Answer for BIR CoW 28 Aug 2022
Rheumatoid arthritis with enhancing thickened synovium with joint effusion – active inflammation Juxta articular osteopenia with multiple marginal erosions in distal femur and proximal tibia Infected Baker’s cyst
Findings
Joint space narrowing seen – more on the lateral side Irregular cartilage erosion predominantly involving medial femoral condyle and articular surface of patella. Sub chondral bone erosion involving medial femoral condyle. Marginal erosions noted in lateral tibial plateau and posterior aspect of bilateral femoral condyles Thickened synovium showing enhancement on contrast seen, with moderate joint effusion. Patchy juxta articular hyperintensities involving tibial tuberosity, lateral tibial plateau and bilateral femoral condyles. Hyperintensity in posterior horn of lateral meniscus – degenerative partial tear. Peripherally enhancing cystic lesion insinuating between medial head of gastrocnemius and semimembranosus tendon
Discussion
Rheumatoid arthritis (RA) is a chronic autoimmune multisystemic inflammatory disease that affects many organs but predominantly attacks the synovial tissues and joints. The overall prevalence is 0.5-1% and the disease is 2-3 times more common in women. Onset is generally in adulthood, peaking in the 4th and 5th decades. The clinical features can be broadly categorized as articular and extra-articular. Generally, the onset of the condition may be insidious or abrupt, and early features commonly include tiredness, malaise, and generalized aches. Articular features generally develop prior to extra-articular features. Pathophysiology: The synovium in rheumatoid arthritis is infiltrated by immune cells, which include innate immune cells (monocytes, dendritic cells, mast cells) and adaptive immune cells (Th1 (T-helper 1), Th17 (T-helper 17), B cells, and plasma cells). Cytokines and chemokines like tumor necrosis factor (TNF), interleukin-6 (IL-6), and granulocyte-monocyte colony-stimulating factors activate endothelial cells and attract immune cells within the synovial compartment. The fibroblast in the rheumatoid synovium changes to an invasive phenotype. Fibroblast and inflammatory cells lead to osteoclast generation resulting in bone erosion, the hallmark feature of rheumatoid arthritis. Common radiographic expressions of rheumatoid arthritis in any joint consist of a number of well-recognized abnormalities. (i) Bilateral Symmetry: Invariably, parallel changes will be seen on both sides of the body simultaneously and to a similar degree of involvement. (ii) Periarticular Soft Tissue Swelling: Owing to soft tissue edema and intra-articular effusion, displacement of fat lines and peripheral skin contours will be visible. The density of the periarticular soft tissues is usually increased. These are typically the first radiographic signs of rheumatoid arthritis. (iii) Juxta-Articular Osteoporosis: Early in the disease, owing to inflammatory hyperemia, there is a localized loss of bone density of the epiphysis and metaphysis adjacent to the involved joint. Later, following disuse and steroid therapy, a more generalized osteopenia may ensue that predisposes the patient to acute and stress-type fractures. (iv) Uniform Loss of Joint Space: The entire joint space is diminished, with no isolated intra-articular compartmentalization as seen in degenerative joint disease. (v) Marginal Erosions (Rat Bite Erosions): A localized loss of articular cortex at the bare area of the joint margin with no definite sclerotic border at its edge is characteristic. (vi) Juxta-Articular Periostitis: Not a frequent sign but, when present, juxta-articular periostitis consists of either a solid or single lamination in the metaphyseal-proximal diaphyseal region adjacent to the involved joint. (vi) Large Pseudo-Cysts: These are analogous to subchondral bone cysts of DJD and are owing to the combination of synovial fluid and intraosseous extension of synovial pannus. Frequently, they will become large, up to 4–6 cm, and simulate a subarticular neoplasm or infection. (vii) Deformity: Owing to a combination of joint destruction, ligamentous laxity, and altered muscular action, subluxations, dislocations, and osseous misalignments are common and predictable. INFLAMMATORY VS METABOLIC VS INFECTIVE ARTHRITIS Inflammatory: The general radiographic features of inflammatory joint disease consist of soft tissue swelling and edema, uniform loss of joint space, bone erosions, juxta-articular osteoporosis, and occasionally periostitis of the adjacent metaphysis. These findings may be monoarticular or polyarticular. When polyarticular, a symmetric pattern of involvement is more frequent. There is a greater predisposition to bony ankylosis with inflammatory arthritis than in any other type of arthropathy. Inflammatory arthropathies include rheumatoid arthritis, psoriasis, ankylosing spondylitis, and Reiter’s syndrome. Metabolic: The radiologic findings of metabolic arthritis are the notable presence of soft tissue masses within the periarticular soft tissues, well marginated bone lesions, and a relative preservation of the joint space. (However, overlapping degenerative changes may occur if the nutrition to the articular cartilage is disturbed as in gout and pseudo-gout (calcium pyrophosphate dihydrate crystal disposition). Tubercular: Most tubercular arthritic lesions begin within the metaphysis as an infectious focus with secondary spread to the joint. With this mode of presentation the inflammatory changes in the synovial membrane are extensive, leading to significant early joint effusion. The infected synovial membrane becomes thickened, and granulation tissue spreads to the free surface of the articular cartilage. The the initial erosive lesions may simulate those of early rheumatoid arthritis. As the entire infective process progresses, a non-uniform destruction of the articular surface occurs. As cartilage and bone destruction ensue, sequestrum formation of variable size may occur. This process often involves both surfaces of the joint, leading to the characteristic kissing sequestrum. The degree of osteoporosis is often disproportionate to the extent of the infectious lesion.
REFERENCES:
1. Gabriel S. The Epidemiology of Rheumatoid Arthritis. Rheum Dis Clin North Am. 2001;27(2):269-81. doi:10.1016/s0889-857x(05)70201-5
2. Yochum And Rowes Essentials Of Skeletal Radiology 3rd SAE/2019 (2 Vols.) by Terry R. Yochum
Findings
Joint space narrowing seen – more on the lateral side Irregular cartilage erosion predominantly involving medial femoral condyle and articular surface of patella. Sub chondral bone erosion involving medial femoral condyle. Marginal erosions noted in lateral tibial plateau and posterior aspect of bilateral femoral condyles Thickened synovium showing enhancement on contrast seen, with moderate joint effusion. Patchy juxta articular hyperintensities involving tibial tuberosity, lateral tibial plateau and bilateral femoral condyles. Hyperintensity in posterior horn of lateral meniscus – degenerative partial tear. Peripherally enhancing cystic lesion insinuating between medial head of gastrocnemius and semimembranosus tendon
Discussion
Rheumatoid arthritis (RA) is a chronic autoimmune multisystemic inflammatory disease that affects many organs but predominantly attacks the synovial tissues and joints. The overall prevalence is 0.5-1% and the disease is 2-3 times more common in women. Onset is generally in adulthood, peaking in the 4th and 5th decades. The clinical features can be broadly categorized as articular and extra-articular. Generally, the onset of the condition may be insidious or abrupt, and early features commonly include tiredness, malaise, and generalized aches. Articular features generally develop prior to extra-articular features. Pathophysiology: The synovium in rheumatoid arthritis is infiltrated by immune cells, which include innate immune cells (monocytes, dendritic cells, mast cells) and adaptive immune cells (Th1 (T-helper 1), Th17 (T-helper 17), B cells, and plasma cells). Cytokines and chemokines like tumor necrosis factor (TNF), interleukin-6 (IL-6), and granulocyte-monocyte colony-stimulating factors activate endothelial cells and attract immune cells within the synovial compartment. The fibroblast in the rheumatoid synovium changes to an invasive phenotype. Fibroblast and inflammatory cells lead to osteoclast generation resulting in bone erosion, the hallmark feature of rheumatoid arthritis. Common radiographic expressions of rheumatoid arthritis in any joint consist of a number of well-recognized abnormalities. (i) Bilateral Symmetry: Invariably, parallel changes will be seen on both sides of the body simultaneously and to a similar degree of involvement. (ii) Periarticular Soft Tissue Swelling: Owing to soft tissue edema and intra-articular effusion, displacement of fat lines and peripheral skin contours will be visible. The density of the periarticular soft tissues is usually increased. These are typically the first radiographic signs of rheumatoid arthritis. (iii) Juxta-Articular Osteoporosis: Early in the disease, owing to inflammatory hyperemia, there is a localized loss of bone density of the epiphysis and metaphysis adjacent to the involved joint. Later, following disuse and steroid therapy, a more generalized osteopenia may ensue that predisposes the patient to acute and stress-type fractures. (iv) Uniform Loss of Joint Space: The entire joint space is diminished, with no isolated intra-articular compartmentalization as seen in degenerative joint disease. (v) Marginal Erosions (Rat Bite Erosions): A localized loss of articular cortex at the bare area of the joint margin with no definite sclerotic border at its edge is characteristic. (vi) Juxta-Articular Periostitis: Not a frequent sign but, when present, juxta-articular periostitis consists of either a solid or single lamination in the metaphyseal-proximal diaphyseal region adjacent to the involved joint. (vi) Large Pseudo-Cysts: These are analogous to subchondral bone cysts of DJD and are owing to the combination of synovial fluid and intraosseous extension of synovial pannus. Frequently, they will become large, up to 4–6 cm, and simulate a subarticular neoplasm or infection. (vii) Deformity: Owing to a combination of joint destruction, ligamentous laxity, and altered muscular action, subluxations, dislocations, and osseous misalignments are common and predictable. INFLAMMATORY VS METABOLIC VS INFECTIVE ARTHRITIS Inflammatory: The general radiographic features of inflammatory joint disease consist of soft tissue swelling and edema, uniform loss of joint space, bone erosions, juxta-articular osteoporosis, and occasionally periostitis of the adjacent metaphysis. These findings may be monoarticular or polyarticular. When polyarticular, a symmetric pattern of involvement is more frequent. There is a greater predisposition to bony ankylosis with inflammatory arthritis than in any other type of arthropathy. Inflammatory arthropathies include rheumatoid arthritis, psoriasis, ankylosing spondylitis, and Reiter’s syndrome. Metabolic: The radiologic findings of metabolic arthritis are the notable presence of soft tissue masses within the periarticular soft tissues, well marginated bone lesions, and a relative preservation of the joint space. (However, overlapping degenerative changes may occur if the nutrition to the articular cartilage is disturbed as in gout and pseudo-gout (calcium pyrophosphate dihydrate crystal disposition). Tubercular: Most tubercular arthritic lesions begin within the metaphysis as an infectious focus with secondary spread to the joint. With this mode of presentation the inflammatory changes in the synovial membrane are extensive, leading to significant early joint effusion. The infected synovial membrane becomes thickened, and granulation tissue spreads to the free surface of the articular cartilage. The the initial erosive lesions may simulate those of early rheumatoid arthritis. As the entire infective process progresses, a non-uniform destruction of the articular surface occurs. As cartilage and bone destruction ensue, sequestrum formation of variable size may occur. This process often involves both surfaces of the joint, leading to the characteristic kissing sequestrum. The degree of osteoporosis is often disproportionate to the extent of the infectious lesion.
REFERENCES:
1. Gabriel S. The Epidemiology of Rheumatoid Arthritis. Rheum Dis Clin North Am. 2001;27(2):269-81. doi:10.1016/s0889-857x(05)70201-5
2. Yochum And Rowes Essentials Of Skeletal Radiology 3rd SAE/2019 (2 Vols.) by Terry R. Yochum
Note:
We do not discourage differential diagnosis. But all the differentials must satisfy the findings noted in the case.
If you feel you have answered rightly but cannot find your name in the above list, please call 09551942599.
Did you Know?
The order in which the names appear in this winner's list is based on the time of submission. The first person to send the correct answer gets his/her name on top of the list!
We do not discourage differential diagnosis. But all the differentials must satisfy the findings noted in the case.
If you feel you have answered rightly but cannot find your name in the above list, please call 09551942599.
Did you Know?
The order in which the names appear in this winner's list is based on the time of submission. The first person to send the correct answer gets his/her name on top of the list!