Cerclages for osteosynthesis augmentation (Cerclage) (M. Windolf) Problem: The stability of cerclage fixation depends on the lasting tension. Up to now, there was only a little insight in the cerclage fixation mechanics. Moreover, the belief of a strangled blood supply owing to cerclage application is still present. Goal: To investigate systematically various aspects of cerclage fixation, involving tightening techniques, cerclage types and configurations, circumferential cerclage-bone contact and performance in periprosthetic fracture fixation in order to draw a comprehensive picture of the cerclage technique. Results: Cerclage-bone contact is dependent on the bone surface geometry. The cerclage provides a point contact fixation which installs non-loaded, spanned zones where the periosteum is not compressed, rendering a strangulation of the blood supply unlikely. Cortical damage and bone resorption underneath the cerclage have to be attributed to micromotion and not to weakness of the cortex itself. Cable cerclages provide increased fixation strength compared to wire cerclages. Double looped cerclages provide better fixation stability in comparison to single looped cerclages. Cerclage-screw combination is a valuable alternative to bicortical screw anchorage especially in osteoporotic bone. When cerclages are used, they should be combined with at least one screw to achieve a stable fixation. Although providing a good fixation against lateral load, even well tightened cable cerclages are susceptible to axial compression and torsion.
Figure 9.5.2: Point contact fixation of wire (a) and cable (b) cerclages.
Partners: Lenz M (MD), UK Jena, Germany Perren SM (Prof, MD, PhD), AO Foundation, Davos, Switzerland Höntzsch D (Prof, MD), BG Unfallklinik Tübingen, Germany Fernandez Dell’Oca A (Prof, MD), British Hospital, Montevideo, Uruguay Pres: Lenz M, Perren SM, Gueorguiev B, Richards RG, Fernandez Dell'Oca A, Höntzsch D, Hofmann GO, Windolf M. The concept of point contact fixation – interface mechanics of cerclages. 2013. ECTES. Lenz M, Gueorguiev B, Richards RG, Mückley T, Hofmann GO, Höntzsch D, Perren SM, Windolf M. Optimierung der Dauerbeanspruchbarkeit von Cerclagen – eine biomechanische Studie. 2013. NOUV. Pub: Lenz M, Perren SM, Gueorguiev B, Höntzsch D, Windolf M. Mechanical behavior of fixation components for periprosthetic fracture surgery. Clin Biomech 2013 Nov-Dec;28(9-10):988-93. Lenz M, Perren SM, Richards RG, Mückley T, Hofmann GO, Gueorguiev B, Windolf M. Biomechanical performance of different cable and wire cerclage configurations. Int Orthop 2013 Jan;37(1):125-30. 64