Bone Failure Research Articles

Long bone failure after intraosseous regional perfusion

SummaryA 5‐year‐old Australian Stock Horse gelding was initially referred to the Charles Sturt University Veterinary Clinical Centre (CSUVCC) for assessment of a penetrating laceration over the medial splint bone (second metacarpal bone) of the left foreleg. Clinical examination failed to reveal a communication with a synovial structure, but radiographs showed a palisading bone reaction on the proximal aspect of the medial splint bone which was thought to be a characteristic of infection. Soft tissue swelling precluded access to a peripheral vein, so a decision was made to use intraosseous regional limb perfusion. This was achieved through an access portal in the lateral diaphysis of the third metacarpal bone (McIII). Subsequently, the horse developed lameness and further investigation revealed a nondisplaced longitudinal fracture of McIII propagating from the intraosseous regional perfusion access portal.

Craved by heart, carved next to it: Ballistic report of a souvenir bullet casing

A bullet which has been lodged in the body encapsulated by dense fibrous tissue for a long time without causing ill effects is a souvenir bullet. The bullet cartridge is divided into 3 parts: bullet, cartridge case holding bullet with gun powder and detonator at the base. Medicolegal consultation was done with Forensic Medicine Department where cartridge case acted as projectile and accidentally got embedded into the chest of the victim. In an attempt of making an ornament from the casing of bullet which was separated from bullet mechanically and gunpowder was partially removed from the bullet case. When he heated the bullet case to melt and mould, the remaining gun powder ignited with release of large amount of gas which resulted in forceful propulsion and acted as the projectile. An oval penetrating keyhole appearance injury measuring 2 cm x 1.5 cm was present on left side of the chest of the victim. The projectile was found just above the 6th rib and was confined within inter-costal muscle. Although late complications may arise from the metallic toxicity from the bullet case showing manifestations like abdominal pain, anorexia, chronic renal failure, abdominal pain, osteomyelitis, and fistula formation in bones, the projectile was left within the body as a souvenir to be intervened in case complications arise during follow-ups, as manipulating it could cause unanticipated therapeutic complications.

Postoperative analysis of a free fibular graft due to bone failure caused by a metatarsal bone tumor

Objective: To evaluate the postoperative clinical outcomes of patients undergoing fibular grafting due to bone loss caused by metatarsal tumors. Methods: This retrospective cross-sectional study was conducted between January 2010 and December 2018 with three patients who were treated with a free fibular graft after bone loss due to metatarsal tumor resection. The patients underwent surgery with a dorsal longitudinal incision over the tumor lesion for subsequent tumor resection. The fibular graft was harvested from the distal third of the ipsilateral leg. The graft was fixed using Kirschner wires and a mini-fragment plate and cortical screws. An analysis of the patients’ ages, sex, tumor types, need for adjuvant or neoadjuvant therapy and postoperative complications was conducted. Results: All three patients who were subjected to fibular grafting for metatarsal replacement were female (100%), with a mean age of 10.3 years (± 0.61). The type of tumor found in the three patients (100%) was an aneurysmal cyst, and only the affected metatarsal showed changes. None of the patients required adjuvant or neoadjuvant therapy. Regarding the postoperative complications, two patients (66.6%) presented pseudoarthrosis, and one did not present any complications. Conclusion: Free fibular grafting is a viable option for the treatment of bone loss caused by metatarsal tumors. Level of Evidence IV, Therapeutic Studies; Case Series.

Biomechanical evaluation of osteoporotic fracture: Metal fixation versus absorbable fixation in Sawbones models

ObjectiveThe failure of osteoporotic fracture after internal fixation is mainly caused by the underlying bone loss and strength compromise. The aim of this study is to investigate whether absorbable internal fixation can provide adequate mechanical stability and a reduction in the incidence of failure of fixation caused by bone loss and stress shielding. MethodsA low density cancellous bone model was selected to compare the insertion of screw (screw-in), removal of screw (screw -out) and pull - out strength of absorbable screw and metal screw. The long bone model of thin cortical bone was used to create the transverse fracture model. The model was fixed with absorbable plate-screw system and metal plate-screw system respectively. The fatigue test and static bending test were compared. Moreover, the size of screw hole area was assessed. ResultsThe maximal screw - in and screw - out torque of the absorbable screw was significantly greater than that of the metal screw (P < 0.05), but there was no significant difference in pull-out test (P > 0.05). No visible failure occurred in fatigue test. There was no significant difference between the maximum load of static bending test (P > 0.05). The screw hole area of absorbable samples was significantly smaller than that of metal samples (P < 0.05). ConclusionsIn this experimental set-up it was found that the stability of absorbable screws in osteoporotic bone was better than metal screws. The absorbable system tested can achieve good stability, and the destruction of osteoporotic bone is small, which can reduce the occurrence of bone failure. Considering that absorbable material avoids the need of second surgery (implant removal) and reduces the stress shielding effect, we believe that absorbable internal fixation can be considered for fixation treatment of osteoporotic fractures.

Proximal radius fracture morphology following axial force impact: a biomechanical evaluation of fracture patterns

BackgroundThe most common location for articular fractures of the radial head is often reported to be the anterior lateral aspect of the radial head with the arm in neutral position. However, these findings mainly base on clinical observations rather than precise biomechanical measurements. The purpose of this study was to evaluate the formation of proximal radius fractures, the association between axial forces and fracture morphology, energy to failure and bone stiffness in a biomechanical in-vitro setup.Methods18 fresh-frozen cadaveric radii performed axial load compression with 10 mm/min loading until bone failure. Energy to failure and bone stiffness were recorded. Proximal radial head fracture morphology and affection of the anterolateral quadrant were optically analyzed.ResultsAll radii survived a compression load of 500 N. The mean compressive forces that lead to failure were 2,56 kN (range 1,30 – 7,32). The mean stiffness was 3,5 kN/mm (range 2,0 – 4,9). 11 radial neck fractures and 7 radial neck and radial head multifragment fractures were documented. The anterolateral quadrant was involved in 78% of tested radii.ConclusionThe anterolateral quadrant of the radial head (in neutral position of the forearm) is confirmed to be the most common location for articular radial head fractures in a biomechanical setting. In case of a fall on the outstretched arm radial neck fractures should be securely ruled out due to prior occurrence to radial neck and head fractures.

Patterns of Bone Failure in Localized Prostate Cancer Previously Irradiated: The Preventive Role of External Radiotherapy on Pelvic Bone Metastases.

Introduction: External beam radiation therapy (EBRT) can cure localized prostate cancer (PCa) by sterilizing cancer cells in the prostate gland and surrounding tissues at risk of microscopic dissemination. We hypothesized that pelvic EBRT for localized PCa might have an unexpected prophylactic impact on the occurrence of pelvic bone metastases.Material and Methods: We reviewed the data of 332 metastatic PCa patients. We examined associations between the number (≤5 vs. >5) and the location of bone metastases (in-field vs. out-of-field), which occurred at first relapse, and a previous history of EBRT for PCa (EBRT vs. No-EBRT).Results: One hundred and ten patients M0 at baseline were eligible. Fifty-six patients (51%) were in the No-EBRT group, and 54 patients (49%) in the EBRT group. The proportion of patients who developed >5 bone metastases in the bony pelvis was higher in the No-EBRT group vs. the EBRT group: 10 patients (18%) vs. 2 patients (4%), respectively (p = 0.02). By multivariate analysis EBRT was associated with a lesser occurrence of patients who had >5 bone metastases in the bony pelvis (OR = 0.17 [95%CI, 0.04–0.87], p = 0.03). Time to occurrence of bone metastases ≥5 years (OR = 0.10 [95%CI, 0.05–0.19], p < 0.01), prior curative prostate treatment (OR = 0.58 [95%CI, 0.36–0.91], p = 0.02), >5 bone metastases in bony pelvis (OR = 2.61 [95%CI, 1.28–5.31], p < 0.01), >5 bone metastases out of bony pelvis (OR = 1.73 [95%CI, 1.09–2.76], p = 0.02) were all predictive of overall survival.Conclusion: Previous pelvic EBRT for PCa is associated with a lower number of pelvic bone metastases, which is associated with better overall survival.

In vitro biomechanical comparison of headless compression versus cortex screws for fixation of simulated midbody proximal sesamoid bone fractures in horses

A midbody fracture of a proximal sesamoid bone (PSB) is a severe injury, especially in racehorses. Screw fixation may be the only option for horses to return to athletic activity. In a cadaveric biomechanical study, fixation of simulated transverse midbody PSB fractures with a 4.5 mm headless compression screw (HCS) was compared to the fixation using a 4.5 mm cortex screw (CS) inserted in lag fashion. The front limbs of 8 horses were prepared with a standardized midbody transverse osteotomy in each medial PSB. The left or the right limb of each pair was randomly assigned to the CS or HCS group. Fracture reduction and fixation was controlled by radiography. Markers were fixed proximal and distal to the osteotomy to document gap opening by an image correlation measurement. Cyclic compressive loading was applied with a hydraulic cylinder in an axial manner leading to tensile cyclic loading in the PSBs. After mechanical testing all limbs were radiographed to document the mode of failure. The mean cycles to total failure were 27,803 for the HCS group and 36,624 for the CS group, respectively. A mean of 14,444 cycles (HCS group) versus 27,464 cycles (CS group) was recorded at a fracture gap opening of 10 %. The mean value of initial stiffness was 300 N/mm (HCS group) versus 590 N/mm (CS group). On post-testing radiographs, failure by screw breakage was detected in 3/8 limbs of the HCS group and in 2/8 limbs of the CS group. Screw pullout and bone failure was noted in 5 limbs in each group. In one limb of the CS group, the medial suspensory branch was disrupted and the fracture fixation was intact. None of the differences between HCS and CS constructs reached statistical significance. However, the lower absolute numbers of cycles sustained before failure, at 10 % gap opening and lower initial stiffness of HCS constructs as well as limitations of the study warrant further investigation before clinical use of the HCS for this indication can be recommended.

Explicit Dynamic Analysis of Tensional &amp;amp; Torsional Propagations on Composite Material with Dog Bone Shaped Testing Specimen

In general the composite are made by percentage of mixed or arrangement or concentration of material properties to increase the strength and advantages of the materials. Toeliminate the holding and gluing problems making the direct tensile strength test hard and torsional momentum loads to be applied, a new method of testing specimens prepared using 3d designing CATIA software to make the dog bone shape is assessed whether it could be applied to determine accurate direct tensile strength values and torsional loads over al alloy materials. In the project, i here considered 3 conditions, High percentage of aluminum alloy and low percentage of the silicon, Low percentage of aluminum alloy and high percentage of the silicon and Balanced percentage of aluminum alloy and silicon A series of modeling and analysis was performed using finite element method (ansys workbench) to investigate the deformation and stress to change of effect by material properties. A proper mechanical material property of the specimens was suggested and ideal failure of the dog bone shaped specimens was determined according to the results obtained from this study.

Long-term clinical and radiographic outcomes and patient satisfaction after adult spinal deformity correction.

Adult spinal deformity surgery has increased with the aging population and modern surgical approaches, although it has high complication and reoperation rates. The permanence of radiographic correction, mechanical complications, predictive factors for poor patient-reported outcomes, and patient satisfaction were analyzed. A total of 79 adult patients were retrospectively analyzed at baseline and 1-9 years after adult spinal deformity correction between 2007 and 2016. Patient-reported outcomes (Oswestry Disability Index, visual analog scale, and Scoliosis Research Society-30 scores), changes in radiographic alignment, indications for reoperation, predictors of poor outcomes according to the Oswestry Disability Index and Scoliosis Research Society-30 scores, and patient satisfaction with management were studied. Oswestry Disability Index and visual analog scale scores (p = 0.001), radiographic correction of thoracic kyphosis, lumbar lordosis, and pelvic retroversion (p ⩽ 0.001) and sagittal vertical axis (p = 0.043) were significantly better at 4-5 years of follow-up than at baseline. The risk for the first reoperation owing to mechanical failure of instrumentation or bone was highest within the first year, at 13.9% (95% confidence interval = 8.0%-23.7%), and 29.8% (95% confidence interval = 19.4%-43.9%) at the 5-year follow-up. Oswestry Disability Index and Scoliosis Research Society-30 total scores had a good correlation (r = -0.78; 95% CI = -0.86 to -0.68; p < 0.001). Satisfaction with management was correlated with patient-reported outcomes. Male sex and depression (p = 0.021 and 0.018, respectively) predicted poor outcomes according to the Oswestry Disability Index and/or Scoliosis Research Society-30 score. The achieved significant radiographic correction was maintained 5 years postoperatively. Despite reoperations, patient satisfaction and clinical outcomes were good. Depression and male sex predicted poor clinical outcomes.

Effect of ionizing radiation after-therapy interval on bone: histomorphometric and biomechanical characteristics.

This study aimed to evaluate the effects of radiotherapy on biomechanical, histomorphometric, and microstructural characteristics of bone, in diverse periods, compared with intact bone tissue. Eighteen adult male New Zealand rabbits were treated with a single radiation dose of 30Gy. The animals were randomly divided into six groups: NoIr, control group, no radiation, and five irradiated groups sacrificed after 24h (Ir24h), 7 (Ir7d), 14 (Ir14d), 21 (Ir21d), and 28 (Ir28d) days. After these periods, the animals were sacrificed and their tibias (n = 6) evaluated using three-point bending test to calculate the ultimate force, work to failure, and bone stiffness. Dynamic indentation test was used to quantify Vickers hardness and elasticity modulus of bone tissue. Micro-CT was used to analyze the cortical volume (CtV), cortical thickness (CtTh), and porosity (Ct.Po). Histomorphometric assessment was based on the lacunarity of bone tissue. Data were analyzed using one-way ANOVA and Kruskal-Wallis tests followed by Tukey, Dunnet, and Dunn's post-tests (P < 0.05). The ultimate force, work to failure, stiffness, elastic modulus, and Vickers hardness values of irradiated bone were significantly lower that non-irradiated bone. Irradiated bone showed significantly lower CtTh and CtV values and higher CtPo than non-irradiated bone. No significant difference was found for lacunarity between non-irradiated bone and irradiated bone. Ionizing radiation decreases normal anisotropy on microarchitecture of cortical bone, and increases bone fragility compared with non-irradiated bone. Further, these changes were seen after longer periods (e.g., 14 and 21days), and not immediately after radiation therapy. The radiotherapy reduces bone mechanical properties and the normal structure of organic and inorganic bone matrix. For studying the protocols to protect the radiotherapy effect using rabbit model, the use of the sacrificing period between 14 and 21days is recommended.

Rate and age-dependent damage elasticity formulation for efficient hip fracture simulations

Prediction of bone failure is beneficial in a range of clinical situations from screening of osteoporotic patients with high fracture risk to assessment of protective equipment against trauma. Computational efficiency is an important feature to consider when developing failure models for iterative applications, such as patient-specific diagnosis or design of orthopaedic devices. The authors previously developed a methodology to generate efficient mesoscale structural full bone models. The aim of this study was to implement a damage elasticity formulation representative of an elasto-plastic material model with age and strain rate dependencies compatible with these structural models. This material model was assessed in the prediction of femoral fractures in longitudinal compression and side fall scenarios. The simulations predicted failure loads and fracture patterns in good agreement with reported results from experimental studies. The observed influence of strain rate on failure load was consistent with literature. The superiority of a simplified elasto-plastic formulation over an elasto-brittle bone material model was assessed. This computationally efficient damage elasticity formulation was capable of capturing fracture development after onset.

Effect of the screw type (S2-alar-iliac and iliac), screw length, and screw head angle on the risk of screw and adjacent bone failures after a spinopelvic fixation technique: A finite element analysis.

PurposeSpinopelvic fixations involving the S2-alar-iliac (S2AI) and iliac screws are commonly used in various spinal fusion surgeries. This study aimed to compare the biomechanical characteristics, specifically the risk of screw and adjacent bone failures of S2AI screw fixation with those of iliac screw fixation using a finite element analysis (FEA).MethodsA three-dimensional finite element (FE) model of a healthy spinopelvis was generated. The pedicle screws were placed on the L3-S1 with three different lengths of the S2AI and iliac screws (60 mm, 75 mm, and 90 mm). In particular, two types of the S2AI screw, 15°- and 30°-angled polyaxial screw, were adopted. Physiological loads, such as a combination of compression, torsion, and flexion/extension loads, were applied to the spinopelvic FE model, and the stress distribution as well as the maximum von Mises equivalent stress values were calculated.ResultsFor the iliac screw, the highest stress on the screw was observed with the 75-mm screw, rather than the 60-mm screw. The bones around the iliac screw indicated that the maximum equivalent stress decreased as the screw length increased. For the S2AI screw, the lowest stress was observed in the 90-mm screw length with a 30° head angle. The bones around the S2AI screw indicated that the lowest stress was observed in the 90-mm screw length and a 15° head angle.ConclusionsIt was found that the S2AI screw, rather than the iliac screw, reduced the risk of implant failure for the spinopelvic fixation technique, and the 90-mm screw length with a 15° head angle for the S2AI screw could be biomechanically advantageous.

BUCKLING AND FAILURE ANALYSIS OF BONES IN HIP JOINT

Free body diagram is drawn to compute the various forces and torques acting on hip joint. The FEA models for hip joint and acetabular cup are drawn with the help of CT Scan reports. The stress distribution and deformations are then obtained by using finite element analysis. Contact stresses, contact area radius and maximum pressure are obtained. Modeling of the hip joint and acetabular cup was done and stress distribution was also determined. Since the thigh bone is slender, it was analyzed both manually and through software for buckling. This analysis is performed in order to predict the failure of bones in the hip joint.

Biomechanical evaluation of location and mode of failure in three screw fixations for a comminuted transforaminal sacral fracture model

BackgroundPelvic ring–comminuted transforaminal sacral fracture injuries are rotationally and vertically unstable and have a high rate of failure. ObjectiveOur study purpose was to use three-dimensional (3D) optical tracking to detect onset location of bone–implant interface failure and measure the distances and angles between screws and line of applied force for correlation to strength of pelvic fracture fixation techniques. Methods3D relative motion across sacral–rami fractures and screws relative to bone was measured with an optical tracking system. Synthetic pelves were used. Comminuted transforaminal sacral–rami fractures were modelled. Each pelvis was stabilised by either (1) two iliosacral screws in S1, (2) one transsacral screw in S1 and one iliosacral screw in S1 and (3) one trans-alar screw in S1 and one iliosacral screw in S1; groups 4–6 consisted of fixation groups with addition of anterior inferior iliac pelvic external fixator. Eighteen-instrumented pelvic models with right ilium fixed simulate single-leg stance. Load was applied to centre of S1 superior endplate. Five cycles of torque was initially applied, sequentially increased until permanent deformation occurred. Five cycles of axial load compression was next applied, sequentially increased until permanent deformation occurred, followed by axial loading to catastrophic failure. A Student t test was used to determine significance (p < 0.05). ResultsThe model, protocol and 3D optical system have the ability to locate how sub-catastrophic failures initiate. Our results indicate failure of all screw-based constructs is due to localised bone failure (screw pull-in push-out at the ipsilateral ilium–screw interface, not in sacrum); thus, no difference was observed when not supplemented with external fixation. ConclusionInclusion of external fixation improved resistance only to torsional loading. Translational Potential of this ArticlePatients with comminuted transforaminal sacral–ipsilateral rami fractures benefit from this fixation.

The Multi-Axial Failure Response of Porcine Trabecular Skull Bone Estimated Using Microstructural Simulations.

The development of a multi-axial failure criterion for trabecular skull bone has many clinical and biological implications. This failure criterion would allow for modeling of bone under daily loading scenarios that typically are multi-axial in nature. Some yield criteria have been developed to evaluate the failure of trabecular bone, but there is a little consensus among them. To help gain deeper understanding of multi-axial failure response of trabecular skull bone, we developed 30 microstructural finite element models of porous porcine skull bone and subjected them to multi-axial displacement loading simulations that spanned three-dimensional (3D) stress and strain space. High-resolution microcomputed tomography (microCT) scans of porcine trabecular bone were obtained and used to develop the meshes used for finite element simulations. In total, 376 unique multi-axial loading cases were simulated for each of the 30 microstructure models. Then, results from the total of 11,280 simulations (approximately 135,360 central processing unit-hours) were used to develop a mathematical expression, which describes the average three-dimensional yield surface in strain space. Our results indicate that the yield strain of porcine trabecular bone under multi-axial loading is nearly isotropic and despite a spread of yielding points between the 30 different microstructures, no significant relationship between the yield strain and bone volume fraction is observed. The proposed yield equation has simple format and it can be implemented into a macroscopic model for the prediction of failure of whole bones.

Stand-alone lumbar cage subsidence: A biomechanical sensitivity study of cage design and placement.

Background and objectiveSpinal degeneration and instability are commonly treated with interbody fusion cages either alone or supplemented with posterior instrumentation with the aim to immobilise the segment and restore intervertebral height. The purpose of this work is to establish a tool which may help to understand the effects of intervertebral cage design and placement on the biomechanical response of a patient-specific model to help reducing post-surgical complications such as subsidence and segment instability. MethodsA 3D lumbar functional spinal unit (FSU) finite element model was created and a parametric model of an interbody cage was designed and introduced in the FSU. A Drucker–Prager Cap plasticity formulation was used to predict plastic strains and bone failure in the vertebrae. The effect of varying cage size, cross-sectional area, apparent stiffness and positioning was evaluated under 500 N preload followed by 7.5 Nm multidirectional rotation and the results were compared with the intact model. ResultsThe most influential cage parameters on the FSU were size, curvature congruence with the endplates and cage placement. Segmental stiffness was higher when increasing the cross-sectional cage area in all loading directions and when the cage was anteriorly placed in all directions but extension. In general, the facet joint forces were reduced by increasing segmental stiffness. However, these forces were higher than in the intact model in most of the cases due to the displacement of the instantaneous centre of rotation. The highest plastic deformations took place at the caudal vertebra under flexion and increased for cages with greater stiffness. Thus, wider cages and a more anteriorly placement would increase the volume of failed bone and, therefore, the risk of subsidence. ConclusionsCage geometry plays a crucial role in the success of lumbar surgery. General considerations such as larger cages may be applied as a guideline, but parameters such as curvature or cage placement should be determined for each specific patient. This model provides a proof-of-concept of a tool for the preoperative evaluation of lumbar surgical outcomes.

Comparison of Different Pullout Test Setups for Evaluation of Bone–Implant Interfacial Strength of Anterior Lumbar Interbody Fusion Devices

Experimental approaches have been widely used to investigate the bone–implant interfacial strength of anterior lumbar interbody fusion (ALIF) devices. However, improper design of experimental jigs and inconsistencies in cadaveric specimens might significantly impede the evaluation of different ALIF device designs. Therefore, this study aimed to investigate and compare various test setups in terms of their feasibility for conducting pullout tests on ALIF devices. Three types of pullout test setups for evaluating the interfacial strength of the ALIF devices were investigated. Then, finite element models of the L4–L5 segment with different ALIF device designs were developed and numerical analysis was performed. Finally, the results from all the pullout test setups were compared with those obtained from numerical analysis. The results indicated that the quasi-material and boundary pullout test setup (QMBPTS), which considered the effects of the composite material of the test specimens and mimicked the lumbar posterior element’s anatomy and loading mechanism, revealed a more realistic bone failure pattern and interfacial pullout strength compared with the general pullout test setup and the quasi-boundary pullout test setup. The finite element models could accurately predict the experimental results obtained using the QMBPTS. It was confirmed that QMBPTS is a feasible and inexpensive pullout test setup for evaluating the bone–implant interfacial pullout strength of ALIF devices. Both the experimental and numerical approaches could provide useful information for designing a biomechanical experiment to solve bone–implant loosening problems.

Effect of modifications in mineralized collagen fibril and extra-fibrillar matrix material properties on submicroscale mechanical behavior of cortical bone.

A key length scale of interest in assessing the fracture resistance of bone is the submicroscale which is composed of mineralized collagen fibrils (MCF) and extra-fibrillar matrix (EFM). Although the processes through which the submicroscale constituents of bone contribute to the fracture resistance in bone have been identified, the extent of the modifications in submicroscale mechanical response due to the changes in individual properties of MCFs and EFM has not been determined. As a result, this study aims to quantify the influence of individual MCF and EFM material property modifications on the mechanical behavior (elastic modulus, ultimate strength, and resistance to failure) of bone at the submicroscale using a novel finite element modeling approach that incorporate 3D networks of MCFs with three different orientations as well as explicit representation of EFM. The models were evaluated under tensile loading in transverse (representing MCF separation) and longitudinal (representing MCF rupture) directions. The results showed that the apparent elastic modulus at the submicroscale under both loading directions for all orientations was only affected by the change in the elastic modulus of MCFs. MCF separation and rupture strengths were mainly dependent on the ultimate strength of EFM and MCFs, respectively, with minimal influence of other material properties. The extent of damage during MCF separation increased with increasing ultimate strength of EFM and decreased with increasing fracture energy of EFM with minimal contribution from elastic modulus of MCFs. For MCF rupture, there was an almost one-to-one linear relationship between the percent change in fracture energy of MCFs and the percent change in the apparent submicroscale fracture energy. The ultimate strength and elastic modulus of MCFs had moderate to limited influence on the MCF rupture fracture energy. The results of this study quantified the extent of changes that may be seen in the energy dissipation processes during MCF rupture and separation relative to the changes in the individual constituents of the tissue. This new knowledge significantly contributes to improving the understanding of how the material property alterations at the submicroscale that can occur due to diseases, age-related changes, and treatments affect the fracture processes at larger length scales.

Wear of historical polyethylenes in hip prostheses. Biomechanical success and a biological failure.

;Polyethylene wear debris induced osteolysis is a major cause of failure in artificial hip joints. Sub micrometre size particles are taken up by macrophages which are stimulated to release osteolytic cytokines such as TNFα. This leads to bone resorption, loosening and failure. In vitro cell culture studies have shown particles in the size range 0.1 to 1 micrometre to be at least six times more reactive than larger particles. Studies of historically used gamma irradiated in air polyethylene show increased wear rate with damaged femoral heads and with aged and oxidised polyethylene. The aged and oxidised polyethylene also produced a greater percentage of smaller particles leading to increased osteolytic potential. Combined tribological and biological simulation models have been developed for pre-clinical assessment of osteolytic potential of artificial hip joints.

Biomarkers for equine joint injury and osteoarthritis.

We report the results of a symposium aimed at identifying validated biomarkers that can be used to complement clinical observations for diagnosis and prognosis of joint injury leading to equine osteoarthritis (OA). Biomarkers might also predict pre-fracture change that could lead to catastrophic bone failure in equine athletes. The workshop was attended by leading scientists in the fields of equine and human musculoskeletal biomarkers to enable cross-disciplinary exchange and improve knowledge in both. Detailed proceedings with strategic planning was written, added to, edited and referenced to develop this manuscript. The most recent information from work in equine and human osteoarthritic biomarkers was accumulated, including the use of personalized healthcare to stratify OA phenotypes, transcriptome analysis of anterior cruciate ligament (ACL) and meniscal injuries in the human knee. The spectrum of "wet" biomarker assays that are antibody based that have achieved usefulness in both humans and horses, imaging biomarkers and the role they can play in equine and human OA was discussed. Prediction of musculoskeletal injury in the horse remains a challenge, and the potential usefulness of spectroscopy, metabolomics, proteomics, and development of biobanks to classify biomarkers in different stages of equine and human OA were reviewed. The participants concluded that new information and studies in equine musculoskeletal biomarkers have potential translational value for humans and vice versa. OA is equally important in humans and horses, and the welfare issues associated with catastrophic musculoskeletal injury in horses add further emphasis to the need for good validated biomarkers in the horse. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:823-831, 2018.