Introduction: Magnetic resonance imaging (MRI) of soft tissues after total hip arthroplasty is of clinical interest for the diagnosis of various pathologies that are usually invisible with other imaging modalities. As a result, considerable effort has been put into the development of metal artifact reduction MRI strategies, such as slice encoding for metal artifact correction (SEMAC). Generally, the degree of metal artifact reduction with SEMAC directly relates to the overall time spent for acquisition, but there is no specific consensus about the most efficient sequence setup depending on the implant material. The aim of this article is to suggest material-tailored SEMAC protocol settings.Materials and Methods: Five of the most common total hip prostheses (1. Revision prosthesis (SRom), 2. Titanium alloy, 3. Muller type (CoNiCR-Mo alloy), 4. Old Charnley prosthesis (Exeter/Stryker), 5. MS-30 stem (stainless-steel)) were scanned on a 1.5 T MRI clinical scanner with a SEMAC sequence with a range of artifact-resolving slice encoding steps (SES: 2 - 23) along the slice direction (yielding a total variable scan time ranging from 1 to 10min). The reduction of the artifact volume in comparison with maximal artifact suppression was evaluated both quantitatively and qualitatively in order to establish a recommended number of steps for each case.Results: The number of SES that reduced the artifact volume below approximately 300mm(3) ranged from 3 to 13, depending on the material. Our results showed that although 3 SES steps can be sufficient for artifact reduction for titanium prostheses, at least 11 SES should be used for prostheses made of materials such as certain alloys of stainless steel.Conclusion: Tailoring SES to the implant material and to the desired degree of metal artifact reduction represents a simple tool for workflow optimization of SEMAC imaging near total hip arthroplasty in a clinical setting.

A case of a medullary osteoidosteoma of the pisiforme bone is presented that appeared as a light bulb on MR-Angiography while causing diffuse hypointensity of the pisiforme bone and of the surrounding soft tissue on T1- and diffuse hyperintensity of these regions on T2-w and T1- w postcontrast images. Although not surprising according to the typical appearance of osteoidostomas on triple phase scintigraphy, the light bulb sign of osteoidosteomas on MRA has not yet been reported and familiarity with this findings may be of value in order to avoid their confusion with vascular lesions such as aneurysms or pseudoaneurysms during MR-angiography.

The purpose of this study was to determine the recovery potential of the posterior tibial muscle after late reconstruction following tendon rupture in stage II of posterior tibial tendon dysfunction. Fourteen patients (18 women, 6 men; mean age 59.8 years) were investigated 47 months (range, 24-76 months) after surgical reconstruction of a completely ruptured posterior tibial tendon (end-to-end anastomosis, side-to-side augmentation with the flexor digitorum longus tendon) in combination with a distal calcaneal osteotomy with a tricortical iliac crest bone graft for lengthening of the lateral column. At follow-up, clinical and radiological investigations were performed, including strength measurement and qualitative and quantitative MRI investigation. The overall clinical results were graded excellent in 12 patients, good in one, fair in one, and poor in none. The average ankle-hindfoot score (American Orthopaedic Foot and Ankle Society) improved from preoperatively 49.1 (range, 32-60) to 93.1 (range, 76-100) at follow-up. The functional result correlated with patient's satisfaction and sports activities (p <.05). All patients showed a significant strength of the posterior tibial muscle on the affected side, but it was smaller than on non-affected side (p <.05). The mean posterior tibial muscle strength was 75.1 N on affected and 104.9 N on nonaffected side, corresponding to a ratio of 0.73 between the two legs. The mean area of the posterior tibial muscle was 1.89 cm(2) on affected side, and 3.48 cm(2) on nonaffected side, corresponding to a ratio of 0.55 between the two legs. While fatty degeneration for the posterior tibial muscle was found in all patients, it was found to decrease with increasing strength of the posterior tibial muscle (p <.05) and muscular size (p <.05). On postoperative MRI, the posterior tibial tendon could be found to be intact in all patients. The recovery potential of the posterior tibial muscle was shown to be significant even after delayed repair of its ruptured tendon. A ruptured and/or diseased posterior tibial tendon should not be transected as it excludes any recovery possibilities of the posterior tibial muscle.

PURPOSE:To investigate the use of magnetic resonance (MR) imaging enhanced with ultrasmall superparamagnetic particles of iron oxide (USPIO) to identify acute, early chronic, and late chronic abscess formation in an experimental model of soft-tissue abscess.MATERIALS AND METHODS:Experimental soft-tissue infection in 15 rats was imaged with an MR imaging unit on days 1 and 2 (acute), days 5 and 6 (early chronic), and days 8 and 9 (late chronic) after inoculation of the infectious agent. All animals were imaged without contrast enhancement and immediately and 24 hours after USPIO administration. MR and histopathologic findings were compared. The changes in relative signal intensity (SI) and in the extent and pattern of contrast enhancement (macrophage distribution) between the animal groups were analyzed. Statistical testing was performed with Kruskal-Wallis analysis of variance and the chi2 test.RESULTS:At 24 hours after USPIO administration, the relative SI of the abscess wall and the relative macrophage extent were 0.50 (0.33-0.73) and 1.03 (0.90-1.08), respectively, for acute infection; 0.11 (0.10-0.18) and 0.94 (0.93-1.01) for early chronic infection; and 0.53 (0.44-0.58) and 0.80 (0.77-0.83) for late chronic infection. The changes in enhancement pattern (P <.001), relative SI (P <.001), and relative macrophage extent (P <.05) with time were significant.CONCLUSION:The macrophage distribution pattern increases the specificity of MR findings in chronic infection and allows differentiation between areas with active inflammation and areas of reparative granulation tissue.

Ziel der vorliegenden Studie war es, an einem in vivo-Modell das Rehabilitationspotential des Tibialis posterior-Muskels wie auch die Sehnenheilung zu bestimmen. 14 Patienten wurden einheitlich mit Naht der Sehne und der Bänder sowie einer Kalkaneusverlängerungsosteotomie versorgt. Nach 47 (24–76) Monaten erhöhte sich der AOFAS-Hindfoot-Score von 49,1 (32–60) Punkten auf 93,1 (76–100) Punkte. Weder die Dauer der Symptome noch das funktionelle Resultat korrelierten mit der maximalen Muskelkraft. Die Patientenzufriedenheit und die sportliche Aktivität hingen weder von der Muskelkraft noch vom Muskelquerschnitt ab. In jedem Fall scheint der Aufwand einer verspäteten Sehnenrekonstruktion selbst bei nachweislich schlechter Gewebequalität und fortgeschrittener Verfettung des Muskels gerechtfertigt. The purpose of this study was to determine the rehabilitation potential of the posterior tibial muscle after late reconstruction of its ruptured tendon in stage II of posterior tibial tendon dysfunction. Fourteen patients having a complete, minimally 3 months old rupture of the posterior tibial tendon were surgically treated by reconstruction of the posterior tibial tendon, medial ankle ligaments, and anterior calcaneal osteotomy for lengthening of the lateral column. After 47 (24–76) months, the average ankle-hindfoot score (AOFAS) improved from preoperatively 49.1 (32 60) to 93.1 (76 100). No correlation was found between duration of the preoperative symptoms and achieved muscular strength nor between AOFAS-Hindfoot-Score and muscular strength. Patient's satisfaction and sports activities depended neither on muscular strength nor muscular size. A ruptured and/or diseased posterior tibial tendon should not longer be discharged as it definitively excludes any rehabilitation of the posterior tibial muscle.

Ziel der vorliegenden Studie war es, an einem in vivo-Modell das Rehabilitationspotential des Tibialis posterior-Muskels wie auch die Sehnenheilung zu bestimmen.

OBJECTIVE:This study was conducted to determine the prevalence of tendinosis and tears of gluteus medius and minimus muscles in patients presenting with buttock, lateral hip, or groin pain; describe the MR imaging findings; and discuss their probable relationship to the greater trochanteric pain syndrome.SUBJECTS AND METHODS:Two hundred fifty MR imaging examinations of the hip were performed for the evaluation of buttock, lateral hip, or groin pain. The findings were reviewed for changes in the morphology or signal intensity of gluteus medius and minimus muscles and tendons and for any peritendinous abnormality including distention of regional bursae.RESULTS:Thirty-five studies met our criterion of showing either tendinosis or tears of gluteus medius and minimus muscles as the primary positive finding. Eight patients had complete retracted tears of the gluteus medius, and 14 patients had partial tears; in 13 patients, MR findings were consistent with tendinosis. The gluteus minimus muscle was also involved in 10 patients. MR imaging findings were the same as those described for tears and tendinosis of other regions of the body. Surgical proof of a tendon tear was obtained in six patients.CONCLUSION:Tendinopathy of the hip abductors and gluteus medius and minimus muscles was a common finding on MR imaging in our patients with buttock, lateral hip, or groin pain. Tendinopathy is probably a frequent cause of the greater trochanteric pain syndrome, a common regional pain syndrome that can mimic other important conditions causing hip pain including avascular necrosis and stress fracture. Moreover, it is likely that trochanteric bursitis is associated with tendinopathy.

PURPOSE To evaluate and optimize a method for producing magnetic resonance (MR) images similar to MR arthrograms of multiple synovial joints with intravenous gadopentetate dimeglumine injection. MATERIALS AND METHODS The authors examined the effects of joint motion, dose of gadopentetate dimeglumine (0.1, 0.2, and 0.4 mmol/kg), and fat saturation on the enhancement rate of the joint cavity and the degree of image contrast generated among articular structures on MR images in 14 healthy volunteers. Shoulder, elbow, wrist, hip, knee, and ankle joints of 10 volunteers were imaged with optimized parameters. Indirect MR arthrographic findings in 17 patients with joint disorders (eg, rotator-cuff tears, meniscal tears, and osteoarthritis) were compared with arthroscopic findings. RESULTS Fat-saturated images obtained after 10 minutes of exercise and administration of 0.1 mmol/kg gadopentetate dimeglumine were similar to those obtained after intraarticular injection of contrast medium. Exercising the joint yielded the strongest joint-cavity enhancement. Increasing the dose of contrast medium in the unexercised joint did not statistically significantly improve the contrast-to-noise ratio. Rotator cuff tears, meniscal tears, and cartilage defects were better delineated with this method than with unenhanced MR imaging and showed good correlation with arthroscopic results. CONCLUSION Indirect MR arthrography of an exercised joint provides homogeneous enhancement and improved delineation of soft-tissue structures.