In-vivo kinematic analysis of forearm rotation using helical axis analysis

Kinematic analysis of forearm rotation using four-dimensional computed tomography

This study aimed to quantify forearm kinematics with a focus on the forearm rotation axis. Ten healthy volunteers were included in the study. One three-dimensional computed tomographic scan and two four-dimensional computed tomographic scans were done in all the arms to capture forearm joint motion. After image processing, the rotation axis and the movement of the radius with respect to various axes were quantified. The rotation axis was calculated using finite helical axis analysis and a circle fitting approach. The mean error of the rotation axis found through circle fitting was 0.2 mm (SD 0.1) distally and 0.1 mm (SD 0.1) proximally, indicating an improvement in precision over the finite helical axis approach. The translations of the radius along the ulnar axis and the forearm rotation axis were 2.6 (SD 0.8) and 0.6 mm (SD 0.9), respectively. The rotation of the radius around the radial axis was 7.2°. The techniques presented provide a detailed description of forearm kinematics.

Morphology of the Ulnar Insertion of the Triangular Fibrocartilage Complex and Related Osseous Landmarks

PURPOSE

In triangular fibrocartilage complex (TFCC) injuries, a foveal tear of the radioulnar ligament often requires surgery. Previous studies have suggested that surgeons should attach the TFCC to the center of the fovea. The TFCC and its insertion points are small structures, and few studies have reported details of the foveal insertion. This study aimed to clarify the morphology of the ulnar insertion of the TFCC and related osseous landmarks with 3-dimensional imaging.

METHODS

This study used 26 formalin-fixed cadavers. At the ulna, the TFCC was inserted from the fovea to the middle part of the ulnar styloid. After gross observation of the TFCC, the ulnar insertion was outlined using a 1.0-mm drill. We then created 3-dimensional images of the ulna using computed tomography and marked (with software) an outline of the foveal insertion of the TFCC. We measured the area and the long and short diameters of the TFCC insertion.

RESULTS

The area of the TFCC insertion was 34 mm² and positively correlated with the height of the ulnar styloid and the area of the ulnar head. The TFCC's highest point was 58% of the ulnar styloid height. The center of the TFCC insertion was 1.3 mm ulnar and 0.6 mm dorsal from the lowest point of the ulnar surface.

CONCLUSIONS

The center of the TFCC insertion was slightly ulnar of the lowest point of the ulnar surface. This study revealed the center, the area, and the osseous relation of the ulnar insertion of the TFCC.

CLINICAL RELEVANCE

When surgeons repair a TFCC foveal tear, they can find the anatomical center of the ulnar insertion efficiently and easily based on its osseous relationship.

The role of the interosseous ligament in forearm rotation: A bio-mechanical study

BACKGROUND

Management of longitudinal forearm instability remains challenging. Chronic forearm stability may be overcome by reconstruction of the interosseous ligament (IOL). Despite the bands of the IOL being inseparable, studies of the IOL have focused on the central band (CB), but have neglected the proximal (PB) and distal (DB) bands. The purpose of this study was to characterize the bio-mechanical properties of the IOL.

MATERIALS AND METHODS

Twelve frozen specimens from individuals of both sexes were bio-mechanically analyzed using a custom-designed jig operated at constant angular speed to simulate forearm rotation. Strain was measured during dynamic forearm simulation using a motion tracking system.

RESULTS

The average strain of the CB, PB, and DB during forearm simulation were 0.08 ± 0.04, 0.83 ± 0.47, and 0.65 ± 0.23 mm (p < 0.001). The IOL was generally shortest during maximal pronation and increased as the forearm was rotated to a neutral position. The strain of the CB remain constant during forearm rotation and was the lowest at full pronation to 20° pronation position. Throughout forearm rotation, the strain of the CB remained constant, whereas the strain of the PB and DB fluctuated.

CONCLUSIONS

The PB, CB, and DB of the forearm IOL have different bio-mechanical properties. CB maintained a constant rotational strain throughout forearm rotation. Strain on the CB was significantly lower than strains on the PB and DB. By contrast, strains on the PB and DB varied, suggesting that their roles differ from those of the CB. When CB reconstruction is needed, graft should be tensioned at 20° forearm pronation to gain optimum tension.

Biomechanics of the Distal Radioulnar Joint During In Vivo Forearm Pronosupination

Background  Ulnar variance (UV) and center of rotation (COR) location at the level of the distal radioulnar joint (DRUJ) change with forearm rotation. Nevertheless, these parameters have not been assessed dynamically during active in vivo pronosupination. This assessment could help us to improve our diagnosis and treatment strategies. Questions/purposes  We sought to (1) mathematically model the UV change, and (2) determine the dynamic COR's location during active pronosupination. Methods  We used biplanar videoradiography to study DRUJ during in vivo pronation and supination in nine healthy subjects. UV was defined as the proximal-distal distance of ulnar fovea with respect to the radial sigmoid notch, and COR was calculated using helical axis of motion parameters. The continuous change of UV was evaluated using a generalized linear regression model. Results  A second-degree polynomial with R 2 of 0.85 was able to model the UV changes. Maximum negative UV occurred at 38.0 degrees supination and maximum positive UV occurred at maximum pronation. At maximum pronation, the COR was located 0.5 ± 1.8 mm ulnarly and 0.6 ± 0.8 mm volarly from the center of the ulnar fovea, while at maximum supination, the COR was located 0.2 ± 0.6 mm radially and 2.0 ± 0.5 mm volarly. Conclusion  Changes in UV and volar translation of the COR are nonlinear at the DRUJ during pronosupination. Clinical Relevance  Understanding the dynamic nature of UV as a function of pronosupination can help guide accurate evaluation and treatment of wrist pathology where the UV is an important consideration. The dynamic behavior of COR might be useful in designing DRUJ replacement implants to match the anatomical motion.

Analysis of forearm rotational motion using biplane fluoroscopic intensity-based 2D-3D matching

Measuring three-dimensional (3D) forearm rotational motion is difficult. We aimed to develop and validate a new method for analyzing 3D forearm rotational motion. We proposed biplane fluoroscopic intensity-based 2D-3D matching, which employs automatic registration processing using the evolutionary optimization strategy. Biplane fluoroscopy was conducted for forearm rotation at 12.5 frames per second along with computed tomography (CT) at one static position. An arm phantom was embedded with eight stainless steel spheres (diameter, 1.5 mm), and forearm rotational motion measurements using the proposed method were compared with those using radiostereometric analysis, which is considered the ground truth. As for the time resolution analysis, we measured radiohumeral joint motion in a patient with posterolateral rotatory instability and compared the 2D-3D matching method with the simulated multiple CT method, which uses CTs at multiple positions and interpolates between the positions. Rotation errors of the radius and ulna between these two methods were 0.31 ± 0.35° and 0.32 ± 0.33°, respectively, translation errors were 0.43 ± 0.35 mm and 0.29 ± 0.25 mm, respectively. Although the 2D-3D method could detect joint dislocation, the multiple CT method could not detect quick motion during joint dislocation. The proposed method enabled high temporal- and spatial-resolution motion analyses with low radiation exposure. Moreover, it enabled the detection of a sudden motion, such as joint dislocation, and may contribute to 3D motion analysis, including joint dislocation, which currently cannot be analyzed using conventional methods.

Human mimetic forearm mechanism towards bionic arm

The paper presents a mechanical forearm mechanism to extend the pronation and supination (P/S) movement of the trans-radial amputee when he/she is able to conduct the P/S motion partially with his/her remaining forearm. The P/S motions of the existing prostheses and robotic arms developed till now are completely different from those of the human. When we are to develop the robotic prostheses for the amputees, two important issues should be considered such as cosmetic issue to look like normal arm and motion harmony issue between robotic prosthesis and the amputated living arm. Most prostheses do not realize the human-like P/S motion, but the simple rotational motion at the wrist by using the electric motor. In this paper, the well-known spatial four-bar mechanism is adopted in order to mimic human P/S motion as if the person does, because it is one of the best candidates to describe actual human forearm movement. To obtain the design parameters of the mechanism, first, 3D data of the amputated arm as well as the opposite side non-amputated arm are captured by using MRI (Magnetic Resonance Imaging) and 3D scanner. The design parameters such as link lengths, joint locations, and volumetric shape are determined from the measured data. Second, mathematical analysis is performed to simulate one degree-of-freedom P/S motion realized from the spatial four-bar mechanism, and the simulation results are suggested to confirm whether or not it acts like the relative movement between human ulnar and radius bones. Finally the effectiveness of the proposed mechanism is verified through two ADL (activities of daily living) tests.

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.

Three-dimensional analysis of acute plastic bowing deformity of ulna in radial head dislocation or radial shaft fracture using a computerized simulation system

BACKGROUND

Little 3-dimensional biomechanical investigation of plastic bowing deformity of the ulna has been reported, and the purpose of this study was to conduct such an investigation to elucidate mechanisms of injury and appropriate treatments.

METHODS

Ten cases of traumatic plastic deformity of the ulna in pediatric patients, 4 with chronic radial head dislocations (Monteggia equivalent) and 6 with malunited radial shaft fractures, were analyzed for rotational deformities in the axial plane and bending deformities in the sagittal and coronal planes in Euler angle space by use of a 3-dimensional computerized simulation system with a markerless registration technique.

RESULTS

Deformed ulnae with radial head dislocations had 18.7° ± 17.4° of external rotation in the axial plane and 10.4° ± 7.0° of extension in the sagittal plane whereas those with malunited radial shaft fractures had 12.5° ± 12.7° of internal rotation and 6.3° ± 5.6° of flexion displacement compared with mirror images of the opposite ulnae. Absolute values of rotational deformities in both groups were larger than those of sagittal and coronal bending deformities.

DISCUSSION

Most major traumatic plastic bowing deformities of the ulna involved rotation rather than bending. External rotational stress on the ulna is suspected to cause radial head dislocation, and internal rotational stress results in radial shaft fracture during falls onto outstretched arms. Therefore the correction of rotational deformities of the ulna should be considered in the treatment of chronic radial head dislocations and malunited radial shaft fractures.

In vivo three-dimensional motion analysis of chronic radial head dislocations

BACKGROUND

Forearm kinematics and interosseous membrane function in chronic radial head dislocations sustained in childhood are unknown. Several procedures have been performed to reduce the radial head on the basis of static preoperative assessment in only one forearm position, but clinical results are not always favorable.

QUESTIONS/PURPOSES

We investigated the in vivo three-dimensional (3D) kinematics and length changes of interosseous membrane ligaments during forearm rotation in chronic radial head dislocations using 3D CT registration techniques.

METHODS

We examined 10 patients with chronic radial head dislocations (seven Type 1 and three Type 4 Monteggia lesions). To quantify kinematics, the axis of rotation (AOR) and radial head motion were investigated using computer bone models constructed from CT data placing the forearm in three positions. We also created six interosseous membrane ligaments and calculated their 3D lengths during forearm rotation.

RESULTS

In Type 1 lesions, the AOR was located 2.4 mm from the center of the radial head (COR). The COR translated 2.8 mm sagittally and 3.4 mm coronally. Three interosseous membrane ligaments showed little change in length. In Type 4 lesions, the AOR was located 6.2 mm from the COR. The COR translated 10.2 mm sagittally and 4.7 mm coronally. No ligament showed an isometric pattern.

CONCLUSIONS

In Type 1 lesions, the radial head showed relatively stable motion in the dislocated position and the isometricity of the interosseous membrane remained, which supports the concept of ulnar osteotomy. Conversely, the radial head was unstable and the normal interosseous membrane ligament tautness pattern was disrupted in Type 4 lesions.

LEVEL OF EVIDENCE

Level IV, diagnostic study. See Guidelines for Authors for a complete description of levels of evidence.

Effect of relative marker movement on the calculation of the foot torsion axis using a combined Cardan angle and helical axis approach

The two main movements occurring between the forefoot and rearfoot segment of a human foot are flexion at the metatarsophalangeal joints and torsion in the midfoot. The location of the torsion axis within the foot is currently unknown. The purpose of this study was to develop a method based on Cardan angles and the finite helical axis approach to calculate the torsion axis without the effect of flexion. As the finite helical axis method is susceptible to error due to noise with small helical rotations, a minimal amount of rotation was defined in order to accurately determine the torsion axis location. Using simulation, the location of the axis based on data containing noise was compared to the axis location of data without noise with a one-sample t-test and Fisher's combined probability score. When using only data with helical rotation of seven degrees or more, the location of the torsion axis based on the data with noise was within 0.2 mm of the reference location. Therefore, the proposed method allowed an accurate calculation of the foot torsion axis location.

Ulnar variance: its relationship to ulnar foveal morphology and forearm kinematics

PURPOSE

It is unclear how individual differences in the anatomy of the distal ulna affect kinematics and pathology of the distal radioulnar joint. This study evaluated how ulnar variance relates to ulnar foveal morphology and the pronosupination axis of the forearm.

METHODS

We performed 3-dimensional computed tomography studies in vivo on 28 forearms in maximum supination and pronation to determine the anatomical center of the ulnar distal pole and the forearm pronosupination axis. We calculated the forearm pronosupination axis using a markerless bone registration technique, which determined the pronosupination center as the point where the axis emerges on the distal ulnar surface. We measured the depth of the anatomical center and classified it into 2 types: concave, with a depth of 0.8 mm or more, and flat, with a depth less than 0.8 mm. We examined whether ulnar variance correlated with foveal type and the distance between anatomical and pronosupination centers.

RESULTS

A total of 18 cases had a concave-type fovea surrounded by the C-shaped articular facet of the distal pole, and 10 had a flat-type fovea with a flat surface without evident central depression. Ulnar variance of the flat type was 3.5 ± 1.2 mm, which was significantly greater than the 1.2 ± 1.1 mm of the concave type. Ulnar variance positively correlated with distance between the anatomical and pronosupination centers.

CONCLUSIONS

Flat-type ulnar heads have a significantly greater ulnar variance than concave types. The pronosupination axis passes through the ulnar head more medially and farther from the anatomical center with increasing ulnar variance.

CLINICAL RELEVANCE

This study suggests that ulnar variance is related in part to foveal morphology and pronosupination axis. This information provides a starting point for future studies investigating how foveal morphology relates to distal ulnar problems.

In vivo 3D kinematics of normal forearms: analysis of dynamic forearm rotation

BACKGROUND

Forearm rotation is an indispensable activity of daily living and comprises complex motions with rotational and translational components. It is thought that changes in these motions with injury or disease may affect diagnostic indices. Several studies have assessed in vivo forearm kinematics with static conditions, but dynamic forearm kinematics have not yet been reported. The purpose of this study was to analyze forearm kinematics during dynamic rotation using radiographic 3D-2D registration methods.

METHODS

Ten forearms of five healthy males with the mean age of 37 years old were enrolled. Lateral fluoroscopic images were taken during forearm rotation from maximum supination to maximum pronation with their elbows flexed to approximately 45°. Geometric bone models were created from CT scans of the humerus, the radius and the ulna. Three-dimensional kinematics were determined using 3D-2D model registration techniques with the images and models, and the arc of axial rotation of the radius, volar/dorsal translation of the ulna at the distal radioulnar joint and rotation axis of forearm were computed.

FINDINGS

The radial rotation arc was 157°. The ulna translated 3.9 mm (SD 1.5mm) dorsally during activity. The rotation axis of the forearm passed through the center of the radial head and the ulnar head at the 1.9 mm (SD 0.7 mm) posterior from its geometric centroid.

INTERPRETATION

The posteriorly deviated rotation axis at the ulnar head may result in the ulnar head translating dorsally during pronation. These data provide a basis for objective assessment of pathological forearm function.