A bone growth stimulator (BGS) is a medical device designed to promote the healing of fractures or fusions that are slow to mend or have failed to heal completely. These devices deliver energy, typically in the form of electrical signals, magnetic fields, or sound waves, directly to the site of the bone injury. They are used as an adjunctive treatment, meaning they work alongside traditional orthopedic care like casting or surgery, and can be either external (non-invasive) or surgically implanted (invasive).
How Bone Growth Stimulators Work
Bone growth stimulators rely on the body’s natural bioelectrical properties, specifically the piezoelectric effect in bone tissue. When bone is stressed, it generates small electrical potentials, which are a signal that triggers the natural healing cascade. External stimulators are designed to mimic or enhance these weak electrical signals to accelerate the biological response.
This externally applied energy translates into cellular activity by stimulating osteoprogenitor cells, which are the precursors to bone-forming cells. The stimulation increases the proliferation of osteoblasts, the cells responsible for synthesizing new bone matrix, and promotes the differentiation of these cells to speed up the process of callus formation and maturation. This accelerated cellular signaling drives faster new bone formation across the fracture gap.
Categorizing Available Stimulation Technologies
Bone growth stimulators are categorized primarily by the type of energy they use to influence cellular activity, ranging from non-invasive external devices to implanted surgical hardware. One widely used non-invasive method is Pulsed Electromagnetic Fields (PEMF), which uses inductive coupling via coils placed around the injury site to generate a time-varying magnetic field. This field induces a perpendicular electric current deep within the tissue, promoting healing without direct contact with the skin’s surface.
Another non-invasive technology is Capacitive Coupling (CC), which involves placing two electrodes on the skin on opposite sides of the fracture to create a low-level electrical field across the bone. In contrast, Low-Intensity Pulsed Ultrasound (LIPUS) devices use acoustic radiation, or mechanical energy, delivered through a transducer applied to the skin over the injury.
Invasive devices utilize Direct Current (DC) stimulation, where electrodes are surgically implanted directly into the fracture site and connected to a power source, either implanted or external. These devices provide a consistent electrical current and are often reserved for specific high-risk or difficult non-unions. All of these devices are regulated by the Food and Drug Administration (FDA) to ensure their safety and intended use.
Evaluating Clinical Effectiveness and Prescription Criteria
The prescription of a bone growth stimulator is determined by medical necessity, primarily focusing on fractures that exhibit delayed union or established non-union. They are also frequently prescribed as an adjunct to spinal fusion surgery, particularly in patients considered high-risk for fusion failure. This high-risk category includes individuals with conditions known to impair bone healing, such as those who smoke, have diabetes, or require a multi-level spinal fusion procedure.
Clinical effectiveness is commonly measured by the time it takes to achieve radiographic union, which is visualized by bridging bone callus on an X-ray, and the overall percentage of successful fusion. Meta-analyses of randomized trials have indicated that electrical stimulation can reduce the relative risk of non-union by around 35% compared to controls in certain populations. For spinal fusion, some studies have shown that the use of an implanted DC stimulator can increase successful fusion rates from approximately 54% to over 80% in high-risk patients.
For instance, most devices are indicated for long bone non-unions, but are generally not recommended if the fracture gap exceeds one centimeter. The efficacy of the device is condition-dependent, and the best predictor of success comes from data matching the patient’s specific injury and risk profile.
Practical Considerations: Cost, Insurance, and Compliance
The retail cost of a bone growth stimulator is substantial, often ranging from several thousand to tens of thousands of dollars, making insurance coverage a major practical consideration. Obtaining coverage nearly always requires a pre-authorization process, where the physician must document strict medical necessity criteria, including the time elapsed since the injury and radiographic evidence of non-union. Coverage varies significantly, often covering non-union of long bones and high-risk spinal fusions, but sometimes excluding use for acute, fresh fractures unless specific risk factors are present.
Even with coverage, patients are typically responsible for deductibles, co-payments, or co-insurance. The actual success of the therapy is heavily dependent on patient compliance with the prescribed daily usage schedule. Non-compliance is one of the most significant factors that reduces the effectiveness of the stimulator.
Depending on the technology, daily treatment times can range from as little as 20 or 30 minutes for some PEMF devices to several hours for others, usually over a total treatment period of three to nine months. Consistent, daily use as directed by the physician is paramount, and many physicians will monitor device usage data to verify adherence to the protocol.