Rohit Madhav and Fares Haddad summarise the latest consensus on how to treat this troublesome injury.
Metatarsal fractures are among a group of sports injuries that seem to have acquired celebrity status alongside their illustrious owners (usually international basketball players or footballers).
But how to manage them most effectively remains a subject of debate, with the greatest controversy reserved for base of fifth metatarsal fractures (also sometimes referred to as proximal fifth metatarsal fractures – see below for a more exact definition). The lack of uniformity in diagnosis and classification is compounded by the generic and misleading use of the term ‘Jones fracture’(1) for all base of fifth metatarsal fractures. Because of these variations in approach, it has become hard to make sense of the literature and therefore problematic, also, to make appropriate treatment recommendations and prognoses for healing and return to sport.
The fifth metatarsal is a prime candidate for stress fracture because it is susceptible to a range of considerable dynamic forces, and the effects of any of these can be magnified by several common foot alignment deformities, such as flat feet.
These injuries often result from activities involving running and making sharp turns on firm surfaces. They generally take longer to heal in athletes, especially if the patient continues with activity, even to a moderate level.
This short review will try to unscramble some of the confusion with injury classification and will update SIB readers on treatment issues and recommendations for managing the fifth metatarsal (see figure 1 below).
The fifth metatarsal consists of a head, neck, shaft, base and tuberosity (or styloid). The base articulates with the cuboid and base of the fourth metatarsal. Some authors refer to the combination of fourth and fifth intermetatarsal and metatarsal cuboid joints as the ‘lateral Lisfranc complex’.
The ‘proximal fifth metatarsal’ area extends from the tip of the tuberosity to 1.5cm along the shaft (towards the toe).
Dameron (2) has a useful practical anatomical classification. The proximal region is divided into three zones (fig 1).
Torg (3) further divides Zone III injuries according to their healing potential: type I fractures are acute injuries; type II are those with evidence of delayed union (slow bone healing); and type III are those with evidence of non-union (failure of fracture to heal).
Zone I fractures
These fractures result from tensile or traction forces. Both the lateral band of the plantar aponeurosis (on the sole of the foot) and the peroneus brevis tendon insertions have been implicated.
These fractures traverse through cancellous (trabecular or spongy) bone with excellent blood supply. They usually begin on the far outside edge of the zone and extend towards the ankle. Concomitant fractures of the lateral malleolus (end of the fibula) can occur and need to be treated separately on their merits. This also highlights the fact that the fifth metatarsal base should be assessed whenever ankle sprains or fractures are evaluated.
There is no generally preferred treatment approach to zone 1 fractures that will speed the healing and relief from symptoms. The vast majority of these fractures can be managed non operatively, using elasticated bandages or soft dressings, stiff soled shoes or a functional brace. If the pain is severe, the foot can be immobilised in a short leg plaster cast with protective weight- bearing. Most tuberosity avulsion fractures heal within eight weeks.
Surgery may be appropriate for:
It is important to remember with zone 1 fractures that the symptoms often subside before the bone is fully healed. Moreover, there are often no symptoms to help identify those instances when a bone is slow to mend or failing to heal.
Zone II fractures
The mechanism of injury here is axial loading with adduction force on a plantar-flexed foot (the foot is twisted inwards and down). Anatomically this zone corresponds to the area between the insertion of peroneus brevis and tertius tendons.
These injuries are usually more painful than those at zone I, and treatment methods may need to be more aggressive. The appropriate treatment for minimally displaced (stable) fractures is conservative, either using a functional metatarsal brace or non- weight-bearing short leg cast for six to eight weeks. Treatment thereafter needs to be individualised.
However, rates of non-union (failure to heal) are reported as anything between 7% and 28%. And while Torg has reported a 93% rate of union at an average of 6.5 weeks, full healing non- operatively can take as long as 22 weeks. So, if the patient ends up having to undergo surgery for a non-healing fracture, they may spend five months or more out of action.
This means it may be reasonable to consider early surgical treatment if an athlete needs to make a prompt return to sport. Where acute fractures are operated on without delay, the average time to union (full healing) is 7.4 weeks.
A supervised rehabilitation programme is recommended, starting with range of movement exercises, with graduated weight bearing progressing to agility and endurance training, followed by return to full sports. Use of a functional brace is recommended for at least one month after the bone is confirmed as healed. Displaced fractures usually require fixing surgically.
Zone III fractures
Delee et al (4) define stress fracture as a spontaneous fracture of normal bone that results from the summation of stresses, any of which by itself would be harmless. Their criteria for a stress fracture include:
Torg defines an acute fracture (type I) as one with sharp margins, without widening, radiolucency or periosteal reaction. A delayed union (type II) is characterised by a previous injury or fracture, widened fracture line with adjacent radiolucency, involvement of cortices, evidence of periosteal reaction, and evidence of sclerosis within the bone shaft (intramedullary damage). The features of non-union (type III) include a history of repeated trauma and recurrent symptoms, a widened fracture line with much more extensive damage to the periosteum and bone shaft.
The current acceptable treatment choice for a Torg type I fracture with no previous symptoms is a non-weightbearing short leg cast for six to eight weeks. An indication for early surgery would be a complete fracture in a patient with a compelling reason to return to athletics.
In type II fractures, prolonged immobilisation may be acceptable for some patients. Otherwise type II and III fractures (as well as those with delayed union or non-union of zone II fractures) are best treated surgically. The average time taken for full healing is 7.5 weeks.
A repeat break is a known complication of proximal fifth metatarsal fractures, occurring in up to one in 10 surgically treated cases at anything from seven weeks to eight months later.
Joseffson et al (5) have found that almost one in four fractures treated conservatively required subsequent surgery either because of delayed union or re-fracture. Glasgow et al (6) report a reoperation rate of 6% for surgically managed cases (a mixture of zone ll and zone lll fractures).
Early re-fractures are thought to occur because of a premature return to weight bearing against advice, an incorrect diagnosis of fracture healing, or failure of the surgical screws or plate because of an early return to sport.
Late re-fractures following full union may suggest a repeat injury, occurring upon the athlete’s return to previous stress loads, and may indicate abnormal biomechanics. Some authors advocate using functional foot orthoses or lateral forefoot stabilisers for a prolonged period.
Fares Haddad BSc MCh (Orth) FRCS (Orth) is a consultant orthopaedic surgeon at University College London Hospital and editorial consultant to Sports Injury Bulletin
Rohit Madhav is a consultant orthopaedic surgeon with a special interest in disorders of the foot and ankle, at the department of trauma, orthopaedics and sports injuries, University College London and The Middlesex Hospitals
Illustrations by Viv Mullett