Implanted bone stimulator and prosthesis system and method of enhancing bone growth

Abstract

An implanted piezoelectric module generates charge which may be applied to tissue or used to power or recharge an implanted device such as a pump or pacemaker. In a system for enhanced bone healing or anchoring of an implanted bone prosthesis such as a plate, stem, articulation component or other structural component, the piezoelectric element is coupled to receive mechanical strain from body activity and generates a charge which is applied to enhance bone growth for anchoring the prosthesis. In one embodiment, the piezoelectric element is attached to a prosthetic hip stem on the medial side in a position on the shoulder or neck of the stem to preferentially undergo compressive strain. Preferably the element attaches near the surface and is poled such that its outer surface constitutes a negative electrode that operates to stimulate bone growth across an opposing receiving gap in the proximal femur. In another embodiment, an electrode lead extends distally from the piezoelectric element to apply the generated charge remotely thereto, such as at a prosthetic stem or fracture plate distal to the element itself. The piezo element may be located on a different bone. A metal mesh screen may apply the piezo-generated charge over a region of the bone surface to enhance growth of a thickening body at a desired region, for example at a region typically subject to stress shielding. The piezoelectric element may also be positioned in a region of tensile strain, with its cathodic pole extending to the desired growth gap or intended region of bone accretion. Oppositely poled elements may be positioned on opposing sides of a long bone or prosthesis so that the tensile and compressive stresses in opposed region produce charge of like polarity. Additional circuit elements may be attached to the implanted piezo elements to modulate or condition the charge electromechanically generated by the element and optimize its growth-stimulating effect.

Dependencies are inferred from the claim text.