Fifth metatarsal fractures

The fifth metatarsal forms the mobile lateral foot border. It has a broad base, expanded laterally to form the tuberosity, a narrow shaft and a fairly small head. The base articulates with the cuboid and with the fourth metatarsal. The detailed anatomy of these joints and their ligaments has not been described in detail.

Also attached to the base of the fifth metatarsal are:

There is also a watershed between a network of vessels supplying the base and the nutrient artery of the shaft (Smith et al 1992). Interestingly, Smith's photographs do not show such a clear-cut hypovascular zone as their diagrams, and Shereff et al (1991), in a similar study, did not comment on such a watershed (although one of their diagrams suggests it!).

The base of the metatarsal is well-supported by the ligaments and plantar fascia while the shaft is free. Hence there is a potential stress riser at the junction of base and shaft.

Arangio et al (1997) used beam theory to calculate the stresses at different points in the fifth metatarsal. They found that:

Vertullo et al (2004) demonstrated torsional strain in the proximal fifth metatarsal under simulated axial loading and tendon contraction. They suggested this is due to the eccentric placement of the tendon insertions.