In this study, a single impact at 27 J of energy with a rigid interface was delivered to one knee of isolated joint preparations of six cadavers resulting in an average peak load of 5 kN. Contralateral knees were impacted with a padded interface at an additional level of energy at approximately the same load. All rigid impact experiments resulted in some form of injury to the patella including occult microcracking and gross fracture of the patella. No injuries were detected in the knees from the padded experiments. Math modeling of the patellae showed significantly reduced tensile and shear stresses in the bone with padding. The study suggests that the current lower extremity injury criterion, based solely on load, may not be sufficiently conservative. Increasing contact area over the knee reduces stresses in the bone, and prevents both gross bone fracture and bone and cartilage microdamage. Such data may be useful in future instrument panel designs, and might suggest revision to the current lower extremity injury criterion. (A)
Samenvatting