Nonunion in Patients with Tibial Shaft Fractures: Is Early Physical Status Associated with Fracture Healing?

Background Nonunions of tibial shaft fractures have devastating physical and psychological consequences for patients. It remains unknown if early functional status can identify patients at risk for nonunion. Questions/Purposes To determine if functional status at three months after surgery, as measured by either the short form 36 (SF-36) or the short form 12 (SF-12) health survey physical component summary (SF-12 PCS) score, can serve as a prognostic indicator for nonunion at one year in patients with fractures of the tibial shaft. Patients/Methods This study was an observational cohort study nested within two multicenter, randomized controlled trials. Patients who met the following eligibility criteria were included: (1) sustained a tibial shaft fracture that was treated with intramedullary nailing, (2) were unhealed at the three-month follow-up, (3) had a reported SF-36 or SF-12 PCS score at three months, (4) had the final 12-month follow-up with a reported radiographic healing status (bone union or nonunion), and (5) were enrolled in either the Study to Prospectively Evaluate Reamed Intramedullary Nails in Patients with Tibial Shaft Fractures (SPRINT) or Fluid Lavage of Open Wounds (FLOW) randomized trials. Multivariable logistic regression was performed to evaluate the association between healing status at 12 months and seven prognostic variables (open fracture, fracture pattern, nailing technique, smoking, fracture gap, three-month PCS score, and FLOW vs. SPRINT trial). Results A total of 940 patients were included in this study with an overall rate of radiographic nonunion of 13.3% (n=125) at the 12-month follow-up. Absolute nonunion risk increased with incrementally lower PCS scores (8.2%, 12.8%, 15.9%, 23.7% for scores ≥ 40, 30.0-39.99, 20.0-29.99, and < 20, respectively). In the multivariable regression analysis, PCS scores of < 20 were associated with a 2.6-times greater odds and 10% absolute risk increase of non-union, as compared to scores of ≥ 40 (OR 2.58, 95%CI: 1.02-6.53, ARI: 10.3, 95% CI: 0.1 - 28.2), whereas scores between 20 and 30 were associated with a nearly two-times greater odds of nonunion and a 6.4% absolute risk increase of nonunion (OR 1.94, 95%CI: 1.08-3.49, ARI: 6.4, 95% CI 0.6 - 15.3). Open fractures also conferred a 2.8-fold increase in odds of nonunion as compared to closed injuries (OR 2.77, 95%CI: 1.58-4.83), as did complex fractures when compared to simple fractures (OR 2.57, 95%CI: 1.64-4.02). Conclusion A considerable portion of patients with fractures of the tibial shaft treated with intramedullary nailing will experience nonunion at one-year postoperatively. Nonunion can be accurately predicted by patient functional recovery at three months as measured by the PCS of the SF-36 and SF-12 instruments.