Recurrent Posterior Shoulder Instability

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Recurrent Posterior

Shoulder Instability

Abstract

Recurrent posterior shoulder instability is an uncommon

condition. It is often unrecognized, leading to incorrect diagnoses,

delays in diagnosis, and even missed diagnoses. Posterior

instability encompasses a wide spectrum of pathology, ranging

from unidirectional posterior subluxation to multidirectional

instability to locked posterior dislocations. Nonsurgical treatment

of posterior shoulder instability is successful in most cases;

however, surgical intervention is indicated when conservative

treatment fails. For optimal results, the surgeon must accuratelydefine the pattern of instability and address all soft-tissue and bony

injuries present at the time of surgery. Arthroscopic treatment of

posterior shoulder instability has increased application, and a

variety of techniques has been described to manage posterior

glenohumeral instability related to posterior capsulolabral injury.

Recurrent posterior shoulder in-stability is an uncommon condi-tion that is often unrecognized, lead-ing to incorrect diagnoses, delays indiagnosis, and even missed diag-noses.1 Posterior instability encom-

passes a wide spectrum of pathoanat-omy that may affect the labrum,capsule, rotator interval, and bony ar-chitecture of the shoulder. Recurrent

posterior subluxation is the mostcommon type of posterior instability.

Background andEpidemiology

Glenohumeral instability is com-mon, affecting approximately 2% ofthe general population.2 However,

posterior instability occurs in only2% to 5% of those with shoulder in-stability.3 Trauma is thought to bethe underlying cause in approxi-

mately half of patients with posteri-or instability.3 Although posterior

dislocation represents only 4% of alljoint dislocations,4 it is often easily

missed on clinical examination. Spe-cific imaging assessment is impor-tant. Recurrent posterior sublux-ation, which may present with

instability symptoms or simply aspain, is more common, particularlyin those who participate in high-riskathletic activities.

Relevant Anatomy andBiomechanics

The shoulder is the most mobile, but

also the least stable, joint in thebody because less than one third ofthe humeral head articulates withthe glenoid. Stability is conferred by

a series of static and dynamic soft-tissue restraints that maintain thearticulation of the humeral headwith the glenoid while simulta-

neously providing for a large range ofmotion.5

Peter J. Millett, MD, MSc

Philippe Clavert, MD

G. F. Rick Hatch III, MD

Jon J. P. Warner, MD

Dr. Millett is Co-Director, Harvard

Shoulder Service/Sports Medicine,Brigham & Womens Hospital,

Massachusetts General Hospital,

Boston, MA, and Assistant Professor,

Department of Orthopaedic Surgery,

Harvard Medical School. Dr. Clavert is

Associate Professor, Department of

Orthopaedics, CHRU Hautepierre,

Strasbourg, France. Dr. Hatch is

Assistant Professor, Sports Medicine/

Shoulder & Elbow Services, Department

of Orthopaedic Surgery, USC Keck

School of Medicine, Los Angeles, CA.

Dr. Warner is Professor, Department of

Orthopaedics, Harvard Medical School,

Boston, MA, and Chief, Harvard

Shoulder Service, Department of

Orthopedics, Massachusetts General

Hospital.

None of the following authors or the

departments with which they are

affiliated has received anything of value

from or owns stock in a commercial

company or institution related directly or

indirectly to the subject of this article:

Dr. Millett, Dr. Clavert, Dr. Hatch, and

Dr. Warner.

Reprint requests: Dr. Millett, Steadman

Hawkins Clinic, 181 West Meadow

Drive, Vail, CO 81657.

J Am Acad Orthop Surg 2006;14:464-

476

Copyright 2006 by the American

Academy of Orthopaedic Surgeons.

464 Journal of the American Academy of Orthopaedic Surgeons


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Static Restraints

Articular factors such as jointcongruency, glenoid version, and hu-meral retrotorsion contribute to

static joint stability. Bony abnormal-ities such as glenoid retroversion orposterior glenoid erosion can be pre-

disposing causative factors for poste-rior shoulder instability.1

The glenoid labrum, a wedge-shaped fibrous structure consistingof densely packed collagen bundles,

increases the depth and surface areaof the glenoid. It serves as an anchorpoint for the capsuloligamentousstructures, deepens the glenoid con-

cavity, and reduces glenohumeraltranslation with arm motion.6 La-bral excision decreases the depth ofthe socket by 50% and reduces resis-tance to instability by 20%.6

The glenohumeral ligaments arethickened fibrous bands within thejoint capsule; these ligaments act atthe end ranges of motion and pro-

vide static stability. Their functionis dependent on the position of thearmand the direction ofthe force ap-plied.7 For example, when the armis

adducted, the superior glenohu-meral ligament (SGHL) and coraco-humeral ligament (CHL) limit infe-

rior translation and externalrotation of the humeral head. Addi-tionally, the SGHL and the CHL re-sist posterior translation of the hu-meral head when the shoulder is in

flexion, adduction, and internal ro-tation. The inferior glenohumeralligament (IGHL) complex is com-posed of discrete anterior and poste-rior bands with an interposed axil-

lary pouch that acts like ahammock, undergoing reciprocaltightening and loosening depending

on arm position. The posterior bandof the IGHL complex is the main re-straint to posteriortranslation of thehumeral head when the arm is ab-ducted.

The posterior capsule is definedas the area superior to the posteriorband of the IGHL complex. Theposterior capsule is the thinnest

(1 mm) and perhaps weakest por-

tion of the shoulder capsule. It may

limit posterior translation when the

arm is flexed, adducted, and inter-

nally rotated.

The rotator interval plays a role

in static stability and is defined by

the borders of the supraspinatus su-periorly, the subscapularis inferi-

orly, the coracoid process medially,

and the biceps and humerus later-

ally. The SGHL, medial glenohu-

meral ligament, and CHL provide

variable reinforcement to the rota-

tor interval. The rotator interval and

its constituents provide stability

against inferior and posterior trans-

lations, particularlywhen the arm is

adducted and externally rotated.8

Evidence suggests that deficiencies

in the rotator interval can contrib-

ute to instability in patients with

excessive inferior or posterior trans-

lation.9 In some individuals, the ro-

tator interval may be composed of

loosely arranged collagen, whereas

in others, it may be completely

devoid of tissue. This represents a

rotator interval capsular defect

that may need to be addressed in

the symptomatic shoulder, but it

may also be considered a normal

anatomic variant in the stableshoulder.

Dynamic Restraints

Dynamic stability is provided by

the rotator cuff, the deltoid, and the

biceps tendon through a concavity-

compression effect on the humeral

head within the glenoid socket.10 Of

the four muscles of the rotator cuff,

the subscapularis provides the great-

est resistance to posterior transla-

tion.10,11

In addition, dynamic stabil-ity of the shoulder also is provided

by the trapezius, serratus anterior,

teres major, and latissimus dorsi

muscles. Scapulothoracic motion

must be properly coordinated with

glenohumeral motion so that theglenoid can be appropriately posi-tioned to provide a stable platform

beneath the humeral head.

Definitions: Laxity andInstability

The term instability is reserved for

symptomatic shouldersspecifical-ly, the sensation of the humeral headtranslating in the glenoid, which is

frequently associated with pain anddiscomfort.12 Instability is defined aspathologic joint translation thatcauses symptoms, or as the inabilityto keep the humeral head centered

within the glenoid cavity during ac-tive motion. Laxity is defined as aspecific translation for a particulardirection or rotation.13 Individuals

may have significant laxity and yetremain asymptomatic. Conversely,others with only minimal degrees oflaxity may have significant symp-

toms of instability. The distinctionis important. Frequently, patientswith excessive shoulder laxity sus-tain a traumatic injury and subse-quently develop symptoms of insta-

bility. Individuals with recurrentposterior subluxation generally havesymptomatic pain yet may or maynot have symptoms of instability.

Classification ofPosterior Instability

Posterior shoulder instability can beclassified by direction, degree, cause,and volition. Unidirectional posteri-or subluxation is the most frequent

form of posterior instability. Posteri-or instability also can occur as bidi-rectional or multidirectional insta-bility.14

The degree of posterior instabili-

ty can range from mild subluxationto frank dislocation. Recurrent pos-terior subluxation is the most com-

mon form.Posterior instability may be trau-

matic (acquired) or atraumatic. Thetraumatic type is the more commonform.1 This can occur as a single

traumatic event with the shoulder inan at risk position (ie, flexion, ad-duction, and internal rotation) or asa culmination of multiple, smaller

traumatic episodes. For example, an

Peter J. Millett, MD, MSc, et al

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electrical shock producing posteriordislocation is a classic example of asingle traumatic event. An offensivelineman with the arms in the block-

ing position would typify a predispo-sition to recurrent posterior sublux-ation because of the repetitive

loading. Posterior instability occur-ring secondary to overhead sportspresents more insidiously because ofthe gradual capsular failure from re-petitive microtrauma. Common pro-

vocative activities include the back-hand stroke in racket sports, thepull-through phase of swimming,and the follow-through phases in a

throwing activity or golf.Posterior instability in the set-

ting of an atraumatic history shouldalert the clinician to the possibility

of an underlying collagen disease orbony abnormality (eg, glenoid hypo-plasia, excessive glenoid retrover-sion). In such situations, surgical in-

tervention should be approachedcautiously.

Finally, posterior instability maybe defined by its volitional compo-nent. Involuntary posterior instabil-

ity typically results from a traumat-ic event (acute or repetitive) andmost commonly manifests as mild

subluxation. The symptoms do notoccur willfully and usually are notcontrollable. Voluntary posterior in-stability occurs when a patient canwillfully dislocate or subluxate the

shoulder. Two different patternshave been describedvoluntarymuscular and voluntary positionalposterior instability. In voluntary

muscular (or habitual) posterior in-stability, an underlying muscularimbalance typically exists thatallows voluntary subluxation/

dislocation of the shoulder with thearm in adduction. Patients with ha-bitual voluntary posterior instabili-ty are generally considered poor sur-

gical candidates. However, patientswith the second voluntary form, po-sitional voluntary posterior instabil-ity, can respond well to surgery pro-vided they do not have underlying

psychiatric or secondary gain is-

sues.15 Typically, these individuals

have instability when the arm is

flexed and adducted. Although these

individuals may be able to voluntar-

ily reproduce their instability, they

usually avoid the provocative ma-

neuvers.

15

Evaluation

History

Although posterior shoulder in-

stability is uncommon, an aware-

ness of the disorder, together with a

thoughtful evaluation beginning

with the clinical history, usually

leads to the proper diagnosis. The

first step is to inquire about a histo-

ry of trauma. In the case of a single

traumatic episode, the direction ofthe applied force and the position of

the arm at the time of injury may

provide insight into the diagnosis.

Classically, posterior subluxation

occurs with a traumatic event when

the arm is in an at-risk position (eg,

forward flexion, adduction, internal

rotation).16 A fall or blow to the arm

while in an at-risk position can re-

sult in a posterior labral detachment

(reverse Bankart lesion).16 Repetitive

stresses on the posterior capsule, ei-ther from sports or other activities,

may lead to acquired posterior sub-

luxation.

Patients with recurrent posterior

subluxation most commonly report

pain and feelings of weakness. Insta-

bility symptoms may or may not be

present. With careful questioning,

the direction, frequency, and severi-

ty of the patients symptoms can be

ascertained. Overhead athletes often

describe insidious pain that may oc-cur in the later phases of their sport-

ing activities, when muscle fatigue

and dynamic stability are compro-

mised. Mechanical symptoms, such

as giving way, slipping, popping,

catching, or clicking, are less com-mon than in anterior instability. Vo-litional components should be as-

sessed.

Physical Examination

The physical findings of patientswith posterior instability often aremore subtle than those of patients

with anterior instability. Active andpassive ranges of motion usually arenormal and symmetric. The posteri-

or joint line may be tender to palpa-tion. Crepitus is sometimes noted asthe arm is internally rotated.Strength testing is usually symmet-ric, except in rare cases of posterior

rotator cuff muscle deficiency ornerve injury with external rotationweakness. In these cases, atrophy ofthe posterior rotator cuff muscles

may be apparent on inspection.Patients should be assessed for

generalized ligamentous laxity byevaluating the contralateral shoul-

der, elbows, and knees, and by test-ing the patients ability to oppose thethumb to the forearm. In addition,sulcus testing should be performed.

The sulcus can be quantified by thedistance from the greater tuberosityto the acromion. A sulcus sign>2 cm is virtually pathognomonicfor multidirectional instability, but

pain and symptoms of inferior insta-bility must also be present for thisdiagnosis. If the sulcus does not re-

duce as the arm is externally rotated,it should be considered pathologic,with a defect in the rotator intervalthat should be addressed at the timeof surgery.

Scapulohumeral rhythm andscapulothoracic mechanics shouldbe assessed to exclude the possibili-ty of scapular winging, which is fre-

quently confused with posterior in-stability.17 In some instances, acompensatory scapular winging mayoccur. As the scapula wings, it effec-

tively anteverts the glenoid and dy-namically increases the bony stabil-ity.17 In such instances, a thoroughneurologic examination should beperformed with appropriate neuro-

logic testing, as indicated.

Specific Posterior

Instability Tests

The posterior stress test (Figure 1)

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is performed with the individual inthe supine position; the arm is flexedto 90 and internally rotated. The ex-aminer axially loads the humerus

against the posterior glenoid bypushing the arm posteriorly withone hand while the other hand is ap-

plied to the back of the shoulder.The posterior stress test is positivewhen a subluxation of the humeralhead over the glenoid rim is palpat-ed or observed.

The jerk test (Figure 2) is per-formed with the patient sitting up-right; the arm is flexed 90 and in-ternally rotated, and the elbow is

flexed to 90. A posterior force isgenerated by applying an axial loadto the humerus by pushing on theflexed elbow. In patients with signif-

icant laxity, this will cause a poste-rior dislocation or subluxation ofthe glenohumeral joint. The arm isthen extended and, as this occurs,

the glenohumeral joint will reducewith a jerk. If a painful relocation oc-curs, the jerk test is positive. Usu-ally the reduction is observed asthere is a sudden change in velocity

as the humeral head reenters theglenoid fossa.

The load and shift test (Figure 3,

A) is performed with the patient

seated upright, arm at the side. Thehumeral head and proximal hu-merus are grasped and compressed

into the glenoid socket, and anteriorand posterior stress is applied withgrading of the degree of translation.This test is used to determine the

amount of glenohumeral transla-tion, but it is difficult to accurately

quantitate results. A 50% displace-ment of the humeral head is consid-ered the upper limit of normal. It is

not unusual to find symmetric pos-terior translation between the af-fected and unaffected shoulders.5,14

The modified load and shift test

(Figure 3, B) is performed with thepatient supine and the affected

Figure 1

Posterior stress test. A posterior force is applied through the humerus. The test ispositive if there is palpable crepitus or subluxation. Often pain is elicited, but this isnot as specific a finding.

Figure 2

Jerk test.A,A posterior force is applied along the axis of the humerus with the arm in forward flexion and internal rotation. Thiswill cause the humeral head to subluxate posteriorly out of the glenoid socket. B,As the arm is brought into extension, a clunkwill be felt as the humerus reduces into the glenoid cavity.




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shoulder at the edge of the examin-ing table. The shoulder is positioned

in the scapular plane and in neutralrotation. Manual force is placed atthe ipsilateral elbow to concentrical-ly reduce the humeral head. Anteri-

or and posterior forces are thenapplied to the proximal humerus invarying degrees of rotation and ele-vation with grading of the amount of

translation.14 The load and shift andmodified load and shift tests are typ-

ically graded as follows: grade 0,minimal translation; grade 1, hu-meral head translates to the glenoidrim; grade 2, humeral head trans-

lates over the glenoid rim but spon-taneously reduces; and grade 3, hu-meral head dislocates and does notspontaneously reduce.

Imaging

Radiographs

Plain radiographs of the shoulder

should include true anteroposterior

views in neutral, internal, and exter-

nal rotation; a transscapular view or

Y view; and an axillary view. Theseviews are needed to ensure that the

joint is located, to evaluate the pos-terior glenoid rim, and to look forimpaction fractures of the humeral

head. In addition to humeral headposition, these studies demonstrateglenoid rim morphology (hypoplasia,excessive retroversion, and/or frac-

ture of the posterior glenoid rim).However, most individuals with re-current posterior instability do nothave bony abnormalities. For those

with a volitional component, dy-namic radiographs can confirm thediagnosis (Figure 4).

Multiplanar Imaging

Computed tomography (CT) ormagnetic resonance imaging (MRI)is essential to assess the version and

morphology of the glenoid. Thesetests also help detect subtle anterior

Figure 3

A,Load and shift test. The patient is seated upright. A compressive force is applied through the humeral head to center thehumeral head within the glenoid cavity. Posterior or anterior forces can then be applied to assess the amount of joint translation.This can be compared with the contralateral shoulder.B,Modified load and shift. The patient is supine. A compressive force isapplied along the long axis of the humerus to center the humeral head in the glenoid cavity. A posterior force can then be appliedto assess the degree of translation of the humeral head.

Figure 4

Axillary radiographs of an individual with voluntary posterior instability showing thehumeral head dislocated(A)and reduced(B).




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humeral head defects and glenoidfractures. Contrast can enhance theability to evaluate the posterior la-

brum and capsule, particularly withinjuries such as capsulolabral disrup-

tions or lateral capsular injuries.

18

Contrast also enhances assessment

of the superior labrum. For surgicalcandidates, it is critically importantto identify the pathoanatomy so thatthe appropriate surgical approach

can be chosen. For example, an indi-vidual with significant retroversionof the glenoid will have an unaccept-ably high failure rate if a soft-tissuecapsulorrhaphy is performed and the

bony abnormality is not addressed.Preoperative diagnosis helps in sur-

gical planning, particularly as ar-throscopic treatment becomes more

popular. Depending on the surgeonsskill level, some injuries (eg, glenoiderosion, posterior humeral avulsionof the glenohumeral ligaments, cap-

sular rupture) are more appropriate-ly addressed through an open surgi-cal approach.

Although the gadolinium-

enhanced magnetic resonance ar-throgram provides excellent soft-tissue detail, we think that a CT

scan with intra-articular contrastprovides the best information withregard to bony anatomy and articularorientation. CT is superior in itsability to determine the glenoid

morphology as well as the degree ofglenoid retroversion. Glenoid retro-version is best measured on axial CTscan images through the mid-glenoid; this corresponds with the

first inferior image, on which the tip

of the coracoid process is no longer

visible.19 At this level, glenoid retro-

version between 2 and 8 is con-

sidered normal.19

Initial Treatment

Nonsurgical treatment is successful

for the great majority of patients

with recurrent posterior sublux-

ation. The aim of physical therapy is

to strengthen the dynamic muscularstabilizers to compensate for the

damaged or deficient static stabiliz-ers.20 The focus should be on exercis-es that strengthen the posterior del-toid, the external rotators, and the

periscapular muscles. These exercis-es are typically used in conjunctionwith activity modification and bio-feedback. Nonsurgical treatment ofposterior instability is successful in

approximately 65% to 80% of cas-es.20,21

Surgical Treatment

Open procedures have been themainstay of treatment when nonsur-gical treatment fails and have led to

good results when implemented ap-propriately1,15,22 During the past de-cade, the arthroscopic treatment ofposterior shoulder instability has at-

tracted increasing interest as ameans to restore stability withoutthe morbidity of open surgery. A va-riety of arthroscopic techniqueshave been described to manage pos-

terior glenohumeral instability in re-

lation to posterior capsulolabral in-

jury and redundancy.

23-26

Theperceived advantages of the arthro-

scopic approach include less morbid-ity, shorter surgery time, improvedcosmesis, and less postoperativepain.27,28

Prerequisites

Because of the multifactorial na-ture of posterior instability, as well

as the lack of a single consistent es-sential pathologic lesion, the sur-geon must consider all potential

contributing factors and correct therelevant pathoanatomy encounteredin that individual case (Table 1). Thebest surgical candidates are thosewith recurrent, posttraumatic, uni-

directional subluxation. These pa-tients are also the ideal candidatesfor arthroscopic stabilization, eitherby suture anchors or simple posteri-

or capsular plication with sutures(Figure 5). The procedures used toaddress posterior instability may besubdivided into soft-tissue and bony

procedures.Before any surgical procedure, an

examination under anesthesia is per-formed. The amount of humeralhead translation on the glenoid sur-

face is graded as follows: 0, stable ortrace laxity; 1, up to 50% transla-tion; 2, dislocatable with spontane-ous reduction; and 3, dislocates and

does not spontaneously reduce. Sul-

Table 1

Surgical Decision Making for Posterior Instability According

to Pathoanatomy

Pathologic Lesion Procedure of Choice

Posterior Bankart lesion Arthroscopic or open posterior Bankart

repairExcessive capsulolabral laxity Arthroscopic or open posterior capsular

shift rotator interval closure

Glenoid erosion Posterior glenoid bone grafting

Increased glenoid retroversion Posterior opening wedge glenoid osteot-omy

Figure 5

Arthroscopic photograph of a posteriorcapsulolabral disruption (posterior orreverse Bankart lesion). The probe is inthe defect.




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cus testing and passive range of mo-

tion are compared with the oppositeshoulder.

Soft-Tissue Procedures

Open Posteroinferior Capsular

Shift

The open posteroinferior capsular

shift procedure is best for patientswith recurrent posttraumatic sub-luxation and those with involuntary,

recurrent, atraumatic subluxation.

The procedure also may be indicatedin those with recurrent voluntary

positional posterior subluxation.15

Positioning

The procedure may be performed

under general anesthesia, regional

anesthesia alone, or general anes-thesia combined with a regional an-esthetic. The patient is positioned

on a full-length beanbag, in the later-

al decubitus position (Figure 6, A). Amechanical arm holder from the op-

posite side of the operating table can

be helpful to support the arm in in-

ternal or external rotation.

Incision

The shoulder is approached poste-riorly; we prefer the incision in theposterior axillary fold. The deltoid

Figure 6

Open posteroinferior capsular shift.A,The patient is positioned in the lateral decubitus position in a beanbag. A posterior axillaryincision is used (broken line).B,The deltoid is split in line with its fibers to expose the underlying infraspinatus and teres minor.Inset, Split in the infraspinatus and the location of the T-plasty in capsule. C,The infraspinatus is split and a T-shapedcapsulotomy is performed. The capsule is opened just lateral to the labrum.D,The capsulotomy is performed at the glenoidside. Labral detachments are repaired.E, The inferior capsule is shifted superiorly. F,This is reinforced with the superior limb ofthe capsule.




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can then be split in line with its fi-

bers, detached from its origin on the

scapular spine, or abducted and ele-

vated to reach the infraspinatus over

the joint line (Figure 6, B). The in-

fraspinatus is then split at the level

of the equator of the glenoid to ex-pose the underlying posterior gleno-

humeral joint capsule. Care is taken

not to divide the muscle more than

1.5 cm medial to the glenoid in order

to avoid damage to the branches of

the suprascapular nerve to the in-fraspinatus.

Capsular Shift

The capsule is then divided hori-zontally from medial to lateral at theequator of the glenoid. Althoughboth medial and lateral capsular

shifts have been described,29,30 we

prefer a medially based shift with aT-plasty of the capsule performed atthe level of the glenoid. The posteri-or capsule is often quite thin and the

medial capsule is of better qualitythan the lateral capsule. We open thecapsule just lateral to the labrum(Figure 6, C). The remaining capsulo-

labral sleeve is then elevated fromthe glenoid rim inferiorly to the sixoclock position. The joint is in-

spected and any posterior labral inju-ry is repaired with two or three bio-absorbable suture anchors (Figure 6,D). The suture anchors are placed atintervals along the posterior glenoid

rim, just at the articular margin. Thecapsulolabral lesion is then repairedanatomically, although the labrumis often quite small.

During capsular repair, the pa-tients arm is positioned in 20 of ab-duction and in neutral rotation. Theinferior flap of capsule is shifted from

inferior to superior to remove redun-dancy (Figure 6, E). The superior flapis then shifted inferiorly over the in-ferior flap to reinforce the posteriorcapsule (Figure 6, F). In the setting of

capsular rupture or insufficiency, theposterior capsule may be augmentedwith the infraspinatus tendon. Non-absorbable transosseous sutures or

suture anchors are used to repair the

infraspinatus.31 The deltoid is closedin a side-to-side fashion withbraided, nonabsorbable sutures.

Arthroscopic Posterior

Stabilization

The indications for the arthro-

scopic approach are identical tothose for the open posteroinferiorcapsular shift. Ideal candidates arethose with a posterior Bankart le-sion. Relative contraindications to

arthroscopic treatment of recurrentposterior instability include failedprior arthroscopic stabilization pro-cedures, humeral avulsions of the

glenohumeral ligaments, or grosssymptomatic bi- or multidirectionalinstability from excessive general-ized laxity, such as with Ehlers-

Danlos syndrome. A distinctionmust be made, however, betweenthese patients and those who havemultidirectional laxity but remainsymptomatic only in the posterior

direction. This latter group makesup a large number of patients withrecurrent posterior instability, andthey respond well to arthroscopic

stabilization. Absolute contraindica-tions to arthroscopic stabilizationare the rare individuals with either

glenoid erosion (acquired or develop-mental) or excessive glenoid retro-version. In these settings, bony pro-cedures are required to reconstructor reorient the glenoid.

Patient Positioning

The procedure can be performedin either the lateral decubitus orbeach chair position. For the lateral

decubitus position, the arm is placedin a traction device (Arthrex StarSleeve; Arthrex, Naples, FL) with 20of abduction and 20 of extension.

Direct lateral traction also can be ap-plied to the proximal humerus.

Arthroscopic Portals

Three or four portal techniques

can be used, with one or two poste-rior portals and two anterior portals.The posterior portal must be placedslightly lateral to allow access to the

posterior glenoid rim and the pos-

teroinferior capsule. If the posterior

portal position is not ideal, a second

posterior portal can be used. Both an

anterosuperior portal and a midante-

rior portal are created in the rotator

interval region. The former is used

for viewing, and the latter for instru-mentation and suture passage (Fig-

ure 7, A).

Arthroscopic Shift

A significant capsulolabral injury

(posterior Bankart lesion) can be

repaired with suture anchors; other-wise the capsular redundancy,which is more typically encoun-

tered, can be reduced with a poste-rior capsular shift. The shift beginsat the 6 oclock position. Using ashuttling-type angled instrument,

the capsule is grasped 10 to 15 mmlateral to the glenoid rim and isshifted to the labrum with three tofive sutures (Figure 7, B through D),

depending on the size of the shoul-der, the laxity present, and the de-gree of shift desired. For patientswith significant inferior laxity, a ro-

tator interval closure is performedto provide additional stabilityagainst inferior translation.8 We per-formthe rotator interval closure as a

capsular closure, plicating the mid-dle glenohumeral ligament to thesuperior glenohumeral ligament.

Bony Procedures

In the setting of severe glenoiddysplasia or retroversion, defined asretroversion >20 (Figure 8, A), anopening wedge posterior glenoid os-teotomy is indicated. For patients

with significant focal posterior gle-noid defects, a bone block or bonyglenoid reconstruction is indicated.

Although corrective humeral rota-tional osteotomies have been de-scribed in several European series,they are not widely used in NorthAmerica.

Opening Wedge Glenoid

Osteotomy

Patients are positioned in the lat-

eral decubitus position, and expo-




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sure is similar to that described for

the open capsular shift. The postero-medial neck of the glenoid is ex-posed. An autologous tricorticalbone graft is used. The width of the

graft is variable depending on the de-gree of correction (10 to 25 mm) andshould be contoured in a wedge fash-

ion (Figure 8, B). The osteotomy

should be incomplete, leaving theanterior glenoid cortex intact tomaintain stability. When the desiredcorrection has been obtained, the tri-

cortical bone graft is inserted to cor-rect the retroversion. The graft maybe press-fit (our preference) or se-

cured by screws (Figure 8, D). Resid-

ual capsular redundancy may then

be treated, as described. This is a

technically challenging procedure;

numerous complications have been

reported, including intra-articular

fracture, nerve injury, loss of reduc-tion, and hardware problems.

Posterior Bone Graft

For patients with acquired focal

glenoid defects, the glenoid can be

reconstructed with an anatomic

intra-articular bone graft to restorethe glenoid arc, or with an extra-articular bone graft that serves as

a buttress for the humeral head (Fig-ure 9). We prefer the extra-articularapproach, advancing the capsule an-

terior and medial to the graft to serveas a soft-tissue interposition. Caremust be taken to avoid either medi-al placement with ineffective but-tressing or excessive lateral place-

ment with impingement on thehumeral head.32 The preferred graftsource is the inner table of the iliaccrest.

PostoperativeRehabilitation

Postoperative management requiresthe use of an orthosis to maintainabduction, neutral rotation, and ex-tension of the shoulder. The elbowshould be positioned posterior to the

plane of the body to decrease tensionon the repair. Immobilization ismaintained for 4 to 6 weeks, depend-ing on the degree of instability, the

quality of the tissue, and the securi-ty of the repair. At 6 weeks, activeassisted range-of-motion exercisesare started. Strengthening is delayed

until the third postoperative month.Collision sports should be avoidedfor the first 6 months.

Results

Published results are summarized inTable 2. Although initial surgical re-sults were so poor that some authors

concluded that recurrent posterior

Figure 7

Arthroscopic posterior stabilization technique.A,Portal placement using a three-portal technique. The arthroscope is initially introduced into the posterior portal butis then switched to the anterosuperior portal to visualize the posterior capsule.The posterior capsule is addressed as viewed arthroscopically from theanterosuperior portal. The superior aspect of the glenoid is oriented to the bottomof the page and the inferior aspect oriented to the top. B, The capsule is beingshifted to the labrum using a shuttling-type suture passer, which is gentle on thetissues.C,Both limbs of a permanent suture are retrieved through the posteriorcannula and tied.D,The steps are repeated from inferior to superior, with three tofive sutures typically being used.




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instability should not be treated sur-gically,1 most of the early failuresand recurrences resulted from a lackof knowledge of the pathoanatomy

and the relevant biomechanics. Im-proved patient selection and surgicaltechniques have led to better out-

comes.Fronek et al30 and Hurley et al21

reported a 63% to 91% success ratewith nonsurgical treatment, with nolimitations in activities of daily liv-

ing and only moderate disability insports activities. Many of these pa-tients had positive examinationfindings for posterior instability but

did not require any further treat-ment. Fronek et al30 also reportedgood results with open posterior cap-sulorrhaphy. Hawkins et al1 advocat-ed the use of the infraspinatus ten-

don to reinforce the capsule andreported an 85% success rate at aver-age follow-up of 7 years (range, 2 to15 years). Pollock and Bigliani32 re-

ported an overall satisfactory rate of80% with this procedure at averagefollow-up of 5 years. When revisioncases were excluded, the success rate

improved to 96%, highlighting theimportance of meticulous soft-tissuerepair at the first surgery.

Over the last decade, advances inarthroscopy have made this ap-proach quite attractive. Although avariety of techniques has been de-scribed, the key features include re-

storing the labrum and eliminatingcapsular redundancy. In 1998, Wolfand Eakin25 reported success in 16 of17 patients who underwent an ar-throscopic posterior capsular plica-

tion for unidirectional posterior in-stability. Eleven returned to theirpreinjury level of function, and there

were no reported complications. An-toniou et al16 reported on 41 patientswith posterior instability treatedwith an arthroscopic posteroinferiorcapsulolabral augmentation proce-

dure. Thirty-five patients noted im-provement, although 28 actually re-ported a perception of shoulderstiffness. Williams et al23 reported on

27 shoulders (26 patients) with trau-

matic posterior Bankart lesions sur-gically treated with arthroscopic re-pair using bioabsorbable tackfixation; 55% of patients (11 pa-

tients) were American football play-ers. Symptoms of pain and instabil-ity were eliminated in 24 patients(92%). Two patients required addi-

tional surgery.

Kim et al24 reported on 27 shoul-ders (27 patients) with traumaticunidirectional recurrent posteriorsubluxation treated with arthroscop-

ic labral repair and posterior capsularshift using suture anchors. In all cas-es, symptoms were preceded by atraumatic event. Symptoms of pain

and instability were eliminated in

Figure 8

Posterior opening wedge osteotomy. Significant retroversion (>20) of the glenoid,as shown here(A),is best addressed with this procedure. The opening wedgeosteotomy should be performed using a standard posterior approach. Theosteotomy(B)should begin approximately 10 mm medial to and parallel to thearticular surface. Stacking multiple broad flat osteotomes (C) helps achievedistraction posteriorly while the anterior cortex is preserved. Care should be takento avoid an intra-articular fracture. The tricortical graft from the iliac crest may bepress-fit (our preference) or carefully secured with small fragment screws (D).




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all patients except one, who had re-

current instability. Postoperatively,

all patients had improved shoulder

scores. Twenty-six of 27 were able to

return to their prior sports with lit-

tle or no limitation.24

Thermal shrinkage of the capsu-lar tissues also has been advocated to

shrink the patulous posterior cap-

sule.33 Reported results for this tech-nique vary from failure rates as lowas 4%33 to as high as 60%,34 with

capsular insufficiency present in upto 33%.35 There have been alarmingreports of capsular necrosis and cap-sular rupture.35 We have found the

visual response of capsular shrink-age at the time of arthroscopy to bevariable and the clinical results of

thermal capsulorrhaphy to be unpre-dictable, with unacceptably highfailure rates. For these reasons, thistechnique is not recommended.

The surgical treatment of volun-

tary posterior instability remainscontroversial. Recurrence after soft-

Figure 9

A,A posterior glenoid bone graft can be used for erosions and osseous defects torestore concavity to the glenoid. B,Care must be taken to position the graftappropriately to effectively lengthen the articular arc while avoiding abutment of thegraft on the humeral head.

Table 2

Results and Complications Reported After Posterior Instability Surgery

Study Procedure (No. of Patients) RecurrenceComplications (Other

Than Recurrence)

Neer and Foster29 Open posterior inferior capsular shift 0% (0/15) DJD 1 patient

Hawkins et al1 Glenoid osteotomy (17), reverse Putti-Platt(6), biceps transfer (3)

50% (13/26) DJD with glenoidosteotomy 35 patients

Hurley et al21 Reverse Putti-Platt without bone block 73% (16/22) DJD 2 patients

Fronek et al30 Open medial-based posterior shift (6) andwith bone block (5)

9% (1/11) 1 superficial infection

McIntyre et al26 Arthroscopic posterior shift with suturestied over clavicle or scapular spine

25% (5/20) Recurrence only

Wolf and Eakin25 Arthroscopic posterior shift with andwithout suture anchors


Antoniou et al16 Arthroscopic posterior shift with andwithout suture anchors

15% (6/41) 28 subjective stiffnesswith normal range ofmotion

Fuchs et al15 Open lateral-based posterior inferior shiftwith and without bone grafting (1) orosteotomy (3)

23% (6/26) 8 discomfort, 1 anteriorsubcoracoidimpingement

Williams et al23 Arthroscopic posterior Bankart repair withbioabsorbable tack fixation


Kim et al24 Arthroscopic posterior Bankart repair andposterior shift with suture anchors


DJD = degenerative joint disease




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tissue procedures has been reported

to vary from 0% (0/15 patients)29 to

72% (18/25 patients).21 A conserva-

tive nonsurgical approach is advo-

cated in these patients. Fuchs et al15

reported good to excellent results in

24 of 26 shoulders (92%) with volun-tary posterior instability treated

with open surgery.

Complications and

Pitfalls

The complications of surgery are in-cluded in Table 2 and are procedure-specific and technique-dependent.

Recurrence is the most frequently re-ported complication.1,30 Recurrencemay result from a new injury or froma failure of the initial procedure. In-dividuals with traumatic recurrence

of the instability usually have betterresults after revision surgery than dopatients with atraumatic recurrenceof the posterior instability.

Stiffness after surgery for posteri-or instability presents as loss of in-ternal rotation. It is infrequently re-ported in the literature, and its

incidence may be underestimated.30

In certain circumstances, stiffnessmay be acceptable to maintain sta-

bility, but it is likely to be patient-specific. For example, internal rota-tion losses of 10 may have fewfunctional consequences for mostindividuals, but they may be devas-

tating for certain populations, suchas professional baseball pitchers,tennis players, or swimmers who, re-spectively, need to throw a ball, hita serve, or pull a stroke at high

speed. The phenomenon of subcora-coid impingement also may occurwhen excessive posterior capsular

tightness creates an obligate anteri-or shift of the humeral head andcauses the subscapularis and anteri-or soft tissues to impinge on the cor-acoid.36

Excessive tightness can have ma-jor consequences on joint kinemat-ics and joint reactive forces, creatingshearing forces on the glenoid rim

that result in cartilage erosion and

early osteoarthrosis.37 This has been

called capsulorrhaphy arthropathy.

Osteoarthrosis is also a complica-

tion that has been reported after pos-

terior glenoid osteotomy and poste-

rior glenoid bone grafting. This

complication is usually the result ofan intra-articular fracture or im-

pingement of the humeral head on

the glenoid rim or the bone block.

Both the axillary38 and suprascap-ular nerves39 are at risk during opensurgery for posterior instability. Inju-

ries may occur during sharp dissec-tion, tissue retraction, and sutureplacement.

Summary

The diagnosis and management ofposterior shoulder instability remainchallenging. Posterior instability is

uncommon, and the diagnosis maybe subtle. The most common pre-senting complaint is pain. Thoroughevaluation and appropriate imaging

will demonstrate the pathoanatomy,which can be variable and may in-volve soft-tissue and/or bony ele-ments. Careful classification of the

instability will yield insight into thenatural history and help guide treat-

ment. In the great majority of indi-viduals, nonsurgical treatment is the

preferred initial management. Inthose who fail conservative mea-sures, surgery may be indicated.Careful preoperative planning, sur-

gery targeted at the specific pathol-ogy, and thoughtful aftercare canmaximize the chance for success andminimize the risk of complications.

Individuals with voluntary instabil-ity, multidirectional instability, orbony defects will require a more care-ful assessment of the cause of the in-stability. If an extended rehabilitation

program is unsuccessful, combinedsoft-tissue and bony procedures maybe needed to restore stability.

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Evidence-based Medicine: Level II

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Recurrent Posterior Shoulder Instability