/double level of fusion. Operative time, blood loss, hospital time, and implant costs were also evaluated. Postsurgical pain and functional results were analyzed by the visual analog scale (VAS), modified Prolo (mProlo) scores, and Oswestry Disability Index (ODI). Radiographic examinations were carried out to assess total fusion rates, screw failure, and general complications.

METHODS

Patients were randomized into the unilateral or bilateral PS instrumented TLIF group based on a computer-generated number list. Patients were asked to return to hospital for follow-up at 4 weeks, 3 months, 6 months, 12 months, and thereafter once a year after surgery.

RESULTS

The mean follow-up was 25.3 months, with a range of 18 to 32 months. There were no significant differences between the two groups in terms of demographic data. The unilateral PS group had a significantly shorter operative time, less blood loss, and reduced implant costs compared with the bilateral PS group, although hospital time was the same for double-level cases. The average postoperative VAS, mProlo, and ODI scores improved significantly in both groups, with no significant difference between groups. The total fusion rate, screw failure, and general complication rate were not significantly different.

CONCLUSIONS

Unilateral PS instrumented TLIF is a viable treatment option generating better results, especially in terms of operative time, blood loss, and hospital time for single-level disease and implant costs. No decrease in the fusion rate or increase in the complication rate was observed in this group. Further improved study design and a longer period of follow-up are needed to confirm this effect.