In previous reports we and others have examined the relative movement of the tibia and femur in the living unloaded knee during flexion to 90° and 120° using MRI.1,2 We have now extended this investigation to the limits of active flexion (133°) and of passive flexion (162°). This study has been based on the knee in Japanese subjects since a position of full passive flexion is used in everyday life in Japan. Subjects and MethodsThe subjects were 20 adult male volunteers without symptoms in their knees and with normal MR images. Their mean age was 29.7 years (26 to 40). The left knee was scanned in an open MR imaging unit (Airis; Hitachi, Tokyo, Japan). The knees were imaged in neutral rotation at 90°, in active maximum flexion and in passive maximum flexion. Measurements were made as described elsewhere.3 At 90° flexion and active maximum flexion, the subject was scanned while lying on his side with the knee to be imaged in contact with the table. The position of maximum passive flexion was maintained by the body-weight (Fig. 1). At this position little tibial rotation was possible, i.e. the knee was rotationally locked. ResultsFrom 90° to full active flexion (133 ± 9°, mean ± SD) the mean posterior translation of the lateral femoral condyle was 13 ± 6 mm whereas for the medial femoral condyle it was 2 ± 2 mm. Therefore, over this arc of flexion, a mean tibial internal rotation of 15 ± 9° occurred around an axis passing through the medial tibial condyle. Passively forcing the knee from active to full passive flexion (i.e., from 133° to 162 ± 4°, mean ± SD) moved the medial femoral condyle back a further 4.5 ± 2 mm and the lateral femoral condyle 15 ± 4 mm. Thus there was a further 13 ± 6° of internal tibial rotation combined with about 4.0 mm of femoral posterior translation. At full passive flexion, the centre of the posterior circular portion of the lateral femoral condyle was 7 ± 5 mm posterior to the posterior tibial cortex and the lateral femoral condyle was only just in contact with the lateral tibial condyle. The medial femoral condyle had lifted away from the tibia.Representative MRIs, confirmatory cryosections of the medial and lateral compartments in Caucasian knees in full flexion, and the displacements of the condyles with flexion from their position at 90° are shown in Figures 2, 3 and 4. ConclusionsPrevious studies 1,2,3 have shown that as the unloaded knee is flexed to 120° in neutral rotation, the lateral femoral Scanning position at passive maximum flexion.

We reviewed a consecutive series of 527 uninfected hip replacements in patients resident in the UK which had been implanted from 1981 to 1993. All had the same basic design of femoral prosthesis, but four fixation techniques had been used: two press-fit, one HA-coated and one cemented. Review and radiography were planned prospectively. For assessment the components were retrospectively placed into two groups: those which had failed from two years onwards by aseptic femoral loosening and those in which the femoral component had survived without revision or recommendation for revision.All available radiographs in both groups were measured to determine vertical migration and examined by two observers to agree the presence of radiolucent lines (RLLs), lytic lesions, resorption of the neck, proximal osteopenia and distal intramedullary and distal subperiosteal formation of new bone. We then related the presence or absence of these features and the rate of migration at two years to the outcome with regard to aseptic loosening and determined the predictive value of each of these variables.Migration of ≥2 mm at two years, the presence of an RLL of 2 mm occupying one-third of any one zone, and subperiosteal formation of new bone at the tip of the stem were predictors of aseptic loosening after two years. There were too few lytic lesions to assess at two years, but at five years a lytic lesion ≥2 mm also predicted failure. We discuss the use of these variables as predictors of femoral aseptic loosening for groups of hips and for individual hips.We conclude that if a group of about 50 total hip replacements, perhaps with a new design of femoral stem, were studied in this way at two years, a mean migration of <0.4 mm and an incidence of <10% of RLLs of 2 mm in any one zone would predict 95% survival at ten years.For an individual prosthesis, migration of <2 mm and the absence of an RLL of ≤2 mm at two years predict a 6% chance of revision over approximately ten years. If either 2 mm of migration or an RLL of 2 mm is present, the chances of revision rise to 27%, and if both radiological signs are present they are 50%. If at five years a lytic lesion has developed, whatever the situation at two years, there is approximately a 50% chance of failure in the following five years.Our findings suggest that replacements using a limited number of any new design of femoral prosthesis should be screened radiologically at two years before they are generally introduced. We also suggest that radiographs of individual patients at two years and perhaps at five years should be studied to help to decide whether or not the patient should remain under close review or be discharged from specialist follow-up.

The direct integration of gallium nitride (GaN) and diamond holds much promise for high‐power devices. However, it is a big challenge to grow GaN on diamond due to the large lattice and thermal‐expansion coefficient mismatch between GaN and diamond. In this work, the fabrication of a GaN/diamond heterointerface is successfully achieved by a surface activated bonding (SAB) method at room temperature. A small compressive stress exists in the GaN/diamond heterointerface, which is significantly smaller than that of the GaN‐on‐diamond structure with a transition layer formed by crystal growth. A 5.3 nm‐thick intermediate layer composed of amorphous carbon and diamond is formed at the as‐bonded heterointerface. Ga and N atoms are distributed in the intermediate layer by diffusion during the bonding process. Both the thickness and the sp2‐bonded carbon ratio of the intermediate layer decrease as the annealing temperature increases, which indicates that the amorphous carbon is directly converted into diamond after annealing. The diamond of the intermediate layer acts as a seed crystal. After annealing at 1000 °C, the thickness of the intermediate layer is decreased to approximately 1.5 nm, where lattice fringes of the diamond (220) plane are observed.

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