Introduction: Muscular atrophy can be caused by several reasons, from neurological disorders to muscular and nervous injuries, to surgery-related complications. Very few devices exist to treat muscular atrophy, as most treatments involve a combination of active and passive exercises through physical therapy. At the request of medical professional and biomedical engineering professor Dr. Ha Vo, a team of three senior biomedical engineering students developed a custom-fabricated orthotic device to increase patient muscle mass and function. Other studies have shown that consistent electrical stimulation, such as transcutaneous electrical nerve stimulation (TENS), can produce muscle hypertrophy. With no commercially available products that utilize electrical stimulation in this way, it was decided to build a custom knee orthotic with built-in electrical stimulation to achieve the desired result of muscle hypertrophy.
Materials and
Methods: Materials were chosen based on projected cost, durability, and patient comfort. The main materials used in manufacturing the device backbone were fiberglass casting tape, plaster, heat-moldable foam, and ⅛th inch polypropylene. Accessory items include the fabric electrodes, stimulation and battery pack, velcro straps, hinges, and D-rings. The team first cast the patient with the fiberglass casting tape to generate a plaster model of the patient’s leg. The foam was heated in an oven and molded to the plaster to create a soft interface for the patient. The ⅛th inch polypropylene was then molded to the foam and cut into an initial shape using an oscillating saw. The shape of the device was further refined using a cone grinder. Quick rivets attached the hinges, D-rings, and straps to the polypropylene backbone. A rotary tool created attachment points between the fabric electrode and stimulation battery pack. The stimulation pack was secured to the backbone using quick rivets and super glue to provide a more secure bond. The team shortened and soldered all wiring to reduce the risk of the wire snagging. Testing was completed using the Ultium Portable Lab to record increases in muscle activation through Electromyography (EMG) readings.
Results, Conclusions, and Discussions: The testing revealed an average increased muscle activation of 8.17% with a standard deviation of 0.912% across all stimulations, with an increasing trend as the stimulation level increased. Several factors influenced both the fabrication process and the data collection and analysis. The prototype was fabricated in the absence of the patient, thus resulting in alignment issues due to the hinges not being parallel, causing it not to bend properly on the patient’s knee. It also lacked a soft interface. Therefore the team worked quickly to refabricate the device with a soft foam interface, and everything was prepared with routine patient fittings to ensure proper alignment. Another hindrance arose as the team exhausted all efforts to contact the patient without a response. Upon contacting the client, an executive decision was made to pivot to a new patient to proceed with testing and data collection. During the last phase of testing, while walking the patient in the device in the gait lab, it was discovered that the electrical interference caused by a remote-controlled electrical stimulation device dramatically skews the data collected by the EMG skin electrodes on the rectus femoris. This problem was overcome by distancing the sensory electrode from the stimulatory electrode to reduce the interference as much as possible with any residual noise filtered out in the Noraxon software. Finally, given the timeline setbacks, there simply was not enough time to test the effect of the device on muscle mass change. The team acknowledges the potential for improvement in multiple aspects. To improve the device's effectiveness, the team recommends using a second stimulation pack and electrode to target the patient’s hamstrings. This was included in the initial design, however, due to time constraints, this second electrode was not included. During patient testing, the team managed the activation of the electrical stimulation and its power levels. In the future, the patient must be instructed on how to set up and control the device to allow for everyday, out-of-clinic use. This will allow for more frequent patient treatment and monitoring of the long-term effects of day-to-day use of the device.
