Metatarsal Fracture

Introduction

Metatarsal fractures are common, and occur in isolation or in conjunction with concomitant other injuries to the foot and other metatarsals. They are ten times more common than Lisfranc injuries. The fifth metatarsal is reported to be the most commonly injured .

 

Mechanism of Injury​

The mechanism of injury may be direct, indirect or repetitive trauma. Direct injuries include falls, motor vehicle accidents, crush injuries or a fall of heavy objects. Indirect injuries include falls on plantarflexed and fixed foot or inversion injuries. Repetitive strain can cause stress type fractures.

Classically fractures of the fifth metatarsal result from indirect inversion type injuries. Cadaveric studies suggest that the lateral band of the plantar aponeurosis tethers the fifth metatarsal to create avulsion fractures of the tuberosity, with the peroneus brevis tendon contributing as the major deforming force to further displacement.

​

Classification

Fractures of the 1st - 4th metatarsals are classified by anatomic location as base, shaft and neck fractures.

​Fifth metatarsal fractures are classically categorised based on location although this system is ambiguous because the precise anatomic location of the physeal junctions is not well defined:

  1. Tuberosity or avulsion fractures
  2. Fractures at the junction of metaphysis and diaphysis
  3. Fractures of the proximal diaphysis
  4. Shaft fractures​

Lawrence and Botte divided the proximal fifth metatarsal into three distinct fracture zones:

  • Zone I - the tuberosity - avulsion fracture (more than 90% fractures in their study)
  • Zone II - the metadiaphyseal region - Jones fracture (at the level of 4th/5th intermetatarsal joint)
  • Zone III - the proximal diaphyseal region - stress fracture

DeLee and colleagues separated proximal fifth metatarsal fractures into:

  • Type IA: acute, undisplaced, metadiaphyseal fractures
  • Type IB: acute, comminuted metadiaphyseal fractures
  • Type II: chronic metadiaphyseal fractures with either a clinical symptoms or radiologic evidence of stress reaction
  • Type IIIA: extra-articular tuberosity avulsions
  • Type IIIB: intra-articular tuberosity avulsions

Torg and colleagues defined three categories of fifth metatarsal base fractures based on healing potential and radiographic appearance:

  • Type I: acute fractures without intramedullary sclerosis
  • Type II: delayed fracture healing with a widened fracture line and intramedullary sclerosis
  • Type III: non-unions with obliteration of the intramedullary canal

 

Imaging

​AP, lateral, and oblique radiographs of the foot are routinely obtained, ideally with the patient bearing weight, however due to initial pain and swelling, weight bearing views may not be possible.

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Treatment

The majority of fractures heal uneventfully with conservative treatment, however a small percentage may lead to non-union or mal-union resulting in significant disability and pain. The Jones fracture is a specific fracture which is discussed in more detail later in this section.

Conservative Treatment

Undisplaced and minimally displaced fractures are usually treated conservatively with immobilization for a period of 4 to 6 weeks. Usual options include a stiff-soled shoe, plaster shoe, walker boot or  below-knee light weight cast. With any of these options weight-bearing is allowed as per comfort. In case of first metatarsal or Jones fractures, more cautious weight-bearing is advised due to higher risk of displacement in view of excessive load bearing. Most fractures heal within 6 weeks and recovery back to normal activities follows soon after. This has generally been observed to result in very satisfactory outcome. However some of these patients may end up with an incompetence or deformity that either exacerbates metatarsalgia or necessitates late surgery.

Surgical Treatment

Indications include:

  • Open fractures
  • Significantly displaced fractures
  • Mal-rotated deformities
  • Multiple metatarsal fractures
  • Fracture angulation >10º
  • Non or delayed union

Sagittal plane displacement is poorly tolerated as it alters the weight-bearing relationship of the metatarsal heads and may result in painful callus and metatarsalgia. Transverse plane displacement is usually better tolerated but can be associated with interdigital nerve impingement. In case of considering surgery, the concept of restoring length, alignment and rotation should be followed.

Surgical options are dependent upon the metatarsal involved, the pattern of fracture and the soft tissue envelope. Closed reduction and K-wire fixation can be employed in the second, third or fourth metatarsals so long as length and alignment can be maintained. However, for oblique or spiral fractures, small lag screw fixation can provide additional stability along with plate fixation. ​

There are very few studies which report the outcomes of fractures of the first four metatarsals. A study comparing fixation management with K-wire fixation (21 patients) and casting (36 patients) reported no significant difference in outcomes. 56% patients had metatarsalgia. Poor outcomes were considered associated with comminution, sagittal plane displacement, open fractures, or severe soft tissue injury.

​An RCT of 50 patients with minimally displaced lesser metatarsal fractures compared cast immobilization with elastic bandage support. All patients achieved radiographic union at mean follow-up of 3 months. Patients with elastic bandage treatment had significantly higher functional scores and less pain.

​Multiple metatarsal fractures have traditionally been an indication for surgical treatment. However, there is little objective evidence to support this approach. Although such fixation has the benefit of restoring the anatomy and stability across the forefoot, but also carries the disadvantage of the wires holding the toes in a non-functional dorsally displaced position for several weeks until adequate bony healing permits hardware removal. Subsequently these patients may have a resultant contracted dorsiflexed toes with little MTP or IP motion, chronic pain, difficulty in shoe wear and toe deformities.

Jones Fracture

These are fractures of the fifth metatarsal occuring in Zone II at the junction of the metaphysis and diaphysis. They were first described by Sir Robert Jones (1902), and usually result from adduction and axial loading of a plantarflexed foot. Since the fracture occurs in an area of relative hypovascularity, there is an increased risk of delayed union or non-union hence why it represents a specific entity to recognise and treat in a more watchful approach.​

Undisplaced or minimally displaced fractures are treated for 6 weeks in a nonweight-bearing cast followed by a progressive increase in weight bearing in a walker boot for further 2 weeks.

​Surgery is considered for displaced fractures, symptomatic non-unions, and for patients who require earlier weight bearing (high-level athletes, other occupational needs). Fixation is most commonly performed using an intramedullary compression screw (solid or cannulated, partially-threaded).

Murawski and Kennedy reported on 26 patients who underwent intramedullary fixation. Radiographic union occurred at a mean of 5 weeks. Only two patients failed to their previous level of sports, and one delayed union and re-fracture occurred.

Mologne and colleagues reported the outcomes of screw fixation versus casting for acute Jones fractures in an RCT (18 casts vs 19 screw fixations) with a mean follow-up of 25.3 months. Eight of 18 (44%) in the cast group were considered treatment failures with 5 non-unions, 1 delayed union, and 2 re-fractures. Only one of 19 patients in the surgery group was considered a treatment failure. For the surgery group, the median times to union and return to sports were 7.5 and 8.0 weeks, respectively. For the cast group, the median times were 14.5 and 15.0 weeks, respectively.

A meta-analysis performed by Roche and Calder examined various treatment options and outcomes after acute fractures, delayed unions, and non-unions, including 26 studies (22 level IV, 1 RCT). Return to sports after intramedullary screw fixation for acute fractures ranged from 4 to 18 weeks. Acute fractures treated non-operatively had a union rate of 76% compared to 96% in fractures treated with a screw. Delayed unions treated non-operatively had a union rate of 44% compared to 97% treated surgically. Non-unions treated with screw fixation healed in 97% of cases.

In general union rates with non-operative treatment have been reported to be 72% to 93%. Kavanaugh and colleagues noted delayed union in 12 of 18 conservatively treated Jones fractures. Torg and coworkers noted one delayed union in 15 Jones fractures treated with nonweight-bearing, but 6 of 10 patients treated with a weight-bearing cast had problems with fracture union.

Several series report 100% union rates for intramedullary screw fixation, but some have suggested failure with this technique. Kavanaugh and colleagues used a 4.5-mm malleolar screw to treat 13 proximal metatarsal fractures with a 100% union rate with no incidence of re-fractures.

DeLee and colleagues reported a 100% union rate with a similar method of fixation in 11 athletes. Reese and colleagues noted union within 8 weeks for all 15 patients treated with cannulated screws, ranging from 4.0 to 6.5 mm in diameter.

Porter and colleagues also observed a 100% clinical healing rate in 23 Jones fractures using 4.5-mm cannulated screws, with all patients returning to sports activity at an average of 7.5 weeks.

Wright and colleagues reported re-fractures in 6 athletes treated with cannulated screw fixation. Despite clinical and radiographic union, 3 patients re-fractured on the day they returned to full activity, and 3 others sustained a re-fracture 2.5 to 4.5 months after return to activity. The authors suggested using larger diameter screws in athletes with high BMIs and orthotics on return to sports.

​Larson and colleagues cautioned that early return to competitive athletic activities before evidence of radiographic union may be predictive of failure. The authors reported 4 re-fractures and 2 symptomatic non-unions in 15 athletes treated with cannulated screw fixation. Although all 15 patients were asymptomatic before returning to full activity, only 1 of the 6 failures had evidence of radiographic healing.

​Hunt and Anderson examined 21 athletes undergoing intramedullary screw fixation with autologous bone graft (12 patients), bone marrow aspirate plus demineralized bone matrix (8 patients), or no bone graft (one patient). All athletes were able to return to their previous level of athletic competition at an average of 12.3 weeks. All fractures showed clinical and radiographic evidence of compete cortical healing. Only one patient subsequently sustained a re-fracture. Given the good outcomes and small study group, it was unclear what the effect of the bone grafting had on healing.

Furia and colleagues reported the use of high-energy shockwave therapy versus intramedullary screw fixation for non-united Jones fracture.  Twenty-three patients with a fracture non-union received high-energy shockwave therapy, and 20 other patients with the same type of fracture non-union were treated with intramedullary screw fixation. Twenty of the 23 non-unions in the shockwave group and 18 of the 20 non-unions in the screw fixation group healed at 3 months after treatment. One of the three non-unions that had not healed by 3 months in the shockwave group was found to be healed by 6 months. There was one complication in the shockwave group (posttreatment petechiae) and 11 complications in the screw-fixation group (1 re-fracture, 1 cellulitis, and 9 symptomatic hardware).

Alvarez and colleagues examined nonunion or delayed union in 34 fractures treated with extracorporeal shockwave therapy and similarly noted a high rate of healing with 90% healing at 12-month follow-up.

 

References​

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