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Claire F. Jones, Jae H. T. Lee, Brian K. Kwon and Peter A. Cripton

Object

Spinal cord injury (SCI) often results in considerable permanent neurological impairment, and unfortunately, the successful translation of effective treatments from laboratory models to human patients is lacking. This may be partially attributed to differences in anatomy, physiology, and scale between humans and rodent models. One potentially important difference between the rodent and human spinal cord is the presence of a significant CSF volume within the intrathecal space around the human cord. While the CSF may “cushion” the spinal cord, pressure waves within the CSF at the time of injury may contribute to the extent and severity of the primary injury. The objective of this study was to develop a model of contusion SCI in a miniature pig and establish the feasibility of measuring spinal CSF pressure during injury.

Methods

A custom weight-drop device was used to apply thoracic contusion SCI to 17 Yucatan miniature pigs. Impact load and velocity were measured. Using fiber optic pressure transducers implanted in the thecal sac, CSF pressures resulting from 2 injury severities (caused by 50-g and 100-g weights released from a 50-cm height) were measured.

Results

The median peak impact loads were 54 N and 132 N for the 50-g and 100-g injuries, respectively. At a nominal 100 mm from the injury epicenter, the authors observed a small negative pressure peak (median −4.6 mm Hg [cranial] and −5.8 mm Hg [caudal] for 50 g; −27.6 mm Hg [cranial] and −27.2 mm Hg [caudal] for 100 g) followed by a larger positive pressure peak (median 110.5 mm Hg [cranial] and 77.1 mm Hg [caudal] for 50 g; 88.4 mm Hg [cranial] and 67.2 mm Hg [caudal] for 100 g) relative to the preinjury pressure. There were no significant differences in peak pressure between the 2 injury severities or the caudal and cranial transducer locations.

Conclusions

A new model of contusion SCI was developed to measure spinal CSF pressures during the SCI event. The results suggest that the Yucatan miniature pig is an appropriate model for studying CSF, spinal cord, and dura interactions during injury. With further development and characterization it may be an appropriate in vivo largeanimal model of SCI to answer questions regarding pathological changes, therapeutic safety, or treatment efficacy, particularly where humanlike dimensions and physiology are important.

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Gregory W. J. Hawryluk, James Rowland, Brian K. Kwon and Michael G. Fehlings

Over the past 2 decades, advances in understanding the pathophysiology of spinal cord injury (SCI) have stimulated the recent emergence of several therapeutic strategies that are being examined in Phase I/II clinical trials. Ten randomized controlled trials examining methylprednisolone sodium succinate, tirilizad mesylate, monosialotetrahexosylganglioside, thyrotropin releasing hormone, gacyclidine, naloxone, and nimodipine have been completed. Although the primary outcomes in these trials were laregely negative, a secondary analysis of the North American Spinal Cord Injury Study II demonstrated that when administered within 8 hours of injury, methylprednisolone sodium succinate was associated with modest clinical benefits, which need to be weighed against potential complications. Thyrotropin releasing hormone (Phase II trial) and monosialotetrahexosylganglioside (Phase II and III trials) also showed some promise, but we are unaware of plans for future trials with these agents. These studies have, however, yielded many insights into the conduct of clinical trials for SCI. Several current or planned clinical trials are exploring interventions such as early surgical decompression (Surgical Treatment of Acute Spinal Cord Injury Study) and electrical field stimulation, neuroprotective strategies such as riluzole and minocycline, the inactivation of myelin inhibition by blocking Nogo and Rho, and the transplantation of various cellular substrates into the injured cord. Unfortunately, some experimental and poorly characterized SCI therapies are being offered outside a formal investigational structure, which will yield findings of limited scientific value and risk harm to patients with SCI who are understandably desperate for any intervention that might improve their function. Taken together, recent advances suggest that optimism for patients and clinicians alike is justified, as there is real hope that several safe and effective therapies for SCI may become available over the next decade.

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Marcel F. Dvorak, Michael G. Johnson, Michael Boyd, Garth Johnson, Brian K. Kwon and Charles G. Fisher

Object. The primary goal of this study was to describe the long-term health-related quality of life (HRQOL) outcomes in patients who have suffered Jefferson-type fractures. These outcomes were compared with matched normative HRQOL data and with the patient's perceptions of their HRQOL prior to the injury. Variables that potentially influence these HRQOL outcomes were analyzed.

No standardized outcome assessments have been published for patients who suffer these fractures; their outcomes have long thought to be excellent following treatment. Determining the optimal surrogate measure to represent preinjury HRQOL in trauma patients is difficult.

Methods. A retrospective review, radiographic analysis, and cross-sectional outcome assessment were performed. The Short Form (SF)—36 and the American Academy of Orthopaedic Surgeons/North American Spine Society (AAOS/NASS) outcome instruments were filled out by patients at final follow-up examination (follow-up period 75 months, range 19–198 months) to represent their current status as well as their perceptions of preinjury status.

In 34 patients, the SF-36 physical component score and the AAOS/NASS pain values were significantly lower than normative values. There was no significant difference between normative and preinjury values. Spence criteria greater than 7 mm and the presence of associated injuries predicted poorer outcome scores during the follow-up period.

Conclusions. Long-term follow-up examination of patients with Jefferson fractures indicated that patients' status does not return to the level of their perceived preinjury health status or that of normative population controls. Those with other injuries and significant osseous displacement (≥ 7 mm total) may experience poorer long-term outcomes. Limitations of the study included a relatively low (60%) response rate and the difficulties of identifying an appropriate baseline outcome in a trauma population with which the follow-up outcomes can be compared.

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John M. Beiner, Jonathan Grauer, Brian K. Kwon and Alexander R. Vaccaro

Postoperative spinal wound infections occur in 1 to 12% of patients. The rate of infection is related to the type and duration of the procedure, comorbidities, nutritional status, and various other risk factors. Antibiotic prophylactic therapy has been clearly shown to decrease the rate of infection dramatically after lumbar surgery. These infections typically manifest with signs and symptoms of wound swelling, erythema, and drainage. Laboratory-detected values such as the erythrocyte sedimentation rate and C-reactive protein can be elevated beyond what is normal for the uncomplicated postoperative course following lumbar surgery, and combined with the clinical symptoms should alert the physician to the possibility of infection. When detected, these infections should be managed aggressively with operative debridment and irrigation, including the deep subfascial layer in all cases except those with clearly demarcated superficial infection. The choice of one versus multiple debridments can be made based on the appearance of the wound, patient factors, and nutritional status. Hardware and incorporated bone graft can be left in place in the majority of cases, adding to stability. Outcomes following aggressive treatment of this complication can be excellent, with no long-term loss of function and complete eradication of the infection.

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Brian K. Kwon, Charles G. Fisher, Michael C. Boyd, John Cobb, Hilary Jebson, Vanessa Noonan, Peter Wing and Marcel F. Dvorak

Object

Unilateral facet injuries can be treated with either anterior or posterior fixation techniques with reportedly good outcomes. The two approaches have not been directly compared, however, and consensus is lacking as to which is the optimal method. The primary objective of this study was to determine whether acute postoperative morbidity differed between anteriorly and posteriorly treated patients with unilateral facet injuries.

Methods

Forty-two patients were prospectively randomized to undergo either anterior cervical discectomy and fusion or posterior fixation. The primary outcome measure was the postoperative time required to achieve a predefined set of discharge criteria. Secondary outcome measures included postoperative pain, wound infections, radiographically demonstrated fusion and alignment, and patient-reported outcome measures.

Results

The median time to achieve the discharge criteria was 2.75 and 3.5 days for anterior and posterior groups, respectively, a difference that did not reach statistical significance (p = 0.096). Compared with those treated using posterior fixation, anteriorly treated patients exhibited somewhat less postoperative pain, a lower rate of wound infection, a higher rate of radiographically demonstrated union, and better radiographically proven alignment. Nonetheless, the anterior approach was accompanied by a risk of swallowing difficulty in the early postoperative period. Patient-reported outcome measures did not reveal a difference between anterior and posterior fixation procedures.

Conclusions

This prospective randomized controlled trial provided level 1 evidence that both the anterior and posterior fixation approaches appear to be valid treatment options. Although statistical significance was not reached in the primary outcome measure, some secondary outcome measures favored anterior fixation and others favored posterior treatment for unilateral facet injuries.

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Christopher S. Bailey, Marcel F. Dvorak, Kenneth C. Thomas, Michael C. Boyd, Scott Paquett, Brian K. Kwon, John France, Kevin R. Gurr, Stewart I. Bailey and Charles G. Fisher

Object

The authors compared the outcome of patients with thoracolumbar burst fractures treated with and without a thoracolumbosacral orthosis (TLSO).

Methods

As of June 2002, all consecutive patients satisfying the following inclusion criteria were considered eligible for this study: 1) the presence of an AO Classification Type A3 burst fractures between T-11 and L-3, 2) skeletal maturity and age < 60 years, 3) admission within 72 hours of injury, 4) initial kyphotic deformity < 35°, and 5) no neurological deficit. The study was designed as a multicenter prospective randomized clinical equivalence trial. The primary outcome measure was the score based on the Roland-Morris Disability Questionnaire assessed at 3 months postinjury. Secondary outcomes are assessed until 2 years of follow-up have been reached, and these domains included pain, functional outcome and generic health-related quality of life, sagittal alignment, length of hospital stay, and complications. Patients in whom no orthotic was used were encouraged to ambulate immediately following randomization, maintaining “neutral spinal alignment” for 8 weeks. The patients in the TLSO group began being weaned from the brace at 8 weeks over a 2-week period.

Results

Sixty-nine patients were followed to the primary outcome time point, and 47 were followed for up to 1 year. No significant difference was found between treatment groups for any outcome measure at any stage in the follow-up period. There were 4 failures requiring surgical intervention, 3 in the TLSO group and 1 in the non-TLSO group.

Conclusions

This interim analysis found equivalence between treatment with a TLSO and no orthosis for thoracolumbar AO Type A3 burst fractures. The influence of a brace on early pain control and function and on long-term 1- and 2-year outcomes remains to be determined. However, the authors contend that a thoracolumbar burst fracture, in exclusion of an associated posterior ligamentous complex injury, is inherently a very stable injury and may not require a brace.

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Nicolas Dea, Anne Versteeg, Charles Fisher, Adrienne Kelly, Dennis Hartig, Michael Boyd, Scott Paquette, Brian K. Kwon, Marcel Dvorak and John Street

Object

Most descriptions of spine surgery morbidity and mortality in the literature are retrospective. Emerging prospective analyses of adverse events (AEs) demonstrate significantly higher rates, suggesting underreporting in retrospective and prospective studies that do not include AEs as a targeted outcome. Emergency oncological spine surgeries are generally palliative to reduce pain and improve patients' neurology and health-related quality of life. In individuals with limited life expectancy, AEs can have catastrophic implications; therefore, an accurate AE incidence must be considered in the surgical decision-making process. The purpose of this study was to determine the true incidence of AEs associated with emergency oncological spine surgery.

Methods

The authors carried out a prospective cohort study in a quaternary care referral center that included consecutive patients admitted between January 1, 2009, and December 31, 2012. Inclusion criteria were all patients undergoing emergency surgery for metastatic spine disease. AE data were reported and collected on standardized AE forms (Spine AdVerse Events Severity System, version 2 [SAVES V2] forms) at weekly dedicated morbidity and mortality rounds attended by attending surgeons, residents, fellows, and nursing staff.

Results

A total of 101 patients (50 males, 51 females) met the inclusion criteria and had complete data. Seventysix patients (76.2%) had at least 1 AE, and 11 patients (10.9%) died during their admission. Intraoperative surgical AEs were observed in 32% of patients (9.9% incidental durotomy, 16.8% blood loss > 2 L). Transient neurological deterioration occurred in 6 patients (5.9%). Infectious complications in this patient population were significant (surgical site 6%, other 50.5%). Delirium complicated the postoperative period in 20.8% of cases.

Conclusions

When evaluated in a rigorous prospective manner, metastatic spine surgery is associated with a higher morbidity rate than previously reported. This AE incidence must be considered by the patient, oncologist, and surgeon to determine appropriate management and preventative strategies to reduce AEs in this fragile patient population.

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John T. Street, R. Andrew Glennie, Nicolas Dea, Christian DiPaola, Zhi Wang, Michael Boyd, Scott J. Paquette, Brian K. Kwon, Marcel F. Dvorak and Charles G. Fisher

OBJECTIVE

The objective of this study was to determine if there is a significant difference in surgical site infection (SSI) when comparing the Wiltse and midline approaches for posterior instrumented interbody fusions of the lumbar spine and, secondarily, to evaluate if the reoperation rates and specific causes for reoperation were similar for both approaches.

METHODS

A total of 358 patients who underwent 1- or 2-level posterior instrumented interbody fusions for degenerative lumbar spinal pathology through either a midline or Wiltse approach were prospectively followed between March 2005 and January 2011 at a single tertiary care facility. A retrospective analysis was performed primarily to evaluate the incidence of SSI and the incidence and causes for reoperation. Secondary outcome measures included intraoperative complications, blood loss, and length of stay. A matched analysis was performed using the Fisher's exact test and a logistic regression model. The matched analysis controlled for age, sex, comorbidities, number of index levels addressed surgically, number of levels fused, and the use of bone grafting.

RESULTS

All patients returned for follow-up at 1 year, and adverse events were followed for 2 years. The rate of SSI was greater in the midline group (8 of 103 patients; 7.8%) versus the Wiltse group (1 of 103 patients; 1.0%) (p = 0.018). Fewer additional surgical procedures were performed in the Wiltse group (p = 0.025; OR 0.47; 95% CI 0.23–0.95). Proximal adjacent segment failure requiring reoperation occurred more frequently in the midline group (15 of 103 patients; 14.6%) versus the Wiltse group (6 of 103 patients; 5.8%) (p = 0.048). Blood loss was significantly lower in the Wiltse group (436 ml) versus the midline group (703 ml); however, there was no significant difference between the 2 groups in intraoperative complications or length of stay.

CONCLUSIONS

The patients who underwent the Wiltse approach had a decreased risk of wound breakdown and infection, less blood loss, and fewer reoperations than the midline patients. The risk of adjacent segment failure in short posterior constructs is lower with a Wiltse approach.

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Khalid M. I. Salem, Aditya P. Eranki, Scott Paquette, Michael Boyd, John Street, Brian K. Kwon, Charles G. Fisher and Marcel F. Dvorak

OBJECTIVE

The study aimed to determine if the intraoperative segmental lordosis (as calculated on a cross-table lateral radiograph following a single-level transforaminal lumbar interbody fusion [TLIF] for degenerative spondylolisthesis/low-grade isthmic spondylolisthesis) is maintained at discharge and at 6 months postsurgery.

METHODS

The authors reviewed images and medical records of patients ≥ 16 years of age with a diagnosis of an isolated single-level, low-grade spondylolisthesis (degenerative or isthmic) with symptomatic spinal stenosis treated between January 2008 and April 2014. Age, sex, surgical level, surgical approach, and facetectomy (unilateral vs bilateral) were recorded. Upright standardized preoperative, early, and 6-month postoperative radiographs, as well as intraoperative lateral radiographs, were analyzed for the pelvic incidence, segmental lumbar lordosis (SLL) at the TILF level, and total LL (TLL). In addition, the anteroposterior position of the cage in the disc space was documented. Data are presented as the mean ± SD; a p value < 0.05 was considered significant.

RESULTS

Eighty-four patients were included in the study. The mean age of patients was 56.8 ± 13.7 years, and 46 patients (55%) were men. The mean pelvic incidence was 59.7° ± 11.9°, and a posterior midline approach was used in 47 cases (56%). All TLIF procedures were single level using a bullet-shaped cage. A bilateral facetectomy was performed in 17 patients (20.2%), and 89.3% of procedures were done at the L4–5 and L5–S1 segments. SLL significantly improved intraoperatively from 15.8° ± 7.5° to 20.9° ± 7.7°, but the correction was lost after ambulation. Compared with preoperative values, at 6 months the change in SLL was modest at 1.8° ± 6.7° (p = 0.025), whereas TLL increased by 4.3° ± 9.6° (p < 0.001). The anteroposterior position of the cage, approach, level of surgery, and use of a bilateral facetectomy did not significantly affect postoperative LL.

CONCLUSIONS

Following a single-level TLIF procedure using a bullet-shaped cage, the intraoperative improvement in SLL is largely lost after ambulation. The improvement in TLL over time is probably due to the decompression part of the procedure. The approach, level of surgery, bilateral facetectomy, and position of the cage do not seem to have a significant effect on LL achieved postoperatively.