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Reverse Total Shoulder Arthroplasty: Current Concepts, Results, and
Component Wear Analysis
D. Nam, C.K. Kepler, A.S. Neviaser, K.J. Jones, T.M. Wright, E.V. Craig and R.F. Warren
J Bone Joint Surg Am. 2010;92:23-35. doi:10.2106/JBJS.J.00769
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C OPYRIGHT Ó 2010
BY
T HE J OURNAL
OF
B ONE
AND J OINT
S URGERY, I NCORPORATED
Reverse Total Shoulder Arthroplasty: Current
Concepts, Results, and Component Wear Analysis
By D. Nam, MD, C.K. Kepler, MD, A.S. Neviaser, MD, K.J. Jones, MD, T.M. Wright, PhD, E.V. Craig, MD, and R.F. Warren, MD
Introduction
fter its introduction in the 1970s, reverse total shoulder
arthroplasty had minimal clinical success, as its constrained design and lateralized glenohumeral center of rotation
led to excessive shear forces and failure of the glenoid component1,2. Modern implant design modifications have emphasized a larger radius of curvature of the glenoid component and
movement of the center of shoulder rotation medially and
distally, creating a more stable and efficient fulcrum and decreasing shear forces at the glenoid-bone interface3,4. Since receiving U.S. Food and Drug Administration (FDA) approval in
2003, reverse total shoulder arthroplasty has become popular
for use for more than rotator cuff-tear arthropathy; its uses
include treatment of failed conventional total shoulder
arthroplasties, rheumatoid arthritis in patients with an irreparable cuff tear, proximal humeral tumors, and proximal humeral fractures with anterosuperior escape5,6. However, with
major complication rates as high as 26%7, limited implant
longevity, and a lack of long-term functional outcome data,
concerns have continued about its widespread use2.
A
Source of Funding
There was no external funding source for this investigation.
Biomechanics of the Glenohumeral Joint
ithout injury, the glenohumeral joint possesses remarkable mobility and is able to remain stable over the majority of an individual’s life span. While both static and dynamic
restraints contribute to its stability, the glenohumeral joint lacks
substantial intrinsic osseous constraints8,9. Although the glenoid
and the humeral head have similar shapes, they differ substantially
in size. Warner demonstrated that the spherical humeral head has
an articular surface area of approximately 21 to 22 cm2, while that
of the glenoid is 8 to 9 cm2, with a maximum contact area of only
4 to 5 cm2 between the two surfaces10. This limited contact area
and the shallow glenoid fossa enhance glenohumeral motion.
The static restraints of the glenohumeral joint consist of
the negative pressure within the glenohumeral joint capsule
due to the quality of the synovial fluid within the closed
compartment; the glenoid labrum, which increases both the
depth of the glenoid fossa and its surface area; and the stabi-
W
lizing properties of the ligaments, tendons, and skeletal muscles
surrounding the joint, with each playing a role in stabilizing the
glenohumeral joint through a particular range of motion9.
The dynamic constraints play a critical role through the
midranges of motion, stabilizing the joint under large external
loads, as the activating shoulder muscles dynamically center the
humeral head within the glenoid fossa. The rotator cuff tendons provide dynamic stabilization of the shoulder, by creating
a compressive force within the concavity of the glenoid fossa, and
are critical for glenohumeral stability throughout its range of motion9. While the rotator cuff creates a net inferior and compressive
vector, the strong deltoid muscle provides a superiorly directed
force, resulting in a balanced ‘‘force coupling’’ of the glenohumeral
joint. In addition, anterior and posterior force vectors are balanced
by the subscapularis, teres minor, and infraspinatus11.
Pathology of Rotator Cuff-Tear Arthropathy
otator cuff-tear arthropathy was originally described in
1983 by Neer et al., who described a massive rotator cuff tear
as the initial event in the development of degenerative arthritis12.
Both mechanical and nutritional factors may precipitate the
development of rotator cuff-tear arthropathy (Fig. 1)13. Mechanical contributors arise from disruption of the force coupling
mechanism, as attempts at elevation or rotation of the humerus
can cause instability and recurrent posterior subluxations as a
result of an unbalanced subscapularis. In addition, a deficient
rotator cuff may allow excessive upward migration of the humeral head, resulting in abnormal pressure and degenerative
changes in the acromion, acromioclavicular joint, and coracoid.
In the most severe situation, with loss of the subscapularis
muscle and a grossly deficient rotator cuff, anterior and superior
escape of the humeral head may occur (Fig. 2). In addition,
without the inferior and compressive action of the rotator cuff,
when the patient attempts to abduct the shoulder, the unopposed contraction of the deltoid creates a force vector that
causes the humeral head to be displaced superiorly, leading to
pseudoparalysis of shoulder elevation (defined as ‘‘an inability
to actively elevate the arm in the presence of free passive range
of motion, and in the absence of a neurologic lesion’’)4.
Nutritional factors also contribute to the onset of rotator
cuff-tear arthropathy, as a full-thickness rotator cuff tear vio-
R
Disclosure: The authors did not receive any outside funding or grants in support of their research for or preparation of this work. Neither they nor a member
of their immediate families received payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity.
J Bone Joint Surg Am. 2010;92 Suppl 2:23-35
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Fig. 1
Both mechanical factors (left) and nutritional factors (right) contribute to joint destruction in rotator cuff-tear arthropathy. (Reproduced with modification from: Neer CS 2nd, Craig EV, Fukuda H. Cuff-tear arthropathy. J Bone Joint Surg Am. 1983;65:1232-44.)
lates the closed joint space, allowing synovial fluid to leak into
the surrounding soft tissue. The negative fluid pressure that is
key for shoulder stability is decreased, as is the quality and
quantity of the synovial fluid, with resultant cartilage and os-
seous atrophy. In addition, reduced shoulder motion and
function of the glenohumeral joint, recurrent bloody effusions,
and loss of glycosaminoglycan content of the cartilage further
accelerate the destruction of both articular and periarticular
structures8,12,14.
The term ‘‘rotator cuff-deficient arthritis’’ is used to describe arthritis in a shoulder with a massive rotator cuff tear,
regardless of whether the cuff tear was the inciting event. Inflammatory causes of rotator cuff-deficient arthritis, emphasizing biomechanical factors rather than instability and deficient
cartilage nutrition, have also been proposed. In 1981, Halverson
et al. hypothesized that calcium phosphate crystals are formed
in the diseased shoulder synovium and articular cartilage and
are then released into the synovial fluid13. Phagocytosis of these
crystals precipitates an immunologic cascade, including the
release of collagenase, leading to destruction of the rotator cuff
tendon and articular cartilage, which then leads to further release of calcium phosphate crystals8,13,15. Therefore, numerous
pathologic causes have been proposed for the development of
rotator cuff-deficient arthritis.
Evolution of Treatment Options for Rotator
Cuff-Tear Arthropathy
otator cuff-deficient arthritis of the shoulder has proved to
be a difficult condition to treat successfully, and a surgical
option that both relieves pain and improves shoulder function has been elusive. Treatment options have included, but are
not limited to, nonoperative management, glenohumeral arthrodesis, resection arthroplasty, constrained or conventional
total shoulder arthroplasty, and hemiarthroplasty16-18. However,
patient dissatisfaction with functional outcomes and high longterm complication rates with traditional management have
revived interest in reverse total shoulder arthroplasty.
R
Fig. 2
Clinical picture of the left shoulder in a patient with rotator cufftear arthropathy, demonstrating anterior (left arrow) and superior
(right arrow) escape of the humeral head resulting from loss of
the subscapularis with a grossly deficient rotator cuff.
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Fig. 3-A
R E V E R S E T O TA L S H O U L D E R A R T H R O P L A S T Y : C U R R E N T C O N C E P T S ,
R E S U LT S , A N D C O M P O N E N T W E A R A N A LY S I S
Fig. 3-B
Fig. 3-A Anteroposterior radiograph of the right shoulder after a glenohumeral arthrodesis. (Reprinted from: Scalise JJ, Iannotti JP.
Glenohumeral arthrodesis after failed prosthetic shoulder arthroplasty. Surgical technique. J Bone Joint Surg Am. 2009;91 Suppl
2[Pt 1]:30-7.). Fig. 3-B Anteroposterior radiograph of the right shoulder after a constrained total shoulder arthroplasty. (Reprinted
from: Post M, Haskell SS, Jablon M. Total shoulder replacement with a constrained prosthesis. J Bone Joint Surg Am. 1980;62:
327-35.)
A trial of nonsurgical management, including activity
modification, oral analgesics and anti-inflammatory medications, corticosteroid injections, fluid aspirations, and gentle
range-of-motion exercises, should initially be considered for
most patients. Patients may remain asymptomatic, or be able to
cope with the pain, while maintaining an acceptable degree of
function if the deltoid remains intact and can thus provide an
adequately stable fulcrum of motion19,20. Of note is the fact that
repeated intra-articular injections have been shown to have diminishing utility in the treatment of rotator cuff-tear arthropathy, in addition to increasing the risk of iatrogenic infection;
thus, repeated injections are not recommended20. Despite the
use of nonoperative modalities, most patients continue to have
unremitting shoulder pain in addition to worsening function,
and thus surgical options must be considered.
The aim of glenohumeral arthrodesis is to provide pain
relief by eliminating shoulder motion. Arntz et al. described the
use of glenohumeral arthrodesis as a salvage procedure for
patients who had had multiple prior surgical procedures and
had rotator cuff-tear arthropathy, an irreparable cuff defect,
and a deficient anterior part of the deltoid muscle (Fig. 3-A)21,22.
However, poor bone quality often makes this procedure tech-
nically difficult, with a high risk of nonunion. In addition, a
lack of motion of the glenohumeral joint, and a compensatory
increase in scapulothoracic motion, may expose the acromioclavicular joint to excessive motion and cause pain22,23.
Resection arthroplasty has been attempted in the past, but
it is very rarely indicated as it produces a flail shoulder, with a high
risk of inferior instability and brachial plexus traction neuritis8.
Shoulder arthroplasty should be considered for a patient
for whom nonoperative management has failed and who has a
functional deltoid muscle and preferably an intact coracoacromial arch24. Numerous arthroplasty implant designs have been
proposed for the treatment of rotator cuff-tear arthropathy, with
constrained total shoulder arthroplasty being one of the earliest.
In this design, the humeral component is allowed to move
within the glenoid component, with the intent of providing a
stable, fixed fulcrum through which the deltoid can move the
humerus (Fig. 3-B). Initially considered a solution for rotator
cuff-tear arthropathy, constrained total shoulder arthroplasty
has been abandoned because of complication rates reportedly as high as 87.5%, as excessive interface stresses due to
the constrained design cause rapid component loosening
and failure25-27.
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Similarly, semiconstrained total shoulder arthroplasty implants have had little clinical success. The goal of this type of
arthroplasty is to utilize an enlarged glenoid component that
possesses a superior hood in order to resist superior humeral
migration. However, Orr et al. demonstrated that these implant
designs create increased tensile stresses at the inferior portion of
the glenoid component-bone interface28, and both Neer et al.29
and Amstutz et al.30 reported that the prevalence of radiolucency
surrounding these hooded glenoid components is higher than
that associated with standard total shoulder arthroplasty implants.
Neer et al. retrospectively reviewed the results of conventional total shoulder arthroplasty in the treatment of rotator
cuff-tear arthropathy in sixteen patients, with all but one patient
demonstrating a successful result with ‘‘limited goals’’ rehabilitation29. In addition, other authors have demonstrated vastly
improved results in patients with a repairable rotator cuff tear
as compared with those with an irreparable tear31,32. However,
Franklin et al. retrospectively reviewed the results in fourteen
patients with rotator cuff-tear arthropathy treated with conventional total shoulder arthroplasty and reported that 50%
demonstrated glenoid component loosening33. In those patients,
superior displacement of the humeral head led to eccentric
loading of the glenoid component, causing a ‘‘rocking horse’’
phenomenon of glenoid loosening (Fig. 4). Because of the high
risks of edge loading and glenoid component failure, conventional total shoulder arthroplasty is no longer considered an option for the treatment of rotator cuff-tear arthropathy associated
with an irreparable rotator cuff tear.
Hemiarthroplasty has proven to be an appropriate surgical
procedure for rotator cuff-tear arthropathy, as it avoids the complications of glenoid loosening, in addition to providing pain
relief and acceptable shoulder motion. Williams and Rockwood34
R E V E R S E T O TA L S H O U L D E R A R T H R O P L A S T Y : C U R R E N T C O N C E P T S ,
R E S U LT S , A N D C O M P O N E N T W E A R A N A LY S I S
reported the use of hemiarthroplasty in twenty-two rotator cuff-deficient shoulders, with eighteen of the twenty-two
patients demonstrating a satisfactory result according to the
limited-goals criteria described by Neer et al.29. In addition, all
patients had better pain scores. However, concerns regarding
limited improvements in shoulder motion and risks of glenoid
and acromion resorption have been raised. In addition, SanchezSotelo et al. reported anterosuperior instability in seven of thirty
patients treated with hemiarthroplasty, with only 67% of the
procedures being graded as successful at an average of five years
postoperatively17. Also, Dines et al. noted that conventional
total shoulder arthroplasty performed as a revision of a hemiarthroplasty in a patient with rotator cuff-tear arthropathy
demonstrated uniformly poor results35. Instability continues to
be a long-term concern, especially in patients with a prior subacromial decompression, resected coracoacromial ligament, incompetent coracoacromial arch, or deltoid weakness17.
Reverse total shoulder arthroplasty has been reintroduced to
treat rotator cuff-tear arthropathy, as implant designs have been
modified in an attempt to solve the dilemma of providing both
glenohumeral stability and improved shoulder biomechanics. While
modern prostheses are not fully constrained, the congruent joint
surfaces of the reverse ball-and-socket design provide inherent stability, while moving the joint center of rotation medially and distally
to increase deltoid function and the range of motion3,36,37. However, a
lack of long-term functional outcome data, questions regarding
implant longevity, and reported major complication rates as high as
26% have continued to raise concerns about this procedure2,7.
The Modern Reverse Total Shoulder Arthroplasty
he modern reverse total shoulder prosthesis is based on
the design that Paul Grammont described in 1985 (Fig. 5)37.
T
Fig. 4
Axillary view radiograph of the right shoulder, demonstrating radiolucencies surrounding the glenoid
component (arrows).
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Distal displacement of the center of joint rotation increases the lever arm of the deltoid and also recruits portions
of the anterior and posterior heads of the deltoid to act as
abductors of the arm, permitting elevation above shoulder
height (Fig. 7). In addition, reestablishment of the subacromial space permits greater potential abduction prior to impingement. However, the contribution of the deltoid to external
rotation may be minimized as a result of medial displacement
of the humerus, which leads to a decreased amount of the
posterior head of the deltoid being recruited for external
rotation37. Whether the theoretical biomechanical benefits of
the Grammont prosthesis will translate into successful longterm results has yet to be proven, but early results have been
promising.
Biomechanical Descriptions of Reverse Total
Shoulder Arthroplasty
everal investigations have provided insight into the functioning of this implant design. Harman et al. performed an
in vitro assessment of glenosphere fixation and loosening utilizing
a Sawbones model. Independent variables analyzed were the offset
magnitude and the screw type and arrangement, while dependent
variables were the shoulder range of motion and baseplate motion39. They noted that, under increased loads, increasing the
offset of the glenosphere resulted in greater micromotion at the
baseplate, which may interfere with osseous ingrowth, thus supporting the advantage of a medialized center of rotation to decrease stress at the bone-implant interface. De Wilde et al. utilized
computer modeling of the glenohumeral joint and deltoid function in the scapular plane to compare reverse total shoulder arthroplasty with the native shoulder and with conventional total
shoulder arthroplasty, with regard to deltoid length and muscle
tension with shoulder motion40. They concluded that the reverse
total shoulder arthroplasty design was superior to the conventional total shoulder arthroplasty in terms of abduction strength
of a rotator cuff-deficient shoulder, as placing the center of rotation distally improved deltoid muscle tension.
Gutiérrez et al. evaluated the stability of the glenosphere
on the basis of the implant abduction angle41. They analyzed the
forces and micromotion in glenoid components attached to
polyurethane blocks placed in an apparatus simulating glenohumeral joint motion. They concluded that 15° of inferior tilt
of the glenoid component provided the most uniform compressive forces and the least amount of micromotion when
compared with baseplates implanted with 0° and 15° of superior
tilt, suggesting that an implantation angle of 15° of inferior tilt
may improve stability.
Chou et al. evaluated the effect of glenosphere geometry
(concentric versus eccentric) and offset on glenohumeral motion in a Sawbones model42. They noted that a larger glenosphere
diameter increased both adduction and abduction of the shoulder, and the addition of an eccentric diameter further increased
adduction while decreasing the amount of lateral positioning of
the center of rotation. Therefore, they concluded that eccentric
glenosphere geometry may minimize notching while also decreasing shear forces at the bone-implant interface.
S
Fig. 5
Grammont’s original reverse total shoulder arthroplasty. (Reprinted, with permission from Elsevier,
from: Boileau P, Watkinson DJ, Hatzidakis AM, Balg
F. Grammont reverse prosthesis: design, rationale,
and biomechanics. J Shoulder Elbow Surg.
2005;14[1 Suppl S]:147S-61S.)
Prior attempts to create a fixed fulcrum for shoulder motion,
through the use of constrained implants, led to limited motion and early failure due to excessive torque on the glenoid
implant and failure to optimize deltoid function. Earlier reverse ball-and-socket designs typically included a small glenoid component and a lateralized center of rotation within the
prosthesis, rather than within the glenoid. This led to increased stresses at the glenosphere (glenoid component)bone interface and thus early component failure (Fig. 6-A)38.
Key aspects of the modern reverse total shoulder arthroplasty
include (1) a large glenosphere component with no neck,
which allows medialization of the center of rotation and reduced torque on the glenoid component; (2) a humeral implant with a nonanatomic valgus angle, which moves the
center of joint rotation distally, thus maximizing the length
and tension of the deltoid to increase its ability to abduct the
humerus, in addition to providing increased stability; and (3)
a greater range of shoulder motion prior to impingement
(Fig. 6-B)37,38.
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TABLE I Summary of Reports of Clinical Outcomes Following Reverse Total Shoulder Arthroplasty
No.
Duration of
Follow-up (mo)
484
52
90% satisfied or very satisfied
Constant, 62.0
80
44
96% no or little pain
Constant, 65.6
45
58
38
Subjective shoulder value, 56%
Constant, 64
3
45
40
82% satisfied or very satisfied
Constant, 58
46
60
33
68% good or excellent
ASES, 68.2
240
40
93% satisfied or very satisfied†
Constant, 60†
49
38
89% good or excellent
ASES, 70
Study
43
Molé and Favard , Rev Chir Orthop
Reparatrice Appar Mot, 2007
44
Sirveaux et al. , J Bone Joint Surg Br, 2004
Werner et al. , J Bone Joint Surg Am, 2005
Boileau et al. , J Shoulder Elbow Surg, 2006
Frankle et al. , J Bone Joint Surg Am, 2006
7
Walch et al. , 2006
47
Wall et al. , J Bone Joint Surg Am, 2007
48
Young et al. , J Shoulder
Elbow Surg, 2009
Subjective Outcomes
Functional Score*
457
*ASES = American Shoulder and Elbow Surgeons. †The percentage is of the patients who retained the implants.
Fig. 6-A
Fig. 6-B
Fig. 6-A and 6-B Diagrams demonstrating an earlier reverse total shoulder prosthesis design, with a small glenosphere component and a
lateralized center of rotation (Fig. 6-A), versus the modern design, with a large glenosphere, a nonanatomic valgus angle of the humeral
implant, and medial and distal positioning of the center of rotation (Fig. 6-B). (Reprinted, with permission from Elsevier, from: Gartsman GM,
Edwards TB, editors. Shoulder arthroplasty. Philadelphia: Saunders; 2008.)
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TABLE I (continued)
Revision Rate
Component
Failure Rate
11% at 10 years
Complication Rate
Other
25.6% intraop. or postop.
Forward flex., 71°/ 130°
4%
6% loosening;
9% dissoc.
12% at 5 years;
71% at 7 years
16% grade-3 or 4 notching
33%
7% loosening;
9% dislocation;
2% dissoc.
50%
Revision reverse total
shoulder arthroplasty had
significantly worse results
22%
0% loosening
24%
7%
11% grade-3 or 4 notching
12%
17%
3%
Forward flex., 55° / 105°;
abduct. 41° / 102°
3% primary; 31%
revision; 26% overall
12% primary;
33% revision
20% had removal
or revision
0%
8% dislocation†
3%*
8%
Reports of Clinical Outcomes after Reverse Total
Shoulder Arthroplasty (Table I)
everse total shoulder arthroplasty has been shown to be
effective in treating pseudoparalysis of shoulder elevation
associated with a massive rotator cuff tear, with numerous
studies demonstrating initial improvements in shoulder motion
and patient satisfaction. However, most reports have presented
only midterm follow-up results, and despite these encouraging
midterm results, rates of complications and revisions have remained inordinately high. In one long-term analysis, Molé and
Favard reported the radiographic appearance of deterioration
after approximately five to six years, with clinical deterioration
appearing after approximately eight years43. Thus, additional
long-term studies are required to assess the duration for which
these implants can be expected to last4,43.
In a study of 484 patients followed for a mean of fifty-two
months, Molé and Favard43 reported improvements in the Constant score from 24 points preoperatively to 62 points postoperatively, significant improvements in pain relief, and increased
shoulder elevation from 71° to 130°. However, the authors noted
that 25.6% of the patients had either an intraoperative or a
postoperative complication, with the most common complication
being residual shoulder instability. In addition, they noted higher
complication rates among patients for whom the reverse total
shoulder arthroplasty was a revision procedure.
In a retrospective review of eighty reverse total shoulder
arthroplasties, with a mean duration of follow-up of forty-four
months and a mean patient age of 72.8 years, Sirveaux et al.44
reported an increase in the mean Constant score from 22.6 points
preoperatively to 65.6 points postoperatively, with 96% of the
patients having little or no pain and an increase in mean active
forward flexion from 73° to 138°. However, at the time of followup, 4% of the implants had failed and been revised. In addition,
R
Infection Rate
0%
Forward flex., 124°;
24% notching
6% were noted to have radiographic signs of loosening and 9%
demonstrated unscrewing of the glenosphere component. Scapular notching was noted radiographically in 64% of the cases, with
16% demonstrating grade-3 or 4 scapular notching. The overall
complication rates were 12% at five years and 71% at seven years.
Of note, the integrity of the teres minor was reported to be vital
for obtaining a good Constant score and postoperative shoulder
external rotation. Despite early promising results, concerns regarding long-term survivorship remain, as Sirveaux et al. noted
the survival rate at eight years was only 29% with ‘‘failure’’ defined
as revision of a component or substantial pain.
Werner et al. retrospectively reviewed the results of fiftyeight consecutive patients who had undergone a Delta III reverse total shoulder arthroplasty (DePuy France, Saint Priest,
France) at an average age of sixty-eight years45. Seventeen of
the procedures were the primary treatment, while forty-one
were revisions. On average, the subjective shoulder value (an
estimation by the patient of the value of his or her shoulder as
a percentage of an entirely normal shoulder) increased from
18% preoperatively to 56% postoperatively, the Constant
score increased from 29% to 64%, the Constant score for pain
increased from 5.2 points to 10.5 points (15 points indicating
pain-free), active anterior elevation increased from 42° to
100°, and active abduction increased from 43° to 90°. However, the total complication rate was noted to be 55%, with a
revision rate of 33%. Nine percent of the patients experienced
dislocation, and 7% demonstrated glenoid or humeral stem
loosening. In addition, it was noted that the reoperation rate was
lower and the final Constant scores and postoperative pain scores
were significantly improved in patients for whom the reverse total
shoulder arthroplasty was the primary procedure.
Frankle et al. reported the results of treatment with the
reverse shoulder prosthesis (RSP; Encore Medical, Austin,
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Fig. 7
55
A: The seven segments of the deltoid muscle, according to Kapandji . B: In a normal shoulder, only the middle deltoid segment (III)
and part of the anterior deltoid segment (II) can participate in active elevation. C: After implantation of a reverse prosthesis, the
medialization of the center of rotation recruits more of the deltoid fibers (segments I and IV) for active elevation. (Reprinted, with
permission from Elsevier, from: Boileau P, Watkinson DJ, Hatzidakis AM, Balg F. Grammont reverse prosthesis: design, rationale, and
biomechanics. J Shoulder Elbow Surg. 2005;14[1 Suppl S]:147S-61S.)
Texas) in sixty patients, who had an average age of seventyone years and were followed for an average of thirty-three
months46. They noted significant improvements in the mean
American Shoulder and Elbow Surgeons (ASES) score, from
34.3 to 68.2 points; the mean function score, from 16.1 to
29.4 points; and the mean pain score, from 18.2 to 38.7
points. Forward flexion increased from 55.0° to 105.1°, and
abduction increased from 41.4° to 101.8°. However, after
only thirty-three months of follow-up, there was a 17%
complication rate and 12% revision rate. Other reported re-
sults of reverse total shoulder arthroplasty are presented in
Table I3,7,43-48.
Thus, while the results of reverse total shoulder arthroplasty are encouraging with regard to the postoperative range
of motion, pain relief, and improvements in clinical outcome
measures, the high complication rates and necessity for revision procedures, especially in patients who have had multiple
operations, are justifiably troubling. Complications include,
but are not limited to, aseptic loosening, instability, glenosphere
dissociation, humeral disassembly, infection, humeral fracture,
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Fig. 8-A
Fig. 8-B
Intraoperative photographs of the glenoid baseplate being inserted via a deltopectoral approach
(Fig. 8-A) and the final positioning of the reverse total shoulder prosthesis (Fig. 8-B).
neurapraxia, and scapular notching3-5,44,49, with overall complication rates as high as 71% and revision rates as high as 33% in
mid-to-long-term follow-up studies44,45.
Key Aspects of Surgical Technique in Reverse Total
Shoulder Arthroplasty
roper implantation of a reverse total shoulder arthroplasty
prosthesis is technically demanding, and high complication
P
rates have led to the suggestion that only the most experienced
shoulder surgeons should utilize these prostheses2. While it is
impossible to review all of the technical aspects of this complex
procedure, certain key aspects will be emphasized.
Most surgeons employ a standard deltopectoral approach,
through which the subscapularis is incised. After implantation,
the subscapularis is repaired with the hope of both improving
humeral internal rotation and creating an anterior envelope to
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Fig. 9
Quadrants and scoring system utilized for grading each damage mode. (Reprinted, with permission
from Elsevier, from: Nho SJ, Nam D, Ala OL, Craig EV, Warren RF, Wright TM. Observations on retrieved
glenoid components from total shoulder arthroplasty. J Shoulder Elbow Surg. 2009;18:371-8.)
Fig. 10
Photographs of retrieved humeral implants demonstrating inferior-quadrant abrasion (a, arrow) and
diffuse third-body debris (b). (Reprinted, with permission from Elsevier, from: Nam D, Kepler CK, Nho
SJ, Craig EV, Warren RF, Wright TM. Observations on retrieved humeral polyethylene components
from reverse total shoulder arthroplasty. J Shoulder Elbow Surg. In press, 2010.)
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help prevent instability. In contrast, some authors have advocated the use of a superolateral approach, which obviates the need
for a subscapularis tenotomy and passes through the deltoid, and
these authors have reported lower rates of dislocation with this
approach. However, reported drawbacks of the superolateral approach are limited visualization leading to improper component
positioning and decreased external rotation postoperatively
compared with that associated with the deltopectoral approach7,50.
Regarding humeral preparation, the humeral head is typically osteotomized in neutral version, although there has been a
recent trend toward cutting the humerus in increased retroversion with the intent of improving postoperative external rotation.
Molé and Favard43 reported improved results with regard to the
Constant score, radiographic evidence of loosening, and glenoid
complications when the humeral cup was implanted in neutral
version. The humerus is reamed and broached in a manner
similar to that used for conventional total shoulder arthroplasty.
Most systems currently allow the same humeral stem to be
utilized for a hemiarthroplasty, conventional total shoulder arthroplasty, or reverse total shoulder arthroplasty, thus leaving
options available for intraoperative decision-making.
Glenoid preparation requires careful attention to the
amount of bone removed, and preoperative planning with
regard to the patient’s available bone stock is crucial. Central
guidewire placement is also critical, and factors that must be
considered include the best bone available for baseplate screw
fixation and placement of the baseplate as inferiorly as possible,
with an inferior tilt, as this has been shown to decrease the rate of
implant loosening and scapular notching51-53. The most critical
screw for fixation is the central screw, which should obtain fixation in the far cortex and is commonly 30 to 40 mm in length.
The most common length of the superior and inferior screws is
30 to 35 mm, while the most common length of the anterior and
posterior screws is 15 mm. Typically, locking screws are utilized
in the superior and inferior holes, while nonlocking screws are
utilized in the anterior and posterior holes (Figs. 8-A and 8-B).
Scapular notching remains a substantial concern in reverse
total shoulder arthroplasty, with rates reported to be as high as
98%, although the long-term clinical relevance remains unclear45. To minimize notching, the baseplate should be placed
flush with the inferior margin of the native glenoid, and the
glenosphere should be implanted with an inferior tilt of 10° to
15° to increase inferior clearance. Some surgeons prefer inferior
overhang of the glenosphere component, to further reduce the
risk of scapular notching. While the long-term effect of scapular
notching remains disputed, the presence of an adduction deficit
due to decreased clearance is consistent with the recent finding
of increased inferior quadrant damage in reverse total shoulder
arthroplasty humeral polyethylene components.
Retrieved Reverse Total Shoulder Arthroplasty
Humeral Polyethylene Components
nalyses of polyethylene components retrieved at revisions of total knee, hip, and shoulder replacements have
been used to study the impact of design, patient, and surgical
factors on implant performance. Recently, damage modes
A
R E V E R S E T O TA L S H O U L D E R A R T H R O P L A S T Y : C U R R E N T C O N C E P T S ,
R E S U LT S , A N D C O M P O N E N T W E A R A N A LY S I S
TABLE II Frequency and Severity of Nine Damage Modes*
Humeral Polyethylene
Components with
Damage (no. [%])
Average Wear
Score
Scratching
14 (100%)
8.79
Abrasion
13 (93%)
4.00
8 (57%)
2.25
Damage Mode
Embedded third-body
debris
Pitting
6 (43%)
2.50
Burnishing
4 (29%)
2.00
Surface deformation
3 (21%)
1.67
Fracture
1 (7%)
3.00
Wear through
1 (7%)
3.00
Delamination
0 (0%)
0.00
*Adapted from: Nam D, Kepler CK, Nho SJ, Craig EV, Warren RF,
Wright TM. Observations on retrieved humeral polyethylene components from reverse total shoulder arthroplasty. J Shoulder Elbow
Surg. In press, 2010. Reprinted with permission from Elsevier.
observed in retrieved reverse total shoulder arthroplasty
humeral polyethylene components have been reported 54 .
Fourteen consecutive reverse total shoulder arthroplasty
humeral polyethylene components retrieved at the time of
revision surgery in eleven patients were analyzed for nine
damage modes (abrasion, burnishing, scratching, pitting, wear
through, third-body wear, delamination, surface deformation,
and fracture) in each of four quadrants on the bearing surface
(Fig. 9). Scratching and abrasion were found in fourteen and
thirteen components, respectively, followed by third-body debris
and pitting (Fig. 10, Table II). All modes of damage were found
to be the greatest in the inferior quadrant.
The authors concluded that impingement of the humeral
polyethylene at the lateral edge of the scapula, consistent with an
adduction deficit, leads to inferior-quadrant wear and associated
polyethylene damage. In addition, the finding of third-body
debris was consistent with impingement leading to separation
between the bearing surfaces, allowing ingress of metallic debris.
Therefore, the results of analyses of reverse total shoulder arthroplasty polyethylene components point to the importance
of appropriate glenosphere positioning to improve component
stability and reduce polyethylene wear and damage.
Discussion
everse total shoulder arthroplasty has been shown to provide pain relief and improve function. Movement of the
glenohumeral center of rotation distally and medially improves
deltoid function and decreases glenoid implant-bone interface
stresses and loosening. Promising results of reverse total shoulder arthroplasty for the treatment of rotator cuff-tear arthropathy have led to its expanded use, and it has now become a surgical
option for failed conventional total shoulder arthroplasties, patients with rheumatoid arthritis and an irreparable rotator cuff
R
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tear, proximal humeral tumors, and proximal humeral fractures
with anterosuperior escape. However, rates of instability, implant
loosening, infection, fracture, and other complications remain
high, demonstrating the importance of strict patient selection,
operative experience, close patient follow-up for several years,
and future design modifications. n
D. Nam, MD
C.K. Kepler, MD
R E V E R S E T O TA L S H O U L D E R A R T H R O P L A S T Y : C U R R E N T C O N C E P T S ,
R E S U LT S , A N D C O M P O N E N T W E A R A N A LY S I S
A.S. Neviaser, MD
K.J. Jones, MD
T.M. Wright, PhD
E.V. Craig, MD
R.F. Warren, MD
Sports Medicine and Shoulder Service,
Department of Orthopaedic Surgery
(D.N., C.K.K., A.S.N., K.J.J., E.V.C., and R.F.W.)
and Department of Biomechanics (T.M.W.),
Hospital for Special Surgery,
535 East 70th Street,
New York, NY 10021.
E-mail address for D. Nam: namd@hss.edu
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