PMC6650580_01
Capability gap and report on muscle operating lengths. (A) Capability gap computed for the two representative patients, before and after the virtual surgery. The continuous black lines represent the joint moments required for the model to reach the desired kinematics [i.e., typically developed (TD) gait cycle]. Dotted black lines represent the moment exerted by the model. The light gray patches represent the capability gap. (B) Information about the operating conditions of the muscles. Blue dots represent the time instants in which muscles are active at short lengths (activation >0.25 and normalized fiber length smaller than 0.6), red dots the intervals in which muscles are stretched, and exert an excessive passive force (>0.5 times the maximum isometric force).
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F3
We compared the predicted motor performances of the patients in terms of the capability gap for the pre-and post-operative conditions (Figure 3).
Effect of treatment options on the capability gap. Data reported are relative to the simulated post-operative condition of the right leg of Patient 2. Capability gap is computed after rectus femoris transfer, femur extension and derotation osteotomy, and patella advancement interventions but before performing any muscle release intervention. The continuous black lines represent the joint moments required for the model to reach the desired kinematics [i.e., typically developed (TD) gait cycle].
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F4
We tested the effect of different treatment options on the capability gap of the right leg of Patient 2 (Figure 4).
Effect of motor control on capability gap. Capability gap computed relative to the pre-operative condition for the right legs of both patients (on the left side is Patient 1, on the right is Patient 2). The continuous black lines represent the joint moments required for the model to reach the desired kinematics [i.e., typically developed (TD) gait cycle]. When synergies are taken into account the muscle activations are computed from the pre-operative weight vectors, which define the muscle coordination specific to the impairment; when synergies are not taken into account muscles are activated selectively, thus simulating an unimpaired motor control.
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F5
We also investigated the effect of including/excluding the altered muscle parameters and motor control on the predicted gait performance (Figure 5) in the pre-operative condition.
Predicted and measured changes in patient performance. Data on the left belong to Patient 1, on the right to Patient 2. (A) Kinematics of the two representative cases measured in both pre- and post-operative conditions (mean and standard deviation). Black dotted line is the average data from typically developed (TD) children used as reference for the computation of the capability gap (CG). (B) Changes in the predicted capability gap, and in the root mean square differences (computed with respect to the TD kinematics) between the pre- and post-operative condition.
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F6
Finally, we tested the ability of our framework to predict post-operative performance by comparing the predicted gait performance (CG) with the gait performance quantified based on the 3D gait analysis performed before and after the intervention (Figure 6).