[Treatment of ankle fractures : Standards, tricks and pitfalls]. / Versorgung der Sprunggelenkfraktur : Standards, Tipps und Fallstricke.

Ankle fractures and associated ligamentous injuries are the most common injuries of a load-bearing joint. There is still no general consensus with respect to the pathomechanism, the treatment indications and surgical techniques. The medium and long-term results are affected by a particularly high risk of posttraumatic arthritis in bimalleolar and trimalleolar fractures and fracture dislocations. There is consensus on the necessity of a thorough preoperative analysis and postoperative control of reduction for which 3D imaging is increasingly generously employed. This detects relevant pathologies, such as bony syndesmotic avulsion and partial impaction of the tibial plafond that may go unnoticed on plain radiographs. Anatomic reconstruction of the ankle mortise, the detection and treatment of syndesmotic instability, reconstruction of the tibial notch and exact placement of the distal fibula into the latter are important prognostic factors.

Decellularized tendon extracellular matrix-a valuable approach for tendon reconstruction?

Tendon healing is generally a time-consuming process and often leads to a functionally altered reparative tissue. Using degradable scaffolds for tendon reconstruction still remains a compromise in view of the required high mechanical strength of tendons. Regenerative approaches based on natural decellularized allo- or xenogenic tendon extracellular matrix (ECM) have recently started to attract interest. This ECM combines the advantages of its intrinsic mechanical competence with that of providing tenogenic stimuli for immigrating cells mediated, for example, by the growth factors and other mediators entrapped within the natural ECM. A major restriction for their therapeutic application is the mainly cell-associated immunogenicity of xenogenic or allogenic tissues and, in the case of allogenic tissues, also the risk of disease transmission. A survey of approaches for tendon reconstruction using cell-free tendon ECM is presented here, whereby the problems associated with the decellularization procedures, the success of various recellularization strategies, and the applicable cell types will be thoroughly discussed. Encouraging in vivo results using cell-free ECM, as, for instance, in rabbit models, have already been reported. However, in comparison to native tendon, cells remain mostly inhomogeneously distributed in the reseeded ECM and do not align. Hence, future work should focus on the optimization of tendon ECM decellularization and recolonization strategies to restore tendon functionality.

Tenocytes, pro-inflammatory cytokines and leukocytes: a relationship?

Leukocyte derived pro-inflammatory mediators could be involved in tendon healing and scar formation. Hence, the effect of autologous leukocytes (PBMCs, peripheral blood mononuclear cells and neutrophils) on primary rabbit Achilles tenocytes gene expression was tested in insert assisted co-cultures. Subsequently, tenocytes gene expression of extra-cellular matrix (ECM) components (type I collagen, decorin, fibronectin), the cell-ECM receptor ß1-integrin, the angiogenic factor myodulin, ECM degrading matrix-metalloproteinase (MMP)1 and pro-inflammatory cytokines (interleukin [IL]-1ß, tumour necrosis factor [TNFα] and IL-6) was analysed. The only significant effect of leukocytes on tenocytes ECM genes expression was a suppression of type I collagen by neutrophils combined with TNFα stimulation. The same effect could be observed analysing the ß1-integrin and myodulin gene expression. However, PBMCs up-regulated significantly cytokine and MMP1 gene expression in tenocytes. These in vitro results suggest that mononuclear cells could present an exogenic stimulus for the induction of pro-inflammatory and catabolic mediators in tendon.