hi thanks for yor question.
it's unlikely that your pars fractures
are acute in the sense that they have likely existed for sometime or happened on a background of a congential abnormality in that region of yor spine.
if you remove the exacerbating activity. i.e. anything where you are repeatedly hyper extending your spine then your symptoms may improve. a TLSO support orthosis or boston brace can also help if warn for long periods of time. surgery can be performed to bone graft and fix the fractures in resistant cases.
I hope this information helps