Bone Growth Stimulation: What The Evidence Reveals

In a thorough review of the literature, this author details current and investigational uses, discusses a variety of modalities and assesses the quality of evidence for bone growth stimulation.   

There are a variety of techniques one may employ to enhance bone healing and surgeons are increasingly utilizing these techniques to assist with fracture healing, and help improve outcomes with arthrodesis and osteotomy procedures.

Bone growth stimulation may involve the use of invasive, semi-invasive or non-invasive techniques. In addition, ultrasonic energy, magnetic field therapy, extracorporeal shockwave therapy (ESWT), low-energy laser therapy and other mechanical therapies are options for the treatment of delayed union, non-union, failed arthrodesis and congenital pseudarthrosis. Researchers have also studied the use of bone growth stimulators for the treatment of Jones fractures.¹

Medicare criteria for bone growth stimulators include the initial administration of appropriate conservative care. After three consecutive months, if there is no clinical healing or radiographic changes (via multiplanar radiographic studies) demonstrating progression of bone healing, Medicare criteria allow for utilization of a bone growth stimulator.² The Food and Drug Administration classifies a non-union as a failure of bony union at nine months.³

Various researchers have discussed investigational uses for bone growth stimulation.^4-7 These uses include the treatment of avascular necrosis, Charcot joint disease, pathologic fractures, stress fractures, osteochondral lesions with or without osteochondral autograft transfer system (OATS) procedures, calcaneal apophysitis and distraction arthrodesis.

Despite the widespread acceptance of bone stimulators for the augmentation and management of bone healing, the literature supporting the utilization of bone stimulators is not strong. There is a heterogeneity of trials and a heterogeneity of devices utilized for study.⁸ Differences exist from study to study for the clinical and radiographic definition of complete healing. Large, randomized, placebo-controlled trials are lacking and most of the data available for review consists of case series and comparative studies.

Addressing Contributing Factors To Non-Unions
It is important to recall that in many instances, one may identify and treat the cause of a non-union. Persistence of a large osteotomy or fracture gap, or the failure to reduce an arthrodesis adequately may result in non-union. Other causes of non-union include inadequate immobilization, significant malalignment, infection and inadequate vascularity. In addition, a variety of patient factors may be responsible for delayed union or non-union. These factors include smoking, corticosteroids, anticoagulation therapy, vascular insufficiency, diabetes, obesity, pathologic fractures or open fractures. Other factors such as vitamin D deficiency or other nutritional factors may play a role in the failure of bone to heal adequately.

Although a healthcare provider’s perception that bone healing may be difficult or impaired would seemingly justify the use of a bone stimulator, the current research has not demonstrated that the utilization of a bone stimulator under certain circumstances is effective. For example, there is no indication that bone growth stimulators are useful for healing stress fractures. Conversely, studies have demonstrated accelerated healing time with the use of bone stimulation in smokers.⁹

In analyzing any delayed union or non-union of a fracture, osteotomy or arthrodesis, it is incumbent upon the treating healthcare provider to seek and identify those factors, such as inadequate immobilization, that may be causative or contributory, and subsequently employ appropriate therapies to interdict or reverse such factors.

What The Research Shows About The Treatment Of Fresh Fractures And Delayed Or Non-Unions
Fresh fractures. Authors have studied electrical stimulation for the treatment of fresh fractures primarily in the tibia and radius, demonstrating accelerated healing rates between 24 and 42 percent.^9,10 The more difficult the fracture, such as comminuted fractures, the greater the benefits for the use of a bone stimulator.

Delayed union and non-union. There has been extensive study of delayed union and non-union of the humerus, radius, tibia, ulna and femur with healing rates ranging between 67 to 90 percent when one employs bone stimulators together with other traditional techniques of management, such as immobilization, bone grafting, revision and rigid fixation.¹¹

What About Implantable Direct Current Devices?
Physicians commonly employ implantable bone growth stimulators for difficult arthrodesis procedures of the ankle and hindfoot. Direct current implantable bone stimulators work from a subcutaneously implanted lithium battery that generates 5-100 mA of energy over six to eight months. The implantable bone stimulators offer a constant uniform current and eliminate the need for patient adherence. The disadvantages of such stimulators include a limited battery life of six to eight months, some degree of difficulty placing hardware in some patients, potential short circuiting, difficulty and management of infection, and the need for a second procedure for removal of the implanted devices.

Interestingly, no level 1 studies exist to support the utilization of implantable direct current devices. The majority of literature consists of case series with no control groups.⁸

What You Should Know About Electromagnetic Bone Growth Stimulation Devices
We can classify electromagnetic bone growth stimulation devices as providing inductive coupling, capacitive coupling or combined therapy.

Inductive devices, commonly referred to as pulsed electromagnetic field (PEMF) devices, consist of an external coil that patients may use over dressings or a cast. Most inductive devices require use of up to 10 hours daily, providing a biphasic, quasi-rectangular waveform to the fracture, osteotomy or arthrodesis site. The device provides program fluctuations in amplitude and frequency.

Capacitive coupling devices consist of an external power source providing a frequency of 20-200 kHz to the fracture site. This delivers 100 V/cm energy within the fracture. The devices are typically small and lightweight, and easily employed. They do require frequent battery changes.

Combined therapy utilizes a static direct current field together with a sinus waveform that flows to the next terminal coil, which one can very easily administer as a 30-minute daily treatment. The ease and brevity of use result in better patient adherence.

Pertinent Insights On Low Intensity Pulsed Ultrasound And Related Therapies
Low intensity pulsed ultrasound produces micromotion detected by integrin receptors within bone. It results in increased cyclooxygenase 2 concentration within the fracture or osteotomy site, increased prostaglandin E2, increased blood flow, increased mineralization and increased growth factors including vascular endothelial growth factor (VEGF) and interleukin-8 as well as calcium within the bone.
Although the exact mechanism of action remains somewhat unclear, it does appear that low intensity pulsed ultrasound applies mechanical pressure to the bone, promoting bone formation in a manner comparable to mechanical stress. Physicians commonly employ low intensity pulsed ultrasound for the treatment of foot and ankle pathology although researchers have primarily studied this modality for the treatment of tibial fractures.¹¹

Low intensity pulsed ultrasound requires a convenient 20 minute daily treatment at 30 mW/cm² and is not associated with any known potential adverse sequelae. Unlike other therapies, ultrasonic bone growth stimulation has indications for the treatment of fresh fractures in cortical bone, bones of poor vascularity, fractures associated with a known high rate of non-union or fractures that are clinically or radiographically slow to heal.

Extracorporeal shockwave therapy (ESWT) is reportedly very successful in assisting the resolution of delayed unions or non-unions.¹² However, as is the case for other modalities utilized for the treatment of problematic bone healing, the overwhelming majority of published works utilize ESWT together with other modalities.¹³ Some studies have demonstrated that the combination of ESWT with immobilization is so successful for the treatment of delayed or non-union that one should consider it as a first-line treatment for such problematic bone pathology.¹⁴

Studies have demonstrated low level laser therapy as having a positive impact on bone healing.¹⁵ Many papers on low level laser therapy utilize a helium-neon laser but the overwhelming majority of these studies are laboratory studies and not clinical studies.

Assessing The Quality Of Evidence On Bone Growth Stimulators
While the utilization of bone stimulators and similar devices would seem to have compelling potential to help facilitate bone healing, a serious review of the literature questions the effectiveness of such devices. Many of the common conditions for bone stimulators such as Charcot joint disease, stress fractures and avascular necrosis have no substantial support in the literature beyond case reviews and series presentations.

A summary of the literature indicates that only capacitive coupling devices have a grade B literature support.⁸ Direct current devices have only a grade C recommendation. Inductive coupling devices have only a C recommendation. Although clinicians commonly utilize combined therapy, there is insufficient data to allow any conclusions regarding clinical effectiveness. While low intensity pulsed ultrasound has a grade B for treatment of fresh fractures, it only has Grade C literature support for delayed or non-unions.

In a comparison of technology, low intensity pulsed ultrasound versus direct current therapy demonstrates no difference in outcome for bone healing.⁸ Similarly, studies comparing direct current versus capacitive coupling versus bone grafting demonstrated no difference in outcome.¹⁶ In the treatment of tibial non-unions, there was no difference in the outcome of surgical management versus pulsed electromagnetic field devices.¹⁷

There is no level 1 study to support the use of bone stimulators for commonly performed arthrodesis procedures, fresh fracture healing and stress fracture management to assist in the healing of foot and ankle osteotomy, avascular necrosis, or Charcot joint disease.

There have been small studies on the use of bone stimulation for the treatment of Charcot joint disease including tibial calcaneal fusion, pantalar fusion, tibiotalocalcaneal arthrodesis, including studies in which researchers also utilized bone grafting and rigid fixation.^4,18 Similarly, one small study utilizing a combined magnetic field demonstrated reduced time to consolidation for the treatment of Charcot joint disease but the small sample size and selection bias prevent firm conclusions regarding the utilization of the combined magnetic field.¹⁹

Bone stimulators are not indicated for fractures of cancellous bone, fracture gaps greater than 50 percent of the diameter of the bone at the level of the fracture, synovial pseudarthrosis, when there is fixation with magnetic materials, in pregnant women or in patients with skeletal immaturity.²⁰ In addition, one would not employ a bone stimulator in patients with pacemakers or defibrillators without the consent of a consulting cardiologist.

In Summary
Although physicians commonly employ bone stimulators for a variety of pathologic conditions, the literature supporting their use for other than delayed union or non-union of the long bones is minimal and frequently nonexistent. It is important to determine the origin of a non-union in any particular patient and consider those factors that we can manage by non-operative or operative means. Consider cost versus benefits in view of the alternatives available.

Dr. Jacobs is a Fellow of the American College of Foot and Ankle Surgeons, and a member of the Association of Physicians in Wound Healing. He is in private practice in St. Louis.

References

1.     Holmes GB. Treatment of delayed unions and nonunions of the proximal fifth metatarsal with pulsed electromagnetic fields. Foot Ankle Int. 1994;15(10):552-556.
2.     Centers for Medicare and Medicaid Services. Decision memo for electrical stimulation for fracture healing. Available at https://tinyurl.com/hy6zxc7 .
3.     Brinker MR. Skeletal Trauma: Basic Science Management, and Reconstruction, Third Edition, Chapter 22. Saunders, Philadelphia, 2003, p. 1.
4.     Hockenbury RT, Gruttadauria M, McKinney I. Use of implantable bone growth stimulation in Charcot ankle arthrodesis. Foot Ankle Int. 2007;28(9):971-976.
5.     Yoshimura I, Kanazawa K, Takeyama A, et al. Arthroscopic bone marrow stimulation techniques for osteochondral lesions of the talus: prognostic factors for small lesions. Am J Sports Med. 2013; 41(3):528-34.
6.     Steinberg ME, Brighton CT, Hayken GD, et al. Early results in the treatment of avascular necrosis of the femoral head with electrical stimulation. Orthop Clin North Am. 1984;15(1):163–75.
7.     Kivel CG, d’Hemecourt CA, Micheli LJ. Treatment of iliac crest apophysitis in the young athlete with bone stimulation: report of 2 cases. Clin J Sport Med. 2011;21(2):144–147.
8.     Griffin M, Bayat A. Electrical stimulation in bone healing: critical analysis by evaluating levels of evidence. Eplasty. 2011; 11:e34.
9.     Cook SD, Ryaby JP, McCabe J, et al. Acceleration of tibia and distal radius fracture healing in patients who smoke. Clin Orthop. 1997;337:198-207.
10.     Heckman JD, Ryaby JP, McCabe J, et al. Acceleration of tibial fracture-healing by non-invasive, low-intensity pulsed ultrasound. J Bone Joint Surg Am. 1994;76(1):26-34.  
11.     Warden SJ, Bennell KL, McMeeken JM, et al. Acceleration of fresh fracture repair using the sonic accelerated fracture healing system (SAFHS): A review. Calcif Tissue Int. 2000;66(2):157-163.  
12.     Valchanou VD, Michaliov P. High energy shock waves in the treatment of delayed and nonunion of fractures. Int Orthop. 1991; 15(3):181-184.
13.     Zelle BA, Gollwitzer H, Zlowodzki M, Buhren V. Extracorporeal shock wave therapy: current evidence. J Orthop Trauma. 2010; 24(Suppl 1):S66-70.
14.     Bara T, Snyder M. Nine years experience with the use of shock waves for treatment of bone union disturbances. Ortop Traumatol Rehabil. 2007; 9(3):254-8.
15.     Mostafavinia A, Masteri Farahani R, Abbasian M, et al. Effect of pulsed wave low-level laser therapy on tibial complete osteotomy model of fracture healing with an intramedullary fixation. Iran Red Crescent Med J. 2015;17(12):e32076.
16.     Brighton CT, Shaman P, Heppenstall RB, et al. Tibial nonunion treated with direct current, capacitive coupling, or bone graft. Clin Orthop Relat Res. 1995;(321):223-34.
17.     Gossling HR, Bernstein RA, Abbott J. Treatment of ununited tibial fractures: a comparison of surgery and pulsed electromagnetic fields (PEMF). Orthopedics. 1992; 15(6):711-19.
18.     Simonis RB, Parnell EJ, Ray PS, Peacock JL. Electrical treatment of tibial non-union: A prospective, randomised, double-blind trial. Injury. 2003;34(5):357-362.
19.     Hanft JR, Goggin JP, Landsman A, Surprenant M. The role of combined magnetic field bone growth stimulation as an adjunct in the treatment of neuroarthropathy/Charcot joint: An expanded pilot study. J Foot Ankle Surg. 1998;37(6):510-515; discussion 550-551.
20.     Health Technology Assessment Final Report: Bone Growth Stimulators. Available at https://www.hca.wa.gov/hta/documents/bgs_final_report_073109_updated.pdf . Published July 31, 2009.

Editor’s note: This article has been adapted from a previously published DPM Blog by Dr. Jacobs at https://tinyurl.com/z352wqv .