Os sustentaculi: depiction on MR images.

We describe a 14-year old patient with pain in the medial ankle. The MR study depicted a rare accessory ossicle called the os sustentaculi. This accessory bone should not be confused with a fracture of the sustentaculum tali of the calcaneus.

Tibiotalar contact area and pressure distribution: the effect of mortise widening and syndesmosis fixation.

An unconstrained cadaver ankle model was designed to reevaluate the effect of ankle mortise widening and syndesmotic fixation on the load-bearing characteristics of the tibiotalar joint. Tibiotalar contact area, centroid shift, and mean contact pressure were quantified using a pressure-sensitive film technique. Six fresh-frozen below-knee amputation specimens were axially loaded with 500 N in three positions: neutral, 10 degrees of dorsiflexion, and 20 degrees of plantarflexion. The tibiotalar contact area and centroid position for each specimen in its intact state were first determined and then compared with values obtained after syndesmotic fixation, mortise widening of 2 and 4 mm, and deep deltoid ligament transection. Syndesmotic fixation significantly decreased joint contact area but did not consistently affect centroid position. However, unlike earlier studies, which used more constrained ankle fracture models, mortise widening with or without deltoid rupture was not found to significantly affect contact area, centroid position, or joint contact pressure. When statically loaded, the talus moved to its position of maximal congruence in the mortise, rather than displacing laterally along with the lateral malleolus.

Posterior intermalleolar ligament of the ankle: normal anatomy and MR imaging features.

OBJECTIVE: The purposes of this study were to delineate the normal anatomy and MR imaging features of the posterior intermalleolar ligament--a normal ligamentous variant of the posterior portion of the ankle--and to identify normal anatomic characteristics that may account for the role of the ligament in the development of posterior impingement syndrome. MATERIALS AND METHODS: The prevalence, size, and shape of the posterior intermalleolar ligament were documented in 36 cadaveric ankles and in 97 MR studies of the ankle in patients with and without symptoms. RESULTS: The posterior intermalleolar ligament was identified in 20 (56%) of the 36 cadaveric feet. It was 1-8 mm wide, and its diameter (anterior to posterior) was 5-8 mm. The ligament often resembled a meniscus, and in one case its anterior lip herniated into the ankle joint. The posterior intermalleolar ligament was detected in 18 (19%) of the 97 MR studies of the ankle. It was visualized on coronal T1- or T2-weighted images as a distinct, hypointense band traversing between the posterior talofibular ligament and the inferior transverse ligament. CONCLUSION: The posterior intermalleolar ligament is a normal variant of the posterior ligaments of the ankle and is present in a significant number of persons. It is best seen on coronal T1- and T2-weighted MR images. Its meniscuslike shape and occasional extension into the ankle joint may account for the development of posterior impingement syndrome in susceptible persons.

Arthroscopic removal of an osteoid osteoma of the talus: a case report.

This article describes a patient with a 10-year history of persistent ankle pain. Differential diagnosis included osteoid osteoma and anterior ankle impingement. This patient subsequently underwent arthroscopic excision of a lesion on the talar neck following a complete radiographic work-up, which was nondiagnostic. The diagnosis of osteoid osteoma was finalized upon pathologic study of the arthroscopic shavings. The use of a motorized instrument for excision did not preclude pathologic evaluation of the specimen. Therefore, in an accessible location on the talar neck, arthroscopic excision of an osteoid osteoma can be performed.

Tuberculosis of the foot as the initial manifestation of acquired immune deficiency syndrome: a report of two cases.

Two cases of tuberculosis of the forefoot are presented to highlight a growing threat in our Western communities. Each represents an initial manifestation of occult infection with the human immunodeficiency virus. Delays in diagnosis and treatment existed because of equivocal and nonspecific clinical, radiographic, and laboratory findings. It is imperative that tubercular infection be considered when evaluating often nonspecific lesions of the foot, particularly in the immunocompromised population.

Medial restraints to anterior-posterior motion of the knee.

We investigated the motion of cadaver knees before and after section of the medial structures and anterior cruciate ligament. The knees were tested using a 5-degrees-of-freedom in vitro knee-testing apparatus that measured anterior-posterior, medial-hateral, and axial displacement as well as internal-external and valgus-varus rotation. The fiexion angle could be varied but was fixed for each individual test. A 125-newton anterior-posterior force was applied perpendicular to the tibial shaft and the resulting motion of the knee was measured. In five knees the anterior cruciate ligament was cut first, followed by progressive cuts of the structures on the medial side (superficial medial collateral ligament, deep medial ligament, oblique fibers of the superficial medial ligament, and the posteromedial part of the capsule). Conversely, in five knees the medial structures were progressively cut first, followed by section of the anterior cruciate ligament. Tests were performed after each cut. With an intact anterior cruciate ligament, progressive cutting of the medial side had no effect on anterior and posterior displacements. When section of the medial structures followed cutting of the anterior cruciate ligament, anterior displacement exceeded that seen after isolated section of the anterior cruciate ligament. The anterior and posterior load-tests were repeated with the tibia fixed in 5 degrees of internal and 5 degrees of external rotation. Fixed external notation had no effect on anterior and posterior displacements. Fixed internal rotation significantly decreased anterior displacement only when both the anterior cruciate ligament and the medial structures were cut. The amounts of tibial rotation and tibial torque resulting from the applied anterior and posterior forces were low compared with our previous results, and we attributed this to decreased constraints on motion of the knee in the current testing apparatus. CLINICAL RELEVANCE: Athletic injuries of the knee frequently involve both the anterior cruciate ligament and the medial side of the knee. Clinical studies have demonstrated that combined injuries of the anterior cruciate and medial collateral ligaments often cannot be successfully managed conservatively. Our in vitro findings support the clinical data and suggest that injuries to the medial structures further compromise anterior stability when they accompany anterior cruciate injuries.