My X-Ray Shows That I Have an Accessory Bone in My Foot – What Does This Mean?

So you’ve seen your podiatrist for pain in your foot, they’ve sent you for an X-ray and the report says that there is an accessory bone – but what does this mean?

In this piece, we’re going to discus s what an accessory bone is, as well as look at the most common accessory bones and what treatments are available.

There are over 20 accessory bones located in the feet and proper diagnosis can be crucial to proper treatment.

There are already 26 bones, 29 muscles, over 30 ligaments and numerous blood vessels and nerves in the feet, so any additional structures can lead to discomfort or pain!

Accessory bones are quite common, with research suggesting that 20-30% of the population will have at least one.

They are formed when the outside areas of the bones do not unite or fuse together properly.

Depending on the type of accessory bone, they may be present on one foot (unilateral) or on both feet (bilateral).

Accessory bones are generally asymptomatic, meaning that they don’t cause pain and most people will never know that they have them!

However, an accessory bone in foot may become painful in some cases and need to be investigated further.

Often, they can be confused with a fracture.

Your podiatrist may suspect that you have an accessory bone through a variety of tests including palpation, range of motion testing and gait assessments.

To confirm this, you may be sent for medical imaging such as an X-ray or MRI, which can also help to rule out other pathologies such as:

  • Fractures
  • Dislocations
  • Osteoarthritis or degenerative changes
  • Inflammation or impingement of surrounding soft tissue structures
  • Osteochondral lesions – damage (tear or fracture) to the cartilage that covers the bone

Let’s have a look at the most common accessory bones.

The most common accessory bones

Os trigonum

This is one of the most common accessory bones in the foot and lies at the back of the foot behind the talus bone.

It is present in up to 14% of the population and is typically triangular in shape, however it can also be round or oval.

This accessory bone can cause chronic ankle pain, particularly through the movement of plantar flexion.

It may also result in swelling of the bone.

It is generally discovered in those participating in activities that require repeated plantar flexion, including football and ballet.

Os tibiale externum

This is also known as an accessory navicular bone as it sits on the navicular bone. This type of accessory bone is more common in women than men, and is present in over 10% of the general population.

It is commonly bilateral, meaning that it is present on both feet.

Accessory navicular bones can be classed into 3 different types:

Type 1

This type sits within the posterior tibialis tendon which attaches to the navicular. It is typically 2-6mm in size and is a round shape.

Type 2

This is a secondary area of bone that originates from the navicular and is typically triangle or heart shaped.

This type is usually the one to produce pain and is associated with a pes planus foot type (flat foot).

Type 3

This type involves a complete fusion of the accessory bone to the navicular itself and looks to be a smooth continuation of the bone.

Os peroneum

This accessory bone is round or oval shaped and is lodged within the peroneus longus tendon.

It sits near the cuboid bone on the lateral aspect (outside) of the foot and is present in approximately 10% of the general population, with almost 60% of these being bilateral.

An os peroneum is often confused with an avulsion fracture, where a small piece of bone is removed from the main part of the bone by a tendon.

Os vesalianum

This accessory bone is located at the base of the 5th metatarsal, also known as the styloid process.

It is often confused with multiple other pathologies including a Jones’ fracture, Iselin’s disease or a stress fracture.

This type of accessory bone is present in approximately 6% of the general population.

Os intermetatarseum

This accessory bone is found between the medial cuneiform and the bases of the 1st and 2nd metatarsals.

It is commonly misdiagnosed as a Lisfranc injury and is present in up to 10% of the population.

An os intermetatarseum can sometimes cause entrapment of the nerves in the area and is often discovered in those in ball kicking sports such as football and soccer due to the repeated pressure on the area.

It is also associated with bunions, also known as a hallux valgus deformity.

Treatment of accessory bones

So, you’ve been diagnosed with an accessory bone and would like to know your options. This will depend on a few factors including:

  • The location of the accessory bone
  • The size of the accessory bone
  • How painful it is
  • What activities you participate in
  • Your age

Sometimes, accessory bones can be treated conservatively. These options are tailored towards reducing your pain and offloading the area of the accessory bone. This can include:

Orthotics

Orthotics can considerably reduce your pain by cushioning the area, as well as providing support to the surrounding structures and redistributing pressure away from the accessory bone to provide relief.

This will also help to reduce pain in other areas of the foot and ankle that may be compensating for an accessory bone.

Footwear modifications

Wearing the right footwear for your feet is always extremely important, as is the case with accessory bones.

Ensuring that your shoes are the correct size, have adequate fixation (laces or velcro) and wide and deep enough will help to alleviate pressure and pain.

Mobilisation and manipulation

Whilst this will not move the accessory bone itself, it may help to reduce tension in the area and place the joints in a more optimal position.

Moon boots in the short term

If you are suffering from acute pain, wearing a moon boot can help to reduce pain and offload the area while it heals.

Surgery

Should these treatments not prove successful or your scans have shown an accessory bone of considerable size, surgery may be the best option available to you.

The type of surgery will again depend on where it is located, but will typically involve a relatively simple removal or shaving of the bone.

Recovery from this surgery is generally up to 6 and you will be placed in a moon boot to offload the foot to allow the bone to heal.

If you’ve been diagnosed as having an accessory bone in your foot or feet, you may be required to visit a podiatrist to have your feet checked regularly, however this will depend on the extent of the condition. If you are experiencing any pain or discomfort in your feet or lower limbs, you can book in to see us here at Watsonia Podiatry. Our superstar podiatrists are highly experienced and happy to help you today.

You can make an appointment to see us by calling 03 9432 2689 or booking online here.

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