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The accessory navicular is an accessory bone located within the foot’s inner arch. While some individuals with this extra bone don’t face any discomfort, others might find it bothersome, especially when it rubs against footwear or becomes strained during physical activities.
Managing the pain from an accessory navicular includes rest and wearing arch supports. In more extreme cases, surgical removal of the bone may be necessary.
This article reviews the causes, symptoms, diagnosis, and treatment of the accessory navicular.
What Is the Definition of an Accessory Navicular?
The accessory navicular is a secondary bone that is present if the navicular bone doesn’t fully fuse. Most foot bones start as cartilage, solidifying at varied phases.
The navicular typically solidifies between the ages of 2 ½ to 5. If it doesn’t, this results in the presence of the accessory navicular.
The primary navicular bone is situated in the midfoots medial portion, with its medial prominence termed the “navicular tuberosity”.
The tibialis posterior tendon, crucial for supporting the foot’s arch and assisting with supination (inward motion of the foot), attaches itself to this bone.
What Causes Accessory Navicular Syndrome?
An accessory navicular bone can become painful from inappropriate shoe gear rubbing on the bone and sporting injuries that cause direct damage to the bone (such as a sprain).
Chronic posterior tibial tendonitis can also cause pain due to its pull on the bone.
There Are Three Types of Accessory Navicular Bones as listed below.
This accessory navicular bone presents as a small 4mm-6mm ossicle that is present in the posterior tibial tendon itself. It rarely is symptomatic, unless the posterior tibial tendon is inflamed/irritated. It is known as the “Os tibialis externum”.
This accessory navicular bone presents as a separate ossicle that appears to be an extension of the navicular bone. It is a heart-shaped or triangular-shaped piece of bone that is located on the inner side of the navicular. T
he accessory bone is connected to the navicular by cartilage, fibrous tissue, or bone. It is known as the “bifurcate navicular”.
This accessory navicular bone presents as an extension of the navicular tuberosity.
A prominent bump can be seen on the inside of the foot. This is called a “cornuate navicular”.
The accessory navicular bone is one of the most common accessory bones in the foot, occurring in 4-21% of people according to N. Coskun in Surgical and Radiologic Anatomy.
What Are the Symptoms of an Accessory Bone in the Midfoot?
Individuals with an accessory bone in the midfoot often experience a range of symptoms. These symptoms are listed below.
- A persistent ache on the inner side of the midfoot.
- Noticeable swelling in the midfoot area.
- Bruising evident on the midfoot.
- Difficulty standing on tip-toes because of pain.
- Pain when placing weight on the foot, which often alleviates with rest.
- A pronounced bump near the foot’s inner arch region.
How Do You Diagnose Accessory Navicular Syndrome?
To diagnose accessory navicular syndrome, an assessment by a foot specialist is important. During this consultation, the doctor will palpate the navicular bone and the posterior tibial tendon that attaches to it.
For those with accessory navicular syndrome, even a slight touch to the area can cause pain.
In addition to the physical examination, the doctor will evaluate the patient’s foot structure. It’s often observed that individuals with flat feet, due to the strain on their arch, feel pain in both the accessory navicular bone and the posterior tibial tendon.
The strength of the posterior tibial tendon is tested by having the patient stand on their tiptoes. If the patient finds this challenging or impossible, this indicates a weakened tendon.
The doctor will order an x-ray to confirm the presence of an accessory navicular bone. In certain cases, an MRI might be ordered to obtain a more detailed view of the region.
An MRI can detect changes in signal intensity and bone marrow edema, signaling chronic stress to the navicular bone. It can also pinpoint potential issues like a tear or rupture in the posterior tibial tendon that the patient may have.
A CT scan may be ordered to examine the bone cortex and the joint connecting with the navicular.
Lastly, a bone scan may be ordered to identify an accessory navicular bone, especially if it shows increased activity in the area of discomfort.
How Is an Accessory Bony Prominence in the Navicular Treated?
Treatment for an accessory navicular bone depends on the severity and individual needs of the patient.
A conservative approach is preferred when treating accessory navicular syndrome. Common interventions include RICE therapy, NSAIDs, and orthotic use.
Given that the posterior tibial tendon frequently experiences inflammation in these cases, arch supports prove invaluable for pain relief.
Powerstep orthotics are highly recommended for this purpose. Their firm arch support, deep heel cup that prevents sliding, and compatibility with various footwear make them an excellent choice.
Typically, these orthotics last anywhere from 6 months to 1 year.
- For those with mild to moderate flat feet, the Powerstep Protech orthotics are ideal. They aid in elevating the foot’s arch.
- For individuals with severe flat feet, the Powerstep Maxx orthotics, which include an extrinsic heel lift for overpronation correction, are recommended.
- For those possessing high-arched feet, the Powerstep Pinnacle High Arch orthotics provide the best support and contouring.
However, if over-the-counter options are insufficient, custom orthotics might be necessary. Custom orthotics are custom-made to fit individuals’ foot structure and can be obtained at a foot doctor’s office.
While they come with a steeper price, ranging from $400 to $800, their durability and customization justify the investment.
Custom orthotics usually last between 5 to 10 years.
In instances where conservative treatment doesn’t produce the desired results, surgical intervention is necessary.
Conducted under anesthesia, the procedure involves the removal of the navicular.
If signs of posterior tibial tendon disease are evident, the affected segment of the tendon is excised.
Subsequently, the tendon is anchored back onto the navicular bone, a procedure known as the “Kidner operation”.
Post-surgery, immobilization in a cast boot or splint is required for 6-8 weeks. This is followed by a 2-4 week period of weight-bearing in the boot, and then a gradual shift to regular athletic shoes.
Physical therapy may also be recommended for optimal postoperative recovery.
In some cases, where the navicular causes pain in conjunction with talonavicular joint arthritis, a fusion of the joint using screws might be suggested.
Recovery post this procedure involves 8 weeks of immobilization, followed by 4 weeks of progressive weight-bearing and then transitioning to athletic shoes.
Full recovery can take up to 3 months.
When Can You Walk After Navicular Foot Surgery?
Following a successful surgery for a painful accessory navicular bone, patients typically resume weight-bearing and walking activities 6-8 weeks post-operation. Their progress is consistently monitored by their surgeon during the recovery phase.
In conclusion, addressing the concerns of accessory navicular syndrome requires a comprehensive understanding and a tailored approach. Physicians specializing in Podiatric and Orthopedic surgery, particularly those adept at treating foot conditions, are valuable, especially in cases where an injury or syndrome prompts surgical intervention.
With the anterior and medial aspects of foot and ankle conditions varying in complexity, recent cases have illuminated the nuances of the accessory navicular syndrome. Such popular cases underscore the importance of initiating a thorough search for and securing timely appointments with reputable centers and skilled surgeons for treatment.
The journey to recovery, whether from pes planus, plantar discomforts, or other related issues, involves dedicated rehabilitation. It’s important for patients to prioritize their health and not hesitate to consult with a foot ankle surgeon for an appointment to ensure optimal treatment and care.
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