Few differences in function were found while comparing children with Syme and transtibial amputations in a study that examined factors including gait analysis, prosthetic foot type and a questionnaire. The gait data revealed subtle differences between the two types of amputees, but the researchers concluded that one type of amputation could not be universally recommended above the other, according to Donald Cummings, CP, LP, director of prosthetics for Texas Scottish Rite Hospital for Children.
Cummings and colleagues examined the data on 64 amputees with unilateral below-the-knee prostheses who had undergone a gait analysis at the hospital’s movement science lab, ranging in age from 2.7 years to 19.2 years.
Difference in motion
“Overall, there were small differences in their ankle motion and power that was generated between the kids with Syme and transtibial amputation,” Cummings told O&P Business News.
The study found a statistically significant difference in ankle motion (of less than 4°), which the authors characterized as “likely irrelevant and more a result of the [prosthetic] foot types rather than the amputation level.” Cummings said because more transtibial amputees have the ability to wear high performance feet, the correlation between the amputation level and the difference in motion is misleading.
“The kids with high performance feet – dynamic response feet – had a greater ankle motion. That makes sense because those feet tend to have a flexible keel. That was compared with medium or low performance feet,” Cummings said.
Cummings said the study, which connects transtibial amputations and dynamic response feet to slightly better ankle motion, shows that transtibial amputations can offer benefits at the same level as Syme amputations, which traditionally have been considered the preferred method among pediatric lower limb amputees.
“One of that things that comes out frequently in discussions of amputation level is [whether] a Syme ankle disarticulation [is] a better or preferable level from a functional standpoint than a transtibial level,” he said. “It is kind of generally assumed that Syme amputation in the pediatric population is a better approach because it preserves the growth plates, it allows distal loading of the residual limb, a longer level arm, and the somewhat more bulbous end of the distal limb also translates rotation to the prosthesis a little bit better. It also gives [the amputee] a way to suspend the prosthesis.”
Weighing the pros and cons
A Syme amputation can offer unique benefits in comparison with the transtibial amputation because it preserves more of the limb.
“In many cases [the amputee] can walk or load when they are not wearing their prosthesis,” Cummings noted. “They can get out of the shower, a swimming pool, et cetera and not have to have a prosthesis on. That is a pretty significant benefit.”
The transtibial amputation, however, allows for a wider range of prosthetic foot options.
“The Syme amputees, in many cases, have a much longer amputation,” Cummings said. “So they have less room for a high performance foot … On a shorter foot you may have plenty of space for a running foot or a foot with shock absorption and rotation.”
Cummings and his fellow researchers hope practitioners will become more aware of the limitations of component options for Syme amputation, which should be weighed against the benefits for each individual patient.
“If you are looking at getting sufficient space below the Syme amputee for fitting a higher end or more flexible dynamic foot, then the prosthetist may want to have that conversation with the orthopedist or the attending physician to help them look at options such as epiphysiodesis at a certain point. Just the ability to have that discussion and kind of be aware of that fact may give some patients the opportunity to take advantage of some of the increased functional capabilities of some of the feet out there. If you wait until [the patient is] an adult, it is too late to do anything about it so they have future options.”
Surprising happiness results
Another aspect of the study was the Pediatric Outcomes Data Collection Instrument (PODCI) questionnaire, completed by the accompanying parent of 36 of the Syme patients and 22 transtibial patients. Parents answered questions meant to assess health, pain and ability to participate in normal daily activities as well as “higher level activities” such as sports. Overall, the parents of young children reported higher happiness sub scores for their children than the parents of adolescents.
Additionally, Cummings said, “The parents of patients fitted with low performance feet reported higher PODCI happiness sub scores. That was interesting. We thought that could be because low performance feet were fitted in the younger population that scores higher on the PODCI than their adolescent counterparts … So it was not necessarily related to the foot at all. There are fewer choices of feet for the younger kids, so they may not have had the option of a higher performance foot.”
The most important takeaway from the study, Cumming said, is the importance of carefully weighing both amputation options for each pediatric amputee based on his or her needs.
“So rather than there being a blanket statement or conclusion that you should opt for a shorter level of amputation … We are saying that you really need to look at it case by case,” he said.
Testing more prostheses
Cummings and colleagues plan to continue their work with pediatric amputees and hope to test more specific types of prosthetic feet in future studies.
“As we get more numbers, we are doing some other studies now that are looking at running rather than just ambulation in a straight gait lane,” he said. “Hopefully we can get some more perspective on performance with those styles of feet on that pediatric population.”
Cummings said the importance of this information will increase as prosthesis options for children continue to develop. – by Amanda Alexander
For more information:
Cummings D. J Bone Joint Surg. 2014;doi:10.2106/JBJS.N.00192.
Disclosure: Cummings has no relevant financial disclosures.