- Present in at least 14% of population, rarely symptomatic
- Commonly bilateral
- Pain over prominence in medial mid foot
- X-rays assist in the diagnosis
- Nonoperative treatment is the mainstay with surgical options for failure of nonoperative management
Description:The accessory navicular was first described in 1605 by Bauhin. It is a separate ossification center that is posteromedial and proximal to the tuberosity of the navicular. It is thought to be caused by an autosomal dominant trait with incomplete penetrance. Appearing radiographically around age 9-11, the accessory navicular will often fuse with the navicular. It can be a source of medial foot pain as the posterior tibialis tendon inserts on the accessory navicular in addition to the tuberosity of the navicular. Symptoms typically begin in adolescence and worsen with activity, weight bearing, and narrow shoe wear. Histopathology of excised specimens show changes associated with chronic tension. Shear forces from the posterior tibialis and compressive forces from increased pronation are likely responsible for symptomatology.
Epidemiology:An accessory navicular is present in at least 14% of the population, with an exact percentage difficult to determine because most are asymptomatic. Up to 50% of patients have bilateral accessory naviculars.
Clinical Findings:Pain is localized over the accessory navicular in the medial midfoot, often reproduced with resisted inversion with the foot in plantarflexion. Patients can develop painful bursa over the prominence. The area can be red and warm from inflammation. Skin irritation and blisters may also be present. Some patients also have flexible flatfoot but this is an inconsistent relationship.
Imaging Studies:Standard AP, internal oblique, and lateral views of the foot may be useful. An external oblique view may best demonstrate the accessory navicular. There are 3 types of accessory navicular described from radiographs: Type 1) Separate ossicle within the posterior tibialis tendon, Type 2) Synchondrosis with navicular, Type 3) Fusion with the navicular to form a cornuate navicular. The most commonly symptomatic accessory navicular is Type 2. Bone scan or MRI can be helpful to determine the source of medial sided foot pain if it is unclear from physical exam and radiographs.
Treatment:Nonoperative management is the mainstay of treatment. This consists of shoe wear modifications, activity modifications, trial of immobilization, orthoses, or oral pain medications. Physical therapy should focus on controlling posterior tibialis tendonitis and strengthening the intrinsic and extrinsic foot muscles.
Operative management should be the last resort. Multiple techniques are described. The classic operation consists of removal of the accessory navicular with detachment and plantar advancementof the posterior tibialis: the Kidner procedure. A modified Kidner procedure without detachment of the posterior tibialis tendon has also been described and is commonly used. Naviculoplasty, contouring of the medial aspect of the navicular, can be completed at the time of excision. Other described surgical treatments include simple excision, percutaneous drilling of the synchondrosis to induce fusion, and percutaneous or open compression screw placement to stabilize and fuse the synchondrosis.
Outcomes of surgical treatment with either simple excision or excision with tendon advancement are generally good. Most patients have improvement of pain and foot fatigue. Few complications are reported (Prichasuk, 1995; Pretell-Mazzini, 2014).
Postoperative management may include cast or removable boot immobilization, protected weight bearing, and eventual physical therapy. Expected return to sport and activities is around 8-12 weeks.
Complications:Few complications are reported (Prichasuk, 1995; Pretell-Mazzini, 2014).
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