Association of KT-1000 measurements with clinical tests of knee stability 1 year following anterior cruciate ligament reconstruction

Study Design: Prospective, observational study. Objectives: To determine the association between KT-1000 measurements with an anterior translation force of 89 N and other measures of outcome (the Te gner activity score, the modified Lysholm score, subjective rating of insta bility, Lachman test, and pivot-shift test) 1 year following anterior cruci ate ligament (ACL) reconstruction. Background: Health care professionals often use the side-to-side difference measured with the KT-1000 arthrometer to determine ACL integrity during pa ssive motion. It has been postulated that a 5-mm or greater difference betw een impaired and nonimpaired knees represents a procedural failure. Methods and Measures: Ninety patients (46 men, 44 women) with a mean age of 30 +/- 8 years were examined 1 year after surgery. Patients were classifie d in 1 of 3 groups depending on the amount of laxity between the impaired k nee and the nonimpaired knee. Seventy percent of the subjects had a side-to -side difference less than or equal to 3 mm (tight), 13% had a difference o f between 3 and 5 mm (moderate), and 17% had a difference greater than or e qual to 5 mm (loose) on examination using the KT-1000. Results: Mean Lysholm and Tegner scores did not differ significantly among groups. Side-to-side differences in KT-1000 measurements at 89 N were nor a ssociated with the Lysholm score (r = -0.09) or Tegner score (r = 0.02). La chman tests were related to involved-knee KT-1000 measurements (r = 0.39) b ut not to side-to-side differences in KT-1000 measurements (r = 0.15). Simi larly, pivot-shift tests were related to involved-knee KT-1000 measurements (r = 0.26) but not to side-to-side differences (r = -0.08). Conclusions: These results suggest that side-to-side KT-1000 measurements o btained with an anterior translation force of 89 N should not be used in is olation to determine ACL reconstruction success or failure 1 year following surgery.