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Orthopaedic Proceedings
Vol. 94-B, Issue SUPP_XXXVII | Pages 433 - 433
1 Sep 2012
Löcherbach C Schmeling A Weiler A
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Introduction

An accurate and reproducible tibial tunnel placement without danger for the posterior neurovascular structures is a crucial condition for successful arthroscopic reconstruction of the posterior cruciate ligament (PCL). This step is commonly performed under fluoroscopic control. Hypothesis: Performing the tibial tunnel under exclusive arthroscopic control leads to accurate tunnel placement according to recommendations in the literature.

Materials and Methods

Between February 2007 and December 2009, 108 arthroscopic single bundle PCL reconstructions in tibial tunnel technique were performed. The routine postoperative radiographs were screened according to defined quality criterions: 1. Overlap of the medial third of the fibular head by the tibial metaphysis on a-p views 2. Overlap of the dorsal femoral condyles within a range of 4 mm on lateral views 3. X-ray beam parallel to tibial plateau in both views. The radiographs of 48 patients (48 knees) were enrolled in the study. 10 patients had simultaneous ACL reconstruction and 7 had PCL revision surgery. The tibial tunnel was placed under direct arthroscopic control through a posteromedial portal using a standard tibial aming device. Key anatomical landmarks were the exposed tibial insertion of the PCL and the posterior horn of the medial meniscus.

During digital analysis of the postoperative radiographes, the centre of the posterior tibial outlet was determined. On the a-p view, the horizontal distance of this point to the medial tibial spine was measured. The distance to the medial border of the tibial plateau was related to its total width. On the lateral view the vertical tunnel position was measured perpendicularly to a tangent of the medial tibial plateau.


Orthopaedic Proceedings
Vol. 88-B, Issue SUPP_I | Pages 159 - 160
1 Mar 2006
Thorey F Floerkemeier T Hurschler C Schmeling A Raschke M Windhagen H
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Introduction: There is a need for new non-invasive, predictable and quantifiable techniques to assess the process of fracture healing and remodelling in bone. There are several methods to monitor the bone healing in-vivo. But these methods either fail as quantitative predictors of the healing process (X-ray) or exhibit complicated and expensive measurement principles. Some known in-vivo stiffness measurement methods have several disadvantages including the risk of bone malalignment. Therefore we compared ex-vivo torsional strength of bone with in-vivo torsional stiffness under minimal load in two animal model of distraction osteogenesis. Additionally the device was tested in an ex-vivo model.

Methods: An external fixator was combined with a rotating double half-ring. The measurement device was fixed to the half-ring during measurements. It was equipped with a linear variable differential transducer, a load cell, and a stepper motor. During measurements the two parts of the half-ring were rotated against each other and the load and displacement were recorded. The slope coefficient after performing a linear regression between data points of moment and displacement curve was defined as stiffness. Afterwards all models were tested in a material testing system as gold standard. This was tested in an in-vivo animal study of tibial distraction (minipigs time of consolidation 10 days/sheeps time of consolidation 50 days).

Results: Between in-vivo initial torsional stiffness and torsional strength in minipigs we found a highly significant (p=0.001) coefficient of determination of 0.82, but we found only a poor correlation (p> 0.05) in sheeps. However, the results of the ex-vivo model showed a high precision and accuracy.

Discussion: The results of this study suggest that the bone regenerate strength of healing bones can be assessed in-vivo by the presented inital stiffness measurement method in the beginning of an early stage of healing as shown in minipigs. But at the end of the healing period the correlation of strength and stiffness leveled off. There is a similar model showing an excellent correlation, that agree with our data. They explained the weakening of the correlation at the end of healing by a transformation of early bone to lamellar bone after a 2/3 consolidation. In summary, the presented device could be a reliable future tool to monitor the healing progress in patients with bone malalignement or fractures in the beginning of the healing period.