BIONs (Bionic Neurons) are microminiature stimulators that can be injected into muscles. They receive power and commands from an external magnetic field. They have been shown to be safe and effective for stimulating muscles in animals. Clinical trials are underway to assess the efficacy and safety of BIONs for therapeutic exercise of weak or paralyzed muscles. In patients with knee osteoarthritis weakness of quadriceps muscle has been shown by different authors to be highly correlated with pain and functional impairment, while quadriceps strengthening is associated with significant improvements of clinical scores. Preliminary results of the use of BIONs to strengthen the quadriceps muscles in patients affected by knee osteoarthritis are reported.

Five patients have been recruited so far, three of them have completed the protocol. Patients are implanted with BIONs near the common femoral nerve and in the vastus medialis muscle, and stimulated for 12 weeks. Therapy starts three days after implantation with two-three stimulation sessions of 10–30 minutes each day. Stimulation parameters are intended to recruit the quadriceps muscles (up to 10 X threshold for muscle twitch) at relatively low frequencies (5–13 pps) in short trains (5–10 s) with pauses between trains (5 s). Outcome measures include WOMAC, Knee Society Score, muscle measurements with MRI, gait analysis, isokinetic tests. All patients found muscle stimulation to be agreeable. No adverse events or complications have been observed. Thresholds for eliciting muscle contractions remained stable over time. In the three patients knee function improved and pain decreased over the stimulation period, while muscle thickness, as measured by MRI, increased.

Results are preliminary but encouraging. We anticipate studying 15 patients to demonstrate clearly the safety and efficacy of this technology in this application. Plans are underway for additional clinical trials in orthopaedic patients as well as in stroke patients.