Development of Proximal Junctional Kyphosis After Minimally Invasive Lateral Anterior Column Realignment for Adult Spinal Deformity.

BACKGROUND: Development of proximal junctional kyphosis (PJK) after correction of adult spinal deformity (ASD) undermines sagittal alignment. Minimally invasive anterior column realignment (ACR) is a powerful tool for correction of ASD; however, long-term PJK rates are unknown. OBJECTIVE: To characterize PJK after utilization of ACR in ASD correction. METHODS: A retrospective multi-institution cohort analysis per STROBE criteria was conducted of all patients who underwent lateral lumbar interbody fusion (LLIF) or ACR for ASD from 2010 to 2015. All patients obtained preoperative and follow-up upright radiographs, assessing spinal alignment and development of PJK. Patients without proper imaging or minimum 1-yr follow-up were excluded. RESULTS: A total of 73 of 112 patients who underwent either LLIF or ACR for ASD met inclusion criteria. Mean follow-up was 22.8 mo. There was significant improvement of all spinopelvic parameters. Overall, PJK and proximal junctional failure (PJF) rates were 20.5% and 11%, respectively. The incidence of PJK increased with greater corrective surgery (0% LLIF, 30% ACR, 42.9% ACR + posterior column osteotomy (PCO); P < .001). PJF rates increased (0% LLIF, 11% ACR, 40% ACR + PCO; P = .005). Risk factors included location of the upper-instrumented vertebra at T10-L1 vs L2-L4 (P = .007), age (P = .029), severity of ASD, and overcorrection of sagittal imbalance. CONCLUSION: The incidence of PJK after minimally invasive ACR is slightly lower than reported after open surgery but greater than in LLIF only and increases with PCO utilization. The PJK rate increases when crossing the TL junction, sagittal imbalance severity, and overcorrection. Elderly patients are at an increased risk, suggesting need for age appropriate correction goals.

Incisional Hernia After Minimally Invasive Lateral Retroperitoneal Surgery: Case Series and Review of the Literature.

BACKGROUND: Minimally invasive lateral retroperitoneal (lateral-MIS) approaches to the spine involve traversing the lateral abdominal wall musculature and fascia. Incisional hernia is an uncommon approach-related complication. OBJECTIVE: To review the incidence, treatment, and preventative measures of incisional hernia after lateral-MIS approaches. METHODS: This is a retrospective review of cases performed by a single surgeon from 2011 to 2016. All patients who underwent lateral-MIS approaches at this institution were included. Patients with a postoperative diagnosis of lateral hernia on physical exam and corroborating advanced imaging findings were included in this study. Cases of flank bulge due to peripheral nerve injury were excluded. RESULTS: Three-hundred three patients underwent lateral-MIS approaches to the spine. Three (1%) patients with incisional hernia were identified. Two patients presented with a clinically symptomatic incisional hernia, while 1 patient was diagnosed incidentally after a routine abdominal magnetic resonance imaging for an unrelated reason. No patients suffered bowel entrapment or strangulation. CONCLUSION: Incisional hernia after lateral-MIS approaches is rare. Patients with incisional hernias may be susceptible to bowel incarceration and ischemia, though the incidence of this is probably low. Meticulous closure of the fascia is critical to avoiding this complication.

Morphometric Analysis of Lumbar Intervertebral Disc Height: An Imaging Study.

BACKGROUND: Little published data exist regarding normal values of disc height. Current literature relies on plain radiographs making accurate measurements of individual lumbar disc height difficult. OBJECTIVE: We seek to establish normal values for lumbar intervertebral discs in different age groups using computed tomography scans in healthy individuals. METHODS: Two hundred forty anonymized abdominal computed tomography scans (131 women) were prospectively collected once institutional review board approval was obtained. Individuals with spinal pathologies were excluded. Disc height measurements were obtained at the anterior edge, center, and posterior edge of each vertebra in the midsagittal plane, averaged, and compared against age and sex. RESULTS: Average age was 45 (14-83) years for women and 48 (14-89) years for men. Average lumbar disc height was 5.6 ± 1.1 mm for men and 4.8 ± 0.8 mm for women at T12/L1, 6.9 ± 1.3 mm for men and 5.8 ± 0.9 mm for women at L1/2, 8.1 ± 1.4 mm for men and 6.9 ± 1.1 mm for women at L2/3, 8.7 ± 1.5 mm for men and 7.6 ± 1.2 mm for women at L3/4, 9.2 ± 1.6 mm for men and 8.5 ± 1.6 mm for women at L4/5, and 8.8 ± 1.6 mm for men and 8.6 ± 1.8 mm for women at L5/S1. Disc height was significantly smaller for women than men (P < 0.001), except at L5/S1. CONCLUSIONS: Variation in disc height is determined much more by sex than age. The maximum height of the interbody space in the adult lumbar spine was at the L4/5 level (8.9 ± 1.7 mm [men], 8.6 ± 1.8 mm [women]). Based on our findings, >10 mm cage height will result in supraphysiologic interbody space restoration and potentially predispose to complications.

The comprehensive anatomical spinal osteotomy and anterior column realignment classification.

OBJECTIVESpinal osteotomies and anterior column realignment (ACR) are procedures that allow preservation or restoration of spine lordosis. Variations of these techniques enable different degrees of segmental, regional, and global sagittal realignment. The authors propose a comprehensive anatomical classification system for ACR and its variants based on the level of technical complexity and invasiveness. This serves as a common language and platform to standardize clinical and radiographic outcomes for the utilization of ACR.METHODSThe proposed classification is based on 6 anatomical grades of ACR, including anterior longitudinal ligament (ALL) release, with varying degrees of posterior column release or osteotomies. Additionally, a surgical approach (anterior, lateral, or posterior) was added. Reliability of the classification was evaluated by an analysis of 16 clinical cases, rated twice by 14 different spine surgeons, and calculation of Fleiss kappa coefficients.RESULTSThe 6 grades of ACR are as follows: grade A, ALL release with hyperlordotic cage, intact posterior elements; grade 1 (ACR + Schwab grade 1), additional resection of the inferior facet and joint capsule; grade 2 (ACR + Schwab grade 2), additional resection of both superior and inferior facets, interspinous ligament, ligamentum flavum, lamina, and spinous process; grade 3 (ACR + Schwab grade 3), additional adjacent-level 3-column osteotomy including pedicle subtraction osteotomy; grade 4 (ACR + Schwab grade 4), 2-level distal 3-column osteotomy including pedicle subtraction osteotomy and disc space resection; and grade 5 (ACR + Schwab grade 5), complete or partial removal of a vertebral body and both adjacent discs with or without posterior element resection. Intraobserver and interobserver reliability were 97% and 98%, respectively, across the 14-reviewer cohort.CONCLUSIONSThe proposed anatomical realignment classification provides a consistent description of the various posterior and anterior column release/osteotomies. This reliability study confirmed that the classification is consistent and reproducible across a diverse group of spine surgeons.

Minimally Invasive Lateral Transpsoas Interbody Fusion at the L4/5 Level: A Review of 61 Consecutive Cases.

BACKGROUND: Reported complication rates for minimally invasive lateral transpsoas interbody fusion (MIS-LIF) vary widely. The risk of lumbar plexus injury is particularly concerning at the L4-5 disc space. We report our experience with MIS-LIF at L4-5, and discuss the risk profile of transpsoas approaches at this level. OBJECTIVE: To evaluate safety of MIS-LIF at the L4/5 level. METHODS: This was a retrospective, IRB-approved cohort study performed at a single institution from 2011 to 2016. Patients who underwent MIS-LIF at L4-5 were included. Patients with multilevel fusions were excluded. We analyzed postoperative sensory and motor deficits, the date of resolution, health-related quality-of-life scores, and rate of fusion. RESULTS: Over a 5-yr period, 303 patients underwent MIS-LIF at our institution. Sixty-one patients had surgery only at the L4-5 level (20.1%). Twelve of these patients (19.6%) had postoperative neurological deficits including 2 motor deficits (2/61 = 3.2%) and 11/61 (18%) sensory deficits. At 12-mo follow-up, 3 of the deficits persisted for a long-term complication rate of 3/61 (4.9%), motor complication 2/61 (3.2%). Hospital stay and follow-up averaged 2.1 d and 15 mo. Average Oswestry Disability Index improved from 51.1 to 31.1 (P < .00001). Visual Analog Scale (VAS) improved from 7.4 to 3.9 (P < .016). There were no reoperations secondary to hardware failure or pseudoarthrosis. Fusion rate was 89% at 12 mo. CONCLUSION: MIS-LIF is a safe and effective approach for interbody fusion at L4-5 with low rate of lumbar plexus injury. Most immediate postoperative deficits will resolve over time.

Limitations and complications of minimally invasive spinal surgery in adult deformity.

Minimally invasive spine (MIS) surgery has rapidly progressed from simple short segment fusions to large adult deformity corrections, with radiographic and clinical outcomes as good as those of open surgery. Anterior longitudinal ligament release (ALLR) and anterior column realignment (ACR) have been key advancements in the ability to correct deformity using MIS techniques. However, patient selection and appropriate preoperative workup is critical to obtain good outcomes and for complication avoidance. Despite favorable outcomes in spinal deformity surgery, MIS techniques are limited in (I) pronounced cervical or thoracic deformity; (II) patients with prior fusion mass; and (III) severe sagittal imbalance necessitating Schwab 5 osteotomy or higher. Guidelines for proper patient selection are needed to guide MIS spine surgeons in choosing the right candidate.

Patients with High Pelvic Tilt Achieve the Same Clinical Success as Those with Low Pelvic Tilt After Minimally Invasive Adult Deformity Surgery.

BACKGROUND: Pelvic tilt (PT) is a compensatory mechanism for adult spinal deformity patients to mitigate sagittal imbalance. The association between preop PT and postop clinical and radiographic outcomes has not been well studied in patients undergoing minimally invasive adult deformity surgery. OBJECTIVE: To evaluate clinical and radiographic outcomes in adult spinal deformity patients with high and low preoperative PT treated surgically using less invasive techniques. METHODS: Retrospective case-control, institutional review board-approved study. A multicenter, minimally invasive surgery spinal deformity patient database was queried for 2-yr follow-up with complete radiographic and health-related quality of life (HRQOL) data. Hybrid surgery patients were excluded. Inclusion criteria were as follows: age > 18 and either coronal Cobb angle > 20, sagittal vertical axis > 5 cm, pelvic incidence-lumbar lordosis (PI-LL) > 10 or PT > 20. Patients were stratified by preop PT as per Schwab classification: low (PT< 20), mid (PT 20-30), or high (>30). Postoperative radiographic alignment parameters (PT, PI, LL, Cobb angle, sagittal vertical axis) and HRQOL data (Visual Analog Scale Back/Leg, Oswestry Disability Index) were evaluated and analyzed. RESULTS: One hundred sixty-five patients had complete 2-yr outcomes data, and 64 patients met inclusion criteria (25 low, 21 mid, 18 high PT). High PT group had higher preop PI-LL mismatch (32.1 vs 4.7; P < .001). At last follow-up, 76.5% of patients in the high PT group had continued PI-LL mismatch compared to 34.8% in the low PT group (P < .006). There was a difference between groups in terms of postop changes of PT (-3.9 vs 1.9), LL (8.7 vs 0.5), and PI-LL (-9.5 vs 0.1). Postoperatively, HRQOL data (Oswestry Disability Index and Visual Analog Scale) were significantly improved in both groups (P < .001). CONCLUSION: Adult deformity patients with high preoperative PT treated with minimally invasive surgical techniques had less radiographic success but equivalent clinical outcomes as patients with low PT.

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.

Biomechanical study of rod stress after pedicle subtraction osteotomy versus anterior column reconstruction: A finite element study.

BACKGROUND: In an effort to minimize rod fractures and nonunion in pedicle subtraction osteotomy (PSO) constructs, surgeons have adopted multirod constructs and interbody cages. Anterior column realignment (ACR) with posterior column osteotomies is a minimally invasive alternative to PSO in sagittal balance correction, however, there is a paucity of evidence with respect to rod survival. METHODS: Three-dimensional (3D) finite-element-model of a T12-sacrum spine segment was used to compare a 25° PSO at L3 and an ACR with a posterior column osteotomy and 30° hyperlordotic interbody cage at L3-4. The amount of overall T12-S1 lordosis correction was the same for each condition. Each simulation included cobalt chromium alloy primary rods with: (1) PSO; (2) PSO with an interbody cage (IB) at L2-3 (PSO+IB); (3) PSO with accessory (A) rods and IB at L2-3 (PSO+IB+A); (4) PSO with satellite (S) rods and IB at L2-3 (PSO+IB+2S); (5) ACR; 6) ACR with satellite rods (ACR + 2S). A 400 N follower preload was simulated for each condition. RESULTS: PSO condition had the largest rod stress of 286 MPa in flexion. Adding interbody support reduced the rod stress by 15%. The 4-rod constructs further reduced rod stress, with the satellite rod condition facilitating the largest reduction. The rod stress in the ACR+2S was equivalent to the PSO+2S, with 50% reduction in rod stress. CONCLUSION: The rod stress with an ACR was comparable to a PSO coupled with interbody support. These results suggest an ACR is a viable MIS alternative to a PSO without the need for a large posterior osteotomy.

Indirect decompression and reduction of lumbar spondylolisthesis does not result in higher rates of immediate and long term complications.

Nerve root decompression and spondylolisthesis reduction is typically reserved for open surgery. MIS techniques have been thought to be associated with higher rates of neurological complications. This study aims to report acute and chronic neurologic complications encountered with MIS surgery for spondylolisthesis, specifically, the incidence of nerve root injury and clinical and radiographic outcomes. A retrospective review of 269 patients who underwent MIS LIF or ALIF treatment for lumbar degenerative or isthmic grade 1 or 2 spondylolisthesis was conducted. Immediate and long-term complication rates were the primary outcome. Only patients who had symptomatic anterolisthesis and 2-year outcome data were included in the study. 52 patients met inclusion criteria with 54 lumbar spondylolisthesis levels treated. Five patients (9.6%) experienced postoperative anterior thigh numbness, which completely resolved within 3months. There were no permanent neurologic deficits; however, 2 patients (3.8%) suffered a transient foot weakness that resolved with physical therapy by 3months follow-up. There was one incidence of wound breakdown that required revision and one incidence of L5/S1 endplate/sacral promontory fracture and relisthesis 3months postoperatively. Overall fusion rate was 98% at 6months. Indirect decompression and closed anatomical reduction for treatment of low-grade spondylolisthesis using ALIF and LIF with posterior percutaneous fixation was not associated with an increased risk of neurologic deficit. This study suggests that this technique is safe, reproducible, durable, and provides adequate fusion rates.

The Potentially Fatal Ogilvie's Syndrome in Lateral Transpsoas Access Surgery: A Multi-Institutional Experience with 2930 Patients.

BACKGROUND: Ogilvie's syndrome (OS) is a relatively uncommon pathology characterized by significant colonic dilation in the absence of mechanical obstruction. If unrecognized and untreated, cecal perforation resulting in a mortality rate of 25%-71% may occur. It is a potentially underdiagnosed condition in the lateral transpsoas approach population because of its uncommon nature and imitation of other well-known pathologies. METHODS: Two thousand nine hundred and thirty patients from 6 separate institutions were retrospectively reviewed since 2007 and screened for OS. All patients underwent a minimum of single-level lateral transpsoas fusion. Diagnostic criteria included signs of a postoperative paralytic ileus combined with abdominal computed tomography showing a cecal diameter greater than 9 cm. Treatment modalities and outcomes were recorded. RESULTS: Eight cases (0.22%) of OS were diagnosed at 6 separate institutions. Most institutions recorded more than 350 lateral access procedures. Four cases were initially diagnosed as a routine postoperative ileus; however, they failed conservative therapy and underwent abdominal CT imaging. Neostigmine treatment was required for 1 patient in the intensive care unit setting, and 3 patients were managed conservatively without complications. Four other patients demonstrated bowel perforation at least 48 hours after surgery and required laparotomy with diversion ileostomy. CONCLUSION: Ogilvie's syndrome is a rare but potentially fatal complication that can mimic a postoperative ileus. It is likely underdiagnosed in the lateral transpsoas approach population because of its uncommon nature and a high index of suspicion should remain. Neostigmine can be administered safely under close observation with immediate and successful outcomes. Patients with perforation require urgent laparotomy and primary repair.

The Usefulness of Diffusion Tensor Imaging and Tractography in Surgery of Brainstem Cavernous Malformations.

BACKGROUND: Diffusion tensor imaging (DTI) estimates the course and connectivity patterns of white matter tracts. The objective of this study is to evaluate whether findings in the brain stem modify the preoperative surgical trajectory planning or postoperative outcome in patients with brain stem cavernous malformations. METHODS: Ten patients with symptomatic brainstem cavernous malformation underwent surgical resection. Five patients received preoperative DTI evaluation and the remaining 5 did not. Reconstructed DTI tracts consisted of corticospinal, medial lemnisci, and cerebellar peduncles. The surgical planning and postoperative outcome were evaluated. RESULTS: In 5 patients with no preoperative DTI evaluation, surgical planning was based on anatomic landmark and the 2-point technique. The other 5 patients underwent preoperative DTI, and findings were factored into the selection of the surgical approach. In 3 of the 5 cases with DTI evaluation, the 2-point technique suggested a similar trajectory. In the other 2, the DTI findings suggested a different approach to avoid damage to the white matter tract. Two patients in the group with no DTI had immediate postoperative new or worsened deficit, which improved at long-term follow-up. No patient in the DTI group had a new neurologic deficit. CONCLUSIONS: Compared with the standard magnetic resonance imaging, DTI provided improved visualization of cavernous malformation involvement in eloquent fiber tracts of the brainstem. This additional information might help in selecting a more appropriate surgical trajectory in selected lesions. Larger patient cohorts are needed to assess the effect of this modality in patients' outcome.

Flow-based evaluation of cerebral revascularization using near-infrared indocyanine green videoangiography.

OBJECT: Indocyanine green (ICG) videoangiography has been established as a noninvasive technique to gauge the patency of a bypass graft; however, intraoperative graft patency may not always correlate with graft flow. Altered flow through the bypass graft may directly cause delayed graft occlusion. Here, the authors report on 3 types of flow that were observed through cerebral revascularization procedures. METHODS: Between February 2009 and September 2013, 48 bypass procedures were performed. Excluded from analysis were those cases in which ICG videoangiography was not performed during surgery (whether it was not available or there was a technical issue with the microscope or the quality of ICG angiography) and/or in which angiography or CT angiography was not done within 24-72 hours after surgery. After anastomosis, bypass patency was assessed first using a noninvasive technique and then with ICG videoangiography, and flow through the graft was characterized. Patients who received a vein or radial artery graft were also evaluated with intraoperative angiography. RESULTS: Thirty-three patients eligible for analysis were retrospectively analyzed. The patients had undergone extracranial-intracranial (EC-IC) or IC-IC bypass for ischemic stroke (13 patients), moyamoya disease (10 patients), and complex aneurysms (10 patients; 6 giant or large aneurysms, 2 carotid blister-like aneurysms, and 2 dissecting posterior inferior cerebellar artery [PICA] aneurysms). Thirty-six bypasses were performed including 26 superficial temporal artery (STA)-middle cerebral artery (MCA) bypasses (2 bilateral and 1 double-barrel), 6 EC-IC vein grafts, 1 EC-IC radial artery graft, 1 PICA-PICA bypass, 1 MCA-posterior cerebral artery bypass, and 1 occipital artery-PICA bypass. Robust anterograde flow (Type I) was noted in 31 grafts (86%). Delayed but patent graft enhancement and anterograde flow (Type II) was observed in 4 cases (11%); 1 of these cases with an EC-IC vein graft degraded gradually to very delayed flow with no continuity to the bypass site (Type III). Additionally, 1 STA-MCA bypass graft revealed no convincing flow (Type III). The 5 patients with Type II or III grafts were evaluated with a flow probe and reexploration of the bypass site, and in all cases the reason the graft became occluded was believed to be recipient-vessel competitive flow. In no case was there evidence of stenosis or a technical issue at the site of the anastomosis. Three patients with Type II and the 1 patient with Type III flow (11% of procedures) did not have a patent bypass on postoperative imaging. CONCLUSIONS: Indocyanine green videoangiography is reliable for evaluating flow through the EC-IC or IC-IC bypass. The type of flow observed through the graft has a direct relationship with postoperative imaging findings. Despite the possibility of competitive flow, Type III and some Type II flows through the graft indicate the need for graft evaluation and anastomosis exploration.