Simulation of the Hip in SCFE Using 3D Models.

Nikhil Kulkarni, F.Amirouche Ph.D, E. Abraham M.D.

This Research mainly involves the study of Wear Characteristic of the Femoral Head in Arthritic States. Patients undergoing THA or in Situ Pinning have a severely worn femur head, due to loss of cartilage, which leads to Osteoarthritis causing unbearable hip pain. Among the patients studied most of them had Slipped Capital Femoral Epiphysis (SCFE) which is the most common cause of adolescent hip disease and some of them suffered from DDH.  

The research consists of two phases, the first phase involves tracing the wear to find out the pattern of wear on the femur heads and the second phase involves doing the contact and stress analysis in trying to understand what causes the deformation leading to SCFE and DDH and how it can be avoided.

In the first phase the Femur heads removed from the patients suffering from SCFE or DDH are brought to the lab. Pictures of the same are taken from two different views and send to the orthopedics department to trace the wear on them.

Pictures of Femur head with Wear area traced

 Also these specimens are CT scanned slice by slice. From the CT scans we make use of Mimics and a Visualization tool kit software made in the lab itself to get a 3-d model of the femur head. The 3-d model obtained is then taken to Pro/E in IGES format and from the pictures of the trace we use Pro/E surfacing to trace the wear on the 3-d model.

3-d Model of Femur heads in Pro/E

Finally using Pro/E we calculate the total area of the femur head and the wear area where by we can get the percentage of wear on the femur head. This is compared with the wear area marked by the surgeon in 2-d and both of them are compared to determine the accuracy of  the two methods.

Wear Area traced on the femur head in Pro/E

About 12 to 15 specimens are used to determine the pattern of the wear and we try to understand the exact nature which leads to the wear.

The second phase of this research involves doing a Finite element study, in understanding the mechanism which causes such deformation so as to delay the same or avoid it.

In the second phase we will be try to understand how the stresses in normal stages change which leads to the deformed state. This involves doing contact analysis between the femur head and the acetabulum for different slip angles of the SCFE.