Faculty Bibliography

Background/UNASSIGNED:Controversy exists over the ability of various lumbar interbody fusion techniques to realign global and regional balance and their effect on patient outcomes. This is a retrospective cohort study to compare thirty-day postoperative outcomes between anterior and posterior interbody fusion techniques within a large national database. Methods/UNASSIGNED:A retrospective cohort study utilizing the National Surgical Quality Improvement Program (NSQIP) database included 2,372 (29.9%) single-level anterior/direct lateral interbody fusions (ALIF/DLIF) and 5,563 (70.1%) single-level posterior/transforaminal lateral interbody fusions (PLIF/TLIF) between 2013 and 2014. Emergent cases, fracture cases, and preoperative compromised wounds were not analyzed. Primary thirty-day outcomes included mortality, return to operating room, readmission, length of stay, and other major complications. Minor outcomes included urinary tract infection, superficial incisional site infection, and perioperative blood transfusion within 72 hours. Results/UNASSIGNED:0.6%, P=0.025), which persisted in the multivariate analysis (OR =2.03; 95% CI, 1.13-3.65; P=0.017). Conclusions/UNASSIGNED:Although numerous techniques can be utilized in the treatment approach to various lumbar pathologies, anterior approaches have an increased risk of developing a perioperative DVT and early mortality. Transfusion risk is more strongly associated with elevated American Society of Anesthesiologists (ASA) class, increased age, preoperative anemia, and patients with bleeding disorders.

STUDY DESIGN/METHODS:Case series. OBJECTIVES/OBJECTIVE:To determine the safety and feasibility of S2 alar-iliac (S2AI) screw placement under robotic guidance. SUMMARY OF BACKGROUND DATA/BACKGROUND:Similar to standard iliac fixation, S2AI screws aid in achieving fixation across the sacropelvic junction and decreasing S1 screw strain. Fortunately, the S2AI technique minimizes prominent instrumentation and the need for offset connectors to the fusion construct. Herein, we present an analysis of the largest series of robotic-guided S2AI screws in the literature without any significant author conflicts of interest with the robotics industry. METHODS:Twenty-three consecutive patients who underwent spinopelvic fixation with 46 S2AI screws under robotic guidance were analyzed from 2015 to 2016. Screws were placed by two senior spine surgeons, along with various fellow or resident surgical assistants, using a proprietary robotic guidance system (Renaissance; Mazor Robotics Ltd., Caesara, Israel). Screw position and accuracy was assessed on intraoperative CT O-arm scans and analyzed using three-dimensional interactive viewing and manipulation of the images. RESULTS:The average caudal angle in the sagittal plane was 31.0° ± 10.0°. The average horizontal angle in the axial plane using the posterior superior iliac spine as a reference was 42.8° ± 6.6°. The average S1 screw to S2AI screw angle was 11.3° ± 9.9°. Two violations of the iliac cortex were noted, with an average breach distance of 7.9 ± 4.8 mm. One breach was posterior (2.2%) and one was anterior (2.2%). The overall robotic S2AI screw accuracy rate was 95.7%. There were no intraoperative neurologic, vascular, or visceral complications related to the placement of the S2AI screws. CONCLUSIONS:Spinopelvic fixation achieved using a bone-mounted miniature robotic-guided S2AI screw insertion technique is safe and reliable. Despite two breaches, no complications related to the placement of the S2AI screws occurred in this series. LEVEL OF EVIDENCE/METHODS:Level IV, therapeutic.

STUDY DESIGN/METHODS:Retrospective review of high-dose tranexamic acid (TXA) use in consecutive patients. OBJECTIVE:To determine the safety profile of a high-dose TXA protocol in complex adult spinal deformity patients. SUMMARY OF BACKGROUND DATA/BACKGROUND:Adult spinal deformity (ASD) surgery may involve significant amounts of blood loss, especially when various osteotomy techniques are used. Antifibrinolytic agents such as TXA have been used to reduce intraoperative blood loss. However, there is no universally accepted dosing protocol for its use during complex ASD surgery. METHODS:Consecutive patients undergoing spinal deformity correction over a 14-month period at a single institution were identified. Inclusion criteria were adults (age ≥18 years) who underwent posterior spinal fusion of at least 5 levels and use of our standard TXA protocol of 50 mg/kg intravenous loading dose followed by a 5-mg/kg/h infusion until skin closure. Patient demographics, estimated blood loss (EBL), operative time, transfusion rates, complications, and other procedure-specific information were recorded. RESULTS:A total of 100 adult patients were included. All operative procedures were performed by the senior surgeon. The mean age was 47.3 years, and 71% of patients were female. Average body mass index was 24.9. The average fusion length was 14 levels; 33/100 patients had fusion constructs of 17 levels or more. Pedicle subtraction osteotomy was performed in 9 patients and vertebral column resections were performed in 14 patients. There were 45/100 patients who had a primary procedure, whereas the rest were revisions. Mean EBL was 1,336 mL (98 mL/level, 31% estimated blood volume). There were three thromboembolic complications, including one pulmonary embolism and two deep vein thromboses (DVTs), which were all treated successfully with anticoagulation. There were no cases of myocardial infarction, seizure, stroke, or acute renal failure. CONCLUSIONS:This is the first study to demonstrate the use of high-dose TXA in a complex ASD population. Larger prospective studies are needed to assess the efficacy and safety of high-dose TXA in ASD. LEVEL OF EVIDENCE/METHODS:Level IV, therapeutic.

STUDY DESIGN/METHODS:Consensus-building using the Delphi and nominal group technique. OBJECTIVE:To establish best practice guidelines using formal techniques of consensus building among a group of experienced spinal deformity surgeons to avert wrong-level spinal deformity surgery. SUMMARY OF BACKGROUND DATA/BACKGROUND:Numerous previous studies have demonstrated that wrong-level spinal deformity occurs at a substantial rate, with more than half of all spine surgeons reporting direct or indirect experience operating on the wrong levels. Nevertheless, currently, guidelines to avert wrong-level spinal deformity surgery have not been developed. METHODS:The Delphi process and nominal group technique were used to formally derive consensus among 16 fellowship-trained spine surgeons. Surgeons were surveyed for current practices, presented with the results of a systematic review, and asked to vote anonymously for or against item inclusion during three iterative rounds. Agreement of 80% or higher was considered consensus. Items near consensus (70% to 80% agreement) were probed in detail using the nominal group technique in a facilitated group meeting. RESULTS:Participants had a mean of 13.4 years of practice (range: 2-32 years) and 103.1 (range: 50-250) annual spinal deformity surgeries, with a combined total of 24,200 procedures. Consensus was reached for the creation of best practice guidelines (BPGs) consisting of 17 interventions to avert wrong-level surgery. A final checklist consisting of preoperative and intraoperative methods, including standardized vertebral-level counting and optimal imaging criteria, was supported by 100% of participants. CONCLUSION/CONCLUSIONS:We developed consensus-based best practice guidelines for the prevention of wrong-vertebral-level surgery. This can serve as a tool to reduce the variability in preoperative and intraoperative practices and guide research regarding the effectiveness of such interventions on the incidence of wrong-level surgery. LEVEL OF EVIDENCE/METHODS:Level V.

BACKGROUND:Spinopelvic fixation is an integral part of achieving solid fusion across the lumbosacral junction, especially in deformity procedures requiring substantial correction or long-segment constructs. Traditional S2-alar-iliac (S2AI) screw-placement techniques utilize fluoroscopy, increasing operative time and radiation exposure to the patient and surgeon. We describe a novel free-hand technique for S2AI screw placement in patients with adult spinal deformity. METHODS:We reviewed the records of 45 consecutive patients who underwent spinopelvic fixation performed with use of S2AI screws by the senior surgeon and various fellows or residents over a 12-month period (2015 to 2016). In each case, the S2AI screws were placed utilizing a free-hand technique without fluoroscopic or image guidance. Screw position and accuracy were assessed by intraoperative O-arm imaging and analyzed using 3-dimensional interactive manipulation of computed tomography images. RESULTS:A total of 100 screws were placed, 51 by the senior surgeon and 49 by trainees. The mean patient age was 57.4 ± 12.7 years at the time of surgery; 37 (82.2%) of the patients were female. Preoperative diagnoses included adult idiopathic scoliosis (n = 19), adult degenerative scoliosis (n = 15), flatback syndrome (n = 2), fixed sagittal imbalance (n = 6), and distal junctional kyphosis (n = 3). Five (5%) of the screws were placed with moderate to severe cortical breaches, all of which perforated the pelvis posteriorly, with no clinically notable neurovascular or visceral complications. The breach rate did not differ significantly between the senior surgeon and trainees. CONCLUSIONS:The free-hand technique for S2AI screw placement, when performed in a standardized manner, was demonstrated to be safe and reliable in constructs requiring spinopelvic fixation. The accuracy of screw placement relies on visible and palpable anatomic landmarks that obviate the need for intraoperative fluoroscopy or image guidance, potentially reducing operative time and radiation exposure. LEVEL OF EVIDENCE/METHODS:Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

STUDY DESIGN:Retrospective review of prospectively collected data. OBJECTIVE:Analyze the Scoliosis Research Society (SRS) Morbidity & Mortality (M&M) database to assess the incidence and characteristics related to postoperative surgical site infection (SSI) after spinal deformity surgery. SUMMARY OF BACKGROUND DATA:Infections involving spinal instrumentation are associated with greater rates of disability. Rates of postoperative SSI after spinal deformity surgery range from 1.9% to 4.4%. Postoperative SSI rates of 4.2% for adult kyphosis, 2.1% for adult spondylolisthesis, and 3.7% for adult scoliosis have been reported. METHODS:The SRS M&M database was evaluated to define patient demographics, perioperative factors, and infection characteristics of spinal deformity patients with postoperative spine infections after deformity surgery in 2012. RESULTS:Of the 47,755 procedures reported to the SRS in 2012, there were 578 (1.2%) diagnosed SSIs. Infection rates for patients with kyphosis were significantly higher compared with patients with scoliosis (2.4% vs. 1.1%, p < .0001) or spondylolisthesis (2.4% vs. 1.1%, p < .0001). Spinal fusions were performed in 86.3% of patients, 75.1% of which were performed posteriorly. Osteotomies were performed in 30.1% of patients. Deep infections below the fascia accounted for 68.0% of infections. Methicillin-sensitive (41.9%) and methicillin-resistant (17.0%) Staphylococcus aureus were the most commonly isolated pathogens, whereas gram-negative bacteria accounted for 25.4% of cases. Long-term antibiotic suppression was required in 18.9% of patients, and overall complications from antibiotics occurred in 4.5% of patients. Operative treatment was required in 81.8% of SSI cases. CONCLUSION:SSIs occur in 1.2% of spine deformity patients, with a rate significantly higher in patients with kyphosis. Approximately 25% of these infections are secondary to gram-negative species. Antibiotic complications occur in 4.5% of patients being treated for SSI. Despite advancements in surgical technique and infection prophylaxis, postoperative SSI remains one of the most common complications in spinal deformity surgery. LEVEL OF EVIDENCE:Level III.

Osteoclasts play key roles in bone remodeling and pathologic osteolytic disorders such as inflammation, infection, bone implant loosening, rheumatoid arthritis, metastatic bone cancers, and pathological fractures. Osteoclasts are formed by the fusion of monocytes in response to receptor activators of NF-κB-ligand (RANKL) and macrophage colony stimulating factor 1 (M-CSF). Calreticulin (CRT), a commonly known intracellular protein as a calcium-binding chaperone, has an unexpectedly robust anti-osteoclastogenic effect when its recombinant form is applied to osteoclast precursors in vitro or at the site of bone inflammation externally in vivo. Externally applied Calreticulin was internalized inside the cells. It inhibited key pro-osteoclastogenic transcription factors such as c-Fos and nuclear factor of activated T cells, cytoplasmic 1 (NFATc1)-in osteoclast precursor cells that were treated with RANKL in vitro. Recombinant human Calreticulin (rhCRT) inhibited lipopolysaccharide (LPS)-induced inflammatory osteoclastogenesis in the mouse calvarial bone in vivo. Cathepsin K molecular imaging verified decreased Cathepsin K activity when rhCalreticulin was applied at the site of LPS application in vivo. Recombinant forms of intracellular proteins or their derivatives may act as novel extracellular therapeutic agents. We anticipate our findings to be a starting point in unraveling hidden extracellular functions of other intracellular proteins in different cell types of many organs for new therapeutic opportunities. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:2658-2666, 2017.

BACKGROUND: Given the increasing societal focus on health care utilization and value-based care, it is essential to understand the demographic and economic data surrounding percutaneous vertebral augmentation procedures performed in the United States. Double-blinded prospective randomized controlled trials have shown no benefit to the use of vertebroplasty over a sham procedure in the treatment of vertebral fractures. Contrastingly, kyphoplasty may be beneficial when appropriately indicated. METHODS: The National Inpatient Sample (NIS) database was queried for patients who underwent either kyphoplasty (ICD-9-CM 81.66) or vertebroplasty (ICD-9-CM 81.65) procedures between 2006 and 2014 across 44 states. Demographic and economic data were obtained which included the annual number of surgeries, age, sex, insurance type, location, and frequency of routine discharge. The NIS database represents a 20% sample of discharges from U.S. hospitals, which is weighted to provide national estimates. RESULTS: In 2014, an estimated total number of 19,420 kyphoplasty and 6,130 vertebroplasty procedures were performed across the United States. The number of vertebroplasty procedures decreased 53% from 13,128 in 2008. Similarly, the number of kyphoplasty procedures decreased 17% from 23,320 in 2007. Based on payer, Medicare patients comprised 83% of those billed for kyphoplasty and vertebroplasty, and 75% of procedures were utilized in areas designated as "not low income". In 2014, patients in the South Atlantic region comprised 24% of vertebroplasty and 28% of kyphoplasty cases, far more than any other region. Additionally, kyphoplasty and vertebroplasty were more often performed in teaching facilities rather than community hospitals (60% and 67%, respectively). CONCLUSIONS: Since the publication of two double-blind, prospective randomized controlled trials showed no benefit of vertebroplasty over a sham procedure, there has been a significant decrease in both kyphoplasty and vertebroplasty procedures.

PURPOSE: To evaluate the current evidence in the literature on treatment strategies for degenerative lumbar spine fusion in patients with osteoporosis. METHODS: A systematic review of the literature from 1950 to 2015. RESULTS: The review of the literature yielded 15 studies on the effect of treatment options for osteoporosis on lumbar fusion rates. This study evaluated only degenerative lumbar spine conditions and excluded deformity patients. One study demonstrated an association between low bone mass as measured by Hounsfield units and lower fusion rates. Six studies evaluated perioperative medical treatment of osteoporosis and showed higher fusion rates in patients treated with alendronate and teriparatide. The strongest evidence was for perioperative teriparatide. Eight studies evaluated surgical treatment strategies in patients with osteoporosis and showed that cement augmentation of pedicle screws and expandable pedicle screws demonstrated improved fusion rates than traditional pedicle screws. The strongest evidence was for expandable pedicle screws. CONCLUSION: There are 15 articles evaluating osteoporosis in patients undergoing lumbar fusion and the highest level of evidence is for perioperative use of teriparatide.

Autograft, while currently the gold standard for bone grafting, has several significant disadvantages including limited supply, donor site pain, hematoma formation, nerve and vascular injury, and fracture. Bone allografts have their own disadvantages including reduced osteoinductive capability, lack of osteoprogenitor cells, immunogenicity and risk of disease transmission. Thus demand exists for tissue-engineered constructs that can produce viable bone while avoiding the complications associated with human tissue grafts. This review will focus on recent advancements in tissue-engineered bone graft substitutes utilizing nanoscale technology in spine surgery applications. An evaluation will be performed of bone graft substitutes, biomimetic 3D scaffolds, bone morphogenetic protein, mesenchymal stem cells and intervertebral disc regeneration strategies.