The Effect of Esophageal Temperature Probes on Postoperative Dysphagia Following Primary Anterior Cervical Discectomy and Fusion: A Randomized Prospective Study

BACKGROUND

The anterior approach to the cervical spine is associated with postoperative dysphagia. It is difficult to predict which patients are most at risk for dysphagia. The objective of this study was to determine if placing an esophageal temperature probe preoperatively would affect the severity and length of postoperative dysphagia. We hypothesize that use of an esophageal temperature probe would result in worse postoperative dysphagia at all measured time points as measured by the Swallowing-Quality of Life (SQAL-QOL) survey after anterior cervical discectomy and fusion (ACDF).

METHODS

A total of 44 patients were enrolled in a prospective, randomized controlled trial and randomized into groups: 1 with an esophageal temperature probe placed at the time of surgery and 2 without. A total of 39 patients filled out postoperative SWAL-QOL questionnaires at their preoperatives. Using the survey results, the data were analyzed between groups and subanalyzed based on number of operative levels and sex.

RESULTS

SWAL-QOL scores for patients undergoing 2-level ACDF with an esophageal temperature probe were significantly better compared with those without a probe at 2 weeks and 6 months postoperatively. These results were not significant at other time points in in the overall analysis, but a trend toward improved dysphagia scores at each time point postoperatively was seen with the probe group. No differences were found between the 2 groups with respect to age at the time of surgery, sex, and preoperative SWAL-QOL score.

CONCLUSIONS

Placement of an esophageal temperature probe at the time of surgery significantly improved postoperative dysphagia scores in patients undergoing 2-level ACDF at 2 weeks and 6 months postoperatively.

LEVEL OF EVIDENCE

2 CLINICAL RELEVANCE: Placement of a temperature probe is a safe and effective technique that is readily available and easily applicable to the practice of spine surgery and may improve postoperative dysphagia after ACDF.

Increased Rates of Septic Shock, Cardiac Arrest, and Mortality Associated With Chronic Steroid Use Following Anterior Cervical Discectomy and Fusion for Cervical Stenosis

OBJECTIVE

Anterior cervical discectomy and fusion (ACDF) is an established treatment modality for cervical spondylosis. Many patients are on immunosuppressant therapy in the management of various inflammatory spinal pathologies and other comorbid conditions. The impact of chronic steroid use on postoperative complications has not been examined in cervical fusion procedures. The objective of this study was to identify specific postoperative complications associated with steroid/immunosuppressant use following ACDF for cervical stenosis.

METHODS

A multi-institutional surgical registry was queried to identify 5377 patients with ACDF diagnosed with cervical stenosis. Patients were stratified into cohorts with a history of steroid/immunosuppressant use for chronic conditions (n = 198, 3.3%) versus those who did not (n = 5179, 96.7%). Propensity-score matching without replacement was implemented to control for preoperative demographics and comorbidities. Pearson χ² and Fischer exact tests were used in comparing the prevalence of demographics, comorbidities, and complication rates.

RESULTS

Upon propensity matching, increased rates of pulmonary embolisms (0.51% vs 0.00%, P = .025), cardiac arrest requiring resuscitation (1.01% vs 0.10%, P = .020), septic shock (0.51% vs 0.00%, P = .025), and mortality (1.52% vs 0.20%, P = .009) in the postoperative 30-day period in patients on chronic steroid/immunosuppressant use were observed.

CONCLUSIONS

The results indicate that steroid use/immunosuppression in patients with ACDF has a higher associated rate of pulmonary embolisms, cardiac arrest, septic shock, and mortality. The risk of mortality and these other complications should be carefully considered prior to operative intervention. Future research may investigate steroid-tapering protocols that reduce the rate of infection and other postoperative complications in the subset of immunosuppressed ACDF patients.

CLINICAL RELEVANCE

By elucidating the complication rates of ACDF patients on steroids for cervical stenosis, orthopedic surgeons can better stratify patients for risk of postoperative morbidity. Surgeons may have deeper risk-benefit discussions with these specific patients before they elect to have the operation.

Risk Factors for Postoperative Urinary Tract Infections Following Anterior Lumbar Interbody Fusion

BACKGROUND

Although risk factors contributing to UTI have been studied in posterior approaches to lumbar fusion, there is a lack of literature on factors contributing to UTI in anterior lumbar interbody fusion (ALIF). Our purpose was to identify preoperative independent risk factors for postoperative urinary tract infection (UTI) following anterior lumbar interbody fusion (ALIF) so that surgeons may be able to initiate preventative measures and minimize the risk of UTI-related morbidity following ALIF.

METHODS

The American College of Surgeons-National Surgical Quality Improvement Program database was queried to identify 10 232 patients who had undergone ALIF from 2005 to 2016; 144 patients (1.41%) developed a postoperative UTI while 10 088 patients (98.59%) did not. Univariate analyses were conducted to compare the 2 cohorts' demographics and preoperative comorbidities. Multivariate logistic regression models were then utilized to identify significant predictors of postoperative UTI following ALIF while controlling for differences seen in univariate analyses.

RESULTS

Age ≥ 60 years (P = .022), female sex (P < .001), alcohol use (P = .014), open wound or wound infections (P = .019), and steroid use (P = .046) were independent risk factors for postoperative UTI. Longer operative times were also independent predictors for developing UTI: 120 minutes ≤ x < 180 minutes (P = .050), 180 minutes ≤ x < 240 minutes (P = .025), and ≥ 240 minutes (P = .001). Postoperative UTI independently increased the risk for pneumonia, blood transfusions, sepsis, thromboembolic events, and extended length of stay as well.

CONCLUSIONS

Age ≥ 60 years, female sex, alcohol use, steroid use, and open wound or wound infections independently increased the risk for UTI following ALIF. Future work analyzing the efficacy of tapering alcohol and steroid use preoperatively and reducing procedural time with the aim of lowering UTI risk is warranted. Preoperative wound care is strongly encouraged to decrease UTI risk.

LEVEL OF EVIDENCE

III.

Characterizing efficiency in the ambulatory surgery setting: An analysis of operating room time and cost savings in orthopaedic surgery

Changing surgical settings for orthopaedic procedures could drive reductions in operative time and reduce healthcare costs. Time-cost differences were calculated using estimated operating room costs by utilizing the ACS-NSQIP database. Multivariate analyses were generated from propensity-matched cohorts to assess differences between inpatient/outpatient outcomes, and whether surgical length increased risk for complications. Outpatient procedures demonstrated time-cost savings of $1716.06. Generally, inpatient procedures demonstrated increased rates of major/minor complications, reoperation, extended LOS, and unplanned readmission (p < 0.001). Overall, longer operative times increased the risk for postoperative complications (p ≤ 0.001). More elective orthopaedic procedures done on an outpatient basis may result in substantial time-cost savings.

The Effect of Alendronate on Subsidence After Lateral Transpsoas Interbody Fusion: A Preliminary Report

Background

Success after lateral transpsoas interbody fusion (LLIF) partially depends on avoidance of subsidence to maintain spinal alignment, disc space height, and indirect neural decompression. Techniques for preventing subsidence have focused largely on surgical and biomechanical properties of spinal reconstruction; however, medical management may also affect subsidence rates as well. The purpose of this study is to examine the effect of alendronate on minimally invasive LLIF patients with regard to radiographic and catastrophic subsidence.

Methods

We followed 26 patients who had LLIF at the L4-5 level (13 on alendronate, 13 control) and 22 patients at the L3-4 level (10 on alendronate, 12 control). Radiographs were reviewed to obtain measurements of subsidence at the 4 corners of the cage at 3 follow-up time points (2-3, 5-8, and 10-12 months). A Tobit mixed model was used to confirm the results.

Results

We found no relationship between alendronate and subsidence for L3-4 fusion. At L4-5 we observed increased subsidence in the control group compared to the alendronate group (difference = 0.07 cm, 95% confidence interval [CI]: -0.01, 0.16, P = .08). There was a decrease in subsidence noted for the alendronate group for each time period (differences: 2-3: -0.06 cm, 95% CI: -0.28, 0.15], P = .27; 5-8: -0.14 cm, 95% CI: -0.36, .08, P = .10; 10-12: -0.21 cm, 95% CI: -0.48, .04, P = .05).

Conclusions

A clear reduction in subsidence was found with the use of postoperative alendronate in patients undergoing L4-5 LLIF. Alendronate had a significant decrease in subsidence at L4-5 after 10-12 months as compared to the control group. Additionally, no patients treated with alendronate had catastrophic subsidence. These data suggest the need for further study of alendronate in the prevention of subsidence after LLIF.

Level of Evidence

3.

Far-lateral Disc Herniation Treated by Lateral Lumbar Interbody Fusion without Complete Fragment Excision: A Case Report and Review of the Literature

Symptomatic far-lateral lumbar disc herniation is a less common causes of lumbar radiculopathy than paracentral or central disc herniation. Treatment of far-lateral disc herniation with a retroperitoneal, transpsoas approach and disc fragment excision has been described. However, treatment of far-lateral disc herniation using lateral lumbar interbody fusion (LLIF) without neural manipulation has not been described. We report one case in which symptom resolution was accomplished via indirect decompression with anterior column support via LLIF without disc fragment excision and review the current literature. The patient noted immediate relief of his preoperative leg pain in the recovery room and ambulation began the same day. Narcotics were effective in treating his incisional pain and mild back pain. The patient was seen two weeks postoperatively and he had stopped all narcotics. At six weeks, the patient continued to have significant improvement and was able to take hour-long walks. At five months, the patient did not have any pain and continued to have improvement in his left quadriceps strength. Minimally invasive lateral lumbar interbody fusion has allowed surgeons to provide both direct and indirect neural decompression through a retroperitoneal approach. This technique may be ideal for far-lateral disc herniation as it also allows a lateral visualization of the herniation without bony, posterior muscular, or ligamentous disruption.

Anterior Lumbar Interbody Fusion With Cement Augmentation Without Posterior Fixation to Treat Isthmic Spondylolisthesis in an Osteopenic Patient-A Surgical Technique

Background

Anterior lumbar interbody fusion (ALIF) has been well established as an effective surgical intervention for chronic back pain due to osteoporotic vertebral collapse. Historically, ALIF has consisted of an anterior approach to disc height restoration with a subsequent posterior pedicle screw fixation. Although the applications of cement augmentation with posterior fixation have been previously reported, treatment of patients with both isthmic spondylolisthesis and decreased bone mineral density using a stand-alone ALIF is controversial because of concerns for decreased fusion rates and increased subsidence risk, respectively. We report a case of stand-alone ALIF used to treat a low-grade isthmic spondylolisthesis in the setting of idiopathic thoraco-lumbar scoliosis in a patient with secondary degenerative changes and discuss the benefits of this surgical technique in a patient with several comorbidities.

Methods

An osteopenic 66-year-old woman with multiple medical comorbidities and 2 years of left radicular leg pain was found to have a Myerding grade I isthmic spondylolisthesis in the setting of idiopathic thoraco-lumbar scoliosis with secondary changes. The patient underwent an L5-S1 stand-alone ALIF with anterior cement augmentation without posterior pedicle screw fixation.

Results

The patient experienced immediate relief of radicular leg pain postoperatively and had an uneventful course. At 2 years follow-up, she remained symptom free, and radiographs showed excellent fusion and maintenance of intervertebral disc height.

Conclusions

The use of stand-alone ALIF with anterior cement augmentation of the vertebral bodies is a surgical technique that could produce excellent improvement in patients with low-grade isthmic spondylolisthesis in the setting of osteopenia. The use of the all-anterior approach in similar patients with multiple medical comorbidities can also be a useful technique, as it decreases associated morbidity of surgery and complication risks associated with prolonged operative times.

Clinical and radiographic analysis of expandable versus static lateral lumbar interbody fusion devices with two-year follow-up

Background

Utilization of static and expandable interbody spacers for minimally invasive lateral lumbar interbody fusion (LLIF) offers favorable clinical results. However, complications such as implant migration and/or subsidence may occur with a static implant. Expandable devices allow for in situ expansion to optimize fit and mitigate iatrogenic endplate damage during trialing and impaction. This study sought to compare clinical and radiographic outcomes of static and expandable spacers following LLIF and report device-related complications.

Methods

This study included 29 patients who underwent LLIF with a static spacer and 27 with an expandable spacer; all procedures were combined with supplemental transpedicular posterior fixation. Patient self-assessment forms and radiographic records were used to assess clinical and radiologic outcomes.

Results

Mean patient age was 62.3±10.3 years (64% female). One-level surgery was performed in 87.5% of patients, and 12.5% underwent two-level surgery. Results showed no significant differences in blood loss or length of hospital stay (P>0.05). However, operative times differed statistically between static (63.3±37.8 min) and expandable (120.2±59.6 min) groups (P=0.000). Mean visual analog scale (VAS) and Oswestry Disability Index (ODI) scores improved significantly from preoperative to 24-month follow-up in both groups (P<0.05). Preoperative intervertebral and neuroforaminal height increased significantly in both groups (P<0.01). Fusion was observed in all operative levels in the static and expandable spacer groups by 24-month follow-up. Implant subsidence was reported in 16.1% of static levels and none of the expandable levels (P<0.01). Postoperative radiographs showed no evidence of implant migration, and no cases required surgical revision at the index or adjacent levels.

Conclusions

LLIF using expandable spacers resulted in similar clinical and radiographic outcomes when compared with using static spacers, and led to a lower subsidence rate.

The unusual presentation of a vascular injury after lumbar microdiscectomy: case report

Vascular injury during lumbar spine surgery is a relatively rare complication but can have devastating outcomes. The injury may not be apparent during surgery and can present acutely or late in various manners, and some injuries can be asymptomatic. This report discusses the unusual case of a 35-year-old woman who underwent a right L4-5 microdiscectomy for disc herniation and 4 days postoperatively presented with a pulmonary embolus. A subsequent CT scan revealed a pseudoaneurysm and arteriovenous fistula of the right common iliac vein and artery, which gave rise to the embolus. The patient received a right iliac artery stent, and at 4 months after surgery she continues to be symptom free. This report describes the atypical presentation of vascular injury after lumbar microdiscectomy and stresses the importance of cautiously using the pituitary rongeur when removing deeper disc fragments.

Biomechanical analysis of an expandable lateral cage and a static transforaminal lumbar interbody fusion cage with posterior instrumentation in an in vitro spondylolisthesis model

OBJECTIVE

Insufficient biomechanical data exist from comparisons of the stability of expandable lateral cages with that of static transforaminal lumbar interbody fusion (TLIF) cages. The purpose of this biomechanical study was to compare the relative rigidity of L4-5 expandable lateral interbody constructs with or without additive pedicle screw fixation with that of L4-5 static TLIF cages in a novel cadaveric spondylolisthesis model.

METHODS

Eight human cadaver spines were used in this study. A spondylolisthesis model was created at the L4-5 level by creating 2 injuries. First, in each cadaver, a nucleotomy from 2 channels through the anterior side was created. Second, the cartilage of the facet joint was burred down to create a gap of 4 mm. Light-emitting-diode tracking markers were placed at L-3, L-4, L-5, and S-1. Specimens were tested in the following scenarios: intact model, bilateral pedicle screws, expandable lateral 18-mm-wide cage (alone, with unilateral pedicle screws [UPSs], and with bilateral pedicle screws [BPSs]), expandable lateral 22-mm-wide cage (alone, with UPSs, and with BPSs), and TLIF (alone, with UPSs, and with BPSs). Four of the spines were tested with the expandable lateral cages (18-mm cage followed by the 22-mm cage), and 4 of the spines were tested with the TLIF construct. All these constructs were tested in flexion-extension, axial rotation, and lateral bending.

RESULTS

The TLIF-alone construct was significantly less stable than the 18- and 22-mm-wide lateral lumbar interbody fusion (LLIF) constructs and the TLIF constructs with either UPSs or BPSs. The LLIF constructs alone were significantly less stable than the TLIF construct with BPSs. However, there was no significant difference between the 18-mm LLIF construct with UPSs and the TLIF construct with BPSs in any of the loading modes.

CONCLUSIONS

Expandable lateral cages with UPSs provide stability equivalent to that of a TLIF construct with BPSs in a degenerative spondylolisthesis model.

3D nano/microfabrication techniques and nanobiomaterials for neural tissue regeneration

Injuries of the nervous system occur commonly among people of many different ages and backgrounds. Currently, there are no effective strategies to improve neural regeneration; however, tissue engineering provides a promising avenue for regeneration of many tissue types, including the neural context. Functional nerve conduits derived from tissue engineering techniques present bioengineered 3D artificial substitutes for implantation and rehabilitation of injured nerves. In particular, nanotechnology as a versatile vehicle to create biomimetic nanostructured tissue-engineered neural scaffolds provides great potential for the development of innovative and successful nerve grafts. Nanostructured conduits derived from traditional and novel tissue engineering techniques have been shown to be superior for successful neural function construction due to a high degree of biomimetic character. In this paper, we will focus on current progress in developing 3D nano/microstructured neural scaffolds via electrospinning, emerging 3D printing and self-assembly techniques, nanobiomaterials and bioactive cues for enhanced neural tissue regeneration.

Recent advances in the prevention and management of complications associated with routine lumbar spine surgery

Lumbar spine surgery is often associated with complications in the perioperative and postoperative periods. Evidence-based literature in the prevention and management of adverse events, including surgical site infection, venous thromboembolism, and positioning-related complications, has advanced the understanding of the etiology of these complications and preventive measures. Cost-effective measures to reduce intraoperative bleeding can lead to a lower incidence of infection, disease transmission, and morbidity in the postoperative period. As the healthcare system receives additional scrutiny with value-based assessments, surgeons, hospitals, and administrators will need to make critical decisions to prevent and manage the complications of lumbar spine surgery.

Use of vertebroplasty to prevent proximal junctional fractures in adult deformity surgery: a biomechanical cadaveric study

BACKGROUND CONTEXT

Vertebral compression fractures at the proximal junction are common complications of long spinal fusion surgeries that can contribute to the development of proximal junctional kyphosis or proximal junctional failure. To our knowledge, no biomechanical studies have addressed the effect of vertebral augmentation at the proximal junction.

PURPOSE

To evaluate the effectiveness of prophylactic vertebroplasty in reducing the incidence of vertebral compression fractures at the proximal junction after a long spinal fusion in a cadaveric spine model.

STUDY DESIGN

Biomechanical cadaveric study.

METHODS

We divided 18 cadaveric spine specimens into three groups of six spines each: a control group, a group treated with one-level prophylactic vertebroplasty at the upper instrumented vertebra, and a group treated with two-level prophylactic vertebroplasty at the upper instrumented vertebra and the supra-adjacent vertebra. In all spines, the pedicles were instrumented from L5 to T10. Using eccentric axial loading, the specimens were then compressed until failure. Failure was defined as a precipitous decrease in load with increasing compression. The effect of augmentation on load-to-failure was checked using linear regression. The effect of augmentation on incidence of adjacent fractures was checked using logistic regression. Differences at the level of p<.05 were considered significant. KyphX cement introducer was donated by Kyphon, and the pedicle screws were donated by DePuy.

RESULTS

Fractures occurred in 12 of 18 specimens: five in the control group, six in the one-level group, and only one in the two-level group; these differences were statistically significant.

CONCLUSIONS

Prophylactic vertebroplasty at the upper instrumented level and its supra-adjacent vertebra reduced the incidence of junctional fractures after long posterior spinal instrumentation in this axially loaded cadaveric model. Additional studies are necessary to determine if these results are translatable to clinical practice.

Deep vein thrombosis and pulmonary embolism after spine surgery: incidence and patient risk factors

Anticoagulation after spine surgery confers the unique risk of epidural hematoma. We sought to determine the incidence of and patient risk factors for deep vein thrombosis (DVT) and pulmonary embolism (PE) after spine surgery. We retrospectively reviewed the charts of 1485 patients who had spine surgery at a single tertiary-care center between 2002 and 2009. DVT and PE incidence were recorded along with pertinent patient history information. Univariate and multivariate analyses were performed on the data. VTE incidence was 1.1% (DVTs, 0.7%; PEs, 0.4%). Univariate analysis demonstrated that VTEs had 9 positive risk factors: active malignancy, prior DVT or PE, estrogen replacement therapy, discharge to a rehabilitation facility, hypertension, major depressive disorder, renal disease, congestive heart failure, and benign prostatic hyperplasia (P<.05). Multivariate analysis demonstrated 4 independent risk factors: prior DVT or PE, estrogen replacement therapy, discharge to a rehabilitation facility, and major depressive disorder (P>.05). Surgeons with an improved understanding of VTE after spine surgery can balance the risks and benefits of postoperative anticoagulation.

Anatomical feasibility of C-2 pedicle screw fixation: the effect of variable angle interpolation of axial CT scans

OBJECT

Anatomical variability of the C-2 pedicle poses a challenge for C-2 fixation. The use of multidimensional CT scanning is not widely used but might be an asset to preoperative planning. Careful preoperative planning is imperative for instrumentation at C-2. Fine-cut, noncontrast CT scanning is a useful tool for delineating anatomy; however, the axis of the images is not always along the anatomical axis of the vertebra in question. The authors evaluated the suitability of C-2 pedicles for screw placement by using OsiriX (Pixmeo) software to change the gantry angle of CT angiograms to measure the anatomical dimensions of the C-2 pedicle.

METHODS

The authors conducted a retrospective review of CT angiograms of the head and neck from 47 trauma patients seen consecutively at George Washington University Hospital. For each patient, 3 independent observers determined length and width of each C-2 pedicle (94 samples) by using OsiriX. OsiriX is a DICOM viewer that enables navigation and visualization in multidimensional imaging, such as 3D imaging, which was used for this study. Sex-specific measurements were also determined. Vertebral anatomy was studied to determine whether aberrant anatomy would preclude pedicle fixation. Statistical analyses were performed.

RESULTS

Of the 47 patients, 27 were male. Overall mean C-2 pedicle widths and lengths were 8.272 ± 1.364 mm and 27.052 ± 3.471 mm, respectively. The average widths and lengths of the pedicle in female patients were 8.040 ± 1.262 mm and 27.241 ± 2.731 mm, respectively, and those in male patients were 8.444 ± 1.414 mm and 26.913 ± 3.933 mm, respectively. The sex difference was statistically significant for width (p = 0.012) but not for length (p = 0.41). On the basis of width, the percentages of pedicles that could tolerate a 3.5-mm and 4.0-mm screw were 98% and 97%, respectively. Vertebral anatomy precluded screw length greater than 14 mm for only 3 patients.

CONCLUSIONS

Using multidimensional CT or 3D imaging, the authors found that C-2 pedicles in over 90% of patients could tolerate 3.5-mm and 4.0-mm pedicle screws. Vertebral anatomy precluded use of screw lengths greater than 14 mm for only 3 (6%) of 47 patients. Therefore, the C-2 pedicle might be more tolerant of fixation than previously reported.

A novel radiographic targeting guide for percutaneous placement of transfacet screws in the cervical spine with limited fluoroscopy: A cadaveric feasibility study

Background

We describe a technique for percutaneous transfacet screw placement in the cervical spine without the need for lateral-view fluoroscopy.

Methods

Previously established articular pillar morphometry was used to define the ideal trajectory for transfacet screw placement in the subaxial cervical spine. A unique targeting guide was developed to allow placement of Kirschner wires across the facet joint at 90° without the guidance of lateral-view fluoroscopy. Kirschner wires and cannulated screws were placed percutaneously in 7 cadaveric specimens. Placement of instrumentation was performed entirely under modified anteroposterior-view fluoroscopy. All specimens were assessed for acceptable screw placement by 2 fellowship-trained orthopaedic spine surgeons using computed tomography. Open dissection was used to confirm radiographic interpretation. Acceptable placement was defined as a screw crossing the facet joint, achieving purchase in the inferior and superior articular processes, and not violating critical structures. Malposition was defined as a violation of the transverse foramen, spinal canal, or nerve root or inadequate fixation.

Results

A total of 48 screws were placed. Placement of 45 screws was acceptable. The 3 instances of screw malposition included a facet fracture, a facet distraction, and a C6-7 screw contacting the C7 nerve root in a specimen with a small C7 superior articular process.

Conclusions

Our data show that with the appropriate radiographic technique and a targeting guide, percutaneous transfacet screws can be safely placed at C3-7 without the need for lateral-view fluoroscopy during the targeting phase. Because of the variable morphometry of the C7 lateral mass, however, care must be taken when placing a transfacet screw at C6-7.

Clinical Relevance

This study describes a technique that has the potential to provide a less invasive strategy for posterior instrumentation of the cervical spine. Further investigation is needed before this technique can be applied clinically.

Superconductivity in the Einstein solid VAl(10.1)

We used magnetic susceptibility, resistivity and heat capacity measurements to characterize the superconducting state in the Einstein solid VAl(10.1). We find that VAl(10.1) is a weak-coupling, type-II superconductor with T(c) = 1.53 K and an upper critical field of H(c2)(0) = 800 Oe. The heat capacity data in the range 0.07 K < T < 1.53 K are consistent with an isotropic energy gap of Δ(0) = 0.23 meV.

Traumatic C4-C5 unilateral facet dislocation with posterior disc herniation above a prior anterior fusion

We report the case of a unilateral cervical facet dislocation above the level of a prior non-instrumented cervical discectomy and fusion, resulting in incomplete neurologic injury. Pre-reduction imaging demonstrated a large posterior disk extrusion. This finding altered our management approach from closed reduction to urgent anterior cervical discectomy, open anterior reduction, and fusion. The patient had excellent neurologic recovery and outcome at 12 months postoperative follow-up.

Anatomical parameters of subaxial percutaneous transfacet screw fixation based on the analysis of 50 computed tomography scans: Clinical article

OBJECT

Cervical transfacet screw placement has been described in the literature. Although the technique shows promise for percutaneous application, parameters for screw placement have not been well delineated. This study used reconstructed CT scans with imaging software to assess the feasibility of percutaneous transfacet screw placement, analyzing potential entry angles, transfacet lengths, and sex differences at each subaxial level.

METHODS

Fifty consecutive cervical CT scans (obtained in 26 males and 24 females [mean age 41.5 years]) were reformatted using OsiriX software, and transfacet lengths, entry angles, and potential occipital clearance were analyzed at all subaxial levels. Statistical analyses were used to determine the differences, if any, between transfacet lengths, entry angle, and occipital clearance across individual cervical levels. Repeatability was quantified by calculating the intraclass correlation coefficient and Cohen kappa value.

RESULTS

A total of 200 transfacet lengths and 200 entry angles in 50 patients were analyzed. The mean transfacet lengths were 17.9 ± 2.6, 17.6 ± 3.2, 16.3 ± 3.6, and 13.1 ± 2.2 mm at C3-4, C4-5, C5-6, and C6-7, respectively, with mean entry angles at 52.7° ± 7.8°, 56.5° ± 8.0°, 55.0° ± 8.8°, and 53.0° ± 8.7°, respectively. Analysis of variance revealed a significant difference between the mean transfacet lengths, while post hoc analysis revealed significantly larger transfacet lengths in the upper 2 cervical levels (C3-4 and C4-5) than in the lower 2 cervical levels (C5-6 and C6-7). Analysis of variance demonstrated no significant difference between the entry angles. Males had significantly larger transfacet lengths at C5-6 (17.4 vs 15.1 mm) and C6-7 (13.7 vs 12.4 mm) than females. The occiput would have blocked percutaneous screw placement in 86%, 78%, 54%, and 20% of the cases at C3-4, C4-5, C5-6, and C6-7, respectively. Transfacet lengths may accommodate longer screws in the upper cervical spine, but potential screw sizes decrease in the lower subaxial levels. A transfacet entry angle of approximately 50° or greater was associated with a higher incidence of occipital clearance. Additionally, the occiput may pose a significant obstruction to percutaneous transfacet fixation in upper subaxial levels. Interrater reliability was poor for screw angle and length measurements, but was satisfactory in intrarater analysis in 6 of 8 measurements. There was moderate to good agreement of occipital clearance in all but one measurement.

CONCLUSIONS

Cervical transfacet screw placement is possible from C-3 to C-7. Because occipital clearance can be difficult at C3-4 and C6-7, the use of curved or flexible instruments may be necessary to obtain the appropriate screw trajectory. Screw lengths varied with spinal level and the sex of the patient.

Minimally invasive lumbopelvic instrumentation for traumatic sacrolisthesis in an elderly patient

PURPOSE

We present a novel minimally invasive technique for lumbopelvic instrumentation in selected elderly patients suffering from traumatic sacrolisthesis. An 82-year-old female suffered from sacrolisthesis after a fall. She developed significant low back pain and bilateral lower extremity radiculopathy. Preoperative radiographs and magnetic resonance imaging sequences demonstrated the fracture dislocation between S1 and S2 with compromise of the spinal canal. Lumbopelvic instrumentation was sought to offer fixation and allow mobilization; however, open lumbopelvic instrumentation techniques have significant morbidity, especially in this patient population of elderly patients with medical comorbidities.

METHODS

A minimally invasive technique employing percutaneous pedicle screws at L5 and S1 coupled with percutaneous S2 iliac screws was employed.

RESULTS AND CONCLUSIONS

The patient tolerated the procedure well without any complications or morbidity. At the last follow-up of 14 months, she was ambulating without assistance with near total resolution of back pain and radicular pain. Radiographs obtained at 8 months' follow-up demonstrated fusion across the fracture line. Although further follow-up data is still needed to establish the durability of this technique in the long-term, this minimally invasive technique for lumbopelvic instrumentation can be considered as an option in elderly patients with traumatic sacrolisthesis, whose need for early mobilization and medical comorbidities preclude the use of an open lumbopelvic fixation procedure.

Occipitocervical junction: imaging, pathology, instrumentation

The occipitocervical junction (OCJ) is a highly specialized area of the spine. Understanding the unique anatomy, imaging, and craniometry of this area is paramount in recognizing and managing the potentially devastating effects that pathology has on it. Instrumentation techniques continue to evolve, the goal being to safely obtain durable, rigid constructs that allow immediate stability, anatomical alignment, and osseous fusion. This article reviews the pathologic conditions at the OCJ and the current instrumentation and fusion options available for treatment. The general orthopedist needs to recognize the pathology common in this region and appropriately refer patients for treatment.

The anatomic suitability of the C2 vertebra for intralaminar and pedicular fixation: a computed tomography study

BACKGROUND CONTEXT

Several methods have been used to stabilize the atlantoaxial joint, including the use of C2 pedicle and laminar screws. No report has used computed tomography (CT) angiograms to compare the risk to the vertebral artery or assess the suitability for each fixation technique.

PURPOSE

To compare the suitability of C2 pedicle versus laminar screws using CT angiograms.

STUDY DESIGN

We retrospectively evaluated the anatomic dimensions of the C2 lamina and pedicle in 50 patients using CT angiograms.

METHODS

We retrospectively reviewed the last 50 patients admitted who underwent CT angiograms of the head and neck. Data recorded included the pedicle length and width and the laminar length and width. Vertebral artery anatomy was also assessed to determine if an aberrant location would preclude pedicle fixation.

RESULTS

Mean pedicle length and width were 15.5±3.5 and 4.7±1.7 mm, respectively, with 24% of patients having anatomy that would preclude 3.5-mm pedicle screw fixation. The mean lamina length and width were 25.2±3.6 and 5.5±1.4 mm, and more than 90% of patients could tolerate a 3.5-mm C2 laminar screw.

CONCLUSION

Preoperative CT angiography or noncontrast CT is an excellent method to delineate the anatomy at C2 to determine the suitability for pedicle or intralaminar fixation. In cases where vertebral artery anatomy precludes C2 pedicle fixation, more than 90% of patients may be a candidate for C2 intralaminar fixation.

Unconventional T-H phase diagram in the noncentrosymmetric compound Yb2Fe12P7

The temperature-(T-)magnetic-field (H) phase diagram for the noncentrosymmetric compound Yb(2)Fe(12)P(7), [corrected] determined from electrical resistivity (ρ), specific heat (C), and magnetization (M) measurements on single crystal specimens, is reported. This system exhibits a crossover from a magnetically ordered non-Fermi-liquid (NFL) phase at low H to another NFL phase at higher H. The crossover occurs near the value of H where the magnetic ordering temperature (T(M)) is no longer observable in C(T,H)/T and ρ(T,H), but not where T(M) extrapolates smoothly to T=0 K at a possible quantum critical point (QCP). This indicates the occurrence of a quantum phase transition between the two NFL phases. The lack of a clear relationship between the extrapolated QCP and NFL behavior suggests an unconventional route to the NFL ground states.

An S-2 alar iliac pelvic fixation. Technical note

Multiple techniques of pelvic fixation exist. Distal fixation to the pelvis is crucial for spinal deformity surgery. Fixation techniques such as transiliac bars, iliac bolts, and iliosacral screws are commonly used, but these techniques may require separate incisions for placement, leading to potential wound complications and increased dissection. Additionally, the use of transverse connector bars is almost always necessary with these techniques, as their placement is not in line with the S-1 pedicle screw and cephalad instrumentation. The S-2 alar iliac pelvic fixation is a newer technique that has been developed to address some of these issues. It is an in-line technique that can be placed during an open procedure or percutaneously.

Open reduction of C1-C2 subluxation with the use of C1 lateral mass and C2 translaminar screws

OBJECTIVE

Spinal cord compression secondary to a subluxation of one vertebral body over another can be achieved with reduction of the translational deformity. Intraoperative reduction of C1-C2 subluxations can be technically challenging when one uses traditional techniques (e.g., wiring and transarticular screw fixation). The popularization of C1 lateral mass and C2 pedicle screws has allowed surgeons to achieve a more complex realignment at this region of the spine. Control of both C1 and C2 with independent fixation can be used to obtain reduction. In certain instances, placement of C2 pedicle screws is not possible. The use of C2 translaminar screws (if the C2 lamina is present and suitable) is an alternative method of fixation in C2 and can be used for intraoperative reduction.

CLINICAL PRESENTATION

A 15-year-old boy with juvenile rheumatoid arthritis presented with spinal cord compression secondary to a C1-C2 subluxation. The C2 pedicle anatomy precluded safe placement of C2 pedicle screws. An alternative method of fixation with the use of C2 translaminar screws and reduction was performed to obtain proper alignment and decompress the spinal cord.

TECHNIQUE

C1 lateral mass screws and C2 translaminar screws are inserted in the usual fashion. Two contoured rods, two rod holders, and two distractors, combined with C1 lateral mass screws and C2 translaminar screws, were used to achieve reduction. Concomitant distraction between the C2 translaminar screw head and the rod holder resulted in ventral translation of C2 on C1, decompressing the spinal cord. The reduction was maintained by tightening the C2 locking nut onto the rod.

CONCLUSION

The use of C2 translaminar screws (if the C2 lamina is present and suitable) is an alternative method of fixation in C2. C1 lateral mass and C2 translaminar screw fixation provide a powerful means of reducing C1-C2 subluxations and maintaining alignment, achieving indirect decompression of the spinal cord.

Platelet and other tests followed sequentially for 14 days after operation

Nineteen patients were studied twice before and sequentially from 1 h to 14 days after operations lasting about 1 h. Eighteen tests were carried out, ideally on all the nine occasions blood collections were planned. Only significant changes are summarized. Immediately after the operation the plasma PF4 and beta TG were raised in parallel suggesting some platelet 'release' had occurred. At this time platelet aggregation to ADP and collagen had decreased by 57% to 64% and the plasma cyclic AMP had doubled. Next day these abnormalities had returned towards normal. By day 2 the fibrinogen and the heparin neutralizing activity were maximal; they returned towards normal by day 14. On day 14, when presumably all platelets present at operation had been removed the new platelets were 53% more numerous and 9.5% smaller; they contained 23% less PF4 and 42% less serotonin and 5-HT uptake was decreased, but the total amount of 5-HT and PF4 in the circulation probably remained constant. In summary these operations transitorily upset platelet function for a few hours and the platelets formed postoperatively were abnormal.

Superconductivity in heavy alkaline-Earth intercalated graphites

We report the discovery of superconductivity below 1.65(6) K in Sr-intercalated graphite SrC(6), by susceptibility and specific heat (C(p)) measurements. In comparison with CaC(6), we found that the anisotropy of the upper critical fields for SrC(6) is much reduced. The C(p) anomaly at T(c) is smaller than the BCS prediction, indicating an anisotropic superconducting gap for SrC6 similar to CaC6. The significantly lower T(c) of SrC(6) as compared to CaC(6) can be understood in terms of "negative" pressure effects, which decreases the electron-phonon coupling for both in-plane intercalant and the out-of-plane C phonon modes. We observed no superconductivity for BaC(6) down to 0.3 K.

Esophageal injury from thoracic pedicle screw placement in a polytrauma patient: a case report and literature review

The authors present a case report illustrating a visceral complication that may occur as result of thoracic pedicle screw placement. The case describes the previously unreported occurrence of esophageal impingement secondary to anterior vertebral body perforation by a pedicle screw at the third thoracic vertebra. This case highlights the challenge of thoracic pedicle screw placement and the importance of preoperatively measuring the maximum anterior-posterior dimension of the vertebral body.

White cell retention compared with platelet retention in the filterometer: controls and abnormal states

Platelets and white cells contribute to thrombus formation. In the filterometer, platelet retention in normal citrated blood increases from 47.5% at 0-5 s to 81.5% at 20-40 s. White cell retention is normally closely related to platelet retention at 0-5 s but less so at 20-40 s. However at 20-40 s the number of white blood cells (WBC) retained has decreased relative to 0-5 s. This apparent paradox is now further explored using antibodies to glycoprotein (GP) Ib, to von willebrand factor (vWf) and to GPIIb-IIIa together with observations on a number of clinical conditions with abnormal platelet retention. In citrated blood, platelet retention of 0-5 s was significantly decreased relative to normal in von Willebrand's disease, in aortic valve stenosis and with the addition of anti-vWf-GPIb and minimally with anti-GPIIb-IIIa antibodies. WBC retention of 0-5 s in these groups was always 41 2%. However when platelet retention 0-5 s was raised (pregnancy and venous occlusion), white cell retention was also raised. At 20-40 s in all the nine conditions studied, the white cell and platelet retention were closely related, but the percentage WBC retained decreased relative to the platelet retention. Granulocyte retention was higher than lymphocyte retention, but both cell types were similarly affected. We conclude that the platelets are retained as previously described. The white cells (all types) initially bind at least in part in an independent unexplained way (0-5 s). Thereafter the degree of platelet activity (retention %) largely determines the degree of WBC retention. This is probably due to a proportional amount of P-selectin liberated by the activated platelets.

Slow spin relaxation in a highly polarized cooperative paramagnet

We report measurements of the ac susceptibility of the cooperative paramagnet Tb2Ti2O7 in a strong magnetic field. Our data show the expected saturation maximum in chi(T) and also an unexpected frequency dependence of this peak at low frequencies (<1 Hz), suggesting very slow spin relaxations are occurring. Measurements on samples diluted with nonmagnetic Y3+ or Lu3+ and complementary measurements on pure and diluted Dy2Ti2O7 strongly suggest that the relaxation is associated with dipolar spin correlations, representing unusual cooperative behavior in a paramagnetic system.

Bleeding time, stroke and myocardial infarction: the Caerphilly prospective study

The stressed bleeding time is a simple 'global' test of haemostasis, dependent upon platelet function, rheology, thrombosis and intimal function. It could be of considerable value in clinical practice if it were shown to be predictive of vascular disease events. A stressed bleeding time test was done on 1319 men aged 55-69 years in the Caerphilly Cohort Study of Heart Disease, Stroke and Cognitive Decline. The men were followed-up and during the following 7-10 years 155 men had a myocardial infarction (MI) and 72 an ischaemic stroke. The mean bleeding time was 323 (SD 113)s. This was shorter in men who smoked by an average of 45 s, and lengthened in men who took aspirin daily by 40s. After making statistical adjustments for numerous possible confounding factors, the relative odds (ROs) of an MI within the third of men with the longest bleeding times, compared to the third with the shortest times, was 0.90 (0.40-2.03). For ischaemic stroke, the ROs in the third of men with the longest times were 1.42 (0.39-5.21). The stressed bleeding time does not predict either MI or ischaemic stroke. It has no place in health screening.

Platelet tests in the prediction of myocardial infarction and ischaemic stroke: evidence from the Caerphilly Prospective Study

A platelet test that is predictive of myocardial infarction (MI) and/or stroke would enable the targeting of anti-platelet drugs towards high-risk patients. The predictive power of several platelet tests for MI and for stroke was examined in 2000 older men in the Caerphilly Cohort Study of Heart Disease, Stroke and Cognitive Decline. The tests were: aggregation to adenosine diphosphate (ADP) in platelet-rich plasma (PRP); aggregation to ADP in whole blood measured using an impedance method and a test of platelet aggregation induced in whole blood by high-shear flow. Around 200 MIs and 100 ischaemic strokes occurred during a 10-year follow-up. Neither primary nor secondary aggregation in PRP was predictive of MI. However, the fifth of men in whom the primary response to ADP was least, showed the highest risk of a subsequent stroke [relative odds (RO) 1.64; 95% confidence interval (CI) 1.12-2.43]. Aggregation in whole blood was not predictive of MI but, again, the fifth of men with the least platelet response showed the highest stroke incidence (RO 1.79; 95% CI 1.06-3.00). Retention of platelets in the high-shear test was not predictive of either event.

A comparison of von Willebrand Factor antigen with platelet activity in vitro in normal and venous occlusion blood

Von Willebrand Factor (vWF) is essential for normal haemostasis involving platelet aggregation induced by high shear forces. In vitro a functional test of platelet aggregation using the filterometer is abnormal in von Willebrand's disease. However in normal people there is no significant correlation between the antigenic assay of vWF and the filter results. To study this discrepancy normal blood before and during venous occlusion, and blood before and after infusion of 1 deamino-(8-D-arginine) vasopressin was studied. During venous occlusion (VO) the increase in vWF due to the release of large multimers correlated precisely with the increase in the filterometer results. That this was due to the plasma vWF and not to any change induced in the platelets was shown as follows: The methodology was altered so that a small amount of the donor's platelet-poor plasma (PPP) was added to homologous normal substrate blood. The effect of the added donor's PPP was then shown to be closely correlated to the increase in the antigenic assay. Analysis of vWF multimer size showed during VO an increase in large multimers. We conclude that the effect of vWF on normal blood may be obscured by variation in platelet aggregability. In the filterometer system as elsewhere the large active multimers probably play a major part in causing platelet adhesion, aggregation and filter blocking. The filterometer test is influenced by the amount of vWF antigen, by the molecular size and activity of the vWF and by platelet sensitivity. Clinically this is a useful global test.

Defective von willebrand factor activity detected by the filterometer in three clinical conditions

When exposed to high levels of shear in a filterometer, platelets bind to von Willebrand factor (vWF) via receptors Ib and IIb/IIIa, forming aggregates that block the filteromer. In this study we used the filterometer to explore the mechanisms by which abnormal vWF-platelet interaction might occur. In the first phase of the study, the global vWF-platelet interaction in native blood was investigated. In the second phase, to eliminate the difference that platelets might contribute, samples of platelet-poor plasma from test individuals were added to normal control blood and the mixtures were investigated by the filterometer. The filterometer results were adjusted for the antigen concentrations to obtain vWF potency ratios. Sodium dodecyl sulphate (SDS) agarose gel electrophoresis and SDS-Polyacylamide gel electrophoresis (PAGE) were used to analyze multimeric size and proteolytic profiles of vWF. Pregnancy was associated with high platelet retention, high vWF antigen concentration, normal multimeric size distribution, but decreased vWF potency ratios. The plasma samples of pregnancy contained one 183-kDa fragment not detected in normal plasma. These results suggested that in pregnancy, platelets were highly active. However, presumably due to abnormal proteolytic cleavage, vWF potency was decreased. This decrease in vWF potency might minimize the risk of thrombosis in association with highly active platelets. Renal transplant patients had normal platelet retention but high vWF levels. The plasma vWF contained normal multimers. A decrease in vWF potency, presumably caused by toxic inhibitors in the plasma, was detected. Aortic valve stenosis patients had decreased platelet retention, normal or slightly increased vWF antigen concentration and a decrease in large multimers. As a result, the vWF potency was markedly decreased. However, the results obtained with the filterometer became normal when the studies were repeated 3 months postpartum, when renal function had improved after transplantation, and when the aortic valves were corrected by surgery. These results indicate that the filterometer is a useful tool for elucidating the mechanisms by which vWF-platelet interaction might be impaired in various clinical conditions.

Platelet aggregation and incident ischaemic heart disease in the Caerphilly cohort

BACKGROUND

Platelets are involved in myocardial infarction but evidence of prediction of infarction by measures of platelet function are sparce.

METHODS

Platelet aggregation to thrombin and to ADP in platelet rich plasma was recorded for 2176 men aged 49-65 years in the Caerphilly cohort study.

RESULTS

Results from 364 men were excluded, 80 of whom had not fasted before venepuncture; most of the others were excluded because antiplatelet medication had been taken shortly before the platelet tests. During the five years following the platelet tests 113 ischaemic heart disease (IHD) events which fulfilled the World Health Organisation criteria were identified--42 fatal and 71 non-fatal. No measure of platelet aggregation was found to be significantly predictive of incident IHD. The possibility that platelet function is predictive for only a limited time after it is characterised, and that prediction falls off with time, was tested. When IHD events are grouped by their time of occurrence after aggregation had been measured, the test results show a gradient suggestive of prediction of early IHD events. Thus, 24% of the men who had an event within 500 days of the test had had a high secondary response to ADP while only 12% of those whose IHD event had been 1000 or more days after the test had shown a high platelet response at baseline. The trend in these proportions is not significant.

CONCLUSIONS

Platelet aggregation to thrombin and ADP in platelet rich plasma was recorded in the Caerphilly cohort study. No measure of aggregation was found to be predictive of IHD.