Bilateral sacroiliac joint fusion in long constructs using self-harvesting porous S2-alar iliac screws with an integrated tulip: technical considerations and early clinical and radiographic experience.

OBJECTIVE: The incidence of sacroiliac joint (SIJ) dysfunction after lumbosacral fusion is high. Upfront bilateral SIJ fusion using novel fenestrated self-harvesting porous S2-alar iliac (S2AI) screws could reduce the incidence of SIJ dysfunction and need for subsequent SIJ fusion. In this study, the authors report their early clinical and radiographic results of SIJ fusion using this novel screw. METHODS: The authors began using self-harvesting porous screws in July 2022. This is a retrospective review of consecutive patients at a single institution who underwent long thoracolumbar surgery with extension to the pelvis using this porous screw. Radiographic parameters of regional and global alignment were collected preoperatively and at the time of last follow-up. The incidence of intraoperative complications and need for revision were collected. The incidences of mechanical complications, including screw breakage, implant loosening/pullout, and screw cap dislocation at the time of last follow-up were also collected. RESULTS: Ten patients with a mean age of 67 years were included, 6 of whom were male. Seven patients had a thoracolumbar construct with extension to the pelvis. Three patients had upper instrumented vertebrae at the proximal lumbar spine. Intraoperative breach was not encountered in any of the patients (0%). Postoperatively, 1 patient (10%) had screw breakage at the neck of the tulip of the modified iliac screw discovered at routine follow-up without clinical sequalae. CONCLUSIONS: Use of self-harvesting porous S2AI screws incorporated into long thoracolumbar constructs was safe and feasible, demanding unique technical considerations. Long-term clinical and radiographic follow-up with a large patient cohort is necessary to determine their durability and efficacy to achieve SIJ arthrodesis and prevent SIJ dysfunction.

Pseudarthrosis after four-level anterior cervical discectomy and fusion without posterior fixation.

OBJECTIVE: Fusion rates and long-term outcomes are well established for anterior cervical discectomy and fusion (ACDF) of 3 levels or fewer, but there is a paucity of similar data on 4-level fusions. The authors evaluated long-term fusion rates and clinical outcomes after 4-level ACDF without supplemental posterior instrumentation. METHODS: The authors retrospectively reviewed patients who underwent 4-level ACDF at a single institution with at least 1-year of radiological follow-up. Fusion was determined by measuring change in interspinous distance at each segment on dynamic radiographs or by the presence of bridging bone on CT scans at minimum 1-year follow-up. Clinical outcomes were assessed using Neck Disability Index and Short Form-36. RESULTS: A total of 63 patients (252 levels) met the inclusion criteria for the study, with a mean follow-up of 2.6 years. Complete radiographic fusion at all 4 levels was observed in 26 patients (41.3%). Of the 37 patients (58.7%) with radiographic pseudarthrosis, there was a mean of 1.35 nonfused levels. The fusion rate per level, however, was 80.2% (202/252 levels). The most common level demonstrating nonunion was the distal segment (C6-7), showing pseudarthrosis in 29 patients (46.8%), followed by the most proximal segment (C3-4) demonstrating nonunion in 9 patients (14.5%). The mean improvement in Neck Disability Index and Short Form-36 was 15.7 (p < 0.01) and 5.8 (p = 0.14), respectively, with improvement in both scores surpassing the minimum clinically important difference. One patient (1.6%) required revision surgery for symptomatic pseudarthrosis, and 5 patients (7.9%) underwent revision for symptomatic adjacent-segment disease. Patient-reported outcomes results are limited by the low rate of 1-year follow-up (50.8%), whereas reoperation data were available for all 63 patients. CONCLUSIONS: More than half of patients undergoing 4-level ACDF without posterior fixation demonstrated pseudarthrosis of at least 1 level-most commonly the distal C6-7 level. One patient required revision for symptomatic pseudarthrosis. Patient-reported outcomes showed significant improvements at 1-year follow-up, but clinical follow-up was limited. This is the largest series to date to evaluate fusion outcomes in 4-level ACDF.

Anatomical positional changes in the lateral lumbar interbody fusion.

INTRODUCTION: ALIFs and LLIFs are now becoming more utilized for adult spinal disease. As technologies advance, so do surgical techniques, with surgeons now modifying traditional supine-ALIF and lateral-LLIF to lateral-ALIF and prone-LLIF approaches to allow for more efficient surgeries. The objective of this study is to characterize the anatomical changes in the surgical corridor that occur with changes in patient positioning. METHODS: MRIs of ten healthy volunteers were evaluated in five positions: supine, prone with hips flexed, prone with hips extended, lateral with hips flexed, and lateral with hips extended. All lateral scans were in the left lateral decubitus position. The anatomical changes of the psoas muscles, inferior vena cava, aorta, iliac vessels were assessed with relation to fixed landmarks on the disc spaces from L1 to S1. RESULTS: The most anteriorly elongated ipsilateral to approach psoas when compared to supine was seen in lateral-flexed position (- 5.82 mm, p < 0.001), followed by lateral-extended (- 2.23 mm, p < 0.001), then prone-flexed (- 1.40 mm, p = 0.014), and finally supine and prone-extended (- 0.21 mm, p = 0.643). The most laterally extending or "thickest" psoas was seen in prone-flexed (- 1.40 mm, p = 0.004) and prone-extended (- 1.17 mm, p = 0.002). The psoas was "thinnest" in lateral-extended (2.03 mm, p < 0.001) followed by lateral-flexed (1.11 mm, p = 0.239). The contralateral psoas did not move as anteriorly as the ipsilateral. 3D volumetric analysis showed that the greatest changes in the psoas occur at its proximal and distal poles near T12-L1 and L4-S1. In lateral-flexed compared to prone-extended, the IVC moves medially to the left (p < 0.001). The aorta moves laterally to the left (p = 0.005). The venous structures appeared more full and open in the lateral positions and flattened in the supine and prone positions. The arteries remain in full calibre. CONCLUSION: The MRI anatomical evaluation shows that the psoas, and therefore lumbar plexus, and vasculature move significantly with changes in positioning. This is important for preoperative planning for proper intraoperative execution from preoperative supine MRI. Understanding that the psoas and vessels move the most anteriorly in the lateral-flexed position and to a least degree in the prone-extended is essential for safe and efficient utilization of techniques such as the traditional LLIF, traditional ALIF, prone-LLIF.

Kickstand rods and correction of coronal malalignment in patients with adult spinal deformity.

PURPOSE: Coronal malalignment (CM) is a challenging spinal deformity to treat. The kickstand rod (KR) technique is powerful for correcting truncal shift. This study tested the hypothesis that the KR technique provides superior coronal alignment correction in adult deformity compared with traditional rod techniques. METHODS: A retrospective evaluation of a prospectively collected multicenter database was performed. A 2:1 matched cohort of non-KR accessory rod and KR patients was planned based on preoperative coronal balance distance (CBD) and a vector of global shift. Patients were subgrouped according to CM classification with a 30-mm CBD threshold defining CM, and comparisons of surgical and clinical outcomes among groups was performed. RESULTS: Twenty-one patients with preoperative CM treated with a KR were matched to 36 controls. KR-treated patients had improved CBD compared with controls (18 vs. 35 mm, P < 0.01). The postoperative CBD did not result in clinical differences between groups in patient-reported outcomes (P ≥ 0.09). Eight (38%) of 21 KR patients and 12 (33%) of 36 control patients with preoperative CM had persistent postoperative CM (P = 0.72). CM class did not significantly affect the likelihood of treatment failure (postoperative CBD > 30 mm) in the KR cohort (P = 0.70), the control cohort (P = 0.35), or the overall population (P = 0.31). CONCLUSIONS: Application of the KR technique to coronal spinal deformity in adults allows for successful treatment of CM. Compared to traditional rod techniques, the use of KRs did not improve clinical outcome measures 1 year after spinal deformity surgery but was associated with better postoperative coronal alignment.

Mini-open lateral retropleural/retroperitoneal approaches for thoracic and thoracolumbar junction anterior column pathologies.

OBJECTIVE: Advancements in less invasive lateral retropleural/retroperitoneal approaches aim to address the limitation of posterolateral approaches and avoid complications associated with anterior open thoracotomy or thoracoabdominal approaches. METHODS: Consecutive patients treated with a mini-open lateral approach for thoracic or thoracolumbar anterior column pathologies were analyzed in a retrospective case series including clinical and radiographic outcomes. Special attention is given to operative techniques and surgical nuances. RESULTS: Eleven patients underwent a mini-open lateral retropleural or combined retropleural/retroperitoneal approach for thoracic or thoracolumbar junction lesions. Surgical indications included chronic fracture/deformity (n = 5), acute fracture (n = 2), neoplasm (n = 2), and osteomyelitis (n = 2). The mean length of postoperative hospital stay was 7.2 days (range 2-19 days). All patients ultimately had successful decompression and reconstruction with a mean follow-up of 16.7 months (range 6-29 months). Axial back pain assessed by the visual analog scale improved from a mean score of 8.2 to 2.2. Complications included 1 patient with deep venous thrombosis and pulmonary embolism and 1 with pneumonia. One patient developed increased leg weakness, which subsequently improved. One patient undergoing corpectomy with only lateral plate fixation developed cage subsidence requiring posterior stabilization. CONCLUSIONS: Mini-open lateral retropleural and retroperitoneal corpectomies can safely achieve anterior column reconstruction and spinal deformity correction for various thoracic and thoracolumbar vertebral pathologies.

Single-position prone lateral approach: cadaveric feasibility study and early clinical experience.

OBJECTIVE: Lateral lumbar interbody fusion (LLIF) is a useful minimally invasive technique for achieving anterior interbody fusion and preserving or restoring lumbar lordosis. However, achieving circumferential fusion via posterior instrumentation after an LLIF can be challenging, requiring either repositioning the patient or placing pedicle screws in the lateral position. Here, the authors explore an alternative single-position approach: LLIF in the prone lateral (PL) position. METHODS: A cadaveric feasibility study was performed using 2 human cadaveric specimens. A retrospective 2-center early clinical series was performed for patients who had undergone a minimally invasive lateral procedure in the prone position between August 2019 and March 2020. Case duration, retractor time, electrophysiological thresholds, implant size, screw accuracy, and complications were recorded. Early postoperative radiographic outcomes were reported. RESULTS: A PL LLIF was successfully performed in 2 cadavers without causing injury to a vessel or the bowel. No intraoperative subsidence was observed. In the clinical series, 12 patients underwent attempted PL surgery, although 1 case was converted to standard lateral positioning. Thus, 11 patients successfully underwent PL LLIF (89%) across 14 levels: L2-3 (2 of 14 [14%]), L3-4 (6 of 14 [43%]), and L4-5 (6 of 14 [43%]). For the 11 PL patients, the mean (± SD) age was 61 ± 16 years, mean BMI was 25.8 ± 4.8, and mean retractor time per level was 15 ± 6 minutes with the longest retractor time at L2-3 and the shortest at L4-5. No intraoperative subsidence was noted on routine postoperative imaging. CONCLUSIONS: Performing single-position lateral transpsoas interbody fusion with the patient prone is anatomically feasible, and in an early clinical experience, it appeared safe and reproducible. Prone positioning for a lateral approach presents an exciting opportunity for streamlining surgical access to the lumbar spine and facilitating more efficient surgical solutions with potential clinical and economic advantages.

Posterior open-wedge anterior longitudinal ligament release: Cadaveric technique analysis.

Anterior column release is a powerful surgical technique for achieving spinopelvic balance in adult patients with sagittal plane deformities. We present an alternative strategy for focal deformity correction from a posterior-only approach. The purpose of this study was to evaluate the feasibility and efficacy of a novel surgical technique called posterior open-wedge diskectomy and anterior longitudinal ligament (ALL) release (POWAR). A cadaveric torso underwent POWARs at the L1-L4 intervertebral disc spaces. Baseline measurements of end-plate angle (EPA), anterior intervertebral disc height (ADH), and posterior intervertebral disc height (PDH) were obtained. These measurements were repeated after three stages of correction: posterior column compression alone, posterior column compression following Schwab grade 2 osteotomies, and posterior column compression following POWAR. A second cadaver underwent posterolateral spinal dissection to demonstrate the pertinent anatomical features relevant to this novel procedure. With each stage of correction, a sequential increase in EPA and ADH and a decrease in PDH were demonstrated. The large increase in ADH seen following POWAR confirmed successful release of the ALL. In situ investigation of the aorta and inferior vena cava following anterior exposure revealed no injury to the great vessels or surrounding structures. Ex vivo testing of the aorta and inferior vena cava took place at the L3-4 level. This testing demonstrated no injury or tears to either vessel. POWAR is a new surgical technique that can provide an alternative to three-column osteotomy for surgeons performing spinal reconstructions in adults through an open, posterior-only approach. Clin. Anat. 32:348-353, 2019. © 2018 Wiley Periodicals, Inc.

Femoral nerve and lumbar plexus injury after minimally invasive lateral retroperitoneal transpsoas approach: electrodiagnostic prognostic indicators and a roadmap to recovery.

Injury to the lumbosacral (LS) plexus is a well-described complication after lateral retroperitoneal transpsoas approaches to the spine. The prognosis for functional recovery after lumbosacral plexopathy or femoral/obturator neuropathy is unclear. We designed a retrospective case-control study with patients undergoing one-level lateral retroperitoneal transpsoas lumbar interbody fusion (LLIF) between January 2011 and June 2016 to correlate electrodiagnostic assessments (EDX) to physiologic concepts of nerve injury and reinnervation, and attempt to build a timeline for patient evaluation and recovery. Cases with post-operative obturator or femoral neuropathy were identified. Post-operative MRI, nerve conduction studies (NCS), electromyography (EMG), and physical examinations were performed at intervals to assess clinical and electrophysiologic recovery of function. Two hundred thirty patients underwent LLIF. Six patients (2.6%) suffered severe femoral or femoral/obturator neuropathy. Five patients (2.2%) had immediate post-operative weakness. One of the six patients developed delayed weakness due to a retroperitoneal hematoma. Five out of six patients (83%) demonstrated EDX findings at 6 weeks consistent with axonotmesis. All patients improved to at least MRC 4/5 within 12 months of injury. In conclusion, neurapraxia is the most common LS plexus injury, and complete recovery is expected after 3 months. Most severe nerve injuries are a combination of neurapraxia and variable degrees of axonotmesis. EDX performed at 6 weeks and 3, 6, and 9 months provides prognostic information for recovery. In severe injuries of proximal femoral and obturator nerves, observation of proximal to distal progression of small-amplitude, short-duration (SASD) motor unit potentials may be the most significant prognostic indicator.

Minimally invasive anterior and lateral transpsoas approaches for closed reduction of grade II spondylolisthesis: initial clinical and radiographic experience.

OBJECTIVE Minimally invasive anterior and lateral approaches to the lumbar spine are increasingly used to treat and reduce grade I spondylolisthesis, but concerns still exist for their usage in the management of higher-grade lesions. The authors report their experience with this strategy for grade II spondylolisthesis in a single-surgeon case series and provide early clinical and radiographic outcomes. METHODS A retrospective review of a single surgeon's cases between 2012 and 2016 identified all patients with a Meyerding grade II lumbar spondylolisthesis who underwent minimally invasive lateral lumbar interbody fusion (LLIF) or anterior lumbar interbody fusion (ALIF) targeting the slipped level. Demographic, clinical, and radiographic data were collected and analyzed. Changes in radiographic measurements, Oswestry Disability Index (ODI), and visual analog scale (VAS) scores were compared using the paired t-test and Wilcoxon signed rank test for continuous and ordinal variables, respectively. RESULTS The average operative time was 199.1 minutes (with 60.6 ml of estimated blood loss) for LLIFs and 282.1 minutes (with 106.3 ml of estimated blood loss), for ALIFs. Three LLIF patients had transient unilateral anterior thigh numbness during the 1st week after surgery, and 1 ALIF patient had transient dorsiflexion weakness, which was resolved at postoperative week 1. The mean follow-up time was 17.6 months (SD 12.5 months) for LLIF patients and 10 months (SD 3.1 months) for ALIF patients. Complete reduction of the spondylolisthesis was achieved in 12 LLIF patients (75.0%) and 7 ALIF patients (87.5%). Across both procedures, there was an increase in both the segmental lordosis (LLIF 5.6°, p = 0.002; ALIF 15.0°, p = 0.002) and overall lumbar lordosis (LLIF 2.9°, p = 0.151; ALIF 5.1°, p = 0.006) after surgery. Statistically significant decreases in the mean VAS and the mean ODI measurements were seen in both treatment groups. The VAS and ODI scores fell by a mean value of 3.9 (p = 0.002) and 19.8 (p = 0.001), respectively, for LLIF patients and 3.8 (p = 0.02) and 21.0 (p = 0.03), respectively, for ALIF patients at last follow-up. CONCLUSIONS Early clinical and radiographic results from using minimally invasive LLIF and ALIF approaches to treat grade II spondylolisthesis appear to be good, with low operative blood loss and no neurological deficits. Complete reduction of the spondylolisthesis is frequently possible with a statistically significant reduction in pain scores.

Complication rates associated with open versus percutaneous pedicle screw instrumentation among patients undergoing minimally invasive interbody fusion for adult spinal deformity.

OBJECTIVE High-quality studies that compare outcomes of open and minimally invasively placed pedicle screws for adult spinal deformity are needed. Therefore, the authors compared differences in complications from a circumferential minimally invasive spine (MIS) surgery and those from a hybrid surgery. METHODS A retrospective review of a multicenter database of patients with spinal deformity who were treated with an MIS surgery was performed. Database inclusion criteria included an age of ≥ 18 years and at least 1 of the following: a coronal Cobb angle of > 20°, a sagittal vertical axis of > 5 cm, a pelvic incidence-lumbar lordosis angle of > 10°, and/or a pelvic tilt of > 20°. Patients were propensity matched according to the levels instrumented. RESULTS In this database, a complete data set was available for 165 patients, and after those who underwent 3-column osteotomy were excluded, 137 patients were available for analysis; 76 patients remained after propensity matching (MIS surgery group 38 patients, hybrid surgery group 38 patients). The authors found no difference in demographics, number of levels instrumented, or preoperative and postoperative radiographic results. At least 1 complication was suffered by 55.3% of patients in the hybrid surgery group and 44.7% of those in the MIS surgery group (p = 0.359). Patients in the MIS surgery group had significantly fewer neurological, operative, and minor complications than those in the hybrid surgery group. The reoperation rates in both groups were similar. The most common complication category for the MIS surgery group was radiographic and for the hybrid surgery group was neurological. Patients in both groups experienced postoperative improvement in their Oswestry Disability Index and visual analog scale (VAS) back and leg pain scores (all p < 0.05); however, MIS surgery provided a greater reduction in leg pain according to VAS scores. CONCLUSIONS Overall complication rates in the MIS and hybrid surgery groups were similar. MIS surgery resulted in significantly fewer neurological, operative, and minor complications. Reoperation rates in the 2 groups were similar, and despite complications, the patients reported significant improvement in their pain and function.

Impact of case type, length of stay, institution type, and comorbidities on Medicare diagnosis-related group reimbursement for adult spinal deformity surgery.

OBJECTIVE The aim of this study was to educate medical professionals about potential financial impacts of improper diagnosis-related group (DRG) coding in adult spinal deformity (ASD) surgery. METHODS Medicare's Inpatient Prospective Payment System PC Pricer database was used to collect 2015 reimbursement data for ASD procedures from 12 hospitals. Case type, hospital type/location, number of operative levels, proper coding, length of stay, and complications/comorbidities (CCs) were analyzed for effects on reimbursement. DRGs were used to categorize cases into 3 types: 1) anterior or posterior only fusion, 2) anterior fusion with posterior percutaneous fixation with no dorsal fusion, and 3) combined anterior and posterior fixation and fusion. RESULTS Pooling institutions, cases were reimbursed the same for single-level and multilevel ASD surgery. Longer stay, from 3 to 8 days, resulted in an additional $1400 per stay. Posterior fusion was an additional $6588, while CCs increased reimbursement by approximately $13,000. Academic institutions received higher reimbursement than private institutions, i.e., approximately $14,000 (Case Types 1 and 2) and approximately $16,000 (Case Type 3). Urban institutions received higher reimbursement than suburban institutions, i.e., approximately $3000 (Case Types 1 and 2) and approximately $3500 (Case Type 3). Longer stay, from 3 to 8 days, increased reimbursement between $208 and $494 for private institutions and between $1397 and $1879 for academic institutions per stay. CONCLUSIONS Reimbursement is based on many factors not controlled by surgeons or hospitals, but proper DRG coding can significantly impact the financial health of hospitals and availability of quality patient care.

Reoperation rates in minimally invasive, hybrid and open surgical treatment for adult spinal deformity with minimum 2-year follow-up.

INTRODUCTION: Minimally invasive surgical (MIS) techniques are gaining popularity in the treatment of adult spinal deformity (ASD). The premise is that MIS techniques will lead to equivalent outcomes and a reduction in perioperative complications when compared with open techniques. Potential issues with MIS techniques are a limited capacity to correct lumbar lordosis, unknown long-term efficacy, and the potential need for revision surgery. This study compares reoperation rates and reasons for reoperation following MIS, hybrid, and open surgery for ASD through multicenter database analysis. METHODS: We retrospectively analyzed a prospective multicenter ASD database comparing open and MIS correction techniques. Inclusion criteria were: age > 18 years with minimum 20° coronal lumbar Cobb angle, a minimum of three levels fused, and minimum 2-year follow-up. Patients were propensity matched for preoperative sagittal vertebral axis (SVA), pelvic incidence-lumbar lordosis (PI-LL), and number of levels fused. We included 189 patients from three propensity-matched subgroups of 63 patients each: (1) MIS: lateral or transforaminal lumbar interbody fusion (LIF) and percutaneous pedicle instrumentation, (2) Hybrid: MIS LIF with open posterior segmental fixation (PSF), and (3) OPEN: open posterior fixation ± osteotomies. RESULTS: With propensity matching, there were significant differences between groups in pre-op SVA or PI-LL (p > 0.05). The MIS group had significantly fewer levels fused (5.4) (0-14) than the OPEN group (7.4) (p = 0.002) (0-17). The rate of revision surgery was significantly different between the groups with a higher rate of revision (27 %) amongst the HYB group versus MIS = 11.1 %, and OPEN = 12.0 %. The most common reason for reoperation in the OPEN and HYB groups was a postoperative neurological deficit (7.9 and 11.1 %), respectively. The most common reason for reoperation in the MIS group was pseudoarthrosis (7.9 %). CONCLUSIONS: Reoperation rates were not statistically different among the MIS, and OPEN surgical groups, but differed significantly on multivariate analysis with HYB group. The incidence of reoperations was twice as high in the Hybrid group compared to OPEN and MIS.

Visceral, vascular, and wound complications following over 13,000 lateral interbody fusions: a survey study and literature review.

PURPOSE: Minimally invasive lateral interbody fusion (MIS-LIF) has become a popular less invasive treatment option for degenerative spinal disease, deformity, and trauma. While MIS-LIF offers several advantages over traditional anterior and posterior approaches, the procedure is not without risk. The purpose of this study was to evaluate the incidence of visceral, vascular, and wound complications following MIS-LIF performed by experienced surgeons. METHODS: A survey was conducted by experienced (more than 100 case experience) MIS-LIF surgeons active in the society of lateral access surgery (SOLAS) to collect data on wound infections and visceral and vascular injuries. Of 77 spine surgeons surveyed, 40 (52 %) responded, including 25 (63 %) orthopedic surgeons and 15 (38 %) neurosurgeons, with 20 % practicing at an academic institution and 80 % in community practice. RESULTS: Between 2003 and 2013, 13,004 patients were treated with MIS-LIF by the 40 surgeons who responded to the survey. Of those patients, 0.08 % experienced a visceral complication (bowel injury), 0.10 % experienced a vascular injury, 0.27 % experienced a superficial wound infection, and 0.14 % experienced a deep wound infection. CONCLUSION: The incidence of surgical site infections and vascular and visceral complications following MIS-LIF in this large series was low and compared favorably with rates for alternative interbody fusion approaches. Although technically demanding, MIS-LIF is a reproducible approach for interbody fusion with a low risk of vascular and visceral complications and infections.

Complications and neurological deficits following minimally invasive anterior column release for adult spinal deformity: a retrospective study.

BACKGROUND: Minimally invasive techniques have become increasing popular and are expanding into deformity surgery. The lateral retroperitoneal transpsoas anterior column release (ACR) is a newer minimally invasive alternative to posterior osteotomy techniques for correcting and promoting global spinal alignment. This procedure attempts to avoid the potential complications associated with conventional osteotomies, but has its own subset of unique complications to be discussed in depth. METHODS: A retrospective review was performed in all patients who underwent the minimally invasive (MIS) ACR procedure from 2010 to present at our institution. All perioperative and postoperative complications were recorded by an independent reviewer. Demographics, spinopelvic parameters, and operative data were collected. The primary etiologic diagnosis was adult spinal deformity. Spinopelvic parameters were measured based on standing 36-inch scoliosis films. RESULTS: Thirty-one patients underwent a total of 47 MIS-ACRs. The mean age of the cohort was 62. Mean follow up was 12 months (range 3-38 months). The average change from in lumbar lordosis (LL) was 17.6°, in pelvic tilt was 4.3°, coronal Cobb was 13.9 and in SVA was 3.8 cm. Of the 47 MIS-ACR procedures, there were 9 (9/47, 19 %) major complications related to the ACR. Iliopsoas weakness was seen in eight patients and retrograde ejaculation in one patient. Only one patient remained with mild motor deficit at the most recent follow-up. No revision surgeries were required for the anterolateral approach. There was no vascular, visceral, or infectious complications associated with the MIS-ACR. CONCLUSION: The MIS-ACR is one of the most technically demanding procedures performed from the lateral transpsoas approach. This procedure has the advantage of maintaining and improving spinal global alignment while minimizing blood loss and excessive tissue dissection. It comes with its own unique set of potentially catastrophic complications and should only be performed by surgeons proficient in both deformity correction and the lateral approach.

Can triggered electromyography monitoring throughout retraction predict postoperative symptomatic neuropraxia after XLIF? Results from a prospective multicenter trial.

PURPOSE: This multicenter study aims to evaluate the utility of triggered electromyography (t-EMG) recorded throughout psoas retraction during lateral transpsoas interbody fusion to predict postoperative changes in motor function. METHODS: Three hundred and twenty-three patients undergoing L4-5 minimally invasive lateral interbody fusion from 21 sites were enrolled. Intraoperative data collection included initial t-EMG thresholds in response to posterior retractor blade stimulation and subsequent t-EMG threshold values collected every 5 min throughout retraction. Additional data collection included dimensions/duration of retraction as well as pre-and postoperative lower extremity neurologic exams. RESULTS: Prior to expanding the retractor, the lowestt-EMG threshold was identified posterior to the retractor in 94 % of cases. Postoperatively, 13 (4.5 %) patients had a new motor weakness that was consistent with symptomatic neuropraxia (SN) of lumbar plexus nerves on the approach side. There were no significant differences between patients with or without a corresponding postoperative SN with respect to initial posterior blade reading (p = 0.600), or retraction dimensions (p > 0.05). Retraction time was significantly longer in those patients with SN vs. those without (p = 0.031). Stepwise logistic regression showed a significant positive relationship between the presence of new postoperative SN and total retraction time (p < 0.001), as well as change in t-EMG thresholds over time (p < 0.001), although false positive rates (increased threshold in patients with no new SN) remained high regardless of the absolute increase in threshold used to define an alarm criteria. CONCLUSIONS: Prolonged retraction time and coincident increases in t-EMG thresholds are predictors of declining nerve integrity. Increasing t-EMG thresholds, while predictive of injury, were also observed in a large number of patients without iatrogenic injury, with a greater predictive value in cases with extended duration. In addition to a careful approach with minimal muscle retraction and consistent lumbar plexus directional retraction, the incidence of postoperative motor neuropraxia may be reduced by limiting retraction time and utilizing t-EMG throughout retraction, while understanding that the specificity of this monitoring technique is low during initial retraction and increases with longer retraction duration.

Finite element analysis of lordosis restoration with anterior longitudinal ligament release and lateral hyperlordotic cage placement.

PURPOSE: Restoring sagittal alignment is an important factor in the treatment of spinal deformities. Recent investigations have determined that releasing the anterior longitudinal ligament (ALL) and placing hyperlordotic cages can increase lordosis, while minimizing need for 3 column osteotomies. The influences of parameters such as cage height and angle have not been determined. Finite element analysis was employed to assess the extent of lordosis achievable after placement of different sized lordotic cages. METHODS: A 3-dimensional model of a L3-4 segment was used. Disc distraction was simulated by inserting interbody cages mid-body in the disc space. Analyses were performed in the following conditions: (1) intact, (2) ALL release, (3) ALL release + facetectomy, and (4) ALL release + posterior column osteotomy. Changes in segmental lordosis, disc height, foraminal height, and foraminal area were measured. RESULTS: After ALL resection and insertion of hyperlordotic cages, lordosis was increased in all cases. The lordosis achieved by the shorter cages was less due to posterior disc height maintained by the facet joints. A facetectomy increased segmental lordosis, but led to contact between the spinous processes. For some configurations, a posterior column osteotomy was required if the end goal was to match cage angle to intradiscal angle. CONCLUSION: Increased segmental lumbar lordosis is achievable with hyperlordotic cages after ALL resection. Increased cage height tended to increase the amount of lordosis achieved, although in some cases additional posterior bone resection was required to maximize lordosis. Further studies are needed to evaluate the impact on regional lumbar lordosis.

Minimally invasive surgical techniques in adult degenerative spinal deformity: a systematic review.

BACKGROUND: Minimally invasive surgery (MIS) approaches have the potential to reduce procedure-related morbidity when compared with traditional approaches. However, the magnitude of radiographic correction and degree of clinical improvement with MIS techniques for adult spinal deformity remain undefined. QUESTION/PURPOSES: In this systematic review, we sought to determine whether MIS approaches to adult spinal deformity correction (1) improve pain and function; (2) reliably correct deformity and result in fusion; and (3) are safe with respect to surgical and medical complications. METHODS: A systematic review of PubMed and Medline databases was performed for published articles from 1950 to August 2013. A total of 1053 papers were identified. Thirteen papers were selected based on prespecified criteria, including a total of 262 patients. Studies with limited short-term followup (mean, 12.1 months; range, 1.5-39 months) were included to capture early complications. All of the papers included in the review constituted Level IV evidence. Patient age ranged from 20 to 86 years with a mean of 65.8 years. Inclusion and exclusion criteria were variable, but all required at minimum a diagnosis of adult degenerative scoliosis. RESULTS: Four studies demonstrated improvement in leg/back visual analog scale, three demonstrated improvement in the Oswestry Disability Index, one demonstrated improvement in treatment intensity scale, and one improvement in SF-36. Reported fusion rates ranged from 71.4% to 100% 1 year postoperatively, but only two of 13 papers relied consistently on CT scan to assess fusion, and, interestingly, only four of 10 studies reporting radiographic results on deformity correction found the procedures effective in correcting deformity. There were 115 complications reported among the 258 patients (46%), including 37 neurological complications (14%). CONCLUSIONS: The literature on these techniques is scanty; only two of the 13 studies that met inclusion criteria were considered high quality; CT scans were not generally used to evaluate fusion, deformity correction was inconsistent, and complication rates were high. Future directions for analysis must include comparative trials, longer-term followup, and consistent use of CT scans to assess for fusion to determine the role of MIS techniques for adult spinal deformity.

Complications in adult spinal deformity surgery: an analysis of minimally invasive, hybrid, and open surgical techniques.

OBJECT: It is hypothesized that minimally invasive surgical techniques lead to fewer complications than open surgery for adult spinal deformity (ASD). The goal of this study was to analyze matched patient cohorts in an attempt to isolate the impact of approach on adverse events. METHODS: Two multicenter databases queried for patients with ASD treated via surgery and at least 1 year of follow-up revealed 280 patients who had undergone minimally invasive surgery (MIS) or a hybrid procedure (HYB; n = 85) or open surgery (OPEN; n = 195). These patients were divided into 3 separate groups based on the approach performed and were propensity matched for age, preoperative sagittal vertebral axis (SVA), number of levels fused posteriorly, and lumbar coronal Cobb angle (CCA) in an attempt to neutralize these patient variables and to make conclusions based on approach only. Inclusion criteria for both databases were similar, and inclusion criteria specific to this study consisted of an age > 45 years, CCA > 20°, 3 or more levels of fusion, and minimum of 1 year of follow-up. Patients in the OPEN group with a thoracic CCA > 75° were excluded to further ensure a more homogeneous patient population. RESULTS: In all, 60 matched patients were available for analysis (MIS = 20, HYB = 20, OPEN = 20). Blood loss was less in the MIS group than in the HYB and OPEN groups, but a significant difference was only found between the MIS and the OPEN group (669 vs 2322 ml, p = 0.001). The MIS and HYB groups had more fused interbody levels (4.5 and 4.1, respectively) than the OPEN group (1.6, p < 0.001). The OPEN group had less operative time than either the MIS or HYB group, but it was only statistically different from the HYB group (367 vs 665 minutes, p < 0.001). There was no significant difference in the duration of hospital stay among the groups. In patients with complete data, the overall complication rate was 45.5% (25 of 55). There was no significant difference in the total complication rate among the MIS, HYB, and OPEN groups (30%, 47%, and 63%, respectively; p = 0.147). No intraoperative complications were reported for the MIS group, 5.3% for the HYB group, and 25% for the OPEN group (p < 0.03). At least one postoperative complication occurred in 30%, 47%, and 50% (p = 0.40) of the MIS, HYB, and OPEN groups, respectively. One major complication occurred in 30%, 47%, and 63% (p = 0.147) of the MIS, HYB, and OPEN groups, respectively. All patients had significant improvement in both the Oswestry Disability Index (ODI) and visual analog scale scores after surgery (p < 0.001), although the MIS group did not have significant improvement in leg pain. The occurrence of complications had no impact on the ODI. CONCLUSIONS: Results in this study suggest that the surgical approach may impact complications. The MIS group had significantly fewer intraoperative complications than did either the HYB or OPEN groups. If the goals of ASD surgery can be achieved, consideration should be given to less invasive techniques.

The minimally invasive spinal deformity surgery algorithm: a reproducible rational framework for decision making in minimally invasive spinal deformity surgery.

OBJECT: Minimally invasive surgery (MIS) is an alternative to open deformity surgery for the treatment of patients with adult spinal deformity. However, at this time MIS techniques are not as versatile as open deformity techniques, and MIS techniques have been reported to result in suboptimal sagittal plane correction or pseudarthrosis when used for severe deformities. The minimally invasive spinal deformity surgery (MISDEF) algorithm was created to provide a framework for rational decision making for surgeons who are considering MIS versus open spine surgery. METHODS: A team of experienced spinal deformity surgeons developed the MISDEF algorithm that incorporates a patient's preoperative radiographic parameters and leads to one of 3 general plans ranging from MIS direct or indirect decompression to open deformity surgery with osteotomies. The authors surveyed fellowship-trained spine surgeons experienced with spinal deformity surgery to validate the algorithm using a set of 20 cases to establish interobserver reliability. They then resurveyed the same surgeons 2 months later with the same cases presented in a different sequence to establish intraobserver reliability. Responses were collected and tabulated. Fleiss' analysis was performed using MATLAB software. RESULTS: Over a 3-month period, 11 surgeons completed the surveys. Responses for MISDEF algorithm case review demonstrated an interobserver kappa of 0.58 for the first round of surveys and an interobserver kappa of 0.69 for the second round of surveys, consistent with substantial agreement. In at least 10 cases there was perfect agreement between the reviewing surgeons. The mean intraobserver kappa for the 2 surveys was 0.86 ± 0.15 (± SD) and ranged from 0.62 to 1. CONCLUSIONS: The use of the MISDEF algorithm provides consistent and straightforward guidance for surgeons who are considering either an MIS or an open approach for the treatment of patients with adult spinal deformity. The MISDEF algorithm was found to have substantial inter- and intraobserver agreement. Although further studies are needed, the application of this algorithm could provide a platform for surgeons to achieve the desired goals of surgery.