Screws or Sutures? A Pediatric Cadaveric Study of Tibial Spine Fracture Repairs

Abstract

Background: Tibial spine fractures are common in the pediatric population because of the biomechanical properties of children’s subchondral epiphyseal bone. Most studies in porcine or adult human bone suggest that suture fixation performs better than screw fixation, but these tissues may be poor surrogates for pediatric bone. No previous study has evaluated fixation methods in human pediatric knees. Purpose: To quantify the biomechanical properties of 2-screw and 2-suture repair of tibial spine fracture in human pediatric knees. Study Design: Controlled laboratory study. Methods: Cadaveric specimens were randomly assigned to either 2-screw or 2-suture fixation. A standardized Meyers-Mckeever type 3 tibial spine fracture was induced. Screw-fixation fractures were reduced with two 4.0-mm cannulated screws and washers. Suture-fixation fractures were reduced by passing 2 No. 2 FiberWire sutures through the fracture fragment and the base of the anterior cruciate ligament. Sutures were secured through bony tunnels over a 1-cm tibial cortical bridge. Each specimen was mounted at 30° of flexion. A cyclic loading protocol was applied to each specimen, followed by a load-to-failure test. Outcome measures were ultimate failure load, stiffness, and fixation elongation. Results: Twelve matched pediatric cadaveric knees were tested. Repair groups had identical mean (8.3 years) and median (8.5 years) ages and an identical number of samples of each laterality. Ultimate failure load did not significantly differ between screw (mean ± SD, 143.52 ± 41.9 7 N) and suture (135.35 ± 47.94 N) fixations (P = .760). Screws demonstrated increased stiffness and decreased elongation, although neither result was statistically significant at the .05 level (21.79 vs 13.83 N/mm and 5.02 vs 8.46 mm; P = .076 and P = .069, respectively). Conclusion: Screw fixation and suture fixation of tibial spine fractures in human pediatric tissue were biomechanically comparable. Clinical Relevance: Suture fixations are not biomechanically superior to screw fixations in pediatric bone. Pediatric bone fails at lower loads, and in different modes, compared with adult cadaveric bone and porcine bone. Further investigation into optimal repair is warranted, including techniques that may reduce suture pullout and “cheese-wiring” through softer pediatric bone. This study provides new biomechanical data regarding the properties of different fixation types in pediatric tibial spine fractures to inform clinical management of these injuries.