Iliopsoas tendon tear: clinical and imaging findings in 4 elderly patients.

Hip pain is a common clinical presentation of elderly patients in the emergency department. We report the clinical and imaging findings in 4 elderly patients with iliopsoas tendon tears who presented at our institution between October 2009 and June 2010. In 2 patients, the imaging diagnosis was significantly delayed. This injury is uncommon, and the clinical presentation in these patients may be misleading. Magnetic resonance is the imaging modality of choice after radiographs to assess these patients, and knowledge of the complex anatomy of the iliopsoas myotendinous unit helps in making the correct diagnosis. With aging of the population, the incidence of iliopsoas tendon tear is likely to increase.

Feasibility study of simultaneous physical examination and dynamic MR imaging of medial collateral ligament knee injuries in a 1.5-T large-bore magnet.

OBJECTIVE: To determine the feasibility of evaluating medial knee joint laxity with dynamic magnetic resonance (MR) imaging and simultaneous physical joint examination in a large-bore 1.5-T system. MATERIALS AND METHODS: The study included 10 patients (5 women, 5 men; mean age 35 years) with clinically diagnosed and categorized acute injuries of the medial collateral ligament (MCL). Intermittent valgus stress was applied separately to both the affected and the contralateral knee joint during dynamic MR imaging with a two-dimensional fast low-angle shot sequence. The width of the medial joint space and the opening angle between the femoral condyles and the tibial plateau were measured. Results obtained from dynamic MR imaging of the affected knee were compared with morphological MCL changes on static MRI, to kinematics of the contralateral side and to the clinical grading of MCL injuries. RESULTS: On clinical examination, all patients had grade 2 MCL injuries except one, who had a grade 1 lesion. Using morphological MRI criteria, 9 grade II and 1 grade III injuries were seen. Mean medial joint space width and opening angles of all affected knees were 2.8 mm and 2.7° respectively, compared with 1.7 mm and 2.1° on the contralateral side. The Wilcoxon signed rank test indicated that the differences in width (P = 0.005) and opening angle (P = 0.037) between the affected and contralateral knees were significant. CONCLUSION: Dynamic MR imaging and simultaneous physical joint examination is feasible. Our results suggest that this technique might enable the imaging documentation of medial ligamentous knee instability.

The snapping iliopsoas tendon: new mechanisms using dynamic sonography.

OBJECTIVE: The purpose of our study was to describe new mechanisms responsible for the snapping iliopsoas tendon using dynamic sonography. MATERIALS AND METHODS: We reviewed the video recordings obtained during dynamic sonography studies used to establish the diagnosis of 18 snapping iliopsoas tendons in 14 patients (nine females and five males; age range, 13-50 years) who presented clinically with either unilateral (n = 10) or bilateral (n = 4) snapping hips. During dynamic imaging, the transducer was positioned in a transverse oblique plane just above the hip joint parallel to the pubic bone. For all patients, the hip movement that generated the snapping consisted of bringing the hip from flexion-abduction-external rotation back to the neutral position. RESULTS: In 14 of 18 hips, the snapping was provoked by the sudden flipping of the iliopsoas tendon around the iliac muscle, allowing abrupt contact of the tendon against the pubic bone and producing an audible snap. Other causes of snapping iliopsoas tendon were bifid tendon heads flipping over one another (n = 3) and iliopsoas tendon impinging over an anterior paralabral cyst (n = 1). CONCLUSION: New mechanisms of snapping iliopsoas tendon have been described using dynamic sonography. Sudden iliopsoas tendon flipping over the iliac muscle was the most common cause of snapping hip.

Role of friction and tangential force variation in the subjective scaling of tactile roughness.

The present study examined the contribution of normal (Fz) and tangential (Fx) forces, and their ratio, kinetic friction (Fx/Fz), to the subjective magnitude estimations of roughness. The results suggested that the rate of variation in tangential stroking force is a significant determinant of roughness perception. In the first experiment, six volunteer subjects scaled the roughness of eight surfaces explored with a single, active scan of the middle finger. The surfaces were 7.5x2.4-cm polymer strips embossed with truncated cones 1.8 mm high with a spatial period of 2.0 mm in the transverse direction and 1.5-8.5 mm in the longitudinal, scanning direction. The surfaces were mounted on a six-axis force and torque sensor that measured the perpendicular, contact force (normal to the skin surface) and the tangential force along the axis of stroking. The results confirmed the findings of an earlier study that magnitude estimates of perceived roughness increase approximately linearly up to a longitudinal spatial period of 8.5 mm. Across subjects, no consistent correlations were found between perceived roughness and either the mean normal or tangential force alone. Although significant positive correlations were found between roughness and mean kinetic friction for all subjects, they were not as consistently robust as one might have expected. Furthermore, instantaneous kinetic friction varied widely over the course of a single stroke because of within trial oscillations in the tangential force. The amplitude of these oscillations increased with the longitudinal spatial period and their frequency was determined by a combination of the spatial period and the stroking velocity. These oscillations were even more conspicuous in the first derivative or rate of change of the tangential force (dFx/d t), which was quantified as the root mean square (RMS) of the tangential force rate. The mean normalized RMS proved to be strongly correlated with subjective roughness, averaging 0.88 for all subjects. In order to dissociate the fluctuations in tangential force from both the surface structure and the mean kinetic friction, a second experiment was performed on six additional subjects who estimated the roughness of identical lubricated and unlubricated (dry) surfaces. Lubrication with liquid soap reduced the mean kinetic friction by approximately 40%, the RMS of the tangential force rate by slightly more than 21% and the subjective estimates of roughness by 16.4%. Taken together, the results suggest that in tactile exploration, the RMS of the tangential force rate may be an important determinant of subjective roughness.