Proximal Tibial Fracture Stability With Intramedullary Nail Fixation Using Oblique Interlocking Screws

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Abstract
The purpose of this study was to evaluate the mechanical stability of oblique interlocking screws in supplementing intramedullary nail fixation of high proximal tibial fractures. In vitro experimental testing. Orthopaedic biomechanics laboratory, Sunnybrook and Women's College Health Sciences Center. Ten paired fresh-frozen human cadaver tibiae. One tibia of each pair was randomized to be instrumented with an intramedullary nail (M/DN; Zimmer, Warsaw, Indiana), while the other was stabilized with a 13-hole stainless steel lateral tibial head plate (Synthes AO/ASIF). Specimens were tested in varus-valgus (v/v), flexion-extension (f/e) and torsion, before and after a 2-cm gap osteotomy was performed in the proximal segment. Testing of the nailed tibiae was performed with and without oblique proximal screws. Bone density was physically determined by removing a core of trabecular bone from the distal end of each tibia following testing. Biomechanical construct stability. The addition of the proximally placed oblique screws increased the stability of the nail construct in v/v by 50% (6.8 mm, P < 0.05), in f/e by 47% (7.2 mm, P < 0.05), and in torsion by 18% (3.0°, P < 0.05). There was no significant difference observed between the stability of the intramedullary nail construct with oblique screws and the plated construct. Trabecular bone density had a significant effect in reducing stability (P < 0.05) in nail and plate fixation. The addition of oblique interlocking screws significantly improves the stability of a nailed proximal tibia fracture and provides comparable stability to a plate osteosynthesis.