Management of tibial defects in total knee arthroplasty. A biomechanical study

Peripheral deficiencies of tibial bone stock must be appropriately addressed at total knee arthroplasty to help ensure stability of the tibial component. Conversion of the oblique shaped peripheral defects into defects with vertical and horizontal surfaces, before repair, should lead to improved stability of tibial component fixation. In vitro testing revealed that conversion of the oblique wedge defect into a stepped pattern resulted in improved rigidity of the system when testing five specimens with a 20 degrees peripheral defect (wedge stiffness 25.5 +/- 1.08 versus step stiffness 32.4 +/- 1.72; p < 0.01) and five specimens with a 35 degrees defect (wedge stiffness 18.7 +/- 0.74 versus step stiffness 25.6 +/- 0.85; p < 0.0001). Improved rigidity of the system was further illustrated when a fibrous interface was introduced between the bone and cement surfaces (wedge stiffness 4.8 +/- 0.6 versus step stiffness 29.9 +/- 1.4; p < 0.0001). One hundred percent of wedge shaped cement constructs failed and slipped off, while none of the step shaped constructs described herein failed at the cement to bone interface. There were no statistically significant differences in stiffness with the incorporation of a metal wedge or block into the system when compared with the cement repaired stepped pattern. These biomechanical studies suggest that alterations in the configuration of peripheral defects can create a more rigid system that should ultimately result in improved support to the tibial component overlying these defects.