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A review of work o d o o t h deformatiohnd load sharing in non-metallic gears is presented. Ahnite element analys;&employing the flexibility method for contacting bodies is used to model tooth deflections and contact patterns 'Betweenheshing g e a r y For metallic gears the change in contact ratio between the theoretical and running values is shown to be small. However, for low modulus, non-Y t a l l i c gears the change in contact ratio is large and cangive cause for concern. The benefits and disadvantages of this increase in +.Qperating contact r a t i a s stated. Finally, the possibility of characterizing the change in operating contact ratio in a non-dimensional form is discussed.

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Study design: A single case study. Objectives: To compare proximal tibia trabecular bone mineral density (BMD) of a participant with complete spinal cord injury (SCI), long-termed functional electrical stimulation-rowing (FES-R) trained, with previously reported SCI and non-SCI group norms. To estimate lower limb joint contact forces (JCFs) in the FES-R trained participant. Setting: UK University and orthopaedic hospital research centre. Methods: Bilateral proximal tibial trabecular BMD of the FES-R trained participant was measured using peripheral quantitative computerised tomography, and the data were compared with SCI and non-SCI groups. An instrumented four-channel FES-R system was used to measure the lower limb JCFs in the FES-R trained participant. Results: Structurally, proximal tibial trabecular BMD was higher in the FES-R trained participant compared with the SCI group, but was less than the non-SCI group. Furthermore, left (184.7 mg cm À3 ) and right (160.7 mg cm À3 ) BMD were well above the threshold associated with non-traumatic fracture. The knee JCFs were above the threshold known to mediate BMD in SCI, but below threshold at the hip and ankle. Conclusion: As pathological fractures predominate in the distal femur and proximal tibia in chronic SCI patients, the fact that the FES-R trained participant's knee JCFs were above those known to partially prevent bone loss, suggests that FES-R training may provide therapeutic benefit. Although the elevated bilateral proximal tibial BMD of the FES-R participant provides circumstantial evidence of osteogenesis, this single case precludes any statement on the clinical significance. Further investigations are required involving larger numbers and additional channels of FES to increase loading at the hip and ankle. Spinal Cord (2014) 52, S4-S5; doi:10.1038/sc.2014.112 INTRODUCTIONOsteoporosis is a known secondary complication of spinal cord injury (SCI) characterised by low bone mineral density (BMD), which results in a high incidence of pathological fractures in the distal femur and proximal tibia. 1 Physical therapy is one strategy under investigation to mediate bone loss in SCI by increasing muscle-induced skeletal loading. 2 In the SCI model, functional electrical stimulation (FES) is required to activate paralysed muscle. Although the dose-response in the SCI model is unknown, compressive loads of 1-2 times body weight, delivered by FES-induced muscle contractions, have been found to partially prevent bone loss after SCI. 2 The aims of this study were to: (1) compare the lower limb BMD of a participant with long-term FESrowing (FES-R) trained with SCI and non-SCI groups, using peripheral quantitative computerised tomography imaging and (2) establish the magnitude of joint contact forces (JCFs) in the lower limbs of the FES-R trained participant. MATERIALS AND METHODSThe participant for these trials (Table 1), and author of this paper, had been FES-R trained for 48 years as described in reference 3 using quadriceps and hamstring controlled FES-activation. Th...

Background Motor vehicle collisions account for 1.3 million deaths and 50 million serious injuries worldwide each year. However, the majority of people involved in such incidents are uninjured or have injuries which do not prevent them exiting the vehicle. Self-extrication is the process by which a casualty is instructed to leave their vehicle and completes this with minimal or no assistance. Self-extrication may offer a number of patient and system-wide benefits. The efficacy of routine cervical collar application for this group is unclear and previous studies have demonstrated inconsistent results. It is unknown whether scripted instructions given to casualties on how to exit the vehicle would offer any additional utility. The aim of this study was to evaluate the effect of cervical collars and instructions on spinal movements during self-extrication from a vehicle, using novel motion tracking technology. Methods Biomechanical data on extrications were collected using Inertial Measurement Units on 10 healthy volunteers. The different extrication types examined were: i) No instructions and no cervical collar, ii) No instructions, with cervical collar, iii) With instructions and no collar, and iv) With instructions and with collar. Measurements were recorded at the cervical and lumbar spine, and in the anteroposterior (AP) and lateral (LAT) planes. Total movement, mean, standard deviation and confidence intervals are reported for each extrication type. Results Data were recorded for 392 extrications. The smallest cervical spine movements were recorded when a collar was applied and no instructions were given: mean 6.9 mm AP and 4.4 mm LAT. This also produced the smallest movements at the lumbar spine with a mean of 122 mm AP and 72.5 mm LAT. The largest overall movements were seen in the cervical spine AP when no instructions and no collar were used (28.3 mm). For cervical spine lateral movements, no collar but with instructions produced the greatest movement (18.5 mm). For the lumbar spine, the greatest movement was recorded when instructions were given and no collar was used (153.5 mm AP, 101.1 mm LAT). Conclusions Across all participants, the most frequently occurring extrication method associated with the least movement was no instructions, with a cervical collar in situ.

Background Motor vehicle collisions are a common cause of death and serious injury. Many casualties will remain in their vehicle following a collision. Trapped patients have more injuries and are more likely to die than their untrapped counterparts. Current extrication methods are time consuming and have a focus on movement minimisation and mitigation. The optimal extrication strategy and the effect this extrication method has on spinal movement is unknown. The aim of this study was to evaluate the movement at the cervical and lumbar spine for four commonly utilised extrication techniques. Methods Biomechanical data was collected using inertial Measurement Units on 6 healthy volunteers. The extrication types examined were: roof removal, b-post rip, rapid removal and self-extrication. Measurements were recorded at the cervical and lumbar spine, and in the anteroposterior (AP) and lateral (LAT) planes. Total movement (travel), maximal movement, mean, standard deviation and confidence intervals are reported for each extrication type. Results Data from a total of 230 extrications were collected for analysis. The smallest maximal and total movement (travel) were seen when the volunteer self-extricated (AP max = 2.6 mm, travel 4.9 mm). The largest maximal movement and travel were seen in rapid extrication extricated (AP max = 6.21 mm, travel 20.51 mm). The differences between self-extrication and all other methods were significant (p < 0.001), small non-significant differences existed between roof removal, b-post rip and rapid removal. Self-extrication was significantly quicker than the other extrication methods (mean 6.4 s). Conclusions In healthy volunteers, self-extrication is associated with the smallest spinal movement and the fastest time to complete extrication. Rapid, B-post rip and roof off extrication types are all associated with similar movements and time to extrication in prepared vehicles.

This in-vitro study reports on a selection of mechanical tests on four wound dressings: Allevyn (Smith and Nephew), Biatain (Coloplast), Lyofoam (Seton Scholl) and Tielle (Johnson and Johnson). The aim of the study was to investigate these dressings in the laboratory by subjecting them to dry and wet compression tests, shearing tests and a cyclical test. As predicted, all dressings performed differently in the range of tests, with Lyofoam deforming the most when subjected to compression testing (5.6 mm). During wet compression, differences in the physical properties of all the materials tested were identified. During shearing testin, Allevyn and Tielle withstood the greatest shear deflection before failure, but Biatain withstood the greatest force before failing. During the cyclical testing, Lyofoam only reduced by 1% of its original thickness, while Biatain reduced by 30%. No one dressing performed better in all the tests. However, as an all-round 'pressure-relieving' dressing, Allevyn consistently outperformed the others in the study.