Endoprosthesis shaft
AssigneeRobert Bosch GmbH
InventorsFriedrich J. Esper, Walter Gohl
Life of this patent
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Abstract
The load P on an artificial hip joint produces a bending moment on the endoprosthesis shaft composed of a shaft proper (1), a collar (2) fitting the resection plane and a cone (3) for carrying the femur ball (14). The extra load B thereby provided on the medial side of the femur is relieved by providing means for resisting the tension force A of the bending moment by providing the shaft with cavities (11) separated by ribs (12) as well as by a median longitudinal rib (broken lines).The bone grows into the cavities thus securing the area against the tension effects. Additional cavities (9) and wedge-shaped nubs (7) and (5) similarly oppose forces A and/or B. Hollows (10) on the underside of the collar (2), as well as the cavities (11) and (9), also oppose twisting forces.
Claims12
Endoprosthesis shaft for a hip joint having tension-release effect, said shaft having front, back, medial and lateral surfaces and being tapered for fitting into a bore in the top of a femur, said shaft having an oblique collar for fitting over the resected surface of the femur;
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- said lateral surface including tension force resisting means along a portion of the length thereof, said medial surface including compression force resisting means along the length thereof, said front and back surfaces including load-bearing means along the length thereof, said front and back surfaces further including a plurality of transversely formed, longitudinally spaced apart cavities located solely in the upper portion of said shaft adjacent said collar, each of said cavities being separated by transverse ribs, wherein said ribs and cavities are continuous about the juncture of said front, back and lateral surfaces and terminate in spaced apart relation on said lateral surface, said lateral surface having a continuous, longitudinally extending rib separating said ribs and cavities and terminating in the region of said tension resisting force means whereby said cavities accept tissue ingrowth thereby relieving tensional forces tending to shift said shaft relative to the bone.
Dependencies are inferred from the claim text.