Anterior cervical decompression and fusion has gained popularity because of its applicability to a variety of cervical spine disorders. The authors of long-term follow-up studies have demonstrated the development of degenerative changes in segments adjacent to fusion. So-called adjacent-segment disease causes symptomatic deterioration in up to 25% of the patients who have undergone anterior cervical decompression and fusion for cervical spondylotic myelopathy. The causes of this condition are debated in the literature. The authors provide a review of the available literature on the pathogenesis, prevention, and treatment of postarthrodesis adjacent-segment degenerative disease.
Hooman Azmi and Richard P. Schlenk
Richard P. Schlenk, Todd Stewart, and Edward C. Benzel
Revision spinal surgery is usually indicated in cases of persistent or recurrent symptoms related to neural compression, spinal deformity, or construct failure. An understanding of fundamental biomechanical principles of both spinal decompression and reconstructive strategies is essential to avoid unnecessary subsequent spinal operations.
Richard P. Schlenk, Robert J. Kowalski, and Edward C. Benzel
The correction of spinal deformity may be achieved by a variety of methods, each of which has advantages and disadvantages. The goals of spinal deformity surgery include reasonable correction of the curvature, prevention of further deformation, improvement of sagittal and coronal balance, optimization of cosmetic issues, and restoration/preservation of function. The failure to consider all these factors appropriately may result in a suboptimal outcome. Understanding fundamental biomechanical principles involved in the formation, progression, and treatment of spinal deformities is essential in the clinical decision-making process.
James K. C. Liu, Varun R. Kshettry, Pablo F. Recinos, Kambiz Kamian, Richard P. Schlenk, and Edward C. Benzel
Surgical education has been forced to evolve from the principles of its initial inception, in part due to external pressures brought about through changes in modern health care. Despite these pressures that can limit the surgical training experience, training programs are being held to higher standards of education to demonstrate and document trainee competency through core competencies and milestones. One of the methods used to augment the surgical training experience and to demonstrate trainee proficiency in technical skills is through a surgical skills laboratory. The authors have established a surgical skills laboratory by acquiring equipment and funding from nondepartmental resources, through institutional and private educational grants, along with product donations from industry. A separate educational curriculum for junior- and senior-level residents was devised and incorporated into the neurosurgical residency curriculum. The initial dissection curriculum focused on cranial approaches, with spine and peripheral nerve approaches added in subsequent years. The dissections were scheduled to maximize the use of cadaveric specimens, experimenting with techniques to best preserve the tissue for repeated uses. A survey of residents who participated in at least 1 year of the curriculum indicated that participation in the surgical skills laboratory translated into improved understanding of anatomical relationships and the development of technical skills that can be applied in the operating room. In addition to supplementing the technical training of surgical residents, a surgical skills laboratory with a dissection curriculum may be able to help provide uniformity of education across different neurosurgical training programs, as well as provide a tool to assess the progression of skills in surgical trainees.
G. Alexander Jones, John Butler, Isador Lieberman, and Richard Schlenk
Deep infections of the spine are a significant cause of morbidity and death. Such infections complicate 0.7 to 11.9% of spinal procedures. Management includes intravenous antibiotic therapy, debridement and irrigation with primary closure, placement of drains, use of irrigation systems, and/or healing through secondary intention with wound packing. Vacuum-assisted closure (VAC) is a new alternative for treatment of patients with complex postoperative spinal infections. The aim of this study was to investigate the safety of this treatment method in this patient population.
The authors reviewed the charts of 16 consecutive patients treated with negative-pressure wound therapy at their institution between 2002 and 2006. All had deep infections of the spine and were treated with surgical debridement and placement of VAC dressings. All infections were postoperative. Members of the infectious disease service were involved in the care of all patients, and all patients received intravenous antibiotic therapy. The authors reviewed operative notes, discharge summaries, and notes from follow-up visits and assessed outcome on the basis of the same records.
Three patients were lost to follow up, leaving a group of 13 with follow up of at least 90 days. Two patients experienced bleeding complications related to the continuous negative pressure of the VAC device. In two cases, the infections persisted and required reoperation. In one case, a skin graft was required because of nonhealing granulation tissue. One of the patients with bleeding complications died as a result of delayed complications related to intraoperative blood loss, blood loss via the VAC system, and refusal of a blood transfusion on religious grounds.
Negative-pressure wound therapy has been employed as a treatment strategy for patients with complex postoperative spinal infections, but little is known of the complications associated with VAC in the spinal surgery patient population. Serious complications, including death, may be associated with use of the VAC system.
Daniel Lubelski, Andrew T. Healy, Prasath Mageswaran, Robb Colbrunn, and Richard P. Schlenk
Lateral mass fixation stabilizes the cervical spine while causing minimal morbidity and resulting in high fusion rates. Still, with 2 years of follow-up, approximately 6% of patients who have undergone posterior cervical fusion have worsening kyphosis or symptomatic adjacent-segment disease. Based on the length of the construct, the question of whether to extend the fixation system to undisrupted levels has not been answered for the cervical spine. The authors conducted a study to quantify the role of construct length and the terminal dorsal ligamentous complex in the adjacent-segment kinematics of the subaxial cervical spine.
In vitro flexibility testing was performed using 6 human cadaveric specimens (C2–T8), with the upper thoracic rib cage and osseous and ligamentous integrity intact. An industrial robot was used to apply pure moments and to measure segmental motion at each level. The authors tested the intact state, followed by 9 postsurgical permutations of laminectomy and lateral mass fixation spanning C2 to C7.
Constructs spanning a single level exerted no significant effects on immediate adjacent-segment motion. The addition of a second immobilized segment, however, created significant changes in flexion-extension range of motion at the supradjacent level (+164%). Regardless of construct length, resection of the terminal dorsal ligaments did not greatly affect adjacent-level motion except at C2–3 and C7–T1 (increasing by +794% and +607%, respectively).
Dorsal ligamentous support was found to contribute significant stability to the C2–3 and C7–T1 segments only. Construct length was found to play a significant role when fixating two or more segments. The addition of a fused segment to support an undisrupted cervical level is not suggested by the present data, except potentially at C2–3 and C7–T1. The study findings emphasize the importance of the C2–3 segment and its dorsal support.
Atilla Akbay, Serkan İnceoğlu, Ryan Milks, Richard Schlenk, Selcuk Palaoglu, and Edward C. Benzel
Object. Pedicle screw instrumentation of the thoracic spine remains technically challenging. Transverse process and costotransverse screw fixation techniques have been described as alternatives to pedicle screw fixation (PSF). In this study, the authors introduce thoracic transfacet PSF and compare its experimental biomechanical results with those of standard PSF in short-term cyclic loading in cadaveric thoracic specimens.
Methods. Specimens were tested intact for six cycles at compressive loads of 250 N offset by 1 cm along appropriate axes to induce flexion, extension, and left and right lateral bending. The specimens were then fixed with either a pedicle screw/rod construct or transfacet pedicle screws and retested in the same fashion. After this sequence, specimens were loaded until failure in flexion mode at a rate of 5 mm/minute was observed.
Both fixation constructs provided significantly greater stiffnesses than that demonstrated when the specimen was intact (p < 0.05, two-way analysis of variance). Additionally, the two constructs were statistically equivalent in terms of stiffness and load-to-failure values (p < 0.05, two-tailed nonpaired t-test). The only difference observed was that the low midthoracic region (T7–9) was biomechanically weaker than the upper midthoracic and lower thoracic areas in flexion after the destabilization and instrumentation-augmented stabilization procedures.
Conclusions. In selected thoracic surgical procedures, transfacet PSF may, after analysis of long-term biomechanical data, potentially become a reasonable alternative to conventional PSF.
Daniel Lubelski, Andrew T. Healy, Alan Friedman, Dyan Ferraris, Edward C. Benzel, and Richard Schlenk
Neurosurgery is among the most competitive residencies, as evidenced by the high number of applicants for relatively few positions. Although it is important to recruit candidates who have the intellectual capacity and drive to succeed, traditional objective selection criteria, such as US Medical Licensing Examination (USMLE) (also known as Step 1) score, number of publications, and class ranking, have not been shown to consistently predict clinical and academic success. Furthermore, these traditional objective parameters have not been associated with specific personality traits.
The authors sought to determine the efficacy of a personality assessment in the selection of neurosurgery residents. Specifically, the aim was to determine the correlation between traditional measures used to evaluate an applicant (e.g., USMLE score, number of publications, MD/PhD status) and corresponding validated personality traits.
Fifty-four neurosurgery residency applicants were interviewed at the Cleveland Clinic during the 2014–2015 application cycle. No differences in validated personality scores were identified between the 46 MD applicants and 8 MD/PhD applicants. The mean USMLE score (± SD) was 252.3 ± 11.9, and those in the high-USMLE-score category (USMLE score ≥ 260) had a significantly lower “imaginative” score (a stress measure of eccentric thinking and impatience with those who think more slowly). The average number of publications per applicant was 8.6 ± 7.9, and there was a significant positive correlation (r = 0.339, p = 0.016) between greater number of publications and a higher “adjustment” score (a measure of being even-tempered, having composure under pressure). Significant negative correlations existed between the total number of publications and the “excitable” score (a measure of being emotionally volatile) (r = −0.299, p = 0.035) as well as the “skeptical” score (measure of being sensitive to criticism) (r = −0.325, p = 0.021). The average medical school rank was 25.8, and medical school rankings were positively correlated with the “imaginative” score (r = 0.287, p = 0.044).
This is the first study to investigate the use of personality scores in the selection of neurosurgical residents. The use of personality assessments has the potential to provide insight into an applicant's future behavior as a resident and beyond. This information may be useful in the selection of neurosurgical residents and can be further used to customize the teaching of residents and for enabling them to recognize their own strengths and weaknesses for self-improvement.
Pranay Soni, Ghaith Habboub, Varun R. Kshettry, Richard Schlenk, Frederick Lautzenheiser, and Edward C. Benzel
The Cleveland Clinic was established in 1921 under the direction of 4 experienced and iconic physicians: George Crile, Frank Bunts, William Lower, and John Phillips. The Clinic initially employed a staff of only 6 surgeons, 4 internists, 1 radiologist, and 1 biophysicist, but Crile was quick to realize the need for broadening its scope of practice. He asked his close friend, Harvey Cushing, for assistance in finding a suitable candidate to establish a department of neurosurgery at the Cleveland Clinic. With his full endorsement, Cushing recommended Dr. Charles Edward Locke Jr., a former student and burgeoning star in the field of neurosurgery. Unfortunately, Locke’s life and career both ended prematurely in the Cleveland Clinic fire of 1929, but not before he would leave a lasting legacy, both at the Cleveland Clinic and in the field of neurosurgery.
Swetha J. Sundar, Andrew T. Healy, Varun R. Kshettry, Thomas E. Mroz, Richard Schlenk, and Edward C. Benzel
Pedicle and lateral mass screw placement is technically demanding due to complex 3D spinal anatomy that is not easily visualized. Neurosurgical and orthopedic surgery residents must be properly trained in such procedures, which can be associated with significant complications and associated morbidity. Current training in pedicle and lateral mass screw placement involves didactic teaching and supervised placement in the operating room. The objective of this study was to assess whether teaching residents to place pedicle and lateral mass screws using navigation software, combined with practice using cadaveric specimens and Sawbones models, would improve screw placement accuracy.
This was a single-blinded, prospective, randomized pilot study with 8 junior neurosurgical residents and 2 senior medical students with prior neurosurgery exposure. Both the study group and the level of training-matched control group (each group with 4 level of training-matched residents and 1 senior medical student) were exposed to a standardized didactic education regarding spinal anatomy and screw placement techniques. The study group was exposed to an additional pilot program that included a training session using navigation software combined with cadaveric specimens and accessibility to Sawbones models.
A statistically significant reduction in overall surgical error was observed in the study group compared with the control group (p = 0.04). Analysis by spinal region demonstrated a significant reduction in surgical error in the thoracic and lumbar regions in the study group compared with controls (p = 0.02 and p = 0.04, respectively). The study group also was observed to place screws more optimally in the cervical, thoracic, and lumbar regions (p = 0.02, p = 0.04, and p = 0.04, respectively).
Surgical resident education in pedicle and lateral mass screw placement is a priority for training programs. This study demonstrated that compared with a didactic-only training model, using navigation simulation with cadavers and Sawbones models significantly reduced the number of screw placement errors in a laboratory setting.