2.4.2. Electrical Stimualtion Using bioNs™ To Treat Muscular Hypotrophy In Individuals With Osteoarthritis

6.12. Background

This trial is being conducted in collaboration with Carlo Romano, M.D. at the Istituto Ortopedico Gaetano Pini in Milan, Italy. Dr. Romano has worked with Drs. Loeb and Richmond for several years on the background research and protocol development that led to the selection of knee arthritis as the first application for BIONs™ in the area of orthopedic rehabilitation. Arthritis of the knee is associated with muscle atrophy as both cause and effect. Many studies have demonstrated objective clinical benefits from exercise programs (Fisher et al., 1993a; Fisher et al., 1993b; Fisher et al., 1997a; Fisher et al., 1997b; Hurley et al., 1998; Laprade et al., 1998; Maurer et al., 1999; O’Reilly et al., 1999). For example, Fisher et al. (1997b) demonstrated that rehabilitation exercises can significantly improve muscle strength (+55%), resistance to fatigue (+42%), and contraction velocity (+34%) of the quadriceps muscle. Such strengthening improved walking speed by 21%, reduced pain by 13% and improved daily activities by 33% (measured with the Jette Functional Status Index – JFSI). However, exercise-based treatment requires a lengthy and costly rehabilitation regime and total patient cooperation. Even then, results are mixed. In fact, in the presence of arthrogenic reflex inhibition of motoneurons, the active exercises do not produce a full return of muscle strength even when performed consistently by the patient because the whole muscle cannot be activated voluntarily.

Transcutaneous electrical stimulation is a well-known method for building up hypotrophic muscle (Callaghan, 1997; Enoka, 1988; Morrissey, 1988; Pocholle et al., 1993). Practical constraints, however, tend to limit widespread application of this technique in a clinical setting. These include demands on caregiver time to apply electrodes and adjust stimulation intensity, difficulty of activating deeper muscles, pain due to activation of cutaneous afferents, and skin irritation from electrodes operated at high current levels.

Imbalance of knee muscle strength is associated with increased severity of symptoms and poor or prolonged recovery in a variety of degenerative and post-traumatic pathologies of the knee. Patellofemoral chondromalacia is a relatively common condition characterized by different degrees of cartilage damage, from cartilage softening to exposed subchondral bone and osteoarthritis. It is usually associated with anterior persistent knee pain, especially worsened by prolonged sitting or descending steps or hills.

Chondromalacia of the knee can be idiopathic, but it is usually associated with patellar malalignment as a result of specific weakness of the vastus medialis muscle (Kannus & Niittymaki, 1994; Thomee et al., 1995; Tria et al., 1992). Muscle strengthening is the most prescribed treatment by many authors with successful results in most cases (cf. Juhn, 1999; Laprade et al., 1998; Mirzabeigi et al., 1999). However, isolation of vastus medialis, although recommended by different investigators, is difficult to ensure using voluntary exercise (Mirzabeigi et al., 1999).