Odontoid fracture of the second cervical vertebra (C2) is the most common spinal fracture type in elderly patients. However, very little is known about the biomechanical fracture mechanisms, but could play a role in fracture prevention and treatment. This study aimed to investigate the biomechanical competence and fracture characteristics of the odontoid process. A total of 42 human C2 specimens (14 female and 28 male, 71.5 ± 6.5 years) were scanned via quantitative computed tomography, divided in 6 groups (n = 7) and subjected to combined quasi-static loading at a rate of 0.1 mm/s until fracturing at inclinations of −15°, 0° and 15° in sagittal plane, and −50° and 0° in transverse plane. Bone mineral density (BMD), specimen height, fusion state of the ossification centers, stiffness, yield load, ultimate load, and fracture type according to Anderson and d'Alonzo were assessed. While the lowest values for stiffness, yield, and ultimate load were observed at load inclination of 15° in sagittal plane, no statistically significant differences could be observed among the six groups (p = 0.235, p = 0.646, and p = 0.505, respectively). Evaluating specimens with only clearly distinguishable fusion of the ossification centers (n = 26) reveled even less differences among the groups for all mechanical parameters. BMD was positively correlated with yield load (R² = 0.350, p < 0.001), and ultimate load (R² = 0.955, p < 0.001), but not with stiffness (p = 0.070). Type III was the most common fracture type (23.5%). These biomechanical outcomes indicate that load direction plays a subordinate role in traumatic fractures of the odontoid process in contrast to BMD which is a strong determinant of stiffness and strength. Thus, odontoid fractures appear to result from an interaction between load magnitude and bone quality.
Cervical spine fractures are frequent in impact sports, such as rugby union. The consequences of these fractures can be devastating as they can lead to paraplegia, tetraplegia and death. Many studies have been conducted to understand the injury mechanisms but the relationship between player cervical spine posture and fracture pattern is still unclear. The aim of this study was to evaluate the influence of player cervical spine posture on fracture pattern due to an impact load. Nineteen porcine cervical spines (C2 to C6) were dissected, potted in PMMA bone cement and mounted in a custom made rig. They were impacted with a mean load of 6 kN. Eight specimens were tested in an axial position, five in flexion and six in lateral bending. All specimens were micro-CT imaged (Nikon XT225 ST Scanner, Nikon Metrology, UK) before and after the tests, and the images were used to assess the fracture patterns. The injuries were classified according to Allen-Ferguson classification system by three independent observers. The preliminary results showed that the main fracture modalities were consistent with those seen clinically. The main fractures for the axial orientation were observed in C5-C6 level with fractures on the articular process and endplates. These findings support the concept that the fracture patterns are related to the spine position and give an insight for improvements on sports rules in order to reduce the risk of injury.
Modification in joint loading, and specifically shear stress, is found to be an important mechanical factor in the development of osteoarthritis (OA). Cartilage shear stresses can be investigated using finite element (FE) modelling, where typically in vivo joint loading as measured by an instrumented hip prosthesis is used as boundary condition. However, subject-specific gait characteristics substantially affect joint loading. The goal of this study is to investigate the effect of subject-specific joint loading as calculated using a subject-specific musculoskeletal model and integrated motion capture data on acetabular shear stress. Three healthy control subjects walked at self-selected speed while measuring marker trajectories (Vicon, Oxford Metrics, UK) and force data (two AMTI force platforms; Watertown, MA). A subject-specific MRI-based musculoskeletal model consisting of 14 segments, 19 degrees of freedom and 88 musculotendon actuators, and including wrapping surfaces around the hip joint, was used. All analyses were performed in OpenSim 3.1. The model was scaled to the dimensions of each subject using the marker positions of a static pose. A kalman smoother procedure was used to calculate joint angles. Muscle forces were calculated using static optimization, minimizing the sum of squared muscle activations, and hip contact forces (HCF) were calculated and normalized to body weight (BW). To calculate shear stress, HCFs and joint angles calculated during the stance phase of gait were imposed to a hip finite element model (hip_n10rb) using FFEbio 2.5. In the model, femoral and acetabular cartilage were represented using the Mooney-Rivlin formulation (c1=6.817, bulk modulus=1358.86) and the pelvis and femur bones as rigid bodies. Peak HCF as well as maximal acetabular shear stress, magnitude and location, and the HCF at the time of maximal shear stress were compared between subjects.Introduction
Methods
Rib fractures (RF) represent the most common bone fracture after blunt trauma, occurring in 10–20% of all trauma patients and leading to concomitant injuries of the inner organs in severe cases. However, a standardized classification system for serial rib fractures (SRF) does still not exist. Basic knowledge about the facture pattern of SRF would help to predict organ damage, support forensic medical examinations, and provide data for in vitro and in silico studies regarding the thoracic stability. The purpose of our study was therefore to identify specific SRF patterns after blunt chest trauma. All SRF cases (≥3 subsequent RF) between mid-2008 and end of 2015 were extracted from the CT database of our University Hospital (n=383). Fractures were assigned to anterior, antero-lateral, lateral, postero-lateral, and posterior location within the transverse plane (36° each) using an angular measuring technique (reliability ±2°). Rib level, fracture type (transverse, oblique, multifragment, infracted), as well as degree of dislocation (none, </≥ rib width) were recorded and each related to the cause of accident. In total, 3747 RF were identified (9.7 per patient, ranging from 3 (n=25) to 33 (n=1)). On average, most RF occurred in crush/burying injuries (15.9, n=13) and pedestrian accidents (12.2, n=14), least in car/truck accidents (8.8, n=76). Altogether, RF gradually increased from rib 1 (n=140) towards rib 5 (n=517) and then decreased towards rib 12 (n=49), showing a bell-shaped distribution. More RF were detected on the left thorax (n=2027) than on the right (n=1720). Overall, most RF were found in the lateral (33%) and postero-lateral (29%) segment. Posterior RF mostly occurred in the lower thorax (63%), whereas anterior (100%), antero-lateral (87%), and lateral (63%) RF mostly appeared in the upper thorax. RF were distributed symmetrically to the sagittal plane, showing a hotspot (up to 98 RF) at rib levels 4 to 7 in the lateral segment and rib level 5 in the antero-lateral segment. In the car/truck accident group, 47% of all RF were in the lateral segment, in case of frontal collision (n=24) even 60%. Fall injuries (n=141) entailed mostly postero-lateral RF (35%). In case of falls >3 m (n=45), 48% more RF were detected on the left thorax compared to the right. CPR related SRF (n=33) showed a distinct fracture pattern, since 70% of all RF were located antero-laterally. Infractions were the most observed fracture type (44%), followed by oblique (25%) and transverse (18%) fractures, while 46% of all RF were dislocated (15% ≥ rib width). SRF show distinct fracture patterns depending on the cause of accident. Additional data should be collected to confirm our results and to establish a SRF classification system.
Clinical investigations show that the cervical spine presents wide inter-individual variability, where its motion patterns and load sharing strongly depend on the anatomy. The magnitude and scope of cervical diseases, including disc degeneration, stenosis, and spondylolisthesis, constitute serious health and socioeconomic challenges that continue to increase along with the world”s growing aging population. Although complex exact finite element (FE) modeling is feasible and reliable for biomechanical studies, its clinical application has been limited as it is time-consuming and constrained to the input geometry, typically based on one or few subjects. The objective of this study was twofold: first to develop a validated parametric subject-specific FE model that automatically updates the geometry of the lower cervical spine based on different individuals; and second to investigate the motion patterns and biomechanics associated with typical cervical spine diseases. Six healthy volunteers participated in this study upon informed consent. 26 parameters were identified and measured for each vertebra in the lower cervical spine from Lateral and AP radiographs in neutral, flexion and extension viewpoints in the standing position. The lower cervical FE model was developed including the typical vertebrae (C3-C7), intervertebral discs, facet joints, and ligaments using ANSYS (PA, USA). In order to validate the FE model, the bottom surface of C7 was fixed, and a 73.6N preload together with a 1.8 N.m pure moment were input into the model in both flexion and extension. The results were compared to experimental studies from literature. Disc degeneration disease (DDD) was used as an example, where the geometry of C5-C6 disc was changed in the model to simulate 3 different grades of disc degeneration (mimicking grades 1 to 3), and the resulting biomechanical responses were evaluated. The average ranges of motion (ROM) were found to be 4.84 (±0.73) degrees and 5.36 (±0.68) degrees for flexion and extension for C5-C6 functional unit, respectively, in alignment with literature. The total ROM of the model with disc generation grades 2 and 3 was found to have decreased significantly as compared to the intact model. In contrast, the axial stresses on the degenerated discs were significantly higher than the intact discs for all 3 degeneration grades. Our preliminary results show that this novel validated subject-specific FE model provides a potential valuable tool for noninvasive time and cost effective analyses of cervical spine biomechanical (kinematic and kinetic) changes associated with various diseases. The model also provides an opportunity for clinicians to use quantitative data towards subject-specific informed therapy and surgical planning. Ongoing and future work includes expanding the studied population to investigate individuals with different cervical spine afflictions.
Rehabilitation systems based on inertial measurement units (IMU) and bio-feedbacks are increasingly used in many different settings for patients with neurological disorders such as Parkinson disease or balance impairment, and more recently for functional recover after orthopedic surgical interventions or injuries especially concerning the lower limb. These systems claim to provide a more controlled and correct execution of the motion exercises to be performed within the rehabilitation programs, hopefully resulting in a better outcomes with respect to the traditional direct support of a physical therapists. In particular recruitment of specific muscles during the exercise is expression of its correct and finalized execution. The objective of this study was to compare muscular activation patterns of relevant lower limb muscles during different exercises performed with traditional rehabilitation and with a new validated system based on IMU and biofeedback (Riablo, Corehab, Trento, Italy). Twelve healthy subjects (mean age 28.1 ± 3.9, BMI 21.8± 2.1) were evaluated in a rehabilitation center. Muscular activation pattern of gluteus maximum, gluteus medium, rectus femoris and biceps femoris was recorded through surface EMG (Cometa; Milan) during six different motion tasks: hip abduction in standing position, lunge, hip flexion with extended knee in standing position, lateral lunge, hip abduction with extended knee in lateral decubitus, squat. Subjects performed 10 repetitions of each task for a total of 100 repetitions per motion task, with and without Riablo System as well as during standard rehabilitation. An additional IMU was positioned on the shank in order to detect beginning and end of each repetition. A single threshold algorithm was used to identify muscle activation timing. During hip abduction in standing position, gluteus maximum and rectus femoris showed a better and longer activation pattern while using Riablo compared to traditional rehabilitation. Gluteus medium showed a similar activation pattern whereas biceps femoris showed no activation from 30% to 80% using Riablo. During squat, rectus femoris and biceps femoris had a similar activation pattern with and without Riablo whereas gluteus maximum and gluteus medium showed a better activation pattern while using Riablo. The recent development of innovative rehabilitation systems meets the need of manageable, reliable and efficient instruments able to reduce rehabilitation costs but with the same good clinical outcomes. Muscular activation patterns of relevant lower limb muscles during selected motion tasks reveal their correct execution. The use of this new rehabilitation system based on IMU and biofeedback seems to allow a more selective and effective muscular recruitment, likely due to the more correct and controlled execution of the exercise, particularly for the identification and interdiction of possible compensation mechanisms.
Civilian fractures have been extensively studied with in an attempt to develop classification systems, which guide optimal fracture management, predict outcome or facilitate communication. More recently, biomechanical analyses have been applied in order to suggest mechanism of injury after the traumatic insult, and predict injuries as a result of a mechanism of injury, with particular application to the field so forensics. However, little work has been carried out on military fractures, and the application of civilian fracture classification systems are fraught with error. Explosive injuries have been sub-divided into primary, secondary and tertiary effects. The aim of this study was to 1. determine which effects of the explosion are responsible for combat casualty extremity bone injury in 2 distinct environments; a) in the open and b) enclosed space (either in vehicle or in cover) 2. determine whether patterns of combat casualty bone injury differed between environments Invariably, this has implications for injury classification and the development of appropriate mitigation strategies. All ED records, case notes, and radiographs of patients admitted to the British military hospital in Afghanistan were reviewed over a 6 month period Apr 08-Sept 08 to identify any fracture caused by an explosive mechanism. Paediatric cases were excluded from the analysis. All radiographs were independently reviewed by a Radiologist, a team of Military Orthopaedic Surgeons and a team of academic Biomechanists, in order to determine the fracture classification and predict the mechanism of injury. Early in the study it became clear that due to the complexity of some of the injuries it was inappropriate to consider bones separately and the term ‘Zone of Insult’ (ZoI) was developed to identify separate areas of injury.Introduction
Method
The purpose is to evaluate the effects of internet usage on new patient referral patterns to identify optimal patient recruitment and communication. Overall, social networking and internet may be an effective way for surgeons to recruit a wider patient population. Prior studies in other medical specialties have shown that social networking and internet usage has become an increasingly important means of patient communication and referral. However, this information is lacking in the orthopaedics literature. In this study, we evaluate the means by which new patients arrive at orthopaedic clinics in a major academic center. The purpose is to evaluate the effects of internet or social media usage on new patient referral patterns to identify avenues to optimise patient recruitment and communication.Summary Statement
Introduction
Primary mechanical stability is important with uncemented THR because early migration is reduced, leading to more rapid osseointegration between the implant and bone. Such primary mechanical stability is provided by the design features of the device. The aim of this study was to compare the migration patterns of two uncemented hip stems, the Furlong Active and the Furlong HAC stem; the study was designed as a randomised control trial. The implants were the Furlong HAC, which is an established implant with good long term results, and the Furlong Active, which is a modified version of the Furlong HAC designed to minimise stress concentrations between the implant and bone, and thus to improve fixation. The migration of 43 uncemented femoral components for total hip replacement was measured in a randomised control trial using Roentgen Stereophotogrammetric Analysis (RSA) over two years. Twenty-three Furlong HAC and twenty Furlong Active stems were implanted into 43 patients. RSA examinations were carried out post-operatively, and at six months, 12 months and 24 months post-operatively. The patients stood in-front of a purpose made calibration frame which contained accurately positioned radio-opaque markers. From the obtained images, the 3-D positions of the prosthesis and the host bone were reconstructed. Geometrical algorithms were used to identify the components of the implant. These algorithms allowed the femoral component to be studied without the need to attach markers to the prosthesis. The migration was calculated relative to the femoral coordinate system representing the anterior-posterior (A-P), medial-lateral (M-L) and proximal-distal (P-D) directions respectively. Distal migration was termed subsidence.Introduction
Materials and methods
A preliminary study to compare continuous sagittal plane lumbar inter-vertebral kinematics in 10 healthy volunteers in recumbent and weight bearing configurations using quantitative fluoroscopy. There are no direct Study Purpose
Background
Human mesenchymal stem cells (hMSCs) have the capacity to differentiate into adipocytes, chondrocytes, or osteoblasts, and are an exciting tool to be used in regenerative medicine and surgery. By manipulating the surface structure and physical properties of a biomaterial on which hMSCs can be incorporated, the biological response of these cells at the implant site can be controlled. Whilst both topography and surface stiffness are known to influence differentiation of hMSC's, little is understood of the molecular mechanisms that underpin these responses. In this study we use immunofluorescence and confocal microscopy techniques to assess the change in both the abundance and the distribution of H3K9me2 or H3K9ac patterns in hMSCs cultured on materials with controlled topography and stiffness, under basal and osteogenic conditions. These data demonstrate that levels and localisation of both H3K9me2 and H3K9ac alter in hMSCs cultured on the different substrates and that these surfaces dictate the response to osteogenic stimuli, suggesting that the control of cytoskeletal structure can be linked to chromatin activity. This regulation of histone modification by MSC interaction with the surrounding scaffold provides not only a mechanistic link to the control of cell fate but also the opportunity to design biomaterials that better influence cell activity.
Pincer deformities are involved in the genesis of femoro-acetabular impingement (FAI). Radiographic patterns suggestive of pincer deformities are common among general population. Prevalence of the pincer deformities among general population may be overestimated if only plain radiographs are considered. Pincer deformities (coxa profunda, protrusio acetabuli, global retroversion, isolated cranial over-coverage) have been advocated as a cause of femoro-acetabular impingement (FAI) and early hip osteoarthritis (OA). Different radiographic patterns may advocate the presence of a pincer deformity. The prevalence of these radiographic patterns among general adult population, as their role in early hip OA, is poorly defined.Summary Statement
Background
Considerable evidence exists that aseptic loosening is initiated by wear particles that recruit macrophages and stimulate their production of pro-inflammatory cytokines. The cytokines primarily act indirectly by inducing production of RANKL, which stimulates osteoclast differentiation, osteolysis, and inflammatory bone loss. There is also considerable evidence that activation of macrophage Toll-like Receptors (TLRs) contributes to this cascade of events. It is however controversial whether bacterially-derived immunostimulatory molecules known as Pathogen-Associated Molecular
Cryotherapy is often applied after injuries of synovial joints. Although positive clinical effects on periarticular swelling and pain are well known, the effects on molecular processes of cartilage and synovial cells remained largely unknown so far. Therefore, the hypothesis was tested that hypothermia alleviates the synovial reaction and prevents chondrocyte death as well as cartilage destructive processes after blunt trauma. Human articular cartilage and synovial tissue was obtained with informed consent from patients undergoing knee joint replacement. Cartilage explants from macroscopically intact cartilage were impacted by a drop-tower apparatus with defined energy (0.59J) and cultivated for 24h or 7d at following temperature conditions: 2h, 16h or throughout at 27°C and afterwards or throughout at 37°C. Furthermore, human fibroblast-like synoviocytes (FLS) were stimulated with conditioned medium from traumatized cartilage (t-CM) and cultivated as indicated above up to 4d. Effects of hypothermia were evaluated by live/dead assay, gene expression (RQ-PCR), and type II collagen synthesis/cleavage as well as release of MMP-2, MMP-13 and IL-6 on protein level (ELISA, gelatin zymography). Statistical analysis was performed by 2-way ANOVA. The experimental study was performed in the research laboratory of the Orthopedic Department, University Hospital Ulm, Germany. Hypothermic treatment significantly improved chondrocyte viability 7d after blunt cartilage trauma (2h: p=0.016; 16h: p=0.036; throughout: p=0.039). 2h posttraumatic hypothermia attenuated expression of MMP-13 (m-RNA: p=0.012; protein: p=0.024). While type II collagen synthesis was significantly increased after 16h hypothermia, MMP-13 expression (mRNA: p=0.003; protein: p<0.001) and subsequent cleavage of type II collagen (p=0.049) were inhibited. Continuous hypothermia for 7d further significantly suppressed MMP release (proMMP-2, active MMP-2 and MMP-13) and type II collagen breakdown. On day 4 t-CM stimulated FLS revealed significantly suppressed gene expression of matrix-destructive enzymes (16h: ADAMTS-4; throughout: ADAMTS-4, MMP-3, MMP-13) and by trend reduced IL-6 expression in case of 16h or continuous hypothermia. Overall, hypothermia for only 2h and/or 16h after blunt cartilage trauma exhibited significant cell- and matrix-protective effects and promoted anabolic activity of surviving chondrocytes. Expression of matrix-destructive enzymes by FLS stimulated with Danger Associated Molecular
