A Closer Look At Fixation For Fifth Metatarsal Fractures
A variation of the percutaneous intramedullary technique is to insert the screw from the base of the metatarsal into the medial cortex distal to the fracture. In a biomechanical study, Moshirfar and co-workers determined that bicortical cancellous screw fixation was much stronger than intramedullary cancellous screw fixation.6 This was supported by Husain and DeFronzo, who also compared the stability of bicortical and intramedullary screw fixation.7 They determined that the bicortical screw had superior load resistance over the intramedullary screw. The advantage of the percutaneous procedure is that one doesn’t have to perform dissection over the fracture site. This preserves both the periosteum and vasculature.
A second fixation option is to use a bone plate. The lead author will usually use a quarter tubular plate with 2.7 mm cortical bone screws. One can employ a one-third tubular plate with 3.5 mm cortical screws but occasionally, the prominent screw heads result in soft tissue irritation. Regardless of the type of plate one uses, the length is usually a four-hole to a six-hole.
The surgeon reduces the fracture and achieves interfragmentary compression by using a 2.7 mm screw from dorsal to plantar across the fracture. Then one would apply the bone plate. If you do not use the lag screw, you can apply the plate with eccentric drilling for compression. Surgeons can use locking plates for osteoporotic bone.
Key Considerations With Avulsion Fractures
Avulsion fractures comprise 45 to 93 percent of all fifth metatarsal fractures and there are several fixation techniques available.2,8-9 The unique consideration is that the fixation must counteract the pull of the peroneus brevis tendon. For larger fracture fragments, one can perform closed reduction with percutaneous intramedullary fixation and a cancellous screw. For smaller displaced fragments, comminuted bone, osteoporosis or patients who must bear weight because of comorbidities, tension band wire is a very effective modality. This is an effective fixation technique that Pauwels advocates.10
The technique involves exposing the fracture and achieving reduction. One would drive 0.062 Kirschner wires from the base across the fracture to just penetrating the medial cortex of the diaphysis. The surgeon would use two wires that are parallel to each other. After drilling a 2 mm hole distal to the fracture from dorsal to plantar, place a tension wire through the hole and loop over the two K-wires in a figure-of-eight fashion. One can tighten the wire dorsally and plantarly to achieve even compression across the fracture as needed.
Surgeons may also employ hook plates for the treatment of avulsion fractures. Surgeons originally used this technique for fixation of distal fibular fractures. Carpenter and Garrett recommend use of the hook plate on the fifth metatarsal base if the bone is comminuted.11 After exposing and reducing the fracture, and placing an appropriate sized plate on the fifth metatarsal, one would tap the hooks into the base of the metatarsal. The surgeon can use fluoroscopy to ensure proper alignment of the fracture and hook plate.
Proceed to insert a bone screw distal to the fracture, inserting it eccentrically to achieve a degree of compression. Then insert the remaining screws. Many times, it is possible to insert a long cancellous screw from a proximal position between the hooks of the plate across the fracture for greater stability if the avulsion fragment is large enough.
Other Pertinent Pearls
Surgeons may use intramedullary cancellous screws for both a Jones fracture and an avulsion fracture if the fragment is large. Use the largest diameter screw that will snugly fit in the medullary canal. If there is lateral bowing of the diaphysis, use a shorter screw that does not engage the diaphyseal curvature.