Biomechanical Analysis of the Fixation System for T-Shaped Acetabular Fracture

This study aims to evaluate the biomechanical mechanism of fixation systems in the most frequent T-shaped acetabular fracture using finite element method. The treatment of acetabular fractures was based on extensive clinical experience. Three commonly accepted rigid fixation methods (double column reconstruction plates (P × 2), anterior column plate combined with posterior column screws (P + PS), and anterior column plate combined with quadrilateral area screws (P + QS)) were chosen for evaluation. On the basis of the finite element model, the biomechanics of these fixation systems were assessed through effective stiffness levels, stress distributions, force transfers, and displacements along the fracture lines. All three fixation systems can be used to obtain effective functional outcomes. The third fixation system (P + QS) was the optimal method for T-shaped acetabular fracture. This fixation system may reduce many of the risks and limitations associated with other fixation systems

Clinical and radiological aspects of traumatic pelvic ring injury

Epidemiological data regarding High-Energy Traumatic Pelvic Ring Injury in Sweden was missing. Further, there was no data regarding current knowledge and level of experience of Swedish first line trauma officers about the management of traumatic pelvic ring injury. While conventional X-ray has been widely criticized as an optimal tool in assessment of pelvic ring injuries, a practical substitute has not been proposed. We planned to study epidemiological aspects of High Energy Traumatic Pelvic Ring Injury using data from the Karolinska Trauma Center. To assess first line trauma medical officer’s knowledge and level of experience regarding acute management of pelvic trauma. To investigate alternative practical options instead of conventional X-ray during the treatment of pelvic fractures. We used data from the Swedish National Trauma Registry (SweTrau). We used the Karolinska University Hospital´s Patient Notes and PACS. We used a questionnaire in order to assess Swedish trauma unit’s medical officers about acute management of pelvic trauma. We further used three dimensional models for image fusion and motion analysis in order to investigate symmetry of human pelvis and to investigate a pelvic fracture model. We found that the incidence of High Energy Traumatic Pelvic Ring Injury was about 3.5/100 000 inhabitants per year in Stockholm. The 30-day mortality was 7.8% and the 1 year mortality was 9%. The main cause of mortality was traumatic brain injury. Intentional injuries had a mortality rate of 15%. The reoperation frequency was 22%. Main cause of reoperation was due to metalwork problems, and a majority of them were potentially avoidable. We found that a majority of the Swedish first line trauma officers were aware of presence of a pelvic binder in their department and knew how to apply it, while there was more experience in the university hospitals. There was a general misconception regarding limitation of pelvic binders as 55% believed that a pelvic binder can stop an arterial bleeding. We were further able to show that human hemi pelvises are symmetrical and the 3D images of the contralateral hemi pelvis can be used for pre-operative templating. We were able to show that using fusion of serial 3D images of a pelvic model, translations of ±0.2 mm and rotations of ±0.2° could be detected. We can hereby conclude that monitoring 30-day mortality seems enough while studying high energy pelvic injuries. Intentional injuries need further future studies as per high mortality rate. Reoperation frequency following fixation of disrupted high energy pelvic fractures is high and needs addressing and early detection. Limitations of pelvic binders should be addressed during the trauma courses. Low dose CT-scan together with serial image fusion can be a future substitute for conventional X-ray. Human hemi pelvises are symmetrical and the contralateral side can be used for templating

Influence of Mechanical Conditions Driving Clinical Performance of Medical Device Constructs and Systems: A Dual-Study Approach in Human and Veterinary Fields for Optimization of the Clinical Outcome

The work performed focused on the investigation of human and veterinary orthopedic devices. The work was accomplished in two parts and focused on different device aspects, with emphasis on biomechanical implications. Part I covers the design, development, and implementation of a novel joint motion replicator and was divided into two sections: (a) Joint Motion Replicator design and development, and (b) Joint Motion Replicator implementation in a toggle rod construct ex vivo study application. The replicator provides a dual-axis, closed-loop, stepper-controlled mechanical testing environment capable of reproducing physiologically relevant loading conditions and dynamic processes. Additionally, the ex vivo study compared biomechanical performance of three toggle rod fixation systems using cyclical testing protocols simulating flexion/extension and abduction/adduction. Part II of this work covers human implantable orthopedic devices, specifically devices used to treat fifth metatarsal base fractures located at the metaphyseal-diaphyseal watershed junction (Jones fractures). This project compares the biomechanical performance of a well-known intramedullary screw construct with a plantar-lateral plating construct applied to replicated Jones fractures in paired cadaver foot specimens

Influence of Mechanical Conditions Driving Clinical Performance of Medical Device Constructs and Systems: A Dual-Study Approach in Human and Veterinary Fields for Optimization of the Clinical Outcome

The work performed focused on the investigation of human and veterinary orthopedic devices. The work was accomplished in two parts and focused on different device aspects, with emphasis on biomechanical implications. Part I covers the design, development, and implementation of a novel joint motion replicator and was divided into two sections: (a) Joint Motion Replicator design and development, and (b) Joint Motion Replicator implementation in a toggle rod construct ex vivo study application. The replicator provides a dual-axis, closed-loop, stepper-controlled mechanical testing environment capable of reproducing physiologically relevant loading conditions and dynamic processes. Additionally, the ex vivo study compared biomechanical performance of three toggle rod fixation systems using cyclical testing protocols simulating flexion/extension and abduction/adduction. Part II of this work covers human implantable orthopedic devices, specifically devices used to treat fifth metatarsal base fractures located at the metaphyseal-diaphyseal watershed junction (Jones fractures). This project compares the biomechanical performance of a well-known intramedullary screw construct with a plantar-lateral plating construct applied to replicated Jones fractures in paired cadaver foot specimens

Advanced Applications of Rapid Prototyping Technology in Modern Engineering

Rapid prototyping (RP) technology has been widely known and appreciated due to its flexible and customized manufacturing capabilities. The widely studied RP techniques include stereolithography apparatus (SLA), selective laser sintering (SLS), three-dimensional printing (3DP), fused deposition modeling (FDM), 3D plotting, solid ground curing (SGC), multiphase jet solidification (MJS), laminated object manufacturing (LOM). Different techniques are associated with different materials and/or processing principles and thus are devoted to specific applications. RP technology has no longer been only for prototype building rather has been extended for real industrial manufacturing solutions. Today, the RP technology has contributed to almost all engineering areas that include mechanical, materials, industrial, aerospace, electrical and most recently biomedical engineering. This book aims to present the advanced development of RP technologies in various engineering areas as the solutions to the real world engineering problems

Patient-Specific Implants in Musculoskeletal (Orthopedic) Surgery

Most of the treatments in medicine are patient specific, aren’t they? So why should we bother with individualizing implants if we adapt our therapy to patients anyway? Looking at the neighboring field of oncologic treatment, you would not question the fact that individualization of tumor therapy with personalized antibodies has led to the thriving of this field in terms of success in patient survival and positive responses to alternatives for conventional treatments. Regarding the latest cutting-edge developments in orthopedic surgery and biotechnology, including new imaging techniques and 3D-printing of bone substitutes as well as implants, we do have an armamentarium available to stimulate the race for innovation in medicine. This Special Issue of Journal of Personalized Medicine will gather all relevant new and developed techniques already in clinical practice. Examples include the developments in revision arthroplasty and tumor (pelvic replacement) surgery to recreate individual defects, individualized implants for primary arthroplasty to establish physiological joint kinematics, and personalized implants in fracture treatment, to name but a few

Experimental and Finite Element Studies of Acetabular Cement Pressurisation and Socket Fixation in Total Hip Replacement

PhDWith time, the rate of symptomatic acetabular component loosening accelerates and overtakes that of the femoral component as the principal reason for the revision of total hip replacement. In the femur extensive study has shown that cement pressurisation and good preparation of the bone bed improves the survival rate, but acetabular fixation requires further investigation. Production of cement pressure in the acetabulum is anatomically difficult. Pressurisation with conventional and novel designs of cement pressurisers has been compared to manual techniques and component insertion. The pressurisers increased peak and mean pressures and pressure duration. Finite element modethng of cup insertion showed that flanges and higher insertion rates increased cement penetration into cancellous bone. Per-operatively, one design of pressuriser produced cement pressures comparable to those found in the laboratory. Structural finite element modelling of the natural hip indicated that the subehondral plate and the relatively dense cancellous bone supporting it distribute the joint contact force into the medial and lateral pelvic cortices. A perfectly bonded cemented polyethylene cup stiffened the acetabulum so that more load was transferred directly to the cortices at the acetabular rim, with consequent interface stress concentrations. However, complimentary experimental studies using a dynamic joint simulator and a servo-hydraulic materials testing machine suggested that perfect fixation between cement and bone at the rim was not possible, even under laboratory conditions. Debonding of the cement bone interface at the rim, where dense bone prevents cement interdigitation, allowed micromotion. Since the clinical mechanism of failure of the acetabular component appears to be progressive debonding, from rim to apex, of the cement-bone interface, these studies support the initiation of the failure mechanism by mechanical factors, which may then allow the ingress of wear debris. The experimental studies suggested that the use of pressurisers reduces the amount of micromotion and thus may improve the long term stability of the interface