Authors

Dr Keran Sundaraj MBBS MSc (Trauma) FRACS FAOA

The metatarsals are the long bones of the foot. The toes arise from the ends of these bones. On the outer aspect of the foot, there is a bony prominence midway between the heel and the little toe - this is the base of the fifth metatarsal. Fractures in this region can be troubling injuries to deal with. These seemingly minor fractures can be painful for months but generally heal with time.

Anatomy

The fifth metatarsal starts with a flared base. This bone shares an articulation (joint) with the fourth metatarsal base and the cuboid (a small bone in the outer aspect of the foot). Attached to the base are several muscles. Most notably, a muscle from the outer aspect of the leg, the peroneus brevis, attaches to the base.

Types of Fractures

It is important to differentiate the type of fifth metatarsal fracture. Causes, like treatments, are determined by the fracture type.

To understand this better, we divide the base into three zones:

Zone 1

• Tuberosity 'avulsion' fractures

• This is the most common type of fracture by far, making up 93% of all metatarsal fractures.

• Zone 1 fractures are usually caused by rolling the foot inward. Peroneus brevis 'avulses' (pulls off) a small piece of bone. On the X-ray, the bone appears to be 'pulled' closer to the heel bone as the muscle of peroneus brevis provides a displacing force.

Zone 2

• Fractures that extend into the joint between the fourth and fifth metatarsal

• This is the true "Jones Fracture".

• These fractures are acute fractures related to an injury.

Zone 3

• These are fractures in the first 1.5cm of the shaft

• These are generally stress fractures due to repetitive motions such as running.

• They are not acute injuries. Commonly symptoms persist for weeks or months prior, without the history of an acute event.

• X-rays may show specific signs of a healing responsive, indicating the injury is not acute.

• Healing in this area is impaired due to the difference in blood supply. This region is located in a 'water-shed' area (between two blood supply areas flowing in different directions). Fractures here are located at the end of the blood supply and can have their nutrition limited in the fracture setting.

Imaging Tests

X-rays

• These are generally all that is required to diagnose and managed fifth metatarsal base fractures.

• For zone 1 and 2 injuries, follow-up X-rays are generally not necessary.

• Occasionally, healing is via fibrous scar tissue that cannot be seen on an X-ray. This is seen as a bone fragment separate from the metatarsal with a rounded-off end. If there is no pain, this is not a finding to be concerned by.

Treatment

Zone 1

• These heal readily in a walking boot, and you are allowed to put weight through your foot as you are able.

• The boot should be worn for 3 to 4 weeks. After this, you can transition into a comfortable shoe. It is recommended you try the shoe at home for short periods and the boot for longer distances outside the home.

• High heels should be avoided for the first 6 to 8 weeks.

• The boot can be removed for sleeping and showering. However, it is recommended that you sleep in the boot for the first couple of weeks to help with pain relief.

• If your pain is improving, X-rays are generally not required.

Zone 2

• Depending on your risk factors for the non-union (bone not healing), weight-bearing may be delayed.

• A boot is used, similar to zone 1 fractures.

• The boot can be removed for sleeping and showering. However, it is recommended that you sleep in the boot for the first couple of weeks to help with pain relief.

• This is generally worn for six weeks.

• If your pain is improving, X-rays are generally not required.

Zone 3

• These are treated differently to zone 1 and 2 fractures.

• A boot or a cast may be used, and weight-bearing is delayed for 6 to 8 weeks.

• Apart from showering, the boot should remain on for the majority of the day and night.

What to Discuss with Dr Sundaraj

• How long can I expect off work?

• When can I start driving?

• How long will I be in a boot/cast?

• Can I remove the boot/cast for sleeping and showering?

• Do I need to be screened for osteoporosis (weak bones)?

• When can I start physiotherapy?

• What is the likely outcome from this treatment?

• When do I need to come back?