Tuberculous Arthritis and Monoarticular Rheumatoid Arthritis in the Knee: Differential Diagnosis using MR Imaging

Role of shear wave elastography of synovium to differentiate rheumatoid and tubercular arthritis

Background:

Synovitis is the underlying pathology in various arthritis, and sometimes, it is difficult to differentiate various arthritis clinically or even by imaging. The purpose of our study was to use shear wave elastography (SWE) to evaluate rheumatoid arthritis (RA) and tubercular (TB) arthritis and to differentiate them using synovial stiffness.

Methods:

The prospective study was performed on Supersonic Imagine Aixplorer Ultrasound (USG) machine using a linear array probe SL10-2 (2–10 MHz). A total of 29 participants, 15 of RA (ACR/EULAR criteria) and 14 of proven TB arthritis were included. Region of interest of 1 mm was applied on the hypertrophied synovium and quantitative SWE data in form of elasticity (kPa) and velocity (m/s) were measured. Discrete categorical data were presented as n (%). Mean values were recorded along with standard deviation and the range of values. To find a maximal cutoff value of elasticity and velocity - receiver operating characteristic curve were plotted.

Results:

The mean elasticity and velocity values were 54.81 ± 10.6 kPa and 4.2 m/s ± 0.42 for RA and 37 ± 10 kPa and 3.4 ± 0.47 m/s for TB group. Significant difference (P < 0.001) was seen in elastic modulus values between rheumatoid and TB group with cutoff of 43.6 kPa to differentiate the two groups (sensitivity – 86.7% and specificity – 80%). Similar significant (P < 0.001) results were seen with velocity values, with cutoff of 3.76 m/s (sensitivity – 86.7% and specificity – 80%).

Conclusion:

SWE shows the potential to be a useful adjunct to gray scale and color Doppler USG in differentiating various arthritis on the basis of elastic properties of the synovium. Elastic modulus and velocity are useful SWE quantitative parameters for synovial evaluation and can differentiate RA and TB arthritis.

Magnetic resonance imaging evaluation of tubercular arthritis of the ankle and foot

BACKGROUND

Ankle and foot tuberculosis is relatively uncommon. Magnetic resonance imaging (MRI) is highly sensitive in detecting the changes but there is limited experience with MRI evaluation and differentiation from other mono-articular arthritis, particularly pyogenic arthritis, is a challenge.

PURPOSE

To report MRI findings in ankle and foot tuberculosis.

MATERIAL AND METHODS

MRI was performed in 17 selected patients with ankle and foot tuberculosis. T1-weighted, proton density (PD) weighted, T2-weighted, and postcontrast sequences were performed in multiple imaging planes. Recorded findings included: number of bones involved; specific bones involved; extent of involvement; erosions; joint effusion, synovial thickening, tenosynovitis; joint effusion; adjacent soft-tissue changes; and involvement of sinus tarsi. Clinical data of all patients were also reviewed. Radiographic correlation at the time of MRI was available in selected patients.

RESULTS

The most common abnormality was synovial thickening. Signal abnormality was noted most frequently in the talus (n = 14). Erosions and intra-osseous abscesses were noted in 10 (58%) and eight (47%) patients, respectively. Tenosynovitis was present in eight (47%) patients. Soft tissue changes were noted in all patients, including abscesses in 13 patients (76%).

CONCLUSION

A multiplicity of findings (both osseous and extra-osseous) on MRI favors the diagnosis of tuberculosis. Three findings (intra-osseous abscess, soft tissue abscess, tenosynovitis), when present together, have a high sensitivity and specificity.