Objectives. Many in vitro studies have investigated the mechanism by which mechanical signals are transduced into biological signals that regulate bone homeostasis via periodontal ligament fibroblasts during orthodontic treatment, but the results have not been systematically reviewed. This review aims to do this, considering the parameters of various in vitro mechanical loading approaches and their effects on osteogenic and osteoclastogenic properties of periodontal ligament fibroblasts. Methods. Specific keywords were used to search electronic databases (EMBASE, PubMed, and Web of Science) for English-language literature published between 1995 and 2017. Results. A total of 26 studies from the 555 articles obtained via the database search were ultimately included, and four main types of biomechanical approach were identified. Compressive force is characterized by static and continuous application, whereas tensile force is mainly cyclic. Only nine studies investigated the mechanisms by which periodontal ligament fibroblasts transduce mechanical stimulus. The studies provided evidence from in vitro mechanical loading regimens that periodontal ligament fibroblasts play a unique and dominant role in the regulation of bone remodelling during orthodontic tooth movement. Conclusion. Evidence from the reviewed studies described the characteristics of periodontal ligament fibroblasts exposed to mechanical force. This is expected to benefit subsequent research into periodontal ligament fibroblasts and to provide indirectly evidence-based insights regarding orthodontic treatment. Further studies should be performed to explore the effects of static tension on cytomechanical properties, better techniques for static compressive force loading, and deeper analysis of underlying regulatory systems. Cite this article: M. Li, C. Zhang, Y. Yang. Effects of mechanical forces on osteogenesis and osteoclastogenesis in human periodontal ligament fibroblasts: A systematic review of in vitro studies. Bone Joint Res 2019;8:19–31. DOI: 10.1302/2046-3758.81.BJR-2018-0060.R1

We have used an experimental model employing the bent tail of rats to investigate the effects of mechanical forces on bones and joints. Mechanical strain could be applied to the bones and joints of the tail without direct surgical exposure or the application of pins and wires. The intervertebral disc showed stretched annular lamellae on the convex side, while the annulus fibrosus on the concave side was pinched between the inner corners of the vertebral epiphysis. In young rats with an active growth plate, a transverse fissure appeared at the level of the hypertrophic cell layer or the primary metaphyseal trabecular zone. Metaphyseal and epiphyseal trabeculae on the compressed side were thicker and more dense than those of the distracted part of the vertebra. In growing animals, morphometric analysis of hemiepiphyseal and hemimetaphyseal areas, and the corresponding trabecular bone density, showed significant differences between the compressed and distracted sides. No differences were observed in adult rats. We found no significant differences in osteoclast number between compressed and distracted sides in either age group. Our results provide quantitative evidence of the working of ‘Wolff’s law’. The differences in trabecular density are examples of remodelling by osteoclasts and osteoblasts; our finding of no significant difference in osteoclast numbers between the hemiepiphyses in the experimental and control groups suggests that the response of living bone to altered strain is mediated by osteoblasts

We investigated factors that were thought to be associated with an increased incidence of squeaking of ceramic-on-ceramic total hip replacements. Between June 1997 and December 2008 the three senior authors implanted 2406 primary total hip replacements with a ceramic-on-ceramic bearing surface. The mean follow-up was 10.6 years. The diagnosis was primary osteoarthritis in each case, and no patient had undergone previous surgery to the hip. We identified 74 squeaking hips (73 patients) giving an incidence of 3.1% at a mean follow-up of 9.5 years (4.1 to 13.3). Taller, heavier and younger patients were significantly more likely to have hips that squeaked. Squeaking hips had a significantly higher range of post-operative internal (p = 0.001) and external rotation (p = 0.003) compared with silent hips. Patients with squeaking hips had significantly higher activity levels (p = 0.009). A squeaking hip was not associated with a significant difference in patient satisfaction (p = 0.24) or Harris hip score (p = 0.34). Four implant position factors enabled good prediction of squeaking. These were high acetabular component inclination, high femoral offset, lateralisation of the hip centre and either high or low acetabular component anteversion. This is the largest study to date to examine patient factors and implant position factors that predispose to squeaking of a ceramic-on-ceramic hip. The results suggest that factors which increase the mechanical forces across the hip joint and factors which increase the risk of neck-to-rim impingement, and therefore edge-loading, are those that predispose to squeaking

Ankylosing spondylitis (AS) is a progressive multisystem chronic inflammatory disorder. The hallmark of this pathological process is a progressive fusion of the zygapophyseal joints and disc spaces of the axial skeleton, leading to a rigid kyphotic deformity and positive sagittal balance. The ankylosed spine is unable to accommodate normal mechanical forces, rendering it brittle and susceptible to injury. Traumatic hyperextension injury of the cervical spine leading to atlantoaxial subluxation (AAS) in AS patients can often be fatal. We report a non-traumatic mechanism of injury in AS progressing to AAS attributable to persistent hyperextension, which resulted in fatal migration of C2 through the foramen magnum. Cite this article: Bone Joint J 2013;95-B:206–9

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To investigate the extent of bone development around the scaffold of custom triflange acetabular components (CTACs) over time.

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To systematically evaluate whether bracing can effectively achieve curve regression in patients with adolescent idiopathic scoliosis (AIS), and to identify any predictors of curve regression after bracing.

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This study investigated vancomycin-microbubbles (Vm-MBs) and meropenem (Mp)-MBs with ultrasound-targeted microbubble destruction (UTMD) to disrupt biofilms and improve bactericidal efficiency, providing a new and promising strategy for the treatment of device-related infections (DRIs).

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The aim of this study is to report the implant survival and factors associated with revision of total elbow arthroplasty (TEA) using data from the Dutch national registry.

Aseptic loosening of the acetabular component continues to be the most common indication for revision of total hip replacements in younger patients. Early in the evolution of the cemented hip, arthroplasty surgeons switched from removal to retention of the acetabular subchondral bone plate, theorising that unfavourable mechanical forces were the cause of loosening at the bone-cement interface. It is now known that the cause of aseptic loosening is probably biological rather than mechanical and removing the subchondral bone plate may enhance biological fixation of cement to bone. With this in mind, perhaps it is time to revive removal of the subchondral bone as a standard part of acetabular preparation

Matrix metalloproteinases (MMPs), responsible for extracellular matrix remodelling and angiogenesis, might play a major role in the response of the growth plate to detrimental loads that lead to overuse injuries in young athletes. In order to test this hypothesis, human growth plate chondrocytes were subjected to mechanical forces equal to either physiological loads, near detrimental or detrimental loads for two hours. In addition, these cells were exposed to physiological loads for up to 24 hours. Changes in the expression of MMPs -2, -3 and -13 were investigated. We found that expression of MMPs in cultured human growth plate chondrocytes increases in a linear manner with increased duration and intensity of loading. We also showed for the first time that physiological loads have the same effect on growth plate chondrocytes over a long period of time as detrimental loads applied for a short period. These findings confirm the involvement of MMPs in overuse injuries in children. We suggest that training programmes for immature athletes should be reconsidered in order to avoid detrimental stresses and over-expression of MMPs in the growth plate, and especially to avoid physiological loads becoming detrimental. Cite this article: Bone Joint J 2013;95-B:568–73

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Surgical reconstruction of deformed Charcot feet carries a high risk of nonunion, metalwork failure, and deformity recurrence. The primary aim of this study was to identify the factors contributing to these complications following hindfoot Charcot reconstructions.

1. There seem to be two distinct methods of destruction of the foot, once pain sensibility has been lost: the first is a slow erosion and shortening associated with perforating ulcers under the distal weight-bearing end of the foot. The second is a proximal disintegration of the tarsus in which mechanical forces often determine onset and progress of the condition. 2. Once the tarsus begins to disintegrate it is difficult to halt the rapid destruction of the foot. 3. It is possible to detect early stages of this condition in time to take preventive measures. Routine palpation of anaesthetic feet will reveal patches of warmth localised to bones and joints which are in a condition of strain. Radiographs of such feet and a study of posture and gait may define early changes which point to one of several possible patterns of disintegration which may follow. 4. These patterns are described and discussed and suggestions made for preventive and corrective measures

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This study compared the cobalt and chromium serum ion concentration of patients treated with two different metal-on-metal (MoM) hinged total knee arthroplasty (TKA) systems, as well as a titanium nitride (TiN)-coated variant.

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Hydroxyapatite (HA)-coated collars have been shown to reduce aseptic loosening of massive endoprostheses following primary surgery. Limited information exists about their effectiveness in revision surgery. The aim of this study was to radiologically assess osteointegration to HA-coated collars of cemented massive endoprostheses following revision surgery.

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To investigate whether idiopathic osteonecrosis of the femoral head (ONFH) is related to impaired osteoblast activities.

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The main advantage of 3D-printed, off-the-shelf acetabular implants is the potential to promote enhanced bony fixation due to their controllable porous structure. In this study we investigated the extent of osseointegration in retrieved 3D-printed acetabular implants.

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Periprosthetic joint infections (PJIs) and osteomyelitis are clinical challenges that are difficult to eradicate. Well-characterized large animal models necessary for testing and validating new treatment strategies for these conditions are lacking. The purpose of this study was to develop a rabbit model of chronic PJI in the distal femur.

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Vertebrates have adapted to life on Earth and its constant gravitational field, which exerts load on the body and influences the structure and function of tissues. While the effects of microgravity on muscle and bone homeostasis are well described, with sarcopenia and osteoporosis observed in astronauts returning from space, the effects of shorter exposures to increased gravitational fields are less well characterized. We aimed to test how hypergravity affects early cartilage and skeletal development in a zebrafish model.

Bone is one of the most highly adaptive tissues in the body, possessing the capability to alter its morphology and function in response to stimuli in its surrounding environment. The ability of bone to sense and convert external mechanical stimuli into a biochemical response, which ultimately alters the phenotype and function of the cell, is described as mechanotransduction. This review aims to describe the fundamental physiology and biomechanisms that occur to induce osteogenic adaptation of a cell following application of a physical stimulus. Considerable developments have been made in recent years in our understanding of how cells orchestrate this complex interplay of processes, and have become the focus of research in osteogenesis. We will discuss current areas of preclinical and clinical research exploring the harnessing of mechanotransductive properties of cells and applying them therapeutically, both in the context of fracture healing and de novo bone formation in situations such as nonunion.

Cite this article: Bone Joint Res 2019;9(1):1–14.