Four-dimensional computed tomographic imaging in the wrist: proof of feasibility in a cadaveric model

Detection of scapholunate interosseous ligament injury using dynamic computed tomography-derived arthrokinematics: A prospective clinical trial

Scapholunate interosseous ligament injuries are a major cause of wrist instability and can be difficult to diagnose radiographically. To improve early diagnosis of scapholunate ligament injuries, we compared injury detection between bilateral routine clinical radiographs, static CT, and dynamic four-dimensional CT (4DCT) during wrist flexion-extension and radioulnar deviation. Participants with unilateral scapholunate ligament injuries were recruited to a prospective clinical trial investigating the diagnostic utility of 4DCT imaging for ligamentous wrist injury. Twenty-one participants underwent arthroscopic surgery to confirm scapholunate ligament injury. Arthrokinematics, defined as distributions of interosseous proximities across radioscaphoid and scapholunate articular surfaces at different positions within the motion cycle, were used as CT-derived biomarkers. Preoperative radiographs, static CT, and extrema of 4DCT were compared between uninjured and injured wrists using Wilcoxon signed rank or Kolmogorov-Smirnov tests. Median interosseous proximities at the scapholunate interval were significantly greater in the injured versus the uninjured wrists at static-neutral and maximum flexion, extension, radial deviation, and ulnar deviation. Mean cumulative distribution functions at the radioscaphoid joint were not significantly different between wrists but were significantly shifted at the scapholunate interval towards increased interosseous proximities in injured versus uninjured wrists in all positions. Median and cumulative distribution scapholunate proximities from static-neutral and 4DCT-derived extrema reflect injury status.

Dynamic CT scanning of the knee: Combining weight bearing with real-time motion acquisition

BACKGROUND

Imaging the lower limb during weight-bearing conditions is essential to acquire advanced functional joint information. The horizontal bed position of CT systems however hinders this process. The purpose of this study was to validate and test a device to simulate realistic knee weight-bearing motion in a horizontal position during dynamic CT acquisition and process the acquired images.

METHODS

"Orthostatic squats" was compared to "Horizontal squats" on a device with loads between 35% and 55% of the body weight (%BW) in 20 healthy volunteers. Intraclass Correlation Coefficient (ICC), and standard error of measurement (SEM), were computed as measures of the reliability of curve kinematic and surface EMG (sEMG) data. Afterwards, the device was tested during dynamic CT acquisitions on three healthy volunteers and three patients with patellofemoral pain syndrome. The respective images were processed to extract Tibial-Tuberosity Trochlear-Groove distance, Bisect Offset and Lateral Patellar Tilt metrics.

RESULTS

For sEMG, the highest average ICCs (SEM) of 0.80 (6.9), was found for the load corresponding to 42%BW. Kinematic analysis showed ICCs were the highest for loads of 42%BW during the eccentric phase (0.79-0.87) and from maximum flexion back to 20° (0.76). The device proved to be safe and reliable during the acquisition of dynamic CT images and the three metrics were computed, showing preliminary differences between healthy and pathological participants.

CONCLUSIONS

This device could simulate orthostatic squats in a horizontal position with good reliability. It also successfully provided dynamic CT scan images and kinematic parameters of healthy and pathological knees during weight-bearing movement.

Assessing carpal kinematics following scapholunate interosseous ligament injury ex vivo using four-dimensional dynamic computed tomography

BACKGROUND

Scapholunate interosseous ligament injuries are prevalent and often challenging to diagnose radiographically. Four-dimensional CT allows visualization of carpal bones during motion. We present a cadaveric model of sequential ligamentous sectionings ("injuries") to quantify their effects on interosseous proximities at the radioscaphoid joint and scapholunate interval. We hypothesized that injury, wrist position, and their interaction affect carpal arthrokinematics.

METHODS

Eight cadaveric wrists were moved through flexion-extension and radioulnar deviation after injuries. Dynamic CT images of each motion were acquired in each injury condition using a second-generation dual-source CT scanner. Carpal osteokinematics were used to calculate arthrokinematic interosseous proximity distributions during motion. Median interosseous proximities were normalized and categorized by wrist position. Linear mixed-effects models and marginal means tests were used to compare distributions of median interosseous proximities.

FINDINGS

The effect of wrist position was significant for both flexion-extension and radioulnar deviation at the radioscaphoid joint; the effect of injury was significant for flexion-extension at the scapholunate interval; and the effect of their interaction was significant for radioulnar deviation at the scapholunate interval. Across wrist positions, radioscaphoid median interosseous proximities were less able to distinguish injury conditions versus scapholunate proximities. Median interosseous proximities at the scapholunate interval are majoritively able to detect differences between less (Geissler I-III) versus more (Geissler IV) severe injuries when the wrist is flexed, extended, and ulnarly-deviated.

INTERPRETATION

Dynamic CT enhances our understanding of carpal arthrokinematics in a cadaveric model of SLIL injury. Scapholunate median interosseous proximities in flexion, extension, and ulnar deviation best demonstrate ligamentous integrity.

Evaluation of Scapholunate Injury and Repair with Dynamic (4D) CT: A Preliminary Report of Two Cases

Background  In predynamic or dynamic scapholunate (SL) instability, standard diagnostic imaging may not identify SL interosseous ligament (SLIL) injury, leading to delayed detection and intervention. This study describes the use of four-dimensional computed tomography (4DCT) in identifying early SLIL injury and following injured wrists to 1-year postoperatively. Description of Technique  4DCT acquires a series of three-dimensional volume data with high temporal resolution (66 ms). 4DCT-derived arthrokinematic data can be used as biomarkers of ligament integrity. Patients and Methods  This study presents the use of 4DCT in a two-participant case series to assess changes in arthrokinematics following unilateral SLIL injury preoperatively and 1-year postoperatively. Patients were treated with volar ligament repair with volar capsulodesis and arthroscopic dorsal capsulodesis. Arthrokinematics were compared between uninjured, preoperative injured, and postoperative injured (repaired) wrists. Results  4DCT detected changes in interosseous distances during flexion-extension and radioulnar deviation. Generally, radioscaphoid joint distances were greatest in the uninjured wrist during flexion-extension and radioulnar deviation, and SL interval distances were smallest in the uninjured wrist during flexion-extension and radioulnar deviation. Conclusion  4DCT provides insight into carpal arthrokinematics during motion. Distances between the radioscaphoid joint and SL interval can be displayed as proximity maps or as simplified descriptive statistics to facilitate comparisons between wrists and time points. These data offer insight into areas of concern for decreased interosseous distance and increased intercarpal diastasis. This method may allow surgeons to assess whether (1) injury can be visualized during motion, (2) surgery repaired the injury, and (3) surgery restored normal carpal motion. Level of Evidence  Level IV, Case series.

Dynamic three-dimensional computed tomographic imaging facilitates evaluation of the equine cervical articular process joint in motion

BACKGROUND

Dynamic computed tomography (CT) imaging has been introduced in human orthopaedics and is continuing to gain popularity. With dynamic CT, video sequences of anatomical structures can be evaluated in motion.

OBJECTIVES

To investigate the feasibility of dynamic CT for diagnostic imaging of the equine cervical articular process joints (APJs) and to give a detailed description of the APJ movement pattern.

STUDY DESIGN

Descriptive cadaver imaging.

METHODS

Cervical specimens of twelve Warmblood horses were included. A custom-made motorised testing device was used to position and manipulate the neck specimens and perform dynamic 2D and 3D CT imaging. Images were obtained with a 320-detector-row CT scanner with a 160 mm wide-area (2D) solid-state detector design that allows image acquisition of a volumetric axial length of 160 mm without moving the CT couch. Dynamic videos were acquired and divided into four phases of movement. Three blinded observers used a subjective scale of 1 (excellent) to 4 (poor) to grade the overall image quality in each phases of motion cycle.

RESULTS

With an overall median score of 1 the image quality, a significantly lower score was observed in the dynamic 3D videos over the four phases by the three observers compared with the 2D videos for both flexion (3D 95% CI: 1-2 and 2D 95% CI: 1-3; P = .007) and extension movement (3D 95% CI: 1-2 and 2D 95% CI: 1-3; P = .008). Median Translational displacement of the APJ surface was significantly greater in flexion than in extension movement (P = .002).

MAIN LIMITATIONS

The small number of specimens included. Excision of spines and removal of musculature.

CONCLUSIONS

The study is a first step in the investigation of the potential of dynamic 3D CT in veterinary medicine, a technique that has only begun to be explored and leaves much room for refinement prior to its introduction in routine practice. CT with a detector coverage of 16 cm and a rotation speed of 0.32 seconds provides high-quality images of moving objects and gives new insight into the movement pattern of equine cervical APJs.

Distance mapping in three-dimensional virtual surgical planning in hand, wrist and forearm surgery: a tool to avoid mistakes

PURPOSE

Three-dimensional planning in corrective surgeries in the hand and wrist has become popular throughout the last 20 years. Imaging technologies and software have improved since their first description in the late 1980s. New imaging technologies, such as distance mapping (DM), improve the safety of virtual surgical planning (VSP) and help to avoid mistakes. We describe the effective use of DM in two representative and frequently performed surgical interventions (radius malunion and scaphoid pseudoarthrosis).

METHODS

We simulated surgical intervention in both cases using DM. Joint spaces were quantitatively and qualitatively displayed in a colour-coded fashion, which allowed the estimation of cartilage thickness and joint space congruency. These parameters are presented in the virtual surgical planning pre- and postoperatively as well as in the actual situation in our cases.

RESULTS

DM had a high impact on the VSP, especially in radius corrective osteotomy, where we changed the surgical plan due to the visualization of the planned postoperative situation. The actual postoperative situation was also documented using DM, which allowed for comparison of the VSP and the achieved postoperative situation. Both patients were successfully treated, and bone healing and clinical improvement were achieved.

CONCLUSION

The use of colour-coded static or dynamic distance mapping is useful for virtual surgical planning of corrective osteotomies of the hand, wrist and forearm. It also allows confirmation of the correct patient treatment and assessment of the follow-up radiological documentation.

Radiographic Evaluation of Carpal Mechanics and the Scapholunate Angle in a Clenched Fist with Dynamic Computed Tomography Imaging

Purpose

The long-term consequences of injuries to the scapholunate joint can severely limit hand function, and the potential for posttraumatic deformity makes early recognition of these injuries important. The purpose of this study was to evaluate the motion of the scapholunate joint in normal wrists through the radial and ulnar deviation using novel dynamic computed tomography (CT) imaging.

Methods

Fifteen participants consented to have their uninjured wrists scanned. A protocol was designed to ensure adequate time, yet limited exposure, for volunteers. Participants began with the hand in a relaxed fist position and then proceeded to clench the hand in a full fist and relax. Once relaxed again, the wrist was maximally ulnarly deviated and then maximally radially deviated in a fluid motion. Dynamic CT imaging was captured throughout the range of motion.

Results

The scapholunate angle was measured on dynamic wrist images. The mean range of the scapholunate angle that the wrists moved through was 37.2°-45.9°, and the mean midpoint angle was 41.2° ± 0.4°. All wrists had small, measurable differences in the scapholunate angle when moving from the maximum ulnar deviation to the maximal radial deviation. The average maximum angle change through the range is 11.7°, whereas the average minimum angle change was 0.9°.

Conclusions

In this study, scapholunate angle calculations using dynamic wrist CT scans were within the range of accepted normal for the angle in uninjured wrists. With the increased focus on dynamic imaging for wrist motion, it may be possible to derive a standardized protocol for mapping the carpal motion that is clinically applicable and reproducible.

Type of study/level of evidence

Diagnostic IV.

Automated Motion Analysis of Bony Joint Structures from Dynamic Computer Tomography Images: A Multi-Atlas Approach

Dynamic computer tomography (CT) is an emerging modality to analyze in-vivo joint kinematics at the bone level, but it requires manual bone segmentation and, in some instances, landmark identification. The objective of this study is to present an automated workflow for the assessment of three-dimensional in vivo joint kinematics from dynamic musculoskeletal CT images. The proposed method relies on a multi-atlas, multi-label segmentation and landmark propagation framework to extract bony structures and detect anatomical landmarks on the CT dataset. The segmented structures serve as regions of interest for the subsequent motion estimation across the dynamic sequence. The landmarks are propagated across the dynamic sequence for the construction of bone embedded reference frames from which kinematic parameters are estimated. We applied our workflow on dynamic CT images obtained from 15 healthy subjects on two different joints: thumb base (n = 5) and knee (n = 10). The proposed method resulted in segmentation accuracies of 0.90 ± 0.01 for the thumb dataset and 0.94 ± 0.02 for the knee as measured by the Dice score coefficient. In terms of motion estimation, mean differences in cardan angles between the automated algorithm and manual segmentation, and landmark identification performed by an expert were below 1°. Intraclass correlation (ICC) between cardan angles from the algorithm and results from expert manual landmarks ranged from 0.72 to 0.99 for all joints across all axes. The proposed automated method resulted in reproducible and reliable measurements, enabling the assessment of joint kinematics using 4DCT in clinical routine.

Quantifying in vivo scaphoid, lunate, and capitate kinematics using four-dimensional computed tomography

OBJECTIVE

We aimed to establish a quantitative description of motion patterns and establish test-retest reliability of the four-dimensional CT when quantifying in vivo kinematics of the scaphoid, lunate, and capitate.

MATERIALS AND METHODS

We assessed in vivo kinematics of both wrists of 20 healthy volunteers (11 men and 9 women) between the ages of 20 and 40 years. All volunteers performed active flexion-extension and radial-ulnar deviation with both wrists. To test for reliability, one motion cycle was rescanned for both wrists approximately 15 min after the first scan. The coefficient of multiple correlation was used to analyze reliability. When two motion patterns are similar, the coefficient of multiple correlation tends towards 1, whereas in dissimilar motion patterns, it tends towards 0. The root mean square deviation was used to analyze the total motion patterns variability between the two scans.

RESULTS

Overall, mean or median coefficient of multiple correlations were higher than 0.86. The root mean square deviations were low and ranged from 1.17° to 4.29°.

CONCLUSION

This innovative non-invasive imaging technique can reliably describe in vivo carpal kinematics of uninjured wrists in healthy individuals. It provides us with a better understanding and reference values of carpal kinematics of the scaphoid, lunate, and capitate.

The use of 4D-CT in assessing wrist kinematics and pathology

The wrist is a complex joint involving many small bones and complicated kinematics. It has, therefore, been traditionally difficult to image and ascertain information about kinematics when making a diagnosis. Although MRI and fluoroscopy have been used, they both have limitations. Recently, there has been interest in the use of 4D-CT in imaging the wrist. This review examines the literature regarding the use of 4D-CT in imaging the wrist to assess kinematics and its ability to diagnose pathology. Some questions remain about the description of normal ranges, the most appropriate method of measuring intercarpal stability, the accuracy compared with established standards, and the place of 4D-CT in postoperative assessment.

Cite this article: Bone Joint J 2019;101-B:1325–1330.

A four-dimensional-CT study of in vivo scapholunate rotation axes: possible implications for scapholunate ligament reconstruction

Additional fixation of the palmar scapholunate interosseous ligament has been advocated to improve the long-term results of dorsal scapholunate interosseous ligament reconstruction. To investigate the validity of this approach, we determined normal scapholunate motion patterns and calculated the location of the scapholunate rotation axis. We hypothesized that the optimal location of the scapholunate interosseous ligament insertion could be determined from the scapholunate rotation axis. Four-dimensional computerized tomography was used to study the wrist motion in 21 healthy participants. During flexion-extension motions, the scaphoid rotates 38° (SD 0.6°) relative to the lunate; the rotation axis intersects the dorsal ridge of the proximal pole of the scaphoid and the dorsal ridge of the lunate. Minimal scapholunate motion is present during radioulnar deviation. Since the scapholunate rotation axis runs through the dorsal proximal pole of the scaphoid, this is probably the optimal location for attaching the scapholunate ligament during reconstructive surgery.

Computational Simulation of Synovial Fluid Kinematics of the Scapholunate Joint

Background: The interaction between wrist kinematics and synovial fluid pressure has yet to be studied. To our knowledge, this is the first study to determine the effect of scapholunate joint kinematics on synovial fluid pressure change using finite volume method. Methods: The carpal bones of a cadaveric hand were obtained from Computed Tomography (CT) scans. CT images of the carpal bones were segmented and reconstructed into 3D model. The 3D synovial fluid model between the scaphoid and lunate was constructed and then used for computational simulations. The kinematics data of scapholunate joint obtained from radioulnar deviation of the wrist was investigated. Results: It was found that the pressure in synovial fluid varied from -1.68 to 2.64 Pa with maximum pressure located at the scaphoid-fluid interface during the radial deviation. For ulnar deviation, the pressure increased gradually from the scaphoid-fluid interface towards the lunate-fluid interface (-1.37 to 0.37 Pa). Conclusions: This new computational model provides a basis for the study of pathomechanics of ligament injury with the inclusion of synovial fluid.

Evaluation of a Quantitative Method for Carpal Motion Analysis Using Clinical 3-D and 4-D CT Protocols

For wrist complaints related to motion, a 2-D radiograph or CT scan of the static wrist may not always be considered diagnostic. 3-D motion imaging, i.e., multiple 3DCT scans in time (4DCT), enables quantifying carpal motion and comparing motion patterns of the affected wrist with those of the healthy contralateral side. The accuracy and precision of the method, however, is limited by noise and motion artifacts. Although, the technique is considered promising in existing literature, the accuracy and precision of carpal motion analysis has never been investigated systematically. In this paper, we introduce and evaluate a semi-automatic segmentation- and registration-based method for 3-D carpal motion analysis. We investigate the accuracy and precision of the method, and its dependency on motion and scan parameters (angular velocity, dose, gantry revolution angle for image reconstruction, and scanner type) using a wrist phantom. During standstill the positioning error was ≤ 0.23 mm and ≤ 0.78°. A partial gantry revolution for 3-D reconstruction introduced image deformation, contributing to a positioning error of approx. 0.8 mm. This error increased with reduced dose, and with increasing angular velocity of the wrist phantom. In cases where the phantom was rotating about an axis parallel to the rotation axis of the gantry, and in a direction opposite to the gantry, the positioning error increased, probably because of the apparent increase in angular velocity with respect to the gantry. Slow carpal motion 4DCT analysis is feasible using a regular CT scanner. A partial gantry revolution angle for 3-D reconstruction may introduce image deformation, which decreases the accuracy of carpal motion analysis. Knowing the positioning error in 4DCT imaging with the proposed method is considered valuable when investigating wrist injury since it enables discrimination of actual motion from apparent motion caused by methodological error.

Four-dimensional CT as a valid approach to detect and quantify kinematic changes after selective ankle ligament sectioning

The objective of the current study was to explore the potential of dynamic computed tomography to detect kinematic changes, induced by sequential sectioning of the lateral collateral ligaments of the ankle, during full motion sequence of the talocrural joint. A custom-made device was used to induce cyclic controlled ankle inversion movement in one fresh frozen cadaver leg. A 256-slice CT scanner was used to investigate four different scenarios. Scenario 1 with all ligaments intact was first investigated followed by sequential section of the anterior talo-fibular ligament (Scenario 2), the calcaneo-fibular ligament (Scenario 3) and posterior talo-fibular ligament (Scenario 4). Off-line image processing based on semi-automatic segmentation and bone rigid registration was performed. Motion parameters such as translation, rotational angles and orientation and position of the axis of rotation were calculated. Differences between scenarios were calculated. Progressive increase of cranio-caudal displacement up to 3.9 mm and flexion up to 10° compared to Scenario 1 were reported. Progressive changes in orientation (up to 20.6°) and position (up to 4.1 mm) of the axis of rotation were also shown. Estimated effective dose of 0.005 mSv (1.9 mGy CTDI_vol) was reported. This study demonstrated that kinematic changes due to the absence of ligament integrity can be detected with 4DCT with minimal radiation exposure. Identifying abnormal kinematic patterns could have future application in helping clinicians to choose patients’ optimal treatment. Therefore, further studies with bigger in vitro sample sizes and consequent investigations in vivo are recommended to confirm the current findings.

The Effect of Dorsally Angulated Distal Radius Deformities on Carpal Kinematics: An In Vitro Biomechanical Study

PURPOSE

The purpose was to quantify the effect of distal radius dorsal angulation (DA) on carpal kinematics and the relative roles of the radiocarpal and midcarpal joints during wrist motion.

METHODS

Six cadaveric specimens (69 ± 17 y) were mounted at 90° elbow flexion in a custom wrist motion simulator. The wrist was guided through planar passive flexion and extension motion trials (∼ 5°/s). A custom modular distal radius implant was used to simulate native alignment and 3 distal radius DA deformities (10°, 20°, 30°). An optical tracking system captured carpal bone motion, from which radiocarpal and midcarpal joint motion was determined.

RESULTS

The radiocarpal joint made a greater contribution to wrist motion than the midcarpal joint in flexion, and the midcarpal joint made a greater contribution to motion than the radiocarpal joint in wrist extension. Increasing DA caused the radiocarpal joint contribution to increase throughout the motion arc, with the effect being more pronounced in wrist flexion. Conversely, as DA increased, the midcarpal joint contributed less rotation to the total wrist motion and its overall motion arc decreased; the magnitude of effect was greater in wrist extension. Dorsal angulation resulted in increased lunate flexion with respect to the distal radius.

CONCLUSIONS

Our findings agree with current literature that suggests that, in an uninjured wrist, the radiocarpal joint predominates flexion, and the midcarpal joint predominates extension. In addition, the radiocarpal joint has an amplified contribution in wrist flexion with greater DA malunion.

CLINICAL RELEVANCE

The altered contributions of the radiocarpal and midcarpal joints may contribute to pain, stiffness, and the development of arthritis, which is commonly seen at the radiocarpal joint after malunion of the distal radius.

Dynamic CT Scan of the Normal Scapholunate Joint in a Clenched Fist and Radial and Ulnar Deviation

BACKGROUND

Injuries to the scapholunate can have severe long-term effects on the wrist. Early detection of these injuries can help identify pathology. The purpose of this study was to evaluate the motions of the scapholunate joint in normal wrists in a clenched fist and through radial and ulnar deviation using novel dynamic computed tomography (CT) imaging.

METHODS

Fifteen participants below 40 years of age consented to have their wrist scanned. Eight participants were randomized to have the right wrist scanned and 7 the left wrist. Volunteers were positioned at the back of the gantry with the wrist placed on the table, palmar side down. Participants began with the hand in a relaxed fist position and then proceeded through an established range of motion protocol. Dynamic CT imaging was captured throughout the range of motion.

RESULTS

The movement in the healthy scapholunate joint through a clenched fist and radial and ulnar deviation is minimal. The averages were 1.19, 1.01, and 0.95 mm, representing the middle, dorsal, and volar measurements, respectively.

CONCLUSIONS

This novel dynamic CT scan of the wrist is a user-friendly way of measuring of the scapholunate distance, which is minimal in the normal wrist below 40 years of age.

Morphology and Mobility of the Reconstructed Basilar Joint of the Pollicized Index Finger

PURPOSE

To evaluate outcome and function of the reconstructed basilar thumb joint after index finger pollicization in patients presenting congenital thumb deficiency.

METHODS

Plain radiographs and 4-dimensional dynamic volume computed tomography scan were used to evaluate the outcome of 23 pollicizations performed on 14 children between 1996 and 2009. The mean follow-up was 8 years. Patients performed continuous movements of thumb opposition during the imaging studies. Four-dimensional scan images made it possible to visualize mobility within the reconstructed joint.

RESULTS

In 14 cases, union occurred in the metacarpal head/metacarpal base interface. In the 9 other cases, there was a nonunion at this interface. The reconstructed joint was mobile in 20 cases, including 3 in which there was also mobility at the site of the nonunion. In 3 cases in our series, mobility was present only at the site of the nonunion, between the base and the head of the second metacarpal. Remodeling and flattening out of the metacarpal head occurred in 16 of 23 cases. The transposed metacarpal head remained spherical in 7 cases.

CONCLUSIONS

The reconstructed joint adapts, both morphologically and functionally, allowing movement on all 3 spatial planes. Existing mechanical constraints on the reconstructed joint may explain its remodeled appearance.

TYPE OF STUDY/LEVEL OF EVIDENCE

Therapeutic IV.

Experimental determination of the elbow's center of rotation using the VICON™ optoelectronic motion capture system

PURPOSE

Knowledge of elbow kinematics is essential to better understand this joint. There is currently no reliable dynamic method to accurately study the elbow joint in a non-invasive manner. The goal of this study was to implement an accurate protocol to study in vivo elbow kinematics using a VICON™ optoelectronic motion analysis system. MéTHODS: The elbow's centers of rotation (CR) were calculated for 10 anatomical specimens. The effect of skin movement was determined by comparing measurements taken using skin surface markers and bone-fixed markers. The validated protocol was then used in 30 healthy subjects who underwent passive elbow joint movements.

RESULTS

The elbow's CR was found to be distal (7 ± 14 mm), lateral (4 ± 9 mm) and anterior (4 ± 10 mm) to the medial epicondyle in vitro. Mean CR values for anatomical specimens did not differ whether calculated using the skin-based or bone-fixed markers.

CONCLUSION

This study has validated a dynamic, non-invasive, and accurate method for locating the elbow's center of rotation. This preliminary study thus found a different center of rotation of the one in the middle of the trochlea previously thought. This could lead us to reflect on the designs of our prostheses to reduce the mechanical stresses and the risk of loosening.

Dart-throwing motion in patients with scapholunate instability: a dynamic four-dimensional computed tomography study

When the normal wrist rotates along the 'dart-throwing' plane, the proximal row remains still, with most motion occurring at the midcarpal joint. Whether this behaviour is maintained when the scapholunate ligaments are torn is not known. If this is the case, patients having a scapholunate ligament repair could benefit from early dart-throwing exercises without the risk of pulling the sutures apart. Using dynamic computer tomography, we analysed the carpal behaviour of six normal wrists and six wrists with scapholunate instability during dart-throwing motion. In the normal wrists, the scaphoid and lunate did not flex or extend, but translated along the frontal plane an average 5.9 and 5.6 mm, respectively. When the scapholunate ligaments were torn, the scaphoid shifted towards the radial styloid considerably more than the lunate (12.8 mm versus 4.8 mm; p = 0.005), inducing a scapholunate gap. Based on these findings, we cannot recommend dart-throwing exercises after scapholunate ligament repair, unless the joint is stabilized with wires or screws.

A novel method to replicate the kinematics of the carpus using a six degree-of-freedom robot

Understanding the kinematics of the carpus is essential to the understanding and treatment of wrist pathologies. However, many of the previous techniques presented are limited by non-functional motion or the interpolation of points from static images at different postures. We present a method that has the capability of replicating the kinematics of the wrist during activities of daily living using a unique mechanical testing system. To quantify the kinematics of the carpal bones, we used bone pin-mounted markers and optical motion capture methods. In this paper, we present a hammering motion as an example of an activity of daily living. However, the method can be applied to a wide variety of movements. Our method showed good accuracy (1.0-2.6°) of in vivo movement reproduction in our ex vivo model. Most carpal motion during wrist flexion-extension occurs at the radiocarpal level while in ulnar deviation the motion is more equally shared between radiocarpal and midcarpal joints, and in radial deviation the motion happens mainly at the midcarpal joint. For all rotations, there was more rotation of the midcarpal row relative to the lunate than relative to the scaphoid or triquetrum. For the functional motion studied (hammering), there was more midcarpal motion in wrist extension compared to pure wrist extension while radioulnar deviation patterns were similar to those observed in pure wrist radioulnar deviation. Finally, it was found that for the amplitudes studied the amount of carpal rotations was proportional to global wrist rotations.

Dynamic CT technique for assessment of wrist joint instabilities

PURPOSE

To develop a 4D [three-dimensional (3D) + time] CT technique to capture high spatial and temporal resolution images of wrist joint motion so that dynamic joint instabilities can be detected before the development of static joint instability and onset of osteoarthritis (OA).

METHODS

A cadaveric wrist was mounted onto a custom motion simulator and scanned with a dual source CT scanner during radial-ulnar deviation. A dynamic 4D CT technique was utilized to reconstruct images at 20 equidistant time points from one motion cycle. 3D images of carpal bones were generated using volume rendering techniques (VRT) at each of the 20 time points and then 4D movies were generated to depict the dynamic joint motion. The same cadaveric wrist was also scanned after cutting all portions of the scapholunate interosseus ligament to simulate scapholunate joint instability. Image quality were assessed on an ordinal scale (1-4, 4 being excellent) by three experienced orthopedic surgeons (specialized in hand surgery) by scoring 2D axial images. Dynamic instability was evaluated by the same surgeons by comparing the two 4D movies of joint motion. Finally, dose reduction was investigated using the cadaveric wrist by scanning at different dose levels to determine the lowest radiation dose that did not substantially alter diagnostic image quality.

RESULTS

The mean image quality scores for dynamic and static CT images were 3.7 and 4.0, respectively. The carpal bones, distal radius and ulna, and joint spaces were clearly delineated in the 3D VRT images, without motion blurring or banding artifacts, at all time points during the motion cycle. Appropriate viewing angles could be interactively selected to view any articulating structure using different 3D processing techniques. The motion of each carpal bone and the relative motion among the carpal bones were easily observed in the 4D movies. Joint instability was correctly and easily detected in the scan performed after the ligament was cut by observing the relative motion between the scaphoid and lunate bones. Diagnostic capability was not sacrificed with a volume CT dose index (CTDI(vol)) as low as 18 mGy for the whole scan, with estimated skin dose of approximately 33 mGy, which is much lower than the threshold for transient skin erythema (2000 mGy).

CONCLUSIONS

The proposed dynamic 4D CT imaging technique generated high spatial and high temporal resolution images without requiring periodic joint motion. Preliminary results from this cadaveric study demonstrate the feasibility of detecting joint instability using this technique.

Four-dimensional real-time cine images of wrist joint kinematics using dual source CT with minimal time increment scanning

PURPOSE

To validate the feasibility of real time kinematography with four-dimensional (4D) dynamic functional wrist joint imaging using dual source CT.

MATERIALS AND METHODS

Two healthy volunteers performed radioulnar deviation and pronation- supination wrist motions for 10 s and 4 s per cycle in a dual source CT scanner. Scan and reconstruction protocols were set to optimize temporal resolution. Cine images of the reconstructed carpal bone of the moving wrist were recorded. The quality of the images and radiation dosage were evaluated.

RESULTS

The 4D cine images obtained during 4 s and 10 s of radioulnar motion showed a smooth stream of movement with good quality and little noise or artifact. Images from the pronation-supination motion showed noise with a masked surface contour. The temporal resolution was optimized at 0.28 s.

CONCLUSION

Using dual source CT, 4D cine images of in vivo kinematics of wrist joint movement were obtained and found to have a shorter scan time, improved temporal resolution and lower radiation dosages compared with those previously reported.

Functional joint imaging using 256-MDCT: Technical feasibility

OBJECTIVE

Musculoskeletal functional imaging should encompass the real-time (dynamic) depiction of joints in motion (kinematic). Our goal was to determine the technical feasibility of performing dynamic-kinematic imaging of the knee and wrist joints using a new technique, 256-MDCT.

CONCLUSION

Dynamic-kinematic imaging of the wrist and knee using 256-MDCT is feasible to depict anatomic and functional information, warranting further study of diagnostic efficacy, and could augment the current repertoire of joint dysfunction diagnostic testing.

Understanding the relationship between image quality and motion velocity in gated computed tomography: preliminary work for 4-dimensional musculoskeletal imaging

OBJECTIVES

To study the effect of motion velocity on image quality to determine the requirements for 4-dimensional (4D; ie, 3D + time) musculoskeletal computed tomographic (CT) imaging.

MATERIALS AND METHODS

A phantom with resolution targets in both axial (x-y) and coronal (x-z) planes was attached to a motion device and scanned with 64-slice CT using a retrospectively gated CT protocol with pitch values of 0.1 and 0.2. Data were acquired with the phantom at rest and while moving periodically along the x axis at several velocities. Spatial resolution and motion artifacts were assessed both for the axial and coronal targets.

RESULTS

A linear relationship was found between motion artifact severity and phantom velocity. Spatial resolution was better preserved in the coronal target. However, coronal images displayed banding artifacts, with band displacements being linearly related to motion velocity.

CONCLUSIONS

The 4D CT imaging of periodically moving objects with velocities up to 20 mm/s is feasible using a pitch value of 0.1 and a motion frequency of 30 cycles per minute.