Interestingly, the devices provided to these subjects with amputation were designed to allow ankle motion, but these subjects did not generate any more power across the ankle joint (Figure 12(b)) than the subjects with Chopart amputation who wore clamshell devices designed to eliminate ankle motion (Figure 12(b)-(c)).
As a result of the clamshell devices fitted to the subjects with Chopart amputation, in whom ankle motion was eliminated, progression to foot flat during loading response was delayed as the shank and foot segments moved synchronously.
In the subject with unilateral Chopart amputation, the hip joints became the primary source of power generation to compensate for the limited power generation across the affected ankle (Figure 10(a)-(b)).
Reductions in velocity, stride length, cadence, and the support phase data were observed in the subject with unilateral Chopart amputation but not in the subject with bilateral Chopart amputation (Tables 2-3), which seems difficult to explain on any basis other than individual variability.
The clamshell devices fitted to the subjects with Chopart amputation seemed capable of restoring the effective foot length and compensating for the limited power generation across the ankle joint--thus normalizing many of the anomalies of PFA gait.