Biomechanics of Artificial Discs
Although few artificial intervertebral discs are currently on the market in the US due to the slow FDA approval process, many are under development by different companies in the US and elsewhere. The biomechanics lab initiated a number of protocols with these companies to evaluate their devices. The ultimate goal is to publish our findings to benefit patients and doctors in understanding how the spine will move differently after implantation of each device. As described on the Testing Techniques page, the BNI lab has at its disposal several advanced testing methods unavailable at other labs and is hoping to set new standards in how such experiments are performed.
Dr. Crawford published a critique of the most recently published studies on biomechanical testing of cervical artificial discs.
Ongoing research includes measurement of range of motion, zone of laxity, coupling patterns, axis of rotation, and facet loads at levels of the spine in specimens with artificial intervertebral discs implanted. One of the hypothetical benefits of implanting an artificial disc instead of fusing a level of the spine is that there is less of a “lever arm” on the adjacent normal levels, and so there is less chance of these normal levels degenerating later in life. New research in the biomechanics lab focuses on studying the biomechanical effects on adjacent levels in conditions of natural disc versus fusion versus artificial disc. This new research will make use of a complex testing apparatus recently designed in collaboration with a local engineering firm that generates external loads on spine representing both muscles and gravity.
| Simulated spinal neurosurgery using a haptic device
Surgical Planning and Rapid Prototyping of the Spine
The biomechanics lab was awarded a grant from the National Institutes of Health to develop a computerized surgical planning tool, which is now in the late stages of development, utilizing a desktop haptic device. With this system, a 3D computer model of the patient’s spine and pathology is generated from the patient’s computerized tomography scan. The surgeon then performs virtual surgery to correct the pathology.
With haptics, the surgeon feels forces during simulated drilling and bone realignment that help to predict the experience that will be encountered in the operating room. After the surgeon completes the mock surgery, computerized analysis is applied to fine tune the surgical plan, and rapid-prototyped spine models help communicate surgical planning information to the patient. Rapid prototyped drill guides are also used to improve accuracy of screw insertion. (See an abstract of this grant on the NIH website.
(A) CT image of a spine and (B) 3-dimensional computerized model.