Simulation study on the effects of cancellous bone structure in the skull on ultrasonic wave propagation.

The transcranial Doppler method (TCD) enables the measurement of cerebral blood flow velocity and detection of emboli by applying an ultrasound probe to the temporal bone window, or the orbital or greater occipital foramina. TCD is widely used for evaluation of cerebral vasospasm after subarachnoid hemorrhage, early detection of patients with arterial stenosis, and the assessment of brain death. However, measurements often become difficult in older women. Among various factors contributing to this problem, we focused on the effect of the diploe in the skull bone on the penetration of ultrasound into the brain. In particular, the effect of the cancellous bone structure in the diploe was investigated. Using a 2D digital bone model, wave propagation through the skull bone was investigated using the finite-difference time-domain (FDTD) method. We fabricated digital bone models with similar structure but different BV/TV (bone volume/total volume) values in the diploe. At a BV/TV of approximately 50-60% (similar to that of older women), the minimum ultrasound amplitude was observed as a result of scattering and multiple reflections in the cancellous diploe. These results suggest that structural changes such as osteoporosis may be one factor hampering TCD measurements.

Cortical unlike trabecular bone loss is not associated with vascular calcification progression in CKD patients.

BACKGROUND: Vascular calcification progression has been associated with the loss of trabecular bone in chronic kidney disease (CKD) patients. There are few data evaluating the relationship between cortical bone loss and vascular calcification in this population. The aim of this study was to prospectively evaluate the association between changes in cortical bone density and coronary artery calcification (CAC) progression in non-dialyzed CKD patients. METHODS: Changes of cortical and trabecular bone, and changes of calcium score, were analyzed using vertebral tomographic images from a prospective study. Automatic delineation of the cortical bone layer was performed by Image J software, and trabecular bone was determined by selecting a region of interest using Vitrea 2® software. Cortical and trabecular bone density (BD) were expressed in Hounsfield Units (HU), and coronary artery calcium score in Agatston Units (AU). RESULTS: Seventy asymptomatic patients [57.8 ± 10.2 years, 63% males, 20% diabetic, estimated glomerular filtration rate (eGFR) = 37.3 (24.8-51.3) mL/min/1.73m2] were followed for 24 months. The mean cortical and trabecular BD did not change over time. While 49 patients lost either bone, 29 (41%) patients lost cortical [- 4.4%/year (ranging from - 7.15 to - 0.5)] and 39 (56%) lost trabecular bone [- 3.15%/year (- 13.7 to - 0.25)]. There was no association between cortical and trabecular BD changes (p = 0.12). CAC was observed in 33 (46%) patients at baseline, and 30 (91%) of them showed CAC progression. While an inverse correlation between trabecular bone and calcium score changes was observed (p = 0.001), there was no correlation between cortical bone and calcium score changes (p = 0.34). CONCLUSION: CKD patients experience either cortical or trabecular bone loss over time, but these changes do not take place simultaneously in all patients. Cortical, unlike trabecular bone loss, is not associated with vascular calcification progression in these patients.

MicroCT vascular network analysis program: Development, validation, and comparison to manufacturer software.

The dependence on angiogenesis for bone repair makes accurate measuring of vascular networks of great importance to orthopedic researchers. A three-dimensional imaging modality like microcomputed tomography (µCT) would better capture these networks than histology. There are commercially available programs to analyze vessel networks in three dimensions, but these may be too costly for laboratories. Alternatively, µCT trabecular software could be used but may not be appropriate. The goal of this project was to develop a vascular network analysis protocol based on freely or commonly available software and compare its performance to that of a µCT trabecular analysis software. The protocol developed, called vascular network analysis or VNA, relies on two modules in Fiji ImageJ and a custom MATLAB program. We validated the software and compared it to a µCT trabecular analysis program (MicroCT) using in silico models of increasing complexity and differing homogeneity. In general, VNA outcomes were significantly different from true values, but most were within an acceptable percent error (<10%). VNA and MicroCT performed almost identically for volume but significantly differently for average vessel diameter. For the homogenous models, the average diameters differed only slightly but were starkly different for the heterogeneous models. In the most heterogeneous system, the MicroCT software overestimated average diameter by about 650% from true. VNA was within 1% of true for the same model. In conclusion, we have developed a program to analyze vascular networks from MicroCT scans which is easily accessible, insensitive to network homogeneity, and of higher accuracy compared to a µCT trabecular analysis software.

Characterization of a prevascularized biomimetic tissue engineered scaffold for bone regeneration.

Significant bone loss due to disease or severe injury can result in the need for a bone graft, with over 500,000 procedures occurring each year in the United States. However, the current standards for grafting, autografts and allografts, can result in increased patient morbidity or a high rate of failure respectively. An ideal alternative would be a biodegradable tissue engineered graft that fulfills the function of bone while promoting the growth of new bone tissue. We developed a prevascularized tissue engineered scaffold of electrospun biodegradable polymers PLLA and PDLA reinforced with hydroxyapatite, a mineral similar to that found in bone. A composite design was utilized to mimic the structure and function of human trabecular and cortical bone. These scaffolds were characterized mechanically and in vitro to determine osteoinductive and angioinductive properties. It was observed that further reinforcement is necessary for the scaffolds to mechanically match bone, but the scaffolds are successful at inducing the differentiation of mesenchymal stem cells into mature bone cells and vascular endothelial cells. Prevascularization was seen to have a positive effect on angiogenesis and cellular metabolic activity, critical factors for the integration of a graft.

Combined Pedicled Vascularized and Wedge Nonvascularized Bone Graft for Treating Scaphoid Waist Nonunion With Humpback Deformity.

Pedicled vascularized bone graft (VBG) is a useful method in treating the scaphoid fracture nonunion, especially when the avascular necrosis exists. Humpback deformity is an important issue that we have to correct it during the treatment. We describe a method by using combined wedge non-VBG to correct the nonunion deformity when treating scaphoid nonunion with pedicled VBG. The wedge bone graft was harvested just proximal to the 2,3 intercompartmental supraretinacular artery VBG and was used as an inlay at the volar site to correct the humpback deformity, whereas the VBG was set at the dorsal site for bone bridging and blood supply. We also present our results of 10 patients with scaphoid fracture nonunion and humpback deformity treated with this method. Bone healing was achieved and the lateral intrascaphoid angles could be improved in all the 10 patients. Functional outcomes, including the Visual Analog Pain Scale for pain during activity, grip strength, the shortened Disabilities of the Arm, Shoulder, and Hand questionnaire (QuickDASH), and the modified Mayo Wrist Scores, were significantly improved.

Volar Radius Vascularized Bone Flaps for the Treatment of Scaphoid Nonunion.

Vascularized bone flaps (VBFs) improve union rates for scaphoid nonunions compared with nonvascularized grafts. Volar VBFs are indicated in cases of scaphoid nonunion with avascular necrosis and/or humpback deformity. Four volar VBFs are described in this article. The volar carpal artery and pronator quadratus VBFs are most commonly used. The pisiform VBF can be used for replacement of the proximal pole of the scaphoid; it is covered by articular cartilage. The ulna VBF has greater donor morbidity; the ulnar artery is harvested and a palpable donor site deformity results.

Microcomputed tomography of the femur of diabetic rats: alterations of trabecular and cortical bone microarchitecture and vasculature-a feasibility study.

BACKGROUND: To better understand bone fragility in type 2 diabetes mellitus and define the contribution of microcomputed tomography (micro-CT) to the evaluation of bone microarchitecture and vascularisation, we conducted an in vitro preliminary study on the femur of Zucker diabetic fatty (ZDF) rats and Zucker lean (ZL) rats. We first analysed bone microarchitecture, then determined whether micro-CT allowed to explore bone vascularisation, and finally looked for a link between these parameters. METHODS: Eight ZDF and six ZL rats were examined for bone microarchitecture (group 1), and six ZDF and six ZL rats were studied for bone vascularisation after Microfil® perfusion which is a radiopaque casting agent (group 2). In group 1, we used micro-CT to examine the trabecular and cortical bone microarchitecture of the femoral head, neck, shaft, and distal metaphysis. In group 2, micro-CT was used to study the blood vessels in the head, neck, and distal metaphysis. RESULTS: Compared to ZL rats, the ZDF rats exhibited significantly lower trabecular bone volume and number and higher trabecular separation in the three locations (p = 0.02, p = 0.02, p = 0.003). Cortical porosity was significantly higher in the ZDF rats at the neck and shaft (p = 0.001 and p = 0.005). We observed a dramatically poorer bone vascularisation in the femur of ZDF rats, especially in distal metaphysis (p < 0.047). CONCLUSIONS: Micro-CT demonstrated not only significant alterations in the bone microarchitecture of the femurs of ZDF rats, but also significant alterations in bone vascularisation. Further studies are required to demonstrate the causal link between poor vascularisation and impaired bone architecture.

Analysis of Trabecular Microstructure and Vascular Distribution of Capital Femoral Epiphysis Relevant to Legg-Calve-Perthes Disease.

Legg-Calve-Perthes disease is characterized by the capital femoral epiphyseal collapse, which occurs more reliably in the anterior quadrant than the more weight-bearing lateral quadrant. The purpose of this study was to determine whether there is a vascular or microstructural predisposition for anterior femoral epiphyseal collapse in Perthes disease. Thirty-two cadaveric proximal femoral epiphyses from 17 subjects (age 4-14 years old) underwent micro-computed tomography at 10-µm resolution. Each quadrant was analyzed for four markers of trabecular architecture: bone volume fraction (BV/TV), trabecular thickness, trabecular separation (TbSp), and trabecular number (TbN). Vascular channels were then mapped in each quadrant, identified by correlating surface topography with cross-sectional imaging. One-way analysis of variance revealed an overall difference between quadrants (p < 0.001) in BV/TV, TbN, and TbSp. However, post hoc analysis revealed there was no significant difference between the anterior and lateral quadrants for any of the four markers of trabecular architecture. Vascular channel mapping illustrated a predominance of vessels in the posterior half of the epiphysis compared to the anterior half (8.7 ± 4.0 vs. 3.4 ± 3.1 vascular channels, p < 0.001). The lack of microstructural differences between the anterior and lateral quadrants, and the predominance of vascular channels in the posterior half of the epiphysis with posteriorly-based medial femoral circumflex and ligamentum teres vessels suggests that the anterior femoral epiphysis may be a relative vascular watershed region, which predisposes it to collapse after the vascular insult of Perthes disease. Clinical significance: Improved understanding of the pathophysiology of anterior femoral epiphyseal collapse may inform future treatments aimed at revascularization. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:1784-1789, 2019.

Progressive ossification of the bone marrow vasculature with advancing age corresponds with reduced red blood cell count and percentage of circulating lymphocytes in male Fischer-344 rats.

OBJECTIVE: Assess the link between bone marrow blood vessel ossification, Tb. and cortical bone, and hematological parameters across the lifespan in rats. METHODS: Right femora and whole blood samples were taken from male Fischer-344 rats at 1, 6, 12, 18 and 24 months. Femora were scanned by micro-computed tomography (MicroCT) to determine bone marrow blood vessel ossification (ie, ossified vessel volume [OsVV], ossified vessel thickness (OsV.Th), ossified vessel density (OsV density), and structural model index [SMI]). Bone microarchitecture (ie, bone volume [BV/TV], trabecular thickness, trabecular number, and trabecular separation), density and SMI, and cortical bone parameters (ie, cortical shell thickness, porosity, and density) were also determined by MicroCT. Complete blood counts with differentials were conducted. RESULTS: Ossified vessel volume increased throughout the lifespan, coinciding with reduced trabecular BV/TV and cortical shell thickness at 24 months. Many of the hematological parameters were unchanged (ie, white blood cells, lymphocyte number) or increased (monocyte number, percent monocyte, granulocyte number, percent granulocyte, hemoglobin, hematocrit, mean corpuscular hemoglobin concentration, red blood cell distribution width, platelet, mean platelet volume) with advancing age; however, red blood cells (RBC) and percent lymphocytes (LY%) were reduced at 24 months. In addition, OsV density was similar to trabecular bone density. CONCLUSIONS: Declines in trabecular BV/TV, cortical shell thickness, RBC, and LY% with advanced age coincided with augmented ossification of bone marrow blood vessels.

Volar Vascularized Strut Graft for Avascular Scaphoid Nonunion Using the 1,2 Intercompartmental Supraretinacular Artery.

In this retrospective study, we report the preliminary results of a novel technique for volar vascularized strut grafting to treat avascular scaphoid nonunion by using the 1,2 intercompartmental supraretinacular artery through a single incision. Forty-three of 45 patients with avascular scaphoid nonunion healed at a mean of 13 weeks (range, 3 to 10 mo). Complications consisted of 1 pin tract infection that resolved with oral antibiotics and 4 cases of transient dysesthesia of the radial sensory nerve. In 4 patients with equivocal radiographs, computed tomography scans confirmed bony union. The 2 patients who remained unhealed subsequently underwent proximal row carpectomy. Two other patients had persistent pain with the progression of radiocarpal arthritis. Our technique provides good results for the treatment of avascular scaphoid fracture nonunion. Notable advantages include performance through a single incision, use of an already established vascularized bone graft, volar graft placement, and no requirement for microvascular free graft reconstruction. It also provides the surgeon with the ability to adjust the procedure intraoperatively in the event of unexpected avascularity, without requiring substantially longer operative time or additional equipment.

Vascularized Bone Graft to the Lunate Combined With Temporary Scaphocapitate Fixation for Treatment of Stage III Kienböck Disease: A Report of the Results, a Minimum of 2 Years After Surgery.

PURPOSE: To report the outcomes of patients with stage III Kienböck disease treated by vascularized bone graft (VBG) followed by temporary scaphocapitate (SC) fixation, a minimum of 2 years after surgery. METHODS: Twenty-six patients (mean age, 35 years) with stage III Kienböck disease (16 with stage IIIA and 10 with stage IIIB), treated with VBG followed by SC fixation for 4 months, were retrospectively followed for at least 2 years (range, 24-121 months; mean, 61.8 months). The preoperative and postoperative assessments included range of motion (ROM) of the wrist, grip strength (GS), wrist pain, the modified Mayo wrist score (MMWS), carpal height ratio (CHR), Ståhl index (STI), and radioscaphoid angle (RSA). The outcomes of each assessment of the stages IIIA and IIIB groups at the final examination were compared with those before surgery. RESULTS: In both stages IIIA and IIIB groups, GS increased after surgery. Decrease of CHR and STI was associated with the increase of RSA in the stage IIIA group after surgery, while RSA decreased, although neither CHR nor STI significantly increased in the stage IIIB patients. No patient demonstrated deterioration of the wrist pain after surgery. Twenty-one of 26 patients had an improved MMWS grade at the final follow-up. CONCLUSIONS: Vascularized bone graft combined with SC fixation for 4 months provided greater GS, pain relief, and functional improvement compared with before surgery in both stages IIIA and IIIB groups. TYPE OF STUDY/LEVEL OF EVIDENCE: Therapeutic IV.

CD31hiEmcnhi Vessels Support New Trabecular Bone Formation at the Frontier Growth Area in the Bone Defect Repair Process.

CD31hiEmcnhi vessels were a subtype of vessels in the murine skeletal system, with high levels of platelet and endothelial cell adhesion molecule-1 (PECAM-1/CD31) and endomucin (Emcn). They were reported coupling angiogenesis and osteogenesis during bone development. We investigated the distribution of these vessels in rat tibiae and their temporal and spatial distribution during the bone defect repair process to improve our understanding of the importance of these vessels. We confirmed that CD31hiEmcnhi vessels were specially distributed around the trabecular bones near metaphysis and endosteum in rat tibiae. At 3 days post bone injury, CD31hiEmcnhi vessels proliferated and were extensively distributed across the entire repair area. At 7 and 14 days post-injury, these vessels decreased but were specially distributed around the growing trabecular bones near the frontier growth area, suggesting that these vessels support new bone formation. The distribution of CD31hiEmcnhi vessels and the transcriptions of Hif-1α and VEGFA, as well as BMP2 and Osterix decreased at 7 and 14 days post-injury under osteoporotic conditions, in combination with insufficient osteogenesis. Our research is of great significance to help understand the important role of CD31hiEmcnhi vessels in supporting new trabecular bones formation during bone defect repair process.

Regeneration of Vascularized Corticocancellous Bone and Diploic Space Using Muscle-Derived Stem Cells: A Translational Biologic Alternative for Healing Critical Bone Defects.

BACKGROUND: Regeneration of functional bone substrate remains a priority in reconstructive surgery especially for patients suffering from complex skeletal defects. Efforts to develop implantable osteoinductive constructs and novel osteoconductive materials remain at the forefront of industry forces and product line development. Despite advancement in clinical practice and bone biology, cancellous autograft remains the gold standard for procedures requiring osteogenic mechanisms of healing. This study investigates the utility of muscle-derived stem cells as a cellular therapy for definitive bone regeneration through a form of neo-osteogenesis. METHODS: Adipose-derived stem cell, bone marrow-derived mesenchymal stem cell, and muscle-derived stem cell populations were isolated separately from C57BL/6 murine tissues and supplemented with collagen scaffolding with or without bone morphogenetic protein-2 to compare relative osteogenic potency and ultrastructure organization in both two- and three-dimensional systems. Parallel populations were bound to a deployable collagen implant within a syngeneic murine cranial defect model. RESULTS: Although all populations provided and maintained mesenchymal stem cell multilineage capacity, adipose-derived stem cell- and bone marrow-derived mesenchymal stem cell-enriched constructs were capable of forming small bone aggregates. Defects receiving muscle-derived stem cells self-assembled a form of organized corticocancellous structures within two- and three-dimensional in vitro systems and within the in vivo model. Muscle-derived stem cells also augmented healing, implant angiogenesis, and diploic space formation. CONCLUSION: Muscle-derived stem cell-enriched implants appear to provide an autologous response to current industry-derived products and an attractive alternative to mesenchymal stem cells for the regeneration of corticocancellous bone and a vascularized diploic space.