BACKGROUND: Surgeons agree on the benefits of operative treatment of tibial fractures - the most common of long bone fractures - with an intramedullary rod or nail. Rates of re-operation remain high - between 23% and 60% in prior trials - and the two alternative nailing approaches, reamed or non-reamed, each have a compelling biological rationale and strong proponents, resulting in ongoing controversy regarding which is better. METHODS/DESIGN: The objective of this trial was to assess the impact of reamed versus non-reamed intramedullary nailing on rates of re-operation in patients with open and closed fractures of the tibial shaft. The study to prospectively evaluate reamed intramedullary nails in tibial fractures (S.P.R.I.N.T) was a multi-center, randomized trial including 29 clinical sites in Canada, the United States and the Netherlands which enrolled 1200 skeletally mature patients with open (Gustilo Types I-IIIB) or closed (Tscherne Types 0-3) fractures of the tibial shaft amenable to surgical treatment with an intramedullary nail. Patients received a statically locked intramedullary nail with either reamed or non-reamed insertion. The first strategy involved fixation of the fracture with an intramedullary nail following reaming to enlarge the intramedullary canal (Reamed Group). The second treatment strategy involved fixation of the fracture with an intramedullary nail without prior reaming of the intramedullary canal (Non-Reamed Group). Patients, outcome assessors, and data analysts were blinded to treatment allocation. Peri-operative care was standardized, and re-operations before 6 months were proscribed. Patients were followed at discharge, 2 weeks post-discharge, and at 6 weeks, 3, 6, 9, and 12 months post surgery. A committee, blinded to allocation, adjudicated all outcomes. DISCUSSION: The primary outcome was re-operation to promote healing, treat infection, or preserve the limb (fasciotomy for compartment syndrome after nailing). The primary outcome was a composite comprising the following re-operations: bone grafts, implant exchanges, and dynamizations, in patients with fracture gaps less than 1 cm post intramedullary nail insertion. Infections and fasciotomies were considered events irrespective of the fracture gap. We planned a priori to conduct a subgroup analysis of outcomes in patients with open and closed fractures. S.P.R.I.N.T is the largest collaborative trial evaluating alternative orthopaedic surgical interventions in patients with tibial shaft fractures. The methodological rigor will set new benchmarks for future trials in the field and its results will have important impact on patient care. The S.P.R.I.N.T trial was registered [ID NCT00038129] and received research ethics approval (REB#99-077).