Sept. 20, 2005

Joshua Baumfeld, MD, David Diduch, MD, UVA Sports Medicine

Fifth metatarsal fractures are common in active people. They can be associated with either an acute injury or chronic, repetitive stress to the bone. The fifth metatarsal is a bone that resides on the outside of the foot. The more proximal (towards your heel) portion can be felt as the bump on the outside of your foot.

There are three varieties of fifth metatarsal fractures and they have different preferred treatments and prognostic implications. The basic three types are divided by zone or region (Figure 1). They are 1) an avulsion fracture, 2) the true "Jones fracture", an acute fracture just beyond the site of the avulsion fracture, and 3) a true stress fracture from repetitive stress to the area. Sir Robert Jones first described these fractures in the early part of the twentieth century. He sustained a fracture while dancing that is of the second variety and his name remains associated with it. These fractures behave very differently and thus it is important to distinguish between them.

The avulsion fracture, which is thought to occur secondary to the pull of a tendon at its insertion on the tuberosity of the fifth metatarsal or the effect of a portion of the plantar fascia at its insertion on the tuberosity, is often associated with a turned ankle. Patients complain of acute pain along the fifth metatarsal, particularly at its base, the bump on the side of the foot. There may be bruising or swelling and difficulty with weight bearing initially. Simple x-rays help in making the diagnosis. It usually heals uneventfully with simple protection in a rigid shoe or boot with weight bearing as tolerated.

The second type of fracture, the Jones fracture, is an acute or sudden fracture, which can, at times, be more difficult to heal. Symptoms and the mechanism of injury may be very similar to an avulsion fracture. The Jones fracture may also occur when a lateral force is applied to the foot while the ankle is in a flexed position (toes pointed to the floor) with the heel off the ground. Again, simple x-rays are used to make the diagnosis and follow the progression of healing. These fractures can be treated with a cast or a removable boot and limited or no weight bearing for 6-8 weeks followed by progressive weight bearing as tolerated. However, in the athletic population early surgery can improve healing rates and expedite return to play in half of the time compared to no surgery. Without surgery, the bone may not heal 7 % to 28 % of the time and it may take as long as 20 weeks for the fracture to heal when non-surgical treatment is successful.

Stress fractures of the fifth metatarsal are also common within the athletic community (Figure 2). There are often low-grade symptoms with activity that can last weeks prior to the diagnosis of fracture, which usually presents as an acute increase in pain. Symptoms may include pain over the outer aspect of the foot particularly with activity and weight bearing. There may be swelling or bruising present. These symptoms may worsen over time before a fracture is evident on x-ray. These low-grade symptoms should not be ignored. There is usually evidence on plain x-rays of stress related changes in the bone. However, in suspected cases of a fifth metatarsal stress fracture without x-ray changes or with questionable changes, MRI has become the most sensitive tool for early diagnosis.

Due to the poor blood supply in this region, it is often difficult to get these fractures to heal. While they can be treated without surgery, there is a significant risk of the bone not healing and of losing time prior to return to play. Non-operative treatment consists of prolonged cast or boot immobilization with non-weight bearing. Surgical intervention can often increase the union rate and decrease the time to union as well as allow earlier rehabilitation.

Surgery, which is the same for stress fractures and acute Jones fractures, consist of a small incision along the outer aspect of foot that allows insertion of a screw down the canal of the fifth metatarsal. There is a growing body of evidence suggesting that the screw should be as long and wide as possible. A minimum diameter of 4 millimeters should be used (Figure 3). Following surgery the foot is protected with a splint while the wound heals. Progressive weight bearing can often begin at 2 weeks after surgery and progress as tolerated. In some studies, the average time to heal was between six and eight weeks. Patients often return to play within three months of surgery. Screw removal may be necessary after healing if the patient develops symptoms related to the head of the screw.

In summary, these fractures are common. They can be disabling and any low grade symptoms should not be ignored. Plain x-rays can often make the diagnosis but if there is a question, an MRI can be obtained. The trend in sports medicine is to surgically fix the acute Jones fracture and stress fracture in order to increase the rate of healing and decrease the time to return to play. Larger diameter and longer screws are preferred.