Fifth metatarsal fractures

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:

• the maximal stress occurs 3.4-4cm from the tuberosity (the zone of stress fractures)
• the maximal stress acting on the fifth metatarsal is 50% of the failure stress, supporting the view that fractures in this area are indeed stress or fatigue fractures.

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.

Orendurff (2009) studied the differences between the pressures under the 5th MT head and base during various sports manoevres as an indirect way of estimating bending forces. The largese pressure differences were during acceleration and running straight. Jump takeoff and landing and cutting right or left had low differences.

Raikin (2008) studied the hindfoot alignment in 21 patients with Jones fractures. Standing hindfoot alignment radiographs showed 18/21 to be in varus, and this was apparent clinically in 16.