The Journal of Bone and Joint Surgery (American). 2005;87:883-892.
doi:10.2106/JBJS.D.02906
© 2005 The Journal of Bone and Joint Surgery, Inc.
Recurrent Posterior Shoulder Instability
C. Michael Robinson, BMedSci, FRCSEd(Orth)1 and
Joseph Aderinto, FRCSEd1
1 Royal Infirmary of Edinburgh, Old Dalkeith Road, Edinburgh EH16 4SU, United
Kingdom. E-mail address for C.M. Robinson:
c.mike.robinson{at}ed.ac.uk
Investigation performed at the Shoulder Injury Clinic, Royal Infirmary
of Edinburgh, Edinburgh, United Kingdom
The authors did not receive grants or outside funding in support of their
research or preparation of this manuscript. They did not receive payments or
other benefits or a commitment or agreement to provide such benefits from a
commercial entity. No commercial entity paid or directed, or agreed to pay or
direct, any benefits to any research fund, foundation, educational
institution, or other charitable or nonprofit organization with which the
authors are affiliated or associated.
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Abstract
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Recurrent posterior shoulder instability is an uncommon, debilitating
condition in young adults that is being diagnosed with increasing
frequency.
Although a number of predisposing factors have been identified, their
relative importance remains poorly understood.
Poor results have been reported following operative intervention to treat
recurrent posterior instability with nonanatomic techniques.
The more recent development of lesion-specific surgery has improved
clinical results, particularly when that surgery has been performed
arthroscopically. Operative treatment is therefore being increasingly
recommended at an earlier stage to patients who do not respond to supervised
rehabilitation programs.
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Epidemiology
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Accurate assessment of the prevalence of posterior glenohumeral instability
is difficult because of the lack of concrete diagnostic criteria, but the
condition is estimated to be present in up to 5% of all patients with shoulder
instability1,2.
With increased awareness of the condition, it is being diagnosed more
frequently, particularly after sports
injuries3,4.
Affected patients are usually men between the ages of twenty and thirty
years and often are active and competitive athletes playing overhead or
contact sports. Although approximately 50% of patients report a discrete
injury to the shoulder that initiated the symptoms, a documented previous
episode of posterior dislocation requiring relocation is relatively uncommon:
only seventeen (23%) of seventy-four patients undergoing operative
stabilization for posterior instability reported such an episode in four
series in which this information was
recorded1,5-7.
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Classification and Pathogenesis
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Recurrent episodes of subluxation or dislocation may occur following
reduction of a first-time traumatic posterior dislocation. However, recurrent
instability most commonly presents with episodes of subluxation and there may
be no history of injury. The etiology of recurrent instability is complex and
multifactorial, and although several classification systems have been
suggested4,8,9
none are entirely satisfactory. Recurrent posterior instability is perhaps
best considered a syndrome in which the pathological processes are
incompletely understood and in which several predisposing factors may coexist
in the same patient (Fig.
1).
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Fig. 1 Venn diagram showing the known complex interactions in the etiology of
recurrent posterior instability.
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Volition
Many patients are able to voluntarily demonstrate the shoulder instability.
Three variations are described, although there is overlap and disagreement
about their exact defining
features4,10-12.
Psychogenic
Patients with psychological problems may be able to subluxate one or both
shoulders voluntarily (under conscious control), often with the arm at the
side, as a result of unbalanced muscle force
couples10,13.
These patients often develop instability during
adolescence8 for
secondary gain (to impress their peers, receive attention, or obtain
medication), and they have been described as
"habitual"10
or
"willful"13
dislocators4. An
involuntary element (without conscious control) to the instability, which
becomes symptomatic, may develop in some patients.
Positional
Some patients have subluxation that occurs involuntarily when the shoulder
is placed in the unstable position of flexion, adduction, and internal
rotation10,13,14.
As the arm moves into abduction from this position, the shoulder visibly and
audibly relocates. These so-called positional dislocators usually show no
evidence of psychological disturbance and are often more troubled by
instability than pain.
Muscular
The final, largest group of patients are commonly physically active,
psychologically normal athletes who play overhead or contact sports. They
present with posterior shoulder pain and involuntary subluxation, which
interferes with their sports performance. In contrast to habitual dislocators,
patients with muscular posterior dislocations most commonly have symptoms in
only one shoulder, which develop in early adult life (between the ages of
twenty and twenty-five
years)8. A subgroup
is able to voluntarily display the instability or has subluxation that is
demonstrable on
examination11,12,15.
Injury to the Shoulder
Recurrent posterior instability may develop following a posterior
dislocation5,16,17.
However, this is less common than recurrent anterior instability following an
anterior dislocation. Another group of patients, who have no confirmed
evidence of a prior dislocation, recall a substantial injury (usually a blow
to the front of the shoulder, or an axial loading injury to the arm, while the
shoulder is flexed) that initiated the problems
("macrotrauma")18-20.
In a third group, the symptoms develop insidiously, aggravated by repetitive
minor injury when the shoulder is in the provocative position of flexion,
adduction, and internal rotation. This "microtrauma" is
particularly associated with locked, straight-arm pass-blocking techniques in
American football; bench-pressing; and overhead sports such as baseball,
tennis, and
swimming20-22.
Degree of Instability
Recurrent posterior dislocation is much less common than recurrent
posterior subluxation. Most patients who experience frank episodes of
recurrent dislocation have had an initial traumatic dislocation, and many are
epileptics whose shoulders dislocate during seizures. Patients more commonly
present with a sense of shoulder instability or looseness when the shoulder is
in flexion, adduction, and internal rotation. A subgroup of patients with
recurrent subluxation have no symptoms of instability but experience a poorly
localized posterior shoulder ache when the arm is placed in this provocative
position.
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Structural Abnormalities of the Shoulder
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Soft Tissue
Tears of the posteroinferior aspect of the capsulolabral complex (a reverse
Bankart lesion) involving the posterior band of the inferior glenohumeral
ligament may be present. These lesions are more commonly found when there has
been a discrete injury to the
shoulder23-27,
and they may be degenerative in origin, caused by recurrent episodes of
instability17,19,27-29.
An incomplete and concealed avulsion of the posteroinferior aspect of the
labrum (a Kim
lesion30) may also
be associated with unidirectional or posteroinferior instability.
With recurrent subluxation, the capsule undergoes plastic deformation,
producing a patulous posteroinferior capsular
pouch1,3,29
and increased joint volume (Fig.
2)21.
Other lesions associated with recurrent instability include a reverse humeral
avulsion of the glenohumeral ligaments (RHAGL
lesion)31,32,
posterior labrocapsular periosteal sleeve avulsion (the POLPSA
lesion)33, osseous
avulsion of the posterior aspect of the glenoid rim (a reverse osseous Bankart
lesion), posterior chondrolabral erosion of the glenoid
rim27,29,34,
and a tear of the posterior aspect of the capsule or rotator
cuff35. Patients
with bidirectional (posterior and inferior) instability often have concomitant
insufficiency of the rotator interval, whereas those with multidirectional
(posterior, inferior, and anterior) instability usually have a generalized
increase in joint volume with posterior, inferior, and anterior capsular
redundancy.
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Fig. 2 T1-weighted magnetic resonance arthrogram of a lax posteroinferior aspect
of the capsule (arrows) in a patient with recurrent posterior instability.
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Bone
Instability may theoretically occur through increased glenoid retroversion,
posterior glenoid erosion, engaging anterior humeral head defects, localized
posteroinferior glenoid hypoplasia, or increased humeral head retrotorsion. No
clear association has been demonstrated between posterior instability and the
latter two
conditions36-38.
Glenoid version varies widely in the normal
population39,40,
and it cannot be assessed with conventional
radiography41,42.
Studies of the degree of association between glenoid retroversion and
posterior instability have produced conflicting
results12,34,43-45.
It is probable that excessive glenoid retroversion is rarely a primary cause
of instability but should be considered as a contributory
factor34,46.
Localized posterior glenoid erosion is often documented in patients with
instability19,21,47.
It may be due to localized glenoid hypoplasia or it may be secondary to
repeated subluxation. A relationship between the extent of glenoid erosion
seen on computerized tomography and recurrent instability was reported in one
study34, although
it has not yet been independently validated. Posterior glenoid erosion has
also been demonstrated in patients with fixed posterior subluxation of the
humeral head and glenohumeral
osteoarthrosis48.
However, these patients have no history of instability, and it is thought that
these changes represent an early form of
osteoarthrosis48.
Anterior humeral head defects caused by traumatic dislocation may cause
recurrent dislocation of the shoulder by engaging with the posterior part of
the glenoid rim as the arm is internally rotated.
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Directions of Instability
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Although recurrent unidirectional posterior subluxation may occasionally
occur in isolation, posterior instability more commonly develops as part of a
more complex bidirectional (posterior and
inferior)29,49
or multidirectional (posterior, inferior, and
anterior)29,50,51
pattern. There is often a family history of joint instability and evidence of
generalized ligament hyperlaxity or instability in both shoulders or in other
joints52.
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Scapulothoracic Dysfunction
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Disturbance of the normal coordinated scapulothoracic and glenohumeral
rhythm may be apparent in patients with
instability53,
although its importance is poorly understood. In many patients with so-called
positional instability, transient winging of the scapula develops as the
shoulder subluxates but there is no evidence of dysfunction of the long
thoracic nerve. It is often unclear whether the asynchrony of scapulothoracic
movement is contributory to the instability or whether it is an acquired
compensatory mechanism to prevent posterior escape of the humeral head.
Scapulothoracic dysfunction has recently been associated with fatigue of
the serratus anterior, which may occur in sports such as golf, in which the
muscle is constantly active in the lead arm of the swing. This may predispose
the shoulder to instability and
impingement54,55.
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Assessment and Diagnosis
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An examiner assessing a patient with suspected posterior instability should
attempt to answer two questions. First, does the patient have true instability
or some other cause for the symptoms? Second, what is the pathological
foundation for the instability? These questions are usually best answered on
the basis of the clinical history and examination, since the findings on
radiographic and arthroscopic assessments may be nonspecific.
Clinical Assessment
Recurrent subluxation typically presents with aching over the posterior
aspect of the shoulder together with a sense of shoulder instability. Symptoms
are usually present during periods of overuse, especially sports
activities18,47.
A history of trauma or volitional instability should be sought, and a
psychological assessment is indicated if habitual dislocation is
suspected.
If the patient has no sensation of
instability3,56,
other causes for the symptoms, including suprascapular nerve
entrapment57,
quadrilateral space
syndrome58, a
posterior glenoid spur (a Bennett
lesion)59,60,
early
osteoarthrosis48,
or a tumor, should be considered.
The physical examination is directed toward reproducing the symptoms and
direction of the shoulder instability. The signs of instability are often
nonspecific, and features of rotator cuff dysfunction or impingement may
coexist6,55.
Posterior shoulder laxity, with the humeral head subluxated by up to 50%, is
common in athletes and may not be pathological. Positive findings on
provocative tests may support the diagnosis of instability by demonstrating
excessive symptomatic posterior translation of the humeral head, rather than
apprehension18,19,22,61.
These tests include the load and
shift61, posterior
stress22, posterior
drawer62, and pivot
shift63 tests. The
patient may be able to demonstrate the instability, which may be associated
with scapular winging. It is important to determine the positions at which
subluxation occurs as well as the muscular activity involved in order to
distinguish among the various types of volitional instability.
The patient should be examined for signs of generalized ligamentous laxity
and to establish whether the instability is unidirectional, bidirectional, or
multidirectional by provocative
testing64. A
positive sulcus sign strongly suggests an inferior component to the
instability, which may be due to rotator cuff insufficiency or inferior
capsular attenuation. The integrity of the rotator interval capsule can be
confirmed by a lessening of the sign on external rotation of the
shoulder4. Patients
with unidirectional instability typically demonstrate subluxation on
provocative testing with the shoulder flexed to 80° to 90°, whereas
those with bidirectional instability exhibit more instability with the
shoulder flexed to 110° to
120°4. Patients
with multidirectional instability usually have more florid signs of
generalized ligamentous laxity and have excessive translation of the humeral
head in all directions on provocative testing. If the diagnosis is in doubt,
an examination with the patient under anesthesia and arthroscopic evaluation
of the shoulder may be
helpful65. Although
the arthroscopic findings may be nonspecific, detection of posterior
capsulolabral pathology is strongly suggestive of
instability1,27.
Imaging Studies
Standard radiographs often show normal findings in patients with suspected
instability23, but
they may be useful for revealing anterior impression defects of the humeral
head17,22,23
or posterior lesions of the glenoid
rim19. Magnetic
resonance arthrography is currently the best method for imaging capsulolabral
lesions66, whereas
computerized tomography is more useful for the assessment of the osseous
anatomy and the orientation of the articular surfaces.
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Treatment
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Operative treatment of posterior instability has a poor
reputation18,56.
Consequently, an initial trial of physical therapy is usually recommended,
irrespective of the predisposing
causes19,45,67.
It is thought that the poor results of operative intervention may have been
due to inappropriate patient selection or a failure to adequately treat all
pathological features of the condition. Operative treatment that corrects the
underlying pathology is therefore being increasingly offered at an earlier
stage to patients whose symptoms are refractory to nonoperative
measures24. The
operative treatment may involve more than one procedure to address the factors
contributing to the
instability24,49.
Factors Influencing the Choice of Operative Intervention
Volition
Operative treatment is contraindicated for patients with voluntary,
habitual instability due to psychological problems. Moreover, these patients
usually do not respond to physiotherapy regimens; hence, psychotherapeutic
treatment is
needed8,10.
The majority of other volitional subluxators, who do not have psychological
problems, usually report a decrease in the involuntary instability symptoms
after completing a program of
physiotherapy15,19,45.
This is particularly true of patients who have evidence of
hyperlaxity10,19,67,68.
Pain management, activity modification, and strengthening of the
scapulothoracic and rotator cuff muscles are all key elements of conservative
treatment67.
Promising results have also been achieved with use of biofeedback in
association with muscle retraining programs in patients with positional
instability14,69.
In the past, high failure rates have been reported following operative
treatment of patients with volitional
instability18,47.
However, recent studies have shown improved
results12, and
operative treatment is usually recommended if nonoperative treatment has
failed after six
months70.
Injury to the Shoulder
There is evidence that nonoperative treatment is less successful for
instability that commenced after a discrete injury to the
shoulder19,67.
Operative treatment is therefore often considered at an earlier stage for
these individuals.
Degree of Instability
Patients with episodes of frank posterior dislocation often have anterior
defects of the humeral head and posterior deficiencies of the glenoid rim,
which may contribute to recurrent
instability17,71.
If the patient has unstable epilepsy and is sustaining dislocations during
seizures, attempts must be made to reduce the frequency of the seizures by
adjusting the patient's medication before operative treatment is
considered.
When performing operative stabilization for recurrent dislocation,
the surgeon should attempt to address all components of the instability; the
operation may include bone-grafting of defects of the humeral head and glenoid
rim as well as posterior soft-tissue reconstruction to address capsulolabral
pathology. In the more common clinical scenario of recurrent
subluxation, a posterior soft-tissue stabilization procedure is
typically performed.
Structural Abnormalities of the Shoulder Soft-Tissue Injury
A wide variety of nonanatomic operative approaches, such as the reverse
Putti-Platt operation (plication of the infraspinatus and teres minor) and the
Boyd-Sisk procedure (transfer of the triceps to the posterior aspect of the
glenoid rim) have been advocated to treat the soft-tissue component of
posterior
instability17. The
recent trend has been toward lesion-specific treatment, whether performed as
open surgery or with arthroscopic techniques. Stabilization typically involves
repair of posteroinferior labral
defects6 and
retensioning of the redundant posteroinferior aspect of the capsule.
Open Techniques
Operative treatment is usually performed through a posterior
approach72. Access
is achieved by incising or splitting the infraspinatus
tendon20 or by
developing a plane between the infraspinatus and teres minor tendons while
protecting the axillary nerve and the posterior circumflex humeral
vessels73. If
improved visualization is required, the infraspinatus tendon can be incised
vertically and retracted medially, while the suprascapular nerve is
protected20.
A T-shaped capsulotomy is performed, and through this the posterior labral
avulsion can be reattached to the decorticated glenoid rim with use of bone
tunnels, bioabsorbable tacks, or suture anchors. Superior advancement and
plication of the posterior aspect of the capsule is then performed with
non-absorbable sutures to retension the posteroinferior capsular complex
(Fig.
3)20,23.
If the capsular tissue is attenuated, it can be reinforced with the
infraspinatus
tendon20,25.
Capsulorrhaphy with metal staples is contraindicated because of the
complications associated with its use, including pain, staple migration,
symptomatic ectopic bone formation, and
arthrosis3,56.
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Fig. 3 Schematic diagram of an open posterior capsular plication. The redundant
posteroinferior aspect of the capsule is retensioned by superiorly advancing
the inferior leaf (B) of the humeral-based T-shaped capsulotomy over the
superior leaf (A). (Printed with permission of Jennifer Fairman, Fairman
Studios, Waltham, Massachusetts.)
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A four to six-week period of postoperative immobilization with an orthosis
holding the shoulder in neutral or external rotation is usually recommended to
reduce stresses on the
repair19,21,25,74.
Physiotherapy with isometric rotator-cuff-strengthening, proprioceptive, and
active range-of-motion exercises is commenced thereafter.
Arthroscopic Techniques
Arthroscopic stabilization has theoretical advantages over open repair,
including a better cosmetic result, less postoperative pain, and a shorter
hospital stay. However, posterior stabilization is technically
demanding2, and
because posterior instability is uncommon it is difficult for surgeons to gain
sufficient experience in its operative treatment. However, arthroscopic
stabilization is being performed with increasing frequency, and patients with
unidirectional instability with capsulolabral lesions are considered ideal
candidates for this
treatment2,6,27.
Arthroscopic procedures for unidirectional instability include posterior
labral repair (Fig. 4), with
use of techniques similar to those used in open repair, and plication,
superior shift, or thermal shrinkage of the posteroinferior aspect of the
capsule1,2,6,7,27,75.
Patients with a Kim lesion (an incomplete and concealed avulsion of the
posteroinferior aspect of the labrum) should be treated with conversion of the
concealed incomplete labral detachment to a complete tear, which is then
repaired with the posterior band of the inferior glenohumeral
ligament30.
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Fig. 4 A schematic diagram of a repair of a posteroinferior labral avulsion. With
use of suture anchors, the repair is effected by approximating the
posteroinferior capsulolabral complex to the decorticated glenoid labrum.
(Printed with permission of Jennifer Fairman, Fairman Studios, Waltham,
Massachusetts.)
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Subacromial decompression, rotator cuff repair, and repair of superior
labral tears (SLAP lesions) can also be performed arthroscopically if
coexistent impingement, cuff tears, or SLAP lesions are
encountered49,55,75,76.
A postoperative regimen similar to that used after open stabilization is
usually adopted.
Distortion of the Osseous Anatomy
Posterior glenoplasty, in the form of an opening wedge osteotomy with
interposition of bone graft, has been used to treat patients with excessive
glenoid
retroversion46,77-79.
A posterior bone-block operation has also been used as a primary procedure in
patients with deficiency of the posterior wall of the
glenoid80,81,
or when the posterior aspect of the capsule is
attenuated19. Both
of those procedures are now much less commonly used primarily.
Soft-tissue techniques, such as the McLaughlin
procedure82, tend
to be ineffective for the treatment of anterior defects of the humeral head
that are large enough to engage with the posterior aspect of the glenoid. The
use of either an osteochondral allograft to fill the defect or a rotational
osteotomy of the proximal part of the humerus theoretically is the most
effective treatment, although there are no clinical data about their use in
these circumstances.
Directions of Instability
Patients who have bidirectional or multidirectional instability usually
respond to a rehabilitation program similar to that prescribed for patients
with volitional instability. The prospects for successful operative treatment
of patients who do not respond to physiotherapy have improved recently.
Whether operative treatment is performed open or arthroscopically, the surgeon
should attempt to treat all directions of
instability49,83,84.
In addition to a posteroinferior capsular shift, an anterior and inferior
shift and closure of the rotator interval may be
required84-86.
Adjuvant arthroscopic thermal or laser-assisted capsular shrinkage has also
been used to reduce joint
volume29,51,84,87.
While successful results have been reported following these techniques, there
may be severe complications.
Scapulothoracic Dysfunction
In addition to the typical rehabilitation program of
rotator-cuff-strengthening, proprioceptive, and range-of-motion exercises,
periscapular strengthening exercises are usually emphasized for patients who
have disturbance of normal scapulohumeral
rhythm88. Only
rarely is scapular winging severe enough to warrant separate surgical
intervention89.
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Outcome of Treatment of Recurrent Posterior Instability
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Although several well-designed Level-IV case-series studies have been
performed, we are not aware of any peer-reviewed comparative Level-I or II
studies. Studies have varied with regard to their inclusion criteria, case
mix, operative techniques, and duration of follow-up (see Appendix). Many
methods, with use of a variety of scoring systems, have been employed to
assess functional outcome, and this makes objective comparisons difficult.
The chief outcome measure that has been consistently recorded is the rate
of recurrent instability, but its use as a benchmark of success is simplistic.
While some patients with postoperative recurrence rate their operation as a
failure, others have a decrease in subjective instability and functional
incapacity despite the continuation of the
subluxations29,45.
The results of open operative treatment of unidirectional soft-tissue
instability have been variable and unpredictable. The overall prevalence of
recurrent instability following open soft-tissue stabilization has been 24%
(forty-nine of 202 shoulders), with reported rates ranging from 0% (zero of
fourteen shoulders) to 83% (five of six shoulders) (see Appendix). However, of
the four studies with the highest recurrence rates, three involved the use of
the nonanatomic reverse Putti-Platt
procedure18,45,78
and one involved the use of staple
capsulorrhaphy3 in
half of the patients. If those studies are excluded, the overall rate of
recurrent instability is only fourteen (11%) of 130 shoulders.
The outcomes following open glenoid osteotomy and bone-block procedures,
whether used in isolation or combined with capsulorrhaphy, have been generally
poor, with recurrence rates of nearly 25% for both techniques (see Appendix).
The methodological quality of some of the older studies of these techniques
was poor, with some authors assessing glenoid version
preoperatively47,77
and others using methodology that is now considered
inaccurate41,78.
As reported in the literature, the overall prevalence of recurrent
instability following arthroscopic stabilization for the treatment of
unidirectional posterior instability is 5% (eight of 154 shoulders), with
rates ranging from 0% (zero of thirteen shoulders) to 10% (two of twenty-one
shoulders) (see Appendix). Arthroscopic surgery was also used successfully in
two small series to treat competitive athletes with posterior instability or
labral
lesions26,55.
The results of arthroscopic stabilization in patients with bidirectional
(posteroinferior) instability, as reported in five studies (see Appendix), are
more heterogeneous but generally poorer than those of arthroscopic
stabilization of unidirectional posterior instability.
Both open and arthroscopic techniques have been used to treat patients with
multidirectional instability in which the major component was thought to be
posterior. Good results have been reported after the use of an anterior
approach to perform an anterior, inferior, and posterior capsular plication
and rotator interval closure to decrease joint
volume86. The
failure rate of open posteroinferior capsular shift through a posterior
approach has been higher in patients with multidirectional instability than it
has been in patients with more simple instability
patterns23,83.
However, patients with multidirectional instability often have undergone
previous, failed repairs for the instability, which may adversely affect the
results23.
Arthroscopic thermal capsulorrhaphy has also yielded poor results in a small
subgroup of patients who have multidirectional instability in which posterior
instability is the pre-dominant
component51.
Factors Associated with Recurrent Instability After Operative Repair
Factors contributing to the failure of posterior repairs include
inappropriate patient selection and surgical
error3,10.
However, irrespective of its quality, a repair can fail if the shoulder is
reinjured1,12,27
or if an athlete returns to a sport that inflicts repetitive microtrauma on
the shoulder90.
Inappropriate selection of patients for surgery is usually due to
inadequate preoperative assessment. Failure is almost inevitable if operative
treatment is performed on a habitual
dislocator10, and
it is more likely if a simple posterior repair without capsular retensioning
is carried out in a patient with bidirectional or multidirectional
instability3,23,83.
Higher rates of failure have also been reported in patients with Workers'
Compensation
claims1,29
and in those with a previous failed
repair12,23,29.
While some authors have reported poorer results in patients with voluntary
instability5,47,
this has not been found in other
studies3,10,19,23,83.
The most common surgical error is a failure to address all components
contributing to instability. Failure to treat a rotator interval lesion, a
concomitant inferior or anterior component of the
instability46,
excessive glenoid retroversion, a Kim lesion, or posterior erosion of the
glenoid rim increases the likelihood of postoperative
recurrence23.
Deficient capsulolabral tissues may also preclude a satisfactory soft-tissue
repair, thus predisposing to
recurrence19.
Failed Operative Repair
The results of the few reports of the outcomes following revision posterior
stabilization suggest high failure rates when compared with those of primary
posterior
stabilization12,23,29.
Evidence-based guidelines for the operative treatment of failed posterior
repairs are lacking, but attempts should be made to address all components of
the instability90
with use of a lesion-specific approach.
Other Complications of Treatment
Complications of open repairs include
infection19,
neurovascular
injury91,
pain86,
weakness25, and
shoulder stiffness (particularly loss of internal
rotation)3,92.
The alteration of joint kinematics following a tight open repair may
predispose a patient to degenerative joint disease. Fuchs et al. reported
asymptomatic degenerative changes in six (23%) of twenty-six shoulders treated
with posterior
stabilization12,
and osteoarthritic changes have been reported in other
studies25,45,83,86.
Staple capsulorrhaphy has been associated with pain, joint erosion and
arthrosis, anterior instability, and staple migration and has fallen out of
favor as a
result3,56.
Because of the high risk of severe complications with both posterior
bone-block19,23,90
and glenoid
osteotomy18,41,44,93,
neither of these treatments is now commonly used as a primary therapeutic
intervention47,77,78,94.
Arthroscopic posterior stabilization is more demanding technically than is
anterior stabilization because of the difficulty of gaining access and the
poor quality of the posterior capsulolabral tissue, which may lead to an
inadequate repair2.
The use of adjunctive thermal capsulorrhaphy has also been associated with an
increased risk of axillary nerve injury, biceps tendon rupture, adhesive
capsulitis, and recurrent instability with capsular
insufficiency51,75,95-98.
Some patients also report pain or subjective stiffness, which may be
associated with loss of internal
rotation7,76.
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Overview
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In summary, most patients with recurrent posterior instability notice
lessening or eradication of the symptoms following a shoulder physiotherapy
rehabilitation program, and this remains the initial treatment of choice. The
results of operative treatment of posterior instability are not as good as
those of operative treatment of anterior
instability99.
However, the use of lesion-specific surgery to correct all components of the
posterior instability appears to have improved results over the last ten
years. Operative stabilization can now offer a good chance of success and
should be recommended to patients who have persistent, symptomatic,
nonhabitual instability following a six-month course of physiotherapy.
The best outcomes appear to follow an open or arthroscopic soft-tissue
procedure to repair posterior labral pathology and to retension the
posteroinferior capsulolabral complex. More complex patterns of instability
may require adjuvant retensioning of the inferior and anterior aspects of the
capsule and a closure of the rotator interval. Osseous procedures should be
reserved for the very rare patient with definite evidence of marked glenoid
erosion or glenoid retroversion that is thought to contribute to the
instability.
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Appendix
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Tables showing reported recurrence rates following various types of
surgical procedures are available with the electronic versions of this
article, on our web site at
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the article citation and click on "Supplementary Material") and on
our quarterly CD-ROM (call our subscription department, at 781-449-9780, to
order the CD-ROM).
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Abstract
Epidemiology