The navicular bone maintains the foot’s medial longitudinal arch and is a key component of hind-foot motion. Athletes that are prone to high-impact injuries, such as the runners, sprinters, jumpers, hurdlers, and gymnasts, have increased susceptibility for navicular fracture. Common navicular injuries include stress fractures, avulsion or traumatic separation of the accessory navicular, and partial or complete tears of the attachment of the plantar calcaneonavicular ligament.
Patients often present with unilateral dorsal foot pain accompanied by swelling. The pain may be of insidious onset or it may follow an injury. It is often described as aching or tenderness at the navicular region. Patients may also have limited weight bearing ability. With continued activity, the onset of pain occurs sooner during the activity and lasts longer after cessation of activity [1] [2] [3] [4]. Swelling is often present at the dorsomedial midfoot; it may be present diffusely as well. The clinician should bear in mind that foot injuries, in addition to navicular fracture, may be present [5].
Workup begins with a history and physical exam. Physical exam consists of a comparison of the arch between the affected and the uninvolved foot. Asymmetry (e.g., loss of longitudinal height of the arch during full weight-bearing) may reveal injuries such as rupture of the navicular ligament or the posterior tibialis tendon. Palpation of the medial arch often elicits pain at the proximal dorsal portion of the navicular (the "N spot"), directly over the navicular body in the superior medial arch alongside the anterior tibialis tendon [6]. This is a key physical finding and highly suggestive of a navicular fracture [7]. During the physical exam, passive eversion, active inversion, and/or hopping while standing on tip-toes will cause pain. In addition to a musculoskeletal exam, a neurovascular examination should be performed. Compartment syndrome should be considered when there is a significant degree of swelling.
X-rays are the most commonly used imaging modality for diagnosis; a computed tomography (CT) scan and/or magnetic resonance imaging (MRI) are more sensitive imaging modalities and may reveal subtle injuries. If a navicular fracture is suspected based on the patient’s history and physical exam findings, and X-rays do not demonstrate a fracture, a CT or MRI should be performed for a more thorough evaluation.
X-rays of both feet are recommended (i.e., the affected foot as well as the opposite foot for purposes of comparison). Foot X-rays consisting of anteroposterior (AP), lateral, and oblique views should be obtained. An external oblique view permits optimal imaging of the navicular tuberosity [10]. Stress views can help rule out acute ligamentous injury. In patients with high-energy injuries, ankle X-rays can help identify any concomitant injuries. X-rays of the contralateral foot may be obtained for comparison of the accessory navicular [8]. Avulsion fractures are characterized by a fleck of cortical bone. Tuberosity fractures should be differentiated from the injury of the accessory navicular [9].
CT scan permits identification of any subtle injuries and/or intra-articular fracture [10]. MRI may be used to identify injuries to the posterior tibial tendon, spring ligament, and/or accessory navicular [11].