Effect of amputation level on energy expenditure during overground walking by children with an amputation.

BACKGROUND:
The oxygen cost of walking by adults with an amputation has been well described, but few studies have focused on this parameter in children who have had an amputation. Children with a transtibial amputation have been reported to maintain walking speed at a 15% higher oxygen cost than able-bodied children. The purpose of this study was to determine if the level of amputation in children has a differential impact on the self-selected speed of walking and the oxygen cost, and how the performance of these children compares with that of a group of able-bodied children.

METHODS:
Seventy-three children who had had an amputation participated in this study. Oxygen consumption was measured with a Cosmed K4b2 oxygen analysis telemetry unit (Rome, Italy) as the participants walked overground for ten minutes at a self-selected speed. One minute of steady-state data were reduced, averaged, and standardized to control values. Children with a unilateral amputation were grouped according to the level of the amputation; there were twenty-nine Syme, thirteen transtibial, fourteen knee disarticulation, five transfemoral, and five hip disarticulation amputations. Seven children had had a bilateral amputation, and they were considered as a separate group. Comparisons were made among the five amputation groups and between all children who had undergone amputation and control subjects. The variables that were analyzed were resting VO(2) rate (mL/kg/min), resting heart rate (beats per minute [bpm]), walking VO(2) rate (mL/kg/min), walking VO(2) cost (mL/kg/m), walking heart rate (bpm), and self-selected walking velocity (m/min).

RESULTS:
Unilateral transfemoral and hip disarticulation amputations resulted in significantly reduced walking speed (80% and 72% of normal, respectively) and increased VO(2) cost (151% and 161% of normal, respectively), while the heart rate was significantly increased in the hip disarticulation group (124% of normal). Compared with the controls, the children with a bilateral amputation walked significantly slower (87% of normal), with an elevated heart rate (119% of normal) but a similar energy cost. Children with a Syme amputation, transtibial amputation, or knee disarticulation walked with essentially the same speed and oxygen cost as did normal children in the same age group.

CONCLUSIONS:
Children with an amputation through the knee or distal to the knee were able to maintain a normal walking speed without significantly increasing their energy cost. Only when the amputation is above the knee do children walk significantly slower and with an increased energy cost.