25
Figure 39a.
Figure 39b.
The Ligament Balancing stage (Figures 39a, 39b)
consists of collecting ligament stress or laxity
information in full extension and flexion.
Joint Laxity Collection in Extension
Technique
Keeping the operative leg in full extension, apply
constant and maximal stress to the contralateral
ligaments, and collect varus and valgus data,
maintaining knee flexion between -10 and +10
degrees. Input can either be continuous, which
requires constant application of stress while the
leg is in extension, or in discrete poses in order to
record the maximum stress that can be applied to
the collateral ligaments.
The bar on the top with blue rectangular fill and
depict the maximum stresses being applied to the
leg in extension, in the terms of varus and valgus
angles of the operative knee. the green indicator
represents the current varus/valgus angle along
that range. The graph below the varus /valgus
reading depicts the “tightness” in the medial or
lateral compartment of the knee, based on the
stress collections, when a distal femur component
resection and tibial resection is to be made
perpendicular to the mechanical axis.
This graphic illustration can be used to determine
the amount of ligament release that may be
required to restore equal gaps in the medial and
lateral compartments.
Joint Laxity Collection in Flexion
Technique
Keeping the operative leg in 90 degrees of
flexion, apply constant and maximal stress to the
contralateral ligaments, and collect varus and
valgus data within 80-100 degrees of knee flexion.
It has been found that keeping the leg stabilized
in a leg holder in flexion and using a Z-retractor or
laminar spreader to open up the medial and lateral
compartment space to capture the maximum joint
laxity in flexion is an effective approach.
Purpose
This data is collected for use during the Implant
Planning and Gap Planning stages (Sections 6 and
7). The user wants to identify how much room the
ligaments have. This will inform the user as to how
much gap (laxity) will be built into the joint balance.
5
Ligament Balancing
