Very interesting and clinically significant article at the latest issue of the Angle Orthodontist:
"The extraction of the deciduous canine is an effective measure in PDC cases, but it must be done in younger patients in combination with early diagnosis, at the age of 10–11 years. Maintenance of the perimeter of the upper arch is an important step during the observation period, and a palatal arch as a space-holding device is recommended"
I would add that removable retention with a plate (Hawlley, Begg retainer, Jensen plate etc), or let's say an MRC trainer could also do the trick! Other than that please take the time to read this article over the Angle's website: