The os intermetatarseum is a rare accessory bone (ossicle) of the foot occurring in approximately 4% of the population, which ossifies during adolescence or preadolescence and may be responsible for midfoot pain.
This accessory bone is typically positioned near the base of the first and second metatarsals bone (long bones in the feet) but has been reported to occur near or between the fourth and fifth metatarsal bases (midfoot).
It can present in a variety of shapes: oval, round, linear, bean shaped and can be classified into three types:
- Free standing – completely detached accessory bone which does not show any connection with any other structure.
- Articulating – forms a joint with first or second, metatarsal or the medial cuneiform bone.
- Fused – forms a bony projection within the first or second intermetatarsal space.
Causes of Os Intermetatarseum (Midfoot Pain):
- Tight shoes, ankle instability and cavus or pes planus foot type exacerbate condition.
Symptoms of Os Intermetatarseum (Midfoot Pain):
- Usually asymptomatic.
- Post trauma, may cause midfoot pain and paraesthesis radiating from the top of the foot to the big toe and second toe.
- Pain and numbness increases with plantar flexion of the foot and dorsiflexion of the toes, if the deep peroneal nerve is trapped.
- Can be a cause of midfoot pain and should be considered in your differential diagnosis.
- Evident on X-ray.
Treatment for Os Intermetatarseum (Midfoot Pain):
- Footwear modification.
- Rest and anti-inflammatory medication.
- Reduction from activity or sports until symptoms reduce.
- Local corticosteriod injection.
- Orthotic therapy to correct foot type and abnormal biomechanics, reducing the impact of the problematic bone with a good foot posture.
- Removal of the problematic bone.
- Deep peroneal nerve release relieves the symptoms of pain and paraesthesia, if conservative treatments fail to reduce symptoms.
If you are experiencing midfoot pain or numbness in the toes come and see us at Well Heeled Podiatry as we are trained and experienced in dealing with all lower limb concerns and pathologies.