Posterolateral Corner Injuries In The New Millenium - A

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Posterolateral Knee Biomechanics
and Pathobiomechanics
ESSKA 2000 – ISAKOS
Knee Course
Robert F. LaPrade, M.D., Ph.D.
Professor
Department of Orthopaedic Surgery
University of Minnesota
Overview of PLC Biomechanics
• The importance of the posterolateral corner knee
structures
–
–
–
–
–
Sectioning studies
Functional assessment
Effect on Orthopaedic
procedures
Healing ?
Osteoarthritis
• Mechanical assessment
of treatments
FCL
PFL
PLT
Varus Instability at 30°
• FCL is primary restraint to varus
• Cutting popliteus tendon and other PLC structures
increases varus
(Nielsen, 1984 & 1986;
Gollehan, 1987;
Grood, 1988;
Veltri, 1995)
• Cruciates are also
important 2° stabilizers
Anterior Translation at 30°
• Sectioning PLC - no increase
in primary anterior translation
(Gollehon 1987;Grood,1988)
• In ACLD knees, absent PLC
results in increased
translation (0°-30°)
(Nielsen 1986; Wroble 1993)
* Think about PLC for 3+ Lachman
Posterior Translation at 90°
• PCL only ligament for
initial posterior restraint
at all flexion angles
(Bantigan and Voshell, 1941;
Gollehon, 1987)
• PLC minor restraint to
posterior translation
(Gollehon, 1987; Grood,1988;
Veltri, 1995)
Posterior Translation at 90°
(Gollehon, 1987; Grood, 1988)
• Combined PCL / PLC
injuries ↑↑↑ posterior
translation
External Rotation (“Dial Test”)
• Sectioning of PLC structures
increases ER
(Gollehon, 1987;Grood, 1988;Lipke, 1981;
Nielsen,1984)
– 30° of flexion = 13° increase ER
– 90° of flexion = 5.3° increase ER
• Additional section of PLC / PCL
increases ER at 90° flexion (Grood,
1988) and ACL/PCL (Wroble, 1993)
increases ER at 90° flexion
Cruciate Ligaments and Varus
• Recruited with deficient PLC
to resist varus
• Section of PLC increases
mean force on ACL at all
flexion angles (Markoff, 1993)
• Section of PLC increases
force on PCL at > 45°
(Markoff, 1993)
Varus instability: severe effect on ACLR / PCLR
and ↑↑ force on medial compartment
Effect of Popliteus on
Posterior Translation
(Harner, 1998)
• Simulated popliteus
contraction decreases in situ
forces on PCL at 30° and 90°
• Also decreases posterior
translation in PCL-deficient
knees
Force Measurement
of PLC Structures
(LaPrade, 2003)
• FCL and PLT / PFL
act synergistically
in ER
• FCL main structure
for varus
External Rotation Torque
• Force in the
popliteus complex
increases with flexion
angle
Load response (N/ Nm)
• FCL force decreases
with flexion angle
FCL
PFL
PLT
30
25
20
15
10
5
0
0
30
60
90
Flexion angle (Degrees)
* Synergy between FCL and PLT/PFL *
Varus Moment
FCL
16
• Peak FCL varus is at 30°
• Load decreases after 30°
Load response (N/ Nm)
14
12
10
8
6
4
2
0
0
30
60
90
Flexion angle (Degrees)
* No load on PLT/PFL with intact FCL *
Biomechanical Failure
Strengths
(LaPrade, 2004)
PFL 229 N
FCL 295 N
PLT 680 N
* Gracilis / ITB grafts may not be strong enough
Deficient PCL / PLC
(Skylar, 1993)
• ↑↑ Stress on medial
compartment
Effect of PLC Injuries on ACL
Reconstructions
• Significant increase in graft
force seen for varus at 0° and
30°
• Repair / reconstruct PLC
injuries at time of ACLR to
reduce risk of ACLR failure
Relative Load in ACL Graft (N)
(LaPrade, 1999)
40
35
30
25
20
15
10
5
0
FCL Cut
PFL Cut
PLTCut
s
ru
Va
30
IR
s
30 aru
V
ro
Ze
IR
ro
Ze
Effects of Tensioning on an ACL Graft
and Integrity of the PLC on
Tibiofemoral Rotation
(Wentorf, 2002)
• Significant increase in ER seen
with increasing ACL graft tension
with PLC cut
• Repair / reconstruct PLC injuries
first, prior to ACL graft fixation, to
reduce risk of ER deformity
External Rotation
10
8
6
PLC Cut
4
Intact
2
0
0
100
200
ACL Graft Tension
300
PLC Repairs / Reconstructions
and ACLR
(Kanamori, 2000)
• High loads on PLC if
concurrent ACLR not
performed
* Need to reconstruct both simultaneously
Effect of PLC Injuries on a PCL
Reconstruction Graft
Relative Change in PCL Graft
Force (N)
(LaPrade, 2002)
50
45
40
35
30
25
20
15
10
5
0
*
PFL Cut
PLT Cut
ALL Cut
*
*
30
60
90
Flexion Angle (Degrees)
• PCL graft force
increased with
Varus loading
Effect of PLC Injuries on a PCL
Reconstruction Graft
Relative Change in PCL Graft
Force (N)
(LaPrade, 2002)
20
18
16
14
12
10
8
6
4
2
0
PFL Cut
PLT Cut
ALL Cut
*
*
30
60
90
Flexion Angle (Degrees)
*
• PCL graft force
increased with PD
& ER
Effect of PLC Injuries on a PCL
Reconstruction Graft
(LaPrade, 2002)
• Repair / reconstruct
posterolateral structures at
time of PCL reconstruction to
decrease chance of postreconstruction PCL graft failure
• Assess for posterolateral knee
injury prior to PCL graft
fixation.
In Vitro Forces in a PCL Graft
(Markolf, 1997)
• With intact posterolateral
structures, no increase in
PCL graft force with a varus
or external rotation moment
Effect of Deficient PLC on PCLR
(Harner, 2000)
• Forces in PCL graft
significantly increased
for PLS deficiency
• PCL graft is ineffective
and overloaded with
PLS deficiency
Animal Models of PLC Instability
• Rabbit anatomy similar (JOR, 2003)
• Rabbit instability created, mild OA
(JOR, 2004; AJSM,2005)
• Goat anatomy similar (JOR, 2005)
• Goat instability created
• Canine anatomy / biomechanics similar
(JOR, 2007)
Does the PLC Heal ???
(LaPrade, JOR, 2004; AJSM, 2005)
• FCL and PLT
ruptured in New
Zealand white rabbits
• Allowed to heal for
three and six months
post-op
In Vivo Rabbit Model
6
Displacement (mm)
5
4
3
Control
2
Operated
1
0
-15
-5
-1
5
15
25
35
-2
-3
Force (N)
Greatly decreased force at maximum varus angulation
* PLC does not heal *
PLC Rabbit Model
• Mild medial
compartment OA
at 6 months
PLC Canine Model
(Griffith, 2007)
• Similar anatomy /
biomechanics
* in vivo studies ongoing *
Effect of Opening Wedge
PTO on PLC Injury
(LaPrade, 2007)
• Chronic PLC injuries in varus
stretch out with PLCR
• Observation that some
patients do not need PLCR
post osteotomy
Results - Varus Opening
• Significant decease in
varus after PTO
• No statistical difference
between intact and after
PTO
30
Intact
PLS Cut
25
Varus Opening (m m )
• Significant increase in
varus opening with PLC
cut at
PTO
20
15
10
5
0
30
90
Knee Flexion Angle (Degrees)
Results - External Rotation
• Significant decease in ER
after performing the PTO
• No statistical difference
between intact and after
PTO
25
Intact
PLS Cut
External Rotation (Degrees)
• Significant increase in ER
with PLC cut
20
PTO
15
10
5
0
30
90
Knee Flexion Angle (Degrees)
The Effect of a PTO on
PLCD Knee
• Opening wedge PTO
significantly decreases varus
opening & ER in a PLC
deficient cadaveric knee.
• Concurrent increase in MCL
forces may account for
increase in knee stability.
Anatomic PLC Reconstruction
(LaPrade, AJSM, 2004)
• FCL, PLT, PFL
anatomically
reconstructed
• Biomechanical testing
intact, cut, and
reconstructed PLC
buckle
transducers
PLCR Results: Varus





avg. varus translation (mm)
35
30



intact
injured
recon.
25
20





15
10
5
0
0 deg.
30 deg.
60 deg.
flexion angle
 - p<0.05 using Student’s ttest
90 deg.
• Injured knee translation
is significantly higher
than that of intact knee
• No significant
difference between
intact and
reconstructed states
PLCR Results: External Rotation



avg. external rotation (deg)
25
20
intact
injured
recon.









15
• ER in cut knee is
significantly higher
• No significant difference
between intact and
reconstructed states
10
5
0
0 deg.
30 deg.
60 deg.
90 deg.
flexion angle
 - p<0.05 using Student’s t-test
Anatomic FCL Reconstruction
(Coobs, 2007)
• Restores varus stability
*
*
* *
* *
12
* *
10
* *
( d e g re e s )
V a ru s R o ta tio n w ith 1 0 N m a p p lie d m o m e n t
14
8
* *
In ta c t
S e c tio n e d
6
Re c o n s tru c te d
4
2
0
0°
15°
30°
60°
Kn e e F le x io n A n g le
90°
Summary of Key Points in
PLC Biomechanics
• FCL prevents abnormal
varus motion
• FCL and popliteus complex
prevent abnormal ER
• PLC does not heal
• Recognize PLC injury prior
to cruciate ligament(s)
reconstruction
• Significant stress on medial
compartment
THANK
YOU
Sports Medicine Institute
University of Minnesota
www.sportsdoc.umn.edu
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