Repeatability of the KT-1000 arthrometer in a normal population

Area of Science:

• Orthopedics
• Biomechanics
• Medical Device Evaluation

Background:

• The MEDmetric KT-1000 arthrometer is widely used for knee laxity assessment.
• Reliability data for the KT-1000, particularly concerning measurement variability, is limited.

Purpose of the Study:

• To quantify the trial-to-trial, installation-to-installation, and day-to-day variability of anterior/posterior translation measurements using the KT-1000 in normal knees.
• To assess the reliability of the KT-1000 arthrometer for clinical use.

Main Methods:

• Six healthy subjects were tested over six consecutive days, with three installations per day.
• Anterior/posterior translation was measured at +/- 89 N and +/- 134 N forces at 25 degrees of knee flexion.
• Analysis of variance (ANOVA) and Fischer's protected least significant difference post hoc test were used for statistical analysis.

Main Results:

• No significant differences were found between trials (within installation) or between installations (within day).
• Significant day-to-day differences were observed for individual knee measurements but not for right-to-left knee differences.
• Ninety percent confidence limits for anterior/posterior translation at 89 N were +/- 1.5 mm (right), +/- 1.4 mm (left), and +/- 1.6 mm (differences).
• First-day measurements were significantly lower than subsequent days, indicating an adjustment period.

Conclusions:

• KT-1000 measurements demonstrate good reliability for paired differences between knees, suggesting this is a more robust metric.
• Reporting paired differences is recommended over individual knee measurements for standard KT-1000 evaluations.
• Follow-up examinations are advised to confirm initial translation values due to potential learning effects.