Photography of Matheny, courtesy of AAD.
On April 24, orthopedic surgeon Richard McGough III, MD, and senior researcher Robert Armiger with the Johns Hopkins University (JHU) Applied Physics Lab (APL), spoke at the Advanced Arm Dynamics (AAD) annual clinical education and business development symposium. They discussed recent advances in transcutaneous osseointegration and neuroprosthetics. Also in attendance was Johnny Matheny, who underwent a left transhumeral amputation in 2008 due to cancer and has since had targeted muscle reinnervation (TMR) surgery and osseointegration surgery that allows him to attach a prosthesis directly to his body.
“The researchers presenting at AAD’s Symposium provide our clinicians with critical insights into emerging upper-limb technologies,” said John Miguelez, CP, FAAOP (D), AADpPresident and senior clinical director.
According to McGough, chief of the Division of Musculoskeletal Oncology at the University of Pittsburgh Medical Center, Matheny is the first person with an arm amputation in the United States to have had both surgeries. Matheny demonstrated his control and range of motion with APL’s modular prosthetic limb (MPL), which he wears for research and presentations, but is not allowed to take home. He works closely with Armiger, who is exploring neural interface systems for the MPL.
Armiger described the growing list of features of the MPL: dexterous in-hand manipulation of objects; 100+ on-board sensors including fingertip sensors that measure force, vibration, and temperature/heat flux; 26 degrees of freedom; 17 individual motors; neural interface for intuitive closed-loop control; and 40 pounds of torque for human-like strength.
“We have also completed studies involving the MPL with eight subjects at Walter Reed National Military Medical Center, [Bethesda, Maryland,] including wrist disarticulation, transradial, transhumeral, and shoulder-level amputations,” Armiger said.
McGough said, based on his experience with Matheny’s procedure, he would make some modifications on future upper-limb osseointegration cases. Specifically, he has learned that the osseointegration procedure can now be done in a single surgery rather than in two phases, and he would prefer to do the osseointegration before the TMR procedure to prevent potential damage to the TMR sites. McGough said that his transcutaneous method, where the skin around the attachment is left intact, instead of trying for skin integration, reduces issues with infection. However, it requires the patient to practice regular basic hygiene around the implant.
Matheny said he’s been asked to expose his implanted limb to numerous potential contaminants. “Because the military is looking at this, I’ve used it to do things that involve dirt, sawdust, pollen, even motor oil,” Matheny said. “I’ve gone in a public swimming pool and swam in saltwater. I have had no infection.”
McGough estimated that transcutaneous osseointegration will undergo at least two more years of trials, including a U.S. Food and Drug Administration study with about 60 people. The procedure could become commercially available in three to four years. Armiger said he is eager to reach the next phase of research that involves a one-year take home trial of the osseointegrated MPL.
