Foot & Ankle

Classifications

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Fifth metatarsal fractures have been classically categorised based on location:

 

1. Tuberosity or avulsion fractures

2. Fractures at the junction of metaphysis and diaphysis

3. Fractures of the proximal diaphysis

4. Shaft fractures

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Although commonly used, this categorisation carries some ambiguity because the precise anatomic location of the physeal junctions is not well defined.

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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

 

Treatment:

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Avulsion Fractures:

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Conservative treatment ranges from a soft bandage to a light weight cast. An RCT including 60 avulsion fractures reported that patients treated with a soft dressing recovered significantly faster than those treated in a cast (33 days vs 46 days).

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Some studies have reported successful outcomes with a removable cast. A comparative cohort study of 39 patients (23 casts, 16 removable boots) showed a shorter mean time to preinjury function and less pain with boots compared to cast.

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Regardless of any specific treatment modality, majority of these fractures heal uneventfully within 6 to 8 weeks. However, radiographic evidence for union may lag behind resolution of clinical symptoms.

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Symptomatic non-union is very rare with these fractures. Asymptomatic non-union may be slightly more common but does not necessarily require any treatment. If indicated, surgery can be considered in symptomatic cases and the options include excision or fixation depending on the size of the fragment.

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Jones Fracture

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First described by Sir Robert Jones (1902), usually results from adduction and axial loading of a plantarflexed foot. These fractures occur in an area of relative hypovascularity, increasing the chance of delayed union or non-union. A single nutrient artery feeding the fifth metatarsal shaft enters the medial cortex near the junction of the proximal and middle third of the diaphysis resulting in a watershed area near the proximal metadiaphyseal junction.

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In the majority of cases, 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.

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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).

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

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In another study, 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.

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Hunt and Anderson examined 21 athletes undergoing intramedullary screw fixation with autologous bone graft (12 patients), bone marrow aspirate plus demineralised 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.

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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).

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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.

 

Shaft Fractures

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These fractures usually occur with an axial load and simultaneous rotational injury or inversion type injury. Moderate displacement in the transverse and oblique planes is commonly seen and well-tolerated even if mal-united, without resulting in metatarsalgia. Due to a long oblique fracture surface and better perfused area majority of fractures heal without requiring surgical intervention.

 

These are treated with a light weight cast, a removable walker boot, or a stiff-soled shoe with weight bearing allowed as tolerated. Surgery may be indicated in cases of comminuted, segmental, significantly displaced or open fractures. It is common for patients to be nearly pain free at 6 weeks from injury, yet radiographs tend to demonstrate only minimal callus.

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Aynardi and colleagues recently published a large series of 142 fractures treated non-operatively. There were only two painful non-unions that required fixation with bone grafting.