MR imaging of inflammatory joint diseases of the foot and ankle

Postoperative Ankle Imaging, 2022

Postoperative ankle imaging requires knowledge of the underlying surgical techniques, the usefulness of various imaging modalities, as well as an appreciation for the desired clinical outcomes. Surgical procedures discussed in this article are tibiotalar fracture fixation, tibiotalar, subtalar, and tibiotalocalcaneal arthrodesis, total ankle arthroplasty, talar osteochondral lesion repair and grafting, lateral ligamentous repair and reconstruction, and peroneal and Achilles tendon repair and reconstruction. Imaging can play a vital role in determining if the expected outcome has been achieved and identifying complications, with particular emphasis placed on the use of radiographs, computed tomography (including weight-bearing), magnetic resonance imaging, and ultrasonography.

[Degenerative forefoot : Diagnostics and treatment]

The hallux valgus deformity is the most common toe deformity of the forefoot and is often associated with a splayfoot. Malpositioning of the small toes may be isolated but are more common in other foot deformities. The understanding of the complex pathoanatomy of the foot is necessary for orthopedic treatment. Conservative treatment is reserved for the early stages. The indications for surgery should be based on clinical and radiographic findings. Countless surgical procedures are available and minimally invasive surgical techniques are also increasingly being used.

Medical Imaging in Differentiating the Diabetic Charcot Foot from Osteomyelitis

Diabetic Charcot neuroarthropathy (DCN) poses a great challenge to diagnose in the early stages and when plain radiographs do not depict any initial signs of osseous fragmentation or dislocation in a setting of a high clinical index of suspicion. Medical imaging, including magnetic resonance imaging, computed tomography, and advanced bone scintigraphy, has its own unique clinical indications when treating the DCN with or without concomitant osteomyelitis. This article reviews different clinical case scenarios for choosing the most accurate medical imaging in differentiating DCN from osteomyelitis.

Lumbar facet joint motion in patients with degenerative spondylolisthesis

STUDY DESIGN

Controlled laboratory study.

OBJECTIVE

To investigate the in vivo biomechanical effect of degenerative lumbar spondylolisthesis (DLS) on the motion of the facet joint during various functional weight-bearing activities.

SUMMARY OF BACKGROUND DATA

Although the morphologic changes of the facet joints in patients with DLS have been reported in a few studies, no data have been reported on the kinematics of these facet joints.

METHODS

Ten patients with DLS at L4-L5 were studied. Each patient underwent a magnetic resonance imaging scan to obtain 3-dimensional models of the lumbar vertebrae from L2-L5 and a dual fluoroscopic imaging scan in different postures: flexion-extension, left-right bending, and left-right torsion. The positions of the vertebrae were reproduced by matching the magnetic resonance imaging-based vertebral models to the fluoroscopic images. The kinematics of the facet joint and the ranges of motion were compared with those of healthy subjects and those of patients with degenerative disk diseases (DDD) previously published.

RESULTS

In DLS patients, the range of rotation of the facet joints was significantly less at the DLS level (L4-L5) than that at the adjacent levels (L2-L3 and L3-L4), whereas the range of translation was similar at all levels. The range of rotation at the facet joints of the DLS level decreased compared with those of both the DDD patients and healthy subjects at the corresponding vertebral level (L4-L5), whereas no significant difference was found in the range of translation. The range of motion of facet joints in DLS and in DDD patients was similar at the adjacent levels (L2-L3 and L3-L4).

CONCLUSIONS

The range of rotation decreased at the facet joints at the DLS level (L4-L5) in patients compared with those in healthy subjects and DDD patients. This decrease in range of rotation implies that the DLS disease may cause restabilization of the joint. The data may help the selection of conservative treatment or different surgical techniques for the DLS patients.

Adjacent tissue involvement of acute inflammatory ankle arthritis on magnetic resonance imaging findings

PURPOSE

The ankle joint and surrounding subtalar joint have several tendons in close proximity. This study was performed to investigate the concurrent adjacent tissue involvement on MRI findings when the surgical treatment is considered for an acute inflammatory arthritis of the ankle joint.

METHODS

Consecutive patients with acute inflammatory ankle arthritis who visited the emergency room and underwent MRI were included. After interobserver reliability testing of MRI findings, adjacent tissue involvement in the acute inflammatory ankle arthritis were evaluated including flexor hallucis longus (FHL), flexor digitorum longus (FDL), tibialis posterior (TP), peroneus longus (PL), peroneus brevis (PB), extensor digitorum longus (EDL), tibialis anterior (Tib Ant), extensor hallucis longus (EHL), subtalar joint, talus, tibia, and calcaneus.

RESULTS

Twenty-five patients (mean age 57.8 years; 16 males and nine females) were included. Of the 25 patients, 23 showed FHL involvement, 21 FDL, 21 TP, 15 PL, 15 PB, three EDL, 21 subtalar joint, six talus, six tibia, and five calcaneus on MR images. No Tib Ant or EHL involvement was observed on MR findings in acute inflammatory ankle arthritis.

CONCLUSIONS

Patients with acute inflammatory ankle arthritis showed frequent concomitant surrounding tissue involvement on MRI, which included FHL, FDL, TP, and subtalar joint. This needs to be considered when surgical drainage is planned for acute inflammatory ankle arthritis.

Bone marrow edema patterns in the ankle and hindfoot: distinguishing MRI features

OBJECTIVE

Many disorders produce similar or overlapping patterns of bone marrow edema in the ankle. Bone marrow edema may present in a few hindfoot bones simultaneously or in a single bone. The purpose of this pictorial essay is to provide guidelines based on clinical history and specific MRI patterns and locations to accurately identify the cause of ankle bone marrow edema. We will first focus on bone marrow edema in general disease categories involving multiple bones, such as reactive processes, trauma, neuroarthropathy, and arthritides. A discussion of bone marrow edema in individual bones of the ankle and hindfoot including the tibia, fibula, talus, and calcaneus will follow. Helpful hints for arriving at the correct diagnosis will be provided in each section.

CONCLUSION

After review of this article, radiologists should be able to use their knowledge of clinical history and specific MRI patterns and locations to accurately distinguish between the various causes of bone marrow edema in the ankle and hindfoot.

Pigmented villonodular synovitis of the ankle: radiologic characteristics

BACKGROUND

Pigmented villonodular synovitis (PVNS) of the ankle is a rare benign proliferative growth of the synovium. Studies of the radiologic characteristics of ankle PVNS are sparse.

METHODS

To characterize the radiologic features of ankle PVNS, five patients with histologically proven ankle PVNS were retrospectively studied. The features of their radiographs, computed tomographic scans, and magnetic resonance images were reviewed, with emphasis on the morphological features, extension, margin, bone involvement, signal intensity, and degree of magnetic resonance enhancement.

RESULTS

All five lesions were diffuse, affecting the ankle and distal tibiofibular joint; three lesions also involved the subtalar joint. Radiography demonstrated extrinsic bone erosions with marginal sclerosis of the involved joints in all of the patients, but computed tomography identified this much better than did radiography. Magnetic resonance imaging revealed multiple lobulated soft-tissue masses in all of the cases. These soft-tissue masses surrounded the flexor hallux longus tendon and were hypointense on T1-weighted images, with a heterogeneous signal in two cases and homogenous hypointensity in three cases on fat-suppressed T2-weighted images. In one patient who underwent gadolinium-enhanced imaging, the masses showed intense enhancement.

CONCLUSIONS

Magnetic resonance imaging is the best way to reveal ankle PVNS. Magnetic resonance imaging findings of predominant hypointensity on all pulse sequences and standard radiography findings of bone erosion with marginal sclerosis are characteristic.

Lumbar facet joint motion in patients with degenerative disc disease at affected and adjacent levels: an in vivo biomechanical study

STUDY DESIGN

Controlled laboratory study.

OBJECTIVE

To evaluate the effect of lumbar degenerative disc diseases (DDDs) on motion of the facet joints during functional weight-bearing activities.

SUMMARY OF BACKGROUND DATA

It has been suggested that DDD adversely affects the biomechanical behavior of the facet joints. Altered facet joint motion, in turn, has been thought to associate with various types of lumbar spine pathology including facet degeneration, neural impingement, and DDD progression. However, to date, no data have been reported on the motion patterns of the lumbar facet joint in DDD patients.

METHODS

Ten symptomatic patients of DDD at L4-S1 were studied. Each participant underwent magnetic resonance images to obtain three-dimensional models of the lumbar vertebrae (L2-S1) and dual fluoroscopic imaging during three characteristic trunk motions: left-right torsion, left-right bending, and flexion-extension. In vivo positions of the vertebrae were reproduced by matching the three-dimensional models of the vertebrae to their outlines on the fluoroscopic images. The kinematics of the facet joints and the ranges of motion (ROMs) were compared with a group of healthy participants reported in a previous study.

RESULTS

In facet joints of the DDD patients, there was no predominant axis of rotation and no difference in ROMs was found between the different levels. During left-right torsion, the ROMs were similar between the DDD patients and the healthy participants. During left-right bending, the rotation around mediolateral axis at L4-L5, in the DDD patients, was significantly larger than that of the healthy participants. During flexion-extension, the rotations around anterioposterior axis at L4-L5 and around craniocaudal axis at the adjacent level (L3-L4), in the DDD patients, were also significantly larger, whereas the rotation around mediolateral axis at both L2-L3 and L3-L4 levels in the DDD patients were significantly smaller than those of the healthy participants.

CONCLUSION

DDD alters the ROMs of the facet joints. The rotations can increase significantly not only at the DDD levels but also at their adjacent levels when compared to those of the healthy participants. The increase in rotations did not occur around the primary rotation axis of the torso motion but around the coupled axes. This hypermobility in coupled rotations might imply a biomechanical mechanism related to DDD.

MRI findings of juvenile psoriatic arthritis

OBJECTIVE

The aim of this study was to describe the magnetic resonance imaging (MRI) features of juvenile psoriatic arthritis (JpsA) in children in order to facilitate early diagnosis and proper management.

MATERIALS AND METHODS

Two pediatric radiologists retrospectively reviewed in consensus a total of 37 abnormal MRI examinations from 31 pediatric patients (nine boys, 22 girls; age range 1-17 years; mean age 9.4 years) who had a definite diagnosis of JpsA and underwent MRI. Each MRI was evaluated for synovium abnormality (thickening and enhancement), joint effusion (small, moderate, and large), bone marrow abnormality (edema, enhancement, and location of abnormality), soft tissue abnormality (edema, enhancement, atrophy, and fatty infiltration), tendon abnormality (thickening, edema, tendon sheath fluid, and enhancement), and articular abnormality (joint space narrowing and erosion). The distribution of abnormal MRI findings among the six categories for the 37 MRI examinations was evaluated. The number of abnormal MRI findings for each MRI examination was assessed. Age at MRI examination and all six categories of abnormal MRI findings according to gender were evaluated.

RESULTS

There were a total 96 abnormal MRI findings noted on 37 abnormal MRI examinations from 31 pediatric patients. The 37 abnormal MRI examinations included MRI of the hand (n = 8), knee (n = 8), ankle (n = 5), pelvis (n = 5), temporomandibular joint (n = 4), wrist (n = 3), foot (n = 2), elbow (n = 1), and shoulder (n = 1). Twenty-eight diffuse synovial thickening and/or enhancement were the most common MRI abnormality (29.2%). Joint effusion comprised 22 abnormal MRI findings (22.9%). There were 16 abnormal MRI bone marrow edema and/or enhancement findings (16.7%), and in seven (7.3%) the edema involved non-articular sites. Soft tissue abnormality manifested as edema and/or enhancement constituted 14 abnormal MRI findings (14.5%). There were ten MRI abnormalities (10.4%) involving tendons. Articular abnormality seen as joint space narrowing and/or bone erosion comprised six abnormal MRI findings (6.2%). Most MRI examinations had more than one abnormal finding (84%). Age at which MRI examinations were performed was not significantly different between boys and girls. All six categories of abnormal MRI findings were not significantly different between boys and girls.

CONCLUSION

Children with JpsA typically present with more than one abnormal finding on their MRI studies. While synovial abnormality is the most common MR finding in children with JpsA, multi-focal bone marrow edema and enhancement at both articular and non-articular sites are also notable findings in children with JpsA. The rate of articular abnormality is much lower in children with JpsA in comparison to adults with psoriatic arthritis. Our findings suggest that MRI can play a useful role in the diagnosis and ongoing assessment of this uncommon, though important, pediatric rheumatologic disorder.

Founder's lecture of the ISS 2006: borderlands of normal and early pathological findings in MRI of the foot and ankle

The purpose of this article is to highlight the anatomical variants, technical pitfalls, and the prevalence of abnormal conditions in the asymptomatic population in magnetic resonance imaging of the foot and ankle. Special attention is drawn to the complex anatomy of the deltoid ligament (the superficial tibionavicular ligament, tibiospring ligament, the tibiocalcaneal ligament, and the deep anterior and posterior tibiotalar ligaments) and the posterior tibial tendon insertion including the magic angle artifact and the high prevalence of asymptomatic findings such as "hypertrophied" peroneal tubercle (abnormal only when larger than 5 mm), peroneus quartus (prevalence 17%), and cysts (vascular remnants) just inferior to the angle of Gissane.

Bone stress injury of the ankle in professional ballet dancers seen on MRI

Background

Ballet Dancers have been shown to have a relatively high incidence of stress fractures of the foot and ankle. It was our objective to examine MR imaging patterns of bone marrow edema (BME) in the ankles of high performance professional ballet dancers, to evaluate clinical relevance.

Methods

MR Imaging was performed on 12 ankles of 11 active professional ballet dancers (6 female, 5 male; mean age 24 years, range 19 to 32). Individuals were imaged on a 0.2 T or 1.5 T MRI units. Images were evaluated by two musculoskeletal radiologists and one orthopaedic surgeon in consensus for location and pattern of bone marrow edema. In order to control for recognized sources of bone marrow edema, images were also reviewed for presence of osseous, ligamentous, tendinous and cartilage injuries. Statistical analysis was performed to assess the strength of the correlation between bone marrow edema and ankle pain.

Results

Bone marrow edema was seen only in the talus, and was a common finding, observed in nine of the twelve ankles imaged (75%) and was associated with pain in all cases. On fluid-sensitive sequences, bone marrow edema was ill-defined and centered in the talar neck or body, although in three cases it extended to the talar dome. No apparent gender predilection was noted. No occult stress fracture could be diagnosed. A moderately strong correlation (phi = 0.77, p= 0.0054) was found between edema and pain in the study population.

Conclusion

Bone marrow edema seems to be a specific MRI finding in the talus of professional ballet dancers, likely related to biomechanical stress reactions, due to their frequently performed unique maneuvers. Clinically, this condition may indicate a sign of a bone stress injury of the ankle.

MR imaging features of foot involvement in patients with psoriasis

OBJECTIVE

To determine alterations of the soft tissues, tendons, cartilage, joint spaces, and bones of the foot using magnetic resonance (MR) imaging in patients with psoriasis.

MATERIALS AND METHODS

Clinical and MR examination of the foot was performed in 26 consecutive patients (52 ft) with psoriasis. As a control group, 10 healthy volunteers (20 ft) were also studied. Joint effusion/synovitis, retrocalcaneal bursitis, retroachilles bursitis, Achilles tendonitis, soft-tissue edema, para-articular enthesophytes, bone marrow edema, sinus tarsi syndrome, enthesopathy at the Achilles attachment and at the plantar fascia attachment, plantar fasciitis, tenosynovitis, subchondral cysts, and bone erosions, joint space narrowing, subchondral signal changes, osteolysis, luxation, and sub-luxation were examined.

RESULTS

Clinical signs and symptoms (pain and swelling) due to foot involvement were present in none of the patients while frequency of involvement was 92% (24/26) by MR imaging. The most common MR imaging findings were Achilles tendonitis (acute and peritendinitis) (57%), retrocalcaneal bursitis (50%), joint effusion/synovitis (46%), soft-tissue edema (46%), and para-articular enthesophytes (38%). The most commonly involved anatomical region was the hindfoot (73%).

CONCLUSION

Our data showed that the incidence of foot involvement was very high in asymptomatic patients with psoriasis on MR imaging. Further MR studies are needed to confirm these data. We conclude that MR imaging may be of importance especially in early diagnosis and treatment of inflammatory changes in the foot.

Bone marrow changes on STIR MR images of asymptomatic feet and ankles

The purpose of this study was to evaluate the prevalence, pattern and size of bone marrow changes on short-tau inversion recovery (STIR) magnetic resonance (MR) images of asymptomatic feet and ankles. In 78 asymptomatic volunteers (41 women, 37 men; median age 47 years; range 23-83 years) sagittal STIR MR images of hindfoot and midfoot were reviewed for various patterns of high signal changes in bone marrow. The size of these bone marrow changes was measured, and signal intensity was rated semi-quantitatively using a scale from 0 (=normal) to 10 (=fluid-like). Fifty percent (39/78) of all volunteers had at least one bone marrow change. Thirty-six percent (28/78) of all volunteers had edema-like changes, 26% (20/78) had necrosis-like changes, and 5% (4/78) had cyst-like changes. The long diameters of all changes varied between 4 mm and 16 mm (median 7.5 mm). The median signal intensity for all changes was 5.0 (range 1-10). Bone marrow changes on STIR MR images are commonly detected in asymptomatic feet and ankles. However, such changes tend to be small (<1 cm) or subtle.

Magnetic resonance imaging of hindfoot involvement in patients with spondyloarthritides: comparison of low-field and high-field strength units

OBJECTIVE

To compare MRI evaluation of a painful hindfoot of patients with spondyloarthritides (SpA) on low-field (0.2 T) versus high-field (1.5 T) MRI.

MATERIALS AND METHODS

Patients with SpA and hindfoot pain were randomly referred to either high-field or low-field MRI. Twenty-seven patients were evaluated (male/female: 17:10; mean age: 39+/-1.4 years). Fifteen patients were examined by low-field and 12 by high-field MRI. Two patients (evaluated by high-field MRI) were excluded. Images were separately read by two radiologists who later reached a consensus. In each patient the prevalence of erosions, fluid, synovitis or bone marrow edema of the hindfoot joints, tendinosis or tenosynovitis of tendons, enthesitis of the plantar fascia and Achilles tendon and retrocalcaneal bursitis were recorded. Clinical and demographic parameters were comparable between both groups.

RESULTS

MRI evaluation of joints and tendons of the hindfoot revealed no significant differences in patients with SpA groups for all parameters. Analyzing all joints or tendons together, there was no statistically significant difference between the two groups.

CONCLUSION

Low-field and high-field MRI provide comparable information for evaluation of inflammatory hindfoot involvement. Thus, low-field MRI can be considered as a reliable diagnostic tool for the detection of hindfoot abnormalities in SpA patients.

Acute bone marrow edema of the hip: role of MR imaging

Acute bone marrow edema of the hip is a diagnostic challenge for both radiologists and clinicians. Marrow edema is often seen in patients with hip pain and restriction of motion. In patients with acute non-traumatic hip pain, whose radiographs are negative or inconclusive, MR imaging is the imaging study of choice. MR imaging is the most sensitive and specific imaging technique for detecting transient osteoporosis and osteonecrosis, as well as for detecting and staging fractures and microfractures. MR imaging is able to show marrow involvement in various inflammatory disorders and to diagnose reactive marrow edema from femoroacetabular impingment and greater trochanteric pain syndrome. In patients with septic arthritis, it may also depict associated marrow edema and suggest its reactive or infectious origin. For the neoplastic disorders, although plain radiographs should be the initial examination, MR imaging may follow for assessing extension to the surrounding soft tissues and/or associated pathologic fracture, facilitating thus the treatment planning. Computed tomography is more accurate compared with MR imaging in diagnosing intra-articular osteoid osteomas.

MRI in psoriatic arthritis with hand and foot involvement

Evaluation of MRI-findings in patients with involvement of psoriatic arthritis (PsA) in small joints in hands and feet. Twenty-five patients with symptomatic joint involvement were studied by MRI. All patients were found to be positive for one or more imaging criteria. Soft tissue oedema was identified in 22/25 (88%) patients. Joint effusion was observed in 23/25 (92%) patients, whereas bone erosion was seen in 20/25 (80%) patients. Bone marrow oedema was evident in 21/25 (84%) cases. In 12/25 (48%) cases, bone proliferation was noted. Tendon sheath effusion was present in 17/25 (68%) patients. Contrast enhancement of the synovia was detected in all patients (n = 25) (100%), whereas adjacent periost was enhanced in 22/25 (88%) and epiphysial bone marrow in 18/25 (72%) patients. MRI allows the assessment of PsA-alterations of soft tissue, cartilage, bone, bone marrow, and adjacent tendon sheath in patients with hand and foot involvement.

Magnetic resonance imaging in the quantitative assessment of gouty tophi

Measurements of tophus size can be important in monitoring the course of gout therapy, as tophus resolution is proposed as one measure of success of treatment. This multicentre study assessed the intra- and interreader reproducibility of quantitative tophus volume measurements from magnetic resonance images (MRI) in subjects with palpable gouty tophi. Subjects first underwent radiographic imaging of a selected tophus followed by MRI before and at <or=5, 10 and 20-min after gadolinium administration. After choosing optimal parameters, subjects underwent pre- and postgadolinium-enhanced MRIs of a selected tophus on two occasions separated by 5-10 days. Unenhanced spin-echo images provided satisfactory tophi images and were less subject to interfering artefacts than gadolinium-enhanced gradient-echo images. Intrareader reproducibility was excellent, with no statistically significant difference in mean tophus volume between visits (mean difference - 0.05 +/- 0.97 cm3). A small but statistically significant difference in interreader mean tophus volume was detected (mean difference 0.89 +/- 2.05 cm3; p < 0.05). MRI can quantify tophus size in gout and deserves further comparison with other techniques for tophus size monitoring in assessing effects of gout therapy.

Ankle MR Arthrography: How, Why, When

MR arthrography has become an important tool for the assessment of a variety of ankle disorders. MR arthrography may facilitate the evaluation of patients with suspected intra-articular pathology in whom conventional MR imaging is not sufficient for an adequate diagnosis and be useful for therapy planning. MR arthrography is valuable in the evaluation of ligamentous injuries, impingement syndromes, cartilage lesions, osteochondral lesions of the talus, loose bodies, and several synovial joint disorders. Indirect MR arthrography is a useful adjunct to conventional MR imaging and may be preferable to direct MR arthrography in cases in which an invasive procedure is contraindicated or when fluoroscopy is not available.

Reactive Carpal Synovitis: Initial Experience with MR Imaging

PURPOSE

To retrospectively evaluate the accuracy of various magnetic resonance (MR) imaging findings in the diagnosis of reactive carpal synovitis.

MATERIALS AND METHODS

Institutional review board approval was obtained, and the need for informed consent was waived. This study was compliant with the Health Insurance Portability and Accountability Act. Thirty-five consecutive patients (19 male and 16 female patients; age range, 13-57 years) who underwent arthroscopy and MR imaging within 4 weeks of surgery were evaluated by two reviewers for the following potential findings of synovitis: (a) distention of the pisotriquetral recess by fluid, (b) distention of the radial and/or prestyloid recess, (c) synovial enhancement (in patients who received contrast material), (d) amount of dorsal capsule distention, and (e) the location of bone marrow edema, if any. The chi2 and paired t tests were used to assess these findings in patients with and patients without arthroscopically proved synovitis. The sensitivity, specificity, positive and negative predictive values, and accuracy of these findings in the detection of synovitis were calculated.

RESULTS

Fluid in the pisotriquetral recess was seen in nine of the 14 patients with synovitis and five of the 21 patients without synovitis (P = .018). Distention of the radial and/or prestyloid recess was observed in six of the 14 patients with synovitis and two of the 21 patients without synovitis (P = .027). Among the 24 patients who received contrast material, synovial enhancement was seen in seven of eight patients with synovitis and three of 16 patients without synovitis (P = .002). The dorsal capsule measured 1-7 mm (mean, 3.07 mm) in the 14 patients with synovitis and 2-7 mm (mean, 3.76 mm) in the 21 patients without synovitis (P = .193). Although bone marrow edema was seen globally in similar frequencies (nine of 14 patients with synovitis, nine of 21 patients without synovitis), pisotriquetral bone marrow edema was seen only in patients with synovitis (two of nine patients).

CONCLUSION

Fluid in the pisotriquetral recess, enhancing synovium, and, less commonly, pisotriquetral bone marrow edema are MR imaging findings that may help in the diagnosis of reactive carpal synovitis.

Imaging the ankle and foot and using magnetic resonance imaging

Magnetic resonance (MR) imaging has improved the possibility of evaluating musculoskeletal structures thus gaining an important role in the diagnosis and treatment of foot and ankle pathologies. In this review, the normal and pathological images of the ankle and foot obtained using MR techniques are presented and discussed. The high soft-tissue contrast resolution and the multiplanar sections of MRI allow the imaging of contiguous tissues where small contrast differences exist, such as ligamentous and tendinous injuries or impingement syndromes. The spatial resolution with high sensitivity for bone signal changes offers an early detection of osseous abnormalities such as stress fractures or osteonecrosis. Here it is specified possibilities and limitations of MRI in the diabetic foot: this technique is superior to nuclear medicine and computed tomography (CT), however it is unable to distinguish between neuro arthropathy and infection.

MR imaging features of foot involvement in ankylosing spondylitis

OBJECTIVE

To determine alterations of the soft tissue, tendon, cartilage, joint space, and bone of the foot using magnetic resonance (MR) imaging in ankylosing spondylitis (AS) patients.

MATERIALS AND METHOD

Clinical and MR examination of the foot was performed in 23 AS patients (46 feet). Ten asymptomatic volunteers (20 feet) were studied on MR imaging, as a control group. MR imaging protocol included; T1-weighted spin-echo, T2-weighted fast-field echo (FFE) and fat-suppressed short tau inversion recovery (STIR) sequences in sagittal, sagittal oblique, and coronal planes using a head coil. Specifically, we examined: bone erosions, tendinitis (acute and chronic), para-articular enthesophyte, joint effusion, plantar fasciitis, joint space narrowing, soft tissue edema, bone marrow edema, enthesopathy in the Achilles tendon and plantar fascia attachment, subchondral signal intensity abnormalities (edema and sclerosis), tenosynovitis, retrocalcaneal bursitis, subchondral cysts, subchondral fissures, and bony ankylosis. Midfoot, hindfoot, and ankle were included in examined anatomic regions.

RESULTS

Clinical signs and symptoms (pain and swelling) due to foot involvement were present in 3 (13%) of the patients while frequency of involvement was 21 (91%) with MR imaging assessment. The MR imaging findings were bone erosions (65%), Achilles tendinitis (acute and chronic) (61%), para-articular enthesophyte (48%), joint effusion (43%), plantar fasciitis (40%), joint space narrowing (40%), subchondral sclerosis (35%), soft tissue edema (30%), bone marrow edema (30%), enthesopathy of the Achilles attachment (30%), subchondral edema (26%), enthesopathy in the plantar fascia attachment (22%), retrocalcaneal bursitis (22%), subchondral cysts (17%), subchondral fissures (17%), tendinitis and enthesopathy of the plantar ligament (13%), and bony ankylosis (9%). The most common involved anatomical region was the hindfoot (83%) following by midfoot (69% ) and ankle (22%).

CONCLUSION

In our experience, MR imaging may detect inflammatory and/or erosive bone, soft tissue, cartilage, tendon, and joint abnormalities in AS patients, even if AS patients did not have clinical signs and symptoms of foot involvement. If these data prove to be confirmed in further MR studies, MR imaging may be of importance especially in early diagnosis of inflammatory changes in the foot.

Involvement of the foot in patients with psoriatic arthritis. A review of 26 cases

OBJECTIVE

To describe the clinical and radiological features of foot involvement in patients with psoriatic arthritis.

METHODS

We retrospectively reviewed the medical records of patients admitted between 1972 and 1999 for psoriatic arthritis with involvement of the foot. We included all patients who had peripheral and/or axial, asymmetric, chronic inflammatory joint disease meeting or not Avila's radiological criteria for psoriatic arthritis, with or without other imaging findings suggestive of psoriatic arthritis and with or without psoriasis.

RESULTS

Twenty-six patients were included. Inflammatory heel pain was reported by 14 patients, whereas forefoot involvement was found in only seven patients. Sausage toe was present in two patients. None of the patients had Bauer's toe (combining arthritis and psoriatic skin and/or nail changes) or psoriatic onychopachydermoperiostitis of the great toe. Radiological abnormalities were found in 20 patients. Half the patients had calcaneal changes. Osteoperiostitis of the great toe was noted in two patients and mushrooming in five.

DISCUSSION

The features of psoriatic arthritis in Morocco seem similar to those in other countries. Hindfoot involvement was present in 53% of patients. Involvement of the forefoot was rarely recorded in the charts, suggesting missed cases because of insufficient attention to the forefoot during the physical examination and availability of anteroposterior radiographs only. Oblique views (Hirtz and Chaumet) should be obtained because they give a clearer image of the distal part of the toes, which is often difficult to analyze on anteroposterior films.

MRI findings of septic arthritis and associated osteomyelitis in adults

OBJECTIVE

The purpose of this study was to describe the soft-tissue, synovial, and osseous MRI findings of septic arthritis.

MATERIALS AND METHODS

At 1.5 T (T1-weighted, T2-weighted or STIR, and contrast-enhanced images), 50 consecutive cases of septic arthritis were evaluated by two observers for synovial enhancement, perisynovial edema, joint effusion, fluid outpouching, fluid enhancement, and synovial thickening. The marrow was assessed for abnormal signal on T1- and T2-weighted images or after contrast enhancement. We noted whether the marrow signal was diffuse or abnormal in bare areas. MRI findings were compared with microbiologic, clinical, and surgical data and diagnoses.

RESULTS

The frequency of MRI findings in septic joints was as follows: synovial enhancement (98%), perisynovial edema (84%), joint effusions (70%), fluid outpouching (53%), fluid enhancement (30%), and synovial thickening (22%). The marrow showed bare area changes (86%), abnormal T2 signal (84%), abnormal gadolinium enhancement (81%), and abnormal T1 signal (66%). Associated osteomyelitis more often showed T1 signal abnormalities and was diffuse.

CONCLUSION

Synovial enhancement, perisynovial edema, and joint effusion had the highest correlation with the clinical diagnosis of a septic joint. However, almost a third of patients with septic arthritis lacked an effusion. Abnormal marrow signal-particularly if it was diffuse and seen on T1-weighted images-had the highest association with concomitant osteomyelitis.

Spondyloarthropathies: ankylosing spondylitis and psoriatic arthritis

As advances in the treatment of ankylosing spondylitis continue, TNF-alpha blocking agents may eventually be used as a first-line treatment. MR imaging could then be used to aid in the early diagnosis of ankylosing spondylitis by identifying early sacroiliitis, followed by immediate initiation of treatment to prevent the progression of the disease with its accompanying morbidities. Currently, radiographic identification of sacroiliitis remains the mainstay in diagnosing ankylosing spondylitis. In ankylosing spondylitis and psoriasis, MR imaging can demonstrate areas that are undergoing active inflammatory changes and enthesitis, aiding in the diagnosis of a spondyloarthropathy.

MR imaging of the diabetic foot

Diabetes is a common disease with potentially devastating complications affecting the foot and ankle. Ischemia and infarction, neuropathic osteoarthropathy, callus, ulceration, and infection result from the underlying neurologic and vascular disease. The MR imaging appearance of these complications is discussed. Recognition of these MR imaging patterns is important for formulation of an appropriate treatment plan.

Imaging sports injuries of the foot and ankle

The complexity of foot and ankle anatomy and function is unique in the musculoskeletal system. Understanding the complex anatomy alone is a daunting task, not to mention transferring that understanding to the two-dimensional planes encountered on imaging studies. When evaluating sports injuries in the foot and ankle, the interpreting radiologist must take into account the type of activity, vector of stress, and inherent characteristics of the involved structures. A strong working relationship with the health care providers managing patient care, ideally orthopedists, is essential. But in this age of decreasing specialization and increasing availability of imaging resources, the interpreting radiologist must use all available tools for clinical investigation. When interpreting an ankle or foot MR imaging, one finding should trigger a search for the next finding along a logical pathway of injury evolution. Bone marrow edema patterns are guides to tendon and ligament failure. And a clinical syndrome without correlative imaging diagnosis should call attention to potential alternative diagnoses. As the number of MR imaging studies performed continues to increase and MR technology continues to improve, we expect further advancements in MR evaluation of foot and ankle injury. We hope to continue to work closely with our referring orthopedists in this arena to improve our diagnostic skills and our understanding of foot and ankle injury.

Regional musculoskeletal conditions: foot and ankle disorders

Foot pain is very common, especially in women, owing to inappropriate footwear. Overuse, repetitive strain and minor, easily forgettable injuries may result in chronic foot and ankle pain. Rheumatoid arthritis, spondyloarthropathies and gout frequently affect the foot, often as a first presentation. Charcot's joints and foot infections are not rare in diabetes. The rheumatologist should be familiar with foot disorders, either localized or as manifestations of generalized disease. History taking, physical examination, identification of the source of pain by intra-articularly given local anaesthetics and imaging methods should be used to reveal the underlying disorder. Correct diagnosis and efficient therapy-including local steroid injections, physiotherapy, orthoses, surgery-are necessary not only for treatment but also for preventing biomechanical chain reactions. This chapter gives an overview of the epidemiology, diagnosis and treatment of foot pain and foot disorders caused by both local and generalized diseases.

Tendon involvement in pedal infection: MR analysis of frequency, distribution, and spread of infection

OBJECTIVE

The objective of our study was to evaluate the frequency, distribution, and extent of tendon involvement in patients with pedal infections.

MATERIALS AND METHODS

Contrast-enhanced MR imaging examinations of 159 infected feet performed at 1.5 T were reviewed by two musculoskeletal radiologists for the presence and location of tendon infection (peritendinous enhancement contiguous to an adjacent ulcer or cellulitis) and for the spread of infection along tendons, which was defined as peritendinous contrast enhancement extending more than 2 cm beyond surrounding cellulitis. The study group was composed of 156 consecutive patients, 82.7% of whom had diabetes; all patients underwent subsequent surgical treatment. Results of MR evaluations were compared with the patients' charts and surgical reports.

RESULTS

Of the 129 MR examinations showing an infection in the forefoot, MR evidence of tendon involvement in the infection was observed in 56 MR examinations (43%). The sum of involved tendons per ray was as follows: first ray (flexor tendon, n = 19; extensor tendon, n = 13), second (flexor tendon, n = 12; extensor tendon, n = 7), third (flexor tendon, n = 5; extensor tendon, n = 4), fourth (flexor tendon, n = 5; extensor tendon, n = 1), and fifth (flexor tendon, n = 11; extensor tendon, n = 6). Of the 32 MR examinations showing infection in the hindfoot, 14 examinations (44%) showed evidence of tendon involvement, most frequently of the distal Achilles tendon (n = 7). MR evidence of the spread of infection along a tendon was seen in 12 examinations, always with proximal spread of infection; and infection led to the development of an abscess in the central plantar compartment in three patients. Intraoperative evidence of a tendon infection was documented in 11 patients. The surgical procedure was altered because of the tendon infection in six patients.

CONCLUSION

MR evidence of tendon infection is present in approximately half the patients who require surgery for pedal infection. Evidence of spread of the infection along tendons is seen infrequently on MR imaging. Detection of a tendon infection could influence surgical therapy.

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.

MR image analysis of pedal osteomyelitis: distribution, patterns of spread, and frequency of associated ulceration and septic arthritis

PURPOSE

To evaluate the anatomic distribution of pedal osteomyelitis and septic arthritis in a large patient group with advanced pedal infection and to compare ulcer location with the distribution of osteomyelitis and septic arthritis.

MATERIALS AND METHODS

Contrast material-enhanced magnetic resonance (MR) imaging findings were reviewed for 161 feet in 51 women and 107 men (82% of whom had diabetes mellitus) who were suspected of having osteomyelitis and who underwent tissue diagnosis. Location of skin ulceration and presence of osteomyelitis (indicated by means of low T1-weighted signal intensity, high T2-weighted signal intensity, and contrast enhancement) and septic arthritis (indicated by synovial enhancement and adjacent cellulitis) were evaluated by two musculoskeletal radiologists.

RESULTS

In the forefoot, osteomyelitis occurred most frequently at the fifth metatarsal (n = 24), first metatarsal (n = 21), and first distal phalanx (n = 15). In the hindfoot, the calcaneus (n = 21) was involved most frequently. Osteomyelitis was directly adjacent to skin ulcers or surgical defects in all cases but one. Spread of osteomyelitis to adjacent bones in the forefoot occurred in 26 (16%) bones. Evidence of septic arthritis on MR images was present in 53 (33%) feet and involved most frequently the fifth (n = 13) and first (n = 8) metatarsophalangeal joints.

CONCLUSION

Pedal osteomyelitis results almost exclusively from contiguous infections and occurs most frequently around the fifth and first metatarsophalangeal joints. One-third of patients with advanced pedal infection show evidence of septic arthritis on MR images.

Quantitative cartilage imaging of the human hind foot: precision and inter-subject variability

Alterations of ankle cartilage are observed in degenerative and inflammatory joint disease, but cartilage cannot be directly visualized by radiography. The purpose of this study was therefore to analyze the feasibility and precision of quantitative cartilage imaging in the human hind foot (talocrural, talotarsal, and intertarsal joints), and to report the inter-subject variability for cartilage volume, thickness and surface areas. The feet of 16 healthy volunteers were imaged using a 3D gradient-echo magnetic resonance imaging sequence with water-excitation. After interpolation to a resolution of 1 x 0.125 x 0.125 mm3 the cartilage plates were segmented, and the cartilage volume, thickness, and surface areas determined. The precision (four repeated measurements) was examined in eight volunteers, the RMS average CV% being 2.1% to 10.9% in single joint surfaces, and < or = 3% for the cumulative values of all joints. The mean cartilage thickness ranged from 0.57+/-0.08 (navicular surface) to 0.89+/-0.19 mm (trochlear surface for tibia). In conclusion this study shows that it is feasible to quantify thin cartilage layers in the hind foot under in vivo imaging conditions, and that the precision errors are substantially smaller than the inter-subject variability in healthy subjects.

Childhood arthritis: classification and radiology

Childhood arthritis has now been reclassified into a single internationally recognized entity of juvenile idiopathic arthritis (JIA). Radiology provides an important role in the management of JIA, in helping in the differential diagnosis, monitoring disease progression and detecting complications. Traditionally, plain radiographs have been the imaging investigation of choice but magnetic resonance imaging (MRI) and ultrasound are now providing a more effective and safer alternative. The appropriate use of sequences in MR imaging is important in the early detection of joint abnormalities in JIA.

Forefoot pain involving the metatarsal region: differential diagnosis with MR imaging

Many disorders produce discomfort in the metatarsal region of the forefoot. These disorders include traumatic lesions of the soft tissues and bones (eg, turf toe, plantar plate disruption, sesamoiditis, stress fracture, stress response), Freiberg infraction, infection, arthritis, tendon disorders (eg, tendinosis, tenosynovitis, tendon rupture), nonneoplastic soft-tissue masses (eg, ganglia, bursitis, granuloma, Morton neuroma), and, less frequently, soft-tissue and bone neoplasms. Prior to the advent of magnetic resonance (MR) imaging, many of these disorders were not diagnosed noninvasively, and radiologic involvement in the evaluation of affected patients was limited. However, MR imaging has proved useful in detecting the numerous soft-tissue and early bone and joint processes that occur in this portion of the foot but are not depicted or as well characterized with other imaging modalities. Frequently, MR imaging allows a specific diagnosis based on the location, signal intensity characteristics, and morphologic features of the abnormality. Consequently, MR imaging is increasingly being used to evaluate patients with forefoot complaints. Radiologists should be familiar with the differential diagnosis and MR imaging features of disorders that can produce discomfort in this region.

Subtendinous bone marrow edema patterns on MR images of the ankle: association with symptoms and tendinopathy

OBJECTIVE

We sought to describe a pattern of subtendinous bone marrow edema on MR images of the ankle and to determine if there is an association with location of symptoms and overlying tendinopathy.

MATERIALS AND METHODS

At 1.5 T, 141 MR examinations of the ankle (116 clinical examinations of patients with chronic pain, 25 of asymptomatic control patients) were performed using T1-weighted, proton density-weighted fast spin-echo, and T2-weighted fat-suppressed fast spin-echo sequences. Images were retrospectively reviewed by two musculoskeletal radiologists for presence of bone marrow edema occurring in a subcortical location associated with the course of the medial or lateral tendon groups, as well as focal thickening or increased T2 signal within the tendons. These findings were correlated with clinical information regarding symptom location. The association of subtendinous marrow edema with tendinopathy and symptom location was statistically analyzed.

RESULTS

Subtendinous bone marrow edema was present at 26 sites on 24 ankle MR examinations (17%) (at the medial malleolus [n = 17] associated with the posterior tibialis tendon, at the lateral malleolus [n = 6] and the calcaneus [n = 2] associated with the peroneus longus and brevis tendons, and at the cuboid [n = 1] associated with the peroneus longus tendon). These subtendinous bone marrow edema patterns were significantly associated with overlying tendon abnormality medially (p = 0.001) and laterally (p = 0.001), and with symptoms medially (p = 0.0016) but not laterally (p = 0.078).

CONCLUSION

On MR images of the ankle, bone marrow edema localized in a subtendinous location is associated with overlying tendinopathy medially and laterally and with ankle pain medially.

From the RSNA Refresher Courses. Radiological Society of North America. MR imaging of the ankle and foot

Magnetic resonance (MR) imaging has opened new horizons in the diagnosis and treatment of many musculoskeletal diseases of the ankle and foot. It demonstrates abnormalities in the bones and soft tissues before they become evident at other imaging modalities. The exquisite soft-tissue contrast resolution, noninvasive nature, and multiplanar capabilities of MR imaging make it especially valuable for the detection and assessment of a variety of soft-tissue disorders of the ligaments (eg, sprain), tendons (tendinosis, peritendinosis, tenosynovitis, entrapment, rupture, dislocation), and other soft-tissue structures (eg, anterolateral impingement syndrome, sinus tarsi syndrome, compressive neuropathies [eg, tarsal tunnel syndrome, Morton neuroma], synovial disorders). MR imaging has also been shown to be highly sensitive in the detection and staging of a number of musculoskeletal infections including cellulitis, soft-tissue abscesses, and osteomyelitis. In addition, MR imaging is excellent for the early detection and assessment of a number of osseous abnormalities such as bone contusions, stress and insufficiency fractures, osteochondral fractures, osteonecrosis, and transient bone marrow edema. MR imaging is increasingly being recognized as the modality of choice for assessment of pathologic conditions of the ankle and foot.