Safety and effectiveness of the three-dimensional-printed guide plate-assisted rotation axis positioning of a hinged external fixator for the elbow

PURPOSE

We aimed to evaluate the safety and effectiveness of three-dimensional (3D)-printed guide plates for assisting in the positioning of the rotation axis of an elbow-hinged external fixator.

METHODS

Terrible triad (TT) patients, who were screened using the predefined inclusion and exclusion criteria, underwent installation of a hinged external fixator on the basis of internal fixation; 3D-printed guide plates, generated from the patient's imaging data, assisted in positioning the rotation axis. All patients received the same peri-operative management and were followed up at six, 12, 24, and 48 weeks postoperatively. The duration of positioning pin placement, the number of fluoroscopies, pin placement success rate, types and incidence of post-operative complications, and the Mayo elbow performance score (MEPS) of the diseased elbow and range of motion (ROM) of both elbows were assessed.

RESULTS

In 25 patients who completed the follow-up, the average time required for positioning pin placement was 329.32 ± 42.38 s (263-443 s), the average number of fluoroscopies was 2.32 ± 0.48 times (2-3 times), and the pin placement success rate was 100%. At the last follow-up, the mean MEPS of the diseased elbow was 97.50 ± 6.92 (75-100), with an excellent and good rate of 100%, and all patients demonstrated stable concentric reduction. The average range of flexion and extension was 135.08° ± 17.10° (77-146°), while the average range of rotation was 169.21° ± 18.14° (108-180°). No significant difference was observed in the average ROM between the both elbows (P > 0.05). Eight (32%) patients developed post-operative complications, including elbow stiffness due to heterotopic ossification in three (12%) patients, all of whom did not require secondary intervention.

CONCLUSION

Utilizing 3D-printed guide plates for positioning the rotation axis of an elbow-hinged external fixator significantly reduced intra-operative positioning pin placement time and the number of fluoroscopies with excellent positioning results. Satisfactory results were also obtained in terms of post-operative complications, elbow ROM, and functional scores.

Quantitative analysis of metacarpophalangeal joints during active flexion using four-dimensional computed tomography

BACKGROUND

The metacarpophalangeal joint has a unique morphology with a high degree of freedom. However, few studies have analyzed the kinematics of fingers owing to the rapid movement of the small bones involved. The in-vivo kinematics of metacarpophalangeal joints were analyzed by four-dimensional computed tomography (4DCT) and associated with its morphology.

METHODS

The flexion motion of the fingers of bilateral hands in 10 volunteers were examined using 4DCT. Iterative surfaces were registered to trace the surface of the proximal phalanges with respect to metacarpals. Rotation angles were calculated using Euler/Cardan angles.

FINDINGS

In the index finger, the proximal phalange supinated to a maximum flexion of 40° and then pronated, and its range of rotation was larger than the previous reports. In the other fingers, the proximal phalanges continued to supinate during flexion. The helical axis of the proximal phalange passed a point extremely close to the center point of bilateral condyles, and it moved toward the proximal and palmar directions until the middle stage of flexion and toward the proximal and dorsal directions during the late stage of flexion. The translation of the rotation axis was larger in the ring and little fingers.

INTERPRETATION

The rotation in the index finger was larger than previously reported. The helical axes moved in the dorsal direction and proximally during the latter phase of the flexion. These results can be employed to better understand the causes of implant failure of the metacarpophalangeal joints.

The relationship between the morphological axis and the kinematic axis of the proximal radius

PURPOSE

Surgical procedures for impaired forearm rotation such as for chronic radial head dislocation remain controversial. We hypothesized that the morphological axis of the proximal radius is important for stable forearm rotation, and we aimed to clarify the relationship between the morphological axis and the kinematic axis of the proximal radius using four-dimensional computed tomography (4DCT).

METHODS

Ten healthy volunteers were enrolled. Four-dimensional CT of the dominant forearm during supination and pronation was obtained. The rotation axis of forearm rotation was calculated from all frames during supination and pronation. The principle axis of inertia, which represents the most stable rotation axis of a rigid body, was calculated for the proximal radius by extending its surface data incrementally by 1% from the proximal end. The angle between the kinematic rotation axis and the morphological rotation axis of each length was calculated.

RESULTS

The rotation axis of the forearm was positioned on the radial head 0.0 mm radial and 0.4 mm posterior to the center of the radial head proximally and 2.0 mm radial and 1.2 mm volar to the fovea of the ulnar head distally. The principle axis at 15.9% of the length of the proximal radius coincided with the forearm rotation axis (kinematic axis). Individual differences were very small (SD 1.4%).

CONCLUSION

Forearm rotation was based on the axis at 16% of the length of the proximal radius. This portion should be aligned in cases of severe morphological deformity of the radial head that cause "rattling motion" of the radial head after reduction procedures.

The measurement of intensities in the Rotation Electron Diffraction Technique

The Rotation Electron Diffraction Technique, recently developed at the University of Stockholm, has been used to acquire three-dimensional electron diffraction data. A mathematical expression to calculate the excitation errors, s_g, is suggested by considering the diffraction geometry and the rotation axis. In order to plot the rocking curves, diffraction patterns taken from CoP₃ cubic structure (a=7.708Å, space group Im3¯) are used as examples. Intensities of some reflections are derived by Multigauge software during the beam tilt series. Rocking curves for two Friedel pair reflections with different angles from the rotation axis are plotted.

Accuracy in identifying the elbow rotation axis on simulated fluoroscopic images using a new anatomical landmark

External fixation of the elbow requires identification of the elbow rotation axis, but the accuracy of traditional landmarks (capitellum and trochlea) on fluoroscopy is limited. The relative distance (RD) of the humerus may be helpful as additional landmark. The first aim of this study was to determine the optimal RD that corresponds to an on-axis lateral image of the elbow. The second aim was to assess whether the use of the optimal RD improves the surgical accuracy to identify the elbow rotation axis on fluoroscopy. CT scans of elbows from five volunteers were used to simulate fluoroscopy; the actual rotation axis was calculated with CT-based flexion–extension analysis. First, three observers measured the optimal RD on simulated fluoroscopy. The RD is defined as the distance between the dorsal part of the humerus and the projection of the posteromedial cortex of the distal humerus, divided by the anteroposterior diameter of the humerus. Second, eight trauma surgeons assessed the elbow rotation axis on simulated fluoroscopy. In a preteaching session, surgeons used traditional landmarks. The surgeons were then instructed how to use the optimal RD as additional landmark in a postteaching session. The deviation from the actual rotation axis was expressed as rotational and translational error (±SD). Measurement of the RD was robust and easily reproducible; the optimal RD was 45%. The surgeons identified the elbow rotation axis with a mean rotational error decreasing from 7.6° ± 3.4° to 6.7° ± 3.3° after teaching how to use the RD. The mean translational error decreased from 4.2 ± 2.0 to 3.7 ± 2.0 mm after teaching. The humeral RD as additional landmark yielded small but relevant improvements. Although fluoroscopy-based external fixator alignment to the elbow remains prone to error, it is recommended to use the RD as additional landmark.

Total elbow arthroplasty: Influence of implant positioning on functional outcomes

BACKGROUND

Restoring the axis of rotation is often considered crucial to achieving good functional outcomes of total elbow arthroplasty. The objective of this work was to evaluate whether variations in implant positioning correlated with clinical outcomes.

HYPOTHESIS

Clinical outcomes are dictated by the quality of implant positioning.

MATERIAL AND METHODS

A retrospective review was conducted of data from 25 patients (26 elbows). Function was assessed using a pain score, the Disabilities of the Arm, Shoulder, and Hand (DASH) Score, and the Mayo Elbow Performance Score (MEPS). The patients also underwent a clinical evaluation for measurements of motion range and flexion/extension strength. Position of the humeral and ulnar implants was assessed by computed tomography with reconstruction using OsiriX software. Indices reflecting anterior offset, lateral offset, valgus, height, and rotation were computed by subtracting the ulnar value of each of these variables from the corresponding humeral value. These indices provided a quantitative assessment of whether position errors for the two components had additive effects or, on the contrary, counterbalanced each other. Elbows with prosthetic loosening or extensive epiphyseal destruction were excluded.

RESULTS

Of the 26 elbows, 5 were excluded. In the remaining 21 elbows, the discrepancy between the humeral and ulnar lateral offsets was significantly associated with pain intensity (P ≤ 0.05) and the MEPS (P ≤ 0.05). Anterior position of the ulna relative to the humerus was associated with decreased extension strength (P ≤ 0.05) and worse results for all functional parameters (P ≤ 0.05).

DISCUSSION

In the absence of loosening, positioning errors seem to adversely affect functional outcomes, probably by placing inappropriate stress on the soft tissues.

LEVEL OF EVIDENCE

III.

Rotation axes analysis of deformed magnesium based on rotation contour contrast in a scanning electron microscope

A crystallographic orientation contrast in the form of cross-shaped and intersecting contours was observed in a backscattered electron (BSE) micrograph of deformed magnesium (Mg) grains in a cold field emission scanning electron microscope (CFE-SEM). This contrast was identified as rotation contour contrast (RCC). A model is presented to link the RCC in the BSE micrograph to the channeling contrast in the corresponding channeling pattern. Based on this model, the appearance of the cross-shaped RCC in the BSE micrograph was attributed to the rotation of the crystal about two rotation axes and the RCC was related to a two dimensional angular scan of the corresponding channeling pattern. This model was experimentally validated using the selected area channeling pattern (SACP) technique. The crystallographic directions of the rotation axes were identified using the electron backscatter diffraction (EBSD) technique.

Effects of the axis of rotation and primordially solicited limb of high level athletes in a mental rotation task

A recent set of studies has investigated the selective effects of particular physical activities that require full-body rotations, such as gymnastics and wrestling (Moreau, Clerc, Mansy-Dannay, & Guerrien, 2012; Steggemann, Engbert, & Weigelt, 2011), and demonstrated that practicing these activities imparts a clear advantage in in-plane body rotation performance. Other athletes, such as handball and soccer players, whose activities do require body rotations may have more experience with in-depth rotations. The present study examined the effect of two components that are differently solicited in sport practices on the mental rotation ability: the rotation axis (in-plane, in-depth) and the predominantly used limb (arms, legs). Handball players, soccer players, and gymnasts were asked to rotate handball and soccer strike images mentally, which were presented in different in-plane and in-depth orientations. The results revealed that handball and soccer players performed the in-depth rotations faster than in-plane rotations; however, the two rotation axes did not differ in gymnasts. In addition, soccer players performed the mental rotations of handball strike images slower. Our findings suggest that the development of mental rotation tasks that involve the major components of a physical activity allows and is necessary for specifying the links between this activity and the mental rotation performance.