Durable Medical Equipment Section - Electrical Bone Growth Stimulators (Osteogenic Stimulation)

IMPORTANT REMINDER

This Medical Policy has been developed through consideration of medical necessity, generally accepted standards of medical practice, and review of medical literature and government approval status.

Benefit determinations should be based in all cases on the applicable contract language. To the extent there are any conflicts between these guidelines and the contract language, the contract language will control.

The purpose of medical policy is to provide a guide to coverage. Medical Policy is not intended to dictate to providers how to practice medicine. Providers are expected to exercise their medical judgment in providing the most appropriate care.

Description

Both noninvasive and invasive methods of electrical bone growth stimulation (EBGS) are available:

• Noninvasive Electrical Bone Growth Stimulators

  Noninvasive bone growth stimulators generate a weak electric current within the target site using a variety of technologies, e.g., pulsed electromagnetic fields, capacitative coupling, or combined magnetic fields. In capacitative coupling, small skin pads/electrodes are placed on either side of the fusion site and worn for 24 hours per day until healing occurs or up to nine months. In contrast, pulsed electromagnetic fields are delivered via treatment coils that are placed into a back brace or directly onto the skin and are worn for six to eight hours per day for three to six months. Combined magnetic fields deliver a time-varying magnetic field by superimposing the time-varying magnetic field onto an additional static magnetic field. This device involves a 30-minute treatment per day for nine months. Patient compliance may be an issue with externally worn devices.

  Noninvasive bone growth stimulators are used to treat fracture nonunions in the appendicular skeleton, failed fusion after spinal fusion surgery, or as an adjunct to spinal fusion surgery to decrease the incidence of failed fusion (i.e., arthrodesis).

• Invasive Electrical Bone Growth Stimulators

  Invasive devices use direct current; these devices require surgical implantation of a current generator in an intramuscular or subcutaneous space, while an electrode is implanted within the fragments of bone graft at the fusion site. The implantable device typically remains functional for six to nine months after implantation. Although the current generator is removed in a second surgical procedure when stimulation is completed, the electrode may or may not be removed.

  Invasive bone growth stimulation is used as an adjunct to spinal fusion surgery, with or without associated instrumentation, to enhance the chances of obtaining a solid spinal fusion. Invasive bone growth stimulation is not used in the appendicular skeleton.

The definition of a fracture nonunion has remained controversial. The original U.S. Food and Drug Administration (FDA) labeling defined nonunion as follows: "A nonunion is considered to be established when a minimum of 9 months has elapsed since injury and the fracture site shows no visibly progressive signs of healing for minimum of 3 months." Others have contended that 9 months represents an arbitrary cut-off that does not reflect the complicated variables that are present in fractures, e.g., degree of soft tissue damage, alignment of the bone fragments, vascularity, and quality of the underlying bone stock. Other proposed definitions of nonunion involve 3 to 6 months time from original healing, or simply when serial x-rays fail to show any further healing. The FDA's most recently approved labeling changes do not impose a time frame for the diagnosis of nonunion.

Delayed union refers to a decelerating bone healing process, as identified in serial x-rays. (In contrast, nonunion serial x-rays show no evidence of healing.) When lumped together, delayed union and nonunion are sometimes referred to as "un-united fractures."

In the appendicular skeleton, electrical stimulation has been used primarily to treat tibial fractures, and thus this technique has often been thought of as a treatment of the long bones. This concept has led to controversy regarding what constitutes long vs. short bones. According to orthopedic anatomy, the skeleton consists of long bones, short bones, flat bones, and irregular bones. Long bones act as levers to facilitate motion, while short bones function to dissipate concussive forces. Short bones include those composing the carpus and tarsus. Flat bones, such as the scapula or pelvis provide a broad surface area for attachment of muscles. Thus the metatarsal is considered a long bone, while the scaphoid bone of the wrist is considered a short bone. Both the metatarsals and scaphoid bones are at a relatively high risk of nonunion after a fracture.

Despite their anatomic classification, all bones are composed of a combination of cortical and trabecular (also called cancellous) bone. Cortical bone is always located on the exterior of the bone, while the trabecular bone is found in the interior. Each bone, depending on its physiologic function, has a different proportion of cancellous to trabecular bone. However, at a cellular level, both bone types are composed of lamellar bone and cannot be distinguished microscopically.

Policy/Criteria

Scientific Background

Invasive and Noninvasive Electrical Bone Growth Stimulation of the Spine

The policy regarding electrical bone growth stimulation as an adjunct to spinal fusion surgery or as a treatment of failed spinal fusion surgery (i.e., salvage therapy) is based on two BlueCross BlueShield Association Technology Evaluation Center (TEC) Assessments, which offered the following conclusions (3,4):

• Data from a randomized controlled clinical trial of patients meeting the criteria for high risk for development of failed fusion suggests that invasive or noninvasive electrical bone stimulation as an adjunct to spinal fusion surgery is associated with a significantly higher spinal fusion success rate in the treated group compared with the control group. (5,6)
• Data from uncontrolled studies of patients with failed spinal fusion suggests that noninvasive electrical stimulation results in a significantly higher fusion rate. The lack of controlled clinical trials is balanced by the fact that these patients served as their own control.

Since publication of the TEC Assessments, several additional controlled clinical trials were identified that focused on different types of electrical stimulation in patients with a variety of risk levels, undergoing different types of surgery (posterolateral, interbody [posterior and anterior] fusion with or without instrumentation). For example, the early trials of electrical stimulation of the spine focused on procedures without instrumentation. Currently, pedicle screws and interbody cages are devices used to facilitate fusion. Therefore, controlled studies were reviewed with a focus on the role of electrical stimulation of the spine for instrumented fusions, and also on electrical stimulation in patients not considered at high risk for fusion failure. Analysis of the data regarding spinal fusion is limited by the following factors:

• Trials frequently include heterogeneous groups undergoing a variety of surgeries, which may have different risk levels for fusion failure.
• Trials frequently include patients undergoing spinal fusion both with and without additional surgical adjuncts, e.g., pedicle screws or back cages, both designed to increase the fusion rate. Therefore, those patients undergoing instrumented spinal fusion procedures may have a decreased risk of fusion failure compared to those without instrumented procedures.
• While most trials have focused on "high-risk" patients, others have also included average-risk patients. The outcomes associated with average-risk patients are often not reported separately.
• Trials have used different outcomes for spinal fusion, based on varying clinical and radiologic outcomes.
• The presence or absence of spinal fusion may be considered an intermediate outcome, with the final health outcomes typically focusing on relief of pain and improved function. Final health outcomes are typically not reported.

With the above limitations in mind, results of controlled trials investigating both invasive and noninvasive electrical bone growth stimulation in the spine are summarized below.

Kucharzyk reported on a controlled prospective nonrandomized trial of implantable electrical stimulation in patients undergoing instrumented posterior spinal fusion with pedicle screws. (7) A series of 65 patients who did not use electrical stimulation were compared with a later series of similar patients who did receive implantable electrical stimulation. Fusion success was 95.6% in the stimulated group compared to 87% in the non-stimulated group, a statistically significant difference. It appears that all patients had at least one or more high risk factors for failed fusion, e.g., smoking history, prior surgery, multiple fusion levels, diabetes. While this trial supports the use of electrical stimulation as an adjunct to instrumented posterior lumber fusion, it did not specifically identify the outcomes in patients considered to be at low risk for failed fusion.

Rogozinski and colleague reported on the outcomes of two consecutive series of patients undergoing posterolateral fusions with autologous bone graft and pedicle screw fixation. (8) The first series of 41 patients were treated without electrical stimulation, while the second group of 53 patients received invasive electrical stimulation. Those receiving electrical stimulation reported a 96% fusion rate, compared to an 85% fusion rate in the non-stimulated group. The fusion rate for patients receiving stimulation versus no stimulation was also significantly higher among those considered at high risk due to previous back surgery or multiple fusion levels. There was not a significant increase in the fusion rate among non-smokers (i.e., without a risk factor), but the comparative fusion rates for all patients without high risk factors is not presented.

Goodwin and colleagues reported on the results of a study that randomized 179 patients undergoing lumbar spinal fusions to receive or not receive capacitively coupled electrical stimulation. (9) A variety of surgical procedures both with and without instrumentation were used, and subjects were not limited to "high-risk" patients. The overall successful fusion rate was 84.7% for those in the active group compared to 64.9% in the placebo group, a statistically significant difference. While the actively treated group reported increased fusion success for all stratification groups (fusion procedure, single or multilevel fusion, smoking or nonsmoking group), in many instances the differences did not reach statistical significance because of small numbers. For example, the subgroups in which there was not a significant difference in fusion between the active and placebo groups included patients who had undergone previous surgery, smokers, and those with multilevel fusion. In addition, there were numerous dropouts in the study and a 10% noncompliance rate with wearing the external device for up to 9 months.

Mooney and colleagues reported on the results of a double-blind study that randomized 195 patients undergoing initial attempts at interbody lumber fusions with or without fixation to receive or not receive pulsed electromagnetic field electrical stimulation. (6) Patients were not limited to high-risk groups. In the active treatment group, there was a 92% success rate, compared to a 65% success rate in the placebo group. On subgroup analysis, the treated group consistently reported an increased success rate. Subgroups included graft type, presence or absence of internal fixation, or presence or absence of smoking.

Linovitz and colleagues conducted a double-blind clinical trial that randomized 201 patients undergoing one or two level posterolateral fusion without instrumentation to active or placebo electrical stimulation using a combined magnetic field device. (10) Unlike capacitively coupled or pulsed electromagnetic field devices, the combined magnetic field device requires a single 30-minute treatment per day with the device centered over the fusion site. Patients were treated for 9 months. Among all patients, 64% of those in the active group showed fusion at 9 months compared to 43% of those with placebo devices, a statistically significant difference. On subgroup analysis, there was a significant difference among women, but not men.

In summary, interpretation of the clinical trial data is limited by the heterogeneous populations studied and the variety of surgical procedures within the populations. A review of the literature suggests that, like many preventive measures, the patients most likely to benefit are those at highest risk. In addition, electrical stimulation may improve the fusion rate in patients undergoing both instrumented and non-instrumented surgeries. However, scientific data are inadequate to determine the magnitude of benefit associated with electrical stimulation in patients considered at average risk for fusion failure. (11,12) An updated search of the MEDLINE database through May 15, 2009 failed to identify any additional studies that alter this conclusion.

Foley and colleagues reported results from a multicenter single-blinded randomized controlled trial in which 323 patients were randomized in a 1:1 ratio to receive either pulsed electromagnetic field (PEMF) stimulation or no stimulation. (19) The PEMF device was designed specifically for treatment of the cervical spine (Cervical-Stim, Orthofix). Intent-to-treat analysis showed an increase in the fusion rate  for the PEMF stimulation group at six months compared to the control group (86% vs. 76%, p = 0.03); however, there was no difference in fusion between groups at twelve months. Visual analog scale (VAS) ratings were similar in the two groups at six and twelve months.

There are currently no clinical trial data on the use of EBGS as an alternative or adjunct to conservative treatment of acute or chronic spondylolysis with or without spondylolisthesis.

In a 2005 clinical practice guideline, Reznick and colleagues recommended use of electrical stimulation in posterolateral fusion among patients at high risk for arthrodesis failure and pulsed electromagnetic field stimulation in similar patients who have undergone lumbar interbody fusion. (23) This recommendation was based on Class II and III evidence, defined as case series, comparative studies, less well-designed and significantly flawed randomized clinical trials and expert opinion. The guideline document pointed out weaknesses in the evidence, particularly high participant dropout rates and use of a nonvalidated functional outcome scale. In spite of the recommendation favoring use of electrical stimulation, the guideline states that “there is no consistent medical evidence to support or refute use of these devices for improving patient outcomes.” Previous TEC and policy update reviews of electrical stimulation as an adjunct to spinal fusion procedures noted that although there were weaknesses in the evidence, comparative studies generally showed an advantage for stimulation in radiographic fusion rates, and to a lesser extent, improved symptoms and function.

Noninvasive Electrical Bone Growth Stimulation of the Appendicular Skeleton

The policy regarding electrical bone growth stimulation as a treatment of nonunion of fractures of the appendicular skeleton is based on the FDA-labeled indications. The FDA approval was based on a number of case series in which patients with nonunions, primarily of the tibia, served as their own control. These studies suggest that electrical stimulation results in subsequent unions in a significant percentage of patients. (13-17) It should be noted that the labeled indications include nonunions or congenital pseudoarthroses of bones of the appendicular skeleton. No distinction is made between long and short bones. The original FDA labeling of fracture nonunions defined nonunions as those fractures that had not shown progressive healing after at least 9 months from the original injury. This time frame is not based on physiologic principles, but was included as part of the research design for FDA approval as a means of ensuring homogeneous populations of patients, many of whom were serving as their own controls. As mentioned above, the presence of a nonunion is related to a variety of factors, such as fracture type and location, degree of soft tissue damage, vascularization, and bone stock. Some fractures may show no signs of healing, based on serial radiographs, as early as 3 months, while a fracture nonunion may not be diagnosed in others until well after 9 months. At the present time, the FDA has approved labeling changes for electrical bone growth stimulators which remove any time frame for the diagnosis. The current policy of requiring a 3-month time frame is still arbitrary, but appears to be consistent with the definition of nonunion, as described in the clinical literature.

The policy regarding electrical stimulation of delayed unions is based on a 1992 TEC assessment (3), which offered the following conclusions (18):

• While data from a double-blind randomized controlled clinical trial of patients with delayed unions (and additional long-term outcome data provided by the investigator) suggests that a 12- week course of noninvasive electrical bone stimulation is associated with a significantly higher healing rate than a control group with a dummy device, there are inadequate data regarding the final health outcomes of the patients, e.g., regained use of limb, minimal pain, avoidance of subsequent surgery. All patients in the trial had an unhealed fracture at an average of 23.8 weeks after injury; all fracture gaps were under 0.5 cm. In terms of long-term outcome, a significantly greater proportion of the treated patients avoided any further surgery.

A search focusing on implantable bone stimulators identified a small number of case series, all of which focused on foot and ankle arthrodesis in patients at high risk for non-union. Risk factors for non-union included smoking, diabetes mellitus, Charcot (diabetic) neuroarthropathy, steroid use and previous nonunion. (20-22) No randomized clinical trial data was found.

An updated search of the MEDLINE database through May 15, 2009 failed to return any new clinical trials that alter the conclusions reached above.

References

1. BlueCross BlueShield Association Medical Policy Reference Manual, Policy No. 7.01.07
2. BlueCross BlueShield Association Medical Policy Reference Manual, Policy No. 7.01.85
3. BlueCross and BlueShield Association Technology Evaluation Center TEC Assessment: Electrical Bone Growth Stimulation as an Adjunct to Spinal Fusion Surgery (Invasive Method), 1992; Vol. 7, Tab III p. 324
4. BlueCross and BlueShield Association Technology Evaluation Center TEC Assessment: Electrical Bone Growth Stimulation in Association with Spinal Fusion Surgery (Noninvasive Method), 1993; Vol 8, Tab 7
5. Kane WJ. Direct current electrical bone growth stimulation for spinal fusion. Spine 1988;13(3):363-5
6. Mooney V. A randomized double-blind prospective study of the efficacy of pulsed electromagnetic fields for interbody lumbar fusions. Spine 1990;15(7):708-12
7. Kucharzyk DW. A controlled prospective outcome study of implantable electrical stimulation with spinal instrumentation in a high-risk spinal fusion population. Spine 1999;24(5):465-9
8. Rogozinksi A, Rogozinski C. Efficacy of implanted bone growth stimulation in instrumented lumbosacral spinal fusion. Spine 1996;21(21):2479-83
9. Goodwin CB, Brighton CT, Guyer RD et al. A double-blind study of capacitively coupled electrical stimulation as an adjunct to lumbar spinal fusions. Spine 1999;24(13):1349-57
10. Linovitz RJ, Pathria M, Bernhardt M et al. Combined magnetic fields accelerate and increase spine fusion: a double-blind, randomized, placebo controlled study. Spine 2002;27(13):1383-9
11. Hodges SD, Eck JC, Humphreys SC. Use of electrical bone stimulation in spinal fusion. J Am Acad Orthop Surg 2003;11(2):81-8
12. Akai M, Kawashima N, Kimura T et al. Electrical stimulation as an adjunct to spinal fusion: a meta-analysis of controlled clinical trials. Bioelectromagnetics 2002;23(7):496-504
13. de Haas WG, Beaupre A, Cameron H et al. The Canadian experience with pulsed magnetic fields in the treatment of ununited tibial fractures. Clin Orthop 1986;208:55-8
14. Ahl T, Andersson G, Herberts P, Kalen R. Electrical treatment of non-united fractures. Acta Orthop Scand 1984;55(6):585-8
15. Connolly JF. Electrical treatment of nonunions. Its use and abuse in 100 consecutive fractures. Orthop Clin Noth Am 1984;15(1):89-106
16. Sharrard WJ, Sutcliffe ML, Robson MJ et al. The treatment of fibrous non-union of fractures by pulsing electromagnetic stimulation. J Bone Joint Surg Br 1982;64(2):189-93
17. Connolly JF. Selection, evaluation and indications for electrical stimulation of ununited fractures. Clin Orthop 1981;161:39-53
18. BlueCross and BlueShield Association Technology Evaluation Center TEC Assessment: Electrical Bone Growth Stimulation for Delayed Union or Nonunion of Fractures, 1992; Vol. 7, Tab III p. 332
19. Foley KT, Mroz TE, Arnold PM et al. Randomized, prospective, and controlled clinical trial of pulsed electromagnetic field stimulation for cervical fusion. Spine J 2007;[Epub ahead of print]
20. Petrisor B, Lau JT. Electrical bone stimulation: an overview and its use in high risk and Charcot foot and ankle reconstructions. Foot Ankle Clin 2005;10(4):609-20
21. Lau JT, Stamatis ED, Myerson MS et al. Implantable direct-current bone stimulators in high-risk and revision foot and ankle surgery: a retrospective analysis with outcome assessment. Am J Orthop 2007;36(7):354-7
22. Saxena A, DiDomenico LA, Widtfeldt A et al. Implantable electrical bone stimulation for arthrodeses of the foot and ankle in high-risk patients: a multicenter study. J Foot Ankle Surg 2005;44(6):450-4
23. Reznick DK, Choudhri TF, Dailey AT et al. Guidelines for the performance of fusion procedures for degenerative disease of the lumbar spine. Part 17: bone growth stimulators and lumbar fusion. J Neurosurg Spine 2005;2(6):737-40

Cross References

None

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