Transpsoas Interbody Fusion Research Articles

Stand-alone minimally invasive lateral lumbar interbody fusion: Multicenter clinical outcomes

Stand-alone minimally invasive lateral transpsoas interbody fusion (MIS-LIF), without posterior instrumentation, is feasible because the technique does not necessitate the disruption of the stabilizing elements. The objectives of this study are to evaluate the efficacy and clinical outcomes of patients who underwent stand-alone lateral interbody fusion. A multicenter chart review was conducted to identify patients who underwent stand-alone MIS-LIF between 2008 and 2012. Patients were classified by spinal pathology (degenerative disc disease [DDD], spondylolisthesis [SL] and adult degenerative scoliosis [ADS]). Routine clinical follow-up was scheduled at 3, 6, and12months. Outcome measures included hospital length of stay, fusion rates, neurologic complications, integrity of construct and clinical outcome questionnaires (Visual Analog Scale [VAS] and Oswestry Disability Index [ODI]). A total of 59 patients met the inclusion criteria. The average age was 60years (range 31–86years). Spinal pathologies treated were DDD in 37 (63%), SL in four (7%) and ADS in 18 (30%) patients. Fusion rate was 93% of patients (95% of levels) at 12months. Two patients required re-operation. Mean hospital stay and follow-up were 3.3days (range 1–10) and 14.6months, respectively. The mean preoperative VAS and ODI were 69.1 and 51.8, respectively. VAS improved to 37.8 (p<0.0005). ODI improved to 31.8 (p<0.0005). Seventy percent of patients had grade 0 subsidence while 30% had grade I and grade II subsidence. Stand-alone MIS-LIF is viable option in a carefully selected patient population for both single and multilevel disease and shows significant improvement in health related quality of life.

Magnetic Resonance Neurography Allows Visualization of the Lumbar Plexus at the L4-5 Disc Space: Development of a Preoperative Surgical Planning Tool for Lateral Transpsoas Interbody Fusion

Magnetic Resonance Neurography Allows Visualization of the Lumbar Plexus at the L4-5 Disc Space: Development of a Preoperative Surgical Planning Tool for Lateral Transpsoas Interbody Fusion

Comparison of the Safety Outcomes between Anterior Lumbar Interbody Fusion and Extreme Lateral Interbody Fusion

Introduction This review compares the safety of the interbody fusion procedures anterior lumbar interbody fusion (ALIF) and extreme lateral transpsoas interbody fusion (ELIF) in the treatment of degenerative spinal disorders. ALIF is well established whereas ELIF is a novel procedure. Materials and Methods We performed a systematic literature search in the databases Cochrane (CENTRAL), MEDLINE, EMBASE, and the FDA register. Information was collected on study design, sample size, population, procedure, indication incl. number, and location of levels involved, follow-up (FU) time and adverse events. Moreover, information on conflict of interest and source of funding was captured. Results Of 32 eligible publications, 22 dealt with ELIF, 9 with ALIF, and 1 compared ELIF with ALIF. All of the ELIF studies were case series. The number of patients was 2,165 and 1,379, with a FU time from 45 days to 24 months and 24 months to 5 years for ELIF and ALIF, respectively. The risk to experience certain types of adverse events (e.g., reoperations, hardware failures, DVT, and cardiac) appeared significantly lower for patients undergoing ELIF. Pseudarthrosis was seen in 0.14 and 1.02% of ELIF and ALIF cases, respectively. Neurological complications occurred in 7.62% of ELIF and 9.43% of ALIF cases. [Table: see text] Conclusion ELIF procedures demonstrated a favorable safety outcome compared with ALIF, nonetheless the lack of comparative studies, length of follow-up, and low level of evidence is a limitation of this review. Disclosure of Interest R. Hartl: Conflict with DePuy Synthes, Spine Wave, Brainlab, Lanx F. Christensen: None declared A. Korge: None declared K. Lam: None declared E. Vialle: None declared J. Zigler: None declared R. McGuire: None declared

Femoral Nerve Strain at L4–L5 Is Minimized by Hip Flexion and Increased by Table Break When Performing Lateral Interbody Fusion

Anatomic studies have demonstrated that nerves and blood vessels have excursion with extremity range of motion. We have measured femoral nerve excursion with the lateral lumbar transpsoas interbody fusion (LLIF) procedure with changes in table flexion and ipsilateral hip flexion on both sides of 5 cadavers. To determine the effect of hip range of motion on femoral nerve strain near the L4-L5 disc space because it pertains to the LLIF procedure. Postoperative thigh symptoms are common after the LLIF procedure. Although nerve strain in general has been shown to impair function, it has not been tested specifically with LLIF. Five cadavers were placed in the lateral position as though undergoing the L4-L5 LLIF procedure. Radiographical markers were implanted into the femoral nerve. Lateral and anteroposterior fluoroscopic images were recorded with 0° initial table flexion and the hip at 0, 20, 40, and 60° flexion. The table was flexed to 40°, and the process repeated. Examination was repeated on the contralateral side and nerve strain and excursion were calculated. Table flexion results in preloading the femoral nerve when approaching L4-L5. Nerve strain was highest with the table flexed to 40° and the hip at 0° (average, 6%-7%). Strain in the femoral nerve decreased with increasing hip flexion for both table flexion angles. Anterior displacement of the nerve by approximately 1.5 mm was noted at 40° table flexion compared with 0°. Strain values with table flexion of 40° approached those associated with reduced neural blood flow in animal studies. Table flexion should be minimized to the extent possible when performing L4-L5 LLIF. Additionally, hip flexion to 60° can neutralize the neural strain that occurs with aggressive table flexion. N/A.

Technical note: Resolution of spontaneous electromyographic discharge following disk-space distraction during lateral transpsoas interbody fusion

PurposeThe lateral transpsoas interbody fusion (LTIF) is an increasingly popular minimally invasive technique for lumbar interbody fusion. Although a posterior approach to the lumbar spine has traditionally been favored for the treatment of canal stenosis and neural foraminal stenosis, a growing body of evidence suggests that indirect decompression of the spinal canal and neural foramen can be achieved using a lateral transpsoas approach to the lumbar spine. We present 2 cases that may suggest a role for spontaneous electromyography (s-EMG) monitoring in assessing the adequacy of decompression during LTIF. MethodsThe 2 cases presented in this technical note illustrate resolution of s-EMG firing during LTIF, following distraction across the disk space. Removal of the distracting device produced the return of s-EMG firing. Both of these cases were operated at the L2-3 level. ResultsIn the first case, s-EMG firing was noted in the bilateral tibialis anterior leads. Resolution of EMG firing may suggest indirect decompression of the canal via ligamentotaxis as the L5 root traverses the L2-3 disk space. In the second case, s-EMG firing was noted in the left abductor hallucis and resolved with distraction of the L2-3 disk space. Again, this may be explained by canal decompression via ligamentotaxis as the S1 root traverses the L2-3 disk space. ConclusionIn both cases, distraction across the disk space resulted in resolution of s-EMG discharges—this correlated with an improvement in symptoms. These findings may suggest a role for s-EMG as a marker for adequacy of decompression in a select subset of patients undergoing LTIF. Further study is needed to determine if resolution of s-EMG is a useful measure of indirect decompression during LTIF.

Nerve injury after lateral lumbar interbody fusion: a review of 919 treated levels with identification of risk factors

Background contextLateral lumbar interbody fusion (LLIF) has become an increasingly common minimally invasive procedure for selective degenerative deformity correction, reduction of low-grade spondylolisthesis, and indirect foraminal decompression. Concerns remain about the safety of the transpsoas approach to the spine due to proximity of the lumbosacral plexus. PurposeTo address risk factors for iatrogenic nerve injury in a large cohort of patients undergoing LLIF. Study designRetrospective analysis of 919 LLIF procedures to identify risk factors for lumbosacral plexus injuries. MethodsThe medical charts of patients who underwent transpsoas interbody fusion with or without supplemental posterior fusion for degenerative spinal conditions over a 6-year period were retrospectively reviewed. Patients with prior lumbar spine surgery or follow-up of less than 6 months were excluded. Factors that may affect the neurologic outcome were investigated in a subset of patients who underwent stand-alone LLIF. ResultsFour hundred fifty-one patients (males/females: 179/272) met the inclusion criteria and were followed for a mean of 15 months (range, 6–53 months). Average age at the time of surgery was 63 years (range, 24–90 years). Average body mass index was 29 kg/m2 (range, 17–65 kg/m2). A total of 919 levels were treated (mean, 2 levels per patient). Immediately after surgery, 38.5% of the patients reported anterior thigh/groin pain, whereas sensory and motor deficits were recorded in 38% and 23.9% of the patients, respectively. At the last follow-up, 4.8% of the patients reported anterior thigh/groin pain, whereas sensory and motor deficits were recorded in 24.1% and 17.3% of the patients, respectively. When patients with neural deficits present before surgery were excluded, persistent surgery-related sensory and motor deficits were identified in 9.3% and 3.2% of the patients, respectively. Among 87 patients with minimum follow-up of 18 months, persistent surgery-related sensory and motor deficits were recorded in 9.6% and 2.3% of the patients, respectively. Among patients with stand-alone LLIF, the level treated was identified as a risk factor for postoperative lumbosacral plexus injury. The use of recombinant human bone morphogenetic protein 2 was associated with persistent motor deficits. ConclusionsAlthough LLIF is associated with an increased prevalence of anterior thigh/groin pain as well as motor and sensory deficits immediately after surgery, our results support that pain and neurologic deficits decrease over time. The level treated appears to be a risk factor for lumbosacral plexus injury.

Lumbar plexopathy following instrumented posterior lumbar interbody fusion: a complication with use of Hohmann’s retractor

A series of 12 patients in our centre following single level instrumented posterior lumbar interbody fusion at L4-L5 developed unexplainable motor weakness in the proximal lumbar nerve roots (L2, L3) and numbness of the whole limb, a clinical picture resembling lumbar plexopathy. Even though lumbar plexopathy has been reported following gynaecological procedures and in transpsoas interbody fusion surgeries, there is no literature reporting this complication following conventional instrumented posterior lumbar interbody fusions. Retrospective observational study. To find the possible mechanism of development of lumbar plexopathy in patients who underwent posterior lumbar interbody fusion surgeries in our centre. We analyzed retrospectively the medical records, electrophysiological reports of the patients, literatures on the anatomy of lumbar plexus and other literature reporting similar complications. We also dissected lumbar plexus of three cadavers and simulated surgical technique on them to find the mechanism of development of this unusual complication. We found injury to lumbar plexus that probably occurred intraoperatively with Hohmann's retractor that was used for retraction of the paraspinal muscles. This theory was favoured by many clinical factors and further confirmed by cadaveric dissections. We conclude that surgical technique with improper use of Hohmann's retractor causes traction and compression injury to the lumbar plexus resulting in this complication. We propose proper technique of insertion of Hohmann's retractor and also recommend use of modified Hohmann's retractor with shorter tips for spinal procedures to prevent such complication.

Supra-psoas Shallow Docking in Lateral Interbody Fusion

Lateral interbody fusion techniques have been linked with considerable postoperative morbidity, often the outcome of direct psoas trauma. The most common neurological postoperative complications are transient motor weakness/palsy and sensory dysesthesia, which can be permanent. It appears that these neural complications are a result of passing through the psoas muscle where the potential for nerve injury is significant. The supra-psoas shallow docking method may be a safer alternative and may help minimize morbidities by eliminating or reducing direct psoas injury. To describe the operative technique of performing lateral interbody fusion using supra-psoas retractor docking. The authors describe the surgical technique including side selection, positioning, and patient outcomes. Fifteen patients were treated with the supra-psoas shallow docking method. Specifically, no patient reported weakness, numbness, and/or pain on the side that underwent the surgery. In these cases, performing lateral transpsoas interbody fusion using supra-psoas shallow docking appeared to minimize the most common neurological postoperative complications of the surgery, motor weakness/palsy and sensory dysesthesia, which may be a result of dilation of the psoas muscle. The shallow docking technique may decrease postoperative morbidities by docking on top of psoas muscle instead of passing through it. An important potential benefit of this approach is direct visualization of the lumbosacral plexus, which may potentially minimize the postoperative neurological morbidity often encountered in patients after this surgery.

Lateral Access Surgery for the Thoracolumbar Spine

The advent of minimally invasive surgery has provided surgeons and patients the same good treatment alternatives. Within the field of spine surgery, techniques for lumbar interbody arthrodesis have shown enormous evolution. The retroperitoneal transpsoas lateral approach for the lumbar spine has revolutionized how interbody fusions can be performed more safely and with significantly less morbidity. In recent years, the role of minimally invasive transpsoas interbody fusion is strongly evolving. Lateral retroperitoneal approaches under direct visualization using expandable retractors have gained space and have been utilized for different purposes rather than interbody fusion. The objective of this special issue was to, for the first time in the literature, gather together articles on Lateral Access Surgery (LAS) and assemble unique peer-reviewed literature with basic and advanced reports focused in this emerging area. The number of scientific articles about minimally invasive spine surgery (MISS) and specially about LAS is growing. The nature of the research tends to go to the same direction and evolve from single-center case reports to a higher level of evidence trials, once a recognized weakness in the MIS literature is the absence of randomized controlled trials. But by the other hand, randomizing patients were found to be challenging faced to patients' expectative and ethical principles. Given the challenges of conducting a randomized controlled trial and although more substantial research remains to be performed, nonrandomized concurrently controlled trials or prospective registries will provide valuable evidence-based medicine data. The level of evidence provided from the clinical and basic studies included in this special issue is not at the highest level of clinical trials, but though they represent different aims and indications for the lateral access, it can identify two patterns across them—safety and efficacy. Among the table of content of this issue, V. S. Patel et al. go through overall indications and outcomes, while M. Malham et al. from Australia show results from their initial experience with the technique. The use of an allograft as bone graft option is well reported by A. G. Tohmeh et al. Basic science developments are illustrated with studies on biomechanics of interbody constructions and on the validation of an animal model. First developed for anterior based discectomy and interbody grafting in simple degenerative diseases, LAS has recently gained space for more complex indications. Over the years, it has been possible to address varied and complex scenarios. In this mindset, this special issue brings important reports that discuss advanced surgical applications of LAS—release of the ALL and sagittal reconstruction, degenerative scoliosis, application for revision surgery and thoracolumbar infection, and for L4-5 grade 2 spondylolisthesis. We look forward to witness the evolution of spine surgery with the evidence based medicine to achieve the highest efficacy and safe to the patient who suffers from any spine-related condition. Luiz Pimenta William Smith William Taylor Juan Uribe

Iliac crest osteotomy to enhance exposure of the L4–5 interspace in minimally invasive lateral transpsoas interbody fusion: a cadaveric feasibility study

Object Minimally invasive lateral transpsoas interbody fusion (LTIF) has emerged as a popular surgical technique in a remarkably short period of time. The authors' experience with this procedure and anecdotal evidence in the literature suggest that the iliac crest may occasionally prevent access to the L4–5 interspace during minimally invasive LTIF. The authors propose that removal of a minimal amount of ilium would allow for successful exposure of the L4–5 interspace in those cases with a “high-riding” iliac crest. Therefore, the objective of this study was to evaluate the feasibility of iliac osteotomy to enhance exposure of the L4–5 interspace for minimally invasive LTIF. Methods Twenty L4–5 minimally invasive LTIF procedures were performed on 10 cadavers. The L4–5 minimally invasive LTIFs were successfully completed in 13 of 20 attempts. In the remaining 7 cases, the iliac crest prevented perfect orthogonal access to the L4–5 interspace. An iliac osteotomy was performed until the tubular retractors could be perfectly aligned with the L4–5 interspace and minimally invasive LTIF accomplished. Anteroposterior fluoroscopic images were obtained before and after the osteotomies. The angle between the working instrument and the superior L-5 endplate was measured, as were craniocaudal displacement and the resected iliac area. Results Iliac osteotomy enabled completion of L4–5 minimally invasive LTIF in the 7 remaining cases. Iliac resection was minimal; an average of 4.92 cm2 of iliac surface was resected (range 2.08–8.27 cm2) to enable L4–5 access. Adequate working angles were maintained (average 3.3° change after resection) while significant caudal displacement of the tubular system was achieved (average 15.7 mm, range 5.2–27.6 mm). Conclusions A significant portion of patients may have a high-riding iliac crest and that may have had an impact on minimally invasive LTIF in this series; L4–5 cases are rare in relation to midlumbar spine cases in most minimally invasive LTIF patient series. Significant caudal displacement of the tubular system was achieved with minimal iliac osteotomy, ensuring access to the L4–5 interspace in all specimens while maintaining the minimally invasive philosophy behind minimally invasive LTIF.

Leg Weakness in Relation to Approach Side Following Single-Level Lateral Ttranspsoas Lumbar Interbody Fusions

Lateral transpsoas interbody fusion (LTIF) is a newer minimally invasive technique for treating lumbar spinal disease. Initial series reported few adverse neurological events, but evidence suggests that although mostly transient, they may be more common than expected. There is increasing interest in the anatomy of the lumbar plexus and its relationship to postoperative deficits. It has been suggested that the side of the approach may be associated with increased risk of neurovascular injury.

Lumbarized Sacrum as a Relative Contraindication for Lateral Transpsoas Interbody Fusion at L5-6

Retrospective review. To determine if lumbarized sacra at the L5-6 level (functional L4-5) are a contraindication to a lateral transpsoas approach. Transitional vertebrae at the lumbosacral junction present mechanical and morphologic changes, though these changes have not been characterized with respect to the feasibility of a lateral transpsoas approach. Three hundred fifty-one patients were scheduled for lumbar interbody fusion using a mini-open lateral transpsoas approach (XLIF) at L4-5 from 2004 to 2008 at a single institution. In patients with 6 lumbar vertebrae, accessibility, based on neuromonitoring, of the L5-6 level (functional L4-5) was reviewed. Qualitative assessments using axial magnetic resonance imaging (MRI) were performed and compared with a sample of patients with normal anatomy treated at L4-5. Of the 351 patients scheduled for treatment at L4-5, 10 (2.8%) were determined to have 6 lumbar vertebrae with the symptomatic level at L5-6. Of those 10, 2 (20%) could be treated using a lateral transpsoas approach, and 8 (80%) were converted to another approach after a corridor through the psoas muscle was not found, based on neuromonitoring feedback. Review of axial MRI showed a teardrop-shaped psoas detached from the lateral border of the disc space in patients with transitional anatomy unapproachable at L5-6, resemblant of L5-S1 in normal anatomy. In the 2 patients who could be safely approached, the psoas anatomy at L5-6 was similar to a normal L4-5 level, with a domed/helmet shape, attached laterally to the disc space. Treating the L5-6 level using a lateral transpsoas approach in individuals with lumbarized sacra can be challenging due to anatomy more similar to the L5-S1 level in normal patients. Preoperative planning using axial MRI and intraoperative adherence to advanced neuromonitoring can aid in identifying and avoiding injury in these rare patients.

Factors Influencing Segmental Lumbar Lordosis After Lateral Transpsoas Interbody Fusion

Although contributions to sagittal alignment have been characterized for anterior, posterior and transforaminal lumbar interbody fusion, sagittal alignment after lateral transpsoas interbody fusion (LTIF) has not yet been characterized. This study examined the ability of LTIF to restore lumbar lordosis and identified factors associated with change in sagittal alignment. Twenty-nine patients and 67 levels were studied. Segmental lordosis, anterior-posterior cage position, and cage obliquity were measured on preoperative and postoperative radiographs and CT scans. Change in sagittal alignment was analyzed with respect to demographic information and measures of cage position and obliquity to identify factors associated with segmental alignment change. Mean lordosis increased 3.7° at instrumented segments, increasing from 4.1° preoperatively to 7.8° postoperatively. Although increases at each level were significant, there were no significant differences between levels. Lordosis increase was inversely-associated with preoperative lordosis; levels with the least preoperative lordosis gained the most lordosis. Cage obliquity and height were not significantly associated with lordosis change. Anterior cage placement resulted in the largest lordosis gain (+7.4°/level) while posterior placement was prokyphotic (-1.2°/level). There were no significant associations with age, sex or body mass index. Anteroposterior cage placement is an important intraoperative determinant of postoperative alignment; anterior placement results in greater lordosis while middle/posterior placement has a minimal effect on sagittal alignment.

Indirect foraminal decompression after lateral transpsoas interbody fusion

Lateral transpsoas interbody fusion (LTIF) permits anterior column lumbar interbody fusion via a direct lateral approach. The authors sought to answer 3 questions. First, what is the effect of LTIF on lumbar foraminal area? Second, how does interbody cage placement affect intervertebral height? And third, how does the change in foraminal area and cage position correlate with changes in Oswestry Disability Index (ODI) and 12-Item Short Form Health Survey (SF-12) scores? Included patients underwent LTIF with or without posterior instrumentation and received preoperative and postoperative CT scans. Disc heights, neural foraminal area between adjacent-level pedicles, and anteroposterior cage position were measured from sagittal CT images. Preoperative and postoperative ODI and SF-12 scores were matched with the change in foraminal area from the clinically most severely affected side for analysis of the relationship between outcomes instruments and change in foraminal area. Average foraminal area increased by 36.2 mm(2), or 35% of the preoperative area (p < 0.01), without statistically significant differences by side, level, or anteroposterior cage position. Preoperative anterior and posterior disc heights measured 6.2 mm and 3.7 mm, respectively, compared with postoperative measurements of 9.8 mm (p < 0.01) and 6.3 mm (p < 0.01), respectively, without significant differences by level or cage position. Despite significant overall improvement in ODI and SF-12 scores, there was no correlation with foraminal area increase. Average foraminal area increased approximately 35% after cage placement without variation based on cage position. While ODI and SF-12 scores increased significantly, there was no significant association with cage position or foraminal area change, likely attributable to the multifactorial nature of preoperative pain.

Early Outcomes of Minimally Invasive Anterior Longitudinal Ligament Release for Correction of Sagittal Imbalance in Patients with Adult Spinal Deformity

The object of this study was to evaluate a novel surgical technique in the treatment of adult degenerative scoliosis and present our early experience with the minimally invasive lateral approach for anterior longitudinal ligament release to provide lumbar lordosis and examine its impact on sagittal balance. Methods. All patients with adult spinal deformity (ASD) treated with the minimally invasive lateral retroperitoneal transpsoas interbody fusion (MIS LIF) for release of the anterior longitudinal ligament were examined. Patient demographics, clinical data, spinopelvic parameters, and outcome measures were recorded. Results. Seven patients underwent release of the anterior longitudinal ligament (ALR) to improve sagittal imbalance. All cases were split into anterior and posterior stages, with mean estimated blood loss of 125 cc and 530 cc, respectively. Average hospital stay was 8.3 days, and mean follow-up time was 9.1 months. Comparing pre- and postoperative 36′′ standing X-rays, the authors discovered a mean increase in global lumbar lordosis of 24 degrees, increase in segmental lumbar lordosis of 17 degrees per level of ALL released, decrease in pelvic tilt of 7 degrees, and decrease in sagittal vertical axis of 4.9 cm. At the last followup, there was a mean improvement in VAS and ODI scores of 26.2% and 18.3%. Conclusions. In the authors' early experience, release of the anterior longitudinal ligament using the minimally invasive lateral retroperitoneal transpsoas approach may be a feasible alternative in correcting sagittal deformity.

Multiplanar Radiological Assessment and Outcomes of Lateral Transpsoas Interbody Fusion in Degenerative Deformity

The current study was undertaken to evaluate one site’s early experience with Latteral Interbody Fusion (LTIF) in lumbar degenerative scoliosis and kyphosis and analyze the role of indirect decompression of the neural elements through restoration of foraminal dimensions and its effect on clinical outcomes. The direct lateral approach (LTIF) offers a less invasive and therefore more tolerable surgical option for these patients. LTIF allows for minimally invasive placement of a large anterior graft, facilitating disk height and alignment restoration.

The Utility and Limitations of XLIF for Adult Scoliosis

Introduction Minimally invasive lateral retroperitoneal transpsoas interbody fusion (LIF) is a surgical approach that is gaining popularity both as a standalone and in conjunction with other surgical techniques to treat adult degenerative scoliosis. It has been shown to minimize tissue destruction, blood loss and length of hospital stay. The technique and degree of correction accomplished by this approach has not been described. Results Two hundred and one patients underwent LIF and 26 patients matched the inclusion criteria. The mean age for the 26 patients was 64 years (range 37-80 years). The mean preoperative curve magnitude was 47.7°, which improved to 28.0° (mean correction of 42.8%) post-LIF and to 13.1° (mean correction of 31.2%), after the second stage. The final mean curve magnitude was 13.1°, for a total mean correction of 34.6° and 73.8%. The preoperative mean L1-L5 lordosis was 32.4° and post LIF it was 49.1°, with a mean increase of 16.6 °. Nineteen of the twenty-six patients had worsening coronal balance after LIF and prior to posterior instrumented fusion. The coronal balance consistently shifted to the side of the convexity in all patients with a 1cm or greater shift in balance. Eight patients had severe decompensation ranging from 3cm to 6.4cm. Fifteen of the nineteen patients with post LIF decompensation of their coronal balance had a partial correction after the second stage of surgery. Mean back pain VAS improved from 7.4 to 2.9 with a mean improvement of 4.5.

Evaluation of Indirect Decompression of the Lumbar Spinal Canal Following Minimally Invasive Lateral Transpsoas Interbody Fusion: Radiographic and Outcome Analysis

The surgical treatment of lumbar stenosis traditionally includes laminectomy for direct decompression of the spinal canal. Selected patients with spinal stenosis may also require lumbar fusion. Minimally invasive lateral transpsoas interbody fusion has the ability of placing a large interbody cage that can increase disc height and distract the spinal level. The purpose of this study was to examine the concept of indirect decompression of the spinal canal in patients with co-existing lumbar spinal stenosis undergoing lateral transpsoas interbody fusion. We reviewed 25 consecutive spinal stenosis patients with instability undergoing lateral transpsoas interbody fusion without laminectomy. All patients had relevant symptoms of back pain, leg pain, and/or spinal claudication and met standard criteria for lumbar fusion. Patients were evaluated by outcome analysis scales (VAS scores, Oswestry disability index and treatment intensity scale). Postoperative MRI scans, when available, were evaluated for change in canal dimensions. Statistical significance was assessed by paired t-test, which compares the mean change. There were 25 patients in the study (mean age 61 years). 15 patients had grade I spondylolisthesis. VAS for back pain intensity improved from 7.74 to 2.07 and for frequency from 7.91 to 2.22. VAS for leg pain intensity improved from 7.24 to 1.87 and frequency from 7.41 to 2.35. All improvements were statistically significant (P<0.0001). The Oswestry disability index improved from 55.1 to 16.4 (P<0.0001), and treatment intensity scale improved from 14.6 to 3.7 (P<0.0001). Radiographic evaluation in 20 treated levels (15 patients) found an increase in dural sac dimension of 54% in the anterior-posterior plane and 48% in the medial-lateral plane (P<0.0001). The calculated area of the dural sac increased an average of 143% (range of - 10.4% to + 495%). Indirect decompression of spinal stenosis can be achieved with lateral transpsoas interbody fusion with improved clinical outcomes. Pre-op and post-op MRI scans showed a significant increase in dural sac dimensions. The mechanism for this indirect decompression may relate to stretching and unbuckling of the spinal ligaments and a decrease in intervertebral disc bulging. Further studies are needed to determine which stenosis patients undergoing this surgery are most appropriate for indirect decompression alone over laminectomy.

Abdominal wall paresis as a complication of minimally invasive lateral transpsoas interbody fusion

The minimally invasive lateral transpsoas approach for interbody fusion has been increasingly employed to treat various spinal pathological entities. Gaining access to the retroperitoneal space and traversing the abdominal wall poses a risk of injury to the major nervous structures. Nerve injury of the abdominal wall can potentially lead to paresis of the abdominal musculature and bulging of the abdominal wall. Abdominal wall nerve injury resulting from the minimally invasive lateral retroperitoneal transpsoas approach has not been previously reported. The authors describe a case series of patients presenting with paresis and bulging of the abdominal wall after undergoing a minimally invasive lateral retroperitoneal approach. The authors retrospectively reviewed all patients who underwent a minimally invasive lateral transpsoas approach for interbody fusion and in whom development of abdominal paresis developed; the patients were treated at 4 institutions between 2006 and 2010. All data were recorded including demographics, diagnosis, operative procedure, positioning, hospital course, follow-up, and complications. The onset, as well as resolution of the abdominal paresis, was reviewed. The authors identified 10 consecutive patients in whom abdominal paresis developed after minimally invasive lateral transpsoas spine surgery out of a total of 568 patients. Twenty-nine interbody levels were fused (range 1-4 levels/patient). There were 4 men and 6 women whose mean age was 54.1 years (range 37-66 years). All patients presented with abdominal paresis 2-6 weeks postoperatively. In 8 of the 10 patients, abdominal wall paresis had resolved by the 6-month follow-up visit. Two patients only had 1 and 4 months of follow-up. No long-term sequelae were identified. Abdominal wall paresis is a rare but known potential complication of abdominal surgery. The authors report the first case series associated with the minimally invasive lateral transpsoas approach.

Vertebral body fractures after transpsoas interbody fusion procedures

Although the frequency of transpsoas lumbar interbody fusion procedures has increased in recent years, complication reports remain scarce in the literature. To present four cases of vertebral body fracture after transpsoas interbody fusion procedures in nonosteoporotic patients without significant trauma and discuss relevant biomechanical factors. Case series and literature review. Patients 1 and 2 were obese men who underwent one- and two-level transpsoas interbody fusion procedures and subsequently experienced coronal plane fracture. Patients 3 and 4 were elderly women who underwent multilevel transpsoas interbody fusion procedures and experienced L5 compression fracture. Patients 2 and 3 were treated nonsurgically after fracture. The fractures healed uneventfully; however, Patient 3 developed a flat back syndrome. Patient 1 underwent posterior instrumented fusion and had solid bridging bone above and below the fracture. Patient 4 was treated with vertebroplasty. Factors potentially contributing to these fractures were discussed. Fracture can occur after transpsoas lumbar interbody fusion, even in nonosteoporotic patients. Factors, such as intraoperative end-plate breach, subsidence, compression by lateral screws, and cage rolling, could contribute to the development of fractures after transpsoas interbody fusion.