Study Design
The standardized protocol for the SPRINT study was approved by the human subjects committees (REB #99-077—Research Ethics Boards/Institutional Review Boards) at each participating site. The study was registered at www.ClinicalTrials.gov (identifier: NCT00038129). The methodological details and the results of the primary SPRINT analysis of reamed compared with unreamed nailing has been published previously48,49.
Briefly, the SPRINT study involved twenty-nine clinical centers in Canada, the United States, and the Netherlands. We standardized the surgical protocols for reamed and unreamed nailing, and all patients underwent the same perioperative protocol. One thousand two hundred and twenty-six patients met the eligibility criteria and completed one year of follow-up (Fig. 1).
Inclusion criteria included skeletal maturity, an open or closed tibial shaft fracture (Tscherne Type 0 to 3 and Gustilo-Anderson Type I to IIIB)1-3,50-52, amenability of the fracture to surgical repair with an intramedullary nail, and informed consent. Exclusion criteria included tibial shaft fractures not amenable to reamed or unreamed nailing, pathologic fractures, patients likely to be lost before completing adequate follow-up, patients who were not skeletally mature, and patients who had not provided consent. Patients were followed for one year after injury.
In the SPRINT trial, the primary outcome was a composite including bone-grafting, implant exchange or removal, debridement of bone and soft tissue because of deep infection, fracture dynamization (due to locking screw removal), removal of locking screws because of screw breakage or loosening, autodynamization (breaking of a locking screw that resulted in the fracture collapsing), fasciotomy, failure of the construct (broken nail), and hematoma drainage. This composite is the primary outcome for the current analysis as well. The events included in our composite vary in severity, but are included in the composite as they are all deemed detrimental to the patient.
Briefly, the SPRINT investigation found that there was a significant interaction between the randomized intervention and open and closed fractures (p = 0.01). In patients with closed fractures, we found a significant decrease in risk for those who had reamed nailing compared with those who had unreamed nailing. This effect was not seen in patients with open fractures.
Selection of Prognostic Factors
On the basis of previous reports in the literature47-49 and variables collected in the SPRINT study, two investigators (M.B. and E.H.S.) independently identified two different types of factors: (1) baseline factors measured before the intramedullary nailing (age, sex, race, mechanism of injury, smoking status, insulin-dependent diabetes, unilateral or bilateral injury, open or closed fracture, anticoagulation medication use, nonsteroidal anti-inflammatory drugs [NSAIDs] use, isolated fracture, AO/OTA [Arbeitsgemeinschaft für Osteosynthesefragen/Orthopaedic Trauma Association] classification, and location of fracture) and (2) surgical factors (reamed or unreamed nailing, surgeon or resident performing the surgery, nail material, number of locking screws used, patellar tendon split or tendon retraction, superior or inferior surgical approach for nail insertion, postoperative fracture gap, time from injury to surgery, fasciotomy at the time of initial surgery, postoperative weight-bearing status, and type of wound coverage in open fractures). With input from the Steering Committee, we agreed that factors needed to have thirty occurrences to be included in our model to ensure stability of the model. As a result, the following factors were not included in the analysis: bilateral fractures (twenty-two patients) and insulin-dependent diabetes (eleven patients).
For our adjusted model, we used multivariable logistic regression. Having fewer than ten events for each factor (predictor variable) can result in overfitted, unstable models53. We had 219 events in the SPRINT trial; therefore, we reduced the candidate list of variables so that there were only twenty-one factors in our analyses, as we describe below.
Steering Committee members independently rated their perceived importance of each factor on a scale of one to ten, with ten being top priority to include in the analysis and one being the lowest priority. We then chose the fifteen highest ranked factors to include in our analysis, which were, in descending order: (1) smoking status, (2) open fracture, (3) fracture gap, (4) mechanism of injury, (5) reamed intramedullary nailing, (6) age, (7) location of fracture, (8) isolated fracture, (9) type of wound coverage, (10) NSAID use, (11) AO/OTA fracture classification, (12) number of locking screws, (13) postoperative weight-bearing status, (14) time from injury to surgery, and (15) nail material. Because some of the variables had more than two categories (e.g., AO/OTA fracture classification), these fifteen factors accounted for twenty-one factors in the model.
Definition of Orthopaedic Factors
We classified the mechanism of injury as either high energy or low energy. High-energy injuries included motor vehicle accidents, pedestrian-motor vehicle accidents, motorcycle accidents, snowmobile accidents, crush injuries, and direct blunt trauma. Low-energy injuries included falls, twists, and direct penetrating trauma. We classified smoking status as current smokers versus previous smokers or nonsmokers. The fracture location data were recorded in five categories: proximal, proximal-middle, middle, distal-middle, and distal. For the current analysis, we classified fracture location as proximal and proximal-middle versus middle versus distal and distal-middle.
Nail material was recorded and analyzed as either stainless steel or titanium. We categorized the number of locking screws as two or more on both the proximal and distal sides compared with less than two on at least one side. The size of the fracture gap was assessed by the Central Adjudication Committee. The Committee reviewed the radiographs of each patient and determined whether there was no fracture gap, a fracture gap of <1 cm, or a fracture gap of ≥1 cm. Fracture gap refers to the magnitude of circumferential bone loss as judged by the adjudicator on review of the postoperative radiograph, or noncircumferential bone loss as judged by the adjudicator in patients with cortical continuity of up to 25% as judged by the surgeon at the time of the operation and recorded on the study case report forms. The time to surgery after injury was recorded as a continuous variable. For this analysis, we classified the time to surgery after injury into three categories: early (less than six hours from injury to surgery), middle (six hours to twenty-four hours), and late (a greater than twenty-four-hour surgical delay).
We classified postoperative weight-bearing as full weight-bearing postoperatively compared with partial or non-weight-bearing. Type of wound coverage was defined as primary closure, delayed primary closure, and additional soft-tissue reconstruction for open fractures. Primary closure was performed at the time of the intramedullary nailing. Patients in the delayed primary closure group had an open wound with a repeat irrigation and debridement and no other documented wound procedures, although they may have had negative-pressure wound therapy. Patients in the additional soft-tissue reconstruction group had documentation of a delayed wound closure procedure, including split-thickness skin grafts, fasciocutaneous flaps, rotational muscle flaps, or free flaps.
Statistical Analysis
Our primary analysis was a multivariable logistic regression using the SPRINT primary outcome as the dependent variable. All tests were two-tailed and p values of <0.05 were considered significant. Because the primary analysis of the SPRINT investigation found that reamed nailing reduced events in patients with closed but not open fractures, we included in the current analysis open or closed fractures, treatment status, and the interaction between the two in our logistic regression model. This was the only interaction investigated. The main multivariable model included fourteen characteristics. The fifteenth characteristic, type of wound closure, could not be included because of confounding with open versus closed fracture. Therefore, a second logistic regression was performed to investigate the type of wound closure. This model included only patients with open fractures and included the type of wound closure variable and all other variables except open compared with closed fracture. The main multivariable analysis was repeated with use of the following revised outcomes: (1) our primary outcome but without including autodynamization in the composite and (2) our primary outcome but without including dynamization and autodynamization in the composite. All analyses were performed with use of SAS software (version 9.1; SAS Institute, Cary, North Carolina).
Source of Funding
Research grants were received from the following: Canadian Institutes of Health Research (MCT-38140); National Institutes of Health (NIAMS-072 and R01-AR48529); Orthopaedic Research and Education Foundation of the American Academy of Orthopaedic Surgeons; Orthopaedic Trauma Association; Hamilton Health Sciences Research Grant; Zimmer; and, in part, by a Canada Research Chair in Musculoskeletal Trauma at McMaster University. The funding sources had no role in influencing the trial or the manuscript.
Note: Data were analyzed by Diane Heels-Ansdell, MSc (Department of Clinical Epidemiology and Biostatistics, McMaster University, Hamilton, Ontario, Canada), under the supervision of Stephen Walter (Senior Biostatistician). Details regarding the authors and investigators are provided below.
Author Contributions:Writing Committee: Emil H. Schemitsch, MD, FRCS(C) (Chair), Mohit Bhandari, MD, PhD, FRCS(C), Gordon Guyatt, MD, David W. Sanders, MD, MSc, FRCS(C), Marc Swiontkowski, MD, Paul Tornetta III, MD, Stephen D. Walter, PhD, Rad Zdero, PhD, J.C. Goslings, MD, PhD, David Teague, MD, Kyle Jeray, MD, and Michael D. McKee, MD, FRCS(C).
SPRINT Investigators: The following persons participated in the SPRINT Study:
Study trial co-principal investigators: Mohit Bhandari, Gordon Guyatt.
Steering Committee: Gordon Guyatt (Chair), Mohit Bhandari, David W. Sanders, Emil H. Schemitsch, Marc Swiontkowski, Paul Tornetta III, Stephen D. Walter.
Central Adjudication Committee: Gordon Guyatt (Chair), Mohit Bhandari, David W. Sanders, Emil H. Schemitsch, Marc Swiontkowski, Paul Tornetta III, Stephen D. Walter.
SPRINT Methods Center staff: McMaster University, Hamilton, Ontario: Sheila Sprague, Diane Heels-Ansdell, Lisa Buckingham, Pamela Leece, Helena Viveiros, Tashay Mignott, Natalie Ansell, Natalie Sidorkewicz. University of Minnesota, Minneapolis, Minnesota: Julie Agel.
Data Safety and Monitoring Board (DSMB): Claire Bombardier (Chair), Jesse A. Berlin, Michael Bosse, Bruce Browner, Brenda Gillespie, Alan Jones, Peter O’Brien.
Site Audit Committee: Julie Agel, Sheila Sprague, Rudolf Poolman, Mohit Bhandari.
Investigators:London Health Sciences Center/University of Western Ontario, London, Ontario: David W. Sanders, Mark D. Macleod, Timothy Carey, Kellie Leitch, Stuart Bailey, Kevin Gurr, Ken Konito, Charlene Bartha, Isolina Low, Leila V. MacBean, Mala Ramu, Susan Reiber, Ruth Strapp, Christina Tieszer.
Sunnybrook Health Sciences Center/University of Toronto, Toronto, Ontario: Hans J. Kreder, David J. G. Stephen, Terry S. Axelrod, Albert J.M. Yee, Robin R. Richards, Joel Finkelstein, Wade Gofton, John Murnaghan, Joseph Schatztker, Michael Ford; Beverly Bulmer, Lisa Conlan.
Hospital du Sacre Coeur de Montreal, Montreal, Quebec: G. Yves Laflamme, Gregory Berry, Pierre Beaumont, Pierre Ranger, Georges-Henri Laflamme, Sylvain Gagnon, Michel Malo, Julio Fernandes, Marie-France Poirier.
St. Michael’s Hospital/University of Toronto, Toronto, Ontario: Emil H. Schemitsch, Michael D. McKee, James P. Waddell, Earl R. Bogoch, Timothy R. Daniels, Robert R. McBroom, Milena R. Vicente, Wendy Storey, Lisa M. Wild.
Royal Columbian Hospital/University of British Columbia, New Westminster/Vancouver, British Columbia: Robert McCormack, Bertrand Perey, Thomas J. Goetz, Graham Pate, Murray J. Penner, Kostas Panagiotopoulos, Shafique Pirani, Ian G. Dommisse, Richard L. Loomer, Trevor Stone, Karyn Moon, Mauri Zomar.
Wake Forest Medical Center/Wake Forest University Health Sciences, Winston-Salem, North Carolina: Lawrence X. Webb, Robert D. Teasdall, John Peter Birkedal, David Franklin Martin, David S. Ruch, Douglas J. Kilgus, David C. Pollock, Mitchel Brion Harris, Ethan Ron Wiesler, William G. Ward, Jeffrey Scott Shilt, Andrew L. Koman, Gary G. Poehling, Brenda Kulp.
Boston Medical Center/Boston University School of Medicine, Boston, Massachusetts: Paul Tornetta III, William R. Creevy, Andrew B. Stein, Christopher T. Bono, Thomas A. Einhorn, T. Desmond Brown, Donna Pacicca, John B. Sledge III, Timothy E. Foster, Ilva Voloshin, Jill Bolton, Hope Carlisle, Lisa Shaughnessy.
Wake Medical Center, Raleigh, North Carolina: William T. Obremskey, C. Michael LeCroy, Eric G. Meinberg, Terry M. Messer, William L. Craig III, Douglas R. Dirschl, Robert Caudle, Tim Harris, Kurt Elhert, William Hage, Robert Jones, Luis Piedrahita, Paul O. Schricker, Robin Driver, Jean Godwin.
Vanderbilt University Medical Center, Nashville, Tennessee: William T. Obremskey, Philip James Kregor, Gregory Tennent, Lisa M. Truchan, Marcus Sciadini, Franklin D. Shuler, Robin E. Driver, Mary Alice Nading, Jacky Neiderstadt, Alexander R. Vap.
MetroHealth Medical Center, Cleveland, Ohio: Heather A. Vallier, Brendan M. Patterson, John H. Wilber, Roger G. Wilber, John K. Sontich, Timothy Alan Moore, Drew Brady, Daniel R. Cooperman, John A. Davis, Beth Ann Cureton.
Hamilton Health Sciences, Hamilton, Ontario: Scott Mandel, R. Douglas Orr, John T.S. Sadler, Tousief Hussain, Krishan Rajaratnam, Bradley Petrisor, Mohit Bhandari, Brian Drew, Drew A. Bednar, Desmond C.H. Kwok, Shirley Pettit, Jill Hancock, Natalie Sidorkewicz.
Regions Hospital, St. Paul, Minnesota: Peter A. Cole, Joel J. Smith, Gregory A. Brown, Thomas A. Lange, John G. Stark, Bruce A. Levy, Marc F. Swiontkowski, Mary J. Garaghty, Joshua G. Salzman, Carol A. Schutte, Linda Tastad, Sandy Vang.
University of Louisville School of Medicine, Louisville, Kentucky: David Seligson, Craig S. Roberts, Arthur L. Malkani, Laura Sanders, Carmen Dyer, Jessica Heinsen, Langan Smith, Sudhakar Madanagopal, Linda Frantz-Bush.
Memorial Hermann Hospital, Houston, Texas: Kevin J. Coupe, Jeffrey J. Tucker, Allen R. Criswell, Rosemary Buckle, Alan Jeffrey Rechter, Dhiren Shaskikant Sheth, Brad Urquart, Thea Trotscher.
Erie County Medical Center/University of Buffalo, Buffalo, New York: Mark J. Anders, Joseph M. Kowalski, Marc S. Fineberg, Lawrence B. Bone, Matthew J. Phillips, Bernard Rohrbacher, Philip Stegemann, William M. Mihalko, Cathy Buyea.
University of Florida–Jacksonville, Jacksonville, Florida: Stephen J. Augustine, William Thomas Jackson, Gregory Solis, Sunday U. Ero, Daniel N. Segina, Hudson B. Berrey, Samuel G. Agnew, Michael Fitzpatrick, Lakina C. Campbell, Lynn Derting, June McAdams.
Academic Medical Center, Amsterdam, The Netherlands: J. Carel Goslings, Kees Jan Ponsen, Jan Luitse, Peter Kloen, Pieter Joosse, Jasper Winkelhagen, Raphaël Duivenvoorden.
University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma: David C. Teague, Joseph Davey, J. Andy Sullivan, William J.J. Ertl, Timothy A. Puckett, Charles B. Pasque, John F. Tompkins II, Curtis R. Gruel, Paul Kammerlocher, Thomas P. Lehman, William R. Puffinbarger, Kathy L. Carl.
University of Alberta/University of Alberta Hospital/Royal Alexandra Hospital, Edmonton, Alberta: Donald W. Weber, Nadr M. Jomha, Gordon R. Goplen, Edward Masson, Lauren A. Beaupre, Karen E. Greaves, Lori N. Schaump.
Greenville Hospital System, Greenville, South Carolina: Kyle J. Jeray, David R. Goetz, David E. Westberry, J. Scott Broderick, Bryan S. Moon, Stephanie L. Tanner.
Foothills General Hospital, Calgary, Alberta: James N. Powell, Richard E. Buckley, Leslie Elves.
Saint John Regional Hospital, Saint John, New Brunswick: Stephen Connolly, Edward P. Abraham, Trudy Steele.
Oregon Health & Sciences University, Portland, Oregon: Thomas Ellis, Alex Herzberg, George A. Brown, Dennis E. Crawford, Robert Hart, James Hayden, Robert M. Orfaly, Theodore Vigland, Maharani Vivekaraj, Gina L. Bundy.
University of California, San Francisco, San Francisco General Hospital, San Francisco, California: Theodore Miclau III, Amir Matityahu, R. Richard Coughlin, Utku Kandemir, R. Trigg McClellan, Cindy Hsin-Hua Lin.
Detroit Receiving Hospital, Detroit, Michigan: David Karges, Kathryn Cramer, J. Tracy Watson, Berton Moed, Barbara Scott.
Deaconess Hospital Regional Trauma Center and Orthopaedic Associates, Evansville, Indiana: Dennis J. Beck, Carolyn Orth.
Thunder Bay Regional Health Science Center, Thunder Bay, Ontario: David Puskas, Russell Clark, Jennifer Jones.
Jamaica Hospital, Jamaica, New York: Kenneth A. Egol, Nader Paksima, Monet France.
Ottawa Hospital–Civic Campus, Ottawa, Ontario: Eugene K. Wai, Garth Johnson, Ross Wilkinson, Adam T. Gruszczynski, Liisa Vexler.