Broader Significance & Importance Some metal implants are placed into bones with the intent of becoming permanently connected. This process is named osseointegration (OI). OI generally takes several weeks and there is an advantage in achieving rapid and complete OI because it accelerated the rehabilitation and training of patients. Several strategies may be used to increase OI of metal implants. They have the advantage to be applied externally and be effective with brief periods of exposure (approx. 20 minutes per day). Little is known about the relative benefits of these modalities and about any potential benefits of combining these modalities.
The goals of this research are to investigate an integrated system to promote bone ingrowth into transdermal OI implants. This includes the following aims: (1) Development and validation of a mechanical actuation system for delivery of controlled LMHF vibration with optimized strain and frequency to the pelvic limbs of rats through a pilot in vivo study in rats, (2) The comparison of the relative effectiveness of LMHF vibration (using the system developed in Objective 1) and commercial LIPUS alone and combined, through an in vivo study in rats, (3) As a secondary objective, the comparison of bone ingrowth and bone density assessment using dual-energy X-ray absorptiometry (DEXA) and micro-computed tomography (micro-CT), (4) As another secondary objective, the comparison of bone surface strains adjacent to an OI implant and acceleration of the implant, measured using an accelerometer. The proposed research is motivated by the fact that OI is slow with some current implant designs. For example, the rehabilitation process after placement of a transfemoral OI implant by the Branemark group takes more than one year and requires two surgical procedures. This research will help evaluate the benefits of LMHF vibration and LIPUS alone and combined for implants with different designs in an in vivo rodent model. Upon successful completion, the proposed work will: (1) yield a better understanding of the bone surface strains generated through various vibration protocols, (2) lead to the development of a device allowing the local application of LMHF vibration, and (3) yield a better understanding of the relative benefit and synergy of LMHF vibration and LIPUS on bone ingrowth of threaded and textures implants. 332,000 total hip replacement and 719,000 total knee replacements are performed annually in the United States. This number is anticipated to grow in the foreseeable future. OI dental implants are a well-established medical procedure. One of the most common complications of dental implants is the lack of OI in patients with preexisting osteoporosis. Approximately 1.7 million people live with a missing limb in the United States and an estimated 185,000 amputations are performed each year. The number of individuals experiencing amputation is predicted to increase to more than 3.6 million by 2050. Lower limb amputees commonly use socket-type prostheses. These prostheses have several limitations: optimal fit is difficult to achieve causing undesirable stresses on tissues that can lead to pressure points, soft tissue sores, and nerve damage. Prostheses fixed by OI address many of the shortcomings resulting from the use of socket prostheses and their applications will most likely grow in the future. Patients fitted with a TOP instead of a socket prosthetics can live more active and healthy lives and more efficiently contribute to society. This research will further our understanding of strategies that may benefit individuals with OI joint prostheses, with dental implants, and with transdermal OI implants. By investigating non-invasive, user-friendly strategies that promote bone ingrowth, this research will benefit all patients receiving implants with the intent of OI.
