Injectable bioactive poly(propylene fumarate) and polycaprolactone based click chemistry bone cement for spinal fusion in rabbits

Degenerative spinal pathology is a widespread medical issue, and spine fusion surgeries are frequently performed. In this study, we fabricated an injectable bioactive click chemistry polymer cement for use in spinal fusion and bone regrowth. Taking advantages of the bioorthogonal click reaction, this cement can be crosslinked by itself eliminating the addition of a toxic initiator or catalyst, nor any external energy sources like UV light or heat. Furthermore, nano-hydroxyapatite (nHA) and microspheres carrying recombinant human bone morphogenetic protein-2 (rhBMP-2) and recombinant human vascular endothelial growth factor (rhVEGF) were used to make the cement bioactive for vascular induction and osteointegration. After implantation into a rabbit posterolateral spinal fusion (PLF) model, the cement showed excellent induction of new bone formation and bridging bone, achieving results comparable to autograft control. This is largely due to the osteogenic properties of nano-hydroxyapatite (nHA) and the released rhBMP-2 and rhVEGF growth factors. Since the availability of autograft sources is limited in clinical settings, this injectable bioactive click chemistry cement may be a promising alternative for spine fusion applications in addressing various spinal conditions.

Bioactive Moldable Click Chemistry Polymer Cement with Nano-Hydroxyapatite and Growth Factor-Enhanced Posterolateral Spinal Fusion in a Rabbit Model

Spinal injuries or diseases necessitate effective fusion solutions, and common clinical approaches involve autografts, allografts, and various bone matrix products, each with limitations. To address these challenges, we developed an innovative moldable click chemistry polymer cement that can be shaped by hand and self-cross-linked in situ for spinal fusion. This self-cross-linking cement, enabled by the bioorthogonal click reaction, excludes the need for toxic initiators or external energy sources. The bioactivity of the cement was promoted by incorporating nanohydroxyapatite and microspheres loaded with recombinant human bone morphogenetic protein-2 and vascular endothelial growth factor, fostering vascular induction and osteointegration. The release kinetics of growth factors, mechanical properties of the cement, and the ability of the scaffold to support in vitro cell proliferation and differentiation were evaluated. In a rabbit posterolateral spinal fusion model, the moldable cement exhibited remarkable induction of bone regeneration and effective bridging of spine vertebral bodies. This bioactive moldable click polymer cement therefore presents a promising biomaterial for spinal fusion augmentation, offering advantages in safety, ease of application, and enhanced bone regrowth.

Cellular Bone Matrix in Spine Surgery - Are They Worth the Risk: A Systematic Review

STUDY DESIGN

Systematic Review.

OBJECTIVE

To review the literature for complications and outcomes after the implantation of cellular bone matrix (CBM) during spine fusion.

METHODS

The PubMed database was queried from inception to January 31, 2023 for any articles that discussed the role of and identified a specific CBM in spinal fusion procedures. Adverse events, reoperations, methods, and fusion rates were collected from all studies and reported.

RESULTS

Six hundred articles were identified, of which 19 were included that reported outcomes of 7 different CBM products. Seven studies evaluated lumbar fusion, 11 evaluated cervical fusion, and 1 study reported adverse events of a single CBM product. Only 4 studies were comparative studies while others were limited to case series. Fusion rates ranged from 68% to 98.7% in the lumbar spine and 87% to 100% in the cervical spine, although criteria for radiographic fusion was variable. While 7 studies reported no adverse events, there was no strict consensus on what constituted a complication. One study reported catastrophic disseminated tuberculosis from donor contaminated CBM. The authors of 14 studies had conflicts of interest with either the manufacturer or distributor for their analyzed CBM.

CONCLUSIONS

Current evidence regarding the use of cellular bone matrix as an osteobiologic during spine surgery is weak and limited to low-grade non-comparative studies subject to industry funding. While reported fusion rates are high, the risk of severe complications should not be overlooked. Further large clinical trials are required to elucidate whether the CBMs offer any benefits that outweigh the risks.

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.

Development of an International AO Spine Guideline for the Use of Osteobiologics in Anterior Cervical Fusion and Decompression (AO-GO)

STUDY DESIGN

Methodological study for guideline development.

OBJECTIVE

AO Spine Guideline for Using Osteobiologics (AO-GO) project for spine degenerative pathologies was an international, multidisciplinary collaborative initiative to identify and evaluate evidence on existing use of osteobiologics in Anterior Cervical Fusion and Decompression (ACDF). The aim was to formulate precisely defined, clinically relevant and internationally applicable guidelines ensuring evidence-based, safe and effective use of osteobiologics, considering regional preferences and cost-effectiveness.

METHODS

Guideline was completed in two phases: Phase 1- evidence synthesis; Phase 2- recommendation development based on the Grading of Recommendations, Assessment, Development and Evaluations (GRADE) approach. In Phase 1, key questions identified by a panel of experts were addressed in a series of systematic reviews of randomized and non-randomized studies. In Phase 2, the GRADE approach was used to formulate a series of recommendations, including expert panel discussions via web calls and face-to-face meetings.

DISCUSSION

AO-GO aims to bridge an important gap between evidence and use of osteobiologics in spine fusion surgeries. Owing to differences in osteobiologics preparation and functional characteristics, regulatory requirements for approval may vary, therefore it is highly likely that these products enter market without quality clinical trials. With a holistic approach the guideline aims to facilitate evidence-based, patient-oriented decision-making processes in clinical practice, thus stimulating further evidence-based studies regarding osteobiologics usage in spine surgeries. In Phase 3, the guideline will be disseminated and validated using prospectively collected clinical data in a separate effort of the AO Spine Knowledge Forum Degenerative in a global multicenter clinical study.

Nonoperative versus operative management of type II odontoid fracture in older adults: a systematic review and meta-analysis

OBJECTIVE

Odontoid fractures are the most common fracture of the cervical spine in adults older than 65 years of age. Fracture management remains controversial, given the inherently increased surgical risks in older patients. The objective of this study was to compare fusion rates and outcomes between operative and nonoperative treatments of type II odontoid fractures in the older population.

METHODS

A systematic literature review was performed to identify studies reporting the management of type II odontoid fractures in patients older than 65 years from database inception to September 2022. A meta-analysis was performed to compare rates of fusion, stable and unstable nonunion, mortality, and complication.

RESULTS

Forty-six articles were included in the final review. There were 2822 patients included in the different studies (48.9% female, 51.1% male), with a mean ± SD age of 81.5 ± 3.6 years. Patients in the operative group were significantly younger than patients in the nonoperative group (81.5 ± 3.5 vs 83.4 ± 2.5 years, p < 0.001). The overall (operative and nonoperative patients) fusion rate was 52.9% (720/1361). The fusion rate was higher in patients who underwent surgery (74.3%) than in those who underwent nonoperative management (40.3%) (OR 4.27, 95% CI 3.36-5.44). The likelihood of stable or unstable nonunion was lower in patients who underwent surgery (OR 0.37, 95% CI 0.28-0.49 vs OR 0.32, 95% CI 0.22-0.47). Overall, 4.8% (46/964) of nonoperatively managed patients subsequently required surgery due to treatment failure. Patient mortality across all studies was 16.6% (452/2721), lower in the operative cohort (13.2%) than the nonoperative cohort (19.0%) (OR 0.64, 95% CI 0.52-0.80). Complications were more likely in patients who underwent surgery (26.0% vs 18.5%) (OR 1.55, 95% CI 1.23-1.95). Length of stay was also higher with surgery (13.6 ± 3.8 vs 8.1 ± 1.9 days, p < 0.001).

CONCLUSIONS

Patients older than 65 years of age with type II odontoid fractures had higher fusion rates when treated with surgery and higher stable nonunion rates when managed nonoperatively. Complications and length of stay were higher in the surgical cohort. Mortality rates were lower in patients managed with surgery, but this phenomenon could be related to surgical selection bias. Fewer than 5% of patients who underwent nonoperative treatment required revision surgery due to treatment failure, suggesting that stable nonunion is an acceptable treatment goal.

Advances in Synthetic Grafts in Spinal Fusion Surgery

Degenerative spine disease is increasing in prevalence as the global population ages, indicating a need for targeted therapies and continued innovations. While autograft and allograft have historically demonstrated robust results in spine fusion surgery, they have significant limitations and associated complications such as infection, donor site morbidity and pain, and neurovascular injury. Synthetic grafts may provide similar success while mitigating negative outcomes. A narrative literature review was performed to review available synthetic materials that aim to optimize spinal fusion. The authors specifically address the evolution of synthetics and comment on future trends. Novel synthetic materials currently in use include ceramics, synthetic polymers and peptides, bioactive glasses, and peptide amphiphiles, and the authors focus on their success in both human and animal models, physical properties, advantages, and disadvantages. Advantages include properties of osteoinduction, osteoconduction, and osteogenesis, whereas disadvantages encompass a lack of these properties or growth factor-induced complications. Typically, the use of synthetic materials results in fewer complications and lower costs. While the development and tuning of synthetic materials are ongoing, there are many beneficial alternatives to autografts and allografts with promising fusion results.

A Novel Multimodal Postoperative Pain Protocol for 1- to 2-Level Open Lumbar Fusions: A Retrospective Cohort Study

BACKGROUND

There has been increased interest in exploring methods to reduce postoperative pain without opioid medications. In 2015, a multimodal analgesia protocol was used involving the perioperative use of celecoxib, gabapentin, intravenous acetaminophen, lidocaine, and liposomal bupivacaine. Overall, the goal was to reduce the utilization of scheduled opioids in favor of nonopioid pain management.

METHODS

The results of a consecutive series of 1- to 2-level open primary lumbar fusions were compared to a cohort of patients after the implementation the perioperative multimodal pain management protocol. Primary endpoints included patient-reported pain scores and secondary endpoints included length of stay.

RESULTS

There were 87 patients in the preprotocol cohort and 184 in the protocol cohort. Comparing protocol and preprotocol patients, there were no significant differences in patient demographics. There was significantly average lower pain in the protocol group on postoperative day (POD) 1 (4.50 vs 5.00, P < 0.02) and POD2 (4.42 vs 5.50, P < 0.03). There was a lower pain score on POD0 (4.80 vs 5.00), but it was only clinically significant. There was a correlation between pain and duration of surgery in the preprotocol patients (POD0 R = 0.23, POD1 R = 0.02, POD2 R = 0.38), but not in the protocol patients (POD0 R = -0.05, POD1 R = -0.08, POD2 R = -0.04). There was a shorter length of stay in the protocol cohort (2.0 vs 3.0, P < 0.01). Finally, there was an approximately 35% reduction in morphine milligram equivalents of opioids in the protocol vs preprotocol cohorts (36.2 vs 57.0, P < 0.05).

CONCLUSION

Our novel multimodal pain management protocol significantly reduced postoperative pain, length of stay, and opioid consumption in this patient cohort. Opioid usage correlated to pain in the protocol patients, while the preprotocol patients had no correlation between opioid use and pain medication.

CLINICAL RELEVANCE

In this study, we demonstrated that preoperative and intraoperative analgesia can reduce postoperative pain medication requirements. Furthermore, we introduced a novel concept of a correlation of pain with opioid consumption as a marker of effective pain management of breakthrough pain.

LEVEL OF EVIDENCE: 4

The Impact of Multimodal Prehabilitation on Patient-Reported Outcomes for a Frail Octogenarian Undergoing Multilevel Lumbar Spinal Fusion Surgery: A Case Report

This case report presents the perioperative optimization pathway of a frail octogenarian who underwent multilevel lumbar spinal fusion surgery. This patient was enrolled in a multimodal prehabilitation program for frail older adults. The multimodal prehabilitation program includes preoperative interventions that prevent further decline in physiological functions before spine surgery. The program focuses on physical exercise, nutritional intervention, and pain neuroscience education. Six weeks postoperatively, clinical and patient-reported outcomes improved in the categories targeted by the preoperative interventions and surgery. This report suggests that prehabilitation is feasible for preoperatively optimizing frail older adults undergoing complex spine surgery.

Implication of nutritional status for adverse outcomes after surgery for metastatic spine tumors

OBJECTIVE

Surgery for metastatic spinal tumors can have a substantial impact on patients' quality of life by alleviating pain, improving function, and correcting spinal instability when indicated. The decision to operate is difficult because many patients with cancer are frail. Studies have highlighted the importance of preoperative nutritional status assessments; however, little is known about which aspects of nutrition accurately inform clinical outcomes. This study investigates the interaction and prognostic importance of various nutritional and frailty measures in patients with spinal metastases.

METHODS

A retrospective analysis of consecutive patients who underwent surgery for spinal metastases between 2014 and 2020 at the Massachusetts General Hospital was performed. Patients were stratified according to the New England Spinal Metastasis Score (NESMS). Frailty was assessed using the metastatic spinal tumor frailty index. Nutrition was assessed using the prognostic nutritional index (PNI), preoperative body mass index, albumin, albumin-to-globulin ratio, and platelet-to-lymphocyte ratio. Outcomes included postoperative survival and complication rates, with focus on wound-related complications.

RESULTS

This study included 154 individuals (39% female; mean [SD] age 63.23 [13.14] years). NESMS 0 and NESMS 3 demonstrated the highest proportions of severely frail patients (56.2%) and nonfrail patients (16.1%), respectively. Patients with normal nutritional status (albumin-to-globulin ratio and PNI) had a better prognosis than those with poor nutritional status when stratified by NESMS. Multivariable regression adjusted for NESMS and frailty showed that a PNI > 40.4 was significantly associated with decreased odds of 90-day complications (OR 0.93, 95% CI 0.85-0.98). After accounting for age, sex, primary tumor pathology, physical function, nutritional status, and frailty, a preoperative nutrition consultation was associated with a decrease in postoperative wound-related complications (average marginal effect -5.00%; 95% CI -1.50% to -8.9%).

CONCLUSIONS

The PNI was most predictive of complications and may be a key biomarker for risk stratification in the 90 days following surgery. Nutrition consultation was associated with a reduced risk of wound-related complications, attesting to the importance of this preoperative intervention. These findings suggest that nutrition plays an important role in the postsurgical course and should be considered when developing a treatment plan for spinal metastases.

Patient Optimization for the Prevention of Proximal Junctional Kyphosis

Proximal junctional kyphosis (PJK) and proximal junctional failure (PJF) are well-recognized challenges of surgery for adult spinal deformity (ASD). Multiple risk factors have been identified for PJK/PJF, including osteoporosis, frailty, neurodegenerative disease, obesity, and smoking. Several surgical techniques to mitigate risk of PJK/PJF have been identified; however, patient optimization is also critical. This review summarizes the data behind these 5 risk factors (osteoporosis, frailty, neurodegenerative disease, obesity, and smoking) and details the related recommendations for patients undergoing surgery for ASD.

Effectiveness of Toothbrushing Technique for Biofilm Removal and Postoperative Infection Control after Spinal Fusion Surgery: A Retrospective Study

This retrospective study was designed to investigate the effectiveness of using a toothbrush, which is commonly used in our daily life, for biofilm removal and infection control in the treatment of spinal infections occurring after spinal fusion surgery. Currently, a biofilm is thought to form on the surface of the metal inserted during spine fusion surgery. We aim to determine the differences in clinical outcomes between using and not using a toothbrush to remove biofilm while performing conventional drainage, curettage, and debridement. A total of 1081 patients who underwent anterior or posterior spinal fusion surgery between November 2018 and October 2022 were screened. The study included 60 patients who developed surgical site infection and underwent incision and drainage surgery either with a toothbrush (n = 20) or without a toothbrush (n = 40). Failure of infection control that requires revision surgery occurred in 2 patients (10%) in the Toothbrush group and in 14 patients (35%) in the No-Toothbrush group (p = 0.039). Thus, the rate of additional surgery was significantly lower in the Toothbrush group. Additionally, normalization of c-reactive protein levels occurred significantly faster in the Toothbrush group (p = 0.044). Therefore, using a toothbrush to treat spinal infections following spinal fusion surgery appears to have beneficial mechanical debridement effects, resulting in improved clinical results, which were also confirmed based on the electron microscopic images.

Specialty Impact on Patient Outcomes: Paving a Way for an Integrated Approach to Spinal Disorders

Spinal surgical procedures are steadily increasing globally due to broad indications of certain techniques encompassing a wide spectrum of conditions, including degenerative spine disorders, congenital anomalies, spinal metastases, and traumatic spinal fractures. The two specialties, neurosurgery (NS) and orthopedic surgery (OS), both possess the clinical adeptness to perform these procedures. With the advancing focus on comparative effectiveness research, it is vital to compare patient outcomes in spine surgeries performed by orthopedic surgeons and neurosurgeons, given their distinct approaches and training backgrounds to guide hospital programs and physicians to consider surgeon specialty when making informed decisions. Our review of the available literature revealed no significant difference in postoperative outcomes in terms of blood loss, neurological deficit, dural injury, intraoperative complications, and postoperative wound dehiscence in procedures performed by neurosurgeons and orthopedic surgeons. An increase in blood transfusion rates among patients operated by orthopedic surgeons and a longer operative time of procedures performed by neurosurgeons was a consistent finding among several studies. Other findings include a prolonged hospital stay, higher hospital readmission rates, and lower cost of procedures in patients operated on by orthopedic surgeons. A few studies revealed lower sepsis rates unplanned intubation rates and higher incidence of urinary tract infections (UTIs) and pneumonia postoperatively among patient cohorts operated by neurosurgeons. Certain limitations were identified in the studies including the use of large databases with incomplete information related to patient and surgeon demographics. Hence, it is imperative to account for these confounding variables in future studies to alleviate any biases. Nevertheless, it is essential to embrace a multidisciplinary approach integrating the surgical expertise of the two specialties and develop standardized management guidelines and techniques for spinal disorders to mitigate complications and enhance patient outcomes.

Evaluation of the Thoracolumbar Injury Classification and Severity (TLICS) Score Over a Two-Year Period at a Level One Trauma Center

Introduction The use of the Thoracolumbar Injury Classification and Severity Score (TLICS) and other classification systems for guiding the management of traumatic spinal injuries remains controversial. TLICS is one of the few classifications that provides treatment recommendations.We sought to analyze intervention modality selection based on the TLICS scoring system. Methods A retrospective review of patients presenting with traumatic thoracolumbar fractures at a level 1 trauma center over a two-year period was performed. Primary endpoints for comparison analysis included visual analog scale (VAS) scores and Cobb angles during follow-up. Results There were 272 patients with thoracolumbar fractures, of whom 212 had TLICS of ≤3, six with TLICS of 4, and 54 with TLICS of ≥5. Of the 272 total patients, 59 were treated via surgery and 213 via non-surgical conservative methods. The VAS scores significantly decreased from presentation to last follow-up in both surgically treated and conservative groups (p<0.0001). This remained consistent in subgroup analyses of TLICS ≤ 3, TLICS = 4, and TLICS ≥ 5 (p<0.0001). Burst fractures treated conservatively had larger fracture Cobb angles versus those treated via surgery at the last follow-up, although this was not significantly associated (p=0.07). The only significant relationship with Cobb angles was in distraction fractures of the TLICS > 4 conservative group, who had significantly lower Cobb angles at the last follow-up than the TLICS > 4 surgical group (p<0.04). The "surgeon's choice" for TLICS = 4 was surgical intervention (4/6 patients, 66.7%). Conclusion Using the TLICS score, thoracolumbar injuries in a level 1 trauma center are more commonly TLICS ≤ 3. For patients with TLICS = 4, the surgeon's choice was most commonly surgical repair. VAS scores decreased over time from presentation between surgically and conservatively managed patients (as well as within-group analyses). The data concerning Cobb angles were more ambiguous, as larger Cobb angles in burst fractures treated conservatively did not show statistically significant differences with surgery.

Carbon Fiber-Reinforced PolyEtherEtherKetone (CFR-PEEK) Instrumentation in Degenerative Disease of Lumbar Spine: A Pilot Study

CFR-PEEK is gaining popularity in spinal oncological applications due to its reduction of imaging artifacts and radiation scattering compared with titanium, which allows for better oncological follow-up and efficacy of radiotherapy. We evaluated the use of these materials for the treatment of lumbar degenerative diseases (DDs) and considered the biomechanical potential of the carbon fiber in relation to its modulus of elasticity being similar to that of bone. Twenty-eight patients with DDs were treated using CRF-PEEK instrumentation. The clinical and radiographic outcomes were collected at a 12-month FU. Spinal fusion was evaluated in the CT scans using Brantigan scores, while the clinical outcomes were evaluated using VAS, SF-12, and EQ-5D scores. Out of the patients evaluated at the 12-month FU, 89% showed complete or almost certain fusion (Brantigan score D and E) and presented a significant improvement in all clinical parameters; the patients also presented VAS scores ranging from 6.81 ± 2.01 to 0.85 ± 1.32, EQ-5D scores ranging from 53.4 ± 19.3 to 85.0 ± 13.7, SF-12 physical component scores (PCSs) ranging from 29.35 ± 7.04 to 51.36 ± 9.75, and SF-12 mental component scores (MCSs) ranging from 39.89 ± 11.70 to 53.24 ± 9.24. No mechanical complications related to the implant were detected, and the patients reported a better tolerance of the instrumentation compared with titanium. No other series of patients affected by DD that was stabilized using carbon fiber implants have been reported in the literature. The results of this pilot study indicate the efficacy and safety of these implants and support their use also for spinal degenerative diseases.

Varenicline Mitigates the Increased Risk of Pseudoarthrosis Associated with Nicotine

BACKGROUND CONTEXT

High serum nicotine levels increase the risk of non-union after spinal fusion. Varenicline, a pharmaceutical adjunct for smoking cessation, is a partial agonist designed to displace and outcompete nicotine at its receptor binding site, thereby limiting downstream activation. Given its mechanism, varenicline may have therapeutic benefits in mitigating non-union for active smokers undergoing spinal fusion.

PURPOSE

To compare fusion rate and fusion mass characteristics between cohorts receiving nicotine, varenicline, or concurrent nicotine and varenicline after lumbar fusion.

STUDY DESIGN

Rodent non-instrumented spinal fusion model.

METHODS

Sixty eight-week-old male Sprague-Dawley rats weighing approximately 300 grams underwent L4-5 posterolateral fusion (PLF) surgery. Four experimental groups (control: C, nicotine: N, varenicline: V, and combined: NV [nicotine and varenicline]) were included for analysis. Treatment groups received nicotine, varenicline, or a combination of nicotine and varenicline delivered through subcutaneous osmotic pumps beginning two weeks before surgery until the time of sacrifice at age 14 weeks. Manual palpation testing, microCT imaging, bone histomorphometry, and biomechanical testing were performed on harvested spinal fusion segments.

RESULTS

Control (p=0.016) and combined (p=0.032) groups, when compared directly to the nicotine group, demonstrated significantly greater manual palpation scores. The fusion rate in the control (93.3%) and combined (93.3%) groups were significantly greater than that of the nicotine group (33.3%) (p=0.007, both). Biomechanical testing demonstrated greater Young's modulus of the fusion segment in the control (17.1 MPa) and combined groups (34.5 MPa) compared to the nicotine group (8.07 MPa) (p<0.001, both). MicroCT analysis demonstrated greater bone volume fraction (C:0.35 vs N:0.26 vs NV:0.33) (p<0.001, all) and bone mineral density (C:335 vs N:262 vs NV:328 mg Ha/cm³) (p<0.001, all) in the control and combined groups compared to the nicotine group. Histomorphometry demonstrated a greater mineral apposition rate in the combined group compared to the nicotine group (0.34 vs 0.24 μm/day, p=0.025).

CONCLUSION

In a rodent spinal fusion model, varenicline mitigates the adverse effects of high nicotine serum levels on the rate and quality of spinal fusion.

CLINICAL SIGNIFICANCE

These findings have the potential to significantly impact clinical practice guidelines and the use of pharmacotherapy for active nicotine users undergoing fusion surgery.

Robot-assisted versus navigated transpedicular spine fusion: A comparative study

BACKGROUND

The aim of this study was to compare the intraoperative and postoperative outcomes between a robot-assisted versus a navigated transpedicular fusion technique.

METHODS

This retrospective analysis included patients who underwent transpedicular posterior fusion of the spine due to trauma, pyogenic spondylodiscitis and osteoporosis. Surgery was done either with a robot-assisted or a percutaneous navigated transpedicular fusion technique. The outcome analysis included the duration of surgery, the radiation exposure, the postoperative screw position and complications.

RESULTS

A total of 60 patients were operated and 491 screws were analysed. No statistical difference was seen in the applied cumulative effective radiation dose per patient. The radiological assessment revealed a more accurate screw placement with robot assistance. A learning curve could be observed in robot-assisted fusion.

CONCLUSION

Robot-assisted and navigated transpedicular fusion techniques are both effective and safe. Robot-assisted transpedicular spine fusion goes along with higher placement accuracy but its implementation needs an adequate learning curve.

Instagram and Spine Fusion: An Analysis of Social Media and Its Relationship to Patient Perception of Surgery

STUDY DESIGN

Cross sectional study.

OBJECTIVES

To analyze posts shared on Instagram referencing spinal fusion for tone, gender, activities of daily living (ADLs), rehabilitation, incision, pain, neurological injury, and content of post.

METHODS

Public instragram posts, which were isolated and evaluated using the hashtags "#spinefusion" and "#spinalfusion." All posts were analyzed by the authors for the variables previously listed. In total, 264 posts were included for investigation and analysis of patient perception of spine fusion through social media.

RESULTS

Of all included posts, approximately 86% of posts had a positive tone. There was statistical significance between positive tone and activities of daily living (ADLs) (P = 0.047), as well as negative tone and persistent pain (P = 0.008). Adequate return to activities of daily living is perceived by patients as a positive outcome after surgery: odds ratio (OR) (95% CI) of 2.11 (1.01-4.39). Persistent post operative pain results negatively on perceived outcomes after surgery OR = 0.38 (0.18-0.78).

CONCLUSIONS

Reported outcomes after spine fusion has not been evaluated through social media avenues. This analysis of patients sharing their experience on social media after spinal fusion demonstrates that returning to activities of daily living is of the utmost importance to patients. Additionally, post-operative pain is a strong metric utilized by patients with their satisfaction after surgery.

Is Indirect Decompression and Fusion More Effective than Direct Decompression and Fusion for Treating Degenerative Lumbar Spinal Stenosis With Instability? A Systematic Review and meta-Analysis

Study design: Systematic Review and Meta-analysis.Objective: Surgical alternatives to treat lumbar spinal stenosis and instability include indirect (ALIF, OLIF, and LLIF) and direct (TLIF or posterior lumbar interbody fusion) decompression and fusion interventions. Although both approaches have proven to be effective in reducing symptoms, it is unknown if there is any difference in effectiveness between them. In this systematic review and meta-analysis, we aimed to evaluate postoperative pain and disability in patients treated whit indirect vs direct decompression and fusion approaches.Methods: We conducted a systematic review of the literature consulting several databases and identified studies that enrolled patients diagnosed with degenerative lumbar spinal stenosis and instability treated with indirect or direct decompression and fusion techniques. Our primary endpoints were the visual analogue scale, Oswestry Disability Index, and the Japanese Orthopedics Association Back Pain Evaluation Questionnaire 1 year after the procedure. Secondary outcomes included complication rate, blood loss, and surgical time.Results: Nine retrospective and comparative studies were included enrolling a total of 1004 participants. Both surgical strategies had satisfactory clinical outcomes with no significant difference at 1 year. Although the complication rate was similar for both groups, the profile of the adverse events was different. In addition, patients treated with indirect decompression and fusion had significantly less blood loss and operative times.Conclusions: Indirect and direct decompression and fusion techniques are similarly effective in treating patients with lumbar spinal stenosis and instability. The ID group had significantly lower intraoperative blood loss and surgical time values.

Postoperative Morbidity and Mortality in Lumbar Spine Surgery Patients With Chronic Kidney Disease and Chronic Steroid Use

BACKGROUND

Perioperative steroids have traditionally been administered during lumbar spine surgery in order to decrease local inflammation and prevent scar tissue formation, which can otherwise contribute to significant, long-lasting postoperative pain due to the formation of epidural fibrosis around lumbar nerve roots. However, the use of steroids in lumbar spine patients has raised concerns of postoperative wound complications caused by corticosteroid-induced immunomodulatory effects and changes in collagen synthesis. Patients with chronic kidney disease (CKD) undergoing spine surgery are at a particularly elevated risk of various complications due to chronic CKD-related systemic inflammation and endothelial dysfunction. It is currently uncertain whether chronic steroid use in CKD patients exerts a protective effect postoperatively due to decreased systemic inflammation or instead is correlated with increased rates of wound complications.

RESULTS

Using adjusted odds ratios to control for CKD-related comorbidities, our study of lumbar spine fusion patients who were chronic steroid users vs nonusers found no significant differences in rates of postoperative wound infections in later stage CKD patients. However, we also did not observe statistically significant reductions in hospital length of stay or rates of 30-day mortality, sepsis, or cardiac, pulmonary, and renal events.

CONCLUSIONS

Our results indicate chronic steroid use neither contributes significantly to rates of wound infections nor exerts a protective effect against postoperative inflammatory complications in lumbar spine patients with CKD.

CLINICAL RELEVANCE

Our findings do not support the practice of holding steroids in chronic users prior to lumbar spine surgery. Perioperative steroids do not appear to increase the risk of postoperative complications, but neither do they improve lumbar spine patient outcomes.

LEVEL OF EVIDENCE: 4

Pre-Emptive Opioid-Sparing Medication Protocol Decreases Pain and Length of Hospital Stay in Children Undergoing Posterior Spinal Instrumented Fusion for Scoliosis

Background

Poorly controlled post-operative pain following Posterior Spinal Instrumented Fusion (PSIF) for scoliosis may be associated with delayed ambulation and longer hospital stays. Multimodal analgesia use has been shown to provide superior analgesia with improved recovery and reduction of post-operative morbidity in other orthopedic subspecialties, but has not been described with pediatric patients undergoing spinal surgery.

Objective

We describe a novel, pre-emptive, opioid-sparing pediatric pain medication protocol that is started two days prior to surgery, in accordance with first-order pharmacokinetics, and continued post-operatively until discharge with the goal of decreasing post-operative pain, improving early mobilization, and ultimately decreasing the patient's length of hospital stay.

Methods

We retrospectively reviewed 116 PSIF cases from March 2014 to November 2017. Fifty-two patients received standard analgesia before August 2016, and 64 patients after August 2016 received the pre-emptive protocol consisting of a standardized combination of acetaminophen, celecoxib, and gabapentin two days prior to surgery and continued during their inpatient stay. Scheduled oxycodone and intravenous hydromorphone via patient controlled analgesia (PCA) were given to both groups equally during the post-operative hospital stay. We analyzed length of stay, total opioid consumption, and maximum pain scores per day from surgical to discharge date.

Results

116 patients were included: 64 patients in the pre-emptive group and 52 patients in the standard group. Length of hospital stay significantly differed, with means of 3.9 days in the pre-emptive group and 4.5 days in the standard analgesia group (p<0.05). Patients in the pre-emptive group recorded significantly lower maximal pain levels than those in the standard analgesia group on post-operative days #1 (4.9 vs. 5.8, p=0.0196), #3 (4.4 vs. 6.1, p=0.0006), and #4 (4.2 vs. 5.4, p=0.0393). Total post-operative morphine equivalents taken did not significantly differ between the two groups.

Conclusion

This is a preliminary report demonstrating a significant decrease in maximal pain score and length of stay following PSIF on a cohort of patients receiving a novel pre-emptive opioid-sparing pain medication protocol based on first order pharmacokinetics. Future studies should investigate degree of mobilization and opioid consumption and maximal pain level after discharge from the hospital. Level of Evidence: III.

Assessment of Spinal Metastases Surgery Risk Stratification Tools in Breast Cancer by Molecular Subtype

BACKGROUND

Breast cancer molecular features and modern therapies are not included in spine metastasis prediction algorithms.

OBJECTIVE

To examine molecular differences and the impact of postoperative systemic therapy to improve prognosis prediction for spinal metastases surgery and aid surgical decision making.

METHODS

This is a retrospective multi-institutional study of patients who underwent spine surgery for symptomatic breast cancer spine metastases from 2008 to 2021 at the Massachusetts General Hospital and Brigham and Women's Hospital. We studied overall survival, stratified by breast cancer molecular subtype, and calculated hazard ratios (HRs) adjusting for demographics, tumor characteristics, treatments, and laboratory values. We tested the performance of established models (Tokuhashi, Bauer, Skeletal Oncology Research Group, New England Spinal Metastases Score) to predict and compare all-cause.

RESULTS

A total of 98 patients surgically treated for breast cancer spine metastases were identified (100% female sex; median age, 56 years [IQR, 36-84 years]). The 1-year probabilities of survival for hormone receptor positive, hormone receptor positive/human epidermal growth factor receptor 2+, human epidermal growth factor receptor 2+, and triple-negative breast cancer were 63% (45 of 71), 83% (10 of 12), 0% (0 of 3), and 12% (1 of 8), respectively ( P < .001). Patients with triple-negative breast cancer had a higher proportion of visceral metastases, brain metastases, and poor physical activity at baseline. Postoperative chemotherapy and endocrine therapy were associated with prolonged survival. The Skeletal Oncology Research Group prognostic model had the highest discrimination (area under the receiver operating characteristic, 0.77 [95% CI, 0.73-0.81]). The performance of all prognostic scores improved when preoperative molecular data and postoperative systemic treatment plans was considered.

CONCLUSION

Spine metastases risk tools were able to predict prognosis at a significantly higher degree after accounting for molecular features which guide treatment response.

Abaloparatide Enhances Fusion and Bone Formation in a Rabbit Spinal Arthrodesis Model

STUDY DESIGN

Prospective randomized placebo controlled animal trial.

OBJECTIVE

Determine the effect of daily subcutaneous abaloparatide injection on the intervertebral fusion rate in rabbits undergoing posterolateral fusion.

STUDY OF BACKGROUND DATA

Despite the wide utilization of spine fusion, pseudarthrosis remains prevalent, and results in increased morbidity. Abaloparatide is a novel analog of parathyroid hormone-related peptide (1-34) and has shown efficacy in a rat posterolateral spine fusion model to increase fusion rates. The effect of abaloparatide on the fusion rate in a larger animal model remains unknown.

MATERIALS AND METHODS

A total of 24 skeletally mature New Zealand White male rabbits underwent bilateral posterolateral spine fusion. Following surgery, the rabbits were randomized to receive either saline as control or abaloparatide subcutaneous injection daily. Specimens underwent manual assessment of fusion, radiographic analysis with both x-ray and high-resolution peripheral quantitative computed tomography, and biomechanical assessment.

RESULTS

Rabbits that received abaloparatide had a 100% (10/10) fusion rate compared with 45% (5/11) for controls ( P <0.02) as assessed by manual palpation. Radiographic analysis determined an overall mean fusion score of 4.17±1.03 in the abaloparatide group versus 3.39±1.21 for controls ( P <0.001). The abaloparatide group also had a greater volume of bone formed with a bone volume of 1209±543 mm 3 compared with 551±152 mm 3 ( P <0.001) for controls. The abaloparatide group had significantly greater trabecular bone volume fraction and trabecular thickness and lower specific bone surface and connectivity density in the adjacent levels when compared with controls. Abaloparatide treatment did not impact trabecular number or separation. There were no differences in biomechanical testing in flexion, extension, or lateral bending ( P >0.05) between groups.

CONCLUSIONS

Abaloparatide significantly increased the fusion rate in a rabbit posterolateral fusion model as assessed by manual palpation. In addition, there were marked increases in the radiographic evaluation of fusion.

Subcutaneous Fat Thickness on Erect Radiographs Is a Predictor of Infection Following Elective Posterior Lumbar Fusion

BACKGROUND

Posterior lumbar fusions are a common and successful procedure, yet surgical site infection (SSI) is still prevalent and causes significant morbidity. Obesity is a well-established risk factor for SSI. Still, the accuracy of the body mass index (BMI) caused some to suggest other metrics that are more representative of the thickness of the soft-tissue envelope in the surgical site.

METHODS

A retrospective review of all cases that developed SSI following posterior lumbar fusion over the past 5 years was done. An age and gender-matched control group was formed from the lumbar fusion cases that did not develop SSI. Demographic and clinical data were collected, and morphometric measurements of the soft-tissue envelope were performed at the level of L4 for all cases on standing x-ray imaging and magnetic resonance imaging (MRI).

RESULTS

A total of 366 patients underwent posterior lumbar fusion, 26 of whom developed SSI. BMI and skin to spinous process measurements on x-ray imaging-not MRI-were found to be significantly associated with SSI. Regression analysis further confirmed the strength of the association.

CONCLUSION

While BMI and MRI measurements are useful, wound depth measurements on x-ray imaging can be predictive of SSI in lumbar fusion cases.

CLINICAL RELEVACE

Wound depth measurements are predictive of lumbar wound infection. The information within this study can help surgeons better predict and manage infections of posterior lumbar wounds.

LEVEL OF EVIDENCE: 3

Combining time-driven activity-based costing and lean methodology: an initial study of single-level lumbar fusion surgery to assess value-based healthcare in patients undergoing spine surgery

OBJECTIVE

Measuring costs across entire episodes of care, time-driven activity-based costing (TDABC) has recently been described as a novel cost accounting arm of value-based care organizations. Lean methodology is a system used to understand pathways of care at a granular level, allowing for standardization. The current work presents an attempt at combining the 2 methodologies to detect meaningful variation in a patient's care following single-level spine fusion. The objective of this study was to evaluate the combination of TDABC and lean methodologies in detecting meaningful variability in time-based care in patients undergoing single-level spine fusion surgery.

METHODS

This study is a consecutive case series of patients who underwent single-level spine fusion performed by 1 of 5 fellowship-trained spine surgeons. Patients were diagnosed with either lumbar stenosis or spondylolisthesis. Additional inclusion criteria included inpatient stays from 1 to 3 days, discharge to home, and no readmission within 30 days of surgery. Patient demographic data were obtained. Time spent on activities for each personnel role was aggregated in 15-minute increments occurring preoperatively, intraoperatively, and postoperatively. Patients were analyzed in 3 groups based on the duration of their in-hospital stay.

RESULTS

Patients discharged on postoperative day (POD) 3 had statistically significantly more total time spent than those discharged on POD 2. Patients discharged on POD 1 had less total time than those in the former 2 groups. The amount of time spent with patients did not differ for personnel in either preoperative or postanesthesia care unit phases of care. There was a statistically significant difference in time spent in surgery for surgeons, anesthesia attendings, circulators, and scrub technicians.

CONCLUSIONS

In a healthcare setting run by lean methodology, TDABC may detect meaningful variability in an episode of care for single-level spine fusion. Clinicians and administrators can use this combination to allocate costs appropriately, optimize value care streams, and help improve patient care.

Indirect Lumbar Decompression Combined With or Without Additional Direct Posterior Decompression: A Systematic Review

STUDY DESIGN

Systematic review.

OBJECTIVE

Indirect decompression via lateral lumbar interbody fusion (LLIF) can ameliorate central and foraminal lumbar stenosis. In severe central stenosis, additional posterior direct decompression is utilized. The aim of this review is to synthesize existing literature on these 2 techniques and identify significant differences in outcomes between isolated indirect decompression via LLIF and combined indirect decompression supplemented with direct posterior decompression.

METHODS

A database search algorithm was utilized to query MEDLINE, COCHRANE, and EMBASE to identify literature reporting adult decompression study groups that involved an oblique or lateral fusion approach through September 2020. Improvement in outcomes measures and complication rates were pooled and tested for significance.

RESULTS

A total of 110 publications were assessed with 15 studies meeting inclusion criteria, including 557 patients and 1008 levels. Mean age was 63.1 years with BMI of 27.5 kg/m². For the combined indirect and direct decompression cohort, lumbar lordosis (LL) increased 133.9%, from 22.8^o to 48.7^o, while the indirect decompression cohort LL increased 8.9%, from 41.9^o to 45.5^o. Difference in LL improvement between cohorts was insignificant (P > .05). Oswestry Disability Index (ODI) decreased from 36.5 to 19.4 in the combined indirect and direct decompression cohort, and from 44.4 to 23.1 in the indirect decompression cohort. ODI reduction was insignificant (P = .053).

CONCLUSIONS

Prior studies of both indirect decompression as well as combined indirect and direct decompression of lumbar spine stenosis are limited by small samples, heterogeneous populations, and lack of direct comparisons. Both procedures result in improved function and pain postoperatively with direct decompression restoring more lordosis in patients with worse preoperative alignment.

Comparing the efficacy of adipose-derived and bone marrow-derived cells in a rat model of posterolateral lumbar fusion

Although bone marrow-derived mesenchymal stem cells (BMCs) have been widely used in spinal fusion procedures, adipose-derived stem cells (ASCs) offer a number of advantages as an alternative clinical cell source. This study directly compares the efficacy of ASCs and BMCs from the same donor animals to achieve successful fusion when combined with a clinical-grade bone graft substitute in a rat lumbar fusion model. ASCs and BMCs were isolated from the same Lewis donor rats and grown to passage 2 (P2). Single-level bilateral posterolateral intertransverse process lumbar fusion surgery was performed on syngeneic rats divided into three experimental groups: clinical-grade bone graft substitute alone (CBGS); CBGS+ rat ASCs (rASC); and, CBGS+ rat BMCs (rBMC). Eight weeks postoperatively, fusion was evaluated via micro-CT, manual palpation and histology. In vitro analysis of the osteogenic capacity of rBMCs and rASCs was also performed. Results indicated that the average fusion volume in the rASC group was the largest and was significantly larger than the CBGS group. Although the rASC group displayed the highest fusion rates via micro-CT and manual palpation, this difference was not statistically significant. Cell-seeded grafts showed more histological bone formation than cell-free grafts. P2 rASCs and rBMCs displayed similar in vitro osteogenic differentiation capacities. Overall, this study showed that, when combined with a clinical-grade bone graft substitute in a rat model, rASCs cells yielded the largest fusion masses and comparable fusion results to rBMCs. These results add to growing evidence that ASCs provide an attractive alternative to BMCs for spinal fusion procedures.

Evaluating frailty, mortality, and complications associated with metastatic spine tumor surgery using machine learning-derived body composition analysis

OBJECTIVE

Cancer patients with spinal metastases may undergo surgery without clear assessments of prognosis, thereby impacting the optimal palliative strategy. Because the morbidity of surgery may adversely impact recovery and initiation of adjuvant therapies, evaluation of risk factors associated with mortality risk and complications is critical. Evaluation of body composition of cancer patients as a surrogate for frailty is an emerging area of study for improving preoperative risk stratification.

METHODS

To examine the associations of muscle characteristics and adiposity with postoperative complications, length of stay, and mortality in patients with spinal metastases, the authors designed an observational study of 484 cancer patients who received surgical treatment for spinal metastases between 2010 and 2019. Sarcopenia, muscle radiodensity, visceral adiposity, and subcutaneous adiposity were assessed on routinely available 3-month preoperative CT images by using a validated deep learning methodology. The authors used k-means clustering analysis to identify patients with similar body composition characteristics. Regression models were used to examine the associations of sarcopenia, frailty, and clusters with the outcomes of interest.

RESULTS

Of 484 patients enrolled, 303 had evaluable CT data on muscle and adiposity (mean age 62.00 ± 11.91 years; 57.8% male). The authors identified 2 clusters with significantly different body composition characteristics and mortality risks after spine metastases surgery. Patients in cluster 2 (high-risk cluster) had lower muscle mass index (mean ± SD 41.16 ± 7.99 vs 50.13 ± 10.45 cm2/m2), lower subcutaneous fat area (147.62 ± 57.80 vs 289.83 ± 109.31 cm2), lower visceral fat area (82.28 ± 48.96 vs 239.26 ± 98.40 cm2), higher muscle radiodensity (35.67 ± 9.94 vs 31.13 ± 9.07 Hounsfield units [HU]), and significantly higher risk of 1-year mortality (adjusted HR 1.45, 95% CI 1.05-2.01, p = 0.02) than individuals in cluster 1 (low-risk cluster). Decreased muscle mass, muscle radiodensity, and adiposity were not associated with a higher rate of complications after surgery. Prolonged length of stay (> 7 days) was associated with low muscle radiodensity (mean 30.87 vs 35.23 HU, 95% CI 1.98-6.73, p < 0.001).

CONCLUSIONS

Body composition analysis shows promise for better risk stratification of patients with spinal metastases under consideration for surgery. Those with lower muscle mass and subcutaneous and visceral adiposity are at greater risk for inferior outcomes.

The lexicon of multirod constructs in adult spinal deformity: a concise description of when, why, and how

The use of multirod constructs in the setting of adult spinal deformity (ASD) began to prevent rod fracture and pseudarthrosis near the site of pedicle subtraction osteotomies (PSOs) and 3-column osteotomies (3COs). However, there has been unclear and inconsistent nomenclature, both clinically and in the literature, for the various techniques of supplemental rod implantation. In this review the authors aim to provide the first succinct lexicon of multirod constructs available for the treatment of ASD, providing a universal nomenclature and definition for each type of supplementary rod. The primary rod of ASD constructs is the longest rod that typically spans from the bottom of the construct to the upper instrumented vertebrae. The secondary rod is shorter than the primary rod, but is connected directly to pedicle screws, albeit fewer of them, and connects to the primary rod via lateral connectors or cross-linkers. Satellite rods are a 4-rod technique in which 2 rods span only the site of a 3CO via pedicle screws at the levels above and below, and are not connected to the primary rod (hence the term "satellite"). Accessory rods are connected to the primary rods via side connectors and buttress the primary rod in areas of high rod strain, such as at a 3CO or the lumbosacral junction. Delta rods span the site of a 3CO, typically a PSO, and are not contoured to the newly restored lordosis of the spine, thus buttressing the primary rod above and below a 3CO. The kickstand rod itself functions as an additional means of restoring coronal balance and is secured to a newly placed iliac screw on the side of truncal shift and connected to the primary rod; distracting against the kickstand then helps to correct the concavity of a coronal curve. The use of multirod constructs has dramatically increased over the last several years in parallel with the increasing prevalence of ASD correction surgery. However, ambiguity persists both clinically and in the literature regarding the nomenclature of each supplemental rod. This nomenclature of supplemental rods should help unify the lexicon of multirod constructs and generalize their usage in a variety of scientific and clinical scenarios.

The effect of local steroid application on bony fusion in a rat posterolateral spinal arthrodesis model

INTRODUCTION

Local steroid administration during anterior cervical spine surgery has been shown to improve postoperative dysphagia. However, concerns over potential complications remain. This study aims to evaluate the effect of local steroid administration on bone regeneration and spine fusion in a preclinical model, as well as the impact on osteogenic differentiation of human bone marrow-derived mesenchymal stem cells (hBM-MSCs) in a 3D culture system.

MATERIALS AND METHODS

Forty-five rats underwent bilateral L4-L5 posterolateral lumbar fusion (PLF) utilizing local delivery of low-dose recombinant human bone morphogenetic protein-2 (rhBMP-2; 0.5 μg/implant). Rats were divided into three groups: no steroid (control), low dose (0.5 mg/kg), and high dose (2.5 mg/kg) of triamcinolone. Bone growth and fusion were assessed using radiography, blinded manual palpation, and micro-CT analysis and were visualized by histology. The impact of triamcinolone exposure on osteogenic differentiation of hBM-MSCs was evaluated by gene expression analysis, alkaline phosphatase activity assay, and alizarin red staining.

RESULTS

No significant differences in fusion scores or rates were seen in the low- or high-dose steroid treatment groups relative to untreated controls. Quantification of new bone formation via micro-CT imaging revealed no significant between-group differences in the volume of newly regenerated bone. Triamcinolone also had no negative impact on pro-osteogenic gene transcript levels, and ALP activity was enhanced in the presence of triamcinolone. Mineral deposition appeared comparable in cultures grown with and without triamcinolone.

CONCLUSIONS

Local steroid application does not seem to inhibit rhBMP-2-mediated spine fusion in rats, though our study may not be adequately powered to detect differences in fusion as measured by manual palpation or bone volume as measured by micro-CT. These findings suggest that local triamcinolone may not increase pseudarthrosis in spine fusion procedures. Further large animal and clinical studies to verify its safety and efficacy are warranted.

A Comprehensive Update of the Treatment and Management of Bertolotti's Syndrome: A Best Practices Review

Bertolotti's Syndrome is defined as chronic back pain caused by transitional lumbosacral vertebra. The transitional vertebra may present with numerous clinical manifestations leading to a myriad of associated pain types. The most common is pain in the sacroiliac joint, groin, and hip region and may or may not be associated with radiculopathy. Diagnosis is made through a combination of clinical presentations and imaging studies and falls into one of four types. The incidence of transitional vertebra has a reported incidence between 4 and 36%; however, Bertolotti's Syndrome is only diagnosed when the cause of pain is attributed to this transitional anatomy. Therefore, the actual incidence is difficult to determine. Initial management with conservative treatment includes medical management and physical therapy. Injection therapy has been established as an effective second line. Epidural steroid injection at the level of the transitional articulation is effective, with either local anesthetics alone or in combination with steroids. Surgery carries higher risks and is reserved for patients failing previous lines of treatment. Options include surgical removal of the transitional segment, decompression of stenosed foramina, and spinal fusion. Recent evidence suggests that radiofrequency ablation (RFA) around the transitional segment may also provide relief. This manuscript is a comprehensive review of the literature related to Bertolotti's Syndrome. It describes the background, including epidemiology, pathophysiology, and etiology of the Syndrome, and presents the best evidence available regarding management options. Bertolotti's Syndrome is considered an uncommon cause of chronic back pain, though the actual incidence is unclear. Most evidence supporting these therapies is of lower-level evidence with small cohorts, and more extensive studies are required to provide strong evidence supporting best practices.

Biomechanical Evaluation of the Effect of Minimally Invasive Spine Surgery Compared with Traditional Approaches in Lifting Tasks

Fusion of spinal vertebrae can be accomplished by different surgical approaches. We investigated Traditional Open Spine Surgery (TOSS) versus Minimally Invasive Spine Surgery (MISS). While TOSS sacrifices spine muscles originating or inserting on the affected vertebrae, MISS seeks to minimize the approach-related morbidity and preserve the tendon attachments of the muscles in the area. We captured 3-D motions of the full body of one healthy subject performing a variety of 10 kg box lifting operations representing activities-of-daily-living that are likely to challenge the spine biomechanically. The motion data were transferred to a full-body biomechanical model with a detailed representation of the biomechanics of the spine, and simulations of the internal spine loads and muscle forces were performed under a baseline configuration and muscle configurations typical for TOSS respectively MISS for the cases of L3/L4, L4/L5, L5/S1, L4/S1 and L3/L5 fusions. The computational model was then used to investigate the biomechanical differences between surgeries. The simulations revealed that joint reaction forces are more affected by both surgical approaches for lateral lifting motions than for sagittal plane motions, and there are indications that individuals with fused joints, regardless of the approach, should be particularly careful with asymmetrical lifts. The MISS and TOSS approaches shift the average loads of different muscle groups in different ways. TOSS generally leads to higher post-operative muscle loads than MISS in the investigated cases, but the differences are smaller than could be expected, given the differences of surgical technique.

Changes in Recombinant Human Bone Morphogenetic Protein-2 Use in Posterior Fusion Over the Past Two Decades

Background

In 2011, studies suggested that complications and cancer rates associated with bone morphogenetic protein (BMP) were greater than previously reported. However, later studies reported complication rates similar to prior literature and no increased cancer rate. We evaluated the pattern of clinical utilization of BMP in posteriorly based lumbar fusion by comparing two periods: 2002-2004 and 2017-2019.

Methods

Patients who received BMP from 2002-2004 (Early) and 2017-2019 (Late) from a single multi-surgeon institution who had a lumbar fusion were identified. One hundred patients from each cohort were randomly selected. Mean total BMP used at each level and the proportion of BMP placed in the interbody space versus posterolateral gutters were evaluated.

Results

In the transforaminal lumbar intebody fusion (TLIF) cohort, the total BMP dose in the Late group (6.15 mg) was nearly half of that used in the Early group (12.04 mg, p<0.000). The amount of BMP used in the posterolateral gutters remained similar (Early: 4.01 mg vs Late: 3.38 mg, p=0.222). The amount of BMP used in the interbody space was less in the Late group (2.76 mg) compared to the Early group (8.03 mg, p<0.000). In the posterior spinal fusion (PSF) cohort, the total BMP dose remained similar between the Early (11.96 mg) and the Late groups (10.82 mg, p=0.007).

Conclusion

Change in the use of BMP in TLIF cases was driven by the complications reported in the literature with no change in outcome. A similar impetus was not seen for PSF.

Application of the IntraSPINE® interlaminar device in patients with osteoporosis and spinal stenosis: two case reports

Osteoporosis is a rising concern in the aging population and should be considered before performing spinal surgery for older patients. Nonfusion surgery using interlaminar or interspinous devices is gradually gaining acceptance because adjacent segment disease seldom occurs postoperatively; however, other complications may occur. This report discusses the surgical outcomes of two women with osteoporosis treated by laminectomy and interlaminar device (IntraSPINE®) placement. Both patients had experienced low back pain for several years and had developed vertebral compression fractures. Several conservative treatments, including rehabilitation and local injections, were ineffective. Their bone mineral density levels were −3.0 and −2.8, indicating severe osteoporosis according to the definition established by the World Health Organization. They chose to undergo nonfusion surgery with IntraSPINE® interlaminar device placement. Their pain significantly decreased postoperatively, and their visual analog scale scores decreased from 8 to 2 and 3. Their extremity numbness and back pain resolved within 3 months. Both patients were satisfied with the surgical outcomes. No complications had occurred by 1 year postoperatively. These cases indicate that osteoporosis may not be an absolute contraindication for nonfusion spinal surgery. This report suggests a possible alternative surgical treatment for patients with osteoporosis that is refractory to conservative treatments.

Epidural hematoma in patients with ankylosing spondylitis requiring surgical stabilization: a single-institution retrospective review with literature analysis

OBJECTIVE

Ankylosing spondylitis (AS) is a chronic inflammatory disease affecting the sacroiliac joints and axial spine that is closely linked with human leukocyte antigen-B27. There appears to be an increased frequency of associated epidural hematomas in spine fractures in patients with AS. The objective was to review the incidence within the literature and a single-institution experience of the occurrence of epidural hematoma in the context of patients with AS requiring spine surgery.

METHODS

Deep 6 AI software was used to search the entire database of patients at a single level I trauma center (since the advent of the institution's modern electronic health record system) to look at all patients with AS who underwent spinal surgery and who had a diagnosis of epidural hematoma. Additionally, a systemic literature review was performed of all papers evaluating the incidence of epidural hematoma in patients with spine fractures.

RESULTS

A single-institution, retrospective review of records from 2009 to 2020 yielded a total of 164 patients with AS who underwent spine surgery. Of those patients, 17 (10.4%) had epidural hematomas on imaging, with the majority requiring surgical decompression. These spine fractures occurred close to the cervicothoracic or thoracolumbar junction. The patients ranged in age from 51 to 88 years, and there were 14 males and 3 females in the cohort. Eight patients were administered an antiplatelet and/or anticoagulant agent, and the rest were not. All patients required surgical stabilization, with 64.7% of patients also requiring decompressive laminectomies for evacuation of the hematoma and spinal cord decompression. Only 1 death was reported in the series. There was a tendency toward neurological improvement after surgical intervention.

CONCLUSIONS

AS has been a well-described pathologic process that leads to an increased risk of three-column injury in spine fracture, with an increased incidence of symptomatic epidural hematoma compared with patients without AS. Early recognition of this entity is important to ensure that appropriate surgical management includes addressing compression of the neural elements in addition to surgical stabilization.

Incidence and Clinical Outcomes of Hypothyroidism in Patients Undergoing Spinal Fusion

Background

Hypothyroidism has been independently associated with the development of several comorbidities and is known to increase complication rates in non-spinal surgeries. However, there are limited data regarding the effects of hypothyroidism in major spine surgery. Therefore, we present the largest retrospective analysis evaluating outcomes in hypothyroid patients undergoing spinal fusion.

Methods

A retrospective review of the National Inpatient Sample (NIS) from 2004-2014 was performed. Patients with an International Classification of Diseases, 9th revision, Clinical Modification (ICD-9-CM) procedure code indicating spinal fusion (81.04-81.08, 81.34-81.38, 81.0x, 81.3x) were included. Patients with an ICD-9-CM diagnosis code indicating hypothyroidism (244.x) were compared to those without. Cervical and lumbar fusions were evaluated independently. Significant covariates in univariable logistic regression were utilized to construct multivariable models to analyze the effect of hypothyroidism on perioperative morbidity and mortality.

Results

A total of 4,149,125 patients were identified, of which 9.4% were hypothyroid. Although, hypothyroid patients had a higher risk of hematologic complications (lumbar - odds ratio [OR] 1.176, p < 0.0001; cervical - OR 1.162, p < 0.0001), they exhibited decreased in-hospital mortality (lumbar - OR .643, p < 0.0001; cervical - OR .606, p < 0.0001). Hypothyroid lumbar fusion patients also demonstrated decreased rates of perioperative myocardial infarction (MI) (OR .851, p < 0.0001). All these results were independent of patient gender.

Conclusions

Hypothyroid patients undergoing spinal fusion demonstrated lower rates of inpatient mortality and, in lumbar fusions, also had lower rates of acute MI when compared to their euthyroid counterparts. This suggests that hypothyroidism may offer protection against all-cause mortality and may be cardioprotective in the postoperative period for lumbar spinal fusions independent of patient gender.

Real-time navigation guidance with intraoperative CT imaging for pedicle screw placement using an augmented reality head-mounted display: a proof-of-concept study

OBJECTIVE

Augmented reality (AR) has the potential to improve the accuracy and efficiency of instrumentation placement in spinal fusion surgery, increasing patient safety and outcomes, optimizing ergonomics in the surgical suite, and ultimately lowering procedural costs. The authors sought to describe the use of a commercial prototype Spine AR platform (SpineAR) that provides a commercial AR head-mounted display (ARHMD) user interface for navigation-guided spine surgery incorporating real-time navigation images from intraoperative imaging with a 3D-reconstructed model in the surgeon's field of view, and to assess screw placement accuracy via this method.

METHODS

Pedicle screw placement accuracy was assessed and compared with literature-reported data of the freehand (FH) technique. Accuracy with SpineAR was also compared between participants of varying spine surgical experience. Eleven operators without prior experience with AR-assisted pedicle screw placement took part in the study: 5 attending neurosurgeons and 6 trainees (1 neurosurgical fellow, 1 senior orthopedic resident, 3 neurosurgical residents, and 1 medical student). Commercially available 3D-printed lumbar spine models were utilized as surrogates of human anatomy. Among the operators, a total of 192 screws were instrumented bilaterally from L2-5 using SpineAR in 24 lumbar spine models. All but one trainee also inserted 8 screws using the FH method. In addition to accuracy scoring using the Gertzbein-Robbins grading scale, axial trajectory was assessed, and user feedback on experience with SpineAR was collected.

RESULTS

Based on the Gertzbein-Robbins grading scale, the overall screw placement accuracy using SpineAR among all users was 98.4% (192 screws). Accuracy for attendings and trainees was 99.1% (112 screws) and 97.5% (80 screws), respectively. Accuracy rates were higher compared with literature-reported lumbar screw placement accuracy using FH for attendings (99.1% vs 94.32%; p = 0.0212) and all users (98.4% vs 94.32%; p = 0.0099). The percentage of total inserted screws with a minimum of 5° medial angulation was 100%. No differences were observed between attendings and trainees or between the two methods. User feedback on SpineAR was generally positive.

CONCLUSIONS

Screw placement was feasible and accurate using SpineAR, an ARHMD platform with real-time navigation guidance that provided a favorable surgeon-user experience.

Cost-Effectiveness of Peptide Enhanced Bone Graft i-Factor versus Use of Local Autologous Bone in Anterior Cervical Discectomy and Fusion Surgery

Study Design

We conducted decision analytical modeling using a Markov model to determine the ICER of i-factor compared to autograft in ACDF surgery.

Objective

The efficacy and safety of traditional anterior cervical discectomy and fusion (ACDF) surgery has improved with the introduction of new implants and compounds. Cost-effectiveness of these innovations remains an often-overlooked aspect of this effort. To evaluate the cost-effectiveness of i-FACTOR compared to autograft for patients undergoing ACDF surgery.

Methods

The patient cohort was extracted from a prospective, multicenter randomized control trial (RCT) from twenty-two North American centers. Patients randomly received either autograft (N = 154) or i-Factor (N = 165). We analyzed various real-world scenarios, including inpatient and outpatient surgical settings as well as private versus public insurances. Two primary outcome measures were assessed: cost and utility. In the base-case analysis, both health and societal system costs were evaluated. Health-related utility outcome was expressed in quality-adjusted life years (QALYs). Cost-effectiveness was expressed as an incremental cost-effectiveness ratio (ICER).

Results

In all scenarios, i-FACTOR reduced costs within the first year by 1.4% to 2.1%. The savings proved to be incremental over time, increasing to 3.7% over an extrapolated 10 years. The ICER at 90 days was $13,333 per QALY and became negative ("dominated") relative to the control group within one year and onwards. In a threshold sensitivity analysis, the cost of i-FACTOR could theoretically be increased 70-fold and still remain cost-effective.

Conclusion

The novel i-FACTOR is not only cost-effective compared to autograft in ACDF surgery but is the dominant economic strategy.

Peri-Surgical Inflammatory Profile Associated with Mini-Invasive or Standard Open Lumbar Interbody Fusion Approaches

BACKGROUND

Different surgical approaches are available for lumbar interbody fusion (LIF) to treat disc degeneration. However, a quantification of their invasiveness is lacking, and the definition of minimally invasive surgery (MIS) has not been biochemically detailed. We aimed at characterizing the inflammatory, hematological, and clinical peri-surgical responses to different LIF techniques.

METHODS

68 healthy subjects affected by single-level discopathy (L3 to S1) were addressed to MIS, anterior (ALIF, n = 21) or lateral (LLIF, n = 23), and conventional approaches, transforaminal (TLIF, n = 24), based on the preoperative clinical assessment. Venous blood samples were taken 24 h before the surgery and 24 and 72 h after surgery to assess a wide panel of inflammatory and hematological markers.

RESULTS

martial (serum iron and transferrin) and pro-angiogenic profiles (MMP-2, TWEAK) were improved in ALIF and LLIF compared to TLIF, while the acute phase response (C-reactive protein, sCD163) was enhanced in LLIF.

CONCLUSIONS

MIS procedures (ALIF and LLIF) associated with a reduced incidence of post-operative anemic status, faster recovery, and enhanced pro-angiogenic stimuli compared with TLIF. LLIF associated with an earlier activation of innate immune mechanisms than ALIF and TLIF. The trend of the inflammation markers confirms that the theoretically defined mini-invasive procedures behave as such.

Investigating the efficacy of allograft cellular bone matrix for spinal fusion: a systematic review of the literature

OBJECTIVE

The use of allograft cellular bone matrices (ACBMs) in spinal fusion has expanded rapidly over the last decade. Despite little objective data on its effectiveness, ACBM use has replaced the use of traditional autograft techniques, namely iliac crest bone graft (ICBG), in many centers.

METHODS

In accordance with PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines, a systematic review was conducted of the PubMed, Cochrane Library, Scopus, and Web of Science databases of English-language articles over the time period from January 2001 to December 2020 to objectively assess the effectiveness of ACBMs, with an emphasis on the level of industry involvement in the current body of literature.

RESULTS

Limited animal studies (n = 5) demonstrate the efficacy of ACBMs in spinal fusion, with either equivalent or increased rates of fusion compared to autograft. Clinical human studies utilizing ACBMs as bone graft expanders or bone graft substitutes (n = 5 for the cervical spine and n = 8 for the lumbar spine) demonstrate the safety of ACBMs in spinal fusion, but fail to provide conclusive level I, II, or III evidence for its efficacy. Additionally, human studies are plagued with several limiting factors, such as small sample size, lack of prospective design, lack of randomization, absence of standardized assessment of fusion, and presence of industry support/relevant conflict of interest.

CONCLUSIONS

There exist very few objective, unbiased human clinical studies demonstrating ACBM effectiveness or superiority in spinal fusion. Impartial, well-designed prospective studies are needed to offer evidence-based best practices to patients in this domain.

Lordosis Restoration With Midline Minimally Invasive Cortical Trajectory Screws (MidLF) and Transforaminal Interbody Fusion: A Safe Technique With a Short Stay

BACKGROUND

The minimally invasive cortical trajectory screw (MidLF) technique has been described accompanied with posterolateral interbody fusion (PLIF). We present our 2-year results of a hybrid technique to show that using transforaminal interbody fusion (TLIF) rather than PLIF in conjunction with MidLF is a less invasive and safe technique.

METHODS

We retrospectively identified 25 patients who underwent MidLF with TLIF from July 2015 through September 2017. The surgical technique was the same for each, with radiological, clinical, and patient-reported outcome data collected and analyzed at a 2-year follow-up.

RESULTS

The cohort showed a mean age of 55 (35-85) years. The length of hospital stay was between 1 and 4 days, with an average of 2.7 days. Postoperatively, lordosis across the motion segment fused increased by a mean of 7.3° (0°-24°), mean pelvic incidence was 53°(31°-80°), and pelvic tilt reduced by an average of 3.5° (0°-11°). The Oswestry Disability Index improved from 34 preoperatively to 19 postoperatively. Visual analogue pain score-leg improved by 4.7 points, from 6 down to 1. One patient showed delayed wound healing. There were no incidences of neurological injury or durotomy.

CONCLUSIONS

Our data suggests that MidLF with TLIF is both less invasive than traditional techniques and safe. It restores lordosis, requires less exposure and retraction of neural elements than the more widely used PLIF, and shows early discharge and satisfactory medium-term patient-reported outcomes.

LEVEL OF EVIDENCE

3.

CLINICAL RELEVANCE

The MidLF technique with PLIF is less invasive than traditional techniques, restores alignment and shows satisfactory medium term results.

The Expanding Frontier of Outpatient Spine Surgery

BACKGROUND

In 2014, inpatient spinal fusion surgery had the highest aggregate cost of any inpatient surgery performed in the United States, costing 12 billion dollars. As the national health care system seeks to improve value-based care, there is increased motivation to perform surgery on an outpatient basis. To ensure improved patient outcomes with this transition, patient selection has become increasingly important to identify who would most benefit from outpatient spine fusion, for example. This demands an improved understanding of the demographics of patients who have been receiving outpatient spine fusion on which the spine surgery community can build to improve cost-effective care delivered.

METHODS

The Healthcare Cost and Utilization Project, State Ambulatory Surgery Databases, and Agency for Healthcare Research and Quality databases were queried for demographic data regarding all-cause outpatient spine surgery between 2012 and 2014. Outpatient surgery volume was compared with inpatient surgery volume-which was provided by the State Inpatient Databases.

RESULTS

A total of 1,164,040 spine fusion procedures were identified between 2012 and 2014, of which 132,900 procedures were performed as outpatient surgery (11.4%). Of all fusion procedures amongst 18- to 44-year-old patients, 18.4% were outpatient. A larger proportion of white patients, rather than black or Hispanic patients, underwent ambulatory procedures (12.14% vs 9.53% vs 7.46%, respectively); 16.54% of spinal fusion procedures for patients with private insurance was performed on an outpatient basis. Based on patient income, 76% of all outpatient fusions were performed on patients who live in "not low" income ZIP codes.

CONCLUSIONS

There has been a gradual trend toward performing more outpatient spinal fusion procedures over the studied period. This study has also revealed unique trends in the demographics of patients who have received outpatient spine fusion during this time.

LEVEL OF EVIDENCE

3.

Allografts and Spinal Fusion

BACKGROUND

Back pain is a common chief complaint within the United States and is caused by a multitude of etiologies. There are many different treatment modalities for back pain, with a frequent option being spinal fusion procedures. The success of spinal fusion greatly depends on instrumentation, construct design, and bone grafts used in surgery. Bone allografts are important for both structural integrity and providing a scaffold for bone fusion to occur.

METHOD

Searches were performed using terms "allografts" and "bone" as well as product names in peer reviewed literature Pubmed, Google Scholar, FDA-510k approvals, and clinicaltrials.gov.

RESULTS

This study is a review of allografts and focuses on currently available products and their success in both animal and clinical studies.

CONCLUSION

Bone grafts used in surgery are generally categorized into 3 main types: autogenous (from patient's own body), allograft (from cadaveric or living donor), and synthetic. This paper focuses on allografts and provides an overview on the different subtypes with an emphasis on recent product development and uses in spinal fusion surgery.

Human perivascular stem cells prevent bone graft resorption in osteoporotic contexts by inhibiting osteoclast formation

The vascular wall stores mesenchymal progenitor cells which are able to induce bone regeneration, via direct and paracrine mechanisms. Although much is known regarding perivascular cell regulation of osteoblasts, their regulation of osteoclasts, and by extension utility in states of high bone resorption, is not known. Here, human perivascular stem cells (PSCs) were used as a means to prevent autograft resorption in a gonadectomy-induced osteoporotic spine fusion model. Furthermore, the paracrine regulation by PSCs of osteoclast formation was evaluated, using coculture, conditioned medium, and purified extracellular vesicles. Results showed that PSCs when mixed with autograft bone induce an increase in osteoblast:osteoclast ratio, promote bone matrix formation, and prevent bone graft resorption. The confluence of these factors resulted in high rates of fusion in an ovariectomized rat lumbar spine fusion model. Application of PSCs was superior across metrics to either the use of unpurified, culture-defined adipose-derived stromal cells or autograft bone alone. Under coculture conditions, PSCs negatively regulated osteoclast formation and did so via secreted, nonvesicular paracrine factors. Total RNA sequencing identified secreted factors overexpressed by PSCs which may explain their negative regulation of graft resorption. In summary, PSCs reduce osteoclast formation and prevent bone graft resorption in high turnover states such as gonadectomy-induced osteoporosis.

Development of AOSpine BOnE (Bone Osteobiologics and Evidence) Classification

STUDY DESIGN

Classification development.

OBJECTIVES

The aim of our study was to develop a 3-tier classification for the levels of evidence for osteobiologics and provide a description of the principles by which osteobiologics can be evaluated. BOnE (Bone Osteobiologics and Evidence) classification evaluates each osteobiologic based on the available evidence, and if the published evidence is based on clinical, in vivo or in vitro studies.

METHODS

The process of establishing the BOnE classification included 5 face-to-face meetings and 2 web calls among members of the AOSpine Knowledge Forum Degenerative.

RESULTS

The 3 levels of evidence were determined based on the type of data on osteobiologics: level A for human studies, level B for animal studies, and level C for in vitro studies, with level A being the highest level of evidence. Each level was organized into 4 subgroups (eg, A1, A2, A3, and A4).

CONCLUSIONS

The use and the variety of osteobiologics for spine fusion has dramatically increased over the past few decades; however, literature on their effectiveness is inconclusive. Several prior systematic reviews developed by AOSpine Knowledge Forum Degenerative reported low level of evidence primarily due to the high risk of bias, small sample size, lack of control groups, and limited patient-reported outcomes. BOnE classification will provide a universal platform for research studies and journal publications to classify a new or an existing product and will allow for creating decision-making algorithms for surgical planning.

Impact of Cirrhosis on Morbidity and Mortality After Spinal Fusion

STUDY DESIGN

Retrospective large database study.

OBJECTIVE

To determine the impact of cirrhosis on perioperative outcomes and resource utilization in elective spinal fusion surgery.

METHODS

Elective spinal fusion hospitalizations in patients with and without cirrhosis were identified using ICD-9-CM codes between the years of 2009 and 2011 using the Nationwide Inpatient Sample database. Main outcome measures were in-hospital neurologic, respiratory, cardiac, gastrointestinal, renal and urinary, pulmonary embolism, wound-related complications, and mortality. Length of stay and inpatient costs were also collected. Multivariable logistic regressions were conducted to compare the in-hospital outcomes of patients with and without cirrhosis undergoing spinal fusion.

RESULTS

A total of 1 214 694 patients underwent elective spinal fusions from 2009 to 2011. Oh these, 6739 were cirrhotic. Cirrhosis was a significant independent predictor for respiratory (odds ratio [OR] = 1.43, confidence interval [CI] 1.29-1.58; P < .001), gastrointestinal (OR = 1.72, CI 1.48-2.00; P < .001), urinary and renal (OR = 1.90, CI 1.70-2.12; P < 0.001), wound (OR = 1.36, CI 1.17-1.58; P < 0.001), and overall inpatient postoperative complications (OR = 1.43, CI 1.33-1.53; P < .001). Cirrhosis was also independently associated with significantly greater inpatient mortality (OR = 2.32, CI 1.72-3.14; P < .001). Cirrhotic patients also had significantly longer lengths of stay (5.35 vs 3.35 days; P < .001) and inpatient costs ($36 738 vs $29 068; P < .001).

CONCLUSIONS

Cirrhosis is associated with increased risk of perioperative complications, mortality and greater resource utilization. Cirrhotic patients undergoing spinal fusion surgeries should be counseled on these increased risks. Current strategies for perioperative management of cirrhotic patients undergoing spinal fusion surgery need improvement.

Osteomyelitis-Discitis at the Thoracolumbar Junction and the Development of Postinfectious Spinal Deformity: A Surgical Case Series

BACKGROUND

Progressive spinal deformity and neural compromise are the main indications for surgical management of vertebral osteomyelitis-discitis. However, when such pathology presents at the thoracolumbar (TL) junction, it remains unclear what the appropriate intervention is. The therapeutic dilemmas of decompression with or without instrumented fusion, the need for circumferential decompression and reconstruction, as well as the prognostic factors for progression of kyphosis, all remained ill-defined in the literature. The objective of this study is to evaluate risk factors for instrumentation at TL junction in spinal osteomyelitis-discitis.

METHODS

A review of patients at a single center with osteomyelitis-discitis at the TL junction between 2014 and 2018 was performed. Patients were 18 years or older with infectious pathologies at T10 to L2.

RESULTS

Sixteen patients were included. Indication for instrumentation included progression of kyphosis following prior laminectomy/medical management. Of the 16 patients, 4 patients received laminectomy at initial treatment versus 12 patients receiving medical management alone. All 4 patients receiving laminectomy experienced progressive kyphosis requiring revision with instrumented fusion versus only 4 of 12 of the medically managed. Laminectomy, epidural compression, and vertebral body collapse were significant risk factors for kyphosis progression requiring instrumentation. The average time to surgical intervention for the indication of progressive kyphosis was 2.6 months after prior laminectomy and 6 months after initiation of medical management.

CONCLUSIONS

Given the proclivity for kyphotic deformity at the TL junction, patients may benefit from long segment instrumentation in addition to decompression at the initial surgery. Laminectomy alone may hasten kyphosis progression.

The Majority of Total Hip Arthroplasty Patients With a Stiff Spine Do Not Have an Instrumented Fusion

BACKGROUND

Total hip arthroplasty (THA) patients with limited lumbar flexion (LF) have increased rates of dislocation. An instrumented spinal fusion is a well-recognized cause whose risk increases with increasing number of levels fused. However, many patients without an instrumented fusion (IF) also exhibit abnormal spinopelvic mobility. The purpose of this study was to understand the proportion of THA patients without an IF that have a stiff spine (SS) and behave as if they are surgically fused.

METHODS

A retrospective analysis was performed on 6340 primary THA patients, all of whom had preoperative spinopelvic measurements. Any IF of the lumbar spine was observed on the lateral standing radiograph and recorded. SS was classified by LF ≤ 20°, and the percentage of patients with an IF and limited LF was determined.

RESULTS

Three hundred fifty-six (6%) patients had a SS, and only 67 (19%) had an IF. Of the entire 6340 patients, 207 (3%) had an IF. Of these 207, only 67 (32%) had a SS.

CONCLUSIONS

The vast majority (81%) of THA patients with a SS do not have an IF. We recommend preoperative spinopelvic assessment of all patients undergoing THA, as only a minority of those with limited LF have an IF and may otherwise be overlooked. Lumbar degenerative disc disease is common in THA patients, limits the available LF in the same way an IF might and potentially increases the risk of dislocation in this subset of patients.

LEVEL OF EVIDENCE

III.

Design and control of an image-guided robot for spine surgery in a hybrid OR

BACKGROUND

Minimally invasive spine (MIS) fusion surgery requires image guidance and expert manual dexterity for a successful, efficient, and accurate pedicle screw placement. Operating room (OR)-integrated robotic solution can provide precise assistance to potentially minimize complication rates and facilitate difficult MIS procedures.

METHODS

A 5-degrees of freedom robot was designed specifically for a hybrid OR with integrated surgical navigation for guiding pedicle screw pilot holes. The system automatically aligns an instrument following the surgical plan using only instrument tracking feedback. Contrary to commercially available robotic systems, no tracking markers on the robotic arm are required. The system was evaluated in a cadaver study.

RESULTS

The mean targeting error (N = 34) was 1.27±0.57 mm and 1.62±0.85°, with 100% of insertions graded as clinically acceptable.

CONCLUSIONS

A fully integrated robotic guidance system, including intra-op imaging, planning, and physical guidance with optimized robot design and control, can improve workflow and provide pedicle screw guidance with less than 2 mm targeting error.

Influence of Geometry and Architecture on the In Vivo Success of 3D-Printed Scaffolds for Spinal Fusion

We previously developed a recombinant growth factor-free, three-dimensional (3D)-printed material comprising hydroxyapatite (HA) and demineralized bone matrix (DBM) for bone regeneration. This material has demonstrated the capacity to promote re-mineralization of the DBM particles within the scaffold struts and shows potential to promote successful spine fusion. Here, we investigate the role of geometry and architecture in osteointegration, vascularization, and facilitation of spine fusion in a preclinical model. Inks containing HA and DBM particles in a poly(lactide-co-glycolide) elastomer were 3D-printed into scaffolds with varying relative strut angles (90° vs. 45° advancing angle), macropore size (0 μm vs. 500 μm vs. 1000 μm), and strut alignment (aligned vs. offset). The following configurations were compared with scaffolds containing no macropores: 90°/500 μm/aligned, 45°/500 μm/aligned, 90°/1000 μm/aligned, 45°/1000 μm/aligned, 90°/1000 μm/offset, and 45°/1000 μm/offset. Eighty-four female Sprague-Dawley rats underwent spine fusion with bilateral placement of the various scaffold configurations (n = 12/configuration). Osteointegration and vascularization were assessed by using microComputed Tomography and histology, and spine fusion was assessed via blinded manual palpation. The 45°/1000 μm scaffolds with aligned struts achieved the highest average fusion score (1.61/2) as well as the highest osteointegration score. Both the 45°/1000 μm/aligned and 90°/1000 μm/aligned scaffolds elicited fusion rates of 100%, which was significantly greater than the 45°/500 μm/aligned iteration (p < 0.05). All porous scaffolds were fully vascularized, with blood vessels present in every macropore. Vessels were also observed extending from the native transverse process bone, through the protrusions of new bone, and into the macropores of the scaffolds. When viewed independently, scaffolds printed with relative strut angles of 45° and 90° each allowed for osteointegration sufficient to stabilize the spine at L4-L5. Within those parameters, a pore size of 500 μm or greater was generally sufficient to achieve unilateral fusion. However, our results suggest that scaffolds printed with the larger pore size and with aligned struts at an advancing angle of 45° may represent the optimal configuration to maximize osteointegration and fusion capacity. Overall, this work suggests that the HA/DBM composite scaffolds provide a conducive environment for bone regeneration as well as vascular infiltration. This technology, therefore, represents a novel, growth-factor-free biomaterial with significant potential as a bone graft substitute for use in spinal surgery. Impact statement We previously developed a recombinant growth factor-free, three-dimensional (3D)-printed composite material comprising hydroxyapatite and demineralized bone matrix for bone regeneration. Here, we identify a range of 3D geometric and architectural parameters that support the preclinical success of the scaffold, including efficient vascularization, osteointegration, and, ultimately, spinal fusion. Our results suggest that this material holds great promise as a clinically translatable biomaterial for use as a bone graft substitute in orthopedic procedures requiring bone regeneration.