November 2014

Below-knee amputation level has subtle functional effects

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Photo courtesy of Fillauer

Syme, transtibial gaits are similar

By Hank Black

The relative functional benefits of transtibial and Syme amputations in adults have been discussed in the medical literature, but few studies have addressed similar issues in pediatric patients. A sizeable recent study found statistically significant kinematic and kinetic differences between the two amputation levels in children and adolescents, but the subtle nature of those differences suggests that decisions about amputation level should be decided on an individual basis.

“We found only subtle differences in gait data between Syme and transtibial-level patients, mostly due to underlying etiology, but in an earlier study we found that this does not result in increased oxygen consumption and heart rate,” said Donald Cummings, CP, a study coauthor and director of the Orthotics and Prosthetics Department at Texas Scottish Rite Hospital for Children in Dallas.

The study, which was published in the October issue of The Journal of Bone and Joint Surgery, used 3D gait analysis to assess 64 children and adolescents, aged 4.7 to 19.2 years, who had undergone unilateral below-knee amputations, with 41 patients in the Syme cohort (which also included three Boyd amputations). Patients wore their current prostheses and walked at a self-selected speed.

A total of 12 types of prosthetic feet were involved, with each categorized as permitting a high, medium, or low activity level as defined by Medicare for prosthesis prescription. Six patients wore high-performance dynamic response feet, and five of those were transtibial amputees; 59% of the study population wore medium-performance feet, and 31% wore low-performance feet. The PODCI (pediatric outcomes data collection instrument) was completed by the accompanying parents.

Total ankle excursion and peak power of the prosthetic ankle were significantly greater in the transtibial patients than the Syme patients. Patients in the Syme group walked with more external hip rotation during stance phase than those in the transtibial group, and also had greater peak coronal-plane hip abductor power. However, the authors noted that the kinematic differences between groups, despite being statistically significant, were small enough that they were unlikely to be clinically relevant. Rather than amputation level, they hypothesized, the kinematic differences at the hip probably were related to the fact that more than half the Syme patients had fibular hemimelia, which is associated with femoral external rotation, and the differences at the ankle probably resulted from the foot types used. PODCI measures did not differ significantly between groups.

Prosthetic ankle range of motion was significantly greater in the patients with high-performance, dynamic response feet than in those with medium- and low-performance feet. Lower-tech feet were actually associated with greater happiness or satisfaction scores than more advanced feet, possibly because the low-tech versions were more likely to be worn by younger children.

“A major challenge facing the clinical team and the parents is coming up with criteria about when we should be fitting higher-end feet, which require more space between the ground and the distal tibia,” Cummings said. “Parents want their kids to develop as normally as possible in their peer group, not necessarily expecting the child to become a top athlete, but at least to be on par with peers in active play and sports. With T-ball, soccer, and other active sports and play that involve running, the controversy starts within a year or two of the first fitting, if not at the start.”

Of course, the space available between the end of the residual limb and the floor, patient size, and available pediatric components often determine prosthesis prescription. Growth modulation or revision surgery can provide patients with a shorter limb and greater choices, but surgical shortening of the residual limb, which allows more choices of high-tech components, remains controversial, Cummings said. A Syme amputation, in addition to having structural advantages in growing children, also offers the potential ability to walk at least very short distances without a prosthesis, which 18 of the study’s Syme patients said they could do.

In a commentary accompanying the online version of the article, orthopedic surgeon Michael Aiona, MD, chief of staff at Shriners Hospital for Children in Portland, OR, suggested the Dallas group’s findings could be used to outline a management program for the child with a limb deficiency. Specifically, he wrote, the data support the current gold standard of an amputation that maximizes limb length; they also suggest that low-cost SACH (solid ankle cushion heel) feet can be worn by young children without compromising their gait, function, or satisfaction, and that more expensive, high-performance feet can wait until a child has reached adolescence.

Hank Black is a medical writer in Birmingham, AL.

Sources:

Jeans KA, Karol LA, Cummings D, Singhal K. Comparison of gait after Syme and transtibial amputation in children. Factors that may play a role in function. J Bone Joint Surg Am 2014;96(19):1641-1647.

Aiona M. See you in the Paralympics in 2022. Commentary on an article by Kelly A. Jeans, MS, et al.: “Comparison of gait after Syme and transtibial amputation in children. Factors that may play a role in function.” J Bone Joint Surg Am 2014;96(19): e173(1-2).

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