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Letters to the Editor to:

Scientific Articles:
Brent Mollon, Vitor da Silva, Jason W. Busse, Thomas A. Einhorn, and Mohit Bhandari
Electrical Stimulation for Long-Bone Fracture-Healing: A Meta-Analysis of Randomized Controlled Trials
J Bone Joint Surg Am 2008; 90: 2322-2330 [Abstract] [Full text] [PDF]
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Electronic letters published:

[Read Letter to the Editor] Dr. Bhandari and colleagues respond to Dr. Pienkowski
Mohit Bhandari, MD, FRCSC, Jason W. Busse, PhD and Brent Mollon, BHSc   (19 February 2009)
[Read Letter to the Editor] Capacitive Coupled Stimulation is Different From Electromagnetic Stimulaltion
David Pienkowski, PhD   (10 February 2009)

Dr. Bhandari and colleagues respond to Dr. Pienkowski 19 February 2009
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Mohit Bhandari, MD, FRCSC,
Orthopaedic Surgeon
CLARITY Research Group, Division of Orthopaedic Surgery, McMaster University,
Jason W. Busse, PhD and Brent Mollon, BHSc

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Re: Dr. Bhandari and colleagues respond to Dr. Pienkowski

bhandam{at}mcmaster.ca Mohit Bhandari, MD, FRCSC, et al.

We thank Dr. Pienkowski for his letter and interest in our study (1). One of our stated eligibility criteria was “inclusion of a treatment arm receiving electromagnetism of any waveform to impact bone-healing” and, as such, both studies by Scott and King (2) and Beck et al. (3) were eligible for our review.

In our methods section we advanced, a priori, that one source of variability between studies may by due to different technical specification of trial devices; however, given the small number of diverse trials available we felt unable to conduct meaningful subgroup analyses according to this parameter.

If we remove the trial by Scott and King from our meta-analysis of rates of long bone union, our pooled relative risk changes from 1.76 (95% CI 0.81, 3.80), with an associated I2 of 60%, to 1.57 (95% CI 0.76, 3.25), with an associated I2 of 64%. Thus, the removal of this trial does not appreciably modify our results or the associated heterogeneity.

On their own, neither trial that applied electrical capacitive coupling to enhance bone healing demonstratred a statistically significant effect (2, 3).

Further trials are required to establish if electromagnetic stimulation or electrical capacitively-coupled stimulation are effective in accelerating fracture healing.

References

1. Mollon B, et al. Electrical stimulation for long-bone fracture- healing: a meta-analysis of randomized controlled trials. J Bone Joint Surg Am, 2008. 90(11): p. 2322-30.

2. Scott, G and JB King, A prospective, double-blind trial of electrical capacitive coupling in the treatment of non-union of long bones. J Bone Joint Surg Am, 1994. 76(6): p. 820-6.

3. Beck BR, et al. Do capacitively coupled electric fields accelerate tibial stress fracture healing? A randomized controlled trial. Am J Sports Med, 2008. 36(3): p. 545-53.
Capacitive Coupled Stimulation is Different From Electromagnetic Stimulaltion 10 February 2009
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David Pienkowski, PhD,
Professor
University of Kentucky

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Re: Capacitive Coupled Stimulation is Different From Electromagnetic Stimulaltion

pienkow{at}uky.edu David Pienkowski, PhD

To the Editor:

Mollon et al. state in their article “Electrical Stimulation for Long-Bone Fracture-Healing: A Meta-Analysis of Randomized Controlled Trials” that their analysis was restricted to publications involving electromagnetic stimulation(1).

However,two of the eleven studies included in their meta-analysis, i.e., Scott and King [2] and Beck et al [3] used capacitive-coupled stimulation exclusively. The term “capacitive-coupling” was clearly denoted in the titles, abstracts, and methods of these two publications.

Electromagnetic stimulation and capacitively-coupled stimulation both involve electrical and magnetic fields, but the means by which stimulation is applied, the tissue-level distribution of applied magnetic and induced electrical fields, and the mechanisms of action differ between these stimulation modalities. Electromagnetic stimulation and capacitively-coupled stimulation are distinct, non interchangeable, and should not be mixed in a meta-analysis restricted to electromagnetic stimulation only.

Mollon et al.(1) noted that two reviewers “read in full” each publication. It is therefore puzzling how these two studies,(2,3) were included in a meta-analysis intended to be restricted to electromagnetic stimulation.

Electrical stimulation is a third modality. It differs from the other two in its means of application, tissue-level field distribution, and mechanism of action. Use of this modifier in the title of the article by Mollon et al.(1) was inaccurate given the restriction of their study to electromagnetic fields. Furthermore, repetitive use of the expression “electromagnetic force” by Mollon et al.(1) was incorrect. This term refers to one of the four fundamental forces in nature, but not to the magnitude of the electrical potential induced in conducting media by a time-varying applied electromagnetic field.

The author did not receive any outside funding or grants in support of his research for or preparation of this work. Neither he nor a member of his immediate family received payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity. No commercial entity paid or directed, or agreed to pay or direct, any benefits to any research fund, foundation, division, center, clinical practice, or other charitable or nonprofit organization with which the author, or a member of his immediate family, is affiliated or associated.

References

1. Mollon, B., et al., Electrical stimulation for long-bone fracture-healing: a meta-analysis of randomized controlled trials. J Bone Joint Surg Am, 2008. 90(11): p. 2322-30.

2. Scott, G. and J.B. King, A prospective, double-blind trial of electrical capacitive coupling in the treatment of non-union of long bones. J Bone Joint Surg Am, 1994. 76(6): p. 820-6.

3. Beck, B.R., et al., Do capacitively coupled electric fields accelerate tibial stress fracture healing? A randomized controlled trial. Am J Sports Med, 2008. 36(3): p. 545-53.