Biomechanical Considerations Research Articles

Extended trochanteric osteotomy: improving the access and reducing the risk in revision THA.

This review article presents a comprehensive literature review regarding extended trochanteric osteotomy (ETO).The history, rationale, biomechanical considerations as well as indications are discussed.The outcomes and complications as reported in the literature are presented, discussed and compared with our own practice.Based on the available evidence, we present our preferred technique for performing ETO, its fixation, as well as post-operative rehabilitation.The ETO aids implant removal and enhanced access. Reported union rate of ETO is high. The complications related to ETO are much less frequent than in cases when accidental intra-operative femoral fracture occurred that required fixation.Based on the literature and our own experience we recommend ETO as a useful adjunct in the arsenal of the revision hip specialist.Cite this article: EFORT Open Rev 2020;5:104-112. DOI: 10.1302/2058-5241.5.190005

Masticatory muscle function affects the pathological conditions of dentofacial deformities.

SummaryThe causes of dentofacial deformities include various known syndromes, genetics, environmental and neuromuscular factors, trauma, and tumors. Above all, the functional effects of muscles are important, and deformation of the mandible is often associated with a mechanical imbalance of the masticatory muscles.With the vertical position of the face, weakness of the sling of the masseter muscle and medial pterygoid muscle causes dilatation of the mandibular angle. In patients with a deep bite, excessive function of the masticatory muscles is reported.Myosin heavy chain (MyHC) properties also affect jawbone morphology. In short-face patients, the proportion of type II fibers, which are fast muscles, is high. The proportions of muscle fiber types are genetically determined but can be altered by postnatal environmental factors. Orthognathic surgery may results in the transition of MyHC to type II (fast) fibers, but excessive stretching enhances the release of inflammatory mediators and causes a shift toward a greater proportion of slow muscle fibers. This feature can be related to postoperative relapse.Bones and muscles are in close crosstalk, and it may be possible to use biochemical approaches as well as biomechanical considerations for the treatment of jaw deformities.

Treating metatarsalgia: current concepts

The objective of this paper is to describe the anatomical and biomechanical considerations for treating metatarsalgia. We describe a method of classification incorporating the causes and lead onto a comprehensive description of the treatment of metatarsalgia. Important clinical findings and investigations are discussed in treating this common pathology and a case study used as an example to illustrate the above. This paper highlights the complex nature of metatarsalgia and describes the factors a surgeon needs to consider prior to embarking on treatment.

Behavioural compass: animal behaviour recognition using magnetometers

BackgroundAnimal-borne data loggers today often house several sensors recording simultaneously at high frequency. This offers opportunities to gain fine-scale insights into behaviour from individual-sensor as well as integrated multi-sensor data. In the context of behaviour recognition, even though accelerometers have been used extensively, magnetometers have recently been shown to detect specific behaviours that accelerometers miss. The prevalent constraint of limited training data necessitates the importance of identifying behaviours with high robustness to data from new individuals, and may require fusing data from both these sensors. However, no study yet has developed an end-to-end approach to recognise common animal behaviours such as foraging, locomotion, and resting from magnetometer data in a common classification framework capable of accommodating and comparing data from both sensors.MethodsWe address this by first leveraging magnetometers’ similarity to accelerometers to develop biomechanical descriptors of movement: we use the static component given by sensor tilt with respect to Earth’s local magnetic field to estimate posture, and the dynamic component given by change in sensor tilt with time to characterise movement intensity and periodicity. We use these descriptors within an existing hybrid scheme that combines biomechanics and machine learning to recognise behaviour. We showcase the utility of our method on triaxial magnetometer data collected on ten wild Kalahari meerkats (Suricata suricatta), with annotated video recordings of each individual serving as groundtruth. Finally, we compare our results with accelerometer-based behaviour recognition.ResultsThe overall recognition accuracy of > 94% obtained with magnetometer data was found to be comparable to that achieved using accelerometer data. Interestingly, higher robustness to inter-individual variability in dynamic behaviour was achieved with the magnetometer, while the accelerometer was better at estimating posture.ConclusionsMagnetometers were found to accurately identify common behaviours, and were particularly robust to dynamic behaviour recognition. The use of biomechanical considerations to summarise magnetometer data makes the hybrid scheme capable of accommodating data from either or both sensors within the same framework according to each sensor’s strengths. This provides future studies with a method to assess the added benefit of using magnetometers for behaviour recognition.

Biomaterial and biomechanical considerations to prevent risks in implant therapy.

This paper is aimed to present a biomaterials perspective in implant therapy that fosters improved bone response and long-term biomechanical competence from surgical instrumentation to final prosthetic rehabilitation. Strategies to develop implant surface texturing will be presented and their role as an ad hoc treatment discussed in light of the interplay between surgical instrumentation and implant macrogeometric configuration. Evidence from human retrieved implants in service for several years and from in vivo studies will be used to show how the interplay between surgical instrumentation and implant macrogeometry design affect osseointegration healing pathways, and bone morphologic and long-term mechanical properties. Also, the planning of implant-supported prosthetic rehabilitations targeted at long-term performance will be appraised from a standpoint where personal preferences (eg, cementing or screwing a prosthesis) can very often fail to deliver the best patient care. Lastly, the acknowledgement that every rehabilitation will have its strength degraded over time once in function will be highlighted, since the potential occurrence of even minor failures is rarely presented to patients prior to treatment.

Musculoskeletal modeling of user groups for virtual product and process development

Although biomechanical digital human models find their way into virtual engineering processes, biomechanical considerations are currently still unrecognized to a large extent. One major obstacle lies in the fact that even though subject-specific modeling procedures are developed, virtual user groups or populations are still missing. The objective of this contribution is to create such groups of musculoskeletal models. Therefore, a modeling procedure based upon population data is described. First of all, two generic three-dimensional models, one with female and one with male average anthropometric dimensions, were obtained. These models constitute the starting point for the following model adjustment phases. Evenly distributed dimensionless values for gender, age, height, mass, range of motion and strength are sampled and translated into more expressive parameters for the mentioned modeling domains serving as input data for the creation of each individual model of the desired population or user group. The most sophisticated step of the adaption is the strength mapping aiming to create models matching arbitrary target joint torques. Finally, the models’ maximal strength is assessed in a manual material handling task and compared to empirical strength data. The approach is shown using the example of the German population.

The influence of aging on the insertion of the Achilles tendon: A magnetic resonance study.

The aim of this study was to examine the variations of the Achilles tendon (AT) insertion point into the calcaneal bone (CB) in relation to age and sex using magnetic resonance imaging (MRI). A total of 202 foot and ankle MRIs were reviewed and patients were allocated into three age groups: (I) <18, (II) 18-65, and (III) >65 years. All measurements were obtained on a mid-sagittal scan. The mean measurement values were used to assess the relationships among the AT insertion point, sex, and age. Our main findings revealed that (1) the distance between the most inferior point of the CB and the most inferior part of the AT insertion into the CB increases with age, (2) the height of the AT insertion into the posterior aspect of the CB decreases with age, and (3) the length of the AT insertion into the posterior aspect of the CB decreases with age. The terminal insertion point of the AT on the CB in younger subjects was more distal, whereas in older individuals it was more proximal. These results could help in developing novel strategies for the treatment and prophylaxis of AT injuries in particular patient age groups. Anatomical data about the AT insertion are crucial for developing a computer model of the AT and for biomechanical considerations regarding this tendon. Clin. Anat. 33:545-551, 2020. © 2019 Wiley Periodicals, Inc.

Biomechanical and radiological considerations for correction of varus deformity in primary osteoarthritis during total knee arthroplasty

Biomechanical and radiological considerations for correction of varus deformity in primary osteoarthritis during total knee arthroplasty

2D1-5 Biomechanical consideration of object's initial orientation and work movement in manual handling tasks

2D1-5 Biomechanical consideration of object's initial orientation and work movement in manual handling tasks

Total Hip Arthroplasty After Spinal Fusion Surgery.

Given the close functional connection between the hip and the spine, their simultaneous degenerative pathology is a common problem seen in orthopedic patients and has been termed the "hip spine syndrome". Demographic change and an increasing number of operations have led to more patients who have undergone both total hip arthroplasty and spondylodesis especially of the lumbar spine. Studies have shown significant dislocation rates in this cohort of as high as almost 30%. Biomechanical studies and considerations show that spinal surgery directly influences the functional acetabular position and, consequently, the position of the acetabular cup, making the correct implantation challenging for the hip surgeon. Spinal fusion affects not only the biomechanics of the spine but also of the hip joint and, for that reason, must accordingly be taken into account when planning total hip arthroplasty.

Implications of Space Suit Injury Risk for Developing Computational Performance Models.

INTRODUCTION: Although a space suit is a technological feat sustaining human life outside the spacecraft, working in the space suit environment can lead to musculotendon and soft tissue injuries in astronauts. In this literature review, we consider the injury risk mechanisms for human-space suit interactions. We first present a review of space suit injury risk founded in empirical, statistical, and experimental studies. We then review efforts in computational modeling of a human and space suit. As the interpretation of models for injury risk has not previously been defined, a review is presented of biomechanical considerations of injury risk to the tissue and joints based on previously observed space suit injuries. A review of risk assessment in occupational health in the workplace is then presented, an adjacent area that informs relevant measures of consideration for human-space suit applications. Finally, we discuss how the work-to-date can inform continued efforts in minimizing risk of musculoskeletal injury to the human when using a space suit. From the literature, this review concludes space suits cause biomechanical alterations, inducing musculoskeletal injury. Combining occupational health kinematic constraints with computational models could enable a trade space evaluation on space suited biomechanics to reduce risk mechanisms. Future work, though, is required to enable computational models to be predictive of individual injury risk. Our findings show there are significant gaps in our current knowledge on tissue injuries that preclude biomechanical models from being used directly as an injury risk assessment model. This review identifies how risk factor monitoring and modeling will enable improved space suit design and evaluation.Stirling L, Arezes P, Anderson A. Implications of space suit injury risk for developing computational performance models. Aerosp Med Hum Perform. 2019; 90(6):553-565.

Why introducing biomechanical considerations into obstetrical management of women from pregnancy to delivery?

Why introducing biomechanical considerations into obstetrical management of women from pregnancy to delivery?

Bioartificial liver: biomechanical considerations

Liver tissue engineering aims at the reconstruction in vitro of a tissue mimicking as much as possible the organ functions. For the liver, the challenge is very high since this organ is in charge o...

Re-expansion of Osteoporotic Compression Fractures Using Bilateral SpineJack Implants: Early Clinical Experience and Biomechanical Considerations.

Thoraco-lumbar osteoporotic compression fractures have a higher incidence of continued collapse with development of deformity and progression to vertebra plana when untreated and even after vertebral augmentation (VA) or balloon kyphoplasty (BKP). Even when there is the restoration of height and improvement in angulation, multiple long-term follow-up series have repeatedly documented that over time, many patients lose the initial height correction and in a smaller group the vertebral body re-collapses leading to the development of progressive deformity with an increased risk for adjacent level fractures. At first, larger balloons and more cement were used to try and avoid these problems, but it did not reduce the risk of adjacent fractures. Several procedures were developed to place various types of intervertebral implants combined with bone cement to maintain the initial height correction. Initial studies with these implants showed a reduction in adjacent level fractures but the systems did not proceed to market. The SpineJackR (SJ) system (Stryker Corp, Kalamazoo, MI), consisting of bilateral expandable titanium implants supplemented with bone cement, was first used approximately 10 years ago in Europe and recently gained FDA approval in the United States. This system provides more symmetric and balanced lateral and anterior support and is effective with lesser amounts of bone cement compared to BKP. Follow-up studies have documented that there is equal or better pain control, with better long-term results based both on maintaining vertebral height restoration and deformity correction. Most importantly, statistically it clearly reduces the risk of adjacent level fractures by at least 60%. The biomechanical effects of intravertebral implants for osteoporotic fractures in regard to the risk of adjacent level fractures and preliminary experience with the use of the SJ is reviewed.

Congenital pseudarthrosis of the tibia: biological and biomechanical considerations to achieve union and prevent refracture.

Congenital pseudarthrosis of the tibia (CPT) is likely to be a primary periosteal disease and secondary bone disease. The primary goal of treatment is to obtain union, correct the diaphyseal deformity, correct any proximal fibular migration and prevent refracture. The pathobiology demonstrates increased osteoclasis by the surrounding fibrous hamartoma and reduced osteogenesis and bone morphogenic protein production by the bone. This leads to a loss of remodelling potential and gradual bowing and atrophy of the bone with eventual fracture of the tibia and or fibula. This recommends the synergistic use of bisphosphonates and bone morphogenic protein. The pathomechanics of CPT implicate the anterolateral bowing, narrow diameter of the atrophic bone ends and proximal fibular migration. These biomechanical factors can be addressed by means of straightening of the deformity, intramedullary support of both bones, stable fixation and reduction of proximal migration of the fibula. A summary of the literature on CPT shows that the mean probability of achieving primary union without refracture, by most treatments is 50% (12% to 80%). Two recent studies have shown a much higher success rate approaching 100%, by creating a cross-union between the tibia and fibula. The cross-union with intramedullary reinforcement of the bone makes refracture unlikely due to the cross-sectional area of union with its two-bar linkage. A new classification to guide such treatment is also proposed.Level of EvidenceV – expert opinion

Treatment Planning the Edentulous Mandible. Review of Biomechanical and Clinical Considerations: An Update.

This review article evaluated biomechanical studies, finite element analyses, and clinical papers on the prosthetic and surgical principles for the survival of implants when reconstructing the edentulous mandible, including the use of a three-implant-supported fixed prosthesis. A comprehensive search of studies published from 1983 to December 2017 listed in the PubMed/MEDLINE databases was performed. Relevant studies were selected according to predetermined inclusion and exclusion criteria. The initial database search yielded 942 titles. After filtering, 157 abstracts were selected, with 68 articles considered relevant and included. Consensus among authors was identified in regard to the number and the distribution of implants; limiting or eliminating distal cantilevers; and the principles of biomechanical loading of a cross-arch splinted prosthesis. The result of this review suggests that reconstruction of the edentulous mandible with a fixed prosthesis using three, four, or six implants is a viable treatment option. However, when using three implants, wider-diameter implants are recommended for favorable force control.

The Y-shaped trabecular bone structure in the odontoid process of the axis: a CT scan study in 54 healthy subjects and biomechanical considerations.

Odontoid process fractures are very common in both young and geriatric patients. The axial trabecular architecture of the dens appears to be crucial for physiological and biomechanical function of the C1-2 joint. The aim of this study is to demonstrate the presence of a Y-shaped trabecular structure of the dens on axial CT and to describe its anatomical and biomechanical implications. Fifty-four C2 odontoid processes in healthy subjects were prospectively examined for the presence of a Y-shaped trabecular structure at the odontocentral synchondrosis level with a dental cone beam CT scan. Length, width, and axial area of the odontoid process were measured in all subjects. In addition, measurements of the one-third right anterior area of the Y-shaped structure were taken. The Y-shaped trabecular structure was found in 79.6% of cases. Length and width of the odontoid process were 13.5 ± 0.6 mm and 11.2 ± 0.9 mm, respectively. The mean area of the odontoid process at the odontocentral synchondrosis was 93.5 ± 4.3 mm2, whereas the mean one-third right anterior area of the odontoid process at the same level was 29.3 ± 2.5 mm2. The mean area of the odontoid process and its length and width were similar in men and women (p > 0.05). No significant difference was found in the mean area of the odontoid process in people older than 65 years (94 ± 4.2 mm2) compared to people younger than 65 years (93.3 ± 4.4 mm2; p > 0.05). The authors identified a new anatomical entity, named the Y-shaped trabecular structure of the odontoid process, on axial CT scans. This structure appears to be the result of bone transformation induced by the elevated dynamic loading at the C1-2 level. The presence of the Y-shaped structure provides new insights into biomechanical responses of C2 under physiological loading and traumatic conditions.

Biomechanical considerations in the design of patient-specific fixation plates for the distal radius

Use of patient-specific fixation plates is promising in corrective osteotomy of the distal radius. So far, custom plates were mostly shaped to closely fit onto the bone surface and ensure accurate positioning of bone segments, however, without considering the biomechanical needs for bone healing. In this study, we investigated how custom plates can be optimized to stimulate callus formation under daily loading conditions. We calculated implant stress distributions, axial screw forces, and interfragmentary strains via finite element analysis (FEA) and compared these parameters for a corrective distal radius osteotomy model fixated by standard and custom plates. We then evaluated these parameters in a modified custom plate design with alternative screw configuration, plate size, and thickness on 5 radii models. Compared to initial design, in the modified custom plate, the maximum stress was reduced, especially under torsional load (− 31%). Under bending load, implants with 1.9-mm thickness induced an average strain (median = 2.14%, IQR = 0.2) in the recommended range (2–10%) to promote callus formation. Optimizing the plate shape, width, and thickness in order to keep the fixation stable while guaranteeing sufficient strain to enhance callus formation can be considered as a design criteria for future, less invasive, custom distal radius plates.Graphical abstractᅟ

Stemless reverse shoulder arthroplasty: indications, technique and European experience

Reverse shoulder prostheses are increasingly used in recent years for treatment of glenohumeral arthropathy with deficient rotator cuff such as: rotator cuff arthropathy, rheumatoid arthritis, proximal humeral fractures sequela, irreparable rotator cuff tears, and failed shoulder replacement. Good mid-term and long-term results with restoration of active elevation have been reported. However, early studies showed relatively high rates of complications (24–50%) and many of them require further surgery. Most of the current designs of rTSA are with a humeral diaphyseal stem. A significant part of the reported intra-operative and postoperative complications, as well as difficulties arising during revision surgery, are related to the diaphyseal humeral component. Therefore, preservation of bone stock has become a major goal. Metaphyseal cementless implants without a diaphyseal stem have been developed to preserve bone and resect only minimal amount of bone. In 2005 the first stemless reverse TSAs were introduced for clinical use in Europe, with the Verso shoulder [Innovative Design Orthopaedics, London, UK (formerly Biomet, UK)] in UK and the TESS reverse shoulder (Biomet, France) in France. This review examines the European experience with stemless metaphyseal reverse TSAs, the history, the design rationale, the indications and the clinical and radiological outcome. The European experience with stemless metaphyseal reverse TSAs now spans over 13 years, with results that are at least equal with the stemmed implants. Specific design biomechanical considerations will be discussed.

Biomechanical considerations are crucial for the success of tendon and meniscus allograft integration—a systematic review

This systematic review intends to give an overview of the current knowledge on how allografts used for the reconstruction of cruciate ligaments and menisci are integrated and specifically perform regarding their biomechanical function. Two reviewers reviewed the PubMed and Central Cochrane library with focus on the biomechanical integration of tendon ligament and meniscus allografts. The literature search was conducted in accordance with the PRISMA statement for reporting systematic reviews and meta-analyses. The analysed literature on tendon allografts shows that they are more vulnerable to overstretching in the phase of degradation compared to autografts as the revascularization process starts later and takes longer. Therefore, to avoid excessive graft loads, allografts for cruciate ligament replacement should be selected that exhibit much higher failure loads than the native ligaments to counteract the detrimental effect of degradation. Further, placement techniques should be considered that result in a minimum of strain differences during knee joint motion, which is best achieved by near-isometric placement. The most important biomechanical parameters for meniscus allograft transplantation are secure fixation and proper graft sizing. Allograft attachment by bone plugs or by a bone block is superior to circumferential suturing and enables the allograft to restore the chondroprotective biomechanical function. Graft sizing is also of major relevance, because too small grafts are not able to compensate the knee joint incongruity and too large grafts may fail due to extrusion. Only adequate sizing and fixation together can lead to a biomechanically functioning allograft. The objective assessment of the biomechanical quality of allografts in a clinical setting is challenging, but would be highly desirable for monitoring the remodelling and incorporation process. Currently, indicators like ap-stability after ACL reconstruction or meniscal extrusion represent only indirect measures for biomechanical graft integration. These parameters are at best clinical indicators of allograft function, but the overall integration properties comprising e.g. fixation and graft stiffness remain unknown. Therefore, future research should e.g. focus on advanced imaging techniques or other non-invasive methods allowing for in vivo assessment of biomechanical allograft properties.