Biomechanical stability of intramedullary nailed high proximal third tibial fractures with cement augmented proximal screws

Objective: Intramedullary nailing of nonarticular proximal tibia fractures can be affected by bone density resulting in loss of stability, fixation, and malalignment in osteopenic bone. This study was designed to quantify the biomechanical effects of augmenting proximal screws with cement in intramedullary nailing of high proximal third tibial fractures. Design: In vitro biomechanical study using anatomic specimens. Methods: Reamed nails were inserted into seven pairs of fresh-frozen cadaveric proximal tibiae and secured using two oblique and two transverse proximal screws. Paired tibiae were randomly assigned into two groups: cemented and noncemented proximal screw-holes. Bone cement was injected into the screw-holes before screw insertion in the cemented tibiae. Specimens were then tested in flexion/extension and varus/valgus to 12 Nm and in torsion to 7 Nm. Physical measurements of bone density were obtained to determine the effect of density on stability. Main Outcome Measures: Stability of the construct in both groups was analyzed and compared statistically using paired t tests. Results: Cement augmentation of the proximal screws significantly increased mechanical stability in torsion and varus/valgus load configurations, with average decreases in rotational motion of 5.4 degrees 1.6 degrees and 5.1 degrees +/- 5 degrees respectively. No change in stability was observed in flexion/extension loading. A trend toward decreased stability was seen in the uncemented construct in varus/valgus; cement augmentation of the proximal screws eliminated this effect. Conclusions: Lower bone density decreased the stability of the uncemented construct; however, cement augmentation of the proximal screws showed a trend to eliminate this effect in the varus/valgus loading configuration and should be considered when nailing proximal third tibial fractures in osteoporotic patients.