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Cases of the Month: Diagnosis Index

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 chondromatosisis 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.