Potential errors in axial alignment using intramedullary instrumentation for total knee arthroplasty.

Area of Science:

• Orthopedic Surgery
• Biomechanical Engineering
• Medical Device Design

Background:

• Long-term success in total knee arthroplasty (TKA) depends on restoring normal limb alignment.
• Malalignment can lead to premature implant failure and revision surgery.
• Intramedullary (IM) guides are commonly used in TKA for alignment, but their accuracy can be affected by instrumentation errors.

Purpose of the Study:

• To mathematically model and quantify the maximum alignment errors (varus/valgus) during TKA.
• To evaluate the impact of intramedullary (IM) guide length and diameter on alignment accuracy.
• To identify strategies for minimizing rotational and coronal malalignment in TKA.

Main Methods:

• Development of a mathematical model to simulate TKA tibial and femoral cuts.
• Analysis of alignment errors based on variations in IM instrumentation insertion points.
• Parametric study of IM rod length and diameter effects on alignment accuracy.

Main Results:

• Minor deviations in IM instrumentation entry points can cause significant alignment errors (several degrees) in TKA.
• Increasing the diameter and length of the IM rod can reduce the potential for malalignment.
• The model demonstrated a quantifiable relationship between instrumentation parameters and final limb alignment.

Conclusions:

• Precise control of the IM instrumentation entry point is critical for accurate TKA alignment.
• Longer and wider IM guides offer improved accuracy and minimize alignment errors during TKA.
• Optimizing IM guide usage is essential for enhancing the long-term survivorship of total knee arthroplasty.