A low-cost solution for the restoration of femoral head centre during total hip arthroplasty

Restoration of joint centre during total hip arthroplasty is critical. While computer-aided navigation can improve accuracy during total hip arthroplasty, its expense makes it inaccessible to the majority of surgeons. This article evaluates the use, in the laboratory, of a calliper with a simple computer application to measure changes in femoral head centres during total hip arthroplasty. The computer application was designed using Microsoft Excel and used calliper measurements taken pre- and post-femoral head resection to predict the change in head centre in terms of offset and vertical height between the femoral head and newly inserted prosthesis. Its accuracy was assessed using a coordinate measuring machine to compare changes in preoperative and post-operative head centre when simulating stem insertion on 10 sawbone femurs. A femoral stem with a modular neck was used, which meant nine possible head centre configurations were available for each femur, giving 90 results. The results show that using this technique during a simulated total hip arthroplasty, it was possible to restore femoral head centre to within 6?mm for offset (mean 1.67?±?1.16?mm) and vertical height (mean 2.14?±?1.51?mm). It is intended that this low-cost technique be extended to inform the surgeon of a best-fit solution in terms of neck length and neck type for a specific prosthesis.

The influence of wear paths produced by hip replacement patients during normal walking on wear rates

Variation in wear paths is known to greatly affect wear rates in vitro, with multidirectional paths producing much greater wear than unidirectional paths. This study investigated the relationship between multidirectional motion at the hip joint, as measured by aspect ratio, sliding distance, and wear rate for 164 hip replacements. Kinematic input from three-dimensional gait analysis was used to determine the wear paths. Activity cycles were determined for a subgroup of 100 patients using a pedometer study, and the relationship between annual sliding distance and wear rate was analyzed. Poor correlations were found between both aspect ratio and sliding distance and wear rate for the larger group and between annual sliding distance and wear rate for the subgroup. However, patients who experienced a wear rate <0.08 mm/year showed a strong positive correlation between the combination of sliding distance, activity levels, and aspect ratio and wear rate (adjusted r2?=?55.4%). This group may represent those patients who experience conditions that most closely match those that prevail in simulator and laboratory tests. Although the shape of wear paths, their sliding distance, and the number of articulation cycles at the hip joint affect wear rates in simulator studies, this relationship was not seen in this clinical study. Other factors such as lubrication, loading conditions and roughness of the femoral head may influence the wear rate.

A comparative assessment of potential components of partial disease resistance to Fusarium head blight detected in a detached leaf assay of wheat, barley and oats.

The relative resistance of 15 winter barley, three winter wheat and three winter oat cultivars on the UK recommended list 2003 and two spring wheat cultivars on the Irish 2003 recommended list were evaluated using Microdochium nivale in detached leaf assays to further understand components of partial disease resistance (PDR) and Fusarium head blight (FHB) resistance across cereal species. Barley cultivars showed incubation periods comparable to, and latent periods longer than the most FHB resistant Irish and UK wheat cultivars evaluated. In addition, lesions on barley differed from those on wheat as they were not visibly chlorotic when placed over a light box until sporulation occurred, in contrast to wheat cultivars where chlorosis of the infected area occurred when lesions first developed. The pattern of delayed chlorosis of the infected leaf tissue and longer latent periods indicate that resistances are expressed in barley after the incubation period is observed, and that these temporarily arrest the development of mycelium and sporulation. Incubation periods were longer for oats compared to barley or wheat cultivars. However, oat cultivars differed from both wheat and barley in that mycelial growth was observed before obvious tissue damage was detected under macroscopic examination, indicating tolerance of infection rather than inhibition of pathogen development, and morphology of sporodochia differed, appearing less well developed and being much less abundant. Longer latent periods have previously been related to greater FHB resistance in wheat. The present results suggest the longer latent periods of barley and oat cultivars, than wheat, are likely to play a role in overall FHB resistance if under the same genetic control as PDR components expressed in the head. However the limited range of incubation and latent periods observed within barley and oat cultivars evaluated was in contrast with wheat where incubation and latent periods were shorter and more variable among genotypes. The significance of the various combinations of PDR components detected in the detached leaf assay as components of FHB resistance in each crop requires further investigation, particularly with regard to the apparent tolerance of infection in oats and necrosis in barley, after the incubation period is observed, associated with retardation of mycelial growth and sporulation.

Components of resistance to Fusarium head blight in wheat detected in a seed germination assay with Microdochium majus and the relationship to FHB disease development and mycotoxin accumulation from Fusarium graminearum infection.

Components of partial disease resistance (PDR) to fusarium head blight (FHB), detected in a seed-germination assay, were compared with whole-plant FHB resistance of 30 USA soft red winter wheat entries in the 2002 Uniform Southern FHB Nursery. Highly significant (P <0·001) differences between cultivars in the in vitro seed-germination assay inoculated with Microdochium majus were correlated to FHB disease incidence (r = -0·41; P <0·05), severity (r = -0·47; P <0·01), FHB index (r = -0·46; P <0·01), damaged kernels (r = -0·52; P <0·01), grain deoxynivalenol (DON) concentration (r = -0·40; P <0·05) and incidence/severity/kernel-damage index (ISK) (r = -0·45; P <0·01) caused by Fusarium graminearum. Multiple linear regression analysis explained a greater percentage of variation in FHB resistance using the seed-germination assay and the previously reported detached-leaf assay PDR components as explanatory factors. Shorter incubation periods, longer latent periods, shorter lesion lengths in the detached-leaf assay and higher germination rates in the seed-germination assay were related to greater FHB resistance across all disease variables, collectively explaining 62% of variation for incidence, 49% for severity, 56% for F. graminearum-damaged kernels (FDK), 39% for DON and 59% for ISK index. Incubation period was most strongly related to disease incidence and the early stages of infection, while resistance detected in the seed germination assay and latent period were more strongly related to FHB disease severity. Resistance detected using the seed-germination assay was notable as it related to greater decline in the level of FDK and a smaller reduction in DON than would have been expected from the reduction in FHB disease assessed by visual symptoms.

A reliable externally fixated murine femoral fracture model that accounts for variation in movement between animals.

Fifty-two CFLP mice had an open femoral diaphyseal osteotomy held in compression by a four-pin external fixator. The movement of 34 of the mice in their cages was quantified before and after operation, until sacrifice at 4, 8, 16 or 24 days. Thirty-three specimens underwent histomorphometric analysis and 19 specimens underwent torsional stiffness measurement. The expected combination of intramembranous and endochondral bone formation was observed, and the model was shown to be reliable in that variation in the histological parameters of healing was small between animals at the same time point, compared to the variation between time-points. There was surprisingly large individual variation in the amount of animal movement about the cage, which correlated with both histomorphometric and mechanical measures of healing. Animals that moved more had larger external calluses containing more cartilage and demonstrated lower torsional stiffness at the same time point. Assuming that movement of the whole animal predicts, at least to some extent, movement at the fracture site, this correlation is what would be expected in a model that involves similar processes to those in human fracture healing. Models such as this, employed to determine the effect of experimental interventions, will yield more information if the natural variation in animal motion is measured and included in the analysis.