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Marlena Jbara: Welcome to podiatric radiology rounds. We are going to begin with the radiographic evaluation of inflammatory arthritis. My name is Marlena Jbara and I am a bone and joint radiologist from Staten Island University Hospital at Northwell Health. Disclosures: I or related party have no financial relationship to disclose. Objectives: In this lecture series, we will review imaging of articular diseases. We begin with the inflammatory and in part 2 move on the degenerative. I will give you an approach to the radiography and a differential diagnosis. A few cases to look at before we begin. If you would like to take out of a piece of paper and take a guess as to what you think is going on an each of these images. We will come to them at the end to review. Case 1, frontal x-ray of the forefoot. Case 2, another frontal x-ray of the forefoot. Case 3, a cone down series of progressive images for a certain index patient complaining of joint pain. Case 4, bilateral AP weight-bearing x-rays of the feet.
Okay, so in this lecture, we will be looking at objectives such as the review of imaging of articular surface disease including inflammatory arthritis such as rheumatoid arthritis and psoriatic arthritis. We will move on to take a look at septic arthritis, reactive arthritis with again an approach using x-rays and a provision for differential diagnosis. The algorithm at the beginning of any radiographic pursuit in the inflammatory arthritis is joint space narrowing. And we will be looking at the difference between that type of joint space narrowing seen with inflammatory versus that type with degenerative, and I encourage you to see this excellent articles from Dr. Jon Jacobson, evaluation of arthritis, inflammatory conditions and radiology 2008 with an adjunct evaluation of arthritis, degenerative joint diseases and variations again in radiology 2008. In that article, Dr. Jacobson points to joint space narrowing, inflammatory versus degenerative. Inflammatory arthritis if we see one joint we think about septic arthritis or infection and of course more than one joint with thinking about whether or not the patient may have periosteal bone formation or no periosteal bone formation. In the absence of bone formation, we will be thinking about rheumatoid arthritis, classically identified for its osteopenia versus those patients who have inflammatory findings of having more than one concentric joint space narrowing with periosteal new bone formation, and therefore have seronegative inflammatory arthritic patterns. In the second series, we will look at degenerative arthritis in terms of typical and atypical patterns including trauma, crystal, neuropathic and hemophilic presentations.
An inflammatory arthritis, the earliest part of the disease is going to point towards periarticular osteopenia. The inflammatory mediators and the synovitis create an osteoclastic effect and you will see soft tissue swelling. The erosions are usually marginal initially created at the junction of the articular cartilage with the joint capsule and an erosion is defined as a cortical discontinuity. The joint space narrowing is uniform and here we can see an example of this patient one year apart where they had joint space narrowing, which was concentric. That later on went on to erode the bone at the bare area, the junction of the articular cartilage and joint capsule. Marginal erosions and rheumatoid arthritis again in these diagrammatic sketches on the bottom showing the pathology on x-rays at the top with a few outlines at the joint capsule and the articular cartilage. That area in red representing that area of the bare area or area of erosion, which we can see on this examination on the right later on down the line with these bone erosions at the bare area. And here you can see this illustrative example of the joint capsule becoming inflamed and red and creating areas of ingress of osteoclastic activity creating bone erosion. So looking at joint space narrowing in the adult for inflammatory arthritis with one joint, we will be thinking about a monoarticular arthritis and of course in that finding they look very similar to that of inflammatory arthritis, namely periarticular osteopenia, soft tissue swelling, erosions, which are initially marginal.
Initially, you have joint space widening and later on you can have joint space narrowing, which is uniform. In this example, which may look familiar to some of you at the beginning for our series, these are two examples of septic arthritis. This example on the left is frontal x-ray demonstrating a monoarticular arthritis with juxta-articular erosion and osteopenia and circumferential soft tissue swelling. Of course, this example on the right, what you are seeing here are erosions along the joint surface with a peculiar subchondral sclerosis and exaggerated soft tissue swelling. A finding that can be seen with TB arthritis namely Phemister triad. Moving on to a joint of inflammatory arthritis where it's more than one joint without periosteal reaction on new bone from rheumatoid arthritis. And the key to this diagnosis is joint inflammation. It is a true synovitis. Osteopenia is created and there is a characteristic distribution of bilateral hands, wrist and feet. In rheumatoid arthritis, this is afflicting the synovial joints with periarticular osteopenia, soft tissue swelling, erosions that are initially marginal, joint space narrowing, cyst formation and subluxations. In rheumatoid arthritis, you will notice that there is a distribution in the feet and other MTP joints but namely the fifth metatarsal head is usually afflicted early. The first IP joint of course can also be affected and there is an association with retrocalcaneal bursitis. Early erosions can be seen rheumatoid arthritis as in this example where you initially notice a small cortical irregularity, which worsens and follow up imaging to erosive changes with juxta-cortical osteopenia and soft tissue swelling.
Later on the erosions of rheumatoid arthritis, you can see quiescent sclerosis denoting partial healing through erosions. Here in this example, on the right you can see that the erosions are becoming more and more corticated at the bare area. Erosions from retrocalcaneal bursitis can be seen, although more often seen in psoriatic arthritis. We can see here erosive changes along the Achilles attachment. Further examples of rheumatoid arthritis has bare area erosions along the fifth metatarsal head and along the fifth proximal phalangeal base and later on with subsequent treatment noticing increasing sclerosis. Later stage rheumatoid arthritis, you are seeing joint subluxation with erosions followed by degenerative secondary changes. Rheumatoid arthritis, you can see in this case of joint space narrowing with MTP joint erosion and IP joint erosion as well in this patient with osteopenia. Rheumatoid arthritis distribution in the hands as seen on this little chart to the right primarily involves the MCP joints and involves the PIP greater than DIP joints. The carpal bones are frequently affected with pisiform triquetral articulation involved early in the disease and one of the most reliable places to look for a rheumatoid arthritis erosion is at the ulnar styloid. In rheumatoid arthritis, we can see these examples here with concentric joint space narrowing in the osteopenic patient with marginal erosions.
Rheumatoid arthritis also affects other sites with its synovitis. In particular, at the C1-2 level, the transverse ligament, which secures the odontoid process to the anterior arch of C1 becomes inflamed. This can allow cranial cervical settling as the odontoid peg tunnels into the foramen magnum or cranial base. The facet joints also can be inflamed, which are peripheral synovial line joints in the spine bare is a resultant uniform joint space loss without osteophytic repair. The disease or rheumatoid arthritis again is characterized by osteopenia and the presence of erosions. Bursae with synovial lining also can become inflamed and distended. Here in this example at the C1-2 articulation in the process with rheumatoid arthritis, we note the Atlanto-Dens interval being less than 1 mm in this x-ray on the left and then with flexion there is abnormal motion at the Atlanto-axial articulation increasing to 2.5 mm here. In rheumatoid arthritis larger joints, this subacromial subdeltoid bursa can become inflamed, decompressed and erode into the humeral head and create rotator cuff tears. In evaluating joint space narrowing, we continue our discussion of inflammatory arthritis, which is characterized by a concentric joint space narrowing. When more than one joint is involved and there is periosteal new bone formation predominantly distal in the digits, we will be considering seronegative spondyloarthropathy as a cause for the concentric joint space narrowing. In seronegative spondyloarthritis, we have the synovial joints involved with erosions, uniform joint space narrowing but in this case we have more propensity for periosteal bone formation or periostitis.
This often affects the cartilaginous joints with erosions and in addition, there is a propensity towards the enthesis to be involved. So that's at the tendon and ligament attachments where you can see fluffy enthesophytes and active disease and erosive changes. In seronegative spondyloarthritis, the key to diagnosis again is in distribution. In the psoriatic patient, the hands greater than the feet, spine and SI joints are involved. In reactive arthritis, there is a propensity to the feet and SI joints with axial arthritis. In ankylosing spondylitis, the axial skeleton followed by the glenohumeral joints are involved in a predictable ascending pathway. In these examples of psoriatic arthritis, in the foot and ankle, the distribution may be variable not affecting bilaterally and symmetric joints but affecting two here and three here mostly in a distal distribution. They can be unilateral or bilateral. Often I used the term oligoarthropathic in my dictation when I am describing this entity. Additional findings can be seen such as the ivory phalanx and we will see examples of that at the distal digits. You can see these scaly skin changes that occur in psoriatic arthritis, which you may encounter in clinical practice. In psoriatic arthritis, we often see the amputated appearance of the heads of phalanges with over hanging edges and pencil and cup deformities. This representing the periosteal new bone formation encapsulating the inflammatory area. In these examples, we can see here this example on the far right the ivory phalanx, the increasing sclerosis of inflammatory arthritis as seen in psoriasis.
Of course, this example on the left showing the whiskering effect on the distal phalanx and the periosteal new bone formation. On the bottom left, you can see the beginning of what's called a pencil and cup deformity as the hallux proximal phalanx tunnels into the distal phalanx. With healing, you can see some sclerotic edges on the central lower image denoting post treatment effect. In psoriatic arthritis in these examples, you can see the oligoarthropathic distribution again of these cone down images of healed erosive changes along bilateral lesser phalangeal articulations. Of course, to be inclusive, psoriatic arthritis in the hand and wrist, the distribution can be variable again in distal, mono or polyarticular, uni or bilateral with additional findings in the soft tissues such as a sausage digit or pencil and cup type erosion again in top resorption as we saw in prior examples. We can see here in psoriatic arthritis involvement of the wrist, we see whiskering in ulnar styloid periosteal new bone formation along its erosion and also along the triquetral pisiform articulation. Moving over here, we see the distal scaphoid tubercle and the trapezium and base of the metacarpal, you can see that fine periostitis in those erosive changes occurring in the patient with psoriatic arthritis. In psoriatic arthritis, we can look at the soft tissues what we were talking about before the sausage digit, which represents a cellular mediated soft tissue reaction sort of a thickened indurated feel to the clinical pattern, which you sometimes can see in the toes.
And the adjacent erosion along the proximal and middle phalanges and the central erosions beginning a pencil and cup type deformity soon. Psoriatic arthritis is characterized by subluxation and erosive destabilizing deformities. There is fusiform soft tissue swelling noted and this is in a bilateral oligoarthropathic asymmetric distribution. Psoriatic arthritis in the spine can include paravertebral ossification commonly in 17% with big comma-shaped syndesmophytes along the thoracolumbar junction thus seen in frontal projections and sacroiliac joints characterized by classic bilateral asymmetric involvement. Examples in psoriatic arthritis here at the left with paravertebral ossifications which bridge, which is best seen in the frontal projection and this example on the right with near fusion of the sacroiliac joints with erosive changes and remodeling in this patient with chronic asymmetric sacroiliitis. Moving on to reactive arthritis, the distribution on the lower extremity particular in the feet, bilateral asymmetric or symmetric pattern, involvement of the distal phalanx first digit, it can also be presenting as an ivory phalanx and inflammatory enthesopathy as we have seen in psoriatic arthritis. This example of reactive arthritis in these three representative x-rays cone down from this great toe, we can note the erosions and whiskering and periosteal new bone formation notable at the distal phalanx and proximal phalanx and the associated soft tissue swelling.
In reactive arthritis, we can see in this example of this active erosion occurring along the heel spur at the plantar aspect of the calcaneus. We can see on the bone scan the areas of increased uptake denoting the active enthesopathy physiologically occurring. And on the MRI on this sagittal STIR image, we can see the insertion of the Achilles tendon with the subcortical high signal changes, the retrocalcaneal bursitis and the plantar heel swelling occurring in this patient with enthesopathy. Reactive arthritis formally known as Reiter's syndrome is a form of inflammatory arthritis that develops in response to an infection. It's characterized by axial involvement. In the spine, imaging findings include paravertebral ossification often comma shaped, best identified on frontal projection at the thoracolumbar junction. Classic findings in sacroiliac joints include a bilateral asymmetric sacroilitis characterized initially by exuberant sclerosis followed by ankylosis. Moving on to ankylosing spondylitis just to be inclusive of the seronegative spondyloarthritis, this is an osteitis that occurs notably in the thoracolumbar junction. Different names have been given to the types of erosions occurring along the endplates, the anterior corners. They have been termed Romanus lesions, and when they heal with sclerosis they are given the name shiny corner and you might see them as squaring of the vertebra and you can see in these examples what I mean. The outer fibers of the annulus notable as Sharpey's fibers begin to lay down mineralization and fusion becomes squared off and here is an example that also has a shiny corner sign lower down.
In ankylosing spondylitis, the enthesopathy will proceed in a predictable direction moving from the sacrum to the lumbar to the thoracic and up to cervical spine. In the sacroiliac joint, there will be a bilateral symmetric sacroiliitis. The erosions will initially be there and seen as widening followed by sclerosis and narrowing of the joint soon to be followed by imperceptible fusion across the joint. Here you can see on this example on the left. There is a bilateral sacroilitis with exuberant sclerosis and moving on to a more chronic stage of the disease where you barely see sacroiliac joints secondary to the fusion that has occurred. An ankylosing spondylitis just for completeness sake, this affects the hips for 93% bilateral. Uniform joint space loss is seen acetabular protrusion. Osteophyte formation can occur secondarily with enthesopathy seen as a color of enthesophytes around the head and neck junction. You can see cyst formation from the synovitis and ankylosing spondylitis also affects all joints. In ankylosing spondylitis, you can see here bilateral symmetric joint space narrowing with subchondral cyst identified secondary to the synovitis occurring. Ankylosing spondylitis causing large erosive changes at the humeral head greater tubercle junction with enthesopathy and new bone repair. So moving back to our initial cases that we began at the onset of our lecture, we can now make some informed decision and I would like to go over them with you.
So here seen in case 1, our patient with a frontal view of his x-ray, what I failed to tell you at that time was that he presented with a fever, a white count and red swollen toe and what you can see here is that there is a juxta-articular monoarticular process occurring with joints space erosion and this is a pattern consistent with septic arthritis. Moving on to case 2, what we can see here is a patient with osteopenia and multiple MTP joint subluxation with a symmetric distribution of bare area erosion, notably a patient who would be afflicted with rheumatoid arthritis. Moving on to the next case patient, we have three x-rays and sequential time initially demonstrating the bare area erosions with fluffy periosteal new bone formation followed by further erosion along the hyaline articular surface followed by further pencil and cup deformity and widening of the edges in a patient who is afflicted with psoriatic arthritis. Moving on to our next patient with bilateral asymmetric oligoarthropathic distribution appearance of amputated metatarsal heads on the left with subluxation in a patient with reactive arthritis. So in summary, what we spent the last minute doing is to discuss inflammatory arthritis. We have looked at solitary joints involvement with erosions. We are going to immediately suspect a monoarticular septic arthritis. We will correlate with white count, fever and get that patient their appropriate antibiotic regimen as clinically necessary.
If we are dealing with multiple joints, we will be looking at whether the pattern is proximal and whether or not there is osteopenia or lack of new bone formation and will be considering a very common entity of rheumatoid arthritis. In the patient with distal disease with periosteal new bone formation, perhaps sausage digits, we will consider seronegative inflammatory arthritis and we will consider rheumatologic evaluation with laboratory followup. In summary, the radiographic algorithm will include assessment of joint space narrowing to differentiate inflammatory versus degenerative patterns. We will be looking for concentric joint space narrowing in inflammatory arthritis versus asymmetric joint space narrowing in degenerative osteoarthritis. And of course, we will be looking for the presence of erosions more likely to be seen in inflammatory arthritis versus osteophytes, which are more commonly seen in degenerative arthritis. Thank you for your time and attention.
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