BackgroundBiologic treatment options for cartilage injuries require chondrocyte expansion using cell culture. Clinical application is accomplished in two surgical sessions and is expensive. If isolation of chondrocytes and stimulus for proliferation and extracellular matrix synthesis can be achieved in vivo, the treatment can be performed in one session and the cost can be reduced.MethodsA 2.5-cm diameter full-thickness chondral defect was created in the knees of five groups of sheep. In one group, some of the chondral tissues obtained from the creation of the defect were diced into small pieces and were placed into the defect and were covered with a collagen membrane (MIV group). In the other group, the collagen membrane was soaked in collagenase prior to usage. In the next group, the collagen membrane was soaked in both collagenase and growth factors. Matrix-induced autologous chondrocyte implantation (MACI) was applied to another group in two sessions, and the last group was left untreated. After 15 weeks of follow-up, repair tissues were compared macroscopically, histomorphometrically, and biochemically for tissue concentrations of glycosaminoglycan and type II collagen.ResultsMACI and MIV groups demonstrated better healing than others and were similar. Addition of collagenase or growth factors did not improve the results. Addition of collagenase did not have detrimental effect on the surrounding cartilage.ConclusionsWith the described method, it is possible to obtain comparable results with MACI. Further studies are also needed to see if it works similarly in humans.

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Purpose Slippage of the wires over the opposite cortex from the endosteal side is frequent and can lead to insufficient stability. This in vitro biomechanical study was planned to investigate the angle of wire insertion that leads to trans cortex perforation. Methods Long bones of sheep were cut longitudinally into two pieces and half bones were stabilised on a frame. Three orthopaedic surgeons performed the experiment using ten wires of four different diameters at two different drilling speeds. Each wire was introduced from the endosteal side at angles starting at 30°in 5°i ncrements until perforation. When perforation was achieved, the angle was recorded. To determinate the critical angle of perforation, receiver operating characteristic (ROC) curve analyses was performed. Two-way factorial analysis of variance (ANOVA) and KruskalWallis tests were used for statistical comparisons. Results Kirschner-wire insertion angles of ≥45°provided perforation with a percentage of 83.9 %. Wire diameter, drilling speed and surgeon variables had no effect on perforation angles (p>0.05).Conclusion If preoperative evaluation of fractures to be fixed by K wires reveals the need for oblique wire insertion angle <45°, a standard trocar-tip K wire application would lead to slippage of the wire tip on the endosteal surface of the opposite cortex. According to this study, the operative plan should be changed if such obliquity of the K wire is mandatory during bicortical applications.

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