They in’cyst’ed that we have a histological review

This 62-year-old female presents with a left wrist mass that has recurred five times after two prior drainages and two prior surgical removals.

Images 1 and 2 are in the short-axis view. Based on image 1 (a proton-density non-fat-suppressed image), and image 2 (a T2 fast spin-echo image with fat suppression):

Q1 – What is your diagnosis?
Q2 – Why do you think this abnormality continues to recur?
Q3 – What is the most likely origin of this mass in the wrist?

Based on image 3 (a coronal fat-suppressed proton-density image):

Q4 – What is the source of this abnormality?

While looking at images 4, 5, and 6, think about the following:

Q5 – How do a ganglion, a perimeniscal cyst of the knee, and a paralabral cyst of the shoulder, associated with meniscal and labral tears, differ histologically?

Axial PD

Axial T2

Coronal PD

Axial PD

Axial T2

Coronal PD

 

A1 – Ganglion pseudocyst.

A2 – The site of weakness or source of the mass has not been addressed.

A3 – The dorsal scapholunate capsule, usually near or proximal to the dorsal intercarpal ligament and / or dorsal long radiolunate ligament.

A4 – Lunatotriquetral capsule.

A5 – They are identical. It is the site of origin that differs. A ganglion, a perimeniscal cyst of the knee, and a paralabral cyst of the shoulder are all pseudocysts lined by fibrous tissue with mucoid content.

While these entities are histologically identical, the:

  • Ganglia arise from diffusion through a microscopic weakness or defect in the capsule or sheath of the tendon. These are often difficult to visualize on MRI.
  • Perimeniscal pseudocysts in the knee arise most commonly from a cleavage tear which usually communicates with the articular surface, but sometimes is intrameniscal and “blows out” the periphery of the meniscus.
  • Paralabral pseudocysts arise from labral tears that are widely gaping, healed, or partially healed (i.e. the tear is not always seen).

Either a perimeniscal or paralabral cyst can be macroscopic events where synovial fluid transgresses an open defect, or similar to a ganglion, can diffuse through very small defects. Frequently, the location or position of the pseudocyst is a dead giveaway to its origin; one must learn where these pseudocysts arise. For example, in the wrist, ganglia are far more common than perimeniscal cysts that arise from triangular fibrocartilage complex (TFC) tears. On the other hand, in the shoulder, ganglion pseudocysts are far less common than paralabral cysts arising from the superior labrum extending over the spinoglenoid rim, and involving the suprascapular notch.

The arrows in images 4, 5, and 6 show ganglion pseudocysts dissecting into the lunatotriquetral interval, a much less common site of origin than the scapholunate dorsal region for this abnormality. Oversewing or repair of the dorsal scapholunate capsule and adjacent extrinsic ligaments is necessary to prevent recurrence. This will require open visualization of the area.

Diagnosis: Dorsal ganglion pseudocyst with a “tail” to the lunatotriquetral capsule, and dissecting into it.

 

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Accessory muscles in the medial ankle

Today, we are examining accessory muscles of the ankle. To start us off, have a look at images 1 through 5. The areas of focus have been highlighted with arrows. What extra structure do you see in the tarsal tunnel?

As a review, the normal tarsal tunnel contains:

  • Posterior tibial tendon (PT) (image 5, red arrow)
  • Flexor digitorum longus tendon (FDL) (image 5, blue arrow)
  • Flexor hallucis longus tendon (FHL) (images 1, 4, 5, and 6, green arrows)
  • Posterior tibial neurovascular bundle comprised of the tibial nerve (divides into the medial and lateral plantar nerves), and the posterior tibial artery and vein

Axial T2 (Right ankle; 50-year-old male)

Axial T1 (Left ankle; 48-year-old female)

Coronal T1 (Right ankle; 16-year-old female)

Sagittal T1 (Right ankle; 16-year-old female)

Axial T1 (Left ankle; 49-year-old male)

 

The additional structure is the peroneocalcaneus internus (PCI) (images 1-5, yellow arrows); a rare accessory muscle in the posteromedial ankle. The PCI can originate from the inner / medial aspect of the distal fibula, and inserts onto a small tubercle on the medial calcaneus, inferior to the sustentaculum tali. The PCI is estimated to be present in approximately 1% of patients, and is usually asymptomatic. When symptoms occur, they may be caused by crowding of the tarsal tunnel, with compression of the neurovascular bundle. PCI can also be associated with posterior impingement.

Although uncommon, the PCI is an important structure to be aware of during endoscopic surgery via the posteromedial portal. In this approach, the surgeon probes anterior to the FHL to reach the medial talar dome for repair of Osteochondritis dissecans (OCD) or removal of loose bodies (see Diagram 1). This path avoids the tarsal tunnel neurovascular bundle. However, if the PCI is mistaken for the FHL, probing anterior to the PCI risks injury to the neurovascular bundle, which can lie medial and anterior to the PCI. The key to identifying the PCI is that it courses posterolateral to the FHL, and hence its alternate name, the “false FHL”.

Diagram 1. Ankle PCI Accessory Tendon – Axial

 

Other accessory muscles of the medial ankle include the flexor digitorum accessorius longus (FDAL) and the tibiocalcaneus internus. The FDAL (images 6, 8, and 9, pink arrows) is actually the most common medial ankle accessory muscle; even more common than the PCI. The FDAL is posteromedial to the FHL, and can either be superficial / medial, or posterior to the tarsal tunnel neurovascular bundle. The FDAL has a variable origin, and can arise from the tibia, fibula, FHL, or the soleus, and inserts onto the quadratus plantae or FDL.

The tibiocalcaneus internus (not shown) is the rarest among the medial accessory muscles, originating from the medial crest of the distal tibia and inserting onto the medial calcaneus, 1-2 cm anterior to the Achilles insertion.

The accessory soleus (images 7, 8, and 9, orange arrows) is another accessory muscle to be aware of in the medial ankle. It is distinguished by the fact that it lies medial to the flexor retinaculum, and is therefore located external to the tarsal tunnel. Whereas, the other accessory muscles lie deep to the flexor retinaculum, and are located within the tarsal tunnel. The accessory soleus originates from the soleus muscle, or the tibia and fibula, and inserts onto the posteromedial calcaneus.

Axial T1 (Right ankle; 43-year-old female)

Axial T2 (Right ankle; 39-year-old female)

Axial T2 (Left ankle; 54-year-old female) **Rare case of two accessory muscles in the same foot**

Sagittal T1 (Left ankle; 54-year-old female) **Rare case of two accessory muscles in the same foot**

 

In summary, the accessory medial ankle muscles are important structures to recognize as potential causes of tarsal tunnel syndrome, as these can contribute to medial pain in otherwise normal-appearing ankle MRI exams.

 

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His villi were filled with fronds

This 60­-year­-old male presents with left shoulder pain. The key areas of focus in this case have been highlighted.

Q1 – What is the most likely diagnosis of the intraarticular mass? For clues, you can also check out this case: Upon checking out the joint, we found lots of bodies

Coronal T1 SE

Coronal T1 SE

Coronal T2

Coronal T2

Axial PD

Axial PD

Sagittal T2

Sagittal T2

 

A1 – Lipoma arborescens.

Lipoma arborescens is an uncommon condition of the synovial lining of the joints and bursae with frond-like deposition of fatty tissue. Patients typically present in the 5th through 7th decades. The most common site of involvement is the suprapatellar bursa of the knee. However, other joints may be infected including the hip, shoulder, wrist, and elbow. Histologically, the normal synovium is replaced by hypertrophic villi demonstrating deposition of mature lipocytes. MRI is the modality of choice for diagnosis of these lesions which follow signal intensity of fat on all sequences.

 

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Upon checking out the joint, we found lots of bodies

This 54-year-old male presents with right knee pain that has continued for a year with no known injury. Have a look at images 1 through 3, and see if anything stands out.

Q1 – What is the most likely diagnosis?

Q2 – What is the differential diagnosis for the intraarticular bodies?

Coronal PD Fat Sat

Sagittal PD Fat Sat

Axial T2

 

A1 – The most likely diagnosis is primary synovial chondromatosis. Synovial chondromatosis is a rare monoarticular process characterized by cartilaginous bodies. Primary synovial chondromatosis has a predilection for the large joints, including the knee, hip, elbow, and shoulder, although it can be identified in any joint or tendon. It affects males more frequently than females, and it is most common in the third to fifth decades. The MRI signal characteristics of the intraarticular bodies varies depending on the amount of calcification and / or ossification (images 5 and 6, arrows). Rare, but primary synovial chondromatosis can undergo malignant degeneration.

A2 – Secondary synovial chondromatosis is more common than primary synovial chondromatosis. It usually presents in the setting of longstanding osteoarthritis. In this patient, note that the medial and lateral compartments of the joint space are preserved. Only a small marginal erosion of the medial tibial plateau is noted (image 4, green arrow). Secondary synovial chondromatosis does not undergo malignant degeneration.

Rice bodies would be an unlikely consideration in this individual who is male, middle-aged, and presents with a monoarticular arthritis as rice bodies are commonly identified in inflammatory arthropathies such as rheumatoid arthritis and tuberculous infections. They are smaller than synovial chondromatosis. Other intraarticular masses to potentially consider are pigmented villonodular synovitis (PVNS) which has diffuse and focal forms, and would not present as nodular densities, but as a mass. Blooming may occur on gradient images due to a lack of refocusing pulse on this sequence, and due to siderotic components. Lipoma arborescens is most commonly found in the suprapatellar bursa and follows fat signal. Synovial hemangiomas are typically high in signal on T2-weighted images.

Coronal PD Fat Sat

Sagittal PD Fat Sat

Axial T2

 

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When one projection just isn’t enough

This 53-year-old male patient presents with pain and catching of the right shoulder when lifting the arm above the head. You are shown proton density fat suppression sequences using STIR short T1 inversion recovery in the coronal and sagittal projections. The patient has a rotator cuff tear.

Q1 – Is the tear full thickness? Look at the blue arrow on image 1 before you make your decision.

Coronal STIR

 

Q2 – When you have made your decision in question 1, check out images 2 and 3. Note the additional pink arrow on image 2, as well. What do you think the blue arrow represents?

Coronal STIR

Sagittal STIR

 

A1 – The tear is not full thickness. It appears ominous and perhaps full thickness in the coronal projection (image 2, pink arrow), but that is because the outer shell fibers are curved and “en face” to the coronal image. However, in the sagittal projection (image 3), a clear hypointense outer shell (pink arrow) covers a partial thickness tear (yellow arrows).

This is a terribly important teaching point, namely that full thickness tears should appear to communicate with the bursal space in two projections. The outer low signal shell (image 3, pink arrow) confirms this in the sagittal projection. Additionally, the patient had surgery affirming the presence of a partial, not full thickness communicating, tear.

A2 – The blue arrow (images 1 and 2) points to the hypertrophied markedly thickened coracoacromial ligament which is often responsible for outlet related stenosis and clinical impingement syndrome. When the patient abducts, the rotator cuff comes in contact with the acromion and thickened coracoacromial ligament where it is repetitively “pinched” or impinged, especially in internal rotation.

 

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It’s hip, it’s obscure, it’s the case of the day

This 39-year-old female presents with hip pain that has continued for four months. Neither a cortisone shot, nor physical therapy could relieve the pain. Have a look at coronal images 1 and 2.

Q1 – What is the most likely diagnosis?
Q2 – Is this entity more common in males or females?

Coronal STIR

Coronal STIR

 

A1 – The most likely diagnosis is proximal iliotibial band (ITB) syndrome.
A2 – Proximal ITB is more common in females.

Proximal ITB syndrome is related to a strain or injury of the iliotibial band enthesis where the ITB attaches to the iliac tubercle. This entity is newly described by Sher et al. in 2011*, with few reports currently existing in literature. As such, little is known about the cause or treatment options.

To date, most results suggest there is a strong female predisposition; some of which are active runners. Others are non-athletic, some of which have a prior traumatic injury. Most commonly, patients are middle aged.

In magnetic resonance imaging, proximal ITB syndrome presents as areas of increased signal intensity adjacent to the iliac tubercle. Partial or complete disruption of the ITB may occur. The appropriate therapy is unknown. It is likely conservative for most patients.

*Reference: Sher I, Umans H, Downie SA, Tobin K, Arora R, Olson TR. Proximal iliotibial band syndrome: what is it and where is it? Skeletal radiology. 2011;40(12):1553-6.

 

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He tried to straighten his elbow, but it proved to be a “sloppy” mess

This 58-year-old male physical therapist, and world-class athletic trainer, now finds himself in need of rehabilitation. Have a look at the following GIF, and see if you can figure out why he cannot completely straighten his elbow.

Coronal STIR

 

Q1 (Advanced) – There are two clinical syndromes that are manifested on imaging in this case. Can you name them?

Coronal T1 FSE

Axial STIR

Sagittal PD FSE Fat Sat

Sagittal PD FSE Fat Sat

Coronal STIR

 

A1 (Advanced) – Image 1, a T1-weighted image, demonstrates a penetrating erosion at the corono-trochlear bump (pink arrow). A subtle fragment of bone or cartilage is indicated by the yellow arrow.

Now have a look at image 2. The blue arrow demonstrates an area of radial chondromalacia that is impacted by an osteochondral defect directly adjacent, and a body that lies between the radius and the humerus.

In image 3, a penetrating defect has produced signal alteration in the radius (pink arrow).

Turn your attention to image 4, and you will see a subtle osteochondral erosion on the humerus (green arrow).

Finally, observe image 5. The pink arrow shows an articular body. The yellow arrow highlights the impaction effect on the radius and its cartilage surface. The green arrows demonstrate inflammation of the common extensor tendon unit, and the adjacent purple arrow shows synovial hypertrophy of the lateral capsule consistent with capsulitis and lateral epicondylitis.

The two syndromes that one might observe on MR that can be translated clinically are:

(a) Lateral epicondylitis syndrome
(b) Sloppy hinge syndrome

The patient has clinical lateral epicondylitis syndrome due to inflammation and microtears of the common extensor mechanism. Go back and review the GIF to see the extensive lateral-sided inflammation both in tendon and soft tissues. This is not the cause for restricted range of motion, though.

The second syndrome is “sloppy hinge syndrome” associated with a loss of the normal smooth undulation of the humerus. Normally the humerus exhibits (a) two depressions, and (b) three bumps which are now interrupted by an osteochondral area of irregularity, and the body that has secondarily damaged the radius preventing full extension of the elbow.

 

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Have you ever measured the alpha angle in a knee?

This 50-year-old female presents with knee pain. There is no known injury, but the patient did have anterior cruciate ligament (ACL) repair 15 years earlier.

Q1 – How would you measure the alpha angle in this case? You may think I have lost my mind, and the wrong case is displayed, but I assure you it is correct.

Q2 – How would you measure the intercondylar notch distance?

Q3 – What is the significance of the alpha angle in the knee?

Q4 – What is the significance of the intercondylar notch distance?

Coronal T1

Sagittal T2 FS (60 TE)

Axial PD FS

 

A1 – A coronal T1 (image 4, pink arrow) shows a spur encroaching on the base of the femoral notch. A sagittal T2 (image 5), at the level of the posterior cruciate ligament, shows how you would measure the alpha angle. The green line is parallel to the long axis of the femur, and the yellow line is parallel to Blumensaat’s line of the femoral roof. In this patient, the angle is 29 degrees. Increasing alpha angles with a more horizontal femoral tunnel roof elevates the risk of notch impingement.

A2 – Have a look at the orange line in axial image 6. At this level, the trochlea is deep, and the insertion of the anterior cruciate ligament along the medial side wall of the lateral femoral condyle is the one to be evaluated (red arrow). The widest transverse dimension of the notch is measured as 1.56cm.

A3 – Alpha angles approaching 55-60 degrees or greater lay out the ACL in a more horizontal position in the native ungrafted knee, and place the ACL at greater risk for stress forces in flexion and extension. On the other hand, several authors have commented that a very vertical roof, and a very narrow alpha angle in ACL grafted knees, may result in an “unforgiving knee”. This would place grafted knees at greater risk for graft failure (American Journal of Sports Medicine, 1995).

A4 – The more narrow the distance, the more at risk the anterior cruciate ligament. A typical distance is 20mm measured at the right level. Patients with distances of approximately 15mm or less are at high risk for ACL deficiency or rupture. Most patients that have intercondylar notch distances of 12mm or less have ACLs that are absent or torn.

NOTES:

  • The alpha angle is similar in normal women and men.
  • The width of the intercondylar distance is more narrow in normal women than men.

Coronal T1

Sagittal T2 FS (60 TE)

Axial PD FS

 

Summary:
Individuals with large alpha angles approaching 55-60 degrees, and narrow intercondylar distances measured where the ACL attaches to the lateral condylar wall of less than 15mm, are at high risk for ACL stressors and subsequent rupture.

 

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Let’s start with the pinky, and see where it takes us

This 20-year-old male fell while skiing. Two weeks after the fall, the patient presented with pain, numbness, and tingling in the left pinky finger.

Can you identify the anatomic correlate of the patient’s symptoms? Have a look at images 1 and 2, and see if you can put the story together.

Axial T1

Axial T2

 

In images 3 and 4, the green arrows point to a mass that is hyperintense on T1 and on T2. This is compatible with a chronic hematoma and consistent with the patient’s history of a fall. The red arrows on image 3 also demonstrate a posteromedial superficial hematoma with T1 hyperintense blood related methemoglobin staining.

The anatomic correlate of the patient’s symptoms is the ulnar nerve. A pink arrow identifies the ulnar nerve as a slightly hyperintense structure on the T2 fat-suppressed image. While the signal of a nerve can be hyperintense to muscle on proton density fat-suppression (PD SPIR or PD STIR), it should be isointense or only slightly hyperintense to muscle on T2 imaging. This nerve is swollen and edematous. In addition, the blue arrow (image 4) identifies an area of cystic injury to the nerve which may be seen with blunt trauma, and is a common sequela in the peroneal nerve after a patient is struck by a car bumper, laterally. This is an analogous type of injury in the ulnar nerve as there was a direct impact. There should be no cystic high signal within a nerve.

Axial T1

Axial T2

 

Diagnosis:
Ulnar nerve contusion and interstitial injury without transection or total failure accompanied by a compressive hematoma.

 

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His ankle went one way, and he went another

This 24-year-old male performance athlete presents with inversion injury. The following axial images are in plantar flexion, 30 degrees.

Q1 – What is the pink arrow pointing to in images 2 and 3?

Q2 – To what is the blue arrow pointing in images 1 through 3?

Q3 – Given the findings highlighted with the pink and blue arrows, what is your imaging checklist?

Axial T1

Axial PD-SPIR

Axial T2

Axial FSE

Axial T1

 

A1 – Torn anterior talofibular ligament.

A2 – Torn calcaneofibular ligament.

A3 – The fact that the patient has a two-part ankle rupture involving the anterior talofibular ligament and calcaneofibular ligament, you should consider evaluating the following structures:

(a) The anterolateral soft tissues for hematoma (image 4, yellow arrow).

(b) The high ankle was normal. High ankle assessment should include the anterior tibiofibular ligament, interosseous ligament, and posterior tibiofibular ligament.

(c) The superior peroneal retinaculum is torn (image 5, green arrow), and peroneus brevis tendon demonstrates a split tear (image 5, red arrow).

(d) The talar dome, which was normal.

(e) Occult fractures; none of which were present.

(f) The subtalar space, and ligaments including the talocalcaneal interosseous ligament, cervical ligament, and lateral extensor retinacular / stem / frondiform ligament were all normal.

 

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