Imaging: Upper Extremity, An Issue of Clinics in Sports Medicine, 1e PDF
Preview Imaging: Upper Extremity, An Issue of Clinics in Sports Medicine, 1e
ClinSportsMed25(2006)xi CLINICS IN SPORTS MEDICINE FOREWORD Imaging of Upper Extremities Mark D. Miller, MD ConsultingEditor Itissomucheasier tosee somethingifyou know what you arelooking for! That is the purpose of the next two issues of the Clinics in Sports Medicine. Dr. Tim Sanders, whom I have known and had the pleasure of working with over the last 10 years, has put together a pair of absolutely outstanding issuesonmusculoskeletalimaging.Thisfirstissuefocusesontheupperextrem- ity, and it will be followed by a lower extremity issue. Tim has already edu- cated many of us with his excellent current concepts articles in the American Journal of Sports Medicine and his podium presentations, including his recent review at the Colorado Orthopaedic Review Course. Dr. Sanders has assembled an ‘‘all star’’ panel of radiologists, who know what they are talking about and, more importantly, can teach even the most imaging-illiterate of us. From the fingers to the shoulder, from kids to adults, from radiographs to ultrasound to MRI, this issue covers it all. This is per- haps one issue thatorthopaedic surgeons may enjoy even more than ournon- operative colleagues, because there are more pictures! Please enjoy this issue. I know I will! Mark D. Miller, MD University of Virginia Department of Sports Medicine McCue Center – 3rd Floor Emmet St. & Massie Rd. Charlottesville, VA 22903, USA E-mail address: [email protected] 0278-5919/06/$–seefrontmatter ª2006ElsevierInc.Allrightsreserved. doi:10.1016/j.csm.2006.04.001 sportsmed.theclinics.com ClinSportsMed25(2006)xiii–xiv CLINICS IN SPORTS MEDICINE PREFACE Imaging of Upper Extremities Timothy G. Sanders, MD GuestEditor Theroleofimagingintheevaluationofsports-relatedinjuriesoftheupper extremities has evolved significantly over the past decade, with MRI becoming the imaging modality of choice for the evaluation of most soft- tissue injuries ranging from overuse injuries to acute traumatic injuries. Ultrasoundhasalsoemergedasausefulproblem-solvingtoolthatcanbeused inthetargetedevaluationofcertainupper-extremityinjuries.Tomaximizethe diagnosticvalueofthesetools,thetreatingphysicianmustpossessasolidfund ofknowledgeregardingtherolesofthevariousimagingmodalitiesandanun- derstanding of which studies are best suited for the evaluation of specific injuries. ThisissuedealsprimarilywiththemorecompleximagingmodalitiesofMRI and ultrasound. First, excellentreview articles providea basic approachto the evaluationofanMRexaminationoftheshoulder,elbow,andwrist.Thesear- ticles provide a framework for the interpretation of these complex exams, re- viewing the pertinent imaging anatomy as well as specific injury patterns that canbeseenonMRI.Next,theroleofMRIisdiscussedasitpertainstospecific clinicalproblemsthatinvolvetheshoulder,includinganarticleontheMReval- uationofshoulderpaininthehigh-performancethrowerandareviewofthecom- plexitiesofimagingthepostoperativeshoulder.Next,areviewofthenumerous nerveentrapmentsyndromesoftheupperextremityspecifictotheathleteispro- vided,andtheroleofMRIinestablishingthesesometimes-elusivediagnosesis discussed.Stressfracturesoftheupperextremityareuncommonandoftenover- lookedclinically.Thevariousstressfracturesoftheupperextremityandtheirim- aging appearance are comprehensively reviewed. The hand and wrist are at 0278-5919/06/$–seefrontmatter ª2006ElsevierInc.Allrightsreserved. doi:10.1016/j.csm.2006.02.004 sportsmed.theclinics.com xxiivv PPRREEFFAACCEE increasedriskforinjuryinmanysports,andimagingofthesmallanatomicsoft- tissuestructuresoftheseareascanbechallenging.Twoarticlesdiscusstheroleof compleximagingmodalitiesintheseanatomicareas.Thefirstprovidesacompre- hensivereviewofMRIofulnar-sidedwristpain,andtheseconddealswiththe imaging of the fingers and thumb. Several unique upper-extremity injuries are seen in the pediatric age group, and these are mostly related to the immature and developing skeleton. Special imaging considerations of pediatric sports- relatedinjuriesarediscussedinaseparatearticle.Thenextarticlereviewstheutil- ity of ultrasound in the evaluation of upper-extremity injuries and provides a comparison of the sensitivity and specificity of ultrasound as it compares to MRI. Finally, in response to the proliferation of low-field-strength magnets, particularly in the outpatient setting, a thorough literature review is provided comparingtheuseoflow-field-andhigh-field-strengthMRI.Thisarticlediscusses thebenefitsanddrawbacksoftheuseoflow-field-strengthmagnets. Iwouldliketothankthemanyauthorswhohavecontributedtheirtimeand expertise to make this issue a reality, and I would also like to thank Deb Del- lapenaofElsevierforhersupportinputtingthisissuetogether.Finally,Ihope that the readers find this issue helpful in furthering their understanding of the role of imaging as it pertains to the evaluation of sports-related injuries of the upper extremities. Timothy G. Sanders, MD National Musculoskeletal Imaging 1930 N. Commerce Parkway Suite #5 Weston, FL 33326, USA E-mail address: [email protected] ClinSportsMed25(2006)371–386 CLINICS IN SPORTS MEDICINE Shoulder Magnetic Resonance Imaging Lida Chaipat, MD, William E. Palmer, MD* MusculoskeletalImaging,MassachusettsGeneralHospital,55FruitStreet,YAW6030,Boston, MA02114,USA MRI provides excellent soft tissue contrast and allows for multiplanar imaginginanatomicplanes.BecauseoftheseadvantagesMRIhasbe- come the study of choice for imaging of shoulder pathology. Some structures, such as the rotator cuff, humeral head contour, and glenoid shape, areevaluatedwellwithconventionalMRI.Whenmoresensitiveevaluationof thelabrum,capsule,articularcartilage,andglenohumeralligamentsisrequired or when a partial-thickness rotator cuff tear is suspected, magnetic resonance (MR)arthrographywithintra-articularcontrastcanbeperformed.ForMRar- thrographycontrastisinjecteddirectlyintotheglenohumeraljoint.Thisarticle reviewstheappearancesofnormalanatomicstructuresinMRIoftheshoulder and disorders involving the rotator cuff and glenoid labrum. TECHNIQUE Imaging is performed with the patient in the supine position, arm at the side, and the shoulder slightly externally rotated [1]. A dedicated surface coil is placed close around the shoulder to optimize signal-to-noise ratio. Imaging time usually is 1 hour or less. Specific imaging protocols vary by institution. At our hospital the standard shoulder MRI protocol includes triplanar imaging. The following sequences are obtained: coronal oblique proton density (PD), coronal oblique T2 with fatsaturation,sagittalobliqueT2,sagittalobliqueT1,andaxialgradientecho. Axial (transverse) images are obtained perpendicular to the long axis of the body. From an axial image through the supraspinatus muscle, the coronal oblique sequences are prescribed parallel to the supraspinatus tendon. Sagittal oblique sequences then are oriented perpendicular to the coronal images. ForMRarthrographygadoliniumcontrastisinjecteddirectlyintothegleno- humeral joint under fluoroscopic guidance. The injected solution distends the capsule, separates the glenohumeral ligaments, and outlines intra-articular structures. *Corresponding author. E-mail address: [email protected] (W.E. Palmer). 0278-5919/06/$–seefrontmatter ª2006ElsevierInc.Allrightsreserved. doi:10.1016/j.csm.2006.03.002 sportsmed.theclinics.com 372 CHAIPAT &PALMER Attheauthors’hospitala22-or20-gauge3.5inspinalneedleisinsertedinto the glenohumeral joint and approximately 12 mL of a solution containing ga- dolinium, normal saline solution, iodinated contrast, and lidocaine is injected. (Solution is made by mixing 0.4 mL of gadopentate dimeglumine with 50 mL ofnormalsaline.Then10mLofthissolutionismixedwith5mLofiodinated contrastand5mLofpreservative-freelidocaine1%.)MRIisinitiatedwithin30 min before fluid in the joint can be resorbed [1]. TriplanarT1sequenceswithorwithoutfatsuppressionareobtainedtotake advantageofthecontrastprovidedbytheinjectedsolution.AT2-weightedse- quence is performed to evaluate the extra-articular structures for pathology, such as bursal surface partial-thickness rotator cuff tear, soft tissue mass, and bone marrow abnormality. NORMAL ANATOMY Theshoulderiscomposedoftwoarticulations:theglenohumeraljointandthe acromioclavicular (AC) joint [2]. Glenohumeral articulation is maintained by the joint capsule, glenohumeral ligaments, rotator cuff musculature, and la- brum. The labrum is a ring of fibrocartilage that is adherent to the glenoid rim.Theintactlabrumincreasestheconcavityofthebonyglenoidandthesu- periorlabrumservesastheanchorforthelongheadofthebicepstendon.The jointcapsulemayinsertvariablyontheperipheryofthelabrumorontheneck of the scapula [3]. Distally, the capsule inserts on the anatomic neck of the humerus. The glenohumeral ligamentsarecordlike thickeningsin the anterior and in- feriorjointcapsule.Theyincludethesuperior,middle,andinferiorglenohum- eral ligaments. The superior and middle glenohumeral ligaments attach to the anterior labrum. The inferior glenohumeral ligament has anterior and poste- rior bands that attach to the anterior inferior and posterior inferior labrum, respectively. The size of glenohumeral ligaments varies from patient to patient. Therotatorcuffiscomprisedoftendonsfromthesupraspinatus,infraspina- tus, teres minor, and subscapularis muscles. The supraspinatus, infraspinatus, and teres minor muscles arise from the posterior surface of the scapula, cross posteriortothehumeralhead,andinsertonthegreatertuberosity.Thesupra- spinatus insertion is most superior and the teres minor insertion most inferior on the tuberosity. The infraspinatus and teres minor tendons may appear fused, and a separate teres minor tendon may not be seen [4]. The subscapularis muscle arises from the anterior surface of the scapula, crosses anterior to the humeral head, and inserts on the lesser tuberosity. Thedeepfibersofthesubscapularistendonblendwiththetransversehumeral ligament across the bicipital groove and help maintain the normal position of the biceps tendon. The supraspinatus and teres minor muscles have single muscle bellies and tendons. The subscapularis and infraspinatus are made up of multiple muscle bellies and small tendons that coalesce to form common tendon insertions. SHOULDER MAGNETIC RESONANCE IMAGING 373 The rotator cuffintervalisthe space between the supraspinatusand subsca- pularis tendons along the anterior superior humeral head. Through this space run the intracapsular portion of the biceps tendon, coracohumeral ligament, and the superior glenohumeral ligament. On their course to their insertion sites on the humeral head the rotator cuff tendonspassunderthecoracoacromialarchandACjoint.Thecoracoacromial archismadeupofthecoracoidprocess,coracoacromialligamentandtheacro- mion.HypertrophicabnormalitiesoftheACjointorarchstructuresmaycause mechanicalimpingementontheunderlyingrotatorcuffmuscleortendon,par- ticularly the supraspinatus tendon. Interposed between the coracoacromial arch and supraspinatus tendon lies thesubacromial-subdeltoidbursa,whichnormallydoesnotcontainfluid.Fluid may be seen within the bursa when there is bursitis or when fluid leaks into it from the glenohumeral joint through a full-thickness cuff tear. Becauseofnormalopeningsinthejointcapsule,theglenohumeraljointisin communicationwiththesubscapularrecess(beneaththesubscapularismuscle) andthelongheadofthebicepstendonsheath.Whenajointeffusionispresent fluidoftenisseenintherecessortendon sheathanddoesnothave pathologic significance. The AC joint is a synovial joint surrounded by a fibrous capsule. This cap- sule is reinforced by fibers of the AC ligament. The coracoacromial and cora- coclavicularligamentsalsoareimportantinmaintainingnormalpositionofthe clavicle andacromialprocess.Tearingoftheseligamentsresultsinvarious de- grees of AC joint separation. NORMAL MRI APPEARANCE The fibrous structures in the shoulder are highly organized tissues with nor- mallylowsignalonallpulsesequences.Thesestructuresincludethejointcap- sule, glenohumeral ligaments, rotator cuff tendons, and the labrum. When there is disruption of the organization structure because of tendinopathy or tear, the signal intensity increases. Unfortunately, there are confounding fac- torsthatmaycauseartifactuallyincreasedsignalintensityintheabsenceofpa- thology. These are discussed in more depth elsewhere in this article. ArticularcartilageisintermediateinsignalintensityonT2andspinechose- quences.FluidappearsashighinsignalintensityonT2-weightedandshorttau inversionrecoveryimaging,whichisafluid-sensitivesequence.Normalmuscu- lature is intermediate in signal intensity on all pulse sequences. Increased T1 signal may be seen with fatty atrophy and increased T2 signal may be seen with edema. Normal cortical bone is dark on all pulse sequences because of the lack of mobileprotons,whereasthemarrowspaceusuallyisT1hyperintensebecause offatcontent.HeterogenousareasoflowT1signalmaybeseenwithredmar- rowconversion.Thisfindingiscommonparticularlyinpatientswhohavesys- temicdiseaseandincreasedredbloodcellturnover.Examplesincludesmokers and patients who have chronic obstructive pulmonary disease or renal 374 CHAIPAT &PALMER insufficiency.Themarrowofpatientswhohavehematologicdisorders,suchas multiple myeloma, may have an identical appearance. APPROACH TO ROTATOR CUFF EVALUATION One approach to evaluating the rotator cuff on MRI is to begin by reviewing thecoronalobliquePDimagestogetanoverviewoftheanatomy(Fig.1).Pro- ton density images are weighted intermediately between T1 and T2 signal. They provide superior signal-to-noise ratio and spatial resolution, albeit at the expense of soft tissue contrast. Large cuff tearsand distortionsof the anat- omy may be identified. Shoulder alignment may be evaluated also. Occasionallybecauseofimproperpositioningorpatientmotiontheshoulder isimagedininternalrotation.Thisimagingleadstooverlapofthesupraspina- tus and infraspinatus tendons on coronal oblique images [5]. The coronal ob- lique plane usually is the most useful plane for cuff evaluation because it parallelsthecourseofthemostcommonlytorncufftendons,thesupraspinatus and infraspinatus [6]. The subscapularis often is seen well in the coronal obli- queplanebutisevaluatedbestonaxialimages.Theteresminortendonisseen best in the sagittal oblique plane but rarely is torn. After a general overview of anatomy is obtained by reviewing the coronal obliquePD images, the T2-weightedimages with fatsuppressionmay beeval- uatedforabnormallyincreasedsignalinthetendonsorbones(Fig.2).Thecor- onal and sagittal oblique fast spin echo (FSE) T2 fat-suppressed images are highly sensitive for pathology; however, they are prone to artifactually in- creased signal and artifact unless the time to echo (TE) is greater than 30 msec. Once a potential abnormality is identified on one of the fat-suppressed sequences the finding should be confirmed on orthogonal images. Next, the axial images should be reviewed with particular attention to the subscapularis muscle. Finally, review of the sagittal T1 sequence is useful to evaluate for muscle atrophy and mechanical impingement of the rotator cuff by hypertrophic degenerative changes in the coracoacromial arch structures. Fig.1. Normalrotatorcufftendon.OnPDobliquecoronalimage,thesupraspinatustendon (arrow)showsuniformthicknessandsignalintensity.Thetendonisintactonthegreatertuber- ositywithoutmuscleatrophyorfattychange.H,humeralhead. SHOULDER MAGNETIC RESONANCE IMAGING 375 Fig.2. Severebonemarrowedemainpatientwithsuspectedrotatorcufftear.Fat-suppressed T2-weightedobliquecoronalimage(A)showshigh-signalbonemarrowedemainvolvingthe distalclavicle(arrow)andadjacentacromion.OnT1-weightedobliquesagittalimage(B),the distalclavicularmarrowedema(arrow)islowinsignalintensity.Thecufftendon(A)andcuff muscles(B)arenormal.G,glenoid;H,humeralhead. ROTATOR CUFF TEARS The spectrum of rotator cuff pathology rangesfrom tendinopathy and fraying topartial-orfull-thicknesstearing.Partial-thicknesstearsmaybeclassifiedfur- ther asoccurring onthe articularor bursal surface ofthe tendon. Athird type ofpartial-thicknesstearistheintrasubstancetear,whichoccurswithinthesub- stanceofthetendonwithoutextendingtothetendonsurface.Thistypeoftear is uncommon but is important to identify on MRI because the tendon surface may appear normal at arthroscopy and the tear may be missed. Tendinopathy is identified by increased signal within the tendon substance. The abnormally increased signal intensity remains below that of fluid on T2- weightedsequences[7].Tendinopathymaybepresentwithorwithouttendon thickening or thinning. [1]. Fraying is described when the normal linear dark signal at the margin of a tendon becomes indistinct, but no gap in the tendon fibers is identified. Themostspecificsignofacufftearisdiscontinuityofthecufffiberswithfluid signalintheinterveninggap(Figs.3and4).Unfortunately,thisgapmayonlybe seeninfairlylargetearsthatmeasuremorethanseveralmillimeters.Forsmaller tears the signal on T2-weighted imaging and secondary signs of cuff tearing shouldbeconsideredcarefully.Secondarysignsincludefluidinthesubacromial or subdeltoid bursa, tendon retraction, and muscular atrophy. The latter two signs may have implications for the type of surgical repair that is required and so should be evaluated routinely on every MRI obtained for rotator cuff evaluation. The appearance of the torn fibers also should be noted, because poor quality, diffusely torn tendon may not be suitable forrepair (Fig.5). ThemyotendinousjunctionnormallyislocatedbeneaththeACjoint.When itismoreproximalafull-thicknesstearshouldbesuspected.Incasesofpartial- thickness tearing only the torn fibers retract. Some partial- and full-thickness 376 CHAIPAT &PALMER Fig.3. Full-thicknessrotatorcufftearin54-year-oldpatient.Onfat-suppressedT2-weighted oblique coronal image (A), distal supraspinatus tendon (arrow) is disrupted by focal high- signalfluidandismildlyretractedfromthegreatertuberosity.Moreposteriorslice(B)shows intactinfraspinatustendon(arrow)andnormalattachmenttothegreatertuberosity.H,humeral head. cuff tears may have a delaminating component with the tear dissecting proxi- mallybetweenthedeepandsuperficialtendonfibers.Thetornfibersmaydem- onstratedifferentdegrees ofretraction(Fig. 6).The degree of retractionofthe cufffibersshouldbemeasuredbecausethishasadirectrelationshiptoprogno- sis. The anterior–posterior dimension of the tear also is important and is mea- sured best on the sagittal sequences. Anintrasubstancetearisdescribedwhenthereisfluidintensitysignalwithin thesubstanceofthetendonthatdoesnotextendtoeitherthearticularorbursal surface. In some chronic cuff tears and following rotator cuff repair, granulation tis- sueandfibrosismayfillthegap,resultinginisointenseordarksignal.Inthese Fig.4. Largepartial-thicknessbursalsurfacerotatorcufftearin56-year-oldpatient.OnT2- weightedobliquecoronalimage,distalsupraspinatustendonshowsfocalfluid(straightarrow) disruptingbursalfibersfromgreatertuberosity.Articularsurfacefibers(curvedarrow)remain intactongreatertuberosity.H,humeralhead.
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