Double-bundle anterior cruciate ligament reconstruction improves tibial rotational instability: analysis of squatting motion using a 2D/3D registration technique

Abstract

Background: The anterior cruciate ligament-deficient (ACLD) knee requires appropriate treatment for the patient to return to sports. The purpose of this study was to clarify the kinematics of the anterior cruciate ligament-deficient knee in squatting motion before and after double-bundle anterior cruciate ligament reconstruction (DB-ACLR) using a 2D/3D registration technique.

Methods: The subjects of this study were 10 men with confirmed unilateral ACL rupture who underwent DB-ACLR. Computed tomography (CT) of the knee joints was performed before DB-ACLR. Fluoroscopic imaging of the knee motion in squatting before and after DB-ACLR was also performed. The 2D/3D registration technique is a method of calculating positional relationships by projecting the 3D bone model created from the CT data onto the image extracted from the fluoroscopic images. The tibial anteroposterior (AP) and rotational positions were analyzed with reference to the femur.

Results: The tibial AP position of the ACLD knees was significantly anterior to the contralateral knees (p = 0.015). The tibial rotational position of the ACLD knees was significantly internally rotated compared to the contralateral knees (p < 0.001). Both tibial AP and rotational positions improved after DB-ACLR (p < 0.001), with no significant differences compared to the contralateral knees.

Conclusion: DB-ACLR improved not only tibial AP instability but also tibial rotational instability at knee flexion with weight-bearing. DB-ACLR appears to be a useful technique for normalizing the knee joint kinematics of ACLD knees.

Keywords: 2D/3D registration technique; Anterior cruciate ligament; Double-bundle anterior cruciate ligament reconstruction; Knee kinematics.

Fig. 1

Coordinate system of the femur. The femoral condyles are regarded as a cylinder. Z-axis: the axis of the cylinder. Y-axis: the line through the origin parallel to the central line of the femoral shaft projected onto the sagittal plane. X-axis: the line perpendicular to the Z-axis and the Y-axis

Fig. 2

Coordinate system of the tibia. The tangent is set behind the tibial condyle (line 1) at the top level of the head of the fibula, and it is fitted onto the medial and lateral tangents perpendicular to the posterior tangent (lines 2 and 3), and the anterior tangent is set to create a rectangle (line 4). Z-axis: transverse bisector line of the rectangle. X-axis: anteroposterior bisector line of the rectangle. Y-axis: vertical line to the X-Z plane

Fig. 3

Anterior tibial translation of the ACLD and contralateral knees measured by KT-2000 knee arthrometer. Average magnitude of tibial anterior translation (mm). There is a significant difference between ACLD knees and contralateral knees before the surgery (Student’s t test, *p < 0.001)

Fig. 4

Anteroposterior translation of the tibia analyzed by 2D/3D registration technique. Y-axis: tibial anterior translation (mm). X-axis: knee flexion angle (°). Dotted line: ACLD knees. Dashed line: DB-ACLR knees. Solid line: contralateral knees. The anteroposterior position of the tibia of the ACLD knees is significantly different from the contralateral knees and the DB-ACLR knees (post hoc pairwise comparisons with a mixed linear model with repeated measures on SPSS, p = 0.015)

Fig. 5

Rotation of the tibia analyzed by 2D/3D registration technique. Y-axis: tibial internal rotation (°). X-axis: knee flexion angle (°). Dotted line: ACLD knees. Dashed line: DB-ACLR knees. Solid line: contralateral knees. The rotational position of the tibia is significantly different between ACLD knees and contralateral knees, and between ACLD knees and DB-ACLR knees (post hoc pairwise comparisons with a mixed linear model with repeated measures on SPSS, p < 0.001)