The current treatment of tarsometatarsal joint injuries is associated
with suboptimal long-term results. The objective of the present
study was to measure the contact mechanics of the tarsometatarsal
joints in normal adult cadaveric feet in order to develop a foundation
for more effective treatment.
Six fresh cadaveric lower legs and feet were subjected to four
different axial compressive loads (0.5, 1.0, 1.5, and 2.0 times
body weight) at each of five different positions. For each position,
load, and tarsometatarsal joint, the contact pressures and areas
were measured with use of pressure-sensitive film. Contact forces
were calculated from the ratio of pressure to area. Contact pressure,
area, and force were analyzed as a function of load, the specific
tarsometatarsal joint, and foot position.
The forces across these joints ranged from 2 to 541 N, but pressures
ranged only from 0.5 to 5.7 MPa. In general, changes in load and
foot position, in both the sagittal and the frontal plane, were
associated with changes (p < 0.05) in tarsometatarsal joint contact
areas and forces. In contrast, the contact pressures across these
joints varied minimally with changes in load and foot position.
These data suggest that the tarsometatarsal joints are designed
to regulate pressure in each joint by means of two mechanisms: (1)
at small loads, an intrajoint mechanism regulates tarsometatarsal
joint pressure by increasing contact area within the joint in response
to increasing force, and (2) at larger loads, an interjoint mechanism
engages to regulate tarsometatarsal joint pressure by redirecting
force to other tarsometatarsal joints.
The data provide both absolute (normal contact forces, areas,
and pressures) and relative (intrajoint and interjoint regulating
mechanisms) performance (functional) criteria for the development
of new treatments for diseased or traumatized tarsometatarsal joints.