we are planning to conduct a comparative study on the effects of Manual Traction and opening techniques on symptoms in patients with cervical radiculopathy???
In my opinion there are some absolute indications for surgery. They include motor deficit and intractable pain in cases with which the conservative treatment fails to improve the symtoms after 6 weeks of systematic application.
So if you plan to conduct a comparative study, the most important point is to randomize comparable cases, which is a difficult task. The second point is to ensure a long enough follow-up which is also difficult for ethical reasons. Good luck.
you should check the trial by Peolsson in Spine 2013, the systematic review by Miller et al. in Man Ther 2010 and the work by the McKenzie Group (Stephen May and others). There is also one trial by Cohen et al. in Anesthesiology 2014.
As far as I know the "side-glide" technique might be partially effective in neuro-dynamic dysfunctions