Assessing bone loss in instability lf 2016

How and why to assess bone loss in shoulder instability

1. Lennard Funk
Assessing Bone Loss
in GHJ Instability
[email protected]

2. Is Bone Loss Important?
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1. Yes
2.No

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How much glenoid loss 

for Bony Reconstruction?
1. 5%
2. 10%
3. 20%
4. 25%

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What is a significant Hill-Sachs
Lesion?
1. 12.5% humeral head surface
2. 20% humeral head surface
3. 40% humeral head surface
4. Engaging at Arthroscopy

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How do you assess Bone Loss?
1. X-Rays
2. MRI
3. CT
4. Arthroscopy
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Do you MEASURE the bone loss?
1. Yes
2.No
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“The extent to which beliefs

are based on evidence

is very much less

than believers suppose”
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Bertrand Russell
The Skeptical Essays, 1928

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The problem with ‘Evidence’
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• 9 cadavers all soft tissues removed
• Defects - 12.5%, 25%, 37.5%, 50%
• Applied compressive + anterior load
• Stability ratio = ant. load / compr. load
• All dislocated at 60deg. ER
• 25% & 37.5% lower stability ratio
The problem with ‘Evidence’

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• 9 cadavers - skin & deltoid removed
• Applied compressive + anterior load
•Three positions: 0/0, 30/30, 60/60
•Translation, ant. capsule force, bony force
•above 30/30 all sig. incr.
The problem with ‘Evidence’

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“The extent to which beliefs

are based on evidence

is very much less

than believers suppose”
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Bertrand Russell
The Skeptical Essays, 1928

12. GLENOID BONE LOSS
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How much?

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Where does 20-25% come from?
Itoi Cadaveric Studies - JBJS, 2000:
Stability of repaired cadaveric shoulders
With no glenoid removed
With 21% anterior glenoid removed
ER and ABER
Yamamoto & Itoi - AJSM, 2009
Stability ratio mechanical test 8 cadavers
At 20% stability ratio greatly decreased
Yamamoto - JBJS, 2010
Same study (with 5 more shoulders)!!
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Pear
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Inverted Pear

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•Glenoid loss 20-30%
•FU 34 months
•15% Recurrence rate
“requiring surgery”
•‘Inverted Pear’
•FU 27 months
•67% Recurrence rate

(89% contact athletes)

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Critical level of bone loss leading to increased
recurrent instability and worse WOSI scores 

= 13.5%
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How much?

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CT Scan reliable?
Griffith Method: AJR 2008
‘En face’ CT compared to opp. normal glenoid in 218
anterior instability cases
High inter- and intra-observer reliability
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BUT:
Only one study validating side-side reliability in Normals…
10 patients! Same authors and Journal: AJR, 2003

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CT Scan reliable?
Griffiths et al. 2007
CT vs. Arthroscopy (gold standard)
Strong Correlation (r=0.79, 95%CI=0.659–0.877, p<0.0001)
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BUT: Measurements based on Bare Spot
Not reliable marker
Miyatake 2014; Kralinger 2006; Sugaya 2014, Huysmans 2006

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Huysmans, JSES 2006
Cadaveric study on 40 cadavers:
Inferior glenoid is a circle
Bare spot variable
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CT Reliable?
‘Pico’ Method: Skeletal Radiol, 2009
40 shoulders compared opp. side
ICC values 0.9-0.98
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BUT:
Two observers, only one intra-observer
Reformatting done prior to observers.

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Problems with en-face methods
Glenoid face not flat
Reformatting not standardised for axial
reference image
Don’t usually CT opposite shoulder
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What about MRI?
MRI vs CT:
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Lee et al. 2013vs. 2D CT r=0.83 YES
Moroder
2013
vs. 3D CT
35% sensitive

100% specific
NO
Gyftopoulous
2012
vs. 2DCT & 3DCT
percent error :

3DCT 2.17-3.5 %, 

2DCT 2.22-17.1 %,
MRI 2.06- 5.94 %
YES
All different methodology & statistical analysis

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Glenoid Summary
No clear evidence on critical degree of bone loss
Discrepancy in outcomes
Arthroscopy not reliable gold standard
En-face measurements ? reproducible
If you do measure - ? need to CT opposite
‘normal’ side
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26. HUMERAL HEAD BONE LOSS
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What is a significant
Hill-sachs lesion?
Bigliani & Flatow (1996) 

[quoted in Cetik (2007)]:
Mild - <20%
Moderate - 20-45%
Severe - >45%
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> 30% = Needs Treatment

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Biomechanical Studies
5/8 radius in ABER; 7/8 radius neural ER 

(Kaar, 2010)
Defects as low as 12.5% dislocate in 60deg ER

(Sekiya, 2009)
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Plain radiographs
Balg & Bouileau (2008) in ISIS:
Visible on AP X-Ray in External Rotation
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Width(x) & depth(y)
AP in 60deg. IR
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Plain radiographs: Hill-Sachs Quotient
Recurrence rate higher with a larger quotient
(Grade I 23.3 %; grade II 16.2 %; grade III 66.7 %)
Reliability and accuracy not been tested
Length(z)
Bernageau view
HSQ = x.y.z
Grade: I <1.5cm
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; II 1.5-2.5cm
2
; III > 2.5cm
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Kralinger, 2002

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Plain radiographs: Radius Technique
Recurrence rate higher with a
larger ratio (Sommaire):
d/R >20% = 40% recurrence
d/R < 20% = 10% recurrence
Arth Stab failure rate (Hardy):
d/R >15% = 60% failure
d/R <15% = 15% failure
Hill-Sachs depth(d)/Humeral head radius(R)

- AP in IR
Charrouset, 2010

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CT
Hardy, 2012:
Larger Width, depth & length = lower Duplay score,
but not tested for reliability
Saito, 2009 & Cho, 2011:
Good intra- & inter-reliability for depth & width on
2DCT
Kodali, 2011:
Moderate reliability on 2DCT
With percentage error of 13.6+/-8.4%
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MRI & Arthroscopy
No reliability studies for MRI!
Kirkley, 2003: MRI = Arthroscopy in detecting
Hill-Sachs lesions (16 patients; no blinding)
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Funky Pizza Method
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‘Large’ Hill-Sachs Lesion
One Pizza Slice = > 12.5% of the humeral head diameter
Defects as low as 12.5% dislocate in 60deg ER

(Sekiya, 2009)

36. Combined
Glenoid + Humeral Head
Methods
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Balance Stability Angle - Matsen
Effective Glenoid Arc = the area of the glenoid’s
articular surface available for humeral head
compression
Balance Stability Angle = the angle between the centre
of the glenoid and the end of the effective glenoid arc
in any direction (18 degrees anterior)
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‘Glenoid Track’ - Itoi & Yamamoto
Yamamoto - Cadaver
Metzger - MRI/MRA
Omori - In-vivo
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Yamamoto N, Itoi E, Abe H, et al. JSES 2007

Metzger et al. AAOSM, 2010

Omori et al. AJSM. March 2014.
Defined as the contact area between the glenoid and the humeral head
while keeping the arm in maximum external rotation, maximum horizontal
extension, and 0° to 90° of abduction relative to the trunk.
If a Hill-Sachs lesion extends medially over the glenoid track, there is a
risk of engagement.

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Largest Track (contact)
found in full ABER
= 84% of glenoid width
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‘Glenoid Track’

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‘Glenoid Track’
If the medial margin of a Hill-
Sach’s lesion lies inside the
glenoid track, this will cause
an engaging Hill-Sach’s.
Bony defect of the glenoid will
narrow the glenoid track

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1. Measure the diameter (D) of the inferior glenoid, either by
arthroscopy or from 3D CT scan.
2. Determine the width of the anterior glenoid bone loss (d).
3. Calculate the width of the glenoid track (GT) by the following
formula: GT=0.83D-d
4. Calculate the width of the HSI, which is the width of the Hill-
Sachs lesion (HS) plus the width of the bone bridge (BB) between
the rotator cuff attachments and the lateral aspect of the Hill-
Sachs lesion: HSI = HS + BB.
5. If HSI > GT, the HS is off track, or engaging. If HSI < GT, the HS is
on track, or non-engaging.
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Normal Glenoid Track
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83%
G

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Anterior Glenoid Deficiency
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D
83%

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The Formula:
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1. Measure the diameter (D) of the inferior
glenoid, either by arthroscopy or from 3D
CT scan (of Opposite shoulder).
2. Determine the width of the anterior
glenoid bone loss (d).
3. Calculate the width of the glenoid track
(GT) by the following formula: GT=0.83D-d
4. Calculate the width of the HSI, which is
the width of the Hill-Sachs lesion (HS) plus
the width of the bone bridge (BB) between
the rotator cuff attachments and the
lateral aspect of the Hill-Sachs lesion: 

HSI = HS + BB.
5. If HSI > GT, the HS is off track, or
engaging. If HSI < GT, the HS is on track, or
non-engaging.
D
83%

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The Formula:
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1. Measure the diameter (D) of the inferior
glenoid, either by arthroscopy or from 3D
CT scan.
2. Determine the width of the anterior
glenoid bone loss (d).
3. Calculate the width of the glenoid track
(GT) by the following formula: GT=0.83D-d
4. Calculate the width of the HSI, which is
the width of the Hill-Sachs lesion (HS) plus
the width of the bone bridge (BB) between
the rotator cuff attachments and the
lateral aspect of the Hill-Sachs lesion: 

HSI = HS + BB.
1. If HSI > GT, the HS is ‘off track’, or
engaging.
2.If HSI < GT, the HS is ‘on track’, or
non-engaging.

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Glenoid:
Best fit circle (Huysmans)
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Humerus:
Hill-Sachs on coronal
GT = 0.84xD-d HS
D
d
1.If HS > GT, the HS is ‘off track’, or engaging.
2.If HS < GT, the HS is ‘on track’, or non-engaging.
Simplified: Not validated

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Two year period of 57 Bankart repairs
On-track (49) - recurrence 4%
Off-track (8) - recurrence 75%
PPV for Glenoid Track = 75%
PPV for Glenoid loss >20% = 43%
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Summary:
Radiography:
Insufficient accuracy
Not sufficient for pre-op planning
Useful for screening
CT:
Most reliable, but need opposite shoulder
Radiation exposure
MRI & Arthroscopy:
No sufficient validation
ALSO:
No consensus measuring technique
No clarity on what a clinically significant lesion is!
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Thank You
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