At CSIE we very often come across gaps and needs in surgery that requires a new implant or tool design or a new material such piezoresistive materials, or metamaterials and structures. Sometimes we need these materials to integrate with our other devices, an example is our work for early diagnosis of implant failure using Electrical Impedance Tomography and piezoresistive bone cement. As an example, we would like to present two examples of these projects here:
Universal Laminoplasty Implant
Laminoplasty is a surgical procedure in which spinal cord compression is relieved through opening of the spinal canal. This is accomplished by creating hinges in the vertebral lamina overlying the spinal cord, and the use of implants to keep the lamina in a permanent open position. In laminoplasty the lamina is lifted but not removed, thus avoiding the complications associated with laminectomy where the lamina bone (and associate muscle/tendon/tissue attachments) is removed permanently. Laminoplasty was developed in Japan to improve the postoperative complexities associated with laminectomy such as kyphosis, instability, axial neck pain, and range of motion. Since then, laminoplasty has grown significantly worldwide. In Japan, laminoplasty is by far the most commonly performed surgery for compressive cervical myelopathy. In the US laminectomy is still the main procedure for compressive cervical myelopathy with 490,000 surgeries performed per year; however, laminoplasty is rapidly replacing laminectomy. The number of laminoplasties performed at Massachusetts General Hospital (MGH) alone doubled from 2012 to 2018 (data from Partners Research Patient Data Registry). In the medium term (up to 10yrs) laminoplasty has proven to be successful in improving kyphosis, axial pain and instability compared to laminectomy; however, long-term postoperative follow-up of laminoplasty shows gradual return of kyphosis, axial neck pain, and decrease in range of motion. Research suggests that new Minimally Invasive Surgery (MIS) techniques that preserve paraspinal muscle structures can reduce these long-term complications; however, the implants and tools needed for these approaches are not yet available. With the rapid uptake of robotic spinal surgeries, MIS procedures are expected to become significantly more common requiring the development of novel implants.
Our Universal Laminoplasty Implant (ULI) is designed to address several limitations of current laminoplasty implants and enable the future wave of robotic MIS procedures by: enabling deployment through MIS tubes, use of routine tools used in operating room, enabling controlled force application to lamina, providing adjustable attachment angles, continuous expandability and enabling implementation of open door and double door cervical laminoplasty with the same implant.
The figure on the right shows the application of this implant on the C6 vertebra during a minimally invasive surgery through a MIS tube.
Piezoresistive bone cement
As part of our collaboration with MIT and Purdue we developed a piezoresistive bone cement to combine it with EIT for early detection of implant failure. The figure on the right shows the conductivity map of the bone cement we developed as a function of carbon fiber volume fraction. To know more about this project please check out our paper freely available on archive, Ghaednia et al, 2019.
Ongoing projects
Currently we are focused on development of acoustic metamaterials using biocompatible materials. If you are interested, make sure to reach out.