Deformation studies of the femur under various loadings and orientations

Abstract

Deformation studies of the femur under static and dynamic vertical loading have been reported by Evans and Lissner ('48) and by Evans, Lissner and Pedersen ('48). Those studies indicated that the " stresscoat" technique was valuable in graphically portraying the transmission of forces through bone and the deformation produced by those forces. I n vertical loading the first deformations occurred in the superior aspect of the neck and the anterolateral aspect of the shaft indicating that those areas were under tension. It was also noted that a small amount of energy (15.8 inch pounds) suddenly applied produced deformations of approximately the same magnitude as the gradual application of a much greater static force (400-700 pounds).The present investigations were undertaken to demonstrate the manner in which forces are transmitted through the femur under varying circumstances. As in the previous studies of this series (loc. cit.) the controlled variables in the various tests have been the orientation of the bone, the point of application of the force and the magnitude of the force. I n some of the tests the latter factor was increased to the point of failure (fracture). In tlie present paper the results of '' stresscoat " tests under the following conditions are presented : vertical dynamic loading when the infracondylar plane of the femur forms a laterally opening angle of 3" with the horizontal plane; static and dyiiamic "abduction" loading ; static torsion loading. MATERIALS AND METHODSThe material used in this study consists of the same femora employed and described in the earlier investigations of this series (Evans et al., '48).The apparatus used for making the dynamic vertical and the "abduction" loading tests are illustrated in figures 1, 2 Fig. 1 Apparatus for vertical dynamic loading tests. The femur is resting on an adjustable brass wedge set so that the infracondylar plane makes a 3" angle (opening laterally) with the horizontal plane. The wedge itself is resting upon a 160-pound steel block. The 7.9-pound weight is released by burning through the supporting cord. General orientation of the bone used in the second series of "abduction" loading tests. The head of the femur is raised 282 mm above the floor upon which the medial condyle is resting. I n other tests the distance of the head of the bone from the floor and the distance through which the weight was dropped were varied. The method of applying the load was the same as in the preceding figures. Fig. 3 162PEDERSEN, EVANS AND LISSNER the weight of the block (7.9 pounds) by the distance through which it fell. Steel and brass blocks were used because they absorbed only a small proportion of the energy applied to the bone resting on them. I n each test the weight was caught by hand on the first rebound so that it struck the bone only once.The static "abduction" loading tests were made in a BaldwinSouthwark materials-testing machine calibrated to an accuracy of one-half per cent. The torsion loading tests were made in a torsion machine of a similar ...

Forces Acting on the Femoral Head-Prosthesis: A Study on Strain Gauge Supplied Prostheses in Living Persons

“…Evans and co-workers have made numerous strain analyses in the upper part of the femur. Stresscoat studies have been performed using a vertical load and with the intracondylar plane horizontal or with a laterally open angle of 3 0 (Evans 1948, Pedersen, Evans andLissner 1949), Evans, Pedersen and Lissner 1951, Lissner and Evans 1956, and Evans 1962. Rauber (1876), Koch (1917) and Knese (1956Knese ( , 1957, pointed out the impaired resistance to tensile stress of bone and this has been verified by Evans and co-workers.…”

Studies in Human Biomechanics

“…That the behavior of the femur was like that of an elastic body was easily demonstrated (Evans and Lissner, 1948) by static vertical loading of the bone. In the unloaded bone (FIGURE lOa), a white thread cxtending vertically from the most medial point on the head of the bone to the shaft was taut.…”

“…FIGURE 2b). Dynamic vertical loading of the femur has a similar effec (Evans, Lissner, and Pedersen, 1948).…”

Mechanics in the Production of Mandibular Fractures: A Study with the "Stresscoat" Technique. I. Symphyseal Impacts

“…In the third set of tests, an area of the Woods metal bar under the loft condyle was est tensile strains.7 13 Therefore, only the minimal amount of energy required to crack the lacquer was used. When a greater magnitude of energy was appliedJ but not sufficienat to break the specimen, extensive deformation patterns appeared and it was not possible to determine which regions were the initial high tensile strain areas.…”