Current Concepts In Treating Fifth Metatarsal Fractures

Given the intricacies of these fractures, these authors offer salient diagnostic pointers, a thorough review of the literature and pertinent pearls from their experience with the treatment of tuberosity fractures, Jones fractures and stress fractures of the fifth metatarsal.

   Fractures of the proximal fifth metatarsal are not uncommon as physicians encounter them in the emergency room and the office setting. Various studies have evaluated the etiology of each type of proximal fifth metatarsal fracture as well as the best therapeutic options. Three types of fractures that occur at the proximal fifth metatarsal are tuberosity fractures, acute metaphyseal-diaphyseal fractures and stress fractures. It is important to distinguish between each type since different treatment methods are indicated for each fracture.

   Jones first brought attention to these fractures in 1902 with a study involving six cases, one of which was his own.1 The Stewart classification attempts to classify the Jones fracture and proximal base fractures.2 It describes the location of each type of fracture as well as joint involvement. This classification system shows a difference in the mechanism of injury and the prognosis of Jones fractures versus fractures of the styloid process.

   Type 1 is a fracture at the metaphyseal-diaphyseal junction. This is the classic Jones fracture. Type 2 is an intra-articular tuberosity fracture without comminution. Type 3 is an extra-articular tuberosity fracture. Type 4 is an intra-articular, comminuted tuberosity fracture. Type 5 is a fracture of the epiphysis.

   The anatomy of the fifth metatarsal strongly influences the fracture pattern. The metatarsal is comprised of a base, tuberosity, shaft, neck and head. The tuberosity is the prominence that protrudes laterally and plantarly. The tuberosity serves as the insertion of the peroneus brevis tendon and the lateral band of the plantar aponeurosis. The peroneus brevis inserts on the dorsolateral aspect of the tuberosity. The peroneus tertius inserts on the dorsal aspect of the fifth metatarsal at the level of the diaphysis, just distal to the tuberosity. The lateral band of the plantar aponeurosis inserts on the plantar aspect of the fifth metatarsal at the level of the styloid process.

Key Insights On Tuberosity Fractures

Tuberosity fractures are usually avulsion fractures that occur at the base of the fifth metatarsal. They account for the majority of proximal fractures. The mechanism of injury involves acute inversion of the foot in a plantarflexed position. One should examine the proximal fifth metatarsal in lateral ankle sprains and ankle fractures as tuberosity fractures can occur with these injuries.

   Researchers originally thought the avulsion fracture occurred because of sudden contracture of the peroneus brevis during hindfoot inversion.3 Theodorou and colleagues felt avulsion fractures arose from a violent pull of the converging fibers of both the plantar aponeurosis and the peroneal brevis tendon.4 More recent studies have shown that the lateral band of the plantar aponeurosis most likely results in avulsion of the tuberosity since its insertion is directly on the tip of the tuberosity.5

   It important to distinguish between an avulsion fracture and the apophysis in children as well as the os vesalianum and os peroneum as these can mimic tuberosity fractures. Ossicles will have smooth, uniform edges whereas fractures will often have a jagged, irregular shape.

   Tuberosity fractures can be displaced or non-displaced. The position of the fracture will determine the treatment. The treatment for non-displaced, small intra-articular or extra-articular fractures should focus on symptoms. This includes protected weightbearing in a hard-soled shoe, fracture brace or short-leg walking cast.6 Pain usually resolves after three weeks and precedes radiographic union, which occurs approximately eight weeks after injury. The prognosis of these fractures is excellent as they typically heal without complications.

   A prospective study by Egol and colleagues in 2007 evaluated the functional outcomes of 49 patients with 50 avulsion fractures treated with hard-soled shoes and weightbearing as tolerated.6 Results at three months showed 20 percent of patients had returned to their pre-injury level activity. One hundred percent of patients returned to pre-injury activity levels at one year post-injury.

   A displaced or large intra-articular fracture commonly involves surgery but depends on the amount of the joint involvement. If more than 30 percent of the articular surface is involved, open reduction with internal fixation (ORIF) is indicated.7 Lawrence and colleagues also state that if there is more than a 2 mm step off within the joint, ORIF is indicated.8 If the patient is active, more aggressive treatment is recommended.

   Surgical treatment can include closed reduction with percutaneous pinning or open reduction with internal fixation, such as Kirschner wire fixation, tension band wiring, intramedullary screw fixation or interfragmental screws. When it comes to symptomatic nonunions, it is best to address these with excision of the fragment.9

   Various studies have evaluated the different methods of fixation for avulsion fractures of the fifth metatarsal. Moshirfar and co-workers compared the use of interfragmental screws with intramedullary screws.10 This study showed that interfragmental screw fixation was superior in terms of load to failure and strength of fixation.

   Giordano and Fallat examined tension band wiring with interosseous wire fixation. This study showed no significant difference in strength between the two fixation techniques.11

   Hussain and DeFronzo compared tension band wiring to interfragmental screw fixation. Their cadaver study showed that interfragmental screw fixation was able to withstand greater than three times the load sustained by tension band fixations.12

What You Should Know About Jones Fractures

Acute diaphyseal/metaphyseal fractures, also known as Jones fractures, are less common than avulsion fractures but the potential for healing well without complications is less favorable. These fractures are located 1.5 mm to 3.0 mm distal to the base of the fifth metatarsal.

   Patients with this type of fracture have an increased incidence of delayed union or nonunion.7 The reason for this is based upon the anatomical location of the fracture within the fifth metatarsal. The pull of the soft tissue attachments, such as the peroneus brevis and the lateral band of the plantar aponeurosis, allow increased motion between the fracture fragments.

   In addition, the blood supply to the fracture fragment is compromised since the nutrient artery is disrupted.13 The blood flow to the proximal diaphysis is supplied by the nutrient artery, which then splits into the longitudinal intramedullary branches. The arterial supply to the tuberosity joins the supply to the proximal diaphysis in the area just distal to the tuberosity. This vascular anatomy suggests that a relative lack of blood supply following a proximal metaphyseal-diaphyseal fracture contributes to delayed unions and nonunions.13

   The mechanism of injury for a Jones fracture is similar to that of avulsion type fractures. Jones originally believed this fracture was caused by body pressure on an inverted foot while the heel was raised.1 Researchers currently believe this fracture occurs by direct vertical ground force with failure of the foot to invert.14,15

   Torg and colleagues developed a classification of diaphyseal/metaphyseal fractures in 1984.16 A type 1 fracture is an acute fracture with a narrow fracture line and absence of any intramedullary sclerosis. A type 2 fracture shows delayed union with widening of the fracture line and evidence of intramedullary sclerosis. A type 3 fracture is a nonunion with complete obliteration of the medullary canal by sclerotic bone. This is also in evidence as a chronic stress fracture in this area.

   Treatment of the Jones fracture can be non-operative or surgical. This depends on patient factors such as age and activity level as well as the functional demands of the patient. Conservative treatment of the Jones fracture consists of six to eight weeks of non-weightbearing cast immobilization followed by an additional six to eight weeks of weightbearing cast immobilization.17

What The Literature Reveals About Surgical Treatment Of Jones Fractures

Surgical management is generally recommended for the athlete and all high-demand patients, such as manual laborers, industrial workers or any patients with any active, demanding occupation.17,18 Surgical management of these fractures is more popular because it allows shorter periods of immobilization with faster healing times.

   Fernandez Fairen and colleagues found that 50 percent of patients treated with cast immobilization healed after 12 weeks whereas those patients treated with screw fixation healed after 9.5 weeks.19 Clapper and co-workers also showed that 72 percent of patients treated with cast immobilization healed at approximately 21.2 weeks.20 The remaining 28 percent of their patients underwent surgical management at 25 weeks post-injury.

   Studies have shown surgical management to decrease the risk for refracture. Quill and co-workers showed that one-third of Jones fractures treated conservatively refracture while Porter and colleagues showed there was no incidence of refracture in 23 athletes treated with screw fixation.21,18

   The likelihood of delayed union and nonunion is also lower with surgical management. Dameron showed that the nonunion rate was approximately 25 percent with non-weightbearing cast immobilization.3

   The various methods of surgical management of the Jones fracture include percutaneous pinning, inlay bone grafting, tension band wiring, intramedullary screw fixation, crossed K-wire fixation, plates and mini external fixation systems.

   The use of the intramedullary screw is the most popular method of fixation.22 Surgical considerations for this technique include screw placement and screw selection. Kavanaugh described technical problems, including penetration of the medial or lateral cortex, fracturing of the metatarsal, missing the medullary canal and pain over the screw head, occurring in 45 percent of patients.15 This shows the importance of screw placement and screw selection.

   In a cadaveric study, Kelly and colleagues compared 5.0 mm screws with 6.5 mm screws.23 The study authors showed that the 6.5 mm screw had significantly higher pull out strength and better thread purchase. Accordingly, they felt that larger diameter screws may be more appropriate. Sides and co-authors also support the use of 6.5 mm screws. They showed that this screw has higher resistance to pullout strength in comparison to a headless, tapered screw.22

   However, a 1999 study by Pietropaoli and co-workers compared a 4.5 mm Association for the Study of Internal Fixation (ASIF) screw to a 4.0 cannulated screw.24 This study showed there was no statistical difference in force to failure, thereby concluding that the choice of screw made no difference.

   Shah and colleagues performed a study comparing the fixation rigidity of 4.0 mm screws and 5.5 mm screws.25 The study showed that failure loads were not significantly different. It also showed the limiting factor with screw fixation was the length of the screw before the lateral bowing of the fifth metatarsal. This can cause disruption of the medial wall if one uses an excessively long screw.

   One should consider the impact of intramedullary screw fixation on the fifth metatarsal anatomy. The medullary canal is narrower by greater than 1 mm in the dorsoplantar diameter in comparison to the medial and lateral diameter. The dorsal to plantar cortices are thinner than the medial and lateral cortices. Also remember that the projection of the medullary canal is bowed laterally.

A Step-By-Step Guide To The Use Of Percutaneous Screw Fixation

Surgeons typically perform percutaneous screw fixation on an outpatient basis with the patient under IV sedation without tourniquet hemostasis. Ensure supine positioning of the patient on the operating table with a bump beneath the ipsilateral hip to rotate the limb internally. Palpate the dorsal and plantar aspect of the metatarsal and outline the styloid process. Then place a cannulated screw guide pin on the skin under image intensification and obtain anteroposterior (AP) and lateral views to guide placement of the pin.

   Make a small incision overlying the base of the metatarsal. Introduce a guide pin into the metatarsal under fluoroscopy. Obtain AP and lateral views to check for correct placement across the fracture and within the medullary canal. One can determine screw length by the amount of lateral bowing. We prefer to use a screw as long as possible to disperse ground reactive force during axial loading. Introduce the screw with all screw threads passing the fracture site in order to ensure the screw is anchored to the metatarsal.

A Closer Look At The Tension Band Wiring Technique

Surgeons may employ the tension band wiring technique for avulsion and tuberosity fractures. Position the patient supine on the operating table with the lateral aspect of the foot close to the distal and lateral edges of the operative table. Place a well padded bolster under the ipsilateral hip to rotate the lower extremity internally and allow easier access to the surgical area. One may or may not use a tourniquet for this procedure.

   Palpate the base of the fifth metatarsal and draw it out with a surgical marker. Be sure to mark the metaphyseal-diaphyseal junction as well. Make a curvilinear incision, extending slightly past these two marks. Given that the surrounding soft tissue assists in stabilizing the fracture. perform minimal soft tissue dissection. Palpate the width of the fifth metatarsal at the level of the metaphyseal-diaphyseal junction and direct a 0.062 K-wire in a dorsal to plantar direction to create a hole in the lateral one-third of the metatarsal.

   Then direct a K-wire under image intensification from a slight posterior-lateral to anterior-medial direction in the transverse plane at the proximal aspect of the tuberosity. Extend the K-wire distal to the fracture and pierce the medial cortex. Using a triple wire guide from the Synthes Small Fragment Set® (Synthes), place a second 0.062 K-wire parallel and inferior to the first.

   Place an 18- or 20-gauge cerclage wire through the distal hole in the metatarsal and wrap it in a figure 8 fashion around the K-wires. Then tension the wire through a repeated twisting motion until the fracture reduces and compression occurs. Bend the K-wires, cut them and tape them into the bone. Cut the cerclage wire and rotate it plantar-medial until it is flush against the tuberosity so as to lessen any soft tissue irritation in shoegear postoperatively. Flush the area, reapproximate the soft tissue and close it with absorbable sutures deep and non-absorbable sutures superficially.

How To Address Stress Fractures Of The Fifth Metatarsal

Stress fractures of the metaphyseal-diaphyseal junction are the least common type of fracture of the proximal fifth metatarsal. This fracture results from vertical and mediolateral forces concentrated over the fifth metatarsal, and is not caused by ankle inversion. Patients commonly present with pre-fracture aching over the lateral border of the foot.15 These fractures are also known as March fractures since they result from repeated cyclical force over this area.

   Stress fractures occur almost exclusively in athletes because of the intense repetition of activity. Patients with a varus deformity are also prone to develop stress fractures of the fifth metatarsal base because of the increased force over the head of the fifth metatarsal, which results in bending stress over the base of the metatarsal. Stress fractures can also result in delayed unions or nonunions if patients do not receive proper treatment.

   Early recognition is important. Radiographically, the fracture resembles incomplete obliteration of the medullary canal with cortical hypertrophy and periosteal reaction. Sixty-seven percent of patients presenting with stress fractures show periosteal reaction in the initial presentation.26 Prolonged non-weightbearing cast immobilization is indicated for inactive patients or non-competitive athletes. One may also use external bone stimulators but stress fractures typically take more than 20 weeks to heal.27

   Active patients and those who fail conservative treatment require surgical management. We surgically treat most stress fractures in the same fashion as Jones fractures. Most stress fractures respond well to intramedullary screw fixation. However, some stress fractures may require resection of the nonunion with bone grafting material.

   Dameron showed that the use of corticocancellous onlay grafts resulted in a higher union rate in comparison to intramedullary screw fixation but required longer time to heal completely.3 Rettig and co-authors recommended surgical excision of the nonunion through a small lateral incision through the peroneal brevis. They believe this facilitates minimal disturbance of the attachment of the tendon if the fragment is small. If one cannot excise the fragment, one can use intramedullary screw fixation from compression across the fracture site from within the same incision.7 However, with the advent of excellent cannulated screw systems, intramedullary screw fixation is the procedure of choice with stress fractures.

In Conclusion

Proximal fractures of the fifth metatarsal continue to challenge foot and ankle surgeons. Accurate diagnosis of the specific fracture type is essential for effective and proper management of these fractures.

   Dr. Miklos is the Chief Resident with the Division of Foot and Ankle Surgery at Western Pennsylvania Hospital in Pittsburgh.

   Dr. Catanzariti is the Director of Residency Training in the Division of Foot and Ankle Surgery at Western Pennsylvania Hospital in Pittsburgh.

   Dr. Mendicino is the Chairman of the Division of Foot and Ankle Surgery at Western Pennsylvania Hospital in Pittsburgh.

   For further reading, see “Essential Insights On Treating Fifth Metatarsal Fractures” in the April 2006 issue of Podiatry Today or “Managing The Jones Fracture In Active Patients” in the November 2008 issue.

References:

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