Randomized Trial of Augmented Pelvic Fixation in Patients Undergoing Thoracolumbar Fusion for Adult Spine Deformity: Initial Results from a Multicenter Randomized Trial

BACKGROUND

The optimal configuration for spinopelvic fixation during multilevel spine fusion surgery for adult spine deformity remains unclear. Postoperative sacroiliac (SI) joint pain, S2AI screw loosening and implant breakage could be related to continued motion of the SI joint with use of only a single point of fixation across the SI joint.

METHODS

Prospective, international, multicenter randomized controlled trial of 222 patients with adult spine deformity scheduled for multilevel (4 or more levels) spine fusion surgery with pelvic fixation. Subjects were randomized to S2AI screws alone for pelvic fixation or S2AI + triangular titanium implants placed cephalad to S2AI screws. Quad rod techniques were not allowed or used. Baseline spinal deformity measures were read by an independent radiologist. Site-reported perioperative adverse events were reviewed by a clinical events committee. Quality of life questionnaires and other clinical outcomes are in process with planned two-year follow-up.

RESULTS

113 participants were assigned to S2AI and 109 to S2AI + TTI. 35/222 (16%) of all subjects had a history of SI joint pain or were diagnosed with SI joint pain during preoperative workup. 3-month follow-up was available in all but 4 subjects. TTI placement was successful in 106 of 109 (98%) subjects assigned to TTI. In 2 cases, TTI could not be placed due to anatomical considerations. Three TTI ventral iliac breaches were observed, all of which were managed non-surgically. One TTI subject had a transverse sacral fracture and one TTI subject had malposition of the implant requiring removal.

CONCLUSIONS

SI joint pain is common in patients with adult spinal deformity who are candidates for multilevel spine fusion surgery. Concurrent placement of TTI parallel to S2AI screws during multilevel spine fusion surgery is feasible and safe. Further follow-up will help to determine the clinical value of this approach to augment pelvic fixation.

Minimally Invasive SI Joint Fusion Procedures for Chronic SI Joint Pain: Systematic Review and Meta-Analysis of Safety and Efficacy

BACKGROUND

Sacroiliac (SI) joint fusion is increasingly used to treat chronic SI joint pain. Multiple surgical approaches are now available.

METHODS

Data abstraction and random effects meta-analysis of safety and efficacy outcomes from published patient cohorts. Patient-reported outcomes (PROs) and safety measures were stratified by surgical technique: transiliac, including lateral transiliac (LTI) and posterolateral transiliac (PLTI), and posterior interpositional (PI) procedures.

RESULTS

Fifty-seven cohorts of 2851 patients were identified, including 43 cohorts (2126 patients) for LTI, 6 cohorts (228 patients) for PLTI, and 8 cohorts (497 patients) for PI procedures. Randomized trials were only available for LTI. PROs were available for pain (numeric rating scale) in 57 cohorts (2851 patients) and disability (Oswestry Disability Index [ODI]) in 37 cohorts (1978 patients).All studies with PROs showed improvement from baseline after surgery. Meta-analytic improvements in pain scores were highest for LTI (4.8 points [0-10 scale]), slightly lower for PLTI (4.2 points), and lowest for PI procedures (3.8 points, P = 0.1533). Mean improvements in ODI scores were highest for LTI (25.9 points), lowest for PLTI procedures (6.8 points), and intermediate for PI (16.3 points, P = 0.0095).For safety outcomes, acute symptomatic implant malposition was 0.43% for LTI, 0% for PLTI, and 0.2% for PI procedures. Wound infection was reported in 0.15% of LTI, 0% of PLTI, and 0% of PI procedures. Bleeding requiring surgical intervention was reported in 0.04% of LTI procedures and not reported for PLTI or PI. Breakage and migration were not reported for any device. Radiographic imaging evaluation reporting implant placement accuracy and fusion was only available for LTI.

DISCUSSION

Literature support for SI joint fusion is growing. The LTI procedure contains the largest body of available evidence and shows the largest improvements in pain and ODI. Only LTI procedures have independent radiographic evidence of fusion and implant placement. The adverse event rate for all procedures was low.

LEVEL OF EVIDENCE: 1

Discrepancy between DXA and CT-based assessment of spine bone mineral density

PURPOSE

Adequate bone mineral density (BMD) is necessary for success in spine surgery. Dual-energy X-ray absorptiometry (DXA) is the gold standard in determining BMD but may give spuriously high values. Hounsfield units (HU) from computed tomography (CT) may provide a more accurate depiction of the focal BMD encountered during spine surgery. Our objective is to determine the discrepancy rate between DXA and CT BMD determinations and how often DXA overestimates BMD compared to CT.

METHODS

We retrospectively reviewed 93 patients with both DXA and CT within 6 months. DXA lumbar spine and overall T scores were classified as osteoporotic (T Score  ≤ - 2.5) or non-osteoporotic (T Score > -2.5). L1 vertebral body HU were classified as osteoporotic or non-osteoporotic using cutoff thresholds of either ≤ 135 HU or ≤ 110 HU. Corresponding DXA and HU classifications were compared to determine disagreement and overestimation rates.

RESULTS

Using lumbar T scores, the CT vs DXA disagreement rate was 40-54% depending on the HU threshold. DXA overestimated BMD 97-100% of the time compared to CT. Using overall DXA T scores, the disagreement rate was 33-47% with DXA greater than CT 74-87% of the time. In the sub-cohort of 10 patients with very low HU (HU < 80), DXA overestimated BMD compared to CT in every instance.

CONCLUSIONS

There is a large discrepancy between DXA and CT BMD determinations. DXA frequently overestimates regional BMD encountered during spine surgery compared with CT. While DXA remains the gold standard in determining BMD, CT may play an important role in defining the focal BMD pertinent to spine surgery.

Rescue Pelvic Fixation in a Patient with Sacral-2-Alar-Iliac and Triangular Sacroiliac Joint Fusion (Bedrock) Instrumentation

The purpose of this report is to demonstrate the creation of a 4-rod lumbosacral construct, when "stacked" sacral-2-alar-iliac (S2AI) screws are not possible due to a concurrent treatment of sacroiliitis with a posterior approach sacroiliac joint fusion device. This technique uses a combined S2AI and subcrestal iliac approach to achieve the 4-rod lumbosacral construct, while simultaneously biomechanically supporting the S2AI screws and treating the sacroiliitis.

Novel 2D long film imaging utility to avoid wrong level spinal surgery

Wrong-level spinal surgery (WLSS) can lead to increased morbidity, cost, and worse long-term outcomes. Current intraoperative localization methods rely on counting spinal levels from a known reference location using fluoroscopy. Miscounting from a reference is an intraoperative error that leads to WLSS, especially for those with anatomical variations. The problem is exacerbated when fluoroscopy is not able to produce images with the clarity needed to confidently count levels, a prevalent issue for obese patients.

A new feature called the “2D Long Film'' is available for the Medtronic (Minneapolis, MN) O-arm Surgical Imaging System. Using this novel technology and standard fluoroscopy, this study reports the imaging of two obese adult female patients with a body mass index of 36.9 and 42.0 undergoing transforaminal thoracic interbody fusion. Fluoroscopy images of obese patients are difficult to capture for two reasons: increased scatter and restricted field of view. This report demonstrates that 2D Long Film can improve both these issues for obese patients in need of thoracic localization. The 2D Long Film captures existing instrumentation, localization needles, and the vertebral levels in a clear single image.

We display the differences between standard fluoroscopy and the 2D Long Film for thoracic level localization, demonstrating a potential new standard of care and better visualization, leading to a less challenging vertebrae localization process, potentially mitigating WLSS risk. The quality of this new 2D Long Film feature could also reduce time in the operating room and the necessity of other visualization methods.

Lymphatic Injury After Vertebral Column Resection from a Posterior Approach for Spinal Deformity Correction: A Case Report

CASE

We describe a case of lymphatic injury that occurred during a 2-level vertebral column resection for spinal deformity correction from a posterior-only approach. Large surgical drain volume output with laboratory findings of high levels of triglycerides and lymphocytes prompted conservative treatment with an elastic wrap bandage and a "no fat" diet. The patient responded to the treatment with no sequelae noted.

CONCLUSION

Lymphatic complications are rare in spine surgery. All reported cases are associated with anterior approaches. The lymphatic injury presented here demonstrates the potential for this complication to occur during posterior-only approaches as well.

Pelvic Fixation Using S2AI and Triangular Titanium Implants (Bedrock Technique)

Pelvic fixation is becoming an increasingly important caudal anchor point for long lumbar constructs, high-grade spondylolisthesis, fixation of sacral fractures, and support for 3-column osteotomies, by adding lumbosacral fixation anterior to the McCord pivot point. Iliac bolts were once common but have become less favorable due to screw head irritation and complications associated with connecting rods. S2-alar-iliac (S2AI) screws have been shown to achieve equivalent anchoring strength of constructs to the pelvis, while being lower profile and in line with the lumbar instrumentation. More recently, surgeons have noted the potential for S2AI screws to toggle and loosen, commonly in the softer sacrum, leading to caudal anchor failure and possible pseudarthrosis. The addition of triangular titanium implants to augment S2AI screws (bedrock technique) is a relatively new adaptation to reduce toggling on the S2AI screw and improve the overall stability of the pelvic fixation. Video 1 shows the placement of an S2AI screw and triangular titanium implant for pelvic fixation. The patient is a 68-year-old woman who presented with flat back syndrome, spinal stenosis, degenerative spondylolisthesis, pseudarthrosis of previously instrumented levels, and bilateral sacroiliitis. She underwent posterior instrumentation and fusion of L1 to S1 with pelvic fixation, open bilateral sacroiliac joint fusion, and multilevel Smith-Peterson osteotomies and transforaminal lumbar interbody fusions.

Incidental extraspinal imaging findings on adult EOS full body radiographs: prevalence and clinical importance

Purpose

The purpose of this study was to review our institutional experience with the EOS machine in order to identify the incidence and clinical significance of incidental extraspinal findings (IESF) in an adult spinal deformity population.

Methods

Our institutional database was queried for all full-length standing radiographs generated by the EOS machine. Dictations were reviewed and the number of incidental extraspinal findings were classified using a previously described system. All findings related to the spine were excluded. A subset of electronic medical records were reviewed to determine further workup for individual findings of suspected clinical significance.

Results

Original database query based on radiology reports returned a total of 1857 EOS studies. Duplicate studies, studies without the entire body, and patients with more than 1 study during the search period were excluded. 503 patient studies (55.5% female, mean age 59-years-old, range 18 to 91-years-old) met inclusion criteria. The overall rate of incidental extraspinal findings in our study was 60.4% (304 findings in 503 patients). Most findings were classified as Minor. The rate of Major and Moderate findings was 4.8%. The final rate of clinically significant incidental extraspinal findings was 0.8% and included 3 presumed metastatic lesions in long bones and 1 pulmonary nodule.

Conclusion

To our knowledge this is the first study that reports the rate of incidental extraspinal findings on full body EOS studies. We report a low rate (0.8%) of clinically significant incidental extraspinal findings which is lower than that of CT or MRI. Further research is warranted in comparing EOS and standard radiography.

2-Dimensional Long Film O-Arm Imaging, an Alternative When Intraoperative Fluoroscopy Is Inadequate

Obtaining intraoperative images of the spine in the obese patient and at the cervicothoracic junction have historically been technically difficult due to variable penetration and x-ray scatter. This is particularly true for spinal deformity cases, where clear visualization of the end plates is needed to determine if functional alignment has been restored to the spine. The novel "2D long film" functionality for the Medtronic O-arm is capable of capturing the x-ray backscatter, producing enhanced intraoperative images. Furthermore, images can be obtained along the gantry translation of the O-arm and combined into a single long image, optimizing the workflow of surgeons who use the O-arm for intraoperative navigation. The purpose of this report is to highlight 2 example spinal deformity cases that underscore the utility of this imaging technology. In both cases, standard intraoperative fluoroscopy visualization was unacceptable, so 2D long film images were obtained to assess postcorrection spinal alignment.

Is the Implant in Bone? The Accuracy of CT and Fluoroscopic Imaging for Detecting Malpositioned Pelvic Screw and SI Fusion Implants

BACKGROUND

Spine fusions to the pelvis have been associated with increased strain to the sacroiliac joint (SI) and possibly continued postoperative low back pain. To minimize this, concomitant SI joint fusion at the time of lumbopelvic fixation has been advocated. This requires concomitant placement of sacral alar iliac screws (S2AI) for lumbopelvic fixation and triangular titanium rods (TTR) for the SI joint fusion. Traditionally, surgeons have mostly relied on fluoroscopic images to confirm final implant position and patient safety after pelvic instrumentation, although computer tomography (CT) has also been used.

METHODS

We wanted to know which imaging modality, if any, was superior in helping to identify malpositioned implants during concomitant lumbopelvic fixation and SI joint fusion. We instrumented pelvic sawbones models with S2AI screws, TTR's, or both in the correct anatomic positions or malpositioned variants that led to known cortical breaches. Pelvic models were then imaged with fluoroscopy and CT, and the images assessed by blinded reviewers (spine surgeons and a musculoskeletal radiologist) for the presence of cortical breaches, the identity of the breached implant, and its direction. The responses of the blinded reviewers were then compared to the known position of the implants and Kappa coefficient calculated to determine agreement.

RESULTS

We found that thorough evaluation of implant position with multiple fluoroscopic views (kappa 0.641) or CT imaging (kappa 0.906) allowed reviewers to assess implant position, identity, and breach direction.

CONCLUSION

These findings suggest that intraoperative CT imaging allows surgeons to make the best decision regarding implant position prior to leaving the operating room, thus potentially improving patient safety and unplanned returns to the operating room.Level of Evidence: V.

Full-spine radiographs: what others are reporting-a survey of Society of Skeletal Radiology members

OBJECTIVE

Full-spine radiographs are frequently ordered by spinal deformity surgeons to assess spinal imbalance. The radiologist interpretation of these films varies amongst providers. Detailed numeric measurements of the deformity are time-consuming. In this study, we hoped to better define current practice patterns for interpretation of spinal deformity films amongst musculoskeletal radiologists in North America.

MATERIALS AND METHODS

An anonymous online survey was conducted amongst Society of Skeletal Radiology members.

RESULTS

Only 26.5% of respondents (n = 57) routinely report pelvic tilt, 23.2% (n = 52) for sagittal vertical axis and 5.1% (n = 11) for Pelvic Incidence Lumbar Lordosis mismatch in adult spinal deformity. Furthermore, the majority of musculoskeletal radiologists (84.96%) dictate the same type of report for both adult and pediatric cases.

CONCLUSIONS

The majority (n = 199, 70%) of 283 respondents state that no institutional standard template for full-spine dictations exists. The development of such templates listing appropriate parameters to include in the dictation may be useful in order to ensure that the radiologist's effort and clinical utility for the ordering provider are optimized.

Thoracic Volumes Correlated With Pulmonary Function Tests in Adult Scoliosis Patients Following Different Treatments in Adolescence

In this paper, a previously developed medical software using orthogonal frontal and lateral X-rays is employed to reconstruct the rib cage and thoracic volume for scoliosis patients. The thoracic volumes of ten adult scoliosis patients with different treatments during their adolescence are followed up. This study provides an evidence that thoracic volume measurement can be used to infer the pulmonary function for spine deformity patients with moderate to severe scoliosis Cobb angle. Based on the calculation of the thoracic volumes in scoliosis patients, we correlate the parameters in the pulmonary function test to the measured thoracic volume through our software. The findings show the strong correlation between total lung capacity and the thoracic volume, and a significant correlation between the vital capacity/residual volume and the thoracic volume. An interpretation of the findings, limitation, and the future application are pointed out.

Alphabet Soup: Sagittal Balance Correction Osteotomies of the Spine-What Radiologists Should Know

Global sagittal malalignment has been demonstrated to have correlation with clinical symptoms and is a key component to be restored in adult spinal deformity. In this article, various types of sagittal balance-correction osteotomies are reviewed primarily on the basis of the 3 most commonly used procedures: Smith-Petersen osteotomy, pedicle subtraction osteotomy, and vertebral column resection. Familiarity with the expected imaging appearance and commonly encountered complications seen on postoperative imaging studies following correction osteotomies is crucial for accurate image interpretation.

Highlights from the First Annual Spinal Navigation, Emerging Technologies and Systems Integration Meeting

This paper provides a detailed report of the "First Annual Spinal Navigation, Emerging Technologies and Systems Integration" meeting held December 3, 2016 at the Seattle Science Foundation.

Does Level of Response to SI Joint Block Predict Response to SI Joint Fusion?

BACKGROUND

The degree of pain relief required to diagnose sacroiliac joint (SIJ) dysfunction following a diagnostic SIJ block (SIJB) is not known. No gold standard exists. Response to definitive (i.e., accepted as effective) treatment might be a reference standard.

METHODS

Subgroup analysis of 320 subjects enrolled in two prospective multicenter trials evaluating SIJ fusion (SIJF) in patients with SIJ dysfunction diagnosed by history, physical exam and standardized diagnostic SIJB. A 50% reduction in pain at 30 or 60 minutes following SIJB was considered confirmatory. The absolute and percentage improvements in Visual Analog Scale (VAS) SIJ pain and Oswestry Disability Index (ODI) scores at 6 and 12 months after SIJF were correlated with the average acute improvement in SIJ pain with SIJB.

RESULTS

The average pain reduction during the first hour after SIJB was 79.3%. Six months after SIJF, the overall mean VAS SIJ pain reduction was 50.9 points (0-100 scale) and the mean ODI reduction was 24.6 points. Reductions at 12 months after SIJF were similar. Examined in multiple ways, improvements in SIJ pain and ODI at 6 and 12 months did not correlate with SIJB findings.

CONCLUSIONS

The degree of pain improvement during SIJB did not predict improvements in pain or ODI scores after SIJF. A 50% SIJB threshold resulted in excellent post-SIJF responses. Using overly stringent selection criteria (i.e. 75%) to qualify patients for SIJF has no basis in evidence and would withhold a beneficial procedure from a substantial number of patients with SIJ dysfunction.

LEVEL OF EVIDENCE

Level 1.

CLINICAL RELEVANCE

The degree of pain improvement during an SIJ block does not predict the degree of pain improvement after SIJ fusion.

Sacroiliac Joint Fusion Using Triangular Titanium Implants vs. Non-Surgical Management: Six-Month Outcomes from a Prospective Randomized Controlled Trial

Background

Sacroiliac (SI) joint pain is a prevalent, underdiagnosed cause of lower back pain. SI joint fusion can relieve pain and improve quality of life in patients who have failed nonoperative care. To date, no study has concurrently compared surgical and non-surgical treatments for chronic SI joint dysfunction.

Methods

We conducted a prospective randomized controlled trial of 148 subjects with SI joint dysfunction due to degenerative sacroiliitis or sacroiliac joint disruptions who were assigned to either minimally invasive SI joint fusion with triangular titanium implants (N=102) or non-surgical management (NSM, n=46). SI joint pain scores, Oswestry Disability Index (ODI), Short-Form 36 (SF-36) and EuroQol-5D (EQ-5D) were collected at baseline and at 1, 3 and 6 months after treatment commencement. Six-month success rates, defined as the proportion of treated subjects with a 20-mm improvement in SI joint pain in the absence of severe device-related or neurologic SI joint-related adverse events or surgical revision, were compared using Bayesian methods.

Results

Subjects (mean age 51, 70% women) were highly debilitated at baseline (mean SI joint VAS pain score 82, mean ODI score 62). Six-month follow-up was obtained in 97.3%. By 6 months, success rates were 81.4% in the surgical group vs. 23.9% in the NSM group (difference of 56.6%, 95% posterior credible interval 41.4-70.0%, posterior probability of superiority >0.999). Clinically important (≥15 point) ODI improvement at 6 months occurred in 75% of surgery subjects vs. 27.3% of NSM subjects. At six months, quality of life improved more in the surgery group and satisfaction rates were high. The mean number of adverse events in the first six months was slightly higher in the surgical group compared to the non-surgical group (1.3 vs. 1.0 events per subject, p=0.1857).

Conclusions

Six-month follow-up from this level 1 study showed that minimally invasive SI joint fusion using triangular titanium implants was more effective than non-surgical management in relieving pain, improving function and improving quality of life in patients with SI joint dysfunction due to degenerative sacroiliitis or SI joint disruptions.

Clinical relevance

Minimally invasive SI joint fusion is an acceptable option for patients with chronic SI joint dysfunction due to degenerative sacroiliitis and sacroiliac joint disruptions unresponsive to non-surgical treatments.

Sacroiliac joint pain: burden of disease

Objectives

The sacroiliac joint (SIJ) is an important and significant cause of low back pain. We sought to quantify the burden of disease attributable to the SIJ.

Methods

The authors compared EuroQol 5D (EQ-5D) and Short Form (SF)-36-based health state utility values derived from the preoperative evaluation of patients with chronic SIJ pain participating in two prospective clinical trials of minimally invasive SIJ fusion versus patients participating in a nationally representative USA cross-sectional survey (National Health Measurement Study [NHMS]). Comparative analyses controlled for age, sex, and oversampling in NHMS. A utility percentile for each SIJ subject was calculated using NHMS as a reference cohort. Finally, SIJ health state utilities were compared with utilities for common medical conditions that were published in a national utility registry.

Results

SIJ patients (number [n]=198) had mean SF-6D and EQ-5D utility scores of 0.51 and 0.44, respectively. Values were significantly depressed (0.28 points for the SF-6D utility score and 0.43 points for EQ-5D; both P<0.0001) compared to NHMS controls. SIJ patients were in the lowest deciles for utility compared to the NHMS controls. The SIJ utility values were worse than those of many common, major medical conditions, and similar to those of other common preoperative orthopedic conditions.

Conclusion

Patients with SIJ pain presenting for minimally invasive surgical care have marked impairment in quality of life that is worse than in many chronic health conditions, and this is similar to other orthopedic conditions that are commonly treated surgically. SIJ utility values are in the lowest two deciles when compared to control populations.

Timing of surgery and radiotherapy in the management of metastatic spine disease: a systematic review

The last decade has witnessed a dramatic change in management of metastatic spine disease, with an increased role for surgery and emerging use of stereotactic radiotherapy, often in combination. Patients may be treated with radiotherapy followed by surgery, or have surgery and then adjuvant radiotherapy. In both cases, the surgeon and oncologist need to select the optimal timing for surgery and radiotherapy to minimize wound complications while obtaining maximum oncolytic effects. The purpose of this review was to determine the optimal timing of surgery and radiotherapy in patients surgically treated for spinal metastases. A systematic review utilizing Medline, Embase, Paper First, Web of Science, Google Scholar, and the Cochrane Database of Systematic Reviews was performed. References were screened to further identify relevant studies and basic science literature reviewed. A total of 46 reports discussing the timing of surgery after radiotherapy, describing experience in 5836 patients, were identified. Only one retrospective study addressed the research question and suggested that surgery within seven days of radiation increases the rate of postoperative wound complications. Timing of adjuvant radiotherapy following surgery was addressed in 51 reports describing 7090 patients. None of the studies specifically answered the research question. The time interval between radiotherapy and surgery was reported as 5-21 days in nine studies. Based on this systematic review together with the understanding of general principles of wound healing and effects of radiation on wound healing, the optimal radiotherapy-surgery/surgery-radiotherapy time interval should be at least one week to minimize wound complications.

MOS short form 36 and Oswestry Disability Index outcomes in lumbar fusion: a multicenter experience

BACKGROUND CONTEXT

Patient-based quality of life scales have become a critical element of post-op assessment for lumbar fusion surgery. The most extensive outcomes data have been generated through FDA-regulated IDE trials for new technologies, which produce excellent data but are constrained by strict enrollment criteria and limited indications. This raises a question as to whether the excellent results seen in these IDE trials can be reproduced in standard clinical practice.

PURPOSE

The purpose of this study was to analyze surgical results based upon standardized outcome tools, across a spectrum of interventions, for one- and two-level lumbar spine fusion procedures.

DESIGN/SETTING

This study is a retrospective review of prospectively collected patient based outcomes data.

PATIENT SAMPLE

Four hundred ninety-seven patients, who underwent 1- or 2-level lumbar spine fusion at five participating spine centers, utilizing a variety of surgical techniques. Enrollment criteria included available demographic, surgical and clinical outcome data. At a minimum, patients had pre-op and one year post-op SF-36 data. In many cases two-year post-op SF-36 data and concomitant Oswestry Disability Index (ODI) data was available.

OUTCOME MEASURES

SF36 and ODI.

METHODS

The patient population included 270 females and 227 males, with a mean age of 47 years. Sixty-five percent (N=324) had one level fusions and 35% (N=173) had two level fusions. Demographic data collected included age, gender, BMI, surgical history, smoking history and work status. Data was analyzed with repeated measures analysis of variance (ANOVA).

RESULTS

SF-36 Physical Composite Score (PCS) improved a mean 9.9 points at one year post-op and 9.5 points at two years post-op. ODI improved a mean 22.2 points at one year post-op and 22.1 points at two years post-op. SF-36 PCS data for surgical approach subgroups revealed greater improvement (p=.03) in the ALIF group as compared to the PSF, PLIF/TLIF, or 360 degrees fusion groups (12.6 points vs. 8.8, 9.3, 8.4 points) at 1 year post-op. At 2 years post-op, there was greater improvement (p=.02) in the ALIF and PSF groups as compared to the PLIF/TLIF and 360 degrees fusion groups (13.8 and 11.2 points vs. 7.7 and 6.3 points). SF-36 PCS data demonstrated similar baseline scores for patients with and without prior decompression, but a significantly greater rate of improvement (11.3 vs. 7.2 points, p=.002) for patients without prior lumbar decompression surgery. The ODI data indicated a significantly greater disability at baseline in the prior decompression group, with greater improvement (21.7 vs. 17.5 points) in patients without prior surgery.

CONCLUSIONS

This study documents improved outcomes, based on SF-36 and ODI scores, in patients undergoing lumbar fusion for one and two level degenerative disc disease. The findings also demonstrate efficacy for all of the surgical techniques studied, suggesting that surgeons can appropriately select the surgical strategy with which they are most adept.

Pedicle screw fixation of the thoracic spine: an in vitro biomechanical study on different configurations

STUDY DESIGN

An in vitro biomechanical study of different pedicle screw configuration usage on the thoracic spine using a cadaveric model.

OBJECTIVES

To investigate the degree of motion afforded different pedicle screw configurations in the thoracic spine using a cadaveric model with 2 different degrees of intrinsic stability.

SUMMARY OF BACKGROUND DATA

Recently, thoracic pedicle screws have become an alternative to hook and wire fixation, and have gained popularity. Clinically, pedicle screw use has ranged from application to every segment, to skipping every other level. There exists no clear consensus as to which strategy is most appropriate.

METHODS

The load-displacement behavior of 6 different constructs was determined on 8 fresh frozen cadaver spine specimens (T4-T12). Each construct was evaluated on 2 destabilization models, including minimum destabilization (bilateral facetectomy) and maximum destabilization (facetectomy and annulotomy). Pure moments were applied, and the resultant range of motion for each scenario was determined.

RESULTS

Facetectomy did not significantly destabilize the thoracic spine. Annulotomy and facetectomy created gross instability that rendered testing of this destabilization model impossible. All constructs significantly reduced the range of motion compared to intact or facetectomized specimens (P < or = 0.001). When different constructs were compared to each other, a pattern of continuously increasing stability emerged, with the "maximum" construct being the most stable and "minimum" configuration being the least, with varying degrees of statistical significance.

CONCLUSIONS

Our results suggest that the most important factor for the acute postoperative stability of spinal fixation is the degree of preoperative or iatrogenic destabilization. The minimum amount of pedicle screws provides adequate stability when there is minimal destabilization of the spine. On the other hand, when anterior column release has been performed or instability exists before surgery, segmental pedicle screw fixation may be necessary to achieve adequate stability.

Serum cefazolin levels during spinal fusion: effect of blood loss and duration of surgery

Perioperative cefazolin prophylaxis is commonly employed in posterior spinal fusion (PSF) procedures, which are often lengthy and involve significant blood loss. In this study, serum levels of prophylactically administered cefazolin were measured serially during spinal fusion procedures, and the possible relationship of antibiotic concentrations to blood loss and fluid therapy were examined. Serum antibiotic levels, measured at 30-min intervals, declined with a half-life of 90 min, similar to the previously reported experience with normal adult volunteers. There was no relationship between serum half-life and blood loss or fluid replacement. An explanation for these findings is offered, along with recommendations for dosing.