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Marlena Jbara: Welcome to podiatric radiology rounds. In this lecture, we are going to evaluate radiographic evaluation of degenerative arthritis. My name is Marlena Jbara and I am a bone and joint radiologist at Staten Island University Hospital at Northwell Health. Disclosures: I or related party have no financial relationship to disclose. Objectives: In this lecture, we are going to review imaging of articular diseases including degenerative types of typical wear and tear degenerative changes and atypical. Those degenerative changes of unusual age, site, severity including gout, hydroxyapatite deposition disease, also known as pseudo gout and neuropathic changes. Again, our main approach will be evaluating with x-rays and we will be able to provide a differential diagnosis at the completion of this lecture. Let's again take a look at some cases. Case 1, in this frontal x-ray, I will give you a second to look at that. Moving on to case 2, a cone down view of the hallux MTP joint. Case 3, a cone down view of the forefoot in this gentleman with an enlarged hallux MTP joint.

[02:06]

Case 4, painful swelling at the medial midfoot, two representative images. And case 5, lateral foot x-ray. So radiographic algorithm for adult. The starting point here will be joint space narrowing again and we will be looking for asymmetric joint space narrowing. Inflammatory arthritis, we saw in our last lecture was concentric joint space narrowing and in this next 30 minutes, we will be exploring diseases that result in asymmetric joint space or degenerative arthritic patterns. Again, you can refer it to landmarks articles by Jon Jacobson for descriptions of the evaluation of arthritis inflammatory and degenerative joint diseases in radiology 2008. Looking at an algorithm approach for joint space narrowing in the adult, in the degenerative pattern, there is asymmetric joint space narrowing, which is indicative of typical osteoarthritis. In the presence of an unusual distribution or an early age or advanced severity for age, we can consider atypical variations of osteoarthritis including trauma related arthritis, crystal deposition disease, neuropathic changes and hemophilia.

[04:01]

Just to review regarding rheumatoid arthritis in the presence of marginal erosions, this is indicative of an underlying synovitis where the synovium is inflamed creating an ingress of inflammatory cells into an area between the Hyaline cartilage and joint capsule known as a bare area. And we can see on this upper right example of this x-rays, these marginal erosions that can be seen in inflammatory arthritis. In contrast, degenerative arthritis the joint space narrowing isn't uniform. There is normal mineralization, the presence of osteophytes, sclerosis and eburnation. In osteoarthritis, you can see here in this example on the left, asymmetric joint space narrowing with tibiotalar osteophytosis and sunchondral sclerosis. We can see here on this lateral cone down view of the hallux MTP joint, the large osteophytes emanating from the hallux metatarsal head and the osteophyte corticated joint bodies along the dorsal aspect of the hallux MTP articulation. Where we saw joint space narrowing in the adult for inflammatory involved one joint, this was indicative of a mono-articular septic arthritis until proven otherwise. In septic arthritis, the articular findings include periarticular osteopenia, surrounding soft tissue swelling, erosions which initially began marginally, joint space widening secondary to joint effusion and then later joint space narrowing as the effusion erodes the cartilage to resultant uniform joint space narrowing.

[06:03]

We can see our familiar example that we showed at the beginning case presentations and this cone down view of the forefoot on the left where you see a mono-articular arthritis with juxta-articular localized osteopenia and erosion indicative of septic arthritis. Again, an example on the right, you may seem familiar where we see erosions along the tibiotalar joint space with subchondral sclerosis and surrounding swelling known as Phemister triad in a patient with tuberculous septic arthritis. Moving on to erosions from retrocalcaneal bursitis, we can see erosive changes here at an enthesophytic insertion of the Achilles tendon. Joint space narrowing in the adult, we are going to return to our charts separating inflammatory from degenerative arthritis. Again in inflammatory arthritis, we are looking for concentric joint space narrowing. But in degenerative osteoarthritis, looking at typical forms of osteoarthritis, this is going to be characterized by asymmetric joint space narrowing. Moving on to grading this entity, we will be looking at the Kellgren-Lawrence grading scale. So asymmetric joint space narrowing, osteophyte formation, sclerosis, subchondral cyst or geode formation are all indicative of underlying osteoarthritis. Kellgren-Lawrence further classified this into normal, doubtful, mild, moderate and severe ranging from no features of osteoarthritis to having an osteophyte, which definitely gives you mild osteoarthritis to having joint space reduction of any type would be moderate and then bone-on-bone phenomenon I reserved for grade 4 or severe osteoarthritis with subchondral sclerosis.

[08:02]

Typical osteoarthritis, this is a result of repetitive wear and tear on cartilage usually afflicting joints after the ages of 40 or 50 depending on your cartilage wear and characteristic joints will be involved. Osteoarthritis commonly involves the first MTP joint. We can see here on these two companion x-rays of frontal and oblique projection, the laterally projecting osteophyte also note that there are dorsal when the patient turns obliquely. The overlying soft tissue prominence, the joint space narrowing and subchondral sclerosis in this person who would be presenting with a hallux rigidus. Osteoarthritis in the foot has a scoring system and the scoring system is based on the presence of osteophytes and joint space narrowing with 0 being absent osteophytes and 3 being large bulky severe osteophytes. Joint space narrowing being none at 0 and almost bone on bone or joint fusion in grade 3 joint space narrowing. And radiographic osteoarthritis can be considered if it's presented a score of 2 or above as documented for either osteophyte or joint space narrowing from either the dorsal plantar or lateral view. And I have refer you to an excellent classification of radiographic osteoarthritis in affected joints of the foot by Benz. You can check that out in osteoarthritis cartilage in 2007. And here are few plates related to that journal article. Osteoarthritis of the first MTP joint ranging from 0, 1, 2, 3 as you can see with bone-on-bone phenomenon, osteophyte formation and asymmetric joint space narrowing.

[10:00]

Benz also provided lateral projections of osteoarthritis in this example of the first MTP joint noticed plate 0 where there is no joint space narrowing. Moving on to the right to plate 1 where you start to see a definite osteophyte here at the head and neck junction. Onto plate 3 where you see asymmetric joint space narrowing and enlargement of the osteophyte. Onto plate 4, which demonstrates asymmetric joint space narrowing, subchondral sclerosis, enlarged bulky osteophytes. Furthermore, osteoarthritis at other joints such as the first cuneometatarsal joint, you can see excellent plates dedicated to this disease where at the base you see no osteophytes or joint space narrowing moving on to mild osteophytes and subchondral cyst formation. Moving onto definite joint space narrowing at this third plate and then bone-on-bone phenomenon with osteophytes in subchondral sclerosis at plate 4. On this lateral projection, you can see going from 0 to 3 where there is normal joint space moving onto bone-on-bone with osteophyte production. To be inclusive, osteoarthritis commonly affects the knee as can be seen here with asymmetric medial femoral tibial compartment joint space narrowing, osteophyte formation and subchondral sclerosis. The same presentation as we will be looking at in the foot. Osteoarthritis in the hip, asymmetric supralateral wear and tear type joint space narrowing with osteophyte formation and the bone-on-bone phenomenon. Moving onto the AC joint where we were seeing some capsular mineralization as well as osteophyte production. In the hand, you are seeing osteophyte formation with bone production and joint space narrowing.

[12:06]

Moving on to our algorithm again a joint space narrowing with atypical wear and tear patterns of degenerative arthritis we can move onto types that have an unusual distribution, age or severity where we will be looking at atypical OA and not devoted to trauma or crystal deposition disorders, neuropathic or diabetic foot related diseases and hemophilia. Again, osteoarthritis the atypical variations aren't unusual distribution in early age of onset less than 40 years and an unusual appearance with secondary excessive subchondral cyst. In atypical osteoarthritis, we will be looking at that arthritis secondary to prior trauma. Also crystal deposition diseases such as gout and CPPD. Neuropathic osteoarthropthy such as the very common affliction of the diabetic foot. In posttraumatic osteoarthritis, there may be history of prior ankle sprains or injuries creating small cartilage fissures along the tibiotalar surfaces leading to subchondral sclerosis asymmetric joint space narrowing. And [indecipherable] [13:27] injuries along attachments of ligamentus such as in this case in syndesmosis. Posttraumatic osteoarthritis, in traumatic osteoarthritis, you can see the tibiotalar subchondral sclerosis, osteophyte formation seen here on the anterior aspect of this lateral x-ray. Of course, an arthrodesis to follow given the joint instability that might occur from having such incongruent articular surfaces and ligamentous chronic injuries.

[14:00]

Moving on to gout, radiographic findings in gout such as erosions notable to be punched out with an overhanging edge secondary to the tophaceous nodule present given the uric acid imbalance forming soft tissue nodules within the soft tissues and creating a pressure erosion with a sclerotic healing margin emanating from the bone obviously away from the joint. There may be a soft tissue prominence with mineralization and dense non-calcified tophi. Presence of frank calcifications may be unusual. Here you can see these dense mineralized gouty soft tissue deposits adjacent to the joint structure with well corticated punched out obvious erosions trying to deal with tophaceous gout as a tunnel towards the bone. Notice the relative preservation of the joint space, even the presence of intraosseous erosions as gouty erosions can be intraarticular marginal or bare area and eccentric as this example on the top right. Of course, gout, you have preserved mineralization. There is no periarticular osteopenia unless there may be a secondary inside it synovitis created or the patient may have two different diseases such as inflammatory arthritis and gout. Further examples of gout can be seen here in this example of having calcifications in our soft tissue tophi with very large well-defined erosions involving the hallux MTP joint. We can see fusion of the hallux MTP joint. Of course, moving away from this large area of interest, we can look towards the fifth metatarsal neck and again see a very large mineralized erosion.

[16:04]

Here across the hallux MTP joint, we see further areas of well-mineralized erosion and soft tissue tophaceous gout occupying at this example on the far upper right not only the hallux MTP but IP joints of great and further destructive changes along the fourth and fifth rays and toes. And this example on the bottom right, again you can see these large tophaceous deposits, well-corticated edges of the erosive changes and preservation of the joint space. Further examples of gout seen here on this example to the left, you have a frontal x-ray denoting a well-defined marginalized erosion with relative preservation of the joint. Notice the coronal T1 long axis view through the fore foot with its soft tissue nodular intermediate signal tophaceous gout creating well-defined erosions without a soft tissue ulcer in this person with gouty arthropathy. Moving on to this example here, where the person presented with a hot swollen great toe, we can see this well-corticated erosions at the hallux MTP joint not only involving the medial hallux metatarsal head but also the proximal phalangeal base. On this long axis coronal T1 weighted central image, we can see the soft tissue nodule, the tophus itself with this intermediate heterogeneous elevated T2 signal intensity. Here, a representative image of the same patient through the lateral aspect of the mid foot denoting these well-corticated erosions replacing the subchondral bone marrow with no reactive edema and an associated soft tissue nodule identified here by this blue arrow and lateral to the base of the fifth metatarsal consistent with gout arthropathy.

[18:07]

Moving on to CPPD or calcium pyrophosphate dihydrate deposition disease, the distribution is predictable at the wrist at the radial carpal at second and third MCP joints. It's also known to be isolated patellofemoral involvement as characteristic of the disease. The appearance is known to have subchondral cyst, chondrocalcinosis involving the wrist, knees, pelvis in particular the pubic symphysis. Examples in the knee, here include meniscal chondrocalcinosis and then in this case Hyaline chondrocalcinosis as well. There is also increased calcium deposition at tendon and ligamentous sites as seen here in the medial gastrocnemius and joint capsule. And of course a classic example of pubic symphyseal chondrocalcinosis denoting CPPD. This atypical crystalline deposition disorder promote advanced osteoarthritis at earlier ages and characteristic findings include TFC or triangular fibrocartilage chondrocalcinosis and important ligament within the wrist with the distribution of the second and third MCP and in this case the basal joint also with subchondral cyst, osteophyte formation and asymmetric joint space narrowing. Moving on to neuropathic osteoarthropathy as described by Jean Martin in 1868. This is a severe progressive arthropathy as denoted by his x-ray on the right. Here what we see is joint destruction, dislocation, debris, disorganization.

[20:03]

The etiology is unknown. There is an increased blood flow with osteopenia followed by sclerotic repair with imbalance occurring from osteoclastic and osteoblastic activity. It's a result of unperceived trauma to an insensate foot. Repetitive micro trauma results in progressive destruction with attempts to repair. This was initially described in disease of syphilis also known as tabes dorsalis and the theories range from neurovascular to neurotraumatic. The pathophysiology of Charcot operates through three pathways of sensory and motor and autonomic. The demyelination occurring from the over-glycosylation throughout the body results in impaired sensory perception of pain, temperature, vibration and touch as a response to injuries of mechanical, thermal and chemical and also may formed followed by an ingress of bacteria and osteomyelitis. Of course, motor pathways are affected through small muscle atrophy given the over firing from demyelinating nerves. Imbalance in flexor and extensor muscles becomes the [indecipherable] [21:21] toe clawing, prominence of the metatarsal heads and altered gait results in calluses, blisters and again ulcer breakdown. In the autonomic department, we have decreased sweating, dry scaly skin, fissures resulting in ulcers and ultimately infection followed by autonomic changes of AV vascular shunting, decreased cell nutrition, decreased capillary pressures, increased soft tissue edema leading to poor healing and infection. All of this will total to 6Ds of dislocation, debris, disorganization, destruction, density increase and joint distention and that is the pathophysiology of a Charcot.

[22:10]

Charcot neuroarthropathy can be seen through this disorganized, debris, sclerotic, dislocated midfoot with chronic new bone formation and you can see the changes in weightbearing resulting in an ulceration plantar to cuboid and resultant osteomyelitis. Charcot versus osteomyelitis, we can predict based on the weightbearing mechanism of the current foot with the pressure points being affected first at the first, fifth and heel being Codman's triangle. Neuropathic changes will occur with greater than 85% distribution not only at the forefoot from the toe clawing or the prominence of the metatarsal head but also at Lisfranc joint at the mid foot and at Chopart articulation between the hind to midfoot region. Charcot and necrotizing infection can result from the ingress of necrotizing bacteria and you could see locules of gas adjacent to disorganized neuropathic midfoot changes. Charcot and septic arthritis can coexist as it's seen in this example here with erosive changes along a disorganized tibiotalar joint with multiple chronic changes of chronic ligamentous sprain along the intraosseous membrane. Neuropathic joint can result in asymmetric joint space narrowing, osteophyte and even rocker bottom deformities as seen here. So moving onto a discussion where we began our cases, we can see case 1 with the history that was withheld again was a gentleman with a swollen hot second toe presenting this way with this x-ray demonstrating erosive changes, juxta-articular osteopenia and erosion in a person with septic mono-articular arthritis.

[24:16]

And take-home point there is going to be just that. In the presence of the a septic of a single joint involved with an erosive process, we will consider septic arthritis as the leading differential and recommend laboratory correlation to begin the early treatment regimen of antibiotics. In case 2, what we can see in this cone down view of the hallux MTP articulation, we see asymmetric joint space narrowing, subchondral sclerosis and osteophytes in someone with grade 4 osteoarthritis. In this third example, we see an enlarged hallux MTP joint with large soft tissue partially mineralized dense tophi, erosions involving the hallux metatarsal head with well corticated edges and relative preservation of the joint space again with intraarticular erosions, a finding notable in gouty arthritis. In this example provided by [indecipherable] [25:15] from diabetes and endocrinology, this x-ray on the left we see a frontal view of the foot with a calcification along the medial border of the medial cuneiform within the soft tissue. On CAT scan, we can see further with its better spatial resolution that calcification is indeed within the substance of the terminal insertion of tibialis anterior and this is the case of hydroxyapatite deposition or calcific tendinosis often presenting with swelling and pain. And of course, case 5 what we see here is a disorganized debris dislocated foot with rocker bottom deformity in this patient with neuropathic osteoarthropathy.

[26:04]

For extra credit, we can see that cuboid plantar soft tissue ulcer, which will provide the ingress of bacteria and create a situation of osteomyelitis in this neuropathic foot. In summary, I provided a radiographic algorithm that begins with the assessment of joint space seeing asymmetric joint space narrowing in degenerative arthritis. Again just to remind you, in inflammatory arthritis, we were looking at concentric or symmetric joint space narrowing as a starting point for our algorithmic evaluation. We are going to be looking toward breaks in the cortex or erosions as seen in inflammatory arthritis versus osteophyte formation as seen in degenerative or atypical arthritis. In inflammatory arthritis, we will remember that if it's a solitary joint involved, a mono-articular arthritis, that will be termed septic until proven otherwise and we will correlate with white count and fever and systemic symptoms. In the case of multiple joints involved, we looked for proximal disease being periostitis. Without periostitis and osteopenic in RA versus having distal with periosteal new bone formation and seronegative inflammatory arthritis. In summary, degenerative arthritis can be divided into typical and atypical forms. The typical form is your typical wear and tear associated with advancing age and the atypical forms are those of an earlier age, the nonweightbearing sites of distribution and severe disease. Diseases such as gout, hydroxyapatite deposition, pseudo gout, and neuropathic osteoarthropathy are included in this latter category. Thank you. This concludes the second part of our radiographic evaluation of arthritis in the lower extremity. Part 1 included inflammatory arthritis and we are concluding now with part 2, degenerative and atypical degenerative patterns. I hope you have found this series useful and thank you for your time and attention.


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