Which Trans Dermal Application Help To Relieve Chronic Lower Back Pain?

I have chronic lover back pain ( left buttock ) after car accident hit behind. I had Physio 24 sessions (dry-needling) and Acupuncture 14 sessions by my Chinese Doctor not responding so far and presently I'm taking Magnesium-Diasporal ( practitioner only ) made in Germany. Some commercial companies producing lotions, magnesium-oil for trans- dermal applications and claiming more effective than magnesium taken orally. Could you please let me know which application is more beneficial.