Recovery of the posterior tibial muscle after late reconstruction following tendon rupture.

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.

Functional-morphologic MR imaging with ultrasmall superparamagnetic particles of iron oxide in acute and chronic soft-tissue infection: study in rats.

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.

MR imaging with ultrasmall superparamagnetic iron oxide particles in experimental soft-tissue infections in rats.

PURPOSE: To investigate the feasibility of macrophage magnetic resonance (MR) imaging in rats by using an experimental soft-tissue infection model. MATERIALS AND METHODS: Thirteen rats with unilateral calf-muscle infection were imaged with a 4.7-T MR imager at an early chronic stage of infection (day 4 before contrast material injection, days 4-7 after injection). Eleven animals were imaged before and 3 and 24 hours after intravenous application of ultrasmall superparamagnetic iron oxide (USPIO), and eight animals were additionally imaged 48 hours and three animals 72 hours after USPIO application. Two infected rats served as controls. T1- and T2-weighted spin-echo and T2*-weighted gradient-echo sequences were applied. All animals were sacrificed, and histopathologic findings were correlated with findings on MR images. Electron microscopy was performed in two rats. For quantitative analysis, signal intensities on T2*-weighted images and T2 values on T2 maps were measured within regions of interest, and the temporal variation was analyzed by using the signed rank test. RESULTS: Visualization of USPIO-loaded macrophages was most sensitive with a T2*-weighted sequence. USPIO distribution pattern and quantitative analysis of T2 and T2* effects 3 hours after USPIO application were significantly different (P <.05) from those at 24 and 48 hours, reflecting the dynamic transit of the particle accumulation from the intravascular to the intracellular compartment by means of macrophage phagocytosis. Local signal intensity alterations could be correlated with iron-loaded macrophages at histopathologic examination. CONCLUSION: Activated macrophages in acute soft-tissue infection can be labeled with USPIOs and detected with MR imaging because of susceptibility effects.

Perthes lesion (a variant of the Bankart lesion): MR imaging and MR arthrographic findings with surgical correlation.

OBJECTIVE: The aim of this study was to evaluate the use of MR imaging in the characterization of the Perthes lesion by correlating MR findings with findings at arthroscopy. CONCLUSION: The use of a combination of axial and abduction-external rotation position sequences on MR images can be helpful in the diagnosis of a Perthes lesion. A fluid-filled joint with capsular distension, caused by either a large amount of effusion or MR arthrography, was found to be helpful in outlining Perthes lesions. Adding the abduction-external rotation position to the protocol in patients in whom Perthes lesion is suspected will increase diagnostic accuracy and may reveal a Perthes lesion not visible on axial images, as was the case in 50% of the patients in our series.