Factors Predictive of Adjacent Segment Disease After Lumbar Spinal Fusion.

OBJECTIVE: Adjacent segment disease (ASD) is a long-term complication of lumbar spinal fusion. This study aims to evaluate demographic and operative factors that influence development of ASD after fusion for lumbar degenerative pathologies. METHODS: A retrospective cohort study was performed on patients undergoing instrumented lumbar fusion for degenerative disorders (spondylolisthesis, stenosis, or intervertebral disk degeneration) with a minimum follow-up of 6 months. RESULTS: Our inclusion criteria were met by 568 patients; 29.4% of patients had developed surgical ASD. Median follow-up was 2.8 years. Multivariate logistic regression analysis showed that decompression of segments outside the fusion construct had higher ASD (odds ratio = 2.6; P < 0.001), and those undergoing fusion for spondylolisthesis had lower ASD (odds ratio = 0.47; P = 0.003). CONCLUSIONS: Results of our study show that the most important surgical factor contributing to ASD is decompression beyond fused levels. Hence caution should be exercised when decompressing spinal segments outside the fusion construct. Conversely, spondylolisthesis patients had the lowest ASD rates in our cohort.

Primary Extradural Tumors of the Spine - Case Review with Evidence-guided Management.

BACKGROUND: Primary extradural tumors of the spine comprise only a small percentage of all spinal tumors. However, given their relative radioresistance and their typical malignant, invasive nature, surgery may be associated with fairly high morbidity and mortality rates. Furthermore, it may be especially difficult to achieve gross total resections with tumor-free margins. CASE DESCRIPTIONS: We present two cases and review the literature regarding the presentation, diagnosis, and evidence-based guidance/treatment of primary extradural spinal tumors. The first patient with an L1 chordoma presented with cauda equina syndrome. Following surgery, the second patient, with a giant cell tumor of the cervicothoracic junction, responded well to the novel drug denosumab, a monoclonal antibody to the RANK ligand. CONCLUSION: Primary extradural spine tumors pose significant challenges to surgeons as the aim is to achieve satisfactory surgical outcomes with clean tumor margins (e.g, thus avoid recurrence) while minimizing morbidity. Improvements in radiotherapy, chemotherapy, and novel molecular drugs may increase survival rates and improve overall outcomes.

Intra- and postoperative very low dose intravenous ketamine infusion does not increase pain relief after major spine surgery in patients with preoperative narcotic analgesic intake.

OBJECTIVE: This study aims to demonstrate the analgesic efficacy and opioid-sparing effect of low dose ketamine in patients with preoperative narcotic intake undergoing major spine surgery. DESIGN: The study used a prospective, randomized, double-blinded, and placebo-controlled clinical trial. SETTINGS AND PATIENTS: We evaluated the analgesic efficacy and safety of low dose IV ketamine infusion after major spine surgery in patients with preoperative narcotic analgesic intake. Ketamine group received IV ketamine infusion (2 µg/kg/min) and saline group received saline intraoperatively and the first 24 hours postoperatively. In addition, all patients received IV patient-controlled hydromorphone and epidural bupivacaine. OUTCOME MEASURES: Pain scores, narcotic requirement, and side effects were compared between the groups for 48 hours postoperatively. RESULTS: Thirty patients completed the study (N = 15 in each group). No difference in pain scores at rest and movement was noted between the groups (P > 0.05). Patients in ketamine group received 40.42 ± 32.86 mg IV hydromorphone at 48 hours compared with 38.24 ± 26.19 mg in saline group (P = 0.84). Central nervous system side effects were observed in five (33%) ketamine group patients compared with nine (60%) in saline group (P = 0.29). CONCLUSION: The addition of IV very low dose ketamine infusion regimen did not improve postoperative analgesia. Side effects were not increased with low dose ketamine.

Electrical stimulation therapies for spinal fusions: current concepts.

Electrical stimulation therapies have been used for more than 30 years to enhance spinal fusions. Although their positive effects on spinal fusions have been widely reported, the mechanisms of action of the technologies were only recently identified. Three types of technologies are available clinically: direct current, capacitive coupling, and inductive coupling. The latter is the basis of pulsed electromagnetic fields and combined magnetic fields. This review summarizes the current concepts on the mechanisms of action, animal and clinical studies, and cost justification for the use of electrical stimulation for spinal fusions. Scientific studies support the validity of electrical stimulation treatments. The mechanisms of action of each of the three electrical stimulation therapies are different. New data demonstrates that the upregulation of several growth factors may be responsible for the clinical success seen with the use of such technologies.

Comparison of methods for determining the presence and extent of anterior lumbar interbody fusion.

STUDY DESIGN: Titanium alloy interbody fusion devices with autogenous bone were placed in the L5-L6 disc space of 31 adult pig-tailed monkeys through an anterolateral (retroperitoneal) approach. Anteroposterior and lateral radiographs, CT imaging, and histologic analysis of the specimens were performed. OBJECTIVES: This study compared the accuracy of plain film radiographs and CT imaging for determining bony fusion of a titanium interbody device implanted in a non-human primate model. The accuracy of the assessments was determined by comparison to histologic analysis. SUMMARY OF BACKGROUND DATA: Interbody fusion assessment is often difficult to compare in clinical studies because of differences in definition of fusion criteria. In addition, the accuracy of plain film radiographs and CT imaging assessments of fusion are debated because of device material radiopacity and introduction of artifacts. METHODS: A uniform grading system evaluating both the presence and extent of bony fusion was applied to all evaluation techniques. Matched-pair nonparametric t tests were used to determine differences in scoring. RESULTS: The radiographic and histologic presence of fusion grades was equivalent in only 13 of 29 cases (45%), while the CT imaging was equivalent to histologic assessment in 24 of 29 cases (83%). However, the extent of bony fusion in CT imaging and histologic assessment was equivalent in only 4 of 29 cases (14%). Grading of CT images significantly overestimated the extent of fusion. CONCLUSIONS: This study demonstrated CT imaging techniques to be superior to plain film radiographs in determining the presence of bony fusion. However, CT imaging did not accurately determine the extent of bony fusion present as confirmed by histologic analysis.

Direct current stimulation of titanium interbody fusion devices in primates.

BACKGROUND CONTEXT: The fusion rate for anterior lumbar interbody fusion (ALIF) varies widely with the use of different interbody devices and bone graft options. Adjunctive techniques such as electrical stimulation may improve the rate of bony fusion. PURPOSE: To determine if direct current (DC) electrical stimulation of a metallic interbody fusion device enhanced the incidence or extent of anterior bony fusion. STUDY DESIGN/SETTING: ALIF was performed using titanium alloy interbody fusion devices with and without adjunctive DC electrical stimulation in nonhuman primates. METHODS: ALIF was performed through an anterolateral approach in 35 macaques with autogenous bone graft and either a titanium alloy (Ti-6Al-4V) fusion device or femoral allograft ring. The fusion devices of 19 animals received high (current density 19.6 microA/cm2) or low (current density 5.4 microA/cm2) DC electrical stimulation using an implanted generator for a 12- or 26-week evaluation period. Fusion sites were studied using serial radiographs, computed tomography imaging, nondestructive mechanical testing and qualitative and semiquantitative histology. RESULTS: Fusion was achieved with the titanium fusion device and autogenous bone graft. At 12 weeks, the graft was consolidating and early to moderate bridging callus was observed in and around the device. By 26 weeks, the anterior callus formation was more advanced with increased evidence of bridging trabeculations and early bone remodeling. The callus formation was not as advanced or abundant for the allograft ring group. Histology revealed the spinal fusion device had an 86% incidence of bony fusion at 26 weeks compared with a 50% fusion rate for the allograft rings. DC electrical stimulation of the fusion device had a positive effect on anterior interbody fusion by increasing both the presence and extent of bony fusion in a current density-dependent manner. CONCLUSIONS: Adjunctive DC electrical stimulation of the fusion device improved the rate and extent of bony fusion compared with a nonstimulated device. The fusion device was equivalent to or better than the femoral allograft ring in all evaluations. The use of adjunctive direct current electrical stimulation may provide a means of improving anterior interbody fusion.

Diastematomyelia presenting as progressive weakness in an adult after spinal fusion for adolescent idiopathic scoliosis.

BACKGROUND CONTEXT: Diastematomyelia is uncommon and rarely presents in adulthood. This report draws attention to the fact that patients who underwent spinal fusion for deformity before the widespread use of computed tomography (CT) and magnetic resonance imaging (MRI) may have unrecognized spinal cord abnormalities. This should be considered if revision surgery is contemplated. PURPOSE: This case report focuses on the late presentation of lower-extremity weakness in a 44-year-old woman with a split cord malformation (diplomyelia), diastematomyelia and tethered cord syndrome. METHODS: The patient underwent instrumented posterior spinal fusion with a Harrington rod as a child for progressive thoracolumbar scoliosis. As an adult, she developed paraparesis after a traumatic event. The patient underwent decompressive laminectomy, subtotal resection of the old fusion mass and resection of the osseous septum. Postoperatively, an anterior spinal fluid leak in the lower thoracic region required repeated fascial grafting, resection of a pseudomeningocele and reverse left latissimus dorsi flap transfer. The leak was controlled, and the patient had near complete resolution of her paraparesis 1 year after her surgery. RESULTS: The case described herein is unusual in that patients with diplomyelia and diastematomyelia rarely are symptomatic in adulthood. However, trauma may precipitate the onset of neurologic symptoms. This patient underwent spinal surgeries to address deformity, pain and progressive lower-extremity weakness. Preoperative CT and MRI studies showed a split cord malformation and diastematomyelia at L1-L2 with spinal stenosis and tethering of both hemicords. CONCLUSIONS: Progressive weakness without any previous neurologic deficit or neurocutaneous stigmas of an underlying spinal cord abnormality may develop in the adult with unrecognized diastemotomyelia. This case demonstrates that a thorough preoperative workup of patients with complex spinal deformities is imperative.

Prevention of postlaminectomy epidural fibrosis using bioelastic materials.

STUDY DESIGN: The use of elastic protein-based polymers for the prevention of epidural fibrosis following lumbar spine laminectomy was investigated in a rabbit model. OBJECTIVES: To determine the safety and efficacy of two bioelastic polymers in matrix and gel forms as interpositional materials in preventing postlaminectomy epidural fibrosis. SUMMARY OF BACKGROUND DATA: Postlaminectomy epidural fibrosis complicates revision spine surgery and is implicated in cases of "failed back syndrome." Materials employed as mechanical barriers to limit tethering of neural elements by the fibrosis tissue have met with little success. A recent family of protein-based polymers, previously reported to prevent postoperative scarring and adhesions, may hold promise in treating this condition. METHODS: Sixteen female New Zealand White rabbits underwent laminectomy at L4 and L6. Two polymer compositions, each in membrane and gel forms, were implanted at a randomly assigned level in four rabbits each, with the remaining level serving as an internal control. The animals were killed at 8 weeks, and qualitative and quantitative histology and gross pathologic examination were performed for both the control and the experimental sites to assess the polymers' efficacy in preventing dorsal epidural fibrosis. RESULTS: The use of the polymers caused no adverse effects. Compared to the control sites, both polymers in either gel or membrane form significantly reduced the formation of epidural fibrosis and its area of contact with the dura postlaminectomy. However, no significant difference in efficacy was detected between either the polymers or their respective forms in preventing epidural fibrosis. CONCLUSIONS: The selected compositions of biosynthetic, bioelastic polymers were safe and effective in the limiting the direct contact and consequent tethering of the underlying neural elements by the postlaminectomy epidural fibrosis in rabbits.