Last Updated on May 6, 2025
Bone healing is typically a well-orchestrated biological process involving inflammation, repair, and remodeling.
[Learn more about fracture healing]
However, in some patients, this process may be delayed or fail altogether, resulting in a nonunion or delayed union. Risk factors such as smoking, diabetes, infection, advanced age, and poor bone quality increase the likelihood of such complications.
In these cases, bone stimulators are often considered. These are non-invasive devices used to promote or accelerate bone healing. But do they work?
Let’s explore the types of bone stimulators, their mechanisms, current clinical evidence, and limitations.
What Are Bone Stimulators?
Bone stimulators are medical devices that apply physical stimuli—electrical, electromagnetic, or ultrasonic—to stimulate bone growth. They are primarily used in cases where bone healing is delayed or at risk of failure.
The basic idea is to create an external stimulus that mimics or enhances the natural electrical or mechanical signals the body uses to initiate bone regeneration.
These devices come in both external (noninvasive) and implantable (invasive) forms, depending on the indication.
Why Bone Stimulators are Needed?
Failure of a fracture to unite may result in nonunion or delayed union. These are common and significant problems faced in fracture healing. Internal or external fixation, bone grafting, and, more radically and rarely, amputation are the recommended invasive options.
The tibia is the most common bone to report nonunion, which could be as high as 35 percent.
A variety of biological, mechanical, and physical interventions have been developed to enhance fracture healing and decrease the requirement surgery. Physical methods to stimulate bone healing include electrical bone stimulators, low-intensity pulsed ultrasound, and extracorporeal shock waves.
Types of Bone Stimulators
Pulsed Electromagnetic Field (PEMF) Stimulators
PEMF devices generate low-frequency electromagnetic fields that penetrate soft tissue and influence cellular behavior. This type of stimulation is believed to promote osteoblast proliferation, increase expression of bone matrix proteins, and accelerate angiogenesis.
Most PEMF devices are worn externally over the fracture or surgical site for several hours a day.
A 2023 multicenter study on PEMF use in spinal fusion patients at risk for pseudarthrosis showed an 88% fusion rate, significantly higher than in non-stimulated controls [1].
Low-Intensity Pulsed Ultrasound (LIPUS)
LIPUS devices deliver mechanical energy in the form of sound waves to the fracture site. This stimulation promotes endochondral ossification, enhances vascularization, and facilitates the differentiation of mesenchymal stem cells into osteoblasts.
Devices like Exogen (Bioventus) are used daily for around 20 minutes. LIPUS is commonly prescribed for tibial shaft fractures and stress fractures in athletes.
A 2023 systematic review found that LIPUS reduced healing time in delayed tibial fractures by an average of 25% [2].
Electrical Bone Growth Stimulators
Electrical stimulators work by applying a direct or alternating current to the bone, either via implanted electrodes (invasive) or through skin-surface electrodes (capacitive or inductive coupling).
Electrical stimulation has been shown to enhance osteogenesis by increasing intracellular calcium levels and activating voltage-gated pathways essential for bone regeneration.
Some devices are surgically implanted during spinal fusions or used in long-standing nonunions with poor healing response.
There are three types:
- Direct-current stimulators
- Inductive coupling stimulators or pulsed electromagnetic fields
- Capacitive coupling stimulators
Direct-current bone stimulators need either implanted or percutaneously applied insulated electrodes. The other two are not invasive.
Newer devices have refined current modulation to better mimic physiological bone healing environments [3].
Indications for Use
Bone stimulators are not for routine fracture healing but are specifically indicated in:
- Nonunion fractures (failure to heal after >6 months)
- Delayed unions (healing slower than expected)
- Spinal fusion (especially in smokers, diabetics, or multilevel fusions where the risk of not uniting is greater)
- Stress fractures (in high-demand patients like athletes)
- Osteotomies or revision surgeries, where healing support is beneficial
Do Bone Stimulators Work- Supportive Evidence
There is a growing body of clinical evidence suggesting benefit in selected populations:
- PEMF has shown improved spinal fusion outcomes in several RCTs and meta-analyses [1,4].
- LIPUS has been associated with reduced healing times in tibial and radial fractures [2,5].
Additionally, newer trials have demonstrated better outcomes in compliance-monitored patients and with longer daily usage.
Limitations and Controversies
Despite promising data, bone stimulators are not universally effective.
- Mixed outcomes: Some studies report no significant difference between stimulator and placebo groups
- Compliance: Daily use (20 minutes to 8 hours) is required, and missed sessions reduce efficacy.
- Cost: Devices can be expensive ($3,000–5,000) and are variably covered by insurance.
- Mechanism uncertainty: While cellular theories exist, exact in vivo mechanisms remain partially understood.
Future Directions
The field is evolving rapidly. Research is focusing on:
- Smart stimulators: Devices with feedback loops that adjust stimulation in real-time
- 3D-printed piezoelectric implants: That generate internal electric fields through motion
- Combined therapies: Using growth factors or stem cells along with physical stimulation
- Patient selection algorithms: Using imaging and biomarkers to predict who will benefit most
Conclusion
Bone stimulators are valuable adjuncts in orthopedics when used appropriately. PEMF, LIPUS, and electrical stimulation all have demonstrated benefits in specific clinical settings, particularly nonunion fractures and spinal fusions.
They should not replace surgical or biological intervention when clearly indicate,d but offer a low-risk, non-invasive option that may avoid reoperation in certain patients.
Their role will likely continue to grow as technology improves and as selection criteria become more precise.
References
- Weinstein MA, Beaumont A, Campbell P, Hassanzadeh H, Patel V, Vokshoor A, Wind J, Radcliff K, Aleem I, Coric D. (2023). Pulsed Electromagnetic Field Stimulation in Lumbar Spine Fusion for Patients With Risk Factors for Pseudarthrosis. International Journal of Spine Surgery, 17(6), 816–823. https://pubmed.ncbi.nlm.nih.gov/37884337/
- McDaniel M, Eltman NR, Pan J, Swanson RL 2nd. Evaluation of Low-Intensity Pulsed Ultrasound on Stress Fractures to Reduce the Time to Return to Sport or Activity in the Physically Active Population: A Systematic Review. Cureus. 2023 Nov 20;15(11):e49129. doi: 10.7759/cureus.49129. PMID: 38024090; PMCID: PMC10659586.
- Nicksic PJ, Donnelly DT, Hesse M, Bedi S, Verma N, Seitz AJ, Shoffstall AJ, Ludwig KA, Dingle AM, Poore SO. Electronic Bone Growth Stimulators for Augmentation of Osteogenesis in In Vitro and In Vivo Models: A Narrative Review of Electrical Stimulation Mechanisms and Device Specifications. Front Bioeng Biotechnol. 2022 Feb 14;10:793945. [Link]
- Dolkart O, Kazum E, Rosenthal Y, Sher O, Morag G, Yakobson E, Chechik O, Maman E. Effects of focused continuous pulsed electromagnetic field therapy on early tendon-to-bone healing. Bone Joint Res. 2021 May;10(5):298-306. [Link]
- Aifantis ID, Ampadiotaki MM, Pallis D, Tsivelekas KK, Papadakis SA, Chronopoulos E. Biophysical Enhancement in Fracture Healing: A Review of the Literature. Cureus. 2023 Apr 17;15(4):e37704. [Link]
