Axial Compressive Load Response of the 90Md Flexed Human Tibiofemoral Joint 99SC08
National Accident Sampling System (NASS) data, for the years
1993-1995, suggests a high frequency of tibiofemoral joint
fractures among automotive accident victims. In addition, the NASS
data also suggests that these injuries may be attributable to
direct axial loading via the floor pan and/or the foot controls.
Hirsch and Sullivan (1965), and Kennedy and Bailey (1968) conducted
quasi-static fracture experiments axially compressing human
tibiofemoral joints at low rates of loading and low angles of
flexion. Hirsch and Sullivan observed a mean fracture load of
approximately 8 kN compared to approximately 16 kN in the Kennedy
and Bailey study. The current tibiofemoral joint injury criterion
used in anthropomorphic dummies is based on Hrisch and
The current study involved impact experiments on human
tibiofemoral joints (aged 71.4±11.2) directed in a superior
direction along the axis of the tibia with the joint flexed 90°.
One joint from each cadaver was impacted sequentially at increasing
velocities to establish a range of loads and impact energies needed
to cause gross fracture. The contralateral joints were impacted
only once at a lower velocity that generated fracture and
nonfracture data. The location of damage on the tibial plateau and
femoral condyles coincided with the location of highest
tibiofemoral contact pressure. Repeated impacts resulted in
tibiofemoral fracture to the medial and lateral tibial plateau,
medial femoral condyle, and femoral notch for a maximum load of 8.0
±1.8 kN. Single impact experiments resulted in a 33% frequency
of fracture at 5.8 ±1.5 kN. A microscopic analysis of the
remaining eight single impact joints indicated occult damage at the
cartilage/subchondral bone interface for a load of 7.1 ±2.4 kN.
These damages were consistent with the location of gross fracture.
The location of these micro-cracks were also consistent with the
location of occult bone trauma in a limited number of motor vehicle
accident MRI trauma patients referred to Michigan State University.
This study helps establish impact injury thresholds for the flexed
human tibiofemoral joint that will be relevant to the automotive