The plantar fasciotomy: MR imaging findings in asymptomatic volunteers

Objective. To determine the postoperative appearance of the plantar fascia on MR imaging after a fasciotomy has been performed, and to compare the postsurgical appearance of the fascia after an open and endoscopic procedure.<@head-abs-p1.lf>Design and patients. Fifteen asymptomatic volunteers (12 women, 3 men; age range 22–49 years, mean age 33 years) with prior fasciotomies for treatment of longstanding plantar fasciitis were studied. Fourteen volunteers had a unilateral release and one volunteer had bilateral releases, allowing for assessment of 16 ankles. Eight fasciotomies were performed through an open incision and eight were performed endoscopically. The average time between surgery and imaging was 24 months (range 11–46 months). The site of surgery was established from the operative reports. Proton density (PD)-weighted and T2-weighted images in three orthogonal planes were obtained on a 1.5-T magnet. In eight studies, T1-weighted sagittal and STIR sagittal images were included. The fascia in each ankle was assessed for morphology and signal intensity. Perifascial soft tissues and bone marrow were assessed for edema. Preoperative MR studies were available in five volunteers.<@head-abs-p1.lf>Results. There was no apparent difference in the postoperative appearance of the ankle after an open or endoscopic procedure except for scar formation in the subcutaneous fat which was common after an open procedure (P<0.05). Three ankles had a gap in the fascia (one open, two endoscopic). The plantar fascia measured a mean of 7.0 mm (range 5–10 mm) at the fasciotomy, and 8.3 mm (range 6–12 mm) at the enthesis. At the fasciotomy, 11 of 13 ankles had an indistinct deep contour and 9 of 13 had an indistinct superficial contour. At the enthesis, 13 of 16 ankles had an indistinct deep contour and 6 of 16 had an indistinct superficial contour. Compared with preoperative MR studies there was an average reduction in the fascial thickness at the enthesis of 14% (range 9–20%), but the thickness at the fasciotomy nearly doubled. No edema was evident in the fascia, perifascial tissues, deep plantar muscles, or calcaneal bone marrow.<@head-abs-p1.lf>Conclusions. The average thickness of the plantar fascia in asymptomatic volunteers after surgery is nearly 2–3 times that of normal. While there is increased thickness at the site of surgery, the changes in morphology and signal intensity were most prominent at the enthesis. The key observation was absence of edema in the fascia and perifascial soft tissues. This baseline information may be of value when assessing MR studies of symptomatic patients. Received: 23 March 1999 Revision requested: 19 May 1999 Revision received: 4 June 1999 Accepted: 9 June 1999     

Heterogeneous signal in bone marrow on MRI of children’s feet: a normal finding?

Objective To describe the magnetic resonance (MR) appearances of the bone marrow of children’s feet and to determine their frequency and significance. Design and patients. A review of MR studies obtained in a retrospective series of 35 children with foot pain and in a prospective series of 19 asymptomatic children was performed. The MR appearances on T1-weighted, T2-weighted and STIR sequences were assessed and the frequency of patchy areas of low signal intenstiy on T1-weighted and high signal intenstiy on T2-weighted or STIR sequences was determined and correlated with clinical features. Results and conclusions. Low signal intenstiy on T1-weighted and high signal intenstiy on T2-weighted and STIR sequences were seen in 63% of symptomatic and 57% of asymptomatic children. In all cases where both feet were imaged, the changes were seen bilaterally. The marrow pattern varied from multiple discrete foci to more extensive confluent areas of high signal on the STIR sequence. These appearances are frequent and represent normal variation in the growing skeleton, and should not necessarily be interpreted as a sign of pathology. Received: 2 October 1998 Revision requested: 20 January 1999 Revision received: 18 February 1999 Accepted: 2 March 1999     

Anatomic variants associated with peroneal tendon disorders: MR imaging findings in volunteers with asymptomatic ankles

PURPOSE: To evaluate prospectively, on magnetic resonance (MR) images in volunteers with asymptomatic ankles, various features of anatomic variants that are potentially associated with peroneal tendon disorders. MATERIALS AND METHODS: The study had institutional review board approval; informed consent was obtained from each volunteer. The prevalence of accessory peroneus quartus muscles, the location of the muscle-tendon junction of the peroneus brevis muscle, the prevalence and size of the peroneal tubercle and the retrotrochlear eminence, and the shape of the retromalleolar fibular groove were evaluated on MR images in 65 volunteers with asymptomatic ankles (35 women, 30 men; age range, 23-70 years; median age, 45 years). MR images were analyzed by two radiologists in consensus. The relationship between anatomic features and age and sex was analyzed by using Spearman rank correlation and the Wilcoxon rank sum test. RESULTS: A peroneus quartus muscle was identified in 11 (17%) ankles. Ninety percent of the musculotendinous junctions of the peroneus brevis muscle were located in a range between 27 mm proximal to and 13 mm distal to the fibular tip (median, 0 mm). A peroneal tubercle was identified in 36 (55%) ankles. Ninety percent of all peroneal tubercles were 4.6 mm or smaller (median height, 2.9 mm). A retrotrochlear eminence was seen in all ankles (median, 3.0 mm; 90% were 4.6 mm or smaller). The retromalleolar groove was concave in 18 (28%), flat in 28 (43%), convex in 12 (18%), and irregular in seven (11%) volunteers. A significant difference (P = .04) for the height of the retrotrochlear eminence was found between men (median, 3.4 mm) and women (median, 2.5 mm). All other P values were greater than .05. CONCLUSION: Anatomic variants thought to predispose individuals to peroneal tendon disorders can be seen in volunteers with asymptomatic ankles.     

Intramedullary chondroid tumors of bone: correlation of abnormal peritumoral marrow and soft-tissue MRI signal with tumor type

 Objective. To determine whether enchondromas and chondrosarcomas can be differentiated on the basis of peritumoral MR signal abnormality. Design. STIR and T2-weighted MRI images were retrospectively assessed for the presence and extent of abnormal peritumoral marrow and soft-tissue signal. The cause of the peritumoral signal abnormality was determined by histologic correlation with resection specimens. The presence or absence of bone destruction was noted. Patients. Twenty-three patients were studied: ten with enchondromas (three men, seven women; ages 33–73 years) and 13 with chondrosarcomas (seven men, six women; ages 25–88 years). Results. Abnormal peritumoral marrow signal was present on STIR images around none of 10 enchondromas and all of 13 chondrosarcomas (P<0.0001). The marrow signal abnormality corresponded histologically to fine marrow fibrosis in all cases. Adjacent abnormal soft-tissue signal was present on STIR images around none of ten enchondromas and eight (62%) of 13 chondrosarcomas (P=0.0026). Abnormal soft-tissue signal was more common around high-grade than low-grade chondrosarcomas (100% vs 38%, P=0.028), and was more extensive (mean extent 28 mm vs 8 mm; P>0.04). In the subset of tumors without bone destruction, peritumoral marrow signal abnormality was present around none of ten enchondromas and all of five chondrosarcomas (P=0.0003); abnormal soft-tissue signal was present around none of ten enchondromas and two of five chondrosarcomas (P>0.05). Conclusion. Abnormal marrow or soft-tissue signal around a chondroid tumor is suggestive of chondrosarcoma, even in the absence of bone destruction. STIR images are necessary for adequate detection of peritumoral signal abnormalities.     

Spring ligament complex: MR imaging-anatomic correlation and findings in asymptomatic subjects

PURPOSE: To use magnetic resonance (MR) imaging to assess the anatomy of the spring ligament complex (SLC) in cadaveric feet and to prospectively evaluate the MR imaging depiction of this complex in asymptomatic subjects. MATERIALS AND METHODS: Cadaveric feet were obtained and used according to institutional guidelines and with institutional approval and consent from the donors (before death) or the appropriate family members. Healthy volunteers were examined, with institutional review board approval and informed consent from each volunteer. MR imaging findings of the SLC in five cadaveric feet were analyzed and correlated with the findings in dissected foot specimens. Then, the MR imaging findings in the feet of 78 asymptomatic subjects were analyzed. For all three parts of the SLC, visibility, optimal imaging plane, and signal intensity characteristics were analyzed. The thicknesses of all SLC parts were measured. The measurements obtained in men and women were compared by using the Mann-Whitney U test, and Pearson correlation coefficients for associations between ligament thickness and subject age and sex were calculated. RESULTS: In the cadaveric feet, MR imaging enabled differentiation of all three parts of the SLC. The superomedial calcaneonavicular ligament (CNL) was visible in all; the medioplantar oblique CNL, in 60; and the inferoplantar longitudinal CNL, in 71 volunteers. The superomedial CNL had a mean thickness of 3.2 mm, was best seen on transverse oblique or coronal MR images, and had mainly intermediate signal intensity on T1-weighted images and low signal intensity on T2-weighted images. The medioplantar oblique CNL had a mean thickness of 2.8 mm, was best seen on transverse oblique MR images, and had mainly a typical striated appearance on T1- and T2-weighted images. The inferoplantar longitudinal CNL was the thickest (mean thickness, 4.0 mm), was best seen on coronal MR images, and had mainly intermediate signal intensity on T1-weighted images and variable signal intensity on T2-weighted images. Women had significantly thinner superomedial (mean thickness, 3.3 vs 3.5 mm; P = .015, Mann-Whitney U test) and inferoplantar longitudinal (mean thickness, 3.8 vs 4.2 mm; P = .02) CNLs than men. There was no significant correlation between ligament thickness and subject age. CONCLUSION: The superomedial and inferoplantar longitudinal CNLs are consistently visible portions of the SLC. The medioplantar oblique ligament is thinner, is seen less consistently, and has mainly a characteristic striated MR imaging appearance.     

Ferumoxtran-10-enhanced MR imaging of the bone marrow before and after conditioning therapy in patients with non-Hodgkin lymphomas

To quantify permeability changes of the “blood–bone marrow barrier” (BMB) and to detect malignant bone marrow infiltrations before and after conditioning therapy for subsequent leukapheresis using ferumoxtran-10-enhanced magnetic resonance (MR) imaging. Twenty-two patients with malignant non-Hodgkin lymphomas (NHL), including 9 patients (group A) before and 13 patients (group B) after conditioning therapy, underwent MR of the spine before and after infusion of ferumoxtran-10 (0.045 mmol Fe/kg BW). Pulse sequences comprised dynamic T1-GE and pre- and post-contrast T1-SE and STIR sequences. Dynamic ΔSI-data were correlated with the quantity of mobilized CD34+ cells. In addition, the number of focal bone marrow lesions was compared before and after ferumoxtran-10 administration. Dynamic ΔSI-data were higher in group B than in group A, indicating an increased BMB permeability after conditioning therapy. However, ΔSI-data did not correlate with the quantity of mobilized CD34+ cells. Ferumoxtran-10-enhanced STIR images demonstrated a significant signal decline of the normal, non-neoplastic bone marrow and a significantly increased detection of focal neoplastic lesions compared to pre-contrast images (P<0.05). Ferumoxtran-10 depicted the bone marrow response to conditioning therapy by an increase in BMB-permeability, which, however, did not correlate with the number of mobilized CD34+ cells. Ferumoxtran-10 improved the detection of focal bone marrow lesions significantly (P<0.05).     

USPIO-enhanced magnetic resonance imaging of the knee in asymptomatic volunteers

The aim of this study was to compare signal characteristics of the synovium in knees of asymptomatic volunteers before and after intravenous administration of ultrasmall superparamagnetic iron oxide particles (USPIO). Ten knees of 10 asymptomatic volunteers were examined before and 36 h after intravenous administration of USPIO on a 1.5-T MR system using T1-weighted spin-echo, T2-weighted fast spin-echo, T2*-weighted gradient-echo (GRE), and short inversion time inversion-recovery sequences. In addition, synovial perfusion was measured using Gd-enhanced GRE imaging during the first imaging session. Images were analyzed qualitatively for any visual changes before and after USPIO administration. Signal-to-noise ratios (SNR) of the synovium were determined on unenhanced and USPIO-enhanced sequences. All MR images were reviewed for presence of any degenerative changes. Qualitative image analysis revealed no visually detectable changes of any knee joint before and after USPIO administration. The SNR values of the synovium on T1w, T2w, and T2*w images before and after USPIO administration showed no significant difference (T1, P = 0.86; T2, P = 0.95; T2*, P = 0.86). None of the volunteers showed any relevant degenerative changes of the knee and synovial perfusion was within normal limits. In knees of asymptomatic volunteers without any relevant degenerative changes and normal synovial perfusion neither visual changes nor changes of SNR values of the synovium can be depicted after USPIO administration. This means that USPIO-enhanced MRI may be used for assessment of knee disorders with increased macrophage activity.     

Chronic medial knee pain without history of prior trauma: correlation of pain at rest and during exercise using bone scintigraphy and MR imaging

Objective  The objective of this study was to correlate chronic medial knee pain at rest and during exercise with bone scintigraphic uptake, bone marrow edema pattern (BMEP), cartilage lesions, meniscal tears, and collateral ligament pathologies on magnetic resonance MR imaging (MRI). Materials and methods  Fifty consecutive patients with chronic medial knee pain seen at our institute were included in our study. Pain level at rest and during exercise was assessed using a visual analog scale (VAS). On MR images, BMEP volume was measured, and the integrity of femoro-tibial cartilage, medial meniscus, and medial collateral ligament (MCL) were assessed. Semiquantitative scintigraphic tracer uptake was measured. Multivariate linear regression analysis was performed. Results  At the day of examination, 40 patients reported medial knee pain at rest, 49 when climbing stairs (at rest mean VAS 33 mm, range 0–80 mm; climbing stairs mean VAS, 60 mm, range 20–100 mm). Bone scintigraphy showed increased tracer uptake in 36 patients (uptake factor, average 3.7, range 2.4–18.0). MRI showed BMEP in 31 studies (mean volume, 4,070 mm³; range, 1,200–39,200 mm³). All patients with BMEP had abnormal bone scintigraphy. Ten percent of patients with pain at rest and 8% of patients with pain during exercise showed no BMEP but tracer uptake in scintigraphy. Tracer uptake and signal change around MCL predicted pain at rest significantly (tracer uptake p = 0.004; MCL signal changes p = 0.002). Only MCL signal changes predicted pain during exercise significantly (p = 0.001). Conclusion  In chronic medial knee pain, increased tracer uptake in bone scintigraphy is more sensitive for medial knee pain than BMEP on MRI. Pain levels at rest and during exercise correlate with signal changes in and around the MCL.     

Iron-oxide-enhanced MR imaging of bone marrow in patients with non-Hodgkin's lymphoma: differentiation between tumor infiltration and hypercellular bone marrow

The aim of this study was to differentiate normal, hypercellular, and neoplastic bone marrow based on its MR enhancement after intravenous administration of superparamagnetic iron oxides in patients with cancer of the hematopoietic system. Eighteen patients with cancer of the hematopoietic system underwent MRI of the spine before and after infusion of ferumoxides ( n=9) and ferumoxtran ( n=9) using T1- and T2-weighted turbo spin-echo (TSE) and short tau inversion recovery sequences (STIR). In all patients diffuse or multifocal bone marrow infiltration was suspected, based on iliac crest biopsy and imaging such as conventional radiographs, MRI, and positron emission tomography. In addition, all patients had a therapy-induced normocellular ( n=7) or hypercellular ( n=11) reconversion of the normal non-neoplastic bone marrow. The MRI data were analyzed by measuring pre- and post-contrast signal intensities (SI) of hematopoietic and neoplastic marrow and by calculating the enhancement as deltaSI(%) data and the tumor-to-bone-marrow contrast as contrast-to-noise ratios (CNR). Changes in bone marrow signal intensity after iron oxide administration were more pronounced on STIR images as compared with T1- and T2-weighted TSE images. The STIR images showed a strong signal decline of normal and hypercellular marrow 45-60 min after iron oxide infusion, but no or only a minor signal decline of neoplastic bone marrow lesions; thus, deltaSI% data were significantly higher in normal and hypercellular reconverted marrow compared with neoplastic bone marrow lesions ( p<0.05). Additionally, the contrast between focal or multifocal neoplastic bone marrow infiltration and normal bone marrow, quantified by CNR data, increased significantly on post-contrast STIR images compared with precontrast images ( p<0.05). Superparamagnetic iron oxides are taken up by normal and hypercellular reconverted bone marrow, but not by neoplastic bone marrow lesions, thereby providing significantly different enhancement patterns on T2-weighted MR images; thus, superparamagnetic iron oxides are useful to differentiate normal and neoplastic bone marrow and to increase the bone marrow-to-tumor contrast.     

MR imaging of epicondylitis

Objective. To systematically evaluate the MR findings in patients with epicondylitis compared with asymptomatic volunteers. Design and patients. We imaged 43 elbows: 24 with epicondylitis (22 lateral, 2 medial) diagnosed by clinical examination, and 19 in 16 normal volunteers. MRI was performed at 1.5 T using axial T1-weighted, axial fat-saturated FSE, and coronal or sagittal Fast STIR sequences. Two independent observers evaluated the images for intratendon signal, tendon thickening, periosteal reaction, fluid in the radial head bursa, and anconeus edema. Results. All 24 patients with epicondylitis had increased signal on fat-saturated FSE and Fast STIR images. Twenty-two of these patients had increased intratendon T1 signal, and 19 had tendon thickening. No patient demonstrated fluid in the radial head bursa or periosteal reaction. Only two patients had subtle anconeus edema, while three patients unexpectedly had increased T2 signal within the involved epicondyle. One asymptomatic volunteer (high-performance athlete) had increased T1 and T2 signal with tendon thickening. An additional two asymptomatic volunteers had increased T1 signal only. Conclusion. MRI of epicondylitis demonstrates tendon thickening with increased T1 and T2 signal, but these findings may be seen in a small minority of asymptomatic individuals. Anconeus edema, previously demonstrated on MRI in epicondylitis, was only rarely found, and distension of the radial head bursa, surgically described, was not seen. Increased marrow T2 signal within the involved epicondyle is occasionally seen.     

Bone bruises: MR characteristics and histological correlation in the young pig

PURPOSE: To correlate magnetic resonance (MR) signal characteristics of bone bruises with histological findings. MATERIALS AND METHODS: In 14 tibiae of young pigs, bone bruises were created in the proximal tibial metaphysis. The signal intensity seen on the MR images were correlated with histological findings. The following findings were evaluated: (a) changes of signal intensity on the tibiae; (b) changes of histology on the tibiae; and (c) changes of (a) and (b) on follow-up examinations. RESULTS: We observed three types of injuries on T1-weighted images: focal or diffuse low signal, normal signal and linear low signal intensities. Severe hemorrhagic areas showed low signal intensities on all sequences of MR imaging. Fast spin-echo (FSE) T2-weighted images showed a more distinct low signal intensity than T1-weighted images. FSE short tau inversion recovery (STIR) and FSE fat saturated (FSE-FS) T2-weighted images showed similar signal intensities with FSE T2-weighted images. FS T1-weighted enhanced images showed low signal intensities with variable enhancements. Upon histological examination, hemorrhages and edemas were prominent at the subcortical areas of the contusion sites. The areas of dense, low signal intensities in all imaging sequences showed signs of severe hemorrhage. The areas of diffuse low signal and enhanced areas showed mixed areas of hemorrhages and edemas. Follow-up MR imaging showed evolution of the processes of hemorrhages and edemas with fatty marrow changes. CONCLUSIONS: MR imaging can depict changes in the bone marrow resulting from direct injury to the bone. MR imaging is a useful tool for evaluating the evolution of bone bruises.     

MR signal intensity characteristics in Legg-Calvé-Perthes disease. Value of fat-suppressed (STIR) images and contrast-enhanced T1-weighted images

PURPOSE: To evaluate the MR signal intensity characteristics in Legg-Calvé-Perthes disease on fat-suppressed (STIR) images and contrast-enhanced T1-weighted spin-echo images, and to develop criteria for the administration of contrast material. MATERIAL AND METHODS: Twenty children with Legg-Calvé-Perthes disease underwent conventional radiography and MR imaging of the hip utilizing fat-suppressed (STIR) sequences and T1-weighted spin-echo sequences before and after i.v. contrast administration. The signal intensity characteristics of the femoral head and the proximal femoral metaphysis were assessed retrospectively by two pediatric radiologists. RESULTS: Evaluation of the MR images revealed six different signal patterns within the femoral head: 1) isointense signal on all images; 2) complete signal void on all images; 3) hyperintense signal on STIR images with; or 4) without contrast enhancement on T1-weighted spin-echo images; 5) isointense signal on STIR images with; or 6) without contrast enhancement on T1-weighted images. Within the metaphysis three different signal patterns were differentiated. CONCLUSION: Combination of fat-suppressed (STIR) sequences and T1-weighted pre- and post-contrast sequences allows an accurate evaluation of Legg-Calvé-Perthes disease. In patients without signal alterations or complete signal loss on fat-suppressed and T1-weighted spin-echo images, administration of i.v. contrast is not necessary. In case of bone marrow edema on fat-supressed images, contrast-enhanced T1-weighted images are required to identify viable osseous fragments.     

Can bone marrow edema be seen on STIR images of the ankle and foot after 1 week of running?

PURPOSE: To evaluate whether initiation of running in sedentary individuals would lead to bone marrow edema on MR images, within the time span of 1 week. MATERIALS AND METHODS: The feet of 10 healthy volunteers were imaged by MR imaging before and after running during 30 min a day for 1 week. The images were evaluated by consensus of 2 musculoskeletal radiologists who graded the presence of bone marrow edema on a 4-point scale. Edema scores and number of bones involved before and after running were compared statistically. RESULTS: Edema was present on the baseline images in 3 subjects. After running edema showed an increase or was present in 5 subjects. The changes after running were statistically significant. Bones involved were the talus, calcaneus, navicular bone, cuboid bone, and 5th metatarsal. CONCLUSION: Edema patterns can be seen in the feet of asymptomatic individuals. During initiation of running an increase of edema or development of new edema areas can be seen.     

MR imaging of the Achilles tendon: overlap of findings in symptomatic and asymptomatic individuals

Objective: To differentiate MR imaging characteristics of symptomatic as compared with asymptomatic Achilles tendons. Design: 1.5 T MR images of 94 feet (88 patients) with ”abnormal” MR examinations were retrospectively evaluated and clinically correlated. Two masked, independent observers systematically evaluated for intratendon T2 signal, tendon thickness, presence of peritendonitis, retrocalcaneal bursal fluid volume, pre-Achilles edema, bone marrow edema at the Achilles insertion, and tears (interstitial, partial, complete). These findings were correlated with symptoms (onset and duration) and physical examination results (tenderness, palpable defects, increased angle of resting dorsiflexion). Results: Of the 94 ankles, 64 ankles (32 females, 29 males) were clinically symptomatic. No relationship between Achilles tendon disorders and age or gender was identified. Asymptomatic Achilles tendons frequently demonstrated mild increased intratendon signal (21/30), 0.747 cm average tendon thickness, peritendonitis (11/30), pre-Achilles edema (12/30), and 0.104 ml average retrocalcaneal bursal fluid volume. Symptomatic patients had thicker tendons (0.877 cm), greater retrocalcaneal fluid volume (0.278 ml), more frequent tears (23/64), a similar frequency of peritendonitis (22/64) but less frequent pre-Achilles edema (18/64). Sixty-four percent of the Achilles tendon tears were interstitial. Except for two interstitial tears in control patients, the majority of Achilles tears were in symptomatic patients (14/16). Only symptomatic tendons demonstrated partial or complete tendon tears. In addition, calcaneal edema was found almost exclusively in actively symptomatic patients. Thicker tendons were associated more often with chronic symptoms and with tears. When present in symptomatic patients, peritendonitis was usually associated with acute symptoms. The presence of pre-Achilles edema, however, did not distinguish acute from chronic disorders. Conclusion: There is significant overlap of MR findings in symptomatic and asymptomatic Achilles tendons. Furthermore, there is apparently a spectrum of disease in symptomatic tendons ranging from subtle intratendinous and peritendinous signal to partial and complete tendon tear. Received: 17 March 2000 Revision requested: 26 May 2000 Revision received: 19 July 2000 Accepted: 19 July 2000     

MR imaging of the forefoot under weight-bearing conditions: position-related changes of the neurovascular bundles and the metatarsal heads in asymptomatic volunteers

PURPOSE: To assess practicability of weight-bearing magnetic resonance (MR) imaging of the forefoot, and to demonstrate position-related changes of the neurovascular bundles and the metatarsal heads in asymptomatic volunteers. MATERIALS AND METHODS: With an open-configuration MR system, 32 feet of 32 asymptomatic individuals aged 20-60 years were studied in supine and weight-bearing body positions. Transverse T1-weighted spin-echo MR images were performed. MR images were evaluated qualitatively with regard to image quality, visibility, and position-dependent changes of the neurovascular bundle. In addition, the position of the metatarsal heads was analyzed quantitatively. RESULTS: Weight-bearing MR imaging was feasible in all 32 feet. Quality of MR images obtained in the weight-bearing position was superior to that obtained in the supine position (P < 0.05). A change in the position of the neurovascular bundle from below a virtual line paralleling the plantar cortical line to above this line was present in 50 of 61 instances (82%) between the supine and the weight-bearing positions. When changing from the supine to the weight-bearing position, there was a significant decrease in the distance between the plantar skin and the metatarsal heads for the second (mean 4.5 mm), third (mean 4.4 mm), and fourth metatarsal heads (mean 3.7 mm) (P < 0.0001). However, the difference for the first (mean 0.5 mm) and fifth (mean 0.9 mm) metatarsal heads was not significant. CONCLUSION: Weight-bearing MR imaging of the forefoot is feasible using an open-configuration MR system and demonstrates position-related changes of the neurovascular bundles relative to the metatarsal heads, as well as position-related changes of the metatarsal heads themselves.     

Plantar fasciitis: MR imaging

The clinical presentation of plantar fasciitis may be mimicked by a number of other painful heel conditions. Thus, magnetic resonance (MR) imaging was used to develop objective morphologic criteria to establish a diagnosis of plantar fasciitis in eight patients. Sagittal T1-weighted and coronal intermediate and T2-weighted images of symptomatic and asymptomatic feet were obtained; additional sequences were used for symptomatic feet. Maximum thickness of the plantar fascia was significantly increased (P less than .0001) in patients with plantar fasciitis (sagittal, 7.40 mm +/- 1.17, and coronal, 7.56 mm +/- 1.01) compared with age- and sex-matched volunteers (sagittal, 3.22 mm +/- 0.44, and coronal, 3.44 mm +/- 0.53) and young male controls (sagittal, 3.00 mm +/- 0.8, and coronal, 3.00 mm +/- 0.0). Furthermore, nine of 10 feet with plantar fasciitis had areas of moderately increased signal intensity in the substance of the fascia. MR imaging may provide an objective assessment of the morphologic changes associated with plantar fasciitis, as well as assist in excluding other causes of heel pain.     

Fluid-fluid levels in bone neoplasms: variation of T1-weighted signal intensity of the superior to inferior layers—diagnostic significance on magnetic resonance imaging

The diagnostic relevance of the relative T1-weighted (T1W) and T2-weighted (T2W)/short tau inversion recovery (STIR) MRI signal intensity characteristics of the superior to inferior fluid layers within fluid-fluid levels (FFLs) found in bone tumours was investigated. A retrospective analysis was performed of MRI studies of 2,568 patients presenting with a suspected bone tumour over an 8-year period. Final diagnosis was made by biopsy/surgical resection or characteristic imaging/clinical findings. Subjects were divided by the absence/presence of FFLs and benign/malignant histology. Cases with FFLs were sub-categorised by the relative signal intensity of the superior/inferior layer as high/low or low/high on T1W and T2W/STIR sequences. Out of the total of 2,568 cases, 214 (8.3%, CI 7.3–9.5%) had FFLs and 2,354 (91.7%, CI 90.5–92.7%) had no FFLs. All 214 cases with FFLs had T2W/STIR sequences available, all demonstrating high/low signal intensity characteristics; 135/214 (63.1%, CI 56.2–69.6%) were benign and 79/214 (36.9%, CI 30.4–43.8%) were malignant. Out of the 214 patients, 151 had T1W sequences performed; 52 showed high/low signal intensity, of which 30 (57.7%, CI 34.2–71.3%) were benign and 22 (42.3%, CI 28.7–56.8%) were malignant (P = 0.06 compared with no FFL group); 50 showed low/high signal intensity, of which 40 (80%, CI 66.3–90.0%) were benign and ten (20%, CI 10.0–33.7%) were malignant (P = 0.0000, compared with the no FFL group). The low/high and high/low groups had a significantly greater proportion of benign and malignant lesions, respectively (P = 0.015). In conclusion, all FFLs showed high/low signal intensity characteristics on T2W/STIR sequences. Low/high signal on T1W was significantly associated with benign disease. Malignancy may occur slightly more frequently with high/low signal on T1W.     

Early and late bone-marrow changes after irradiation: MR evaluation

Knowledge of the chronologic evolution of bone-marrow changes during and after radiation therapy is essential in differentiating normal postradiation changes from other marrow abnormalities. The appearance of the lumbar vertebral bone marrow was studied on 55 serial spin-echo and short-T1 inversion-recovery (STIR) MR images obtained in 14 patients receiving radiation therapy for Hodgkin disease, seminoma, or prostate carcinoma. Images were obtained before, at weekly intervals during, and at various monthly intervals up to 14 months after a 3- to 6-week course of fractionated paravertebral lymph-node irradiation of 1500-5000 rad (15-50 Gy). During the first 2 weeks of therapy, there was no definite change in the appearance of the marrow on spin-echo images; however, there was an increase in signal intensity on the STIR images, apparently reflecting early marrow edema and necrosis. Between weeks 3 and 6, the marrow showed an increasingly heterogenous signal and prominence of the signal from central marrow fat, shown best on T1-weighted images. Late marrow patterns (6 weeks to 14 months after therapy) varied and consisted of either homogenous fatty replacement or a band pattern of peripheral intermediate signal intensity, possibly representing hematopoietic marrow surrounding the central marrow fat. No focal marrow lesions or soft-tissue edema were identified during the course of radiation therapy; their presence should raise the possibility of the presence of a pathologic process other than radiation change. These data suggest that MR can detect radiation-induced marrow changes as early as 2 weeks after starting therapy, and that there are at least two distinct types of late marrow MR patterns.     

Low-field-strength MR imaging of failed hip arthroplasty: association of femoral periprosthetic signal intensity with radiographic, surgical, and pathologic findings

PURPOSE: To investigate the association between periprosthetic signal intensity at low-field-strength magnetic resonance (MR) imaging after failed hip arthroplasty and radiographic, surgical, and pathologic findings. MATERIALS AND METHODS: The study group comprised 22 consecutive women who underwent hip arthroplasty (mean age, 62 years; age range, 35-74 years). All patients underwent MR imaging prior to revision surgery. Coronal fast short inversion time inversion-recovery (STIR) images and spin-echo T1-weighted images were obtained with a 0.5-T MR imaging unit before and after administration of contrast material. The periprosthetic region was divided into the seven femoral Gruen zones. Two observers retrospectively analyzed signal intensity patterns. Association of signal intensity patterns with radiographic, surgical, and pathologic findings was determined with chi2 analysis and generalized estimating equations. RESULTS: Diagnostic-quality images were obtained for 150 zones. Periprosthetic signal intensity was greater than that of bone marrow in the distal femur on the fast STIR images, and no contrast enhancement was seen on the T1-weighted images (type I signal intensity pattern) in 11 zones. Signal intensity was greater than that of bone marrow on the fast STIR images, and contrast enhancement was seen on the T1-weighted images (type II signal intensity pattern) in 45 zones. Signal intensity was less than or equal to that of bone marrow on the fast STIR images, and no contrast enhancement was seen on the T1-weighted images (type III signal intensity pattern) in 94 zones. Type I and II patterns were associated with focal or nonfocal lucency, an unstable stem, and fibrosis or granuloma. A type III pattern was associated with a normal radiographic appearance, a stable stem, and normal bone tissue. Significant association was demonstrated between periprosthetic signal intensity and radiographic (P <.001, chi2 test and generalized estimating equations), surgical (P <.05, Mantel-Haenszel chi2 test and generalized estimating equations), and pathologic findings (P <.05, chi2 test). CONCLUSION: Low-field-strength MR imaging depicted periprosthetic tissue signal intensity that was significantly associated with radiographic, surgical, and pathologic findings.     

Idiopathic bone marrow edema lesions of the femoral head: predictive value of MR imaging findings.

PURPOSE: To determine the frequency of several subchondral magnetic resonance (MR) imaging features observed in bone marrow edema lesions of the femoral head and to determine their value for differentiation of irreversible from transient lesions. MATERIALS AND METHODS: The authors reviewed MR images of 72 femoral head lesions in 42 men and 25 women (median age, 48 years) with equivocal radiographic findings and bone marrow edema seen at MR imaging (T1- and T2-weighted images in all patients and contrast material-enhanced T1-weighted images in 39 patients). Follow-up MR images showed 57 lesions to be transient and 15 to be irreversible. The presence and size of subtle subchondral features observed on initial MR images were compared for both types of lesion. RESULTS: Lack of any additional subchondral change on T2-weighted or contrast-enhanced T1-weighted images had 100% positive predictive value for transient lesions. For irreversible lesions, presence of a subchondral area of low signal intensity at least 4 mm thick or 12.5 mm long had positive predictive values of 85% and 73%, respectively, on T2-weighted images and 87% and 86%, respectively, on contrast-enhanced T1-weighted images. CONCLUSION: Careful assessment of subchondral changes enables confident differentiation between early irreversible lesions and transient bone marrow edema lesions.