Cellular Patterning Alone Using Bioprinting Regenerates Articular Cartilage Through Native-Like Cartilagenesis.

Few studies have proved that bioprinting itself helps recapitulate native tissue functions mainly because the bioprinted macro shape can rarely, if ever, influence cell function. This can be more problematic in bioprinting cartilage, generally considered more challenging to engineer. Here a new method is shown to micro-pattern chondrocytes within bioprinted sub-millimeter micro tissues, denoted as patterned micro-articular-cartilages tissues (PA-MCTs). Under the sole influence of bioprinted cellular patterns. A pattern scoring system is developed after over 600 bioprinted cellular patterns are analyzed. The top-scored pattern mimics that of the isogenous group in native articular cartilage. Under the sole influence of this pattern during PA-MCTs bio-assembling into macro-cartilage and repairing cartilage defects, chondrogenic cell phenotype is preserved, and cartilagenesis is initiated and maintained. Neocartilage tissues from individual and assembled PA-MCTs are comparable to native articular cartilage and superior to cartilage bioprinted with homogeneously distributed cells in morphology, biochemical components, cartilage-specific protein and gene expression, mechanical properties, integration with host tissues, zonation forming and stem cell chondrogenesis. PA-MCTs can also be used as osteoarthritic and healthy cartilage models for therapeutic drug screening and cartilage development studies. This cellular patterning technique can pave a new way for bioprinting to recapitulate native tissue functions via tissue genesis.

Anterior vertebral tethering: imaging of tether rupture.

Anterior vertebral tethering, also known as vertebral body tethering, is an evolving, minimally invasive surgical technique to correct spinal curvature in skeletally immature patients. The procedure involves placement of vertebral screws that are connected by an anterolateral tether. This procedure may be complicated by rupture of the non-radiopaque tether. The radiologist should be aware of imaging findings that suggest this complication on follow-up spine radiographs.

Correlation between the efficacy of stem cell therapy for osteonecrosis of the femoral head and cell viability.

BACKGROUND: Osteonecrosis of the femoral head (ONFH) is a common disease that greatly affects the quality of life of patients. Repair of the necrotic area is key to successful treatment. Currently, the combination of stem cell transplantation and decompression is used clinically to promote the repair of necrotic areas based on the characteristics of stem cells. However, a considerable number of patients do not achieve a satisfactory outcome in terms of repair of the femoral head necrotic area, and it is very important to determine the reasons for the poor curative effect. The aim of this study was to investigate the correlation between stem cell viability and the repair efficacy of stem cell therapy combined with core decompression for early-stage ONFH. METHODS: A total of 30 patients with idiopathic ONFH underwent core decompression combined with autologous stem cell transplantation. The Harris hip score (HHS) and difference in necrosis area before and after surgery were measured. The mean repair ratio was set as the threshold to divide the patients into group A (ratio above the mean) and group B (ratio below the mean). The ultrastructure, proliferative capacity, and multidirectional differentiation ability were compared between the groups. RESULTS: At 9 months after surgery, the HHS and magnetic resonance imaging (MRI) findings improved by varying degrees. Based on the mean repair ratio of (62.2 ± 27.0)%, the threshold for dividing the patients into groups A and B was set to 62.2%. Better repair (group A) was associated with more rapid proliferation and a healthier ultrastructure. The cells in group A showed stronger specific staining signifying osteogenic and chondrogenic differentiation; alkaline phosphatase (ALP) activity, an indicator of osteogenic differentiation, was higher in group A than in group B (OD, 2.39 ± 0.44 and 1.85 ± 0.52; p <  0.05). CONCLUSIONS: The quality of implanted stem cells is closely related to treatment efficacy and determines whether the defective self-repair in the necrotic area can be corrected to enhance repair and thus achieve the desired therapeutic outcome. TRIAL REGISTRATION: The trial registration number: ChiCTR-ORC-17011698 (retrospectively registered at 2017-06-19).

A Novel 3D Bioprinter Using Direct-Volumetric Drop-On-Demand Technology for Fabricating Micro-Tissues and Drug-Delivery.

Drop-on-demand (DOD) 3D bioprinting technologies currently hold the greatest promise for generating functional tissues for clinical use and for drug development. However, existing DOD 3D bioprinting technologies have three main limitations: (1) droplet volume inconsistency; (2) the ability to print only bioinks with low cell concentrations and low viscosity; and (3) problems with cell viability when dispensed under high pressure. We report our success developing a novel direct-volumetric DOD (DVDOD) 3D bioprinting technology that overcomes each of these limitations. DVDOD can produce droplets of bioink from < 10 nL in volume using a direct-volumetric mechanism with < ± 5% volumetric percent accuracy in an accurate spatially controlled manner. DVDOD has the capability of dispensing bioinks with high concentrations of cells and/or high viscosity biomaterials in either low- or high-throughput modes. The cells are subjected to a low pressure during the bioprinting process for a very short period of time that does not negatively impact cell viability. We demonstrated the functions of the bioprinter in two distinct manners: (1) by using a high-throughput drug-delivery model; and (2) by bioprinting micro-tissues using a variety of different cell types, including functional micro-tissues of bone, cancer, and induced pluripotent stem cells. Our DVDOD technology demonstrates a promising platform for generating many types of tissues and drug-delivery models.

Rapid Fabrication of Anatomically-Shaped Bone Scaffolds Using Indirect 3D Printing and Perfusion Techniques.

Fused deposit modeling (FDM) 3D printing technology cannot generate scaffolds with high porosity while maintaining good integrity, anatomical-surface detail, or high surface area-to-volume ratio (S/V). Solvent casting and particulate leaching (SCPL) technique generates scaffolds with high porosity and high S/V. However, it is challenging to generate complex-shaped scaffolds; and solvent, particle and residual water removal are time consuming. Here we report techniques surmounting these problems, successfully generating a highly porous scaffold with the anatomical-shape characteristics of a human femur by polylactic acid polymer (PLA) and PLA-hydroxyapatite (HA) casting and salt leaching. The mold is water soluble and is easily removable. By perfusing with ethanol, water, and dry air sequentially, the solvent, salt, and residual water were removed 20 fold faster than utilizing conventional methods. The porosities are uniform throughout the femoral shaped scaffold generated with PLA or PLA-HA. Both scaffolds demonstrated good biocompatibility with the pre-osteoblasts (MC3T3-E1) fully attaching to the scaffold within 8 h. The cells demonstrated high viability and proliferation throughout the entire time course. The HA-incorporated scaffolds demonstrated significantly higher compressive strength, modulus and osteoinductivity as evidenced by higher levels of alkaline-phosphatase activity and calcium deposition. When 3D printing a 3D model at 95% porosity or above, our technology preserves integrity and surface detail when compared with FDM-generated scaffolds. Our technology can also generate scaffolds with a 31 fold larger S/V than FDM. We have developed a technology that is a versatile tool in creating personalized, patient-specific bone graft scaffolds efficiently with high porosity, good scaffold integrity, high anatomical-shaped surface detail and large S/V.

Fishtail deformity--a delayed complication of distal humeral fractures in children.

BACKGROUND: Concavity in the central portion of the distal humerus is referred to as fishtail deformity. This entity is a rare complication of distal humeral fractures in children. OBJECTIVE: The purpose of this study is to describe imaging features of post-traumatic fishtail deformity and discuss the pathophysiology. MATERIALS AND METHODS: We conducted a retrospective analysis of seven cases of fishtail deformity after distal humeral fractures. RESULTS: Seven children ages 7-14 years (five boys, two girls) presented with elbow pain and history of distal humeral fracture. Four of the seven children had limited range of motion. Five children had prior grade 3 supracondylar fracture treated with closed reduction and percutaneous pinning. One child had a medial condylar fracture and another had a lateral condylar fracture; both had been treated with conservative casting. All children had radiographs, five had CT and three had MRI. All children had a concave central defect in the distal humerus. Other imaging features included joint space narrowing with osteophytes and subchondral cystic changes in four children, synovitis in one, hypertrophy or subluxation of the radial head in three and proximal migration of the ulna in two. CONCLUSION: Fishtail deformity of the distal humerus is a rare complication of distal humeral fractures in children. This entity is infrequently reported in the radiology literature. Awareness of the classic imaging features can result in earlier diagnosis and appropriate treatment.

Fabricating vascularized, anatomically accurate bone grafts using 3D bioprinted sectional bone modules, in-situ angiogenesis, BMP-2 controlled release, and bioassembly.

Bone grafting is the most common treatment for repairing bone defects. However, current bone grafting methods have several drawbacks. Bone tissue engineering emerges as a promising solution to these problems. An ideal engineered bone graft should exhibit high mechanical strength, osteogenic properties, and pre-vascularization. Both top-down (using bulk scaffold) and bottom-up (using granular modules) approaches face challenges in fulfilling these requirements. In this paper, we propose a novel sectional modular bone approach to construct osteogenic, pre-vascularized bone grafts in anatomical shapes. We 3D-printed a series of rigid, thin, sectional, porous scaffolds from a biodegradable polymer, tailored to the dimensions of a femur bone shaft. These thin sectional modules promote efficient nutrition and waste removal due to a shorter diffusion distance. The modules were pre-vascularized viain-situangiogenesis, achieved through endothelial cell sprouting from the scaffold struts. Angiogenesis was further enhanced through co-culture with bioprinted fibroblast microtissues, which secreted pre-angiogenic growth factors. Sectional modules were assembled around a porous rod incorporated with Bone Morphogenetic Protein-2 (BMP-2), which released over 3 weeks, demonstrating sustained osteogenic activity. The assembled scaffold, in the anatomical shape of a human femur shaft, was pre-vascularized, osteogenic, and possessed high mechanical strength, supporting 12 times the average body weight. The feasibility of implanting the assembled bone graft was demonstrated using a 3D-printed femur bone defect model. Our method provides a novel modular engineering approach for regenerating tissues that require high mechanical strength and vascularization.

Anterior vertebral tethering for adolescent idiopathic scoliosis: our initial ten year clinical experience.

BACKGROUND: Anterior vertebral tethering (AVT) is a minimally invasive alternative to fusion surgery for adolescent idiopathic scoliosis (AIS) that offers the potential for definitive scoliosis treatment with the possibility of preservation of the growth, motion, function and overall health of the spine. This study represents our first ten years using AVT to treat AIS. METHODS: In this retrospective review we analyzed our first 74 AIS patients treated with AVT 2010-2020. Multiple Lenke curve types 33-70° were treated with skeletal maturity spanning Risser -1 to 5. RESULTS: Of 74 consecutive AIS patients treated with AVT, 52 patients (47 female, 5 male) had sufficient 2-year follow-up for inclusion. Forty-six of these 52 patients (88%) with 65 curves (35T, 30TL/L) were satisfactorily treated with AVT demonstrating curve correction from 48.6° pre-op (range 33°-70°) at age 15.1 years (range 9.2-18.8) and skeletal maturity of Risser 2.8 (range -1 to 5) to 23.2° post-op (range 0°-54°) and 24.0° final (range 0°-49°) at 3.3 years follow-up (range 2-10 years). Curve corrections from pre-op to post-op and pre-op to final were both significant (p < 0.001). The 0.8° change from post-op to final was not significant but did represent good control of scoliosis correction over time. Thoracic kyphosis and lumbar lordosis were maintained in a normal range throughout while axial rotation demonstrated a slight trend toward improvement. Skeletal maturity of Risser 4 or greater was achieved in all but one patient. Four of the 52 patients (8%) required additional procedures for tether rupture (3 replacements) or overcorrection (1 removal) to achieve satisfactory treatment status after AVT. An additional 6 of the 52 patients (12%), however, were not satisfactorily treated with AVT, requiring fusion for overcorrection (2) or inadequate correction (4). CONCLUSIONS: In this study, AIS was satisfactorily treated with AVT in the majority of patients over a broad range of curve magnitudes, curve types, and skeletal maturity. Though late revision surgery for overcorrection, inadequate correction, or tether rupture was not uncommon, the complication of overcorrection was eliminated after our first ten patients by a refinement of indications. LEVEL OF EVIDENCE: IV.

Adipose stem cells originate from perivascular cells.

Recent research has shown that adipose tissues contain abundant MSCs (mesenchymal stem cells). The origin and location of the adipose stem cells, however, remain unknown, presenting an obstacle to the further purification and study of these cells. In the present study, we aimed at investigating the origins of adipose stem cells. α-SMA (α-smooth muscle actin) is one of the markers of pericytes. We harvested ASCs (adipose stromal cells) from α-SMA-GFP (green fluorescent protein) transgenic mice and sorted them into GFP-positive and GFP-negative cells by FACS. Multilineage differentiation tests were applied to examine the pluripotent ability of the α-SMA-GFP-positive and -negative cells. Immunofluorescent staining for α-SMA and PDGF-Rß (platelet-derived growth factor receptor ß) were applied to identify the α-SMA-GFP-positive cells. Then α-SMA-GFP-positive cells were loaded on a collagen-fibronectin gel with endothelial cells to test their vascularization ability both in vitro and in vivo. Results show that, in adipose tissue, all of the α-SMA-GFP-positive cells congregate around the blood vessels. Only the α-SMA-GFP-positive cells have multilineage differentiation ability, while the α-SMA-GFP-negative cells can only differentiate in an adipogenic direction. The α-SMA-GFP-positive cells maintained expression of α-SMA during multilineage differentiation. The α-SMA-GFP-positive cells can promote the vascularization of endothelial cells in three-dimensional culture both in vitro and in vivo. We conclude that the adipose stem cells originate from perivascular cells and congregate around blood vessels.

Articular Cartilage Regeneration through Bioassembling Spherical Micro-Cartilage Building Blocks.

Articular cartilage lesions are prevalent and affect one out of seven American adults and many young patients. Cartilage is not capable of regeneration on its own. Existing therapeutic approaches for articular cartilage lesions have limitations. Cartilage tissue engineering is a promising approach for regenerating articular neocartilage. Bioassembly is an emerging technology that uses microtissues or micro-precursor tissues as building blocks to construct a macro-tissue. We summarize and highlight the application of bioassembly technology in regenerating articular cartilage. We discuss the advantages of bioassembly and present two types of building blocks: multiple cellular scaffold-free spheroids and cell-laden polymer or hydrogel microspheres. We present techniques for generating building blocks and bioassembly methods, including bioprinting and non-bioprinting techniques. Using a data set of 5069 articles from the last 28 years of literature, we analyzed seven categories of related research, and the year trends are presented. The limitations and future directions of this technology are also discussed.

A Thoracoscopic Technique Used in Anterior Vertebral Tethering for Adolescent Idiopathic Scoliosis.

Anterior vertebral tethering (AVT) is a relatively recent alternative to posterior spinal fusion for progressive curves in growing patients with idiopathic scoliosis. AVT uses a thoracoscopic approach to minimize trauma to the thoracic wall and chest cavity. There are limited technical descriptions of this method. Patients benefit from proficiency and reproducibility to allow for appropriate spinal curve correction over time. This Technical Note outlines the steps of the thoracoscopic approach to AVT and reviews the current indications for AVT over posterior spinal fusion, as well as the most recently published clinical outcomes of this procedure.

3D-printed insert-array and 3D-coculture-array for high-throughput screening of cell migration and application to study molecular and cellular influences.

Collective cell migration refers to the movement of groups of cells and collective cell behavior and relies on cell-cell communication and cell-environment interactions. Collective cell migration plays a fundamental role in many aspects of cell biology and pathology. Current protocols for studying collective cell migration either use destructive methods or are not convenient for liquid handling. Here we present a novel 3D-printed insert-array and a 3D-coculture-array for collective cell migration study in high-throughput. The fabricated insert-array is comprised of 96 cylinder shaped inserts which can be placed in each well of a 96-well plate generating watertight contact with the bottom of each well. The insert-array has high manufacturing tolerance, and the coefficient of variations of the insert diameter and circularity are 0.67% and 0.03%, respectively. Each insert generates a circular cell-free area within the well without cell damage and provides convenient access for both manual and robotic liquid handling. Using the 3D-printed insert-array, we studied the migration of human umbilical vein endothelial cells (HUVECs) under the molecular influences of vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF) and under the cellular influences of human mesenchymal stem cells (hMSCs) using the 3D-coculture-array. Our results show that the migration of HUVECs was dose-dependent on the VEGF and bFGF with different correlation patterns. They also generated a synergic pro-migration effect. When cocultured with hMSCs, the migration rate increased significantly while dependent on the number of hMSCs. The effects were partially blocked by VEGF inhibitor which suggests that VEGF secreted from hMSCs plays an important role in cell-to-cell communication during cell migration. The 3D-coculture-array can be manufactured at very low cost and shows higher biomolecule transport efficiency than the commercially available transwell. The calculated Z-factor is 0.66, which classifies our system as a perfect high-throughput assay. In summary, our newly developed insert-array and 3D-coculture-array provide a versatile platform to study collective cell migration in high-throughput as well as the molecular and cellular influences upon it.

Biofabrication of valentine-shaped heart with a composite hydrogel and sacrificial material.

3D bioprinting represents a potential solution for organs regeneration, however, the production of complex tissues and organs that are in large size, randomly shaped, hollow, and contain integrated pre-vascularization still faces multiple challenges. This study aimed to test the feasibility of our 3D printing scheme for the manufacturing of micro-fluid channel networks complex three-dimensional tissue structures. The reverse engineering software was used to design the CAD model and polyvinyl alcohol (PVA) was used as the sacrificial material to print the sacrificial stent use the bioprinter nozzle 1. Hydrogel composite H9c2 and human umbilical vein endothelial cells (HUVECs) were mixed with sodium alginate, agarose solution and platelet-rich plasma (PRP) as cellular bioink, which was extruded through nozzle 2 to deposit the internal pores of the sacrificial scaffold. The scaffold dissolved, change to a flexible, hollow and micro-fluid channel networks complex structure. The 3D-bioprinting technology can construct a micro-fluid channel networks valentine heart with a self-defined height and hollow in suitable mechanical properties. The cells proliferate and maintain their biological properties within the printed constructs. This study demonstrates that valentine heart-like constructs can be fabricated with 3D bioprinting using sacrificial and hydrogel materials.

In vivo range of motion of the lumbar spinous processes.

The study design included an in vivo laboratory study. The objective of the study is to quantify the kinematics of the lumbar spinous processes in asymptomatic patients during un-restricted functional body movements with physiological weight bearing. Limited data has been reported on the motion patterns of the posterior spine elements. This information is necessary for the evaluation of traumatic injuries and degenerative changes in the posterior elements, as well as for improving the surgical treatment of spinal diseases using posterior procedures. Eight asymptomatic subjects with an age ranging from 50 to 60 years underwent MRI scans of their lumbar segments in a supine position and 3D models of L2-5 were constructed. Next, each subject was asked to stand and was positioned in the following sequence: standing, 45 degrees flexion, maximal extension, maximal left and right twisting, while two orthogonal fluoroscopic images were taken simultaneously at each of the positions. The MRI models were matched to the osseous outlines of the images from the two orthogonal views to quantify the position of the vertebrae in 3D at each position. The data revealed that interspinous process (ISP) distance decreased from L2 to L3 to L4 to L5 when measured in the supine position; with significantly higher values at L2-3 and L3-4 compared with L4-5. These differences were not seen with weight-bearing conditions. During the maximal extension, the ISP distance at the L2-3 motion segment was significantly reduced, but no significant changes were detected at L3-4 and L4-5. During flexion the ISP distances were not significantly different than those measured in the MRI position at all segments. Going from the left to right twist positions, the L4-5 segment had greater amounts of ISP rotation, while all segments had similar ranges of translation in the transverse plane. The interspinous process distances were dependent on body posture and vertebral level.

Postoperative Radiographic Evaluation Following Adult Spine Deformity Correction: The Impact on Subsequent Management and Associated Risk of Radiation Exposure.

BACKGROUND: During the follow-up visits after Adult Spine Deformity (ASD) surgery, obtaining surveillance radiographs is a usual practice, and this study tried to identify evidence to support or refute such practice. METHODS: This is a retrospective, diagnostic case series (Level IV) of 49 patients. We identified the abnormal radiographic findings and their association with need for revision surgery. We determined the odds of obtaining an abnormal radiographs that lead to revision surgery at each of the given time intervals of follow-up. We also estimated the risk versus benefit of obtaining radiographs at each of the given time intervals of follow-up. RESULTS: We identified a total of 11 individual types of abnormal postoperative radiographic findings. Of them, the two radiographic findings that always needed revision surgery because of the associated clinical presentation were pedicle screw pullout and bilateral rod fracture. One abnormal radiographic finding that was never associated with revision surgery was the halo around a pedicle screw. In each of the given postoperative time intervals of follow-up at which the routine radiographs were obtained, we noted that the odds of noticing abnormal radiographic finding that lead to revision surgery was always >1. We found that the cumulative hazard rate for exposure to radiation was significantly higher during the initial follow-up visits when compared to subsequent follow-up visits. CONCLUSION: This study finds evidence to support the practice of routine postoperative radiographic evaluation of patients who come for follow-up after ASD surgery.

The Relationship Between Lumbar Lateral Listhesis and Radiculopathy in Adult Scoliosis.

STUDY DESIGN: Retrospective review and prospective validation study. OBJECTIVE: To develop a classification system of lumbar lateral listhesis that suggests different likelihoods of having radiculopathy in adult scoliosis. SUMMARY OF BACKGROUND DATA: The association of lumbar lateral listhesis with radiculopathy remains uncertain. METHODS: A retrospective cohort of patients with adult scoliosis enrolled from 2011 to 2015 was studied to develop a classification system of lateral listhesis that can stratify the likelihood of having radiculopathy. Four radiological aspects of lateral listhesis, including Nash and Moe vertebral rotation, L4-L5 lateral listhesis, the number of consecutive listheses, and the presence of a contralateral lateral listhesis at the thoracolumbar junction above a caudal listhesis, were evaluated on radiographs. Their associations with the presence of radicular leg pain were evaluated using multivariable logistic regression. The classification system of lateral listhesis was thus developed using the most influential radiological factors and then validated in a prospective cohort from 2016 to 2017. RESULTS: The retrospective cohort included 189 patients. Vertebral rotation is more than or equal to grade 2 (odds ratio [OR] = 9.45, 95% confidence interval [CI]: 4.07-25.14) and L4-5 listhesis (OR = 4.56, 95%CI: 1.85-12.35) were the two most influential listhesis factors associated with radiculopathy. The classification system of lateral listhesis was thus built based on the combinations of their respective presence: Type 0, 1, 2, 3 were defined as not having listhesis at all, none of the two factors present, one of the two presents, and both present, respectively. This classification significantly stratified the probability of radiculopathy, in both the retrospective cohort (0%, 6.4%, 33.8%, and 68.4% in Type 0, 1, 2, and 3, respectively; P < 0.001) and a prospective cohort of 105 patients (0%, 16.7%, 46.9%, and 72.7%; P < 0.001). CONCLUSION: Lumbar lateral listhesis is associated with the presence of radiculopathy in adult scoliosis. Types 2 and 3 lateral listhesis on radiographs may alert surgeons treating patients with spinal deformity. LEVEL OF EVIDENCE: 2.

Correction to: Bone Marrow Derived Pluripotent Cells are Pericytes which Contribute to Vascularization.

Please note the following errors in the original version.

Discoid lateral meniscus in children.

The discoid lateral meniscus is the most common abnormal meniscal variant in children. It affects the shape and mobility of the menisci, altering the normal mechanical relationships between the articulating surfaces of the knee and predisposing it to injury. The incidence of discoid lateral meniscus is estimated to be 1%-3% in the pediatric population and the condition is bilateral in 10%-20% of patients (Stanitski, 2002). An otherwise asymptomatic knee with an incidentally detected discoid meniscus does not require surgical intervention. However, a discoid lateral meniscus is much more likely to tear, and many children develop pain as well as mechanical symptoms (popping, snapping, locking, or giving way of the knee). Recent improvements in arthroscopic technique have led to greater attempts to stabilize, sculpt, and repair the torn discoid lateral meniscus. This article will review the classification, clinical presentation, diagnostic/imaging studies, and treatment options for a discoid lateral meniscus in children.