Journal club on Alignment and Balance Methods in TKR

1. Journal club on Alignment and
ligament balancing in
Total Knee Arthroplasty
By Dr Pushpendra

2. Balanced knee
• Babazadeh et al defined a balanced knee as one which has:
• A full range of movement.
• Symmetrical medial-lateral balance at full extension and 90 degrees
of flexion resulting in a rectangular tibio femoral gap.
• Correct valgus / varus alignment in both flexion and extension.
• Balanced flexion-extension gap without medial-lateral tightness or
laxity.
• A well-tracking patella during full motion.
• Maximal flexion occurring with the patella reduced and without
excessive rollback of the femur on the tibia.
• Correct rotational balance between the tibial and femoral
components

3. • Total knee arthroplasty (TKA) is an effective intervention for
managing end-stage degenerative joint disease of the knee.
• The classical concept of TKA is the achievement of equal
medial and lateral gaps as well as equal flexion and
extension gaps
The clinical outcome relies upon surgical factors such as:-
• Adequate soft-tissue balancing
• Implant alignment
• Sizing
• Rotation

4. Ligament balancing
Sub-categorised into four parts:
Medial extension gap
Medial flexion gap
Lateral extension gap
Lateral flexion gap

5. Medial extension gap
How ?tight the knee can be left in extension intraoperatively
to avoid postoperative flexion contracture ..
• The tight group (medial component gap: <0 mm) showed
10% flexion contracture at 1 year postoperatively,
• medial component gap: 0-1 mm still had 8% flexion
contracture.
• The group with knees with >1 mm medial component
gap showed no flexion contracture.
• These results suggest that >1 mm laxity at the medial
side after implantation is necessary to avoid flexion
contracture.

6. Medial flexion gap
Recommend that the medial flexion gap should be
close to the medial extension gap to achieve near-
normal knee conditions as well as to improve
postoperative function and patient satisfaction.
Lateral extension gap
• Lateral laxity of 3 degree is close to normal
conditions,
• which would not cause a feeling of instability.
• Lateral laxity increases the risk of lift-off motion,
however, these risks would decrease with neutral
alignment.
• Lateral laxity up to 5 degree in extension would be
acceptable when neutral alignment is achieved.

7. Recommend that the following principles should be
followed for ligament balancing in TKA for varus knees
1. The medial extension gap should be within 1-3 mm to
avoid flexion contracture and a feeling of instability.
2. The medial flexion gap should be equal to the medial
extension gap (or1-2 mm larger), because this provides
close to normal stability and a larger medial flexion gap
would worsen knee function.
3. Lateral extension laxity up to 3 does not cause severe
clinical problems, or a risk of lift-off motion decreases
with neutral alignment.
4. The femoral component should not be internally
rotated to adjust the flexion gap.

8. • The medial aspect of the flexion gap is stabilized by the
superficial medial collateral ligament .
• The lateral aspect of the flexion gap is stabilized by the
lateral collateral ligament and popliteus tendon.
• When the superficial medial tibial ligament is deficient,
tensioning of the medial flexion gap will result in an
excessive medial flexion gap.
• When superficial medial collateral ligament is deficient & if
the femoral component is placed in parallel to the tibial cut
in the flexion it has tendency for excessive internal rotation.
• When lateral collateral ligament & popliteus complex
deficient in this situation it has tendency for excessive
external rotation.

9. Joint alignment and rotation
Native knee
Alignment
The average normal distal femoral alignment is 9° of the
anatomical valgus, and the normal proximal tibial
alignment is 3° of anatomical varus. Therefore, in the native
knee there is an increase in the load transmitted through
the medial compartment.
Rotation
The tibia internally rotates relative to the femur with
increasing flexion due to a greater posterior translation of
the lateral femoral condyle relative to the medial femoral
condyle.

10. Total knee arthroplasty
Mechanical alignment
The native knee has more load transmitted through the
medial compartment, this was to be avoided in a TKA
as it would lead to uneven wear and early failure
described by Insall et al mechanical alignment rather
than anatomical alignment. In an effort to equalize the
pressures in the medial and lateral compartments the
tibia is aligned in neutral varus/valgus, and hence the
3° of anatomic tibial varus is lost and 3° of external
rotation of the femoral component is required to
compensate and thus balance the flexion gap.

13. • The two most commonly utilized approaches
to achieving joint alignment and rotation are
• Measured resection and
• Gap-balancing.

14. Measured resection.
Femoral and tibial cuts are made independently of each other.
Soft tissue releases are then made
as necessary

15. Femoral bone resection
The distal femur is cut perpendicular to its mechanical axis. The level
of bone cutting is adjusted so that the same thickness of bone as
the implant is resected from the medial side. The thickness of the
resected bone should be measured using callipers.
Rotational alignment of the femoral component is adjusted to the
surgical epicondylar axis to improve patellar tracking. The size of
the femoral component is determined on the basis of the posterior
reference.
The amount of bone resected is very important for achieving proper
tension of the MCL and PCL. Considering that the distal part of the
femur is more worn than the posterior Part,the size and location of
the femoral component are determined so that the resected bone
at the medial posterior condyle is 1-2 mm thicker than the implant
thickness.
This procedure avoids excessive tension of the MCL or PCL throughout
knee motion.

17. Tibial bone resection
• The tibia should also be cut perpendicular to the mechanical
axis in the coronal plane. Maintaining the preoperative tibial
slope is important for achieving PCL function.
• However, to preserve the PCL attachment and avoid excessive
slope, we may cut the proximal tibia with a posterior slope
that is 2-3 degree less than the preoperative slope
• Approximately 10 mm of bone is resected from the most
proximal part of the lateral tibial plateau, however, resection
level and posterior slope should be changed according to the
knee implant system.
• Rotational alignment of the tibial component is adjusted to
the anteroposterior axis of the tibia (i.e., the Akagi line) to
avoid rotational mismatch between the femoral and tibial
components.

18. Gap-balancing.
The tibial bone cut is made first, then femoral bone cuts are
made to produce rectangular extension and flexion gaps based
on equally tensioned ligaments.

23. Take home massage
• S