Definition: Given an abstract, generate a keyword (a noun phrase) that best describes the focus or contribution of the paper. Such keywords can be directly from the given abstract or outside it.
Input: Abstract: In reconstructing the anterior cruciate ligament (ACL) it is important to place the inner ends of the drill channels correctly, to get the ACL into an isometric position. Anatomic studies demonstrate the value of a modified surgical technique using a special drill guide for standardized positioning of the anterior cruciate substitute. The drill guide consists of a metal frame with one adjustable and one fixed guide tube. Drilling is done from the anteromedial aspect of the tibia, upwards, through the joint space and the femur in a straight line, both channels being drilled in a single procedure. The precision of guided drilling was superior to that of free-hand drilling in positioning the ligament in the correct anatomic place.

Child