Repeated measures ANOVA with intra group factor ? Which model to use ? Clinical trial


I have a question concerning the model I should use for my experiment:

Presentation of the experiment:
I have two groups of children: 12 healthy children and 9 hemiplegic children (they have a movement disorders only in one arm). So I have really 3 groups:
- healthy children
- sick children_healthy arm
- sick children_sick arm,
(but the two last groups are dependent: same subjects).

I measure their arm movement velocity under 3 different conditions.

The thing is for healthy children I measure only one arm, and for hemiplegic children I measure both their arms.
I have in conclusion 90 measures of velocity ((12healthy+9hemi*2arms)*3conditions).

What I would like is to compare my three groups (healthy, sick with healthy arm, sick with sick arm) by taking into account that the three conditions are applied to the same subjects (ANOVA Repeated Measures) AND that I have a repeated factor (arm 2 levels) only in the hemiplegic group…

How can I present my data to have these results ? I didn’t find any example yet which can be applied to my experiment.

Thanks a lot !