5/31/15 The Problem
Surgical Treatment of ACL Tears Optimizing Femoral Tunnel Positioning •  ACL footprint area is 3.5 x the size
of the midsubstance of the ACL
Andrew D. Pearle, MD •  5 mm slot between notch and PCL
thru which ACL must fit
–  Harner Arthroscopy 1999
•  Proximal ACL is flat (9-16 mm x
2-4mm)
–  Siebold KSSTA 2014
Associate Attending Orthopedic Surgeon Sports Medicine and Shoulder Service Hospital for Special Surgery Director, HSS CAS Center –  Triantafyllidi Arthroscopy 2013
•  Discrepancy between size and
shape of femoral footprint and
midsubstance of the ACL
Life is full of Compromises…
•  ACL footprint area is 3.5 x the size
of the midsubstance of the ACL
–  Harner Arthroscopy 1999
Every Decade We Change Our Minds The Journey Around the Notch… •  1980s –  Isometric •  1990s •  10mm tunnel - area 79 mm2
•  Femoral footprint area ranges
85-200 mm2
–  Transtibial •  2000s –  Kopf KSSTA 2009
–  Anatomic •  Can’t fill the footprint –
Must be strategic!!
•  2015 and beyond –  IDEAL?? 50 years ago..
Isometric concept
Definitions
Ridge •  1960s - full range of knee motion can be
achieved without causing ligament
elongation and plastic deformation
•  1974- Artmann & Wirth- found “the
isometric point”
1 5/31/15 The Drift Up the wall… 1990s – Transtibial Endoscopic
Optimizing Isometry
Guided Tunnel Positioning in 1980s
Hefzy, Grood & Noyes
Use of an Endoscopic Aimer for Femoral Tunnel Placement
in Anterior Cruciate Ligament Reconstruction
David A. McGuire, M.D., Stephen D. Hendricks, and Geri L. Grinstead, Ph.D.
Arthroscopy 1996
Definitive Landmarks for Reproducible Tibial Tunnel
Placement in Anterior Cruciate Ligament Reconstruction
Craig D. Morgan, M.D., Victor R. Kalman, D.O., and Daniel M. Grawl, P.A.C.
Arthroscopy 1995
• 
• 
Transtibial Results
Often Impressive
•  Overall satisfactory
outcomes
–  Harner JBJS 2000
–  75-90% good and excellent
results
Center of tunnel at “over the
top” position
6-8 mm anterior to the truck
back wall, extreme post cortex;
at the junction of the roof & the
lateral wall of the femoral
intercondylar notch, resulting in
a 1-2 mm proximal cortical
margin (back wall thickness)
Dynamic kinematic evaluation
Concerns led to reevaluation of tunnel position
• 
Logan (Vertically open MRI) AJSM 04
• 
Tashman, Anderson AJSM 04
• 
Tashman CORR 07
• 
Gill, Li AJSM 06
• 
Chouliaras Geogoulis AJSM 07
–  After ACL reconstruction, lateral tibial plateau
displaced anteriorly relative to the femur by 5 mm
–  Abnormal rotational knee motion during running
after ACL reconstruction
–  Reconstructed knee more ER and adducted
–  ACL reconstruction failed to restore normal
rotational knee kinematics during dynamic loading
and some degradation of graft function occurred
–  Anterior translation of reconstructed knee
compared to intact (3mm)
–  Increased ER beyong 30 degrees flexion
–  Sig increased tibial rotation compared with
controls
Standard ACL reconstruction fails to restore
normal knee kinematics
Biomechanical Data • 
• 
• 
• 
30 trans2bial ACL Femoral socket too high and outside femoral footprint Above the ridge • 
• 
• 
• 
• 
Lim et al. Clin Orthop Surg 2012 Driscoll, Noble et al. Arthroscopy 2012 Debandi, Fu et al. Arthroscopy 2012 Kondo, Amis et al. AJSM 2011 Bedi et al. Arthroscopy 2011 Placing the graft in the center of the footprint restores AP and rotational stability more than vertical nonanatomic grafts 2 5/31/15 Concerns
The Drift Down…
Higher forces on graft with lower position
•  Anatomic Approach
–  Fill the footprint or…
–  CENTRALIZE within the footprint
–  Avoid high Nonanatomic position
Did we take it too far? Too Low on the Wall? Clinical Outcomes Clinical Outcomes AM 5.6% TT 3.2% Journal of Arthroscopy Jan 2013 •  2 incision technique 1980s •  Transtibial endoscopic 1990s •  AM portal anatomic 2000s •  9,239 ACLR’s from Danish Knee Ligament Registry •  1945 AM and 6430 TT Primary ACLR’s The Anatomy Re-­‐Revisited Footprint fibers are not all created equally! Histology Direct and Indirect types of ACL fiber insertions •  Flat insertion; Not 2 bundles •  Stout band of fibers at the ridge with wispy posterior extension Direct Indirect 3 5/31/15 High (Direct) ACL Footprint Insertion –  At the ridge –  Posterior to direct insertion blending with posterior articular cartilage. –  Direct insertion of ACL fibers histologic –  Simpler ultrastructure –  More robust fibers macroscopically Low (indirect) ACL Footprint Insertion Fan like expanse of fibers –  Ligament directly anchors to bone without transition zone (sMCL) –  Strength theoretically weaker than direct –  “Ideal to make the femoral tunnel at the direct insertion” Biomechanically not proven Biomechanical Study (Pearle et al) Or
Within Anatomic Region of ACL femoral footprint: High ACL Fibers Inserting on the ‘Ridge’ -­‐ Carry the Greatest Loads (80%) during stability exam -­‐ Are Most Isometric during ROM Summary
There and Back Again
Conclusion •  We were There!!
AMB
PLB
It would appear wise to avoid going too low on the wall when performing anatomic AM portal ACLR Our data suggests that femoral tunnel placement encroaching on the ridge may be a good idea 4 5/31/15 Summary
There and Back Again
Summary
There and Back Again
•  We were There!!
•  We were There!!
•  Transtibial approach
•  Transtibial approach
–  Drifter into nonanatomic high position
–  Vertical graft, recurrent pivot
•  Anatomic approach
–  Drifter into non-isometric low position –
increased tension on graft, higher clinical
failure
•  Functional approach
–  Reconstruction most functional and
isometric region of ACL
–  Back again to the Sweet Spot!!
Summary
There and Back Again
•  We were There!!
•  Transtibial approach
–  Drifter into nonanatomic high position
–  Vertical graft, recurrent pivot
•  Anatomic approach
–  Drifter into non-isometric low position –
increased tension on graft, higher clinical
failure
•  Functional approach
–  Reconstruction of most functional and
isometric region of the ACL footprint
–  Back again to the Sweet Spot!!
I.D.E.A.L Femoral Tunnel Position
–  Drifter into nonanatomic high position
–  Vertical graft, recurrent pivot
•  Anatomic approach
–  Drifter into non-isometric low position –
increased tension on graft, higher clinical
failure
•  Functional approach
–  Reconstruction most functional and
isometric region of ACL
–  Back again to the Sweet Spot!!
Recommended Position
Based on Anatomic, Histologic, and Biomechanical Data
–  Tunnel should encroach
on ridge!!
–  Anatomic but in the
most “functional”
portion of the footprint
–  Covers the direct fibers
–  Optimizes isometry
(minimizes tension on
graft during ROM)
–  Time-honored approach
Thank You
•  Isometric
•  Direct Insertion
•  Eccentrically located in
footprint
–  Encroaching the ridge
•  Anatomic
–  In most functional
portion of footprint
•  Low Tension
throughout ROM
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