Stem Cell-Friendly Scaffold Biomaterials: Applications for Bone Tissue Engineering and Regenerative Medicine

Bone is a dynamic organ with high regenerative potential and provides essential biological functions in the body, such as providing body mobility and protection of internal organs, regulating hematopoietic cell homeostasis, and serving as important mineral reservoir. Bone defects, which can be caused by trauma, cancer and bone disorders, pose formidable public health burdens. Even though autologous bone grafts, allografts, or xenografts have been used clinically, repairing large bone defects remains as a significant clinical challenge. Bone tissue engineering (BTE) emerged as a promising solution to overcome the limitations of autografts and allografts. Ideal bone tissue engineering is to induce bone regeneration through the synergistic integration of biomaterial scaffolds, bone progenitor cells, and bone-forming factors. Successful stem cell-based BTE requires a combination of abundant mesenchymal progenitors with osteogenic potential, suitable biofactors to drive osteogenic differentiation, and cell-friendly scaffold biomaterials. Thus, the crux of BTE lies within the use of cell-friendly biomaterials as scaffolds to overcome extensive bone defects. In this review, we focus on the biocompatibility and cell-friendly features of commonly used scaffold materials, including inorganic compound-based ceramics, natural polymers, synthetic polymers, decellularized extracellular matrix, and in many cases, composite scaffolds using the above existing biomaterials. It is conceivable that combinations of bioactive materials, progenitor cells, growth factors, functionalization techniques, and biomimetic scaffold designs, along with 3D bioprinting technology, will unleash a new era of complex BTE scaffolds tailored to patient-specific applications.

Applications of Biocompatible Scaffold Materials in Stem Cell-Based Cartilage Tissue Engineering

Cartilage, especially articular cartilage, is a unique connective tissue consisting of chondrocytes and cartilage matrix that covers the surface of joints. It plays a critical role in maintaining joint durability and mobility by providing nearly frictionless articulation for mechanical load transmission between joints. Damage to the articular cartilage frequently results from sport-related injuries, systemic diseases, degeneration, trauma, or tumors. Failure to treat impaired cartilage may lead to osteoarthritis, affecting more than 25% of the adult population globally. Articular cartilage has a very low intrinsic self-repair capacity due to the limited proliferative ability of adult chondrocytes, lack of vascularization and innervation, slow matrix turnover, and low supply of progenitor cells. Furthermore, articular chondrocytes are encapsulated in low-nutrient, low-oxygen environment. While cartilage restoration techniques such as osteochondral transplantation, autologous chondrocyte implantation (ACI), and microfracture have been used to repair certain cartilage defects, the clinical outcomes are often mixed and undesirable. Cartilage tissue engineering (CTE) may hold promise to facilitate cartilage repair. Ideally, the prerequisites for successful CTE should include the use of effective chondrogenic factors, an ample supply of chondrogenic progenitors, and the employment of cell-friendly, biocompatible scaffold materials. Significant progress has been made on the above three fronts in past decade, which has been further facilitated by the advent of 3D bio-printing. In this review, we briefly discuss potential sources of chondrogenic progenitors. We then primarily focus on currently available chondrocyte-friendly scaffold materials, along with 3D bioprinting techniques, for their potential roles in effective CTE. It is hoped that this review will serve as a primer to bring cartilage biologists, synthetic chemists, biomechanical engineers, and 3D-bioprinting technologists together to expedite CTE process for eventual clinical applications.

Notch signaling: Its essential roles in bone and craniofacial development

Notch is a cell–cell signaling pathway that is involved in a host of activities including development, oncogenesis, skeletal homeostasis, and much more. More specifically, recent research has demonstrated the importance of Notch signaling in osteogenic differentiation, bone healing, and in the development of the skeleton. The craniofacial skeleton is complex and understanding its development has remained an important focus in biology. In this review we briefly summarize what recent research has revealed about Notch signaling and the current understanding of how the skeleton, skull, and face develop. We then discuss the crucial role that Notch plays in both craniofacial development and the skeletal system, and what importance it may play in the future.

Leptin Potentiates BMP9-Induced Osteogenic Differentiation of Mesenchymal Stem Cells Through the Activation of JAK/STAT Signaling

Mesenchymal stem cells (MSCs) are multipotent progenitors that have the ability to differentiate into multiple lineages, including bone, cartilage, and fat. We previously demonstrated that the least known bone morphogenetic protein (BMP)9 (also known as growth differentiation factor 2) is one of the potent osteogenic factors that can induce both osteogenic and adipogenic differentiation of MSCs. Nonetheless, the molecular mechanism underlying BMP9 action remains to be fully understood. Leptin is an adipocyte-derived hormone in direct proportion to the amount of body fat, and exerts pleiotropic functions, such as regulating energy metabolism, bone mass, and mineral density. In this study, we investigate the potential effect of leptin signaling on BMP9-induced osteogenic differentiation of MSCs. We found that exogenous leptin potentiated BMP9-induced osteogenic differentiation of MSCs both in vitro and in vivo, while inhibiting BMP9-induced adipogenic differentiation. BMP9 was shown to induce the expression of leptin and leptin receptor in MSCs, while exogenous leptin upregulated BMP9 expression in less differentiated MSCs. Mechanistically, we demonstrated that a blockade of JAK signaling effectively blunted leptin-potentiated osteogenic differentiation induced by BMP9. Taken together, our results strongly suggest that leptin may potentiate BMP9-induced osteogenesis by cross-regulating BMP9 signaling through the JAK/STAT signaling pathway in MSCs. Thus, it is conceivable that a combined use of BMP9 and leptin may be explored as a novel approach to enhancing efficacious bone regeneration and fracture healing.

A New Culture of Transparency: Industry Payments to Orthopedic Surgeons

Under the Physician Payments Sunshine Act, "payments or transfers of value" by biomedical companies to physicians must be disclosed through the Open Payments Program. Designed to provide transparency of financial transactions between medication and device manufacturers and health care providers, the Open Payments Program shows financial relationships between industry and health care providers. Awareness of this program is crucial because its interpretation or misinterpretation by patients, physicians, and the general public can affect patient care, clinical practice, and research. This study evaluated nonresearch payments by industry to orthopedic surgeons. A retrospective cross-sectional review of the first wave of Physician Payments Sunshine Act data (August through December 2013) was performed to characterize industry payments to orthopedic surgeons by subspecialty, amount, type, origin, and geographic distribution. During this 5-month period, orthopedic surgeons (n=14,828) received $107,666,826, which included 3% of those listed in the Open Payments Program and 23% of the total amount paid. Of orthopedic surgeons who received payment, 45% received less than $100 and 1% received $100,000 or more. Median payment (interquartile range) was $119 ($34-$636), and mean payment was $7261±95,887. The largest payment to an individual orthopedic surgeon was $7,849,711. The 2 largest payment categories were royalty or license fees (68%) and consulting fees (13%). During the study period, orthopedic surgeons had substantial financial ties to industry. Of orthopedic surgeons who received payments, the largest proportion (45%) received less than $100 and only 1% received large payments (≥$100,000). The Open Payments Program offers insight into industry payments to orthopedic surgeons. [Orthopedics. 2016; 39(6):e1058-e1062.].

SATB2: A versatile transcriptional regulator of craniofacial and skeleton development, neurogenesis and tumorigenesis, and its applications in regenerative medicine

SATB2 (special AT-rich sequence-binding protein 2) is a member of the special AT-rich binding protein family. As a transcription regulator, SATB2 mainly integrates higher-order chromatin organization. SATB2 expression appears to be tissue- and stage-specific, and is governed by several cellular signaling molecules and mediators. Expressed in branchial arches and osteoblast-lineage cells, SATB2 plays a significant role in craniofacial pattern and skeleton development. In addition to regulating osteogenic differentiation, SATB2 also displays versatile functions in neural development and cancer progression. As an osteoinductive factor, SATB2 holds great promise in improving bone regeneration toward bone defect repair. In this review, we have summarized our current understanding of the physiological and pathological functions of SATB2 in craniofacial and skeleton development, neurogenesis, tumorigenesis and regenerative medicine.

FAMSi: A Synthetic Biology Approach to the Fast Assembly of Multiplex siRNAs for Silencing Gene Expression in Mammalian Cells

RNA interference (RNAi) is mediated by an ∼21-nt double-stranded small interfering RNA (siRNA) and shows great promise in delineating gene functions and in developing therapeutics for human diseases. However, effective gene silencing usually requires the delivery of multiple siRNAs for a given gene, which is often technically challenging and time-consuming. In this study, by exploiting the type IIS restriction endonuclease-based synthetic biology methodology, we developed the fast assembly of multiplex siRNAs (FAMSi) system. In our proof-of-concept experiments, we demonstrated that multiple fragments containing three, four, or five siRNA sites targeting common Smad4 and/or BMPR-specific Smad1, Smad5, and Smad8 required for BMP9 signaling could be assembled efficiently. The constructed multiplex siRNAs effectively knocked down the expression of Smad4 and/or Smad1, Smad5, and Smad8 in mesenchymal stem cells (MSCs), and they inhibited all aspects of BMP9-induced osteogenic differentiation in bone marrow MSCs (BMSCs), including decreased expression of osteogenic regulators/markers, reduced osteogenic marker alkaline phosphatase (ALP) activity, and diminished in vitro matrix mineralization and in vivo ectopic bone formation. Collectively, we demonstrate that the engineered FAMSi system provides a fast-track platform for assembling multiplexed siRNAs in a single vector, and thus it may be a valuable tool to study gene functions or to develop novel siRNA-based therapeutics.

BMP9-initiated osteogenic/odontogenic differentiation of mouse tooth germ mesenchymal cells (TGMCS) requires Wnt/β-catenin signalling activity

Teeth arise from the tooth germ through sequential and reciprocal interactions between immature epithelium and mesenchyme during development. However, the detailed mechanism underlying tooth development from tooth germ mesenchymal cells (TGMCs) remains to be fully understood. Here, we investigate the role of Wnt/β‐catenin signalling in BMP9‐induced osteogenic/odontogenic differentiation of TGMCs. We first established the reversibly immortalized TGMCs (iTGMCs) derived from young mouse mandibular molar tooth germs using a retroviral vector expressing SV40 T antigen flanked with the FRT sites. We demonstrated that BMP9 effectively induced expression of osteogenic markers alkaline phosphatase, collagen A1 and osteocalcin in iTGMCs, as well as in vitro matrix mineralization, which could be remarkably blunted by knocking down β‐catenin expression. In vivo implantation assay revealed that while BMP9‐stimulated iTGMCs induced robust formation of ectopic bone, knocking down β‐catenin expression in iTGMCs remarkably diminished BMP9‐initiated osteogenic/odontogenic differentiation potential of these cells. Taken together, these discoveries strongly demonstrate that reversibly immortalized iTGMCs retained osteogenic/odontogenic ability upon BMP9 stimulation, but this process required the participation of canonical Wnt signalling both in vitro and in vivo. Therefore, BMP9 has a potential to be applied as an efficacious bio‐factor in osteo/odontogenic regeneration and tooth engineering. Furthermore, the iTGMCs may serve as an important resource for translational studies in tooth tissue engineering.

Comparison of rod fracture rates in long spinal deformity constructs after transforaminal versus anterior lumbar interbody fusions: a single-institution analysis

OBJECTIVE

Pseudarthrosis is a common complication of long-segment fusions after surgery for correction of adult spinal deformity (ASD). Interbody fusions are frequently used at the caudal levels of long-segment spinal deformity constructs as adjuncts for anterior column support. There is a paucity of literature comparing rod fracture rates (proxy for pseudarthrosis) in patients undergoing transforaminal lumbar interbody fusion (TLIF) versus anterior lumbar interbody fusion (ALIF) at the caudal levels of the long spinal deformity construct. In this study the authors sought to compare rod fracture rates in patients undergoing surgery for correction of ASD with TLIF versus ALIF at the caudal levels of long spinal deformity constructs.

METHODS

We reviewed clinical records of patients who underwent surgery for correction of ASD between 2008 and 2014 at a single institution. Data including demographics, comorbidities, and indications for surgery, as well as postoperative variables, were collected for each patient. All patients had a minimum 2-year follow-up. Patients were dichotomized into two groups for comparison on the basis of undergoing a TLIF versus an ALIF procedure at the caudal levels of long spinal deformity constructs. The primary outcome of interest was the rate of rod fractures.

RESULTS

A total of 198 patients (TLIF 133 patients; ALIF 65 patients) underwent a long-segment fusion to the sacrum with iliac fixation. The mean ± standard deviation follow-up period was 62.23 ± 29.26 months. Baseline demographic variables were similar in both patient groups. There were no significant differences between groups in the severity of the baseline sagittal plane deformity (i.e., baseline lumbar-pelvic parameters) or the final deformity correction achieved. Mean total recombinant human bone morphogenetic protein 2 (rhBMP-2) dose for L1-sacrum fusion was significantly higher in the ALIF (100 mg) than in the TLIF (62 mg) group. The overall rod failure rate (cases with rod fracture/total cases) within this case series was 19.19% (38/198); 10.60% (21/198) were unilateral rod fractures and 8.58% (17/198) were bilateral rod fractures. At last clinical follow-up, there were no statistically significant differences in bilateral rod fracture rates between the group of patients who had a TLIF procedure and the group who had an ALIF procedure at the caudal levels of the long spinal deformity constructs (TLIF 10.52% vs ALIF 4.61%, p = 0.11). However, the incidence rate (cases per patient follow-up years) for bilateral rod fractures was significantly higher in the TLIF than in the ALIF cohort (TLIF 2.20% vs ALIF 0.70%, p < 0.0001). The reoperation rate for rod fractures was similar between the patient groups (p = 0.40).

CONCLUSIONS

Although both ALIF and TLIF procedures at the caudal levels of long spinal deformity constructs achieved similar and satisfactory deformity correction, ALIFs were associated with a lower rod fracture incidence rate. There were no differences between groups in the prevalence of rod fracture or revision surgery, however, and both groups had low bilateral rod fracture prevalence and incidence rates. One technique is not clearly superior to the other.

Development of a simplified and inexpensive RNA depletion method for plasmid DNA purification using size selection magnetic beads (SSMBs)

Plasmid DNA (pDNA) isolation from bacterial cells is one of the most common and critical steps in molecular cloning and biomedical research. Almost all pDNA purification involves disruption of bacteria, removal of membrane lipids, proteins and genomic DNA, purification of pDNA from bulk lysate, and concentration of pDNA for downstream applications. While many liquid-phase and solid-phase pDNA purification methods are used, the final pDNA preparations are usually contaminated with varied degrees of host RNA, which cannot be completely digested by RNase A. To develop a simple, cost-effective, and yet effective method for RNA depletion, we investigated whether commercially available size selection magnetic beads (SSMBs), such as Mag-Bind® TotalPure NGS Kit (or Mag-Bind), can completely deplete bacterial RNA in pDNA preparations. In this proof-of-principle study, we demonstrated that, compared with RNase A digestion and two commercial plasmid affinity purification kits, the SSMB method was highly efficient in depleting contaminating RNA from pDNA minipreps. Gene transfection and bacterial colony formation assays revealed that pDNA purified from SSMB method had superior quality and integrity to pDNA samples cleaned up by RNase A digestion and/or commercial plasmid purification kits. We further demonstrated that the SSMB method completely depleted contaminating RNA in large-scale pDNA samples. Furthermore, the Mag-bind-based SSMB method costs only 5-10% of most commercial plasmid purification kits on a per sample basis. Thus, the reported SSMB method can be a valuable and inexpensive tool for the removal of bacterial RNA for routine pDNA preparations.

Rod fractures and nonunions after long fusion to the sacrum for primary presentation adult spinal deformity: a comparison with and without interbody fusion in the distal lumbar spine

STUDY DESIGN

Retrospective cohort study.

OBJECTIVES

To investigate the prevalence and incidence rate of rod fractures (RF) in patients undergoing surgery for correction of adult spinal deformity (ASD) with or without the use of interbody fusions in the caudal levels of the fusion construct.

BACKGROUND

Data: Pseudarthrosis and rod fracture after long spinal fusion to the sacrum for correction of ASD remain a concern.

METHODS

We reviewed clinical records of patients who underwent surgery for correction of ASD between 2004 and 2014. All cases were primary (no prior spine fusion) surgeries with long fusion to the sacrum and bilateral spinopelvic fixation. Patients were dichotomized into one of two groups based on whether an interbody fusion was performed at the caudal levels of the fusion construct. The primary outcome of interest was the prevalence and incidence rate of RFs.

RESULTS

A total of 230 patients underwent a long segment fusion for correction of ASD with mean follow-up of 55 months. 117 patients had an interbody fusion (IF) while 113 patients did not (NIF). At last follow-up, there was no significant difference in the prevalence of RFs between the cohort of patients IF vs NIF (IF cohort: n = 20, 17.9% vs NIF cohort: n = 15, 14.2%, p = 0.49). However, the incidence rate for bilateral rod fractures was 1.6%/year for IF group vs 1.0%/year for NIF group (p = 0.02). Location of RF was different between the two groups; RF (unilateral and bilateral) above L4 was the most common location in the IF group (n = 17/20; 85%) compared to L4-S1 in the NIF group (n = 11/15; 73%) (p = 0.02).

CONCLUSION

Interbody fusion does not fully protect against rod failure in the lumbar spine in ASD patients with long posterior spinal fusion and may encourage failure at L2-L4, the levels above the interbody fusion.

LEVEL OF EVIDENCE

III.

Long-term rates of bladder dysfunction after decompression in patients with cauda equina syndrome

BACKGROUND CONTEXT

Cauda equina syndrome (CES) occurs due to compression of the lumbar and sacral nerve roots and is considered a surgical emergency. Although the condition is relatively rare, the associated morbidity can be devastating to patients. While substantial research has been conducted on the timing of treatment, the literature regarding long-term rates of bladder dysfunction in CES patients is scarce.

PURPOSE

The aim of this study was to identify long-term rates of bladder dysfunction in CES patients and to compare those rates to non-CES patients who underwent similar spinal decompression.

STUDY DESIGN/SETTING

Retrospective database study.

PATIENT SAMPLE

The CES cohort was comprised of 2,362 patients who underwent decompression surgery following CES diagnosis with a 5-year follow-up. These patients were matched to 9,448 non-CES control patients who underwent spinal decompression without a diagnosis of CES.

OUTCOME MEASURES

Diagnosis of bladder dysfunction, surgical procedure to address bladder dysfunction METHODS: Using the national insurance claims database, PearlDiver, CES patients who underwent decompression surgery were identified and 1:4 matched to non-CES patients who underwent similar spinal decompression surgery. The 1-year, 3-year, and 5-year rates of progression to a bladder dysfunction diagnosis and surgical intervention to manage bladder dysfunction were recorded. The CES and non-CES groups were compared with univariate testing, and an analysis of risk factors for bladder dysfunction was performed with multivariate logistic regression analysis.

RESULTS

A total of 2,362 CES patients who underwent decompression surgery were identified and matched to 9,448 non-CES control patients. After 5 years, CES patients had a 10%-12% increased absolute risk of continued bladder dysfunction and a 0.7%-0.9% increased absolute risk of undergoing a surgical procedure for bladder dysfunction, as compared to matched non-CES patients. Multivariate analysis controlling for age, sex, obesity, tobacco use, and diabetes, identified CES as independently associated with increased 5-year risk for bladder dysfunction diagnosis (odds ratio [OR]: 1.72; 95% confidence interaval [CI] 1.56-1.89; p<.001) and procedure (OR: 1.40; 95% CI 1.07-1.81; p=.012).

CONCLUSIONS

Understanding the long-term risk for bladder dysfunction in CES patients is important for the future care and counseling of patients. Compared to non-CES patients who underwent similar spinal decompression, CES patients were observed to have a significantly higher long-term likelihood for both bladder dysfunction diagnosis and urologic surgical procedure.

The Influence of Selective Serotonin Reuptake Inhibitors on Lumbar Arthrodesis

STUDY DESIGN

Retrospective analysis using the PearlDiver national insurance claims database.

OBJECTIVE

To investigate the relationship between chronic preoperative selective serotonin reuptake inhibitor (SSRI) prescriptions and nonunion following spine fusion surgery.

SUMMARY OF BACKGROUND DATA

Contemporary literature has linked SSRIs to decreased bone mineral density and increased rates of future bone fracture. Furthermore, a recent murine model has suggested a potential role in the quality of fracture healing itself.

METHODS

All single-level lumbar fusion patients were identified. The rate of nonunion diagnosis between 6 and 24 months following surgery was assessed. A stratified analysis of chronic SSRI use and a number of comorbidities was conducted, followed by a multiple logistic regression analysis of nonunion accounting for qualifying risk factors. Finally, subanalyses of individual procedure codes were carried out.

RESULTS

In total, 7905 single-level lumbar fusion patients were included. In the multivariate analysis, chronic SSRI [odds ratio (OR): 1.558, P=0.004] and tobacco use (OR: 1.500, P=0.011) were identified as independent risk factors for nonunion, whereas patient age over 60 years (OR: 0.468, P<0.001) was observed to be negatively associated with nonunion. In the individual procedure subanalyses, SSRIs were significantly associated with nonunion in 2 of 3 univariate analyses and observed to be an independent risk factor for nonunion in 2 of the 3 procedure populations.

CONCLUSIONS

These data suggest that patients treated concomitantly for mental health disorders with SSRIs before arthrodesis may be at an increased risk of postoperative nonunion. Closer follow-up may be indicated in this patient population.

Migration of an Anterior Cervical Discectomy and Fusion Screw into the Constrictor Muscle of the Hypopharynx: A Case Report

CASE

A 53-year-old man developed dysphagia 4 years after anterior cervical discectomy and fusion (ACDF), and radiographs revealed a dislodged screw anterior to the ACDF plate. Intraoperatively, the screw was found to be completely embedded within the pharyngeal constrictor muscle fibers and was removed with assistance from otolaryngology without injury to the pharyngeal mucosa.

CONCLUSION

Implant migration after ACDF can variably damage tracheoesophageal and retropharyngeal structures, and a multidisciplinary approach involving otolaryngology or thoracic surgery may be required to diagnose and treat these complications.

Duration and Magnitude of Opioid Use After Minimally Invasive Sacroiliac Joint Fusion

STUDY DESIGN

Retrospective cohort study performed in a nationwide insurance claims database.

OBJECTIVE

To evaluate the duration and magnitude of post-operative opioid prescriptions after minimally invasive surgical sacroiliac joint fusion (MIS SIJF) as compared to other common spine surgeries.

SUMMARY OF BACKGROUND DATA

MIS SIJF has been reported to significantly improve quality of life and reduce pain. However, there is a paucity of reported data on post-operative opioid use in patients undergoing MIS SIJF for sacroiliac joint dysfunction.

METHODS

A nationwide insurance claims database was queried to identify 4,666 patients who underwent MIS SIJF. Patients were stratified by pre-operative opioid use: Opioid naïve, sporadic use, or chronic use were respectively defined as 0,1, or≥2 opioid prescriptions filled within 6 months prior to surgery. Duration of opioid use was defined by the time between MIS SIJF and last opioid prescription filled while magnitude of opioid use was determined by milligram morphine equivalents filled by 30 days post-operation. This opioid use data was compared to that of other common spine surgeries.

RESULTS

Patients undergoing MIS SIJF continued to fill opioid prescriptions 1-year post-operatively at significantly higher proportions than those undergoing other common spine procedures assessed by prior literature within each of the pre-operative opioid use cohorts (chronic: 73% vs. 49-62%; P <0.0001, sporadic: 39% vs. 23-28%; P <0.0001, opioid naïve: 22% vs. 15-18%; P <0.0001). Chronic users filled the highest opiate dosages during the 30-day post-operative period, filling on average 64.75 MME/d compared to 19.75 MME/d and 24.25 MME/d by the opioid naïve and sporadic users, respectively.

CONCLUSION

After MIS SIJF, opioid naïve patients use fewer opioids and for a shorter period of time compared to patients with sporadic or chronic pre-operative opioid use. MIS SIJF may result in less effective pain reduction when compared to other common spine surgeries evaluated via identical methodology.

LEVEL OF EVIDENCE

3.

Civilian Ballistic Injuries to the Atlantoaxial Spine: A Single Institution Case Series

STUDY DESIGN

Retrospective case series.

OBJECTIVE

Describe the injury characteristics of ballistic fractures involving the atlantoaxial spine.

SUMMARY OF BACKGROUND DATA

Civilian gunshot wounds to the spine are an increasingly common injury in the United States. Civilian studies have focused on ballistic injuries to the entire spine as opposed to a region-specific fashion. Only a single 10-patient case series investigating ballistic fractures to the upper cervical spine (C1 and C2) exists, leaving a large gap in the understanding of this injury complex.

METHODS

A retrospective chart review was performed. Extracted data included patient demographics, neurological status on presentation, fracture morphology, assessment of stability, other associated injuries, and surgical procedures performed. Proportional analysis was performed to characterize the fractures and their associated neurological injuries.

RESULTS

Thirty-six patients were identified, with 86% being male with an average patient age of 30.0 ± 10.36 years (mean ± SD). Fracture morphology was characterized using proportional analysis. Initial neurological exams were either ASIA A or ASIA E, without any incomplete injuries noted. Patients who sustained a transcanal injury did not show any neurological improvement. The initial in-hospital mortality rate was 5.6%, with a 1-year mortality rate of 8.3%. There is a high incidence of associated vascular injury (66%) and mandible fracture (33%).

CONCLUSIONS

Ballistic penetrating trauma to the atlantoaxial spine often results in complex injury patterns necessitating multidisciplinary care with high rates of morbidity and mortality. If neurological deficits are present initially, they are often complete. Two thirds of patients sustained an associated vascular injury, which should be screened for with CT angiography.

Study of host immunity in patients with Helicobacter pylori-related idiopathic thrombocytopenia

To test the role of T helper cell Th1 immunity we recruited 24 patients with idiopathic thrombocytopenia associated with H. pylori seropositivity. They were divided into 2 groups: 12 with immune-mediated thrombocytopenia (Group 1) and 12 with non-immune mediated thrombocytopenia (Group 2). We also recruited 10 individuals seronegative for H. pylori (Group 3) as controls. Initial platelet count was significantly lower in Group 1 than Group 2. H. pylori was eradicated in 10 of 12 patients in Group 1 and in all patients in Group 2. Transient improvement (< 3 months) in the platelet count occurred in only 2 patients in Group 1 while improvement for > 6 months was observed in all patients in Group 2. There was a statistically significant direct correlation between platelet count and levels of TNF- and IFN-gamma in both study groups, while a non-significant correlation was seen in Group 3. Thus, H. pylori infection should be considered in the differential diagnosis of all cases of thrombocytopenia, and should be eradicated in all H. pylori-positive patients with thrombocytopenia.

Implant Migration After Anterior Cervical Spine Surgery: A Systematic Literature Review

STUDY DESIGN

Systematic literature review.

OBJECTIVE

To summarize the demographics, diagnosis, clinical course, management, and outcomes for implant migration after anterior cervical spine surgery.

SUMMARY OF BACKGROUND DATA

Implant migration following anterior cervical spine surgery is a rare event that may predispose patients to high morbidity due to the proximity of cervical implants to critical structures. Due to the infrequency of this complication, most of the literature on this topic is described in case reports or series.

METHODS

We screened the PubMed database for relevant publications from January 1975 to December 2023 using the terms: (screw OR hardware OR plate OR implant OR instrumentation) AND (pull-out OR migration OR displacement OR erosion OR perforation) AND (anterior cervical OR ACDF OR ACCF). The PRISMA systematic review template guided the identification and screening of full-text articles in English.

RESULTS

Fifty-five studies with 76 patients were included. The median age was 50.0 (32.0, 60.0) years, with a median time-to-diagnosis of 15 months (2.0, 60.8). Seventy-five percent were symptomatic, while 20% were asymptomatic. Common symptoms included dysphagia (54%), neck pain (22%), and fever or cervical abscess (13%). Treatments included complete implant removal (59%), partial removal (20%), spontaneous gastrointestinal elimination (11%), and retention of all instrumentation (5%). In addition, 25% underwent revision spinal fusion. Sixty-one percent experienced major complications (eg, perforation, fistula, abscess). However, 84% had resolution of symptoms without further treatment at the most recent follow-up.

CONCLUSIONS

Implant migration after anterior cervical spine surgery is rare yet may occur many years after a patient's initial surgery without heralding symptoms. For this reason, surgeons should consider extended routine follow-up with radiographic imaging in these patients, for the first 5 years postoperatively since this complication transpired most frequently within this time frame. We recommend an individualized, patient-centered approach for radiographic follow-up to balance the risk of unnecessary radiation exposure in addition to practical risks like travel-related accidents. Extended routine follow-up may be most beneficial for patients with identified risk factors for late complications or early migration, that is, complex deformity or poor bone quality.

A predictive model of motor deficit in civilian ballistic lumbosacral spine injuries

BACKGROUND CONTEXT

Civilian gunshot wounds to the spine are an increasingly common injury in the USA. A majority of the available research is focused on a military population suffering high energy missile injury. Minimal research has focused on civilian ballistic injuries to the lumbosacral spine as the available studies focus on the entire spine due to limited numbers.

PURPOSE

Characterize ballistic injuries to the lumbosacral spine and develop a model to predict the presence of neurological deficit based upon a patients presenting fracture morphology.

STUDY DESIGN

Retrospective chart review.

PATIENT SAMPLE

One hundred forty-eight consecutive patients that were presented to an urban level 1 trauma center with ballistic injures to the spine involving the levels L1-S2.

OUTCOMES MEASURES

Neurological status at presentation and final follow up using the American Spinal Injury Association (ASIA) Impairment Scale.

METHODS

IRB approval was obtained, and retrospective chart review was performed. Extracted data included patient demographics, neurological status on presentation and final follow-up, fracture morphology, assessment of stability, other associated injuries, and surgical procedures performed. Proportional analysis was performed to characterize the fractures and their associated neurological injuries. Chi-square testing was done to identify fracture characteristics associated with neurologic injury. A multiple logistical regression was performed using fracture characteristics highly associated with neurological deficit to develop a model to predict neurologic deficit. The model was then validated with a receiver operator curve.

RESULTS

Of the 148 patients, 14 patients underwent spinal surgery with the most common indication being decompression and foreign body removal. There was a high incidence of intra-abdominal injury (73.6%). Fractures were characterized by level, affected vertebral component, and spinal canal involvement. Neurological injury was classified using the ASIA scale at presentation and final follow up. Odds-ratios of vertebral fracture characteristics showed neurologic deficit was highly associated with pedicle fractures (OR=9.07 [4.14-21.54] - 95% CI), lamina fractures (OR=6.42 [3.16-13.62] - 95% CI), facet fractures (OR=5.95 [2.90-12.79] - 95% CI), intra-canal bone (OR=12.79 [5.98-29.05] - 95% CI), and an intra-canal trajectory (OR=1078 [4.48-28.98]) - 95% CI. Multiple logistic regression was performed to construct a predictive model of neurologic deficit which showed that intra-canal trajectory, pedicle fracture and facet fracture are associated with neurologic deficit. An ROC curve was made with an area of 0.849 ([0.7853 to 0.9128 - 95% CI], p<.0001) demonstrating a good model fit.

CONCLUSIONS

Ballistic injuries to the lumbosacral spine involve complex injury patterns in an often polytraumatized patient. Fractures involving the pedicle, lamina, and facet are highly associated with neurologic injury, as is a trans-canal trajectory. A patients fracture morphology can be used to predict if a neurologic deficit is present.

Does lumbar spine fusion predispose patients to future total hip replacement?

OBJECTIVE

Hip-spine syndrome has been well studied since it was first described by Offierski and MacNab in 1983. Today, strong evidence links symptoms of hip and spine pathology to postsurgical outcomes. Recent studies have reported increased rates of hip dislocation in patients previously treated with total hip arthroplasty (THA) who had undergone lumbar fusion procedures. However, the effect of this link on native hip-joint degeneration remains an area of ongoing research. The purpose of this study was to characterize the relationship between use of lumbar fusion procedures and acceleration of hip pathology by analyzing the rate of future THA in patients with preexisting hip osteoarthritis.

METHODS

This population-level, retrospective cohort study was conducted by using the PearlDiver research program. The initial patient cohort was defined by the presence of diagnosis codes for hip osteoarthritis. Patients were categorized according to use of lumbar fusion after diagnosis of hip pathology. Survival curves with respect to THA were generated by comparison of the no lumbar fusion cohort with the lumbar fusion cohort. To assess the impact of fusion construct length, the lumbar fusion cohort was then stratified according to the number of levels treated (1-2, 3-7, or ≥ 8 levels). Hazard ratios (HRs) were then calculated for the risk factors of number of levels treated, patient age, and sex.

RESULTS

A total of 2,275,683 patients matched the authors' inclusion criteria. Log-rank analysis showed no significant difference in the rates of THA over time between the no lumbar fusion cohort (2,239,946 patients) and lumbar fusion cohort (35,737 patients; p = 0.40). When patients were stratified according to number of levels treated, again no differences in the incidence rates of THA over the study period were determined (p = 0.30). Patients aged 70-74 years (HR 0.871, p < 0.001), 75-79 years (HR 0.733, p < 0.001), 80-84 years (HR 0.557, p < 0.001), and ≥ 85 years (HR = 0.275, p < 0.001) were less likely to undergo THA relative to the reference group (patients aged 65-69 years).

CONCLUSIONS

Although lumbar fusion was initially hypothesized to have a significant effect on rate of THA, lumbar fusion was not associated with increased need for future THA in patients with preexisting hip osteoarthritis. Additionally, there was no relationship between fusion construct length and rate of THA. Although lumbar fusion reportedly increases the risk of hip dislocation in patients with prior THA, these data suggest that lumbar fusion may not clinically accelerate native hip degeneration.

Degenerative cervical myelopathy in HIV: Rates of postoperative complications and revision following decompression surgery

Background

HIV has been associated with cervical myelopathy, but it is unclear if HIV leads to earlier presentation of DCM and need for decompression surgery. Furthermore, long-term rates of postoperative complications and revision following decompression surgery have not been investigated in this patient population. The aim of this study was to identify the age of surgery for degenerative cervical myelopathy (DCM) in patients with human immunodeficiency virus (HIV) and investigate postoperative revision and complication rates.

Methods

Patients who underwent decompression surgery for DCM were identified in a national database and stratified by preexisting diagnosis of HIV. Demographic characteristics were identified. The 2-year rates of revision surgery, 2-year rates of postoperative surgical complications, and 90-day rates of postoperative medical complications were calculated.

Results

1,014 patients with HIV and 153,974 patients without HIV were identified. The HIV group was younger at the time of decompression (53.6 ± 8.8; Non-HIV: 57.1 ± 11.0; p<.0001). There were no statistically significant differences in 2-year rates of revision (HIV: 7.6 %; Non-HIV 7.72 %; p=.88), removal of implants (HIV: 0.99 %; Non-HIV 1.06 %; p=.82), or I&D (HIV: 1.78 %; Non-HIV 1.31 %; p=.19). There were significant differences in the 2-year rates of infection diagnosis (HIV 4.93 %, non-HIV 3.59 %; p=.022) and neurological deficit (HIV 6.02 %, non-HIV 4.20 %; p<.001). 90-day medical complications of pneumonia, UTI, and renal failure were higher in the HIV group.

Conclusions

Patients with HIV who develop cervical myelopathy undergo decompression at a younger age; this age difference may not be clinically significant. While patients with HIV are more likely to have higher rates of short-term medical complications, they do not experience higher 2-year rates of revision or surgical complications requiring reoperation.