The gearmotor enables extension of the prosthesis without surgery.
Frequent hospital stays for young cancer patients with prostheses replacing diseased bone may be a thing of the past, thanks to research done at University College London. They have developed a prosthesis with a small gearbox physicians can use to extend the prosthesis to match the growth of the patient’s leg—on an outpatient basis. Up to now, surgeons extended the prosthesis by making a small incision and turning a key in a telescopic mechanism in the prosthesis, a procedure that required anesthesia and a hospital stay.
In the new prosthesis, a stator surrounding the patient’s leg produces a rotating magnetic field, which turns a small magnet rotor in the implant at 3,000 rpm. The rotor drives a reduction gearbox to extend the prosthesis 1 mm in about four minutes.
The researchers have licensed the technology to Stanmore Implants, a subsidiary of the University College London.
The device uses an ABB 180-frame-size motor lamination core wound to meet specs of 522 turns of 1.06-mm wire in a star connection. The device also has inverter controls from Danfoss.
Thirteen patients are using the prosthesis now. Stanmore is studying the long-term effects, and plans to eventually market the prosthesis worldwide.