Human biological variation in sesamoid bone prevalence: the curious case of the fabella

The fabella is a sesamoid bone located in the gastrocnemius behind the lateral femoral condyle. In humans, fabellae are 3.5 times more common today than they were 100 years ago, with prevalence rates varying between and within populations. In particular, fabellae have been assumed to be more common in Asians than non‐Asians, equally common in men and women, potentially more common in older individuals, and bilateral cases (one per knee) appear to be more common than unilateral ones. The roles of genetic and environmental factors in this phenotypic variation have been hypothesized, but not rigorously investigated. Given its clinical and evolutionary significance (i.e. being associated with several knee ailments, causing medical issues on its own, interfering with medical devices, and being less common in humans than in other mammals), it is important comprehensively to understand prevalence rate variation, and the roles of genetics and environmental factors in that variation. To address these questions, we performed a meta‐analysis on data from studies published from 1875 to 2018 to investigate possible variation in sexual dimorphic (n = 22 studies, 7911 knees), ontogenetic (n = 10 studies, 4391 knees), and global (n = 65 studies, 21 626 knees) fabella prevalence rates. In addition, we investigated what proportion of cases are bilateral (n = 37 studies, 900 individuals), and among unilateral cases (n = 20 studies, 204 individuals), if fabellae are more common in the left or right knee. Our results show that, today, fabellae are 2.47–2.60% more common in men than women, and prevalence rates increase ontogenetically in old age (i.e. 70 years old), implying that fabellae can ossify early (i.e. 12 years old) or late in life. Approximately 72.94% of cases are bilateral, and among unilateral ones, fabellae are equally common in right and left knees. There is marked regional variation in fabella prevalence rates, with rates being highest in Asia, followed by Oceania, South America, Europe, Middle East, and North America, and lowest in Africa. Worldwide, an average of 36.80% of knees has ossified fabellae detectable by dissection. These results imply that, while the ability to form a fabella may be genetically controlled, the mechanisms that trigger fabella ossification may be environmentally controlled. What these environmental factors are, can only be speculated

Low-cost locally manufacturable unilateral imperial external fixator for low- and middle-income countries

Treating open fractures in long bones can be challenging and if not performed properly can lead to poor outcomes such as mal/non-union, deformity, and amputation. One of the most common methods of treating these fracture types is temporary external fixation followed by definitive fixation. The shortage of high-quality affordable external fixators is a long-recognised need, particularly in Low- and Middle-Income Countries (LMICs). This research aimed to develop a low-cost device that can be manufactured locally to international standards. This can provide surge capacity for conflict zones or in response to unpredictable incidents and situations. The fixator presented here and developed by us, the Imperial external fixator, was tested on femur and tibia specimens under 100 cycles of 100 N compression-tension and the results were compared with those of the Stryker Hoffmann 3 frame. The Imperial device was stiffer than the Stryker Hoffmann 3 with a lower median interfragmentary motion (of 0.94 vs. 1.48 mm). The low-cost, easy to use, relatively lightweight, and easy to manufacture (since minimum skillset and basic workshop equipment and materials are needed) device can address a critical shortage and need in LMICs particularly in conflict-affected regions with unpredictable demand and supply. The device is currently being piloted in three countries for road traffic accidents, gunshot wounds and other conflict trauma—including blast cohorts

Mental health outcomes of male UK military personnel deployed to Afghanistan and the role of combat injury: analysis of baseline data from the ADVANCE cohort study

Background: The long-term psychosocial outcomes of UK armed forces personnel who sustained serious combat injuries during deployment to Afghanistan are largely unknown. We aimed to assess rates of probable post-traumatic stress disorder (PTSD), depression, anxiety, and mental health-associated multimorbidity in a representative sample of serving and ex-serving UK military personnel with combat injuries, compared with rates in a matched sample of uninjured personnel. Methods: This analysis used baseline data from the ADVANCE cohort study, in which injured individuals were recruited from a sample of UK armed forces personnel who were deployed to Afghanistan and had physical combat injuries, according to records provided by the UK Ministry of Defence. Participants from the uninjured group were frequency-matched by age, rank, regiment, deployment, and role on deployment. Participants were recruited through postal, email, and telephone invitations. Participants completed a comprehensive health assessment, including physical health assessment and self-reported mental health measures (PTSD Checklist, Patient Health Questionnaire-9, and Generalised Anxiety Disorder-7). The mental health outcomes were rates of PTSD, depression, anxiety, and mental health-associated multimorbidity in the injured and uninjured groups. The ADVANCE study is ongoing and is registered with the ISRCTN registry, ISRCTN57285353. Findings: 579 combat-injured participants (161 with amputation injuries and 418 with non-amputation injuries) and 565 uninjured participants were included in the analysis. Participants had a median age of 33 years (IQR 30–37 years) at the time of assessment. 90·3% identified as White and 9·7% were from all other ethnic groups. The rates of PTSD (16·9% [n=89] vs 10·5% [n=53]; adjusted odds ratio [AOR] 1·67 [95% CI 1·16–2·41], depression (23·6% [n=129] vs 16·8% [n=87]; AOR 1·46 [1·08–2·03]), anxiety (20·8% [n=111] vs 13·5% [n=71]; AOR 1·56 [1·13–2·24]) and mental health-associated multimorbidity (15·3% [n=81] vs 9·8% [n=49]; AOR 1·62 [1·12–2·49]) were greater in the injured group than the uninjured group. Minimal differences in odds of reporting any poor mental health outcome were noted between the amputation injury subgroup and the uninjured group (AOR range 0·77–0·97), whereas up to double the odds were noted for the non-amputation injury subgroup compared with the uninjured group (AOR range 1·74–2·02). Interpretation: Serious physical combat injuries were associated with poor mental health outcomes. However, the type of injury sustained influenced this relationship. Regardless of injury, this cohort represents a group who present with greater rates of PTSD than the general population, as well as increased psychological burden from multimorbidity. Funding: The ADVANCE Charity

A Theoretical Model of a Molecular-Motor-Powered Pump

The motion of a cylindrical bead in a fluid contained within a two-dimensional channel is investigated using the boundary element method as a model of a biomolecular-motor-powered microfluidics pump. The novelty of the pump lies in the use of motor proteins (kinesin) to power the bead motion and the few moving parts comprising the pump. The performance and feasibility of this pump design is investigated using two model geometries: a straight channel, and a curved channel with two concentric circular walls. In the straight channel geometry, it is shown that increasing the bead radius relative to the channel width, increases the flow rate at the expense of increasing the force the kinesins must generate in order to move the bead. Pump efficiency is generally higher for larger bead radii, and larger beads can support higher imposed loads. In the circular channel geometry, it is shown that bead rotation modifies the force required to move the bead and that shifting the bead inward slightly reduces the required force. Bead rotation has a minimal effect on flow rate. Recirculation regions, which can develop between the bead and the channel walls, influence the stresses and force on the bead. These results suggest this pump design is feasible, and the kinesin molecules provide sufficient force to deliver pico- to atto- l/s flows.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/44478/1/10544_2005_Article_6168.pd

Optimising and validating an electromagnetic tracker in a human performance laboratory

Measurement errors have previously been observed using electromagnetic motion trackers in applied laboratories. The aims of this study were to optimize the layout of a human performance laboratory for assessing ergometer rowing technique, and to assess the precision and repeatability of measured rotations and trajectories using the Flock of Birds electromagnetic tracker. Four experiments investigated system performance over a large experimental volume: optimization of laboratory space, repeatability of laboratory layout, precision of measured rotations, and repeatability of measured displacements. Measurement accuracy was influenced by varying the global position of the system transmitter; results suggested a correlation with increasing distance between the electromagnetic source and equivalent sensors. Bringing the transmitter or sensors into closer proximity of metallic items may be another source of measurement error. An optimal location for the transmitter was identified, into which the transmitter was repositioned with good repeatability. Measurements were not negativelyaffected by the presence of a rowing ergometer in the experimental volume. Induced sensor rotations were reconstructed with high precision, and the system calculated small changes in sensor displacement with good repeatability. The system is a suitable technology for measuring the trajectory and rotation of moving body segments in applied human movement laboratories

Prediction of the lumbosacral joint centre location from external landmarks

This paper discusses prediction of the lumbosacral joint centre location from external landmarks. It was presented at the 9th Meeting of the Clinical Movement Analysis Society in 2010

Dynamic response of the cervical spine to posteroanterior mobilisation

Background. Posteroanterior mobilisation is a manual therapy technique that is commonly used in the examination and treatment of neck pain, but little is known about its biomechanical effect. The purpose of this study was to determine the intervertebral movements of the cervical spine produced by posteroanterior mobilisation. Methods. The cervical spines of nineteen healthy subjects were scanned using an open interventional magnetic resonance imaging scanner. Posteroanterior mobilisation forces were applied to the fifth cervical vertebra whilst they were in the prone position. Sagittal images of the spine were obtained before and during mobilisation. Findings. It was shown that posteroanterior mobilisation of the cervical spine generally produced extension of the upper motion segments and flexion of the lower segments. The middle segments were inconsistent in the direction of rotation. The cervical lordosis was found to increase with repeated PA loading cycles. Interpretation. The magnitude of intervertebral movement produced by mobilisation is small. Forces applied at one spinous process produced not only movements at the target vertebra but also movements of the entire cervical spine resulting in an increase in lordosis. Mobilisation should be interpreted as three-point bending of the entire cervical spine, rather than simple gliding of one vertebra upon another.Department of Rehabilitation Science

Dynamic response of the human spine to anteroposterior mobilisation manual therapy: an interventional magnetic resonance imaging study

Department of Rehabilitation Science