False-negative meniscal tear in MR imaging using non fat-suppressed techniques.

Magnetic resonance (MR) imaging of menisci has a diagnostic accuracy of more than 90 per cent when the images are properly obtained. Errors in the interpretation of MR images may be related to many problems, resulting in false positive or false negative readings. We conducted this study to evaluate the prevalence of false negative results, using arthroscopy as gold standard. Matched MR imaging (performed before July 1997) and arthroscopic findings of the menisci in 63 consecutive patients were retrospectively reviewed separately by imaging planes and sequences used, by the site of tear, and by the site of meniscus (medial or lateral meniscus). The number and percentage of false-negative results were recorded. We found that with non fat-suppressed MR techniques, missed tear (false negative reading) of both menisci occurred predominantly in the meniscal body. The prevalence depends on imaging plane and sequence used. Among the techniques reviewed, sagittal T2-weighted (T2W) sequence had the highest prevalence of undetected meniscal tear.

The patellar tilt angle: correlation of MRI evaluation with anterior knee pain.

The purpose of this study was to analyze the degree of patella tilt and its correlation with the symptoms of anterior knee pain. We used magnetic resonance imaging (MRI) to measure the angle of patella tilt. The patients (n = 128) were classified into two groups. Group 1 (n = 78) included patients who had never had symptoms of anterior knee pain but had MRI for evaluation of the menisci and the ligaments. Group 2 (n = 50) included patients who had MRI for evaluation of anterior knee pain syndrome. Patients who had gross deformities like patellar dislocation, tricompartmental osteoarthritis, or inflammatory arthritis were excluded. The average patella tilt angle was 6.3 (SD = 3.9) and 12.8 (SD = 8.4) degrees, respectively, for the two groups of patients. Twenty-three patients in group 2 underwent arthroscopy because of failure of conservative treatment, and the average patella tilt angle in this subgroup was 16.4 degrees. Our study suggests that patella tilt angle is correlated with the symptoms of anterior knee pain, and indicated that the cause of pain came from the tight lateral retinaculum. In addition, MRI was found to be an accurate and reproducible method of measurement of the patellar tilt angle.

Slipped capital femoral epiphysis in Ramathibodi Hospital.

Slipped capital femoral epiphysis is rare in Asiatic Indonesian-Malays. Seven cases (9 hips) of this condition in Ramathibodi Hospital including five boys (average age, 12.5 years) and two girls (average age, 13 years) were reviewed. Most of the cases (4 out of 7) were acute on chronic and mild slips. No endocrine disorder was observed in all cases. All of the patients had a body weight above the mean of the normal population, four of which were obese. For the treatment, a single screw fixation including one case with cancellous and six cases with cannulated type were used. In the follow-up of average 2.5 years, six cases had satisfactory results. Avascular necrosis occurred in one case with mild and chronic slips in which a cancellous screw was used. It is concluded that obesity is the important factor related to the etiology in this study and probably is the same in other developing countries. The effect of a cancellous screw causing avascular necrosis is still questionable.