b) Ideally, the pylon connecting the knee and foot should end up vertical. Of course,
there may be a variance due to the foot alignment recommendations. In this case, the
maximum anterior tilt of the pylon should not to exceed 4 degrees, and it may be
necessary to utilize offset adapters like the 1222T off set tube clamp
c) The weight line should pass through the centerline of the knee in the Coronal or M/L
plane (Fig. 4). Excessive outset or inset will put undue stress on the knee joint.
d) The weight line for Sagittal or A/P plane should have the plumb line passing through T
(Tg) line. Ideally, Tg line should pass through the knee center (red colored pivot) and be
perpendicular to the ground. (Fig. 3)
e)
When to use ZONE 1 option
- For the higher weight spectrum patients, Tg line
should pass slightly into the “Zone I” area (up to 2mm), which is indicated as up to “T1”
(Fig. 3) so that it will reduce stance flexion moment forces of the 5th bar. It is
recommended to have controlled stance flexion action of the 5th bar, and not to lock it
out or have excessively long duration of it. Excessive stance flexion moment and/or
duration can be adjusted through tightening the “Flexion Control Adjusting Screw” in,
and/or adjusting alignment (of socket and/or foot) into the T1 zone (up to 2mm). The goal
is to have smooth transition from stance flexion to neutral mid-stance motion, and not
excessive stance flexion duration.
f)
When to use ZONE 2 option
- For the lighter weight spectrum patients, such as
women and children, Tg line should pass slightly into the “Zone II” area (up to 2mm),
which is indicated as up to “T2” (Fig.3) so that it will increase stance flexion moment
forces of the 5th bar linkage. It is recommended to have controlled stance flexion action
of the 5th bar, and not excessively short duration, or abrupt motion of it. Excessive short
stance flexion moment and/or duration can be adjusted through loosening the “Flexion
Control Adjusting Screw” out, and/or adjusting alignment (of socket and/or foot) into the
T2 zone (up to 2mm). The goal is to have smooth transition from stance flexion to neutral
mid-stance motion, and not abrupt motion or excessively short stance flexion duration.
CAUTION:
Please pay extra caution on Tg line passing towards the maximum (up to 2mm) or
past Zone I because it will cause excessive knee head extension force, which will generate
excessive leverage pressure on "back linkage" and "fifth axial bar" and could result in knee
breakage as shown in Fig. 5.
It is highly recommended that Tg line should ONLY pass through the "Red Dot". (Fig. 3)
Fig. 5 An exaggerated
schematic diagram to show
affect on 5-bar linkage with
excessive anterior alignment