An in vivo biomechanical analysis of the soft-tissue envelope of osteoarthritic knees☆
Section snippets
Materials and methods
The surgical technique and soft-tissue balancing procedure for TKA utilizing the ligament tensioning device (Fig. 1) used in this study has been previously reported in detail [11]. Since that report [11], the torque meter handle has been added to the ligament-balancer device. The calibration of the device was performed by the manufacturer (Stryker Howmedica Osteonics, Allendale, NJ).
Following the distal femoral and proximal tibial bone cuts, the knee is balanced in extension. The tensioner
Results
The generalized load versus displacement curves for both posterior cruciate-retaining and posterior cruciate-substituting knees are indicated in Fig. 2. Mean effective stiffness (MES) was not affected by age in either posterior cruciate-substituting knees (r2=.09) or posterior cruciate-retaining knees (r2=.07). For posterior cruciate-substituting knees, no significant difference in the average effective stiffness could be demonstrated between men and women in either flexion (P=.42) or
Discussion
To the best of our knowledge, this is the first time in vivo measurements of the effective stiffness of the soft-tissue envelope of osteoarthritic knees have been measured using a balancer. Attfield et al. [12] used an electronic tensioning device during 8 TKAs; however, the goal of their study was to determine soft-tissue imbalance of the medial compartment compared with the lateral compartment. They found that the medial-lateral imbalance reached a maximum before decreasing to a lower level
Conclusions
The MES of the soft-tissue envelope around osteoarthritic knees has been approximated and the load versus displacement curve has been characterized. The only factor that appears to affect this biomechanical property is retention of the PCL, which increases the effective stiffness. In addition, the mean resting force on the polyethylene implant has been estimated in this series of TKAs. These data serve as a baseline in our attempt to establish quantifiable guidelines for how “tightly” or how
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No benefits or funds were received in support of this study.