gms | German Medical Science

Deutscher Kongress für Orthopädie und Unfallchirurgie (DKOU 2019)

22. - 25.10.2019, Berlin

Novel Variable Fixation technology stimulates bone callus formation in osteotomies stabilized with locking plates

Meeting Abstract

  • presenting/speaker Michael Plecko - Trauma Hospital Styria, UKH Graz, Graz, Austria
  • Karina Klein - Musculoskeletal Research Unit (MSRU), Vetsuisse Faculty ZH, Zurich, Switzerland
  • Katrin Planzer - Musculoskeletal Research Unit (MSRU), Vetsuisse Faculty ZH, Zurich, Switzerland
  • Dirk Wähnert - University Hospital Münster, Münster, Germany
  • Stefano Brianza - Biomech Innovations, Nidau, Switzerland
  • Stephen J. Ferguson - Institute for Biomechanics, ETH Zurich, Zürich, Switzerland
  • Vincent A. Stadelmann - Lower extremity research group, Schulthess Clinic Zurich, Zürich, Switzerland
  • Brigitte Von Rechenberg - Musculoskeletal Research Unit (MSRU), Vetsuisse Faculty ZH, Zurich, Switzerland

Deutscher Kongress für Orthopädie und Unfallchirurgie (DKOU 2019). Berlin, 22.-25.10.2019. Düsseldorf: German Medical Science GMS Publishing House; 2019. DocAB48-519

doi: 10.3205/19dkou434, urn:nbn:de:0183-19dkou4343

Veröffentlicht: 22. Oktober 2019

© 2019 Plecko et al.
Dieser Artikel ist ein Open-Access-Artikel und steht unter den Lizenzbedingungen der Creative Commons Attribution 4.0 License (Namensnennung). Lizenz-Angaben siehe



Objectives: The population of developed countries is aging. In the coming decades we can thus expect an increase in number of fractures to treat, number and severity of complications and costs dedicated to fractures treatment. Aiming at stimulating the formation of bone callus as strategy to promote fracture healing in all patients, standard locking screws (LS) have been reengineered into a new locking screw technology, called Variable Fixation.

Variable Fixation Locking Screws (VFLS) feature a degradable sleeve that changes the stability of fracture fixation over the healing time. The screws provide initially high interfragmentary stability and later progressive dynamisation of the fracture gap.

The goal of this study was to compare the healing of tibia osteotomies in an established ovine model using a locking plate in combination with either VFLS or state-of-the-art LS. We hypothesized that Variable Fixation technology can lead to more callus compared to standard locking technology.

Methods: A transverse tibia osteotomy was performed on 12 female Swiss Alpine sheep (age: Ø 35.4 months; body weight: Ø 75.8 kg). Bone fragments were fixed leaving a 3 mm gap with a 6-hole 4.5/5.0 broad LCP (DePuy Synthes 426.561) and either 6 LS (DePuy Synthes 413.332) or 6 VFLS (Biomech Innovations, S540032S).

Fracture healing was monitored weekly with radiographs and by means of fluorochrome injections until sacrifice at 9 weeks.

After dissection, the following variables were evaluated with microCT: bone volume and density, callus overall volume, medial and lateral distribution and callus density. Torsional mechanical properties of the operated and contralateral limbs were biomechanically tested. New bone formation and distribution were characterized histomorphometrically.

Results and conclusion: No complication occurred during or after surgery. No significant differences between groups were found for bone volume and density. However, total callus volume was significantly higher and distributed farther from the bone axis and the fracture gap in VFLS compared to LS (p=0.004). While no significant differences were detected for callus volume on the lateral side, significantly higher values were found on the medial side in VFLS compared to LS (p=0.0023). Callus density showed significantly lower values in VFLS compared to LS (p=0.0024). There were no significant differences between groups concerning any mechanical property. Histomorphometry revealed good healing for both groups with a significant larger amount of endosteal callus in VFLS (p=0.012) and no significant difference in fluorochrome deposition between groups.

In conclusion, Variable Fixation technology promotes the formation of a larger and more evenly distributed callus compared to standard locking technology. This callus features an important endosteal component, has no inferior mechanical properties and comparable maturation with respect to that of the predicate device.

Variable Fixation technology has the potential to promote fracture healing.