Abstract
Summary
A laboratory based study investigating fracture forces and implant subsidence rates in embalmed human femurs undergoing impaction grafting.
Methods
Human femurs were harvested from cadavers for destructive impaction testing. An initial group of femurs underwent destructive impaction testing, using the impaction grafting technique as described by Gie et al, modified, allowing increasing, controlled impaction forces to be applied until femoral fracture occurred.
A second group of embalmed human femurs underwent impaction bone grafting at constant force, with varied impaction frequencies. An Exeter stem was cemented into the neo-medullary canals. These constructs underwent subsidence testing simulating the first 2 months post-operative weight-bearing.
Results
In a group of 17 femurs, none fractured below a 0.5kN impaction force. 82% of the femurs fractured at or above 1.6kN of applied force. No massive implant subsidence occurred in the second group of 8 femurs, all undergoing femoral impaction grafting at 1.6kN. There was no correlation between implant subsidence and frequency of impaction. Average subsidence was 3.2mm.
Conclusions
It is possible to calculate a force below which no fracture occurs in the embalmed human femur undergoing impaction grafting. Increasing impaction frequency, at constant force, doesn't decrease rates of implant subsidence.
