Topical tranexamic acid in spinal surgery: A systematic review and meta-analysis.

Tranexamic acid (TXA) is a commonly used antifibrinolytic agent for perioperative blood conservation in several surgical specialties. Although historically administered intravenously, such systemic administration may be accompanied by severe side effects. Thus, the topical usage of TXA has been established in several fields but remains poorly evaluated in spine surgery. In this study, the authors aimed to review the medical literature on topical TXA usage in spine surgery to evaluate its safety and efficacy. We reviewed manuscripts and clinical trials exploring topical TXA usage in spine surgery published by April 1st, 2018. Postoperative blood loss volumes and hospitalization lengths of stay were evaluated with separate meta-analyses. We identified five articles and one unpublished clinical trial that were placebo-controlled and comprised 218 patients receiving topical TXA in spine surgery. Patients receiving topical TXA demonstrated significantly lower postoperative blood loss as compared to the placebo group (Standardized Mean Difference [SMD] 2.21, 95% CI 0.79-3.62, p < 0.001) and had a lower hospitalization duration (MD 0.99, 95% CI 0.49-1.49, p < 0.001). Overall, topical TXA favorably reduced postoperative blood loss and hospitalization duration in patients undergoing spinal surgery. However, further randomized controlled trials will be needed to definitively establish the optimal therapeutic doses needed for hemorrhage management, and the pharmacodynamics of tTXA in spinal surgery.

Preventing Pseudoarthrosis and Proximal Junctional Kyphosis: How to Deal with the Osteoporotic Spine.

The increase in the aging population has led to an overall increase in the number of elderly patients undergoing spinal fusion surgery. This patient population, however, exhibits significant treatment challenges because of poor bone quality. By virtue of exhibiting decreased pullout strength and insertional torque, osteoporotic patients are at a substantial risk of developing vertebral fractures, instrumentation failure, pseudoarthrosis, and proximal junctional failures. It is, therefore, imperative for the treating surgeon to optimize bone health before recommending a spinal fusion surgery. Several preoperative medical therapies (vitamin D, calcium, bisphosphonates, parathyroid hormone, and so forth) exist to optimize bone health.

Contributions of Material Properties and Structure to Increased Bone Fragility for a Given Bone Mass in the UCD-T2DM Rat Model of Type 2 Diabetes.

Adults with type 2 diabetes (T2D) have a higher fracture risk for a given bone quantity, but the mechanisms remain unclear. Using a rat model of polygenic obese T2D, we demonstrate that diabetes significantly reduces whole-bone strength for a given bone mass (µCT-derived BMC), and we quantify the roles of T2D-induced deficits in material properties versus bone structure; ie, geometry and microarchitecture. Lumbar vertebrae and ulnae were harvested from 6-month-old lean Sprague-Dawley rats, obese Sprague-Dawley rats, and diabetic obese UCD-T2DM rats (diabetic for 69 ± 7 days; blood glucose >200 mg/dL). Both obese rats and those with diabetes had reduced whole-bone strength for a given BMC. In obese rats, this was attributable to structural deficits, whereas in UCD-T2DM rats, this was attributable to structural deficits and to deficits in tissue material properties. For the vertebra, deficits in bone structure included thinner and more rod-like trabeculae; for the ulnae, these deficits included inefficient distribution of bone mass to resist bending. Deficits in ulnar material properties in UCD-T2DM rats were associated with increased non-enzymatic crosslinking and impaired collagen fibril deformation. Specifically, small-angle X-ray scattering revealed that diabetes reduced collagen fibril ultimate strain by 40%, and those changes coincided with significant reductions in the elastic, yield, and ultimate tensile properties of the bone tissue. Importantly, the biomechanical effects of these material property deficits were substantial. Prescribing diabetes-specific tissue yield strains in high-resolution finite element models reduced whole-bone strength by a similar amount (and in some cases a 3.4-fold greater amount) as the structural deficits. These findings provide insight into factors that increase bone fragility for a given bone mass in T2D; not only does diabetes associate with less biomechanically efficient bone structure, but diabetes also reduces tissue ductility by limiting collagen fibril deformation, and in doing so, reduces the maximum load capacity of the bone. © 2018 American Society for Bone and Mineral Research.

Hypoalbuminemia Is Associated With Septic Revisions After Primary Surgery and Postoperative Infection After Revision Surgery.

STUDY DESIGN: Retrospective database review. OBJECTIVE: To determine (1) the relationship between hypoalbuminemia and body mass index (BMI); (2) the association between malnutrition and revision spine surgery for septic reasons; and (3) the association between malnutrition and infection after aseptic revision spine surgery. SUMMARY OF BACKGROUND DATA: Although malnutrition has been suggested to increase the risk of infection after spine surgery, evidence supporting this hypothesis is conflicting. METHODS: Patients undergoing revision spine surgery were identified in the American College of Surgeons National Surgical Quality Improvement Program (ACS-NSQIP) from 2006 to 2014. Hypoalbuminemia (albumin < 3.5 g/dL) was used as a surrogate marker of malnutrition. Multivariate analysis was used to assess the association of hypoalbuminemia with septic versus aseptic revision spine surgery. The association between hypoalbuminemia and deep infection postoperatively within 30 days of aseptic revision surgeries was also assessed. RESULTS: A total of 3136 patients who underwent revision spine surgery were identified; 2922 (93.2%) underwent surgery for aseptic reasons, and 214 (6.8%) for septic reasons. Hypoalbuminemia was present in all BMI groups including obese patients, though it was highest in underweight patients (22.4%). Patients who underwent surgery for septic reasons had a higher rate of hypoalbuminemia than those undergoing surgery for aseptic reasons (49.1% vs. 8.5%, P < 0.001) with nine times the odds of having hypoalbuminemia (adjusted odds ratio, OR = 9.17, P < 0.001). Of the 2922 patients undergoing revision spine surgery for aseptic reasons, hypoalbuminemia was independently associated with acute deep infection within 30 days of surgery (adjusted OR = 2.85, P = 0.019). CONCLUSION: Malnutrition is more common in revision spine surgery for septic reasons when compared with aseptic revision surgery. Acute postoperative infection following aseptic revision surgery is also more common in patients with malnutrition. Further study, in the form of prospective trials, will help to increase our understanding of the effects of malnutrition in spine surgery. LEVEL OF EVIDENCE: 3.

Spine deformity surgery in the elderly: risk factors and 30-day outcomes are comparable in posterior versus combined approaches.

Objectives Risk factors portending poor outcome following elective spine deformity fusion remain in need of characterization and stratification in the elderly population. Methods Cases aged ≥60 years who underwent elective posterior or anterior-posterior ('combined') fusion were extracted from the American College of Surgeons National Surgical Quality Improvement Program years 2007-2013 and analyzed by surgical cohort (posterior vs. combined). The 30-day outcomes included operation time, hospital length of stay (HLOS), perioperative complications, and discharge destination. Multivariable regressions controlling for demographic/clinical variables were performed. Odds ratios (OR) and mean differences (B) were reported with 95% confidence intervals (CI). Results A total of 881 cases (18.2% combined; 81.8% posterior) aged 70 ± 6.2 years, 32.8% male, and 87.2% Caucasian were included. Posterior fusions associated with extreme body habitus (obese class II/III and underweight; P = 0.027), functional independence (97.5% vs. 91.8%; P = 0.010), and multi-level fusions (7-12 levels: 24.8% vs. 18.1%; ≥13 levels: 8.9% vs. 3.1%; P = 0.004). Overall operation time was 338.0 ± 150.2-min and HLOS 7.4 ± 6.6-days; 17.1% suffered early complications and 54.5% were discharged home. On multivariable analysis, combined (B = 63.8-min; P < 0.001), and multi-level fusions (7-12: 61.0-min; P < 0.001; ≥13: 133.8-min; p < 0.001) associated with increased operation time. HLOS increased for multi-level fusions (7-12 levels: 1.3-days; P = 0.012; ≥13 levels: 2.2-days; P = 0.008). Overall complications did not differ by cohort or levels; on post hoc analysis combined fusions associated with pneumonia (OR = 3.05; P = 0.008). Multi-level fusions showed decreased odds of discharge home (7-12 levels: OR = 0.57; P = 0.003; ≥13-levels: OR = 0.41; P = 0.003). Conclusions The 30-day outcomes and early perioperative complications are comparable for posterior vs. combined approaches to correct deformity in the elderly. Multi-level fusions are associated with increased operation time, HLOS, and discharge to higher level of care.

Machine Learning-Based Classification of 38 Years of Spine-Related Literature Into 100 Research Topics.

STUDY DESIGN: Retrospective review. OBJECTIVE: To identify the top 100 spine research topics. SUMMARY OF BACKGROUND DATA: Recent advances in "machine learning," or computers learning without explicit instructions, have yielded broad technological advances. Topic modeling algorithms can be applied to large volumes of text to discover quantifiable themes and trends. METHODS: Abstracts were extracted from the National Library of Medicine PubMed database from five prominent peer-reviewed spine journals (European Spine Journal [ESJ], The Spine Journal [SpineJ], Spine, Journal of Spinal Disorders and Techniques [JSDT], Journal of Neurosurgery: Spine [JNS]). Each abstract was entered into a latent Dirichlet allocation model specified to discover 100 topics, resulting in each abstract being assigned a probability of belonging in a topic. Topics were named using the five most frequently appearing terms within that topic. Significance of increasing ("hot") or decreasing ("cold") topic popularity over time was evaluated with simple linear regression. RESULTS: From 1978 to 2015, 25,805 spine-related research articles were extracted and classified into 100 topics. Top two most published topics included "clinical, surgeons, guidelines, information, care" (n = 496 articles) and "pain, back, low, treatment, chronic" (424). Top two hot trends included "disc, cervical, replacement, level, arthroplasty" (+0.05%/yr, P < 0.001), and "minimally, invasive, approach, technique" (+0.05%/yr, P < 0.001). By journal, the most published topics were ESJ-"operative, surgery, postoperative, underwent, preoperative"; SpineJ-"clinical, surgeons, guidelines, information, care"; Spine-"pain, back, low, treatment, chronic"; JNS- "tumor, lesions, rare, present, diagnosis"; JSDT-"cervical, anterior, plate, fusion, ACDF." CONCLUSION: Topics discovered through latent Dirichlet allocation modeling represent unbiased meaningful themes relevant to spine care. Topic dynamics can provide historical context and direction for future research for aspiring investigators and trainees interested in spine careers. Please explore https://singdc.shinyapps.io/spinetopics. LEVEL OF EVIDENCE: N A.

Increase in spinal deformity surgery in patients age 60 and older is not associated with increased complications.

BACKGROUND CONTEXT: Surgical treatment for adult spinal deformity improves patient quality of life; however, trends in surgical utilization in the elderly, who may be at higher risk for complications, remain unclear. PURPOSE: To identify trends in the utilization of adult deformity and determine complication rates among older patients. STUDY DESIGN: This is a retrospective database analysis. PATIENT SAMPLE: The Nationwide Inpatient Sample database was queried from 2004 to 2011 to identify adult patients who underwent spinal fusion of eight or more levels using International Classification of Diseases, Ninth Revision (ICD-9) coding. OUTCOME MEASURES: Incidence of surgery, complication rates, length of stay, and total hospital charges. METHODS: The incidence of surgery was normalized to United States census data by age group. Trends in complications, length of stay, and inflation-adjusted hospital charges were determined using linear regression and Cochran-Armitage trend testing. RESULTS: An estimated 29,237 patients underwent adult spinal deformity surgery with an increase from 2,137 to 5,030 cases per year from 2004 to 2011. Surgical incidence among patients 60 years and older increased from 1.9 to 6.5 cases per 100,000 people from 2004 to 2011 (p<.001), whereas utilization in patients younger than 60 increased from 0.59 to 0.93. Linear regression revealed that the largest increase in surgical utilization was for patients aged 65-69 years with an increase of 0.68 patients per 100,000 people per year (p<.001), followed by patients aged 70-74 years with a rate of 0.56 patients per 100,000 people per year (p=.001). Overall complication rates were 22.5% in 2004 and 26.7% in 2011. Although complication risk increased with age (≥60 vs. <60: relative risk 1.91 [1.83, 1.99], p<.001), within-age group rates were stable over time. Mean length of stay was 9.6 days in 2004 and 9.0 days in 2011. Inflation-adjusted mean hospital charges increased from $171,517 in 2004 to $303,479 in 2011 (p<.001). CONCLUSIONS: Operative management of adult spinal deformity increased 3.4-fold among patients ≥60 years from 2004 to 2011, with an associated 1.8-fold increase in hospital charges. Although the exact reasons for the striking increase in hospital charges remain unclear, some of the increase is likely related to decreasing reimbursement of charges by payors over the same period of time. The large majority of cases were performed in large academic centers, and growth in deformity trained spine specialists in these centers may have contributed to this trend. Despite the increased utilization of surgery for adult spinal deformity, in-hospital complications remained stable across all ages.

Increasing Rates of Surgical Management of Multilevel Spinal Curvature in Elderly Patients.

STUDY DESIGN: Retrospective analysis of Nationwide Inpatient Sample (NIS) database. OBJECTIVE: To analyze trends in utilization and hospital charges for multilevel spinal curvature surgery in patients over 60 from 2004 to 2011. SUMMARY OF BACKGROUND DATA: Multilevel spinal curvature has been increasingly recognized as a major source of morbidity in patients over sixty years of age. The economic burden of non-operative management for spinal curvature is elusive and likely underestimated. Though patient reported outcomes suggest that surgical treatment of spinal curvature may be superior to non-operative treatment in selected patients, surgical utilization trends remain unclear. METHODS: Data were obtained from the NIS between 2004 and 2011. The NIS is the largest all-payer inpatient care database with approximately eight million annual patient discharges throughout the United States. Analysis included patients over age 60 with a spinal curvature diagnosis treated with a multi-level spinal fusion (≥3 levels fused) determined by ICD-9-CM diagnosis and procedure codes. Population-based utilization rates were calculated from US census data. RESULTS: A total of 84,302 adult patients underwent multilevel spinal curvature surgery from 2004 to 2011. The annual number of ≥3 level spinal curvature fusions in patients over age 60 increased from 6,571 to 16,526, representing a 107.8% increase from 13.4 cases per 100,000 people in 2004 to 27.9 in 2011 (p < .001). Utilization rates in patients 65-69 years old experienced the greatest growth, increasing by 122% from 15.8 cases per 100,000 people to 35.1. Average hospital charges increased 108% from $90,557 in 2007 to $188,727 in 2011 (p < .001). CONCLUSIONS: Rates of surgical management of multilevel spinal curvature increased from 2004 to 2011, exceeding growth of the 60+ age demographic during the same period. Growth was observed in all age demographics, and hospital charges consistently increased from 2004 to 2011 reflecting a per-user increase in expenditure. LEVEL OF EVIDENCE: III.

Variations in Occipitocervical and Cervicothoracic Alignment Parameters Based on Age: A Prospective Study of Asymptomatic Volunteers Using Full-Body Radiographs.

STUDY DESIGN: Cross-Sectional Cohort Study OBJECTIVE.: To describe age-stratified normative values of novel occipitocervical, cervical, and cervicothoracic alignment parameters. SUMMARY OF BACKGROUND DATA: Full-body radiographic images obtained without stitching or vertical distortion represent an ideal method to evaluate occipitocervical alignment and horizontal gaze. METHODS: One hundred twenty adults with no back or neck symptoms were recruited. Age, sex, body mass index, Neck Disability Index (NDI), and Oswestry Disability Index scores were recorded. Radiographic parameters measured included: center sacral vertebral line, chin brow vertical angle (CBVA), orbital tilt (OrT), orbital slope, occipital slope (OS), occipital incidence, occiput-C2 (O-C2) lordosis, cervical lordosis (C2-C7, CL), T1 slope (TS), neck tilt, thoracic inlet angle (TIA), cervicothoracic kyphosis (C6-T4), and C2-C7 sagittal vertical axis (C2-7 SVA). Interobserver reliability was calculated for all measurements (intraclass correlation coefficient, ICC). A Pearson correlation was used to determine relationships between variables. RESULTS: A total of 115 patients were analyzed; average age as 50.1 years (range 22-78). All measured variables had an ICC >0.6. CL (r = -0.33, P < 0.001), TS (r = 0.42, P < 0.001), TIA (r = 0.24, P = 0.010), and C7 SVA (r = 0.48, P < 0.001) all increased with age. OrT (r = -0.88, P < 0.001) and OS (r = 0.73, P < 0.001) were both strongly correlated with CBVA and each other (r = -0.83, P ≤ 0.001). Both measures were also correlated with the C2-C7 SVA (OrT, r = 0.41, P < 0.001; OS, r = -0.29, P = 0.002) and O-C2 angle (OrT, r = 0.46, P < 0.001; OS, r = -0.28, P = 0.003). C6-T4 angulations was negatively correlated with NDI scores in this population (r = -0.25, P = 0.007). CONCLUSION: We present age-based normative values for occipitocervical, cervicothoracic, and cervical alignment parameters using a novel biplanar radiographic imaging technique. We introduce measures of craniocervical alignment that might provide surgeons with an intuitive way to account for the position of the orbit when planning cervical deformity correction. LEVEL OF EVIDENCE: 4.

Obesity Is an Independent Risk Factor of Early Complications After Revision Spine Surgery.

STUDY DESIGN: Retrospective cohort analysis of risk factors in revision spine surgery using a prospectively collected database. OBJECTIVE: To examine the risk of developing early (30-day) complications across obesity level after adjusting for comorbidities in patients undergoing revision spine surgery. SUMMARY OF BACKGROUND DATA: Prior studies suggest obesity influences early complications after primary surgery. The association between obesity and early complications after revision surgery remains to be characterized. METHODS: Data were abstracted from the American College of Surgeons National Surgical Quality Improvement Program (ACS-NSQIP) database from 2005 to 2012. Adult Caucasian patients undergoing removal/revision of instrumentation or exploration of fusion were included. Patients were categorized by WHO body mass index (BMI, kg/m): Non-Obese (18.5-29.9), Obese Class I (30-34.9), and Obese Class II/III (≥35). Univariate regression was performed to assess the predictive value of obesity level and baseline risk factors in the presence of at least one early complication, and significant predictors were entered into the multivariable model. RESULTS: Of 2538 patients, 57.6% were nonobese, 23% Obese Class I, and 19.4% Obese Class II/III. Obesity was associated with diabetes, hypertension, respiratory disease, and American Society of Anesthesiologists (ASA) score of 3-4 (all P < 0.001). BMI group (P = 0.01), older age (P = 0.008), functional dependence (P < 0.001), ASA 3-4 (P = 0.008), bleeding disorder (P = 0.04), and diabetes (P = 0.016) were identified as univariate predictors for early complications. In the multivariable model, higher BMI (P = 0.04), older age (P = 0.014), and functional dependence (P < 0.001) remained significant predictors for early complications. Notably, patients who were Obese Class II/III (OR 1.66, 95% CI [1.12-2.45]), age ≥75 (OR 1.83, [1.20-2.81]), and functionally dependent (OR 3.02 [1.85-4.94]) had significantly higher risk compared with their reference groups. CONCLUSION: Obesity is an independent risk factor for early complications after revision spine surgery. Although obesity may not contraindicate revision surgery, its status as a modifiable risk factor warrants disclosure and preoperative counseling to optimize outcomes. LEVEL OF EVIDENCE: 3.

Complications of Morbid Obesity in Total Joint Arthroplasty: Risk Stratification Based on BMI.

This study stratifies complication risk in primary total joint arthroplasty (TJA) based on body mass index (BMI). Demographics, co-morbidities, perioperative variables, and complications were reviewed for 22,808 patients. Chi-squared, one-way ANOVA, univariate and multivariable regression analysis were performed. Increasing BMI led to an increase (P<0.05) in combined complications, acute kidney injury (AKI), cardiac arrest (CA), reintubation, reoperation, and superficial infection (SI). Univariate analysis for BMI>40 revealed an increase in combined complications (15.21-vs-17.40%), AKI (1.93-vs-3.87%), CA (0.22-vs-0.57%), reintubation (0.47-vs-0.95%), reoperation (2.36-vs-3.37%), and SI (0.82-vs-1.65%). Multivariable regression showed BMI>40 as an independent predictor for combined complications (OR=1.18), AKI (OR=1.79), CA (OR=3.94), reintubation (OR=2.56), reoperation (OR=1.44), and SI (OR=2.11). Morbid obesity confers increased risk for complications in TJA.

Alterations in intervertebral disc composition, matrix homeostasis and biomechanical behavior in the UCD-T2DM rat model of type 2 diabetes.

Type 2 diabetes (T2D) adversely affects many tissues, and the greater incidence of discogenic low back pain among diabetic patients suggests that the intervertebral disc is affected too. Using a rat model of polygenic obese T2D, we demonstrate that diabetes compromises several aspects of disc composition, matrix homeostasis, and biomechanical behavior. Coccygeal motion segments were harvested from 6-month-old lean Sprague-Dawley rats, obese Sprague-Dawley rats, and diabetic obese UCD-T2DM rats (diabetic for 69 ± 7 days). Findings indicated that diabetes but not obesity reduced disc glycosaminoglycan and water contents, and these degenerative changes correlated with increased vertebral endplate thickness and decreased endplate porosity, and with higher levels of the advanced glycation end-product (AGE) pentosidine. Consistent with their diminished glycosaminoglycan and water contents and their higher AGE levels, discs from diabetic rats were stiffer and exhibited less creep when compressed. At the matrix level, elevated expression of hypoxia-inducible genes and catabolic markers in the discs from diabetic rats coincided with increased oxidative stress and greater interactions between AGEs and one of their receptors (RAGE). Taken together, these findings indicate that endplate sclerosis, increased oxidative stress, and AGE/RAGE-mediated interactions could be important factors for explaining the greater incidence of disc pathology in T2D.

Infectious, inflammatory, and metabolic diseases affecting the athlete's spine.

Sports and weight-bearing activities can have a positive effect on bone health in the growing, mature, or aging athlete. However, certain athletic activities and training regimens may place the athlete at increased risk for stress fractures in the spine. In addition, some athletes have an underlying susceptibility to fracture due to either systemic or focal abnormalities. It is important to identify and treat these athletes in order to prevent stress fractures and reduce the risk of osteoporosis in late adulthood. Therefore, the pre-participation physical examination offers a unique opportunity to screen athletes for metabolic bone disease through the history and physical examination. Positive findings warrant a thorough workup including a metabolic bone laboratory panel, and possibly a DEXA scan, which includes a lateral spine view.

Anterior arthrodesis with instrumentation for thoracolumbar scoliosis: comparison of efficacy in adults and adolescents.

STUDY DESIGN: A retrospective review was performed of adult and adolescent patients who underwent anterior spinal fusion for thoracolumbar idiopathic scoliosis; radiographic and clinical outcomes were compared. OBJECTIVE: The objective of this study was to compare the efficacy of anterior instrumentation to treat thoracolumbar scoliosis in adults and adolescents by evaluating radiographic and clinical outcomes. SUMMARY OF BACKGROUND DATA: Anterior spinal arthrodesis is an effective treatment for idiopathic scoliosis. Deformity characteristics and clinical outcomes of adults versus adolescents have not been compared. METHODS: A retrospective review of patients undergoing anterior fusion for thoracolumbar scoliosis was performed. Clinical outcomes were assessed using SRS-22. Preoperative and postoperative long films were evaluated independently. Flexibility, curve correction, and clinical outcomes were compared between adult and adolescents. RESULTS: Fifteen adults and 15 adolescents who underwent anterior spinal fusion and instrumentation were evaluated. Mean follow-up was 47 and 46 months, respectively. Flexibility of the major curve in adults (63%) was less than in adolescents (79%) (P < 0.05). Mean preoperative, major curve Cobb angles were 51 degrees and 49 degrees for adults and adolescents, respectively. Mean postoperative Cobb angles improved less for adults (17 degrees ) than for adolescents (10 degrees ) (P < 0.05). The SRS-22 questionnaire revealed no statistical difference between populations. CONCLUSION: Anterior spinal fusion is an option for both adults and adolescents with flexible, moderate thoracolumbar/lumbar curves. Flexibility significantly decreased with increased age and curve magnitude. This significantly affected curve correction. Adult patients may develop early degeneration at primary curve and compensatory curves. Careful patient selection is critical with this technique.

Computer-assisted surgical planning and image-guided surgical navigation in refractory adult scoliosis surgery: case report and review of the literature.

STUDY DESIGN: Case report and literature review. OBJECTIVE: In this case report, we present the utility of computer-assisted surgical planning and image-guided surgical navigation in the planning and execution of a major osteotomy to correct severe kyphoscoliosis. SUMMARY OF BACKGROUND DATA: Computer-assisted surgical planning is useful to appreciate the three-dimensional nature of scoliotic deformities and allows for operative maneuvers to be simulated on a computer before their implementation in the operating room. Image-guided surgical navigation improves surgical accuracy and can help translate a virtual surgical plan to the operative setting. METHODS: We report the case of a 38-year-old woman with severe, congenital kyphoscoliosis refractory to many previous surgeries, who presents with moderate progressive myelopathy and severe pain attributable to a sharp angular deformity at T12. Three-dimensional computed tomography reconstruction and computer-assisted surgical planning were used to determine the optimal corrective osteotomy. The surgical plan was translated to the operating room where a posterior vertebrectomy and instrumented correction were executed with the aid of image-guided surgical navigation. RESULTS: The osteotomy was safely performed resulting in improved sagittal and coronal alignments, as well as, correction of the sharp kyphoscoliotic deformity at the thoracolumbar junction. At 6-month follow-up, the patient's myelopathy and pain had largely resolved and she expressed high satisfaction with the procedure. CONCLUSION: We advocate this novel application of virtual surgical planning and intraoperative surgical navigation to improve the safety and efficacy of complex spinal deformity corrections.

Low-grade spondylolisthesis.

Spondylolisthesis is an often painful condition affecting millions of people in North America with some ethnic variability. It is characterized by the displacement, usually anterior, of on vertebral body upon another. There are familial predispositions to having the lesion, and a family history of spondylolisthesis may raise one's clinical suspicion. Although the diagnosis is easily made on radiographic evaluation, the pathoetiology and appropriate treatment modality are not always as clear. In the absence of severe neurological symptoms or an unsafe component of instability, a trial of conservative management is reasonable and prudent. Nevertheless, surgical management is more efficacious for enduring symptomatic relief and restoration of physical function. Whereas assessment of postoperative radiographic results lends insight to surgical technique, the true barometer of treatment success is improvement in patient quality of life.

Anterior instrumented arthrodesis for adult idiopathic scoliosis.

Anterior spinal arthrodesis with instrumentation is a useful alternative to posterior surgery in the management of thoracolumbar deformity in the adolescent and young adult. In adults, flexibility of primary and compensatory curves significantly decreases with increased age and curve magnitude. Curve flexibility is an important determinant of postoperative outcome. Anterior surgery is most appropriate for patients with moderate thoracolumbar or lumbar curves and good flexibility of adjacent segments. Adult patients may develop early degeneration at primary and compensatory curves, and these curves should be evaluated carefully before surgery and monitored closely during the postoperative period. Good results can be obtained in well-selected patients with a rigid instrumentation system and anterior structural grafts.

Histomorphometric analysis of the effects of osteocyte density on osteonal morphology and remodeling.

Osteocytes, the most abundant cells in the cortical bone matrix, are thought to have mechanosensory and chemosensory regulatory roles. Marotti theorized that osteocytes signal to osteoblasts to recruit them into the osteocyte lineage. Martin extended this theory, assuming that osteocytes display a general inhibitory effect on osteoblast function. The current study provides a quantitative analysis of the relationships between osteonal osteocyte density (Ot.N/BV), wall width (W.Wi), individual osteon porosity (IOP), and formation period (FP) in ulnar cortices from sheep labeled with tetracycline and calcein double labels. We postulated that osteocytes inhibit refilling so that the osteon wall width is thin enough, and the haversian canal is large enough, to allow adequate delivery of nutrients to the osteocytes throughout the forming and completed osteon. Therefore we tested the hypotheses that Ot.N/BV correlates negatively to FP and W.Wi, and positively to IOP, and that FP correlates positively with W.Wi. We found that Ot.N/BV correlated positively with IOP (P < 0.0001) and W.Wi correlated positively with FP (P < 0.0001). Significant negative correlations were observed between Ot.N/BV and both W.Wi (P < 0.0001) and FP (P = 0.006). These data support the general hypothesis that osteocytes contribute to the regulation of osteon morphology via the control of refilling rate and formation period, and the specific hypotheses that, for a given cement line diameter, high osteocyte density (1) reduces the rate of refilling and decreases the formation period and (2) decreases wall width and increases individual osteon porosity.