Gel Liner with Pin versus Foam Liner with Sleeve
This research done by Kim Coleman and colleagues some years ago has finally appeared in a peer-reviewed journal. [Coleman KL, Boone DA, Lang LL, Mathews DE, Smith DG. Quantification of prosthetic outcomes: elastomeric gel liner with locking pin suspension versus polyethylene foam liner with neoprene sleeve suspension. JRRD 2004; 41(4): 591-602.] The original presentation was the subject of an article in the October 2001 Corner .
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This well-conceived randomized crossover study provides a very intriguing comparison of two commonly-used transtibial liner-suspension alternatives. It is noteworthy for the lengthy period for the subjects to become accustomed to the differing components and because it gathered both subjective and objective information about patient satisfaction, pain, socket comfort, daily ambulation, physical changes, and patient comments. These parameters are widely acknowledged as clinically important factors in the prescription and use of prostheses.
Ten male and three females with mature unilateral transtibial amputations due to trauma were studied. Contrary to expectations, use of the well-validated Stepwatch™ Activity Monitor [SAM] indicated that subjects used both prostheses with equal intensity: that is, they walked approximately the same number of steps with either the gel or the PE foam liner. However, they wore the gel liner for a shorter period of time and therefore walked less than with the PE foam lined prosthesis. Even with this small sample, the results were statistically significant in demonstrating that subjects achieved 83% more steps per day with the foam liner, spent 82% more time wearing that prosthesis than the gel one, and spent 72% more time in high intensity activity. This is a very counter-intuitive finding. I have reviewed the protocol in detail and spoken with the authors on several occasions, and cannot identify any flaws in the study that might account for this result.
Even more interestingly, the subjects did not report any increased dissatisfaction with the gel liner in terms of satisfaction, pain, or socket comfort - yet the large majority [9 of 12] indicated they would prefer the PE foam liner if they were restricted to only one prosthesis. The authors do a very nice job of discussing various possible explanations for these findings in the Discussion section of this paper. All clinicians with an interest in prosthetic liners and suspensions should read that section with care. One flaw may be that there were two variables: the liner material and the mode of suspension. It would be quite interesting to repeat the study using only sleeve suspensions, to eliminate the clinical concerns with pin alignment, distal traction on the soft tissues, and similar issues that may have confounded these results.
The authors conclude that these results highlight the need for a larger number of independent, well-controlled outcome studies in lower limb prosthetic rehabilitation, even though such research is time-consuming, costly, and rarely a funding priority. The article is posted at www.vard.org/jour/04/41/4/coleman.html .
