Saturday, December 18, 2010

Shoulder Instability and Upside Down Pears

Have you ever seen someone that reminds you of someone else? Above is a striking comparison between Gordan Freeman from Half-Life and Dr. House from the TV show House. There is even a website devoted to this topic, that you may find amusing. Doctors are no different, and when they see something in the body that looks like something else, they will often point that out, as we will see below.

The shoulder joint is composed primarily of the humeral head (red arrows), which fits into the glenoid portion of the scapula (blue arrows):

The glenoid portion of the scapula is best seen looking at the shoulder from the side, with the humeral head removed:

The shape of the glenoid can be compared to a pear:

The normal pear shape of the glenoid helps keep the humeral head in place. With repeated anterior dislocations, bone along the anterior margin of the glenoid can become worn down, and the glenoid can lose its normal shape.
The curve of the anterior glenoid becomes flattened, and the loss of the normal convexity of the glenoid can be part of the syndrome of recurrent anterior instability. The normal pear shape of the glenoid is lost; when the inferior part of the glenoid appears narrower than the superior part, one is said to have an "inverted-pear" glenoid.

In this case, a 29 year old male with a history of multiple left shoulder anterior dislocations was sent for an MR arthrogram. An axial intermediate image shows a large Bankart lesion:

A sagittal T1 weighted image reveals extensive flattening of the anterior margin of the glenoid, with an inverted pear appearance:

A CT scan shows the loss of the normal cup shape of the left glenoid on axial images (red arrow), with maintenance of the normal glenoid shape (green arrow) in the asymptomatic right shoulder:

A 3D volume rendered CT image better depicts the abnormal shape of the left glenoid:

For comparison, here is the shape of a normal glenoid:

Joe de Beer and his colleagues have recently written an excellent article on anterior shoulder instability in the elite athlete, with specific reference to bony deficiencies (Shoulder & Elbow 2010 2, pp 63–70). They note that:
--->Diagnosis of anterior glenoid bone loss can be missed at arthroscopy if one looks examines the glenoid solely from the posterior portal. This diagnosis is best made using the antero-superior portal.
--->Significant bone loss cut-off has been widely quoted as greater than 25%. This may not be the correct number in all patients: "What experience has taught us is that....the higher the demand, the less bone loss that is tolerated. We therefore deem significant even small bony deficiencies in the elite athlete".
Percentage bone loss can be measured on imaging studies (Griffith et al., AJR 2003;180:1423-1430) as well as at arthroscopy (Burkhart et al., Arthroscopy 2002; 18:488–91). The radiologist should alert the surgeon when there is appreciable bone loss along the anterior margin of the glenoid, as this information can alter the surgical procedure that is used to treat the patient.

Vic David MD

Monday, November 15, 2010

Football and a Meniscal Tear

Between Thanksgiving and Christmas, citizens in the United States eat too much, and watch a lot of football. They also get out in the backyard, and play the game, typically "touch" or "flag football".

Photo by frohner1

There is a spike of football-related injuries during this time, typically resulting in bone contusions, ligament injuries, and meniscal tears. Most of these are typical in character, but every once in a while one will see an unusual variant.

In this case, a 38 year-old male was playing flag football, and sustained an injury. His knee swelled almost immediately, and he had an MRI a few days after the injury.

There is an obvious ACL tear:

A coronal image through the posterior knee identifies the medial meniscus (green arrow), but the posterior horn of the lateral meniscus is missing in action, with only fluid found in the expected location of the lateral meniscus (red arrow):

A coronal image through the mid-joint reveals that the torn posterior horn has been flipped out of the joint:

An axial image identifies the torn, flipped meniscus (red arrow), situated between the fibular collateral ligament (yellow arrow) and the popliteus tendon (green arrow).

Most flap tears of the meniscus that are displaced out of the joint are found inferior to the joint line, but these flap tears can also displace superiorly, as in this case. MRI can provide valuable preoperative information, allowing the surgeon to counsel the patient and plan his surgical approach.

Football is a great sport (both the American and European versions), but it does come with its risks...

Vic David MD

Monday, October 18, 2010

Tennis and Hand Pain

High level tennis players place a great deal of stress on their hands:

Photo by splitmilk

In an earlier entry, we looked at the shape of the hamate, which has a hook (blue arrow):

In sports where an instrument is swung, fractures of the carpal hamate bone can be due to blunt trauma or a sharp strike against the hook of the hamate. The swinging motion that accompanies golf, baseball, tennis racquet are all well-known causes of this injury. Patients present with pain localized over the ulnar aspect of the wrist and reduction in grip strength.

In this case, a 40 year-old female tennis player presented with ulnar-sided pain of two weeks duration. She had no direct trauma to hand, but developed the pain after playing tennis. Axial T2 fatsat images reveal intense bone marrow edema in the body of the hamate (yellow arrow) and a fracture of the hook of the hamate (red arrow), with accompanying bone marrow edema:

A sagittal T1 weighted image confirms the presence of the fracture:

(click on image to enlarge)

Thus, one should consider this injury when assessing an athlete with ulnar-sided hand pain.

Vic David MD

Sunday, September 19, 2010

Shadows in the Knee

Photo by ambrown

In the early days of medical imaging, radiologists used only x-rays to image the body. These pioneers saw shadowy representations of the tissue that is inside all of us. With the advent of cross-sectional imaging techniques such as CT, ultrasound, and MRI, we are now able to visualize anatomic structures directly, and no longer have to deduce the anatomy from a shadow-like representative object.

Occasionally, however, events conspire to create ghost-like shadows even on cross-sectional imaging such as MRI. In this case, a 31 year old male presented with knee pain, and was referred for an MRI:

(A) Sagittal proton-density image reveals an unusual appearance to the bones, with visualization of the ghostly outline of the femoral secondary epiphysis (blue arrows) and the tibial secondary epiphysis (red arrows). (B) Sagittal T2 fatsat image is less striking, with areas of nonspecific increased signal visualized in the femur and tibia.

A sagittal proton-density image through the patella reveals the ghostly outline of the patellar epiphysis:

A manifestation of growth arrest was suspected. Further questioning of the patient revealed that he had a serious ski accident in childhood, resulting in a femur fracture requiring prolonged immobilization, confirming the diagnosis. Epiphyseal growth arrest lines have been described (Yao L, Seeger LL, Clin Imaging. 1997 Jul-Aug;21(4):237-40) and can lead to a "bone-in-bone" appearance, as in this case. Causes of a "bone-in-bone" appearance on conventional radiographs include bone infarction, osteopetrosis, and Paget's disease. On MRI, however, this appearance is highly suggestive of an epiphyseal growth arrest event in the patient's past.

Vic David MD

Saturday, August 7, 2010

"Pop" and an Unusual Meniscus

A common complaint that is heard in doctor's offices after a knee injury is, "I heard a pop, and then my knee swelled up". This complaint is usually related to a tear of the anterior cruciate ligament, but can sometimes also indicate a tear of the meniscus.

Occasionally, a "pop" can be felt by the examining physician as well, but this is relatively rare. Conditions that may cause painful snapping about the knee include congenital snapping knee, discoid lateral meniscus in children, a torn meniscus, intraarticular rheumatoid nodules, synovial plicae, and iliotibial band syndrome. Subluxation of tendons has been reported to cause this painful snapping syndrome about the knee, medially by the gracilis and semitendinosus tendons, and laterally by the biceps femoris and popliteus tendons (Bach and Minihane, AJSM 2001, 29:93-95).

In this case, a 32 year-old female presented to her orthopedic surgeon with knee pain. The surgeon noted that as the patient extended her knee into full extension, there was a "pop" in the posterolateral knee. She was referred for an MRI, to evaluate for internal derangement.

A sagittal proton-density weighted image reveals abnormal signal in the anterior horn of the lateral meniscus (red arrow), but is otherwise unremarkable:

The astute MRI technologist (a former naval medic) was puzzled by the relatively innocuous nature of the finding in the anterior aspect of the meniscus, particularly given the strong clinical history of a pop in the posterolateral knee. At the end of the examination, he asked the patient if she could do anything that would elicit the "pop". She obliged, and squatted downwards, and the "pop" occurred. The MRI technologist gingerly placed her back in the magnet, and repeated the sagittal:

Here, after the provocative maneuver, we see a striking peripheral tear of the posterior horn of the lateral meniscus which has been displaced anteriorly, leaving only fluid where the meniscus should be (green arrow).

An axial image better reveals the avulsed lateral meniscus (blue arrows), which has been displaced anteriorly:

Compare this to the position of the meniscus (yellow arrow) on the initial (before the provocative maneuver) axial scan:

Intermittent meniscal dislocation has been discussed in the literature (Lyle et al.Br J Radiol. 2009, 82:374-9). They described three patients with a strong history of intermittent knee locking, who had negative initial MR scans. The patients were able to reproduce locking of their knee voluntarily, as in our case. Further MR imaging of the knee in the "locked" position demonstrated meniscal dislocation in all three patients. All three were confirmed arthroscopically to have deficiency of the corresponding menisco-capsular ligaments (as was our patient).

When there is a strong clinical history of knee locking, all the structure of the knee must be carefully inspected on MRI, particularly the menisci, anterior cruciate ligament, and the hyaline cartilage. When no abnormality can be detected, it is a good idea to scrutinize the peripheral attachments of the meniscus. The meniscocapsular junction is a difficult area to analyze, with abnormalities easily missed (and overcalled as well). With higher resolution imaging now becoming increasingly common, it has become easier to detect abnormalities in this area with greater confidence.

In the exceptional case, provocative imaging can be performed, and may help demonstrate an intermittently dislocating mensicus.

Vic David MD

Friday, July 9, 2010

Ants and a Shoulder Mass

Photo by TillinKa

A surgical suture is used to close the edges of a wound or incision and to repair damaged tissue. The closure of wounds has a dramatic history, with some inventive methods. In ancient times, beetles or ants were used to close wounds. The living creatures were attached to the edges of the wound, which they clamped shut with their pincers. The insect body was then cut off, leaving the jaws in place. Army ants can be used for this purpose, due to their impressive pincers

We have made some advances since that time, and here is a nice summary:

Sutures are made from both man-made and natural materials. Natural suture materials include silk, linen, and catgut, which is actually the dried and treated intestine of a cow or sheep. Synthetic sutures are made from a variety of textiles such as nylon or polyester, formulated specifically for surgical use. A suture can also be classified according to its diameter. In the United States, suture diameter is represented on a scale descending from 10 to 1, and then descending again from 1-0 to 12-0. A number 9 suture is 0.0012 in (0.03 mm) in diameter, while the smallest, number 12-0, is smaller in diameter than a human hair.

64 year-old woman with a history of a humeral fracture, who presents with an arm mass. Oblique sagittal T1-weighted image reveals a 7 mm subcutaneous mass (red arrow), along with extensive metal artifact (yellow arrows):

The presence of extensive metal artifact made fat suppression difficult, and an ultrasound was performed to determine if the mass was solid or cystic:

The ultrasound confirmed the existence the mass, depicting an oval mass (red arrows) with irregular margins and no posterior acoustic enhancement. The mass was thus confirmed to be solid. In addition, within the posterior aspect of the mass, there was a linear, hyperechoic focus (yellow arrow), not conforming to a tissue plane.

Pathologic analysis revealed a suture granuloma. Suture granulomas can mimic neoplasms, especially at imaging. They are most commonly reported in the setting of inguinal herniorrhaphy, but can occur in other post-surgical settings as well. They can present as enhancing masses on MRI or CT, and can be associated with increased uptake at F-18 fluorodeoxyglucose (FDG)-positron emission tomography (PET)/CT imaging (Kim et al., Kor J Rad 2009; 10:313-318). Suture granulomas have been reported to mimic recurrent thyroid carcinoma on ultrasound (Chung et al., Yonsei Med J. 2006; 47:748-751) and urachal tumor on CT (Gan and Wastie, J HK Col Radiol 2007; 10:59-61).

A recent report assessed the ultrasound features of suture granulomas at the thyroid bed after thyroidectomy for papillary thyroid carcinoma with an emphasis on their differentiation from locally recurrent thyroid carcinomas. Shape, heterogeneity, and the presence of central or paracentral internal echogenic foci (as in this case) were helpful criteria for differentiating suture granulomas from locally recurrent tumors in the thyroid bed.(Kim et al., Ultrasound in Med Biol 2009; 35,1452-1457). Thus, if you suspect that a mass may be a suture granuloma on MRI, a follow-up ultrasound may identify linear hyperechoic suture material within the lesion, and help suggest the diagnosis of a suture granuloma.

Vic David MD

Sunday, June 6, 2010

Jujitsu and a Shoulder Injury

Photo by icantcu

Hand-to-hand, testosterone-fueled combat has existed for centuries. As long as violence, power, and sex exist (and I see no signs of them going away soon), fighting will thrive. Boxing and ultimate cage fighting are the more recent variations of an ancient drive to display power and conquer the other.

Jujitsu, a form of hand-to-hand mayhem, is a Japanese martial art style that emphasizes pins, joint locks, and throws. This sport can cause significant torque forces on the body, and lead to injury.

In this case, a twenty-six year old male experienced an upper body injury two weeks ago during jujitsu. He had torso pain and a clinical exam notable for glenohumeral instability. An MR arthrogram of the shoulder was obtained to clarify the extent and nature of his injuries.

An oblique coronal intermediate-weighted image from an MR arthrogram depicts a tear of the latissimus dorsi and teres major tendons (red arrows), with increased fluid (yellow arrow) adjacent to the torn tendons:

An oblique sagittal T2 fatsat image demonstrates the torn, retracted latissimus dorsi (red arrow) and teres major (green arrow) tendons. Also seen is a paralabral cyst (yellow arrow) adjacent to the posterior labrum. There is fluid in the joint (blue arrow) related to the MR arthrogram:

The pectoralis major, latissimus dorsi, and teres major tendons all insert on the humerus, next to one another. A good mnemonic for the pattern of insertion is "lady between two majors", with "lady" = latissimus dorsi (red line) and "major" = pec major (blue line) and teres major (green line):

Sagittal images from a normal patient (medial to lateral) illustrate the anatomy of latissimus dorsi (red arrows) and teres major (green arrows).

(click on image to enlarge)

The teres major tendon is smaller and more compact than the tendon of the latissimus dorsi. The quadrilateral space (Q) is found between the teres minor (blue arrows) and teres major (green arrows) muscles. T = long head of the triceps
Oblique axial intermediate images through the upper arm of our injured patient better demonstrate the torn, retracted latissimus dorsi (red arrows) and teres major (green arrows) tendons.

(click on image to enlarge)

Note the intact pectoralis major (pink arrow) tendon, as well fluid (yellow arrow) at the expected insertion site of the latissimus dorsi and teres major tendons. The footprint of the latissimus dorsi and teres major tendons is "naked".

For comparison, consider these oblique axial images from a normal patient (superior to inferior), showing the intact latissimus dorsi (red arrows) and teres major (green arrows) tendons at their insertion. The intact pectoralis major (pink arrow) tendon is also seen:

In addition to tears of the latissimus dorsi and teres major, this patient had a posterior labral tear (red arrow) and an associated paralabral cyst (yellow arrows), additional information provided by the MR arthrogram:

Tears of the latissimus dorsi and teres major are uncommon injuries, usually seen in competitive athletes, such as baseball pitchers (Leland et al., J. Shoulder Elbow Surg.18, e1-e5, 2009). The clinical signs and symptoms for both injuries are similar (Schickendantz et al., AJSM 37, 2016-2020, 2009).Typical management is non-operative, as operative intervention does not seem to improve outcome (although published studies are small in number and limited in study design). Tears or reactive tendinosis of the latissimus dorsi tendon at its insertion may present as a pseudotumor (Anderson et al., AJR 185, 1145-1151, 2005).

It is important to note that these injuries will often be seen only at the edge of the field-of-view of a standard shoulder MRI (or completely missed). Thus, if this injury is suspected clinically, it is a good idea to alert the radiologist, so that the anatomic coverage of the examination can be increased (as was done in this case).

Vic David MD

Monday, May 10, 2010

Orchids and Subscapularis Tears

Photo by van swearingen

The Star of Bethlehem orchid is one of the best arguments for the existence of evolution and natural selection.

This orchid (the Madagascan star orchid Angraecum sesquipedale) has a foot long nectar tube that hangs from its back. Darwin predicted what the pollinator of this orchid would look like, over forty years before its actual discovery:

"In several flowers sent to me by Mr. Bateman I found nectaries eleven and a half inches long, with only the lower inch and a half filled with nectar....It is, however, surprising that any insect should be able to reach the nectar....In Madagascar there must be moths with proboscides capable of extension to a length of between ten and eleven inches! This belief of mine has been ridiculed by some entomologists."

In 1903, a giant Madagascan hawk moth with such a long tongue was discovered, and was given the name Xanthopan morganii praedicta, Latin for "predicted moth".

Photo by kqedquest

Darwin was able to predict the existence of an unexpected moth in Madagascar, a striking example of the predictive and explanatory power of the theory of evolution.

In a different sphere of science, the powerful technology of MRI can predict the existence of an unexpected clinical condition. Twelve year-old boy who is a baseball pitcher, with pain after an injury:

Axial T2 fatsat image reveals a complete avulsion of the subscapularis muscle and tendon (yellow arrows). The avulsed bone and cartilage fragment (red arrows) are also seen.

A sagittal T2 fatsat image depicts visualizes the subscapularis tendon footprint, which is now replaced by fluid:

Injuries to the rotator cuff of children are often not suspected by the clinician, due to their rarity. There are only a few reports in the literature, and most of these describe injuries to the subscapularis, often avulsion fractures. The few reports that do exist about subscapularis tendon injuries often describe this injury in throwing athletes, although other sports can be involved, including wrestling and hockey.

Conventional radiographs and CT may reveal a flake of bone related to the avulsion injury. Even when radiographs are initially normal, repeat radiographs several weeks after injury may reveal soft tissue calcification in some cases (Tarkin et al, AJSM 2005, 33:596-601). MRI is very useful in this patient population, as it will assess the shoulder area for multiple causes of pain, including growth plate injuries, rotator cuff tears, and glenohumeral instability.

Thus, when evaluating an adolescent athlete with shoulder pain, one must keep in mind the possibility of an injury to the rotator cuff, particularly when symptoms suggest rotator cuff dysfunction.

1) Tarkin et al., "Rotator Cuff Tears in Adolescent Athletes", AJSM 2005, 33:596-601.
2) Kleposki et al., "Rotator Cuff Injuries in Skeletally Immature Patients", Orthop Nursing 2009, 28:134-138.
3) Sugalski et al., " Avulsion Fracture of the Lesser Tuberosity in an Adolescent Baseball Pitcher", AJSM 2004, 32:793-796.
4) White and Riley, "Isolated avulsion of the subscapularis insertion in a child. A case report". JBJS Am 1985, 67:635-636.

Vic David MD

Sunday, April 11, 2010

Ecclesiastes and an Ankle Fracture

Photo by jimforest

"What has been will be again, what has been done will be done again; there is nothing new under the sun."

This is perhaps the most famous quote from Ecclesiastes, one of the books of the Bible, and it certainly rings true. Although there are many exciting new developments in medicine every year, patients still
contract the same illnesses and undergo the same injuries they did long ago.

24 year-old male with a history of a twisting injury to the foot:

(A) Sagittal T2 fatsat and (B) sagittal T1 images reveal an avulsion fracture (red arrows) of the extensor digitorum brevis (EDB) tendon, at its origin from the calcaneus.

A small flake of bone can be seen on a conventional radiograph:

(A) Oblique axial intermediate and (B) oblique axial T2 fatsat images also show avulsed bone fragment (red arrows):

This injury was described by Norfray et al. in 1980 (AJR 134:119-123, 1980), who described the distinctive conventional radiographic findings of this injury. Radiographs of 100 consecutive emergency room patients with clinically suspected ankle fractures occurring during the winter of 1978-79 were reviewed. Most resulted from slipping on ice, or falling over snow-covered obstacles. The avulsion fracture was identified in 10 of 100 patients. Clinically, the point of maximum tenderness was similar to the area of maximum tenderness in fractures of the anterior process of the calcaneus. Thus, these fractures of the anterior process of the calcaneus and EDB avulsion fractures cannot be differentiated clinically, but only by imaging.

Avulsion fractures of the calcaneus can occur at multiple sites, including the attachment of the Achilles tendon, bifurcate ligament, plantar fascia, and the abductor hallucis (Pelletier and Kanat, J Foot Surg, 29:268-271, 1990). All of these injuries can be identified by MRI.

Avulsion fractures were common thirty years ago, and were usually found on x-rays. Avulsion fractures are still common today; there truly is nothing new under the sun. The only thing that is different is that some of these patients will have MRI scans, and the radiologist must be able to recognize these injuries.

Vic David MD

Sunday, February 14, 2010

Pearls and Ganglion Cysts

Our bodies can develop various lumps and bumps, and when they are near the skin surface, they become noticeable. Various terms are used to describe these bumps, often at the whim and creativity of the clinician e.g. "pea-sized", "pearl sized", and the like.

A real pearl is a hard, rounded object composed of calcium carbonate, created within a living mollusk:

They come in various colors, and are treasured for their beauty. The vast majority of pearls are cultured pearls, as natural pearls are quite rare.

A common pearl-sized bump in the area of the wrist is a ganglion cyst. Here is an example of a ganglion cyst on the volar side of the wrist:

Photo by Glen E. Malone

When they arise from the volar aspect of the wrist, common locations include the radioscaphoid/scapholunate interval, scaphotrapezial joint, pisotriquetral joint, and the metacarpotrapezial joint. When they arise dorsally, they are typically near the scapholunate joint and dorsal wrist capsule. Other sites include the extensor tendons, the carpal tunnel, and the Guyon canal. Ganglions may also arise within bone; these are called intraosseous ganglion cysts. Finally, ganglions can also arise near and within tendons and ligaments.

In this case, a 34 year-old female presented with a dorsal wrist mass. Axial T1 image reveals a smoothly marginated mass (red arrows) deep to the ECRL and ECRB tendons:

Axial T2 fatsat image shows the mass to be of homogeneous fluid signal intensity:

Coronal intermediate and T2 fatsat images depict the ganglion cyst (red arrows) and demonstrate a small neck (green arrows) leading to the scapholunate ligament (yellow arrows):

Dorsal ganglion cysts are often related to the scapholunate (SL) ligament. The SL ligament typically can still be identified, but is often increased in signal, indicating tissue degeneration.

When one detects a ganglion cyst on imaging, it is important to look for a "neck" or "pedicle", as in this case. The neck often points to the origin of the cyst, which can be important presurgical information. Small dorsal ganglia may not be palpable clinically, but may be painful. Cysts can get larger and smaller over time, and can resolve spontaneously in some cases. An excellent review of wrist ganglion cysts has been written by Gude and Morelli, and is worth reading. They have a nice section on management of ganglion cysts, with a fascinating description of alternate, historical methods of treatment:

Heister in 1743 had this recommendation: “The inspissated matter of a ganglion may often be happily dispersed by rubbing the tumor well each morning with fasting saliva and binding a plate of lead upon it for several weeks successively … Others … prefer a bullet that has killed some wild creature, especially a stag. Sometimes, indeed, a recent ganglion will speedily vanish … by adding a repeated pressure with the thumb or a wooden mallet. If none of these means prove effectual … they may be safely removed by incision provided you are careful to avoid the adjacent tendons and ligaments. But as for rubbing them with the hand of a dead man and the like … I presume, my reader will excuse me from insisting on them”

We now have different means to manage ganglion cysts, typically surgical excision. Not as creative as the methods described by Heister, but more effective....

Vic David MD