MATERIALS AND METHODS. The MR images of 192 patients who underwent arthroscopy and MRI of the knee from July 2003 through March 2006 were retrospectively reviewed. MR images were independently scored by two observers for the presence of radial tear of the medial meniscal root. Interobserver agreement in detection of these tears was assessed with kappa values. The differences in areas under the receiver operating characteristic curves were assessed with a univariate z-score test.

RESULTS. Arthroscopy revealed that 29 patients had radial tears of the medial meniscal root. The sensitivity, specificity, and accuracy of MRI for one reader were 90% (26/29), 94% (154/163), and 94% (180/192) and for the other reader were 86% (25/29), 95% (155/163), and 94% (180/192). Interobserver agreement for radial tears of the medial meniscal root was very high ( = 0.93). The areas under the receiver operating characteristic curves for each reader were 0.97 and 0.96, which were not significantly different. There was no significant difference in detection of medial meniscal root tears on T2-weighted coronal images compared with the overall interpretation for both readers. Other image sequences had significantly different sensitivity or specificity for one or both readers (McNemar statistic).

CONCLUSION. MRI of the knee is reliable and accurate for detection of radial tears of the medial meniscal root. Coronal T2-weighted imaging is the most useful MRI sequence.

MATERIALS AND METHODS. Seventy patients underwent 1.5-T MRI of the knee and arthroscopy within 3 months. MR images were reviewed by two radiologists for parameniscal cysts, bowing and edema around the collateral ligament, meniscal extrusion, cartilage loss, and nonlinear and linear subchondral marrow edema. The findings were correlated with the arthroscopic findings. The positive predictive value (PPV), sensitivity, and specificity of indirect signs were calculated.

RESULTS. Fifty-three medial and 28 lateral meniscal tears were found at arthroscopy. The PPV of indirect signs of meniscal tear was 0.17–1.00 for reader 1 and 0.37–1.00 for reader 2. The PPV of parameniscal cysts was 1.00 for medial and lateral meniscal tears for both readers. The specificity and PPV of periligamentous edema and cruciate ligament bowing for medial meniscal tear were 0.94 and 0.98 for both readers, 0.88 and 0.94 for reader 1, and 0.94 and 0.97 for reader 2. The specificity and PPV of subchondral marrow edema for medial meniscal tear were 0.88 and 0.96 for reader 1 and 0.94 and 0.97 for reader 2 and for lateral meniscal tear were 0.98 and 0.92 for reader 1 and 1.00 and 1.00 for reader 2. The specificity and PPV of linear subchondral marrow edema for medial meniscal tear were 0.94 and 0.97 for reader 1 and 1.00 and 1.00 for reader 2. For lateral meniscal tear, the values were 0.98 and 0.89 for reader 1 and 1.00 and 1.00 for reader 2. The specificity and PPV of nonlinear subchondral marrow edema for medial meniscal tear were 0.94 and 0.89 for reader 1 and 1.00 and 1.00 for reader 2. For lateral meniscal tear, the values were 0.89 and 0.97 for reader 1 and 1.00 and 1.00 for reader 2. The specificity and PPV of cartilage loss for medial meniscal tear were 0.88 and 0.94 for reader 1 and 0.88 and 0.93 for reader 2. For lateral meniscal tear, the values were 0.85 and 0.56 for reader 1 and 0.97 and 0.80 for reader 2.

CONCLUSION. Indirect MRI signs occur in association with meniscal tears and can aid diagnostic confidence when the MRI meniscal appearance is equivocal.

MATERIALS AND METHODS. We reviewed the records of 559 patients who underwent knee MR examinations and arthroscopy. We compared the positive predictive values (PPVs) of an MR diagnosis of a medial meniscal tear for differences in tear location or type, delay between knee injury and MRI, delay between MRI and arthroscopy, and the presence of an anterior cruciate ligament (ACL) tear. We also retrospectively reviewed the MR examinations of 50 longitudinal tears to compare the PPVs of various MRI findings of a longitudinal tear.

RESULTS. There was no association between either the delay between injury and MRI or the delay between MRI and arthroscopy and false-positive diagnoses. The PPV of 64% (32/50) for longitudinal tears was lower than the values of 83% (15/18) to 100% (116/116) for other types of medial meniscal tears. False-positive diagnoses of medial meniscal tears were more common in patients who had a prior episode of acute trauma (p = 0.004) or an ACL tear (p < 0.0001). Review of longitudinal tears revealed a decreased PPV when MRI showed signal contacting only the superior surface (p = 0.016) or when MRI showed signal contacting the surface at the meniscocapsular junction (p = 0.004). Four of the 18 menisci with a false-positive diagnosis of a longitudinal tear had a healed ACL tear noted at arthroscopy.

CONCLUSION. False-positive MR diagnoses of medial meniscal tears are more common for longitudinal tears than other tear types and are also more common with MR abnormalities at either the superior surface or the meniscocapsular junction. Spontaneous healing of longitudinal tears accounts for some false-positive MR diagnoses.

MATERIALS AND METHODS. Cortical irregularities and cysts of the lesser tuberosity were evaluated on radiographs and MR images in 70 patients: 31 with normal subscapularis tendons and 39 with subscapularis tendon tears. These imaging findings were correlated with subscapularis tendon tears diagnosed during arthroscopy and with fatty atrophy of the subscapularis muscle seen on MR images. Correlations between imaging findings, patient age, history of trauma, and the reference standards were assessed using gamma coefficients. Interreader agreement was calculated using kappa values.

RESULTS. For the diagnosis of subscapularis tendon tears, the sensitivity of cortical irregularities and cysts on radiographs was 44%/51% (reader 1/reader 2) and 21%/21%, respectively; specificity was 65%/68% and 87%/87%. The sensitivity of cortical irregularities and cysts on MRI was 64%/72% and 36%/39%. Specificity was 48%/45% and 81%/77%. For fatty atrophy of the subscapularis muscle, the sensitivity of cortical irregularities and cysts on radiographs was 67%/73% and 17%/27%, respectively; the specificity was 63%/63% and 83%/85%. Significant (p < 0.05) positive correlations were found between cortical irregularities and surgical grade of subscapularis tendon tear for reader 2 (radiography, = 0.39; MRI, = 0.45) and between lesser tuberosity abnormalities and patient age ( = 0.11 and 0.43) for both readers. Interobserver agreement of imaging findings varied from moderate to substantial ( = 0.50–0.76).

CONCLUSION. Abnormalities of the lesser tuberosity are moderately associated with subscapularis tendon tears and patient age. Cysts seen in the lesser tuberosity on shoulder radiographs or MR images are relatively specific for subscapularis tendon tears and muscle atrophy.

SUBJECTS AND METHODS. The volar wrists of 12 healthy volunteers and 22 consecutive patients with sensory deficit in the palmar triangle and thenar eminence suggesting neuropathy of the palmar cutaneous branch of the MN were examined with high-frequency sonography. Nine patients underwent carpal tunnel release, five had a history of penetrating trauma, six had symptoms suggesting concurrent carpal tunnel syndrome, one received surgery for palmaris tendon transfer, and one underwent resection of a ventral carpal ganglion cyst. Correlative 1.5-T MRI was performed in six patients.

RESULTS. In 83% of the healthy volunteers, 17-5–MHz sonography was able to identify the palmar cutaneous branch of the MN from its origin down to slightly distal to the wrist crease. In the patient group, sonography allowed detection of nerve abnormalities in 55% of the cases. Focal hypoechoic swelling of the nerve at the fascial crossing was observed in patients who had either concurrent carpal tunnel syndrome (four cases) or previous carpal tunnel release (three cases). Sonography performed after a penetrating trauma revealed nerve encasement by scar tissue (two cases) or complete transection of the nerve ending in a terminal neuroma (one case). Nerve transection secondary to resection of a ventral carpal ganglion cyst (one case) or to carpal tunnel release (one case) was also observed.

CONCLUSION. Sonography can identify the palmar cutaneous branch of the MN and characterize its abnormalities, providing unique information about this small nerve branch.

MATERIALS AND METHODS. Two radiologists retrospectively reviewed MR images of 47 patients with Gaucher's disease and determined bone marrow burden scores by consensus on the basis of previously published criteria. The bone marrow burden scores were correlated with genotype, liver volume, spleen status, age, and cumulative duration of enzyme replacement therapy.

RESULTS. Subjects with compound heterozygous N370S alleles had significantly higher overall, lumbar spinal, and femoral bone marrow burden scores than did N370S homozygotes. There was a significant positive correlation between an enlarged or surgically absent spleen and bone marrow burden score. There were no significant associations between bone marrow burden score and liver volume, age, cumulative duration of enzyme replacement therapy, or cumulative duration of untreated disease. Femoral and lumbar spinal bone marrow burden scores had a weak but significant positive correlation across all patients.

CONCLUSION. Skeletal pathologic findings in Gaucher's disease encapsulated as bone marrow burden score correlate significantly with the number of copies of the N370S allele, which has an ameliorative effect on bone marrow disease. Splenectomy or splenomegaly is associated with greater risk of bone marrow disease. Femoral and lumbar spinal bone marrow burden scores, although only weakly correlated, independently illustrated both the protective role of the N370S allele and the unfavourable implication of splenectomy. This finding suggests that axial and appendicular bone marrow burdens are related but distinct and justifies multiple-compartment evaluation in Gaucher's disease.

CONCLUSION. The MR corner sign was defined as a triangular and sharply marginated corner abnormality in a vertebral body unassociated with osteophytes or Schmorl's node. MR corner lesions were significantly more common in the ankylosing spondylitis group than in the control group (Fisher's exact test, p < 0.001). The sensitivity, specificity, and positive and negative predictive values of the MR corner sign were 44%, 96%, 92%, and 63%, respectively. The most frequent feature of signal intensity was a Modic type II change (77%). In patients with ankylosing spondylitis, the MR corner sign was fre quently seen at the thoracolumbar junction, whereas degenerative corner lesions were commonly seen in the lower lumbar spine. When the MR corner sign is detected on spinal MR images in daily practice, it should not be overlooked because it suggests the possibility of ankylosing spondylitis, which should then be further evaluated.

CONCLUSION. MRI can be a useful technique in the diagnosis of costal cartilage injuries.

MATERIALS AND METHODS. We retrospectively reviewed 449 consecutive routine knee MR examinations for the presence of enchondromas. MRI was considered positive when a focal geographic area of lobular marrow replacement (nonsubchondral) was identified on T1 weighting and high signal intensity was seen on T2 weighting. Patients with enchondromas were further evaluated for demographics; lesion site, size, and relationship to the physeal plate; aggressive imaging features described with chondrosarcoma; concurrent internal derangement; and study indication.

RESULTS. The prevalence of incidental enchondromas was 2.9% on routine knee MR examinations. The prevalence was highest in the distal femur (2.0%), followed by the proximal tibia (0.7%) and the proximal fibula (0.2%). The average lesion size was 1.9 x 1.2 x 1.3 cm (57% of lesions were < 1 cm). Most lesions were located in the metaphysis (71%) or diaphysis (21%). Enchondromas were within 1.5 cm of the physeal plate in 72% of cases. No aggressive imaging features to suggest chondrosarcoma were seen. All patients had evidence of internal derangement as the cause of symptoms and the request for imaging.

CONCLUSION. Incidental enchondromas can be identified on 2.9% of routine MR knee examinations, most frequently in the distal femur (2.0%). This significant prevalence is much higher than in an autopsy series (0.2%), likely reflecting the increased sensitivity of MRI for detecting small lesions, and is important to recognize to avoid confusion with other pathologic entities.

CONCLUSION. Long-distance runners with hip or groin pain and abnormal MRI findings involving the insertion of the iliopsoas tendon and marrow edema in the lesser trochanter may be at risk of stress injuries at the femoral neck.

CONCLUSION. Musculoskeletal sonography is an important complementary tool to MRI and is essential for radiologists who want to provide patients with state-of-the-art musculoskeletal imaging.