Responses Re: Thermoplastic joints (metal)

Responses Re: Thermoplastic joints (metal)

Thanks to all who resonded to my inquiry. Below is the original post
followed by the replies:

What metal, free motion thermoplastic joints have you felt have had the best
endurance, i.e. Gaffney, Becker, OTS etc...?

Definately the Gaffney joints, although the most difficult to install
properly, they are the best in my experience. I have some patients wearing
the same bi-lateral AFO's with Gaffney joints for over 6 years now and the
only reason for replacement of the AFO's is due to a combination of plastics
fatigue and atrophy of the soft tissues. The joints are still working fine.

Without a doubt the best are the Becker Scotty joint for these reasons...
a. They have a reciprocal bend which instantly makes them more cosmetically
appealing than the Gaffney joints.
b. They utilize a screw that won,t pop off like the Gaffney's little
c-clamp. The only thing is that you must defect the inside of the screw to
prevent it from backing out. This takes two-three good smacks with the
hammer of your choice straight out of the package. My only recommendation is
that you make sure that you don't need to micro-contour the joint before you
deface the threads. Usually you don't need to contour them very much if at
all...
c. Easy to insall. I always recommend putting the joints on the mold and
heating before the plastic is put on (especially if thin plastics are used
and possibly a time consuming item like a posterior stop is
implemented...they do suck the heat out of the plastic quickly.)

I go strictly with the Gaffney family of joints when I need strength. The
Beckers and Kid Deelites have been nothing but problems. OTS are simple and
wear well but are generally too bulky.

 I have tested most of the mechanical ankle joints on the market for
fatigue life and signs of wear. I am happy to share with you the data but I
am a little confused by your question.
    Free motion mechanical ankle joints, whether they are made from metal,
plastic, or a combination, experience very little stress and hence the joint
or mounting screws would likely come loose before fatigue or wear were
noticed.
    Unfortunately endurance is not a mechanical property usually associated
with such an articulation.
    When these joints are used to restrain DF or PF in stance phase, then the
pathomechanical forces are transmitted to the joint screws/bushing and the
mounting screws (or rivets) which can elongate the mounting holes in the
plastic. This generally does not result in a catastrophic failure, but
degraded control of the gait deviation in question. Also, the stress can
tend to loosen the joint and mounting screws which leads to loss of gait
deviation correction and/or a catastrophic failure.
    The plastic DFA joint tends to experience early fracture of the elastic
member when used to prevent excessive PF in swing phase and the Camber axis
have chronic problems with mounting and joint screws loosening and failing in
shear when used for restraining excessive DF in terminal stance. The horse
joints appear to be the most prone to fail, except for the free motion
application.

I've used a variety of joints but have generally chosen the Tamaracks. With
adults I have generally gotten about a full year before replacement was
required, typically for the DFA Tamarack. I have also used Wally Motloch's
Center for Orthotic Design for free ankle or PFStop. This joint has worked
quite nicely for vigorous wearers.