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Socket Design for Use with the Harmony® System
By Paul P. Singh, Todd Anderson, CP, FAAOP
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Paul P. Singh |
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Socket design is certainly a recurring theme in
the field of prosthetics. New ideas are frequently on the horizon,
such as those found in the technological advances of the Harmony
System. Often, new hybrid ways of socket design are discovered
right in your facility and used to best accommodate each individual
patients need. However, there are two socket design ideas specific
to using the Harmony System that are simple concepts, but important
for improving outcomes.
1. The three-part casting technique recommended by Otto Bock for
use with the Harmony System is done primarily to make room for the
femoral condyles to roll forward when the knee is flexed. The
topography of the limb changes quite substantially when the knee is
bent. (See pictures below). If the socket design does not make the
accommodation for this change, the condyles have a tendency to push
against the anterior wall, forcing the limb posterior and thus
creating a levering effect in the socket. Since the vacuum force in
the socket does such a superb job of holding the limb in place with
the Harmony System, it becomes especially important to accommodate
this phenomenon. If overlooked, patients often report a feeling of
distal-end discomfort, since the vacuum is holding the limb in
place while proximal end levering is trying to displace the limb
proximally.
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Todd Anderson, CP, FAAOP |
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2. Another similar scenario involves the medial
and lateral hamstrings. Again, it is important to create a socket
that matches that of the limb topography. When using the Harmony
System, Otto Bock recommends the W-shaped posterior trim line,
which allows room for the hamstrings to move as the knee flexes.
Leave a bit more room for the medial hamstring, as it is slightly
more prominent. Trim lines that are cut straight across or at a
slight angle can create pinching and excessive pressure along the
posterior region as the knee is flexed. As you guessed, trim lines
that are not cut using the W-shape can also create levering
problems. Although this may seem elementary, it becomes extremely
important to pay particular attention to detail when using the
Harmony System, since the limb is locked into the socket from the
elevated vacuum force.
Paul P. Singh is a product support specialist for patient
comfort/prosthetics at Otto Bock Health Care. Contact him at
800.328.4058, ext. 5669; paul.singh@ottobockus.com.
Todd Anderson, CP, FAAOP, is Otto Bocks director of
professional services. Contact him at 800.328.4058, ext.
5166; todd.anderson@ottobockus.com 
Table Of Contents - February 2004
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