Bone Coordinate System Research Articles

A New Coordinate System for Magnetic Resonance Imaging of the Vestibular System.

Objectives: To develop and evaluate a new coordinate system for MRI of the vestibular system.Methods: In this study, 53 internal auditory canal MRI and 78 temporal bone CT datasets were analyzed. Mimics Medical software version 21.0 was used to visualize and three-dimensionally reconstruct the image data. We established a new coordinate system, named W–X, based on the center of the bilateral eyeballs and vertex of the bilateral superior semicircular canals. Using the W–X coordinate system and Reid's coordinate system, we measured the orientations of the planes of the anterior semicircular canal (ASCC), the lateral semicircular canal (LSCC), and the posterior semicircular canal (PSCC).Results: No significant differences between the angles measured using CT and MRI were found for any of the semicircular canal planes (p > 0.05). No statistical differences were found between the angles measured using Reid's coordinate system (CT) and the W–X coordinate system (MRI). The mean values of ∠ASCC & LSCC, ∠ASCC & PSCC, and ∠LSCC & PSCC were 84.67 ± 5.76, 94.21 ± 3.81, and 91.79 ± 5.22 degrees, respectively. The angle between the LSCC plane and the horizontal imaging plane was 15.64 ± 3.92 degrees, and the angle between the PSCC plane and the sagittal imaging plane was 48.79 ± 4.46 degrees.Conclusion: A new W–X coordinate system was developed for MRI studies of the vestibular system and can be used to measure the orientations of the semicircular canals.

Evaluation of a Bone Coordinate System Constructed Using MR Image Composing

To evaluate the accuracy of a bone coordinate system constructed using MR image composing. A femoral coordinate system constructed using image composing of MR images of a whole bovine femur was evaluated using CT images. The MR images were acquired by moving the table and were processed with 3D distortion correction and composing. To evaluate the reproducibility of the measurements, the same operator repeated the construction of the femoral coordinate system. In addition, distortions in the MR images were evaluated in comparison with those in the CT images. The center position of the femoral coordinate system constructed using the MR image composing was 1.6±0.9 mm on the X-axis, 1.5±0.8 mm on the Y-axis, and 0.2±0.3 mm on the Z-axis, and the rotation of each axis was 1° or less. The distortion of the composed MR image was about 0.3%. The femoral coordinate system constructed using MR image composing had the same accuracy as a system constructed with CT images. The effect of MR image composing on the construction of the femoral coordinate system was small.

The influence of soft tissue artifacts on multi-segment foot kinematics

Movement of skin markers with respect to their underlying bone (i.e. soft tissue artifacts (STAs)) might corrupt the accuracy of marker-based movement analyses. This study aims to quantify STAs in 3D for foot markers and their effect on multi-segment foot kinematics as calculated by the Oxford and Rizzoli Foot Models (OFM, RFM). Fifteen subjects with asymptomatic feet were seated on a custom-made loading device on a computed tomography (CT) table, with a combined OFM and RFM marker set on their right foot. One unloaded reference CT-scan with neutral foot position was performed, followed by 9 loaded CT-scans at different foot positions. The 3D-displacement (i.e. STA) of each marker in the underlying bone coordinate system between the reference scan and other scans was calculated. Subsequently, segment orientations and joint angles were calculated from the marker positions according to OFM and RFM definitions with and without STAs. The differences in degrees were defined as the errors caused by the marker displacements. Markers on the lateral malleolus and proximally on the posterior aspect of the calcaneus showed the largest STAs. The hindfoot-shank joint angle was most affected by STAs in the most extreme foot position (40° plantar flexion) in the sagittal plane for RFM (mean: 6.7°, max: 11.8°) and the transverse plane for OFM (mean: 3.9°, max: 6.8°). This study showed that STAs introduce clinically relevant errors in multi-segment foot kinematics. Moreover, it identified marker locations that are most affected by STAs, suggesting that their use within multi-segment foot models should be reconsidered.

A robust method for automatic identification of femoral landmarks, axes, planes and bone coordinate systems using surface models

The identification of femoral landmarks is a common procedure in multiple academic fields. Femoral bone coordinate systems are used particularly in orthopedics and biomechanics, and are defined by landmarks, axes and planes. A fully automatic detection overcomes the drawbacks of a labor-intensive manual identification. In this paper, a new automatic atlas- and a priori knowledge-based approach that processes femoral surface models, called the A&A method, was evaluated. The A&A method is divided in two stages. Firstly, a single atlas-based registration maps landmarks and areas from a template surface to the subject. In the second stage, landmarks, axes and planes that are used to construct several femoral bone coordinate systems are refined using a priori knowledge. Three common femoral coordinate systems are defined by the landmarks detected. The A&A method proved to be very robust against a variation of the spatial alignment of the surface models. The results of the A&A method and a manual identification were compared. No significant rotational differences existed for the bone coordinate system recommended by the International Society of Biomechanics. Minor significant differences of maximally 0.5° were observed for the two other coordinate systems. This might be clinically irrelevant, depending on the context of use and should, therefore, be evaluated by the potential user regarding the specific application. The entire source code of the A&A method and the data used in the study is open source and can be accessed via https://github.com/RWTHmediTEC/FemoralCoordinateSystem.

An automated method for defining anatomic coordinate systems in the hindfoot

The absence of a standardized method for defining hindfoot bone coordinate systems makes it difficult to compare kinematics results from different research studies. The purpose of this study was to develop a reliable and robust procedure for defining anatomical coordinate systems for the talus and calcaneus. Four methods were evaluated based upon their anatomic consistency across subjects, repeatability, and their correspondence to functional axes of rotation. The four systems consisted of: 1) interactively identified bony landmarks, 2) a principal component analysis, 3) automatically identified bony landmarks, and 4) translating the tibial coordinate system to the hindfoot bones. The four systems were evaluated on 40 tali and 40 calcanei. The functional axes of rotation were determined using dynamic biplane radiography to image the hindfoot during gait. Systems 2 and 3 were the most repeatable and consistent due to the lack of operator intervention when defining coordinate systems. None of the coordinate systems corresponded well to functional axes of rotation during gait. System 3 is recommended over System 2 because it more closely mimics established bone angles measured clinically, especially for the calcaneus. This study presents an automated method for defining anatomic coordinate systems in the talus and calcaneus that does not rely on manual placement of markers or fitting of spheres to the bone surfaces which are less reliable due to operator-dependent measurements. Using this automated method will make it easier to compare hindfoot kinematics results across research studies.

Rotational Laxity Control by the Anterolateral Ligament and the Lateral Meniscus Is Dependent on Knee Flexion Angle: A Cadaveric Biomechanical Study.

Injury to the anterolateral ligament (ALL) has been reported to contribute to high-grade anterolateral laxity after anterior cruciate ligament (ACL) injury. Failure to address ALL injury has been suggested as a cause of persistent rotational laxity after ACL reconstruction. Lateral meniscus posterior root (LMPR) tears have also been shown to cause increased internal rotation of the knee. The purpose of this study was to determine the functional relationship between the ALL and LMPR in the control of internal rotation of the ACL-deficient knee. Specifically: (1) We asked if there was a difference in internal rotation among: the intact knee; the ACL-deficient knee; the ACL/ALL-deficient knee; the ACL/LMPR-deficient knee; and the ACL/ALL/LMPR-deficient knee. (2) We also asked if there was a difference in anterior translation among these conditions. Sixteen fresh frozen cadaveric knee specimens (eight men, mean age 79years) were potted into a hip simulator (femur) and a 6 degree-of-freedom load cell (tibia). Rigid optical trackers were inserted into the proximal femur and distal tibia, allowing for the motion of the tibia with respect to the femur to be tracked during biomechanical tests. A series of points on the femur and tibia were digitized to create bone coordinate systems that were used to calculate internal rotation and anterior translation. Biomechanical testing involved applying a 5-Nm internal rotation moment to the tibia from full extension to 90° of flexion. Anterior translation was performed by applying a 90-N anterior load using a tensiometer. Both tests were performed in 15° increments tested sequentially in the following conditions: (1) intact; and (2) ACL injury (ACL-). The specimens were then randomized to either have the ALL sectioned (3) first (M+/ALL-); or (4) the LMPR sectioned first (M-/ALL+) followed by the other structure (M-/ALL-). A one-way analysis of variance was performed for each sectioning condition at each angle of knee flexion (α=0.05). At 0° of flexion there was an effect of tissue sectioning such that internal rotation of the M-/ALL- condition was greater than ACL- by 1.24° (p=0.03; 95% confidence interval [CI], 0.16-2.70) and the intact condition by 2.5° (p=0.01; 95% CI, 0.69-3.91). In addition, the mean (SD) internal rotations for the M+/ALL- (9.99° [5.39°]) and M-/ALL+ (12.05° [5.34°]) were greater by 0.87° (p=0.04; 95% CI, 0.13-3.83) and by 2.15°, respectively, compared with the intact knee. At 45° the internal rotation for the ACL- (19.15° [9.49°]), M+/ALL- (23.70° [7.00°]), and M-/ALL- (18.80° [8.27°]) conditions was different than the intact (12.78° [9.23°]) condition by 6.37° (p=0.02; 95% CI, 1.37-11.41), 8.47° (p<0.01; 95% CI, 3.94-13.00), and 6.02° (p=0.01; 95% CI, 1.73-10.31), respectively. At 75° there was a 10.11° difference (p<0.01; 95% CI, 5.20-15.01) in internal rotation between the intact (13.96° [5.34°]) and the M+/ALL- (23.22° [4.46°]) conditions. There was also a 4.08° difference (p=0.01; 95% CI, 1.14-7.01) between the intact and M-/ALL- (18.05° [7.31°]) conditions. Internal rotation differences of 6.17° and 5.43° were observed between ACL- (16.28° [6.44°]) and M+/ALL- (p<0.01; 95% CI, 2.45-9.89) as well as between M+/ALL- and M-/ALL- (p=0.01; 95% CI, -8.17 to -1.63). Throughout the range of flexion, there was no difference in anterior translation with progressive section of the ACL, meniscus, or ALL. The ALL and LMPR both play a role in aiding the ACL in controlling internal rotation laxity in vitro; however, these effects seem to be dependent on flexion angle. The ALL has a greater role in controlling internal rotation at flexion angles>30o. The LMPR appears to have more of an effect on controlling rotation closer to extension. Injury to the ALL and/or LMPR may contribute to high-grade anterolateral laxity after ACL injury. The LMPR and the ALL, along with the iliotibial tract, appear to act in concert as secondary stabilizers of anterolateral rotation and could be considered as the "anterolateral corner" of the knee.

The Synergistic Role of the Lateral Meniscus Posterior Root and the ALL in Providing Anterolateral Rotational Stability of the Knee

Objectives:Injury to the anterolateral ligament (ALL) has been reported to contribute to high-grade anterolateral laxity following anterior cruciate ligament (ACL) injury. Failure to address ALL injury has been suggested as a cause of persistent rotational laxity following ACL reconstruction. However, lateral meniscus posterior root (LMPR) tears have also has been shown to cause increased internal rotation and anterior translation of the knee. Due to the anatomic relationship of the ALL and the lateral meniscus, we hypothesize that the ALL and lateral meniscus work synergistically, and that a tear to the LMPR will have the same effect on anterolateral laxity as an ALL tear in the ACL deficient knee.Methods:Sixteen fresh frozen cadaveric knee specimens (mid -femur to mid-tibia) were potted into a hip simulator (femur) and a six degree-of-freedom load cell (tibia). Two rigid optical trackers were inserted into the proximal femur and distal tibia, allowing for the motion of the tibia with respect to the femur to be tracked during biomechanical tests. A series of points on the femur and tibia were digitized to create bone coordinate systems that were used to calculate the kinematic variables. Biomechanical testing involved applying a 5 Nm internal rotation moment to the tibia while the knee was in full extension and tested sequentially in the following three conditions: i) ACLintact; ii) Partial ACL injury (ACLam) -anteromedial bundle sectioned; iii) Full ACL injury (ACLfull). The specimens were then randomized to either have the ALL sectioned first (ALLsec) followed by the LMPRsec or vice versa. Internal rotation and anterior translation of the tibia with respect to the femur were calculated. A mixed two-way (serial sectioning by ALL section order) repeated measures ANOVA (α = 0.05).Results:Compared to the ACLintact condition, internal rotation was found to be 1.78° (p=0.06), 3.74° (p=0.001), and 3.84° (p=0.001) greater following ACLfull, LMPRsec and ALLsec respectively. LMPRsec and the ALLsec resulted in approximately 20 of additional internal rotation (p=0.004 and p=0.01, respectively) compared with the ACL deficient knee (ACLfull). No difference was observed between the ALL and LMPR sectioned states, or whether the ALL was sectioned before or after the LMPR (p=0.160). A trend of increasing anterior translation was observed when the 5 Nm internal rotation moment was applied up until the ACL was fully sectioned; however, these differences were not significant (p=0.070).Conclusion:The ALL and LMPR seem to have a synergistic relationship in aiding the ACL in controlling anterolateral rotational laxity. High-grade anterolateral laxity following ACL injury may be attributed to injuries of the ALL and/or the LMPR. During ACL reconstruction, the posterior roots of both menisci should be inspected carefully to rule out concomitant injury, and if found, should be addressed surgically to aid in both stability and chondroprotection. We suggest that the lateral meniscus should be thought of as part of the anterolateral capsulomeniscal complex (i.e., LM, ITB, and ALL) that acts as a stabilizer of anterolateral rotation in conjunction with the ACL.

Bone Surface Mapping Method

Bone shape is an important factor to determine the bone's structural function. For the asymmetrically shaped and anisotropically distributed bone in vivo, a surface mapping method is proposed on the bases of its geometric transformation invariance and its uniqueness of the principal axes of inertia. Using spiral CT scanning, we can make precise measurements to bone in vivo. The coordinate transformations lead to the principal axes of inertia, with which the prime meridian and the contour can be set. Methods such as tomographic reconstruction and boundary development are employed so that the surface of bone in vivo can be mapped. Experimental results show that the surface mapping method can reflect the shape features and help study the surface changes of bone in vivo. This method can be applied to research into the surface characteristics and changes of organ, tissue or cell whenever its digitalized surface is obtained.

A Determination Method of the Femoral Bone Coordinate System by Integrating an Ultrasound Device with a 3D Electromagnetic Device

A Determination Method of the Femoral Bone Coordinate System by Integrating an Ultrasound Device with a 3D Electromagnetic Device

Analysis of skin movement with respect to flexional bone motion using MR images of a hand

This study describes the methodology for analyzing skin movement with respect to the predefined flexional motion of the hand. The 3D in vivo geometric data were acquired through magnetic resonance (MR) scanning of multiple hands in various postures. Custom software was developed to segment MR images and to generate polygonal isosurfaces. A new bone coordinate system (BCS) was defined to describe the skin movement measured with the skin-surface markers. The BCS was defined by the surface registration technique, which could minimize the distance among the 3D polygonal surfaces of different postures. MR images of six subjects in the 3 postures were captured with skin-surface markers for the experiment. Skin movement on the second metacarpal bone, which was fixed during the flexional motion, ranged from 1.169 to 10.885 mm. While the distance of the skin movement varied from one subject to another, a common skin movement direction was observed among the six subjects. For the repeatability evaluation of the proposed method, the MR images of the same subject were independently processed 10 times by a trained operator. The standard deviation of the skin movement on the second metacarpal of the index finger with respect to the predefined flexional motion ranged from 0.45 to 0.74 mm.