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The PCL in TKR:
to preserve or to cut ??
Francesco Giron
SOD Traumatologia e Ortopedia Generale AOU Careggi –FirenzeDirector: Prof. R Buzzi
Kinematics Roll-back Flexion
Gait Strength Proprioception
Exposure Balancing Joint line
Patella Instability Loosening Wear
CR vs PS: Controversy
Results
Surgical
Clinical
Kinematics Roll-back Flexion
Gait Strength Proprioception
Patella Instability Loosening Wear
Results
Surgical
Clinical
CR vs PS: Controversy
Exposure Balancing Joint line
W. Müller, 1982
Roll -back
Motion is guided along a unique
path by constant tension
fascicles of ACL & PCL
Four-bar linkage
Posterior Cruciate Ligament
Provides 95% of total restraint to posterior displacement of the tibia on the femur
Tensile forces increase with knee flexion
Posterior Cruciate Ligament
Roll back occurs during knee flexion which benefits:
Posterior clearance
Increased quadriceps moment arm
Tibial internal rotation in flexion
Freeman, JBJS-B 2000
Medial Condyle Lateral Condyle
Dynamic MRI studies
Lateral mobility:
1) Mobility of
lateral meniscus
2) Lateral plateu
convex and downsloped
3) Longer distal radius LFC
LFC
MFC
1) Fixed medial meniscus
2) Medial plateu
cup-shaped & “upsloped”
3) Ligament colums in
tension
MFCLFC
MCLPCL
Medial stability:
Freeman, NOV-BVOT 2002Kadoya, in press
0
5
10
15
20
25PCL elongation (%)
20° 40° 60° 80° 100° 120°
PCL tightens from 45° to more flexion
PCL tension
Roll -back : PS knees
Knee flexion
Dennis D, CORR 1996
Predictable kinematics
0° 30° 60° 90° 120°
0
4
-4
-8
-12
AP position (mm)
Knee 1Knee 2Knee 3Knee 4 Knee 5
LFC
Knee flexion
Roll -back : CR knees
0° 30° 60° 90° 120°
0
4
-4
-8
-12
AP position (mm)
Knee 1Knee 2Knee 3Knee 4 Knee 5
Symmetric condylar design
Erratic pattern
LFC
19/20 subjects experienced av. 4 mm lat. roll-back
Asymmetric condylar design
Bertin KC, Komistek RD, J. Arthropl 2002
MEDLAT
Roll -back : CR knees
Surgeon A
0° 30° 60° 90°
0
-5
-10
AP position (mm) Anterior
Posterior
Surgeon B
p<.05
Nozaki H, CORR 2002
Asymmetric condylar designLFC
Maximum flexion
CR PS
Tanzer M. Nexgen 112° Nexgen 111°J. Arthropl. 2002
Rorabeck C.H. AMK 108° AMK 108°CORR 2001
Dorr L.D. Apollo 120° Apollo 119°CORR 2000
Shoji H. * Y/S 114° Y/S 117°CORR 1994
Becker M.W. * AGC 111° IB-I 112°CORR 1991 *bilateral knees
Non weight-bearing
Kinematics Roll-back Flexion
Gait Strength Proprioception
Patella Instability Loosening Wear
Results
Surgical
Clinical
CR vs PS: Controversy
Exposure Balancing Joint line
Wilson, J. Arthroplasty 1996Bolanos, J. Arthroplasty 1998
14 bilateral TKR: one CR, one PS
No difference
Knee flexion angle
Knee flexion moment
Gait analysis (stair climbing)
Percent of cycle
100%
100%
20°
40°
60°
0
-6
-4
-2
Degree
% Body weight
*leg length
PSCR
CR better
Warren, CORR 1993
No difference
Simmons, CORR 1996
Cash, CORR 1996
Lattanzio, J. Arthropl. 1998
Wada, CORR 2002
Position sense (electrogoniometer)
Proprioception
Huang, J. Arthropl. 1998Ishii, J. Orthop. Sci. 1998
Wada M, C0RR 2002
No differences
in isokinetic strength
Strength
Kinematics Roll-back Flexion
Gait Strength Proprioception
Patella Instability Loosening Wear
Results
Surgical
Clinical
CR vs PS: Controversy
Exposure Balancing Joint line
PCL balancing is difficult
Normal PCL strain
Lotke PA, Am. J. Knee Surg. 1993 10%
Mahoney OM, J. Arthropl 1994 37%
Incavo SJ, CORR 1994 25%
PCL too tight
Limited flexionExcessive posterior poly contact stress and shear forces due to exaggerated rollback
Rocking movement of the tibial component may precipitate loosening, especially in uncemented cases.
Increased femoral rollback in flexion with posterior 1/3 contact rather than mid 1/3 contact of the tibiofemoral articulation
PCL too lose
Flexion instabilityPagano, CORR, 1998
May occur in the CR TKAs with prior patellectomyLaskin, JBJS, 1995
Possible increase in poly wear due to cyclic slidingWalker, ORS, 1991
PCL deficiency in rheumatoid patients with recurrent synovitisLaskin, CORR, 1997
PCL release often required
Ritter, J. Arthropl. 1988; Scott, CORR 1994; Worland , J. Arthropl. 1997; Arima-Whiteside, CORR 1998
Severe deformity (varus>15°)
65 Tricon-CR vs 50 IB-PS
Laskin, CORR 1996
CR showed worse
clinical results &
higher revision rate
Mihalko-Krackow, CORR 1999
Cadaveric measurementsGap increase (mm)
2
4
6
8
Extension Flexion
p<0.05
F/E gaps changes after PCL section
Kadoya, CORR 2001
Intraoperative measurements
Baldini-Scuderi, J Arthropl in press
F/E gaps changes after PCL section
Gap increase (mm)
0.5
1.0
p>0.05
Extension Flexion
1.5
2.0
Kinematics Roll-back Flexion
Gait Strength Proprioception
Patella Instability Loosening Wear
Results
Surgical
Clinical
CR vs PS: Controversy
Exposure Balancing Joint line
Distally prolonged throclea
Synovial entrapment
Incidence 13.5% 3.8% 0%p<0.01
Pollock D.C., Engh G.A., JBJS-A 2002
AMK-PS AMK-PScongruency
PFC-PS
Flexion instability
More of a problem with old design CRs
202 AMK (FU: 4 yrs)8% AP instability
Waslewski, J. Arthropl. 1998
Persistent pain
Sense of instability
Recurrent effusions
Pes and retinacular tenderness
Posterior drawer sign
Above average range of motion
Clinical features
Healthy
Alexiades, Scott, AJKS 1989Hagena, Int Orthop 1989
Reduced PCL strength
OA
300
600
Rupture force (N)
p<.0001
Rheumatoid arthritis
F.U. (yrs) Flexion instability
Laskin, Tricon-M 8.2 40% CORR 1997
Schai-Scott, PFC 11.0 2% CORR 1999
Archibeck, MG-I 10.5 3%JBJS-A 2001
F.U. Loosening
All poly (IB-I) 10 yrs 3%Stern, JBJS-A 1992
Monoblock Metalback (IB-I) 11 yrs 0%Colizza, JBJS-A 1995
Modular (IB-II) 8 yrs 0%Aglietti, J. Arthropl. 2002
LooseningPS knees
F.U. Loosening
Monoblock Metalback (AGC) 15 yrs 0.4%Ritter, CORR 2001
Monoblock Metalback (Kinematic-I) 16 yrs 1.7%Rand, CORR 2001
Modular (MG-I) 11 yrs 0.0%Berger, CORR 2001
CR knees
Andriacchi, 1993
Increasing conformity reduces stresses
4
Contact stress (MPa)
3
2
1
5 10 15 20 25Radius ratio R2/R1
1
1
1
1
5
1.5
Benjamin, CORR 2001
Retrieved CR inserts
Length of implantation (yrs) 4.5 8.5
Linear wear (mm/year) 0.4 0.2
Volumetric wear (mm3/year) 959 356
Flat Curved
More stresses if conforming
0
5
10
15
20
25
30
35
40
0 1 2 3 4 5 6 7 8 9 10
Axial rotation
MPa
CONFORMING
FLAT
Malrotation in fixed CR
D’Lima-Colwell, CORR 2001
Implant stresses
Stresses are lower for mobile CR
05
10
152025
303540
4550
FixedMobile
MPaMPa
Neutral 15° E.R. 15° I.R.
Matsuda, J. Arthropl., 1998
Malrotation in fixed vs mobile CR
0,0000,0100,0200,0300,0400,0500,0600,0700,0800,0900,1000,1100,1200,1300,1400,150
1 2 3 4 5
cycles in the lab (million)
wea
r (g
r)
Wear in PS
Traditionally less of a problem due to improved conformity
Walker, Proc Inst Mech Eng, 1998Walker, CORR, 2000
IB-IIB-II
Wear location
.04
.08
Wear score/period of implantation
KinematicKinemax
Genesis AMKCoordinate
IB-II/CCK
AnteriorPosteriorMedialLateral
Pulosky, JBJS-A, 2001
Backside wear: CR & PS
Axial load
MicromotionElastic
deformation
Shear forces
Wasielewski, CORR 2002Parks-Engh, CORR 1998
Implant sources of micromotion
Locking mechanism
Conformity
Cam & post
Common to both prostheses:
PS specific:
F.U.(yrs) E/G Survivorship
Aglietti, 1999 IB-I 10 83% 92%
Li-Bentley, 1999 IB-II 10 94% 92%
Vince, 2000 IB-I 12 84% 92%
Insall, 2001 IB-I 10 96% 96%
IB-II 10 95% 98%
PS knees
Long-term results
F.U.(yrs) E/G Survivorship
Rand, 1995 Kinematic 10 87% 96%
Schai-Scott, 1998 PFC 10 -- 90%
Berger, 2001 MG-I 11 84% 84%
MG-II 9 92% 100%
Ritter, 2001 AGC 11 -- 99%
CR knees