Flexible Fixation in Foot and Ankle Surgery

Aging-Induced Discrepant Response of Fracture Healing is Initiated from the Organization and Mineralization of Collagen Fibrils in Callus

Fracture healing is a complex process during which the bone restores its structural and mechanical integrity. Collagen networks and minerals are the fundamental components to rebuild the bone matrix in callus. It has been recognized that bone quality could be impaired during aging. However, how the structural and mechanical recovery of fracture healing is influenced by aging, particularly from the perspective of organization and mineralization of the collagen network in callus, remains unclear. A tibial fracture model was established for both the young (5 weeks) and aged mice (68 weeks). On the 21st day postfracture, the characteristics of the collagen network, mineralization, and the nanoscale mechanical properties of the callus were assessed. The results indicated that aging postpones the fracture healing process, leading to incomplete microstructure, less mineral content and mineralization, and weaker mechanical properties of callus. In the aged mice, the internal fixation and mechanical immobilization promoted the mineralization of callus by increasing mineral crystal length and mineral-to-matrix ratio by 48 and 42% compared to the internal fixation and free movement control group, respectively. By contrast, in the young mice, the internal fixation and mechanical immobilization induced disordered collagen fibrils and decreased the crystal length and mineral-to-matrix ratio by 32 and 36%, compared to the internal fixation and free movement control group, respectively. The present findings suggested that the aging-induced structure and mechanical differences of callus during fracture healing initiate from the organization and mineralization of collagen fibrils. Multiscale structural and mechanical analysis suggested mechanical immobilization is beneficial to the structure, composition, and mechanics of callus in the aged mice while impairing the organization and mineralization of collagen fibril in the callus of the young mice. These findings suggested that different mechanical intervention strategies should be adopted for fracture healing at different ages, which provides valuable insights for the clinical treatment of bone fracture.

Evidence-Based Surgical Treatment Algorithm for Unstable Syndesmotic Injuries

Background: Surgical treatment of unstable syndesmotic injuries is not trivial, and there are no generally accepted treatment guidelines. The most common controversies regarding surgical treatment are related to screw fixation versus dynamic fixation, the use of reduction clamps, open versus closed reduction, and the role of the posterior malleolus and of the anterior inferior tibiofibular ligament (AITFL). Our aim was to draw important conclusions from the pertinent literature concerning surgical treatment of unstable syndesmotic injuries, to transform these conclusions into surgical principles supported by the literature, and finally to fuse these principles into an evidence-based surgical treatment algorithm. Methods: PubMed, Embase, Google Scholar, The Cochrane Database of Systematic Reviews, and the reference lists of systematic reviews of relevant studies dealing with the surgical treatment of unstable syndesmotic injuries were searched independently by two reviewers using specific terms and limits. Surgical principles supported by the literature were fused into an evidence-based surgical treatment algorithm. Results: A total of 171 articles were included for further considerations. Among them, 47 articles concerned syndesmotic screw fixation and 41 flexible dynamic fixations of the syndesmosis. Twenty-five studies compared screw fixation with dynamic fixations, and seven out of these comparisons were randomized controlled trials. Nineteen articles addressed the posterior malleolus, 14 the role of the AITFL, and eight the use of reduction clamps. Anatomic reduction is crucial to prevent posttraumatic osteoarthritis. Therefore, flexible dynamic stabilization techniques should be preferred whenever possible. An unstable AITFL should be repaired and augmented, as it represents an important stabilizer of external rotation of the distal fibula. Conclusions: The current literature provides sufficient arguments for the development of an evidence-based surgical treatment algorithm for unstable syndesmotic injuries.