ACL Reconstruction: The Anatomic Approach

Steven P. Brantley, MDSpero G. Karas, MD

Head Team Physician- Atlanta FalconsTeam Physician- Georgia Tech Baseball

Associate Professor of OrthopaedicsDirector, Orthopaedic Sports Medicine Fellowship

Emory Healthcare Sports Medicine

Background• ACL is second most

commonly injured ligament in the knee

• ACL rupture is estimated to occur in 1 in 3000 people in the U.S.

• Resulting in an estimated 100,000 reconstructions a year

• 6th most common orthopaedic procedure performed in the U.S.

ACL Anatomy• ACL origin: posterior

aspect of the medial surface of the lateral femoral condyle

• It courses anteriorly and medially to insert on the tibial plateau in an area medial to the insertion of the anterior horn of the lateral meniscus and anterolateral to the the anterior tibial spine

ACL Anatomy

• 1o blood supply from the middle geniculate artery– Its osseous attachments provide little to its

vascularity

• Innervation from the posterior articular nerve

ACL’s Two Bundles

• ACL Consist of 2 bundles– Anteromedial (AM)

bundle• Originates more

proximally and posteriorly.

• Inserts anteriorly and medial.

– Posterolateral (PL) bundle

Two Bundles• AM and PL bundle tension

different depending on the position of the knee:– 90o flexion: the AM bundle

taut while the PL bundle relaxed.

– Full extension: the PL bundle tensed and the AM bundle relaxed

• Girgis et al, CORR 1975

AMPL

Pictures Courtesy Dr. Freddie Fu, M.D.

ACL Biomechanics• The ACL functions to resist

anterior translation of the tibia on the femur– AM bundle– Provides 85% of resistance to

the anterior drawer in 90o of flexion

• Resists tibial rotation– PL bundle

• Helps provide varus-valgus stability when the knee is in full extension.

ACL Injuries• The majority of ACL

injuries occur from non-contact injuries– Pivot shift injury

• Occurs as individual decelerates and try to change directions abruptly or lands from a jump

• Females are 6 times more likely to suffer an ACL tear as their male counterparts

ACL Tear

Goals of ACL Reconstruction• To provide a stable and

pain-free knee under physiologic loads

• To provide an expedient return to previous level of function

Goal of ACL Reconstruction

• To help prevent future injury to the meniscus and cartilage

• To help prevent future degenerative arthritis- ?

ACL Reconstruction

• Jones et al in 1963 JBJS was 1st to describe modern technique of ACL reconstruction.

• Used Patellar tendon attached distally to reconstruct ACL in 12 patients.

ACL Reconstruction

• Despite advances in surgical technique and rehabilitation protocols, there are still failures of ACLR– Only 78% of athletes in the WNBA have been able

to return to sport after undergoing ACL reconstruction.

Namdari S et al, Physician and Sports Med, 2011

Risk of ACL Reinjury• The rates of re-tearing

after ACL reconstruction ranges from 3-30% in the literature

• Biggest Risk Factor:– RTP < 7 months- 15.3%– RTP > 7 months- 5.2%

Laboute et al Ann Phys Med Rehab, 2010

Traditional ACL Reconstruction

• Traditional ACL reconstructions placed femoral tunnel in a vertical non-anatomic position.

• Reconstructed primarily the AM bundle but not the PM.

Picture Courtesy Dr. Freddie Fu.

Traditional ACL Reconstuction• With AM bundle

reconstructed anterior translation controlled- negative Lachman’s Exam.

• Not very good rotatory stability- continued pivot shift.

Abnormal Mechanics

• Tashman et al in AJSM 2004 demonstrated abnormal external rotation of the tibia and limb adduction during running activities in patient who had underwent nonanatomical ACL reconstruction.

• Woo et al in JBJS 2002 illustrated in cadavers that a conventional single bundle ACL was successful in restoring anterior translation control, but was ineffective at restoring the native ACL’s rotatory stability.

Double Bundle ACL Reconstruction

• Attempts to restore both the AM and PL bundle of ACL

• Restore both anterior translation and rotatory control

Double Bundle

• Yagi et al in AJSM 2002 demonstrated in cadeveric studies that double bundle ACL reconstruction restored anterior translation and rotatory control significantly closer to that of the native ACL than did a single bundle reconstruction.– Had 97% and 91% of the in situ forces of the intact ACL for

controlling anterior tibial translation and rotation compared to 89% and 66% for the single bundle non-anatomic reconstruction.

Double Bundle ACL- Is it the Answer?

• Technically more difficult

• Limited in graft selection

• May over constrain the knee, Markolf et al in JBJS 2008

AOSSM Traveling Fellowship 2005

Single Bundle Anatomical ACL Reconstruction

• Places bone tunnels in correct anatomical positions in hopes of restoring knee mechanics closer to natural ACL

• Improves rotatory stability

Anatomic Reconstruction

Pictures Courtesy of Dr. Freddie Fu

Bone Tunnels

• Tunnels are drilled independently to allow for anatomic positioning of tunnels

• Allows for a more oblique graft in the coronal and sagittal plane

• This orientation better prevents pivot shift

Bone Tunnels

• Traditional ACL reconstruction uses a trans-tibial approach to drill the femoral tunnel

• This places tibial tunnel too posterior in order to drill in the anatomic femoral position

• Strauss et al in AJSM 2011 demonstrated in a cadaveric study that it is not possible to drill an anatomic femoral tunnel through an anatomic tibial tunnel position– Placed femoral tunnel too superior and posterior to

anatomic position

Femoral Tunnel

• Able to drill an anatomic femoral tunnel by adding an accessory medial portal or placing medial portal more medial than normal

Femoral Tunnel

Trans-Tibial Approach?

Tunnel Position• Loh et al in Arthroscopy 2003

looked at knee stability in a cadaveric model comparing ACL reconstruction with either the femoral tunnel in the 11 o’clock or 10 o’clock position.– Demonstrated that the 10

o’clock position was more effective in resisting rotatory loads.

– No difference between the two positions in preventing anterior tibial translation.

Anatomic ACL Reconstruction: Single vs. Double Bundle

• Kondo E et al in AJSM 2011 performed a biomechanical study comparing anterior translation and pivot shift stability in double bundle, anatomic single bundle, and trans-tibial ACL reconstruction

• The double bundle and anatomic single bundle ACL reconstructions demonstrated significantly improved rotational stability compared to the nonanatomic reconstruction

• No difference biomechanically detected between the anatomic double and single bundle reconstruction

Anatomic Reconstuction vs Non-Anatomic

• Sadoghi P et al in Athroscopy 2011 compared clinical outcomes of patient who underwent either anatomic or non-anatomic single bundle ACL reconstruction

• Found that anatomic ACL reconstruction had significantly improved outcomes in clinical scores and rotatory stability when compared to non-anatomic reconstruction

Conclusion• Rotatory control a key to restoring function• Non-anatomic “vertical” ACL reconstruction

does not restore the rotatory stability of the native ACL

• Single-bundle anatomic ACL reconstruction decreases the pivot shift phenomenon and more closely mimics native ACL biomechanics

Thank You !Spero G. Karas, MDSKaras@emory.edu

www.sperokaras.com