This zone runs from the proximal end of the joint between the 4th and 5th metatarsals (the 4:5 joint) to just distal to this joint. Fractures here may be acute or stress fractures.
"True Jones" fractures
Stewart (1960) related Sir Robert Jones' original paper to a new clinical series and emphasised the fractures at the level of the 4:5 joint (although one of his Xrays probably shows a slightly more distal fracture).
Subsequent work suggests these fractures are caused by adduction forces on the forefoot.
Some authors, particularly Lawrence and Botte distinguish between a “true Jones fracture” at the level of the 4:5 joint, always acute and due to adduction force, and a “proximal diaphyseal stress fracture”, just distal to the 4:5 joint. However, it is not clear how distinct these fracture types really are.
There is little information on the outcome or treatment of the "Jones fracture", partly because they are not always distinguished from diaphyseal stress fractures.
Konkel reported 10, but did not separate their treatment from other groups. There were 2 delayed unions but no non-unions. Portland et al included these fractures in their study of primary screw fixation. All united in a mean time of 6.2 weeks.
We have seen delayed and non-union in fractures at the level of the 4:5 joint which appear indistinguishable from those distal to the 4:5 joint, suggesting that “Jones fractures” may be a heterogenous group which require further study. We tend to treat the more proximal fractures like tuberosity fractures, but distal fractures like diaphyseal stress fractures.
Stress fractures
Stress fractures occur mainly in athletes between 15 and 25. Basketball players may be particularly prone to this injury.
Torg subclassified stress fractures into:
- acute fractures with no prodromal symptoms, sharp fracture margins and minimal cortical hypertrophy
- delayed unions with previous injury, widened fracture line, cortical hypertrophy and medullary sclerosis
- non-unions with wide radiolucency at the fracture line and obliteration of the medullary canal
Non-surgical management
Torg (1984), Zogby (1987), Clapper (1995) and Acker (1986) showed that most “acute” stress fractures will heal in a cast, although healing times may be very prolonged – the median time to union was 21 weeks in Clapper’s study and 11 months in Torg’s initial series.
Torg found that patients kept non-weightbearing initially (mean time of 6 weeks) were more likely to unite and did so quicker than those who bore weight immediately. Even delayed unions may heal in cast – 8/12 in Torg’s series, although the mean time to union was 14 months.
Surgery
Mologne et al (2005) reported the first RCT comparing medullary screw fixation with casting. Although the numbers were small, there was a large and significant difference in outcome between the groups. The surgical group united in a mean of 7.5 weeks and returned to sport at 8 weeks, with one non-union. The non-surgical group united in a mean of 14.5 weeks and returned to sport at 15 weeks, with 5 non-unions.
Based on these results, surgery should be offered at least to young, physically active patients with stress fractures. Casting remains an acceptable option for patients who prefer it.
Intramedullary screw fixation is the method most commonly reported. Comparisons between 4.5mm, 5mm and 6.5mm screws have not shown reproducible clinical or biomechanical differences.
Kelly et al (2001) found pullout strength for 6.5mm screws better than 5mm. However, Shah et al (2001) found no difference and commented that larger screws could increase the risk of intra-operative or post-operative fracture. Wright et al (2000) suggested using large diameter screws in athletic patients with high body mass
Mologne et al used 4.5mm screws in their RCT.
Tension band wire and plate fixation have also been reported.