Biomechanical Analysis of Pedicle Screw Fixation for Thoracolumbar Burst Fractures.

Treatment of unstable thoracolumbar burst fractures remains controversial. Long-segment pedicle screw constructs may be stiffer and impart greater forces on adjacent segments compared with short-segment constructs, which may affect clinical performance and long-term out come. The purpose of this study was to biomechanically evaluate long-segment posterior pedicle screw fixation (LSPF) vs short-segment posterior pedicle screw fixation (SSPF) for unstable burst fractures. Six unembalmed human thoracolumbar spine specimens (T10-L4) were used. Following intact testing, a simulated L1 burst fracture was created and sequentially stabilized using 5.5-mm titanium polyaxial pedicle screws and rods for 4 different constructs: SSPF (1 level above and below), SSPF+L1 (pedicle screw at fractured level), LSPF (2 levels above and below), and LSPF+L1 (pedicle screw at fractured level). Each fixation construct was tested in flexion-extension, lateral bending, and axial rotation; range of motion was also recorded. Two-way repeated-measures analysis of variance was performed to identify differences between treatment groups and functional noninstrumented spine. Short-segment posterior pedicle screw fixation did not achieve stability seen in an intact spine (P<.01), whereas LSPF constructs were significantly stiffer than SSPF constructs and demonstrated more stiffness than an intact spine (P<.01). Pedicle screws at the fracture level did not improve either SSPF or LSPF construct stability (P>.1). Long-segment posterior pedicle screw fixation constructs were not associated with increased adjacent segment motion. Al though the sample size of 6 specimens was small, this study may help guide clinical decisions regarding burst fracture stabilization. [Orthopedics. 2016; 39(3):e514-e518.].

Antagonism of the Met5-enkephalin-opioid growth factor receptor-signaling axis promotes MSC to differentiate into osteoblasts.

Chronic opioid therapy is associated with bone loss. This led us to hypothesize that the opioid antagonists, that include naloxone, would stimulate bone formation by regulating MSC differentiation. The opioid growth factor receptor (OGFR) is a non-canonical opioid receptor that binds naloxone with high affinity whereas the native opioid growth factor, met5-enkephalin (met5), binds both the OGFR and the canonical delta opioid receptor (OPRD). Naloxone and an shRNA OGFR lentivirus were employed to disrupt the OGFR-signaling axis in cultured MSC. In parallel, naloxone was administered to bone marrow using a mouse unicortical defect model. OPRD, OGFR, and the met5-ligand were highly expressed in MSC and osteoblasts. A pulse-dose of naloxone increased mineral formation in MSC cultures in contrast to MSC treated with continuous naloxone or OGFR deficient MSC. Importantly, SMAD1 and SMAD8/9 expression increased after a pulse dose of naloxone whereas SMAD1, SMAD7, and ID1 were increased in the OGFR deficient MSC. Inhibited OGFR signaling decreased proliferation and increased p21 expression. The addition of naloxone to the unicortical defect resulted in increased bone formation within the defect. Our data suggest that novel mechanism through which signaling through the OGFR regulates osteogenesis via negative regulation of SMAD1 and p21. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:1195-1205, 2016.

Wound hematoma after anterior cervical spine surgery: in vitro study of the pathophysiology of airway obstruction.

Airway obstruction by wound hematoma is a serious adverse event associated with anterior cervical spine surgery. Although intrinsic airway edema is the most plausible pathophysiologic mechanism of obstruction, we hypothesized that extrinsic compression of the trachea by a hematoma can result in airway occlusion at an angle to the sagittal plane. A silicone indenter and a servohydraulic test frame were used to apply pressure to the ventral neck of 7 human cadaveric specimens. Increasing pressure was applied in the anteroposterior (AP) and oblique planes until the trachea collapsed, as visualized with fluoroscopy. A paired t test was used to determine any statistically significant differences in maximum pressure or indenter displacement at tracheal occlusion between the 2 test modes. Mean (SD) pressure required to cause complete tracheal collapse was 227.9 (54.8) mm Hg in the AP test mode and 135.6 (73.4) mm Hg in the oblique test mode. The difference was statistically significant (P = .004). Indenter displacement was significantly higher in the AP mode than in the oblique mode (P = .031). The trachea can collapse from external force within a physiologic pressure range when pressure is applied in an oblique orientation. The mass effect of a wound hematoma appears to be a viable mechanism of airway occlusion.

Predicting pulmonary embolus in orthopedic trauma patients using the Wells score.

The decision to perform computed tomography pulmonary angiography (CTPA) to rule out pulmonary embolism (PE) in orthopedic trauma patients is challenging. The Wells score is a commonly used clinical probability tool developed to determine the likelihood of PE and assist in determining the need for CTPA examination. This study evaluated the usefulness of the Wells score for predicting PE in patients admitted to the orthopedic trauma service. All patients who were admitted to the orthopedic trauma service at the authors' institution between 2001 and 2011 who underwent CTPA were identified. The Wells score was calculated retrospectively for each patient, and risk categories using the traditional and alternative interpretations of the Wells score were assigned. Pulmonary embolism was diagnosed in 27 (16%) of 169 patients who underwent CTPA. In total, 27 (0.39%) of 6854 patients admitted to the orthopedic trauma service were diagnosed with PE during initial hospitalization. Mean Wells score was 3.31 (95% confidence interval, ±.28) for the entire population, 3.32 for those without PE (95% confidence interval, ±.31), and 3.28 for those with PE (95% confidence interval, ±.72) (P=.91). Average times from admission to CTPA examination for those with and without PE were 6.18 and 5.7 days, respectively (P=.94). No significant correlation existed between the Wells score and CTPA results, indicating that the Wells score is limited in predicting PE risk in orthopedic trauma patients.

Evaluation of the utility of the Wells score in predicting pulmonary embolism in patients admitted to a spine surgery service.

STUDY DESIGN: A retrospective medical chart review of 4179 patients admitted to the spine surgery service. OBJECTIVE: To evaluate the utility of the Wells score in predicting pulmonary embolism (PE) in patients admitted to a spine surgery service. SUMMARY OF BACKGROUND DATA: The decision to perform computed tomography pulmonary angiography (CTPA) to diagnose PE in patients who have undergone spine surgery requires consideration of multiple factors: false-positive CTPA results may lead to unnecessary anticoagulation treatment, and computed tomography scans are costly and expose patients to ionizing radiation. The Wells score was developed to assign risk categories to patients with suspected PE and thereby indicate the need for CTPA. However, the utility of the Wells score in predicting the likelihood of PE, specifically in spine surgery patients, has not been described to date. We identified all patients who were admitted to the spine surgery service at our institution from January 1, 2001 to December 31, 2011 and underwent CTPA. Each patient's CTPA result was classified as positive or negative for PE, and the reason for ordering the CTPA was recorded. The Wells score was calculated retrospectively for each patient, and risk categories were assigned by using the traditional and alternative interpretations of the Wells score. The reason for the CTPA, the Wells score, and Wells risk category were compared for patients who were classified as being positive or negative for PE. RESULTS: Sixty-six of the 4179 patients who were admitted to the spine surgery service underwent CTPA for suspected PE. Nineteen of the 66 patients (28.8%) were diagnosed with acute PE, and the overall PE rate was 0.45% (19 of 4179 patients). The mean Wells score for patients diagnosed with PE was 5.3, whereas the mean score for the remaining patients was 4.9 (P = 0.793). Neither the traditional nor the alternative interpretation of the Wells score was predictive of PE (P = 0.394 and P = 0.178, respectively). Our study examined the utility of the Wells score in predicting PE in spine surgery patients. CONCLUSION: The results of the CTPA did not show a significant correlation with the Wells score or the reason for the test. Our findings indicate the need to develop a predictive scoring system that assesses the risk of PE and assists in the decision-making process for ordering CTPA in spine surgery patients.

Benign tumors of the spine.

Benign tumors in the spine include osteoid osteoma, osteoblastoma, aneurysmal bone cyst, osteochondroma, neurofibroma, giant cell tumor of bone, eosinophilic granuloma, and hemangioma. Although some are incidental findings, some cause local pain, radicular symptoms, neurologic compromise, spinal instability, and deformity. The evaluation of spinal tumors includes a thorough history and physical examination, imaging, sometimes laboratory evaluation, and biopsy when indicated. Appropriate treatment may be observational (eg, eosinophilic granuloma) or ablative (eg, osteoid osteoma, neurofibroma, hemangioma), but generally is surgical, depending on the level of pain, instability, neurologic compromise, and natural history of the lesion. Knowledge of the epidemiology, common presentation, imaging, and treatment of benign bone tumors is essential for successful management of these lesions.

Injury patterns causing isolated foot compartment syndrome.

BACKGROUND: The true incidence and primary predictors of foot compartment syndrome remain controversial. Our aim was to better define the overall incidence of foot compartment syndrome in relation to the frequency and location of various foot injuries. We hypothesized that (1) the incidence would increase in proportion to the number of anatomic locations of injury, (2) the incidence would be higher in association with hindfoot and crush injuries compared with any other injury categories, and (3) not only would the incidence associated with calcaneal fractures be lower than the often quoted 10% but foot compartment syndrome would also be fairly uncommon after such fractures. METHODS: The National Trauma Data Bank was used to identify patients who had undergone a fasciotomy for the treatment of isolated foot compartment syndrome. Strict inclusion and exclusion criteria were used to identify only patients with foot injuries who had undergone fasciotomy for foot compartment syndrome. RESULTS: Three hundred and sixty-four patients with an isolated foot compartment syndrome were identified. The highest incidence of foot compartment syndrome was seen in association with a crush mechanism combined with a forefoot injury (18%, nineteen of 106), followed by an isolated crush injury (14%, twenty-three of 162). Only 1% (thirty-two) of 2481 patients with an isolated calcaneal fracture underwent fasciotomy. An increase in the number of anatomic locations of injury did not appear to correspond to an increased incidence of foot compartment syndrome. CONCLUSION: Our results demonstrate that injuries involving a crush mechanism, either in isolation or in combination with a forefoot injury, should raise suspicion about the possibility that a foot compartment syndrome will develop.

Airway compromise due to wound hematoma following anterior cervical spine surgery.

One of the most serious adverse events associated with anterior cervical spine surgery is wound hematoma resulting in airway compromise. The reported incidence of this postoperative complication has varied from 0.2% to 1.9%. Obstruction of the airway secondary to bleeding presents a challenging clinical scenario given the rapidity of onset, distorted anatomy of the upper respiratory tract, urgent need to act and potential for catastrophic consequences. This high-risk, life-threatening clinical scenario requires specialized knowledge and a well-designed treatment protocol to achieve a positive outcome. In this review, we report a case of airway compromise secondary to wound hematoma following anterior cervical discectomy and fusion, followed by a review of relevant literature, anatomy, etiologic factors and diagnostic considerations. We also propose guidelines for the prevention and management of postoperative airway obstruction due to wound hematoma.

Examination of cervical spine kinematics in complex, multiplanar motions after anterior cervical discectomy and fusion and total disc replacement.

BACKGROUND: The biomechanical behavior of total disc replacement (TDR) and anterior cervical discectomy and fusion (ACDF) incomplex multiplanar motion is incompletely understood. The purpose of this study was to determine whether ACDF or TDR significantly affects in vitro kinematics through a range of complex, multiplanar motions. METHODS: Seven human cervical spines from C4-7 were used for this study. Intact cervical motion segments with and without implanted TDR and ACDF were tested by use of unconstrained pure bending moment testing fixtures in 7 mechanical modes: axial rotation (AR); flexion/extension (FE); lateral bending (LB); combined FE and LB; combined FE and AR; combined LB and AR; and combined FE, LB, and AR. Statistical testing was performed to determine whether differences existed in range of motion (ROM) and stiffness among spinal segments and treatment groups for each mechanical test mode. RESULTS: ACDF specimens showed increased stiffness compared with the intact and TDR specimens (P < .001); stiffness was not found to be different between TDR and intact specimens. ACDF specimens showed decreased ROM in all directions compared with TDR and intact specimens at the treated level. For the coupled motion test, including AR, LB, and FE, the cranial adjacent level (C4/C5) for the intact specimens (2.7°) showed significantly less motion compared with both the TDR (6.1°, P = .009) and ACDF (6.8°, P = .002) treatment groups about the LB axis. Testing of the C4/C5 and C6/C7 levels in all other test modes yielded no significant differences in ROM comparisons, although a trend toward increasing ROM in adjacent levels in ACDF specimens compared with intact and TDR specimens was observed. CONCLUSIONS: This study compared multiplanar motion under load-displacement testing of subaxial cervical motion segments with and without implanted TDR and ACDF. We found a trend toward increased motion in adjacent levels in ACDF specimens compared with TDR specimens. Biomechanical multiplanar motion testing will be useful in the ongoing development and evaluation of spinal motion-preserving implants.

Perioperative management of chronic anticoagulation in orthopaedic surgery.

The orthopaedic patient on chronic anticoagulation therapy is at risk of thromboembolism and hemorrhage in the perioperative period. To establish the most effective anticoagulation regimen, patients should be stratified according to the risk of arterial or venous thromboembolism. Timing of surgery, thromboembolic risk, and bleeding risk should be considered when developing an anticoagulation protocol. Retrievable inferior vena cava filters may be a viable alternative to bridging therapy in patients at high risk of venous thromboembolism and/or bleeding.

Klebsiella pneumoniae-associated vertebral osteomyelitis after laparoscopic cholecystectomy.

We report a case of a patient who underwent elective laparoscopic cholecystectomy and subsequently developed Klebsiella pneumoniae-associated vertebral osteomyelitis after 2 months. Development of vertebral osteomyelitis after laparoscopic cholecystectomy has never been reported previously. Diagnosis was made via magnetic resonance imaging. The patient was successfully treated with intravenous antibiotics and had a complete recovery with no neurologic sequelae.

Inappropriate transfer of patients with orthopaedic injuries to a Level I trauma center: a prospective study.

OBJECTIVE: The objective of this study was to analyze the appropriateness of transfer of patients with orthopaedic injuries to a Level I trauma center from surrounding Level II to IV centers. DESIGN: A prospective study was conducted over a 5-month period by collecting data on all orthopaedic patients being transferred to our facility. All transfer diagnoses were designated as appropriate or inappropriate. Patient demographics were calculated. SETTING: The transfer of patients occurred from 23 Level II to IV hospitals to a Level I trauma center. These hospitals service 1 to 1.5 million people a year. PATIENTS/PARTICIPANTS MAIN OUTCOME MEASUREMENTS: All patients transferred with orthopaedic injuries were recorded. Patient variables such as transfer diagnosis, age, gender, insurance status, time of arrival, day of transfer, transferring and accepting physicians, previous imaging studies, and patient disposition were recorded. Outcome measurements included chi tests to determine variation in demographics based on insurance and appropriateness of transfer. Multivariate regression analysis was also performed to determine influence of individual patient variables on the main outcome variable: appropriateness of transfer. RESULTS: Two hundred sixteen patients were transferred of which we considered 52% inappropriate. Sixty-eight percent of transfers occurred between 6:00 pm and 5:59 am and 60% of all transfers were over the weekend. Also, 69% of inappropriate transfers were discharged directly from the emergency department. Insurance was an independent factor affecting appropriateness of transfer. A larger percentage of inappropriate patients transferred were uninsured. The inappropriate patient who was transferred had more likelihood of being uninsured than insured. Moreover, there was a significantly higher percentage of inappropriate uninsured patients transferred after hours and over the weekend as compared with insured patients. More than 97% of inappropriate transfers were accepted by the emergency department physician without communication with the on-call orthopaedist at our facility. CONCLUSIONS: There is a trend among community hospitals to transfer uninsured patients with benign orthopaedic injuries inappropriately to a Level I trauma center. This effect is magnified on weekends and at night. Strict regulation of the Emergency Labor Act and better communication between Level II to IV hospitals and Level I orthopaedic surgeons can decrease the inappropriate transfer of patients and reduce the burden on our healthcare system.

Brace management in adolescent idiopathic scoliosis.

UNLABELLED: Skeletally immature patients with adolescent idiopathic scoliosis are at risk for curve progression. Although numerous nonoperative methods have been attempted, including physical therapy, exercise, massage, manipulation, and electrical stimulation, only bracing is effective in preventing curve progression and the subsequent need for surgery. Brace treatment is initiated as either full-time (TLSO, Boston) or nighttime (Charleston, Providence) wear, although patient compliance with either mode of bracing has been a documented problem. We review the natural history of adolescent idiopathic scoliosis, identify the risks for curve progression, describe the types of braces available for treatment, and review the indications for and efficacy of brace treatment. LEVEL OF EVIDENCE: Level IV, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.

An improved method for cable grip fixation of the greater trochanter after trochanteric slide osteotomy.

This study proposes a novel method for reattachment of the trochanteric slide osteotomy. The strength of this new fixation system was compared to established configurations. Fifteen sawbone femurs were used. Our configuration used cables above and below the lesser trochanter with a third cable around the shaft of the femur while passing the loose ends through the inferior hole of the cable grip. Displacement of the trochanter was measured with increasing load. Force required for catastrophic failure was also measured. The 3-cable construct resulted in significantly less displacement with increasing load and required a larger force to cause failure (1 cm and 2 cm). We theorize that our configuration produces a biomechanically stronger construct than previously used methods.

Recombinant bone morphogenic protein-2 in orthopaedic surgery: a review.

Bone morphogenic proteins (BMPs) are pleiotropic regulators of bone volume, skeletal organogenesis and bone regeneration after a fracture. They function as signaling agents to affect cellular events like proliferation, differentiation and extracellular matrix synthesis. Clinically utilized rhBMP-2 combines rhBMP-2 with an osteoconductive carrier to induce bone growth and acts as a bone graft substitute. rhBMP-2, initially released in 2002, has been used primarily in spinal fusions in the lumbar and cervical regions. Recently, the application of rhBMP-2 has extended into the orthopedic trauma setting with increased application in open tibia fractures. This review outlines the history of development, molecular characteristics, toxicity and clinical applications.

Impact of donor lung organisms on post-lung transplant pneumonia.

BACKGROUND: Fear of transmission of donor organisms that may result in recipient pneumonia has a negative impact on donor lung utilization. We reviewed our experience with routine donor bronchial aspiration and culture at the time of transplantation to study the impact of donor bronchial organisms on the development of recipient post-lung transplant pneumonia (PTP) and other outcomes. METHODS: We reviewed 80 consecutive single and bilateral lung transplants (SLTs and BLTs) from August 1998 to August 2001. Pediatric recipients and those not surviving >3 days were excluded. All donors met standard criteria for donor acceptance. All recipients received broad-spectrum antibiotics pending the results of final operating room cultures. PTP required clinical evidence (fever, leukocytosis and hypoxia), radiologic evidence (infiltrate), and culture confirmation during initial hospitalization or within 30 days. RESULTS: Sixty-four donors for 71 recipients (39 SLTs, 32 BLTs) comprised the study population. Organisms were grown from 57 (89%) donors and 46 were polymicrobial. A total of 149 organisms were cultured consisting of 21 different species, with Staphylococcus (n = 35) and Streptococcus (n = 33) being the most common. PTP was seen in 31 (41%) recipients, with Pseudomonas species (n = 13) the most prevalent. Of the 71 donor-recipient pairs, 2 had both donor and recipient with no growth and PTP. The donor organisms had a sensitivity of 0.75 with a low specificity of 0.04 and were negatively correlated with development of PTP. PTP was an independent predictor of overall mortality. CONCLUSIONS: The presence of donor organisms does not predict PTP. Therefore, donor acceptance criteria need to be re-examined.