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Accessory Navicular

What Is An Accessory Navicular?

An accessory navicular is an extra bone found next (proximal) to the navicular bone. It occurs in up to 1 in 10 of the normal population. It is the most common accessory bone in the foot. It is in continuity with the tibialis posterior tendon which inserts into the navicular tuberosity.

Please see foot & ankle anatomy for more information about the navicular and the tibialis posterior tendon.

What Can Cause It?

The underlying cause is unknown but there may be a genetic predisposition.

What Are The Symptoms?

Most people with an accessory navicular are asymptomatic and not even aware that they have an “extra” bone. However it can cause symptoms particularly around adolescence. It can be associated with a flat foot deformity, and certainly if this is a unilateral finding, needs to be investigated.

The joint between the navicular and the accessory bone is know as a synchondrosis. Trauma or repetitive sprains to the foot can result in injury to the synchondrosis or the tibialis posterior tendon, resulting in abnormal motion and pain.

Typical symptoms include:

  • Medial arch pain
  • Pain in the accessory navicular (deep ache, sharp and throbbing)
  • Swelling medial aspect of the midfoot
  • Bony prominence on the inside of the foot that rubs against footwear
  • Difficulty raising the heel
  • Flat foot

What Investigations May Be Required?

Radiographs will be arranged at your initial clinic consultation. These will help confirm the diagnosis, the severity of the deformity and aid in pre operative planning.

Accessory navicular is classified according to the radiographic features:

  1. Sesamoid bone in the substance of the tibialis posterior tendon insertion
  2. Accessory bone attached to navicular through synchondrosis
  3. Bony enlargement of the navicular
Clinical radiograph demonstrating Type 1 Accessory Navicular in the right foot

Clinical radiograph demonstrating Type 1 Accessory Navicular in the right foot

Clinical radiograph demonstrating Type 2 Accessory Navicular in the left foot and a Type 3 Accessory Navicular in the right foot

Clinical radiograph demonstrating Type 2 Accessory Navicular in the left foot and a Type 3 Accessory Navicular in the right foot

Occasionally an MRI scan may be requested to assess the state of the tibialis posterior tendon, rule out a navicular stress fracture and determine whether there has been any irritation or damage to the synchondrosis.

Can The Problem Get Worse?

The vast majority of people with an accessory navicular are asymptomatic. It is a condition that can get worse with trauma or repetitive stress injury.

If there is a history of increasing pain, inability to do sports and development of deformity you may wish to consult with your orthopaedic foot & ankle surgeon, Mr Malik.

Non-Operative Treatment Options

Non-operative management aims at relieving pain and limiting deformity progression. It is likely to be most effective in the early stages of the condition.

It should always be the first line of treatment. Options include:

Activity modification

A period of rest from sports and strenuous exercise.


Local padding

Made of gel or foam, can be worn over the prominent bump to protect from direct pressure and rubbing against footwear.


Ankle brace

Provide more support to the ankle and prevent it from turning in.


Insoles & orthotics

Custom insoles with an arch support will minimise forces going through the tibialis posterior tendon. It will also prevent the foot from rolling inwards.


Non steroidal anti-inflammatories

The use of non-steroidal anti-inflammatory drugs (NSAIDs) can decrease discomfort from a painful and inflamed synchondrosis.


Footwear

Wearing a wider shoe to accommodate the bump. A shoe with a stiff sole may also help.


Physiotherapy

Calf stretches will minimise the deforming force a tight calf muscle has on the foot. Tibialis posterior strengthening exercises.


Plaster cast immobilisation

A short period of cast immobilisation may help alleviate symptoms.

Operative Treatment Options

Surgical management is reserved for patients who have failed to respond to non operative treatment.

Patients should understand that the decision to undergo surgery should not be taken lightly.

Any intervention is considered in a step wise manner, with the least invasive procedure carried out first.


Injection

Injection under image guidance and a short general anaesthetic can help confirm the diagnosis as well as treat an acutely inflamed synchondrosis.

An injection may offer short to mid term relief and occasionally may cure any symptoms. An injection will not correct any underlying bony or foot deformity.

Injection under x-ray control with correct placement of needle confirmed with dye

Injection under x-ray control with correct placement of needle confirmed with dye


Surgical excision (Kidner procedure)

This procedure involves excising the accessory navicular and re-insertion of the tibialis posterior tendon. This is done with the use of bone anchors.

This procedure will not on its own correct a fallen (acquired) arch. Please read flat feet for further information regarding surgical correction of a flat foot deformity.

Potential Complications

It should be borne in mind that complications can result from a condition with or without surgery.


Potential complications of non-operative treatment include:

  • Worsening pain
  • Increasing flat foot deformity
  • Formation of ulcers on the inner (medial) aspect of the foot
  • Infection of ulcers

Complications can occur as with any type of surgery. Please see Complications for more detailed explanation of post surgical complications.

Potential general complications of any operative treatment include:

  • Risks and complications of anaesthesia
  • Bleeding
  • Infection (superficial and deep)
  • Blood clots
  • Need for further surgery
  • Complex regional pain syndrome
  • Nerve injury
  • Wound healing problems

Potential specific complications of operative treatment of accessory navicular include:

  • Painful scar
  • Persistent pain

Note – these complications are not exhaustive and are meant as a guide

Post Operative Period & Recovery

Please read the information regarding what to expect post surgery on this website.

Remember that below is a guide to recovery and that everyone heals at different rates and some people do take longer. Use this information to help you understand your condition, possible treatment and recovery. The timeframes given below are a minimum, it is important that you appreciate this when considering surgery as your healing and recovery may take longer.


Immediate post operative period

Almost all surgical procedures for an accessory navicular excision will be undertaken as a day case.

You will have a backslab applied post operatively for two weeks.

A picture of a backslab cast

A picture of a backslab cast

Please do not remove your backslab until you are seen by your surgeon Mr Malik at the two week post operative clinic appointment.

You will be non weight bearing for 2 weeks post operatively. The physiotherapist will guide you with the use of crutches after your operation and before your discharge from hospital.

For the first two weeks following your surgery please keep your foot elevated to the level of your heart for 95% of the time.

A picture demonstrating high elevation of a foot with a backslab cast

A picture demonstrating high elevation of a foot with a backslab cast

Naturally most people do not have a hospital bed at home. The same effect can be achieved by lying in a bed or lengthways on a sofa, with pillows behind your back and under your foot. You cannot have your leg elevated sitting in a chair. It is strongly advised that during the first two weeks you are house bound.

To minimise risk of infection keep the foot dry and cool. Avoid humid and hot environments. Keep the foot dry and when showering wear a Limbo bag.

To minimise the risk of blood clots please move your foot and ankle at regular intervals. Please ensure you are well hydrated. If you have a risk of blood clots please notify Mr Malik who may organise for you to have blood thinning injections as a precaution.


Two weeks post operatively

You will be reviewed at the clinic and your dressings removed. Your wound will be checked and if completely healed you will be given advice regarding soft tissue massage and scar desensitisation. Scar desensitisation should start as soon as the wound has completely healed. You can do this by massaging cream (E45 for example) into the scar and around the wound area. You may shower and get the area wet only if the wound has completely healed and is dry.

At this stage if the swelling has subsided sufficiently you will be advised to keep your foot in an elevated horizontal position whenever possible to minimise swelling. You will require to wear a special walking boot for another 4 weeks. Short trips can be made outside, within limits of pain and swelling.

Driving will be permitted for short trips if the left foot has been operated on and you drive an automatic. If the right foot has been operated on it will be at least 6 to 8 weeks before any driving is advisable.

You may be referred at this stage for physiotherapy for early rehabilitation and tibialis posterior strengthening exercises.


Six weeks post operatively

At this stage if your healing is progressing satisfactorily swelling and bruising should have subsided considerably, although expect some degree of swelling for at least 3 to 4 months.

You will be able to start wearing normal footwear (swelling permitted), although stiff soled shoes are advisable. You will require physiotherapy for approximately 3-6 months. This will help optimise the outcome of your operation.


Three months post operatively

Final clinical examination. Discharge if satisfactory.

FAQs

When can I drive?

Please see guidance above and information here. Ultimately it is the responsibility of the patient to decide if they are safe to drive. A good way of knowing is if you can stamp your right foot heavily on the ground to mimic an emergency brake. If you have any hesitation or pain then it should suggest you are not safe to drive. Remember prolonged driving involves keeping your feet in a dependant position. This will worsen the post operative swelling.

When can I return to work?

This really depends on you and your job. If you have a job that involves a lot of standing, walking and is manual it may be 8 to 12 weeks. If you have a sedentary job, for example in an office and you have a reasonable commute you may be able to go back to work at 2 weeks, although this would be exceptional and not the norm.

What should the final outcome be?

Excellent pain relief and removal of the obvious “bump”. Ability to participate in sports by 6 months. Sometimes up to a year before the foot feels “normal” and fully healed.

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