Allan D Levi

University of Miami Miller School of Medicine, Miami, FL, United States

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Publications (75)165.03 Total impact

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    ABSTRACT: To evaluate the safety and feasibility of modest hypothermia as a potential strategy for intraoperative neuroprotection during the removal of intradural spinal tumors. A retrospective review was performed for two groups of patients of a single surgeon who underwent intradural extrameduallary and intramedullary spinal tumor resection of tumors located between cervical level 1 and lumbar 2 over a 10-year period between 2001 and 2010. One cohort received intraoperative moderate hypothermia (33°C) via intravascular catheter cooling during tumor surgery and the second cohort, a historical control group of the same surgeon, underwent surgery at normothermia (≥36°C). The main outcome measured was safety as determined by surgical, medical, and neurological complications. The hypothermia (n=38) and nonhypothermia (n=34) groups were homogenous for patient demographics and baseline comorbidities. There were no differences between the groups regarding tumor level (p=0.51), tumor pathology, or intramedullary versus intradural extramedullary location (p=0.11). The hypothermia group had a lower mean body temperature (33.7°C±0.72 vs. 36.6°C±0.7, p≤0.001) longer postoperative hospital stays (10.8±14.0 vs. 7.3±4.72, p<0.001), but there were no significant differences in operative and perioperative variables such as, total anesthetic time (8.2±2.4 vs. 7.8±2.7 hours, p=0.45), total surgical time (5.9±2.1 vs. 5.7±2.5 hours, p=0.58), or estimated blood loss (483±420 vs. 420±314 mL, p=0.65). There were no statistically significant differences between the two groups with respect to the rate of surgical (3 vs. 2, p=1.0), medical (4 vs. 3, p=1.0), neurological (3 vs. 4, p=0.7), or overall complications (10 vs. 9, p=1.0). In this study, moderate hypothermia via intravascular cooling catheters was successfully performed during 38 intradural spinal tumor surgeries. Compared to the historical control group, the hypothermia patients had longer hospital stays, but did not have higher complication rates. Intraoperative moderate hypothermia during spinal tumor resection is feasible and appeared safe in this limited cohort; however, further studies with larger cohorts will be needed to determine whether peri-operative hypothermia is an effective neuroprotectant strategy in spinal tumor surgery.
    Therapeutic hypothermia and temperature management. 09/2014; 4(3):137-44.
  • Faiz U Ahmad, Allan D Levi
    Journal of neurosurgery. Spine. 08/2014;
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    ABSTRACT: Object The object of this study was to highlight the challenge of insufficient donor graft material in peripheral nerve surgery, with a specific focus on sciatic nerve transection requiring autologous sural nerve graft. Methods The authors performed an anatomical analysis of cadaveric sciatic and sural nerve tissue. To complement this they also present 3 illustrative clinical cases of sciatic nerve injuries with segmental defects. In the anatomical study, the cross-sectional area (CSA), circumference, diameter, percentage of neural tissue, fat content of the sural nerves, as well as the number of fascicles, were measured from cadaveric samples. The percentage of neural tissue was defined as the CSA of fascicles lined by perineurium relative to the CSA of the sural nerve surrounded by epineurium. Results Sural nerve samples were obtained from 8 cadaveric specimens. Mean values and standard deviations from sural nerve measurements were as follows: CSA 2.84 ± 0.91 mm(2), circumference 6.67 ± 1.60 mm, diameter 2.36 ± 0.43 mm, fat content 0.83 ± 0.91 mm(2), and number of fascicles 9.88 ± 3.68. The percentage of neural tissue seen on sural nerve cross-section was 33.17% ± 4.96%. One sciatic nerve was also evaluated. It had a CSA of 37.50 mm(2), with 56% of the CSA representing nerve material. The estimated length of sciatic nerve that could be repaired with a bilateral sural nerve harvest (85 cm) varied from as little as 2.5 cm to as much as 8 cm. Conclusions Multiple methods have been used in the past to repair sciatic nerve injury but most commonly, when a considerable gap is present, autologous nerve grafting is required, with sural nerve being the foremost source. As evidenced by the anatomical data reported in this study, a considerable degree of variability exists in the diameter of sural nerve harvests. Conversely, the percentage of neural tissue is relatively consistent across specimens. The authors recommend that the peripheral nerve surgeon take these points into consideration during nerve grafting as insufficient graft material may preclude successful recovery.
    Journal of Neurosurgery 04/2014; · 3.15 Impact Factor
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    Journal of Neurosurgery 02/2014; 120(2):574. · 3.15 Impact Factor
  • Article: Response.
    Journal of neurosurgery. Spine 01/2014; 20(1):120-1. · 1.61 Impact Factor
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    ABSTRACT: Study design:Retrospective case-controlled study.Objectives:To understand the incidence of gastrointestinal hemorrhage (GIH) and subsequent mortality rate associated with steroid use after acute spinal cord injury (SCI).Setting:Miami, Florida, USA.Methods:This case-controlled study investigates two sequential study groups with SCI treated by a single surgeon in a level I trauma center. The first study cohort (1997-2005) received steroids according to the NASCIS II protocol and the second (2005-2012) received no steroid treatment. The groups were comparable with respect to age, sex, severity and level of injury (43 vs 45 years old/3:1 male-female/AIS scale %-43.5 vs 41.7 A, 10.6 vs 11.1 B, 20.3 vs 13.4 C, 25.4 vs 33.5 D/64.3 vs 73.8% cervical, 35.6 vs 25.7% thoracic and lumbar). The incidence and mortality from GIH were the primary outcome measures.Results:A total of 350 patients were evaluated during the study period. The incidence of GIH in the SCI group receiving steroids was 6/216 (2.77%) with 2 mortalities (33.3%). No gastrointestinal (GI) complications were noted in the 134 patients that did not receive any steroids (P=0.086). All GIH cases in the steroid group were in cervical SCI patients-6/139 (4.32%; P=0.043). Average time to onset of GIH was 16 days.Conclusion:The use of steroids in acute SCI appears to be a key risk factor in increasing the incidence of clinically overt GI complications with a subsequent high mortality rate, particularly in patients with cervical SCI.Spinal Cord advance online publication, 22 October 2013; doi:10.1038/sc.2013.122.
    Spinal Cord 10/2013; · 1.90 Impact Factor
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    ABSTRACT: Object Segmental nerve defects pose a daunting clinical challenge, as peripheral nerve injury studies have established that there is a critical nerve gap length for which the distance cannot be successfully bridged with current techniques. Construction of a neural prosthesis filled with Schwann cells (SCs) could provide an alternative treatment to successfully repair these long segmental gaps in the peripheral nervous system. The object of this study was to evaluate the ability of autologous SCs to increase the length at which segmental nerve defects can be bridged using a collagen tube. Methods The authors studied the use of absorbable collagen conduits in combination with autologous SCs (200,000 cells/μl) to promote axonal growth across a critical size defect (13 mm) in the sciatic nerve of male Fischer rats. Control groups were treated with serum only-filled conduits of reversed sciatic nerve autografts. Animals were assessed for survival of the transplanted SCs as well as the quantity of myelinated axons in the proximal, middle, and distal portions of the channel. Results Schwann cell survival was confirmed at 4 and 16 weeks postsurgery by the presence of prelabeled green fluorescent protein-positive SCs within the regenerated cable. The addition of SCs to the nerve guide significantly enhanced the regeneration of myelinated axons from the nerve stump into the proximal (p < 0.001) and middle points (p < 0.01) of the tube at 4 weeks. The regeneration of myelinated axons at 16 weeks was significantly enhanced throughout the entire length of the nerve guide (p < 0.001) as compared with their number in a serum-only filled tube and was similar in number compared with the reversed autograft. Autotomy scores were significantly lower in the animals whose sciatic nerve was repaired with a collagen conduit either without (p < 0.01) or with SCs (p < 0.001) when compared with a reversed autograft. Conclusions The technique of adding SCs to a guidance channel significantly enhanced the gap distance that can be repaired after peripheral nerve injury with long segmental defects and holds promise in humans. Most importantly, this study represents some of the first essential steps in bringing autologous SC-based therapies to the domain of peripheral nerve injuries with long segmental defects.
    Journal of Neurosurgery 06/2013; · 3.15 Impact Factor
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    ABSTRACT: The authors present the case of a 20-year-old man who, 3 months after his initial injury, underwent repair of a 1.7-cm defect of the ulnar nerve at the wrist; repair was performed with an acellular nerve allograft. Given the absence of clinical or electrophysiological recovery at 8 months postrepair, the patient underwent reexploration, excision of the "regenerated cable," and rerepair of the ulnar nerve with sural nerve autografts. Histology of the cable demonstrated minimal axonal regeneration at the midpoint of the repair. At the 6- and 12-month follow-ups of the sural nerve graft repair, clinical and electrophysiological evidence of both sensory and motor reinnervation of the ulnar nerve and associated hand muscles was demonstrated. In this report, the authors describe a single case of failed acellular nerve allograft and correlate the results with basic science and human studies reporting length and diameter limitations in human nerve repair utilizing grafts or conduits devoid of viable Schwann cells.
    Journal of Neurosurgery 06/2013; · 3.15 Impact Factor
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    ABSTRACT: Object The goal of this study was to compare the rates of solid arthrodesis and complications following multilevel, instrumented anterior cervical fusion in patients treated with and without bone morphogenetic protein (BMP). Methods The authors conducted a retrospective cohort study of patients who underwent multilevel (2+ level) anterior cervical fusions performed for degenerative disc disease with or without the concurrent use of BMP-2 from 1997 to 2012. The dosage throughout the study ranged from 2.1 to 0.26 mg/level (mean 1.0 mg/level). All patients were evaluated postoperatively by means of radiographs and CT scans to determine fusion status. Results The overall fusion rate for the patients treated without BMP (n = 23) was 82.6% compared with a 100% fusion rate in the group treated with BMP (n = 22) (p = 0.04). The pseudarthrosis rates increased with number of fusion levels in patients who did not receive BMP, whereas all patients in the group treated with BMP had solid arthrodesis. Furthermore, there were 2 instrumentation failures in the non-BMP group. There was a direct correlation between the incidence of complications and the dosage of BMP used per level, with no complications reported at doses equal to or less than 1.1 mg/level. Conclusions The overall rate of bony arthrodesis was increased following the use of BMP in multilevel anterior cervical fusion. Traditional methods without BMP had a high rate of pseudarthrosis. The complications associated with the use of BMP appeared to be dose related and of low incidence when BMP is used in doses equal to or less than 1.1 mg/level.
    Journal of neurosurgery. Spine 01/2013; · 1.61 Impact Factor
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    ABSTRACT: BACKGROUND: Iliac crest autograft is the historical gold standard for bone grafting but is associated with a significant patient morbidity. OBJECTIVE: Fusion rates of C1-C2 up to 88.9% using allograft and 96.7% using autologous iliac crest bone graft can be achieved when combined with rigid screw fixation. We sought to determine our fusion rate when combining allograft with rh-BMP2 and rigid screw fixation. METHODS: We reviewed our experience using allograft, bone morphogenetic protein (rh-BMP2) and screw fixation of C1-C2 in 52 patients and examined indications, surgical technique, fusion rates and complications. In 28 patients, corticocancellous allograft pieces were laid along decorticated bone after a C2 neurectomy was performed. In 24 patients, unicortical iliac crest allograft was precision-cut to fit between the C1 lamina and C2 spinous processes. RESULTS: Fifty-two C1-C2 fusions were performed with allograft, rh-BMP2 and rigid screw fixation. There were 25 female and 27 male patients ranging in age from 6 to 92 (mean 65.8) years. Operative indications included: trauma (56%), degenerative disease (21%), rheumatoid arthritis (15%), congenital anomalies (6%), and synovial cyst (2%). The mean follow-up was 23.9 (+/- 2.1) months (range 2 - 55 months). The mean dose of rh-BMP2 used for all cases was 4.5 mg (range 2.2-12 mg). In patients who achieved sufficient follow-up, 100 % achieved solid fusion: 45/50 Lenke A, 5/50 Lenke B. There were no known complications attributable to the use of rh-BMP2. CONCLUSION: The use of small doses of rh-BMP2 added to allograft in addition to rigid screw fixation is a safe and highly effective means of promoting a solid fusion of the atlantoaxial complex and spares the patient the morbidity of iliac crest harvest.
    World Neurosurgery 01/2013; · 1.77 Impact Factor
  • Faiz Ahmad, Michael Y Wang, Allan D Levi
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    ABSTRACT: OBJECTIVES: Spinal cord injury (SCI) is a catastrophic neurological event with no proven treatments that protect against its consequences. Potential benefits of hypothermia in preventing/limiting central nervous system (CNS) injury are now well known. There has been an interest in its potential use after SCI. This article reviews the current experimental and clinical evidence on the use of therapeutic hypothermia in patients with SCI. METHOD: Review of literature. RESULTS: There are various mechanisms by which hypothermia is known to protect the CNS. Modest hypothermia (32-34 °C) can deliver the potential benefits of hypothermia without incurring the complications associated with deep hypothermia. Several recent experimental studies have repeatedly shown that the use of hypothermia provides the benefit of neuroprotection after SCI. While older clinical studies were often focused on local cooling strategies and demonstrated mixed results, more recent data from systemic hypothermia use demonstrates its safety and its benefits. Endovascular cooling is a safe and reliable method of inducing hypothermia. CONCLUSION: There is robust experimental and some clinical evidence that hypothermia is beneficial in acute SCI. Larger, multicenter trials should be initiated to further study the usefulness of systemic hypothermia in SCI.
    World Neurosurgery 01/2013; · 1.77 Impact Factor
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    ABSTRACT: Spondylolysis of the lumbar spine has traditionally been treated using a variety of techniques ranging from conservative care to fusion. Direct repair of the defect may be utilized in young adult patients without significant disc degeneration and lumbar instability. We used minimally invasive techniques to place pars interarticularis screws with the use of an intraoperative CT scanner in three young adults, including two athletes. This technique is a modification of the original procedure in 1970 by Buck, and it offers the advantage of minimal muscle dissection and optimal screw trajectory. There were no intra- or postoperative complications. The detailed operative procedure and the postoperative course along with a brief review of pars interarticularis defect treatment are discussed.
    Case Reports in Medicine 01/2013; 2013:659078.
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    ABSTRACT: Introduction:Systemic hypothermia remains a promising neuroprotective strategy. There has been recent interest in its use in patients with spinal cord injury (SCI). In this article, we describe our extended single center experience using intravascular hypothermia for the treatment of cervical SCI.Methods:Thirty-five acute cervical SCI patients received modest (33 °C) intravascular hypothermia for 48 h. Neurological outcome was assessed by the International Standards for Neurological Classification of Spinal Cord Injury scale (ISNCSCI) developed by the American Spinal Injury Association. Local and systemic complications were recorded.Results:All patients were complete ISNCSCI A on admission, but four converted to ISNCSCI B in <24 h post injury. Hypothermia was delivered in 5.76 (±0.45) hours from injury if we exclude four cases with delayed admission (>18 h). Fifteen of total 35 patients (43%) improved at least one ISNCSCI grade at latest follow up 10.07 (±1.03) months. Even excluding those patients who converted from ISNCSCI A within 24 h, 35.5% (11 out of 31) improved at least one ISNCSCI grade. Both retrospective (n=14) and prospective (n=21) groups revealed similar number of respiratory complications. The overall risk of any thromboembolic complication was 14.2%.Conclusion:The results are promising in terms of safety and improvement in neurological outcome. To date, the study represents the largest study cohort of cervical SCI patients treated by modest hypothermia. A multi-center, randomized study is needed to determine if systemic hypothermia should be a part of SCI patients' treatment for whom few options exist.Spinal Cord advance online publication, 18 December 2012; doi:10.1038/sc.2012.161.
    Spinal Cord 12/2012; · 1.90 Impact Factor
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    ABSTRACT: Iatrogenic spinal cord injury (SCI) is an uncommon (0%-3%), yet devastating, complication of spine surgery. Recent evidence based on small clinical studies indicates that modest hypothermia is a feasible treatment option for severe SCI. We extended this treatment modality to patients with devastating iatrogenic SCI. We conducted a retrospective case series of five male patients (cervical trauma-1, cervical degenerative-2, thoracic trauma-1, and thoracic scoliosis-1) with an age range of 16-51 years (average age of 46 years) with intraoperative motor-evoked potential/somatosensory-evoked potential loss secondary to catastrophic events during the spinal operation associated with new SCI. Modest hypothermia was instituted immediately postsurgery for 24 hours. Four patients also received methylprednisolone. Preoperative American Spinal Injury Association (ASIA) scores were D (n=3) and E (n=2), while immediate postoperative scores were A (n=1), B (n=1), C (n=2), and D (n=1). Immediate postoperative MRI revealed new cord signal change in three patients. Two patients required subsequent surgery. ASIA scores at last follow-up were C (n=1), D (n=3), and E (n=1) with an improvement of 1-2 grades per patient. Adverse events such as pulmonary embolism, deep venous thrombosis, coagulopathy, or infection were not observed. Hypothermia is a feasible treatment option for patients with iatrogenic SCI. While hypothermia has not been proven to improve outcomes in these situations, aggressive medical management, including cooling, resulted in better-than-expected outcomes in this small cohort.
    Therapeutic hypothermia and temperature management. 12/2012; 2(4):183-92.
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    ABSTRACT: OBJECTIVE: The clinical differences in tubular versus open micro-discectomy have been recently studied in randomized trials and overall clinical outcomes appear to be similar between the two approaches. The objective of this study is to determine if tubular micro-discectomy is associated with differences in hospital charges when compared to open micro-discectomy. METHODS: A retrospective review of patients that underwent tubular or open micro-discectomy by the senior authors from 2007 to 2010 was performed. The primary outcome was inflation-adjusted total hospital charges for each procedure using itemized charge data obtained from the hospital finance department. Secondary outcomes included length of stay, complications, and operative times. RESULTS: 76 eligible patients (33 open and 48 tubular) were identified during the study period. In the open group the mean total charge was $27,811 (standard deviation $11,198) compared to $22,358 (standard deviation $8,695) in the tubular group. Total charges in the tubular group were on average $5,453 less than the open group (p=0.02). There were no significant differences in the operative times or complications. Length of stay was significantly shorter in the tubular group (mean 1.5 days open versus 0.9 days tubular, p=0.01) CONCLUSIONS: This analysis demonstrated significantly lower acute hospital charges associated with tubular micro-discectomy versus open micro-discectomy at an academic tertiary care hospital. These differences appear to the related to decreased post-operative resource utilization in the tubular group.
    World Neurosurgery 09/2012; · 1.77 Impact Factor
  • Article: In reply.
    Neurosurgery 08/2012; 71(2):E521-2. · 2.53 Impact Factor
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    ABSTRACT: The aim of this study was to determine the incidence of motor nerve injuries during the minimally invasive lateral interbody fusion procedure at a single academic medical center. A retrospective chart review of 118 patients who had undergone lateral interbody fusion was performed. Both inpatient and outpatient records were examined to identify any new postoperative motor weakness in the lower extremities and abdominal wall musculature that was attributable to the operative procedure. In the period from 2007 to 2011 the lateral interbody fusion procedure was attempted on 201 lumbar intervertebral disc levels. No femoral nerve injuries occurred at any disc level other than the L4-5 disc space. Among procedures involving the L4-5 level there were 2 femoral nerve injuries, corresponding to a 4.8% injury risk at this level as compared with a 0% injury risk at other lumbar spine levels. Five patients (4.2%) had postoperative abdominal flank bulge attributable to injury to the abdominal wall motor innervation. The overall incidence of femoral nerve injury after the lateral transpsoas approach was 1.7%; however, the level-specific incidence was 4.8% for procedures performed at the L4-5 disc space. Approximately 4% of patients had postoperative abdominal flank bulge. Surgeons will be able to minimize these motor nerve injuries through judicious use of the procedure at the L4-5 level and careful attention to the T-11 and T-12 motor nerves during exposure and closure of the abdominal wall.
    Journal of neurosurgery. Spine 06/2012; 17(3):227-31. · 1.61 Impact Factor
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    Paul McMahon, Marina Dididze, Allan D Levi
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    ABSTRACT: Incidental durotomies (IDs) are an unfortunate but anticipated potential complication of spinal surgery. The authors surveyed the frequency of IDs for a single spine surgeon and analyzed the major risk factors as well as the impact on long-term patient outcomes. The authors conducted a prospective review of elective spinal surgeries performed over a 15-year period. Any surgery involving peripheral nerve only, intradural procedures, or dural tears due to trauma were excluded from analysis. The incidence of ID was categorized by surgery type including primary surgery, revision surgery, and so forth. Incidence of ID was also examined in the context of years of physician experience and training. Furthermore, the incidence and types of sequelae were examined in patients with an ID. Among 3000 elective spinal surgery cases, 3.5% (104) had an ID. The incidence of ID during minimally invasive procedures (3.3%) was similar, but no patients experienced long-term sequelae. The incidence of ID during revision surgery (6.5%) was higher. There was a marked difference in incidence between cervical (1.3%) and thoracolumbar (5.1%) cases. The incidence was lower for cases involving instrumentation (2.4%). When physician training was examined, residents were responsible for 49% of all IDs, whereas fellows were responsible for 26% and the attending for 25%. Among all of the cases that involved an ID, 7.7% of patients went on to experience a neurological deficit as compared with 1.5% of those without an ID. The overall failure rate of dural repair was 6.9%, and failure was almost 3 times higher (13%) in revision surgery as compared with a primary procedure (5%). The authors established a reliable baseline incidence for durotomy after spine surgery: 3.5%. They also identified risk factors that can increase the likelihood of a durotomy, including location of the spinal procedure, type of procedure performed, and the implementation of a new procedure. The years of physician training or resident experience did not appear to be a major risk for ID.
    Journal of neurosurgery. Spine 04/2012; 17(1):30-6. · 1.61 Impact Factor
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    ABSTRACT: BACKGROUND: Acute compartment syndrome (ACS) after posterior spinal surgery is very uncommon. Most of the reported cases have ACS in the legs related to positioning in the knee-chest position; postoperative ACS in the thighs is exceedingly rare, with only one reported case (17). CASE DESCRIPTION: This study reports two patients who had local muscle necrosis/ACS after spine surgery in the prone position and discusses preventive measures. Both of our complications were probably related to reversing the position of the iliac crest and hip pads on a Jackson operating table, which was done to achieve better lumbar lordosis. CONCLUSIONS: Our cases indicate the need for a high index of suspicion of ACS in patients who have persistent unresolved pain and local swelling. Tissue pressure monitoring is an option in suspected cases. Iliac crest and thigh pads should not be reversed during positioning on a Jackson table.
    World Neurosurgery 04/2012; · 1.77 Impact Factor
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    ABSTRACT: Controversy exists as to the best posterior operative procedure to treat multilevel compressive cervical spondylotic myelopathy. To determine clinical, radiological, and patient satisfaction outcomes between expansile cervical laminoplasty (ECL) and cervical laminectomy and fusion (CLF). We performed a prospective, randomized study of ECL vs CLF in patients suffering from cervical spondylotic myelopathy. End points included the Short Form-36, Neck Disability Index, Visual Analog Scale, modified Japanese Orthopedic Association score, Nurick score, and radiographic measures. A survey of academic North American spine surgeons (n = 30) demonstrated that CLF is the most commonly used (70%) posterior procedure to treat multilevel spondylotic cervical myelopathy. A total of 16 patients were randomized: 7 to CLF and 9 to ECL. Both groups showed improvements in their Nurick grade and Japanese Orthopedic Association score postoperatively, but only the improvement in the Nurick grade for the ECL group was statistically significant (P < .05). The cervical range of motion between C2 and C7 was reduced by 75% in the CLF group and by only 20% in the ECL group in a comparison of preoperative and postoperative range of motion. The overall increase in canal area was significantly (P < .001) greater in the CLF group, but there was a suggestion that the adjacent level was more narrowed in the CLF group in as little as 1 year postoperatively. In many respects, ECL compares favorably to CLF. Although the patient numbers were small, there were significant improvements in pain measures in the ECL group while still maintaining range of motion. Restoration of spinal canal area was superior in the CLF group.
    Neurosurgery 02/2012; 70(2):264-77. · 2.53 Impact Factor

Publication Stats

843 Citations
165.03 Total Impact Points

Institutions

  • 2000–2013
    • University of Miami Miller School of Medicine
      • Department of Neurological Surgery
      Miami, FL, United States
  • 2005–2009
    • University of Miami
      • Department of Neurological Surgery
      كورال غيبلز، فلوريدا, Florida, United States
    • Jackson Memorial Hospital
      Miami, Florida, United States
  • 2003–2006
    • University of Southern California
      • Department of Neurological Surgery
      Los Angeles, CA, United States