Petra Klein

Publications (3)7.3 Total impact

• Article: On the influence of mechanical conditions in osteochondral defect healing.

  Georg N Duda, Zully M Maldonado, Petra Klein, Markus O W Heller, Justin Burns, Hermann Bail
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  ABSTRACT: Despite the introduction of new surgical techniques, the treatment of cartilage defects remains challenging. Delay or complete failure of cartilage healing is associated with problems in biological regeneration. The influence of mechanical conditions on this process, however, remains unevaluated. Osteochondral defects were generated on the left femoral condyle in 18 Yucatan minipigs. After 4, 6 and 12 weeks the defect filling, trabecular orientation and bone density were compared to the intact contralateral side. The mechanical straining during this period was then analyzed using an adaptive finite element technique. Histologically, the osteochondral defects showed bone resorption at the base and bone formation from the circumference. At 12 weeks, the macroscopically healed specimens showed fibrous cartilage formation, a minimally organized trabecular structure and increased trabecular volume fraction compared to the controls (p < 0.002). The amount of cancellous, cartilagineous, and fibrous tissue and the defect size as measured in histomorphometric analysis for the three time points (4, 6 and 12 weeks) was comparable in magnitude to that predicted by finite element analysis. The simulated osteochondral healing process was not fully capable of re-establishing a hyaline-like cartilage layer. The correlation between simulation and histology allows identification of mechanical factors that appear to have a larger impact on the healing of osteochondral defects than previously considered.
  Journal of Biomechanics 04/2005; 38(4):843-51. · 2.43 Impact Factor
• Article: The initial phase of fracture healing is specifically sensitive to mechanical conditions.

  Petra Klein, Hanna Schell, Florian Streitparth, Markus Heller, Jean-Pierre Kassi, Frank Kandziora, Hermann Bragulla, Norbert P Haas, Georg N Duda
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  ABSTRACT: Interfragmentary movements affect the quality and quantity of callus formation. The mounting plane of monolateral external fixators may give direction to those movements. Therefore, the aim of this study was to determine the influence of the fixator mounting plane on the process of fracture healing. Identically configured fixators were mounted either medially or anteromedially on the tibiae of sheep. Interfragmentary movements and ground reaction forces were evaluated in vivo during a nine week period. Histomorphological and biomechanical parameters described the bone healing processes. Changing only the mounting plane led to a modification of interfragmentary movements in the initial healing phase. The difference in interfragmentary movements between the groups was only significant during the first post-operative period. However, these initial differences in mechanical conditions influenced callus tissue formation significantly. The group with the anteromedially mounted fixator, initially showing significantly more interfragmentary movements, ended up with a significantly smaller callus diameter and a significantly higher callus stiffness as a result of advanced fracture healing. This demonstrates that the initial phase of healing is sensitive to mechanical conditions and influences the course of healing. Therefore, initial mechanical stability of an osteosynthesis should be considered an important factor in clinical fracture treatment.
  Journal of Orthopaedic Research 08/2003; 21(4):662-9. · 2.81 Impact Factor
• Article: The potential of dielectrophoresis for single-cell experiments.

  Torsten Müller, Annette Pfennig, Petra Klein, Gabriele Gradl, Magnus Jäger, Thomas Schnelle
  IEEE Engineering in Medicine and Biology Magazine 22(6):51-61. · 2.06 Impact Factor