ArticlePDF AvailableLiterature Review

Abstract and Figures

Background: Scapular anatomy, as measured by the acromial index (AI), critical shoulder angle (CSA), lateral acromial angle (LAA), and glenoid inclination (GI), has emerged as a possible contributor to the development of degenerative shoulder conditions such as rotator cuff tears and glenohumeral osteoarthritis. The purpose of this study was to investigate the published literature on influences of scapular morphology on the development of degenerative shoulder conditions. Methods: A systematic review of the Embase and PubMed databases was performed to identify published studies on the potential influence of scapular bony morphology on the development of degenerative rotator cuff tears and glenohumeral osteoarthritis. The studies were reviewed by 2 authors. The findings were summarized for various anatomic parameters. A meta-analysis was completed for parameters reported in more than 5 related publications. Results: A total of 660 unique titles and 55 potentially relevant abstracts were reviewed with 30 published articles identified for inclusion. The AI, CSA, LAA, and GI were the most commonly reported bony measurements. Increased CSA and AI correlated with rotator cuff tears, whereas lower CSA appeared to be related to the presence of glenohumeral osteoarthritis. Decreased LAA correlated with degenerative rotator cuff tears. Five articles reported on the GI with mixed results on shoulder pathology. Discussion: Degenerative rotator cuff tears appear to be significantly associated with the AI, CSA, and LAA. There does not appear to be a significant relationship between the included shoulder parameters and the development of osteoarthritis.
Content may be subject to copyright.
Anatomic shoulder parameters and their
relationship to the presence of degenerative
rotator cuff tears and glenohumeral
osteoarthritis: a systematic review
and meta-analysis
Musa B. Zaid, MD*, Nathan M. Young, PhD, Valentina Pedoia, PhD,
Brian T. Feeley, MD, C. Benjamin Ma, MD, Drew A. Lansdown, MD
Department of Orthopaedic Surgery, University of California, San Francisco, San Francisco, CA, USA
Background: Scapular anatomy, as measured by the acromial index (AI), critical shoulder angle (CSA),
lateral acromial angle (LAA), and glenoid inclination (GI), has emerged as a possible contributor to the
development of degenerative shoulder conditions such as rotator cuff tears and glenohumeral osteoar-
thritis. The purpose of this study was to investigate the published literature on influences of scapular
morphology on the development of degenerative shoulder conditions.
Methods: A systematic review of the Embase and PubMed databases was performed to identify pub-
lished studies on the potential influence of scapular bony morphology on the development of degener-
ative rotator cuff tears and glenohumeral osteoarthritis. The studies were reviewed by 2 authors. The
findings were summarized for various anatomic parameters. A meta-analysis was completed for param-
eters reported in more than 5 related publications.
Results: A total of 660 unique titles and 55 potentially relevant abstracts were reviewed with 30 pub-
lished articles identified for inclusion. The AI, CSA, LAA, and GI were the most commonly reported
bony measurements. Increased CSA and AI correlated with rotator cuff tears, whereas lower
CSA appeared to be related to the presence of glenohumeral osteoarthritis. Decreased LAA correlated
with degenerative rotator cuff tears. Five articles reported on the GI with mixed results on shoulder pa-
thology.
Discussion: Degenerative rotator cuff tears appear to be significantly associated with the AI, CSA, and
LAA. There does not appear to be a significant relationship between the included shoulder parameters
and the development of osteoarthritis.
Level of evidence: Level IV; Systematic Review
Ó2019 Journal of Shoulder and Elbow Surgery Board of Trustees. All rights reserved.
Keywords: Critical shoulder angle; acromial index; glenoid inclination; acromial center-edge angle;
scapular morphology; shoulder shape; scapular shape; anatomic shoulder parameters
*Reprint requests: Musa B. Zaid, MD, Department of Orthopaedic
Surgery, University of California, San Francisco, 500 Parnasssus Ave, MU-
320 W, San Francisco, CA 94143, USA.
E-mail address: Musa.Zaid@ucsf.edu (M.B. Zaid).
J Shoulder Elbow Surg (2019) 28, 2457–2466
www.elsevier.com/locate/ymse
1058-2746/$ - see front matter Ó2019 Journal of Shoulder and Elbow Surgery Board of Trustees. All rights reserved.
https://doi.org/10.1016/j.jse.2019.05.008
Shoulder pain is a common complaint prompting evalu-
ation by orthopedic surgeons and primary care physicians,
with an annual estimated incidence of 14.7 per 1000 patients
in primary care and a lifetime prevalence of up to
70%.
23,26,52
With an aging population, degenerative shoulder
conditions such as rotator cuff tears and glenohumeral oste-
oarthritis are accounting for a majority of these complaints
and are the source of significant pain and disability.
Numerous studies have demonstrated the prevalence of ro-
tator cuff tears to be as high as 22% to 23%,
29,47
whereas the
prevalence of glenohumeral osteoarthritis has been estimated
to be as high as 26%.
48
As patients desire to remain active as
they age, we are beginning to see an increase in the utilization
of surgical resources for rotator cuff repair and shoulder
arthroplasty.
14,17
The development of degenerative shoulder conditions
such as rotator cuff tears and glenohumeral osteoarthritis is
likely multifactorial in nature, with contributors such as age,
sex, genetics, and trauma, although recent attention has been
directed to scapular morphology as a risk factor for the
development of these degenerative conditions.
37,40,53
The
relationship between scapular shape and the development of
rotator cuff tears was first described by Neer
33
in 1972 with
his observation of varying acromial morphology leading to
direct compression on the rotator cuff and resulting pathol-
ogy and has since been explored by numerous other authors
as well.
35
More recently, the critical shoulder angle (CSA),
acromial index (AI), lateral acromial angle (LAA), and gle-
noid inclination (GI) (Fig. 1), as well as myriad other scapular
measurements, have been introduced as potential radio-
graphic measurements that can distinguish which patients are
at risk of the development of rotator cuff tears or gleno-
humeral osteoarthritis.
The primary purpose of this study was to investigate the
influence of scapular morphology on the presence of
degenerative rotator cuff tears and glenohumeral osteoar-
thritis, as well as to identify the supporting literature for
these conclusions. A systematic review of the literature was
performed to summarize the currently available evidence
on this topic, and a meta-analysis was performed to
determine the influence of scapular morphologic parame-
ters on the presence of rotator cuff tears and glenohumeral
osteoarthritis.
Methods
Search strategy and inclusion terms
A systematic review of the literature was performed following the
standardized PRISMA (Preferred Reporting Items for Systematic
Reviews and Meta-analyses) protocol.
42
Prior to initiation of data
abstraction, this review was registered with PROSPERO (Inter-
national Prospective Register of Systematic Reviews). The search
criteria and objectives of the review were defined before a search
of the literature was conducted. Per the protocol, a search of the
English-language literature using PubMed and Embase was con-
ducted for all studies published prior to November 1, 2018. The
search terms used included the following: (rotator cuff tear and
acromial index) or (rotator cuff and critical shoulder angle) or
(rotator cuff and anatomic parameters) or (rotator cuff and scap-
ular shape) or (rotator cuff and scapular morphology) or (rotator
cuff and glenoid inclination) or (rotator cuff and predisposition) or
(arthritis and acromial index) or (arthritis and critical shoulder
angle) or (arthritis and anatomic parameters) or (arthritis and
scapular shape) or (arthritis and scapular morphology) or (gleno-
humeral arthritis and predisposition) or (glenohumeral arthritis
and predisposed).
All titles were reviewed independently by 2 reviewers
(D.A.L. and M.B.Z.) to determine the appropriateness for in-
clusion. All identified abstracts were then reviewed by both re-
viewers. The complete article from any abstract was
subsequently reviewed by 1 reviewer with data verification
performed by a second reviewer. Studies were included if they
included radiographic measurements of bony morphology at the
shoulder in patients with either symptomatic rotator cuff tears or
symptomatic osteoarthritis. Studies were excluded if they re-
ported on only biomechanical data, computer modeling, or
cadaveric findings.
Methodologic study assessment was performed using the Na-
tional Institutes of Health Quality Assessment Tool for Cross-
Sectional Studies. Each reviewer performed the study quality
assessment and recorded his responses (Supplementary Table S1).
Any discrepancies were reviewed by the 2 authors until a
consensus was reached.
Data extraction
Data extraction was performed with items of interest identified a
priori, including sample size of the study, demographic informa-
tion of each cohort, radiographic measurements, and disease
prevalence. The means and standard deviations of the included
anatomic parameters were recorded for analysis.
Meta-analysis
Anatomic parameters reported in more than 5 independent studies
were pooled in a meta-analysis using RStudio software (RStudio,
Boston, MA, USA). As all anatomic parameters were reported as
continuous measures, the pooled effects were presented as mean
differences with confidence intervals (CIs) with an inverse-
variance weighted method. Study heterogeneity was determined
by calculating the I
2
value; a random-effects model was used as
there was significant heterogeneity (I
2
>75%) among all studies.
Results
A search of the literature as outlined earlier resulted in
a total of 427 titles from MEDLINE and 404 from Embase.
A total of 660 unique titles were identified between the
2 searches. Fifty-five unique abstracts were identified
for further review based on the title alone. A total of
30 unique articles were included in the final anal-
ysis
2-5,8-10,12,13,15,16,19-21,24,27,30-32,38,39,41,43-46,49-51
(Fig. 2).
2458 M.B. Zaid et al.
All articles were published after 2004. One study was
longitudinal in nature,
12
with the remainder being cross-
sectional.
Of the studies, 19 examined the
CSA,
2,4,5,9,10,11,13,16,19,21,27,30-32,38,39,44,46,51
8 measured the
AI,
2,3,20,21,24,31,38,45
5 measured the LAA,
2,3,21,32,45
5
examined the GI,
4,5,8,11,16
2 measured the acromial
slope,
2,3
1 measured the acromial center-edge angle
(ACEA),
45
1 measured the acromial coverage index,
49
1
measured the greater tuberosity angle (GTA),
15
1 measured
the coracoid cavity ratio,
41
and 1 measured the coracoid
inclination.
49
All 30 studies included in this review
included a rotator cuff tear group, whereas 10 of these
studies included a glenohumeral osteoarthritis group as
well.
4,5,9,10,16,21,27,30,44,46
For the assessment of scapular parameters, 18 studies
used radiographs alone,
2,3,9,10,11,13,15,19-21,24,27,30-32,38,41,44
5
used plain radiographs and computed tomography (CT)
scans,
4,5,8,16,45
1 used magnetic resonance imaging and CT
scans,
11
and 1 used CT scans alone.
39
Critical shoulder angle
The CSA was significantly elevated in patients with isolated
rotator cuff tears compared with healthy controls in
numerous studies (Table I).
10,11,13,16,19,31,32,39,51
This
finding was consistent across multiple studies. When data
were pooled in a meta-analysis, the mean difference in the
CSA between patients with rotator cuff tears and control
patients was 1(95% CI, 0.59-1.44;P<.05; I
2
¼91%)
(Fig. 3).
In the only longitudinal study identified, Chalmers
et al
11
evaluated the CSA and its effect on the rotator
cuff over time. Although they found that patients with
rotator cuff tears had a significantly elevated CSA at the
time of enrollment (34vs. 32,P¼.003), the CSA did
not correlate with baseline tear size nor was the CSA
different in patients in whom tear enlargement occurred
over time.
One study examined how the CSA differed in patients
with full-thickness vs. partial-thickness tears and found that
the CSA was elevated in both groups compared with
healthy controls (41.01and 38.83vs. 37.28;P<.001
and P¼.02, respectively).
38
In addition, patients with
degenerative rotator cuff tears were found to have an
elevated CSA compared with those with traumatic rotator
cuff tears in 1 study (36.8vs. 35.3,P¼.007).
2
The CSA
appeared to be significantly elevated in patients with iso-
lated degenerative rotator cuff tears compared with those
with isolated glenohumeral osteoarthritis, with the mean
Figure 1 Radiographic measurements of selected anatomic shoulder parameters: critical shoulder angle (CSA) (A), glenoid inclination
(GI) (bangle method of Maurer et al
28
)(B), acromial index (AI) (GA, glenooid-acromial distance; GH, glenoid-humeral distance) (C), and
lateral acromial angle (LAA) (D).
Shoulder anatomy and degenerative conditions 2459
CSA ranging from 34to 34.5in patients with degenera-
tive cuff tears compared with 27.2to 28in patients with
glenohumeral osteoarthritis (P<.001 in all studies).
4,5,10
When comparing patients with cuff tear arthropathy with
those with isolated rotator cuff tears and those with isolated
glenohumeral osteoarthritis, 1 study found that the CSA
was significantly elevated in patients with isolated rotator
cuff tears compared with those with cuff tear arthropathy
(36.3vs. 35.2,P¼.006).
21
In addition, the CSA appeared
to be significantly elevated in patients with cuff tear
arthropathy compared with those with isolated gleno-
humeral osteoarthritis (35-35.2vs. 27.3-30,P<.001
for both studies).
27,38
A lower CSA appeared to be related to the presence
of isolated glenohumeral osteoarthritis. Although
numerous studies concluded this,
9,10,21,27,30,46
multivariate
analysis completed in 1 of the included studies did not
find any significant relationship between the CSA and the
presence of glenohumeral osteoarthritis.
44
When data
were pooled in a meta-analysis, the mean difference in
the CSA in patients with glenohumeral osteoarthritis was
1.42(95% CI, –2.50to –0.35;P<.01; I
2
¼94%)
less than that in controls (Fig. 4). One study did not find
a significant relationship between the CSA and the
presence of rotator cuff tears; however, the authors did
conclude that a lower CSA is associated with
glenohumeral osteoarthritis (rotator cuff tear group: 33.9
vs. 33.6,P¼.063; glenohumeral osteoarthritis group:
31.1vs. 33.2; odds ratio, 2.25; P¼.002).
9
Acromial index
Eight studies reported on the relationship between the AI
and rotator cuff tears,
2,3,20,21,24,32,38,45
and 1 of these 8
studies examined the relationship between the AI and the
presence of glenohumeral osteoarthritis.
21
The AI was
consistently significantly elevated in patients with rotator
cuff tears compared with healthy controls in all but 1 of the
included studies (Table II).
3,20,24,32,45
In the 1 study that did
not find a significant difference between groups, patients
with full-thickness rotator cuff tears were compared with a
composite group of patients with partial or no tears.
20
One study examined the AI in patients with full-thick-
ness tears vs. those with only partial-thickness tears, as well
as a control group.
38
The authors did not find a significant
difference in the AI between patients with full- and partial-
thickness tears; however, the AI in these 2 groups was
significantly elevated compared with the control group
(0.76 for full thickness, 0.74 for partial thickness, and 0.70
for healthy control; P¼.006 between full-thickness group
and no-tear group). In addition, the AI was noted to be
significantly elevated in patients with degenerative rotator
Figure 2 Flowchart of study design and included studies.
2460 M.B. Zaid et al.
cuff tears compared with those with traumatic rotator cuff
tears (0.77 vs. 0.73, P¼.0239).
2
When data were pooled in a meta-analysis, the mean
difference in the AI for patients with rotator cuff tears
compared with healthy controls was 0.75 (95% CI, 0.23-
1.27; P<.01; I
2
¼88%) (Fig. 5). One study examined the
relationship between the AI and rotator cuff tears, as well
as glenohumeral osteoarthritis, and found that the AI was
significantly elevated in patients with rotator cuff tears
compared with those with isolated glenohumeral osteoar-
thritis (0.74 vs. 0.63, P<.001).
21
Lateral acromial angle
A total of 5 studies examined how the LAA correlates with
the presence of rotator cuff tears, and 1 of these studies
examined how the LAA related to the presence of gleno-
humeral osteoarthritis. The LAA was consistently lower in
patients with rotator cuff tears compared with healthy
controls in all included studies (Table III).
3,32,45
One study found that the LAA was significantly lower in
patients with degenerative rotator cuff tears compared with
those with traumatic rotator cuff tears.
2
In addition, the LAA
appeared to be significantly lower in patients with isolated
rotator cuff tears compared with patients with glenohumeral
osteoarthritis (76.7vs. 89.5,P<.001), as well as patients
with cuff tear arthropathy (76.6vs. 82,P<.001).
21
Glenoid inclination
Five studies reported on the GI with varying results
regarding its relationship with rotator cuff tears. Different
methods to measure the GI were used by the various
authors.
Two studies concluded that the GI was significantly
lower in patients with rotator cuff tears compared with
patients with isolated glenohumeral osteoarthritis when
measured on plain radiographs using the bangle method of
Maurer et al
28
(78.7vs. 81.5,P¼.008),
4
as well as when
measured on CT scans (78.8vs. 82.0,P¼.008).
5
Simi-
larly, when examining patients with unilateral degenerative
rotator cuff tears, one study found that the GI was signifi-
cantly lower in the shoulder with the cuff tear than in the
healthy contralateral shoulder using methods previously
described by Hughes et al
22
to measure the GI (90.7vs.
92.3,P¼.04).
8
Two studies primarily used CT scans to measure the GI
and reported opposite results to those in the aforementioned
studies. Chalmers et al
11
measured the superior GI on
coronal CT scans that had been corrected such that the
glenoid was placed in the scapular plane. Using this
method, they found that patients with rotator cuff tears had
a significantly increased superior GI compared with control
patients (11vs. 9,P<.001). Daggett et al
16
measured the
GI on anteroposterior radiographs using the method of
Maurer et al
28
in which the bangle was subtracted from
90, as well as on coronal CT scans corrected to be in the
scapular plane. When measured on CT scans, the GI was
significantly elevated in the rotator cuff tear group
Table I Critical shoulder angle in rotator cuff tear patients
vs. control population
Critical shoulder angle,
mean (SD),
Pvalue
Rotator
cuff tear
Control
Blonna et al
10
(2016) 40 (3.5) 34 (3) <.001*
Chalmers et al
12
(2017) 34 (4) 32 (4) .013*
Cherchi et al
13
(2016) 36.4 (4.4) 33.3 (3.8) .02*
Daggett et al
16
(2015) 37.9 (3) 27.2 (3.4) <.001*
Gomide et al
19
(2017) 39.75 (3.37) 33.59 (5.35) <.007*
Moor et al
31
(2014) 37.8 (3.8) 31.9 (3.8) <.0001*
Moor et al
32
(2014) 38 (3.2) 33 (3.4) <.001*
Peltz et al
39
(2015) 36.9 (5) 34.5 (4.7) .03*
Watanabe et al
51
(2018)
34.4 (3.4) 32.1 (3.1) <.001*
SD, standard deviation.
*
Statistically significant (P<.05).
Table II Acromial index in rotator cuff tear patients vs.
control population
Acromial index, mean (SD) Pvalue
Rotator
cuff tear
Control
Balke et al
3
(2013) 0.75 (0.1) 0.67 (0.1) <.001*
Hamid et al
20
(2012) 0.692 (NR) 0.691 (NR) .92
Kum et al
24
(2017) 0.68 (NR) 0.63 (NR) <.001*
Moor et al
32
(2014) 0.75 (0.06) 0.66 (0.06) <.001*
Singleton et al
45
(2017)
0.755 (0.005) 0.69 (0.003) <.001*
SD, standard deviation; NR, not reported.
*
Statistically significant (P<.05).
Table III Lateral acromial angle in rotator cuff tear patients
vs. control population
Lateral acromial angle, mean
(SD),
Pvalue
Rotator
cuff tear
Control
Balke et al
3
(2013) 77 (6) 84 (6) <.001*
Moor et al
32
(2014) 80 (6.3) 86 (7.7) <.001*
Singleton et al
45
(2017)
76.48 (0.37) 79.71 (0.27) <.001*
SD, standard deviation.
*
Statistically significant (P<.05).
Shoulder anatomy and degenerative conditions 2461
compared with controls (13.6vs. 4.7,P<.001); however,
when measured on plain radiographs, the GI showed no
significant difference in patients with rotator cuff tears
compared with patients without rotator cuff tears (13.6vs.
7.6,P¼not significant).
16
Acromial slope
Two studies examined how the acromial slope relates to the
presence of rotator cuff tears, with different conclusions.
One study found no difference in acromial slope in patients
with rotator cuff tears compared with healthy controls (25
vs. 25,P¼.7),
3
whereas the other study found that the
acromial slope was significantly elevated in patients with
degenerative rotator cuff tears compared with those with
traumatic rotator cuff tears (21.2vs. 19.1,P¼.026).
2
No
study examined how acromial slope related to gleno-
humeral osteoarthritis.
Acromial center-edge angle
One study measured the ACEA and how it relates to the
presence of rotator cuff tears. Singleton et al
45
found that
the ACEA was significantly higher in patients with rotator
cuff tears than in controls (23.89vs. 16.66,P<.001).
Acromial coverage index
One study measured the acromial coverage index and its
relationship to rotator cuff tears. Torrens et al
50
found
that the acromial coverage index was significantly higher
in patients with surgically treated rotator cuff tears than
in healthy controls (0.687 vs. 0.591, P<.001). In addi-
tion, no significant difference was found between patients
with rotator cuff tears treated surgically and those with
tears were managed conservatively (0.687 vs. 0.725, P¼
.219).
Figure 4 Forest plot of studies examining how the critical shoulder angle relates to the presence of symptomatic glenohumeral osteo-
arthritis. The mean difference in the critical shoulder angle in patients with glenohumeral osteoarthritis was –1.42(95% confidence in-
terval [CI], –2.50to –0.35;P<.01; I
2
¼94%) compared with controls. Std, standardized; SD, standard deviation; IV, inverse variance.
Figure 3 Forest plot of studies examining how the critical shoulder angle relates to the presence of symptomatic rotator cuff tears. The
mean difference in the critical shoulder angle in patients with rotator cuff tears compared with controls was 1.01(95% confidence interval
[CI], 0.59-1.44;P<.05; I
2
¼91%). Std, standardized; SD, standard deviation; IV, inverse variance.
2462 M.B. Zaid et al.
Greater tuberosity angle
One study measured the GTA and its effect on rotator cuff
tears and found that the GTA was significantly elevated in
patients with rotator cuff tears compared with healthy
controls (72.5vs. 65.2,P<.001); in addition, a GTA of
more than 70resulted in 93-fold higher odds of detecting a
rotator cuff tear (P<.001).
15
Coracoid cavity ratio
One study measured the coracoid cavity ratio and its impact
on the presence of rotator cuff tears and concluded that
patients with an isolated supraspinatus tendon tear had a
significantly elevated coracoid cavity ratio compared with
healthy controls (65 vs. 43, P¼.0002).
41
Coracoid inclination
One study measured the coracoid inclination from CT scans
by measuring the angle between the coracoid and glenoid
surface (A1), the angle between the coracoid tip and gle-
noid surface (A2), and the angle created by the coracoid
body and coracoid tip (A3).
49
The authors found that all
angles (A1, A2, and A3) were significantly lower in the
rotator cuff tear group compared with the control group
(A1, 49.7vs. 56.1[P¼.011]; A2, 76.45vs. 93.6[P<
.001]; and A3, 132.33vs. 144.34[P<.001]).
Discussion
Scapular morphology as well as how it relates to the
development of degenerative rotator cuff tears and gleno-
humeral osteoarthritis continues to be an area of interest in
modern orthopedics as physicians hope to identify risk
factors for these common degenerative conditions.
Although numerous quantifiable anatomic parameters to
characterize scapular morphology have been identified in
the literature, the AI, CSA, GI, and LAA were the most
commonly examined in the studies in our review.
Overall, the AI, CSA, and LAA are reliably associated
with the presence of degenerative disorders of the shoul-
der. The results of the meta-analysis on the CSA demon-
strate that an increased CSA compared with controls is
associated with the development of degenerative rotator
cuff tears whereas a lower CSA compared with controls is
associated with the presence of glenohumeral osteoar-
thritis. Furthermore, the meta-analysis showed that an
increased AI is associated with degenerative rotator cuff
tears. The majority of studies found that an elevated AI,
usually greater than 0.74, was associated with the pres-
ence of degenerative rotator cuff tears. A conclusion on
how the AI relates to glenohumeral osteoarthritis is
difficult to make as only 1 study looked at this and did not
have a healthy control population; rather, the arthritis
group was compared with a rotator cuff tear group.
21
Similarly to the AI, the CSA was almost consistently
found to be elevated in patients with degenerative rotator
cuff tears compared with healthy controls, and it was
decreased in patients with glenohumeral osteoarthritis in
numerous studies, as well as in our meta-analysis. Because
of the large variation in the measured values of the CSA
between articles (range of 33.9-37.9for patients with
rotator cuff tears and 27.2-37.3for patients without ro-
tator cuff tears), it is difficult to assume an abnormal cutoff
value.
8,21,27,44,46
In addition to the AI and CSA, the LAA
consistently related to the presence of degenerative rotator
cuff tears. A lower LAA was universally associated with
the presence of degenerative rotator cuff tears in the
studies included in this review, usually with a value of less
than 80correlating with cuff tears. As only a single study
looked at how the LAA relates to glenohumeral osteoar-
thritis, it is difficult to assume a conclusion on this
relationship.
The pathomechanics of how scapular morphology re-
lates to the development of degenerative shoulder condi-
tions remains an area of controversy. Whereas numerous
authors have hypothesized that impingement of the rotator
Figure 5 Forest plot of studies examining how the acromial index relates to the presence of symptomatic rotator cuff tears. The mean
difference in the acromial index for patients with rotator cuff tears was 0.75 (95% confidence interval [CI], 0.23-1.27; P<.01; I
2
¼88%)
compared with healthy controls. Std, standardized; SD, standard deviation; IV, inverse variance.
Shoulder anatomy and degenerative conditions 2463
cuff by the underside of the acromion can lead to the
development of rotator cuff tears,
6,7,10,18,34
others have
argued that changes in acromial morphology may occur as
a result of rotator cuff tears.
1,25
For example, Li
et al
25
theorized that rotator cuff degeneration leads to an
imbalance in forces around the shoulder, ultimately
resulting in anterior-superior instability followed by the
formation of bone spurs along the coracoacromial arch with
a resultant deformity in the acromion. Nonetheless, there is
convincing evidence
36
to suggest that increased lateral
extension of the acromion may relate to the development of
rotator cuff tears. Nyffeler et al
36
have hypothesized
that with increasing lateral extension of the acromion,
the deltoid is able to exert a larger force vector on the
glenohumeral joint, leading to increased joint contraction
and subacromial impingement, which in turn may lead
to degenerative rotator cuff tears. This increase in the
lateral extension of the acromion would manifest as an
increased CSA and AI and a decrease in the LAA; these are
the changes that were consistently associated with the
presence of degenerative rotator cuff tears in the published
literature.
Integrating the data from these studies into clinical
practice may allow for the identification of patients at risk
of having degenerative rotator cuff tears and possibly gle-
nohumeral osteoarthritis. As these changes in scapular
morphology are intrinsic in nature, they cannot be changed
without surgical intervention, which is unlikely to be per-
formed. In addition, clinicians should have a higher index
of suspicion for a degenerative rotator cuff injury in pa-
tients with these alterations in scapular shape who may
present with shoulder pain.
Although there was significant consistency in the
aforementioned parameters, there were some studies that
did not come to similar conclusions. The most variable
findings involved the GI: 2 studies concluded that a more
superior GI related to rotator cuff tears,
11,16
whereas 3
concluded the opposite.
4,5,8
These discordant results may
be attributed to a difference in methods used to measure the
GI, as well as the fact that some authors measured this
parameter on plain radiographs whereas others used CT
scans. This point may serve to highlight the importance of
radiographic and measurement techniques in determining
these anatomic parameters. Furthermore, differences in
patient populations between studies may contribute to this
discordance. As with the GI, all of the aforementioned
parameters are subject to variability based on measurement
techniques and the quality of the imaging used for the
measurements. Numerous studies have demonstrated that
these quantitative measures are highly dependent on the
rotation of the image used.
11,12,20
Although some of the
studies included in this review used CT scans, which are
not dependent on patient rotation, the majority used plain
radiographs.
This study comes with strengths and limitations. It
is one of the first of its kind to review the currently
available literature on how anatomic shoulder pa-
rameters affect the development of degenerative ro-
tator cuff tears and glenohumeral osteoarthritis. As it
is a systematic review, it is dependent on the quality
of the studies included. The majority of studies
included in this analysis were retrospective in nature
but did have sufficient sample sizes and control
groups. Although numerous parameters were measured
in the literature, the AI, CSA, and LAA were the
most highly represented. In addition, although some
studies completed a multivariate analysis to control
for confounding factors, this analysis was not
completed in all of the included sources, possibly
introducing some error.
Conclusion
The presence of degenerative rotator cuff tears ap-
pears to be associated with an increased AI and CSA
and a decreased LAA. In addition, a lower CSA ap-
pears to be associated with the presence of gleno-
humeral osteoarthritis. It must be highlighted that
these quantifiable anatomic parameters are highly
dependent on the technique used to obtain the radio-
graphs. Although a few studies used cross-sectional
imaging such as CT scans and magnetic resonance
imaging to more accurately quantify these parameters,
future studies should continue to use these methods to
perhaps look for associations between anatomic
shoulder parameters and the presence of glenohumeral
osteoarthritis.
Disclaimer
Brian T. Feeley reports that he has received grants from
the National Institutes of Health and serves as a journal
editor for the Journal of Shoulder and Elbow Surgery
and CRMSM for work related to the subject of this
article.
C. Benjamin Ma reports that he has received grants
from Zimmer Biomet during the conduct of the study;
grants from Anika, Samumed, and Zimmer; personal
fees from ConMed Linvatec, Medacta, SLACK, and
Stryker; and grants and personal fees from Histogenics
for work related to the subject of this article.
Drew A. Lansdown reports that he has received
grants from Arthrex and Smith & Nephew for work
related to the subject of this article.
The other authors, their immediate families, and any
research foundations with which they are affiliated have
not received any financial payments or other benefits
from any commercial entity related to the subject of this
article.
2464 M.B. Zaid et al.
Supplementary data
Supplementary data to this article can be found online at
https://doi.org/10.1016/j.jse.2019.05.008.
References
1. Anderson K, Bowen MK. Spur reformation after arthroscopic acro-
mioplasty. Arthroscopy 1999;15:788-91.
2. Balke M, Liem D, Greshake O, Hoeher J, Bouillon B, Banerjee M.
Differences in acromial morphology of shoulders in patients with
degenerative and traumatic supraspinatus tendon tears. Knee Surg
Sports Traumatol Arthrosc 2016;24:2200-5. https://doi.org/10.1007/
s00167-014-3499-y
3. Balke M, Schmidt C, Dedy N, Banerjee M, Bouillon B, Liem D.
Correlation of acromial morphology with impingement syndrome and
rotator cuff tears. Acta Orthop 2013;84:178-83. https://doi.org/10.
3109/17453674.2013.773413
4. Beeler S, Hasler A, Getzmann J, Weigelt L, Meyer DC, Gerber C.
Acromial roof in patients with concentric osteoarthritis and massive
rotator cuff tears: multiplanar analysis of 115 computed tomography
scans. J Shoulder Elbow Surg 2018;27:1866-76. https://doi.org/10.
1016/j.jse.2018.03.014
5. Beeler S, Hasler A, G
otschi T, Meyer DC, Gerber C. The critical
shoulder angle: acromial coverage is more relevant than glenoid
inclination. J Orthop Res 2019;37:205-10. https://doi.org/10.1002/jor.
24053
6. Bigliani L, Levin W. Current concepts reviewdsubacromial
impingement syndrome. J Bone Joint Surg Am 1997;79:1854-68.
7. Bigliani LU, Ticker JB, Flatow EL, Soslowsky LJ, Mow VC. The
relationship of acromial architecture to rotator cuff disease. Clin
Sports Med 1991;10:823.
8. Bishop J, Kline S, Aalderink K, Zauel R, Bey M. Glenoid inclination:
in vivo measures in rotator cuff tear patients and associations with
superior glenohumeral joint translation. J Shoulder Elbow Surg 2009;
18:231-6. https://doi.org/10.1016/j.jse.2008.08.002
9. Bjarnison AO, Sørensen TJ, Kallemose T, Barfod KW. The critical
shoulder angle is associated with osteoarthritis in the shoulder but not
rotator cuff tears: a retrospective case-control study. J Shoulder Elbow
Surg 2017;26:2097-102. https://doi.org/10.1016/j.jse.2017.06.001
10. Blonna D, Giani A, Bellato E, Mattei L, Cal
o M, Rossi R, et al.
Predominance of the critical shoulder angle in the pathogenesis of
degenerative diseases of the shoulder. J Shoulder Elbow Surg 2016;25:
1328-36. https://doi.org/10.1016/j.jse.2015.11.059
11. Chalmers PN, Beck L, Granger E, Henninger H, Tashjian RZ. Superior
glenoid inclination and rotator cuff tears. J Shoulder Elbow Surg 2018;
27:1444-50. https://doi.org/10.1016/j.jse.2018.02.043
12. Chalmers PN, Salazar D, Steger-May K, Chamberlain A,
Yamaguchi K, Keener J. Does the critical shoulder angle correlate with
rotator cuff tear progression? Clin Orthop Relat Res 2017;475:1608-
17. https://doi.org/10.1007/s11999-017-5249-1
13. Cherchi L, Ciornohac J, Godet J, Clavert P, Kempf J. Critical shoulder
angle: measurement reproducibility and correlation with rotator cuff
tendon tears. Orthop Traumatol Surg Res 2016;102:559-62. https://doi.
org/10.1016/j.otsr.2016.03.017
14. Colvin AC, Egorova N, Harrison AK, Moskowitz A, Flatow EL.
National trends in rotator cuff repair. J Bone Joint Surg Am 2012;94:
227-33. https://doi.org/10.2106/JBJS.J.00739
15. Cunningham G, Nicod
eme-Paulin E, Smith MM, Holzer N, Cass B,
Young AA. The greater tuberosity angle: a new predictor for rotator
cuff tear. J Shoulder Elbow Surg 2018;27:1415-21. https://doi.org/10.
1016/j.jse.2018.02.051
16. Daggett M, Werner B, Collin P, Gauci MO, Chaoui J, Walch G.
Correlation between glenoid inclination and critical shoulder angle: a
radiographic and computed tomography study. J Shoulder Elbow Surg
2015;24:1948-53. https://doi.org/10.1016/j.jse.2015.07.013
17. Day J, Lau E, Ong K, William G, Ramsey M, Kurtz S. Prevalence and
projections of total shoulder and elbow arthroplasty in the United
States to 2015. J Shoulder Elbow Surg 2010;19:1115-20. https://doi.
org/10.1016/j.jse.2010.02.009
18. Flatow EL, Soslowsky LJ, Ticker JB, Pawluk RJ, Hepler M, Ark J,
et al. Excursion of the rotator cuff under the acromion. Am J Sports
Med 1994;22:779-88.
19. Gomide LC, Carmo TCd, Bergo GHM, Oliveira GA, Macedo IS.
Relationship between the critical shoulder angle and the develop-
ment of rotator cuff lesions: a retrospective epidemiological study.
Rev Bras Ortop 2017;52:423-7. https://doi.org/10.1016/j.rboe.2017.
06.002
20. Hamid N, Omid R, Yamaguchi K, Stager-May K, Stobbs G, Keener J.
Relationship of radiographic acromial characteristics and rotator cuff
disease: a prospective investigation of clinical, radiographic, and
sonographic findings. J Shoulder Elbow Surg 2012;21:1289-98.
https://doi.org/10.1016/j.jse.2011.09.028
21. Heuberer PR, Plachel F, Willinger L, Moroder P, Laky B,
Pauzenberger L, et al. Critical shoulder angle combined with age
predict five shoulder pathologies: a retrospective analysis of 1000
cases. BMC Musculoskelet Dis 2017;18:259. https://doi.org/10.1186/
s12891-017-1559-4
22. Hughes RE, Bryant CR, Hall JM, Wening J, Huston LJ, Kuhn JE, et al.
Glenoid inclination is associated with full-thickness rotator cuff tears.
Clin Orthop Relat Res 2003;407:86-91.
23. Hutchinson M. The burden of musculoskeletal diseases in the United
States: prevalence, societal and economic cost. Rosemont, IL: Amer-
ican Academy of Orthopaedic Surgeons; 2008.
24. Kum DH, Kim JH, Park KM, Lee ES, Park YB, Yoo JC. Acromion
index in Korean population and its relationship with rotator cuff tears.
Clin Orthop Surg 2017;9:218-22. https://doi.org/10.4055/cios.2017.9.
2.218
25. Li X, Xu W, Hu N, Liang X, Huang W, Jiang D, et al. Relationship
between acromial morphological variation and subacromial impinge-
ment: a three-dimensional analysis. PLoS One 2017;12:e0176193.
https://doi.org/10.1371/journal.pone.0176193
26. Luime JJ, Koes BW, Hendriksen I, Burdorf A, Verhagen AP,
Miedema HS, et al. Prevalence and incidence of shoulder pain in the
general population; a systematic review. Scand J Rheumatol 2004;33:
73-81.
27. Mantell MT, Nelson R, Lowe JT, Endrizzi DP, Jawa A. Critical
shoulder angle is associated with full-thickness rotator cuff tears in
patients with glenohumeral osteoarthritis. J Shoulder Elbow Surg
2017;26:e381. https://doi.org/10.1016/j.jse.2017.05.020
28. Maurer A, Fucentese S, Pfirrmann C, Wirth S, Djahangiri A, Jost B,
et al. Assessment of glenoid inclination on routine clinical radiographs
and computed tomography examinations of the shoulder. J Shoulder
Elbow Surg 2012;21:1096-103. https://doi.org/10.1016/j.jse.2011.
07.010
29. Minagawa H, Yamamoto N, Abe H, Fukuda M, Seki N, Kikuchi K,
et al. Prevalence of symptomatic and asymptomatic rotator cuff tears
in the general population: from mass-screening in one village. J
Orthop 2013;10:8-12. https://doi.org/10.1016/j.jor.2013.01.008
30. Miswan M, Saman M, Hui T, Al-Fayyadh M, Ali M, Min N. Corre-
lation between anatomy of the scapula and the incidence of rotator
cuff tear and glenohumeral osteoarthritis via radiological study. J
Orthop Surg (Hong Kong) 2017;25. 2309499017690317. https://doi.
org/10.1177/2309499017690317
31. Moor BK, Rothlisberger M, Muller D, Zumstein M, Bouaicha S,
Ehlinger M, et al. Age, trauma and the critical shoulder angle accu-
rately predict supraspinatus tendon tears. Orthop Traumatol Surg Res
2014;100:489-94. https://doi.org/10.1016/j.otsr.2014.03.022
32. Moor BK, Weiser K, Slankamenac K, Geber C, Bouaicha S. Rela-
tionship of individual scapular anatomy and degenerative rotator cuff
Shoulder anatomy and degenerative conditions 2465
tears. J Shoulder Elbow Surg 2014;23:536-41. https://doi.org/10.1016/
j.jse.2013.11.008
33. Neer CS II. Anterior acromioplasty for the chronic impingement
syndrome in the shoulder: a preliminary report. J Bone Joint Surg Am
1972;54:41-50.
34. Neer CS II. Anterior acromioplasty for the chronic impingement
syndrome in the shoulder. J Bone Joint Surg Am 2005;87:1399.
https://doi.org/10.2106/JBJS.8706.cl
35. Nicholson GP, Goodman DA, Flatow EL, Bigliani LU. The acromion:
morphologic condition and age-related changes. A study of 420
scapulas. J Shoulder Elbow Surg 1996;5:1-11.
36. Nyffeler R, Werner C, Sukthankar A, Schmid M, Gerber C. Associ-
ation of a large lateral extension of the acromion with rotator cuff
tears. J Bone Joint Surg Am 2006;88:800-5. https://doi.org/10.2106/
JBJS.D.03042
37. Oh J, Chung S, Oh C, Kim S, Park S, Kim K, et al. The prevalence of
shoulder osteoarthritis in the elderly Korean population: association
with risk factors and function. J Shoulder Elbow Surg 2011;20:756-63.
https://doi.org/10.1016/j.jse.2011.01.021
38. Pandey V, Vijayan D, Tapashetti S, Agarwal L, Kamath A, Acharya K,
et al. Does scapular morphology affect the integrity of the rotator cuff?
J Shoulder Elbow Surg 2016;25:413-21. https://doi.org/10.1016/j.jse.
2015.09.016
39. Peltz C, Divine G, Drake A, Ramo N, Zauel R, Moutzouros V, et al.
Associations between in-vivo glenohumeral joint motion and
morphology. J Biomech 2015;48:3252-7. https://doi.org/10.1016/j.
jbiomech.2015.06.030
40. Sayampanathan AA, Andrew THC. Systematic review on risk factors
of rotator cuff tears. J Orthop Surg (Hong Kong) 2017;25.
2309499016684318, https://doi.org/10.1177/2309499016684318
41. Schulz CU, Anetzberger H, Glaser C. Coracoid tip position on frontal ra-
diographs of the shoulder: a predictor of common shoulder pathologies? Br
J Radiol 2005;78:1005-8. https://doi.org/10.1259/bjr/27340997
42. Shamseer L, Moher D, Clarke M, Ghersi D, Liberati A, Petticrew M,
et al. Preferred reporting items for systematic review and meta-
analysis protocols (PRISMA-P) 2015: elaboration and explanation.
BMJ 2015;349:g7647. https://doi.org/10.1136/bmj.g7647
43. Shim SB, Jeong JY, Kim JS, Yoo JC. Evaluation of risk factors for
irreparable rotator cuff tear in patients older than age 70 including
evaluation of radiologic factors of the shoulder. J Shoulder Elbow Surg
2018;27:1932-8. https://doi.org/10.1016/j.jse.2018.07.011
44. Shinagawa K, Hatta T, Yamamoto N, Kawakami J, Shiota Y,
Mineta M, et al. Critical shoulder angle in an east Asian population:
correlation to the incidence of rotator cuff tear and glenohumeral
osteoarthritis. J Shoulder Elbow Surg 2018;27:1602-6. https://doi.org/
10.1016/j.jse.2018.03.013
45. Singleton N, Agius L, Andrews S. The acromiohumeral centre edge
angle: a new radiographic measurement and its association with ro-
tator cuff pathology. J Orthop Surg (Hong Kong) 2017;25.
2309499017727950, https://doi.org/10.1177/2309499017727950
46. Spiegl U, Horan M, Smith S, Ho C, Millett P. The critical shoulder
angle is associated with rotator cuff tears and shoulder osteoarthritis
and is better assessed with radiographs over MRI. Knee Surg Sports
Traumatol Arthrosc 2016;24:2244-51. https://doi.org/10.1007/s00167-
015-3587-7
47. Tempelhof S, Rupp S, Seil R. Age-related prevalence of rotator cuff
tears in asymptomatic shoulders. J Shoulder Elbow Surg 1999;8:
296-9.
48. Thomas M, Bidwai A, Rangan A, Rees JL, Brownson P, Tennent D,
et al. Glenohumeral osteoarthritis. Shoulder Elbow 2016;8:203-14.
https://doi.org/10.1177/1758573216644183
49. Torrens C, Alentorn-Geli E, Sanchez JF, Isart A, Santana F. Decreased
axial coracoid inclination angle is associated with rotator cuff tears. J
Orthop Surg (Hong Kong) 2017;25. 230949901769032, https://doi.
org/10.1177/2309499017690329
50. Torrens C, L
opez JM, Puente I, C
aceres E. The influence of the
acromial coverage index in rotator cuff tears. J Shoulder Elbow Surg
2007;16:347-51. https://doi.org/10.1016/j.jse.2006.07.006
51. Watanabe A, Ono Q, Nishigami T, Hirooka T, Machida H. Differences
in risk factors for rotator cuff tears between elderly patients and young
patients. Acta Med Okayama 2018;72:67. https://doi.org/10.18926/
AMO/55665
52. Windt V, Koes B, Jong B, Bouter L. Shoulder disorders in general-
practicedincidence, patient characteristics, and management. Ann
Rheum Dis 1995;54:959-64.
53. Yucesoy B, Charles LE, Baker B, Burchfiel CM. Occupational and
genetic risk factors for osteoarthritis: a review. Work 2015;50:261-73.
https://doi.org/10.3233/WOR-131739
2466 M.B. Zaid et al.
... In addition, the more severe the rotator cuff tear is, the higher is CSA [43]. A recent systematic review by Zaid et al. demonstrated that several studies have reported significantly higher CSA in patients with rotator cuff tear compared to control groups [44]. Similarly, our results revealed significant differences in CSA between the SS tendinopathy and non-SS tendinopathy groups. ...
... This result may be attributed to the following reasons. First, our study included patients with shoulder pain, which increased the possibility of shoulder impingement caused by a high CSA; by contrast, previous studies were not limited to patients with shoulder pain [24,44]. Second, a study reported a higher CSA in degenerative rotator cuff tear than in traumatic rotator cuff tear (36.8 • vs. 35.3 ...
Article
Full-text available
Critical shoulder angle (CSA) is the angle between the superior and inferior bony margins of the glenoid and the most lateral border of the acromion. The acromial index (AI) is the distance from the glenoid plane to the acromial lateral border and is divided by the distance from the glenoid plane to the lateral aspect of the humeral head. Although both are used for predicting shoulder diseases, research on their accuracy in predicting supraspinatus tendinopathy in patients with shoulder pain is limited. Data were retrospectively collected from 308 patients with supraspinatus tendinopathy between January 2018 and December 2019. Simultaneously, we gathered the data of 300 patients with shoulder pain without supraspinatus tendinopathy, confirmed through ultrasound examination. Baseline demographic data, CSA, and AI were compared using the independent Student’s t test and Mann–Whitney U test. Categorical variables were analyzed using the chi-square test. A receiver operating characteristic curve (ROC) analysis was performed to investigate the accuracy of CSA and AI for predicting supraspinatus tendinopathy, and the optimal cut-off point was determined using the Youden index. No statistical differences were observed for age, sex, body mass index, evaluated side (dominant), diabetes mellitus, and hyperlipidemia between the groups. The supraspinatus tendinopathy group showed higher CSAs (p < 0.001) than did the non-supraspinatus tendinopathy group. For predicting supraspinatus tendinopathy, the area under the curve (AUC) of ROC curve of the CSA was 76.8%, revealing acceptable discrimination. The AUC of AI was 46.9%, revealing no discrimination. Moreover, when patients with shoulder pain had a CSA > 38.11°, the specificity and sensitivity of CSA in predicting supraspinatus tendinopathy were 71.0% and 71.8%, respectively. CSA could be considered an objective assessment tool to predict supraspinatus tendinopathy in patients with shoulder pain. AI revealed no discrimination in predicting supraspinatus tendinopathy in patients with shoulder pain.
... This finding was mainly attributed to impingement between the malrotated humeral head and the glenoid edge as well as to the increased articular contact stress. As Zaid reviewed, numerous studies confirmed that anatomy parameters of the shoulder, as measured by acromial index (AI), critical shoulder angle (CSA), lateral acromial angle (LAA), and glenoid inclination (GI), appeared to be significantly associated with glenohumeral osteoarthritis [9]. Therefore, we have reason to speculate about the potential impact of humeral head retroversion angle (HRA) change with postoperative malrotation on the shoulder joint. ...
Article
Full-text available
Objectives The humerus fracture is one of the most commonly occurring fractures. In this research, we attempted to evaluate and compare the extent of malrotation and biomechanical environment after surgical treatment of humeral shaft fractures. Methods A finite element (FE) model of the shoulder was built based on Computed Tomography (CT) data of a patient with a humeral shaft fracture. The muscle group around the shoulder joint was simulated by spring elements. The changes of shoulder stresses under rotation were analyzed. The biomechanics of the normal shoulder and postoperative malrotation of the humeral shaft was analyzed and compared. Results During rotations, the maximum stress was centered in the posterosuperior part of the glenoid for the normal shoulder. The von Mises shear stresses were 4.40 MPa and 4.89 MPa at 40° of internal and external rotations, respectively. For internal rotation deformity, the shear contact forces were 7–9 times higher for the shoulder internally rotated 40° than for the normal one. For external rotation deformity, the shear contact forces were about 3–5 times higher for the shoulder with 40° external rotation than the normal one. Conclusion Postoperative malrotation of humeral shaft fracture induced the changes of the biomechanical environment of the shoulders. The peak degree of malrotation was correlated with increased stresses of shoulders, which could be paid attention to in humeral shaft fracture treatment. We hoped to provide information about the biomechanical environment of humeral malrotation.
... Progressive disease causes extensive morphological changes in articular cartilage and subchondral bone, which may result in narrowed joint gap, subchondral sclerosis, osteophytes and deformation of the glenoid including alterations of glenoid angles. An ideal range is not clearly defined to date, but the geometry of the glenoid may predispose for alterations [15,17,36,39,55]. To achieve an optimal treatment outcome, e.g., positioning of the prosthetic glenoid component, a profound knowledge on optimal geometry, particularly the glenoid angles, and bone mineralisation is essential [3, 15-17, 29, 33, 39]. ...
Article
Full-text available
Background For optimal prosthetic anchoring in omarthritis surgery, a differentiated knowledge on the mineralisation distribution of the glenoid is important. However, database on the mineralisation of diseased joints and potential relations with glenoid angles is limited. Methods Shoulder specimens from ten female and nine male body donors with an average age of 81.5 years were investigated. Using 3D-CT-multiplanar reconstruction, glenoid inclination and retroversion angles were measured, and osteoarthritis signs graded. Computed Tomography-Osteoabsorptiometry (CT-OAM) is an established method to determine the subchondral bone plate mineralisation, which has been demonstrated to serve as marker for the long-term loading history of joints. Based on mineralisation distribution mappings of healthy shoulder specimens, physiological and different CT-OAM patterns were compared with glenoid angles. Results Osteoarthritis grades were 0-I in 52.6% of the 3D-CT-scans, grades II-III in 34.3%, and grade IV in 13.2%, with in females twice as frequently (45%) higher grades (III, IV) than in males (22%, III). The average inclination angle was 8.4°. In glenoids with inclination ≤10°, mineralisation was predominantly centrally distributed and tended to shift more cranially when the inclination raised to > 10°. The average retroversion angle was − 5.2°. A dorsally enhanced mineralisation distribution was found in glenoids with versions from − 15.9° to + 1.7°. A predominantly centrally distributed mineralisation was accompanied by a narrower range of retroversion angles between − 10° to − 0.4°. Conclusions This study is one of the first to combine CT-based analyses of glenoid angles and mineralisation distribution in an elderly population. The data set is limited to 19 individuals, however, indicates that superior inclination between 0° and 10°-15°, and dorsal version ranging between − 9° to − 3° may be predominantly associated with anterior and central mineralisation patterns previously classified as physiological for the shoulder joint. The current basic research findings may serve as basic data set for future studies addressing the glenoid geometry for treatment planning in omarthritis.
... While the mechanism and pathogenesis of RCT remain unclear, genetic predisposition, extrinsic impingement and biomechanical imbalance from surrounding structures and intrinsic degeneration within the tendon are considered the most likely relevant factors. After a review of more than 700 studies, Zaid MB concluded that scapular anatomy parameters, as measured by the acromial index (AI), critical shoulder angle (CSA), lateral acromial angle (LAA), and glenoid inclination (GI), appeared to be significantly associated with rotator cuff tears as well as glenohumeral osteoarthritis 11 ; this suggests that RCTs could probably be induced by anatomic variance. ...
Article
Full-text available
We hypothesized that postoperative malrotation of humeral shaft fractures can alter the bio-mechanical environment of the shoulder; thus, rotator cuff and cartilage degeneration could be induced. Therefore, we designed an animal experiment to evaluate the impact of malrotation deformities after minimally invasive surgery for humeral fractures on the rotator cuff and cartilage, which has rarely been described in previous studies. Twenty-four New Zealand white rabbits were randomly divided into the sham control group (A), negative control group (B) and malrotated group (C). A sham operation with surgical exposure alone was performed in group A. Humeral shaft osteotomy was performed in Group B and C. In Group B, the fractures were fixed in situ with plate -screw system. While in Group C, iatrogenic rotational deformity was created after the proximal end of the fracture being internally rotated by 20 degrees and then subsequently fixed. The animals with bone healing were sacrificed for pathological and biochemical examination. In group C, the modified Mankin scale for cartilage pathology evaluation and the modified Movin scale for tendon both showed highest score among groups with statistical significance (P < 0.05); Disordered alignment and proportion of collagen I/III of rotator cuff were confirmed with picrosirius red staining; Transmission electron microscopy also showed ultrastructural tendon damage. Immunohistochemistry showed that both MMP-1 and MMP-13 expression were significantly higher in group C than groups A and B(P < 0.05). Minimally invasive techniques for humerus shaft fracture might be cosmetically advantageous, but the consequent postoperative malrotation could increase the risk of rotator cuff and cartilage degeneration. This conclusion is supported here by primary evidence from animal experiments.
Article
The critical shoulder angle (CSA) reflects the lateral extent of the acromion and the inclination of the glenoid. In 2013, CSA was first introduced and its association with rotator cuff (RC) tears and glenohumeral osteoarthritis (GHOA) was shown. It was speculated that with a high CSA, there was an increased superior force vector from the deltoid and that this superior force led to RC tears. Conversely, when the CSA was low, there was a greater compressive force from the deltoid and that this compressive force led to GHOA. CSA serves as a further development of 2 previously reported measurements (glenoid inclination and acromial index). A key potential therapeutic aspect of the CSA is the ability to modify it surgically, which theoretically could protect RC repairs or prevent progression. In our current clinical practice, we perform lateral acromioplasty (LA) in patients undergoing treatment of subacromial impingement with an “at-risk” rotator cuff (partial rotator cuff tear and severe tendinopathy on magnetic resonance imaging) with a CSA > 38° or all patients with a CSA >35° after an RC repair to protect the RC repair construct. The relationships of high and low CSA, the anatomic safe zone, and thus clinical applicability of LA are well established and performed in our daily surgical practice. However, we do not yet have widespread clear clinical evidence on potential benefits regarding the clinical outcome after LA. Finally, at this time, the downsides seem minimal, so we continue to use LA as an adjunct in patients with RC tears and RC tendons that are at risk.
Article
Objective Shoulder pain is commonly attributed to rotator cuff injury or osteoarthritis. Ovine translational models are used to investigate novel treatments aimed at remedying these conditions to prevent articular cartilage degeneration and subsequent joint degradation. However, topographical properties of articular cartilage in the ovine shoulder are undefined. This study investigates the biomechanical, morphological, and biochemical attributes of healthy ovine humeral head articular cartilage and characterizes topographical variations between surface locations. Design Ten humeral heads were collected from healthy skeletally mature sheep and each was segregated into 4 quadrants using 16 regions of interest (ROIs) across the articular surface. Articular cartilage of each ROI was analyzed for creep indentation, thickness, and sulfated glycosaminoglycan (sGAG) and collagen quantity. Comparisons of each variable were made between quadrants and between ROIs within each quadrant. Results Percent creep, thickness, and sGAG content, but not collagen content, were significantly different between humeral head quadrants. Subregion analysis of the ROIs within each surface quadrant revealed differences in all measured variables within at least one quadrant. Percent creep was correlated with sGAG (r = −0.32, P = 0.0001). Collagen content was correlated with percent creep (r = 0.32, P = 0.0009), sGAG (r = −0.19, P = 0.049), and thickness (r = −0.19, P = 0.04). Conclusions Topographical variations exist in mechanical, morphologic, and biochemical properties across the articular surface of the ovine humeral head. Recognizing this variability in ovine humeral head cartilage will provide researchers and clinicians with accurate information that could impact study outcomes.
Article
Background The purpose of this study was to determine if scapular anatomy differs between younger and older patients with atraumatic full-thickness supraspinatus tears. Methods The critical shoulder angle, acromial index and lateral acromial angle were measured on standardized radiographs of two groups of patients who underwent arthroscopic repair of full-thickness degenerative supraspinatus tears. Group 1 included 61 patients under the age of 50 years while Group 2 included 45 patients over the age of 70 years. The mean critical shoulder angle, acromial index, and lateral acromial angle were then compared. Results There was no significant difference between groups for the critical shoulder angle (p = .433), acromial index (p = .881) or lateral acromial angle (p = .263). Interobserver reliability for critical shoulder angle, acromial index, and lateral acromial angle was nearly perfect (interclass correlation coefficient 0.996, 0.996, 0.998, respectively). No significant correlation existed between age and critical shoulder angle (p = .309), acromial index (p = .484) or lateral acromial angle (p = .685). Discussion While the critical shoulder angle and acromial index were found to be high and in the typical range for patients with rotator cuff tears in both groups, there were no significant differences in acromial morphology between Groups 1 and 2.
Article
Purpose This study is aiming to evaluate some specific anatomic shoulder parameters such as the lateral acromial angle (LAA), acromial index (AI), coracohumeral distance (CHD), and critical shoulder angle (CSA) in rotator cuff tears. Methods A total of 100 cases consisting of 50 patients with rotator cuff tears and 50 patients without rotator cuff tears, who underwent shoulder MRI (mangnetic resonance imaging) examination in Istanbul Medipol University Orthopedics and Traumatology Department, participated in this study. In this retrospective study, CCA, LAA, AI and CSA were evaluated in MRI in order to shed light on the theories of rotator cuff tears. Results There was no significant difference (p ˃ 0.05) in acromial index and coracohumeral distance in the patient group. Lateral acromial angle and critical shoulder angle were significantly different in the patient group compared to the control group (p <0.05). There was a weak negative correlation between CSA and CHD. Conclusion In our study, we found that patients with smaller LAA and higher CSA values in MRI images are prone to have rotator cuff tears. Further studies are needed in order to evaluate whether this association has predictive value.
Article
Full-text available
Background: There is evidence for differences of scapular shape between shoulders with rotator cuff tears (RCT) and osteoarthritic shoulders (OA). This study analyzed orientation and shape of the acromion in patients with massive RCT and concentric OA (COA) in a multiplanar computed tomography (CT) analysis. Methods: CT scans of 70 shoulders with degenerative RCT and 45 shoulders with COA undergoing primary shoulder arthroplasty were analyzed. The 2 groups were compared in relation of (1) shape of the acromion, (2) its orientation in space, and (3) the anteroposterior glenoid coverage in relation to the scapular plane. Results: Lateral acromial roof extension was an average of 4.6 mm wider and the acromial area was an average of 156 mm2 larger in RCT than in COA (P < .001). Significant differences of the lateral extension of the acromion margin were limited to the anterior two-thirds. Acromial roof orientation in RCT was average of 10.8° more "externally rotated" (axial plane: P < .001) and an average of 7.8° more tilted downward (coronal plane: P < .001) than in COA. The glenoid in RCT was an average of 5.5° (P < .001) more covered posteriorly compared with COA. Conclusions: A more externally rotated (axial plane), more downward tilted (coronal plane), and wider posterior covering acromion was more frequent in patients with massive RCT than COA.
Article
Full-text available
Background: The implication of scapular morphology in rotator cuff tears has been extensively studied. However, the role of the greater tuberosity (GT) should be of equal importance. The aim of this study was to propose a new radiographic marker, the GT angle (GTA), which measures the position of the GT in relation to the center of rotation of the humeral head. The hypothesis was that a higher angle value would be associated with a higher likelihood in detecting a rotator cuff tear. Methods: During 1 year, patients were prospectively recruited from a single institution specialized shoulder clinic in 2 different groups. The patient group consisted of individuals with a degenerative rotator cuff tear involving at least the supraspinatus. The control group consisted of individuals with no rotator cuff pathology. Individuals in both groups with congenital, post-traumatic, or degenerative alterations of the proximal humerus were excluded. The GTA was measured on an anteroposterior shoulder x-ray image with the arm in neutral rotation by 3 observers at 2 different times. Results: The study recruited 71 patients (33 patients, 38 controls). Mean GTA value was 72.5° (range, 67.6°-79.2°) in patients and 65.2° (range, 55.8°-70.5°) for controls (P <.001). A value above 70° resulted in 93-fold higher odds of detecting a rotator cuff tear (P <.001). Interobserver and intraobserver reliability were high. Conclusions: GT morphology is implicated in rotator cuff tears. The GTA is a reliable radiographic marker, with more than 70° being highly predictive in detecting such lesions.
Article
Full-text available
Background: Various radiographic measurements that describe humeral head coverage by the acromion and the effect on rotator cuff pathology have been reported. This study aimed to describe and validate a new radiographic measurement, the acromiohumeral centre edge angle (ACEA). Methods: We compared the ACEA on computed tomography (CT) and plain X-ray to determine whether X-ray is accurate for measuring this angle. We then compared the results from this control population with 107 patients with acute rotator cuff tears. We compared functional outcomes in rotator cuff tear patients to determine whether the ACEA has any effect on outcome after surgery. An intra- and inter-observer variability analysis was performed and we compared the ACEA to the acromial index (AI) on rotation X-rays. Results: The ACEA was comparable on CT and plain X-ray and was most accurate when true anteroposterior glenohumeral X-rays were used (15.94° vs. 15.87° on CT, p = 0.476). The ACEA showed high intra- and inter-observer reproducibility and was unchanged on internal and external rotation X-rays (20.48 vs. 20.47, p = 0.842), whereas the AI was significantly different (0.74 vs. 0.70, p < 0.001). The ACEA was significantly higher in our rotator cuff tear patients than the control population (23.9° vs. 16.6°, p < 0.001), although a higher ACEA was not associated with poorer outcomes. Conclusion: The ACEA is a valid measurement for describing humeral head coverage by the acromion and can be accurately measured on plain radiographs with good reproducibility. It is unaffected by shoulder rotation and was significantly higher in patients with acute rotator cuff tears.
Article
Background: Rotator cuff tears (RCTs) are generally considered to occur at the age of 40 to 50, but some becomes massive tears at the age of 60 to 70 if neglected. This study evaluated preoperative factors affecting tear size and reparability of rotator cuffs based on magnetic resonance imaging findings among patients older than age 70. Methods: We identified 270 patients with full-thickness RCTs (175 reparable tears, group A; 95 irreparable tears, group B) that were confirmed with magnetic resonance imaging findings from January 2009 to March 2016. Irreparable tear was identified if all of the following criteria were met: (1) a large to massive RCT based on the DeOrio and Cofield classification, (2) sum of preoperative global fatty degeneration index of the supraspinatus and infraspinatus ≥6, and (3) positive tangent sign. Preoperative variables included demographic data, medical history, and radiologic data. Acromial index, critical shoulder angle, and acromiohumeral interval (AHI) were evaluated to investigate the relationship between anatomic factors and reparability of RCT. Results: Stepwise multivariated regression analysis revealed older age, longer symptom duration, longer duration of overhead sports activity, lower preoperative forward elevation of the shoulder joint, and shorter AHI as risk factors for irreparable RCTs. Conclusions: This study suggests that older age at surgery, longer duration of symptoms, longer duration of overhead sports activity, lower preoperative forward elevation of the shoulder joint, and shorter AHI are independent risk factors for irreparable RCT.
Article
It is still unknown whether glenoid inclination or lateral acromial roof extension is a more important determinant for development of rotator cuff tears (RCT) or osteoarthritis (OA) of the shoulder. It was the purpose of this study, to evaluate whether there is a potential predominance of one of these factors in pathogenesis of RCT or concentric OA. We analyzed 70 shoulders with advanced degenerative RCT and 54 shoulders with concentric OA undergoing primary shoulder arthroplasty (anatomical or reverse) using antero‐posterior radiography and multiplanar computed tomography. The two groups were compared in relation to glenoid inclination, lateral acromion roof extension, acromial height and critical shoulder angle (CSA). All measured parameters were highly significantly different between RCT and concentric OA (p < 0.001). Based on Cohen's d effect size, group differences were most distinct in lateral acromial roof extension (1.36x‐ray, 0.92ct) compared with acromial height (1.06x‐ray, 0.73ct) and glenoid inclination (0.60x‐ray, 0.61ct). However, no single factor showed an effect size which was as high as that of the CSA (1.63x‐ray). Interestingly, a ratio of lateral acromion roof extension and acromial height could enhance the effect size (1.60x‐ray, 1.16ct) near to values of the CSA (1.63x‐ray). In summary, lateral acromial roof extension has a greater influence in pathogenesis of degenerative RCT and concentric OA than acromial height or glenoid inclination. This article is protected by copyright. All rights reserved
Article
Background: Focus has recently been on the critical shoulder angle (CSA) as a factor related to rotator cuff tear and osteoarthritis (OA) in the European population. However, whether this relationship is observed in the Asian population is unclear. Methods: The correlation between the CSAs measured on anteroposterior radiographs and the presence or absence of rotator cuff tears or OA changes was assessed in 295 patients. Rotator cuff tears were diagnosed with magnetic resonance imaging or ultrasonography. OA findings were classified using the Samilson-Prieto classification. The CSAs among the patients with rotator cuff tears, OA changes, and those without pathologies were compared. Multivariable analyses were used to clarify the potential risks for these pathologies. Results: The mean CSA with rotator cuff tear (33.9° ± 4.1°) was significantly greater than that without a rotator cuff tear (32.3° ± 4.5°; P = .002). Multivariable analysis also showed that a greater CSA had a significantly increased risk of rotator cuff tears, with the odds ratio of 1.08 per degree. OA findings showed no significant correlation to the CSAs. Conclusions: Our study demonstrates that the CSA is greater in those with a rotator cuff tear than in those without a tear or OA changes, which may be an independent risk factor for the incidence of rotator cuff tears in the Japanese population.
Article
Background: The objectives of this study were to determine whether glenoid inclination (1) could be measured accurately on magnetic resonance imaging (MRI) using computed tomography (CT) as a gold standard, (2) could be measured reliably on MRI, and (3) whether it differed between patients with rotator cuff tears and age-matched controls without evidence of rotator cuff tears or glenohumeral osteoarthritis. Methods: In this comparative retrospective radiographic study, we measured glenoid inclination on T1 coronal MRI corrected into the plane of the scapula. We determined accuracy by comparison with CT and inter-rater reliability. We compared glenoid inclination between patients with full-thickness rotator cuff tears and patients aged >50 years without evidence of a rotator cuff tear or glenohumeral arthritis. An a priori power analysis determined adequate power to detect a 2° difference in glenoid inclination. Results: (1) In a validation cohort of 37 patients with MRI and CT, the intraclass correlation coefficient was 0.877, with a mean difference of 0° (95% confidence interval, -1° to 1°). (2) For MRI inclination, the inter-rater intraclass correlation coefficient was 0.911. (3) Superior glenoid inclination was 2° higher (range, 1°-4°, P < .001) in the rotator cuff tear group of 192 patients than in the control cohort of 107 patients. Conclusions: Glenoid inclination can be accurately and reliably measured on MRI. Although superior glenoid inclination is statistically greater in those with rotator cuff tears than in patients of similar age without rotator cuff tears or glenohumeral arthritis, the difference is likely below clinical significance.
Article
It has been unclear whether the risk factors for rotator cuff tears are the same at all ages or differ between young and older populations. In this study, we examined the risk factors for rotator cuff tears using classification and regression tree analysis as methods of nonlinear regression analysis. There were 65 patients in the rotator cuff tears group and 45 patients in the intact rotator cuff group. Classification and regression tree analysis was performed to predict rotator cuff tears. The target factor was rotator cuff tears; explanatory variables were age, sex, trauma, and critical shoulder angle≥35°. In the results of classification and regression tree analysis, the tree was divided at age 64. For patients aged≥64, the tree was divided at trauma. For patients aged<64, the tree was divided at critical shoulder angle≥35°. The odds ratio for critical shoulder angle≥35° was significant for all ages (5.89), and for patients aged<64 (10.3) while trauma was only a significant factor for patients aged≥64 (5.13). Age, trauma, and critical shoulder angle≥35° were related to rotator cuff tears in this study. However, these risk factors showed different trends according to age group, not a linear relationship.
Article
Background: In 2013 Moor et al introduced the concept of the critical shoulder angle (CSA) and suggested that an abnormal CSA was a leading factor in development of rotator cuff tear (RCT) and osteoarthritis (OA) of the shoulder. This study assessed whether the CSA was associated with RCT and OA and tested the inter- and intrarater reliability of the CSA when measuring RCT and OA. Materials and methods: The study was performed as a retrospective case-control study. The cases comprised 2 groups: 97 patients with RCT and 87 patients with OA. The controls were matched 3:1, by age and sex, from a population of 795 patients with humeral fractures. The CSA was measured as described by Moor et al. Analysis of the relation with CSA for RCT and OA was done by logistic regression. Models were fitted separately for RCT and OA and used the controls matched to the respective cases. Inter- and intrarater reliability was determined by measuring the intraclass correlation coefficient and minimal detectable change. Results: The mean CSA was 33.9° in the RCT group and 33.6° in the matched control group. The odds ratio for developing RCT for people with a CSA above 35° was 1.12 (P = .63). The mean CSA in the OA group was 31.1° and in the matched control group 33.3°. The odds ratio for developing OA for people with a CSA below 30° was 2.25 (P = .002). The CSA measurements showed strong intra- and inter-rater reliability, with intraclass correlation coefficient values above 0.92 and minimal detectable change values below 0.4°. Conclusions: This study did not find any association between CSA and RCT but did show association between CSA and OA, with a 2.25 odds ratio of developing OA given the patient had a CSA below 30°. The results do not support the suggested praxis of shaving away the lateral border of the acromion to make the CSA smaller because it might increase the risk of developing OA without decreasing the risk of developing RCT. The CSA measurements showed excellent intra- and inter-rater reliability.
Article
Background: Higher critical shoulder angle (CSA) is correlated with rotator cuff tears (RCTs), whereas lower CSA is associated with glenohumeral osteoarthritis (OA). Our goal was to investigate whether patients with concurrent glenohumeral OA and full-thickness RCTs demonstrate a higher CSA than patients with OA alone. Methods: Using a 2-surgeon shoulder arthroplasty registry, we identified 31 patients with glenohumeral OA and full-thickness RCTs confirmed by plain radiography and magnetic resonance imaging, respectively. Sixty-two age- and gender-matched controls (1:2 ratio) with glenohumeral OA and an intact rotator cuff were identified from the same registry. Two independent observers evaluated the radiographs for CSA and acromiohumeral index. Results: The average CSA was 30° in the OA control group and 35° in the concurrent RCT and OA group (P < .0001). Acromiohumeral index was comparable between the groups (P = .13). Interobserver reliability of the independent reviewers was excellent (κ = 0.89; Ρ = 0.95). The receiver operating characteristic curve for CSA demonstrated that a value >35° was 90% specific and 52% sensitive for a full-thickness RCT in the setting of OA (area under curve = 0.84). Conclusion: Concurrent glenohumeral OA and full-thickness RCT are associated with greater CSA values compared with patients with glenohumeral OA alone. The CSA measurement may be useful in determining the need for magnetic resonance imaging to assess rotator cuff integrity in the arthritic population.