The Proximal Biceps The Proximal Biceps TendonTendonAnatomy and BiomechanicsAnatomy and Biomechanics

Geoff Wilkin, PGY-2Geoff Wilkin, PGY-2Upper Extremity RoundsUpper Extremity Rounds

June 24, 2011June 24, 2011

AnatomyAnatomy

Biceps BrachiiBiceps Brachii

Two-heads - Short & LongTwo-heads - Short & Long

Innervation: Innervation: Musculocutaneous nerveMusculocutaneous nerve

Major forearm supinator and Major forearm supinator and elbow flexor elbow flexor

Two joint muscle (shoulder & Two joint muscle (shoulder & elbow)elbow)

OriginOrigin

Supraglenoid tubercle ~40-60%Supraglenoid tubercle ~40-60%

Glenoid Labrum ~50%Glenoid Labrum ~50%

Variable Fibre location/orientationVariable Fibre location/orientation

22%22% 33%33% 37%37% 8%8%

BB

GGLL

Intra-articular portionIntra-articular portion

Glides up to 18mmGlides up to 18mm

Relatively avascular zone (more later)Relatively avascular zone (more later)

Rotator IntervalRotator IntervalBordersBorders

Coracoid ProcessCoracoid ProcessSupraspinatus tendonSupraspinatus tendonSubscapularis tendonSubscapularis tendonTransverse lig. humerusTransverse lig. humerus

ContentsContents

LHB tendonLHB tendonCoracohumeral lig.Coracohumeral lig.Superior Glenohumeral lig.Superior Glenohumeral lig.

Biceps Reflection PulleyBiceps Reflection PulleyEntrance to bicipital grooveEntrance to bicipital groove

Confluence of CHL, SGHL & Subscap.Confluence of CHL, SGHL & Subscap.

30° turn of LHB tendon30° turn of LHB tendon

Bicipital GrooveBicipital Groove

Opening angle ~101-120°Opening angle ~101-120°

Large variability (18-172°)Large variability (18-172°)

Very acute and very flat Very acute and very flat angles assoc. with biceps angles assoc. with biceps pathologypathology

Transverse humeral ligamentTransverse humeral ligament

Anchors tendon in grooveAnchors tendon in groove

Blood SupplyBlood Supply

Two Distinct Patterns:Two Distinct Patterns:

2-source2-source

MusculotendinousMusculotendinous

(Brachial a.)(Brachial a.)

OseotendinousOseotendinous

(Thoracoacromial a.)(Thoracoacromial a.)

Blood SupplyBlood Supply

Two Distinct Patterns:Two Distinct Patterns:

3-source3-source

MusculotendinousMusculotendinous

OseotendinousOseotendinous

MesotenonMesotenon

(Ant. Humeral (Ant. Humeral circumflex a.)circumflex a.)

Watershed AreasWatershed Areas

In both patterns:In both patterns:

~1.2 - 3cm from origin~1.2 - 3cm from origin

If mesotendon present:If mesotendon present:

~9 - 10cm from origin~9 - 10cm from origin

Common sites of ruptureCommon sites of rupture

HistologyHistologyDistal:Distal:

““Traction” tendon - parallel collagen, Traction” tendon - parallel collagen, tenocytestenocytes

Proximal:Proximal:

Capsular surface - “Traction” tendonCapsular surface - “Traction” tendon

Humeral surface - “Gliding” tendonHumeral surface - “Gliding” tendon

Irregular/interwoven collagen, Tenocytes Irregular/interwoven collagen, Tenocytes more similar to chondrocytesmore similar to chondrocytes

AvascularAvascular

Biomechanics & Biomechanics & FunctionFunction

““The proximal biceps has been likened to the The proximal biceps has been likened to the uninvited guest who never leaves the party.”uninvited guest who never leaves the party.”

““Pain generator”Pain generator”

““Vestigial structure”Vestigial structure”

““Vital structure”Vital structure”

Glenohumeral StabilityGlenohumeral StabilityA secondary stabilizerA secondary stabilizer

Pagnani et al., 1996Pagnani et al., 1996

55N load reduced translation in all directions55N load reduced translation in all directions

Glenohumeral StabilityGlenohumeral StabilityA secondary stabilizer in cuff A secondary stabilizer in cuff pathologypathology

Su et al., Su et al., (Arthroscopy, 2010)(Arthroscopy, 2010)

Simulated cuff tearsSimulated cuff tears

55N LHB force decreased 55N LHB force decreased superior & anterosuperior superior & anterosuperior translationtranslation

May be cause of biceps May be cause of biceps hypertrophy & “hour-glass” hypertrophy & “hour-glass” findingfinding

Glenohumeral StabilityGlenohumeral StabilityStabilizer during elbow motionStabilizer during elbow motion

Kumar et al. Kumar et al. (CORR 1989)(CORR 1989)

Simulated elbow flexion & supinationSimulated elbow flexion & supination

Upward migration of humeral head with LHB Upward migration of humeral head with LHB cut, none when intactcut, none when intact

Glenohumeral StabilityGlenohumeral StabilityDynamic stabilizer throughout ROMDynamic stabilizer throughout ROM

A “Centring” effect at extremes of rangeA “Centring” effect at extremes of range

Youm et al., 2009 Youm et al., 2009 (J Shoulder Elbow Surg)(J Shoulder Elbow Surg)

EMG StudiesEMG Studies

Physiologic force in LHB not knownPhysiologic force in LHB not known

Estimates made based on cross-sectional Estimates made based on cross-sectional areaarea

How active really is the LHB with shoulder How active really is the LHB with shoulder motion?motion?

EMG StudiesEMG StudiesLevy et al, 2001 Levy et al, 2001 (J Shoulder Elbow Surg)(J Shoulder Elbow Surg)

Elbow locked in braceElbow locked in brace

Almost zero EMG activity with shoulder motionAlmost zero EMG activity with shoulder motion

In vivo StudiesIn vivo Studies

Warner & McMahon, Warner & McMahon, (JBJS-Am 1995)(JBJS-Am 1995)

Superior migration of humeral head on Xray Superior migration of humeral head on Xray in proximal biceps rupturein proximal biceps rupture

Kido et al., Kido et al.,

Humeral head depression on Xray when Humeral head depression on Xray when biceps contracted assoc. with rotator cuff biceps contracted assoc. with rotator cuff teartear

ConclusionsConclusions

Avascular area vulnerable to Avascular area vulnerable to degeneration/rupturedegeneration/rupture

Static stabilizerStatic stabilizer

Probably humeral head depressorProbably humeral head depressor

Probably a dynamic “centring” forceProbably a dynamic “centring” force

Maybe only with concomitant elbow motionMaybe only with concomitant elbow motion