Allan D Levi

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

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Publications (109)301.65 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Insufficient donor nerve graft material in peripheral nerve surgery remains an obstacle for successful long distance regeneration. Schwann cells (SCs) can be isolated from adult mammalian peripheral nerve biopsies and can be grown in culture and retain their capacity to enhance peripheral nerve regeneration within tubular repair strategies in multiple animal models. Human Schwann cells (hSCs) can be isolated, expanded in number and retain their ability to promote regeneration and myelinate axons but have never been tested in a clinical case of peripheral nerve injury. A sural nerve biopsy and peripheral nerve tissue from the traumatized sciatic nerve stumps was obtained after Food and Drug Administration (FDA) and Institutional Review Board (IRB) approval as well as patient consent. The SCs were isolated after enzymatic digestion of the nerve and expanded with the use of heregulin β1 (0.1 μg/ml) and forskolin (15 mM). After 2 passages - the Schwann cell isolates were combined with sural nerve grafts to repair a large sciatic nerve defect (7.5 cm) after a traumatic nerve injury. The sural nerve and the traumatized sciatic nerve ends both served as an excellent source of purified (90 and 97 % respectively) human Schwann Cells (hSCs). Using ultrasound and Magnetic Resonance Imaging (MRI) we were able to determine continuity of the nerve graft repair and the absence of tumor formation. The patient had evidence of proximal sensory recovery and definitive motor recovery distal to the repair in the distribution of the tibial and common peroneal nerve. The patient did experience an improvement in her pain scores over time. The goals of this approach were to determine the safety and clinical feasibility of implementing a new cellular repair strategy. In summary, this approach represents a novel strategy in the treatment of peripheral nerve injury and represents the first reported use of autologous cultured SCs after human peripheral nerve injury.
    Cell Transplantation 11/2015; DOI:10.3727/096368915X690198 · 3.13 Impact Factor
  • Michael Y. Wang · Gabriel Widi · Allan D. Levi ·
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    ABSTRACT: Object The aging of the population will require that surgeons increasingly consider operating on elderly patients. Performing surgery safely in the elderly will require an understanding of the factors that predict successful outcomes and avoid complications. Methods Records of patients 85 years and older undergoing elective lumbar spinal surgery were retrospectively reviewed. Microdiscectomies were excluded. Preexisting medical illnesses measured using the Charlson Comorbidity Index (CCI), American Society of Anesthesiologists (ASA) Physical Status class, age, and surgical parameters were analyzed as factors potentially predictive of complications. Ambulatory function was rated on a 4-point scale. Results During the study 26 consecutive patients (mean age 87 years) with a mean ASA class of 2.6 ± 0.65 and CCI of 1.1 ± 1.27 were enrolled. The average number of levels treated was 2.17 ± 1.23, and 73% underwent fusion. The mean follow-up was 41.9 months with a minimum of 24 months, and all patients were alive at last follow-up. Average blood loss was 142 ± 184 ml, and the operative time was 183.3 ± 80.6 minutes. The mean number of levels treated was 2.17 ± 1.13 (range 1-4). Ambulatory function improved significantly by 0.59 ± 1.0 points. Five complications (19.2%) occurred in 4 patients, 2 major and 3 minor. Four complications were temporary and 1 was permanent. Patient age, blood loss, CCI score, ASA class, the number of levels treated, and fusion surgery were not statistically associated with a complication. Operative time of longer than 180 minutes (p = 0.0134) was associated with complications. Conclusions Lumbar spine surgery in patients 85 years and older can be accomplished safely if careful attention is paid to preoperative selection. Prolonged operative times are associated with a higher risk of complications.
    Neurosurgical FOCUS 10/2015; 39(4):E3. DOI:10.3171/2015.7.FOCUS15180 · 2.11 Impact Factor
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    ABSTRACT: Background: Perioperative blood loss is a frequent concern in spine surgery and often necessitates the use of allogeneic transfusion. Minimally invasive technique (MIS) is an option that minimizes surgical trauma and therefore intra-operative bleeding. The purpose of this study is to evaluate the blood loss, surgical complications, and duration of inpatient hospitalization in patients undergoing open posterolateral lumbar fusion (PLF), open posterior lumbar interbody fusion (PLIF) with PLF, or MIS transforaminal lumbar interbody fusion (MIS TLIF). Methods: Operative reports and perioperative data of patients undergoing single-level, primary open PLF (n=41), open PLIF/PLF (n=42), and MIS TLIF (n=71) were retrospectively evaluated. Patient demographics, operative blood loss, use of transfusion products, complications, and length of stay were tabulated. Patient data was controlled for age, BMI, and gender for statistical analysis. Results: Patients undergoing open PLF and open PLIF/PLF respectively experienced a significantly higher blood loss (p<0.001), higher volume of blood transfusion (p<0.001), higher volume of cell saver transfusion (p<0.001), and more surgical complications (dural injury, wound infections, screw malposition) (p=0.02) than those undergoing MIS TLIF. There was no statistically significant difference in duration of hospital stay (p=0.11). Conclusions: MIS TLIF provides interbody fusion with less intraoperative blood loss and subsequently a lower transfusion rate compared to open techniques, but this did not influence length of hospital stay. MIS TLIF is at least as safe as open techniques with respect to dural tear, wound infection, and screw placement. Level of evidence: Level III, Therapeutic.
    The Iowa orthopaedic journal 09/2015; 35:130-134.
  • J Serak · S Vanni · A D Levi ·
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    ABSTRACT: In addition to radiotherapy, the utility of surgical decompression and stabilization in patients with metastatic vertebral body tumors causing cord compression, progressive deformity and/or intractable pain has been well demonstrated. Minimally invasive approaches are an attractive alternative to traditional procedures as they may reduce the degree of disruption of normal anatomy, decrease blood loss, shorten hospital stays and reduce the risk of infection or wound dehiscence. The extreme lateral approach is a procedure that provides access to the anterior spine through a small incision along the flank utilizing a unique retractor system without disruption of posterior vertebral elements, spinal musculature and ligaments. A review of two senior surgeons' databases was performed between June 2010 and October 2014 to identify patients with metastatic vertebral body tumors who were treated surgically at the University of Miami during this period. We report the results of eight cases in which the extreme lateral approach was employed to perform a corpectomy and cage reconstruction for metastatic disease of the thoracic and lumbar vertebral bodies. Each case was supplemented by posterior percutaneous or less commonly open pedicle screw instrumentation. Post-operative imaging demonstrated excellent decompression of neural elements as well as deformity correction, and all patients maintained or improved neurologic function. There were no instances of wound dehiscence or infection. Our results indicate that the extreme lateral approach can be effectively used to excise metastatic vertebral body lesions of the thoracolumbar spine causing spinal cord and/or nerve root compression and spinal deformity.
    Journal of neurosurgical sciences 09/2015; · 1.16 Impact Factor
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    ABSTRACT: Ultrasound technology continues to improve with better image resolution and availability. Its use in evaluating peripheral nerve lesions is increasing. The current review focuses on the utility of ultrasound in traumatic injuries. In this report, the authors present 4 illustrative cases in which high-resolution ultrasound dramatically enhanced the anatomical understanding and surgical planning of traumatic peripheral nerve lesions. Cases include a lacerating injury of the sciatic nerve at the popliteal fossa, a femoral nerve injury from a pseudoaneurysm, an ulnar nerve neuroma after attempted repair with a conduit, and, finally, a spinal accessory nerve injury after biopsy of a supraclavicular fossa lesion. Preoperative ultrasound images and intraoperative pictures are presented with a focus on how ultrasound aided with surgical decision making. These cases are set into context with a review of the literature on peripheral nerve ultrasound and a comparison between ultrasound and MRI modalities.
    Neurosurgical FOCUS 09/2015; 39(3):E3. DOI:10.3171/2015.6.FOCUS15214 · 2.11 Impact Factor
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    ABSTRACT: Schwannomas of the brachial plexus are rare and typically present as slowly growing masses. We describe a case of a 37-year-old female who presented with acute onset of severe left upper extremity pain. Magnetic resonance imaging (MRI) showed a 2.3 × 2.1 cm peripherally enhancing centrally cystic lesion in the left axilla, along the cords of the left brachial plexus, with significant surrounding edema and enhancement. The mass was surgically removed. Pathology was consistent with a schwannoma with infarction. The pain completely resolved immediately after surgery. © The Author(s) 2015.
    06/2015; 28(3):333-6. DOI:10.1177/1971400915594923
  • Kevin S Cahill · Paul C McCormick · Allan D Levi ·
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    ABSTRACT: The risk of postoperative cancer following the use of recombinant human bone morphogenetic protein (BMP)-2 in spinal fusion is one potential complication that has received significant interest. Until recently, there has been little clinical evidence to support the assertion of potential cancer induction after BMP use in spinal surgery. This report aims to summarize the findings from clinical data available to date from the Yale University Open Data Access (YODA) project as well as more recently published large database studies regarding the association of BMP use in spinal fusion and the risk of postoperative cancer. A detailed review was based on online databases, primary studies, FDA reports, and bibliographies of key articles for studies that assessed the efficacy and safety of BMP in spinal fusion. In an analysis of the YODA project, one meta-analysis detected a statistically significant increase in cancer occurrence at 24 months but not at 48 months, and the other meta-analysis did not detect a significant increase in postoperative cancer occurrence. Analysis of 3 large health care data sets (Medicare, MarketScan, and PearlDiver) revealed that none were able to detect a significant increase in risk of malignant cancers when BMP was used compared with controls. The potential risk of postoperative cancer formation following the use of BMP in spinal fusion must be interpreted on an individual basis for each patient by the surgeon. There is no conclusive evidence that application of the common formulations of BMP during spinal surgery results in the formation of cancer locally or at a distant site.
    Journal of neurosurgery. Spine 04/2015; 23(1):1-8. DOI:10.3171/2014.10.SPINE14338 · 2.38 Impact Factor
  • Faiz U. Ahmad · Allan D. Levi ·

    Journal of Neurosurgery Spine 11/2014; 21(5):843-844. · 2.38 Impact Factor
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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.
    09/2014; 4(3):137-44. DOI:10.1089/ther.2014.0006
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    Faiz U Ahmad · Allan D Levi ·

    Journal of Neurosurgery Spine 08/2014; 21(5):1-2. DOI:10.3171/2014.4.SPINE14330 · 2.38 Impact Factor
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    ABSTRACT: BACKGROUND: Neuromata formation in the infrapatellar branch of the saphenous nerve (IPBSN) has been well described as a potential complication of arthroscopic knee surgery and knee trauma. Resection has been proven to provide improvement of pain and increased range of motion. Currently, physical examination and surgical exploration based on anatomic landmarks are the standard for intraoperative localization of IPBSN neuromas. OBJECTIVE: To demonstrate the anatomy of the IPSBN and the use of preoperative ultrasound and needle placement for localization of the nerve before sectioning. METHODS: Using both anatomic dissections and the combination of preoperative ultrasound and curved-needle placement, we demonstrate the technical nuances to localize the IPBSN before operative section. RESULTS: Cadaveric dissection is used to illustrate the main trunk of the IPSBN and its branches. In 2 cases, ultrasound guidance was effectively used to localize the saphenous nerve and its branches and facilitate the operative treatment of patients with symptomatic IPBSN neuromas. CONCLUSION: Ultrasound is a widely accepted and commonly utilized imaging modality; however, in this report, ultrasound-guided needle localization was used to aid in the resection of neuromas of small, painful sensory nerves. ABBREVIATIONS: ACL, anterior cruciate ligament IPBSN, infrapatellar branch of the saphenous nerve SBDGA, saphenous branch of the descending genicular artery US, ultrasound
    Neurosurgery 07/2014; 75(6). DOI:10.1227/NEU.0000000000000515 · 3.62 Impact Factor
  • S Shelby Burks · David J Levi · Seth Hayes · Allan D Levi ·
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    ABSTRACT: Unlabelled: 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; 121(1). DOI:10.3171/2014.2.JNS131667 · 3.74 Impact Factor
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    ABSTRACT: Complex sacral midline defects following spinal surgery have been traditionally closed with either muscle or musculocutaneous flaps. We present a case with a complicated sacral wound extending to the medulla spinalis after a lipomeningomyelocele excision in an ambulating adult. Wound was repaired with a lumbar perforator-based rotation flap. This well-vascularized flap is relatively easy to harvest, and results in minimal donor site morbidity, provides adequate dimensions, and permits primary closure of donor defect. In addition, the flap allows for anatomic muscle approximation without sacrificing the muscle functions, and provides reliable soft tissue coverage. Level of Evidence: Level V, therapeutic study.
    European Journal of Plastic Surgery 03/2014; 37(3). DOI:10.1007/s00238-013-0894-4
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    Yerko A Berrocal · Vania W Almeida · Allan D Levi ·

    Journal of Neurosurgery 02/2014; 120(2):574. · 3.74 Impact Factor
  • Article: Response.

    Journal of neurosurgery. Spine 01/2014; 20(1):120-1. · 2.38 Impact Factor
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    M F Khan · S S Burks · H Al-Khayat · AD Levi ·
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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; 52(1). DOI:10.1038/sc.2013.122 · 1.80 Impact Factor
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    Yerko A Berrocal · Vania W Almeida · Allan D Levi ·
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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; 119(3). DOI:10.3171/2013.4.JNS121938 · 3.74 Impact Factor
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    Yerko A Berrocal · Vania W Almeida · Ranjan Gupta · Allan D Levi ·
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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; 119(3). DOI:10.3171/2013.4.JNS121189 · 3.74 Impact Factor
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    Gabriel A Widi · Seth K Williams · Allan D Levi ·
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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 04/2013; 2013(236):659078. DOI:10.1155/2013/659078
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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; 18(3). DOI:10.3171/2012.12.SPINE12607 · 2.38 Impact Factor

Publication Stats

3k Citations
301.65 Total Impact Points


  • 1995-2015
    • University of Miami Miller School of Medicine
      • • Department of Neurological Surgery
      • • Miami Project to Cure Paralysis
      Miami, Florida, United States
  • 1994-2014
    • University of Miami
      • • Department of Neurological Surgery
      • • Miller School of Medicine
      • • Miami Project to Cure Paralysis
      كورال غيبلز، فلوريدا, Florida, United States
    • University of Toronto
      • Department of Surgery
      Toronto, Ontario, Canada
  • 2000-2011
    • Jackson Memorial Hospital
      • Department of Radiology
      Miami, Florida, United States
    • Laval University
      Quebec City, Quebec, Canada
  • 2005
    • Miami University
      Оксфорд, Ohio, United States
  • 2003
    • Keck School of Medicine USC
      Los Ángeles, California, United States
  • 1997-1998
    • Barrow Neurological Institute
      • Department of Neurosurgery
      Phoenix, Arizona, United States