TF SOCKET DESIGNS AND H-SOCKET --RESPONSES

TF SOCKET DESIGNS AND H-SOCKET --RESPONSES

A LINCOLN

5/23/2004

Dear List,
On May 10th the following question was asked and few responses were
received. I regret for the delay in the response.
Original question:
>Can I be fovored to get the archive references or direct info on current
>highly recommended A.K. socket designs, their indications, merits and
>demerits. I have to prepare a presenttation before orthopedic surgeons on
>'why and when we use a particular socket ( Quadrilateral, Isch.
>Containment,
>Plug, or others) in TF prosthetics. I am of the view that when no vacuum
>valve/ suction socket is used then it is quadrilateral and when silicon gel
>liner is used there are different contours.I also want to know the
>H-Socket.
>I shall post the responses.
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RESPONSES


If you are going to make a presentation to orthopedic surgeons on this topic
I would ask that you make a concerted effort to become much more familiar
with the subject than your email suggests. Your statements included in your
email are incorrrect. I would highly suggest that you may want to contact
John Michael CPO for the information that you seek. He can be found at
oandp.com and is listed in the resources. You might also try him on his
cell at 612-281-4290, Good luck with your presentation.

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I use the ischial containment designs all the time except when I have
someone who has worn another socket design for a long time, needs a new
prosthesis and is happy with their old one. I am reluctant to change
someone to a new design, unless they come to me and ask about new designs.

The quadrilateral and plug designs are antiquated and should only be used in
unusual cases. Orthopedic surgeons are not still using Harrington rods for
spinal fusions (that I am aware of) since newer and more effective methods
have been developed.

--------------------------------------------------------------------------------

The socket is different from the suspension. For the socket, the
description really tells how it limits rotation. The ischial containment
limits rotation by locking into the ischial seat, great trochanter, and
adductor longus tendon. The quadrilateral socket uses a square shape and
tries to equalize the pressure. A plug-fit tries to mirror the shape of the
limb and have even pressures around a round area. The gel liner with pin
has some issues with rotation, but practitioners have used a plug fit style,
equal pressure, and defined muscle groups (such as isolating the adductor
longus muscle). The issue with the gel liner is that the lip created is
often lower than the ischial seat, so some practitioners cannot get a good
lock on the pelvis due to the irritation caused by the lip edge.
As for suspension, this is how the socket is held on in swing phase. The
gel liner and pin are good because it is easy, a firm lock, and does not
require much hand stregnth. The suction socket works well for firm tissues
and people who are strong. however, with fleshier limbs and poor hand
stregnth and balance, it is hard for people to pull hard enough to cause
enough pressure inside their residual limb to effectively transfer the
weight and hold the prosthesis on. The firmer the soft tissue, the easier
it is to transfer the weight of walking into the skeletal system. However,
there is also a self suspension socket for knee disartics that lock onto the
condyles. Knee disartics are nice for end bearing capabilities, leverage,
and the balance between ad- and ab- ductor muscles (adductor mangus is not
cut), but poses a real issue when making the socket and the fitting of the
leg from the practitioners side and sitting issues from the patients side
because the knee center is lowered. You can also have a waist-belt and sock
fit...which is really good for new amputees who will be shrinking
dramatically.
As to the papers on the subject, I would suggest you talk with Mr. Tim
Staats who teaches at CSU dominguez hills/Ossur. He likely will know the
references and may have copies of them.

Hope this helps.
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    Quadrilateral design held paradigm status for approximately 30 years
from 1950's to the 1980's. There were a number of consistent problems with
this design. Today, there are a number of new design approaches that have
shown clinical superiority - greater comfort, stability, and function.
Common to all of these newer designs is anatomic shape, more intimate
musculo-tendinous-skeletal stabilization, containment of the ischial
tuberosity within the socket margin, a narrow M-L dimension, a wider A-P
dimension, and greater conformity of the socket to the lateral surface of
the residual-limb's femur. Long was the first to describe such a socket
design calling it NSNA [Natural Shape Natural Alignment]. Other clinicians
have used acronyms to describe their particular approach.
    For a more complete discussion on this topic, see pages 309-314 in,
LOWER EXTREMITY AMPUTATION, by Wes Moore, Jim Malone - Saunders.
Yours in Prosthetics
    ��������������������������.

  I am a prosthetic technician, working on a biomechanical engeneering
degree
with an emphasis in prothetics. And I would be honored to have a copie of
your
thesis related to this topic. You have my utmost word that I would not place
forgery over your thaughts and words, and would mention your name if source,
and
would gladly send you a copie of any work of mine siting your work.
I am trying to design a prosthesis for an AK amputee,and any information I
can
receive related to this topic will be helpful.
P.S. I am greatly impressed with the Sabolich socket. John and Kevin are
amazing
creatures. And I've seen it do marvelous things.
Thank you

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