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Electrical Stimulation as a Therapy for Bone Growth

IP.com Disclosure Number: IPCOM000006589D
Publication Date: 2002-Jan-16
Document File: 5 page(s) / 57K

Publishing Venue

The IP.com Prior Art Database

Abstract

Described herein is a means of providing chronic direct and/or alternating electrical stimulation to a fractured or otherwise diseased bone with one or more microstimulators that can be implanted with a minimal surgical procedure. Prior research suggests that stimulation of a fractured bone may promote effective bone growth and fracture healing. Electrical stimulation may also assist in the healing of related disorders in bones such as pseudoarthrosis or avascular necrosis. Non-healing bone fractures of clinical significance, generally in the limbs or the spine, may be relatively easily accessed. Other non-healing bone fractures (e.g., in the pelvis) may be accessed percutaneously with the use of a syringe, a cannula, an endoscope, or a laparoscope. A miniature implantable electrical stimulator (a.k.a., a microstimulator) capable of delivering a direct and/or alternating electric current may be implanted within or adjacent to a non-healing bone via a minimal surgical procedure (e.g., injection or small incision) for the promotion of bone growth and fracture healing. As used herein, stimulation refers to supplying a direct electrical current, including a low-level direct electrical current, or an alternating current. Thus a microstimulator is sometimes referred to herein as a current generator, and electrical current parameters are sometimes referred to herein as stimulation parameters. Such electrical stimulation of non-healing bones may promote effective bone growth and fracture healing through the stimulation and promotion of circulation, production of growth factors, stimulation of osteogenesis, and through piezoelectric effects on bone. Electrical stimulation may additionally treat symptoms of non-healing fractures and related disorders, such as pain.

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Electrical Stimulation as a Therapy for Bone Growth

Summary & Background

Fractures in the US are increasing in both absolute numbers and as a percentage of hospital admissions. The expanding and aging of the population leads to greater risks for forearm, femoral neck, and trochanteric fractures. Interestingly, age-specific and age-corrected fracture rates are also increasing throughout North America and northern Europe. In fact, recent projections predict a 20% increase in fractures over the next two decades. More accurate reporting of data might modify the apparent secular increase in bone fracture rates. Increased hospital use for the management of simple fractures may also contribute to these statistics. Possibly, the same fracture may be recorded several times as separate hospital admissions, including cast removal appointments and subsequent follow-up visits. However, evidence supporting increased fracture rates is demonstrated on an international scope, spanning Canada, the United Kingdom, Scandinavia, and the United States. In addition, it is verified in the well-maintained records of major urban hospitals.

Sedentary life styles, substantial television viewing, decreased energy, and decreased mineral intake, especially calcium, phosphorus, and magnesium, all contribute to bone deterioration and fracture initiation. The minerals required for healthy bones are highly calorie-dependent; people may be consuming inadequate nutrient amounts needed for maintenance of the skeletal system and to preserve the integrity of round, flat, and tubular bones.

Fractures are the major clinical consequence of osteoporosis. In 1990, there were 250,000 hip fractures in the U.S. and 1.7 million worldwide. Alarmingly, by the year 2040, this rate may soar to 840,000 hip fractures in the U.S. and 6.26 million worldwide. Monetary costs of bone fractures may grow inordinately given America's aging population.

CONVENTIONAL METHODS OF BONE FRACTURE HEALING

Bone Grafting: For centuries, skeletal deficits have been successfully repaired with osseous grafts, as documented by numerous medical records of varying credibility. The choice of appropriate bone graft substitutes is extensive and should be based upon biological and biomechanical advantages and disadvantages and a clear understanding of the clinical circumstances and goals of the reparative procedure. Bone graft incorporation is an interactive process between the graft and its host bed. Serving as a passive scaffold or template for osteoconduction, the grafts are invaded with blood vessels replete with multipotential cells that differentiate into populations specialized in bone formation or resorption. The graft may also direct active signals to the host for regulating and influencing the incorporation process.

Internal Fixation: Rigid internal fixation initiates primary vascular repair, fracture healing without callus formation. The fracture must be stable, anatomically aligned, and surfaces must remain in in...