Summary

The purpose of the present study was to clarify screw home movement (SHM) in anterior cruciate ligament deficient (ACLD) knee during dynamic motion using four-dimensional computed tomography, and the conclusion was that SHM was absent in ACLD knee.

Abstract

Introductions:
The tibia externally rotates to the femur during the last 20 degrees of the knee extension motion. This kinematic phenomenon is well known as screw home movement (SHM). However, little attention has been paid to difference between anterior cruciate ligament deficient (ACLD) knee and intact (ACLI) knee in SHM. The present study aimed to clarify the SHM in ACLD during dynamic knee motion using four-dimensional computed tomography (4DCT).

Methods

A total of 6 patients with a unilateral isolated ACLD knee (1 male and 5 females; mean age, 28.3±12 years; age range, 17-49 years; mean body mass index, 20.4±0.8 kg/m2) were enrolled. All subjects provided written informed consent, which was approved by our institutional review board. The subjects were scanned by static computed tomography (CT) and 4DCT on both limbs. In the static position, CT scan of the both limbs of the femur and tibia were performed. Then 4DCT was performed using a 320-detector CT scanner (Aquilion ONE, Canon Medical Systems, Otawa, Japan). In the CT gantry, subjects were positioned in supine position with 60 degrees of knee flexion on a triangle pillow, and were asked to extend the knee to full extension within 10 seconds on each limb. 5 frames of CT volumetric data were obtained for one second. The CT data were accumulated in digital imaging and communication in medicine (DICOM) data format. From the static CT DICOM data, three-dimensional surface data of whole femur and tibia were reconstructed using three-dimensional visualization software (Aviso 6.3, Materials & Structural Analysis, Tokyo, Japan). From 4DCT DICOM data, surface of the partial femur and tibia of all frames were also reconstructed. The partial femur surface of the knee joint surface in 4DCT was matched into the whole femur data in static CT by surface matching technique using iterative closet point (ICP) algorithm, from the Visualization Toolkit 8.1.0 (Kitware Inc, NY, USA). Then the whole tibia surface was matched into the matched partial tibia surface of that frame. In each frame, knee flexion, knee abduction and knee external rotation angle were defined as the tibia angle with respect to the femur were calculated. As a statistical analysis, Wilcoxon signed rank-test was used to evaluate the relationship between ACLD and ACLI. Values of P < 0.05 were considered significant.

Results

Knee external rotation angle was significantly smaller on the ACLD side than on the ACLI side in 0-15 degrees of knee flexion, while the angle was similar during 15 to 60 degrees of knee flexion. In terms of the abduction angle, no significant difference was found.

Discussion

From the present study, SHM was significantly different between ACLD and ACLI. According to previous studies, abnormal kinematics was observed in ACLD under static condition, which might not reflect the dynamic knee motion. The absence of SHM in ACLD knee using 4DCT is clinically important information.

Significance

The dynamic motion in ACLD knee was assessed using 4DCT with 3D-3D image registration technique. SHM was absent in ACLD knee.