The concomitance of cervical spondylosis and adult thoracolumbar spinal deformity

Study Design Retrospective cross-sectional study.

Clinical Question What is the prevalence of cervical spondylosis (CS) and thoracolumbar (TL) spinal deformity in an administrative database during a 4-year study period? Is the prevalence of CS or TL deformity higher in patients who have the other spine diagnosis compared with the overall study population? Are patients with both diagnoses more likely to have undergone spine surgery?

Patients and Methods An administrative claims database containing 53 million patients with either Medicare (2005–2008) or private payer (2007–2010) insurance was used to identify patients with diagnoses of CS and/or TL deformity. Disease prevalence between groups was compared using a χ² test and reported using prevalence ratios (PR).

Results The prevalence of CS was higher in patients with TL deformity than without TL deformity, for both Medicare (PR = 2.81) and private payer (PR = 1.79). Similarly, the prevalence of TL deformity was higher in patients with CS than without CS for both Medicare (PR = 3.19) and private payer (PR = 2.05). Patients with both diagnoses were more likely to have undergone both cervical (Medicare, PR = 1.44; private payer, PR = 2.03) and TL (Medicare, PR = 1.68; private payer, PR = 1.74) spine fusion. All comparisons were significant with p < 0.0001.

Conclusions Patients with either CS or TL deformity had a higher prevalence of the other spinal diagnosis compared with the overall disease prevalence in the study population. Patients with both diagnoses had a higher prevalence of having spine surgery compared with patients with only one diagnosis. More studies to identify a causal mechanism for this relationship are warranted.

Expression of immediate-early genes in the inferior colliculus and auditory cortex in salicylate-induced tinnitus in rat

Tinnitus could be associated with neuronal hyperactivity in the auditory center. As a neuronal activity marker, immediate-early gene (IEG) expression is considered part of a general neuronal response to natural stimuli. Some IEGs, especially the activity-dependent cytoskeletal protein (Arc) and the early growth response gene-1 (Egr-1), appear to be highly correlated with sensory-evoked neuronal activity. We hypothesize, therefore, an increase of Arc and Egr-1 will be observed in a tinnitus model. In our study, we used the gap prepulse inhibition of acoustic startle (GPIAS) paradigm to confirm that salicylate induces tinnitus-like behavior in rats. However, expression of the Arc gene and Egr-1 gene were decreased in the inferior colliculus (IC) and auditory cortex (AC), in contradiction of our hypothesis. Expression of N-methyl d-aspartate receptor subunit 2B (NR2B) was increased and all of these changes returned to normal 14 days after treatment with salicylate ceased. These data revealed long-time administration of salicylate induced tinnitus markedly but reversibly and caused neural plasticity changes in the IC and the AC. Decreased expression of Arc and Egr-1 might be involved with instability of synaptic plasticity in tinnitus.

Intervertebral discs from spinal nondeformity and deformity patients have different mechanical and matrix properties

BACKGROUND CONTEXT

It is well-established that disc mechanical properties degrade with degeneration. However, prior studies utilized cadaveric tissues from donors with undefined back pain history. Disc degeneration may present with pain at the affected motion segment, or it may be present in the absence of back pain. The mechanical properties and matrix quantity of discs removed and diagnosed for degeneration with patient chronic pain may be distinct from those with other diagnoses, such as spinal deformity.

PURPOSE

To test the hypothesis that discs from nondeformity segments have inferior mechanical properties than deformity discs owing to differences in matrix quality.

STUDY DESIGN/SETTING

In vitro study comparing the mechanical and matrix properties of discs from surgery patients with spinal nondeformity and deformity.

METHODS

We analyzed nucleus and annulus samples (8-11 specimens per group) from surgical discectomy patients as part of a fusion or disc replacement procedure. Tissues were divided into two cohorts: nondeformity and deformity. Dynamic indentation tests were used to determine energy dissipation, indentation modulus, and viscoelasticity. Tissue hydration at a physiologic pressure was assessed by equilibrium dialysis. Proteoglycan, collagen, and collagen cross-link content were quantified. Matrix structure was assessed by histology.

RESULTS

We observed that energy dissipation was significantly higher in the nondeformity nucleus than in the deformity nucleus. Equilibrium dialysis experiments showed that annulus swelling was significantly lower in the nondeformity group. Consistent with this, we observed that the nondeformity annulus had lower proteoglycan and higher collagen contents.

CONCLUSIONS

Our data suggest that discs from nondeformity discs have subtle differences in mechanical properties compared with deformity discs. These differences were partially explained by matrix biochemical composition for the annulus, but not for the nucleus. The results of this study suggest that compromised matrix quality and diminished mechanical properties are features that potentially accompany discs of patients undergoing segmental fusion or disc replacement for disc degeneration and chronic back pain. These features have previously been implicated in pain via instability or reduced motion segment stiffness.

Proximal junctional kyphosis and clinical outcomes in adult spinal deformity surgery with fusion from the thoracic spine to the sacrum: a comparison of proximal and distal upper instrumented vertebrae

Object

Proximal junctional kyphosis (PJK) is a common and significant complication after corrective spinal deformity surgery. The object of this study was to compare—based on clinical outcomes, postoperative proximal junctional kyphosis rates, and prevalence of revision surgery—proximal thoracic (PT) and distal thoracic (DT) upper instrumented vertebra (UIV) in adults who underwent spine fusion to the sacrum for the treatment of spinal deformity.

Methods

In this retrospective study the authors evaluated clinical and radiographic data from consecutive adults (age > 21 years) with a deformity treated using long instrumented posterior spinal fusion to the sacrum in the period from 2007 to 2009. The PT group included patients in whom the UIV was between T-2 and T-5, whereas the DT group included patients in whom the UIV level was between T-9 and L-1. Perioperative surgical data were compared between the PT and DT groups. Additionally, segmental, regional, and global spinal alignments, as well as the sagittal Cobb angle at the proximal junction, were analyzed on preoperative, early postoperative, and final standing 36-in. radiographs. Patient-reported outcome measurements (visual analog scale, Scoliosis Research Society Patient Questionnaire-22, Oswestry Disability Index, and the 36-Item Short-Form Health Survey) were compared.

Results

Eighty-nine patients, 22 males and 67 females, had a minimum follow-up of 2 years, and thus were eligible for participation in this study. Sixty-seven patients were in the DT group and 22 were in the PT group. Operative time (p = 0.387) and estimated blood loss (p < 0.05) were slightly higher in the PT group. The overall rate of revision surgery was 48.0% and 54.5% in the DT and PT groups, respectively (p = 0.629). The prevalence of PJK according to radiological criteria was 34% in the DT group and 27% in the PT group (p = 0.609). The percent of patients with PJK that required surgical correction (surgical PJK) was 11.9% (8 of 67) in the DT group and 9.1% (2 of 22) in the PT group (p = 1.0). The onset of surgical PJK was significantly earlier than radiological PJK in the DT group (p < 0.01). The types of PJK were different in the PT and DT groups. Compression fracture at the UIV was more prevalent in the DT group, whereas subluxation was more prevalent in the PT group. Postoperatively, the PT group had less thoracic kyphosis (p = 0.02), less sagittal imbalance (p < 0.01), and less pelvic tilt (p = 0.04). In the DT group, early postoperative radiographs demonstrated that the proximal junctional angle of patients with surgical PJK was greater than in those without PJK and those with radiological PJK (p < 0.01). Clinical outcomes were significantly improved in both groups, and there was no significant difference between the groups.

Conclusions

Both PT and DT UIVs improve segmental and global sagittal plane alignment as well as patient-reported quality of life in those treated for adult spinal deformity. The prevalence of PJK was not different in the PT and DT groups. However, compression fracture was the mechanism more frequently observed with DT PJK, and subluxation was the mechanism more frequently observed in PT PJK. Strategies to avoid PJK may include vertebral augmentation to prevent fracture at the DT spine and mechanical means to prevent vertebral subluxation at the PT spine.

Spontaneous improvement of cervical alignment after correction of global sagittal balance following pedicle subtraction osteotomy

Object

Sagittal spinopelvic malalignment is a significant cause of pain and disability in patients with adult spinal deformity. Surgical correction of spinopelvic malalignment can result in compensatory changes in spinal alignment outside of the fused spinal segments. These compensatory changes, termed reciprocal changes, have been defined for thoracic and lumbar regions but not for the cervical spine. The object of this study was to evaluate postoperative reciprocal changes within the cervical spine following lumbar pedicle subtraction osteotomy (PSO).

Methods

This was a multicenter retrospective radiographic analysis of patients from International Spine Study Group centers. Inclusion criteria were as follows: adults (>18 years old) with spinal deformity treated using lumbar PSO, a preoperative C7–S1 plumb line greater than 5 cm, and availability of pre- and postoperative full-length standing radiographs.

Results

Seventy-five patients (60 women, mean age 59 years) were included. The lumbar PSO significantly improved sagittal alignment, including the C7–S1 plumb line, C7–T12 inclination, and pelvic tilt (p <0.001). After lumbar PSO, reciprocal changes were seen to occur in C2–7 cervical lordosis (from 30.8° to 21.6°, p <0.001), C2–7 plumb line (from 27.0 mm to 22.9 mm), and T-1 slope (from −38.9° to −30.4°, p <0.001). Ideal correction of sagittal malalignment (postoperative sagittal vertical alignment < 50 mm) was associated with the greatest relaxation of cervical hyperlordosis (−12.4° vs −5.7°, p = 0.037). A change in cervical lordosis correlated with changes in T-1 slope (r = −0.621, p <0.001), C7–T12 inclination (r = 0.418, p <0.001), T12–S1 angle (r = −0.339, p = 0.005), and C7–S1 plumb line (r = 0.289, p = 0.018). Radiographic parameters that correlated with changes in cervical lordosis on multivariate linear regression analysis included change in T-1 slope and change in C2–7 plumb line (r2 = 0.53, p <0.001).

Conclusions

Adults with positive sagittal spinopelvic malalignment compensate with abnormally increased cervical lordosis in an effort to maintain horizontal gaze. Surgical correction of sagittal malalignment results in improvement of the abnormal cervical hyperlordosis through reciprocal changes.

COX-2 and fatty acid amide hydrolase can regulate the time course of depolarization-induced suppression of excitation

BACKGROUND AND PURPOSE

Depolarization-induced suppression of inhibition (DSI) and excitation (DSE) are two forms of cannabinoid CB(1) receptor-mediated inhibition of synaptic transmission, whose durations are regulated by endocannabinoid (eCB) degradation. We have recently shown that in cultured hippocampal neurons monoacylglycerol lipase (MGL) controls the duration of DSE, while DSI duration is determined by both MGL and COX-2. This latter result suggests that DSE might be attenuated, and excitatory transmission enhanced, during inflammation and in other settings where COX-2 expression is up-regulated.

EXPERIMENTAL APPROACH

To investigate whether it is possible to control the duration of eCB-mediated synaptic plasticity by varied expression of eCB-degrading enzymes, we transfected excitatory autaptic hippocampal neurons with putative 2-AG metabolizing enzymes: COX-2, fatty acid amide hydrolase (FAAH), α/β hydrolase domain 6 (ABHD6), α/β hydrolase domain 12 (ABHD12) or MGL.

KEY RESULTS

We found that overexpression of either COX-2 or FAAH shortens the duration of DSE while ABHD6 or ABHD12 do not. In contrast, genetic deletion (MGL(-/-)) and overexpression of MGL both radically altered eCB-mediated synaptic plasticity.

CONCLUSIONS AND IMPLICATIONS

We conclude that both FAAH and COX-2 can be trafficked to neuronal sites where they are able to degrade eCBs to modulate DSE duration and, by extension, net endocannabinoid signalling at a given synapse. The results for COX-2, which is often up-regulated under pathological conditions, are of particular note in that they offer a mechanism by which up-regulated COX-2 may promote neuronal excitation by suppressing DSE while enhancing conversion of 2-AG to PGE(2) -glycerol ester under pathological conditions.

Surgical compared with nonoperative treatment for lumbar degenerative spondylolisthesis. four-year results in the Spine Patient Outcomes Research Trial (SPORT) randomized and observational cohorts

BACKGROUND

The management of degenerative spondylolisthesis associated with spinal stenosis remains controversial. Surgery is widely used and has recently been shown to be more effective than nonoperative treatment when the results were followed over two years. Questions remain regarding the long-term effects of surgical treatment compared with those of nonoperative treatment.

METHODS

Surgical candidates from thirteen centers with symptoms of at least twelve weeks' duration as well as confirmatory imaging showing degenerative spondylolisthesis with spinal stenosis were offered enrollment in a randomized cohort or observational cohort. Treatment consisted of standard decompressive laminectomy (with or without fusion) or usual nonoperative care. Primary outcome measures were the Short Form-36 (SF-36) bodily pain and physical function scores and the modified Oswestry Disability Index at six weeks, three months, six months, and yearly up to four years.

RESULTS

In the randomized cohort (304 patients enrolled), 66% of those randomized to receive surgery received it by four years whereas 54% of those randomized to receive nonoperative care received surgery by four years. In the observational cohort (303 patients enrolled), 97% of those who chose surgery received it whereas 33% of those who chose nonoperative care eventually received surgery. The intent-to-treat analysis of the randomized cohort, which was limited by nonadherence to the assigned treatment, showed no significant differences in treatment outcomes between the operative and nonoperative groups at three or four years. An as-treated analysis combining the randomized and observational cohorts that adjusted for potential confounders demonstrated that the clinically relevant advantages of surgery that had been previously reported through two years were maintained at four years, with treatment effects of 15.3 (95% confidence interval, 11 to 19.7) for bodily pain, 18.9 (95% confidence interval, 14.8 to 23) for physical function, and -14.3 (95% confidence interval, -17.5 to -11.1) for the Oswestry Disability Index. Early advantages (at two years) of surgical treatment in terms of the secondary measures of bothersomeness of back and leg symptoms, overall satisfaction with current symptoms, and self-rated progress were also maintained at four years.

CONCLUSIONS

Compared with patients who are treated nonoperatively, patients in whom degenerative spondylolisthesis and associated spinal stenosis are treated surgically maintain substantially greater pain relief and improvement in function for four years.

Spondylolisthesis and spondylolysis

Spondylolisthesis is a common condition that can be managed both nonsurgically and surgically. More than 80% of children treated nonsurgically have resolution of symptoms. For those patients requiring surgical treatment, fusion in situ may provide adequate treatment for young patients. Patients with neural compression may require decompression to relieve symptoms, and fusion is also usually indicated. High-grade and degenerative spondylolisthesis require care that is unique to those conditions. Spondylolysis is a defect in the pars interarticularis that occurs in approximately 5% of the general population. Approximately 15% of individuals with a pars interarticularis lesion have progression to spondylolisthesis.

High thoracic spinal infection following upper gastrointestinal work-up

Spinal infections originating from the gastrointestinal tract are rare. We report a patient in whom esophageal rupture during endoscopy led to spinal infection with neurological deficit. An 80-year-old Asian man with a history of recent endoscopic gastrointestinal investigation presented to our clinic with the chief complaints of upper thoracic discomfort, chest pain and mild intermittent fever. Progressive weakness and numbness in both lower extremities had developed during the previous two weeks. A thoracic spine MRI showed a space-occupying lesion with involvement of the T2 and T3 vertebral bodies including an epidural abscess. After surgical decompression, the patient gradually recovered power in his lower extremities. Early diagnosis is a key factor to avoid neurologic sequelae in the treatment of patients with spinal infection. Physicians need to be aware of this potential complication following endoscopic gastrointestinal investigation.

Recombinant activated factor VII in spinal surgery: a multicenter, randomized, double-blind, placebo-controlled, dose-escalation trial

STUDY DESIGN

Randomized, placebo-controlled, double-blind, multicenter, Phase IIa study.

OBJECTIVE

To assess the safety and efficacy of recombinant-activated Factor VII (rFVIIa) in major spinal surgery.

SUMMARY OF BACKGROUND

Spinal fusion surgery can cause substantial blood loss and blood product transfusions. Recombinant FVIIa is approved for treatment of bleeding in patients with coagulation abnormalities and has been shown to reduce blood loss and transfusion requirements in surgery in patients with no underlying coagulopathy.

METHODS

Forty-nine patients undergoing fusion of 3 or more vertebral segments were randomized and treated on losing 10% of their estimated blood volume (with total expected surgical blood loss > or = 20%) and received 3 doses (2-hour intervals) of placebo (n = 13) or 30, 60, or 120 microg/kg rFVIIa (n = 12 per group). The primary endpoint was safety. A priori-defined efficacy endpoints included blood loss and transfusion requirements between placebo and each rFVIIa dose group, adjusted for surgery duration, number of segments fused, and estimated blood volume.

RESULTS

Serious adverse events did not occur at any greater frequency in any of the treatment groups. One patient (3 x 30 microg/kg rFVIIa) with advanced cerebrovascular disease (undiagnosed, trial exclusion criterion) died 6 days after surgery due to an ischemic stroke. Mean blood loss was as follows: 2270 mL for placebo; 1909, 1262, and 1868 mL for 3 x 30, 3 x 60, and 3 x 120 microg/kg rFVIIa, respectively (differences not statistically significant). Mean adjusted surgical blood loss was as follows: 2536 mL for placebo; 1120, 400, and 823 mL for 3 x 30, 3 x 60, and 3 x 120 microg/kg rFVIIa, respectively (P < or = 0.001). Mean surgical transfusion volume was reduced by 27% to 50% with rFVIIa treatment (not significant). The mean adjusted surgical transfusion volume was reduced by 81% to 95% with rFVIIa treatment (P < or = 0.002).

CONCLUSION

No safety concerns were indicated for the use of rFVIIa in patients at all doses tested; rFVIIa reduced adjusted blood loss and adjusted transfusions during spinal surgery.

A modified cannulating technique for the BVS5000

The aim of this study was to report on a modified cannulating method for the BVS5000 left ventricular assist device. From April 2005 to April 2006, a BVS5000 device was implanted using a modified cannulating method in 7 postcardiotomy male patients after coronary artery bypass grafting for left ventricular support. The inflow cannula was inserted into the left atrial artery through a segment of bovine jugular vein and the arterial cannula into the femoral artery. Five patients were successfully weaned from the BVS5000 after recovery of heart function and were discharged from hospital. The BVS5000 was explanted using a minimally invasive technique. The weaning procedure was completed bedside in the intensive care unit under local anesthesia; resternotomy was not necessary. The modified technique is a simpler, safer and more minimally invasive method for selected patients supported by the BVS5000.

Surgical versus nonsurgical treatment for lumbar degenerative spondylolisthesis

BACKGROUND

Management of degenerative spondylolisthesis with spinal stenosis is controversial. Surgery is widely used, but its effectiveness in comparison with that of nonsurgical treatment has not been demonstrated in controlled trials.

METHODS

Surgical candidates from 13 centers in 11 U.S. states who had at least 12 weeks of symptoms and image-confirmed degenerative spondylolisthesis were offered enrollment in a randomized cohort or an observational cohort. Treatment was standard decompressive laminectomy (with or without fusion) or usual nonsurgical care. The primary outcome measures were the Medical Outcomes Study 36-Item Short-Form General Health Survey (SF-36) bodily pain and physical function scores (100-point scales, with higher scores indicating less severe symptoms) and the modified Oswestry Disability Index (100-point scale, with lower scores indicating less severe symptoms) at 6 weeks, 3 months, 6 months, 1 year, and 2 years.

RESULTS

We enrolled 304 patients in the randomized cohort and 303 in the observational cohort. The baseline characteristics of the two cohorts were similar. The one-year crossover rates were high in the randomized cohort (approximately 40% in each direction) but moderate in the observational cohort (17% crossover to surgery and 3% crossover to nonsurgical care). The intention-to-treat analysis for the randomized cohort showed no statistically significant effects for the primary outcomes. The as-treated analysis for both cohorts combined showed a significant advantage for surgery at 3 months that increased at 1 year and diminished only slightly at 2 years. The treatment effects at 2 years were 18.1 for bodily pain (95% confidence interval [CI], 14.5 to 21.7), 18.3 for physical function (95% CI, 14.6 to 21.9), and -16.7 for the Oswestry Disability Index (95% CI, -19.5 to -13.9). There was little evidence of harm from either treatment.

CONCLUSIONS

In nonrandomized as-treated comparisons with careful control for potentially confounding baseline factors, patients with degenerative spondylolisthesis and spinal stenosis treated surgically showed substantially greater improvement in pain and function during a period of 2 years than patients treated nonsurgically. (ClinicalTrials.gov number, NCT00000409 [ClinicalTrials.gov].).

Surgical Strategies and Choosing Levels for Spinal Deformity: How High, How Low, Front and Back

The purpose of this article is to describe general strategies in the surgical treatment of adolescent and adult scoliosis, including radiographic evaluation, curve selection, principles guiding the selection of the upper and lower instrumented vertebrae, and indications for anterior surgery. Sagittal plane deformity, including Scheuermann's kyphosis, is discussed. Avoidance and treatment of postoperative flatback deformity is also briefly mentioned. There are multiple and sometimes conflicting considerations that must be reviewed when planning surgical stabilization of spinal deformity. Although there may be significant variation in surgeon decision making, careful adherence to primary principles, such as achieving coronal and sagittal balance in all patients and minimizing fusion levels, particularly in young patients, should be of paramount importance.

[Research on development of gold immunochromagraphic assay test kit for serum Coxsackievirus IgM antibody.]

BACKGROUND

To develop gold immunochromatographic assay (GICA) test kit for serum Coxsackievirus IgM antibody and optimize the key experiment conditions.

METHODS

Colloidal gold particles of 20 nm were prepared and coupled with sheep anti-human IgM, the gold immunochromatography assay test kit was setup for serum Coxsackievirus IgM antibody.

RESULTS

The spheroidal colloid gold particles of 20 nm showed bright red in color. The minimal stable concentration (MSC) of gold sheep anti-human IgM was 1 ug/ml, and the suitable stable concentration (SSC) was 1.5 ug/ml. The pH 8.2 was appropriate; 30 sera samples were tested by GICA and ELISA, there was no significant difference between the two methods.

CONCLUSION

The quality of gold immunochromatography assay test kit is associated with such factors as the quality and quantity of antigen or antibody, colloid gold particles, buffers, etc.

Preparing the adult deformity patient for spinal surgery

STUDY DESIGN

Review article of preoperative evaluation of surgical patients as relates to adult spine patients.

OBJECTIVE

To determine which patients should undergo preoperative evaluation and review options for improved preoperative preparation for these patients.

SUMMARY OF BACKGROUND DATA

There is increasing attention paid to preoperative preparation for surgical patients to decrease perioperative morbidity. Better preoperative evaluation may lead to decreased complication rates and may improve outcomes.

METHODS

The literature to date, including surgical, hospitalist, and critical care, was reviewed and combined with the authors' experience.

RESULTS

Suggestions for preoperative screening questions are summarized.

CONCLUSION

Better recognition of preoperative risk factors may help spine surgeons improve preoperative preparation in their patients, leading to decreased complication rates.

Disc arthroplasty design influences intervertebral kinematics and facet forces

BACKGROUND CONTEXT

Total disc replacement is a novel approach for dynamically stabilizing a painful intervertebral segment. While this approach is gaining popularity, and several types of implants are used, the effect of disc arthroplasty on lumbar biomechanics has not been widely reported. Consequently, beneficial or adverse effects of this procedure may not be fully realized, and data for kinematic optimization are unavailable.

PURPOSE

To characterize kinematic and load transfer modifications at L5/S1 secondary to joint replacement.

STUDY DESIGN

A human cadaveric biomechanical study in which the facet forces and instant axes of rotation (IAR) were measured for different spinal positions under simulated weightbearing conditions before and after total disc replacement at L5/S1 using semiconstrained (3 degrees of freedom [DOF]; Prodisc) and unconstrained (5 DOF; Charité) articulated implants.

METHODS

Twelve radiographically normal human cadaveric L5/S1 joints (age range 45-64 years) were tested before and after disc replacement using Prodisc II implants (Spine Solutions, Paoli, PA) in six specimens and SB Charité III (Johnson & Johnson, New Brunswick, NJ) in six other specimens. Semiconstrained fixtures in combination with a servo-hydraulic materials testing system subjected the test specimens to a physiologic combination of compression and anterior shear. Multiple intervertebral positions were studied and included up to 6 degrees of flexion, extension, and lateral bending. The IAR was calculated for every 3-degree intervals, and the force through the facet joints was simultaneously measured using flexible intra-articular sensors. Data were analyzed using repeated-measures analysis of variance.

RESULTS

During flexion/extension, the average IAR positions and directions were not significantly modified by implantation with the exception that the IAR was higher relative to S1 end plate with the Charité (p=.028). The IAR had a vertically oriented centrode throughout flexion/extension with the Prodisc (p<.001) and the Charité (p<.016). The centrode tended to be greater with the Prodisc. There was a trend that the facet force was decreased throughout flexion/extension for the Prodisc; however, this was statistically significant only at 6 degrees extension (27%, p=.013). In lateral bending, the IAR was significantly modified by Prodisc replacement, with a decreased inclination relative to S1 end plate, (ie, increased coupled axial rotation). While the IAR moved in the horizontal plane toward the side of bending, this effect was more pronounced with the Prodisc. The ipsilateral facet force was significantly increased in 6 degrees lateral bending with the Charité (85%; p=.001).

CONCLUSIONS

The degree of constraint affects post-implantation kinematics and load transfer. With the Prodisc (3 DOF), the facets were partially unloaded, though the IAR did not match the fixed geometrical center of the UHMWPE. The latter observation suggests joint surface incongruence is developed during movement. With the Charité (5 DOF), the IAR was less variable, yet the facet forces tended to increase, particularly during lateral bending. These results highlight the important role the facets play in guiding movement, and that implant constraint influences facet/implant synergy. The long-term consequences of the differing kinematics on clinically important outcomes such as wear and facet arthritis have yet to be determined.

Intradiscal thermal therapy does not stimulate biologic remodeling in an in vivo sheep model

STUDY DESIGN

Thermal energy was delivered in vivo to ovine cervical discs and the postheating response was monitored over time.

OBJECTIVES

To determine the effects of two distinctly different thermal exposures on biologic remodeling: a "high-dose" regimen intended to produce both cellular necrosis and collagen denaturation and a "low-dose" regimen intended only to kill cells.

SUMMARY OF BACKGROUND DATA

Thermal therapy is a minimally invasive technique that may ameliorate discogenic back pain. Potential therapeutic mechanisms include shrinkage of collagenous tissues, stimulation of biologic remodeling, and ablation of cytokine-producing cells and nociceptive fibers.

METHODS

Intradiscal heating was performed using directional interstitial ultrasound applicators. Temperature and thermal dose distributions were characterized. The effects of high (>70 C, 10 minutes) and low (52 C-54 C, 10 minutes) temperature treatments on chronic biomechanical and architectural changes were compared with sham-treated and control discs at 7, 45, and 180 days.

RESULTS

The high-dose treatment caused both an acute and chronic loss of proteoglycan staining and a degradation of biomechanical properties compared with low-dose and sham groups. Similar amounts of degradation were observed in the low-dose and sham-treated discs relative to the control discs at 180 days after treatment.

CONCLUSIONS

While a high temperature thermal protocol had a detrimental effect on the disc, the effects of low temperature treatment were relatively minor. Thermal therapy did not stimulate significant biologic remodeling. Future studies should focus on the effects of low-dose therapy on tissue innervation and pro-inflammatory factor production.

Risk factors for infection after spinal surgery

STUDY DESIGN

A retrospective case control analysis of 48 cases of postoperative infection following spinal procedures.

OBJECTIVES

Spinal procedures that became infected after surgery were analyzed to identify the significance of preoperative and intraoperative risk factors. Characterization of the nature and timing of the infections was also performed.

SUMMARY OF BACKGROUND DATA

The rate of postoperative infection following spinal surgery varies widely depending on the nature of the procedure and the patient's diagnosis. Preoperative comorbidities and risk factors also influence the likelihood of infection.

METHODS

A review of 1629 procedures performed on 1095 patients revealed that a postoperative infection developed in 48 patients (4.4%). Data regarding preoperative and intraoperative risk factors were gathered from patient charts for these and a randomly selected control group of 95 uninfected patients. For analysis, these patient groups were further divided into adult and pediatric subgroups, with an age cutoff of 18 years. Preoperative risk factors reviewed included smoking, diabetes, previous surgery, previous infection, steroid use, body mass index, and alcohol abuse. Intraoperative factors reviewed included staging of procedures, estimated blood loss, operating time, and use of allograft or instrumentation.

RESULTS

The majority of infections occurred during the early postoperative period (less than 3 months). Age >60 years, smoking, diabetes, previous surgical infection, increased body mass index, and alcohol abuse were statistically significant preoperative risk factors. The most likely procedure to be complicated by an infection was a combined anterior/posterior spinal fusion performed in a staged manner under separate anesthesia. Infections were primarily monomicrobial, although 5 patients had more than 4 organisms identified. The most common organism cultured from the wounds was Staphylococcus aureus. All patients were treated with surgical irrigation and débridement, and appropriate antibiotics to treat the cultured organism.

CONCLUSIONS

Aggressive treatment of patients undergoing complex or prolonged spinal procedures is essential to prevent and treat infections. Understanding a patient's preoperative risk factors may help the physician to optimize a patient's preoperative condition. Additionally, awareness of critical intraoperative parameters will help to optimize surgical treatment. It may be appropriate to increase the duration of prophylactic antibiotics or implement other measures to decrease the incidence of infection for high risk patients.

Blood loss in adult spinal surgery

Spinal surgery in adults can vary from simple to complex and can also have variable anticipated surgical blood loss. There are several factors that can put patients at increased risk for greater intraoperative blood loss. These factors, including a review of the literature, will be discussed.