Submetatarsal Adventitial Bursitis
The Clinical Syndrome
The foot is supported by a complex arrangement of transverse, longitudinal, and vertical structures that do an amazing job helping protect the bones and absorbing the myriad forces placed on it. With repetitive microtrauma, this supporting matrix begins to break down and becomes dysfunctional, resulting in soft tissue abnormalities, including adventitial submetatarsal bursae. In contradistinction to the many bursa that we are born with, for example, subdeltoid bursa, the submetatarsal bursa are acquired. They form in the areas of excessive friction between the metatarsal heads and overlying supporting soft tissues and skin. When these adventitial bursa become inflamed, pain and difficulty walking result.
Signs and Symptoms
The onset of submetatarsal adventitial bursitis is usually acute, occurring after overuse or misuse of the foot. Inciting factors include activities such as running and sudden stopping and starting, as when playing tennis. The pain of submetatarsal adventitial bursitis is constant and severe and is localized over the metatarsal heads. It is worse with weight bearing and walking. The patient may attempt to splint the inflamed submetatarsal adventitial bursa by adopting an antalgic gait to avoid weight bearing on the affected foot. Patients with submetatarsal adventitial bursitis exhibit pain with palpation over the metatarsal heads. Warmth may be noted, and an appreciable localized mass may be identified with careful palpation. As the condition becomes chronic, fibrosis of the plantar fascia adjacent to the inflamed bursa may be appreciated.
How is Submetatarsal Adventitial Bursitis diagnosed
Plain radiographs are indicated in all patients with forefoot pain. Based on the patient’s clinical presentation, additional tests, including complete blood cell count, erythrocyte sedimentation rate, and antinuclear antibody testing, may be indicated. Magnetic resonance imaging (MRI) of the foot is indicated to confirm the diagnosis and identify commonly occurring concomitant forefoot pathological conditions, such as metatarsalgia, metatarsal stress fractures, and Morton neuroma. Radionucleotide bone scanning is useful to identify stress fractures of the metatarsals not seen on plain radiographs. Ultrasound imaging and color Doppler evaluation are also useful in helping identify submetatarsal adventitial bursitis.
Submetatarsal adventitial bursitis generally is identified easily on clinical grounds. Because other forefoot pathological conditions, including metatarsalgia, stress fractures, and Morton neuroma, frequently accompany submetatarsal adventitial bursitis, the specific diagnosis may be unclear. Stress fractures of the metatarsals are easily missed on plain radiographs, and radionucleotide bone scanning may be required to confirm the diagnosis.
Initial treatment of the pain and functional disability associated with submetatarsal adventitial bursitis should include a combination of nonsteroidal antiinflammatory drugs (NSAIDs) or cyclooxygenase-2 (COX-2) inhibitors and physical therapy. Avoidance of painful shoes or shoes with a narrow toe box should be considered, as should the use of thick-soled shoes with an orthotic device to relieve pressure on the inflamed bursa. Local application of heat and cold may be beneficial. The patient should be encouraged to avoid repetitive activities responsible for the evolution of the bursitis, such as jogging. For patients who do not respond to these treatment modalities, injection with a local anesthetic and steroid may be a reasonable next step. Ultrasound guidance may help improve the accuracy of needle placement and decrease the incidence of needle-related complications. Sometimes, surgical excision of the bursa and shaving of the offending metatarsal head may be the only option to provide long-lasting relief of the forefoot pain.
Complications and Pitfalls
The possibility of trauma to the forefoot from the injection is ever present. Approximately 25% of patients report a transient increase in pain after this injection technique, and patients should be warned of this possibility. The clinician should consider the possibility of more than one pathological process coexisting with submetatarsal adventitial bursitis, to optimize treatment.CLINICAL PEARLS
Submetatarsal adventitial bursitis occurs in the areas of excessive friction between the metatarsal heads and overlying supporting soft tissues and skin. It frequently coexists with other forefoot pathological conditions, which may require additional treatment with a more localized injection of a local anesthetic and depot steroid.
The injection of submetatarsal adventitial bursitis is a safe procedure if careful attention is paid to the clinically relevant anatomy in the areas to be injected. The key to the successful treatment of submetatarsal adventitial bursitis is to identify the underlying pathology responsible for the formation of this adventitial bursa and treat it aggressively.