Augmentation of the screw fixation in the femoral head by cement application through the implant - a biomechanical study.

Purpose: Osteoporosis reveals a higher risk of fractures. Due to the lack o f possibilities to anchor fixation elements, fracture treatment often turns out to be complicated. An experimental study served to investigate the ext ent to which the application of bone cement through a modified gliding scre w (Dynamic Hip Screw DHS) would improve the screw anchoring in osteorporoti c femoral heads. Methods: Quasi-static compressive and torsional load tests were used to assess the desired improvement of the screw anchoring. Cadave r femur pairs served to compare the cement augmentation to the uncemented c ontralateral control. Results: The improvement of the holding strength of t he screw under static compressive and torsional load depended on the cement flow into the adjacent bone tissue. The filling with additional cement was only successful after having created a small hollow space at the screw tip with a special instrument. Consequently, under compression as well as tors ion, the cement application yielded improvements from 17% up to several tim es as much. Conclusion: In the application of gliding screws in osteoporoti c femoral heads, the locally limited cement application through the implant has been shown to be a biomechanical possibility to improve screw fixation .