Richard Schlenk

The biomechanics of 1, 2, and 3 levels of vertebral augmentation with polymethylmethacrylate in multilevel spinal segments.

Study Design. Experimental biomechanics of multilevel segments with 0, 1, 2, and 3 vertebral levels of polymethylmethacrylate augmentation. Objective. To compare multilevel spinal segments with different numbers (0, 1, 2, and 3) of vertebral levels augmented with polymethylmethacrylate. Summary of Background Data. The stiffness and strength of single-level polymethylmethacrylate augmentations in individual and multilevel vertebrae treated by kyphoplasty and vertebroplasty have been studied, but the biomechanics of multilevel segments with more than 1 vertebral level augmented with polymethylmethacrylate are lacking, yet this is clinically relevant in multilevel compression fracture treatment. Materials And Methods. A total of 48 multilevel segments (T3–T5, T6–T8, T9–T11, T12–L2, and L3–L5) from 12 spines with known bone mineral density (BMD) were allocated into 6 groups based on the number of vertebral levels augmented: 0 levels (n = 13), control group; 1 level (n = 7), group 2; 2 levels, groups 3, 4, and 5 (n = 7 in each); and 3 levels (n = 7), group 6. They were compressed to failure, disarticulated into individual vertebrae, and retested. Stiffness and strength were statistically analyzed using a univariate analysis of variance comparing the main effects, using least significant difference comparisons with 0.05 probability level. Results. Strength was dependent on BMD (P < 0.001 multilevel segments, P < 0.001 individual vertebrae), with no differences among the 6 different augmentation groups, and no significant differences between augmented and nonaugmented individual vertebrae. Stiffness was dependent on BMD (P = 0.009 multilevel segments, P < 0.004 individual vertebrae), with no significant differences among the 6 different augmentation groups, and no significant differences between augmented and nonaugmented individual vertebrae. Conclusions. Multilevel segment biomechanics are dependent on BMD and not the pattern of augmentation, so the augmentation of fractured vertebrae can be extended to adjacent levels at risk for fracture to maintain stiffness and strength, thus preventing further fractures.

Simulated diagnostic cerebral angiography in neurosurgical training: a pilot program

Introduction Surgical simulation provides a zero-risk setting in which technical skills can be obtained through repetition. The feasibility and utility of simulated diagnostic cerebral angiography among neurosurgical residents and fellows was studied using an endovascular biplane angiography simulator. Methods Ten neurosurgical residents and four endovascular neurosurgery fellows were recruited into a standardized training protocol consisting of a didactic, demonstration and hands-on learning environment using the Simbionix simulator. Participants were instructed to catheterize the right internal carotid artery, left internal carotid artery and left vertebral artery. The task was repeated five times. Results All participants demonstrated improvement over the five trials. Residents performed actions that were perceived as potentially dangerous (n=8) while fellows performed the procedure with superior technique. Residents performed the task with an initial total procedure and fluoroscopy time of 6.6±4.3 min and 4.9±3.7 min, respectively, and improved on the fifth trial to 3.4±1.3 min (p=0.03) and 2.3±0.78 min (p=0.004), respectively. Residents approximated the efficiency of fellows for the third and fourth trial. Conclusions Incorporating an endovascular simulator is feasible for training purposes in a neurosurgical residency program. This study provides objective documentation of the facilitation of technical angiography skill acquisition by the use of simulation technology.

MULTIPLE LEVEL DISCECTOMY AND FUSION

THE VENTROLATERAL APPROACH for surgical decompression of the cervical spine is widely used and well known to most spinal surgeons. Because compression of the spinal cord and nerve roots usually occurs ventral to the spinal cord, and the spinal cord does not tolerate traction, this approach allows safe and direct decompression of most compressive pathology. This article reviews the indications, diagnostic evaluation, and technique for multiple level discectomy and fusion. It further addresses the advantages and disadvantages of this technique compared with alternate surgical procedures.

The role of adjuvant radiation therapy in the treatment of spinal myxopapillary ependymomas

OBJECT the goal in this study was to determine the role of radiation therapy (RT) in the treatment of spinal myxopapillary ependymomas (MPEs). METHODS thirty-seven patients with histologically verified spinal MPEs were reviewed. Kaplan-Meier analyses and Cox proportional hazard regression were used to determine what patient and treatment factors influenced overall survival (OS) and recurrence. RESULTS at the time of initial diagnosis, the median age was 33 years and the Karnofsky Performance Scale score was 80. In 86.5% of cases, the most common presenting symptom was pain. All patients received surgery as their initial treatment. Nine patients also received RT along with surgery, with a median total dose of 50.2 Gy. The mean survival time was 12.2 years; however, only 4 of 37 patients had died at the time of this study. None of the patient or treatment parameters significantly correlated with OS. Sixteen patients (43.2%) were found to have a recurrence, with a median time to recurrence of 7.7 years. None of the patient or treatment parameters correlated with recurrence-free survival for an initial recurrence. The median time to the second recurrence (recurrence following therapy for initial recurrence) was 1.6 years. Use of RT as salvage therapy after initial recurrence significantly correlated with longer times to a second recurrence. The median recurrence-free survival time before the second recurrence was 9.6 years for those who received RT versus 1.1 years for those who did not receive RT (p = 0.0093). None of the other parameters significantly correlated with a second recurrence. CONCLUSIONS radiation therapy may have a role as salvage therapy in delaying recurrences of spinal MPEs.

A pilot study of the utility of a laboratory-based spinal fixation training program for neurosurgical residents

OBJECTIVE 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. METHODS 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. RESULTS 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). CONCLUSIONS 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.

Establishing a surgical skills laboratory and dissection curriculum for neurosurgical residency training.

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.

In Vivo Assessment of Bone Graft/Endplate Contact Pressure in a Caprine Interbody Pseudarthrosis Model: A Preliminary Biomechanical Characterization of the Fusion Process for the Development of a Microelectromechanical Systems (MEMS) Biosensor

Background In this preliminary study we used a goat model to quantify pressure at an interbody bone graft interface. Although the study was designed to assess fusion status, the concept behind the technology could lead to early detection of implant failure and potential hazardous complications related to motion-preservation devices. The purpose of this study was to investigate the feasibility of in vivo pressure monitoring as a strategy to determine fusion status. Methods Telemetric pressure transducers were implanted, and pressure at the bone graft interfaces of cervical interbody fusion autografts placed into living goats (Groups A and B) was evaluated. Group A constituted the 4-month survival group and Group B the 6-month survival group. One goat served as the study control (Group C) and was not implanted with a pressure transducer. An additional six cadaveric goat cervical spines (Group D) were obtained from a local slaughterhouse and implanted with bone grafts and ventral plates and used for in vitro biomechanical comparison to the specimens from Groups A and B. Results All goats demonstrated an increase in interface pressure within the first 10 days postoperatively, with the largest relative change in pressure occurring between the sixth and ninth days. The goats from Groups A and B had a 200% to 400% increase in relative pressure. Conclusions Although this was a pilot study to assess pressure as an indicator for a fusion or pseudarthrosis, the preliminary data suggest that early bone healing is detectable by an increase in pressure. Thus, pressure may serve as an indicator of fusion status by detecting altered biomechanical parameters.

Retro-Odontoid Calcium Pyrophosphate Dehydrate Deposition: Surgical Management and Review of the Literature

Study Design Case report and review of the literature. Objective A retro-odontoid mass is a rare cause of cervical compression and myelopathy. The differential diagnosis includes the following: metastatic disease, primary tumor, collagen disorder, or inflammatory disease. Calcium pyrophosphate dihydrate (CPPD) deposition has been referred to as “crowned dens syndrome” when there are periodontoideal calcifications. There are only a few reported cases where CPPD presents as a cystic retro-odontoid mass in the atlanto-dens interval. In previous descriptions of surgical intervention, transoral resection of the mass is associated with significant morbidity and usually requires stabilization. The objective of this article is to report a case of an unusual presentation of CPPD disease of C1/C2, where we used a novel, minimally invasive surgical technique for decompression without fusion. Patients and Methods An 83-year-old female patient presented with progressive cervical myelopathy over a 3-month period. Computed tomography and magnetic resonance imaging demonstrated a cystic odontoid mass with a separate retro-odontoid compressive mass. A novel, minimally invasive transoral aspiration was performed. Histologic confirmation of CPPD was obtained. Results Postop imaging showed satisfactory decompression, which was maintained at the 6-month follow-up. This correlated with clinical improvement postop and 6-month follow-up. Conclusion CPPD in the atlanto-dens interval may present as a cystic retro-odontoideal mass and should be included in the differential. We used a transoral minimally invasive approach to aspirate the cyst. This novel technique avoided the need for a stabilization procedure or morbid transoral resection and provided excellent results immediately and at 6 months.

Informatic Surgery: The Union of Surgeon and Machine

W s t b m m i c e w a b i e r nformatic surgery—what a concept! If Dr. Apuzzo would have asked us to write a commentary regarding informatic surgery 15 years, 10 years, or even 5 years ago, we would ave thought that he was not “in his right mind.” Today, owever, is another story. Yet, in spite of the recent and ongoing xponential growth of information acquisition and accumulation obviously, we accumulate information as it is presented to us; in ther words, information does not “evaporate”—it accumulates s time passes), it remains difficult to find a definition of nformatic surgery. If you don’t believe us, try searching the nternet for such. Today, informatic surgery is a surrealistic oncept that is literally taking shape and form as you read this ommentary.

The Residency Match: Interview Experiences, Postinterview Communication, and Associated Distress

Background Interview experiences and postinterview communication during the residency match process can cause distress for applicants, and deserve further study. Objective We both quantified and qualified the nature of various interview behaviors during the 2015-2016 National Resident Matching Program (NRMP) Match and collected applicant perspectives on postinterview communication and preferences for policy change. Methods An anonymous, 31-question survey was sent to residency candidates applying to 8 residency programs at a single academic institution regarding their experiences at all programs where they interviewed. Results Of 6693 candidates surveyed, 2079 (31%) responded. Regarding interview experiences, applicants reported being asked at least once about other interviews, marital status, and children at the following rates: 72%, 38%, and 17%, respectively, and such questions arose at a reported mean of 25%, 14%, and 5% of programs, respectively. Female applicants were more frequently asked about children than male applicants (22% versus 14%, P < .0001). Overall, 91% of respondents engaged in postinterview communication. A total of 70% of respondents informed their top program that they had ranked it highly; 70% of this subset reported associated distress, and 78% reported doing this to improve match success. A total of 71% would feel relief if postinterview communication was actively discouraged, and 51% would prefer applicants to be prohibited from notifying programs of their rank. Conclusions Applicants to several residency programs reported being asked questions that violate the NRMP Code of Conduct. The majority of applicants would prefer postinterview communication to be more regulated and less prevalent.