Instrumented Arthrometry for Diagnosing Partial Versus Complete Anterior Cruciate Ligament Tears

Abstract

Nineteen patients with the clinical diagnosis of anterior cruciate ligament injury were examined by KT-1000 arthrometry before arthroscopy in an effort to differentiate partial from complete tears. To this end, the KT-1000 arthrometer was equipped with a strain gauge and processor that permitted the required force to increase the anterior displacement by 1-mm increments, to be read on a light-emitting diode. The measured force has been plotted against anterior displacement expressed in non-linear increments along the x-axis to allow for the viscoelastic nature of the ligament. The results show that stress-strain diagrams of partially torn and completely torn ligaments are similar to those obtained by graded stress radiography. Using arthroscopy as the standard of measurement, partial tears can be differentiated from complete tears with a sensitivity of 80% and a specificity of 100%. The figures for complete tears versus partial tears are 100% and 80%, respectively. Graded arthrometry with x-y recording of the force-displacement relationship that allows for the viscoelastic qualities of ligament further extends the capabilities of instrumented arthrometry.