Alexander Aichmair

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

BACKGROUND CONTEXT Lateral 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. PURPOSE To address risk factors for iatrogenic nerve injury in a large cohort of patients undergoing LLIF. STUDY DESIGN Retrospective analysis of 919 LLIF procedures to identify risk factors for lumbosacral plexus injuries. METHODS The 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. RESULTS Four 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/m(2) (range, 17-65 kg/m(2)). 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. CONCLUSIONS Although 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.

Nerve injury and recovery after lateral lumbar interbody fusion with and without bone morphogenetic protein-2 augmentation: a cohort-controlled study

BACKGROUND CONTEXT Despite common use of intraoperative electrophysiologic neuromonitoring, injuries to the lumbar plexus during lateral lumbar interbody fusion (LLIF) have been reported. Emerging data suggest that recombinant human bone morphogenetic protein-2 (rhBMP-2) use during an anterior or transforaminal lumbar interbody fusion may be associated with an increased risk of neurological deficit. Clinical data on the sequelae of rhBMP-2 implantation in close proximity to the lumbosacral plexus during LLIF remains to be understood. PURPOSE The purpose of this study was to compare the incidence of neurologic deficits and pain in patients undergoing LLIF with and without rhBMP-2. STUDY DESIGN/SETTING Retrospective outcome analysis in controlled cohorts undergoing the lateral exposure technique for LLIF with and without rhBMP-2. METHODS The electronic medical records of patients undergoing LLIF with and without supplemental posterior fusion for degenerative spinal conditions were retrospectively reviewed over a 6-year period. Patients with previous lumbar spine surgery or follow-up of less than 6 months were excluded. Patients were divided into 2 groups, Group 1 (rhBMP-2 use; n=72) and Group 2 (autograft/allograft use; n=72), and were matched according to the age at the time of surgery, gender, weight, body mass index, side of approach, total number of treated spinal segments, use of supplemental posterior fusion, and length of follow-up. RESULTS Immediately after surgery, a sensory deficit was recorded in 33 patients in Group 1 and 35 patients in Group 2 (odds ratio [OR] 0.895; 90% confidence interval [CI] 0.516-1.550; p=.739). At last follow-up, a persistent sensory deficit was identified in 29 patients whose LLIF procedure was supplemented by rhBMP-2 and 20 patients in whom autograft/allograft was used (OR 1.754; 90% CI 0.976-3.151; p=.115). A motor deficit was recorded in 37 patients immediately after the rhBMP-2 procedure and 28 patients treated with autograft/allograft (OR 1.661; 90% CI 0.953-2.895; p=.133). A persistent motor deficit was recorded in 35 and 17 patients in Groups 1 and 2, respectively, at last follow-up (OR 3.060; 90% CI 1.681-5.571; p=.002). During the first postoperative examination, 37 patients in Group 1 and 25 patients in Group 2 complained of anterior thigh or groin pain (OR 1.987; 90% CI 1.133-3.488; p=.045). At last follow-up, there was a significantly higher number of patients in Group 1 who complained of persistent anterior thigh or groin pain than Group 2 (8 vs. 0 patients) (OR 16.470; 90% CI 1.477-183.700; p=.006). CONCLUSIONS Our results provide evidence of an increased rate of postoperative neurologic deficit and anterior thigh/groin pain after LLIF using rhBMP-2, when compared with matched controls without rhBMP-2 exposure. This study suggests a potential direct deleterious effect of rhBMP-2 on the lumbosacral plexus.

Rate of revision surgery after stand-alone lateral lumbar interbody fusion for lumbar spinal stenosis.

Study Design. Retrospective case series. Objective. To examine the reoperation rate, specifically the need for posterior decompression and/or fusion, in a cohort of patients who underwent stand-alone lateral lumbar interbody fusion for symptomatic spinal stenosis with instability or deformity. Summary of Background Data. Lateral lumbar interbody fusion provides a minimally invasive means of achieving interbody arthrodesis and indirect foraminal decompression while avoiding the potential morbidity of traditional anterior or posterior approaches. The revision rate for formal posterior decompression after isolated lateral lumbar interbody fusion for spinal stenosis is unknown. Methods. One hundred seventeen patients who underwent stand-alone lateral lumbar interbody fusion for symptomatic spinal stenosis with an indication for fusion were included in the analysis. Detailed demographic and intraoperative data were collected. Clinical evaluation was done both preoperatively and at the final follow-up, and radiographical evaluation was done preoperatively and with the first postoperative standing radiographs. Results. A total of 10.3% of patients who underwent stand-alone lateral lumbar interbody fusion ultimately required revision surgery, most commonly for persistent radiculopathy and symptomatic implant subsidence. Average time to revision was 10.8 months. There was no difference in radiographical correction between patients who did and did not require revision surgery. Conclusion. Lateral lumbar interbody fusion provides a minimally invasive means to treat lumbar spinal stenosis with an acceptable revision rate for formal posterior decompression at early follow-up. Level of Evidence: 4

Incidental Durotomy During Spinal Surgery: A Multivariate Analysis for Risk Factors

Study Design. Multivariate analysis. Objective. The purpose of this study was to investigate risk factors for incidental durotomy (ID) in modern spine surgery techniques. Summary of Background Data. ID, a relatively common complication of spine surgery, has been associated with postoperative complications such as durocutaneous fistulas, pseudomeningoceles, and arachnoiditis. Revision surgery may be necessary if the dural tear is not recognized and repaired during the initial procedure. Methods. ID was prospectively documented in patients who underwent spine surgery at a single institution during a 2-year period (n = 4822). Patients with ID (n = 182) from lumbar or thoracolumbar cases were matched 1:1 to a control cohort without ID. Demographic, diagnostic, and surgical procedure data were retrospectively collected and analyzed. Results. Multivariate analysis identified revision spine surgery (adjusted odds ratio [aOR]: 4.78, 95% confidence interval [CI]: 2.84–8.06, P < 0.01), laminectomy (aOR: 3.82, 95% CI: 2.02–7.22, P < 0.01), and older age (aOR: 1.03, 95% CI: 1.01–1.04, P < 0.01) as independent risk factors for ID. Fusion (aOR: 0.59, 95% CI: 0.35–0.99, P = 0.04), foraminectomy, (aOR: 0.42, 95% CI: 0.25–0.69, P < 0.01), and lateral approach (aOR: 0.29, 95% CI: 0.14–0.61, P < 0.01) were independent protective factors. Conclusion. Prior spine surgery, laminectomy, and older age were significant independent risk factors for ID. The recently developed lateral approach to interbody fusion was identified as a significant protective factor for ID, along with fusion and foraminectomy. These findings may help guide future surgical decisions regarding ID and aid in the patient informed-consent process. Level of Evidence: 3

Aortic perforation during lateral lumbar interbody fusion.

Study Design: A case report. Objective: To report a unique case of aortic perforation during lateral lumbar interbody fusion (LLIF). Summary of Background Data: Among the reported advantages of this minimally invasive transpsoas procedure is the avoidance of an anterior intraperitoneal approach to the lumbar spine, thus avoiding visceral and vascular injuries typically associated with the latter. Methods: We report a single case of aortic perforation during LLIF, which occurred in the setting of an incidental endplate and anterior vertebral cortex violation. Results: During the implantation of an interbody prosthetic device at the L3–L4 level, the proximal aspect of the implant broke which caused cage misplacement. During the attempt to advance the well-fixed cage, distal violation of the endplate and anterior cortex of the L3 vertebra was noted, concomitant with immediate loss of blood pressure. A presumptive diagnosis of injury to a major vascular structure was quickly made, along with the decision to proceed with emergency laparotomy to repair a through-and-through laceration of the aortic terminus. After successful suture repair of the aortic lesions, the patient was kept intubated, and transferred to the intensive care unit in stable condition. Conclusions: The distal endplate and anterior vertebral cortex violation can result in the formation of an anterior bony spur in close proximity to the major abdominal vascular structures, and despite the avoidance of an anterior approach to the lumbar spine, surgery-related injury to major abdominal vessels can occur during LLIF. Aortic perforation is a rare, yet potentially lethal intraoperative complication of LLIF, which requires emergency laparatomy and vascular suture repair.

Associations between lumbosacral transitional anatomy types and degeneration at the transitional and adjacent segments

BACKGROUND CONTEXT The relation between specific types of lumbosacral transitional vertebra and the degree of degeneration at and adjacent to the transitional level is unclear. It is also unknown whether the adjacent cephalad segment to a transitional vertebra is prone to greater degeneration than a normal L5-S1 level. PURPOSE The purpose of this study was to evaluate the relation between specific lumbosacral transitional vertebra subtypes according to the Castellvi classification, and to determine the severity of degeneration at the transitional level and the adjacent cephalad segment. STUDY DESIGN This study was a retrospective review. PATIENT SAMPLES Ninety-two subjects with lumbosacral transitional vertebra grade 2 or higher and 94 control subjects without were retrieved from a picture archiving and communication system (PACS) search. OUTCOME MEASURES Disc degeneration parameters at the transitional and at the adjacent cephalad level were measured. METHODS After institutional review board approval, 92 subjects (42 men; mean age, 57±16 years) with lumbosacral transitional vertebra grade 2 or higher and 94 control subjects (41 men; mean age, 51±16 years) without were retrieved from a PACS search. Degeneration of the last two segments of the lumbar spine was quantified using the Pfirrmann and Modic classifications, along with documentation of annular tears, disc herniations, and disc height, and were compared between the two groups. Furthermore, L5-S1 levels in the control subjects were compared with the adjacent cephalad segments of the transitional vertebrae for the same parameters. RESULTS Although the control subjects, at L5-S1, had moderate to severe degeneration by Pfirrmann grades (31%) and Modic changes ([MC] 20%), in comparison, the discs at the transitional level of the lumbosacral transitional vertebra group demonstrated significant less degeneration (3% and 1%, respectively; each p<.05). The adjacent cephalad segments of the lumbosacral transitional vertebra group showed significantly greater degeneration (Pfirrmann grade 5, 39%; MC, 30%) compared with the L4-L5 level in control subjects (16% and 11%, respectively; each p<.05). The severity of disc degeneration using all parameters correlated with the type of lumbosacral transitional vertebra. The degree of degeneration of L5-S1 in control subjects was similar to the adjacent cephalad segment in lumbosacral transitional vertebrae. CONCLUSION Increasing the mechanical connection of a lumbosacral transitional vertebra protects the disc at the transitional level and predisposes the adjacent cephalad segment to greater degeneration. The adjacent cephalad segment had a comparable degree of degeneration as the L5-S1 level in control subjects.

Multivariate analysis on risk factors for postoperative ileus after lateral lumbar interbody fusion.

Study Design. Retrospective cohort study. Objective. To assess for independent risk factors of postoperative ileus (POI) after lateral lumbar interbody fusion (LLIF). Summary of Background Data. POI is frequently observed in anterior lumbar interbody fusion due to significant bowel manipulation during the approach. LLIF is a minimally invasive approach to the anterior column with reduced bowel manipulation and surgical time. However, there is a paucity of literature on POI after LLIF. Methods. A retrospective review was performed of records of patients who underwent LLIF from January 2006 to December 2011 at a single institution. Patients with prolonged and recurrent POI were identified by review of hospital stay documentation by a fellowship-trained spine surgeon and a research fellow. POI patients were matched 1:1 to a control cohort without POI. Uni- and multivariate analyses were performed on demographic, comorbidity, surgical indication, medication, and perioperative details to identify independent risk factors for POI. Results. Incidence of prolonged or recurrent POI after LLIF was 7.0% (42/596). Postoperative length of stay was significantly higher for patients with POI (9.9 ± 4.3 d) than control patients (5.6 ± 4.1 d) (P < 0.001). The incidence of ileus in the first 100 LLIF cases (11%) was not significantly higher than in the last 100 LLIF cases (6%) (P = 0.21). Independent risk factors were history of gastroesophageal reflux disease (P < 0.01, adjusted odds ratio [aOR]: 24.31), posterior instrumentation (P = 0.002, aOR: 19.48), and LLIF at L1–L2 (P = 0.04, aOR: 7.82). A history of prior abdominal surgery approached significance as an independent protective factor (P = 0.07, aOR: 0.29). Conclusion. There was a relatively high incidence of POI after LLIF. Independent risk factors for POI were a history of gastroesophageal reflux disease, posterior instrumentation, and LLIF at L1–L2. A history of prior abdominal surgery approached significance as an independent protective factor. Level of Evidence: 3

Contralateral motor deficits after lateral lumbar interbody fusion.

Study Design. Retrospective case series. Objective. To report on the rare finding of motor deficits contralateral to the transpsoas approach in patients who underwent lateral lumbar interbody fusion (LLIF). Summary of Background Data. Although sensorimotor deficits occurring ipsilaterally to a transpsoas approach have more fully been elucidated, there seems to be a paucity of data on motor deficits contralateral to an LLIF approach. Methods. The electronic medical records and radiographical studies of 244 patients who underwent LLIF at a single institution between 2006 and 2009 were retrospectively reviewed for reports on motor deficits contralateral to the surgical approach. Results. Of the patients reviewed, 2.9% (7/244) presented with a postoperative contralateral motor deficit, the most severe of which was a 1/5 weakness of the quadriceps muscle. An average of 3 levels (range: 2–4) was fused in 7 patients who developed a contralateral motor deficit, and in 3 of the 7 patients, an anterior lumbar interbody fusion (ALIF) was performed in addition to the LLIF. At 1 year follow-up, 3 patients presented with complete resolution of their muscle weakness, 1 patient still had mild weakness, 1 patient had decreased range of motion in the affected joint, and 1 patient had a 2/5 foot drop. One patient was lost to follow-up. Conclusion. These data are among the largest reports of contralateral motor deficits after LLIF. Among possible underlying mechanisms are entrapment of the contralateral nerve root through translational correction of spondylolisthesis, front-to-back misalignment of the cage resulting in contralateral nerve root impingement, pressure on the contralateral peroneal nerve during positioning, and overdistraction neurapraxia when using ALIF at L5–S1 concomitantly. Awareness of the possibility of this rare complication can play an important role in surgical consideration and preoperative patient counseling. Level of Evidence: 4

Current concepts on spinal arthrodesis in degenerative disorders of the lumbar spine

Back pain is a common chronic disorder that represents a large burden for the health care system. There is a broad spectrum of available treatment options for patients suffering from chronic lower back pain in the setting of degenerative disorders of the lumbar spine, including both conservative and operative approaches. Lumbar arthrodesis techniques can be divided into sub-categories based on the part of the vertebral column that is addressed (anterior vs posterior). Furthermore, one has to differentiate between approaches aiming at a solid fusion in contrast to motion-sparing techniques with the proposed advantage of a reduced risk of developing adjacent disc disease. However, the field of application and long-term outcomes of these novel motion-preserving surgical techniques, including facet arthroplasty, nucleus replacement, and lumbar disc arthroplasty, need to be more precisely evaluated in long-term prospective studies. Innovative surgical treatment strategies involving minimally invasive techniques, such as lateral lumbar interbody fusion or transforaminal lumbar interbody fusion, as well as percutaneous implantation of transpedicular or transfacet screws, have been established with the reported advantages of reduced tissue invasiveness, decreased collateral damage, reduced blood loss, and decreased risk of infection. The aim of this study was to review well-established procedures for lumbar spinal fusion with the main focus on current concepts on spinal arthrodesis and motion-sparing techniques in degenerative disorders of the lumbar spine.

Clinical predictors of surgical outcome in cervical spondylotic myelopathy: An analysis of 248 patients

The purpose of this study was to investigate the clinical predictors of surgical outcome in patients with cervical spondylotic myelopathy (CSM). We reviewed a consecutive series of 248 patients (71 women and 177 men) with CSM who had undergone surgery at our institution between January 2000 and October 2010. Their mean age was 59.0 years (16 to 86). Medical records, office notes, and operative reports were reviewed for data collection. Special attention was focused on pre-operative duration and severity as well as post-operative persistence of myelopathic symptoms. Disease severity was graded according to the Nurick classification. Our multivariate logistic regression model indicated that Nurick grade 2 CSM patients have the highest chance of complete symptom resolution (p < 0.001) and improvement to normal gait (p = 0.004) following surgery. Patients who did not improve after surgery had longer duration of myelopathic symptoms than those who did improve post-operatively (17.85 months (1 to 101) vs 11.21 months (1 to 69); p = 0.002). More advanced Nurick grades were not associated with a longer duration of symptoms (p = 0.906). Our data suggest that patients with Nurick grade 2 CSM are most likely to improve from surgery. The duration of myelopathic symptoms does not have an association with disease severity but is an independent prognostic indicator of surgical outcome.