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Introduction The radiological assessment of osteoarthritis of the knee joint in longitudinal studies is usually performed with established classifications. It is disadvantageous that these features are always combined to describe a certain stage of the disease, even though they can develop independently. Methods A german score based on a publication by Scott et al. (1993) was designed. At first 100 X-ray series of knees were evaluated using the Jager & Wirth, the Kellgren & Lawrence classification and the point score. Six observers then evaluated 200 anonymised radiographs of knee joints twice within 3 months. Results The most reliable criteria for the inter-observer reliancy were medial osteophytes, medial joint-line narrowing, patella osteophytes and chondrocalcinosis. At least 4 out of 6 observers had a high match in these criteria. The reproducability of most of the individual radiographic features was good, with a higher level of orthopaedic training resulting in a higher consistency of the score. Discussion A certain level of orthopaedic training is necessary for consistent results. The main focus of the score will be less the daily routine assessment of radiographs of the knee joint, but more the scientific assessment of radiographic progression of osteoarthritis in longitudinal studies.

Aim and method This review article summarises new knowledge about knee kinematics and induces a new discussion about the design of total knee arthroplasty (TKA) components. Results According to these new observations, knee flexion is not linked to femoral rollback but to a rotational movement between tibia and femur. The axis of this rotation is situated in the medial compartment of the knee when an intact anterior craciate ligament is present and not centrally through the tibial spines. In case of ACL insufficiency, such as that following TKA, the center of rotation shifts into the lateral compartment. Furthermore, the form of the posterior femoral condyle is not elliptical but round. Conclusion Rotational movements between femoral component and tibial baseplate with the polyethylene-inlay have to be possible. One needs an asymmetric surface of the polyethylene-inlay, because different movements occur in the medial compartment than in the lateral compartment. The option to construct the posterior femoral condyle with a single radius allows a high congruency with the articulating inlay. The surgeon should let the new findings influence his choice of a TKA system. A closer analysis of modern prosthetic designs with either fixed or mobile bearings reveals that a few systems have already incorporated some of the new kinematic aspects of the knee.

Problem: To what extent are carbon fibre-reinforced plastics (CFRP) suitable as an osseous integration surface for implants? Method: CFRP test implants having a plexus-structured, rhombus-structured, and plexus-structured, hydroxyapatite surface were implanted in the femura of mini-pigs. Exposure time lasted 12 weeks. The implants were subjected to a macroradiological, a histological-histomorphometrical, and a fluorescence-microscopical evaluation. Results: One half of the uncoated, plexus-structured implants were not osteointegrated, the other half displayed an osteointegration rate of 11.8% in the spongy area and 29.8% in the cortex layer. The HA-coated test implants showed an osteointegration of 29.5% in the spongiosa and 56.8% in the cortex layer. The rhombusstructured test implants had an osteointegration of 29.2% (spongiosa) and 46.2% (cortex layer). Conclusion: Compared to the osteointegration of metallic, especially titanium surfaces the CFRP surfaces tested by us fared worse, especially the uncoated, plexus-structured surfaces. For this reason we view very critically the use of carbon-fibre reinforced plastics together with the surfaces tested by us as osteointegrating surfaces.

This review article summarises new knowledge about knee kinematics and induces a new discussion about the design of total knee arthroplasty (TKA) components.According to these new observations, knee flexion is not linked to femoral rollback but to a rotational movement between tibia and femur. The axis of this rotation is situated in the medial compartment of the knee when an intact anterior craciate ligament is present and not centrally through the tibial spines. In case of ACL insufficiency, such as that following TKA, the center of rotation shifts into the lateral compartment. Furthermore, the form of the posterior femoral condyle is not elliptical but round.Rotational movements between femoral component and tibial baseplate with the polyethylene-inlay have to be possible. One needs an asymmetric surface of the polyethylene-inlay, because different movements occur in the medial compartment than in the lateral compartment. The option to construct the posterior femoral condyle with a single radius allows a high congruency with the articulating inlay. The surgeon should let the new findings influence his choice of a TKA system. A closer analysis of modern prosthetic designs with either fixed or mobile bearings reveals that a few systems have already incorporated some of the new kinematic aspects of the knee.

To what extent are carbon fibre-reinforced plastics (CFRP) suitable as an osseous integration surface for implants?CFRP test implants having a plexus-structured, rhombus-structured, and plexus-structured, hydroxyapatite surface were implanted in the femura of mini-plgs. Exposure time lasted 12 weeks. The implants were subjected to a macroradiological, a histological-histomorphometrical, and a fluorescence-microscopical evaluation.One half of the uncoated, plexus-structured implants were not osteointegrated, the other half displayed an osteointegration rate of 11.8% in the spongy area and 29.8% in the cortex layer. The HA-coated test implants showed an osteointegration of 29.5% in the spongiosa and 56.8% in the cortex layer. The rhombus-structured test implants had an osteointegration of 29.2% (spongiosa) and 46.2% (cortex layer).Compared to the osteointegration of metallic, especially titanium surfaces the CFRP surfaces tested by us fared worse, especially the uncoated, plexus-structured surfaces. For this reason we view very critically the use of carbon-fibre reinforced plastics together with the surfaces tested by us as osteointegrating surfaces.

The situation, described in this casuistry, shows the fatal consequences of the huge amount of wear particles from the PE-PMMA-components of a total hip prosthesis. The prosthesis had been implanted in Russia. It was made of a PE-ball fixed to a titanium stem and a socket, which had been molded intraoperatively in situ. The combination of PMMA and PE in the bearing surface caused an extreme osteolysis in the proximal femur and the acetabulum and the loosening of the cup and the stem within only a few months.

The situation, described in this casuistry, shows the fatal consequences of the huge amount of wear particles from the PE-PMMA-components of a total hip prosthesis. The prosthesis had been implanted in Russia. It was made of a PE-ball fixed to a titanium stem and a socket, which had been molded intraoperatively in situ. The combination of PMMA and PE in the bearing surface caused an extreme osteolysis in the proximal femur and the acetabulum and the loosening of the cup and the stem within only a few months.

The radiological assessment of osteoarthritis of the knee joint in longitudinal studies is usually performed with established classifications. It is disadvantageous that these features are always combined to describe a certain stage of the disease, even though they can develop independently.A german score based on a publication by Scott et al. (1993) was designed. At first 100 X-ray series of knees were evaluated using the JägerWirth, the KellgrenLawrence classification and the point score. Six observers then evaluated 200 anonymised radiographs of knee joints twice within 3 months.The most reliable criteria for the inter-observer reliancy were medial osteophytes, medial joint-line narrowing, patella osteophytes and chondrocalcinosis. At least 4 out of 6 observers had a high match in these criteria. The reproducability of most of the individual radiographic features was good, with a higher level of orthopaedic training resulting in a higher consistency of the score.A certain level of orthopaedic training is necessary for consistent results. The main focus of the score will be less the daily routine assessment of radiographs of the knee joint, but more the scientific assessment of radiographic progression of osteoarthritis in longitudinal studies.