3. ∗ Insall and others, its introduction in 1973 marked the
beginning of the modern era of total knee
arthroplasty The Total Condylar prostesis
∗ The duopatellar prosthesis evolved into the kinematic
prosthesis, which was widely used in the 1980s
Implant Evolution
4. ∗ To correct these problems, the Insall-Burstein posterior
cruciate–substituting or posterior-stabilized design was
developed in 1978 by adding a central cam mechanism to
the articular surface geometry of the total condylar
prosthesis
∗ The cam on the femoral component engaged a central
post on the tibial articular surface at approximately 70
degrees of fl exion and caused the contact point of the
femoral-tibial articulation to be posteriorly displaced,
effecting femoral rollback and allowing further flexion
5. ∗ 1980s and 1990s, patellofemoral complications became the
primary cause for reoperation in TKA. Consequently,
improved reconstruction of the patellofemoral joint has
received attention in more recent designs
∗ Some total knee systems have incorporated a deep-dish
design as one of their available modular tibial polyethylene
options. This design is similar to the original total condylar
design that uses sagittal plane concavity or dishing alone
to control anteroposterior stability
6. ∗ The CCK design has been used extensively for revision
arthroplasty when instability is present and for difficult
primary arthroplasties in patients with extreme valgus
deformity and medial collateral ligament insuffi ciency.
∗ Enlarging the central post of the tibial polyethylene insert,
constraining it against the medial and lateral walls of a
deepened central box of the femoral component . Varus-
valgus stability is controlled by this mechanism
7. ∗ Many current prosthesis designs attempt to reproduce normal
knee kinematics closely
∗ Knee motion during gait occurs in flexion and extension,
abduction and adduction, and rotation around the long axis of
the limb
∗ Average of 2 mm of posterior translation of the medial femoral
condyle on the tibia during flexion compared with 21 mm of
translation of the lateral femoral condyle medially based
pivoting of the knee explains the observed external rotation of
the tibia on the femur during extension, known as the “screw-
home mechanism’ and internal rotation of the tibia during knee
fl exion
Biomechanic of Knee Artroplasty
Kinematics…..
8. ∗ Transverse axis of fl exion and extension of knee
constantly changes and describes J-shaped curve
around femoral condyles.
9. ∗ Triaxial motion of normal knee during walking, as
measured by electrogoniometer. Flexion and
extension are about 70 degrees during swing phase
and 20 degrees during stance phase. About 10
degrees of abduction and adduction and 10 to 15
degrees of internal and external rotation occur during
each gait cycle. FF, fl atfoot; HO, heel-off; HS,
heelstrike; TO, toe-off.
10. ∗ relative merits of each design have been debated,
PCL-retaining and PCL-substituting prostheses
∗ PCL retention achieves an increased potential range
of motion by effective femoral rollback and a
relatively fl at tibial articular surface.
∗ PCL substitution achieves femoral rollback by a tibial
post and femoral cam mechanism
Role of the Posterior Cruciate Ligament in Total
Knee Arthroplasty
11. ∗ In PCL-substituting designs, posterior displacement in
fl exion is produced by the tibial post contacting the
femoral cam, with the resultant stress borne by the
prosthetic construct and ultimately transferred to the
bone-cement interface PCL-substituting designs
would have higher failure rates than PCL-retaining
devices because of loosening??? The loosening
rates of these two designs are similar at 10-year
follow-up
PCL-retaining VS PCL-substituting
prostheses
12. ∗ The relationship of the patella to the joint line is potentially
altered more with PCL-substituting prostheses than with
PCL-retaining designs. Figgie et al. suggested that joint line
elevation may alter patellofemoral mechanics and result in
postoperative pain and subluxation
∗ PCL-substituting femoral components have a cutout for a
cam mechanism. The patella and hypertrophic synovium
on the undersurface of the quadriceps tendon can bind in
this mechanism. This clinical entity, termed patellar clunk
syndrome
PCL-retaining VS PCL-substituting
prostheses
13. ∗ Another argument in favor of PCL substitution is that
significant deformity can be more reliably corrected
with its use.
∗ Scott and Volatile stated that extensive collateral
ligament release on the concave side of a fixed knee
deformity may not be effective without release of the
contracted PCL
14. ∗ This less conforming geometry in the sagittal plane is
responsible for higher tibial polyethylene contact
stresses in PCL-retaining prostheses
Retaining
20. To achieve the goals, TKR should:
1. Restore knee alignment and stability.
2. Restore patellofemoral tracking.
3. Be done with good fixation technique.
21. Alignment
∗ Vertical axis
∗ Perpendicular to transverse knee axis
∗ Mechanical axis
∗ Line from center of hip to center of
ankle
∗ Anatomical axis
∗ Line from tip of greater trochanter to
center of ankle (5-7 degrees from
mechanical axis)
22. Alignment
∗ Articular surface of tibia
∗ 3 degrees of varus
∗ Articular surface of femur
∗ 9 degrees of valgus
∗ Femoro-tibial axis
∗ 6 degrees of valgus
23. Prosthetic alignment
∗ Tibial component
∗ Placed at 90 degrees to longitudinal axis of tibial shaft
∗ Femoral component
∗ Placed in 6 degrees of valgus
25. Surgical plan
∗ Assessment of intraoperative difficulty
∗ Range of motion
∗ Sufficient flexion involve adequate exposure
∗ Inability to flex knee prevent removal of residual posterior bone
∗ Deformity
∗ MCL deficient indicate for constrained condylar prosthesis
∗ Ligamentous balance
26. Pre-operative x-ray analysis
Standing AP, lateral, skyline view of patella
Show distal femur and proximal tibia
Anatomical axis in neutral rotation
Long leg film
Determine bowing of tibia
For IM tibia alignment guide
Full length film
Determine mechanical axis
Template for component size
27. Tibia and Femur film
Degree of bone loss at femur and tibia
Typical greater on concave side of deformity
Appearance of attenuated ligament at convex side of
deformity
Subluxation
Typical lateral subluxation of tibia
Osteophyte
Diaphysis
Hardware
Extra articular bony
Deformity
Unusual canal size
Lateral film
Loose body, osteophyte
32. Surgical exposure
∗ Standard approach (anterior midline skin incision with medial
parapatellar arthrotomy)
∗ Gold standard
∗ Dissect directly to extensor mechanism
∗ Medial retinaculum incision can curve or straight
∗ Weakening quad & possible quad lag
33.
34. Surgical
exposure
Subvastus approach
Save the entire quadriceps
insertion on the patella
Minimal disruption of
quad’s mechanism
Preservation of patellar
blood supply
Improve PF stability
May injury to femoral a. in
adductor hiatus
35. Preservation of Quad’s mechanism
Advantage
Lead to decrease post-op. pain
Earlier to return of quadriceps function and strength
Improve patellar tracking and stability
Decrease lateral release
Disadvantage
Limited operative exposure
May damage to neurovascular structures
36. Surgical
exposure
Midvastus approach
Vastus medialis muscle fiber
divided in midsubstance
along the line and direction
of muscle fibers (muscle
splitting approach)
Begin at superior medial
border of patella
Quad sparing, preserve
supreme geniculate a.
37. Surgical exposure
∗ Lateral approach
∗ SevereValgus knee
∗ Plan lateral arthrotomy
∗ Increase visualization of ligamentous balancing
38. Theories of surgical technique
∗ The gap technique
∗ Develop in conjuction with the design of cruciate-substituting
prostheses
∗ The measured resection technique
∗ Develop by surgeon and designer who favored cruciate retention,
measure femoral and tibial resection
39. Bone work
Soft tissue release (in extension) to achieve alignment
Perpendicular tibial resection
Entry hole femoral IM guide
Distal femoral resection
Size the femur
Set rotational alignment of femur to achieve rectangular flexion gap
External rotation of femoral component in flexion
Lateralize of femoral component
Chamfer cut and housing cut (PS)
Posterior clearance
Balance flexion and extension gap
41. Tibia cut
∗ Tibia alignment in TKA
∗ Classic alignment
∗ Distal femur 5-6 degrees valgus
∗ Proximal tibia perpendicular to anatomical
axis
∗ Anatomic alignment (joint line technique)
∗ Distal femur 9-10 degrees valgus
∗ Proximal tibia 2-3 degrees varus
42. Step of bone cut
∗ Distal femur first
∗ Does not effect alignment of tibia cut
∗ May effect level of tibia resection
∗ Tibia first (tibial shaft axis technique)
∗ May effect both femoral rotation and resection level if use “Gap
technique”
∗ No effect if use “Measure resection”
44. Extramedullary guide
∗ Align the guide with center of tibial plateau, medial 1/3 of tubercle,
crest and center of ankle
∗ Usually need to shift the guide medially about 5-10 mm at the ankle
∗ Difficult to obese patient
45. Intramedullary guide
∗ Entry point is critical to alignment
∗ Must have pre-op template
∗ Limitation in bowed tibia
46.
47. Tibial component alignment
∗ Coronal plane
∗ Perpendicular to anatomical axis and mechanical axis
∗ Varus cut > 3 degrees has resulted in early failure
48. Tibial component alignment
∗ Sagittal plane
∗ PS TKA
∗ 3-7 degrees posterior tilt depending on each design
∗ CR TKA
∗ Follow each patient’s own posterior tilt for optimal PCL tension
49. Tibial component alignment
∗ Rotational alignment
∗ Center at medial 1/3 of tibial tubercle
∗ Slight posterolateral overhang usually occurred
when using symmetrical tibial tray
∗ Self align
∗ Insert trial implant without broaching then put
knee through range of motion and tray will
rotate to rest at certain position
∗ Recheck and landmark
50. Level of bone cut
∗ Two method for resection level
∗ 10 mm resection from less damaged compartment
∗ Lower limit of recommended PE thickness
∗ 2 mm resection below most eroded articular surface
∗ Bone preserving
∗ Gap may be to tight if only mild or moderately eroded
51. Effect of tibial cut on F-E gap
∗ Tibia cut effect both flexion and extension gap
∗ Increase posterior slope can loosen flexion gap but only slightly
52. Effect of tibial cut on F-E gap
∗ Resection too high
∗ Tight both flexion and extension
∗ Sclerotic bone not ideal for cement interdigitation
∗ Solution
∗ Recut tibia
53. Effect of tibial cut on F-E gap
∗ Resection too low
∗ Loose both flexion and extension
∗ Weaker bony support for implant
∗ Risk of peroneal nerve injury
∗ Solution
∗ Use thicker PE insert
54. FEMORAL PREPARATION
1. Remove all osteophyt . 2. Determine the entry point
of femoral rod.
The entry point of femoral rod:
. 7-10 mm anterior to the origin of the PCL.
. 3-5 mm medial to intercondylar notch.
Error in determining the point will alter the degree of valgus cutting.
55. Femoral Rod Entry Point.
. It is usually 3-5 mm medial to intercondylar notch.
Varus knee Valgus knee Varus deformity
(more medial) (far lateral)
59. Posterior condylar axis
∗ Advantage
∗ Simple instrumentation
∗ Usually accurate
∗ Neutral/Varus knees
∗ Minimal deformity
∗ No bone erosion
∗ Disadvantage
∗ Less reliable in valgus knee
∗ Severe deformity
∗ Femoral condyle hypoplasia
∗ Revision case
60. AP axis
∗ Advantage
∗ Easy to locate
∗ Primary TKA
∗ Enhance PF tracking
∗ Useful if condylar hypoplasia or mark
osteophyte
∗ Disadvantage
∗ Less reliable
∗ Trochlear dysplasia
∗ Advance PF arthritis
∗ High variability
∗ Error in presentation of
osteophtye at intercondyar
notch
61. Epicondylar axis
∗ Advantage
∗ Numerous study show it most
accurate axis
∗ Available in revision TKA
∗ Accurate in knees with condylar
hypoplasia/erosion
∗ Decrease femoral condylar lift-off
∗ Disadvantage
∗ Difficult to palpate medial epicondyle
∗ Can not seen in small incision
62. Flexion gap method
∗ Advantage
∗ Better flexion stability
∗ More reproducible
∗ Disadvantage
∗ Unreliable if
∗ Ligamentous
imbalance/insufficiency
∗ Inaccurate tibial resection
67. Patellar resurface
Surgical technique
Prepare the patella
Measure thickness
Patellar osteotomy
Inset or onset
Patellar position
PF tracking
+- Lateral release
68. Patellar resurface
Prepare patella
Remove osteophyte and synovial tissue
Measure thickness
Not less than 12 mm after resection
Patellar osteotomy surgical method
Inset (inlay) technique
Onset (onlay) technique
69. Patellar resurface
Patellar position
Medial to midline
Decrease Q angle
Better tracking
Lateral wear decrease
Lateral contact stress decrease
Tracking evaluation
No thumb technique
Tower clip
Lateral release
Good exposure
Avoid cut superior lateral geniculate artery
70. Cementing technique
∗ Cementing of both baseplate and stem are still recommended
∗ Both manual packing and cement gun work well
∗ Pulsatile larvage can reduced incidence of radiolucent line
∗ 3 mm cement mantle is ideal
71. Correct deformity
∗ Correct balancing and handling of the soft tissues
∗ Ligaments
∗ Tendons
∗ Joint capsule