An isolated cuneiform fracture of the foot is rare. However, they can occur and should be caught early. In many cases, cuneiform fractures occur along with other midfoot fractures in the foot.
Cuneiform fractures can occur from high-impact injuries such as falls, motor vehicle accidents, and direct blows to the foot. They can also occur from twisting injuries in the foot. Stress fractures of the cuneiform bones occur due to repetitive stress on the midfoot.
Anatomy of the Cuneiform Bone
There are three cuneiform bones: the medial cuneiform, the intermediate cuneiform, and the lateral cuneiform.
The lateral cuneiform forms at 6 months of age. The intermediate cuneiform forms at 1 year of age. The medial cuneiform forms at 1-2 years of age.
The cuneiform bones are triangular. The cuneiform bones make up the inner midfoot and are located between the navicular bone and the metatarsal bones. They help form the midfoot and distribute forces evenly across the midfoot.
The cuneiform bones are connected to each other, the navicular, and the metatarsal bones by strong ligaments.
The posterior tibial tendon attaches to the bottom of the medial cuneiform. The anterior tibial tendon attaches to the inner surface of the medial cuneiform bone.
The intermediate cuneiform is the smallest of the three cuneiform bones. It sits slightly higher than the other two cuneiform bones and thus is dislocated more easily during an injury.
The Lisfranc ligament (the ligament that maintains alignment of the midfoot joint) connects the medial cuneiform to the second metatarsal base.
The dorsalis pedis and plantar arteries provide blood supply to the cuneiform bones. The cuneiform bones are innervated by the deep peroneal nerve, the superficial peroneal nerve, and the plantar nerves of the foot.
Classification of Cuneiform Fractures
Cuneiform fractures have been classified using letters and numbers by A. Mehlhorn et al in the Journal of Foot and Ankle Surgery.
The letters represent how many bones are fractured:
A: Injury to a single cuneiform bone
B: Injury to two cuneiform bones
C: Injury to all three cuneiform bones.
They are further classified by the type of injury:
Type 1: Fracture of the cuneiform
Type 2: Dislocation of the cuneiform bone
Type 3: Fracture and dislocation of the cuneiform bone
So for example, a Type 1C fracture would indicate that all three cuneiforms are fractured but not dislocated.
Causes of Cuneiform Fractures in the Foot
Cuneiform fractures can occur from direct blows to the foot, motor vehicle accidents, and falls from heights. They are often diagnosed in addition to other midfoot fractures. Your doctor will identify the fracture using an x-ray.
It’s important to not confuse a cuneiform fracture with a bipartite medial cuneiform. A bipartite medial sesamoid is a normal foot variant, and can sometimes look like a fracture on an x-ray.
An isolated fracture of the cuneiform can occur from an axial force being placed on a plantarflexed foot. “Axial force on a plantarflexed foot” means force that is pushing down on the foot when it is bent downwards.
Cuneiform fractures can occur at the body of the cuneiform bones, or they can be avulsion fractures. Avulsion fractures occur when a ligament pulls a piece of bone away during the time of injury.
Cuneiform fractures can be intra-articular (fracture extends into the joint space) or extra-articular (fracture does not extend into the joint space).
Cuneiform fractures can be nondisplaced (fracture fragments are in appropriate alignment) or displaced (fracture fragments are shifted).
Cuneiform stress fractures occur when there is repetitive stress placed on the cuneiform bones. This can fatigue the bone and cause it to fracture. A cuneiform stress fracture is often seen in athletes. Stress fractures can occur from activities that require jumping, dancing, and marching. Isolated fractures of the cuneiform bones that occur due to stress are rare.
Symptoms of a Cuneiform Fracture
Symptoms of a cuneiform fracture can vary depending on whether it is an acute fracture or a stress fracture.
Some of the symptoms of a cuneiform fracture include:
- Pain in the midfoot
- Midfoot swelling
- Foot deformity
- Numbness/tingling in the midfoot
- Inability to bear weight on the foot
- Pain that is relieved with rest
- Gradual onset of pain and swelling in the midfoot (in the case of a cuneiform stress fracture)
Cuneiform fractures are serious injuries and should be treated as such. Treatment for non-displaced cuneiform fractures includes immobilization in a cast, rest, and physical therapy.
Displaced cuneiform fractures will need surgical repair to ensure that the fracture heals properly. Once the fracture heals, the individual can return to normal activities.
If you suspect that you have a cuneiform fracture, make sure you contact your local foot doctor or go to the emergency room.
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