To evaluate the kinematic characteristics and efficacy of knees following anterior cruciate ligament(ACL) restoration with remnant preservation, and to guide clinical treatments and choose better rehabilitation methods.

The clinical data of 50 patients with ACL deficiency and 25 healthy volunteers from August 2017 to March 2018 were analyzed. Inclusion criteria: age less than 55 years old; body mass index (BMI) less than 30 kg/m²; no limitation of movement of the operated or healthy knee; no nervous system disease; no injury of other ligaments of the ipsilateral knee and no injury of the contralateral knee; complete data were retained one year after operation. Exclusion criteria: age>55 years; BMI>30 kg/m²; knee joint movement limitation; accompanied by other knee ligament injury or contralateral knee joint injury; existence of nervous system disease; clinical data was incomplete and could not be counted. The six degrees of freedom (6-DOF) ranges of knee joints and kinematic function score were calculated by Opti_Knee. Lysholm score, International Knee Documentation Committee (IKDC) score, Tegner score, proprioceptive (position and motion) data and the distance error from the center of the tibial tunnel inner mouth to the center of the footprint of the anterior horn ligament of the lateral meniscus were also analyzed. The statistical differences of 6-DOF in each group were analyzed by two-way ANOVA and t test. The statistical differences of basic data in each group were analysed by one-way ANOVA and t-test, while the counting units were tested by chi-square test. The kinematic function scores, subjective scores, proprioceptive data and center distance errors were detected by t-test.

In remnant preservation group, the ranges of internal-external rotation, flexion-extension rotation at three months and the range of internal-external rotation at six months were lower than those in control group (t=-2.365, P<0.05; t=-3.123, P<0.01; t=-2.419, P<0.05). In non-remnant preservation group, the ranges of adduction-abduction rotation, internal-external rotation, flexion-extension rotation, proximal-distal translation, medial-lateral translation at three months, the ranges of internal-external rotation, flexion-extension rotation at six months and the range of internal-external rotation at 12 months were lower than those in control group (F=9.554, P<0.05; t=-5.067, P<0.01; t=-5.119, P<0.01; t=-2.655, P<0.05; t=-2.863, P<0.01; t=-3.516, P<0.01; t=-4.100, P<0.01; t=-3.076, P<0.01), while the range of anterior-posterior translation at six months was larger than control group (t=2.464, P<0.05). Besides, the range of internal-external rotation, flexion-extension rotation at three months and the range of flexion-extension rotation at six months in non-remnant preservation group were also lower than remnant preservation group at the corresponding time (t=2.512, P<0.05; t=2.428, P<0.05; t=2.267, P<0.05). Kinematic function score of operative knees at three months in the remnant preservation group was higher than that in the non-remnant preservation group(t=2.272, P<0.05). The Lysholm score at three months and six months and the IKDC score at three months in the remnant preservation group were higher than the non-remnant preservation group (t=4.706, P<0.01; t=2.106, P<0.05; t=2.987; P<0.01), and the medial-lateral distance error in remnant preservation group was smaller than non-remnant preservation group (t=-2.600, P<0.05). The position perceptions of 60° in the remnant preservation group were smaller than that in the non-remnant preservation group at three and six months after operation(t=-2.063, P<0.05; t=-2.147, P<0.05).

The kinematic characteristics of the remnant preservation group are closer to those of normal people and the rehabilitation of the remnant preservation group is better than that of non-remnant preservation group in the early and mid-term period.