A Closer Look At Fixation For Fifth Metatarsal Fractures
Fifth metatarsal fractures are the most common of all metatarsal fractures.1 Avulsion fractures, Jones fractures and proximal diaphyseal fractures occur most frequently, but diaphyseal, neck and head fractures also occur.2 Clinicians can treat most of these fractures conservatively if the fractures are not significantly displaced.
The Jones fracture is well known for poor healing with immobilization, even if there is no displacement, making surgery an appropriate initial option. Diaphyseal fractures are almost always displaced, necessitating open reduction with internal fixation (ORIF). Avulsion fractures are the most common of all fifth metatarsal fractures. Authors have suggested that the mechanism of injury is the pull of the lateral band of the plantar aponeurosis in the supinated (inverted) foot. The peroneus brevis tendon has a broad lateral attachment at the base of the fifth metatarsal that may further contribute to displacement.3,4
The literature is filled with various types of fixation implants and techniques that advocate superior strength against axial load, pull out strength, bending and torque. Given the variety of fixation options, how does the surgeon select appropriate fixation? What is effective when you need to have a stable construct to prevent postoperative displacement, achieve optimal healing and resist the weightbearing forces of a non-adherent patient? What kind of fixation is best in patients with soft bone, those who smoke or for addressing other risk factors that surgeons typically encounter?
Salient Tips On Fifth Metatarsal Neck Fractures
Fifth metatarsal neck fractures are usually characterized by a transverse fracture resulting in lateral displacement of the head. The head may be displaced dorsally or plantarly, depending on the mechanism of injury. Although one could use a bone plate, the simple Kirschner wire (K-wire) is the fixation modality of choice. This is a fairly easy fracture to reduce by distraction. The surgeon can insert an 0.062 K-wire plantarly under the fifth toe through the base of the proximal phalanx and the fifth metatarsal head into the diaphysis. I would recommend inserting the K-wire as far proximally as possible even into the base.
When it comes to osteoporotic bone, one may use an additional K-wire for further stability to prevent rotation and add more stability against axial load. If the head is impacted into the diaphysis and one cannot distract it with closed methods, the surgeon can open the fracture site and use an elevator to separate the fracture. In this case, you can tilt the head dorsally so you can drive the K-wire through the fracture site of the head and out distally through the plantar aspect of the foot. Surgeons can use the wire as a joystick to aid in reduction and subsequently drive it proximally into the diaphysis.
How To Address Diaphyseal Fractures
Little has been written about diaphyseal fractures. These fractures begin at the lateral side of the neck or distal aspect of the shaft, and extend medially and proximally through the diaphysis. The fracture can be short and oblique, or extend into the proximal diaphysis and have a long spiral orientation. This fracture may be comminuted at the metatarsal neck and at the spike. This fracture is usually shortened, displaced medially and elevated. Given the displacement and diaphyseal location of this injury, one should reduce and fixate the fracture.