What to do when "all else fails"
Shane Glasford C.P.(c); Bloorview MacMillan Children's Centre
Fitting of the very short trans-radial amputee often poses some difficulties for a prosthetic team. In addition there are some clients whose situation exacerbates the problem and past innovations or old techniques fail. What then? K. was introduced to the readers in an earlier issue of the ACPOC NEWS in an article outlining the management of very short trans-radial amputees. For the past four years we were successful in keeping K. in a below elbow self suspending myoelectric prosthesis. Recently K. came back to us with an obviously too tight socket, so we went about the job of fitting her with a new socket.
K. was cast, the plaster modified, and a check socket fabricated. At the check socket fitting all went well and we sent K. out with a weight check over the lunch hour. We were feeling pretty good with another difficult case fit successfully. However, we were a little premature with the self-congratulations as after lunch K. came back with the socket and weight check in her hand and a grin on her face. "It fell off!" We made a few adjustments to get the socket to stay on longer with limited success. K. has grown but, as expected, the segment below the elbow did not grow proportionally. Additionally K.‘s condyles have not developed, the distal humerus has the shape of a broom handle, smooth and round and she now has more soft tissue coverage
We could not go further into the cubital fold as the current trim lines were already higher than normal and having even higher M/L walls was not an option, as it would serve no purpose. We did try tightening the socket in various areas but to no avail. The longest K. could wear it was two hours. Additionally we decided to let another prosthetist try to cast, modify and fit, all with similar results. K.'s combination of very short residum, soft tissue, non-defined humeral condyles, perspiration, and activity level meant that the longest she could wear the prosthesis was two hours. The socket had to be so tight in order to maintain suspension that we were uncomfortable with letting her wear it any longer than the two hours (although she did not complain about it being too tight). We let K. try the prosthesis at home to see if there would be any improvement if she was not subject to the constant donning and doffing experienced in the clinic.
The next chapter in our experience occurred at the MEC symposium at the University of New Brunswick. At that meeting many of the presenters were discussing the use of remote electrodes in a silicone liner (the Alpha liner specifically) for their adult clients. We were intrigued and discussed whether it might be feasible with the pediatric population.
Fast forward to the beginning of the next week - back at home. The first client that we see is K. telling us with a grin that "it fell off"
We were hoping to do some planing before embarking on a fitting using this silicone approach, but we had a client with a need that we felt had exhausted all other options. So K. was to be our "guinea pig". Mom was very supportive and was excited about the possibilities. A second cast was taken and modified for a silicone suspension sleeve. The Alpha liner that was used on the adults does not come small enough for K.. So first we fabricated a custom silicone sleeve, ordered remote electrodes from LTI, and then modified some old Otto Bock electrodes. We started by drilling and tapping the electrodes but later broke the cover off and soldered directly to the circuit board, as the screws came loose on occasion. At a later date we discovered that Otto Bock had special electrodes for use with liners and used them. There were a few false starts but we were able to solve most of the problems and K. is now wearing her "experimental" prosthesis as her full time myoelectric prosthesis. And we have not heard those three little words "it fell off"
We still have some concerns with the overall prosthesis: 1/. The range of motion is decreased when using a silicone liner. 2/. The liner is wired to the socket and therefore can't be removed for cleaning; the fact that it is hard wired also means that we expect failure of the wires at some time. 3/. The forearm had to be widened (even with the short residum) in order to route the extra cabling, electrodes, and lock mechanism.
Next on our wish list is a quick disconnect mechanism so we can separate the liner from the forearm ... And I am pleased to report that we have successfully convinced our colleagues in Rehab Engineering to assist us, and one is in development here at The Bloorview MacMillan Children's Centre. Stay tuned for further developments at the ACPOC Annual Meeting in Banff.
Shane Glassford CP
Bloorview Mac Millan Medical Center
350 Rumsey Rd.