Multipoint rank-order study methodology: observer issues

RATIONALE AND OBJECTIVES

We performed a multipoint rank-order experiment to evaluate variability in observers' sensitivity to small differences in image presentation and to assess observers' performance as a function of the type and number of tasks included.

METHODS

Five experienced observers were presented with four sets of chest images that had been compressed at five different levels. Each set contained six images ranging from noncompressed to approximately 60:1-compressed images. Observers were asked to review all images of each case side by side and rank-order the "quality" of each to enable determination of the presence or absence of interstitial disease and/or pneumothoraces.

RESULTS

Observers varied significantly in their ability to detect very small differences among the images (P < 0.001). Those who performed well did so regardless of whether they ranked a specific abnormality in a multidisease or a single-disease setting.

CONCLUSIONS

Selected observers can reliably detect very small differences among similar images. These readers could be used to confirm or rule out the need for objective observer-performance-type studies.

Transverse ligament and its effect on meniscal motion. Correlation of kinematic MR imaging and anatomic sections

RATIONALE AND OBJECTIVES

To evaluate the effect of the transverse ligament on translation of the menisci.

METHODS

Six cadaveric knees were examined by MR imaging inside a positioning device before and after transecting the transverse ligament. The knees were examined at various positions: extension, 30 degrees of flexion, 60 degrees of flexion, and full flexion. Sagittal T1-weighted spin-echo images were generated at each knee position and evaluated for statistical differences with regard to anterior-posterior meniscal excursion.

RESULTS

Statistically significant differences in meniscal excursion were found before and after transsecting the transverse ligament for anterior-posterior meniscal motion of the anterior horn of the medial meniscus at 30 degrees of knee flexion. No such significant differences were found, however, at 60 degrees of flexion and full flexion in anterior-posterior meniscal excursion of the anterior or posterior horn of either meniscus before and after transsecting the transverse ligament.

CONCLUSIONS

The transverse ligament has a restricting effect on anterior-posterior excursion of the anterior horn of the medial meniscus at lower degrees of knee flexion.

Open complex metacarpophalangeal joint dislocation. Two cases: index finger and long finger

Two patients with open complex dislocation of a metacarpophalangeal joint were treated by cleansing of the wound, open reduction, primary wound closure, and early motion. One dislocation occurred in the index finger, the other in the long finger which is only the second such case to be described. Antibiotics were given before and continued for 5 days after operation. There were no infections, and both patients regained an excellent range of motion without pain.