Diagnosis of spine pseudoarthrosis based on the biomechanical properties of bone.

BACKGROUND CONTEXT: Failure to fuse following anterior cervical discectomy and fusion (ACDF) may result in symptomatic pseudoarthrosis. Traditional diagnosis involves computerized tomography to detect bridging bone and/or flexion-extension radiographs to assess whether segmental motion is above specific thresholds; however, there are currently no well-validated diagnostic tests. We propose a biomechanically rational approach to achieve a reliable diagnostic test for pseudoarthrosis. PURPOSE: Develop and test a biomechanically based approach to the diagnosis of pseudoarthrosis. STUDY DESIGN: Literature review, development of theory, re-analysis of a previously published study with surgical exploration as the gold-standard, and retrospective analysis of pooled studies to understand time to fusion. METHODS: Fully automated methods were used to measure disc space strains (change in disc space height divided by initial height). Measurement error combined with the reported failure strain of trabecular bone led to a proposed strain threshold for diagnosis of pseudoarthrosis following ACDF. We reanalyzed previously reported flexion-extension radiographs for asymptomatic volunteers to assess whether flexion-extension radiographs, in the absence of fusion surgery, can be expected to provide sufficient stress on motion segments to allow for reliable strain-based fusion assessment. The sensitivity and specificity of strain- and rotation-based pseudoarthrosis diagnosis were assessed by reanalysis of previously reported post-ACDF flexion-extension radiographs, where intraoperative fusion assessments were also available. Finally, we assessed changes in strain over time using 9,869 flexion-extension radiographs obtained 6 weeks to 84 months post-ACDF surgery from 1,369 patients. RESULTS: The estimated error in automated measurement of disc space strain from radiographs was approximately 3%, and the reported failure strain of bridging bone was less than 2.5%. On that basis, we propose a 5% strain threshold for pseudoarthrosis diagnosis. Reanalysis of a study in which intraoperative fusion assessments were available revealed 67% sensitivity and 82% specificity for strain-based diagnosis of pseudoarthrosis, which was comparable to rotation-based diagnosis. Analysis of post-ACDF flexion-extension radiographs revealed rapid strain reduction for up to 24 months, followed by a slower decrease for up to 84 months. When rotation is less than 2 degrees, the strain-based diagnosis differed from the rotation-based diagnosis in approximately 14% of the cases. CONCLUSIONS: We propose steps for standardizing diagnosis of pseudoarthrosis based on the failure strain of bone, measurement error, and retrospective data. These steps include obtaining high-quality flexion-extension studies, the application of proposed diagnostic thresholds, and the use of image stabilization for conclusive diagnosis, when motion is near thresholds. The necessity for an accurate diagnosis with minimal radiation exposure underscores the need for further optimization and standardization in diagnosing pseudoarthrosis following ACDF surgery. CLINICAL SIGNIFICANCE: In a symptomatic postspine fusion patient, it is important to diagnose or rule-out pseudoarthrosis. There are currently no well-validated diagnostic tests for this condition. Incorporating strain-based intervertebral motion analysis into the diagnosis could lead to a standardized and validated test for detecting spine pseudoarthrosis.

Post-Operative Spinal Epidural Hematoma: Are We Discontinuing Aspirin Early Enough?

STUDY DESIGN: Retrospective cohort study. OBJECTIVES: (1) To compare the risk of Spinal Epidural Hematoma (SEH) associated with specific pre-operative and post-operative anticoagulation (AC) and antiplatelet medications (APM). (2) To define the incidence of SEH and identify risk factors for SEH in our population. METHODS: Thoracolumbar surgeries between October 2009 and March 2020 were collected. Patients who underwent incision and drainage of a symptomatic SEH were identified. AC and APM was recorded 14 days pre-operatively and post-operatively. Demographics and intra-operative factors were recorded. Relative risk with 95% confidence interval was used, with Bonferroni-corrected P-values <.05 used for significance. RESULTS: 9307 surgeries were identified. 177 (1.9%) patients returned to the OR within 30 days, 37 of whom (.39%) returned due to SEH. Seven patients were on either AC or APM pre-op, and sixteen post-op. Five were on aspirin pre-operatively (RR 3.2, 95% CI 1.25-8.22, P = .015). Risk was not increased in patients on multiple agents. No AC or APM demonstrated increased risk of hematoma post-operatively, despite trends toward significance with multiple agents. The use of a drain and complicated hypertension were associated with increased risk of SEH. CONCLUSIONS: Pre-operative aspirin is associated with increased risk of SEH, even when appropriately discontinued. Appropriately dosed post-operative anticoagulation does not increase the risk of SEH, though being on multiple agents trends toward statistical significance and should be better studied. Surgeons should be vigilant and carefully monitor patients on pre-operative antiplatelet medications for spinal epidural hematoma.

Use of Allogenic Mesenchymal Cellular Bone Matrix in Anterior and Posterior Cervical Spinal Fusion: A Case Series of 21 Patients.

STUDY DESIGN: Retrospective case series. PURPOSE: To report our early experience using allogenic mesenchymal cellular bone matrix (CBM) products in cervical spine fusion. OVERVIEW OF LITERATURE: Multi-level cervical fusions have historically yielded lower fusion rates than single level fusions, especially in patients with high risk medical comorbidities. At this time, significant literature in cervical fusion outcomes with this cellular allograft technology is lacking. METHODS: Twenty-one patients underwent either multilevel (3 or 4 level) anterior cervical discectomy and fusion, anterior cervical corpectomy and fusion, or posterior cervical fusion. ViviGen (DePuy Synthes Spine, Raynham, MA, USA), an allogenic bone matrix product, was used in addition to standard instrumentation. Radiographic evaluation was performed at 2 weeks, 12 weeks, 24 weeks and 1 year postoperative. Visual analog scale (VAS) and neck disability index (NDI) scores along with return to work and leisure activity were recorded. RESULTS: At 6 months postoperative, all patients had radiographic evidence of bone fusion regardless of age or medical comorbidities. All patients reported subjective improvement with a mean decrease in VAS from 8.3 to 1.5 and a mean decrease in NDI from 40.3% to 6.0% at 1 year. All patients also returned to work and/or regular leisure activity within 3 months. CONCLUSIONS: Twenty-one patients undergoing high-risk anterior and posterior cervical spine fusion, with the use of a commercially available mesenchymal CBM product, went on to radiographic fusion and all had improvement in subjective outcomes. While further effort and research is needed to validate its widespread use, this study shows favorable use of CBM in cervical fusion for high-risk cases.

Extensive Deep Venous Thrombosis Resulting from Anterior Lumbar Spine Surgery in a Patient with Iliac Vein Compression Syndrome: A Case Report and Literature Review.

Study Design Case report. Objective Although May-Thurner syndrome or iliac vein compression syndrome is covered in the vascular literature, it remains absent from the orthopedic and neurosurgery literature and has not been previously reported to occur in concordance with spine surgery. We review the salient points of disease presentation, diagnosis, and treatment. Methods A 33-year-old woman was followed postoperatively via clinical and radiographic findings. Her presentation, operative treatment, postoperative extensive deep venous thrombosis (DVT) formation, and management are described. Results We present a unique case of a healthy 33-year-old woman who developed an extensive left iliac vein DVT after anterior lumbar spine fusion. Although she had multiple risk factors for thrombosis, the size of the thrombus was atypical. A subsequent venogram showed compression of the left common iliac vein by the right common iliac artery, consistent with May-Thurner syndrome. Conclusions May-Thurner syndrome or iliac vein compression syndrome is a rare diagnosis that is absent from the spine literature. The condition can predispose patients to extensive iliac vein DVT. The contributing anatomy and subsequent clot often require catheter-directed thrombolysis and stenting to achieve a favorable outcome.

Number of recent inpatient admissions as a risk factor for increased complications, length of stay, and cost in patients undergoing posterior lumbar fusion.

STUDY DESIGN: Retrospective cohort study. OBJECTIVE: To identify risk factors for increased complication rate, hospital charges, and length of stay in patients undergoing posterior lumbar fusion. SUMMARY OF BACKGROUND DATA: A better understanding of risk factors for perioperative complications in patients undergoing posterior lumbar fusion can aid with patient selection and postoperative monitoring. Previous studies have assessed the impact of factors such as body mass index, age, and American Society of Anesthesiologists physical status classification on complication rate. METHODS: Data were acquired from the institution's quality improvement data set. Preoperative demographic factors included sex, age, number of inpatient admissions in the prior year, body mass index, Charlson comorbidity score, American Society of Anesthesiologists physical status classification, number of levels fused, operative duration, and medications on admission. Complications recorded included pneumonia, myocardial infarction, venous thromboembolic event, hardware failure, readmission, or unplanned return to the operating room. Multivariate regression was used to identify predictors of increased complication rate, hospital charges, and length of stay. RESULTS: A total of 462 patients were included. A history of more than 1 admission in the prior year was the only variable significantly associated with increased complication rate (odds ratio 10.56, P < 0.0001). History of more than 1 admission in the prior year (+1.92 d, P < 0.0001), operative duration more than 5 hours (+0.81 d, P = 0.008), and American Society of Anesthesiologists physical status classification 3 or greater (+0.75 d, P = 0.01) were associated with increased length of stay, whereas history of more than 1 admission in the prior year (+$27,798, P < 0.0001), fusion of 4 or more levels (+$38,043, P < 0.0001), and operative duration more than 5 hours (+$40,298, P < 0.0001) were associated with increased total charges. CONCLUSION: The number of inpatient admissions in the prior year was found to be a more powerful predictor of perioperative risk after lumbar fusion than metrics evaluated in prior studies, such as age, body mass index, and comorbidities. LEVEL OF EVIDENCE: 3.

Calcium pyrophosphate dihydrate crystal deposition disease (pseudogout) of lumbar spine mimicking osteomyelitis-discitis with epidural phlegmon.

Calcium pyrophosphate dihydrate crystal deposition disease (pseudogout) of the axial spine is rare. To our knowledge, there are few reports of the disease presenting with a presumed diagnosis of infection in the lumbar spine. As reported here, the diagnosis of osteomyelitis-discitis with epidural phlegmon was presumed before intervention. We present the case of a 60-year-old man with radiographic imaging and worsening clinical presentation at 2 consecutive hospitalizations. Axial magnetic resonance imaging originally showed increased signal intensity at the L5-S1 disk, which suggested an infectious rather than inflammatory process. Aspiration and biopsy at the time were nondiagnostic and showed no evidence of organisms. Two months after conservative treatment, the patient was readmitted with intractable low back pain and radiating bilateral leg pain. Repeat imaging showed increased interval signal in the L5-S1 disk, as well as enhancing soft-tissues that now extended to adjacent levels with extensive erosive changes. After surgical intervention for suspected infection, all cultures and stains for organisms were negative. Final pathology showed granulation tissue with focal inflammatory changes and calcium pyrophosphate crystal deposition. Although pseudogout is rare, physicians should add the disorder to the differential diagnosis for low back pain with radiculopathy and presumed infection.

Cervical spine surgery: cervical laminaplasty.

Multilevel cervical spondylosis resulting in myelopathy is a complex condition to treat surgically. Several anterior and posterior procedures have been described. Cervical laminaplasty is a procedure that provides multilevel posterior cord decompression while attempting to eliminate the postoperative development of instability and kyphosis by retaining the posterior elements. Because laminaplasty does not involve arthrodesis, more postoperative motion is preserved and early range of motion is encouraged to avoid stiffness. Although laminaplasty is a relatively straightforward procedure, understanding several key points can help avoid common technical challenges and ensure the best possible outcomes for patients. A variety of fixation techniques, each with advantages and limitations, are available to keep the laminaplasty door open. The surgeon should be aware of the complications associated with cervical laminaplasty.

High-grade adult isthmic L5-s1 spondylolisthesis: a report of intraoperative slip progression treated with surgical reduction and posterior instrumented fusion.

Adult isthmic spondylolisthesis most commonly occurs at the L5-S1 level of the lumbar spine. Slip progression is relatively rare in adults with this condition and slippage is typically associated with advanced degeneration of the disk below the pars defect. When symptomatic, radiculopathy is the typical complaint in adults with isthmic spondylolisthesis. When considering options for surgical treatment of adult isthmic spondylolisthesis, the surgeon must consider several different options, such as decompression, fusion, instrumentation, reduction, and type of bone graft to be used. All of these decisions must be individualized as deemed appropriate for each particular patient. This report presents a case of intraoperative slip progression of a L5-S1 adult isthmic spondylolisthesis to a high-grade slip, which was treated with complete surgical reduction and posterior instrumented fusion. This case demonstrates the potential instability of this condition in adults and has not been previously reported. The case details and images are reviewed and the intraoperative decisions, treatment options, and patient outcome are discussed.

Minimally invasive cervical spine foraminotomy and lateral mass screw placement.

STUDY DESIGN: This technique article describes accomplishing multilevel posterior cervical decompression and lateral mass screw placement through a tubular retraction system. OBJECTIVE: Multilevel foraminotomy and instrumented fusion using lateral mass screw fixation can be achieved through a minimally invasive technique using specialized retractors and intraoperative fluoroscopic imaging. SUMMARY OF BACKGROUND DATA: Minimally invasive surgical techniques have been adapted to the cervical spine with good results. These techniques have the theoretical advantages of reducing morbidity, blood loss, perioperative pain, and length of hospital stay associated with conventional open posterior spinal exposure. METHODS: Minimally invasive access to the posterior cervical spine was performed with exposure through a paramedian muscle-splitting approach. With the assistance of a specialized tubular retraction system with a deep soft tissue expansion mechanism, multilevel posterior cervical decompression and fusion can be accomplished. RESULTS: Minimized access to perform multilevel posterior cervical foraminotomy and fusion can be safely accomplished with tubular retraction systems. Complications associated with these techniques can include inadequate decompression, improper instrumentation placement, or neurologic injury due to poor access and visualization. CONCLUSION: Multilevel foraminotomy and instrumented fusion using lateral mass screw fixation can be safely achieved using these techniques. Complications associated with these strategies are typically due to inadequate visualization, incomplete decompression, or poor placement of instrumentation. As with all minimally invasive spine techniques, the surgeon must ensure that goals of the surgery, both technical and clinical outcomes, are comparable to those of a conventional open procedure.

Minimally invasive approaches to the cervical spine.

Minimally invasive approaches and operative techniques are becoming increasingly popular for the treatment of cervical spine disorders. Minimally invasive spine surgery attempts to decrease iatrogenic muscle injury, decrease pain, and speed postoperative recovery with the use of smaller incisions and specialized instruments. This article explains in detail minimally invasive approaches to the posterior spine, the techniques for posterior cervical foraminotomy and arthrodesis via lateral mass screw placement, and anterior cervical foraminotomy. Complications are also discussed. Additionally, illustrated cases are presented detailing the use of minimally invasive surgical techniques.

Postoperative culture positive surgical site infections after the use of irradiated allograft, nonirradiated allograft, or autograft for spinal fusion.

STUDY DESIGN: Retrospective chart review. OBJECTIVE: We report the rate of postoperative infection at our institution following the use of irradiated allograft, nonirradiated allograft, or autograft for spinal fusion procedures. SUMMARY OF BACKGROUND DATA: Infection after a spinal fusion procedure is a devastating complication. It has not been defined whether spine bone graft preparation has any correlation with postoperative infection in spinal fusion procedures. METHODS: We retrospectively identified 1435 patients who underwent spine fusion procedures with a minimum 1-year follow-up. Irradiated allograft was used in 144 patients, nonirradiated allograft was used in 441 patients, and autograft was used in 850 patients. Postoperative spinal infection was based on documented positive spine cultures at the time of re-exploration for presumed infection. Infection rates were estimated using the method of Kaplan and Meier; estimates were calculated out to 1-year postsurgery, and rates were compared using log-rank tests. RESULTS: No significant difference in the rate of surgical site infection at 1 year was observed after the use of irradiated allograft (1.7%), nonirradiated allograft (3.2%), or autograft (4.3%), P = 0.51. CONCLUSION: There is no significant difference in the rate of infection following spine fusion using irradiated allograft, nonirradiated allograft, or autograft. The selection of bone graft to aid in spinal fusion should be based on the requirements of surgical technique and availability of the desired tissue and not on a perceived association with postoperative infection.

Multilevel diskitis and vertebral osteomyelitis after diskography.

Diskitis is a rare but serious complication following diskography. The signs and symptoms may be easily confused or attributed to patients' preexisting chronic axial degenerative conditions. Unrecognized, it can progress to deep-seated infection with vertebral osteomyelitis. This article presents a case involving a 4-level destructive vertebral osteomyelitis following multilevel diskography despite prophylactic antibiotics and a double-needle technique. A 38-year-old man with radicular symptoms underwent a microdiskectomy at L4-5. Due to only minimal improvement in pain postoperatively, the patient underwent a diagnostic lumbar diskography at L2-3, L3-4, L4-5, and L5-S1 at an outside institution in consideration for repeat surgical treatment. Following this procedure, the patient continued to have debilitating symptoms and presented to our institution, where evaluation revealed elevated inflammatory biomarkers. Magnetic resonance imaging (MRI) suggested diskitis and vertebral osteomyelitis with compression fractures at the 4 levels where the diskography was performed. The patient was successfully treated with parenteral antibiotics targeted at Staphylococcus saccharolyticus, which was isolated in the culture from an open biopsy specimen after an initial percutaneous biopsy was inconclusive. Magnetic resonance imaging is the best radiologic modality for early diagnosis of this complication. This case demonstrates that early changes on MRI should warrant immediate workup and treatment. Treatment involves at least 6 weeks of parenteral antimicrobial therapy.

Mechanical strength of bone allografts subjected to chemical sterilization and other terminal processing methods.

Infectious disease transmission through the use of human donor allografts can be a catastrophic complication in an otherwise straightforward surgical procedure. The use of bone allograft in reconstructive orthopedic surgeries is increasing, yet severe complications, including death, can result if the transplanted tissues transmit a communicable disease to the tissue recipient. The BioCleanse tissue sterilization process is a fully automated, low-temperature chemical sterilization process that renders allograft tissue sterile. The purpose of this study was to evaluate the effect of a chemical tissue sterilization process on the mechanical strength of cortical bone allografts prior to implantation. Cylindrical cortical bone specimens were harvested from seven human cadaver donors and treated either by: chemical sterilization alone; chemical sterilization and terminal sterilization by gamma irradiation; chemical sterilization, lyophilization, terminal sterilization by STERRAD and rehydration; or untreated. The specimens were tested to failure in axial compression, diametral compression, shear, or bending. There were no significant differences in ultimate stress, strain, or fracture energy between the chemically sterilized and control groups in any of the testing modes.