Fred C. Lam and Michael W. Groff
Surgical pathology in the region of the upper thoracic spine (T1–4) is uncommon compared with other regions of the spine. Often times posterior and posterolateral approaches can be used, but formal anterior decompression often requires a low anterior cervical approach combined with a sternotomy, which yields significant perioperative morbidity. The authors describe a modified low anterior cervical dissection combined with a partial manubriotomy that they have used to successfully access and decompress anterior pathology of the upper thoracic spine. Their modified approach spares the sternoclavicular joints and leaves the sternum intact, decreasing the morbidity associated with these added procedures.
Viren S. Vasudeva, John H. Chi, and Michael W. Groff
Vertebral hemangiomas are common tumors that are benign and generally asymptomatic. Occasionally these lesions can exhibit aggressive features such as bony expansion and erosion into the epidural space resulting in neurological symptoms. Surgery is often recommended in these cases, especially if symptoms are severe or rapidly progressive. Some surgeons perform decompression alone, others perform gross-total resection, while others perform en bloc resection. Radiation, embolization, vertebroplasty, and ethanol injection have also been used in combination with surgery. Despite the variety of available treatment options, the optimal management strategy is unclear because aggressive vertebral hemangiomas are uncommon lesions, making it difficult to perform large trials. For this reason, the authors chose instead to report their institutional experience along with a comprehensive review of the literature.
A departmental database was searched for patients with a pathological diagnosis of “hemangioma” between 2008 and 2015. Medical records were reviewed to identify patients with aggressive vertebral hemangiomas, and these cases were reviewed in detail.
Five patients were identified who underwent surgery for treatment of aggressive vertebral hemangiomas during the specified time period. There were 2 lumbar and 3 thoracic lesions. One patient underwent en bloc spondylectomy, 2 patients had piecemeal gross-total resection, and the remaining 2 had subtotal tumor resection. Intraoperative vertebroplasty was used in 3 cases to augment the anterior column or to obliterate residual tumor. Adjuvant radiation was used in 1 case where there was residual tumor as well. The patient who underwent en bloc spondylectomy experienced several postoperative complications requiring additional medical care and reoperation. At an average follow-up of 31 months (range 3–65 months), no patient had any recurrence of disease and all were clinically asymptomatic, except the patient who underwent en bloc resection who continued to have back pain.
Gross-total resection or subtotal resection in combination with vertebroplasty or adjuvant radiation therapy to treat residual tumor seems sufficient in the treatment of aggressive vertebral hemangiomas. En bloc resection appears to provide a similar oncological benefit, but it carries higher morbidity to the patient.
Fred C. Lam, Michael W. Groff, and Ron N. Alkalay
The use of fixed-axis pedicle screws for correction of thoracolumbar deformity in adult surgery is demanding because of the challenge of assembling the bent rod to the screw in order to achieve curve correction. Polyaxial screw designs, providing increased degrees of freedom at the screw-rod interface, were reported to be insufficient in achieving correction of thoracic deformity in the axial plane. Using a multisegment bovine calf spine model, this study investigated the ability of a new uniplanar screw design to achieve derotation correction of the vertebrae and maintain a degree of correction comparable to that of fixed-axis and polyaxial screw designs.
Eighteen calf thoracolumbar spine segments from T-6 to L-1 (n = 6 per screw design) underwent bilateral facetectomies at the T9–11 levels and were instrumented bilaterally with pedicle screws and rods. To assess the efficacy of each screw design in imparting rotational correction, each instrumented level was tested under applied torsional moments designed to simulate the motion applied during derotation surgery. Once rotation was achieved, the whole spine was tested to assess the overall stiffness of the construct.
The fixed-axis construct showed increased efficacy in imparting rotation compared with the uniplanar (115% increase, p > 0.05) and polyaxial (210% increase, p < 0.05) constructs. Uniplanar screws showed a 21% increase in torsional stiffness compared with the polyaxial screws, but this difference was not statistically significant.
The design of screw heads plays a significant role in affecting the rotation of the vertebrae during the derotation procedure. Uniplanar screws may have the advantage of maintaining construct stiffness after derotation.
Yakov Gologorsky, John J. Knightly, John H. Chi, and Michael W. Groff
The rates of lumbar spinal fusion operations have increased dramatically over the past 2 decades, and several studies based on administrative databases such as the Nationwide Inpatient Sample (NIS) have suggested that the greatest rise is in the general categories of degenerative disc disease and disc herniation, neither of which is a well-accepted indication for lumbar fusion. The administrative databases classify cases with the International Classification of Disease, Ninth Revision, Clinical Modification (ICD-9-CM). The ICD-9-CM discharge codes are not generated by surgeons but rather are assigned by trained hospital medical coders. It is unclear how accurately they capture the surgeon's indication for fusion. The authors sought to compare the ICD-9-CM code(s) assigned by the medical coder to the surgeon's indication based on a review of the medical chart.
A retrospective review was undertaken of all lumbar fusions performed at our institution by the department of neurosurgery between 8/1/2011 and 8/31/2013. Based on the authors' review, the indication for fusion for each case was categorized as spondylolisthesis, deformity, tumor, infection, nonpathological fracture, pseudarthrosis, adjacent-level degeneration, stenosis, degenerative disc pathology, or disc herniation. These surgeon diagnoses were compared with the primary ICD-9-CM codes that were submitted to administrative databases.
There were 178 lumbar fusion operations performed for 170 hospital admissions. There were 44 hospitalizations in which fusion was performed for tumor, infection, or nonpathological fracture; the remaining 126 were for degenerative diagnoses. For these degenerative cases, the primary ICD-9-CM diagnosis matched the surgeon's diagnosis in only 61 of 126 degenerative cases (48.4%). When both the primary and all secondary ICD-9-CM diagnoses were considered, the indication for fusion was identified in 100 of 126 cases (79.4%).
Characterizing indications for fusion based solely on primary ICD-9-CM codes extracted from large administrative databases does not accurately reflect the surgeon's indication. While these databases may accurately describe national rates of lumbar fusion surgery, the lack of fidelity in the source codes limits their role in accurately identifying indications for surgery. Studying relationships among indications, complications, and outcomes stratified solely by ICD-9-CM codes is not well founded.
Joseph Driver and Michael W. Groff
Luke G. F. Smith, E. Antonio Chiocca, Gregory J. Zipfel, Adam G. F. Smith, Michael W. Groff, Regis W. Haid, and Russell R. Lonser
The Neurosurgery Research and Education Foundation (NREF) provides research support for in-training and early career neurosurgeon-scientists. To define the impact of this funding, the authors assessed the success of NREF awardees in obtaining subsequent National Institutes of Health (NIH) funding.
NREF in-training (Research Fellowship [RF] for residents) and early career awards/awardees (Van Wagenen Fellowship [VW] and Young Clinician Investigator [YCI] award for neurosurgery faculty) were analyzed. NIH funding was defined by individual awardees using the NIH Research Portfolio Online Reporting tool (1985–2014).
Between 1985 and 2014, 207 unique awardees were supported by 218 NREF awards ($9.84 million [M] in funding), including 117 RF ($6.02 M), 32 VW ($1.68 M), and 69 YCI ($2.65 M) awards. Subspecialty funding included neuro-oncology (79 awards; 36% of RF, VW, and YCI awards), functional (53 awards; 24%), vascular (37 awards; 17%), spine (22 awards; 10%), pediatrics (18 awards; 8%), trauma/critical care (5 awards; 2%), and peripheral nerve (4 awards; 2%). These awardees went on to receive $353.90 M in NIH funding that resulted in an overall NREF/NIH funding ratio of 36.0:1 (in dollars). YCI awardees most frequently obtained later NIH funding (65%; $287.27 M), followed by VW (56%; $41.10 M) and RF (31%; $106.59 M) awardees. YCI awardees had the highest NREF/NIH funding ratio (108.6:1), followed by VW (24.4:1) and RF (17.7:1) awardees. Subspecialty awardees who went on to obtain NIH funding included vascular (19 awardees; 51% of vascular NREF awards), neuro-oncology (40 awardees; 51%), pediatrics (9 awardees; 50%), functional (25 awardees; 47%), peripheral nerve (1 awardees; 25%), trauma/critical care (2 awardees; 20%), and spine (2 awardees; 9%) awardees. Subspecialty NREF/NIH funding ratios were 56.2:1 for vascular, 53.0:1 for neuro-oncology, 47.6:1 for pediatrics, 34.1:1 for functional, 22.2:1 for trauma/critical care, 9.5:1 for peripheral nerve, and 0.4:1 for spine. Individuals with 2 NREF awards achieved a higher NREF/NIH funding ratio (83.3:1) compared to those with 1 award (29.1:1).
In-training and early career NREF grant awardees are an excellent investment, as a significant portion of these awardees go on to obtain NIH funding. Moreover, there is a potent multiplicative impact of NREF funding converted to NIH funding that is related to award type and subspecialty.
Kevin T. Huang, Michael A. Silva, Alfred P. See, Kyle C. Wu, Troy Gallerani, Hasan A. Zaidi, Yi Lu, John H. Chi, Michael W. Groff, and Omar M. Arnaout
Recent advances in computer vision have revolutionized many aspects of society but have yet to find significant penetrance in neurosurgery. One proposed use for this technology is to aid in the identification of implanted spinal hardware. In revision operations, knowing the manufacturer and model of previously implanted fusion systems upfront can facilitate a faster and safer procedure, but this information is frequently unavailable or incomplete. The authors present one approach for the automated, high-accuracy classification of anterior cervical hardware fusion systems using computer vision.
Patient records were searched for those who underwent anterior-posterior (AP) cervical radiography following anterior cervical discectomy and fusion (ACDF) at the authors’ institution over a 10-year period (2008–2018). These images were then cropped and windowed to include just the cervical plating system. Images were then labeled with the appropriate manufacturer and system according to the operative record. A computer vision classifier was then constructed using the bag-of-visual-words technique and KAZE feature detection. Accuracy and validity were tested using an 80%/20% training/testing pseudorandom split over 100 iterations.
A total of 321 total images were isolated containing 9 different ACDF systems from 5 different companies. The correct system was identified as the top choice in 91.5% ± 3.8% of the cases and one of the top 2 or 3 choices in 97.1% ± 2.0% and 98.4 ± 13% of the cases, respectively. Performance persisted despite the inclusion of variable sizes of hardware (i.e., 1-level, 2-level, and 3-level plates). Stratification by the size of hardware did not improve performance.
A computer vision algorithm was trained to classify at least 9 different types of anterior cervical fusion systems using relatively sparse data sets and was demonstrated to perform with high accuracy. This represents one of many potential clinical applications of machine learning and computer vision in neurosurgical practice.
Muhammad M. Abd-El-Barr, Wenya Linda Bi, Biji Bahluyen, Samuel T. Rodriguez, Michael W. Groff, and John H. Chi
Spinal epidural abscess (SEA) is a rare but often devastating infection of the epidural space around the spinal cord. When an SEA is widespread, extensive decompression with laminectomy is often impossible, as it may subject the patient to very long operative times, extensive blood loss, and mechanical instability. A technique called “skip laminectomy” has been described in the literature, in which laminectomies are performed at the rostral and caudal ends of an abscess that spans 3–5 levels and a Fogarty catheter is used to mechanically drain the abscess, much like in an embolectomy. In this report of 2 patients, the authors present a modification of this technique, which they call “apical laminectomies” to allow for irrigation and drainage of an extensive SEA spanning the entire length of the vertebral column (C1–2 to L5–S1).
Two patients presented with cervico-thoraco-lumbar SEA. Laminectomies were performed at the natural apices of the spine, namely, at the midcervical, midthoracic, and midlumbar spine levels. Next, a pediatric feeding tube was inserted in the epidural space from the thoracic laminectomies up toward the cervical laminectomy site and down toward the lumbar laminectomy site, and saline antibiotics were used to irrigate the SEA. Both patients underwent this procedure with no adverse effects. Their SEAs resolved both clinically and radiologically. Neither patient suffered from mechanical instability at 1 year after treatment.
For patients who present with extensive SEAs, apical laminectomies seem to allow for surgical cure of the infectious burden and do not subject the patient to extended operating room time, an increased risk of blood loss, and the risk of mechanical instability.