EDUCATION EXHIBIT 1227

Disorders of the DistalBiceps Brachii Tendon1

Michael L. Chew, MBBS, BA ● Bruno M. Giuffre, MBBS, FRANZCR

Pathologic conditions of the distal biceps brachii tendon are of clinicalinterest, with partial and complete tears being the most common.However, the anatomy of the distal biceps brachii tendon makes imag-ing of the distal tendon somewhat difficult. An innovation in patientpositioning for magnetic resonance (MR) imaging of the distal bicepstendon was recently described in which the patient lies prone with thearm overhead, the elbow flexed to 90°, and the forearm supinated, sothat the thumb points superiorly. The acronym FABS (f lexed elbow,abducted shoulder, forearm supinated) has been used to describe thisposition. The FABS position creates tension in the tendon and mini-mizes its obliquity and rotation, resulting in a “true” longitudinal viewof the tendon. MR imaging and, to a lesser extent, ultrasonography areuseful in visualizing the distal tendon and in detecting other pathologicconditions in the cubital fossa. Partial tears are usually characterized byenlargement and abnormal contour of the tendon, along with abnor-mal intratendinous signal intensity. In complete tears, there is disconti-nuity and, if the bicipital aponeurosis is also disrupted, retraction. Im-aging with FABS positioning can complement conventional MR imag-ing, especially in the axial plane, in the assessment of the distal bicepstendon.©RSNA, 2005

Abbreviation: FABS � f lexed elbow, abducted shoulder, forearm supinated

RadioGraphics 2005; 25:1227–1237 ● Published online 10.1148/rg.255045160 ● Content Codes:

1From the Radiology Department, Royal North Shore Hospital, St Leonards, NSW 2065 Australia. Presented as an education exhibit at the 2003RSNA Annual Meeting. Received August 25, 2004; revision requested October 5 and received December 8; accepted December 9. All authors haveno financial relationships to disclose. Address correspondence to M.L.C. (e-mail: mchew@doh.health.nsw.gov.au).

©RSNA, 2005

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IntroductionThe biceps brachii muscle is one of the main flex-ors and supinators of the elbow, and disordersinvolving this muscle often give rise to significantmorbidity. Injury of the distal biceps tendon ismuch less common than injury occurring proxi-mally and can present imaging challenges arisingfrom the complex anatomic course of the tendon.In this article, we review the relevant anatomy ofthe distal biceps tendon and discuss optimal tech-niques for magnetic resonance (MR) imaging andultrasonography (US) of the tendon. We also dis-cuss and illustrate tears and other pathologic con-ditions (tendinopathy, enthesophyte formation,cubital bursitis) of the distal biceps tendon as wellas appropriate treatment options.

Normal AnatomyThe distal biceps tendon is typically a flat tendon,forming about 7 cm above the elbow joint (Fig 1)(2), with the flat surface of the tendon facing an-teriorly. As the tendon courses distally, it movesobliquely from anterior to posterior and from me-dial to lateral, twisting 90° so that the anteriorsurface faces laterally. The tendon expands at itsattachment to the radial tuberosity, spreadingover an area of 3 cm2 (3). It also attaches to thebicipital aponeurosis, which descends medially toinsert onto the subcutaneous border of the upperulna via the deep fascia of the forearm.

Imaging Techniques

Magnetic Resonance ImagingTraditionally, optimal MR imaging of the distalbiceps tendon is performed in the axial plane, of-ten with the patient’s arm extended. Longitudinalviews are difficult to obtain because of the obliquecourse of the tendon. A recently described inno-vation in patient positioning for MR imaging ofthe distal biceps tendon minimizes this difficulty(4). For this procedure, the patient lies pronewith the arm overhead, the elbow flexed to 90°,and the forearm supinated, so that the thumbpoints superiorly. The acronym FABS—f lexedelbow, abducted shoulder, forearm supinated—

has been used to describe this imaging technique(Figs 2, 3).

With FABS positioning, a longitudinal viewof the tendon, often in one section, is obtained,and partial volume averaging effects due to theoblique course of the tendon are minimized. Flex-ion of the elbow results in contraction of the bi-ceps muscle belly; thus, the tendon is taut. FABSimaging provides a detailed view of the distal bi-ceps tendon, including the difficult-to-assess re-gion near its insertion on the radial tuberosity(Fig 4), and is often helpful in differentiating par-tial from complete tears. The “center-of-the-mag-net” position of the elbow makes fat-suppressedimaging optimal, improving visualization of smallamounts of fluid (Fig 5). The FABS view is ob-tained in addition to conventional views specifi-cally to evaluate disease of the distal bicepsbrachii tendon.

Figure 1. Drawing (cubital fossa dissection) illus-trates the biceps tendon and adjacent structures. (Re-printed, with permission, from reference 1.)

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Figure 2. Photograph illustrates the FABS position.(Reprinted, with permission, from reference 4.)

Figure 3. Localization image shows a FABS viewwith planned sections oriented perpendicular to theradial shaft. (Reprinted, with permission, from refer-ence 4.)

Figure 4. Fast spin-echo proton-density–weightedMR image (repetition time msec/echo time msec �3000/34) obtained with the patient in the FABS posi-tion shows a normal distal biceps tendon (curved ar-row), the musculotendinous junction (straight arrow),and the radial tuberosity (arrowhead). (Reprinted, withpermission, from reference 4.)

Figure 5. Fat-suppressed fast spin-echo proton-den-sity–weighted MR image (3000/45) demonstrates aminor partial tear of the distal biceps tendon (arrow)with a trace of peritendinous fluid (arrowhead). (Re-printed, with permission, from reference 4.)

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UltrasonographyUS has many advantages: It is less expensive andmore rapidly performed than MR imaging andcan be performed even when there are relativecontraindications for MR imaging. US also hasthe advantages of allowing (a) easy comparisonwith the contralateral side and (b) the use of dy-namic imaging. However, demonstration of theentire tendon at US is less reliable, particularlydemonstration of the distal tendon at its insertionsite. Other disadvantages of US are that it is lessreproducible, more operator dependent, and (be-cause it is a more focused study) less likely to helpdetect other disease at the elbow than is MR im-aging.

US is performed from the volar aspect of theelbow, where the tendon and free edge of the bi-cipital aponeurosis are often palpable in the ante-rior cubital fossa. Real-time scanning allows easyoptimization of imaging in the longitudinal andperpendicular axial planes. Imaging is best per-formed with the forearm in supination, since thisbrings the radial tuberosity into view on the me-dial aspect of the radius (Figs 6–8). Dynamicimaging (with slight supination-pronation or flex-ion-extension) can be performed and is especiallyuseful in differentiating complete from partialtears.

Occasionally, the inserting distal tendon can bedemonstrated from the dorsal aspect of the upperforearm. Pronation and supination are used toidentify the tendon as it inserts on the radial tu-berosity: When the arm is pronated, the tuberos-ity and the inserting distal tendon rotate into viewon scans that are obtained from the dorsal aspect(Figs 9, 10) (5).

Figures 6–8. (6) Photograph illustrates the scan-ning technique for obtaining a longitudinal US imagefrom the volar surface of the left arm. (7) Longitudi-nal (a) and transverse (b) US images show a normaldistal biceps tendon (arrows). (8) Transverse US im-age obtained from the volar aspect of the arm shows anormal distal biceps tendon. Note that the tendon isvisible to its insertion site on the radial tuberosity (ar-rows).

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Tears of theDistal Biceps Tendon

Complete rupture of the distal biceps tendon isoften an avulsion from the radial attachment andclinically evident. However, differentiation ofcomplete from partial tears is sometimes difficultclinically, particularly if the bicipital aponeurosisremains intact. Precise delineation of the extent ofthe abnormality can aid in the management ofcomplete tears without retraction or of partialtears (6).

Complete tears are usually associated with asingle traumatic event, often involving a fairlylarge force (40 kg or more) acting against resis-tance from an elbow flexed to 90° (7). Partialtears are often precipitated by minor trauma ornot even associated with a traumatic event (8);the latter situation suggests preexisting degenera-tion in the tendon.

Most tears occur 1–2 cm above the radial tu-berosity, where there is relative hypovascularityand a histologic structural transition point (3,7,8). Degeneration secondary to hypoxic tendi-nopathy occurs in this region. With increasingage, there is a progressive decrease in perfusion,elasticity, and hydration, and the processes of ten-don repair slow further. Mechanical impingementduring pronation (9) and irritation by an osteo-phyte-enthesophyte at the radial tuberosity (acommon finding) may also lead to tears of thedistal biceps tendon (7,9).

In complete rupture of the distal biceps ten-don, there is discontinuity with or without re-traction. The longitudinal view of the tendon

Figures 9, 10. (9) Photograph illustrates the scanningtechnique for obtaining a transverse US image of the pro-nated arm from the dorsal aspect. (Reprinted, with permis-sion, from reference 5.) (10) US images obtained from thedorsal aspect with the arm in supination (a) and pronation (b)show the distal insertion site of the biceps tendon (arrows inb). Note that in supination the radial tuberosity is not seen,whereas in pronation it lies close to the probe. (Reprinted,with permission, from reference 5.)

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Figures 11, 12. (11) FABSfat-suppressed (a) and axial (b)fast spin-echo proton-density–weighted MR images show acomplete tear of the distal bi-ceps tendon. Note the thick-ened proximal part of the ten-don (long arrow in a) and thediscontinuity starting 2 cmproximal to the radial tuberos-ity (short arrow in a). Notealso the nonvisualizationof the tendon close to its in-sertion site (arrow in b).(12) FABS (a) and axial (b)fast spin-echo proton-density–weighted MR images demon-strate a complete tear of thedistal biceps tendon with anintact bicipital aponeurosis(arrowhead in b). Note thatthe aponeurosis extends froman enlarged proximal tendon(arrow).

Figure 13. FABS (a) and sagittal (b, c) fast spin-echo proton-density–weighted MR images show a minor partialtear of the distal biceps tendon. Arrow in a, black arrow in b, and arrow in c indicate the tendon; white arrow in bindicates the radial tuberosity. Note the partial volume averaging effect in b and c, which makes confident diagnosisdifficult on sagittal views. However, the intratendinous signal intensity and peritendinous fluid seen on the FABSview tend to help confirm the diagnosis of a minor partial tear.

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acquired with FABS imaging often best demon-strates the discontinuity (Fig 11). The proximaltendon is enlarged and demonstrates abnormalsignal intensity. If the bicipital aponeurosis is in-tact, there may be no retraction, and at clinicalexamination the patient may even appear to retainsome flexion and supination capability. The axialview is best for appreciating an intact bicipitalaponeurosis (Fig 12).

US, particularly dynamic imaging, can be usedto confirm continuity of the tendon or the abnor-mal movement of a disconnected proximal ten-don, but this region is not always well demon-strated. In a well-developed, muscular forearm in

which the tendon is deeper, or in the acute settingin which hemorrhage may obscure detail, thecourse of the distal tendon can be difficult to visu-alize.

In partial tears, findings include a change (usu-ally an increase) in caliber and abnormal contourof the tendon. Abnormal intratendinous signalintensity is seen at MR imaging. The US equiva-lent, reduced echogenicity, is often more difficultto confidently assess. Peritendinous fluid (edema,bursitis, or hemorrhage) may also be visible (Figs13–15) (10–12).

Figure 14. Axial (a) and FABSfat-suppressed (b) fast spin-echoproton-density–weighted MR im-ages show a minor partial tear of thedistal biceps tendon close to its in-sertion site on the radial tuberosity.Note the abnormal intratendinoussignal intensity of the tear (arrow).

Figure 15. (a, b)Longitudinal (a) andtransverse (b) US im-ages show a moderatepartial tear of the distalbiceps tendon (arrowsin a, arrowheads in b).(c, d) FABS (c) andaxial (d) fast spin-echo proton-density–weighted MR imagesshow the partial tear.Note the tendon thick-ening (long arrow) andthe abnormal intraten-dinous signal intensity(short arrow).

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Other RelatedPathologic Conditions

Enthesophyte formation at the radial tuberosity iscommon and is thought to be a contributing fac-tor in some tears of the distal biceps tendon (Figs16, 17) (13).

The bicipitoradial bursa lies between the distalbiceps tendon and the anterior part of the radialtuberosity (Fig 18). As the forearm moves fromsupination to pronation, the radial tuberosity ro-tates from a medial to a posterior position. Thebiceps tendon curls around the radius, compress-ing the interposed bursa. Medial to the bicipitora-dial bursa and lying in contact with the interosse-ous membrane is the interosseous bursa. Whennormal, neither bursa is visible at US or MR im-

aging. Rarely, enlargement of the bursae maycause compression of the median or posterior in-terosseous nerves (14).

Cubital bursitis is diagnosed by identifying awell-defined cystic lesion in the vicinity of eitherthe bicipitoradial or the interosseous bursa. Thiscondition may result from repeated mechanicaltrauma (15), inflammatory arthropathies, infec-tion, chemical synovitis, bone proliferation, orsynovial chondromatosis (14). The most commoncause of cubital bursitis is thought to be repeatedmechanical trauma, which is often associated withpartial tears of the tendon (Fig 19).

TreatmentThe treatment of choice for complete rupture ofthe distal biceps tendon is early surgical repair(7,16–19). The techniques used in this treatmentvary. Some surgeons use an anterior approachonly, with a suture anchor to reattach the tendonto the radial tuberosity (Fig 20).

Figure 16. Diagrams illus-trate cross-sectional views of aspur at the radial tuberositycausing tendon degeneration.In pronation (A), the sharpmargin of the spur impingeson the tendon. In supination (B),the tendon is no longer in con-tact with the spur. (Reprinted,with permission, from refer-ence 13.)

Figure 17. (a) FABS MRimage obtained in a youngvolunteer shows a normal dis-tal biceps tendon. (b) MRimage obtained in an olderasymptomatic volunteershows a small spur at the in-sertion site of the tendon (ar-row).

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Figure 18. Drawings illustrate the relationship of the bursae to the nerves (a) and changes that occur as the fore-arm moves from supination to pronation (b). BRB � bicipitoradial bursa, BT � biceps tendon, R � radius, rt �radial tuberosity, U � ulna. (Reprinted, with permission, from reference 2.)

Figure 19. Axial (a) and FABS fat-suppressed (b) fast spin-echo proton-density–weightedMR images show bursitis associated with a partial tendon tear. Note the fluid collection inthe bicipitoradial bursa (arrowhead), with abnormal intratendinous signal intensity in thepartial tear close to the insertion site of the tendon (curved arrow in a, arrow in b). Straightsolid arrow in a indicates the median nerve, open arrow in a indicates the posterior interosse-ous nerve.

Figure 20. Radiograph shows a previ-ously repaired biceps tendon with su-ture anchors in place. Note the minorheterotopic bone formation (arrow).

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Many surgeons use a two-incision technique, alimited anterior approach that allows the proxi-mal stump to be fed down and reattached into asmall excavation on the radial tuberosity. Thetuberosity is reached by using a muscle-splittingapproach from the dorsal aspect of the forearm,carefully avoiding the posterior interosseous nerve(Fig 21) (7).

The repaired tendon is abnormally enlargedand demonstrates mixed signal intensity (Fig 22).Complications include ectopic bone formation(Fig 20), occasionally with radioulnar synostosisand posterior interosseous nerve palsy.

Partial tears are often treated conservativelywith local or systemic analgesics. Imaging-guidedinjection of a steroid or local anesthetic can pro-vide symptomatic relief (Fig 23). If symptomspersist, complete removal of the remaining fibers

(thereby converting the tear from a partial to acomplete tear), debridement of the distal tendon,and reattachment as performed for a completetear are sometimes necessary.

Figure 21. Drawing illustrates the two-incision tech-nique for treatment of complete rupture of the distalbiceps tendon. The detached tendon is milked outthrough a transverse incision of the antecubital space.The tendon is then trimmed and an incision made dor-solaterally to allow exposure of the radial tuberosity,which is then excavated. Finally, the tendon is broughtthrough the previous tract and reinserted onto the tuber-osity. (Reprinted, with permission, from reference 7.)

Figure 22. FABS fast spin-echo proton-den-sity–weighted MR image shows a surgically re-paired tendon. Note the bone defect at the radialtuberosity (arrow) and the diffuse enlargementand abnormal signal intensity of the successfullyrepaired tendon (arrowheads).

Figure 23. Computed tomographic scan showsimaging-guided injection of a steroid and localanesthetic around the biceps tendon (arrow).

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ConclusionsAlthough less common than disease at the shoul-der insertion site of the long head of the bicepsbrachii tendon, pathologic conditions at the distalbiceps brachii tendon are of clinical interest. USand MR imaging can provide useful informationregarding these clinical problems. Acquisition of aFABS view can complement MR imaging in theassessment of this tendon.

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3. Koch S, Tillmann B. The distal tendon of the bi-ceps brachii: structure and clinical correlations.Anat Anz 1995;177:467–474.

4. Giuffre BM, Moss MJ. Optimal positioning forMRI of the distal biceps brachii tendon: flexedabducted supinated view. AJR Am J Roentgenol2004;182:944–946.

5. Giuffre BM, Lisle D. Tear of the distal bicepsbrachii tendon: a new method of ultrasound evalu-ation. Australas Radiol (in press).

6. Falchook FS, Zlatkin MB, Erbacher GE, MoultonJS, Bisset GS, Murphy BJ. Rupture of the distalbiceps tendon: evaluation with MR imaging. Radi-ology 1994;190:659–663.

7. Morrey BF. Injury of the flexors of the elbow: bi-ceps in tendon injury. In: Lampert R, ed. The el-bow and its disorders. 3rd ed. Philadelphia, Pa:Saunders, 2000; 468–478.

8. Vardakas DG, Musgrave DS, Varitimidis SE,Goebel F, Sotereanos DG. Partial rupture of thedistal biceps tendon. J Shoulder Elbow Surg 2001;10:377–379.

9. Seiler JG, Parker LM, Chamberland PD, Sher-bourne GM, Carpenter WA. The distal biceps ten-don: two potential mechanisms involved in its rup-ture—arterial supply and mechanical impinge-ment. J Shoulder Elbow Surg 1995;4:149–156.

10. Miller TT, Adler RS. Sonography of tears of thedistal biceps tendon. AJR Am J Roentgenol 2000;175:1081–1086.

11. Durr HR, Stabler A, Pfahler M, Matzko M, RefiorHJ. Partial ruptures of the distal biceps tendon.Clin Orthop 2000;374:195–200.

12. Williams BD, Schweitzer ME, Weishaupt D, et al.Partial tears of the distal biceps tendon: MR ap-pearance and associated clinical findings. SkeletalRadiol 2001;30:560–564.

13. Davis WM, Yassine Z. An etiological factor in tearof the distal tendon of the biceps brachii: a reportof two cases. J Bone Joint Surg Am 1956;38-A:1365–1368.

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15. Karanjia ND, Stiles PJ. Cubital bursitis. J BoneJoint Surg Br 1988;70:832–833.

16. Agins HJ, Chess JL, Hoekstra DV, Teitge RA.Rupture of the distal insertion of the biceps brachiitendon. Clin Orthop 1988;234:34–38.

17. Baker BE, Bierwagen D. Rupture of the distal ten-don of the biceps brachii: operative versus non-operative treatment. J Bone Joint Surg Am 1985;67:414–417.

18. Norman WH. Repair of avulsion of insertion ofbiceps brachii tendon. Clin Orthop 1985;193:189–194.

19. Louis DS, Hankin FM, Eckenrode JF, Smith PA,Wojtys EM. Distal biceps brachii tendon avulsion:a simplified method of operative repair. Am JSports Med 1986;14:234–236.

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