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Posterior Slope of the Tibial Component


- See: 
       - tibial component 
       - proximal tibial cut 
       - extra-medullary cutting guide;

- Discussion:
    - viewed in saggital plane, line drawn between anterior & posterior rims of the tibial plateaus is approx 10 deg posteriorly;
          - this radiographic tilt does not take the menisci into consideration (which minimize the tilt to about 3 deg);
    - this tilt produces a component of shear during simple stance;
    - this posterior tilt actually minimizes the magnitude of shear stress when compressive stress increases during flexion;

- Operative Considerations for Posterior Tibial Slope:
    - sagittal alignment of the tibial component is determined by amount of posterior slope of the proximal tibial cut;
          - most current systems strive for 3-7 deg of posterior slope, because bone in the anterior portion of the cut surface is weaker;
          - if proximal tibia is cut perpendicular to long axis of tibia in saggital plane, tibial component subsidence is more likely;
    - implant considerations:
          - if implant has a thickness = anteriorly and posteriorly, then tibia must be resected w/ a downward slope of approx 10 deg;
          - if tibial implant has built in slope (that is the anterior portion is thicker than the posterior portion), then the tibia may be resected at 90 deg;
    - excessive posterior slope:
          - posterior sloping of prosthetic joint line should not be over done, since it may lead to posterior tibiofemoral subluxation (excessive flexion gap);
          - excessive posterior slope combined w/ a deep proximal tibial cut may result in valgus instability (from loss of  posterior oblique ligament) and may result in loss
                   of the PCL (in which case a posterior stabilized prosthesis will be required);
    - inadequate posterior tibial slope:
          - under no circumstances should tibia be cut with an upward slope since this diminishes size of flexion space posteriorly;
          - a transverse tibial cut more bone is removed anteriorly than posteriorly, which may result in anterior subsidence;
          - quality of anterior cancellous bone quality of anterior cancellous bone decreases rapidly as one progresses downward below joint surface;
                  - to prevent subsidence into soft bone, one needs to preserve as much anterior bone as possible and use a posteriorly sloped resection line 

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In vitro investigation of the influence of tibial slope on quadriceps extension force after total knee arthroplasty.

Influence of tibial component posterior slope on in vivo knee kinematics in fixed-bearing total knee arthroplasty.

The influence of tibial slope on maximal flexion after total knee arthroplasty.

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The Effect of Posterior Tibial Slope on Range of Motion After Total Knee Arthroplasty.

Angled Polyethylene Insert Exchange for Sagittal Tibial Malalignment in Total Knee Arthroplasty

Anatomical References to Assess the Posterior Tibial Slope in Total Knee Arthroplasty: A Comparison of 5 Anatomical Axes

Factors affecting flexion gap tightness in cruciate-retaining total knee arthroplasty.

[Effect of increased posterior tibial slope or partial posterior cruciate ligament release on knee kinematics of total knee arthroplasty]

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Optimization of the posterior condylar offset, tibial slope, and condylar roll-back in total knee arthroplasty