Computed tomographic demonstration of the vacuum phenomenon in the subtalar and tibiotalar joints.

Gas has been identified within diarthrodial joints for more than eight decades. From a radiologic standpoint, the so-called "vacuum phenomenon" is the most common demonstration of gas. We retrospectively reviewed computed tomographic scans of 495 feet and ankles performed over a 24-month period. We found 12 patients (2.4%) with clearly demonstrable gas within the tibiotalar or subtalar joints. This gas was not associated with the presence of fixation hardware or infection. Each patient with gas in the subtalar joint had plain radiographic changes consistent with subtalar arthritis. We conclude that gas in the subtalar joint can be effectively demonstrated by high-resolution CT techniques in the subtalar and tibiotalar joints in patients with advanced degenerative disease.

Magnetic resonance diagnosis of an occult metastatic colon carcinoma of the calcaneus.

This is a case report which shows the potential benefit of magnetic resonance imaging in accurately visualizing occult metastatic lesions to bone. The case involves a relatively young patient with metastatic colon carcinoma to the calcaneus who ultimately required amputation.

Surgical management of a ruptured peroneus longus tendon with a fractured multipartite os peroneum.

Injury of the peroneus longus tendon with concurrent fracture of the os peroneum is a seldom reported injury. This injury is probably underdiagnosed or misdiagnosed. The mechanism of this injury often involves sudden inversion, and therefore may often be misdiagnosed as a lateral ankle sprain or tendonitis. From the author's research review, this is the first reported case involving a fractured multipartite os peroneum with rupture of the peroneus longus tendon. The injury was diagnosed preoperatively by magnetic resonance imaging (MRI) as well as radiographs.

Aneurysmal bone cyst.

Key findings that aid in the diagnosis of an aneurysmal bone cyst are: 1) typically the patients are young individuals less than 20 years old; 2) an expansile bone lesion is bordered by a thin, low signal intensity rim mass; 3) the lesion is inhomogenously increased in signal on T2-weighted images; and 4) multiple fluid-fluid levels are seen with the mass on T2-weighted magnetic resonance imaging scans.

Complete avulsion of the triceps tendon: MRI diagnosis.

Avulsion of the triceps tendon is a rare injury. We report a case of complete avulsion of the triceps tendon diagnosed by magnetic resonance imaging (MRI) and confirmed surgically. The excellent soft tissue contrast and multiplanar imaging capability of MRI makes it an ideal tool to diagnose this disorder. To our knowledge, this is the first reported case of MRI diagnosis of complete avulsion of the triceps tendon.

Magnetic resonance arthrography of the ankle.

Magnetic resonance (MR) arthrography is a useful technique in evaluating the articular structures of the ankle. With intra-articular administration of gadolinium-DTPA (Gd-DTPA), visualization and delineation of anatomic structures, that would not be depicted by other traditional imaging techniques, are achieved. It is a technique that proves to be advantageous as it does not require the use of ionizing radiation, nor iodinated contrast material as other conventional diagnostic modalities. MR arthrography also allows multiplanar imaging and provides excellent resolution.

MRI diagnosis of biceps tendon rupture.

Distal biceps tendon rupture is a rare injury. While plain radiographs are usually not helpful in visualizing the defect, evaluation of the tendon with MRI has proven to be useful as it depicts complete anatomic detail of the tendon and associated structures. Its multiplanar imaging capability and superior soft tissue contrast resolution makes MRI a prime diagnostic tool in the diagnosis of tendon disorders. We report a case of complete rupture of the biceps tendon diagnosed by MRI.

Magnetic resonance imaging in localization of EEG depth electrodes for seizure monitoring.

Preoperative evaluation of patients with medically refractory complex partial seizures requires intensive EEG monitoring. Part of this process may include insertion of depth electrodes into temporal lobe structures. Although many imaging methods have been used for stereotactic placement of the electrodes, only computed tomography (CT) has been used to verify position after implantation. We studied 30 patients in whom magnetic resonance imaging (MRI) was used to visualize the position of stainless-steel electrodes stereotactically implanted in the temporal lobes. The procedure is noninvasive, does not utilize radiation, and has the additional advantages of multiplanar capability, increased soft tissue contrast, and lack of bony artifacts commonly associated with CT.

Intracanalicular arachnoid cyst mimicking acoustic neuroma: CT and MRI.

A patient with a surgically proven intracanalicular arachnoid cyst was studied using computed tomography, magnetic resonance imaging, and air CT cisternography. The lesion had a similar radiographic appearance to acoustic neuroma and therefore, although rare, must be considered in the differential diagnosis of intracanalicular mass lesions. We report a case in which examination was performed, in evaluating the lesion, utilizing high-resolution air CT cisternography and magnetic resonance imaging (MRI).

Computed tomography of odontogenic keratocysts.

Epithelium-lined cysts of the jaw can be either odontogenic or non-odontogenic. Cysts that exhibit keratinization of their epithelial lining are called odontogenic keratocysts. They compose approximately 8% of all odontogenic cysts. There is a frequent association with unerrupted teeth, and a high incidence of occurrence of keratocysts in the multiple basal cell nevus syndrome. The significance of odontogenic keratocysts is their high potential for recurrence after their removal. There is no specific radiographic feature, however, that distinguishes them from non-keratinized odontogenic cysts. High resolution computed tomography (CT) studies can exquisitely determine the extent of these lesions and pinpoint areas of cortical breakthrough as well as involvement of the teeth. This information is invaluable in surgical planning for excision of these lesions.

Magnetic resonance imaging of calcaneal aneurysmal bone cyst.

A 7-year-old black male presented with a lytic, expansile lesion of the calcaneus. This lesion was studied with conventional x-rays as well as MRI. The MR examination demonstrated a multiloculated lesion with material of a high- and low-signal intensity appreciated within each loculation. Pathologic review of the lesion demonstrated an aneurysmal bone cyst.

Parosteal lipoma of the finger: preoperative evaluation with computed tomography.

Lipomas are very common benign soft tissue neoplasms arising from fatty tissue and may occur anywhere in the body. They are usually slow growing, painless masses often noted in the extremities of adult women. Occurrence in the hands and feet is unusual and those found in the digits are extremely rare. We describe a case of a lipoma presenting as a soft tissue mass of the index finger and show how computed tomography was extremely helpful in preoperative assessment by accurately defining the size of the lesion, the degree of bone involvement, and even giving indication of its underlying pathology.