Cortical Wall Research Articles

Biomechanical evaluation of femoral neck fracture osteosynthesis

Bone geometry, density, and thickness of the cortical layer of the femoral neck (FN) contribute to the mechanical strength in osteosythesis of femoral neck fractures (FNF) in young adults. The available techniques for fracture fixation of the FN are reviewed with respect to the biomechanical stability.A biomechanical study of the osteosynthesis stability of the FNF with three cannulated screws was carried out using synthetic models of the proximal part of the femoral bone (FB). The experimental models were divided into 4 groups. Each group related to the configuration of screws in the FN. The vertical and horizontal FNF stability was assessed using two series of load. In series I, models were loaded with forces in the longitudinal axis to the FB and in series II, forces acted in the perpendicular direction to the FB axis. The loading forces were evaluated when the displacement of 2 mm fragments was achieved. The highest stability strengths were obtained in group I in the both series ‒ 1898 N with a vertical load and 1046 N with a horizontal load. Further, in decreasing order, the results of stability were obtained in groups II, III and IV.In this study, it was found that the consideration of the position of screws according to architectonics of the FN is crucial for fragment stability. The triangular position of screws with three points of contact with the compact bone ensures the maximum stability of the construct in osteosynthesis of the FN fractures, which is comparable to the normal walking load conditions.We hypothesize that osteosynthesis of FN fractures with three screws in a triangular manner could provide a better stability when inserted into the dense tissues of the proximal FB with relation to bone architectonics. To ensure a maximum stability, each screw should have three points of contact with the compact bone – the lateral cortical wall of the subtrochanteric region of the FB, the inner wall of the FN, and the compact part of the FB head. New triangular configuration of screws’ placement could have a better neutralization of share forces in FN fractures.

Study of correlation between preoperative high resolution computed tomography temporal bone and intraoperative surgical findings in 60 cases of unsafe chronic otitis media

<p><strong>Background:</strong> Cholesteatoma is a serious health hazard which can give rise to alarming intracranial and extracranial complications as it can progressively enlarge and invade into neighbouring structures. Thus, early diagnosis and prompt management of a suspected cholesteatoma is necessary. High resolution computed tomography (HRCT) temporal bone scan clearly defines the extent and location of soft tissue density in middle ear with adjoining bony erosions. The aim of the study was to determine the role of HRCT temporal bone in early detection of cholesteatoma and finding the correlation between preoperative HRCT temporal bone and intraoperative surgical findings.</p><p><strong>Methods: </strong>Total 60 cases with unsafe chronic otitis media (COM) attending ENT OPD of Rajindra hospital, Patiala were selected for this prospective study. All patients were scanned for HRCT temporal bone and preoperative radiological data was correlated with intraoperative surgical findings. The results were calculated and analysed statistically.</p><p><strong>Results:</strong> This study demonstrated good correlation between preoperative temporal bone HRCT scans with intraoperative surgical findings, particularly in ossicular erosion (except stapes), LSC erosion, facial canal erosion, lateral cortical wall erosion and dural and sinus plate erosion.</p><p><strong>Conclusions: </strong>HRCT temporal bone scan evidently demarcates the soft tissue density in middle ear and mastoid with adjacent bone erosions and it also provide details of anatomical variations. Hence HRCT temporal bone is valuable in diagnosing and guiding surgical management of unsafe COM making it prerequisite before any surgical manipulation.</p>

CALCIFYING ODONTOGENIC CYST WITH 10 YEARS OF EVOLUTION: A CASE REPORT

Calcifying odontogenic cyst (COC) is a rare, benign odontogenic lesion that sometimes may be present along with odontogenic tumors. A 22-year-old female patient was referred for evaluation of an asymptomatic swelling on the anterior maxilla with approximately 10 years of evolution. Physical examination showed firm swelling with cortical expansion within intact bluish mucosa. Computed tomography showed a unilocular hypodense image with hyperdense foci, causing loss of bone structure in the vestibular cortical and anterior wall of maxillary sinus. Diagnostic hypotheses were calcifying epithelial odontogenic tumor, ameloblastic fibro-odontoma, and complex odontoma, and incisional biopsy was performed. Microscopic analysis revealed a pathologic cavity lined by odontogenic epithelium with variable thickness, along with ghost cells, eosinophilic acellular material resembling dentinoid, and foci of dystrophic calcifications. The cyst was surrounded by a fibrous capsule. Histopathologic diagnosis was COC. The patient was referred for enucleation of the lesion for complete analysis and final diagnosis.

Root angle is controlled by EGT1 in cereal crops employing an antigravitropic mechanism

Root angle in crops represents a key trait for efficient capture of soil resources. Root angle is determined by competing gravitropic versus antigravitropic offset (AGO) mechanisms. Here we report a root angle regulatory gene termed ENHANCED GRAVITROPISM1 (EGT1) that encodes a putative AGO component, whose loss-of-function enhances root gravitropism. Mutations in barley and wheat EGT1 genes confer a striking root phenotype, where every root class adopts a steeper growth angle. EGT1 encodes an F-box and Tubby domain-containing protein that is highly conserved across plant species. Haplotype analysis found that natural allelic variation at the barley EGT1 locus impacts root angle. Gravitropic assays indicated that Hvegt1 roots bend more rapidly than wild-type. Transcript profiling revealed Hvegt1 roots deregulate reactive oxygen species (ROS) homeostasis and cell wall-loosening enzymes and cofactors. ROS imaging shows that Hvegt1 root basal meristem and elongation zone tissues have reduced levels. Atomic force microscopy measurements detected elongating Hvegt1 root cortical cell walls are significantly less stiff than wild-type. In situ analysis identified HvEGT1 is expressed in elongating cortical and stele tissues, which are distinct from known root gravitropic perception and response tissues in the columella and epidermis, respectively. We propose that EGT1 controls root angle by regulating cell wall stiffness in elongating root cortical tissue, counteracting the gravitropic machinery's known ability to bend the root via its outermost tissues. We conclude that root angle is controlled by EGT1 in cereal crops employing an antigravitropic mechanism.

Full digital workflow in prosthetically guided implantology associated with crestal sinus lift

Resolution of edentulism of 2.4, 2.5, and 2.6 in a 60-year-old woman treated with bisphosphonates per os. CBCT (Planmeca ProMax 3D): good horizontal bone volume not enough vertical on 2.6 IOS (Planmeca Emerald): CAD design of three crowns before virtual implant placement Virtual placement of three implants in 2.4, 2.5, 2.6 positions guided by the virtual crowns previously designed (PlanCad). Regarding area 2.6, having only 4 mm of bone tissue was available in height, it was decided to virtually position the implant (4.2 × 6 MM) 2 mm out of the ridge, so as to arrive with the 6-mm burs, in the osteotomy phase, up to the cortical sinus without going beyond it. The lab .stl file was removed and matching of the intraoral scan stl file with dicom cbct file for the creation of the surgical guide with dental support was performed. The guide was printed using a 3D printer (Planmeca Creo C5). Osteotomies on 2.4 and 2.5 were performed and implants were inserted through the surgical guide. On 2.6 the osteotomy was performed only for 4 mm in depth in order to stop with the burs at the cortical wall of the maxillary sinus and to fracture it by the osteotomes. The implant was inserted manually. Endoral x-ray post-op showed the perfected match between virtual and real surgery. Intraoral scan was performed for an immediate load with a cad-cam zirconia bridge. Full digital workflow in implantology is a reliable technique to perform minimally invasive surgery.

Computer 3D modeling of radiofrequency ablation of atypical cartilaginous tumours in long bones using finite element methods and real patient anatomy

BackgroundRadiofrequency ablation (RFA) is a minimally invasive technique used for the treatment of neoplasms, with a growing interest in the treatment of bone tumours. However, the lack of data concerning the size of the resulting ablation zones in RFA of bone tumours makes prospective planning challenging, needed for safe and effective treatment.MethodsUsing retrospective computed tomography and magnetic resonance imaging data from patients treated with RFA of atypical cartilaginous tumours (ACTs), the bone, tumours, and final position of the RFA electrode were segmented from the medical images and used in finite element models to simulate RFA. Tissue parameters were optimised, and boundary conditions were defined to mimic the clinical scenario. The resulting ablation diameters from postoperative images were then measured and compared to the ones from the simulations, and the error between them was calculated.ResultsSeven cases had all the information required to create the finite element models. The resulting median error (in all three directions) was -1 mm, with interquartile ranges from -3 to 3 mm. The three-dimensional models showed that the thermal damage concentrates close to the cortical wall in the first minutes and then becomes more evenly distributed.ConclusionsComputer simulations can predict the ablation diameters with acceptable accuracy and may thus be utilised for patient planning. This could allow interventional radiologists to accurately define the time, electrode length, and position required to treat ACTs with RFA and make adjustments as needed to guarantee total tumour destruction while sparing as much healthy tissue as possible.

Direct anterior approach hip arthroplasty: How to reduce complications - A 10-years single center experience and literature review.

BACKGROUNDThe direct anterior approach for total hip arthroplasty (DAA-THA) is increasing in popularity due to some advantages such as less surgical trauma, minimal dissection of soft tissues, shorter rehabilitation times, faster return to daily activities, lower incidence of dislocation. On the other hand, the literature reports a high rate of intraoperative complications, with many different rates and complication types in the published papers. AIMTo analyze our complications comparing results with the literature; to report measures that we have taken to reduce complications rate.METHODSAll DAA-THA patients with one year minimum follow up who were operated at a single high-volume centre, between January 2010 and December 2019 were included in this retrospective study. All surgeries were performed using cementless short anatomical or straight stems and press fit cups. Patients’ follow-up was performed, at 6 wk, 3 mo, then annually post-surgery with clinical and radiological evaluation. Primary outcomes were stem revision for aseptic loosening and all-cause stem revision. Second outcome was intra-operative and post-operative complications identification.RESULTSA total of 394 patients underwent DDA-THA from January 2010 and December 2019, for a total of 412 hips; twelve patients lost to follow-up and one patient who died from causes not related to surgery were excluded from the study. The average age at the time of surgery was 61 years (range from 28 to 78 years). Mean follow-up time was 64.8 mo (range 12-120 mo). Seven stems were revised. One cortical perforation, one trochanteric and lateral cortical wall intraoperative fracture, one diaphyseal fracture, three clinically symptomatic early subsidence and one late aseptic loosening. We also observed 3 periprosthetic fractures B1 according to the Vancouver Classification. Other minor complications not requiring stem revision were 5 un-displaced fractures of the calcar region treated with preventive cerclage, one early infection, one case of late posterior dislocation, 18 case of asymptomatic stem subsidence, 6 cases of lateral cutaneous femoral nerve dysesthesia.CONCLUSIONDAA is associated to good outcomes and lower incidence of dislocation. Complication rate can be reduced by mindful patient selection, thorough preoperative planning, sufficient learning curve and use of intraoperative imaging.

Triphasic calcium‐based implant material resorbs and is replaced with bone in ovariectomized rats with or without bisphosphonate treatment

This study evaluated the effects of AGN1, a triphasic calcium-based material, and alendronate (A) on distal femoral defect bone repair in ovariectomized (OVX) rats. Of 106 rats, 92 were OVX'ed at 12 weeks old and underwent a 12-week induction period. Animals were randomized into five groups: OVX Control, OVX Alendronate Control, Normal Control, OVX Implantation, OVX Alendronate + Implantation. OVX Alendronate Control and OVX Alendronate + Implantation groups received alendronate injection twice weekly (0.015 mg/kg) from 6 weeks until sacrifice. Twelve weeks after OVX, 2.5 mm diameter by 4.0 mm long cylindrical, bilateral distal femoral defects were created in experimental animals. One defect was left empty, and one filled with AGN1. Dual-energy X-ray absorptiometry, microcomputed tomography, and histomorphometry were performed 0-, 6-, 12-, and 18-week postdefect/implantation surgery (N = 6-8/group). Results showed OVX induced significant and progressive bone loss which alendronate prevented. Histomorphometry demonstrated rapid AGN1 resorption: AGN1 resorbed from 95.1 ± 0.7% filling of the implant site (week 0) to 1.3 ± 1.0% (18 weeks) with no significant alendronate effect (1.6 ± 1.1%, 18 weeks). Bone formation in empty defects consisted primarily of cortical wall healing, whereas AGN1 implants demonstrated cortical wall healing with new trabecular bone filling the subcortical space. Alendronate dramatically increased bone formation in empty and AGN1 defects. We conclude AGN1 is resorbed and replaced by new cortical and trabecular bone in this OVX model, and alendronate did not compromise these effects.

Image-based radiodensity profilometry measures early remodeling at the bone-callus interface in sheep

Bone healing has been traditionally described as a four-phase process: inflammatory response, soft callus formation, hard callus development, and remodeling. The remodeling phase has been largely neglected in most numerical mechanoregulation models of fracture repair in favor of capturing early healing using a pre-defined callus domain. However, in vivo evidence suggests that remodeling occurs concurrently with repair and causes changes in cortical bone adjacent to callus that are typically neglected in numerical models of bone healing. The objective of this study was to use image processing techniques to quantify this early-stage remodeling in ovine osteotomies. To accomplish this, we developed a numerical method for radiodensity profilometry with optimization-based curve fitting to mathematically model the bone density gradients in the radial direction across the cortical wall and callus. After assessing data from 26 sheep, we defined a dimensionless density fitting function that revealed significant remodeling occurring in the cortical wall adjacent to callus during early healing, a 23% average reduction in density compared to intact. This fitting function is robust for modeling radial density gradients in both intact bone and fracture repair scenarios and can capture a wide variety of the healing responses. The fitting function can also be scaled easily for comparison to numerical model predictions and may be useful for validating future mechanoregulatory models of coupled fracture repair and remodeling.

A RETROSPECTIVE STUDY ONFUNCTIONAL OUTCOME OF OPERATED INTERTROCHANTERIC FEMUR FRACTURES REDUCEDWITH A POSITIVE BEAK VS NEUTRAL VS NEGATIVE BEAK - AN ARTICLE AND REVIEW OF LITERATURE

Background: Inter-trochanteric fracture is one of the most common fractures in elderly population around the world due to global rise of osteoporosis, which is generally due to a simple slip and fall in the house hold[1]. It is growing to be a disease burden for orthopedics of our era to manage. With its rise Understanding the important factors in management of IT fracture like stability, reduction, role of posterior-medial wall support, intact lateral wall configuration, will help in choosing implant for better outcome ,thus helping to achieve better post operative results[2]. Hence, understanding the role of posteriomedial wall support in IT fracture reduction in terms of positive, neutral(anatomic) or negative beak and its impact on the post operative fracture stability and early ambulation is of great importance. We conducted a retrospective comparative study in our institution to study the outcome of these configuration and its effect post operatively. Methods: A retrospective comparative study was conducted on 60 patients with Intertrochanteric fracture(38 males and 12 females with a mean age of 64.8years) without any associated fractures in elderly population in a time frame between February 2019 to August 2021 using Cephalo-mudullary nailing and Sliding hip screw in our institution. The subject population was graded into 3 groups based on the postero medial cortical wall support in post operative fracture reduction into positive, neutral(anatomic) and negative beak configuration and its effects on post operative fracture stability and early mobilization. Results: In the post operative analysis it was found that the 24 subjects who had positive configuration in the neck shaft angle versus 16 neutral(anatomic) and 10 negative configuration in their neck shaft angle had a superior and better outcome in terms of early ambulation and better long term stability without any statistical differences in terms of age, sex, post traumatic day or any co-morbidities. Conclusion: Thus, we concluded that the fracture reduction with positive reduction achieved a greater stability in terms of early mobilization and better post operative stability and fracture healing than the neutral and negative neck shaft angle. Further it was seen that neutral configuration also had a superior advantage over negative configuration in post operative follow up with a lesser incidence of varus collapse or implant failure.

Immediate Implant Placement in the Maxillary Aesthetic Zone: A Cone Beam Computed Tomography Study.

This study aimed to investigate the factors that could be associated with the risk of labial cortical bone wall perforation with immediate implant placement (IIP) in the maxillary aesthetic zone, in a cone-beam computed tomography (CBCT) virtual study. CBCT exams from 126 qualified subjects (756 teeth) were included. Implants were virtually positioned in two different positions: in the long axis of the tooth (prosthetically-driven position) and in an ideal position in relation to adjacent anatomical structures (bone-driven position). Two different implant diameters were planned for each tooth position, namely, 3.75 and 4.3 mm for central incisors and canines, and 3.0 and 3.3 mm for lateral incisors. The incidence of perforation was nearly 80% and 5% for prosthetically- and bone-driven position, respectively. Factors associated with a higher risk of cortical bone wall perforation (bone-driven position), according to logistic regression analysis, were women, wider implants, Sagittal Root Position class IV, and decrease of the labial concavity angle. Perforation of the labial cortical bone wall can be greatly minimized when the implant is placed in a bone-driven position compared to a prosthetically-driven position. It is important to preoperatively evaluate the morphological features of the implant site for risk assessment and to individualize the treatment plan.

Bacterial Colonization of the Condyle in Patients with Advanced Mandibular Osteoradionecrosis: Analysis of Hemimandibulectomy Specimens.

Advanced mandibular osteoradionecrosis (ORN) sometimes requires extended resection (e.g., hemimandibulectomy). Bacterial infection contributes to ORN pathogenesis. To control infection and determine the extent of debridement required, an understanding of bacterial spread within sites of mandibular ORN is important. The current study used a histopathological approach to assess bacterial colonization in the mandibular condyle and elucidate possible paths of bacterial spread towards the mandibular condyle. Four hemimandibulectomy specimens were selected. Areas of bone destruction were macroscopically assessed and confirmed using hematoxylin and eosin staining. Bacterial presence within mandibular condyle was confirmed with Gram staining. Bone exposure was observed in the molar area in all specimens. Macroscopic bone destruction was apparent especially near the medial side of the cortical wall. Gram staining revealed bacterial colonization of the mandibular condyle in three of the four specimens. In conclusion, bacteria tended to spread posteriorly and through the medial side of the mandibular cortical wall. In patients with advanced ORN, the potential for bacterial colonization of the mandibular condyle should be considered during treatment.

Zn tolerance in the evergreen shrub, Aucuba japonica, naturally growing at a mine site: Cell wall immobilization, aucubin production, and Zn adsorption on fungal mycelia.

Aucuba japonica Thunb. is an evergreen understory shrub that grows naturally at a mine site. The mine soil contains high concentrations of heavy metals, and A. japonica appears to maintain detoxification mechanisms against heavy metals in the study site’s understory. This study aimed to investigate the heavy metal tolerance mechanisms in A. japonica, considering the possible roles of arbuscular mycorrhizal and root-endophytic fungi. We conducted fieldwork in summer (canopy-foliation season) and winter (canopy-defoliation season) to measure the heavy metal concentrations in leaves, branches, and roots and analyze possible detoxicants in the roots. The infection rates of arbuscular mycorrhizal and root-endophytic fungi were evaluated via microscopic observation, and heavy metal (Zn) localization in A. japonica roots was observed using confocal laser scanning microscopy. Field analysis showed that A. japonica accumulated excessive Zn and produced aucubin and citric acid in the roots in both summer and winter. Zn localization observations clarified that Zn was distributed in thickened epidermal and cortical cell walls, suggesting that the cell walls functioned as Zn deposition sites, reducing Zn toxicity. It was further clarified that Zn was contained within cortical cells, indicating that Zn might be detoxified by aucubin and citric acid. Arbuscular mycorrhizal and root-endophytic fungi within cortical cells adsorbed Zn on fungal cell walls, indicating that these fungi would reduce Zn content within root cells and might alleviate Zn toxicity. Our results indicated that A. japonica would maintain Zn tolerance in both summer and winter via Zn immobilization in the cell walls and production of aucubin and citric acid, and that arbuscular mycorrhizal and root-endophytic fungi might play important roles in the Zn tolerance of A. japonica.

Surgical Precision and Efficiency of a Novel Electromagnetic System Compared to a Robot-Assisted System in Percutaneous Pedicle Screw Placement of Endo-LIF.

Retrospective database study. To compare the accuracy and safety of 2 types of a computer-assisted navigation system for percutaneous pedicle screw placement during endoscopic lumbar interbody fusion. From May 2019 to January 2020, data of 56 patients who underwent Endo-LIF with a robot-assisted system and with an electromagnetic navigation system were compared. The pedicles in all patients were subjected to postoperative CT scan to assess screw correction by measuring the perpendicular distance between the pedicle cortical wall and the screw surface. The registration and matching time, guide-wire insertion time, the entire surgery time, and X-ray exposure time were recorded. In the robot-assisted group, 25 cases with 100 percutaneous pedicle screws were included, and the excellent and good rate was 95%. In the electromagnetic navigation group, 31 cases with 124 screws were included, and the excellent rate was 97.6%. There was no statistical difference between the two groups (P > 0.05). The registration time and the total time for the surgery also showed no statistical differences (P > 0.05). The main difference between the two groups was the guide-wire insertion time and the X-ray exposure time (P < 0.05). Both electromagnetic navigation and robot-assisted are safe and efficient for percutaneous pedicle screw placement. Electromagnetic navigation system has obvious advantages over robot-assisted in terms of faster guide-wire placement and less X-ray exposure. Robot-assisted for percutaneous pedicle screw placement offers a preoperative planning system and a stable registration system, with obvious drawbacks of a strict training curve.

Positive effect of compound amino acid chelated calcium from the shell and skirt of scallop in an ovariectomized rat model of postmenopausal osteoporosis.

Osteoporosis has become an important public health issue with the increase of aging population, and afflicts millions of people worldwide, particularly elderly or postmenopausal women. In the present study, we prepared compound amino acid chelated calcium (CAA-Ca) from processing by-products of Chlamys farreri, and evaluated its effect on postmenopausal osteoporosis with an ovariectomized (OVX) rat model. A 60-day treatment of OVX rats with CAA-Ca significantly enhanced the bone mineral density (BMD) and the bone calcium content. Meanwhile, some bone morphometric parameters, trabecular bone number (Tb.N), trabecular bone volume fraction (BV/TV), trabecular bone thickness (Tb.Th) and cortical bone wall thickness (Ct.Th), were also increased by 8.20%, 118.18%, 32.99% and 19.10%, respectively. In addition, the alkaline phosphatase (ALP) levels in serum were significantly reduced after CAA-Ca treatment, while the blood calcium levels were increased. Mechanistically, CAA-Ca down-regulated the levels of receptor activator of nuclear factor-κB (RANK) and receptor activator of nuclear factor-κB ligand (RANKL), and up-regulated osteoprotegerin (OPG) levels in osteoclasts, inhibiting bone resorption and bone loss. Meanwhile, CAA-Ca treatment raised β-catenin levels and lowered Dickkopf1 (DKK1) levels in the Wnt signaling pathway of osteoblasts, which can promote calcium absorption and bone formation. The results suggested that CAA-Ca promoted bone formation, inhibited bone resorption and improved bone microstructure. Therefore, this study contributes to the potential application of CAA-Ca as a functional food resource in the treatment of postmenopausal osteoporosis. © 2021 Society of Chemical Industry.

Brain-trait-associated variants impact cell-type-specific gene regulation during neurogenesis

Interpretation of the function of non-coding risk loci for neuropsychiatric disorders and brain-relevant traits via gene expression and alternative splicing quantitative trait locus (e/sQTL) analyses is generally performed in bulk post-mortem adult tissue. However, genetic risk loci are enriched in regulatory elements active during neocortical differentiation, and regulatory effects of risk variants may be masked by heterogeneity in bulk tissue. Here, we map e/sQTLs, and allele-specific expression in cultured cells representing two major developmental stages, primary human neural progenitors (n = 85) and their sorted neuronal progeny (n = 74), identifying numerous loci not detected in either bulk developing cortical wall or adult cortex. Using colocalization and genetic imputation via transcriptome-wide association, we uncover cell-type-specific regulatory mechanisms underlying risk for brain-relevant traits that are active during neocortical differentiation. Specifically, we identified a progenitor-specific eQTL for CENPW co-localized with common variant associations for cortical surface area and educational attainment.

Virtual implantation technique to estimate endoprosthetic contact of percutaneous osseointegrated devices in the tibia

Percutaneous osseointegrated (OI) devices have an endoprosthesis attached to the residual bone of an amputated limb, then pass permanently through the skin to be connected to the distal prosthetic componentry outside of the body. Whether the bone-anchoring region of current OI endoprostheses are cylindrical, and/or conical, they require intimate bone-endoprosthesis contact to promote stabilizing bone attachment. However, removing too much cortical bone to achieve more contact leads to thinner and, subsequently, weaker cortical walls. Endoprostheses need to be designed to balance these factors, namely maximizing the contact, while minimizing the volume of bone removed. In this study, 27 human tibias were used to develop and validate a virtual implantation method. Then, 40 additional tibias were virtually implanted with mock cylindrical and conical bone-anchoring regions at seven residual limb lengths to measure resultant bone-endoprosthesis contact and bone removal. The ratio of bone-endoprosthesis contact to bone volume removed showed the conical geometry had more contact area per volume bone removed for all amputation levels (p ≤ 0.001). In both mock devices, cortical penetration of the endoprosthesis at 20% residual length occurred in 74% of cases evaluated, indicating that alternative endoprosthesis geometries may be needed for clinical success in that region of bone.

Issue Cover (June 2021)

Front cover: Cover image: Bone microstructure of the naked mole-rat, Heterocephalus glaber under polarized light microscopy showing thick cortical walls and the formation of different bone tissue matrices in the humerus. See G. Montoya-Sanhueza et al., ‘Long bone histomorphogenesis of the naked mole-rat: histodiversity and intraspecific variation’, this issue.

Anatomical factors in medication-related osteonecrosis of the jaws

Introduction Medication-related osteonecrosis of the jaws (MRONJ) is a serious adverse event of antiresorptive and antiangiogenic drugs that affects bone and soft tissue of the maxilofacial region [1]. Clinical features and risk factors of MRONJ have been described in several publications, however few studies address the anatomical factors involved [2,3]. This study aims to: (a) describe in detail the anatomical location of MRONJ lesions; (b) identify the most susceptible areas and association with other factors. Materials and methods A retrospective study was conducted including all patients with MRONJ diagnosis in an Oral Surgery Clinic between 2004 and 2018. The data was collected from the patient clinical records. Lesion extension was determined by the physical exam and/or computer tomography. Statistical significance was defined as p < .05. Chi-square, Student t-test, ANOVA and log-linear analysis were used as appropriate. All were performed using IBM SPSS® version 23. Results A total of 147 patients were included in the sample, 95 (64.6%) females and 52 (35.4%) males, with a mean age at diagnosis of 68.12 ± 11.02 years. A total of 182 lesions were diagnosed, 67 (36.8%) in the maxilla and 115 (63.2%) in the mandible. The molars and premolars regions were most affected both in the maxilla (1st and 3rd sextants) with 46 (68.7%) lesions, and in the mandible (4th and 6th sextants) with 96 lesions (83.4%). The alveolar bone was affected in 170 (93.9%) the lesions, whereas 18 (9.9%) had involvement of the basal bone, 7 (3.8%) arose in the mylohyoid line and only 5 (2.7%) occurred in the hard palate. At least one of the cortical walls was involved in 125 (68.7%) lesions, the buccal wall in 53 (29.1%) lesions, the palatal or lingual wall in 32 (17.6%) lesions and both walls in 40 (22%) lesions. Male patients were more likely to have multiple lesions located both in the maxilla and mandible (17.3%) than female patients (5.3%) (p < .017). In absence of any traumatic factor, periodontal disease was found in 34.4% of patients with anterior lesion location (2nd or 5th sextants) vs 10.2% with posterior lesion location, although not statistically significant (p < .89). We found no statistically significant differences or association between lesion location or lesion extension and dentoalveolar surgery, use of dental prosthesis, age at diagnosis, type of drug and length of antiresorptive or antiangiogenic medication. Discussion and conclusions MRONJ lesions were more frequently located in the mandible as expected from previous studies [2,3]. The molars and premolars regions were most affected and at least one cortical wall was involved in most lesions. Some authors have concluded that areas with thin mucosa are more susceptible, our results are in accordance as we identified several lesions in the mylohyoid line [3]. Our study results can reflect the importance of anatomical factors such as occlusal forces, blood supply and bone density vary in these locations.

Developmental Differences Between the Limbic and Neocortical Telencephalic Wall: An Intrasubject Slice-Matched 3T MRI-Histological Correlative Study in Humans.

The purpose of the study was to investigate the interrelation of the signal intensities and thicknesses of the transient developmental zones in the cingulate and neocortical telencephalic wall, using T2-weighted 3T-magnetic resonance imaging (MRI) and histological scans from the same brain hemisphere. The study encompassed 24 postmortem fetal brains (15-35 postconceptional weeks, PCW). The measurements were performed using Fiji and NDP.view2. We found that T2w MR signal-intensity curves show a specific regional and developmental stage profile already at 15 PCW. The MRI-histological correlation reveals that the subventricular-intermediate zone (SVZ-IZ) contributes the most to the regional differences in the MRI-profile and zone thicknesses, growing by a factor of 2.01 in the cingulate, and 1.78 in the neocortical wall. The interrelations of zone or wall thicknesses, obtained by both methods, disclose a different rate and extent of shrinkage per region (highest in neocortical subplate and SVZ-IZ) and stage (highest in the early second half of fetal development), distorting the zones' proportion in histological sections. This intrasubject, slice-matched, 3T correlative MRI-histological study provides important information about regional development of the cortical wall, critical for the design of MRI criteria for prenatal brain monitoring and early detection of cortical or other brain pathologies in human fetuses.