Tripolar Hip Implant Range of Motion Simulation

Principal Investigator: Daniel J. Berry, M.D.
Project Coordinator: Frank Chen — chen.qingshan@mayo.edu

Figure 14: Animation software for ROM simulation.

Management of total hip dislocation remains a challenging problem. Several clinical studies report successful use of a tripolar implant for recurrent instability. Using a large inside diameter acetabular cup and a bipolar femoral component these devices are expected to provide a greater range of motion (ROM) and to reduce dislocation.

Using Solidworks™ software (Solidworks Corporation, Concord, MA) we designed a ROM to impingement simulation of a tripolar and a conventional implants. The animation software was used to simulate ROM in six directions (flexion, extension, abduction, adduction, internal and external rotation). 3-D bone surface models were made from computer tomography and by using the software we could place the components within bony structures at any orientation (Figure 14).

Tripolar implants showed greater ROM than the conventional implants. The extremes of motion measured in certain directions may exceed what occurs in vivo, as effects of muscles and soft tissues are not included in the study. Tripolar implants can dramatically increase the ROM and delay prosthetic impingement in situations at risk for dislocation.