Collected marine litter - A growing waste challenge.

Marine litter, in particular plastic debris, poses a serious threat to marine life, human health and the economy. In order to reduce its impact, marine litter collections such as beach clean-ups are frequently conducted. This paper presents a systematic review of temporal developments, geographical distribution, quantities and waste treatment pathways of collected marine litter. Results from over 130 studies and projects highlight the worldwide increase in collection efforts. Many of these are in wealthy countries that do not primarily contribute to the problem. Over 250 thousand tonnes, have already been removed, but there is little or no information available regarding how this waste is treated or used post collection. This paper highlights the need for a whole-system quantitative assessment for the collection and waste treatment of marine litter, and identifies the challenges associated with utilising this waste in the future.

The influence of tibial component malalignment on bone strain in revision total knee replacement.

Revision total knee replacement is a challenging surgical procedure typically associated with significant loss of bone stock in the proximal tibia. To increase the fixation stability, extended stems are frequently used for the tibial component in revision surgery. The design of the tibial stem influences the load transfer from tibial component to the surrounding bone and is cited as a possible cause for the clinically reported pain in the location of the stem-end. This study aimed to analyse the strain distribution of a fully cemented revision tibial component with a validated finite element model. The model was developed from a scanned composite tibia (Sawbones), with an implanted, fully cemented stemmed tibial component aligned to the mechanical axis of the tibia. Loading was applied to the tibial component with mediolateral compartment load distributions of 60:40 and 80:20. Three strain gauged composite tibias with implanted tibial components of the same design using the same loading distribution were tested to obtain experimental strains at five locations in the proximal tibia. The finite element model developed was validated against strain measurements obtained in the experimental study. The strains displayed similar patterns (R(2) = 0.988) and magnitudes with those predicted from the finite element model. The displacement of the stem-end from the natural mechanical axis in the finite element model demonstrated increased strains in the stem-end region with a close proximity of the distal stem with the cortical bone. The simulation of a mediolateral compartment load of 80:20 developed peak cortical strain values on the posterior-medial side beneath the stem. This may possibly be related to the clinically reported pain at the stem-end. Furthermore, stem positioning in close proximity or contact with the posterior cortical bone is a contributory factor for an increase in distal strain.