Combined Internal and Small Monolateral External Fixation Lapidus Arthrodesis: Finite Element Analysis and Biomechanical Study

Principle Investigator: David Pontell
Co-investigators: Jihui Li
Funded by: Inova Health System & Biomet Inc.

Fusion of the first metatarsal-cuneiform joint (1st MTCJ) is indicated in the treatment of symptomatic, moderate-severe hallux valgus (great toe deformity/rotation with either osteoarthritis or instability of this joint complex). The utility of this procedure to correct high intermetatarsal angles with or without dorsal instability (hypermobility) is well-appreciated. Like other “basal” procedures, however, the extended period of non-weight bearing is a risk factor for potentially-serious complications such as deep vein thrombosis and pulmonary embolus, and compliance is difficult to maintain. These may deter patients and their surgeons from pursuing this valued surgical approach.

Some providers have begun to advocate small, monolateral external fixation (percutaneous half-pins with external, rigid rails) as a useful adjunct to internal fixation (conventional cancellous bone screws) which may allow safe, early weight-bearing while joint fusion proceeds. However, no peer-reviewed studies have been published to support the efficacious or safe use of this approach. In this study, we will develop finite element analysis (FEA) models of foot-ankle complex with the MTCJ cured by either combined internal and small, monolateral external fixation or internal fixation. The models will be validated by biomechanical testing on cadaveric foot-ankle specimens. FEA is also used to compare the stability of MTCJ fixed by the two methods. A series of biomechanical testing on the cadaveric MTCJ will be performed to evaluate the two methods. Paired t-test will be used to check the significance of the two methods regarding to MTCJ stiffness and strength.