Cadaveric Bones Research Articles

Bactericidal coating to prevent early and delayed implant-related infections

The occurrence of an implant-associated infection (IAI) with the formation of a persisting bacterial biofilm remains a major risk following orthopedic biomaterial implantation. Yet, progress in the fabrication of tunable and durable implant coatings with sufficient bactericidal activity to prevent IAI has been limited. Here, an electrospun composite coating was optimized for the combinatorial and sustained delivery of antibiotics. Antibiotics-laden poly(ε-caprolactone) (PCL) and poly`1q`(lactic-co glycolic acid) (PLGA) nanofibers were electrospun onto lattice structured titanium (Ti) implants. In order to achieve tunable and independent delivery of vancomycin (Van) and rifampicin (Rif), we investigated the influence of the specific drug-polymer interaction and the nanofiber coating composition on the drug release profile and durability of the polymer-Ti interface. We found that a bi-layered nanofiber structure, produced by electrospinning of an inner layer of [PCL/Van] and an outer layer of [PLGA/Rif], yielded the optimal combinatorial drug release profile. This resulted in markedly enhanced bactericidal activity against planktonic and adherent Staphylococcus aureus for 6 weeks as compared to single drug delivery. Moreover, after 6 weeks, synergistic bacterial killing was observed as a result of sustained Van and Rif release. The application of a nanofiber-filled lattice structure successfully prevented the delamination of the multi-layer coating after press-fit cadaveric bone implantation. This new lattice design, in conjunction with the multi-layer nanofiber structure, can be applied to develop tunable and durable coatings for various metallic implantable devices. This is particularly appealing to tune the release of multiple antimicrobial agents over a period of weeks to prevent early and delayed onset IAI.

Biomechanical properties and thermal characteristics of frozen versus thawed whole bone.

Biomechanics research often requires cadaveric whole bones to be stored in a freezer and then thawed prior to use; however, the literature shows a variety of practices for thawing. Consequently, this is the first study to report the mechanical properties of fully frozen versus fully thawed whole bone as 'proof of principle'. Two groups of 10 porcine ribs each were statistically equivalent at baseline in length, cross-sectional area, and bone mineral density. The two groups were stored in a freezer for at least 24 h, thawed in air at 23 °C for 4 h while temperature readings were taken to establish the time needed for thawing, and once again returned to the freezer for at least 24 h. Mechanical tests to failure using three-point bending were then done on the 'frozen' group immediately after removal from the freezer and the 'thawed' group when steady-state ambient air temperature was reached. Temperature readings over the entire thawing period were described by the line-of-best-fit formula T = (28.34t - 6.69)/(t + 0.38), where T = temperature in degree Celsius and t = time in hours, such that frozen specimens at t = 0 h had a temperature of -17 °C and thawed specimens at t = 1.75 h reached a steady-state temperature of 20 °C-23 °C. Mechanical tests showed that frozen versus thawed specimens had an average of 32% higher stiffness k, 34% higher ultimate force Fu, 28% lower ultimate displacement δu, 40% lower ultimate work Wu, 43% higher elastic modulus E, 37% higher ultimate normal stress σu, and 33% higher ultimate shear stress τu. Whole ribs failed at midspan primarily by transverse cracking (16 of 20 cases), oblique cracking (three of 20 cases), or surface denting (one of 20 cases), each having unique shapes for force versus displacement graphs differentiated mainly by ultimate force location.

Impact of freeze‐thaw on isolation of viable CD34+ cells from human cadaveric bone marrow

IntroductionThe CD34 surface protein is a marker used to distinguish hematopoietic stem and progenitor cells (HSPCs). CD34+ cells are currently used in stem cell transplantation to treat hematological malignancies following myeloablation of bone marrow (BM). Ossium Health is creating a large and genetically diverse bank of cryopreserved deceased donor BM for medical purposes such as hematopoietic stem cell transplantation (HSCT) as well as biomedical research. Given the growing diversity of the bank, it would be advantageous to cryogenically store whole BM for future isolation of CD34+ cells possessing desirable genetic and demographic attributes. While current protocols are designed to select cells from fresh BM aspirated from live donors, there are no reports of selecting these cells from either previously frozen or cadaveric BM. Therefore, the purpose of this study was to determine (1) whether cadaveric BM is an acceptable source of CD34+ cells, (2) whether functional CD34 cells could be selected from previously frozen BM, and (3) the integrity of CD34+ cells following multiple freeze‐thaw cycles.MethodsWhole BM was obtained from vertebral bodies recovered from deceased donors consented for research use. CD34+ cells were selected from fresh and thawed BM by Ficoll separation followed by immunomagnetic bead isolation (EasySep, Stem Cell Technologies). Selected cells were subjected to further freeze‐thaw cycles and analyzed by flow cytometry and colony forming unit (CFU) assays to enumerate and evaluate CD34+ cell functionality, viability, purity, and population dynamics.Results and discussionResults thus far indicate no difference in CFU counts between fresh and thawed BM. Furthermore, 7‐AAD staining indicated a CD34+ average cell viability of 99+0% from fresh and 98+0% from thawed BM. Finally, long‐term hematopoietic stem cells (LT‐HSC) as defined by the cell surface protein markers CD34+ CD38‐CD90+CD45RA‐CD49f+, comprised 1.94% and 2.18% of CD34+ cells selected from fresh and previously frozen BM, respectively.Conclusions and future directionsTogether, these results indicate the suitability of deceased donor BM and the comparability of CD34+ cells selected from fresh and previously frozen BM. Ongoing experiments include evaluation of BM from additional donors as well as xenotranplantation studies in an irradiated immunocompromised mouse model. Validation of previously frozen cadaveric BM as an acceptable substrate for viable CD34+ cell isolation will enable a large and genetically diverse source of HSPC for both medical and research uses. Furthermore, due to the large volumes obtainable, BM from a single donor yields >100 million CD34+ cells, which is vastly greater than available from living donors, thus, providing a consistent source for study and to be used in therapeutic development.Support or Funding InformationThank you to the Marian University College of Osteopathic Medicine for their financial support of this project.

Relationships Among Bone Morphological Parameters and Mechanical Properties of Cadaveric Human Vertebral Cancellous Bone.

Mechanical properties and morphological features of the vertebral cancellous bone are related to resistance to fracture and capability of withstanding surgical treatments. In particular, vertebral strength is related to its elastic properties, whereas the ease of fluid motion, related to the success of incorporation orthopedic materials (eg, bone cement), is regulated by the hydraulic permeability (K). It has been shown that both elastic modulus and permeability of a material are affected by its morphology. The objective of this study was to establish relations between local values of K and the aggregate modulus (H), and parameters descriptive of the bone morphology. We hypothesized that multivariate statistical models, by including the contribution of several morphology parameters at once, would provide a strong correlation with K and H of the vertebral cancellous bone. Hence, μCT scans of human lumbar vertebra were used to determine a set of bone morphology descriptors. Subsequently, indentation tests on the bone samples were conducted to determine local values of K and H. Finally, a multivariate approach supported by principal component analysis was adopted to develop predictive statistical models of bone permeability and aggregate modulus as a function of bone morphology descriptors. It was found that linear combinations of bone volume fraction, trabecular thickness, trabecular spacing, structure model index, connectivity density, and degree of anisotropy provide a strong correlation (R 2 ~ 76%) with K and a weaker correlation (R 2 ~ 47%) with H. The results of this study can be exploited in computational mechanics frameworks for investigating the potential mechanical behavior of human vertebra and to develop strategies to treat or prevent pathological conditions such as osteoporosis, age-related bone loss, and vertebral compression fractures. © 2020 The Authors. JBMR Plus published by Wiley Periodicals, Inc. on behalf of American Society for Bone and Mineral Research.

Development of a novel minimally invasive technique to washout necrotic bone marrow content from epiphyseal bone: A preliminary cadaveric bone study

IntroductionLegg-Calvé-Perthes disease is a juvenile ischemic osteonecrosis which produces extensive necrotic cell debris and release of damage associated molecular patterns (DAMPs) in the femoral head. The necrotic bone environment induces a chronic inflammatory repair response with excessive bone resorption leading to deformity and early osteoarthritis. Currently there is no minimally invasive method to clear the necrotic materials from the bone to decrease the inflammatory burden of the necrotic environment and to improve the healing process. HypothesisWe hypothesized that a novel minimally invasive two-needle saline washing technique would be effective to remove cell debris, proteins, and fat from the marrow space of porcine cadaveric humeral heads (HHs). Materials and methodsTwenty-two HHs were subjected to three freeze-thaw cycles to simulate osteonecrosis prior to the wash procedure which consisted of placement of two 15-gauge intraosseous needles followed by incremental saline wash. After the washout procedure, the solutions were collected for measurements of turbidity, protein concentration, and cell count. The HHs were analyzed by optical scanning and histology. ResultsThe solution collected after each wash showed a significant decrease in the turbidity, cell count, and protein concentration (p<0.05). Histologic assessment showed significantly decreased cell debris and adipocytes in the washed group compared to the unwashed group (p<0.001). Discussion/conclusionThe two-needle intraosseous wash technique effectively removed cell debris and proteins from the marrow space. The technique may be used to reduce the necrotic cell debris and DAMPs present in the necrotic bone. Level of evidenceIII, in vitro comparative study.

Is intramedullary screw fixation biomechanically superior to locking plate fixation and/or tension band wiring in transverse olecranon fractures? A cadaveric biomechanical comparison study

ObjectivesTo compare clinically important mechanical properties of three techniques used to fix transverse olecranon fractures (Arbeitsgemeinschaft fur Osteosynthesefragen and Orthopaedic Trauma Association class 2U1B1): (1) intramedullary (IM) screw, (2) locking plate, and (3) tension band wire in a realistic loading protocol using a cadaveric model. MethodsFresh frozen cadaveric transverse olecranon fracture models were fixed with an IM screw (n = 6), a locking plate (n = 6), or a tension band (n = 6). Compression after fixation was recorded using a pressure sensor in the fracture before samples were loaded through the triceps tendon for 500 cycles of 0–500 N, assessing implant survival. The primary outcome measure was compression force before loading. The secondary outcome was frequency of implant failure defined as breakage of the implant itself or fracture gapping >5 mm. Binary outcomes were compared with χ2, and continuous variables were compared with unadjusted analysis of variance and a multivariable regression model adjusting for age, sex, dual-energy X-ray absorptiometry T-score, and testing order. ResultsNo statistically significant difference was shown in fracture compression between IM screw (mean, 162 N; 95% confidence interval [CI], 27–297 N), locking plate (mean, 125 N; 95% CI, −9–260 N), and tension band (mean, 163 N; 95% CI, 29–298 N) in unadjusted (p = 0.89) and adjusted (p = 0.82) analyses. A 100% implant failure rate was observed with tension band compared with 0% implant failure with IM screw or locking plate (p < 0.01). ConclusionWe found no statistically significant differences in compression across the fracture site among techniques. We did find a higher risk of implant failure with tension band compared with IM screw and locking plate during cyclic loading in cadaveric bone.

Calcium Phosphate Bone Void Filler Increases Threaded Suture Anchor Pullout Strength: A Biomechanical Study

To compare the response to cyclical loading and ultimate pull-out strength of threaded suture anchor with and without calcium phosphate bone void filler augmentation in a polyurethane foam block model and invitro proximal humerus cadaveric model. This controlled biomechanical study consisted of 2 parts: (1) preliminary polyurethane foam block model, and (2) invitro cadaveric humeri model. The preliminary foam block model intended to mimic osteoporotic bone using a 0.12 g/mL foam material. Half of the foam block models were first filled with injectable calcium phosphate bone substitute material (CP-BSM), whereas the other half were not augmented with CP-BSM. Each specimen was then instrumented with a threaded suture anchor. The same technique and process was performed in a matched cadaveric humeri model. Testing then consisted of a stepwise, increasing axial load protocol for a total of 40 cycles. If the anchor remained intact after cyclic loading, the repair was loaded to failure. The number of completed cycles, failure load, and failure modes were compared between groups. Average pull-out strength for suture anchor with CP-BSM in the osteoporotic foam block model was significantly higher at 332.68 N ± 47.61 compared with the average pull-out strength of suture anchor without CP-BSM at 144.38 N ± 14.58 (P= .005). In the matched cadaveric humeri model, average pull-out strength for suture anchor with CP-BSM was significantly higher at 274.07 N ± 102.07 compared with the average pull-out strength of suture anchor without CP-BSM at 138.53 N ± 109.87 (P= .029). In this time zero, biomechanical study, augmentation of osteoporotic foam block and cadaveric bone with calcium phosphate bone substitute material significantly increases pull-out strength of threaded suture anchors. Considering concerns about suture anchor pull-out from osteoporotic bone, augmentation with calcium phosphate bone substitute material increases load to failure resistance.

Multi-functional intramedullary self-locking ulna nailing system: Proximal oblique locking without the need of fluoroscopic guidance, and it's effects on olecranon joint surface

Aim: Due to the necessity of using the small diameter nails in the ulna, negative outcomes such as failure in the self-locking, long term exposure to radiation, and increased operation time are expected. Several clinical trials propose that an ideal nail system for unlar fixation challenge has not been developed yet. Material and Methods: This study involved the use of a new multifunctional intramedullary self-locking ulna nailing system and 36 intact dry cadaveric ulna bones. The relationship between the oblique self-locking screw, which has made a crucial contribution to the nailing system, and the joint surface of olecranon was investigated because this screw does not necessitate the use of fluoroscopic guidance and is easy to apply.Results: In our study, during anterior or medial or posterior oblique locking, no olecranon joint surface damage occurred on any bone with a locking rate of 100%. Conclusion: The clinical trials demonstrated that the proximal oblique locking was achieved easily in a short period of time, indicating the device’s immense value for the patient and the surgeon.

Morphometric Analysis of Superior Articular Surface of Tibia in Dry Cadaveric Bones

Background: Total knee arthroplasty is the most cost effective and rapidly evolving technique. The success of procedure relies on appropriate sizing of tibial component, for which elaborate information of various dimensions of upper surface of tibia is mandatory. Hence, this study is aiming to generate baseline data on antero-posterior and transverse measurements of medial and lateral condyles and intercondylar area of upper surface of tibia. Methods: The study was conducted in 42 dry human cadaveric tibia with unidentified age and sex, in the Department of Anatomy, College of Medical Sciences and Teaching Hospital, Chitwan. The antero-posterior and transverse measurements of medial and lateral condyles and intercondylar area of tibia were recorded in millimeter (mm) with digital Vernier calipers. The data was analysed using SPSS version 16.0. Results: The antero-posterior and transverse measurements of medial condyle of tibia were 43.00±5.95 mm and 25.21±8.08 mm respectively on the right side and 45.33±5.36 mm and 27.43±8.57 mm respectively on the left side and that of lateral condyle were 37.94±5.64 mm and 25.21±8.71 mm respectively on the right side and 41.03±3.65 mm and 27.06±8.83 mm respectively on the left side. The antero-posterior and transverse measurements of intercondylar area of tibia were 47.49±6.31 mm and 15.71±3.93 mm respectively on the right side and 49.24±6.91 mm and 15.02±3.88 mm respectively on the left side. The variation in the measurements between right and left tibia showed significant difference only for antero-posterior measurement of lateral condyle (p&lt;0.05). Conclusions: The study generates baseline data regarding various anthropometric measurements of upper surface of tibia, which will assist the orthopedic surgeon to create a resected bony surface identical to the tibial component of an implant in unilateral and total knee arthroplasty.&#x0D; Keywords: measurement; morphometric; superior articular surface; tibial condyles.

Quantitative characterisation of impaction events during femoral broaching in total hip arthroplasty

Total hip arthroplasty (THA) broaching involves impacting a broach handle with a mallet, facilitating force transmission to progress broaches into the femoral medullary canal. Limited surgical access during direct anterior THAs increases off-axis forces, potentially contributing to tissue damage. The aim was to characterise impactions during broaching.In a cadaver lab, movement of handle, femur and instrumented mallet was tracked during direct-anterior approach (DAA) and posterior approach (PA). Mallet velocity, broach displacement and input energy were calculated. Following the cadaver lab, different impaction strategies were investigated using bone simulants for a simulated DAA. The effects of reduced mallet velocity inputs and the influence of different impaction locations on the broach handle strike plate were investigated.To seat the broach in cadaveric bone, lower impaction energy (−59%) and number of strikes (−53%) were observed during PA compared to DAA. Suboptimal broach progression was reached in bone simulant at low mallet velocities (3.1 ± 0.3 m/s). Impacting the strike plate's upper part caused larger deflections (p < 0.001) of the Sawbones femur which suggested that higher off axis forces occurred.Awareness of reduced load transmission during DAA broaching using off-axis broach handles, compared to the traditional PA, could help promoting a more efficient and careful impaction strategy in surgeries.

A Comparison of Intra-Observer and Inter-Observer Reliability of Plain Radiographs, Standard Computed Tomography Scans and Mobile Computed Tomography Scans in the Assessment of Distal Radius Fractures: A Cadaveric Study

Objective: Diagnosis of a distal end radius fracture relies on various imaging studies. However, the relative usefulness of these studies is still a matter of some controversy. The aim of this study was to compare the intra-observer and inter-observer reliability of plain radiographs, standard computed tomography (CT) scans and mobile CT scans in the assessment of distal radius fractures as categorized by the Fernandez classification method. The secondary objective was to compare the dosages of radiation between the different imaging modalities. Material and Methods: Sixteen fresh cadaveric wrist bones were used in this experimental study. The desired fractures were created in the bones to mimic Fernandez types I-V fractures and plain radiographs were taken in 4 views. Standard CT and mobile CT scans were also taken with the fractured bones in the same four positions. Interobserver reliability was assessed using Kappa statistics to determine the diagnostic consistency among the nine observers. Inter-observer agreement was assessed based on the Fernandez classification system diagnoses. Results: Overall, the inter-observer agreement was substantial for the Fernandez classifications (Kappa range 0.636 0.727) in all types of imaging. For intra-observer agreement, the analysis found higher agreement for both standard CT scans and mobile CT scans. The standard CT images imparted a higher average dose of radiation than both the mobile CT scans and the plain radiographs.Conclusion: The mobile CT scan can provide an alternative imaging method for precise diagnosis of distal end radius fractures, with the additional benefits of mobility and lower radiation exposure.

Relating mechanical properties of vertebral trabecular bones to osteoporosis

Osteoporosis is an osteometabolic disease, which promotes structural degradation of bone tissue and reduction of mineral density. We reported here a mechanical resistance assay from normal, osteopenic and osteoporotic trabecular vertebral bones of human cadavers. We performed a compressed test on ninety samples, evaluating Young’s modulus and X-ray microtomography to measure bone volume fraction and trabecular thickness. This experimental data are employed for computing the orthotropic macroscopic behavior of vertebral trabecular bones using known analytical formulae that were obtained by Galka et al. (Arch Mech 51: 335-355, 1999) via an asymptotic homogenization model. A geometrical model with a periodic orthogonal plate-like structure is applied. The properties of the bone-trabecular mass are considered linear, homogeneous and orthotropic. Average values for all technical or engineering elastic properties are computed for three important regions of the trabecular bones corresponding to thirty individuals classified as normal, osteopenic or osteoporotic by calcaneus ultrassometry. This study could be useful for a better understanding of the elastic behavior of trabecular bones in human vertebral bodies, allowing an estimation of bone answer under stress in different directions and the risk of fracture associated with osteoporosis.HighlightsDescribing the elastic behavior of trabecular bones in human vertebral bodies at the micro and macroscopic.Allow a better estimation of the stress in different directions and risk of fracture associated with osteoporosis.Model request a very low computational cost.Offer a better understand the global effective coefficients of samples of trabecular bone, from the model of a periodic unit cell, in the format orthogonal plate-like structure with homogeneous bone mass.

Experimental investigations and statistical modeling of cutting force and torque in rotary ultrasonic bone drilling of human cadaver bone.

Cutting force and torque are important factors in the success of the bone drilling process. In the recent past, many attempts have been made to reduce the cutting force and torque in the bone drilling process. In this work, drilling on human cadaver bones has been performed using rotary ultrasonic bone drilling process to investigate the effect of drilling parameters on cutting force and torque. The experimental work was carried on a recently developed rotary ultrasonic bone drilling machine for surgical operations. The experimental work was performed in two phases. The first phase includes a comparative study between rotary ultrasonic bone drilling and conventional surgical bone drilling, to study the influence of various drilling parameters (rotational speed, drill diameter, and drilling tool feed rate) on the cutting force and torque. The results revealed that the cutting force and torque produced during drilling operations in rotary ultrasonic bone drilling were lesser (30%-40%) than conventional surgical bone drilling. In the second phase, response surface methodology was used to perform the statistical modeling of cutting force and torque in rotary ultrasonic bone drilling process. Analysis of variance was performed at a confidence interval of 95% to analyze the significant contribution (p < 0.05) of process parameters (drilling speed, feed rate, drill diameter, and abrasive particle size) on the responses (cutting force and torque). The confirmatory experiments were performed to validate the developed statistical models. It was found that both cutting force and torque decrease with increase in drilling speed and increases with the increasing drill diameter, feed rate, and abrasive particle size.

Variation of the clavicle\u2019s muscle insertion footprints \u2013 a cadaveric study

The muscle footprint anatomy of the clavicle is described in various anatomical textbooks but research on the footprint variation is rare. Our goal was to assess the variation and to create a probabilistic atlas of the muscle footprint anatomy. 14 right and left clavicles of anatomical specimens were dissected until only muscle fibers remained. 3D models with muscle footprints were made through CT scanning, laser scanning and photogrammetry. Then, for each side, the mean clavicle was calculated and non-rigidly registered to all other cadaveric bones. Muscle footprints were indicated on the mean left and right clavicle through the 1-to-1 mesh correspondence which is achieved by non-rigid registration. Lastly, 2 probabilistic atlases from the clavicle muscle footprints were generated. There was no statistical significant difference between the surface area (absolute and relative), of the originally dissected muscle footprints, of male and female, and left and right anatomical specimens. Visualization of all muscle footprints on the mean clavicle resulted in 72% (right) and 82% (left) coverage of the surface. The Muscle Insertion Footprint of each specimen covered on average 36.9% of the average right and 37.0% of the average left clavicle. The difference between surface coverage by all MIF and the mean surface coverage, shows that the MIF location varies strongly. From the probabilistic atlas we can conclude that no universal clavicle exists. Therefore, patient-specific clavicle fracture fixation plates should be considered to minimally interfere with the MIF. Therefore, patient-specific clavicle fracture fixation plates which minimally interfere with the footprints should be considered.

Synthetic open cell foams versus a healthy human vertebra: Anisotropy, fluid flow and μ-CT structural studies.

Commercial synthetic open-cell foams are an alternative to human cadaveric bone to simulate in vitro different scenarios of bone infiltration properties. Unfortunately, these artificial foams do not reproduce the anisotropic microstructure of natural bone and, consequently, their suitability in these studies is highly questionable. In order to achieve scaffolds that successfully mimic human bone, microstructural studies of both natural porous media and current synthetic approaches are necessary at different length scales. In this line, the present research was conducted to improve the understanding of local anisotropy in natural vertebral bone and synthetic bone-like porous foams. To attain this objective, small volumes of interest within these materials were reconstructed via micro-computed tomography. The anisotropy of the microstructures was analysed by means of both their main local histomorphometric features and the behaviour of an internal flow computed via computational fluid dynamics. The results showed that the information obtained from each of the micro-volumes of interest could be scaled up to understand not only the macroscopic averaged isotropic and/or anisotropic behaviour of the samples studied, but also to improve the design of macroscopic porous implants better fitting specific local histomorphometric scenarios. The results also clarify the discrepancies in the permeability obtained in the different micro-volumes of interest analysed. STATEMENT OF SIGNIFICANCE: A deep insight comparative study between the porous microstructure of healthy vertebral bone and that of synthetic bone-like open-cell rigid foams used in in vitro permeability studies of bone cement has been performed. The results obtained are of fundamental relevance to computational studies because, in order to achieve convergence values, the computation process should be limited to small computation domains or micro-volumes of interest. This makes the results specific spatial dependent and for this reason computation studies cannot directly capture the macroscopic average behaviour of an anisotropic porous structure such as the one observed in natural bones. The results derived from this study are also important because we have been able to show that the specific spatial information contained in only one healthy vertebra is enough to capture, from a geometric point of view, the same information of "specific surface area vs. porosity" - in other words, the same basic law - that can also be found in other human bones for different patients, even at different biological ages. This is an important finding that, despite the efforts made and the controversies formulated by other authors, should be studied more thoroughly with other bone species and tissues (healthy and/or diseased). Moreover, our results should help to understand that, with the extensive capabilities of current 3D printing technologies, there is an enormous potential in the design of biomimetic porous bone-like scaffolds for bone tissue engineering applications.

Predicting bone strength from CT data: Clinical applications

In this review we summarise over 15 years of research and development around the prediction of whole bones strength from Computed Tomography data, with particular reference to the prediction of the risk of hip fracture in osteoporotic patients. We briefly discuss the theoretical background, and then provide a summary of the laboratory and clinical validation of these modelling technologies. We then discuss the three current clinical applications: in clinical research, in clinical trials, and in clinical practice. On average the strength predicted with finite element models (QCT-FE) based on computed tomography is 7% more accurate that that predicted with areal bone mineral density from Dual X-ray Absorptiometry (DXA-aBMD), the current standard of care, both in term of laboratory validation on cadaver bones and in terms of stratification accuracy on clinical cohorts of fractured and non-fractured women. This improved accuracy makes QCT-FE superior to DXA-aBMD in clinical research and in clinical trials, where the its use can cut in half the number of patients to be enrolled to get the same statistical power. For routine clinical use to decide who to treat with antiresorptive drugs, QCT-FE is more accurate but less cost-effective than DXA-aBMD, at least when the decision is on first line treatment like bisphosphonates. But the ability to predict skeletal strength from medical imaging is now opening a number of other applications, for example in paediatrics and oncology.

High-resolution Imaging of the Human Cochlea through the Round Window by means of Optical Coherence Tomography

The human cochlea is deeply embedded in the temporal bone and surrounded by a thick otic capsule, rendering its internal structure inaccessible for direct visualization. Clinical imaging techniques fall short of their resolution for imaging of the intracochlear structures with sufficient detail. As a result, there is a lack of knowledge concerning best practice for intracochlear therapy placement, such as cochlear implantation. In the past decades, optical coherence tomography (OCT) has proven valuable for non-invasive, high-resolution, cross-sectional imaging of tissue microstructure in various fields of medicine, including ophthalmology, cardiology and dermatology. There is an upcoming interest for OCT imaging of the cochlea, which so far was mostly carried out in small animals. In this temporal bone study, we focused on high-resolution imaging of the human cochlea. The cochlea was approached through mastoidectomy and posterior tympanotomy, both standard surgical procedures. A commercially available spectral-domain OCT imaging system was used to obtain high-resolution images of the cochlear hook region through the intact round window membrane in four cadaveric human temporal bones. We discuss the qualitative and quantitative characteristics of intracochlear structures on OCT images and their importance for cochlear implant surgery.

Hindfoot Bone Viscoelasticity and Stress Relaxation

Category:Ankle, Ankle Arthritis, Basic Sciences/Biologics, HindfootIntroduction/Purpose:Hindfoot arthrodeses have a non-union rate as high as 40%. Compression at the arthrodesis site plays a key role in stimulating bone growth leading to successful fusion. The ability to obtain and maintain compression depends not only on the surgical technique and the hardware which develop the compressive force but also on the response of the bone to compression. Bone, like other musculoskeletal tissues, is viscoelastic meaning that it has properties of both fluids and solids.Because bone is viscoelastic, it experiences stress relaxation (decrease in compressive force over time). The rate and magnitude of such stress relaxation is unknown. Our primary objective was to quantify stress relaxation of the hindfoot bones when subjected to a fixed compression displacement as would be done during arthrodesis.Methods:10 human cadaveric bone cylinders measuring 10 mm in both diameter and height were cut from the articular surfaces of the talus, calcaneus, and distal tibia using a disposable cylindrical osteochondral harvester (OATS, Arthrex inc, Naples, FL).Each bone cylinder sample included subchondral and trabecular bone, and articular cartilage was removed during preparation. Each sample was scanned with a micro-computed tomography (uCT) scanner (Biomedical Micro CT Scanner, Scanco Medical, Switzerland) to quantify bone volume/total volume ratio (BV/TV), trabecular thickness, trabecular separation, trabecular number, and connectivity density. Each specimen was submerged in a saline bath and compressed by 1 mm at a strain rate of 1mm/sec using a material testing machine (System 810, MTS Systems, Eden Prairie, MN), and load data was gathered by an Interface load cell. Displacement was held constant for 3 hours, after which each sample was removed from the test machine and immediately rescanned with the uCT scanner.Results:The ensemble load curve of the ten samples displayed uniform exponential decay. After the initial load was placed on the bone, a steep, negative load velocity was apparent. Rapid decay occurred within the first 3 minutes, after which the load plateaued, holding constant over the subsequent 3 hours of compression. The average peak load was 515.53 N (SD: 254.58 N). The average percent load loss was 65.77% over 30 minutes (SD: 20.95%). Discrete time periods (B1, B2, B3, B4) were established corresponding to 0-3 min, 3-10 min, 10-20 min, and 20-30 min, respectively. Time periods B1, B2, B3, and B4 demonstrated an average percent load loss per time period of 43.35% (SD: 10.09%), 13.80% (SD: 14.77%), 18.65% (SD: 24.97%) and 7.95% (SD: 13.37%), respectively.Conclusion:Our data suggest that a significant percentage of compressive load placed across a bone is lost within the first 3 minutes as compared to any subsequent time period. Moreover, approximately 65.77% of the compressive load is lost over the first 30 minutes. These data suggest that when performing arthrodesis with compressive hardware, the majority of the initially applied compressive load may dissipate over the first 3-30 minutes, which may contribute to nonunion. Thus, a re-tightening of screws after 5-30 minutes or the use of a continuous compressive device may help to maintain compression at the arthrodesis site throughout healing.

The influence of the chosen in vitro bone simulation model on intraosseous temperatures and drilling times

There is no consensus about the most suitable in vitro simulating material investigating heat generation during bone preparation. The aim was to compare heat increases and drilling times of bone removals in different bone simulating materials and to compare them to fresh human cadaver bone. A cavity was drilled in the following samples: (1) bovine rib; (2) pig rib; (3) 20 PCF (lb/ft3) polyurethane (PU) block with 3 mm (50 PCF) cortical layer; (4) 20PCF PU without cortical; (5) 30 PCF PU with 2 mm (40 PCF) cortical; (6) 30 PCF PU with 1 mm (40 PCF) cortical; (7) 30PCF PU without cortical; (8) poly-methyl-methacrylate (PMMA); (9) fresh human cadaver rib. Data were analyzed with ANOVA followed by Tukey’s post hoc tests. P < 0.05 was considered significant. Highest heat increases and slowest drilling times were found in bovine ribs (p < 0.001). Regarding temperatures, human ribs were comparable to the pig rib and to PUs having cortical layers. Considering drilling times, the human rib was only comparable to the 20 PCF PU with 3 mm cortical and to 30 PCF PU without cortical. By the tested in vitro bone removals, only the 20 PCF PU with 3 mm cortical was able to simulate human ribs, considering both temperature increases and drilling times.

Biomechanical properties of an intramedullary suture anchor fixation compared to tension band wiring in osteoporotic olecranon fractures- A cadaveric study

IntroductionThe aim of the study is to compare three different fixation techniques for transverse olecranon repair in cadaveric osteoporotic bone: (1) current recommended AO tension band technique with K-wire fixation; (2) Suture anchor fixation and (3) Polyester suture fixation. MethodsEvaluated with bone densitometry, 7 osteoporotic human elbow specimens were included in the study. A transverse olecranon fracture was reduced anatomically and were fixated first using a K-wire tension band technique, second using two suture anchors, and third using polyester suture. Static simulations of the kinetics associated with active range of motion (AROM) and push up from a chair exercises were performed with cyclic loading using Instron hydraulic testing apparatus. Fracture displacement was measured using videographic analysis. Failure was defined as 2 mm fracture displacement. ResultsThe biomechanical analysis found no statistical difference in displacements between the three fixation methods when testing AROM. In simulated push-up exercises, polyester suture fixation failed after 17 cycles and had significantly higher displacement compared to the other two methods. No difference between the K-Wire fixation versus Suture anchor fixation was observed, p = 0.162. ConclusionSuture anchor fixation might be a viable surgical treatment option for osteoporotic transverse elbow fractures in geriatric patients.