Cervical spine degenerative disease is an independent risk factor for increased revision rate following total knee arthroplasty.

INTRODUCTION: The relationship between cervical degenerative pathology and total knee arthroplasty (TKA) revision rates is not well understood. The aim of the study was to determine whether cervical spine degenerative diseases have a role in complications following TKA within 2 years. METHODS: Data were collected from the Humana insurance database using the PearlDiver Patient Records Database from 2007-2017. Patients who had a primary TKA were identified using Current Procedural Terminology (CPT) code 27,447, and patients with degenerative cervical disease were identified using CPT and International Classification of Diseases (ICD) codes. Data on patients' demographics, comorbidities and postoperative complications were recorded and analyzed with univariate and multivariate analysis with significance set at p < 0.05. A Kaplan-Meier analysis was conducted to estimate the 1- and 2-year rates of survival free from revision. RESULTS: A total of 81,873 patients were included in this study. Following multivariate analysis, cervical spine degenerative disease patients were at increased risk of all-cause revision surgery following 1 year (OR: 1.342 95% CI: 1.149-1.569; p < 0.001) and 2 year (OR: 1.338; 95% CI: 1.184-1.512; p < 0.001). At 2 years, patients with cervical spine degenerative disease had a survival rate of 97.7%, while the survival rate was 99.2% among the non-cervical degenerative cohort. CONCLUSIONS: Based on these results, patients with cervical spine degenerative pathology should be counseled that their spinal pathology may impair outcomes following TKA.

3D Printed scaffolds with hierarchical biomimetic structure for osteochondral regeneration.

Osteochondral defects resulting from trauma and/or pathologic disorders are critical clinical problems. The current approaches still do not yield satisfactory due to insufficient donor sources and potential immunological rejection of implanted tissues. 3D printing technology has shown great promise for fabricating customizable, biomimetic tissue matrices. The purpose of the present study is to investigate 3D printed scaffolds with biomimetic, biphasic structure for osteochondral regeneration. For this purpose, nano-hydroxyapatite and transforming growth factor beta 1 nanoparticles were synthesized and distributed separately into the lower and upper layers of the biphasic scaffold, which was fabricated using 3D stereolithography printer. Our results showed that this scaffold design successfully promoted osteogenic and chondrogenic differentiation of human bone marrow mesenchymal stem cells, as well as enhanced gene expression associated with both osteogenesis and chondrogenesis alike. The finding demonstrated that 3D printed osteochondral scaffolds with biomimetic, biphasic structure are excellent candidates for osteochondral repair and regeneration.

3D bioprinting mesenchymal stem cell-laden construct with core-shell nanospheres for cartilage tissue engineering.

Cartilage tissue is prone to degradation and has little capacity for self-healing due to its avascularity. Tissue engineering, which provides artificial scaffolds to repair injured tissues, is a novel and promising strategy for cartilage repair. 3D bioprinting offers even greater potential for repairing degenerative tissue by simultaneously integrating living cells, biomaterials, and biological cues to provide a customized scaffold. With regard to cell selection, mesenchymal stem cells (MSCs) hold great capacity for differentiating into a variety of cell types, including chondrocytes, and could therefore be utilized as a cartilage cell source in 3D bioprinting. In the present study, we utilize a tabletop stereolithography-based 3D bioprinter for a novel cell-laden cartilage tissue construct fabrication. Printable resin is composed of 10% gelatin methacrylate (GelMA) base, various concentrations of polyethylene glycol diacrylate (PEGDA), biocompatible photoinitiator, and transforming growth factor beta 1 (TGF-ß1) embedded nanospheres fabricated via a core-shell electrospraying technique. We find that the addition of PEGDA into GelMA hydrogel greatly improves the printing resolution. Compressive testing shows that modulus of the bioprinted scaffolds proportionally increases with the concentrations of PEGDA, while swelling ratio decreases with the increase of PEGDA concentration. Confocal microscopy images illustrate that the cells and nanospheres are evenly distributed throughout the entire bioprinted construct. Cells grown on 5%/10% (PEGDA/GelMA) hydrogel present the highest cell viability and proliferation rate. The TGF-ß1 embedded in nanospheres can keep a sustained release up to 21 d and improve chondrogenic differentiation of encapsulated MSCs. The cell-laden bioprinted cartilage constructs with TGF-ß1-containing nanospheres is a promising strategy for cartilage regeneration.

Radiographic characterization of prevertebral soft tissue shadow in the cervicothoracic region of normal adults.

BACKGROUND: Many studies have found measurement of prevertebral soft tissue shadow (PVSTS) on a lateral cervical radiograph to be a useful indicator of cervical spine injury. The purpose of this study is to define, measure, and establish a normative set of values for radiographic width of the PVSTS in the cervicothoracic region of the spine (C7-T4), using swimmer's view in subjects with no trauma to the region. MATERIALS AND METHODS: Radiographic PVSTS widths were measured at each vertebral level from C7 to T4 on 131 patients who had "normal" radiographic examination (mean age 31.5 y, range 18-58 y). Intra-observer repeatability was assessed on a random subset of 24 subjects. The range, mean, and standard error of these measurements were calculated and documented. Stepwise forward regression analysis was conducted on PVSTS data and those normalized with respect to the C7 vertebral body width (rPVSTS) to study the influences of age, sex, disk level, and tracheal curve shape. RESULTS: Regression analysis showed that, in order of influence, the vertebral level, sex, and age were three significant factors that affected PVSTS, whereas tracheal curve shape was not significant. Similar results were obtained using normalized rPVSTS data, with the exception that the influence of sex was not significant in this instance. CONCLUSIONS: This study provides a reliable normative database of PVSTS in the North American population, and shows that measurement of prevertebral soft tissue shadow on a swimmer's view radiograph can be used as a valuable screening tool in the evaluation of cervicothoracic spine injury.

Biomechanical comparison of supplemental posterior fixations for two-level anterior lumbar interbody fusion.

Posterior instrumentations have been used to supplement anterior lumbar interbody fusion with cages. Biomechanical studies on single-level anterior lumbar interbody fusion show that stand-alone cages supplemented with posterior translaminar facet or transfacet screw fixation exhibit comparable stability to those supplemented with pedicle screw/rod fixation, while stability of multilevel anterior lumbar interbody fusion remains mostly unknown. The objectives of this study are to compare the stabilization of three supplemental posterior fixations to two-level anterior lumbar interbody fusion, including translaminar facet fixation, transfacet screw fixation, and pedicle screw/rod fixation. Flexibility tests were conducted on fresh-frozen calf spines with moment up to 8.5 N m in flexion, extension, lateral bending, and axial rotation. Each specimen was tested at three stages: intact, anterior lumbar interbody fusion using Polyetheretherketone (PEEK) interbody cage at L3-L4 and L4-L5, and the same anterior lumbar interbody fusion plus one of the three supplemental posterior fixations. The addition of the supplemental posterior fixation increased stiffness at the fusion levels significantly in flexion (9.9 times), extension (5.4 times), and lateral bending (4.1 times). The pedicle screw/rod and translaminar screw fixations provide approximately 40% higher stiffness than the transfacet screw in lateral bending. The pedicle screw/rod fixation also displayed a trend of superior fixation in extension. Supplemental posterior fixation significantly improved stability of two-level anterior lumbar interbody fusion when compared to the stand-alone cages. Pedicle screw/rod system is still the "gold standard" in providing supplemental stability. However, both translaminar facet screws and transfacet screws are good alternatives to provide adequate fixation.

Single-level transforaminal interbody fusion for traumatic lumbosacral fracture-dislocation: a case report.

L5S1 fracture-dislocations are rare three-column injuries. The infrequency of this injury has led to a lack of a universally accepted treatment strategy. Transforaminal lumbar interbody fusion (TLIF) has been shown to be an effective approach for interbody fusion in degenerative indications, but has not been previously reported in the operative management of traumatic lumbosacral dislocation. The authors report a case of traumatic L5S1 fracture-dislocation in a 30-year-old male, presenting with a right-sided L5 neurologic deficit, following a street sweeper accident. Imaging revealed an L5S1 fracture-dislocation with fracture of the S1 body. Open reduction with TLIF and L5S1 posterolateral instrumented fusion was carried out within 24 hours of injury. Excellent reduction was obtained, and maintained at long-term follow-up, with complete resolution of pain and neurologic deficit. In this patient, L5S1 fracture-dislocation was treated successfully, with an excellent outcome, with a single level TLIF and instrumented posterolateral fusion at L5S1.

Industry payments to spine surgeons from 2014 to 2019: trends and comparison of payments to spine surgeons versus all physicians.

BACKGROUND CONTEXT: The ethics of industry payments to physicians and the potential impact on healthcare costs and research outcomes have long been topics of debate. Industry payments to spine surgeons are frequently scrutinized. Transparency of industry relationships with physicians provides insight into their possible impact on clinical decision-making and utilization of care. PURPOSE: To analyze trends in medical industry payments to spine surgeons and all physicians from 2014 to 2019, and further evaluate whether specific payments to spine surgeons vary based on company size. STUDY DESIGN/SETTING: Cross-sectional investigation of publicly reported Center for Medicare and Medicaid Services (CMS) Open Payments Database (OPD) POPULATION SAMPLE: All US providers listed as receiving industry payments with further evaluation of payments to neurosurgeons and orthopedic spine surgeons. OUTCOME MEASURES: Main measures were the magnitude and trends of industry general and research payments and subcategories of general payments, such as royalty/license and consulting fees, to spine surgeons and comparison to all physicians over the six-year period. Variations in payment patterns among spine device manufacturers with the highest reported level of spine surgeon payments in 2019. METHODS: From 2014 to 2019 publicly reported general and research industry payments in the CMS OPD were analyzed. Trends in payments to all physicians were compared to trends in payments to neurosurgeons and orthopedic spine surgeons. Trends in payment patterns among spine device manufacturers with the highest payments in 2019 were determined. Linear regression analysis was completed to find statistically significant outcomes. RESULTS: Our investigation found an aggregate of $42,710,365,196 general and research payments reported to all physicians over the 6-year period, 2.6% ($1,112,936,203) of which went to spine surgeons. Industry general and research payments to spine surgeons decreased by 17.5% ($195,571,109, 2014; $161,283,683, 2019), while increasing by 8.7% ($6,706,208,391, 2014; $7,288,003,832, 2019) to all physicians. Industry research payments to spine surgeons were notably low each year and decreased to only 0.5% of research payments made to all physicians in 2019. Median payment received by spine surgeons as well as the overall distribution of payments to the 75th and 95th percentile significantly increased over the six-year period in comparison to the stable distribution of payments to all physicians. Top eight spine device manufactures with the highest level of spine surgeon payments accounted for 72.9% payments in 2014 but decreased payments by 17.6% to 2019 ($120,409,083.75, 2014; $99,283,264.49, 2019). CONCLUSIONS: Industry general and research payments to all physicians increased from 2014 to 2019 but decreased to spine surgeons, largely due to decreasing payments from eight device manufacturers with the highest level of surgeon payments. A small subset of spine surgeons continues to receive increasing payments. The implications of decreasing investments in research by industry and of large payments made to a small group of spine surgeons bears cautious oversight, both for the future of the specialty and any impact on patient care outcomes.

Effect of Change in USMLE Step 1 Grading on Orthopaedic Surgery Applicants: A Survey of Orthopaedic Surgery Residency Program Directors.

INTRODUCTION: Recently, the Federation of State Medical Boards and the National Board of Medical Examiners, cosponsors of the United States Medical Licensing Examination (USMLE), changed the USMLE Step 1 results from a three-digit score to a pass/fail format. The purpose of this study was to analyze the opinions of program directors (PDs) to predict how the evaluation of orthopaedic surgery residency applicants will change following the change. METHODS: A 17-question online survey was distributed to PDs via e-mail. This survey covered program demographics, questions regarding the relative importance of various factors for selection of interviews, and perceived changes and effect of the scoring change. Responses were aggregated and analyzed. RESULTS: PDs indicated that the three highest scored factors were (1) failure in prior attempts in USMLE/COMLEX examinations (4.7), (2) audition elective/rotation within your department (4.5), and (3) personal prior knowledge of the applicant (4.1). In addition, 38 PDs (81.1%) anticipate that they will require USMLE Step 2 clinical knowledge scores for interview consideration. CONCLUSION: Most orthopaedic surgery PDs think that the change in score reporting for the USMLE Step 1 will result in additional requirements and changes in how programs select applicants and do not support the decision.

Cervical fusion for treatment of degenerative conditions: development of appropriate use criteria.

BACKGROUND CONTEXT: High quality evidence is difficult to generate, leaving substantial knowledge gaps in the treatment of spinal conditions. Appropriate use criteria (AUC) are a means of determining appropriate recommendations when high quality evidence is lacking. PURPOSE: Define appropriate use criteria (AUC) of cervical fusion for treatment of degenerative conditions of the cervical spine. STUDY DESIGN/SETTING: Appropriate use criteria for cervical fusion were developed using the RAND/UCLA appropriateness methodology. Following development of clinical guidelines and scenario writing, a one-day workshop was held with a multidisciplinary group of 14 raters, all considered thought leaders in their respective fields, to determine final ratings for cervical fusion appropriateness for various clinical situations. OUTCOME MEASURES: Final rating for cervical fusion recommendation as either "Appropriate," "Uncertain" or "Rarely Appropriate" based on the median final rating among the raters. METHODS: Inclusion criteria for scenarios included patients aged 18 to 80 with degenerative conditions of the cervical spine. Key modifiers were defined and combined to develop a matrix of clinical scenarios. The median score among the raters was used to determine the final rating for each scenario. The final rating was compared between modifier levels. Spearman's rank correlation between each modifier and the final rating was determined. A multivariable ordinal regression model was fit to determine the adjusted odds of an "Appropriate" final rating while adjusting for radiographic diagnosis, number of levels and symptom type. Three decision trees were developed using decision tree classification models and variable importance for each tree was computed. RESULTS: Of the 263 scenarios, 47 (17.9 %) were rated as rarely appropriate, 66 (25%) as uncertain and 150 (57%) were rated as appropriate. Symptom type was the modifier most strongly correlated with the final rating (adjusted ρ2 = 0.58, p<.01). A multivariable ordinal regression adjusting for symptom type, diagnosis, and number of levels and showed high discriminative ability (C statistic = 0.90) and the adjusted odds ratio (aOR) of receiving a final rating of "Appropriate" was highest for myelopathy (aOR, 7.1) and radiculopathy (aOR, 4.8). Three decision tree models showed that symptom type and radiographic diagnosis had the highest variable importance. CONCLUSIONS: Appropriate use criteria for cervical fusion in the setting of cervical degenerative disorders were developed. Symptom type was most strongly correlated with final rating. Myelopathy or radiculopathy were most strongly associated with an "Appropriate" rating, while axial pain without stenosis was most associated with "Rarely Appropriate."

The impact of long-term corticosteroid use on acute postoperative complications following lumbar decompression surgery.

BACKGROUND: Corticosteroids have a negative impact on the human immune system's ability to function at an optimal level. Studies have shown that patients on long-term corticosteroids have higher infection rates. However, the rates of infection and other complications following lumbar decompression surgery remains under-investigated. The aim of our study was to determine the impact of preoperative long-term corticosteroid usage on acute, 30-day postoperative complications in a subset of patients undergoing lumbar spine decompression surgery, without fusion or instrumentation. We hypothesize that patients on long-term corticosteroids will have higher rates of infection and other postoperative complications after undergoing lumbar decompression surgery of the spine. METHODS: A retrospective cohort study was conducted using data collected from the National Surgical Quality Improvement Program database data from 2005 to 2016. Lumbar decompression surgeries, including discectomies, laminectomies, and others were identified using CPT codes. Chi-square analysis was used to evaluate differences among the corticosteroid and non-corticosteroid groups for demographics, preoperative comorbidities, and postoperative complications. Logistic regression analysis was done to determine if long-term corticosteroid use predicts incidence of postoperative infections following adjustment. RESULTS: 26,734 subjects met inclusion criteria. A total of 1044 patients (3.9%) were on long-term corticosteroids prior to surgical intervention, and 25,690 patients (96.1%) were not on long-term corticosteroids. Patients on long-term corticosteroids were more likely to be older (p < 0.001), female (p < 0.001), nonsmokers (p < 0.001), and have a higher American Society of Anesthesiologist class (p < 0.001). Multivariate analysis demonstrated that long-term corticosteroid usage was associated with increased overall complications (odds ratio [OR]: 1.543; p < 0.001), and an independent risk factor for the development of minor complications (OR: 1.808; p < 0.001), urinary tract infection (OR: 2.033; p = 0.002), extended length of stay (OR: 1.244; p = 0.039), thromboembolic complications (OR: 1.919; p = 0.023), and sepsis complications (OR: 2.032; p = 0.024). CONCLUSION: Long-term corticosteroid usage is associated with a significant increased risk of acute postoperative complication development, including urinary tract infection, sepsis and septic shock, thromboembolic complications, and extended length of hospital stay, but not with superficial or deep infection in patients undergoing lumbar decompression procedures. Spine surgeons should remain vigilant regarding postoperative complications in patients on long-term corticosteroids, especially as it relates to UTI and propensity to decompensate into sepsis or septic shock. Thromboembolic risk attenuation is also imperative in this patient group during the postoperative period and the surgeon should weigh the risks and benefits of more intensive anticoagulation measures.

Three-Dimensional Printing: A Catalyst for a Changing Orthopaedic Landscape.

Three-dimensional (3D) printing is an emerging tool in provider and patient education, surgical planning, and the design and implementation of medical devices and implants. Recent decreases in the cost of 3D printers along with advances in and cost reduction of printable materials have elevated 3D printing within the medical device industry. The advantages of 3D printing over traditional means of implant manufacturing lie in its ability to use a wide array of materials, its fine control of the macro- and microarchitecture, and its unprecedented customizability. Barriers to the widespread adoption of 3D-printed implants include questions of implant durability, U.S. Food and Drug Administration (FDA) approval for patient-specific implants, and insurance coverage of those implants.

Adult isthmic spondylolisthesis.

Isthmic spondylolisthesis is present in a small subset of the adult population. Although the incidence of low back pain in these persons is similar to that of the general population, both pars interarticularis defect and forward slip can serve as unique pain generators. Neurologic symptoms may result from nerve root impingement related to the pars defect or degenerative changes associated with the deformity. Most symptomatic cases are successfully managed nonsurgically, but patients with intractable pain or neurologic symptoms may benefit from surgical decompression and stabilization. Surgical intervention has shown >80% success in appropriately selected patients, with a low incidence of complications. Surgical techniques include decompression, posterolateral fusion, anterior lumbosacral interbody fusion, and circumferential fusion methods. Circumferential fusion results in improved fusion rates and, in some studies, superior clinical outcomes. The choice of procedure is generally guided by the patient's radiographic and clinical findings as well as risk-benefit considerations.

Autograft containment in posterolateral spine fusion.

BACKGROUND CONTEXT: Pseudoarthrosis rates in lumbar intertransverse fusion remain high. Compression and displacement of the developing fusion mass by the paraspinal musculature may be a contributory factor. Biocontainment devices have been clinically used in the skull and mandible to guide bone regeneration. The role of a mechanical device in containing graft material in the developing posterolateral lumbar spine fusion is unclear. PURPOSE: To determine the benefits of using a bioabsorbable graft-containment device for lumbar intertransverse fusion, and to evaluate the biocompatibility of this implant by histological analysis of the host tissue reaction. STUDY DESIGN: A rabbit intertransverse spine fusion model was used to evaluate a bioabsorbable graft-containment implant. Study and control groups were compared with regard to the rate, volume, and quality of fusion, as well as host tissue reaction to the graft and implant. METHODS: Fourteen adult male New Zealand White rabbits underwent bilateral posterolateral intertransverse spine arthrodesis at L3-L4. The control group (n=7) received autograft alone, and the study group received autografts placed in open meshed hemicylinders fashioned from LactoSorb sheets (LactoSorb; Biomet Orthopedics Inc., Warsaw, IN). Spines were harvested at 6 weeks and imaged. Radiographs and computed tomography (CT) images were used to calculate the rate, area, and volume of fusion mass. Sections were fixed and stained with hematoxylin-eosin and Mallory trichrome for histological analysis of fusion and host tissue response. The Mann-Whitney nonparametric statistical test was used for the radiographic and CT qualitative assessments. The CT volume quantitation was analyzed using the Student t test. A p value of <.05 was used to assign statistical significance. RESULTS: The fusion rates on radiographs and CT imaging did not show a significant difference (p>.05) between the biocontainment and control groups. The volume of fusion revealed a significant increase with biocontainment (mean+/-standard error; total left+right fusion sides=2.88+/-0.30 cc) compared with controls (2.12+/-0.15 cc) (p<.05). Histology revealed no difference in the maturity or the quality of the fusion mass between the two groups. Inflammatory response around the developing fusion mass and muscle necrosis were slightly increased in the study group. The LactoSorb biocontainment material led to variable inflammatory reaction, with some areas showing little or no response and other showing an inflammatory response with fibrous connective tissue, lymphocyte infiltration, and focal foreign body giant cell reaction. CONCLUSIONS: The incidence of fusion was similar with or without a containment device for onlay bone graft. A significant increase in the volume of the fusion suggests that a biocontainment device does play a role in protecting the developing fusion mass from the mechanical effects of the paraspinal musculature. The clinical use of this device cannot be justified at this time, and further studies will determine whether this increase in fusion volume will translate into a better incidence and volume of fusion in primate and human models.

Alteration of load sharing of anterior cervical implants with change in cervical sagittal alignment.

Anterior cervical discectomy and fusion (ACDF) is often supplemented with the application of an anterior plate to improve the stability of the fusion segment. While plate design has been shown to influence stress shielding of the graft, little is known about how the kyphotic alignment of a fused cervical segment affects the load sharing between the anterior plate and the osteoligamentous structures of the spine. The aim of this study was to characterize load sharing between an anterior plate and the osteoligamentous structures of the cervical motion segments in kyphotic versus normal lordotic alignment following single-level ACDF using fresh ovine cervical spines (C3-C6). The loading protocol involved preloading the spine with a 20 N compressive force and applying quasi-static moments (up to 2.1 Nm) in the sagittal plane to simulate flexion and extension. Stiffness of the fusion segment was measured from the moment-rotation plot. Normal lordotic alignment was replicated by insertion of a fibular allograft 2 mm taller than the interbody space. Kyphotic alignment was simulated by removing the graft and reapplying a shorter anterior cervical plate. The average segmental sagittal angulation at C4-C5 was 5.2+/-1.6 degrees of lordosis for the normal lordotic group and 6.8+/-2.3 degrees of kyphosis for the kyphotic group. With flexion, the plate shared 52.8% of the applied load in the normal lordotic group, and 70.1% in the kyphotic group (p<0.03). In extension, the amount of load-share by the plate in the normal lordotic group was comparable to that of the kyphotic group (52.7% vs. 40.7%, p=0.16). This study shows that kyphotic alignment of the cervical fusion segment increases the load sharing of the anterior plate under flexion loading.

Degenerative cervical spondylosis: clinical syndromes, pathogenesis, and management.

Degenerative changes in the cervical spinal column are ubiquitous in the adult population, but infrequently symptomatic. The evaluation of patients with symptoms is facilitated by classifying the resulting clinical syndromes into axial neck pain, cervical radiculopathy, cervical myelopathy, or a combination of these conditions. Although most patients with axial neck pain, cervical radiculopathy, or mild cervical myelopathy respond well to initial nonsurgical treatment, those who continue to have symptoms or patients with clinically evident myelopathy are candidates for surgical intervention.

Comparison of Short-term Complication Rates Between Cephalomedullary Hip Screw Devices and Sliding Hip Screws: An Analysis of the National Surgical Quality Improvement Program Database.

BACKGROUND: The literature pertaining to the management of intertrochanteric hip fractures using cephalomedullary hip screws (CMHSs) and sliding hip screws (SHSs) has shown varying results. CMHS use has increased over time without validation of its superiority in the literature. METHODS: We conducted a retrospective cohort study using the American College of Surgeons National Quality Improvement Program database. Patients who had sustained a peritrochanteric hip fracture were identified. Short-term (<30 day) complications were identified with adjustments made for preoperative comorbidities. We also examined the relative percentages of CMHS and SHS surgeries over time. RESULTS: A total of 14,415 subjects met the inclusion criteria. Patients undergoing SHS surgery were generally healthier, having a lower American College of Surgeon class, preoperative bleeding, hypertension, pulmonary risk factors, congestive heart failure, and higher preoperative hematocrit. After adjusting for demographics and comorbidities, we noted a higher rate of 30-day mortality (odds ratio [OR] = 1.19; P = 0.024), bleeding (OR = 1.10; P = 0.007), pulmonary complications (OR = 1.19; P = 0.049), and clotting events (OR = 1.35; P = 0.035) in the CMHS group. We observed a higher rate of urinary tract infection (OR = 0.81; P = 0.023) and length of stay (1.0 days; P < 0.0001) in the SHS group. The overall percentage of SHS cases was 33% and trended lower over time. CONCLUSIONS: Although differences in complication subtypes and the overall complication rate were found, further multicenter, randomized controlled trials would be helpful in elucidating differences between the treatment groups. The popularity of the CMHS continues to increase over time.

Posterolateral intertransverse lumbar fusion in a mouse model: surgical anatomy and operative technique.

BACKGROUND CONTEXT: Animal models are frequently used for studying the effect of bone graft substitutes or allogeneic materials on osterolateral lumbar fusion. Transgenic technology in the mouse provides a unique opportunity to further understand the biology of spine fusion. PURPOSE: To describe pertinent lumbar spine anatomy and formulate a surgical protocol for posterolateral fusion in the mouse model. STUDY DESIGN: Diagnostic model: development of an animal model for biologic evaluation of posterolateral spine fusion. METHOD: Ten mice were killed to study relevant lumbar spine anatomy and develop a protocol for lumbar spine fusion. The L4-L6 fusion protocol was validated in 46 mice for ease of exposure, preparation of the posterolateral fusion bed, introduction of bone inductive agents, and perioperative care. RESULTS: Anatomy and surgical technique for posterolateral intertransverse lumbar fusion in the mouse model are described. A paraspinal approach allows exposure of the transverse processes, decortication, and graft placement at the L4-L6 intertransverse fusion site. Decortication alone did not result in fusion, whereas the use of bone graft resulted in satisfactory fusion rates. Perioperative morbidity and mortality rates were low. CONCLUSION: The mouse posterolateral lumbar spine fusion model is reproducible, inexpensive, and has low complication rates. Knowledge of the relevant anatomy and adherence to a well-defined surgical protocol provides a reliable and reproducible experimental spine fusion model.

Changes in the lumbar foramen following anterior interbody fusion with tapered or cylindrical cages.

BACKGROUND CONTEXT: Anterior lumbar interbody fusion (ALIF) using both cylindrical and tapered threaded interbody cages has been shown to restore disc height, reduce segmental motion, and relieve low back pain. The effectiveness of these stand-alone cage designs in restoration and maintenance of intervertebral foraminal dimensions has received little attention. PURPOSE: To investigate the effects of anterior implantation of cylindrical and tapered interbody cages on morphologic changes of the lumbar neuroforamen and maintenance of foraminal dimensions under dynamic loading. STUDY DESIGN/SETTING: A biomechanical study using bovine calf spine model to compare the deformation of foraminal space after ALIF with either tapered cages or cylindrical cages. METHODS: Sixteen fresh calf spines were randomly assigned to undergo ALIF at the L3-L4 level using either two threaded cylindrical or two tapered cages. Lumbar spines were subjected to unconstrained loading in flexion, extension, and lateral bending. Rotation of the L3-L4 segment and dynamic deformation in foraminal height were obtained through a motion analysis system, and compared between the two cage groups. Foraminal dimensions were assessed before and after tapered or cylindrical cage implantation with digitized measurement of bilateral foraminal molds. RESULTS: Regardless of cage design, anterior implantation of cages increased neuroforaminal area by 17% (p=.0005) and increased the foraminal height by 9% (p=.0004) in the neutral unloaded position. In dynamic loading conditions, foraminal height was significantly stabilized in all loading directions by the cylindrical cages (p=.01) and on both sides during lateral bending by the tapered cages (p<.03). Foraminal stabilization provided by either cage was most prominent in the direction of lateral bending (26-37% of the intact values), while cylindrical cages also provided substantial stabilization in flexion (26% of the intact value). Significant linear relationships were found between foraminal height and residual fusion segment motion under dynamic loading conditions. CONCLUSION: Results from this bovine model biomechanical study indicate that stand-alone anterior interbody fusion cages with either tapered or cylindrical design are effective in restoring neuroforaminal height and stabilize the spine to withstand foraminal deformation during daily loading. The degree of stabilization was influenced substantially by the loading direction, to a lesser degree by the cage type, and was strongly dependent on the segment mobility. Although bovine lumbar spine is widely accepted for comparative studies, direct clinical interpretation should be made with caution owing to the anatomical differences from human.

Factors Motivating Medical Students in Selecting a Career Specialty: Relevance for a Robust Orthopaedic Pipeline.

INTRODUCTION: Selection of a career specialty by medical students is a complex and individualized decision. Our goals were to understand the factors that influenced medical students in selecting their career specialty, identify the stage at which this decision was made, and understand the role of demographics, mentors, and curricula in this process. METHODS: Medical students from 10 institutions participated in a web-based survey. Results were stratified by sex, race/ethnicity, and level of interest in orthopaedic surgery. RESULTS: A total of 657 students responded to the survey. Specialty content (mean rating, 8.4/10) and quality of life/lifestyle/stress level (7.5/10) were the primary motivating factors in selecting a specialty. Interest in orthopaedic surgery was lower in women than in men (2.7 versus 3.9; P < 0.01) and was equivalent among race/ethnicity groups. Although 27% of students reported moderate or extensive medical school curriculum exposure to orthopaedics, this education did not sway them toward the specialty. CONCLUSIONS: Levels of interest in orthopaedics among medical students may be lower than generally assumed. Increasing the attractiveness of the specialty will require a multifaceted approach, including recognition of lifestyle factors, adjustments in the orthopaedic clerkship to make the specialty more appealing, mentorship by orthopaedic faculty, and conversion of high levels of interest in the specialty among minority medical students into successful residency applications. LEVEL OF EVIDENCE: IV.

Bilateral C5 motor paralysis following anterior cervical surgery--a case report.

Numerous authors have reported C5 root palsies following posterior cervical surgery, and several mechanisms of injury have been proposed. Similar deficits after anterior cervical procedures are considered to occur less commonly. We report on a 48-year-old male who underwent multi-level anterior discectomy and fusion for cervical spondylotic myelopathy. Bilateral C5 nerve root deficits were noticed in the immediate postoperative period, and treated non-operatively. A postoperative magnetic resonance imaging (MRI) scan showed an increase in cervical lordosis accompanied by a posterior shifting of the spinal cord. Potential mechanisms of nerve root injury in this situation are discussed, and the literature on postoperative C5 root deficits is reviewed. The patient returned to his preoperative occupation as an operating room nurse 6 months following surgery, with complete neurologic recovery occurring over an 11-month period. C5 deficits following anterior cervical surgery occur more frequently than generally assumed. Improved lordosis and longitudinal lengthening of the cervical spinal column in multilevel anterior decompression and interbody fusion can paradoxically result in a traction injury to the spinal cord and C5 nerve roots.