Restoring blackland prairies in Mississippi: remnant-restored prairie comparisons and techniques for augmenting forbs

One knowledge gap hindering prairie restoration is uncertainty about when a restored prairie communities sufficiently resemble remnant prairie. I surveyed plant communities in remnant prairies, prairies \u3e 5 years post-restoration, and prairies ≤ 5 years post-restoration in Mississippi. Remnants had the greater species richness. Restored prairies had less cover of woody plants and forbs but greatest non-natives. Restored prairies were not similar to remnant prairies (similarity index = 28.9 - 25.9%), primarily because restored prairies had fewer prairie forbs. Thus, restoration may take decades. Transplanting locallyapted prairie forbs into restored prairies may accelerate restoration, but this has not been evaluated adequately. I transplanted a prairie forb (Liatris pycnostachya) into prepared beds, oldields, and restored prairies. Prepared beds had greater growth and seed production, but survival and flowering was high in oldields and restored prairies. Augmenting restored prairies with locallyapted forbs has promise for accelerating prairie restoration

Guideline update for the performance of fusion procedures for degenerative disease of the lumbar spine. Part 15: Electrophysiological monitoring and lumbar fusion

pre-printIntraoperative monitoring (IOM) is commonly used during lumbar fusion surgery for the prevention of nerve root injury. Justification for its use stems from the belief that IOM can prevent nerve root injury during the placement of pedicle screws. A thorough literature review was conducted to determine if the use of IOM could prevent nerve root injury during the placement of instrumentation in lumbar or lumbosacral fusion. There is no evidence to date that IOM can prevent injury to the nerve roots. There is limited evidence that a threshold below 5 mA from direct stimulation of the screw can indicate a medial pedicle breach by the screw. Unfortunately, once a nerve root injury has taken place, changing the direction of the screw does not alter the outcome. The recommendations formulated in the original guideline effort are neither supported nor refuted with the evidence obtained with the current studies

Dynamic cervical plates: biomechanical evaluation of load sharing and stiffness

Journal ArticleStudy Design. An in vitro biomechanical study using a simulated cervical corpectomy model to compare the load-sharing properties and stiffnesses of two static and two dynamic cervical plates. Objectives. To evaluate the load-sharing properties of the instrumentation with a full-length graft and with 10% graft subsidence and to measure the stiffness of the instrumentation systems about the axes of flexion-extension, lateral bending, and axial torsion under these same conditions. Summary of Background Data. No published reports comparing conventional and dynamic cervical plates exist. Methods. Six specimens of each of the four plate types were mounted on ultra-high molecular weight polyethylene-simulated vertebral bodies. A custom four-axis spine simulator applied pure flexion-extension, lateral bending, and axial torsion moments under a constant 50 Naxial compressive load. Load sharing was calculated through a range of applied axial loads up to 120 N. The stiffness of each construct was calculated in response to 62.5 Nm moments about each axis of rotation with a full-length graft, a 10% shortened graft, and no graft. ANOVA and Fisher's post hoc test were used to determine statistical significance (alpha # 0.05). Results. The two locked cervical plates (CSLP and Orion) and the ABC dynamic plate were similar in flexion-extension, lateral bending, and torsional stiffness. The DOC dynamic plate was consistently less stiff. The Orion plate load shared significantly less than the other three plates with a full graft. Both the ABC and the DOC plates were able to load share with a shortened graft, whereas the conventional plates were not. Conclusions. All plates tested effectively load share with a full-length graft, whereas the two dynamic cervical plates tested load share more effectively than the locked plates with simulated graft subsidence. The effect of dynamization on stiffness is dependent on plate design. [Key words: cervical spine, anterior plates, dynamic instrumentation, biomechanics, load sharing

Variations in surgical treatment of cervical facet dislocations

Journal ArticleObjective. To explore surgeon preference in the choice of surgical approach in the treatment of traumatic cervical facet dislocations. Summary of Background Data. The choice of surgical approach in the treatment of traumatic cervical dislocations is highly variable and maybe influenced by a variety of factors. The purpose of this study was to examine inter-rater reliability in choice of surgical approach. Methods. Twenty-five members of the Spine Trauma Study Group evaluated 10 cases of traumatic cervical dislocations. Evaluation of the case as a unilateral or bilateral injury and surgeon interpretation of the presence of a disc herniation as well as preferred surgical approach were assessed. Results. Only slight agreement was observed among surgeons in the choice of surgical approach (Kappa < 0.1). This improved slightly when patients were assumed to have a complete spinal cord injury (Kappa - 0.15). Surgeons used more anterior approaches either alone or as the first stage in a combined approach when a disc herniation was present regardless of neurologic status of the patient. When a patient was neurologically intact, an anterior approach was more common than a posterior approach even when a disc herniation was not present. Combined approaches were preferred for the treatment of bilateral facet dislocations. Conclusion. The poor agreement on the treatment of these injuries likely reflects a combination of factors including surgeon training and experience. Treatment decisions are likely to be affected by the neurologic status of the patient, interpretation of a disc herniation, and the classification of the injury as a unilateral or bilateral injury

Comparison of computerized tomography and direct visualization in thoracic pedicle screw placement

Journal ArticleObject. To validate computerized tomography (CT) scanning as a tool to assess the accuracy of thoracic pedicle screw placement, the authors compared its accuracy with that of direct visualization in instrumented cadaveric spine specimens. Methods. A grading scale was devised to score the placement of the pedicle screw. The grades ranged from 0 to 3 depending on the extent to which the pedicle had been violated. One hundred fifty-five pedicles were fitted with instrumentation in eight cadaveric spines. A single observer graded the appearance of the screw based on CT scans (3-mm axial sections with 1-mm overlap) and direct visualization of the specimen. The authors arrived at a Kappa value of 0.51, which suggested only moderate agreement between the two measurement techniques. Whereas CT had a positive predictive value of 95%, it had a negative predictive value of 62%. Conclusions. The authors thus conclude that although CT scanning is the most valid tool to assess the accuracy of thoracic pedicle screw placement, it tends to overestimate the number of misplaced screws

Guideline update for the performance of fusion procedures for degenerative disease of the lumbar spine. Part 12: Pedicle screw fixation as an adjunct to posterolateral fusion

pre-printThe utilization of pedicle screw fixation as an adjunct to posterolateral lumbar fusion (PLF) has become routine, but demonstration of a definitive benefit remains problematic. The medical evidence indicates that the addition of pedicle screw fixation to PLF increases fusion rates when assessed with dynamic radiographs. More recent evidence, since publication of the 2005 Lumbar Fusion Guidelines, suggests a stronger association between radiographic fusion and clinical outcome, although, even now, no clear correlation has been demonstrated. Although several reports suggest that clinical outcomes are improved with the addition of pedicle screw fixation, there are conflicting findings from similarly classified evidence. Furthermore, the largest contemporary, randomized, controlled study on this topic failed to demonstrate a significant clinical benefit with the use of pedicle screw fixation in patients undergoing PLF for chronic low-back pain. This absence of proof should not, however, be interpreted as proof of absence. Several limitations continue to compromise these investigations. For example, in the majority of studies the sample size is insufficient to detect small increments in clinical outcome that may be observed with pedicle screw fixation. Therefore, no definitive statement regarding the efficacy of pedicle screw fixation as a means to improve functional outcomes in patients undergoing PLF for chronic low-back pain can be made. There appears to be consistent evidence suggesting that pedicle screw fixation increases the costs and complication rate of PLF. High-risk patients, including (but not limited to) patients who smoke, patients who are undergoing revision surgery, or patients who suffer from medical conditions that may compromise fusion potential, may appreciate a greater benefit with supplemental pedicle screw fixation. It is recommended, therefore, that the use of pedicle screw fixation as a supplement to PLF be reserved for those patients in whom there is an increased risk of nonunion when treated with only PLF

Guideline update for the performance of fusion procedures for degenerative disease of the lumbar spine. Part 14: Brace therapy as an adjunct to or substitute for lumbar fusion

pre-printThe utilization of orthotic devices for lumbar degenerative disease has been justified from both a prognostic and therapeutic perspective. As a prognostic tool, bracing is applied prior to surgery to determine if immobilization of the spine leads to symptomatic relief and thus justify the performance of a fusion. Since bracing does not eliminate motion, the validity of this assumption is questionable. Only one low-level study has investigated the predictive value of bracing prior to surgery. No correlation between response to bracing and fusion outcome was observed; therefore a trial of preoperative bracing is not recommended. Based on low-level evidence, the use of bracing is not recommended for the prevention of low-back pain in a general working population, since the incidence of low-back pain and impact on productivity were not reduced. However, in laborers with a history of back pain, a positive impact on lost workdays was observed when bracing was applied. Bracing is recommended as an option for treatment of subacute low-back pain, as several higher-level studies have demonstrated an improvement in pain scores and function. The use of bracing following instrumented posterolateral fusion, however, is not recommended, since equivalent outcomes have been demonstrated with or without the application of a brace

Guideline update for the performance of fusion procedures for degenerative disease of the lumbar spine. Part 2: Assessment of functional outcome following lumbar fusion

pre-printAssessment of functional patient-reported outcome following lumbar spinal fusion continues to be essential for comparing the effectiveness of different treatments for patients presenting with degenerative disease of the lumbar spine. When assessing functional outcome in patients being treated with lumbar spinal fusion, a reliable, valid, and responsive outcomes instrument such as the Oswestry Disability Index should be used. The SF-36 and the SF-12 have emerged as dominant measures of general health-related quality of life. Research has established the minimum clinically important difference for major functional outcomes measures, and this should be considered when assessing clinical outcome. The results of recent studies suggest that a patient's pretreatment psychological state is a major independent variable that affects the ability to detect change in functional outcome

Diagnosis and treatment of craniocervical dislocation in a series of 17 consecutive survivors during an 8-year period

Journal ArticleObject. Craniocervical dissociation (CCD) is a highly unstable and usually fatal injury resulting from osseoligamentous disruption between the occiput and C-2. The purpose of this study was to elucidate systematic factors associated with delays in diagnosing and treating this life-threatening condition and to introduce an injury-severity classification with therapeutic implications. Methods. In a retrospective evaluation of institutional databases, the authors reviewed medical records and original images obtained in 17 consecutive surviving patients with CCD treated between 1994 and 2002. Images and clinical results of treatment were evaluated, emphasizing the timing of diagnosis, clinical effect of delayed diagnosis, potential clinical or imaging warning signs, and response to treatment. Craniocervical dissociation was identified or suspected on the initial lateral cervical spine radiograph acquired in two patients (12%) and was diagnosed based on screening computerized tomography findings in two additional patients (12%). A retrospective review of initial lateral x-ray films showed an abnormal dens-basion interval in 16 patients (94%). The 2-day average delay in diagnosis was associated with profound neurological deterioration in five patients (29%). Neurological status declined in one patient after a fixation procedure was performed. There were no cases of craniocervical pseudarthrosis or hardware failure during a mean 26-month follow-up period. The mean American Spinal Injury Association (ASIA) motor score of 50 improved to 79, and the number of patients with useful motor function (ASIA Grade D or E) increased from seven (41%) preoperatively to 13 (76%) postoperatively. Conclusions. The diagnosis of CCD was frequently delayed, and the delay was associated with an increased likelihood of neurological deterioration. Early diagnosis and spinal stabilization protected against worsening spinal cord injury

Guideline update for the performance of fusion procedures for degenerative disease of the lumbar spine. Part 3: Assessment of economic outcome

pre-printA comprehensive economic analysis generally involves the calculation of indirect and direct health costs from a societal perspective as opposed to simply reporting costs from a hospital or payer perspective. Hospital charges for a surgical procedure must be converted to cost data when performing a cost-effectiveness analysis. Once cost data has been calculated, quality-adjusted life year data from a surgical treatment are calculated by using a preference-based health-related quality-of-life instrument such as the EQ-5D. A recent cost-utility analysis from a single study has demonstrated the long-term (over an 8-year time period) benefits of circumferential fusions over stand-alone posterolateral fusions. In addition, economic analysis from a single study has found that lumbar fusion for selected patients with low-back pain can be recommended from an economic perspective. Recent economic analysis, from a single study, finds that femoral ring allograft might be more cost-effective compared with a specific titanium cage when performing an anterior lumbar interbody fusion plus posterolateral fusion