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.     

Sonography of hip joint in infective arthritis

The most important determinant of outcome of a hip infection is the delay between the onset of the infection and treatment. Transient synovitis, and septic and tubercular arthritis of the hip remain common diagnostic problems. Conventional radiographic examinations are of little help in early diagnosis. Computed tomography, scintigraphy and magnetic resonance imaging, though informative, are expensive and not universally available. Ultrasonography (US) of the hip was done in 50 patients to define sonographic anatomy, detect joint effusions and correlate sonographic features with the etiology of the disease. Even small collections of fluid could be detected with accuracy. Both hypo- and hyperechoic synovial fluid was seen in septic arthritis, but hyperechoicity and a thickened capsule were the most characteristic findings. Synovial fluid had mixed echogenicity in tubercular and transient synovitis. The use of other (invasive) imaging modalities can be minimized because US can be used not only to demonstrate effusions early in the disease but also the status of the intra-articular compartment, joint capsule, bony surface and adjacent soft tissues. Ultrasonography should be used more commonly to diagnose infective arthritis, and no patient should be subjected to arthrotomy or drainage if US has ruled out the presence of a fluid collection.     

Concentric joint space narrowing of the hip associated with hemosiderotic synovitis (HS) including pigmented villonodular synovitis (PVNS)

Concentric joint space narrowing of the hip is an expected radiographic finding in cases of inflammatory arthritis such as rheumatoid arthritis or sepsis. However, similar joint space narrowing is associated with chronic hemorrhagic conditions that produce hemosiderotic synovitis. Hemosiderotic synovitis results from chronic intraarticular bleeding such as occurs in pigmented villonodular synovitis, generalized bleeding diathesis, synovial hemangioma, and chronic trauma. Five hips in five patients with concentric joint space narrowing not associated with inflammatory arthritis or with hemophilia were reviewed clinically, radiographically, and pathologically. All patients had a hemosiderotic synovitis. The definitive diagnosis of pigmented villonodular synovitis was made pathologically in two cases that demonstrated nodular areas of giant cell proliferation, collagen production, and lipid-laden histiocytes on histologic samples.     

In vitro and in vivo spin echo diffusion imaging characteristics of synovial fluid: potential non-invasive differentiation of inflammatory and degenerative arthritis

Objective. This study was undertaken to analyse the diffusion characteristics of synovial fluid in degenerative and inflammatory arthropathies. Design and patients. Ten in vitro specimens of synovial fluid from patients with both degenerative and inflammatory arthropathy were studied at body temperature with a navigator-corrected spin echo diffusion sequence (B values 0–512 s/mm²), on a Philips 1.5-T Gyroscan. Subsequently synovial fluid from knee joint effusions of 25 patients (10 patients with osteoarthritis, 10 patients with effusions following trauma and 5 patients with effusions secondary to inflammatory arthritis) was evaluated with the same navigator-corrected spin echo diffusion sequence. Results. Both in vitro and in vivo study demonstrated decreased diffusion in patients with effusions secondary to degenerative joint disease (less than 2.40×10^–5 cm²/s) relative to patients with effusions accompanying knee trauma (greater than 2.75×10^–5 cm²/s) and inflammatory arthritis (in vitro and in vivo greater than 3.00×10^–5 cm²/s). Conclusion. Synovial fluid in degenerative arthritis shows less diffusion or free water movement than synovial fluid in inflammatory arthritis. Diffusion characteristics of synovial fluid may be used to predict the nature of the underlying form of arthritis in patients presenting with knee joint effusions. Received: 22 October 1999 Revision requested: 10 January 2000 Revision received: 10 March 2000 Accepted: 14 March 2000     

Ultrasonography of musculoskeletal infections in children

Ultrasonography is an important modality for evaluation of musculoskeletal infections in children because it is rapid, nonionising and very sensitive for (infectious) fluid collections and joint effusions. Moreover, the images are not degraded by metallic or motion artefacts (as with CT and MRI) and finally, ultrasonography offers the possibility of fine-needle aspiration to confirm the infectious nature of a fluid collection without unnecessary contamination of adjacent anatomical compartments. Ultrasonography should be combined with radiography because both imaging techniques are complimentary. The purpose of this article is to emphasise the role of ultrasonography in the diagnosis of various diseases in childhood, including cellulitis, subcutaneous abscess, necrotizing fasciitis, pyomyositis, infectious bursitis and arthritis, osteomyelitis, foreign bodies and infectious lymphadenitis. Along with conventional radiography, ultrasonography is a very valuable modality for early diagnosis and follow-up of musculoskeletal infections in children.     

Ultrasonography of musculoskeletal infections in children

Ultrasonography is an important modality for evaluation of musculoskeletal infections in children because it is rapid, nonionising and very sensitive for (infectious) fluid collections and joint effusions. Moreover, the images are not degraded by metallic or motion artefacts (as with CT and MRI) and finally, ultrasonography offers the possibility of fine-needle aspiration to confirm the infectious nature of a fluid collection without unnecessary contamination of adjacent anatomical compartments. Ultrasonography should be combined with radiography because both imaging techniques are complimentary. The purpose of this article is to emphasise the role of ultrasonography in the diagnosis of various diseases in childhood, including cellulitis, subcutaneous abscess, necrotizing fasciitis, pyomyositis, infectious bursitis and arthritis, osteomyelitis, foreign bodies and infectious lymphadenitis. Along with conventional radiography, ultrasonography is a very valuable modality for early diagnosis and follow-up of musculoskeletal infections in children.     

Expression levels of matrix metalloproteinase (MMP)-9 and its specific inhibitor TIMP-1, in septic and aseptic arthritis of the knee

Purpose

In cases of septic knee arthritis, there is excess of matrix metalloproteinases (MMPs) over tissue inhibitors of metalloproteinases (TIMPs), due to enhanced expression and activation that are induced by bacteria in comparison with rheumatic or degenerative arthritis. The aim of this study was to explore the expression levels of synovial gelatinase MMP-9 and its specific inhibitor TIMP-1 in septic and aseptic arthritis and their potential use as additional aids to clinical investigation.

Methods

Gelatin zymography and western blot analysis were applied in effusions from knees of the patients with septic (SA—10 patients), rheumatic (RA—10 patients) and osteoarthritis (OA—10 patients).

Results

Zymographic analysis revealed that all samples contained latent MMP-2 activity, albeit activated MMP-2 appeared in more of the septic than aseptic effusions. MMP-9 was not detected in osteoarthritic synovial fluid samples. Only trace amounts of MMP-9 activity were detected in 4 of 10 patients with RA, whereas higher MMP-9 levels were evident in all samples from SA (P = 0.0241). In immunoblotting assays, samples from SA showed significantly higher levels of MMP-9 compared with samples from RA (P = 0.0052), confirming zymographic results. Although no significant difference in TIMP-1 levels was observed, the estimated MMP-9/TIMP-1 ratio of septic effusions was significantly higher compared with aseptic ones (P = 0.0029).

Conclusions

The data presented suggest enhanced expression and activation of MMP-9 in septic native knee arthritis compared with aseptic. The presence of high levels of MMP-9 with concomitantly increased MMP-9/TIMP-1 ratio and activated gelatinases in effusions, independent of neutrophilic counts, may be indicative for infection.     

Septic arthritis of the hip joint: sonographic and CT findings

Two patients with acute bacterial arthritis of the hip joint were suspected clinically to have a psoas abscess. For this reason a computed tomographic scan of the abdomen and pelvis (two patients) and ultrasonography (one patient) were requested. These scans showed no evidence of an abscess in the abdominal cavity nor retroperitoneum but did demonstrate a hip joint effusion which was compatible with septic arthritis.     

Pigmented villonodular synovitis of the hip: review of radiographic features in 58 patients

Clinical and radiographic findings were retrospectively reviewed in a multicentric survey of 58 patients with histologically proven pigmented villonodular synovitis (PVNS) of the hip. The most common clinical features were mechanical pain (47 cases) and limitation of joint motion (47 cases). On plain films, a classic form with large and multiple lucencies was found in 36 cases, followed by an osteoarthritis-like form (9 cases), an arthritis-like form (8 cases), normal radiographic appearance (3 cases), osteonecrosis of the femoral head (one case) and joint destruction with acetabular protrusion (one case). Bilateral involvement of the hips was probable in two patients. In contrast to the knee, the hip showed a high prevalence of bony lesions and joint space narrowing. Although an uncommon disease, PVNS of the hip has to be considered when arthritis is associated with uncharacteristic clinical or radiographic findings.     

MRI features of Lyme arthritis in children

OBJECTIVE: Oligoarthritis is the most common manifestation of late Lyme disease in children. Considerable overlap can occur in the clinical presentation of Lyme arthritis and acute septic arthritis. Early differentiation is critical, given the disparate therapeutic implications; Lyme arthritis is treated with outpatient oral antibiotics, while septic arthritis requires hospitalization, IV antibiotics, and, often, surgical drainage. We wanted to identify MRI features that may distinguish Lyme arthritis from septic arthritis in children. MATERIALS AND METHODS: Knee MR images in 11 children with Lyme arthritis and 7 with septic arthritis, with a mean age 10.6 years old and 11.7 years old, respectively, were reviewed by a radiologist blinded to the final diagnosis. Joint effusion size, synovial thickness, adenopathy, subcutaneous, marrow, and muscle edema on MRI; and clinical parameters including age, sex, fever, WBC, erythrocyte sedimentation rate, C-reactive protein, and joint fluid WBC in the two patient groups were compared using univariate and multivariate analyses. RESULTS: Subcutaneous edema was seen in all septic arthritis patients but in only one of 11 patients with Lyme arthritis (p < 0.01). Myositis and adenopathy were present in all Lyme arthritis patients and two of seven patients with septic arthritis (both p < 0.01). No significant difference was present in synovial thickness, marrow edema, or joint fluid size. There were no statistically significant differences in the clinical parameters assessed. CONCLUSION: Our results identified three MRI features, specifically, myositis, adenopathy, and lack of subcutaneous edema, that strongly suggest the diagnosis of Lyme arthritis rather than septic arthritis in children with acute inflammation of the knee. Awareness of these characteristic MRI features may avoid unnecessary invasive procedures and cost.     

Musculoskeletal infections: US manifestations.

One of the most important prognostic factors in patients with musculoskeletal infections is the delay in establishing therapy. Early diagnosis of septic arthritis requires analysis of joint fluid. Ultrasonography (US) is a rapid, portable, sensitive technique for confirming the presence of joint effusions. The study can be easily repeated for follow-up of lesions. US allows real-time guidance of fluid aspiration and can reduce the risk of contaminating other anatomic compartments, especially in the hands, wrists, and feet. Radiography provides complementary information and should be performed in conjunction with US. US is the imaging modality of choice for diagnosis of superficial abscesses. Dynamic compression with the US probe and color Doppler imaging can facilitate detection of superficial abscesses. US may help in the early diagnosis of osteomyelitis by demonstrating subperiosteal or juxtacortical fluid collections and by providing guidance for aspiration of these collections. Evaluation of osseous involvement requires additional imaging; a US examination with normal results does not allow exclusion of bone infection. US is not degraded by metallic artifact and may be useful in cases of osteomyelitis complicating metallic fixation in an extremity. After initial radiography, US can play an important role in the management of musculoskeletal infections.     

Arthritis in children: conventional and advanced imaging

Imaging is crucial for the diagnosis and differential diagnosis of arthritis. Plain radiography is the primary tool used to assess and monitor the progression of arthritis or its response to therapy. The newer imaging modalities offer a more complete assessment of the joints in health and disease. Magnetic resonance (MR) imaging with gadolinium administration allows direct visualization of the inflamed synovium and pannus. With MR imaging articular cartilage can be seen as well as joint effusion and hemosiderin, if present. Small (and large) joint effusions are readily revealed using ultrasonography, which is a relatively easy and inexpensive technique.     

Second Wind — Trying to Catch It in the Lab

A wrestler developed septic arthritis in his glenohumeral joint. His case is unusual because septic arthritis most commonly affects weight-bearing joints and is usually seen in the very young, the very old, and people who are immunocompromised. Other risk factors include concurrent infection, endocarditis, invasive procedures, and intra-articular corticosteroid injection. Disease onset is usually insidious. Nonspecific findings include restricted motion, mild pain, and joint effusions; systemic signs of toxicity are often mild or absent. Diagnosis is confirmed with joint aspiration and analysis and culture of synovial fluids; definitive treatment often involves arthroscopic debridement followed by 2 to 6 weeks of antibiotics.     

Role of high resolution ultrasonography in diagnosing septic hip arthritis in premature neonates admitted to the neonatal intensive care unit

Aim

The aim of this study is to evaluate the role of high resolution ultrasonography (HRUS) of the hip in premature neonates admitted to the neonatal intensive care unit (NICU) in diagnosis of septic hip arthritis.

Septic arthritis: a rare cause of drooping shoulder

Drooping shoulder, or inferior subluxation of the glenohumeral joint, must be differentiated from true dislocation of the humeral head. In some instances, widening of the glenohumeral joint can be attributed to a large volume of intra-articular fluid. Three patients with septic arthritis leading to drooping shoulder are described, representing the largest series with this development reported to date.     

Demonstration of an infected popliteal (Baker's) cyst with three-phase skeletal scintigraphy

A case is reported of an infected popliteal (Baker's) cyst demonstrated with triple phase skeletal scintigraphy. Although double-contrast arthrography and ultrasonography are currently the modalities most frequently employed to diagnose the presence of popliteal cysts, they may also be detected utilizing this radionuclide technique in the course of evaluation for knee joint disease or septic arthritis. Radionuclide studies may be more sensitive for the evaluation of associated inflammatory disease involving the knee joint.     

Traumatic hip dislocation: early MRI findings

Purpose Objective of this study was to present the spectrum of early magnetic resonance imaging (MRI) findings following traumatic dislocation of the femoral head, and to identify any associated injuries that may have therapeutic or prognostic significance and be better delineated by MRI than by conventional radiography.Patients and methods Prospective MRI of both hips was performed on 18 patients (14 male, 4 female; age range 14–54 years; average age 30.5 years) within 5 weeks of a traumatic femoral head dislocation. The interval between the time of injury and the imaging studies ranged from 2 to 35 days (average 13.2 days). Posterior dislocation was present in 14 patients and anterior dislocation in 4 patients. In the majority of cases, we performed axial T1, coronal T1, and coronal T2^* (MPGR) sequences. Images were retrospectively evaluated by consensus of three radiologists for possible abnormalities of the bone and cartilage, joint space, and soft tissues. Because all patients were treated with closed reduction, surgical correlation was not obtained.Results All patients had a joint effusion or hemarthrosis. Of the 14 patients with posterior dislocation, isolated femoral head contusions (trabecular microfractures) were identified in 6 patients. Four patients had small femoral head fractures, and one had an osteochondral defect. Acetabular lip fractures were seen in six patients, and one patient had a labral tear. Four patients had intra-articular loose bodies and one had ligamentum teres entrapment. Twelve patients had iliofemoral ligament injury. All patients had muscle injury involving the gluteal region and medial fascial compartment, and 13 patients had anterior fascial compartment muscle injury. Seven patients with posterior dislocation had posterior fascial compartment injury. Of the four patients with anterior dislocation, two had bony contusion, two had cortical infraction, one had a labral tear, and all four had an iliofemoral ligament injury. All four patients in this group had muscle injury of the gluteal region and of the anterior and medial fascial compartments.Conclusions MRI can effectively identify and quantify the muscle injury and joint effusion that invariably accompany traumatic hip dislocations. It is also useful for demonstrating trabecular bone contusion (trabecular injury) and iliofemoral ligament injury, which occur commonly with acute hip dislocation.     

Familiar Mediterranean fever mimicking septic arthritis: distinguishing with diffusion weighted imaging

FMF arthritis is generally monoarticular in origin. The affected joint is hot, tender, red and mimics septic arthritis. Conventional imaging findings, including magnetic resonance imaging (MRI) and ultrasound, do not help differentiate between these two entities. The final diagnosis depends on culture of the synovial fluid, and therefore initiation of proper drug therapy can be delayed. Diffusion weighted imaging (DWI), with its ability to detect altered water-proton mobility, might play an important role as a fast and non-invasive problem-solving tool in this setting. We here present MRI and DWI findings of a case of FMF arthritis mimicking septic arthritis.     

The knee joint in early juvenile idiopathic arthritis. An ROC study for evaluating the diagnostic accuracy of contrast-enhanced MR imaging

Purpose: Diagnosis of juvenile idiopathic arthritis (JIA) remains difficult due to unspecific clinical and laboratory findings, especially in early stages of the disease. The purpose of our study was to determine the sensitivity and specificity of MR imaging in diagnosing JIA of the knee joints.Material and Methods: Forty children (3-17 years old) clinically diagnosed with JIA (follow-up >1 year) of a knee joint and a control group of 40 children with painful knee joints (MR diagnosis: bone bruise of the knee (n=7), normal knee joint (n=12), osteomyelitis (n=6), septic arthritis (n=2), bone tumor (n=7) and miscellaneous bone lesions (n=6)) were examined using a 1.5 T MR unit. T1-weighted spin-echo (SE), T2-weighted fast SE, contrast-enhanced T1-weighted SE and 2D gradient echo sequences were performed. The receiver operating characteristic (ROC) curves evaluation was conducted by 5 independent radiologists.Results: The positive criteria for diagnosing JIA were joint effusions (n=40), contrast-enhancing synovitis (n=39), cartilage lesions (n=15), subchondral erosions and bony destruction (n=1). Sensitivity and specificity were 93.5% and 92.5%, respectively. Both cases of septic arthritis were misdiagnosed as JIA by all radiologists.Conclusion: Contrast-enhanced MR imaging seems to be a highly sensitive tool in establishing the diagnosis of JIA.     

The diabetic foot: magnetic resonance imaging evaluation

Fourteen diabetic patients with suspected foot infection and/or neuropathic joint (Charcot Joint) were evaluated with magnetic resonance imaging (MRI) in an attempt to assess the extent of the infection and also to distinguish infection from the changes seen with neuroarthropathy. The majority of patients with infection had more than one site of involvement and the following diagnoses were made by MRI evaluation: osteomyelitis (n = 8), abscess (n = 7), neuropathic joint (n = 5), septic arthritis (n = 4), and tenosynovitis (n = 4). Clinical or surgical/pathological confirmation of the MRI diagnoses was obtained in all but nine sites of infection or cases of neuropathic joint. If the two diagnostic categories of septic arthritis and tenosynovitis are excluded, all but four of the MRI diagnoses were confirmed. A distinctive pattern for neuroarthropathy was identified in five cases, consisting of low signal intensity on T1- and T2-weighted images within the bone marrow space adjacent to the involved joint. We conclude that MRI is a valuable adjunct in the evaluation of the diabetic foot, and that it provides accurate information regarding the presence and extent of infection in this subset of patients. MRI has proven particularly helpful in differentiating neuroarthropathy from osteomyelitis.