The trochlear cleft: the "black line" of the trochlear trough.

OBJECTIVE: The "cartilage black line sign" is a recently described T2 dark cartilage lesion that we have identified appearing as a cleft in the trochlear trough. The purpose of our study was to define the MR imaging characteristics of a trochlear cleft, determine its incidence, and correlate the MR findings with arthroscopy. MATERIALS AND METHODS: A total of 1,300 consecutive MR examinations of the knee were retrospectively reviewed by consensus of two fellowship-trained musculoskeletal radiologists. The MR imaging characteristics and location of a trochlear cleft were determined. Imaging results were compared to arthroscopy when available. Patient age and gender were compared to 25 randomly selected control patients without trochlear clefts. RESULTS: A total of 25 (1.9%) individuals (11 females and 14 males; age range 19­45 years; mean age 28 years) were diagnosed with a trochlear cleft. The control group consisted of 11 females and 14 males; age range 19­83 years; mean age 46 years. Mean cleft length was 7 mm (range 6­12 mm); cleft location was consistently in the lower trochlear trough. No full-thickness cartilage defects were identified in the eight individuals in whom arthroscopic correlation was available. A grade 2 cartilage lesion was identified in a single individual; another progressed from grade 0 to a full-thickness trochlear lesion over an 8-month interval. Eight individuals were athletes. No significant difference in gender was noted between the two groups, however, the study group was significantly younger p<0.0001. CONCLUSIONS: A trochlear cleft is a rare finding in young active individuals. It most likely indicates an incomplete cartilage fissure which may rarely progress to a full-thickness defect.

Cysts within and adjacent to the lesser tuberosity: correlation with shoulder arthroscopy.

OBJECTIVE: The purpose of our study was to determine if cysts in and adjacent to the lesser tuberosity are associated with rotator cuff pathology found at arthroscopy. MATERIALS AND METHODS: A retrospective review was undertaken of the magnetic resonance (MR) imaging of 286 consecutive arthroscopic procedures performed by a single orthopedic shoulder surgeon from February 2001 to June 2009. Images of the shoulders were reviewed by an experienced fellowship-trained musculoskeletal radiologist, reader 1, and a musculoskeletal fellow, reader 2, for the presence and location of lesser tuberosity cysts. Cysts were grouped by their location into those within the lesser tuberosity and those adjacent to the lesser tuberosity. Interreader agreement was calculated using kappa values. RESULTS: A total of 26 patients (17 men, 9 women; age range 14­84 years; mean of 61 years) had cysts in or adjacent to the lesser tuberosity. For reader 1, patients with cysts located in the lesser tuberosity were found to be significantly older(p=00.03) and more likely to have subscapularis tendon tears(p=00.02) than patients with cysts located adjacent to the tuberosity. No significant difference in any category between patients with a cyst located in the lesser tuberosity and those adjacent to the tuberosity was identified for reader 2. Interreader agreement of imaging findings ranged from fair to near perfect agreement. CONCLUSION: Cysts located in the lesser tuberosity at the insertion of the subscapularis tendon are suggestive of subscapularis tendon pathology and may occur in older individuals.

The os supranaviculare and navicular stress fractures.

Tarsal navicular stress fractures are injuries more commonly observed in athletes involved in sprinting and jumping sports. Known risk factors for the development of navicular stress fractures include pes cavus, metatarsus adductus, limited subtalar or ankle motion, medial narrowing of the talonavicular joint, as well as a short first metatarsal. The presence of an os supranaviculare has yet to be described as a predisposing factor in the occurrence of navicular stress fractures. We present two cases of navicular stress fractures in patients with an os supranaviculare and discuss possible reasons for such an association.