Tkr

1. How I would do an
uncomplicated TKR
Dr. Tan Jin Aun

2. Introduction
•Patient selection
•Implant selection
•Templating
•Soft Tissues
•Bony Cuts
•Trial of Implant
•Implant
•Post Operative

3. Patient Selection
Indication
• Progressive pain
• Deterioration of ADL
• Analgesic dependent
• Disturb sleep Depression
Contraindication
• Active Infection
• Charcot joint
• Poor skin coverage
• Lack of muscle control
• Inability to participate in
post-op rehab

4. Implant selection- Principles
• PCL sacrifice vs retaining
• Fixed vs mobile bearing
• Cemented vs uncemented vs hybrid
• Patella resurfacing vs non-resurfacing
• Unicondylar Knee
• Constraint vs Non-constraint
• Bio-materials

5. Templating Femur

6. Templating Tibia

7. Accuracy?
Unnanuntana A, JMAT, 2007
• A retrospective study of 98 patients and 113 knees was
carried out. The operative records were then reviewed
to determine the size of the implant used during the
operation.
• Approximately 50% of the patients had a preoperative
template size that matched the actual implant used.
• Many factors influence the final choice of the
prosthesis used during total knee replacement;
therefore, the preoperative template size can only be
used as a rough guide.

8. Alignment and Ligament
Balancing

9. PATELLA BIOMECHANICS: Q ANGLE
• Angle formed by line drawn from ASIS to
centre of patella and second line drawn from
centre of patella to tibial tubercle
• Normal: 14 degrees males / 17 degrees
females
• Any factor that causes an increase in the Q
angle can cause lateral maltracking of the
• patella
• Increased by:
– Genu valgum
– Patella subluxation (lateral release)
– Tight lateral retinaculum (lateral release)

10. PATELLA BIOMECHANICS: PATELLA ALTA &
PATELLA BAJA
INSALL’S INDEX
• Length of Patella
Tendon to Length of
Patella
• Normal: 1:1
• Patella Alta (Long
patella tendon) >
1.3:1
• Patella Baja (Short
patella tendon) <
1:1

11. MECHANICAL AXIS OF KNEE JOINT
• Line extending from
centre of Hip Joint to
centre of Ankle Joint
• Perpendicular to ground
• In normal knee,
mechanical axis passes
through centre of knee
• Axis of Tibio-Femoral
articulation is horizontal
and parallel to horizontal
axis of Ankle Joint

12. Mechanical axis of tibia
• Mechanical axis of tibia is
3 degrees valgus of it’s
anatomical axis.
• In view of this difference,
therefore need to
externally rotate the
femoral component about
3 degrees in relation to
the posterior condyles, to
get it perpendicular to the
mechanical axis.

14. ANATOMICAL AXIS OF KNEE
• Axis extending along
shafts of femur and
tibia
• Not important

15. Preparation of soft tissue + removal of
osteophytes
• Marginal osteophytes removed to provide for proper
balancing
• Posterior osteophyte removed with curve osteotome
to prevent impingement during flexion
• In general, it is advisable to remove all osteophytes and
reevaluate for the soft tissue imbalance.
• Usually after the osteophytes are removed and normal
anatomic planes have been reestablished, no specific
releases or additional ligamentous balancing are
necessary.

16. When to do ligamentous balancing?
• Open the knee joint and make a preliminary balancing of the soft
issue structures appropriate to the situation. Remove osteophytes.
• Perform bone cuts according to the preoperative plan.
• Make a fine adjustment of soft tissues after checking the flexion
and extension gaps with the gap gauge or at the latest after
inserting the trial prosthesis.
• This prevents the release being too extensive, which would result in
laxity of the ligaments after insertion of the final implant.
• Based on their observations it is recommended undertaking a 1⁄2-
to 3⁄4- resection of the Hoffa fat pad. This is independent of
surgical approach. Fibrosis or a fat pad impingement can cause
anterior knee pain.
• In order to maintain the continuity of the joint capsule, the base of
the meniscus should be left intact when resecting the meniscus or
its remnants.

17. Bone Cuts
• There are five essential bony cuts for any TKA.
• The essential bone cuts are made regardless of
the amount of bone loss, ligamentous imbalance,
or osteophytes presence about the knee.
• Bone cuts
– Minimise bone resection
– Maintain joint line
– Horizontal joint line
– Balance flexion and extension gap

18. The five essential bone cuts
• Transverse osteotomy of the proximal tibia, tilted
5 degrees posteriorly
• Resection of the distal femoral condyles,
angulated at 50 to 70 of valgus alignment
• Anterior and posterior condylar resections to
accept a prosthesis of the appropriate size
• Chamfers from the distal femur anteriorly &
posteriorly
• Resection of the intercondylar notch & PCL

19. Tibia Cut
• Cut the tibia
perpendicular to
the mechanical axis
of the limb with a
posterior slope of 0-
5 degrees
depending on the
design of prosthesis

20. POSTERIOR SLOPE ?
•Advantage
– Opening up the flexion gap to make PCL balancing
easier & enhancing metal-to-plastic contact in
max knee flexion
• Disadvantage
– The promotion of too much rollback of the femur
on the tibia in a nonconforming design

21. Tibia Cut
•The tibial guide is
usually set to engage
the ankle 3 to 6mm
medial of centre, as
the centre of talus is
usually medial to the
line bisecting the
distance between the
malleoli

24. Femoral Cut

25. • Femoral Cuts
– Create normal valgus angle (5-9 degrees)
and original joint line
– Equal flexion and extension gap
– Slight external rotation (3 degree) to
improve patella tracking
• Rotational femoral alignment is
assessed by
– Posterior condylar axis
– Anterioposterior axis (Whiteside’s Line)
– Transepicondylar axis

26. Posterior Condylar Axis

27. Trans-epicondylar Axis

28. Whiteside’s line

29. • Drill hole in distal femur and
insert femoral IM alignment
guide
• The medullary canal of the
femur is entered approximately
1 cm above the origin of the PCL
& a few millimeters medial to
the true center of the
intercondylar notch

33. Referencing and sizing
• Determine the size of the femoral component in both the A/P and
the M/L directions.
• Mount the femoral size gauge on the intramedullary alignment rod
to determine the A/P dimension of femoral component.
• Both feet of the femoral size gauge must have good contact with
the posterior condyles. The point of the stylus should rest on the
anterior femoral cortex.
• Place the point of the stylus on the deepest point of the anterior
femoral cortex above the edge of the cartilage in order to obtain
optimal measurement.
• The size of the femoral component is read on the vertical scale. In
the case of intermediate sizes, choose the smaller size.

35. • Check the dimension in the M/L direction with
the femoral gauge.
• In cases of intermediate sizes, this
measurement can facilitate the choice of the
final component.
• The size determined in the A/P direction can
be checked with the other side of the femoral
gauge.

38. EXTENSION –FLEXION GAP
• After the bone cut, there will be a flexion and
extension gap between the distal femur and
proximal tibia.
• If the knee can be aligned passively, the
conditions for a stable and mobile knee are that
the flexion and extension gaps are normal and
equal.
• This involves the femoral and tibial cuts so that
both the flexion and the extension spaces, or
‘gaps’, are rectangular and roughly equal in size.

39. • The flexion gap is determined with the knee
in 90 degrees of flexion and the extension
gap is determined with the knee in full
extension.
• Balance of the flexion and extension gaps can
be determined by placing spacer blocks or a
tensor within the gaps with the knee in both
flexion and extension

41. Equal extension and Flexion gap
•Tibial cut affects
flexion and extension
gaps equally
•Distal femoral cut
affects extension gap
only
•Posterior femoral cut
affects flexion gap only

42. • If the extension gap is too small or tight,
extension will be limited.
• If the flexion gap is too tight, flexion will be
limited.
• If extension gap is smaller than the flexion gap,
remove more bone from the distal femoral cut
surface.
• If the flexion gap is smaller than the extension
gap, more bone can be removed from the
posterior femoral condyles.

43. • If the flexion and extension gap is equal, but
there is not enough space for the desired
prosthesis, remove more bone from the
proximal tibia, because it will affect equally
the flexion and extension gaps.
• If the flexion and extension gaps are equal but
lax, a larger spacer block and ultimately a
larger tibial polyethylene insert are required
to obtain stability (Guyton 1998).

44. • In theory, the amount of bone taken from the
distal femur is equivalent to the thickness of
the distal femoral component of the
prosthesis
• The amount of bone resected from the
proximal tibia is equivalent to the thickness
of the tibial plateau that is being replaced.

45. • The femoral component is placed onto the distal
femur and securely fitted, and the tibial plateau
placed on the tibial surface. Trial component of
the tibial insert then inserted.
• With flexion and extension the tibial plateau will
tend to rotate itself into the correct alignment
with the distal femur.
• Varus and valgus stresses applied to look for the
knee stability and appropriate tibial insert can be
determined.

46. • Rotation of the tibial component of the prosthesis on
the tibial plateau must be checked carefully.
• If the tibial component is internally rotated and the
tibial tubercle is externally rotated to the midportion of
this component there will be tendency for the patella
to sublux or dislocate.
• It is imperative to externally rotate the tibial
component so that it’s midportion lies directly under
the patellar tendon.
• A general guideline is to have the center of the tibial
tray align over the medial one third of the tibial
tubercle.

48. • Patella stability is then check. The knee is
taken into flexion to be sure that the patella
tracks centrally.
• If the rotation of the femoral component is
appropriate, the patella will remain seated
squarely in the intercondylar notch.
• If the retinaculum is too tight laterally, the
patella will begin to tilt or dislocate, requiring
lateral release.

50. Closure

51. • TKR WITH GOOD
ALIGNMENT: Mechanical Axis
passes through Joint Centre

52. • A total knee prosthesis put in
bad alignment will be
abnormally stressed
• Whole knee joint will loosen or
break down.

53. Thank You