Effect of knee component alignment on tibial load distribution with clinical correlation

Area of Science:

• Biomechanical Engineering
• Orthopedic Surgery
• Medical Device Design

Background:

• Asymmetric loading of tibial components in total knee prostheses is linked to loosening and radiolucent lines.
• Component misalignment can significantly alter load distribution across the tibial plateau.
• Understanding ideal alignment is critical for improving implant longevity and patient outcomes.

Purpose of the Study:

• To determine the ideal alignment and component placement for Kinematic (K) and Total Condylar (TC) knee prostheses.
• To correlate laboratory findings on interface forces with clinical roentgenographic observations.
• To investigate the impact of misalignment on load distribution and the incidence of radiolucent lines.

Main Methods:

• Physiological loading of K and TC prostheses on artificial tibiae with pressure-sensitive film.
• Measurement of interface forces and calculation of load distribution on medial and lateral tibial plateaus.
• Analysis of roentgenograms from 532 K and 21 TC patients to assess component orientation and radiolucency.

Main Results:

• Ideal load distribution for K prostheses occurred with 9° femoral valgus and 2° tibial varus tilt; for TC, 7° femoral valgus and 0° tibial varus.
• A 10° misalignment significantly altered load distribution: 34% change for K and 62% for TC.
• Small alignment variations correlated with radiolucent lines, with the lowest incidence (8%) for K prostheses at specific optimal alignments.

Conclusions:

• Precise alignment of total knee prostheses is essential for balanced load distribution and minimizing radiolucent lines.
• The study identified specific optimal alignment parameters for K and TC devices based on biomechanical testing.
• Clinical correlation suggests that achieving these ideal alignments may reduce the incidence of implant loosening and radiolucency.