R. Jonges

Computer-Assisted Planning and Navigation for Corrective Distal Radius Osteotomy, Based on Pre- and Intraoperative Imaging

Malunion after a distal radius fracture is very common and if symptomatic, is treated with a so-called corrective osteotomy. In a traditional distal radius osteotomy, the radius is cut at the fracture site and a wedge is inserted in the osteotomy gap to correct the distal radius pose. The standard procedure uses two orthogonal radiographs to estimate the two inclination angles and the dimensions of the wedge to be inserted into the osteotomy gap. However, optimal correction in 3-Dspace requires restoring three angles and three displacements. This paper introduces a new technique that uses preoperative planning based on 3-D images. Intraoperative 3-D imaging is also used after inserting pins with marker tools in the proximal and distal part of the radius and before the osteotomy. Positioning tools are developed to correct the distal radius pose in six degrees of freedom by navigating the pins. The method is accurate (derr <; 1.2 mm, φerr <; 0.9°, mTRE = 1.7 mm), highly reproducible (SEd <; 1.0 mm, SEφ ≤ 1.4°, SEmTRE = 0.7 mm), and allows intraoperative evaluation of the end result. Small incisions for pin placement and for the osteotomy render the method minimally invasive.

In-vivo three-dimensional carpal bone kinematics during flexion-extension and radio-ulnar deviation of the wrist: Dynamic motion versus step-wise static wrist positions

An in-vivo approach to the measurement of three-dimensional motion patterns of carpal bones in the wrist may have future diagnostic applications, particularly for ligament injuries of the wrist. Static methods to measure carpal kinematics in-vivo only provide an approximation of the true kinematics of the carpal bones. This study is aimed at finding the difference between dynamically and statically acquired carpal kinematics. For eight healthy subjects, static and a dynamic measurements of the carpal kinematics were performed for a flexion-extension and a radio-ulnar deviation movement. Dynamic scans were acquired by using a four-dimensional X-ray imaging system during an imposed cyclic motion. To assess static kinematics of the wrists, three-dimensional rotational X-ray scans were acquired during step-wise flexion-extension and radio-ulnar deviation. The helical axis rotations and the rotation components. i.e. flexion-extension, radio-ulnar deviation and pro-supination were the primary parameters. Linear mixed model statistical analysis was used to determine the significance of the difference between the dynamically and statically acquired rotations of the carpal bones. Small and in most cases negligible differences were observed between the dynamic motion and the step-wise static motion of the carpal bones. The conclusion is that in the case of individuals without any pathology of the wrist, carpal kinematics can be studied either dynamically or statically. Further research is required to investigate the dynamic in-vivo carpal kinematics in patients with dynamic wrist problems.

Three-dimensional assessment of bilateral symmetry of the radius and ulna for planning corrective surgeries.

PURPOSE The contralateral unaffected side is often used as a reference in planning a corrective osteotomy of a malunited distal radius. Two-dimensional radiographs have proven unreliable in assessing bilateral symmetry, so we assessed 3-dimensional configurations to assess bilateral symmetry. METHODS We investigated bilateral symmetry using 3-dimensional imaging techniques. A total of 20 healthy volunteers without previous wrist injury underwent a volumetric computed tomography of both forearms. The left radius and ulna were segmented to create virtual 3-dimensional models of these bones. We selected a distal part and a larger proximal part from these bones and matched them with a mirrored computed tomographic image of the contralateral side. This allowed us to calculate the relative displacements (Δx, Δy, Δz) and rotations (Δφx, Δφy, Δφz) for aligning the left bone with the right bone segments. We investigated the relation between longitudinal length differences in radiuses and ulnas. RESULTS Relative differences of the radiuses were (Δx, Δy, Δz): -0.81 ± 1.22 mm, -0.01 ± 0.64 mm, and 2.63 ± 2.03 mm; and (Δφx, Δφy, Δφz): 0.13° ± 1.00°, -0.60° ± 1.35°, and 0.53° ± 5.00°. The same parameters for the ulna were (Δx, Δy, Δz): -0.22 ± 0.82 mm, 0.52 ± 0.99 mm, 2.08 ± 2.33 mm; and (Δφx, Δφy, Δφz): -0.56° ± 0.96°, -0.71° ± 1.51°, and -2.61° ± 5.58°. There is a strong relation between absolute length differences (Δz) between the radiuses and ulnas of individuals. CONCLUSIONS We observed substantial length and rotational differences around the longitudinal bone axis in healthy individuals. Surgical planning using the unaffected side as a reference may not be as useful as previously assumed. However, including the length difference of the adjacent forearm bones can be useful in improving length correction in computer-assisted planning of radius or ulna osteotomies and in other reconstructive surgery procedures. CLINICAL RELEVANCE Bilateral symmetry is important in reconstructive surgery procedures where the contralateral unaffected side is often used as a reference for planning and evaluation.

Determination of consistent patterns of range of motion in the ankle joint with a computed tomography stress-test

BACKGROUND Measuring the range of motion of the ankle joint can assist in accurate diagnosis of ankle laxity. A computed tomography-based stress-test (3D CT stress-test) was used that determines the three-dimensional position and orientation of tibial, calcaneal and talar bones. The goal was to establish a quantitative database of the normal ranges of motion of the talocrural and subtalar joints. A clinical case on suspected subtalar instability demonstrated the relevance the proposed method. METHODS The range of motion was measured for the ankle joints in vivo for 20 subjects using the 3D CT stress-test. Motion of the tibia and calcaneus relative to the talus for eight extreme foot positions were described by helical parameters. FINDINGS High consistency for finite helical axis orientation (n) and rotation (theta) was shown for: talocrural extreme dorsiflexion to extreme plantarflexion (root mean square direction deviation (eta) 5.3 degrees and theta: SD 11.0 degrees), talorucral and subtalar extreme combined eversion-dorsiflexion to combined inversion-plantarflexion (eta: 6.7 degrees , theta: SD 9.0 degrees and eta:6.3 degrees , theta: SD 5.1 degrees), and subtalar extreme inversion to extreme eversion (eta: 6.4 degrees, theta: SD 5.9 degrees). Nearly all dorsi--and plantarflexion occurs in the talocrural joint (theta: mean 63.3 degrees (SD 11 degrees)). The inversion and internal rotation components for extreme eversion to inversion were approximately three times larger for the subtalar joint (theta: mean 22.9 degrees and 29.1 degrees) than for the talocrural joint (theta: mean 8.8 degrees and 10.7 degrees). Comparison of the ranges of motion of the pathologic ankle joint with the healthy subjects showed an increased inversion and axial rotation in the talocrural joint instead of in the suspected subtalar joint. INTERPRETATION The proposed diagnostic technique and the acquired database of helical parameters of ankle joint ranges of motion are suitable to apply in clinical cases.

Accuracy of a CT-based bone contour registration method to measure relative bone motions in the hindfoot

For measuring the in-vivo range of motion of the hindfoot, a CT-based bone contour registration method (CT-BCM) was developed to determine the three-dimensional position and orientation of bones. To validate this technique, we hypothesized that the range of motion in the hindfoot is equally, accurately measured by roentgen stereophotogrammetric analysis (RSA) as by the CT-BCM technique. Tantalum bone markers were placed in the distal tibia, talus and calcaneus of one cadaver specimen. With a fixed lower leg, the cadaveric foot was held in neutral and subsequently loaded in eight extreme positions. Immediately after acquiring a CT-scan with the foot in a position, RSA radiographs were made. Bone contour registration and RSA was performed. Helical axis parameters were calculated for talocrural and subtalar joint motion from neutral to extreme positions and between opposite extreme positions. Differences between CT-BCM and RSA were calculated. Compared with RSA, the CT-BCM data registered an overall root mean square difference (RMSd) of 0.21 degrees for rotation about the helical axis, and 0.20mm translation along the helical axis for the talocrural and subtalar joint and for all motions combined. The RMSd of the position and direction of the helical axes was 3.3mm and 2.4 degrees , respectively. The latter errors were larger with smaller helical rotations. The differences are similar to those reported for validated RSA and thus are not clinically relevant. Concluding, CT-BCM is an accurate and accessible alternative for studying joint motion, as it does not have the risk of infection and overlapping bone markers.

Interactions between colon cancer cells and hepatocytes in rats in relation to metastasis

Adhesion of cancer cells to endothelium is considered an essential step in metastasis. However, we have shown in a previous study that when rat colon cancer cells are administered to the vena portae, they get stuck mechanically in liver sinusoids. Then, endothelial cells retract rapidly and cancer cells bind to hepatocytes. We investigated the molecular nature of these interactions between colon cancer cells and hepatocytes. Cancer cells in coculture with hepatocytes became rapidly activated with distinct morphological changes. Cancer cells formed long cytoplasmic protrusions towards hepatocytes in their close vicinity and these protrusions attached to microvilli of hepatocytes. Then, adhering membrane areas were formed by both cell types. Integrin subunits αv, α6 and β1 but not αL, β2, β3 and CD44 and CD44v6 were expressed on the cancer cells. In conclusion, colon cancer cells show an active behaviour to bind to hepatocytes, likely involving the integrin subunits av, a6 and B1, indicating that early events in colon cancer metastasis in liver are distinctly different than assumed thus far.

CART: a controlled algebraic reconstruction technique for electron microscope tomography of embedded, sectioned specimen.

Reconstruction of thick, embedded, sectioned material has to cope with the restricted tilt view of the electron microscope, with information not stemming from the object of interest in the projections, with aberrations of the objective lens and with a distorted relationship between the projected densities in the micrographs and the specimen mass densities due to incoherent electron interactions within the specimen. Micrograph densities over a full tilt-range show in general an averaged mass increase which is more than should be expected from the cosine dependency of the tilt-angles of the projections. The hereby presented reconstruction technique finds a solution for the under-determined system by a controlled algebraic iteration procedure. For this solution the procedure stabilises the region of interest by dynamically scaling the input data during the procedure. A model for the electron transport through thick specimens is proposed and microscope projection simulations are carried out to test the algorithms.

The effect of tendon loading on in-vitro carpal kinematics of the wrist joint

Measurements of in-vitro carpal kinematics of the wrist provide valuable biomechanical data. Tendon loading is often applied during cadaver experiments to simulate natural stabilizing joint compression in the wrist joint. The purpose of this study was to investigate the effect of tendon loading on carpal kinematics in-vitro. A cyclic movement was imposed on 7 cadaveric forearms while the carpal kinematics were acquired by a 4-dimensional rotational X-ray imaging system. The extensor- and flexor tendons were loaded with constant force springs of 50 N, respectively. The measurements were repeated without a load on the tendons. The effect of loading on the kinematics was tested statistically by using a linear mixed model. During flexion and extension, the proximal carpal bones were more extended with tendon loading. The lunate was on the average 2.0 degrees (p=0.012) more extended. With tendon loading the distal carpal bones were more ulnary deviated at each angle of wrist motion. The capitate was on the average 2.4 degrees (p=0.004) more ulnary deviated. During radioulnar deviation, the proximal carpal bones were more radially deviated with the lunate 0.7 degrees more into radial deviation with tendon loading (p<0.001). Conversely, the bones of distal row were more flexed and supinated with the capitate 1.5 degrees more into flexion (p=0.025) and 1.0 degrees more into supination (p=0.011). In conclusion, the application of a constant load onto the flexor and extensor tendons in cadaver experiments has a small but statistically significant effect on the carpal kinematics during flexion-extension and radioulnar deviation.

Three-point repositioning of axes: Three-dimensional alignment procedure for electron microscope tomography using three markers

A description is given of a new procedure to align series of tilted graphs, made with an electron microscope, for computer tomographic purposes. The procedure uses the coordinates of three projected markers to calculate parameters needed for the reconstruction. To that end the procedure computes the direction of the tilt‐axis, the translation and rotation parameters, the tilt‐angle of every micrograph, and the spatial coordinates of the individual markers with their centre of gravity as origin of the coordinate system. A searching technique, based on cross‐correlation, is described to locate accurately the micrographs markers.

CT measurement of range of motion of ankle and subtalar joints following two lateral column lengthening procedures.

Background: Lateral column lengthening (LCL) has become an accepted procedure for the operative treatment of the flexible flatfoot deformity. Hindfoot arthrodesis via a calcaneocuboid distraction arthrodesis (CCDA) has been considered a less favourable surgical option than the anterior open wedge calcaneal distraction osteotomy (ACDO), as CCDA has been associated with reduced hindfoot joint motion postoperatively. The ankle and subtalar joint ranges of motion were measured in patients who underwent an ACDO or CCDA procedure for flatfoot deformity. Methods: CT scanning was performed with the foot in extreme positions in five ACDO and five CCDA patients. A bone segmentation and registration technique for the tibia, talus and calcaneus was applied to the CT images. Finite helical axis (FHA) rotations representing the range of motion of the joints were calculated for the motion between opposite extreme foot positions of the tibia and the calcaneus relative to the talus. Results: The maximum mean FHA rotation of the ankle joint (for extreme dorsiflexion to extreme plantarflexion) after ACDO was 52.2 degrees ± 12.4 degrees and after CCDA 49.0 degrees ± 12.0 degrees. Subtalar joint maximum mean FHA rotation (for extreme eversion to extreme inversion) following ACDO was 22.8 degrees ± 8.6 degrees, and following CCDA 24.4 degrees ± 7.6 degrees. Conclusion: An accurate CT-based technique was used to assess the range of motion of the ankle and subtalar joints following two lateral column lengthening procedures for flatfoot deformity. Comparable results with a considerable amount of variance were found for the range of motion following the ACDO and CCDA procedures. Level of Evidence: III, Comparative Case Series