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- Björling, Marcus, et al.
(author)
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The influence of DLC coating on EHL friction coefficient
- 2012
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In: Tribology letters. - : Springer Science and Business Media LLC. - 1023-8883 .- 1573-2711. ; 47:2, s. 285-294
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Journal article (peer-reviewed)abstract
- High hardness, high elastic modulus, low friction characteristics, high wear and corrosion resistance, chemical inertness, and thermal stability are factors that make diamond-like carbon (DLC) coatings the subject of many studies. For the same reasons they also seem suitable for use in, amongst others, machine components and cutting tools. While most studies in the literature focus on the influence of coatings on wear and friction in boundary lubrication and pure sliding contacts, few studies can be found concerning rolling and sliding elastohydrodynamic lubrication (EHL) friction, especially in the mixed and full film regime. In this article tests are carried out in a Wedeven Associates Machine tribotester where an uncoated ball and disc pair is compared to the case of coated ball against uncoated disc, coated disc against uncoated ball, and coated disc against coated ball. The tests are conducted at two different temperatures and over a broad range of slide-to-roll ratios and entrainment speeds. The results are presented as friction maps as introduced in previous work (Björling et al. in J Eng Tribol 225(7):671, 2011). Furthermore a numerical simulation model is developed to investigate if there is a possibility that the hard, thin DLC coating is affecting the friction coefficient in an EHL contact due to thermal effects caused by the different thermal properties of the coating compared to the substrate. The experimental results show a reduction in friction coefficient in the full film regime when DLC-coated surfaces are used. The biggest reduction is found when both surfaces are coated, followed by the case when either ball or disc is coated. The thermal simulation model shows a substantial increase of the lubricant film temperature compared to uncoated surfaces when both surfaces are coated with DLC. The reduction in friction coefficient when coating either only the ball or the disc are almost the same, lower than when coating both the surfaces but still higher than the uncoated case. The findings above indicate that it is reasonable to conclude that thermal effects are a likely cause for the decrease in coefficient of friction when operating under full film conditions, and in the mixed lubrication regime when DLC-coated surfaces are used
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- Karlsson, Emma, et al.
(author)
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Combined volar and dorsal plating vs. volar plating of distal radius fractures : A single-center study of 105 cases
- 2020
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In: Hand surgery & rehabilitation. - : Elsevier. - 2468-1229 .- 2468-1210. ; 39:6, s. 516-521
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Journal article (peer-reviewed)abstract
- Despite recent advances in the surgical management of distal radius fractures (DRFs), the optimal treatment remains controversial as different fixation methods often have similar clinical functional and radiographic outcomes. The objective of this study was to assess the differences in outcomes 1 year postoperatively between volar plating and combined plating for DRFs. In a retrospective cohort study, we evaluated 105 consecutive patients operated with either a volar locking plate or combined dorsal and volar plating. The primary outcome was wrist range of motion (ROM). Secondary outcome measures included hand grip strength, visual analog scale (VAS) pain scores, radiographic examination and patient-related outcome measures. Patients treated with combined plating had significantly inferior wrist flexion, extension and ulnar deviation. The radiographic Batra score 1 year postoperatively was similar for both groups. The PRWE (patient-rated wrist evaluation) score was 16 for the volar plating group and 14 for the combined plating group. The QuickDASH (Quick disabilities of the hand arm and shoulder) score was 9 for the volar plating group and 16 for the combined plating group. VAS pain scores were 0 at rest and 2 during activity for both groups. Grip strength was similar between the two groups. Hardware removal was done in 18/78 patients for the combined plating group and 1/27 for the volar plate group. Two patients operated with combined plating had tendon ruptures. Our findings indicate that both methods can yield satisfactory clinical and radiographic outcomes. However, combined plating resulted in inferior wrist ROM and substantially higher frequency of hardware removal. The potential advantages of combined plating in stabilizing a comminuted DRF must be balanced by the potential drawbacks such as inferior wrist ROM and higher frequency of hardware removal.
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- Sagerfors, Marcus, 1977-, et al.
(author)
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Combined Volar T-Plate and Dorsal Pi-Plate for Distal Radius Fractures : A Consecutive Series of 80 AO type C2 and C3 Cases
- 2019
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In: Journal of wrist surgery. - : Thieme Medical Publishers. - 2163-3916 .- 2163-3924. ; 8:3, s. 180-185
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Journal article (peer-reviewed)abstract
- Background The distal radius fracture (DRF) is the most common fracture among adults. In recent years, there has been a shift toward volar locking plates in the treatment of DRFs, and this shift has taken place with a low degree of evidence.Question/purposes Can combined volar T-plating and dorsal pi-plating of AO type C fractures yield a good functional and radiographic outcome 1 year postoperatively?Patients and Methods In a retrospective cohort study, we evaluated 102 consecutive patients operated with combined dorsal and volar plating, of whom 80 completed the 1-year follow-up. The DRFs were operated between 2012 and 2013. All cases were AO type C2 and C3 fractures. The primary outcome was functional scoring including radiographic examination. Secondary outcome measures included range of motion, visual analog scale (VAS) pain scores, and hand grip strength.Results The median Batra radiographic score was 84.5. Wrist extension was 74% of the uninjured side, flexion was 70%, pronation was 94%, and supination was 90%. The Patient-Rated Wrist Evaluation score was 21 points, and the Disabilities of the Arm, Shoulder, and Hand score was 19.4 points. VAS pain scores were 0 at rest and 3 during activity. Hand grip strength was 80% of the uninjured side. Radiographic outcome did not correspond to a patient-reported outcome. Hardware removal was performed in 15/80 cases.Conclusions We conclude that a good outcome can be expected after combined dorsal and volar plating of DRFs. Radiographic outcome is not necessarily associated with functional outcome 1 year postoperatively. The rate of hardware removal was acceptable.
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