Graduate Research Assistants

As an academic institution, we work with a variety of promising young researchers. Here are some profiles of some graduate students who recently have contributed to the research effort:

Hrishikesh Keshavan

My duty as a graduate student working under the supervision of Dr. Sonny Bal was to develop a new, but inexpensive, “nano-sized” ceramic material that could be used for hip and knee prostheses. As nano-sized ceramic powder is more expensive to use than conventional sized powder, it was used only at the surface to reduce cost. Slip casting is one of the processes used widely in the ceramic industry to develop a material. A modified version of slip casting was used to create the four layer ceramic compact. This compact was then heated to a high temperature at which the powder coalesces to form a permanent bonds.

This work was presented as a poster at the 28th Annual Meeting of the Society for Biomaterials, Tampa Bay, Florida in April 2002. It has also been published as two papers in the Journal of Material Science: Materials in Medicine and Journal of Material Science. You can download a copy of the poster here (requires Microsoft PowerPoint.)

I am currently pursuing my second-year doctoral studies at Rutgers, The State University of New Jersey. My project here involves developing new materials for energy efficient application. I will finish my studies in another two years and hope to find a job where my knowledge and skills in the field of ceramics and material science can be utilized to full possible extent.

Aaron Molina

Aaron is a mechanical engineering student with strong interests in medicine. He has been working with Dr. Bal since July 2003, on the design and/or modification of surgical instruments for either total hip or knee replacement surgeries. Recently, research has become the focus of their attention, their current research agenda is the inspection of blind insertion of femoral stem effects of a mini two-incision hip techniques.

Education:
Master of Science Candidate, Mechanical & Aerospace Engineering
University of Missouri - Columbia
Bachelor of Science with Honors, Mechanical & Aerospace Engineering
University of Missouri - Columbia

Career Goals:
Ideally the medical research and design work completed through his education and Master’s thesis will lead to a career in the medical industry as a research and design engineer. Aaron’s ultimate goal, however, is to advance his knowledge to the design of mechatronic prosthetic limbs for persons with lost limbs.

Instrument Designs:
Cancellous Plug Punch: During a total knee replacement surgery a hole is drilled into the center of the patellar sulcus of the distal femur in order to insert a cutting guide. The drilled hole serves no purpose once the femur is cut and leveled. However, the issues of blood loss and bone regeneration at this hole are of great importance to the patient’s recovery. A simple design was developed and manufactured to solve this dilemma. The patient’s own cancellous bone (cut from the distal femur) is placed in the bowl and covered with the cap. The cap includes a ledge that will prevent the cutter’s blade from impact with the bowl. The cutter is inserted through the center of the cap and rests on the bone. With a mallet the bone cutter is struck cutting an ideal plug. The plug is designed to have a slight interference fit with the drilled hole.

Finishing Block Modification: A recent change in the femoral component for total knee replacement surgery in conjunction with the proclivity to minimize incision size has led to a modification of a finishing block. The finishing block acts as a cutting guide for the femoral component. Currently, the system involves a cutting guide block that is compatible for both knees. There are two primary adverse effects of the finishing block designed for bilateral use. First, because the block is bilaterally compatible, hence symmetric, the block is found to be larger than necessary. Thus, the incision size must be large enough to allocate enough room for the block to fit into the incision. Secondly, the skin must be stretched back wide enough to allow for cutting normal to the surface of the knee. The new finishing block designed by Aaron incorporates right/left specific blocks that are 75% the original size, rounded in shape for ease of insertion, and modified with a angled cutting slots to reduce incision gap to a 60° opening.

Research:
"Characterization of Femur with Respect to Femoral Stem Insertion with Loss of Direct Visualization during Total Hip Replacement Surgery"
Crack propensity due to loss of direct visualization is the focus of this research. The study inspects two femoral stems, the fiber-metal taper stem and ML taper stem, both of which are designed by Zimmer, Inc. Loss of direct visualization is found when employing a mini two-incision hip technique. With this technique there is an increase in crack propagation in the femoral neck due to lack of direct visualization. The goal is to model the process and possible deviations of insertion for both femoral stems. That is, ABAQUS, a finite element analysis (FEA) program, will develop the crack potential in the femur due to small incremental offset angles from the recommended position. This observed data will deliver the most crucial variables that surgeons must account for.

Activities:
Society of Hispanic Professional Engineers (SHPE), Vice-President
Society of Manufacturing Engineers (SME), Member
Habitat for Humanity, Volunteer

Contact Information:
Aaron Molina
E2411 Engineering Building East
University of Missouri - Columbia
Columbia, MO 65211
(573) 882-0422
axm754@mizzou.edu

Efrat Yagil-Kelmer

Dr. Kelmer completed her bachelor's and veterinary degrees in Israel in January 2001, after which she relocated to Columbia, Mo. Upon arrival, she enrolled as a graduate student in immunology at the department of Veterinary Pathobiology, while perusing an American veterinary license. She was mentored by Dr. Mark Estes and Dr. Sonny Bal. Her research focused on immune responses to ceramic total hip replacements and was published in the Journal of Orthopaedic Research in July of 2004. In addition, this research work won first place for presentation on the Phi Zeta research day in March of 2002 and second place in the Research and Creative activities Forum, UMC graduate school in March of 2003. It was also presented in the MU Comparative Orthopaedic Day in May 2003.

After completing her master's degree, Dr. Kelmer continued on with her veterinary career and started a one year internship in small-animal emergency and critical care. She completed her internship in June 2004 and is currently enrolled in a residency program in small animal emergency and critical care at the Veterinary Medical Teaching Hospital, University of Missouri-Columbia.