En bloc resection for primary bone tumours and isolated metastasis are complex surgeries associated with a high rate of adverse events (AEs). The primary objective of this study was to explore the relationship between frailty/sarcopenia and major perioperative AEs following en bloc resection for primary bone tumours or isolated metastases of the spine. Secondary objectives were to report the prevalence and distribution of frailty and sarcopenia, and determine the relationship between these factors and length of stay (LOS), unplanned reoperation, and 1-year postoperative mortality in this population.

This is a retrospective study of prospectively collected data from a single quaternary care referral center consisting of patients undergoing an elective en bloc resection for a primary bone tumour or an isolated spinal metastasis between January 1st, 2009 and February 28th, 2020. Frailty was calculated with the modified frailty index (mFI) and spine tumour frailty index (STFI). Sarcopenia, determined by the total psoas area (TPA) vertebral body (VB) ratio (TPA/VB), was measured at L3 and L4. Regression analysis produced ORs, IRRs, and HRs that quantified the association between frailty/sarcopenia and major perioperative AEs, LOS, unplanned reoperation and 1-year postoperative mortality.

One hundred twelve patients met the inclusion criteria. Using the mFI, five patients (5%) were frail (mFI ³ 0.21), while the STFI identified 21 patients (19%) as frail (STFI ³ 2). The mean CT ratios were 1.45 (SD 0.05) and 1.81 (SD 0.06) at L3 and L4 respectively. Unadjusted analysis demonstrated that sarcopenia and frailty were not significant predictors of major perioperative AEs, LOS or unplanned reoperation. Sarcopenia defined by the CT L3 TPA/VB and CT L4 TPA/VB ratios significantly predicted 1-year mortality (HR of 0.32 per one unit increase, 95% CI 0.11-0.93, p=0.04 vs. HR of 0.28 per one unit increase, 95% CI 0.11-0.69, p=0.01) following unadjusted analysis. Frailty defined by an STFI score ≥ 2 predicted 1-year postoperative mortality (OR of 2.10, 95% CI 1.02-4.30, p=0.04).

The mFI was not predictive of any clinical outcome in patients undergoing en bloc resection for primary bone tumours or isolated metastases of the spine. Sarcopenia defined by the CT L3 TPA/VB and L4 TPA/VB and frailty assessed with the STFI predicted 1-year postoperative mortality on univariate analysis but not major perioperative AEs, LOS or reoperation. Further investigation with a larger cohort is needed to identify the optimal measure for assessing frailty and sarcopenia in this spine population.

Summary Statement

Spinal flexibility in bending and axial torque has been shown to exhibit very modest changes with advancing disc degeneration. This study is the first to address the possible relationship in pure anterior shear and no clear relationship was observed.

The aim of this study is to determine evidence-based guidelines on functional outcomes following common thoracolumbar injuries using a synthesis of systematic literature reviews and consensus expert opinion

A questionnaire was created comprising five cases representative of common thoracolumbar injuries (a thoracic compression fracture, a flexion distraction injury and burst fractures each with varied location, patient demographics and treatment strategies). For each scenario five questions about expected functional outcomes were posed. Questionnaires were distributed to the Spine Trauma Study Group. Responses were combined with available data from a systematic review of the same injuries and outcomes to create consensus evidence based guidelines.

The survey was completed by 31 (57%) of 53 surgeons representing 20 centres across North America. The systematic reviews identified 49 appropriate studies. One year following a L1 burst fracture, a heavy laborer, treated with protective mobilization (cast or brace) has a 40% chance of being pain free, 70% chance of regaining pre-injury range of motion, can expect to be re-employed within 4–6 months and be able to participate in high impact exercise and contact sport with no or minimal limitation. Length of inpatient stay averages 4–5 days. One year following posterior short segment stabilization of a L1 bust fracture in a college football player, there is an expected 45% chance of being pain free and 55% chance of regaining pre-injury ROM. While an ultimate return to high impact exercise and contact sports is anticipated, 32% of experts expect the injury to end a college football career.

Results for the other trauma scenarios are included.

This combination of literature and expert opinion represents the best available evidence on functional prognosis after thoracolumbar trauma. By providing consistent, accurate information surgeons and other care path providers will help patients develop realistic expectations, which may shape and improve their ultimate outcome.

Introduction

While there is a desperate need for effective treatments for acute spinal cord injury (SCI), the clinical validation of novel therapeutic interventions is severely hampered by the need to recruit relatively large numbers of patients into clinical trials for sufficient statistical power. While a centre might annually admit 100 acute SCI patients, only a fraction may satisfy the basic inclusion criteria for an acute clinical trial, which typically requires patients of a certain injury severity (eg ASIA A), within a specific time window (eg. 12 hours from injury), and without other major injuries or conditions that would cloud the baseline neurologic assessment. This study was conducted to define that “fraction” of SCI patients that would theoretically satisfy standard inclusion criteria of an acute clinical trial.

Purpose: There is very little evidence to guide treatment of patients with spinal surgical site infection (SSI) who require irrigation and debridement (I& D) with respect to need for single or multiple I& D’s. The purpose of this study is to build a predictive model which stratifies patients with spinal SSI to determine which patients will go on to need single versus multiple I& D.

Method: A consecutive series of 128 patients from a tertiary spine center (collected from 1999–2005) who required I& D for spinal SSI, were studied based on data from a prospectively collected outcomes database. Over 30 variables were identified by extensive literature review as possible risk factors for SSI, and tested as possible predictors of risk for multiple I& D. Logistic regression was conducted to assess each variable’s predictability by a “bootstrap” statistical method. Logistic regression was applied using outcome of I& D – single or multiple as the “response”.

Results: 24/128 patients required multiple I& D. Primary spine diagnosis was approximately represented by ¼ trauma, ¼ deformity, ¼ degenerative and ¼ oncology/inflammatory/other. Six predictors: spine location, medical comorbidities, microbiology of the SSI, presence of distant site infection (ie. UTI or bacteremia), presence of instrumentation and bone graft type, proved to be the most reliable predictors of need for multiple I& D. Internal validation of the predictive model yielded area under the curve (AUC) of .84

Conclusion: Infection factors played an important role in need for multiple I& D. Patients with +MRSA culture or those with distant site infection such as bacteremia with or without UTI or pneumonia, were strong predictors of need for multiple I& D. Presence of instrumentation, location of surgery in the posterior lumbar spine and use of non-autograft bone predicted multiple I& D. Diabetes also proved to be the most significant medical comorbidity for multiple I& D.

Purpose: Multiple studies have described the general injuries associated with mountain biking. However, no detailed assessment of mountain biking associated spinal column fractures and spinal cord injuries (SCI) has previously been reported. The purpose of this study is to describe the patient demographics, injuries, mechanisms, treatments, outcomes and resource requirements associated with spine injuries sustained while mountain biking.

Method: Patients who were injured while mountain biking, and presented to a provincial spine referral centre between 1995 and 2007 inclusive, with SCI and/ or spine fracture were included. A chart review was performed to obtain demographic data, and details of the injury, treatment, outcome and resource requirements.

Results: 102 men and 5 women were identified for inclusion. The mean age at injury was 32.7 years 95%CI[30.6,35.0]. 79 patients (73.8%) sustained cervical injuries, while the remainder sustained thoracic or lumbar injuries. 43 patients (40.2%) sustained a SCI. Of those with cord injuries, 18(41.9%) were ASIA A, 5(11.6%) were ASIA B, 10(23.3%) ASIA C, and 10(23.3%) ASIA D. 67 patients (62.6%) required surgical treatment. The mean length of stay in an acute hospital bed was 16.9 days 95%CI[13.1,30.0]. 33 patients (30.8%) required ICU care, and 31 patients (29.0%) required inpatient rehabilitation. Of the 43 patients (39.6%) who presented with SCI, 14(32.5%) improved by one ASIA category, and 1 (2.0%) improved by two ASIA categories. Two patients remained ventilator-dependent at discharge.

Conclusion: Spine fractures and SCI due to mountain biking accidents typically affect young, male, recreational riders. The medical, personal, and societal costs of these injuries are high. Injury prevention should remain a primary goal, and further research is necessary to explore the utility of educational programs, and the impact of helmets and other protective gear on spine injuries sustained while mountain biking.

Purpose: Clinical practice guideline (CPG) concordant treatment (Ctx) has been shown to be more effective than CPG discordant care (Dtx) in a heterogeneous cohort of patients with acute lower back pain (ALBP). However, patients with underlying spine pathology (e.g. stenosis, disc degeneration, facet joint arthropathy) or without identifiable spine pathology may all present solely with ALBP. At present, it is unknown if underlying spine pathology influences the outcome of Ctx. The purpose of this study was to determine if Ctx is more effective than Dtx in patients with differing underlying spine pathology who present with ALBP.

Method: A Two-arm, randomized control trial with stratified analysis. Inclusion: Ages 19–59; QTFSD I, II ALBP < 4 weeks. Exclusion: “Red Flag” conditions, comorbidities contraindicating Ctx. The primary outcome was the difference between Ctx and Dtx Roland Morris Disability (RDQ) scores at 16 weeks post baseline between study groups. Secondary outcomes: differences in Bodily Pain (BP), Physical Functioning (PF) SF-36 domain scores at 16 weeks. Patients were assessed by a spine physician and randomized to Ctx or Dtx. Patients were stratified on the basis of CT or MRI evidence of:

spinal stenosis;

Hospital / University Ethics approval was obtained.

Results: Eighty-eight patients were recruited; 39 in Ctx & 38 in Dtx group completed the study. Baseline prognostic variables were evenly distributed between groups. Outcomes: mean difference in 16 week RDQ, BP and PF scores between Ctx and Dtx was statistically greatest in group 4 (p< 0.001). There was no significant clinical improvement in RDQ, BP or PF scores in either the Ctx or Dtx in group 2.

Conclusion: Ctx was more effective than Dtx in patients with no identifiable spine pathology and ineffective and equivalent to Dtx in patients with underlying disc degeneration.

Purpose: Apoptosis of osteoblasts and osteoclasts regulates bone homeostasis. Vertebral osteoporotic insufficiency fractures are characterised by pathological rates of osteoblast apoptosis. Skeletal injury in humans results in ‘angiogenic’ responses primarily mediated by vascular endothelial growth factor(VEGF), a protein essential for bone repair in animal models. Osteoblasts release VEGF in response to a number of stimuli and express receptors for VEGF in a differentiation dependent manner. This study investigates the putative role of VEGF in regulating the lifespan of primary human vertebral osteoblasts (PHVO) in-vitro.

Method: PHVO were cultured from biopsies taken at time of therapeutic vertebroplasty and were examined for VEGF receptors. Cultures were supplemented with VEGF(0–50ng/mL), a neutralising antibody to VEGF, mAB VEGF(0.3ug/mL) and Placental Growth Factor (PlGF), an Flt-1 receptor-specific VEGF ligand(0–100 ng/mL) to examine their effects on mineralised nodule assay, alkaline phosphatase assay and apoptosis. The role of the VEGF specific antiapoptotic gene target BCl2 in apoptosis was determined.

Results: PHVO expressed functional VEGF receptors. VEGF 10 and 25 ng/mL increased nodule formation 2.3- and 3.16-fold and alkaline phosphatase release 2.6 and 4.1-fold respectively while 0.3ug/mL of mAB VEGF resulted in approx 40% reductions in both. PlGF 50ng/mL had greater effects on alkaline phosphatase release (103% increase) than on nodule formation (57% increase). 10ng/mL of VEGF inhibited spontaneous and pathological apoptosis by 83.6% and 71% respectively, while PlGF had no significant effect. Pretreatment with mAB VEGF, in the absence of exogenous VEGF resulted in a significant increase in apoptosis (14 versus 3%). BCl2 transfection gave a 0.9% apoptotic rate. VEGF 10 ng/mL increased BCl2 expression four fold while mAB VEGF decreased it by over 50%.

Conclusion: VEGF is a potent regulator of osteoblast life-span in-vitro. This autocrine feedback regulates survival of these cells, mediated via the KDR receptor and expression of BCl2 antiapoptotic gene. This mechanism may represent a novel therapeutic model for the treatment of osteoporosis.

Purpose: To determine whether neural axis level of injury (SCI, CMI, or CEI) is related to motor improvement, as defined by the International Standards for Neurological Classification of Spinal Cord Injury motor score (MS), in patients with a thoracolumbar (T11-L3) spine injury.

Method: Fifty-three patients who sustained a neurological deficit secondary to a thoracolumbar spinal injury between 1995–2003 had injury details and MS collected prospectively. An independent evaluation determined the follow-up MS and SF-36 generic health-related quality of life (HrQOL) at a mean of 6.6 (SD 2.5) years post-injury. All patients had an MRI reviewed by a spine surgeon and neuroradiologist to determine the location of their conus medullaris and precise level of neural axis injury.

Results: Nineteen patients (37%) had SCI, 20 (39%) had CMI, and 12 (24%) had CEI, while two could not be classified. Patients with SCI improved their MS by an average 7.0 motor points (SD 9.8); CMI improved 11.9 (SD 11.8); and CEI improved 16.8 (SD 16.0). This trend did not achieve statistical significance (p=0.09). Multivariate analyses demonstrated that initial MS had a significant interaction with neural axis level of injury with respect to the primary outcome. Specifically, CEI showed the greatest improvement in MS only when the initial MS was less than 75. Absence of initial anal sensation, a fracture-dislocation injury type and increasing time to surgery were all statistically associated with less improvement in MS. The mean follow-up SF-36 physical component score (PCS) was 37.3 (SD 10.1) and the mean mental component score (MCS) was 51.4 (SD 11.8). There was no significant difference in mean PCS and MCS for varying levels of neural axis injury.

Conclusion: Patients with a CEI demonstrated the most improvement in MS, while absent anal sensation, a fracture-dislocation, and long delay to surgery were poor prognostic indicators for motor recovery. The HrQOL outcomes did not vary with neural axis level of injury. The results of this study assist in determining a prognosis for patients that sustain these common injuries. Future research should focus on how specific pre- and peri-operative variables affect outcomes in patients with neurological deficits secondary to thoracolumbar injuries.

Purpose: The average age of people suffering spinal cord injuries in many countries is shifting toward an older population, with a disproportionate number occurring in the spondylotic cervical spine. These injuries are typically due to low energy impacts, such as a fall from standing height. Since a stenotic spinal canal (a common feature of a spondylotic cervical spine) can cause myelopathy when the spine is flexed or extended, traumatic flexion or extension likely causes the injury during the low energy impact. However, this injury mechanism has not been observed experimentally.

Method: To better understand this injury mechanism an in-vitro study, using six whole cervical porcine spines, was conducted. The following techniques were combined to directly observe spinal cord compression in a stenotic spine during physiologic and super-physiologic motion:

A radio-opaque surrogate cord, with material properties matched to in-vivo specimens, replaced the real spinal cord.

Results: Initial results show that a stenotic occlusion that removes all extra space in the canal in the neutral posture, without compressing the cord, can lead to spinal cord compression within physiologic ranges of flexion and extension. The spinal cord can also be compressed during slightly super-physiologic flexion and extension with only 25% canal occlusion. Physiologic loads and motions in the same spines did not cause cord compression when canal occlusion was 0%.

Conclusion: These results support the hypothesis that cervical spinal canal stenosis increases the risk of spinal cord injury because spinal cord compression was observed during motions and loads that would be safe for a non-stenotic spine. These results are limited primarily due to the use of a porcine spine. However, this new stenosis model and experimental technique will be applied to in-vitro human spine specimens in future work.

Purpose: To evaluate the demographics, presentation, treatment and outcomes of spinal infection in a population of Intravenous Drug Users.

Method: Data on all patients with pyogenic spinal infection presenting to a quaternary referral center was obtained from a prospectively maintain database.

Results: Over the five-year study period, there were 102 patients treated for Primary Pyogenic Infection of the Spine of which 51 were Intravenous Drug Users (IVDU). Of this IVDU group there were 34 males. Mean age was 43 years (range 25 – 57). Twenty-three had HIV, 43 Hepatitis C and 13 Hepatitis B. All were using cocaine, 26 were also using Heroin and 44 more than three recreational drugs. Thirty patients presented with axial pain with a mean duration of 51 days (range 3–120). Thirty-one were ASIA D or worse with eight ASIA A. Mean Motor Score of patients with deficit was 58.6. Most common ASIA Motor Levels were C4 and C5. Mean duration of neurological symptoms was seven days (range 1–60). Blood parameters on admission were in keeping with sepsis in immunocompromised patients. None had previous surgery for spinal infection. Twenty-sex were receiving IV antibiotics for known spinal infection. 44 patients were treated surgically. 32 had infection of the cervical spine, 9 Thoracic and 3 Lumbar. 22 had a posterior approach alone, 13 had anterior only while 9 required combined. Mean operative time was 263 mins (range 62 – 742). 13 required tracheostomy. 7 required early revision for hardware failure and 2 for surgical wound infection. Mean duration of antibiotic treatment was 49 days (range 28–116). 26 patients had single agent therapy. 17 had MSSA and 17 MRSA. At discharge 28 patients had neurological improvement (mean 20 ASIA points, range 1–55), 11 had deterioration (mean 13, range 1–50) and 5 were unchanged. There were no in-hospital deaths. At 2 years after index admission 13 patients were dead and none were attending the unit for follow-up.

Conclusion: Primary pyogenic spinal infection in IVDU’s typically presents with sepsis and acute cervical quadriplegia. Surgical management must be prompt and aggressive with significant neurological improvement expected in the majority of patients.

Purpose: Prospective Observational Population Study to describe the incidence, demographics and pattern of spinal cord injury in British Columbia, Canada, for 10 years to 2004.

Method: Systematic analysis of prospectively collected spine registry data (Vertebase) at Vancouver General Hospital, B.C., Canada from 1995–2004.

Results: During the 10-year study period the 938 patients were admitted with a traumatic spinal cord injury. The Annual Population-Standardized Incidences ranged from 19.94 to 27.27 per million, with a median incidence of 23.34/million and with no significant change over the study period. The mean age was 39.7 years (34.73 in 1995 and 42.1 in 2004, p< 0.05) with a range of 16–92 years. 79.74 % were males. 48.2% of patients were AISA A on admission, of which 48% were quadraparetic. The most common levels of spinal cord injury were C5 (17.3%), C6 (10%), T1 (9.4%), T12 (5.8%). The Mean ASIA score was 50.22 with a range from 0–100. 19.8% of patients had a GCS£13. The mean ISS was 26.02, range of 0 – 75. Motor vehicle collisions and falls were responsible for 59% and 30% of admissions respectively. Mean length of in-hospital stay was 34 days, ranging from 1 – 275 days. In hospital mortality rate was 2.9%. ASIA Grade, Total Motor Score and anatomical level of injury all correlated directly with Length of stay (p< 0.0001).

Conclusion: Acute Traumatic Spinal Cord Injury remains a major cause of significant morbidity among young males. The incidence appears to be increasing in the elderly. Modern multidisciplinary care has greatly reduced the associated acute mortality. Despite multiple prevention strategies the Annual Population-Standardized Incidence remained unchanged over the study period.

Purpose: Oncologic management of primary bone tumors of the spine is inconsistent, controversial and open to individual interpretation. Tumor margin violation intraoperatively increases local recurrence and mortality. The purpose of this study is to determine whether applying Enneking’s principles to the surgical management of primary bone tumors of the spine significantly decreases local recurrence and/or mortality.

Method: A prospective and retrospective multicenter Cohort Study: Inclusion of patients undergoing en bloc or intralesional resection of primary tumors of the spine at four separate quaternary care centers, between January 1994 and January 2008. Patients were staged, using the Enneking system, prior to surgery and baseline demographic and surgical variables were recorded. Outcomes measured were disease local recurrence, or death. The results were statistically analyzed for significance.

Results: One hundred-fifty patients with primary tumors of the spine were recruited. Average age was 47.0 (range 8 to 83). Sixty-two patients were identified to have local recurrence. A statistically significant decrease in local recurrence (p=0.0001) was observed in favor of en bloc resection. In patients with local recurrence there was a significant increased risk of mortality, (p< 0.0001). There was a trend to decreased mortality in the en bloc resection group, not statistically significant (p=0.64).

Conclusion: Wide resection of primary tumors of spine with reconstruction is the standard of care. Application of Enneking’s principles to the spine when managing primary bone tumors significantly reduces local recurrence of the disease process, without an adverse outcome on mortality, and with acceptable HRQOL. Further cohort studies based on stringent data collection prospectively will provide a basis for more detailed study of individual tumor types.

The aetiology of idiopathic scoliosis, despite of long-lasting efforts to disclose it, remains unknown.

The purpose of the study was to evaluate the spine development after pinealectomy or cortical sensory motor area damage in the growing rats.

Method: The authors operated 69 Wistar albino rats (aged three to four weeks) in antraperitoneal anaesthesia. In the first group (22 rats) pinealectomy – PIN was performed, in the second one (25) the sensory motor cortical area 2x1x1 mm bellow the coronal suture was removed – SMCA. The sham operation consisted of craniotomy – CRA (11 rats) and craniotomy with durotomy – CRDU (11 rats). All surgeries were performed from the left side. Radiography was made three months after surgery. Scoliosis, C2-T7 lordosis, T7-S1 kyphosis were measured. Results have been processed by software Statistica 7.1. StatSoft, Inc. (2005). We used ANOVA test for evaluation of potential difference between groups, in the case of approving the difference between groups, we tested difference between each two groups by two-sample t-test. Those tests were realised on 0,05 significant level.

Results: In the PIN group scoliosis 9–14 degrees (mean value 10,8) developed in five animals, in SMCA group scoliosis 10 – 24 degrees (mean value 15,9) was observed in eight animals.

These statistically significant differences were found: higher surgery weight in PIN, longer surgery time in PIN and SMCA, lower lordosis in PIN and higher in CRDU, differences of all groups in kyphosis and in an end weight.

Conclusion: Our results indicate the importance of cortical area damage, together with craniotomy and durotomy in the development of growing rat spine. We cannot exclude the influence of peri-operative bleeding, brain hypoxia or metabolic effect of anaesthetics.

These damages could cause a disorder of balance between smaller inhibitory and greater facilitating area of CNS, controlling the muscular tone and resulting in the development of lordosis and scoliosis due to muscle imbalance.

A biomechanical study assessing pedicle screw fixation with three different augmentation methods was performed in human cadaveric vertebrae. Precision opto-electronic measurement of screw motion assessed motion magnitude and patterns, ie translation and/or rotation. Physiological cyclic loads were applied as opposed to the simple pull out test. Augmentation with wires, hook or cement decreased overall motion. There were no significant differences in motion magnitude between the three augmentation methods. Motion patterns for screws with cement augmentation were mainly rotational and differed from the other two methods. Rigid body translations were observed with wires or hook augmentation, suggesting a loosening behaviour. Augmentation with cement resulted in better fixation than wires or hook.

Augmentation of loosened pedicle screws in poor quality bone is often necessary. The purpose of this study was to contrast the kinematics of loosened pedicle screws augmented with laminar hooks, sublaminar wires or calcium phosphate cement.

Cyclic tests of pedicle screws with compressive force and bending moment were carried out on forty-eight screws in twenty-four cadaveric vertebrae (L3-L5) augmented with hooks, wires or cement. Motion at the screw tip and screw head were measured using an optoelectronic camera system and the magnitudes compared in a paired manner using non-parametric statistics. Motion patterns of the screws were determined for each augmentation method.

Augmentation with hook, wire or cement decreased screw motion. There was no significant difference between augmentation methods when the magnitudes of motion, described as ranges and offsets, were compared. Augmentation with cement resulted in mainly rotations of the screws while there were rigid body translations with wires or hooks.

Comparing magnitudes of motion at the screw head and screw tip were insufficient. The screw head and screw tip could be moving in synchronous, indicating rigid body translations. Using simple pull out tests would not detect such differences.

The method used in this study contrasted pedicle screws motion with different augmentations. While there was no detected significant difference in motion magnitude of the pedicle screws, the motion pattern of the screws suggested better augmentation with cement.

Motion of pedicle screws in situ had not been described in the literature. Previous work comparing pedicle screws fixation used the pull out test, while the current method applied physiological loads.

Funding: Funding from the Canadian Institutes for Health Research, Funding from Synthes

Spine Please contact author for diagrams and/or graphs.

The purpose of this study was to investigate the strength profile of the thoracolumbar endplate. Indentation testing was performed on the T9, T12, and L2 endplates of six fresh-frozen human cadaver vertebrae. Indentations were performed in a standardized rectangular grid pattern of seven columns and five rows. There was an incremental increase in the strength of each row moving anterior and posterior from the central row. The relative strength of the anterior regions of the endplate increased with rostral ascent into the thoracic spine.

The purpose of this study was to map the strength profile of the thoracolumbar endplates using indentation testing.

Indentation testing was performed on the T9, T12, and L2 endplates of six fresh-frozen human cadaver spines using a materials testing machine (Dynamight, Instrom Corporation, Canton, MA). A minimum of twenty-five indentations was performed in a rectangular grid (seven columns by five rows). A 3mm hemispherical indendor was lowered at 0.2mm/s to a depth of 3mm producing endplate failure.

The failure load significantly varied with the AP and LAT positions (p< .0001). Each row was significantly stronger than the rows anterior to it (p < 0.04), except for the most row. The most lateral columns were stronger than the central (range: p = .04 – .0002). The mean strength of the L2 posterior row was greater than that for the thoracic endplates (p< .01), while no difference existed between levels within the two anterior rows. The ratio of the mean strength for the posterior row compared to that of the anterior row was significantly different across level (P< 0.036). The ratios for L2, T12, and T9 were 1.35, 0.97, and 0.91 respectively.

The periphery of the thoracolumbar endplate is stronger than the centre. The interaction identified between position and level suggests a relative strength increase in the anterior aspect of the endplate with rostral ascent into the thoracic spine.

This knowledge may assist in preventing intervertebral inplant subsidence by influencing implant positioning and design.

Funding: Canadian Institutes of Health Research Please contact author for figures and/or graphs.

Purpose: The objectives of this study were to determine the effect of posterior instrumentation extension and/or cement augmentation on immediate stabilization of the instrumented level and biomechanical changes adjacent to the spinal instrumentation.

Methods: This study was designed for repeated measures comparison, using 12 T9-L3 human cadaveric segments, to test the effects of posterior rod extension and cement augmentation following T11 corpectomy. The spine was stabilized with a vertebral body replacement device and with posterior instrumentation from T10 to T12. The T12 pedicle tracts were over-drilled to simulate loosened screws in an osteoporotic spine. The T10 screws were not over-drilled but cemented so as to keep the superior segments constant. Flexibility tests were first carried out on the intact specimen, followed by 3 randomized surgical conditions without cement and lastly the 3 conditions after cement augmentation. The 3 conditions were: 1) no posterior extension rods to L1, 2) flexible extension rods, and 3) rigid extension rods. A combined testing/analysis protocol that used both the traditional flexibility method and a hybrid technique [Panjabi 2005] was adopted. Flexibility tests with +/−5 Nm pure moments in flexion-extension, axial rotation and lateral bending were carried out and vertebral bodies’ motion in 3-D were collected. Two-way repeated measures ANOVA analyses were carried out on ROM between cement augmentation (factor 1) and the posterior rod extension (factor 2) on each flexibility test direction. An alpha of 0.05 was chosen. Newman-Keuls post-hoc analyses were carried out to compare between surgical techniques.

Results: Using the flexibility protocol, a reduction in ROMs at the destabilized level was observed with cement augmentation of screws or extension with rigid or flexible posterior rods to adjacent distal level. With the hybrid protocol, ROMs at adjacent level (T12-L1) were reduced with rod extension, but not with cement.

Conclusions: The results of this study suggest that cement augmentation would enhance stabilization, but create possible adjacent level effects due to increased motion and strain, while additional flexible extension rods would reduce biomechanical changes at the level of extension. Funding: 2 Funding Parties: CIHR

A prospective cohort outcome evaluation of unstable thoracic spine fractures treated with posterior pedicle screw fixation. The purpose of this study was to determine the accuracy of placement and safety of pedicle screws in open reduction of unstable thoracic spine fractures. The surgeries were performed by one of five fellowship trained spinal surgeons. CT scans were formed on twenty-three patients totaling two hundred screws using 3mm cuts. Three independent reviewers assessed and categorized the screw position as within the pedicle or as a violation of the pedicle wall. 98% of the screws were accurate and we recommend the use of pedicle screws in thoracic fractures .

A prospective cohort outcome evaluation of unstable thoracic spine fractures treated with posterior pedicle screw fixation.

This study is to determine the accuracy of placement, safety of pedicle screws in open reduction of unstable thoracic spine fracture

Surgery was performed by one of five fellowship trained spine surgeons. CT scans were performed on twenty-three patients using 3mm cuts in both sagittal and transverse planes. Pedicle screw position was assessed by three independent reviewers. Screw position was categorized as within the wall of the pedicle or in violation of the wall. Further sub-classification of pedicle wall violation reviewed the direction and distance of perforation. Independent perioperative and postoperative surveillance for complications was done.

Twenty-three unstable thoracic spine fractures treated with two hundred posterior pedicle screws were analyzed. The pedicle screws spanned from T1-T12 with the majority of screws in the mid-thoracic region. Of the two hundred thoracic pedicle screws placed, 70% were fully contained within the pedicle wall. The remaining screws were deemed “out” with cortical perforation (30%). Of these, 20% were lateral perforations, 5% were medial perforations and 5% were anterolateral perforations. No superior, inferior, or anteromedial perforations were found. There was no regional area variation in incidence of perforations. 10% of all perforations were directly related to pedicle diameter to screw diameter mismatch. There were no adverse neurological, vascular, or visceral injuries detected intraoperatively or postoperatively.

Surgical management of unstable thoracic spine fractures with posterior pedicle screw fixation is safe. 98% of screws had satisfactory accuracy. Although very minor misplacement of pedicle screws occurred, there were no complications and we recommend the use of pedicle screws in thoracic fractures.

Purpose: The clinical sequelae associated with acute sciatica have been traditionally attributed to mechanical compression of the spinal nerve root by a herniated disc (HD). More recent studies have demonstrated that the HD induces the release of inflammatory mediators and that a tumor necrosis factor alpha-inhibiting agent can resolve the symptoms.|Selective nerve root block (SNRB) involves the transforaminal application of steroid under fluoroscopic guidance adjacent to the selected nerve root. Well-defined criteria for patients that will most likely benefit from SNRB remain unclear. The goal of this study was to determine whether or not the morphology (i.e. posterolateral, sequestrated, foraminal, far lateral) of HD influences the therapeutic value of SNRB treatment.

Methods: An observational cohort study of 37 patients with acute sciatica of less than 12 weeks duration, McCulloch scores of 4 or 5 and evidence of HD on MRI scan at the appropriate level was completed. Disc morphology was determined by blinded interpretation of the MRI scans by a Musculoskeletal Radiologist. Outcome measures included the Modified Roland-Morris Disability Questionnaire (RDQ), administered on the day of, and 6 weeks following, the SNRB procedure and the Visual Analogue Scale (VAS) filled out by the patient immediately before, 30 minutes after and 6 weeks after SNRB.

Results: Of the 37 patients enrolled in this study, the HD morphology was classified as: posterolateral 20, sequestrated 9, foraminal 6, far lateral 2. 35 of 37 patients (95%) reported a 30 minute VAS score of less than 3/10. 14 of 20 patients (70%) with posterolateral HD reported > 3 point improvement in RDQ and > 5 point improvement in VAS at 6 weeks post procedure. 1 of 9 patients (11%) with sequestrated HD showed the same level of improvement in RDQ and VAS scores. None of the patients with foraminal or far lateral HD reported > 1 point improvement in RDQ or > 2 point improvement in VAS scores.

Conclusions: Patients with posterolateral HD were found to have significantly more favorable outcomes from SNRB than those with sequestrated, foraminal or far lateral HD morphology.

Spinal cord damage was compared after an injury was inflicted by three clinically relevant mechanisms (contusion, dislocation, and distraction). A novel SCI multi-mechanism system has been developed. Central hemorrhage was common to all mechanisms. Increased membrane permeability was localized to the injury epicenter in contusion but spread further in distraction. Dislocation showed intermediate characteristics exhibiting both local neuronal losses at the epicenter and extended regions of membrane permeability. These preliminary observations suggest that distinct injury mechanisms result in differences in the primary damage of the spinal cord.

This work compared primary damage after spinal cord injury (SCI) inflicted by three clinically relevant mechanisms.

Different injury mechanisms result in regional differences in damage to the spinal cord.

Differences in acute damage may help guide targeted therapies following SCI.

At greater distances from the lesion, dextran was excluded from neuronal somata and in the white matter only distinct accumulation was seen at the Nodes of Ranvier. At the injury site, hemorrhage was common to all mechanisms although more diffuse in the distraction injuries. Increased membrane permeability was localized to the injury epicenter in contusion but spread further in distraction. Dislocation showed intermediate characteristics exhibiting both local neuronal losses at the epicenter and extended regions of permeability.

A novel SCI multi-mechanism system was developed which uses an electromagnetic actuator to permit the modeling of injuries along any direction. Dextran was infused into the cisterna magna 1.5 to 2 hours prior to injury in order to visualize increases in membrane permeability. Stereotaxic clamps were designed to rigidly hold the lower cervical vertebrae of deeply anaesthetized rats permitting displacements at speeds of 100cm/s. A range of displacements was used in this pilot series: 0.9 to 1.1mm contusion, 2 to 6mm dislocation and 3 to 8mm axial distraction. Animals were sacrificed at five minutes in order to analyse the primary injury. These preliminary observations suggest that distinct injury mechanisms result in regional differences in the primary damage of spinal cord gray and white matter.