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Executive Summary
This poster outlines the issues that our patient Freida Pinto suffers and our proposed hip implant to be used in a total hip arthroplasty for her joint. Freida Pinto has had hip pain and poor mobility since she was eight years old after a bout of fever and sickness which resulted in pain and muscle loss. Our group suspects that Freida’s hip issues stem from polio which fits symptoms from her childhood sickness. Despite a lack of development in her left leg and hip throughout her life, she was able to maintain her independence using crutches. However, recently her hip pain increased significantly and her mobility was severely hampered. In order to remediate her hip pain and lack of mobility and to help her keep her independent lifestyle, our group has designed a hip implant for Freida.
The stem is cemented so that it is more stable since Freida’s underdeveloped femur would make osseointegration difficult. The design incorporates a tapered profile for better pressurization of cement during insertion and features vertical ridges for better stability. It is made out of Ti75Fe20Sn5, which is an alloy with a very high yield strength and overall strength meaning it is less likely to fracture despite Freida’s narrow femoral canal. Additionally, the alloy has a remarkably low elastic modulus, reducing stress shielding. According to calculations in our python program, Freida will be able to use the implant for 32 years before risking femoral fracture due to stress shielding. The cement will have a micro silver powder mixed into it to prevent postoperative infection.
The acetabular component is un-cemented to promote osseointegration. Due to Freida’s small and weak ilium, the acetabular component was extended to hook over the anterior inferior iliac crest. Doing so allowed the force placed on the implant to be spread over a greater area. The acetabular component is made of a TiNi alloy which has a low elastic modulus for better stress shielding. It is also super-elastic meaning that it can elastically absorb stress and return to its original shape giving it great strength. For better osseointegration, the acetabular component is coated in hydroxyapatite which is osteoconductive allowing for bone to grow along the implant. Additionally, the implant is screwed to the iliac along the iliac ridge so that it will not move around for better bone growth while not allowing as much plastic wear particles to leave the acetabular cup. The liner to be used is made of UHMWPE for low wear.
For the surgical fixation, the stem will by implanted similar to typical cemented stems where the femur is reamed and cleaned before the cement is delivered and pressurized. After the cement is pressurized, the stem is inserted. As for the acetabular component, the acetabulum and the iliac crest are reamed and cleaned before having the implant hammered into place for a secure fit. The implant will then be screwed to the iliac for a more secure fit.
