Assessing bone loss in instability lf 2016
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Transcript of Assessing bone loss in instability lf 2016
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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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“The extent to which beliefsare based on evidence is very much less than believers suppose”
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Bertrand Russell The Skeptical Essays, 1928
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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 beliefsare based on evidence is very much less than believers suppose”
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Bertrand Russell The Skeptical Essays, 1928
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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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• 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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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. 2013 vs. 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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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 <1.5cm2; II 1.5-2.5cm2; III > 2.5cm2
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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‘Large’ Hill-Sachs LesionOne Pizza Slice = > 12.5% of the humeral head diameter Defects as low as 12.5% dislocate in 60deg ER(Sekiya, 2009)
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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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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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