Absence of Evidence May Not Mean Evidence of Absence: Commentary on an article by Bernard H. van Duren, BEng, MBChB, DPhil, et al.: "The Effect of Perioperative Biologic Disease-Modifying Anti-Rheumatic Drugs on the Risk of Postoperative Complications. Surgical Site Infection, Delayed Wound Healing, and Disease Flares Following Orthopaedic Surgical Procedures".