166 Bulletin ul' the NYU Hospilal for Joint Diseases Vt)kinie 64. Numbers 3 & 4. 2006

Elbow InstabilityDerrick G. Hickey, M.D., and Mark I. Loebenberg, M.D.

Avariety ol" conditions can manifest as elbow instabil-ity, making diagnosis and irealment problematic lorthe clinician. However, important progress has beenmade in the understanding of the un.stable elbow that impactstrealnient. Crucial has been an increased understanding offunctional anatomy ofthe elbow and its relationship to thebiomechanics of elbow stability. This article reviews thefunctional anatomy of ihe elbow, with an emphasis on thebiomechanics of instability as well as emerging concepts inthe treatment of Ihe most common entities.

AnatomyBony ArticulationThe elbow is a modilied hinged joint composed of three dis-tinct articulations: the radiocapitellar joint, the ulnohumeraljoint, and the proximal radioulnar it)int. The configurationof the joints provide for much of the stability of the elbowagainst varus and valgus stress at the extremes of extensionand flexion. The ulnohuincral articulation provides 55% ofthe vai'us stability in extension and up to 15'^/( in 90"" of flex-ion; valgus stability is equally divided between the medialcollateral ligament (MCL). tbe anterior capsule, and the bonyarticulation, in both full extension and 90" of llexion.'

Ligamentous StructuresMedial Collateral LigamentThe MCL is composed of an anterior bundle, posteritirbundle, and transverse ligament (Fig. 1). The anterior bundleis the most discrete and functionally important portion of

Derrick G. Hickey, M.D.. was a Chief Resident in the NYU Hospilalfor Joint Diseases Department of Oilhopacdic Surgery. New York,New York. Mark I. Loebenberg, M.D.. is Senior Consultant Sur-geon, Department of Orthopaedic Surgery. Assaf Harofc MedicalCenter, Tel Aviv University School of Medicine, Tel Aviv, Israel.Correspondence: Derrick G. Hickey. M.D., Port City Orthopaedics.Suite G, 5305 Wrightsville Avenue, Wilmington. North Carolina28403.

the MCL, contributing 557< to llYk to valgus stability. Thebundle originates on the anteroinferior aspect ol'the medialepicondyle and inserts onto the medial aspect of the coro-noid process.- The anterior bundle is further subdivided i ntodistinct anterior and posterior bands that perform reciprocalfunctions. Sequential tightening occurs within the fibers ofthe anterior bundle, progressing from anterior to posterior asthe elbow Hexes.' The anterior band is the primary restraintlo valgus stress up to 90" of flexion; the posterior band is asecondary restraint at lesser degrees of llexion. but becomesmore important between 60" and full tlexion. '"* The posteriorbundle is thinner and weaker than the anterior bundle andprovides secondary valgus stability at flexion beyond 90".The transverse ligamenl contributes liule to elbow stability,as it does not cross the elbow joint.

Lateral Collateral LigamentThe lateral collateral ligament (LCL) complex consists oftheannular ligamenl. tbe radial collateral ligament, tbe lateralulnar collateral ligament (LUCL). and a variably presentaccessory LCL. The radial collateral ligament originatesfrom the lateral epicondyle and terminates indistinguish-abiy in the annular ligament, which stabilizes the proximalradioulnar joint (Fig. 2).^ Tbe LUCL originates from thelateral epicondyle. blending witb fibers from the annularligament but arching superlicial and distal to it. This liga-ment is the primary restraint to varus stress and is deficientin posterolateral rotatory instability of the joint.''

Biomechanics of Elbow InstabilityO"Driscoll and colleagues described a mechanism for elbowsubluxation and dislocation, in which increasing HgamcEi-tous and capsular damage prt)gressed from lateral to medialacross the i()int {Fig. 3).' In stage I, the LUCL is disrupted,resulting in posterolateral lotalory subluxation of the elbow.In stage 2, additional Injury occurs anteriorly and posteriorly,resulting in an incomplete posterolateral dislocation ofthe

Bulletin of the NYU Hospital lor Joint Diseases Volume 64. Numbers 3 & 4, 2006 167

Posterior Bundle

Transverse Ligament

Figure 1 Medial collateral ligament. (Reprinted from Morrcy BF.Anatomy ofthe elbow joint. In: Money BF (ed): The Elhow andIts Disorders (3rd ed). Philadelphia: Saundt'rs. 2000. p. 23. Per-mission of Mayo Foundation for Medical Education and Research.All rights reserved.)

Annular LigamentAccessory Collateral Ligament

RadialCollateral Ligament

Lateral Ulnar Collateral Ligament

Figure 2 Radial collateral ligamcnl complex. (Reprinted fromMorrey BK: Anatomy ol'thc elbow joint. ///. Morrey BF (ed): TheElbow and Us Disorders (3rd ed). Philadelphia: Saunders. 2000,p. 24. Permission of Mayo Foundation tor Medieal Education andResearch. All rights reserved.)

elbow, radiographieally represenled by a perched disloca-tion. Stage 3 is divided further into three levels of severity.Stage 3 A involves disruption ofthe medial side of the elbowjoint, leaving only the anterior band of the MCL inlact. Theelbow pivots on the intact anterior band ofthe MCL. whiehallows eomplete dislocation by a posterolateral rotatorymeehanism. The intact anterior MCL provides stability ifthe forearm is kept in pronation to prevent poslerolaleralrotatory subluxation during valgus stress testing. In stage3B. the entire MCL complex is disrupted; valgus, varus, androtatory instability are all present. In stage 3C. the entiremuscular origins ofthe flexor and extensor origins have beenstripped off the distal humerus. The instability beeomes sosevere that the elbow can dislocate, even if immobili/.ed ina cast at 90 of tlexion.'-'*

Acute Elbow DislocationAcute elbow dislocation is a relatively common type ofelbow instability. Dislocation constitutes 10% to 257c of

all injuries to the elbow'* and has an annual incidence of sixcases per 100.000. second in frcL|uency only to shoulderdislocation.'" The mechanism of elbow dislocation is mostcommonly a fall onto an outstretched hand, resulting inan axial compressive and valgus load on the supinated ex-tremity. Although radiographs reveal periarticular fracturesin \2% to 607c of cases, operative exploration documentsdemonstrate osteochondral injuries that went undetected inprior radiographs in nearly 100% of acute dislocations.''

Evaluation and Nonsurgical ManagementA thorough neurovascular examination is required beforeand after reduction of the joint. The wrist and shouldershould be examined for concomitant upper extremity in-jury. The distal radioulnar joint and interosseous membraneshould also be evaluated for tenderness to exclude an EssexLopresti injury variant.

Following reduction, instability is assessed by gentlymoving the elbow through a range of motion. Most elbows

Dislocated

Figure 3 A. Hori circle ofsof\ tissue injury. B. Spectrum of elbow instability. (Reprinted from O'DHscoll SW. Jupiter JB. KingGJW. etal: The unstable elbow. In: Sim FH (ed): AAOS In.striivtiomil Course Lectures. Vol. 50. Rosemont. IL: Ameriean Academy of OrthopaedieSurgeons, 2001, p. 90. Reprinted by pemiission of Mayo Foundation for Medical Education and Research. All rights reserved.)

168 Bulletin ol' Ihe NYU Hospilal for Joinl Diseases Volume 64. Numbers 3 & 4. 2006

are unstable to valgus stress. Competency of Ihe medialstructures to valgus stress is tested in pronation to preventposterolateral rotatory instability. It is essential to evaluatethe tendency for redi.slocation to occur in extension, whichsignifies a potentially unstable joint. Postreduction radio-graphs should then be evaluated to document concentricreduction of the elbow joint in two planes. Widening ofthe joint .space may indicate an enlrapped osteochondralIVagment(s) or posterolateral rotatory instability.

If the reduction is concentric and the joint is stable, thejoint is splinted within its arc of stability. Reevaluatit)nshould be performed in live to seven days. If the elbowsubluxalcs or dislocates in extension or is noncongruent onradiographs, the forearm should be pronated and stabilityreassessed. If stability is restored with pronation, a hingedbrace is applied with the elbov*/ in full pronation. An exten-sion block of 30" is sometimes necessary. Extension blocksshould be gradually eased so that, by three weeks, the elbowallows full motion.

Prospective studies have shown no advantage of earlycollateral ligament repair over early motion following simpleelbow dislocation. Josefsson and associates'- reported thatnt)nsurgically treated elbows demonstrated less flexion con-tracture. averaging 10" at two and five years, than surgicallytreated elbows, in which flexion contracture averaged morethan 15" at two and five years. Surgery is indicated when theelbow requires flexion beyond 50*^ to 60 to remain reducedand for dislocations associated with unstable fractures.

Posterolateral Rotatory InstabilityO' Driscoll and coworkers'' have identified dcliciency of theLUCL complex as the essential pathologic lesion leading toposterolateral rotatory instability. This lesion most common-ly occurs as a consequence of acute dislocation. Althoughmost studies have indicated that both the MCL and LCLcomplex are acutely disrupted with an elbow dislocation,"the residual insufficiency most commonly involves the LCLcomplex.'Deficiency ofthe LCL complex may also occur asan iatrogenic complication of a tennis elbow relea.se.

The diagnosis of elbow instability is made on (he basis

of a history of elbow dislocation, followed by the patientcomplaining of painful clicking, catching, or snapping as theelbow goes from flexion to extension; pain may only pres-ent on the lateral aspect of tbe elbow. Symptoms typicallyoccur during the extcnsit)n pt)rtion ol' the motit)n arc withthe forearm in supination. Symptoms that occur with flexionand pronation are. therefore, likely related to reducti(n ofthe subluxation. Pushing down on the arm rest of a chairwhen rising from a seated position or performing push-upexercises places the elbow in an at-risk position and may beused as provocative tests.

The most sensitive test reported is tbe lateral pivot shiftapprehension test, performed with the patient supine.''Withthe forearm fully supinated. the examiner grasps the wristor forearm and slowly extends the elbow, simultaneouslyapplying valgus and supination movements and an axialcompressive force. This maneuver produces radiohumeralsubluxation. Additional flexion results in a sudden reductionas the radius and ulna snap into place on the humerus (Fig.4).

Stress radiographs may be helpful to confirm the actualdiagnosis, because plain radiographs typically appear normalin posterolateral rotatoi'y instability. Fluoroscopic evaluationperformed during a pivot shift test is preferable, but gravity-assisted stress radiographs also frequently demonstrate theinstability. Magnetic resonance imaging (MR!) is usually notrequired to make the diagnosis of posterolateral instabilitybut may be helpful.'"'

TreatmentAn incompetent LUCL will not restabilize over time withoutintervention.^ For the less active patient who is willing tomodify his activities, nonsurgical management may be ap-propriate. The majority of patients with recurrent instabilitywho experience significant interference in daily activitiesrequire surgical reconstruction.

Reconstruction of the LUCL using a free tendon graftis recommended for patients with symptomatic recurrentlateral instability.''^ The Kocher interval is entered and theanconeus muscle is reflected, allowing identification ofthe

Axial compression Valgus

Figure 4 PostcroUitera! rotalory inslabiUty test. (Reprinted from Mon'ey BT: Aeute and chronic instability of ihc elbow. J Am AcadOrthop Surg 1996:4(3): 124, Copyright'

Btillcunorthe NYU Hospital for Joint Diseases - Volume 64. Ntinibcrs 3 & 4. 2006 169

crista supinatoris. Two holes are placed 7 mm to tO iiiniuparl at ihc base of ihe crista supinaloris. and a sLilure i.spassed through this tunnel to mark the i.sometric point onthe humerus. Bone tunnels are made in the humerus at thisisometric point, it is important that the graft be placed atthe isometric point of the etbow or the reconstruction willL-onslrain normal motion. A 3-ply passage ofthe graft acrossthe joint is preferred.'^

Postoperative care consists of immobilization in pronationfor 2 weeks, followed by a hinged splint with a 30^ exten-sion block for an additional 4 to 6 weeks. A mitd flexioncontracture is acceptable, as the most vulnerable position ofinstability is full extension. Thereafter, the patient is alloweduse ofthe extremity, but varus .stress should be avoided torfour to six months. Athtclic activities may resume betweensix to eight months.'''

ResultsNestor and colleagues''' reported on the results of LUCLreconstruction at the Mayo Clinic. If no other injuries werepresent, approximately 90% of elbows were rendered stable.If there were significant degenerative changes, the likelihoodof a satisfactory result decreased to 5{V/c although stabilitywas achieved.

Medial InstabilityAcute MCL ruptures that occur with elbow dislocationgenerally heal and rarely result in valgus instability, withthe exception of athletes."' Injury to the MCL. initiallyrecognized in javelin throwers, has been reported to occurwith increasing tVequency in other types of overhead athletes.Micro tears of the MCL occur once the valgus forces, gener-ated during the cocking and acceleration phases of throwing,exceed the intrinsic strength ofthe MCI-.'' Attenuation andeven rupture of the MCL can result.

Patients with an acute MCL injury after throwing usuallyexperience a "pop'" and a sudden onset of pain, with swellinglocalized to the medial aspect ot'the elbow."*'''Patients withchronic injury typically describe a gradual onset of localized

media! elbow pain during the late-cocking and accelerationphases of throwing (Fig. 5). Athletes may describe pain thatresults in an inability to throw at more than 50'7r to 75% oftheir normal velocity. Up to 40% of patients with valgusinstability present wilh uhiar nerve symptoms.-" Ulnar nervesymptoms may occur due lo compression of the nerve byinflammatory components ofthe irritated ligament within thetunnel or with traction from repealed valgus loading.-'"

Physical examination ofthe elbow for valgus instabilityis performed by applying a valgus stress while flexing theelbow between 20"' to 30 '^ to unlock the olecrant)n from itsfossa (Fig. 6). This maneuver stresses the anterior band oftheanterior bundle of the MCL.-"-^-'' It is important to palpatethe MCL during the application of valgus stress to localizepoint tenderness. Valgus laxity is manifested by an increasedmedial joint space opening, as compared to the contralateralside. It is now recognized that this test should be performedwith the forearm in full pronation to prevent posterolateralrotatory instability.'' The milking maneuver can be used totest the functionally more important posterior band oftheanterior bundle of the MCL. The maneuver is performedby pulling on the patient's thumb with the patient's forearmsupinated; the shoulder is extended and the elbow flexed to90. The difference in valgus rotation between intact elbowsand those in which the anterior bundle is deticienl has beenshown to be signiticanlly greater at 70'^ to 90 '^ of flexionthan at 30.-'-^-"

R(Hitine radit)graphs may show changes consistent withchronic instability, such as calcification and occasionallyossitication of the ligament. Stress radiographs can be usedU) confirm the diagnosis; a side-to-side difference of morethan 2 mm is consistent with instability.-*'^ MRI is currentlythe modality of choice for evaluating the MCL; completeligamentous tears are readily identified.-*'^ "'" The use of in-tra-aiiicular gadolinium may provide useful information forpartial tears thai occur on the inner surface of the MCL butmay be missed on standard MRL' ' ' Arthroscopy has alsobeen described for the diagnosis of MCL tears. Although theligament cannot be directly visualized, the amount of joint

Start Handsapart

Footdown

Maximalexternalrotation

Balirelease

Finish

Figure 5 Overhead throwing motion. (Reprint-ed from Chen FS. Rokito AS\ .tobe FW: Medialelbow problems in the overhead-throwing ath-lete. .1 Am Acad Orthop Surg. 2001 ;y{2?:101.Copyright 2001 American Academy ofOrthopaedic Surgeons, with permission. Modi-fled fmin DiGio\ine MN. Jobe KW. Pink M. ctal. An electromyographic analysis olthe upperextremity in pitching. J Shoulder Hlbow Surg|yy2; 1:16. Copyright t 1992. with permissionfrom the Joumal of Shoulder and Flbow SurgeryBoard ol'Trustces.)

170 Bulletin of the NYU Hospilal foi Joint Diseases Vokiiiic 64. Numbers 3 & 4, 2006

Opening to valgus stress can be observed, with greater than3 mm considered indicative of a complete tear.''

TreatmentInitially, nonoperative treatment of a brief period of rest,ice, and nonsteroidal anti-inlianimatory drugs (NSAIDs)is instituted to reduce pain and inflammation. Once theacute inllammation has subsided, a supervised flexibilityand strengthening program is instituted, aimed at restoringmuscle tone, strength, and endurance to provide dynamicelbow stability. A supervised throwing and conditioningprogram is started at three months, once the athlete hasregained full range of motion and strength. Nonoperativemanagement instituted at an early stage has been shown toarrest the progression of instability and functional impair-ment, with as many as 50% of athletes being able to returnto a preinjury level of throwing.-''"'

Surgical intervention is indicated in throwing athletes whohave acute complete ruptures of the MCL or suffer chronicsymptoms that have not substantially improved after three tosix months of nonoperative management. Primary repair isgenerally reserved lor an acute tear related to a deli ned trau-matic event in which the MCL is avulsed from the humeralor coronoid insertions. More commonly, chronic repetitivetrauma leads to attenuation ofthe MCL and midsubstancetears, which precludes an effective primary repair. In thesecases, graft reconstruction is preferable.-"''^ For partial-thick-ness tears, the ligament is preserved but augmented with agraft reconstruction.

Surgical reconstruction begins with an approach centeredover the medial epicondyle. Care tnust be taken lo preservethe medial antebrachial cutaneous nerve. Next, the commonflexor mass is split longittidinally, in line with its fibers in theposterior-third near the flexor carpi tilnaiis (FCU); enoughexposure can be obtained without a transverse incision ofthe flexor pronator muscles or transposition of the ulnarnerve. The ligamentous-capsuiar complex is then incised toallow access to the elbow joint and associated intra-articulai'pathology for treatment. The anatotnic origin and inser-tion ofthe MCL is identified and bone tunnels are placedto allow isometric positioning of the graft. The harvestedgraft is placed in the bone tunnels and tensioned with the

Figure 6 lixamination of ulnar eoilateralligament complex. (Reprinted from Chen KS,Rokito AS, Jobe I'W. Medial elbow problemsin the overhead-throwing athlete. J Am AcadOrthop Surg. 2001 ;9(2):99-l 1 3, Copyright 2001 Ameriean Aeademy of OrthopaedieSurgeons, with permission. Modified fromKvitne RS, Jobe FW. Ligamentous and poste-rior compartment injuries. In: Jobe FW [ed]:Opcnttivc Techniques in Upper E.\!rciiiity SportsInjuries. Philadelphia: Mosby-Year Book, 1996,p. 415, Copyright 1996, with pemiission fromElsevier.)

elbow at 45" flexion and neutral varus-valgus alignment.A concurrent ulnar nerve transposition tnay be perf\)rmedin cases of concotnitant ulnar neuritis, ulnar nerve sublux-ation, or pathologic nerve constrictions noted at the time ofsurgery.-'"' Routine transpositions are no longer performed,because ofthe risk of tierve injury secondary to segmentaldevascularization, intraoperative compression or traction,and postoperative scarring.

Postoperatively, the elbow is immobilized in supina-tion and yC of flexion for seven to ten days. Flexion andextension are protected in a hinged brace for an additional4 weeks. At six weeks, elbow strengthening exercises arestarted, however, valgus stress is avoided until four monthsafter surgery.

ResultsIn 1992, Conway and associates reported that 85% of 56patients who had undergone MCL reconstruction, and hadnot undergone prior sui-gery. had a satisfactory result versus55% of patients wht> had undergone prior surgery. Moresignificantly. 74% of patients who had nol undergone a priorprocedure had excellent results, compared with 33% of thosewho had undergone an unsuccessful prior procedure.-" An-drews and Timmerman reported on 1 I professional pitchers:nine underwent reconstruction ofthe ligament and two hadprimary repair. Seven of the pitchers who had reconstruc-tion returned to competition." More recently, Thompsonand coworkers reported on 83 athletes with medial elbowinstability who underwent an MCL reconstruction with amuscle splitting approach but without ulnar nerve transposi-tion. Postoperatively, 5% had transient ulnar nerve sympt(jm,sthat resolved with nonoperative management. There wereno reoperations for nerve dysfunction and no permanentnerve problems. At two to four year follow-up. 93% of thehighly competitive athletes who had not had a prior surgicalprocedure had an excellent result.'**

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