> Skip repeated content

Cases of the Month: Diagnosis Index

Case 151 Accessory Soleus Muscle 

I hope I did not give this case away but felt it only appropriate to label this accessory muscle as a “mass” during this presentation. There are numerous accessory muscles especially around the foot and ankle. They are always diagnosed by the same signal and architecture as skeletal muscle just in an aberrant location. By in large these muscles are of no consequence but at times they may become symptomatic. Particularly as relates to this accessory muscle, it lies superficial to the flexor retinaculum and within Kager’s fat pad and hence on a radiograph a soft tissue structure is seen effacing or obliterating Kager’s fat pad. Although many other accessory muscles can be present in the posterior aspect of the ankle, most lie deep to the flexor retinaculum and hence do not produce an effacement of the fat pad.

When accessory muscles are in close proximity to neurovascular structures they can cause mass effect upon these structures. In this case, the tibial nerve is adjacent to the muscle and it is easy to see how there may be mass effect upon the nerve especially if there is muscle hypertrophy. The same process occurs for the anconeus epitrochlearis and the ulnar nerve. The accessory soleus is known to have varied insertions including directly into the calcaneus and either via a tendinous or muscular attachment to the superior or medial calcaneus. As seen here, if the attachment is separate from the Achilles, it is always anterior and medial to the Achilles attachment to the calcaneus. Although knowing the names of accessory muscles is nice, recognizing them and identifying if they have mass effect upon critical structures is much more important.

Case 150 SAPHO Syndrome 

SAPHO is an acronym of synovitis, acne, pustulosis, hyperostosis, and osteitis. A still somewhat vague entity which is not completely understood. It is an inflammatory/auto immune process which many feels represent the adult form of CRMO although it does have differences. Often SAPHO also incorporates more so findings of seronegative arthropathies than CRMO. SAPHO typically will cause lesions of the vertebrae at the corners thought related to enthesopathic changes at the Sharpey fibers attachment and longitudinal ligament attachments. In the active phase, edema is precipitated and over time fatty replacement ensues. This can produce a spiculated architecture of the vertebrae on axial images. As compared to a metastatic process with random distribution, these findings are found at the corners of the vertebrae. Not shown in this example, but an inflammatory spondylodiscitis similar to an Andersson lesion of ankylosing spondylitis can occur.

SAPHO very characteristically causes inflammation of the SC and MS joints which in this case produced the increased uptake on the bone scan. It can cause an inflammatory sacroiliitis or as seen in this case areas of focal bony abnormality of the iliac bones adjacent to the SI joints as these areas are metaphyseal equivalents which frequently show focal abnormalities. This diagnosis frequently is delayed as often the constellation of findings is needed to come to the correct diagnosis.

Case 149 Aponeurotic Expansion of the Supraspinatus Tendon (ASET)

Diagnosis: Aponeurotic Expansion of the Supraspinatus Tendon (AEST) In earnest, the supraspinatus tear and to some degree the subscapularis tear are not the thrust of this case although the subscapularis tear is important to highlight this normal variant. The subscapularis tear in this case allows a dislocation of the long head of the biceps which is severely tendinotic. Tissue is present in the bicipital groove which on first look appears to represent the biceps tendon but with closer inspection ends at the level of the pectoralis major tendon. The structure on the axial images with ?LHBT represents the AEST. The structure with the ? what is this structure represents the dislocated and tendinotic long head of the biceps.

There are many variants about the long head of the biceps . In some individuals there is an accessory attachment to the anterior or leading edge of the supraspinatus. Some people have a prominent vincula which is a thin band of connective tissue providing blood supply to the LHBT. This would be found along the anterior aspect of the tendon and attach to the tendon sheath. The AEST is a tendon like structure that extends from the far anterior supraspinatus tendon, traverses anterior and lateral to the LHBT, and inserts onto the superior aspect of the pectoralis major tendon. This is imperative to recognize and not mistake for the LHBT as the dislocated LHBT will frequently require surgical management to eradicate patient symptoms. 78

Case 148 Fractured Polyethylene Post of TKA

A rare complication and one that the surgeon was alert to in this case particularly given the patient’s history and physical exam. As in this case there is often not a high energy traumatic event but a gradual wearing of the tibial post with a low grade injury causing the final displacement (the low signal, geometric focus is a portion of the displaced post). The tibial post fits into the metal cam or box of the femur to help allow for greater rollback of the femur and a greater degree of knee flexion. The post also helps prevent a posterior displacement of the femur during this maneuver. The keys in this case are one, assistance from the referring surgeon in terms of what to look for but also understanding what the normal architecture of the prosthesis should be. Once that normal architecture is distorted it alerts the radiologist to seek out the specific abnormality. This case also illustrates the marked utility of advanced protocols tailored around metal to allow accurate diagnoses. Not seen in this case but with a hyperflexion x-ray, a posterior displacement of the tibia can be seen. This patient underwent subsequent revision without any complication.

Case 147 Seymour Fracture

Seymour fracture is a pediatric injury similar to the mallet finger in the adult. It occurs when forced flexion causes an extension moment about the DIP. In the skeletally immature patient a mallet finger injury can occur where the fracture is seen to extend into the joint or a Seymour fracture can be sustained. As seen in this case, the injury causes a widening of the physis and may cause low grade injury to the metaphysis but does not extend into the DIP joint. Because of the injury about the extensor apparatus the distal phalanx falls into mild flexion.

With the injury propagating into the germinal matrix and nail plate or nail bed these injuries are treated as open fractures necessitating anitibiotics, nail plate removal with irrigation and debridement, nailbed repair, and fracture reduction. Although the injury appears somewhat innocuous, if not treated appropriately it can lead to chronic osteomyelitis, flexion deformity, growth disturbance, or nail abnormalities.

Case 146 Superior Capsular Reconstruction Disruption

The low signal band of tissue shown in this case is a dermal allograft which is utilized to perform a superior capsular reconstruction (SCR). First performed utilizing a fascia latagraft it is now performed with a dermal allograft. The procedure is performed in the setting of an irreparable rotator cuff tear of the SST or SST/IST in patients without advanced arthritis, a functioning deltoid, and an intact or reparable SS tear. As part of the technique, the graft has multiple fixation sites at the glenoid and the tuberosity but in between the areas of fixation the graft sits at the glenoid and the tuberosity. Additional fixation is also performed of the graft to the IST tendon or muscle to prevent humeral head subluxation.

The spot of graft failure has been studied in the literature although with most case series being small. The sites of potential graft failure are at the glenoid, midsubstance, the greater tuberosity, the fixation to the IST, or at multiple locations (global failure). Some reports have had greater failure at the tuberosity, but many others including one of my colleague’s investigations had greater failure at the glenoid. Although midsubstancefailures seem to be the least prevalent, the important point is to be aware that failure can occur at multiple locations.

Special thanks to Tate Greditzer, MD for his assistance in the preparation of this case presentation.

Case 145 Ramp Lesion

The entity of meniscal ramp lesion is one that has gained recent, great popularity given new findings in the literature as relates to healing capacity and persistent instability if ramp lesions are not fixed/healed. Adding to this is the difficulty in often seeing these injuries at the time of arthroscopy and awareness to recognize these injuries at the time of preoperative MRI. As such these injuries have gained a lot of traction in the literature but are still extremely poorly defined. Probably at best, ramp lesions are defined as vertically oriented tears often along the longitudinal course of the C shaped meniscus which are present about the periphery of the posterior horn medial meniscus. They are in the vascularized zone and/or within the adjacent meniscocapsulartissue.

The meniscocapsulartissue is broken up by some authors into a more complex architecture with a so called superiormeniscocapsularligament and a more inferior meniscotibialligament. These injuries are often heralded by the edema pattern of the posterior medial tibia as seen in this case. Whether the ramp injury is a contrecoupimpaction or avulsion injury is yet to be determined. Additionally, further data is likely to come out arguing for or against greater or less need to repair these injuries. At this time it is probably most important to be aware of these injuries at the time of ACL disruption so at the time of arthroscopy they can be adequately visualized and probed to help render an opinion if they need to be repaired or not.

Case 144 Posterior TibialTendon (PTT) Dislocation

A rare entity and one that can frequently go with a prolonged delay in diagnosis given the rarity of the entity. As in this case there is frequently a disruption of the flexor retinaculum running from the medial malleolus to the calcaneus which allows a medial and anterior dislocation of the PTT. At times the retinaculum is stripped and other times lax, but by in large it is disrupted. Also as seen in this case is that the posterior groove of the distal tibia for the PTT can be shallow giving a proclivity for this still rare event. As in this case operative treatment was mandated. The surgery performed varies with most frequently repair/augmentation of the flexor retinaculum and a deepening of the groove for the PTT being performed.

Case 143 Congenital Vertical Talus

A rare entity and one of the two causes of rigid flat foot ( the other being coalition). This represents a dorsal dislocation of the navicular on the talus. The calcaneus has abnormal plantar flexion or equinusdeformity. As this is a fixed deformity it does not change on maximum plantar flexion views. This confirms the diagnosis and helps differentiate from a less severe pathology of an oblique talus which does show a reduced architecture on the maximum plantar flexion views.

Unfortunately, the navicular does not ossify until 3 years of age so a surrogate has to be utilized to indicate orthotopicalignment of the talonavicularjoint. In the normal situation a line along the axis of the talus in the lateral view should fall dorsal to the cuboid (which can be seen at birth) in neutral or maximum plantar flexion. In the case of congenital vertical talus, the axis of the talus falls plantar to the cuboid in both the neutral and maximum plantar flexion views.

Case 142 Diagnosis: Prostate Metastasis

The most common malignancy of bone to see in adults is metastatic disease but the appearance shown in this case can be a bit confusing. Many primary malignancies produce bony metastases (mets) and some have a proclivity for lytic mets, blasticmets, or a mixed pattern. Prostate cancer very typically gives blastic(sclerotic) metsbut often they are rounded foci of dense productive bone. Occasionally, prostate metscan produce lesions as seen here with a large area of sclerosis and aggressive periosteal reaction. This appearance has a striking resemblance to osteosarcoma (OSA).

OSA is a disease of younger patients from children to young adults. OSA is found in the older patient population but typically in the setting of underlying abnormal bone often previously treated with radiation or Paget disease of the bone. A bone producing malignancy would look very similar with dense bone, aggressive periosteal reaction, and surrounding edema of the bone and periostitis. It is interesting to note that in most blasticmetsthere is typically at least a small amount of surrounding edema in the bone. Given the somewhat atypical appearance of this lesion, an approach was performed to help preserve the posterior compartment of the hip if per chance this lesion was a primary malignancy of bone. This shows the need for inter disciplinary communication to provide the best treatment of patients as the approach was discussed with the referring clinician.

Case 141 Radiation Changes of the Bone

The important portion of the history not given is that this patient underwent prior radiation therapy for ovarian cancer slightly greater than 10 years before the original set of images shown. Radiation is known to alter the bone in many ways by altering the microvascular environment, collagen synthesis, alkaline phosphatase activity, and number of osteoblasts to name some. This sets up a situation where bone is predisposed to fracture as seen in this case and frequently with a poor healing response. Depending on the dose of radiation imparted the bone may suffer damage and become ischemic leading to radiation osteitis or become frankly necrotic. Discerning between these two processes can be very difficult radiographically as both produce irregular, markedly sclerotic bone with areas of demineralization/radiolucency. Both of these processes also predispose to fracture.

Not germane to this case but radiation can also induce growth disturbances in the skeletally immature patient. The last set of processes induced by radiation are neoplasms. The most common neoplasm is an osteochondroma. Radiation sarcoma (most commonly osteosarcoma or fibrosarcoma) is precipitated many years following radiation treatment. The marrow after radiation treatment can be very heterogeneous on MRI or CT. The key to the diagnosis of sarcoma is a destructive mass and particularly if this represents a change from prior imaging. As a differential diagnosis, particularly Paget disease of bone can mimic radiation changes. However, as in this case notice there is just sclerotic bone and not really coarse trabeculae. There is also not the marked thickening/enlargement of the bone as seen in Paget and it would be uncommon for Paget to involve both sides of the pelvis. That being said, at times discerning these two entities can be difficult.

Case 140 IntraneuralGanglion

I will admit the diagnosis in this case has not been proven and the findings are not classic for a peroneal intraneuralganglion. I think this is, however, a good case to discuss the entity and help in distinguishing different ganglia about the proximal tibiofibular joint. Both the deep peroneal nerve and the tibialnerve send an articular branch to the proximal tibiofibiularjoint. At times, ganglia extend from the proximal tibiofibular joint along the course of these nerves as intraneuralganglia and at other times ganglia extend from the joint but not along the course of the articular branches as extraneuralganglia. In the references listed, nicely shown is typical architecture for a peroneal intraneuralganglion that extends along the articular branch as a “transverse limb sign” and then also there is a small ganglion within the common peroneal nerve or so called “signet ring sign”. This case does not have those findings but does show the ganglion emanating along the anterior aspect of the joint which is referred to as a tail sign. This represents the connection of the articular branch to the joint. Also the focal process involving the EDL much more so favors an intraneuralganglion of the branch of the deep peroneal nerve to the EDL. An extraneuralganglion would be unlikely to stay limited to just one muscle belly and present with neurogenic findings of a muscle. The issue is that in addressing the intraneuralganglia as compared to extraneuralganglia difference in technique/what is resected may ensue. In both types of ganglia addressing the proximal tibiofibular joint is mandated to help prevent against recurrence.

Case 139 Iliotibial Band Friction Syndrome

The iliotibial (IT) band or tract is an independent structure that begins at the pelvis and receives contributions from many structures but principally the tensor fascia lataand gluteus maximus at the level of the hip. The IT band then becomes a focal area of thickening or condensation of the lateral aspect of the cruralfascia which is the investing fascia surrounding the musculature of the lower extremity. IT band friction syndrome is the most common injury in runners at the lateral aspect of the knee but is also seen commonly in cycling or other sports with repetitive knee flexion. In the normal situation there should be a fat plane between the IT band at the level of the knee and the underlying lateral condyle. In IT band friction syndrome this area of fat gets effaced by inflammatory tissue.

This case represents one of the more florid cases that we have seen. Although some think there may be an underlying bursa, if a focal area of fluid is present it most likely represents an adventitial and not a true bursa. A focal fluid collection is however very rarely seen. Although originally thought related to anterior posterior shifting of the IT band over the lateral condyle, many now believe this relates to a compression of the IT band over the condyle precipitating these inflammatory changes. Interestingly, as in this case, the IT band itself has a normal architecture and the pathology is present in the tissue deep to the IT band. This pathology is frequently amenable to conservative measures but at times recalcitrant cases necessitate excision of the inflammatory tissue or adventitial bursa.

Case 138 Osteoid Osteoma

I have presented a case of osteoid osteoma years ago and on the CT this is not a diagnostic dilemma as there is a radiolucent, round focus (nidus) containing central bone within the nidus. Osteoid osteoma are benign bone producing lesions which are most often found in children and young adults.

This case highlights how this entity can unfortunately be missed. In this example the nidus is more conspicuous than in many cases on the MRI but still the correct diagnosis was not made. Over the years unfortunately we have seen this scenario many times and have probably fell victim to it as well. The inclination in the young, active patient is always to assume there is a stress fracture when massive edema is present. At times even, an osteoid osteoma may become aggravated with activity making it so the classic history of night time pain relieved by aspirin or NSAID may not be present or the history may not be as straight forward as we would like. The fixation in this case was for a presumed fracture but again no fracture is present. The lesion was ultimately treated by ablation.

On an aside, the use of fat suppression after instrumentation, employed on this outside institution MRI, shows the marked artifact that chemical fat suppression produces and why IR or Dixon techniques are recommended for fat suppression with hardware in place.

Case 137 Painful Os Peroneum Syndrome

Somewhat of a wastebasket term for lateral sided pain related to either an osperoneum( a sesamoid bone situated in the peroneus longus tendon at the level of the calcaneocuboid joint) and/or tendinosis and tearing of the peroneus longus tendon. The osperoneumis a common finding said to be present in anywhere from 5-30% of the population. It may be present as a single bone, bipartite structure, or multipartite and can be unilateral or involve both feet. Both an acute injury or chronic inversion stress of the foot can lead to pathology of the osperoneumand the peroneus longus tendon. As the peroneus longus contracts the osperoneumcan become compressed against the cuboid and cause stress injuries of the osperoneum, fracture, or diastasis across the components of a bipartite or multipartite osperoneum. Similar forces can lead to tendinosis or tearing of the peroneus longus.

Depending on the location of the tear of the peroneus longus different findings can be found of the osperoneum. If the tear of the longus is directly at the site of the osperoneumthe bone can fracture and a portion of the bone can become proximally retracted. If the tear of the longus is distal to the osperoneumthen the entire osperoneumcan be proximally displaced. The degree of proximal displacement of the osperoneumis also in part related to the integrity of the peroneal retinacula. If the inferior and then superior peroneal retinacula additionally become disrupted marked proximal displacement of the bone can ensue. It is stated with lower grade tears of the longus there is less proximal retraction of the osperoneumor diastasis of a bipartite bone. With complete longus disruption a greater degree of retraction (more than 1cm proximal to the calcaneocuboid joint) of the osperoneumis present. The crux of the matter is that isolated injuries can occur to an osperoneumbut given their frequent association with peroneus longus injuries if there is an injury to an osperoneuminvestigation for peroneus longus injury is warranted.

Case 136 Ligament insufficiency in AAFD (adult acquired flatfoot deformity)

This case is a bit different than many others as the overall diagnosis of AAFD is not difficult but I think this is a nice illustration of many of the other drivers of more advanced levels of AAFD. The PTT is the dynamic support of the arch and the vast majority of the time by this stage the PTT is torn or so abnormal just distal to the ankle extending to the navicular tuberosity that it is easy to ascertain how it is not functioning. In this case though it is the ligamentous structures which have particularly failed helping lead to the higher levels of AAFD. In particular the superomedial band of the spring (plantar calcaneonavicular) ligament is structurally the most important part of the spring ligament (the other two portions being the medial plantar oblique and inferoplantar longitudinal components) to help prevent plantar flexion of the talus. This component in particular should be a stout band of low signal collagen running from the sustentaculum talus to the dorsal medial navicular and not the flimsy structure shown in this case.

Case 135 Metastatic Disease

Whole tomes have been and unfortunately can be written about metastatic disease. As practitioners concerned so much with orthopedic entities and musculoskeletal health we all sometimes have blinders on to look for other entities that are also very common in the population at large. Malignancy and metastatic disease have to always remain as a concern in our assessment of adult and elderly patients. This case just highlights that need. As in this case, metastatic lesions frequently present as rounded foci of abnormal signal and often have a surrounding edema pattern. A less circumscribed or infiltrative pattern of bone can also be seen although not as commonly.

Case 134 Post-partum Edema of the SI Joints Mimicking Sacroilitis

During pregnancy, mechanical stress and additionally increased amount of the hormone relaxin allow for the ligaments about the pubis and sacroiliac joints to accommodate for pregnancy and the birthing process. As a consequence many women suffer from pain at these locations often referred to as “pelvic girdle syndrome”. On MRI, it has been shown that there can often be a marked edema pattern about the SI joints as in this case. A little bit more of an “eye test” than some of the previous cases were the clues to recent pregnancy in this patient.

The widened pubis and recently gravid uterus are subtle but not intended to be the thrust of the case. The main issue is understanding that many women can have persistent back pain for up to 2 years following delivery and it is an important diagnostic consideration. The findings on the MRI and particularly the marked edema pattern of the SI joints would quickly make one entertain the diagnosis of an inflammatory arthritis and rightfully so. History would help in coming to the appropriate diagnosis but in addition, in the setting of postpartum changes about the SI joints erosions and subchondral fatty deposition are frequently absent which is the case here. Clearly an inflammatory arthritis can present in women of this age but paying close attention to imaging findings, obtaining pertinent history, and most importantly being aware of this entity should hopefully point us in the right direction.

Case 133 Carpal Boss Syndrome/Os Styloideum

This is one of those pathologies that some people lump and some people split. Any osseous protuberance typically at the base of the 3rd MC, capitate, 2nd MC, and less likely trapezoid are often lumped together under the issue of carpal boss. Some people like to classify if the bone is not a separate fragment but just protruding from the posterior aspect of the bones as a carpal boss. Where if there is a separate bone fragment, most often adjacent to the base of the 3rd MC and having an adjacent fibrous union or synchondrosis, that is classified as an os styloideum. These can be painful manifest by edema on MRI and show degenerative changes as shown by sclerosis or cystic changes. Recently, articles have shown a high prevalence of os styloideum in professional athletes and not of a carpal boss as defined above. This gives some credence to the thought of a traumatic etiology particularly of an os styloideum.

One other difference is also that anecdotally, patients undergoing ultrasound guided injections for painful os styloideum have fared better in our practice than those injected for a painful carpal boss. This being said the underlying etiologies as relates to either a carpal boss or os styloideum is not known. Favored is overuse/post-traumatic, developmental/congenital, and degenerative. In all cases conservative management is tried because of the difficulty in obtaining good results and lack of recurrence following surgery.

Case 132 Gout

Gout is often a difficult diagnosis as it can present in so many ways. Of course related to a disturbance in uric acid metabolism, uric acid deposition induces an inflammatory/tophaceous response which can be juxta/periarticular or within a joint. Often on MRI gout will present with intermediate to lower signal on all pulse sequences but may also have higher signal on more T2 weighted or inversion recovery pulse sequences.

On radiographs, soft tissue masses can be found and when subtle calcifications are present within the masses gout should be entertained as a diagnosis. The calcification is thought to be dystrophic or perhaps related to a degree of concomitant calcium pyrophosphate. Around the knee gout loves to involve the extensor mechanism and also the anterior synovialy lined bursae as seen in this case. In addition, it also anecdotally has a proclivity for the popliteal groove so much that any mass in that location should bring gout to mind. Any one finding in this case would be difficult to render a diagnosis but when placed in concert, the correct diagnosis can be deduced.

Case 131 Secondary Synovial Chondromatosis

Primary synovial chondromatosis is a metaplastic process of the synovium which almost invariably involves one joint. There is a proliferation of the synovium which becomes calcified and ossified and by erosion eventually leads to loss of cartilage. This is typically stated to yield innumerable bodies to count. In degenerative joint disease, some individuals generate a marked synovial response giving prominent synovitis. As in the primary process this eventually becomes calcified and then ossified. As compared to the primary form there are often multiple bodies but they can be counted and advanced cartilage wear is identified. The primary process also would typically come to light in a younger individual than the patient in this case. At the end stage, both processes can yield areas of massive conglomeration that become calcified/ossified as in this case. As for the concern of aneurysm, it is important to identify the popliteal artery as normal and although in close proximity, distinct from this mass. Additionally, an understanding of this process allows one to exclude neoplastic processes that could arise around the knee in an adult such as soft tissue sarcoma.

Case 130 Complex tear UT ligament with longitudinal and distal components

More recently, there has been description of a longitudinal tear of the UT ligament (along the long axis of the ligament) which may produce pain but is not typically associated with DRUJ instability. On arthroscopy these injuries are typically associated with prominent synovitis which once removed, reveals the longitudinal split within the UT ligament. In this case there was the longitudinal component accounting for the T2 hyperintensity of the ligament but also a small, distal disruption accounting for the small flap that was interposed between the triquetrum and the TFCC articular disc. At the time of surgery there was prominent synovitis about the TFCC and the flap was found and resected.

Case 129 Scapular Notching

One of the unique complications of the reverse total shoulder arthroplasty is scapular notching related to the impaction of the medial aspect of the humeral component/polyethylene along the inferior border of the scapula with shoulder adduction. The process is thought to relate not only to mechanical wear but polyethylene wear engendering an even greater degree of bone resorption. The concept has been a matter of debate for many years but with most in present day feeling that notching does correlate with increased pain and decreased performance. The grading/classification was described by Sirveaux and progresses from bone wear of the so called scapular pillar, to the inferior screw, involvement of the entirety of the inferior screw, and then involving the central screw/post or the metaglene/baseplate. Progressed degrees of notching are thought related to a greater possibility of glenoid loosening and poorer clinical outcomes.

Great efforts over the last decade have been made to try and understand how to better implant/design this prosthesis. Because of notching there is now a greater lateralizing of the center of rotation of the prosthesis and the metaglene/base plate are now placed at the far inferior aspect of the glenoid (even with inferior overhang) and with inferior tilt (often approximately 10-15 degrees). Although these changes themselves may have ramifications, at present this is working well. Interestingly as in this case when notching is seen it is often found early after the index procedure within a couple of months to one year. However, it frequently shows little progression after many years of follow up although some authors have shown substantial progress over years follow up. As there is little in terms of how to direct surgeons in the management of scapular notching, although this patient is limited she is opting for no additional surgery at this time.

Case 128 Congenital Posteromedial Tibial Bowing

Tibial bowing can be related to many underlying etiologies. The key is to recognize the direction of the apex of the bow which is how the bowing is described. Posteromedial bowing is a congenital condition, thought to be related to intrauterine positioning or a packing abnormality. It can be seen with another packing abnormality of a calcaneovalgus foot but can occur in isolation. Posteromedial bowing is considered benign because although it does frequently yield a limb length discrepancy as in this case, the bowing resolves and the overall course is much less difficult than the other causes of bowing. Anterolateral bowing is seen in congenital pseudoarthrosis either alone or in the setting of neurofibromatosis. This process is notoriously difficult to treat. Anteromedial bowing is seen in the setting of fibular hemimelia which is then associated with many other orthopedic abnormalities. Anterior bowing can be seen in a very rare syndrome called Weissman Netter syndrome or in the setting of some congenital infections or metabolic disorders such as rickets. As in this case there is frequently a marked decrease in the bowing in the first year and them a limited degree of remodeling after 4-5 years. As the proportionate difference of leg lengths remains stable through growth accurate estimates can be made to the final limb length discrepancy. Surgery is frequently performed if and when limb length discrepancies reach 2-5cm.

Case 127 Diagnosis: Aggressive Vertebral Hemangioma

Vertebral hemangioma (VH) is a very common entity seen while reading CT or MRI of the spine and especially the lumbar spine. VH are described radiographically as typical, atypical, or aggressive. VH pathologically have blood vessels interspersed with fatty tissue, interstitial edema, and thickened/coarsened bony trabeculae. Particularly, these thickened trabeculae account for the “polka-dot” appearance seen on axial CT images and the “corduroy” appearance seen on sagittal and coronal reformations. Typical hemangioma have a greater amount of fatty tissue giving the typical high T1 signal. The atypical hemangioma has less fatty tissue and will have less or no high T1 signal and will appear similar to many other processes with low T1/high T2 characteristics. This makes evaluation of the atypical hemangioma difficult on MRI as it can mimic many entities including metastases, myeloma, or lymphoma. However, on CT, the “polka-dot” and “corduroy” appearance will still be appreciated allowing an accurate diagnosis. The aggressive hemangioma typically has similar MRI characteristics to the atypical hemangioma but has broken through the bone and has an associated soft tissue mass. Hence on MRI these masses look very aggressive but when a CT is performed, the “polka-dot” or “corduroy” architecture is typically still able to be identified to render an accurate diagnosis. At times as in this case, aggressive hemangioma may have some fatty tissue accounting for high T1 signal but often no high T1 signal at all can be identified. Because this mass has such an aggressive appearance, biopsy is frequently performed. In fact, in this case a biopsy was performed in 2005 to help come to the appropriate diagnosis.

Case 126 Diagnosis: Osteosarcoma

This case was terrifying to me and a number of my colleagues. In looking at just the second set of radiographs, the radiolucency with sclerosis of the distal femur and the aggressive periosteal reaction would make osteosarcoma a relatively easy diagnosis. However, given the recent, normal radiographs predating the abnormal radiographs, the thought was perhaps this was more likely infection or eosinophilic granuloma. Given the unbelievably rapid progression of this process it is thought that this is going to be a very high grade malignancy but that pathology is not yet available. This case just elucidates the limitations of radiographs at times and the sometimes terrifying nature of practicing medicine.

Case 125 Diagnosis: Venous Congestion/Ischemia and Cord Edema in Cervical Spondylosis

In over ten years of putting together these cases this was one of the more fascinating and perplexing cases, I’ve had and required a great number of resources to get to the correct interpretation. In innumerable cervical spine mri’ssevere central canal stenosis is present and in cases typically with moderate or severe compression of the cord we may see a mild to moderate amount of T2 hyperintensityof the cord. It is extremely uncommon to see this very slight degree of mass effect of the cord be associated with such a massive amount of T2 hyperintensityof the cord. On initial interpretation, given the enlargement of the left side of the cord a mass was favored over cervical spondylotic changes inducing the markedly abnormal cord.

However, after contrast administration, there is no rounded or mass like focus of enhancement but rather this vague or hazy type enhancement. Histology has been obtained in other cases where again the diagnosis has been thought to be tumor and on biopsy only inflammatory changes and findings of edema of the cord were found. This has led to the belief that in some patients with severe central canal/spinal stenosis but with only slight deformity of the cord venous hypertension/congestion is precipitated that leads to venous ischemia, a break down of the blood cord barrier/hyperpermeability, and then marked edema within the spinal cord. Interestingly, as in this case the hazy, vague enhancement has been most commonly seen at the affected disc space level. In the cases reported in the literature, patients have responded very well to decompression and our patient is to have surgery next week.

Case 124 Diagnosis: Osteopoikilosis

Perhaps not a diagnostic dilemma for many but this is a nice representation of osteopoikilosis which as seen here is manifest by multiple bone islands/areas of cortical bone within the medullary cavity or cancellous bone. The foci of cortical bone are typically centered around the joints in the ends of the bone/epiphyseal equivalents and metaphysis and parallel to the longitudinal axis of the bone. This is an incidental finding of no significance but as to otherwise appreciate that there is no more aggressive process at hand.

Case 123 Diagnosis: Tensor Fascia Latae Pseudomass

A rare diagnosis and frankly one I did not know existed until this case. Found typically in older women it is thought to arise in the setting of abnormal gait that produces a hypertrophy of the tensor fascia latae. It is most typically found in the setting of total hip arthroplasty with deficient hip abductors. Although no arthroplasty is present in this case, there is clear deficiency of the hip abductors. The thought is that there is a compensatory hypertrophy of the tensor fascia latae to accommodate/mitigate the effects of the deficient hip abductors.

Case 122 Diagnosis: Anteromedial Meniscofemoral Ligament

Different than many of the cases presented in the past the area in question represents a normal, albeit rare variant. Important in this situation so as the surgeon does not mistake this process for a displaced fragment of meniscus. Well known is the transverse meniscal ligament extending from the anterior horn of the lateral meniscus to the anterior horn medial meniscus. Infrequently an oblique meniscal meniscal or intermeniscal ligament can be seen. This extends from the anterior horn of one meniscus to the posterior horn of the other and is named for the anterior horn attachment on the medial or lateral side. The ligament shown here is the most uncommon normal variant.

This ligament also sometimes called the anterior meniscofemoral ligament extends along the course of the ACL to insert into the anterior horn of the medial meniscus. It looks similar to the infrapatellar plica or ligamentum mucosum but does not run into Hoffa’s fat pad/inferior pole of the patella. We typically think of only two structures in the notch, the ACL and PCL. Anything else we think is going to be a displaced mensical fragment but these normal, variant ligaments also need to be entertained. A helpful clue often is that there does not seem to be a deficiency of any meniscus to be the donor site but also keeping in mind normal variant anatomy is crucial.

Case 121 Diagnosis: Subchondral Fracture

The very subtle area of irregularity of the femoral head represents a subchondral fracture. There is typically as shown here a marked amount of edema even in the setting of the very subtle deformity. Patients typically have marked pain and difficulty with activity. It is my belief as well as many others that the concept previously described as transient osteoporosis of the hip in fact represents these very subtle subchondral fractures. In years past, we were limited by resolution to see these very subtle fractures but given current techniques and equipment these subtle fractures can now be seen.

Interestingly, in this case the patient had an outside MRI that was read as necrosis. Areas of AVN do not have a striking degree of edema unless they have collapsed or are collapsing. In that situation, again there is subchondral fracturing that is precipitating the edema. In a subchondral fracture or AVN with collapse, the marked edema relates to fracture of the bone. This patient is being treated with crutches as well as a metabolic analysis and will be rescanned to assess for healing.

Case 120 Diagnosis: Oncogenic Osteomalacia

Osteomalaciacan be produced by numerous causes but one in particular relates to neoplasms that secrete fibroblast growth factor 23 which inhibits phosphate resorption in the kidney and produces osteomalacia. These tumors are classified as phosphaturicmesenchymal tumors (PMT) and the most common is a soft tissue hemangiopericytoma. As in this case there is often a protracted course and marked disability. The osteomalaciacauses repetitive episodes of fracturing which leads to the marked sclerosis of the bone and in this case varusdeformity of the femoral necks.

The findings on the MRI of the bone and the soft tissue mass are classic for this rare diagnosis. Octreotide works as a somatostatin analog that binds to somatostatin receptors frequently in neuroendocrine tumors as well as in the PMTs.Octreotide shows normal uptake in the liver, spleen, kidneys/urinary tract, and bowel. Variable uptake is present in the thyroid and pituitary. In addition, newer Ga isotopes with PET CT are being utilized to localize these tumors which can often be small and not clinically recognizable. This patient is to undergo removal of the soft tissue mass.

Special thanks to Robert Schneider MD, Douglas Mintz MD, and Alissa Burge MD for their assistance in this case.

Case 119 Diagnosis: 4th/5th Carpometacarpal Dislocation

The most common of the CMC fracture dislocations involve the small and then ring fingers. These articulations are more mobile than the remainder of the articulations and particularly the pull of the ECU attachment at the base of the fifth metacarpal makes these locations most susceptible to injury. Invariably there is dorsal displacement of the metacarpals. There is typically impacted fracturing along the dorsum of the hamate and at times as in this case along the dorsum of the capitate.

As was mentioned previously, on the CT examination this is not a diagnostic dilemma. However, this case again underscores the necessity for at the least orthogonal radiographs for adequate assessment. In addition, this shows how radiographs at times can underestimate/belie the overall extent of injury. Well delineated is the importance of understanding typical presentations of pathology and the need for further imaging for confirmation and as in this case, preoperative planning.

Case 118 Diagnosis: Stener Lesion

Perhaps not a diagnostic dilemma on this case but a nice representation of a Stener lesion. The UCL is torn when a valgus force is imparted to the thumb as when holding a ski pole when falling and hence the term skier’s thumb. When gamekeepers would break the necks of small animals such as rabbits the repetitive motion would cause scarring of the UCL and hence a chronic analagous process is now often referred to as gamekeeper’s thumb. The architecture of the collateral ligaments in the hand and foot are complicated with proper and accessory components. In the Stener lesion typically both components are disrupted although typically on imaging we do not separate the individual components. In a Stener lesion, the adductor aponeurosis or the slip of tissue of the adductor pollicis that continues distal to the proximal phalangeal attachment to join the extensor apparatus, lies inward or deep to the UCL.

The aponeurosis blocks the ligament from apposition to the underlying bone and hence does not allow ligament healing. Without repair there is a loss of strength of the thumb and typically precipitated early arthritis. As in this case, the injury is often not a simple valgus moment and the RCL is frequently injured. Additionally, the adductor myotendinous unit is often frequently injured. Stener lesions or UCL ligament injuries with clinical and radiographic evidence of instability are indicated for surgery.

Case 117 Diagnosis: Post traumatic Pneumothorax

As compared to many of the cases we have shown this case is much more of an "eye test". The findings particularly on the radiographs although difficult can be made and are imperative. More frequently present in the setting of rib fractures with a clavicle fracture as in this case, isolated clavicle fractures can also rarely present with a pneumothorax. Given the size of the pneumothorax this patient underwent chest tube decompression with re-expansion of the lung and then subsequent clavicle fracture fixation.