DupuytrEn Treatment EffeCtiveness Trial (DETECT): a protocol for prospective, randomised, controlled, outcome assessor-blinded, three-armed parallel 1:1:1, multicentre trial comparing the effectiveness and cost of collagenase clostridium histolyticum, percutaneous needle fasciotomy and limited fasciectomy as short-term and long-term treatment strategies in Dupuytren's contracture.