Bone is a dynamic tissue with a quarter of the trabecular and a fifth of the cortical bone being replaced continuously each year in a complex process that continues throughout an individual’s lifetime. Bone has an important role in homeostasis of minerals with non-stoichiometric hydroxyapatite bone mineral forming the inorganic phase of bone. Due to its crystal structure and chemistry, hydroxyapatite (HA) and related apatites have a remarkable ability to bind molecules. This review article describes the accretion of trace elements in bone mineral giving a historical perspective. Implanted HA particles of synthetic origin have proved to be an efficient recruiting moiety for systemically circulating drugs which can locally biomodulate the material and lead to a therapeutic effect. Bone mineral and apatite however also act as a waste dump for trace elements and drugs, which significantly affects the environment and human health. Cite this article:
Adductor canal blocks offer an alternative to femoral nerve block for postoperative pain relief in knee arthroplasty. They may reduce the risk of quadriceps weakness, allowing earlier mobilisation of patients postoperatively. However, little is known about the effect of a tourniquet on the distribution of local anaesthetic in the limb. Ultrasound-guided adductor canal blocks were performed on both thighs of five human cadavers. Left and right thighs of each cadaver were randomised to tourniquet or no tourniquet for one hour. Iohexol radio-opaque contrast (Omnipaque 350) was substituted for the local anaesthetic for X-Ray imaging. All limbs underwent periodic flexion and extension during this hour to simulate positioning during surgery. The cadavers were refrozen. Fiducial markers were inserted into the frozen tissue. X-rays were obtained in 4 planes (AP, lateral 45° oblique/medial oblique, lateral). University Research Ethics Approval was obtained and cadavers were all pre-consented for research, imaging and photography according to the Anatomy Act (1984). Analysis of radiographs showed contrast distribution in all thighs to be predominantly on the medial aspect of the thighs. The contrast margins were entire and well circumscribed, strongly suggesting it was largely contained within the aponeurosis of the adductor canal. Tourniquets appeared to push the contrast into a narrower and more distal spread along the length of the thigh compared to a more diffuse spread for those without. Proximal spread towards the femoral triangle was reduced in limbs without tourniquets. The results suggest that contrast material may remain within the adductor canal structures during adductor canal blocks. Tourniquets may cause greater distribution of contrast proximally and distally in the thigh, but this does not appear to be clinically significant. Further studies might include radio-stereo photometric analysis using the fiducial markers in the limbs and in vivo studies to show the effect of haemodynamics on distribution.
An injectable material consisting of calcium sulphate mixed with hydroxyapatite was investigated as a possible alternative to autograft in the restoration of bone defects. The material was studied both in vitro in simulated body fluid (SBF) and in vivo when implanted in rat muscles and into the proximal tibiae of rabbits. Variation in the strength and weight of the material during ageing in SBF was measured. Tissue response, material resorption and bone ingrowth were studied in the animal models. A good tissue response was observed in both the rat muscles and rabbit tibiae without inflammatory reactions or the presence of fibrous tissue. Ageing in SBF showed that during the first week carbonated hydroxyapatite precipitated on the surfaces of the material and this may enhance bone ingrowth.
We present a new approach for the accurate reconstruction of three-dimensional skeletal positions using roentgen single-plane photogrammetric analysis (RSPA). This technique uses a minimum of three markers embedded in each segment which allow continuous, real-time, internal skeletal movement to be measured from single-plane images, provided that the precise distance between the markers is known. A simulation study indicated that the error propagation in this approach is influenced by focus position, object position, the number of control points, the accuracy of the previous measurement of the distance between markers and the accuracy of image measurement. For reconstruction of normal movement of the knee with an input measurement error of Our results showed that the accuracy of RSPA is sufficient for the analysis of most movement of joints. This approach can be applied in combination with force measurements for dynamic studies of the musculoskeletal system.
