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.

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."

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.

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.

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.

Abstract PD8-12: Safety and efficacy of palbociclib and radiotherapy in metastatic breast cancer patients: Initial results of a novel combination

Purpose: Palbociclib is a selective CDK4/6 inhibitor approved for the treatment of metastatic ER+/HER2- breast cancer. Inhibition of CDK4/6 prevents cell cycle progression from G1 to the more radioresistant S phase, raising the possibility of an enhanced therapeutic effect if combined with radiotherapy (RT). Despite this potential benefit, clinicians seldom use this combination due to fear that RT may exacerbate palbociclib toxicity, particularly leukopenia. Our aim is to report the preliminary results of patients with metastatic breast cancer who received RT while receiving palbociclib.

Methods: We retrospectively reviewed records of all patients who were treated with palbociclib at our institution from 2015-2018. Patients who received RT for symptomatic metastases concurrently or within 14 days of last drug administration were included in our analysis. Local treatment effect was assessed by clinical exam and subsequent CT or MRI imaging, if applicable. Toxicity was graded based on CTCAE v5.0.

Results: A total of 16 females received palliative RT in association with palbociclib. The median age of the treated patients was 59.6 (range 33.3-91.0) years. The median time of closest palbociclib use to RT administration was 5 (range 0-14) days.

The following sites were treated in order of frequency: bone (10-axial skeleton [8-vertebra]; 1-ilium), brain (4: 3-WBRT & 1-SRS), and mediastinum (1). RT dose/fractionation for bone was 30 Gy/10 fxn (7), 35 Gy/14 fxn (2), 37.5 Gy/15 fxn (1), and 18 Gy/1 fxn (1). WBRT dose/fractionation was 30 Gy/10 fxn for all patients. SRS brain dose was 25 Gy/5 fxn. The patient treated to the mediastinum received 36 Gy/18 fxn.

At most recent follow-up, 12 patients are still living. The median time from RT to last known follow-up or death is 10.3 (range 1.7-29.6) months. Pain relief was achieved in 15 of 16 (93.8%) patients. No radiographic local failure was noted in the 13 patients with evaluable follow-up imaging.

The combination of RT and palbociclib was well-tolerated. Grade 1 fatigue, dermatitis, and nausea was noted in 5, 3, and 1 patient, respectively. One patient with WBRT developed Grade 1 headache. Six of 16 patients were leukopenic prior to RT initiation. Following RT, 7 patients were observed to have a drop in WBC count, of which 2 dropped into the leukopenic range. Only a total of 5 patients were leukopenic following RT, of which 3 were leukopenic before receiving RT. No acute or late Grade 2 or higher cutaneous, neurological, gastrointestinal, or hematologic toxicities were noted.

Conclusions: The use of RT in patients receiving palbociclib resulted in minimal Grade 1 and no Grade 2+ toxicities, including leukopenia. This treatment can be used safely in symptomatic patients without discontinuation of systemic therapy. Further larger prospective studies with longer follow-up are needed to confirm these results.

Citation Format: Chowdhary M, Sen N, Chowdhary A, Usha L, Cobleigh M, Patel KR, Wang D, Barry PN, Rao RD. Safety and efficacy of palbociclib and radiotherapy in metastatic breast cancer patients: Initial results of a novel combination [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr PD8-12.

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-β1) 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-β1 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-β1-containing nanospheres is a promising strategy for cartilage regeneration.

Radiographic Changes in the Cervical Spine Following Anterior Arthrodesis: A Long-Term Analysis of 166 Patients

BACKGROUND

Adjacent segment degeneration frequently develops following anterior cervical discectomy and fusion. The objectives of the present study were to characterize the long-term evolution of degenerative radiographic changes at segments adjacent to anterior cervical fusion and to identify factors associated with the development of these changes, including the preoperative condition of the cervical spine and parameters related to arthrodeses.

METHODS

One hundred and sixty-six patients who underwent anterior cervical discectomy and fusion for symptomatic cervical spondylosis or disc herniation were followed radiographically for a mean time of 12.7 years (range, 5 to 30 years). Radiographic changes representing degeneration at adjacent levels, including disc height loss, osteophyte formation, end-plate sclerosis, and facet arthrosis, along with changes in sagittal alignment of the fusion segment and cervical spine, were recorded preoperatively and at the time of the latest follow-up. Regression models were used to identify the parameters that affect these degenerative changes.

RESULTS

More than 90% of patients had worsened anterior and posterior osteophytes at segments immediately adjacent to the fusion. Degenerative changes were significantly affected by the proximity of the level to the fusion and were inversely affected by the preoperative degenerative changes present at the segment (p < 0.0001). The time elapsed since the surgical procedure was a significant predictor of degenerative changes (p < 0.0001). However, the patient age, the number of levels fused, and the sagittal alignment of the fusion segment had no influence on the degenerative changes at adjacent segments.

CONCLUSIONS

Multiple factors likely contribute to adjacent segment degeneration following cervical arthrodesis. Although mechanical parameters associated with arthrodesis, such as length and alignment of the fusion, did not appear to play a role, the preoperative degenerative condition of the spine and inclusion of C5-C6 in the arthrodesis influenced the incidence of adjacent segment degeneration.

LEVEL OF EVIDENCE

Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Incidence and mechanism of neurological deficit after thoracolumbar fractures sustained in motor vehicle collisions

OBJECT To determine the incidence of and assess the risk factors associated with neurological injury in motor vehicle occupants who sustain fractures of the thoracolumbar spine. METHODS In this study, the authors queried medical, vehicle, and crash data elements from the Crash Injury Research and Engineering Network (CIREN), a prospectively gathered multicenter database compiled from Level I trauma centers. Subjects had fractures involving the T1-L5 vertebral segments, an Abbreviated Injury Scale (AIS) score of ≥ 3, or injury to 2 body regions with an AIS score of ≥ 2 in each region. Demographic parameters obtained for all subjects included age, sex, height, body weight, and body mass index. Clinical parameters obtained included the level of the injured vertebra and the level and type of spinal cord injury. Vehicular crash data included vehicle make, seatbelt type, and usage and appropriate use of the seatbelt. Crash data parameters included the principal direction of force, change in velocity on impact (ΔV), airbag deployment, and vehicle rollover. The authors performed a univariate analysis of the incidence and the odds of sustaining spinal neurological injury associated with major thoracolumbar fractures with respect to the demographic, clinical, and crash parameters. RESULTS Neurological deficit associated with thoracolumbar fracture was most frequent at extremes of age; the highest rates were in the 0- to 10-year (26.7% [4 of 15]) and 70- to 80-year (18.4% [7 of 38]) age groups. Underweight occupants (OR 3.52 [CI 1.055-11.7]) and obese occupants (OR 3.27 [CI 1.28-8.31]) both had higher odds of sustaining spinal cord injury than occupants with a normal body mass index. The highest risk of neurological injury existed in crashes in which airbags deployed and the occupant was not restrained by a seatbelt (OR 2.35 [CI 0.087-1.62]). Reduction in the risk of neurological injuries occurred when 3-point seatbelts were used correctly in conjunction with the deployment of airbags (OR 0.34 [CI 1.3-6.6]) compared with the occupants who were not restrained by a seatbelt and for whom airbags were not deployed. Crashes with a ΔV greater than 50 km/hour had a significantly higher risk of spinal cord injury (OR 3.45 [CI 0.136-0.617]) than those at lower ΔV values. CONCLUSIONS Deployment of airbags was protective against neurological injury only when used in conjunction with 3-point seatbelts. Vehicle occupants who were either obese or underweight, very young or elderly, and those in crashes with a ΔV greater than 50 km/hour were at higher risk of thoracolumbar neurological injury. Neurological injury at thoracic and lumbar levels was associated with multiple factors, including the incidence of fatality, occupant factors such as age and body habitus, energy at impact, and direction of impact. Current vehicle safety technologies are geared toward a normative body morphology and need to be reevaluated for various body morphologies and torso compliances to lower the risk of neurological injury resulting from thoracolumbar fractures.

Occupant and crash characteristics in thoracic and lumbar spine injuries resulting from motor vehicle collisions

BACKGROUND CONTEXT

Motor vehicle collisions (MVC) are a leading cause of thoracic and lumbar (T and L) spine injuries. Mechanisms of injury in vehicular crashes that result in thoracic and lumbar fractures and the spectrum of injury in these occupants have not been extensively studied in the literature.

PURPOSE

The objective was to investigate the patterns of T and L spine injuries after MVC; correlate these patterns with restraint use, crash characteristics, and demographic variables; and study the associations of these injuries with general injury morbidity and fatality.

STUDY DESIGN/SETTING

The study design is a retrospective study of a prospectively gathered database.

PATIENT SAMPLE

Six hundred thirty-one occupants with T and L (T1-L5) spine injuries from 4,572 occupants included in the Crash Injury Research and Engineering Network (CIREN) database between 1996 and 2011 were included in this study.

OUTCOME MEASURES

No clinical outcome measures were evaluated in this study.

METHODS

The CIREN database includes moderate to severely injured occupants from MVC involving vehicles manufactured recently. Demographic, injury, and crash data from each patient were analyzed for correlations between patterns of T and L spine injuries, associated extraspinal injuries and overall injury severity score (ISS), type and use of seat belts, and other crash characteristics. T and L spine injuries patterns were categorized using a modified Denis' classification to include extension injuries as a separate entity.

RESULTS

T and L spine injuries were identified in 631 of 4,572 vehicle occupants, of whom 299 sustained major injuries (including 21 extension injuries) and 332 sustained minor injuries. Flexion-distraction injuries were more prevalent in children and young adults and extension injuries in older adults (mean age, 65.7 years). Occupants with extension injuries had a mean body mass index of 36.0 and a fatality rate of 23.8%, much higher than the fatality rate for the entire cohort (10.9%). The most frequent extraspinal injuries (Abbreviated Injury Scale Grade 2 or more) associated with T and L spine injuries involved the chest (seen in 65.6% of 631 occupants). In contrast to occupants with major T and L spine injuries, those with minor T and L spine injuries showed a strikingly greater association with pelvic and abdominal injuries. Occupants with minor T and L spine injuries had a higher mean ISS (27.1) than those with major T and L spine injuries (25.6). Among occupants wearing a three-point seat belt, 35.3% sustained T and L spine injuries, whereas only 11.6% of the unbelted occupants sustained T and L spine injuries. Three-point belted individuals were more likely to sustain burst fractures, whereas two-point belted occupants sustained flexion-distraction injuries most often and unbelted occupants had a predilection for fracture-dislocations of the T and L spines. Three-point seat belts were protective against neurologic injury, higher ISS, and fatality.

CONCLUSIONS

T and L spine fracture patterns are influenced by the age of occupant and type and use of seat belts. Despite a reduction in overall injury severity and mortality, seat belt use is associated with an increased incidence of T and L spine fractures. Minor T and L spine fractures were associated with an increased likelihood of pelvic and abdominal injuries and higher ISSs, demonstrating their importance in predicting overall injury severity. Extension injuries occurred in older obese individuals and were associated with a high fatality rate. Future advancements in automobile safety engineering should address the need to reduce T and L spine injuries in belted occupants.

Geometrical properties of the human child cervical spine with a focus on the C1 vertebra

OBJECTIVE

Child dummies and injury criteria used in automotive crashworthiness environments are based on scaling from the adult and/or between children of different ages. Cartilage-to-bone ossification, spinal canal and joint developments of the spine, and strength attainments do not grow linearly from birth to maturity. Though this is known to medical professionals, age-based quantitative analyses are needed to accurately model the pediatric spine. The objective of this study was to quantify longitudinal growths of various regions of the first cervical vertebrae, responsible for transmitting the axial load from the base of the skull through the condyles to the neck/torso.

METHODS

Computed tomography (CT) images of 54 children from one day to 18 years of age were retrospectively used to determine the following geometrical properties: bilateral neurocentral synchondroses widths, the width of posterior synchondrosis, outer and inner anteroposterior and transverse diameters, spinal canal area, and depths of the anterior and posterior arches of the C1 vertebra. Both axial and sagittal CT images were used in the analysis. Sagittal images were used to quantify data for the anterior and posterior arches and axial images were used for all described cross-sectional parameters.

RESULTS

Geometrical properties were extracted and reported for the various parameters at 6 months; one year; 18 months; and 3, 6, and 10 years of age corresponding to the dummy family ages routinely used in motor vehicle crashworthiness research and other applications. The outer transverse diameter ranged from 4.97 to 7.08 cm; outer and inner antero-posterior diameters ranged from 2.99 to 4.18 and 2.19 to 3.03 mm; and spinal canal area ranged from 4.34 to 6.68 mm(2). Other data are given in the body of the article. The growths of the first cervical vertebra quantified in terms of the above variables occurred nonlinearly with age and the degree of nonlinearity depended on the type of the geometrical parameter. Growths did not match with the simple scaling ratios based on the adult spine, used in different studies reported in the current literature.

CONCLUSIONS

These early nonlinear and nonuniform age- and local geometry-specific variations should be considered in human finite element models for an accurate transfer of the external load from the atlas to the subaxial spine and to improve their fidelity and biomechanical capabilities.

Developmental morphology and ossification patterns of the C1 vertebra

BACKGROUND

The first cervical vertebra (C1) is a unique ring-shaped structure and is largely cartilaginous at birth. Our objectives were to retrospectively analyze the age of closure of the synchondroses and determine age-dependent morphological characteristics of the C1 vertebra using computed tomographic (CT) scans.

METHODS

Helical CT scans were made in fifty-four children as part of routine imaging of patients presenting to the emergency room with head injury, to exclude cervical spine trauma. Axial and sagittal reconstruction images of the C1 ring were analyzed for widths of the anterior and posterior synchondroses, outer and inner anteroposterior diameters, outer and inner transverse diameters, inner area of the spinal canal at C1, and heights of the anterior and posterior arches. Variations in these parameters were evaluated in age groups from infancy to eighteen years.

RESULTS

As ossification progressed, the widths of the anterior neurocentral and posterior synchondroses decreased with increasing age. Closure of the posterior synchondrosis was complete in all by thirty-six months, except in one fifty-five-month-old subject in whom the posterior synchondrosis was open. Closure of the anterior synchondrosis was generally found after thirty-six months. Growth of the mean outer and inner anteroposterior diameters, mean outer transverse diameter, and increase in canal area occurred with age up to the three to six-year group, following which measurements increased minimally or stayed relatively constant. The inner transverse diameter was largely unchanged from birth to maturity and appeared to be independent of age. Anterior and posterior ring heights showed a similar distribution, with an increase up to the nine to twelve-year age group, and relatively constant values thereafter.

CONCLUSIONS AND CLINICAL RELEVANCE

Data from this retrospective review of fifty-four CT scans of the cervical spine, weighted toward the youngest population, assist in understanding the age-dependent osseous anatomy and biomechanical stability of the C1 vertebra in the growing child, help to distinguish fractures from incomplete ossification, and help to formulate decisions on the use of internal fixation of C1 in the growing child.

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.

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.

Upright magnetic resonance imaging measurement of prevertebral soft tissue in the cervical spine of normal volunteers

BACKGROUND CONTEXT

Anteroposterior width of prevertebral soft tissues (PVSTs) in the cervical spine has long been considered a valuable radiographic measurement for evaluation of occult cervical spine pathology. These measurements, generally obtained from lateral radiographs of the cervical spine, have been used clinically as references for the evaluation of patients with traumatic, neoplastic, or other cervical spine disorders. Magnetic resonance imaging (MRI) offers a subtle delineation of the soft-tissue structures anterior to the vertebral column, with the potential for more accurate and sensitive determination of PVST width. Upright magnetic resonance images permit comparison with and validation of previously reported upright lateral radiographic measurements of PVST width. To our knowledge, evaluation of cervical spine PVST width using upright MRI has not been previously published in the English literature.

PURPOSE

The purposes of this study were to validate lateral radiographic measurements of PVST width using upright weight-bearing MRI in healthy subjects and quantify effects of spinal level and gender.

STUDY DESIGN

Clinical study in asymptomatic volunteers.

METHODS

Eleven male and eight female volunteers consented and were enrolled in the study. All volunteers were asymptomatic and had no history of cervical spine injury or degenerative disease. Prevertebral soft-tissue width was measured at each cervical level from C2 to C7 using upright weight-bearing MRI. Statistically significant differences in PVST width based on spinal level and gender were determined using two-factor analysis of variance.

RESULTS

Width magnitudes were significantly dependent on gender (p<.0001) and spinal level (p<.0001). All C3 and C6 measurements were below the traditionally accepted values of 7 and 20 mm, respectively, that would be considered "abnormal." Prevertebral soft-tissue width was greater in men at upper and lower extents of the cervical spine. Prevertebral soft-tissue widths reported in the present study were similar in magnitude and level-by-level trends to measurements of asymptomatic volunteers obtained using lateral radiography.

CONCLUSION

The present study validated the use of lateral radiography to measure PVST width, presented level-by-level and gender-specific normative data, and provided a weighted statistical analysis of differences between normal volunteers and injured patients.

The effect of platelet-rich plasma and bone marrow on murine posterolateral lumbar spine arthrodesis with bone morphogenetic protein

BACKGROUND

Recombinant human bone morphogenetic protein-2 (rhBMP-2) has had limited success in stimulating osteogenesis at the site of posterolateral lumbar spine arthrodesis when used at the currently approved human dose for anterior lumbar interbody arthrodesis. The objective of the present study was to investigate the effect of co-administration of fresh harvested autologous bone marrow aspirate and platelet-rich plasma on rhBMP-2-mediated in vivo murine posterolateral lumbar spine arthrodesis.

METHODS

Forty adult male mice underwent posterolateral intertransverse process arthrodesis from L4 to L6. In three experimental groups, a collagen sponge was placed on each side, overlaying the decorticated transverse processes. Each collagen sponge was presoaked for fifteen minutes with 31 microg of rhBMP-2 in a 100-microL solution containing either saline solution (n = 10), platelet-rich plasma (n = 10), or donor bone-marrow cells (n = 10). Control mice underwent decortication alone (n = 10). The lumbar spine was harvested four weeks after surgery, and spinal fusion was evaluated on the basis of radiographs, computed tomography, and histological analysis.

RESULTS

Control mice showed no evidence of spinal fusion. The rate of fusion was radiographically and histologically similar in all three experimental groups. The area, volume, and density of the fusion mass were significantly greater (p < 0.05) for the group treated with rhBMP-2 and bone marrow as compared with the group treated with rhBMP-2 alone. The group treated with rhBMP-2 and platelet-rich plasma had intermediate fusion area and density. Histologically, the spines treated with rhBMP-2 alone consistently showed the presence of cortical bone between the two transverse processes but fewer trabeculae within the fusion mass; bone marrow co-augmentation resulted in more trabeculae within the fusion mass and a thicker cortical perimeter.

CONCLUSIONS

The present study quantitatively confirmed a synergistic effect of bone marrow cells when added to rhBMP-2 in an in vivo mouse posterolateral lumbar spine fusion model. The volume, area, and density of the fusion mass were significantly increased by augmentation with bone marrow cells.

Computerized tomographic morphometric analysis of subaxial cervical spine pedicles in young asymptomatic volunteers

BACKGROUND

Although cervical spine pedicle screws have been shown to provide excellent fixation, widespread acceptance of their use is limited because of the risk of injury to the spinal cord, nerve roots, and vertebral arteries. The risks of pedicle screw insertion in the cervical spine can be mitigated by a three-dimensional appreciation of pedicle anatomy. Normative data on three-dimensional subaxial pedicle geometry from a large, young, and asymptomatic North American population are lacking. The purpose of the present study was to determine three-dimensional subaxial pedicle geometry in a large group of young volunteers and to determine level and sex-specific morphologic differences.

METHODS

Helical computerized tomography scans were made from the third cervical to the seventh cervical vertebra in ninety-eight volunteers (sixty-three men and thirty-five women) with an average age of twenty-five years. Pedicle width, height, length, and transverse and sagittal angulations were measured bilaterally. Pedicle screw insertion positions were quantified in terms of mediolateral and superoinferior offsets relative to readily identifiable landmarks.

RESULTS

The mean pedicle width and height at all subaxial levels were sufficient to accommodate 3.5-mm screws in 98% of the volunteers. Pedicle width and height dimensions of <4.0 mm were rare (observed in association with only 1.7% of the pedicles), with 82% occurring in women and 72% occurring unilaterally. Screw insertion positions generally moved medially and superiorly at caudal levels. Transverse angulation was approximately 45 degrees at the third to fifth cervical levels and was less at more caudal levels. Sagittal angulation changed from a cranial orientation at superior levels to a caudal orientation at inferior levels. Mediolateral and superoinferior insertion positions and sagittal angulations were significantly dependent (p < 0.05) on sex and spinal level. Transverse angulation was significantly dependent (p < 0.05) on spinal level.

CONCLUSIONS

Pedicle screw insertion points and orientation are significantly different (p < 0.05) at most subaxial cervical levels and between men and women. Preoperative imaging studies should be carefully templated for pedicle size in all patients on a level-specific basis. Although the prevalence was low, women were more likely to have pedicle width and height dimensions of <4.0 mm.

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.

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.

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.

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.

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.

Anterior longitudinal ligament injuries in whiplash may lead to cervical instability

Although whiplash injuries account for a significant annual cost to society, the exact mechanism of injury and affected tissues remain unknown. Previous investigations documented injuries to the cervical anterior longitudinal ligament in whiplash. The present investigation implemented a comprehensively validated computational model to quantify level-dependent distraction magnitudes of this structure in whiplash. Maximum ligament distractions approached failure levels, particularly in middle to lower cervical levels, and occurred during the initial phase of head-neck kinematics. In particular, the C5-C6 anterior longitudinal ligament sustained distraction magnitudes as high as 2.6mm during the retraction phase, corresponding to 56% of distraction necessary to result in ligament failure. Present results demonstrated that anterior structures in the lower cervical spine may be susceptible to injury through excess distraction during the retraction phase of whiplash, which likely occurs prior to head restraint contact. Susceptibility of these structures is likely due to non-physiologic loading placed on the cervical spinal column as the head translates posteriorly relative to the thorax. Injury to anterior spinal structures can result in clinical indications including cervical instability in extension, axial rotation, and lateral bending modes. Mitigation of whiplash injury may be achieved by minimizing head retraction during initial stages of whiplash.

Reflex muscle contraction in the unaware occupant in whiplash injury

STUDY DESIGN

Computer modeling and parametric analysis were used to determine the effect of reflex contraction of the neck muscles in the unaware occupant in whiplash.

OBJECTIVE

To delineate effects of reflex contraction on spinal segmental kinematics during the retraction phase.

SUMMARY OF BACKGROUND DATA

The ability of reflex neck muscle contraction to mitigate whiplash injury in the unaware occupant remains unclear. Analyzing relative timing between electromyographic and head-neck kinematics, previous investigators theorized that muscle contraction alters spinal kinematics, decreasing injury likelihood. Other investigators suggested that injury occurs during the initial (retraction) phase of head-neck kinematics, before significant muscle force generation.

METHODS

Computer modeling was used to determine reflex contraction effects on segmental angulations, implementing parametric analysis techniques to vary reflex delay and impact severity.

RESULTS

Shorter reflex delays had a greater effect on segmental angulations later in the event and at lower impact severities. However, the magnitude of this effect, particularly at higher impact severities and during maximum cervical S-curvature (factors implicated in the whiplash injury mechanism) was minimal, altering segmental angulations by a maximum of 19%.

CONCLUSIONS

Because reflex contraction did not substantially alter spinal kinematics, muscle contraction likely does not initiate in sufficient time to mitigate whiplash injuries that may occur during the retraction phase.

Biomechanical changes at adjacent segments following anterior lumbar interbody fusion using tapered cages

STUDY DESIGN

A biomechanical evaluation of anterior cages in a calf lumbar spine model.

OBJECTIVES

To determine changes in spinal motion and intradiscal pressures at immediately adjacent lumbar motion segments following anterior insertion of tapered cages.

SUMMARY OF BACKGROUND DATA

Stand-alone anterior lumbar interbody fusion (ALIF) is an effective approach in the treatment of discogenic low back pain. A tapered lumbar (LT) cage design attempts to restore physiologic lordosis and sagittal balance. We are not aware of any previous biomechanical evaluation of the effects of LT cages on adjacent motion segments.

METHODS

Nine fresh calf spines (L2-L5) were procured for the study. Pure moments (up to 8.5 Nm) in flexion, extension, and lateral bending were applied to the L2 vertebra in five steps through a nonconstrained loading system. With each step of loading, three-dimensional rotation at three intervertebral disc levels was obtained through a three-camera motion analysis system, and intradiscal pressures within the nucleus pulposus of the two nonoperated discs were measured with miniature transducers. The spines were tested initially intact and following paired anterior LT cage insertion.

RESULTS

Following ALIF, small to moderate increase in motion was found at both adjacent segments in flexion (superior: 12.5%, P < 0.05; inferior: 11.3%, P < 0.02) and lateral bending (superior: 7.8%, P < 0.02; inferior: 6.6%, P < 0.02). An increase in intradiscal pressure was noted at the superior adjacent segment under flexion (21%, P < 0.01) and lateral bending (16%, P < 0.03). Intradiscal pressure changes at the inferior adjacent level were not significant.

CONCLUSIONS

Statistically significant changes in intradiscal pressures and motion were found at the adjacent levels following a single-level stand-alone ALIF procedure using paired LT cages.

Does anterior plating of the cervical spine predispose to adjacent segment changes?

STUDY DESIGN

In a human cadaveric model, the effects of plate supplementation on the mechanical behaviors of adjacent segments were investigated.

OBJECTIVES

The objective was to determine the effects of anterior cervical fusion and plating on the adjacent segments.

SUMMARY OF BACKGROUND DATA

Increases in intradiscal pressure and intervertebral motion at adjacent segments have been reported in the lumbar spine following an instrumented fusion. It is unclear if the same phenomenon presents in the cervical spine.

METHODS

Seven human cadaveric cervical spines (C2-T1) were used, and fusion of the C5-C6 segment was chosen for the purpose of this study. Two miniature pressure transducers were implanted within each adjacent disc. Flexion, extension, lateral bending, and torsion loads up to 2.5 Nm were applied to the intact spine, and following each of the two procedures, anterior discectomy and grafted fusion, and anterior plating of the C5-C6 motion segment.

RESULTS

At the surgical level, a significant increase in segmental stiffness was observed after plating in all directions. Following the grafted fusion, there were no statistically significant changes at the superior adjacent segment, and there was a 13.7% increase in axial rotation in the inferior adjacent segment. Once anterior plating was applied, slight increase (<12%) over the intact spines was noted in lateral bending in both adjacent segments. However, there was no significant difference between the grafted fusion and anterior plated fusion at either adjacent segment. At both adjacent disc levels, the differences in intradiscal pressures between grafted fusion and plated fusion were less than 30% in all directions, and none of these differences was statistically significant.

CONCLUSIONS

Intradiscal pressures and intervertebral motion at the adjacent levels are not significantly affected by the instrumented anterior fusion. The clinically observed degenerative change at adjacent segments in the cervical spine is more likely to be attributed to natural progression of the spondylotic process as opposed to biomechanical effect of the instrumentation or fusion.

Influence of thoracic ramping on whiplash kinematics

BACKGROUND

Some experimental whiplash investigations using human volunteers and full-body cadavers reported thoracic ramping, characterized by superior translation and extension rotation of the cervico-thoracic junction. The effect of this phenomenon on cervical spinal kinematics has not been quantitatively determined.

METHODS

A comprehensively validated computational model exercised in 2.7 m/s rear impact was used to determine effects of superior translation and extension rotation of T1 on cervical segmental kinematics during the retraction phase.

FINDINGS

In general, thoracic ramping had a minimal effect on cervical intervertebral kinematics during retraction.

INTERPRETATION

Results of the present study demonstrated that magnitude of thoracic ramping plays a minimal role in the whiplash injury mechanism due to decreased effect on cervical segmental kinematics.

Mechanical evaluation of posterior wiring as a supplement to anterior cervical plate fixation

STUDY DESIGN

An in vitro experimental study was performed to examine 3-dimensional biomechanical stability of cervical fixations.

OBJECTIVES

To determine whether posterior interspinous wiring contributes to the rigidity of a single-level motion segment that has been plated anteriorly, and to determine the effects of this combined fixation on intradiscal pressure and spinal motion at the adjacent segments.

SUMMARY OF BACKGROUND DATA

Combined anterior and posterior column fixation is being increasingly used in a variety of clinical situations that do not involve complete disruption of the motion segment. The biomechanical validity of combined anterior posterior fixation in the absence of overt posterior ligamentous disruption has not been studied.

METHODS

Six human fresh-frozen cadaveric cervical spines (C3-T1) were used. Three-dimensional intersegmental motion and intradiscal pressure were measured while the spine was loaded in flexion, extension, lateral bending, and torsion (up to 2.5 Nm). Fixation stability at the operative level (C5-C6) and influence of the fixation on adjacent segments were evaluated after an anterior plating procedure and combined anterior plating and posterior wiring.

RESULTS

Comparing the combined approach with anterior plating alone, significant reductions in C5-C6 motion was noted: 49% in flexion (P <0.05), 48% in extension (P <0.003), and 33% and 39%, respectively, in left and right torsion (P <0.05). Reduction in the left and right lateral bending was not significant (18% and 12%, respectively). The improved fixation had minimal influence on the adjacent segments.

CONCLUSIONS

Combined anterior posterior fixation further reduces the segmental motion by almost 50% in flexion and extension, 33% and 39% in torsion, and does not significantly alter intradiscal pressure and spinal motion at adjacent segments.

Changes in galactose and lactic acid content of sweet whey during storage

Whey is often stored or transported for a period of time prior to processing. During this time period, galactose and lactic acid concentrations may accumulate, reducing the quality of spray-dried whey powders in regard to stickiness and agglomeration. This study surveyed industry samples of Cheddar and mozzarella cheese whey streams to determine how galactose and lactic acid concentrations changed with storage at appropriate (4 degrees C) and abuse (37.8 degrees C) temperatures. Samples stored at 4 degrees C did not exhibit significant increases in levels of lactic acid or galactose. Mozzarella whey accumulated the greatest amount of galactose and lactic acid with storage at 37.8 degrees C. Whey samples derived from cheese made from single strains of starter culture were also evaluated to determine each culture's contribution to galactose and lactic acid production. Starter cultures evaluated included Streptococcus salivarius ssp. thermophilus. Lactobacillus helveticus, Lactobacillus delbrueckii ssp. bulgaricus, Lactococcus lactis ssp. cremoris, and Lactococcus lactis ssp. lactis. Whey derived from L. helveticus accumulated a significantly greater amount of lactic acid upon storage at 37.8 degrees C as compared with the other cultures. Galactose accumulation was significantly decreased in whey from L. lactis ssp. lactis stored at 37.8 degrees C in comparison with the other cultures. Results from this study indicate that proper storage conditions (4 degrees C) for whey prevent accumulation of galactose and lactic acid while the extent of accumulation during storage at 37.8 degrees C varies depending on the culture(s) used in cheese production.

Aerosol therapy for malignancy involving the lungs

The lungs are common sites of involvement by primary and metastatic malignant disease. Patients with malignancies in the lung have limited treatment options and are usually not curable. Numerous investigators have studied the potential of delivering various therapeutic agents directly to the lungs and pulmonary lymphatics by nebulization. Most of the research involves the use of immunomodulatory strategies; a few aerosol studies of chemotherapy and gene therapy have also been conducted. Most of these studies have been conducted in animal models. A few human trials have also been completed. Results suggest that aerosol therapies have the potential to shrink pulmonary metastases of selected histologies, and that survival in selected patients with metastatic renal cell cancer may be prolonged. The approach to therapy of cancer in the lungs holds promise as a means to avoid systemic toxicity and obtain an improved therapeutic effect. Research is currently underway to address issues of local versus systemic toxicity, optimal drug delivery and selection of optimal drugs and schedules including outpatient aerosol therapy. Future issues in design of aerosol cancer treatment include identifying effective combinations of agents, schedules, and use of aerosol therapy at home as adjuvant therapy.

Intradiscal pressure and kinematic behavior of lumbar spine after bilateral laminotomy and laminectomy

BACKGROUND CONTEXT

Bilateral laminotomy has been proposed as an alternative to laminectomy for decompression of lumbar spinal stenosis. Preservation of the posterior midline ligaments with laminotomy is presumed to maintain spinal segment stability. There have been no previous studies that directly compare the amount of destabilization and increase in disc pressures between the two procedures.

PURPOSE

To quantify spinal segmental instability caused by bilateral laminotomy and laminectomy, and to compare the central and peripheral intradiscal pressures after the two procedures.

STUDY DESIGN/SETTING

Mechanical testing of the lumbar motion segments of calf spines.

METHODS

Nine fresh calf spines were tested under flexion, extension, lateral bending and axial rotation, intact first, then after laminotomy and laminectomy at the level of L4-L5. Four miniature pressure transducers were implanted in the central and peripheral disc at L4-L5 to measure intradiscal pressures. Three-dimensional motion was measured with motion analysis system.

RESULTS

Comparing with bilateral laminotomy, laminectomy showed significant increase in segmental motion at the surgical level in flexion (16%, p<.05), extension (14%, p<.04) and right axial rotation (23%, p<.03). In flexion, the stress at the anterior annulus increased a nonsignificant 20% after laminotomy, but significant 130% after laminectomy (p<.02). In the intact spine, the posterolateral annulus experienced the highest stress with lateral bending to the same side when compared with other loading directions. This stress remained unchanged after laminotomy but increased 9% after laminectomy (p<.06). In rotation, axial intradiscal stresses were evenly distributed and unchanged after each procedure.

CONCLUSIONS

Laminectomy causes more destabilization of a spinal motion segment than laminotomy and significantly increases disc stress in the anterior annulus.

Late recurrence of a primitive neuro-ectodermal tumor

Late recurrences after therapy are rare in primitive neuro-ectodermal tumor (PNET). Most recurrences occur within the first 2 years after therapy, although a small number of recurrences may occur up to 5 years after therapy. We present a rare case of a recurrence of PNET in a 31-year-old woman 17 years after her initial presentation. The potential biological implications of this late recurrence as well as responses to subsequent therapy, including temozolomide, are discussed.

Whiplash injury determination with conventional spine imaging and cryomicrotomy

STUDY DESIGN

Soft tissue-related injuries to the cervical spine structures were produced by use of intact entire human cadavers undergoing rear-end impacts. Radiography, computed tomography, and cryomicrotomy techniques were used to evaluate the injury.

OBJECTIVES

To replicate soft tissue injuries resulting from single input of whiplash acceleration to whole human cadavers simulating vehicular rear impacts, and to assess the ability of different modes of imaging to visualize soft tissue cervical lesions.

SUMMARY OF BACKGROUND DATA

Whiplash-associated disorders such as headache and neck pain are implicated with soft tissue abnormalities to structures of the cervical spine. To the authors' best knowledge, no previous studies have been conducted to determine whether single cycle whiplash acceleration input to intact entire human cadavers can result in these soft tissue alterations. There is also a scarcity of data on the efficacy of radiography and computed tomography in assessing these injuries.

METHODS

Four intact entire human cadavers underwent single whiplash acceleration (3.3 g or 4.5 g) loading by use of a whole-body sled. Pretest and posttest radiographs, computed tomography images, and sequential anatomic sections using a cryomicrotome were obtained to determine the extent of trauma to the cervical spine structures.

RESULTS

Routine radiography identified the least number of lesions (one lesion in two specimens). Although computed tomography was more effective (three lesions in two specimens), trauma was not readily apparent to all soft tissues of the cervical spine. Cryomicrotome sections identified structural alterations in all four specimens to lower cervical spine components that included stretch and tear of the ligamentum flavum, anulus disruption, anterior longitudinal ligament rupture, and zygopophysial joint compromise with tear of the capsular ligaments.

CONCLUSIONS

These results clearly indicate that a single application of whiplash acceleration pulse can induce soft tissue-related and ligament-related alterations to cervical spine structures. The pathologic changes identified in this study support previous observations from human volunteers observations with regard to the location of whiplash injury and may assist in the explanation of pain arising from this injury. Although computed tomography is a better imaging modality than radiography, subtle but clinically relevant injuries may be left undiagnosed with this technique. The cryomicrotome technique offers a unique procedure to understand and compare soft tissue-related injuries to the cervical anatomy caused by whiplash loading. Recognition of these injuries may advance the general knowledge of the whiplash disorder.

Interleukin-6 and nerve growth factor levels in peripheral nerve and brainstem after trigeminal nerve injury in the rat

Earlier studies have demonstrated that inflammation plays a role in the development of evoked pain following partial nerve injury. In this report, we demonstrate bilateral changes in interleukin-6 (IL-6) and nerve growth factor (nerve growth factor) levels following unilateral infraorbital nerve (infraorbital nerve) constriction. infraorbital nerve constriction resulted in an initial period of decreased mechanical sensitivity (1 and 3 days), followed by recovery (7 days) and then a marked bilateral mechanical hypersensitivity (10 and 28 days). nerve growth factor levels in the injured infraorbital nerve were elevated on all days, but peak concentrations of nerve growth factor were observed on day 3. A smaller increase was also observed on days 1, 3, and 7 in the uninjured nerve. A bilateral elevation of IL-6 was also seen on days 3 and 10 in the infraorbital nerve, and in the brainstem on days 3, 7 and 10 after constriction. No changes in mechanical sensitivity were found after a sham-injury, but there was a small increase in brainstem IL-6 ipsilaterally at 7 days. We conclude from these data that increases in IL-6 and nerve growth factor may contribute to the development of mechanical allodynia after trigeminal nerve injury, but they are not specifically correlated with the onset or duration of pain behaviors.

Sequence information, distinction and quantitation of C-terminal leucine and isoleucine in ternary complexes of tripeptides with Cu(II) and 2,2'-bipyridine

Tripeptides form ternary complexes with Cu(2+) and 2,2'-bipyridine (bpy) that self-assemble upon mixing the components in aqueous methanol solution. Electrospray ionization (ESI) of the complex solutions provides abundant singly charged [Cu(peptide -- H)bpy](+) and doubly charged [Cu(peptide)bpy](2+) ions. Collision-induced dissociation (CID) at low ion kinetic energies of several tripeptides, AGG, GGA, LGG, GGL, GGI, FGG, GGF, LGF, GLF, GFL, GYA and GAY, showed fragments that were indicative of the amino acid sequence in the peptide. In addition, CID of single and doubly charged complexes of isomeric tripeptides GGL and GGI provided unambiguous distinction of the isomeric leucine and isoleucine residues. Leucine peptides eliminated C(3)H(7) radicals from the amino acid side-chain whereas isoleucine eliminated C(2)H(5) radicals. CID of gas-phase doubly charged peptide complexes in a quadrupole ion trap produced a series of singly charged sequence fragments that following isolation and further CID furnished distinct fragments that allowed quantitation of leucine and isoleucine-containing peptides in mixtures.

Non-Hodgkin's tumor and Pancoast's syndrome

A 60-year old man presented with Horner's syndrome, and acute right hand and lower extremity weakness. Chest X-ray and MRI revealed a right apical lung tumor (presumed to be a primary lung cancer), with brachial plexus infiltration and spinal cord compression. Emergent radiotherapy was initiated for spinal cord compression and a biopsy was obtained 24 h later. A careful review of pathology demonstrated a non-Hodgkin's lymphoma. The patient subsequently received chemotherapy, and is now in remission. This case illustrates the importance of a tissue diagnosis before initiating therapy for a Pancoast's tumor.

Holmium:YAG percutaneous nephrolithotomy: the laser incident angle matters

PURPOSE

Laser physics dictate that maximal radiant exposure occurs when the laser strikes the target at a normal incidence. Since the renal collecting system often limits nephroscope movements during percutaneous nephrolithotomy, the laser-calculus incidence angle may vary. We have observed during holmium:YAG percutaneous nephrolithotomy that the side firing fiber more easily approaches a normal incidence compared to the end firing fiber. We test the hypothesis that holmium:YAG percutaneous nephrolithotomy is faster with a side firing fiber compared to an end firing fiber.

MATERIALS AND METHODS

Consecutive holmium:YAG percutaneous nephrolithotomy cases were studied retrospectively. The calculus size and composition, surgical time, fragmentation speed (size/time) and stone-free rates were compared between 11 patients treated with end and 8 treated with side firing fibers.

RESULTS

When the end and side firing groups were compared, calculus sizes (mean plus or minus standard deviation) were 22 +/- 13 versus 48 +/- 17 mm. (p = 0.004), calcium oxalate monohydrate incidence was 55 versus 75% (p = 0.3), surgical times were 168 +/- 87 versus 124 +/- 51 minutes, computed fragmentation speeds were 0.15 +/- 0.09 versus 0.43 +/- 0.15 mm. per minute (p = 0.0009) and stone-free rates were 73 versus 88% (p = 0.4), respectively.

CONCLUSIONS

The side firing fiber is faster than the end firing fiber for holmium:YAG percutaneous nephrolithotomy. These results are consistent with principles of laser physics.

Ureteroscopic management of ureteral calculi: electrohydraulic versus holmium:YAG lithotripsy

PURPOSE

This study compared electrohydraulic and holmium:YAG lithotripsy for ureteral calculi.

MATERIALS AND METHODS

Two cohorts of consecutive patients with ureteral calculi treated with ureteroscopic electrohydraulic or holmium:YAG lithotripsy were retrospectively compared. Electrohydraulic lithotripsy was done using a 1.9F fiber at energy settings between 50 and 100 v. Holmium:YAG lithotripsy was done using a 365 microm. fiber at energy settings of 0.6 to 1.5 J.

RESULTS

A total of 23 and 47 consecutive patients underwent electrohydraulic and holmium:YAG lithotripsy, respectively. For preoperative calculi less than 15 mm. mean stone size plus or minus standard deviation was 9 +/- 3 versus 9 +/- 3 mm. (p = 0.5), mean operative time was 72 +/- 21 versus 102 +/- 38 minutes (p = 0.004), stone-free rate at the end of ureteroscopy was 65 versus 97 (p < 0.01) and 3-month stone-free rate was 94 versus 97% (p = 0.4) for electrohydraulic versus holmium:YAG lithotripsy. For preoperative calculi 15 mm. or greater stone size was 19 +/- 5 versus 19 +/- 4 mm. (p = 0.9), operative time was 159 +/- 61 versus 108 +/- 27 minutes (p = 0.01), stone-free rate at the end of ureteroscopy was 33 versus 87% (p = 0.001) and 3-month stone-free rate was 67 versus 100% (p = 0.02). Complications were not significantly different in either comparison.

CONCLUSIONS

The overall likelihood that a patient would be rendered stone-free at ureteroscopy and 3 months after ureteroscopy favored holmium:YAG over electrohydraulic lithotripsy. For ureteral calculi less than 15 mm. electrohydraulic lithotripsy was more rapid than the holmium:YAG procedure but for ureteral calculi 15 mm. or greater the holmium:YAG technique was more rapid than electrohydraulic lithotripsy. The outcomes differences may have resulted from the different mechanisms of electrohydraulic and holmium:YAG lithotripsy.