The document discusses the "medial ridge sign" seen on CT scans of patients with recurrent shoulder dislocations as an indicator of glenoid bone loss. The study aimed to evaluate if the medial ridge sign reliably indicates significant bone loss. It found the sign had high sensitivity but low specificity for significant loss. While the sign suggested some bone loss, glenoid bone loss measurements were still needed to determine if augmentation was required rather than just Bankart repair. So the medial ridge sign is not reliable in deciding between the two surgical procedures.

1. Medial Ridge Sign- Is it a reliable indicator of Glenoid
Bone loss?
Dr. Dhanasekaraprabu, Dr. Aravindh Palaniswamy,
Prof H L Nag, Dr. Vivek Morrey, Dr. Deep Srivastava
All India Institute of Medical Sciences,
New Delhi

2. Introduction:
• Glenohumeral instability affects approximately 2% of general population
and anterior dislocations occuring 95% TO 98% of the time1.Recurrent
shoulder instability is a major problem among athletes and the young
adult population.
• Anterior shoulder dislocation is more common than the posterior shoulder
dislocations and the recurrence of shoulder dislocations is increased in the
young adults and also in athletes.
• The recurrence rates following the primary dislocation in patients who
were less than 20 years old was almost 90%2.
• The management of recurrent anterior shoulder instability has been
mainly surgical and bankart’s repair is the gold standard. Recently the
trend towards arthroscopic bankart’s repair is on the rise3

3. • Arthroscopic treatment of
shoulder instability introduced
some advantages compared with
the open procedure.
• These include short surgical times,
less morbidity, less postoperative
pain, reduced hospitalization time,
and a decreased risk of
complications4.
• In the treatment of traumatic
recurrent anterior shoulder
instability, patients with bone loss
are at risk for recurrent instability
after arthroscopic Bankart Repair5.
• The major reason for failure of
surgeries in recurrent shoulder
instability has been the inability to
assess the glenoid bone loss
causing instability even after
bankart’s repair.

4. • Recurrent shoulder
dislocations present with
glenoid bony defects especially
its anterior part and they are
the major cause of failure of
surgery.
• Glenoid defects have been
termed significant if they are
more than 19% of glenoid
height or 25% of its width
according to Yamamoto et al6.
• But how to assess and look for
a glenoid bone defect in the
first place?

5. • Traditionally 2D CT images were
used to look for glenoid bone loss
but they were not helpful, and
recently 3D CT scans have been
proposed as the best way to look
for a significant glenoid bone
defect.
• Various measurement techniques,
mostly involving 2D or 3D CT
scans, have been introduced for
quantification of defect size.7, 8, 9.
• Most measurement methods rely
on glenoid shape comparison with
the unaffected contra lateral side
or the best-fit circle technique,
which is based on the fact that the
inferior portion of the glenoid
resembles a circle10, 11

6. So what is the Medial ridge sign?
• The sign was first described by
Philipp Moroder et al11.
According to them medial ridge
sign represents a nonanatomic
ridge on the scapular neck
slightly medial to anterior
glenoid rim visible on 2D CT
images especially axial images.
According to them the bony
bankart lesion on the anterior
glenoid rim migrates medially
and gets absorbed over a
period of time.
• The medial ridge sign is due to
the osseous integration of this
fragment to the glenoid neck.
Medial Ridge Sign
12. Philipp Moroder, Mark Tauber : The medial-ridge sign as an indicator of anterior
glenoid bone loss J Shoulder Elbow Surg (2013) 22, 1332-1337

7. The Medial Ridge sign demonstrated on a 3D CT scan

9. Goals of our study:
• The goal of this study was to look for medial ridge sign in patients with
recurrent shoulder dislocations and find out whether the sign was useful
in assessing the percentage of bone loss in such patients.
• We wanted to find out if the medial ridge sign was helpful in pointing to
patients with significant glenoid bone loss so that a decision for
arthroscopic bankart’s vs bone augmentation procedure may be made in
these patients.

10. Materials and Methods:
• The study was conducted at our institution. 35 patients with unilateral
recurrent anterior instability of shoulder were evaluated with Computer
tomography preoperatively before undergoing definitive surgical
procedure.
• Study Design : Observational Study
• The patients who were included in the study were 15-40 years old, and
had more than one episode of dislocation.
• Patients with habitual dislocation and bilateral dislocations were excluded
from the study.
• The patients enrolled in the study were subjected to a 3D CT of bilateral
shoulder with arms by the side of the chest wall.

11. • CT films were acquired in MDCT
scanners (Somatom sensation,
Siemens, Erlanger, Germany) with a
volume data acquisition of 0.6 X 40,
slice thickness of 0.6 mm.
• The scanning plane extended from
the acromion to just below the
glenoid following which 3D volume
rendered standardized images were
reconstructed and then en face view
of the glenoid cavity was obtained
after subtracting the humeral head.

12. • On en face view of the glenoid a
line was drawn along the long axis
of the glenoid and a second line
was drawn perpendicular to the
long axis of glenoid at the inferior
glenoid from the posterior margin
to the anterior margin and was
calculated as the width of the
glenoid (glenoid index) in
millimetres. It was also then
calculated in the contralateral
normal side.
• Percentage of bone loss was
calculated using the formula [ (D-d)/
D] x 100.

13. Fig 4: 3D CT scans were used to calculate the percentage of bone loss

14. Results:
• Out of the 35 patients included in our study we found out that the medial
ridge sign was present in 31 patients.
• Some amount of glenoid bone loss was present in about 32 patients when
their CT images were reviewed.
• The sign had a sensitivity of 81% and a specificity of about 100% in those
patients with a glenoid bone loss.
• The Glenoid bone loss was calculated using the method described earlier
and ‘significant’ bone loss was found only in 4 patients in the study group.
• So the medial ridge sign had a high sensitivity(100%) but only low
specificity (29%) in cases with significant bone loss.

15. Discussion:
• One of the most common
surgical procedures performed
for recurrent shoulder
instability is Bankart’s repair
and
• An Important cause of failure of
arthroscopic surgery in the
condition is glenoid bone loss5.
• As we had already mentioned
even though various authors
differ on the estimates of
“significant” glenoid bone loss
the consensus seems to be
about 25% of the glenoid
surface6.

16. • CT scans are more sensitive in picking
up the bony defects than MRI or
routine radiography13.
• 3D CT scans were in fact more
accurate in predicting bone loss than
2D CT scans 13
• However the glenoid bone loss is not
routinely measured on the CT scans
preoperatively leading to
underestimating the amount of
glenoid loss resulting in failure of
surgery.
• Various methods have been
developed that estimate the glenoid
bone loss on CT scans as we had
mentioned earlier including
comparing it with the contralateral
side and also the best fit technique10,
11

17. • The medial ridge sign was
described by Philipp Moroder et
al12 after the analysis of CT scans
of patients with recurrent
shoulder instability and they
propose it as a indicator of
anterior glenoid bone loss in their
study
• But as our results point out the
medial ridge sign even though
present in cases with anterior
glenoid bone loss was not specific
enough to pick up cases with
significant bone loss in which
there is a difficulty in making a
clinical decision

18. • Hence even though the medial ridge sign
may be present in cases of recurrent
shoulder instability, it will not help the
surgeon in choosing a bone augmentation
procedure over the routine bankart’s
procedure.
• The medial ridge sign is just an indicator of
glenoid bone loss and eventually 3D CT
scans need to be analysed and the loss
measured. And when the loss is found to be
significant the surgeon may decide upon the
need for a bone augmentation procedure
lessening the chances of failure in the post
op period.

19. References:
1.Zacchilli MA, Owens BD. Epidemiology of shoulder dislocations presenting to emergency departments in the united states. J Bone Joint Surg
Am 2010;92(3):542-9
2. Mclaughlin HL, Cavallaro WU: Primary anterior dislocation of the shoulder, Am J Surg 80:615, 1950
3. Owens BD, Harrast JJ : Surgical trends in Bankart repair: an analysis of data from the American Board of Orthopaedic Surgery certification
examination, Am J Sports Med. 2011 Sep;39(9):1865-9
4. Green MR, Christensen KP. Arthroscopic versus open Bankart procedures: a comparison of early morbidity and complications. Arthroscopy
1993;9:371-374.
5. Risk factors for recurrence of shoulder instability after arthroscopic Bankart repair. Boileau P , Villalba M J Bone Joint Surg Am. 2006
Aug;88(8):1755-63.
6. Yamamoto N, Muraki T, Sperling JW, Steinmann SP, Cofield RH, Itoi E, et al. Stabilizing mechanism in bone-grafting of a large glenoid defect.
J Bone Joint Surg Am 2010; 92:2059-66. http://dx.doi.org/ 10.2106/JBJS.I.00261
7. Baudi P, Righi P, Bolognesi D, Rivetta S, Rossi Urtoler E, Guicciardi N, et al. How to identify and calculate glenoid bone deficit. Chir Organi
Mov 2005; 90:145-52.
8. Chuang TY, Adams CR, Burkhart SS. Use of preoperative three dimensional computed tomography to quantify glenoid bone loss in shoulder
instability. Arthroscopy 2008; 24:376-82. http://dx.doi.org/ 10.1016/j.arthro.2007.10.008
9. Dumont GD, Russell RD, Browne MG, Robertson WJ. Area-based determination of bone loss using the glenoid arc angle. Arthroscopy 2012;
28:1030-5. http://dx.doi.org/10.1016/j.arthro.2012.04.147
10. Huysmans PE, Haen PS, Kidd M, Dhert WJ, Willems JW. The shape of the inferior part of the glenoid: a cadaveric study. J Shoulder Elbow
Surg 2006; 15:759-63.
11. Jeske HC, OberthalerM, KlingensmithM, Dallapozza C, Smekal V, WambacherM, et al. Normal glenoid rim anatomy and the reliability of
shoulder instability measurements based on intrasite correlation. Surg Radiol Anat 2009; 31:623-5.
12. Philipp Moroder, Mark Tauber : The medial-ridge sign as an indicator of anterior glenoid bone loss J Shoulder Elbow Surg (2013) 22, 1332-
1337
13. Rerko MA, Pan X, Donaldson C, Jones GL, Bishop JY. Comparison of various imaging techniques to quantify glenoid bone loss in shoulder
instability. J Shoulder Elbow Surg 2013;22:528-34

20. 3D CT scans showing the presence of the medial ridge sign (arrow) when compared with the contra lateral normal shoulder.
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