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Biomedical subjects

E L Radin

Publications and source records attributed to E L Radin.

At least 19 recordsLinked to original sources
PubMed1991

Stress wave effects in a finite element analysis of an impulsively loaded articular joint.

A dynamic contact finite element formulation was used to study transient stresses in the impulsively loaded rabbit knee, an established experimental model of mechanically induced osteoarthrosis. The computations were used to test the hypothesis that stress wave propagation and reflection, from juxtarticular interfaces of material property discontinuity, could be responsible for markedly increased levels of transient local cartilage stress. The finite element results demonstrated intuitively credible stress wave propagation and interfacial reflection phenomena. However, the magnitude of these waves was not nearly large enough to appreciably alter the quasi-static stress distributions otherwise prevailing. Thus, local stress wave reflection from interfaces of modulus discontinuity (for example the cartilage/subchondral plate) probably does not contribute appreciably to the heightened tissue sensitivity to impulsive loading experimentally observed in this animal model.

Animals↗
PubMed1979

A rational approach to the treatment of patellofemoral pain.

Chondromalacia of the patella should be considered a separate entity and not the necessary precursor of osteoarthrosis. It is rarely associated with significant discomfort. Isolated softening, fibrillation of the central medial facet, and a diagnosis of chondromalacia of the patella should be limited, in our view, to isolated fibrillation occurring in the central medial facet and is probably asymptomatic. Symptomatic patellar pain can be treated by realignment if the patella is malaligned, by lateral release and synovial fringe excision if there is an anomalous facet or synovial fringe entrapment syndrome, and by drilling and curettage and stress-relieving operations (if necessary) if there is an osteochondral injury. For osteoarthrosis stress can be relieved on a permanent basis by the Maquet anterior tibial tubercle advancement operation. We recommend approaching patellofemoral pain by establishing a specific diagnosis and applying a specific treatment.

Cartilage Diseases↗
PubMed1979

Chondromalacia as a separate entity: new perspectives on osteoarthrosis.

Cartilage fibrillation does not necessarily progress. There appears to be different mechanical factors involved in the initiation and the progression of cartilage changes in osteoarthrosis. This means there is some rationale behind what we see clinically happening after successful osteotomy or other operations that lower the stress on degenerating joints, and it means that if we can do something about the level of stress and, therefore, the level of bone remodeling in patients with fibrillation, we may be able to keep that cartilage from further degenerating.

Adult↗
PubMed1978

Is chondromalacia patellae a separate clinical entity?

The articular cartilage of the patella was studied in 100 knees at necropsy. In twenty-one of these knees the cartilage changes were related to the trabecular architecture of the underlying bone. It would appear that the initiation and location of cartilage damage and its rate and degree of progression are related to the relative stiffness of the underlying cancellous bone. On the basis of our observations we suggest that the diagnosis "chondromalacia of the patella" should be reserved for patients with asymptomatic or transiently symptomatic fibrillation of the articular cartilage of the central medial patellar facet. Those patients with persistent patellofemoral pain should be considered to have some other syndrome.

Cartilage Diseases↗
PubMed1975

"Stiction-friction" of total hip prostheses and its relationship to loosening.

The static friction, or "stiction-friction", in McKee-Farrar and Charnley-Müller prostheses in a hip joint simulator was compared with dynamic friction determined while the prostheses were oscillated. Under physiological conditions stiction-friction differed little from dynamic friction in both metal-on-metal and metal-on-plastic prostheses, and was affected very little by the lubricant as long as some fluid was present. Stiction-friction increased significantly only after relatively long stationary periods and high loads. However, the frictional forces generated in total hip-replacement prostheses were at least forty times higher than those generated in normal joints and may well be enough to cause late loosening of acetabular components by fatigue failure.

Acetabulum↗
PubMed1975

Rationale and indications for the "hanging hip" procudure: a clinical and experimental study.

A series of 71 patients treated by "hanging hip" procedures was followed for up to 12 years. The procedure provided a satisfactory result in patients even with severe hip joint degeneration as long as the congruity of the joint is preserved and there was no concentration of stress. When these conditions are not fulfilled the results are poor. An experimental study was carried out to try and ascertain the physiological rationale for the "healing" seen in patients with good preoperative indications. The articular cartilage of one hip in cats was denuded with a curette. This was accompanied in half the animals with a "hanging hip" procedure. The hips of the animals with "hanging hip" went onto fibrocartilaginous and chondroid healing of their articular surfaces and clinically did well. The hips of the animals who did not have multiple tenotomies developed osteoarthrosis. Full thickness cartilage defects in weight-bearing areas in adult animals are capable of functional healing if the mechanical stress on the joint is sufficiently decreased. The "hanging hip" operation should no longer be considered a salvage procedure. A physiological rationale exists for it in properly selected patients and represents a reasonable alternative to total hip replacement.

Adolescent↗
PubMedDate not supplied

On the origins of high in vivo wear rates in polyethylene components of total joint prostheses.

Scanning electron microscope examination of the polyethylene components of 8 total hip and 16 total knee prostheses which had been implanted 4--96 months revealed that in many cases severe wear may not necessarily be caused by the presence of acrylic cement debris or other abrasives. The craters and cracks observed on severely worn surfaces are associated with fusion defects in the plastic itself. The fusion defects were seen to occur as a result of the low temperature necessary to mold ultrahigh molecular weight polyethylene and are (at least at present) difficult to avoid. As a consequence of the above and variability of molecular weight in this material, relatively wide variations in wear rate should be expected even in the absence of acrylic debris.

Acrylates↗