Evaluation of the anterior cruciate ligament function: a new non-invasive quantitative technique

Purpose of the study The purpose of the study was to develop a new non-invasive and quantitative method for evaluation of the anterior cruciate ligament function. Patients and methods The new method was tested in 24 asymptomatic subjects and in 58 patients (3 9 males and 19 females) with arthroscopically proven unilateral rupture of the anterior cruciate ligament. Anterior displacement of the tibia with the knee in 20 degrees flexion was achieved by using a redesigned device, cons tructed originally for stressradiography, and detected by a 3-D optical mot ion analysis system. Results In the normal group, the average difference (d) in anterior displacement of the tibia between the left and the right side under a displacement force o f 250N was 0.56 mm (range 0.1 mm to 1.9 mm) or 17 p. 100 (range 2 p. 100 to 64 p. 100), while in patients the average difference (d) in anterior displ acement of the tibia between the injured and uninjured side under a displac ement force of 250N was 4.02 mm (range 0.6 mm to 9.4 mm) or 133.6 p; 100 (r ange 26 p. 100 to 451 p. Inn). By the criteria for false negative results, i.e. the maximum value of the p arameter d in normal subjects (1.9 mm and 64 p. 100), 10 p. 100 of the pati ents (6 patients) fell into the normal group. According to the criteria of false positive results, i.e. the minimum-value of the parameter d in patien ts (0.6 mm and 26 p. 100), 17 p. 100 of the normal subjects (4 normal subje cts) fell into the group of patients. The achieved level of differentiation Is in the similar range as the most frequently used present methods. Discussion The main advantage of the newly developed noninvasive optical measurement t echnique is that the direction of force and the ampitude and site of applic ation are accuretely defined and documented, and that dislocation movement of the tibia towards the femur during the application of a growing force is continuously monitored with the 3-D optical system and that it allows for several consecutive assessments based on statistical data.