Preventing CRPS after wrist fracture

The last post described a new paper in BMC Neurology suggesting guidelines for the treatment of CRPS. They also discussed prevention. They concluded that people who fracture their wrist should be given 500 mg daily vitamin C because two RCT’s show a reduction in incidence of CRPS in those who do this[1,2] both papers from the same group as the guidelines paper.  This is good and well, but I am intrigued about the incidence data from these RCT’s – in the first, those who were untreated had an incidence of CRPS of about 25% and in the second RCT it was about 11%. The treated group incidence was about 2% with confidence intervals easily covering more conservative, and I would suggest probably more accurate, estimates of incidence – about 3-4%.  So,  were these groups of wrist fracture patients really 2-4 times more likely to develop CRPS than other study groups are, or were the criteria by which someone was said to have CRPS different? I would argue the latter here, which is why I think we really don’t know if vitamin C reduces incidence until we show it to do so in a group for whom the untreated people have an incidence of about 3-4%.
ResearchBlogging.org
[1] Zollinger PE, Tuinebreijer WE, Kreis RW, & Breederveld RS (1999). Effect of vitamin C on frequency of reflex sympathetic dystrophy in wrist fractures: a randomised trial. Lancet, 354 (9195), 2025-8 PMID: 10636366

[2] Cazeneuve JF, Leborgne JM, Kermad K, & Hassan Y (2002). [Vitamin C and prevention of reflex sympathetic dystrophy following surgical management of distal radius fractures] Acta orthopaedica Belgica, 68 (5), 481-4 PMID: 12584978