The forelock sign: A new arthroscopic finding in partial subscapularis tears

Abstract

Objectives:
This study aims to identify the forelock sign of partial tears of the subscapularis and to compare the incidences of this sign and air bag sign.

Patients and methods:
One hundred and twenty patients (39 males, 81 females; mean age 51.3 years; range, 25 to 79) diagnosed as isolated subscapularis tear or isolated supraspinatus tear from among patients who underwent shoulder arthroscopy between January 2013 and January 2016 were divided into four groups of 30 patients each as the subscapularis tear (group 1), full-thickness supraspinatus tear (group 2), bursal-side supraspinatus tear (group 3), and articular-side supraspinatus tear (group 4) groups. All patients had video records of their operation. The integrity of the long head of biceps tendon (LHBT), Lafosse classification of the subscapularis tear, and the incidence of the forelock and air bag signs were evaluated.

Results:
The incidence of the air bag sign in group 1 was 10% and that of the forelock sign was 60%. The forelock sign was significantly more frequent in group 1 than in the other groups (odds ratio 10.46: 3.9-27.8 with 95% confidence interval) and the air bag sign (p<0.001). The LHBT was mostly pathologic in this group, which was also statistically significant (p<0.01). The incidence of the forelock sign in group 1 was similar in each LHBT pathology and Lafosse subgroups.

Conclusion:
The forelock sign identified in this study was significantly frequent (60%) in partial subscapularis tendon tears with strong inter- and intra-observer consistency while the air bag sign was rare (10%). The LHBT disorders were strongly associated with subscapularis tears; however, the forelock sign was not an indicator of the condition of the LHBT and type of partial subscapularis tendon tear according to the Lafosse classification.

Full text

Eklem Hastalıkları ve
Cerrahisi
Joint Diseases and
Related Surgery Original Article /
Özgün Makale
Eklem Hastalik Cerrahisi
2019;30 (3):185-192
do i: 10.5 606/eh c. 2019.6 6814
The forelock sign: A new arthroscopic finding in
partial subscapularis tears
Kakül işareti: Parsiyel subskapularis yırtıklarında yeni bir artroskopik bulgu
Received: June 10, 2019 Accepted: July 10, 2019
Published online:
October 24, 2019
Correspondence: Mehmet Çeti nkaya, MD. Erzincan Üniversitesi Mengücek Gazi Eğitim ve Ara ştır ma Hastanesi Ortopedi ve Travmatoloji Kliniği,
2403 0 Erzincan, Turkey. Tel: +90 532 - 796 98 87 e-ma il: drcetink@gmail.com
ÖZ
Amaç: Bu çalışmada, subskapula ris parsiyel yırtık larının kakül
işareti tanımlandı ve bu işaret ile hava yastığı işaretinin insidansları
karşılaştırıldı.
Hastalar ve yöntemler: Ocak 2013-Ocak 2016 tarihleri
arasında omuz artroskopisi uygulanan hastalar arasından
izole subskapula ris yırtığı veya izole supraspinatus yırtığı
tanısı konulan 120 hasta (39 erkek, 81 kadın; ort. yaş 51.3
yıl; dağılım, 25-79 yıl) subskapularis yırtığı (grup 1), tam
kat supraspinatus yırtığı (grup 2), bursal yüz supraspinatus
yırtığı (grup 3) ve eklem yüzü supraspinatus yır tığı (gr up 4)
grubu olmak üzere 30’ar hastalık dört gruba ayrıldı. Tüm
hastaların ameliyatının video kaydı vardı. Biseps tendonunun
uzun başı (BTUB)’nın bütünlüğü, subskapularis yırtığının
Lafosse sınıflandırması ve kakül ve hava yastığı işaretlerinin
insidansı değerlendirildi.
Bulgular: Grup 1’de hava yastığı işaretinin insidansı %10, kakül
işaretininki %60 idi. Kakül işareti grup 1’de diğer gruplardan
(olasılık oranı %95 güven aralığında 10.46: 3.9-27.8) ve hava
yastığı işaretinden anlamlı olarak daha sıktı (p<0.001). Biseps
tendonunun uzun başı bu grupta çoğunlukla patolojikti ve bu da
istatistiksel olarak anlamlıydı (p<0.01). Grup 1’de kakül işareti
insidansı her BTUB patolojisinde ve Lafosse alt gruplar ında
benzerdi.
Sonuç: Bu çalışmada tanımlanan kakül işareti parsiyel
subskapularis tendonu yırtıklarında güçlü gözlemciler arası ve
gözlemciler içi tutarlılık la anlamlı olarak sık (%60) iken hava
yastığı işareti nadirdi (%10). BTUB’nin bozuklukları subskapularis
yırtıklar ıyla güçlü bir şekilde ilişk iliydi fakat ka kül işareti
BTUB’nin durumunun veya Lafosse sınıflandırmasına göre
parsiyel subskapular is tendon yırtığı tipinin bir göstergesi değildi.
Anahtar sözcükler: Artroskopi, rotator manşet yı rtığı, omuz, subskapularis.
ABSTRACT
Objectives: This study aims to identify the forelock sign of
partial tears of the subscapularis and to compare the incidences of
this sign and air bag sign.
Patients and methods: One hundred and twenty patients
(39 males, 81 females; mean age 51.3 years; range, 25 to 79)
diagnosed as isolated subscapularis tear or isolated supraspinatus
tear from among patients who underwent shoulder arthroscopy
between January 2013 and January 2016 were divided into four
groups of 30 patients each as the subscapularis tear (group 1), full-
thickness supraspinatus tear (group 2), bursal-side supraspinatus
tear (group 3), and articular-side supraspinatus tear (group 4)
groups. All patients had video records of their operation. The
integrity of the long head of biceps tendon (LHBT), Lafosse
classification of the subscapularis tear, and the incidence of the
forelock and ai r bag signs were evaluated.
Results: The incidence of the air bag sign in group 1 was 10%
and that of the forelock sign was 60%. The forelock sign was
significantly more frequent in group 1 than in the other groups
(odds ratio 10.46: 3.9-27.8 with 95% confidence interval) and
the air bag sign (p<0.001). The LHBT was mostly pathologic in
this group, which was also statistically significant (p<0.01). The
incidence of the forelock sign in group 1 was similar in each LHBT
pathology and Lafosse subgroups.
Conclusion: The forelock sign identified in this study was
significantly frequent (60%) in partial subscapularis tendon tears
with strong inter- and intra-observer consistency while the air
bag sign was rare (10%). The LHBT disorders were strongly
associated with subscapularis tears; however, the forelock sign was
not an indicator of the condition of the LHBT and type of partial
subscapularis tendon tea r according to the Lafosse classification.
Keywor ds: Arthroscopy, rotator cuff tear, shoulder, subscapularis.
Citation:
Çetinkaya M, Kanatlı U, Ataoğl u MB, Özer M, Aya noğlu T, Bölükbaşı S. T he forelock sig n: A new ar throscopic finding in par tial s ubscapula ris tea rs.
Eklem Hastalik Cerrahisi 2019;30(3):185-192.
Mehmet Çetinkaya, MD1, Ulunay Kanatlı, MD2, Muhammet Baybars Ataoğlu, MD2,
Mustafa Özer, MD3, Tacettin Ayanoğlu, MD2, Selçuk Bölükbaşı, MD2
1Department of Orthopedics and Traumatology, Erzincan University Mengücek Gazi Training and Research Hospital, Erzincan, Turkey
2Department of Orthopedics and Traumatology, Gazi University School of Medicine, Ankara, Turkey
3Department of Orthopedics and Traumatology, Necmettin Erbakan University Meram Medical School, Konya, Turkey

Eklem Hastalik Cerrahisi 186
Interest in subscapularis tears increases day by
day. The studies of Gerber and Krushell[1] and Lo and
Burkhart[2] were two giant leaps for understanding
the clinical relevance of the subscapularis tendon
repair which improves the outcomes after rotator
cuff repair, and these are not the only ones providing
data of improved outcomes following the surgical
intervention for subscapularis tears.[3- 6]
The recognition of partial subscapularis tears
may be challenging because of the difficulty to
acquire an appropriate angle of view and obscuring
intra-articular structures like an inflamed biceps
tendon with scuffing. Neyton et al.[7] suggested an
arthroscopic technique to view the subscapularis
insertion site. However, it is necessary to place
traction sutures to the subscapularis tendon through
the subacromial space and then to re-evaluate the
subscapularis insertion by intra-articular gazing
under the traction of these sutures. Other than
this, Sahu et al.[8] reported an arthroscopic finding,
named sentinel sign with a high inter- and intra-
observer reliance which indicates scuffing, abrasion,
or tear of the anterior part of the long head of
biceps tendon (LHBT) that may show a subscapularis
tendon rupture apparent or hidden on arthroscopy.
Similarly, Wani et al.[9] and Saremi[10] reported the
nodular scarring of a partially torn subscapularis
tendon as an arthroscopic finding, which is named
as air bag sign by Saremi. These efforts to reveal the
hidden lesions of the subscapularis tears provided
some advance in recognition of these lesions and
drove scientists forward to make new investigations
and find new viewpoints. In this study, we reported
another arthroscopic finding named the forelock
sign which is residual fringes of the superior
glenohumeral ligament (SGHL) and coracohumeral
ligament (CHL) lying down adjacent to the anterior
aspect of the humeral head originating between the
subscapularis tendon and LHBT. Our hypothesis
was that the forelock sign would be more frequent
in partial subscapularis tears than it was in full-
thickness, partial articular-side, and partial bursal-
side supraspinatus tears and that the incidence of
the forelock sign would be significantly higher than
that of the air bag sign. Therefore, in this study, we
aimed to identify the forelock sign of partial tears of
the subscapularis and to compare the incidences of
this sign and air bag sign.
PATIENTS AND METHODS
The prospectively collected surgery videos
of 120 patients (39 males, 81 females; mean age
51.3 years; range, 25 to 79) diagnosed as isolated
subscapularis tear or isolated supraspinatus tear
and who underwent arthroscopic rotator cuff repair
at the Gazi University School of Medicine by a
senior surgeon between January 2013 to January
2016 were reviewed. Four groups were constituted
with patients selected randomly by a randomization
software. These groups including patients with
each of the isolated rotator cuff pathologies
were as follows: subscapularis tear (group 1),
full-thickness supraspinatus tear (group 2), bursal-
side supraspinatus tear (group 3), and articular-side
supraspinatus tear (group 4). The senior surgeon who
performed the procedures was blinded to patients
included in the study. The observers were not blinded
to the diagnosis of the patients since they were
allowed to watch the whole video. Being close to
the SGHL-CHL complex was the reason why the
supraspinatus tear types were chosen for comparison
with subscapularis tears. The isolated term defined
only the pathology regarding the rotator cuff, which
means each patient might have additional shoulder
pathologies such as superior labrum tear, subacromial
impingement, acromioclavicular degenerative
arthritis, or LHBT pathology. Only the accompanying
LHBT pathologies were recorded. The videos with
surgical repair of labrum pathologies for anterior
or posterior instability were not included, since the
forelock sign has only been observed in cases with
rotator cuff tears. The massive rotator cuff pathologies
were excluded to better reveal the each rotator cuff
part’s contribution to the constitution of the forelock
sign. The intratendinous tears of the supraspinatus
tendon were excluded. Patients having a history of
prior surgery or severe trauma in the vicinity of
involved shoulder (including fractures, dislocations,
and falling from a height), traumatic subscapularis
tears, osteoarthritis, and inflammatory joint diseases
were also excluded. The study protocol was approved
by the Erzincan Binali Yıldırım University Ethics
Committee. A written informed consent was obtained
from each patient. The study was conducted in
accordance with the principles of the Declaration of
Helsinki.
Forelock sign is the residual fringes of the SGHL
and CHL lying down adjacent to the anterior aspect of
the humeral head (Figure 1a-d). The reason for calling
it as forelock is the resemblance of the humeral head
to a face looking towards the glenoid fossa, and of the
fibers of the SGHL and CHL to a piece of hair lying
downwards (as in the horses) adjacent to the opposite
side of this face, when the joint is viewed through the
posterior portal of the shoulder. In some cases, SGHL
and CHL were intact, therefore, there was no forelock
sign (Figure 1e and f). Following the tear of the

187
The forelock sign: A new arthroscopic nding in partial subscapularis tears
subscapularis tendon, the biceps tendon subluxates
anteriorly, and the stabilizers of the biceps tendon
including SGHL and CHL, which envelope the biceps
tendon, begin fraying and lose their integrity.[11,12] The
fringes of these ligaments launch from the interval
between the subscapularis tendon anteriorly and
biceps tendon posteriorly, which conceal the partially
torn subscapularis tendon near its insertion side. A
hidden subscapularis tendon tear may be diagnosed
following the debridement of these fibers by an
arthroscopic shaver. Fraying of the LHBT (occurred
secondary to tendinitis or degeneration) or a torn
subscapularis tendon was not assumed as forelock
sign (Figure 2). The fringes moving along with the
biceps tendon when examining on arthroscopy are
also not assumed as forelock sign. The videos were
evaluated by two independent researchers of this
study, except the senior surgeon who performed the
procedures. The inter- and intra-observer correlations
were calculated.
All of the procedures were performed in the
same institute by the senior surgeon of this study
and two assistants. General anesthesia, general
anesthesia with interscalene brachial plexus block,
and single interscalene block were the anesthesia
options. The procedures were performed in semi-
lateral position by rotating patients 20-30° posteriorly
to place the glenoid fossa parallel to the floor.[13]
The standard posterior portal was used for initial
examination of the shoulders. Additional portals
Fig ure 1. (a, b, c, d) Represent some presentation forms of forelock sign. (e, f) Represent sole partial subscapularis
tendon tear without any forelock or sentinel signs.
HH: Humeral head; CHL: Coracohumeral ligament; LHBT: Long head of biceps tendon; SGHL: Superior glenohumeral ligament; Ssc: Superior-most
tendon of subscapularis.
(a) (c) (e)
(b)
(d)
(f)
Figure 2. Scuffing of long head of biceps tendon, also known
as sentinel sign.
LHBT: Long head of biceps tendon; HH: Humeral head; Ssc: Superior-most tendon
of subscapularis.

Eklem Hastalik Cerrahisi 188
were constituted according to the pathology and
planned arthroscopic intervention. The diagnoses of
intra-articular pathologies were established with an
arthroscopic probe. The tears of subscapularis tears
were graded according to the Lafosse subscapularis
tear classification system.[14] Tears including upper 1/3
and 2/3 subscapularis tendon (Lafosse types 1, 2, and 3)
were assumed as partial tears. The superior cuff tears
were recorded as full-thickness tear, partial bursal-
side tear, and partial articular-side tear. Long head of
biceps tendon pathologies were classified as healthy,
tendinopathic (tendinitis or degenerated), dislocated,
both dislocated and tendinopathic, and ruptured, as
described previously.[15] The subscapularis tears were
also scrutinized in terms of intratendinous nodules
which was first described by Wani et al.[9] in 2013 as
nodules (Figure 3) arising from the intra-articular
surface of a partially torn subscapularis tendon.
Statistical analysis
Power analysis tests were conducted to determine
the number of control cases to be able to reject the
null hypothesis that the failure rates for experimental
and control subjects are equal with probability
(power) 0.8 (1-type II error) and a=0.05 (type I error).
Dichotomous variables were assessed by crosstabs
and Pearson’s chi-square test. Normally distributing
and homogenous numeric variables were assessed by
analysis of variance and post hoc analysis. The inter-
observer agreement was measured by calculating the
Kappa statistic. The intra-observer agreement was
measured by calculating the inter-class coefficient
(ICC). For all comparisons, statistical significance
was reported at the value of p<0.05 level (2-tailed).
Statistical analyses were performed with the IBM
SPSS version 21.0 software (IBM Corp., Armonk, NY,
USA).
RES U LT S
The power analysis tests revealed the number of
patients needed to reject the null hypothesis that the
failure rates are equal with probability (power) 0.8
[1-type II error (b)] and a=0.05 (type I error) as four in
each control and study groups, when it was assumed
that the rate of forelock sign was 50% in the study
group and 10% in the control group. Nevertheless,
the number of patients in each group was set to 30
to be able to apply parametric tests when evaluating
normally distributing and homogenous numeric
variables.
There were 292 full-thickness supraspinatus
tears, 80 partial bursal-side supraspinatus tears, 36
articular-side supraspinatus tears, and 35 isolated
subscapularis tears (totally 194 subscapularis tears)
in 1,009 shoulder arthroscopy cases performed in the
designated time period. Thirty randomly selected
patients from each type of aforementioned tears were
evaluated.
Figure 3. Nodular scarring of a partially torn subscapularis
tendon, which is also known as air bag sign.
HH: Humeral head; LHBT: Long head of biceps tendon; Ssc: Superior-most tendon
of subscapularis.
TAB LE I
Mean age, gender, involved shoulder side, and dominant shoulder side of patients
Female-Male Involved shoulder Dominant side shoulder**
Number Mean±SD Range Left-right*
Group 1 30 48.5±10.0 18-12 17-13 11
Group 2 30 59.7±8.3 24-6 7- 23 24
Group 3 30 52.9±10.0 17-13 15-15 17
Group 4 30 51.3±10.3 22-8 7-23 24
* and ** describe a statistical significance of p<0.01. SD: Standard deviation.

189
The forelock sign: A new arthroscopic nding in partial subscapularis tears
The mean age, gender, and involved shoulder data
are presented in Table I. Group 1 was the youngest
group and group 2 was the oldest group. Group 4 was
younger than group 3. The difference was statistically
significant (p<0.001). The involved shoulder side was
mostly right in groups 2 and 4 while it was fifty-fifty
in group 3 and mostly left in group 1 (p<0.01). The
gender distribution of the groups was statistically
similar (p>0.05).
The forelock sign was positive in 60% of isolated
subscapularis tears (group 1). This rate differed from
the other groups presented in Table II (p<0.001).
The odds ratio (OR) of forelock sign for isolated
subscapularis tears compared with other groups was
calculated as 10.46 with 95% confidence interval (CI):
3.9-27.8. The incidence of the air bag sign was 10% in
group 1 and was significantly less frequent than the
forelock sign (p<0.001). As expected, there was no air
bag sign of the subscapularis tendon in groups 2, 3,
or 4, and therefore, the OR of the air bag sign for the
cohort of this study cannot be calculated. The LHBT
was most commonly pathologic in group 1 followed
by group 2 (p<0.01) (Table III). Although a statistical
significance cannot be suggested due to the limited
number of patients in the LHBT subgroups, the
dislocation of the LHBT was always associated with
subscapularis tears. The incidence of the forelock
sign in group 1 was similar in each LHBT pathology
and Lafosse subscapularis tear classification
subgroups (p>0.05). There was no retracted isolated
subscapularis tear (type 4 or 5) which may present
with comma sign or sentinel sign defined previously
by Burkhart et al.[16] and Sahu et al.,[8] respectively.
Although not included in this study, there was
TABLE III
Long head of biceps tendon pathology types of groups
Healthy
LHBT
Tendinitis-
degeneration
Dislocation Rupture Dislocation and
tendinitis-degeneration
Total number of
LHBT pathologies
Group 1 13 10 1 2 4 17
Group 2) 15 14 - 1 - 15
Group 3 25 5 - - - 5
Group 4 21 9 - - - 9
LHBT: Long head of biceps tendon.
TAB LE I I
Incidence of forelock sign incidence in groups
Forelock sign (+) Forelock sign (-) Odds ratio
(with CI of 95%)
Group 1 18 12 10.46 (3.9-27.8)
Group 2 228 0.19 (0.04-0.8
Group 3 723 1.07 (0.4-2.8)
Group 4 129 0.09 (0.01-0.7)
CI: Confidence interval.
TAB LE IV
Lafosse type distribution of subscapularis tears
Number (Percentage) Forelock (Percentage)
Lafosse type n%n%
1 7 23.3 457.1
213 43.3 861.5
310 33.3 660
4 -
5 -

Eklem Hastalik Cerrahisi 190
no forelock sign recorded in the retracted tears
of subscapularis tendon in our patient database.
Table IV demonstrates the frequency of forelock sign
in each subscapularis tear type classified according
to the Lafosse system.
The Kappa value and ICC were calculated to be
0.861 and 0.865, respectively, which revealed strong
inter- and intra-observer agreement levels.
There were only three cases with subscapularis
nodules, and they were all intratendinous type tears.
There was no other intratendinous subscapularis tear
in this group. Two of them also had positive forelock
sign.
DISCUSSION
The most important outcome of the current
study was the rate of positive forelock sign in the
subscapularis tear group (group 1) as 60% (OR: 10.46
with 95% CI: 3.9-27.8), which was significantly higher
than the other groups.[17] Inter- and intra-observer
agreement levels were excellent indicating strong
consistency and reproducibility. It revealed similar
incidence rates among LHBT pathology types and
Lafosse subscapularis tear classification subgroups.
The mean age of the patients in group 1 was
younger than the others. This could be due to the
later onset of superior rotator cuff pathologies
secondary to subacromial impingement or different
anatomical variations causing a rotator cuff tear while
subcoracoid impingement is still a debated issue.[18 ,19]
Eventually, the etiologic factors causing a rotator cuff
tear seems to be making it quicker in subscapularis
tears than in supraspinatus tears. The increase in the
mean age was not assumed to be a contributing factor
for the forelock sign because despite the younger
mean age, subscapularis tears revealed higher rate of
SGHL-CHL injury and forelock sign positivity.
The involved shoulder was mostly left and non-
dominant side. This was not concordant with the
literature.[20] In this study, there was no data to
interpret and explain this finding.
Long head of biceps tendon curves sharply in the
inter-tubercular groove through the intra-articular
space to attach to the supraglenoid tubercle, thus tends
to dislocate anteromedially. What retain the LHBT in
the groove are soft tissue structures rather than bony
tunnel.[21] The close relationship among the insertion of
the superior-most tendon of the subscapularis, CHL,
and SGHL was pointed out previously by Walch et
al.[22] The contribution of the subscapularis insertion as
a stabilizer of the LHBT in the inter-tubercular groove
was previously demonstrated by a number of studies
and recently reported by Arai et al.[23] It inserts to the
upper margin of the lesser tuberosity and supports
the LHBT anteriorly and inferiorly.[24] The dislocated
type LHBT pathologies in this study (five patients)
were all included in the subscapularis tear group. The
SGHL inserts to fovea capitis of the humeral head and
has three types of origin: (i) the middle glenohumeral
ligament, LHBT, and superior labrum; (ii) LHBT and
superior labrum; and (iii) the LHBT only.[25] The CHL
originates from the lateral aspect of the coracoid
process and inserts mainly lateral rotator interval.[23]
The SGHL, CHL, and superior-most tendon of the
subscapularis play a critical role for the stabilization
of the LHBT. The SGHL and CHL fibrils converge
and intricate at the lateral interval and act as a pulley
system for the LHBT while the subscapularis supports
it anteromedially.[22, 26] According to Arai et al.[23] and
also in our opinion, the main structure stabilizing
the LHBT in the groove at the lateral rotator interval
is the superior-most tendon of the subscapularis, and
SGHL and CHL are the minor supporters which act as
a pulley to provide fine-tuning for the course of the
LHBT. The SGHL and CHL alone are not sufficient
enough to stabilize the LHBT without subscapularis.
Therefore, they detach from their insertion or origin
when the integrity of the subscapularis tendon is
deteriorated because of the insufficiency in stabilizing
the LHBT by themselves.[23] We believe that is why
the forelock sign develops following a subscapularis
tendon tear. The reason for partial subscapularis tears
without any forelock sign cannot be determined with
this study, but it might be due to the resorption of the
SGHL-CHL fibers in time.
The LHBT was more frequently pathologic in
the isolated subscapularis and full-thickness
supraspinatus tear groups (groups 1 and 2) than the
isolated bursal-side and articular-side tear groups
(groups 3 and 4). Therefore, the LHBT alone is not a
predictive finding for subscapularis tears. However,
the dislocated LHBTs (five cases) were only present
in the subscapularis tear group, which makes LHBT
dislocation seeming specific to subscapularis tears.
Nevertheless, the forelock sign was present in 18 of
the subscapularis tears while it was present in only
two of full-thickness supraspinatus tears.
Previously, Sahu et al.[8] have described sentinel
sign indicating scuffing, abrasion, or tear of
the anterior part of LHBT that may indicate a
subscapularis tendon rupture apparent or hidden
on arthroscopy. Long head of biceps tendon stability
is provided mainly by the most superior tendon
of the subscapularis. Following the deterioration

191
The forelock sign: A new arthroscopic nding in partial subscapularis tears
of this structure, LHBT subluxation develops, and
the sentinel sign arises. This sign is similar with
the forelock sign described in the current study.
However, the fringes are originated from biceps
tendon in sentinel sign while those are originated
from SGHL-CHL complex in forelock sign. The
fringes that the authors observed on arthroscopy in
their study could also be arising from SGHL-CHL
complex since whether the fringes at the anterior
side of the biceps tendon move along with the biceps
tendon during the biceps stability examination by
pulling it into the joint with an arthroscopic probe
was undetermined by the authors. Besides, they did
not specify through which portal the sentinel sign
was observed. The figures in their paper look like
as if the sign was evaluated through anterior portal
or trough a 70° arthroscope. For the forelock sign
described by the current study, there was no need to
change the viewing portal or the arthroscope during
the arthroscopic examination. On the other hand,
when the biceps tendon of the patient is ruptured,
the sentinel sign can no longer exist in subscapularis
tears. However, the forelock sign can still be present
in those cases because of being unrelated to biceps
tendon. Moreover, the biceps tendon degeneration
and scuffing could be irrelevant to subscapularis
tendon pathology and may arise from another intra-
articular disorder.[27]
Another arthroscopic sign indicating a partial
subscapularis tear described in the literature is the
nodular formation in the substance of the torn tendon.
The incidence of this lesion in the current study was
10% (three of 30 patients) in the subscapularis tear
group, which was very rare when compared to the
forelock sign. Furthermore, this sign was only positive
in intratendinous subscapularis tears, and the number
of intratendinous tears was three. The forelock sign
was positive in two of them. The nodular formation
was first described by Wani et al.[9] as the healing with
nodular scar tissue of a partially torn subscapularis
tendon. Subsequently in 2016, Saremi described the
air bag sign which was posteriorly bulging of the
partially torn subscapularis tendon and added that
this lesion was only seen in interstitial tears and in
the internally rotated arms during the arthroscopy.[10]
These two lesion types described in two different
articles were actually same lesions in our opinion and
were comparable with the forelock sign. However,
they were not so frequent as the forelock sign in
partial subscapularis tears.
This study has some limitations. The thought
that the fibrils constituting the forelock sign belong
to the SGHL-CHL complex has not been proved by
histopathological assessment. However, the origin of
the fibers constituting this sign is not within the scope
of this study. The forelock sign describes the fibers
lying downwards adjacent to the anterior side of the
humeral head. Another important limitation was that
there was no true control group. Therefore, whether
this sign occurs in patients without rotator cuff tears
is still unknown.
In conclusion, the forelock sign identified in the
current study was found to be significantly frequent
in the partial subscapularis tendon tears with strong
inter- and intra-observer consistency while the
nodules were not. This sign can be a very useful
finding in shoulder arthroscopies for surgeons to
diagnose the hidden partial subscapularis tears. The
LHBT disorders, particularly the dislocations, are
also strongly associated with subscapularis tears, and
the forelock sign was irrelevant with the condition
of the LHBT and the type of partial subscapularis
tendon tear according to the Lafosse classification.
Declaration of conflicting interests
The authors declared no conflicts of interest with respect to
the authorship and/or publication of this article.
Funding
The authors received no financial support for the research
and/or authorship of this article.
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