Bone Stimulation For Nonunions: What The Evidence Reveals
Numerous methods of bone stimulation have emerged in recent years but how effective are they at facilitating healing? These authors take a critical look at the evidence on the efficacy of electrical stimulation, low-intensity pulsed ultrasound and extracorporeal shockwave therapy.
Bone stimulators currently represent a $500 million market in the United States alone.1 They are becoming an increasingly popular conservative treatment option for delayed unions and nonunions.
Numerous studies have estimated that 5 to 10 percent of fractures occurring in the United States annually have impaired healing.1-11
Impaired bone healing not only causes chronic pain and disability for the patient, but also leads to considerable socioeconomic costs including healthcare costs and lost wages. When impaired healing occurs, it presents a frustrating problem for both the patient and the surgeon. Both parties desire a non-surgical option to stimulate bone healing. Bone stimulators present an attractive option to augment healing due to the conservative nature and relative ease of operation.
In regard to research on bone stimulation, Griffin and colleagues reviewed 49 studies and found that electromagnetic stimulation is an effective adjunct to conventional therapy when it comes to managing nonunions of long bone fractures.3 However, when one is determining whether to use bone stimulators, it is important to consider several factors including cost, length of treatment and the current body of evidence on the efficacy of bone stimulators.
Currently, there are three main types of bone stimulators: electrical stimulation, low-intensity pulsed ultrasound and extracorporeal shockwave therapy (ESWT).
A Closer Look At The Evidence On Electrical Stimulation
The oldest and most studied method of bone stimulation is electrical stimulation. The first report of utilizing electricity to induce healing was in 1841.12 In that paper, Hartshorne described a patient who underwent treatment in 1812 for a tibial nonunion with “shocks of electric fluid passed daily through space between the ends of the bones.” Subsequent work by Lente in 1850 further recognized the potential for electricity to heal bone.13
However, there was little work done in this regard until 1953 when Yasuda published his work on rabbit femurs and demonstrated new bone growth near the cathode.14 The first work involving human patients was in 1971 when Friedenberg and colleagues used direct current for the management of a nonunion of the medial malleolus in a case study of a 51-year-old woman.15 Since that time, there has been an extensive focus on electrical stimulation in the literature.
There are currently three different methods of electrical stimulation devices available: direct current, capacitively coupled and pulsed electromagnetic fields. Direct current devices require surgical implantation and extraction, necessitating two additional surgeries. With direct current devices, one would use a negative cathode directly over the impaired healing site. Capacitively coupled and pulsed electromagnetic field devices utilize electrodes that one places externally on the skin.
The electrical bone stimulators as a group create an electrical potential that mimics the electrical potential created when one applies mechanical stress to bone. In 1957, Fuhada and Yasuda demonstrated that when one applies mechanical stress to bone, this creates electrical potentials in bone.16 The electrical potentials, whether they are created from mechanical stress or generated by an electrical bone stimulator, lead to osteogenesis by numerous cellular mechanisms. These cellular effects include: increased DNA synthesis by chondroblasts; alteration of the cellular calcium content; increased collagen synthesis; increased mineralization and angiogenesis; and an increased rate of amino acid transportation.17,18