Clinical comment

The classification and description of fractures of the proximal fifth metatarsal can be confusing and central to this has been the regular mis‐use of the term Jones’ fracture. Sir Robert Jones was one of the forefathers of British orthopedics and founder of the British Orthopaedic Association. In 1902, he wrote a case series on fractures of the fifth metatarsal, one of which was his sustained through dancing.3,4 A zone 1 (avulsion) fracture is proximal to the fourth/fifth intermetatarsal joint and represents an avulsion of the tuberosity. A zone 2 (Jones) fracture is in the vascular watershed zone between the diaphysis and metaphysis, at the level of the intermetatarsal joint. A zone 3 (diaphyseal stress) fracture is distal to this in the proximal diaphysis (Figure 108.1).2 Zone 3 fractures were qualified further by Torg et al., who described a classification system with a type 1 indicating an acute fracture, a type 2 representing delayed union with a wide fracture line and intramedullary sclerosis, and type 3 is a nonunion with a wide fracture line and extensive intramedullary sclerosis.5 Further work has differentiated fractures into complete and incomplete fractures, where an incomplete fracture is more likely to progress to nonunion in weightbearing as there are tensile forces over the lateral cortex and compressive forces medially.6

Available literature and quality of the evidence

Level IV studies have further demonstrated the anatomical location affecting fracture location and union. Clapper et al. reviewed a series of 100 patients with fifth metatarsal fractures which were followed prospectively to determine outcomes of their injuries: three distinct subgroups were identified depending on fracture location.7 The study showed 68 zone 1 (avulsion), 25 zone 2 (Jones), and 7 zone 3 (diaphyseal stress) and provided a treatment algorithm, which yielded 100% union at 4.7 weeks for zone 1 (avulsion) injuries treated nonoperatively, and 100% union at 5.8 weeks for zone 3 (diaphyseal stress) injuries treated nonoperatively, and only 72% union at an average of 21.2 weeks for zone 2 (Jones) injuries treated nonoperatively.7 A similar union rate was demonstrated by Kavanaugh et al., with a series of 22 zone 2 (Jones) fractures having delayed healing in two‐thirds of those cases treated conservatively.8

Other level IV studies have reported on union rates in zone 1 (avulsion) fractures. Dameron reported a case series of 100 tuberosity fractures (zone 1) treated conservatively, all but one healed clinically within three weeks.9 Vorlat et al. reported on a case series of 38 patients with zone 1 (tuberosity) fractures, and found the most significant predictor of poor functional outcome was prolonged nonweightbearing. Gender, age, and fracture type did not affect outcome.10 A single level II study has also demonstrated 100% union rates in 60 patients with zone 1 (avulsion) fractures with nonoperative treatment.11

Lee et al. reviewed a cohort of 75 patients (level III), and introduced the concept of the plantar gap in the zone 3 (diaphyseal stress) injury; the distance between the fracture margins, measured on the lateral cortex of an oblique radiograph. The mean time for bone union in those patients with a plantar gap <1 mm was 71.21 ± 29.95 days compared to 126.4 ± 51.99 days in those with a plantar gap >1 mm (p <0.001).6

Findings

Overall, there are many level IV studies that have been used to define proximal fifth metatarsal fractures, with Clapper et al. reporting on fracture pattern and union rates in 100 proximal fifth metatarsal fractures.7 Torg et al. provided further understanding and classification with description of the acuity of zone 3 injuries,5 and Lee et al. introduced the concept of plantar gap distance having an effect on time to union.6

Multiple level IV studies9,10 and a single level II11 study have demonstrated excellent union rates in zone 1 (avulsion) fractures treated nonoperatively. Other level IV studies have shown that union rates in zone 2 (Jones) and zone 3 (diaphyseal stress) fractures are far less reliable with nonoperative treatment.6–8 A retrospective study of 22 patients with zone 2 (Jones) fractures or zone 3 (diaphyseal stress) fractures treated surgically showed all fractures united (mean 6.25 weeks) with no to rare pain reported during athletic activity.12

Resolution of clinical scenario

• Zone 1 (avulsion) fractures should be treated nonoperatively, with symptomatic treatment being sufficient, with patients resuming normal activities as their symptoms permit irrespective of radiological appearance.
  
• Zone 2 fractures (Jones fracture) are slower to heal and more prone to re‐fracture. A short leg cast or a functional brace may be used; however, surgical fixation should be considered, particularly in an athletic population.
  
• Zone 3 (diaphyseal stress) fractures are prone to nonunion and surgical fixation results in a quicker time to union and return to sport and this may be beneficial in selected patients.