Electrical Stimulation

Electrical and electromagnetic devices have been shown to be effective in the management of delayed unions and nonunions [2]. The development of these treatment methods is based on the discovery that dry bone [3] and hydrated bone [4] have electrical properties. In brief, mechanically stimulated bone cells produce an electrical field, which mediates cell proliferation [5]. In the past few years, some studies gave further information about the action of the electrical fields on signal transduction pathways and on GFs [2,6].

Three modalities of electrical stimulation of bone growth are presently available for nonunion treatment:

- Direct current (DC) stimulation employing percutaneously implanted electrodes (invasive method). With this method a constant current of about 20 ^A and 1 V is generated between two electrodes inserted in the nonunion site. This technique has quite a high rate of good results (78%-86%), according to some Authors [7,8] (Fig. 1).

- Electromagnetic stimulation by inductive coupling (IC) uses magnetic fields (noninvasive method). This technique, developed by Bassett et al. [9], is based on the action of pulsed electromagnetic fields produced by external devices that generate a current of 20 mV and about 10 ^A/cm2 in the tissues. Bassett et al. [9] reported a success rate of 87% in the management of nonunions.

- Capacitive coupling (CC) stimulation employs electrodes placed on the skin (noninvasive method). Disk-shaped electrodes to which transducer gel has been applied are placed on the skin and transmit a uniform electric current (3-6 V, 5-10 mA) at the nonunion site. A success rate of 82% has been reported [10].

Fig. 1a, b. Atrophic nonunion of the distal metaphysis of the left femur in a 26-year-old man treated with plating, autologous bone grafting, and electric stimulation

Double-blind studies to test the efficacy of electrical stimulation on long bone nonunions were performed and gave statistical evidence of these good results [11,12]. In conclusion, this treatment has proven to be effective, particularly in hypertrophic nonunions.

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