Magnetic ResonanceArthrography of the Wrist

and Elbow Gary M. LiMarzi, MDa,b, M. Cody O’Dell, MDa,b,Kurt Scherer, MDa,b, Christopher Pettis, MDa,b,Christopher W. Wasyliw, MDa,b, Laura W. Bancroft, MDa,b,*

KEYWORDS

� MR arthrography � Scapholunate ligament tear � Ulnar collateral ligament tear� Olecranon stress fracture � Osteochondritis dissecans

KEY POINTS

� Magnetic resonance (MR) arthrography is highly sensitive and specific for the diagnosis of scapho-lunate ligament tears.

� MR dictations should state if tears are partial-thickness or full-thickness, and if the tearing involvesthe dorsal, membranous, and/or volar components of the ligament.

� Partial-thickness tears of the anterior band of the ulnar collateral ligament in overhead-throwingathletes are well evaluated with MR arthrography.

� Repetitive valgus elbow stress and rapid elbow extension during the late stages of throwing mayresult in an olecranon stress fracture, with propagation from a structural weak point in the trochleargroove.

� Osteochondritis dissecans of the elbow is an osteochondral injury classically seen in adolescent oryoung adult athletes, especially baseball pitchers, due to repetitive valgus impaction injury of theradial head and developing ossification center of the capitellum.

MAGNETIC RESONANCE ARTHROGRAPHY OFTHE WRIST

Wrist pain is a common, nonspecific patientcomplaint that may be secondary to a variety ofunderlying processes, both degenerative and trau-matic. Wrist trauma can be divided into 2 cate-gories: low impact and high impact. High-impacttrauma can lead to displaced fractures, disloca-tions, andacute tearsof the ligaments and tendons,whereas low-impact trauma can lead to moreoccult injuries.1 Both mechanisms can result in

The authors have nothing to disclose.a Florida Hospital Diagnostic Radiology Residency Progrversity of Central Florida College of Medicine, 601 East Roology, Florida Hospital, University of Central Florida ColleFL 32827, USA* Corresponding author.E-mail address: Laura.bancroft.md@flhosp.org

Magn Reson Imaging Clin N Am 23 (2015) 441–455http://dx.doi.org/10.1016/j.mric.2015.04.0031064-9689/15/$ – see front matter � 2015 Elsevier Inc. All

injuries to the intrinsic and extrinsic carpal liga-ments, as well as the triangular fibrocartilage com-plex (TFCC). Because the TFC is discussed indepth in the article by Cody et al, elsewhere inthis issue, this article will not focus on its normal im-aging appearance or pathology. Because clinicalpresentations can overlap significantly, magneticresonance (MR) arthrography is essential in thediagnostic workup of such injuries. MR arthrogra-phy of the wrist is generally preferred over conven-tional MR imaging or computed tomography (CT)arthrography because of its high intrinsic contrast

am, Department of Radiology, Florida Hospital, Uni-llins, Orlando, FL 32803, USA; b Department of Radi-ge of Medicine, 6850 Lake Nona Boulevard, Orlando,

rights reserved. mri.th

eclinics.com

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resolution, as well as the ability to evaluate extra-articular soft tissue pathology. MR arthrography isindicated to evaluate TFCC, intrinsic and extrinsiccarpal ligaments, and the distal radial ulnar joint(DRUJ).2

Fig. 1. Wrist arthrogram in a 70-year-old man beforeMR arthrography. Anteroposterior view of the wristat the beginning of arthrogram demonstrates radio-carpal injection of 1:250 ratio of gadolinium to iodin-ated contrast through a 25-gauge needle (arrowhead)before MR arthrogram. Asterisk indicates site for mid-carpal injection, and circle indicates site for distalradioulnar injection.

Technique

The use of intra-articular contrast agents providesan effective means of evaluating the TFCC and in-terosseous ligaments of the wrist. There is vari-ability among institutions as to whether to performsingle-compartment (most commonly radiocarpal),2-compartment, or rarely 3-compartment (radio-carpal, DRUJ, and midcarpal) arthrography beforeMR arthrography. Injections are most commonlyperformed under fluoroscopic guidance, butsome radiologists prefer sonographic guidance.3

Radiocarpal injections are approached mostcommonly from a dorsal approach; however,some radiologists choose a lateral approach.4

With the patient supine on the fluoroscopy table,the patient’s wrist is placed in a flexed positionand bolstered with a rolled towel. The radiocarpaljoint is visualized in profile and the skin overlyingthe joint is marked at the level of the mid scaphoid.After prepping and draping the dorsumof thewrist,local anesthesia is administered with a 25-gauge,1.5-inch anesthesia needle from a dorsalapproach, and the needle is advanced into theradiocarpal joint. Connector tubing flushed withinjectate from the syringe is connected to the nee-dle after dripping contrast into the needle hub todisplace any air. Although some radiologists injectonly a small amount of iodinated contrast toconfirm needle placement before injecting thedilute gadolinium mixture, it is also acceptable tocombine the iodinate contrast and gadoliniumtogether. While taking rapid cine images, anapproximately 3-mL mixture of iodinated contrastand dilute gadolinium is injected into the radiocar-pal joint, or until resistance is perceived (Fig. 1).The gadolinium-based contrast used in MR ar-thrography is usually diluted in normal saline and/or iodinated contrast to a concentration of 1:250,which optimizes the paramagnetic effects of gado-linium at 1.5-T field strengths. After removal of theneedle, the wrist is then briefly exercised and con-ventional arthrographic images are obtained in theanteroposterior, lateral, and oblique images beforeMR arthrography. Some radiologists also prefertaking dedicated spot imaging of the scapholunate(SL) ligament with ulnar deviation or clenched fiststress maneuver. This arthrographic imaging isdiagnostic, and is instrumental in cases of patientsunable to complete theMR portion of the examina-tion for a variety of reasons.

Midcarpal joint injections are most commonlyperformed from a dorsal approach into to the cen-tral portion of the 4-part junction of the lunate, tri-quetrum, hamate, and capitate. Distal radioulnarjoint injection is performed from a dorsalapproach, with the needle extending to the radialaspect of the ulnar head.

Contraindications

Besides the normal contraindications for MRimaging, the only absolute contraindication for ar-thrography is local infection of the skin or subcu-taneous tissue.5 One would not want tocontaminate a joint by crossing a needle throughinfected tissues. Usually, patients who cannot un-dergo MR arthrography are able to tolerate imag-ing with CT arthrography. For example, patientswith implantable cardiac pacemakers who, withsome recent exceptions due to new MR imaging-safe pacemakers, cannot undergo MR arthrogra-phy, can be safely evaluated with CT.5–8 A historyof adverse contrast reactions with either iodinatedor gadolinium-based agents is considered a rela-tive contraindication and should be evaluated ona case-by-case basis.5

Complications

Arthrography is a generally well-tolerated proce-dure with few significant risks, and complications

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following arthrography are uncommon and usuallyin the form of pain. This can be due to overdisten-tion of the joint space, irritation of surroundingnerves, or from intravasation of injected contrastinto adjacent muscles.5,7,8 Synovitis caused bythe contrast also may be irritating and painful.Infection is an inherent risk to all percutaneousprocedures, but is very rare.

Fig. 2. Axial scout for prescription of coronal andsagittal views. A plane intersecting the hook of thehamate (H) and the palmar margin of the trapezium(T) serves as the reference plane for coronal acquisi-tions (single line). Sagittal images are prescribedfrom the axis perpendicular (double lines) to the cor-onal plane.

Magnetic Resonance Acquisition

Wrist MR arthrography should be obtained on a1.5-T or preferably a 3.0-T magnet in a dedicatedwrist coil for optimal image quality, and thin-section imaging and small field of view should beused (Table 1).9–13 Patients are optimally scannedin the prone position with the arm extended over-head and the wrist in neutral positioning near theisocenter of the magnet (“Superman” position).13

If patients cannot tolerate this positioning, imagingis done with the wrist by the patient’s side, withcare to optimize fat suppression. MR arthrographyincludes axial, coronal, and sagittal imagingplanes, and the coronal and sagittal sequencesare prescribed relative to a plane intersecting thehook of the hamate and the palmar margin of thetrapezium (Fig. 2). Most sequences are obtainedwith turbo spin echo (TSE) T1-weighting with fatsuppression, to take advantage of the T1 proper-ties of the injected gadolinium; T1-weighted im-ages without fat suppression and T2-weightedimages with fat suppression also are obtained.T2-weighted fat-suppressed and non–fat-sup-pressed T1-weighted images are useful in evalu-ating the marrow. T2-weighted images candetect noncommunicating tears of the intrinsicligaments and TFCC on the opposite side of theinjected joint, marrow edema, and noncommuni-cating periarticular fluid collections. Some centers

Table 1Sample wrist MR arthrogram protocol, using1.5-T or 3.0-T magnet and dedicated wrist coilafter radiocarpal injection of dilute gadoliniummixture

Plane Sequence FOV, cmSlice Thickness,mm

Axial TSE T1 FS 15 3

Coronal TSE T1 FS 15 2

Sagittal TSE T1 FS 15 3

Coronal TSE T2 FS 15 2

Coronal TSE T1 15 2

Abbreviations: FOV, field of view; FS, fat saturation; TSE,turbo spin echo.

also prefer using gradient-echo sequences or3-dimensional volumetric sequences. Althoughuncommonly used, some investigators use fingertrap distraction with weights suspended from thefingers to accentuate the amount of contrast inthe SL interval, widening of the space, and disrup-tion of Gilula carpal arcs.14,15

NORMAL ANATOMYIntrinsic Ligaments

The intrinsic and extrinsic interosseous ligamentsof the wrist provide stability to the carpus. The SLligament is the most commonly injured intrinsiccarpal ligament and can predispose to carpalinstability.1,16–20 Patients with ligamentous injurytypically present with dorsal wrist pain, crepituswith motion, weakness, and swelling. The SL liga-ment consists of the bandlike dorsal and volarcomponents connected by the membranousportion composed of a proximal fibrocartilaginousmembrane; the dorsal component is consideredthe primary SL stabilizer (Fig. 3).16–20 The lunotri-quetral (LT) ligament is similar in composition tothe SL ligament; however, the volar rather thanthe dorsal component is considered the primarystabilizer of the LT ligament.16–21 These ligamentsprovide a barrier between the radiocarpal andmidcarpal spaces.20 CT and MR arthrographyhave been shown to be more sensitive than stan-dard MR for detecting abnormalities of these liga-ments, andMR is superior to CT in detecting othercauses of patient’s symptoms, such as osteonec-rosis, tendon and tendon sheath pathology, syno-vitis, fluid collections, and masses.20

Fig. 3. Normal wrist MR arthrogram. (A) Coronal TSE fat-suppressed image after radiocarpal joint injection ofdilute gadolinium mixture demonstrates normal appearance of the SL ligament (gray arrowhead), LT ligament(white arrowhead), and the TFC (arrows). (B) Axial image through the SL (arrows) and LT (arrowheads) ligamentsshow the thicker bandlike portions of the dorsal ligaments compared with the volar components. L, lunate; S,scaphoid; T, triquetrum.

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Extrinsic Ligaments

The extrinsic ligaments of the wrist are shown tobetter advantagewithMR arthrography due to jointdistention. Dorsally, the extrinsic ligaments are thedorsal radiocarpal ligament (DRCL) and the dorsalintercarpal ligament (DICL) (Fig. 4).13,22,23 Theseligaments generally demonstrate homogeneouslylow signal intensity on MR imaging.13,22,23 Volarextrinsic ligaments include the radioscaphocapi-tate ligament (RSCL), radiolunotriquetral ligament(RLTL, also known as the long radiolunate liga-ment), and the short radiolunate ligament. TheRSCL is the most important volar extrinsic liga-ment, and the RSCL and RLTL can contain normalbands of higher signal on MR imaging/MR arthrog-raphy.13,22,23 The radial collateral ligament (RCL) ofthe wrist arises as a focal condensation of the jointcapsule, just deep to the extensor tendon sheath; it

Fig. 4. Extrinsic ligaments. (A) Coronal image through thesal radiocarpal (arrows) and dorsal intercarpal (arrowheadter advantage with MR arthrography due to joint distentioshows the volar radiolunotriquetral (RLT) ligament (asteri

originates from the radial styloid and inserts ontothe scaphoid waist.13,22 Carpal instability mayoccur when there is concomitant injury to theintrinsic and extrinsic interosseous ligaments.1,22

PATHOLOGYScapholunate Ligament

MR arthrography’s ability to localize the preciselocation of the tear can help distinguish stablefrom potentially unstable injuries. Tears of themembranous portion of the SL ligament are usu-ally degenerative and are not associated with car-pal instability.17 Complete SL ligament tears areidentified on conventional and MR arthrographyby contrast extending from the radiocarpal to themidcarpal joint space through a SL interval defect.In advanced cases, widening of the SL intervalalso can be seen.17 Partial tears result in variable

dorsal joint capsule of the wrist shows the normal dor-s) ligaments. These intact ligaments are shown to bet-n. (B) Coronal MR arthrogram through the volar wristsks). L, lunate; T, triquetrum.

Fig. 6. Complete SL ligament rupture. Coronal MR ar-throgram shows contrast filling the widened SL inter-val (arrowheads) due to complete rupture of the SLligament and SL dissociation.

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intravasation of contrast through the torn fibersand outline the abnormal morphology of the tear.SL ligament injuries typically occur in the settingof axial overload or hyperextension with supina-tion, often in the setting of a fall.1 There also isincreased association of SL ligament tears withintra-articular fractures. When isolated, SL liga-ment tears usually do not cause carpal malalign-ment (Figs. 5 and 6). Disruption of the secondarystabilizers of the scaphoid leads to rotation of thescaphoid with proximal subluxation, as well asdorsal extension of the lunate, resulting in dorsalintercalated segmental instability (DISI).1,16,17,24

Magnetic Resonance Arthrography Accuracy:Scapholunate Ligament

Although conventional MR imaging can detectpartial and complete tears of the intrinsic carpalligaments by the presence of focal thinning ordiscontinuity, MR arthrography is widely preferreddue to improved sensitivity.17 Arthrographic sensi-tivity for SL ligament tears has been shown torange widely. Scheck and colleagues12 demon-strated 90% sensitivity/87% specificity with MRarthrography, compared with 52% sensitivity/34% specificity on conventional MR imaging. Leeand colleagues8 also demonstrated superior accu-racy of MR arthrography (85.0% sensitivity/96.4%specificity) when compared with conventional MRimaging (65% sensitivity/100% specificity) in theevaluation of SL ligament tears. Compared witharthroscopy, Magee and colleagues25 reportedthat MR arthrography with 3 T yielded 100% sensi-tivity and specificity for the detection of SL liga-ment tears.

Dorsal Intercalated Segmental Instability

The 4 main categories of carpal instability includedissociative carpal instability, nondissociative

Fig. 5. SL ligament tears. (A) Coronal MR arthrogram inthickness tear of the SL ligament (arrow), with opacificatication from the tear. (B) Coronal TSE T2-weighted imagepain shows irregular tearing of the volar aspect of the SL

carpal instability, complex carpal instability, andadaptive carpal instability.16,24 Although carpalinstability may be suggested radiographically incases of static instability, patients will invariablyundergo MR imaging for evaluation of dynamicinstability and treatment planning. DISI is one ofthe dissociative instabilities that occurs whenthere is disruption of the SL.17 As on radiographs,MR will also show dorsal tilt of the lunate with acapito-lunate angle greater than 30�, hyperflexionof the scaphoid, and incongruity of Gilula arcs inthe presence of DISI deformity (Fig. 7). MRarthrography may be helpful to also assess tearsor excessive stretching of the secondary stabi-lizers of the scaphoid, such as the volar distalscaphotrapezial, dorsal intercarpal and SLligaments.17

a 29-year-old man with wrist pain demonstrate full-on of the midcarpal joint space due to the communi-from MR arthrogram in 70-year-old man with wristligament (arrowhead).

Fig. 7. Dorsal intercalated instability in 43-year-old man with traumatic SL and extrinsic dorsal ligament tears. (A)Sagittal MR arthrogram shows dorsal tilt of the lunate ‘L’ relative to the capitates ‘C,’ with increased lunate-capitate angle greater than 30�. (B) Axial MR arthrogram also shows rupture of the DRCL (black arrowhead)and full-thickness tears of the dorsal and membranous portions of the SL ligament (white arrowheads), account-ing for contrast extension into the midcarpal joint.

Fig. 8. LT ligament tear and ulnolunate impaction in49-year-old man with chronic wrist pain. Coronal MRarthrogram shows a linear tear of the LT ligament(arrowhead) with extension of contrast into the mid-carpal joint and Palmer 2E TFCC defect (arrows) withinjected contrast and synovitis in the DRUJ. The sub-chondral cyst and enhancing marrow in the proximal,medial lunate, chondromalacia involving the abuttingsurfaces of the ulnar and lunate, and mild ulnar posi-tive variance are classic findings of ulnolunateimpaction.

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Lunatotriquetral Ligament

Injuries to the LT ligament are much less commonthan those involving the SL ligament; LT ligamenttears may be misdiagnosed clinically as TFCCpathology in patients presenting with ulnar-sidedwrist pain.1,17 As with SL ligament injury, isolatedLT ligament tears are generally stable. Disruptionof the secondary triquetral stabilizer, the radiolu-notriquetral ligament, predisposes to volar interca-lated segmental instability, in which there is palmarrotation of the lunate and scaphoid.16,17,24

Magnetic Resonance Arthrography Accuracy:Lunatotriquetral Ligament

Conventional MR imaging is unreliable inexcluding pathology of the LT ligament due toinconsistent visualization in healthy patients. MRarthrography has been shown to have sensitivityfor LT ligament tears of up to 56%, when consid-ering both complete and partial tears (Fig. 8).17 Aseries of 35 patients demonstrated a sensitivityand specificity of 100% for complete tears of theSL and LT ligaments with 3-T MR arthrography.13

LT ligament tearing may be accompanied bytearing of the TFCC and lunate chondromalaciain the setting of ulnolunate impaction (see Fig. 8).Compared with arthroscopy, Magee and col-leagues25 reported that MR arthrography yielded100% sensitivity and specificity for the detectionof LT ligament tears.

Ulnocarpal Impaction Syndrome

Ulnocarpal impaction syndrome is caused byrepetitive impaction injury between the ulnar

head, TFCC, and carpus, resulting in a spectrumof pathology. Ulnocarpal impaction is usuallyseen in the setting of positive ulnar variance, eithercongenital or posttraumatic, with distal radial mal-union.16,17,24 The TFC is thinner in patients with

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positive ulnar variance and loading of the ulnarcarpus is increased, both factors that may predis-pose to increased rates of TFCC pathology.11,17,21

Increasing the ulnar variance by 2.5 mm willincrease the ulnar load by 42%, more than twicethe normal amount.9 In rare cases, similar degen-erative findings may be seen in the setting of ahypertrophic ulnar styloid with negative ulnar vari-ance, referred to as ulnar styloid impaction syn-drome (see Fig. 8).

MAGNETIC RESONANCE ARTHROGRAPHY OFTHE ELBOW

In North America, MR arthrographic evaluation ofthe elbow is most commonly performed to investi-gate pain in throwing athletes and patients sus-taining trauma from severe valgus stresses,posterorlateral rotator subluxation, and disloca-tion.5 Typically, the pain is medial and occurs dur-ing the late-cocking phase of throwing, at the pointof maximal valgus stress on the medial elbow sta-bilizers. Unsurprisingly, baseball pitchers, bothamateur and professional, comprise a significantportion of patients undergoing arthrography inthis part of the world.5,26 Elsewhere, elbowarthrography is generally used to evaluate acutetraumatic injury, namely posterolateral rotatorysubluxation and severe valgus injuries.5 Althoughless commonly performed than arthrography ofthe shoulder and knee, elbow arthrography is animportant means of investigating intra-articularand ligamentous pathology. Direct arthroscopy israrely performed as a first-line examinationbecause of the excellent ability of MR and CTarthrography to demonstrate relevant pathologythat can then guide arthroscopic evaluation or sur-gical intervention. Distention of the joint capsulewith intra-articular contrast greatly improves visu-alization of articular and ligamentous structures,which would be overlooked on conventional imag-ing, increasing the sensitivity of the examination.5

Contrast in the joint space helps separate closelyrelated structures and provides improved imagecontrast. Detection of subtle pathology, includingpartial ligament tears and early osteochondralinjury, also is improved.

MR arthrography is typically considered supe-rior to CT arthrography because of improved softtissue contrast resolution and the ability to obtainsource images in multiple planes; however, CTpossesses better spatial resolution and is thepreferred modality for select patients.26 Individualswith pacemakers, non-MR safe implantabledevices, or who cannot tolerate gadolinium-based contrast agents are excellent candidatesfor CT arthrography.5,26 Both modalities are

considered far superior to conventional arthrogra-phy, which has been largely replaced in modernpractice. The most common clinical indicationsfor MR arthrography include detecting injuries tothe capsule and supporting ligaments, the pres-ence of intra-articular bodies, and focal osteo-chondral injury.5,26

Technique

The lateral approach into the radiocapitellar joint isthe most commonly used approach for accessingthe elbow joint. After palpating the radiocapitellarjoint with patient pronating and supinating theforearm, the overlying skin is marked. The patientshould preferably be positioned prone (in case ofvasovagal reaction) or seated with the elbowflexed at 90� and in supination so that the thumbpoints toward the ceiling.5 The radiocapitellar jointis visualized and marked under fluoroscopy. Usingthe general arthrographic principles describedpreviously, local anesthetic is administered froma direct lateral approach with 25-gauge needle,and then the needle is advanced into the radioca-pitellar joint. Intra-articular needle placement isconfirmed when contrast can be seen flowingfreely away from the needle (Fig. 9). The solutionof diluted gadolinium is then injected for a total vol-ume of 6 to 10 mL or until resistance is felt.

Occasionally, practitioners may elect to aban-don the lateral approach in favor of a posterome-dial approach.27 This is usually done when thereis clinical concern regarding the lateral ligamentcomplex, because the lateral approach may leadto a small amount of contrast leaking through thepercutaneous access site, which can lead to afalse-positive diagnosis of lateral ligamentous pa-thology.5,28 The patient is positioned supine withthe shoulder abducted over the head and theelbow in pronation and approximately 30� offlexion. The medial epicondyle is identified andthe skin entry site is marked approximately 1 cmlateral to the epicondyle on the posterior aspectof the arm, reducing the risk of injury to the ulnarnerve.5 Once the patient is prepped and draped,the needle is directed anterolaterally toward theolecranon fossa. At this point, the examinationproceeds in an identical fashion to that of a lateralapproach.

Magnetic Resonance Acquisition

During the actual MR image acquisition, the pa-tient may be positioned either prone with theelbow extended overhead, the “Superman” posi-tion, or supine with the elbow extended along thebody (Table 2).29 Images are obtained in axial, cor-onal, and sagittal planes. A plane intersecting the

Fig. 9. Fluoroscopically guided elbow arthrography from standard lateral (A) and posterior (B) approaches in a 9-year-old boy and an 11-year-old girl, respectively. (A) After palpating the radiocapitellar joint, with the patientpronating and supinating the forearm, the overlying skin is marked for direct lateral approach into the radioca-pitellar joint with 25-gauge needle. (B) The posterior approach (arrowheads) is an alternate route that will avoidmisinterpretation of extravasated contrast about the lateral collateral ligament as pathology.

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medial and lateral humeral epicondyles serves asthe reference plane for coronal acquisitions, andsagittal images are prescribed from the axisperpendicular to the coronal plane (Fig. 10). MRarthrography uses T1-weighted sequences, whichprovide a higher signal-to-noise ratio than T2-weighted sequences and also require less time,therefore causing less motion artifact.5,30 Fat-suppressed T1-weighted sequences are per-formed in the axial, coronal, and sagittal planes.Fat-suppressed T2-weighted images also are ob-tained, usually in the axial and coronal planes. Bycombining contrast-enhanced and fluid-sensitivesequences, the elbow can be evaluated for stressfractures/contusions and extra-articular pathol-ogy, such as nerve and muscle pathology, andtendon injuries (particularly enthesopathicchanges of the common extensor and flexortendon origins).5 Some institutions also prefer us-ing gradient-echo sequences or 3-dimensionalvolumetric sequences.

Table 2Sample elbow MR arthrogram protocol using1.5-T or 3.0-T magnet and dedicated elbow coilafter injection of dilute gadolinium mixture

Plane Sequence FOV, cmSlice Thickness,mm

Coronal TSE T1 FS 15 2.5

Sagittal TSE T1 FS 15 2.5

Axial TSE T1 FS 15 2.5

Coronal TSE T2 FS 15 2.5

Coronal TSE T1 15 2.5

Abbreviations: FOV, field of view; FS, fat saturation; TSE,turbo spin echo.

Normal Anatomy

The elbow is a synovial-lined, encapsulated jointcomposed of 3 distinct articulations: the radioca-pitellar, ulnohumeral, and proximal radioulnarjoints.30 Of these, the biggest contributor to elbowstability is the ulnohumeral joint, responsible for55% to 75% of joint restriction in extension andflexion, respectively.29 The radiocapitellar joint,although playing a lessor role in joint stability, isresponsible for transmitting 60% of the axial loadfrom the forearm.29 There is a normal, mild degreeof lateral angulation of the humerus and ulna,referred to as the valgus carrying angle of the

Fig. 10. Axial scout for prescription of coronal andsagittal views. A plane intersecting the medial andlateral humeral epicondyles serves as the referenceplane for coronal acquisitions (single line). Sagittal im-ages are prescribed from the axis perpendicular (dou-ble lines) to the coronal plane.

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elbow. This is usually between 10 and 20� and pre-disposes the elbow to valgus instability, whereasvarus instability remains uncommon.29

Ligamentous supporting structures of the elbowarise as focal condensations of the joint capsuleand are divided into medial and lateral com-plexes.29,30 These provide stability under valgusand varus stresses, respectively. The medial com-plex consists of the anterior and posterior bundlesof the ulnar collateral ligament (UCL, also knownas the medial collateral ligament) as well as thetransverse ligament (Fig. 11A). The lateral complexincludes the RCL, the lateral UCL (LUCL), and theannular ligament (see Fig. 11B). The most impor-tant component of the medial ligament complexis the anterior bundle of the UCL, which providesthe most resistance against valgus forces.29,31

Both bundles of the UCL originate from the inferioraspect of the medial epicondyle; the anteriorbundle inserts on the sublime tubercle of the ulnaand the posterior bundle forms the floor of thecubital tunnel.26,29 The posterior bundle insertson the trochlear notch and helps resist internalrotation. The transverse ligament spans betweenthe anterior and posterior bundles of the UCLand is poorly visualized with MR.29 Superficially,the UCL is in close relationship to the flexor musclegroup. On MR imaging, the UCL has a striatedappearance in more than 90% of healthy volun-teers, which should not be confused with injury.

The annular ligament serves an important role asa stabilizer of the proximal radioulnar joint and ismore clinically relevant in pediatric patients thanadults.29 It inserts twice on the lesser sigmoidnotch of the ulna after enveloping the radialhead. The LUCL provides most of the support to

Fig. 11. Normal MR imaging arthrogram of the elbow inshows the normal fan-shaped configuration of the anteincreased signal intensity in the proximal ligament. (B) Codeep to the intact common extensor tendon origin (arrowwhen there is the suspicion of partial-thickness tearing of

the lateral elbow ligaments and is a key restraintagainst posterolateral rotatory instability.29,30 Itoriginates from the lateral epicondyle and coursesposterior to the radial head before inserting on thesupinator crest of the ulna. In this way, the LUCLprevents the ulna from rotating about its longaxis away from the trochlea.29 On conventionalMR imaging, the LUCL is incompletely visualizedin up to 23% of healthy volunteers.29 Althoughthe RCL also originates from the lateral epicon-dyle, this fan-shaped ligament runs longitudinallyand blends distally with the annular ligament.

PATHOLOGY

The most common indication for MR arthrographyof the elbow is medial joint pain, especially ifoccurring during overhand throwing. It is impor-tant to carefully assess all supporting structures,which should be easily visualized due to capsulardistention by intra-articular contrast. Additionally,extra-articular etiologies for elbow pain should beevaluated as with any nonarthrographic study.

Ulnar Collateral Ligament Tear

Because the anterior bundle of the UCL is the mostimportant stabilizer against valgus stress, it is nosurprise that this ligament is most frequentlyinjured in pitchers as a result of the high stressesplaced on the joint during the late-cocking phaseof throwing.5,26,28,29 The UCL should be easilyvisualized on MR arthrography and is normally ho-mogeneously hypointense along its superficialaspect proximally. The deep margin can be moreheterogeneous in signal, which should not beconfused with injury.5,29

a 17 year-old girl with elbow pain. (A) Coronal imagerior bundle of the UCL (arrowheads), with normallyronal image show the normal RCL proper (arrowhead)). MR arthrography adds value over conventional MRthe collateral ligaments in high-level athletes.

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When the heterogeneity of the proximal UCLextends to involve the superficial aspect of the lig-ament, a partial-thickness tear should be sus-pected. Partial tears also can appear as a focaltear in the proximal UCL with its apex directedtoward the superficial surface (Fig. 12).5,26 Visual-ization of these partial tears is improved with ar-thrography, as contrast can be seen filling thetear and extending into the ligament (Fig. 13).These tears are of uncertain clinical significance,and athletes often continue to throw without surgi-cal repair.5,29

The characteristic appearance of a partial tear ofthe distal UCL is referred to as the “T sign,” due tocontrast entering the defect and extending a shortdistance distally between the UCL and the prox-imal ulna (see Fig. 12). The anterior bundle nor-mally inserts approximately 3 mm distal to theproximal margin of the sublime tubercle, so if thereis contrast extending more than 3 mm distally, apartial tear should be suspected.5,31 Whether ornot these tears require surgical repair largely de-pends on the percentage of ligament involvedand the degree to which contrast extends distalto the sublime tubercle. Schwartz and col-leagues32 demonstrated 86% sensitivity/100%specificity for detection of partial-thickness tearson arthrography.Traumatic injury to the UCL also can be as-

sessed with MR arthrography, although the abnor-malities associated with acute trauma follow aless-reproducible pattern than those secondaryto recurrent valgus stresses.5 In cases of acutetrauma, there are frequently associated injuriesto the surrounding structures, including capsulardisruption, fractures of the coronoid process of

Fig. 12. Partial-thickness tear of the UCL. (A) Injected controf the anterior band of the UCL in a 44-year-old who previplayer producing the “T sign.” Coronal MR arthrogram shthe undersurface of the UCL producing the “T sign” of a

the ulna, articular cartilage delamination, andcontusion.5 The best indicator of traumatic disrup-tion of the UCL is contrast extending medial to thejoint line; the location of tear (ie, proximal or distal)is less important in the setting of trauma and thesetears infrequently require reconstruction.

ULNAR COLLATERAL LIGAMENTRECONSTRUCTION

Reconstruction of the UCL is commonly performedin patients with medial elbow instability secondaryto complete tears. In high-performing athletes,the tendency to return to a normal level of activitysoon after surgery can lead to postoperative pa-thology.33 In certain cases, evaluation with MRarthrography can be useful to evaluate the recon-struction as well as the adjacent elbow stabilizers.Due to the variable appearance of the recon-structed UCL in terms of thickness and signal char-acteristics, the best indicator of pathology isopacification of the fibers of the graft by intra-articular contrast (Fig. 14).33 The reconstructedligament is expected tobe thickenedandheteroge-neous compared with the native ligament, and isanchored into the sublime tubercle more distalthan the native ligament, allowing a small amountof contrast to extend into the recessnormally.How-ever, extravasation of medial joint fluid into the re-constructed ligament would be considered a tear.

Radial Collateral Ligament Complex

The radial collateral ligament complex iscomposed of the radial collateral ligament (RCL)proper, the lateral ulnar collateral ligament(LUCL), and the annular ligament.34 The LUCL is

ast extends into the deep proximal fibers (arrowhead)ously worked as a stuntman. (B) A 17-year-old baseballows contrast dissecting proximally and distally alongpartial UCL tear (white arrowhead).

Fig. 13. Partial-thickness tear of the UCL. Fluoroscopic (A) and coronal MR arthrogram (B) both demonstratingcontrast extending past the expected location of the UCL (black arrowhead). The MR arthrogram shows the par-tial tear with retraction of some of the torn fibers (white arrowhead).

MR Arthrography of the Wrist and Elbow 451

the most frequently injured lateral ligament in thesetting of traumatic subluxation or dislocation ofthe elbow.5 The incidence of traumatic elbowdislocation is 5 to 6 per 100,000, surpassed onlyby dislocations of the shoulder.29 The course ofthe LUCL along the inferior aspect of the proximalradius predisposes it to damage from translationalforces. The normal LUCL should be taut and ho-mogeneously low signal on MR arthrography; thepresence of focal ligamentous thickening or laxityshould raise suspicion for a tear. Complete tearscan be seen as focal disruption with extravasationof contrast through the defect in the LUCL.5 TheRCL is located anterior to the LUCL and is also

Fig. 14. Intact UCL reconstruction in a 27-year-old professifrom MR arthrogram shows the normal postoperative appstructed ligament is expected to be thickened and heterogligament, and is anchored into the sublime tubercle (graylowing a small amount of contrast (arrow) to extend intomedial joint fluid (arrow) into the reconstructed ligament

susceptible to injury in the setting of trauma(Fig. 15).5 Detection of any abnormality involvingthe RCL or LUCL should prompt close scrutiny ofthe remaining lateral ligament. Posterolateralelbow instability can occur in the setting of chronicrecurrent injury to the LUCL, as the ability of theligament to resist rotational forces is diminishedover time.

Laxity of the LUCL near its ulnar insertion allowsrotation and possible subluxation of the ulnohum-eral joint with eventual secondary dislocation ofthe radiohumeral joint.5 Importantly, the annularligament is not disrupted and the proximal radioul-nar joint remains intact.

onal baseball pitcher. Coronal (A) and axial (B) imagesearance of an intact UCL ligament repair. The recon-eneous (white arrowheads) compared with the nativearrowhead) more distal than the native ligament, al-the recess. (B) Axial image shows no extravasation of(arrowheads).

Fig. 15. High-grade tearing of the RCL in a 17-year-old boy after elbow dislocation 1 year prior. CoronalMR arthrogram shows high-grade tearing of thedeep fibers of the proximal RCL (arrowhead), withintact overlying common extensor tendon origin. Pa-tient also had healed coronoid process fracture (notshown).

LiMarzi et al452

Olecranon Stress Fracture

Osseous stress reaction, contusion, and fracturealso may be detected on the fluid-sensitive se-quences of elbow MR arthrography. Olecranonstress fractures in throwing athletes are caused byshear forces in the posterior compartment andchronic impingement.1 Repetitive valgus elbowstress and rapid elbow extension during the latestages of throwing may result in olecranon

Fig. 16. Olecranon apophyseal stress fracture in a 17-year-otear of the UCL. (A, B) Sagittal T1-weighted fat-suppressedsided stress fracture through the olecranon physis (arrow),tions (arrowheads) of the physis.

microtrauma. These repetitive excessive forcesmay lead to olecranon stress fracture, with propa-gation from a structural weak point in the trochleargroove.35MR imaging is reserved for cases inwhichradiographsare inconclusive: injected contrastmayextend into portions of incomplete fractures(Fig. 16) and associated bone marrow edema willbeevident on fluid-sensitive sequences. Initial treat-ment of olecranon stress fractures is conservativeand consists of rest and splinting. Screw fixationmay be preferable so as to achieve early union inelite athletes and hasten return to play.36,37

Osteochondral Injuries and OsteochondritisDissecans

Instability of the elbow predisposes to osteochon-dral and articular cartilage injury; these lesions areoptimally evaluated with MR arthrography, as thiscarries greater sensitivity than routine MR imagingorCTarthrography.5 Arthrographic evaluationof os-teochondral injury is crucial for determining the sta-bility of these lesions,whichwill determine if surgicalintervention is required. Along the same diseasespectrum, the presence of intra-articular bodiescan bemuch better demonstratedwithMR arthrog-raphy thanwith conventional imaging, as the insinu-ationofcontrast between the fragment andadjacentbone greatly improves contrast resolution.Osteochondritis dissecans (OCD) of the elbow is

a specific manifestation of osteochondral injuryseen classically in adolescent or young adult ath-letes, especially baseball pitchers. The character-istic distribution involves the radiocapitellar joint

ld baseball player who also sustained partial-thickness(A) and coronal T1-weighted (B) images show medial-with contrast extending into the medial and deep por-

Fig. 17. OCD of the elbow. (A) Sagittal MR arthrographic images in a 14-year-old female athlete show a focalosteochondral defect along the articular surface of the capitellum (white arrowheads). (B) The presence of anintra-articular body (white arrowhead) in the olecranon recess on axial image demonstrates the end result of os-teochondral instability with fragmentation.

MR Arthrography of the Wrist and Elbow 453

most frequently due to repetitive valgus impactioninjury of the radial head and developing ossifica-tion center of the capitellum during the late-cocking phase of pitching.38 The pathogenesis ofOCD is believed to be secondary to compromisedvascular supply to the capitellum, resulting inosteochondral fragmentation and eventually,instability.26,38 Arthrography plays a key role indetermining the treatment pathway for thesepatients. Osteochondral injuries are visualized asirregularities along the articular surface, which fillin with intra-articular contrast.5,38 Osteochondralinstability is demonstrated by the insinuation ofcontrast between the fragment and underlyingbone; these patients invariably require surgicalrepair with either pinning or excision of the osteo-chondral fragment. Intra-articular bodies may bepresent in advanced cases, and their detection isgreatly improved with MR arthrography over con-ventional MR imaging, especially when the bodiesare incompletely ossified (Fig. 17).5,28,39

SUMMARY

In conclusion, MR arthrography of the wrist andelbow is useful for detecting a variety of intra-articular pathologies, and has proven to be moresensitive and specific than conventional MR imag-ing. MR dictations should address whetherintrinsic ligament tears of the wrist are partial-thickness or full-thickness, and involve the dorsal,membranous, and/or volar components of the lig-aments. With regard to the elbow soft tissuepathology, partial-thickness tears of the anteriorband of the UCL in overhead-throwing athletesare well evaluated with MR arthrography. The “T

sign” should be sought by the radiologist in casesof partial tearing at the attachment of ligamentonto the sublime tubercle. Repetitive valgus elbowstress and rapid elbow extension during the latestages of throwing may result in olecranon stressfracture, with propagation from a structural weakpoint in the trochlear groove. And finally, MRarthrography is helpful in staging OCD of the cap-itellum, caused by repetitive valgus impactioninjury in adolescent or young adult baseballpitchers.

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