The effect of rotational malalignment on X-rays of the wrist

The Sensitivity of the Scapholunate Interval and Bony Landmarks to Wrist Rotation on Posteroanterior Radiographs

BACKGROUND

The objective of this study was to examine the effect of wrist rotation on the scapholunate interval in the posteroanterior radiograph and to identify radiographic landmarks on the posteroanterior projection that can be used to assess position.

METHODS

Eleven healthy cadaveric wrists were radiographed in the neutral position and subsequently were rotated and imaged from 30° pronation to 30° supination in 10° intervals. At each interval, the scapholunate interval was measured as well as the following landmarks: (1) the visible perimeter of the base of the hook of the hamate; (2) the radial-ulnar distribution of the dorsal nonarticular surface of the distal third metacarpal head; (3) the radial-ulnar distribution of the pisiform about the longitudinal axis of the ulna; and (4) the overlap of the pisiform and triquetrum.

RESULTS

The scapholunate interval was largest in the neutral position and linearly decreased by 34% for every 10° of pronation and decreased nonlinearly by 86% after the first 10° of supination. The appearance of the distal third metacarpal head was shown to be sensitive to both pronation and supination. The perimeter of the hook of the hamate and the distribution of the pisiform compared to the ulna were both shown to be sensitive to supination, whereas overlap of the pisiform and triquetrum was not shown to be sensitive to either direction of rotation.

CONCLUSIONS

Our results highlight the significant effect of rotation on radiographic landmarks at the wrist, indicating that 10° of supination can drastically alter the developed radiograph.

Comparison of computer-aided and manual measurements in the evaluation of carpal alignment

The purpose of this study was to compare computer-aided analysis and different methods of manual measurements in the evaluation of carpal alignment. The radioscaphoid, radiolunate, radiocapitate and radiometacarpal angles were measured on cone-beam computed tomography (CT) scans of 30 healthy wrists by automated software (Disior Ltd.) and by hand surgeons using lateral radiographs reconstructed from the CT data. Hand surgeons were either given (n = 6) or not given (n = 7) prior instructions on how to perform the measurements. Inter- and intra-observer reliability of manual measurements ranged from good to excellent (intra-class correlation coefficients [ICC] 0.77-0.99), being highest in specialists with standardized methods and in reconstructed radiographs with bone overlap digitally removed. Computer-aided software provided excellent intra-observer reliability (ICC 0.94-1.00) consistently and values that were highly comparable (mean difference range 1°-7°) with the manual measurements made in optimal settings. Computer-aided software provides an accurate and repeatable method to measure carpal alignment in CT scans, minimizing observational errors.

Accuracy of radiographic measurements of fracture-induced deformity in the distal radius

Background

Management of the distal radius fracture (DRF) is to some extent based on radiographic characterization of fracture displacement. It remains unclear, however, if the measurements used to quantify displacement are accurate.

Purpose

To quantify accuracy of two radiographic measurements: dorsal/volar tilt and fracture compression, measured indirectly as ulnar variance (UV), using radiostereometric analyses (RSA) as reference standard.

Material and Methods

Twenty-one fresh frozen non-fractured human cadaveric forearms (right = 11, left = 10) were thawed and eligible for inclusion. The forearms were mounted on a custom made platform that allowed for controlled forearm rotation, and they underwent two rounds of imaging (both rounds consisted of RSA and radiographs). In round one, the non-fractured forearms were radiographed. In round two, artificial DRF´s with compression and dorsal angulation were created and imaging procedures repeated. Change in tilt and UV between the non-fractured and later fractured forearms was defined as fracture-induced deformity. Deformity was measured radiographically and additionally calculated using RSA. Bland Altman analyses were used to estimate agreement between radiographically measured, and RSA calculated, fracture-induced deformity.

Results

Our results indicated that radiographs underestimate the amount of fracture-induced deformity. Mean measured differences (bias) in dorsal tilt deformity between radiographs and RSA were -2.5° for both observers. The corresponding values for UV were -1.4 mm and -1.5 mm.

Conclusion

Quantifying fracture-induced deformity on radiographs underestimated the actual deformity when compared to RSA calculated deformity. These findings suggest that clinicians, at least in part, base fracture management and potentially corrective surgery on inaccurate measurements.

The lateral wrist radiograph - To retake or not to retake

INTRODUCTION

Patient positioning may impact diagnostic quality when obtaining radiographs of the musculoskeletal (MSK) system. Hence, knowledge on patient positioning, as seen in the radiograph, followed by informed adjusted retake if appropriate, is key when undertaking MSK radiographs. Forearm positioning is particularly important in lateral wrist radiographs where rotation impacts anatomic measurements. The purpose was to evaluate the accuracy of MSK and non-MSK radiographers' immediate assessments of wrist positioning including need for retake.

METHODS

A questionnaire including images of 18 lateral wrist radiographs and questions regarding positioning, i.e. forearm rotation and flexion of the wrist, were developed and distributed to radiographers worldwide via the European Federation of Radiographer Societies (EFRS) and the Research Hub at the European Congress of Radiology (ECR) 2021. Demographic data such as area of expertise, years of experience etc. were collected.

RESULTS

In total, 156 replies were included in the analyses. The inter-observer agreement of radiographers' assessment of the need for a retake was 47% (kappa = .25) and the intra-observer agreement was 81% (kappa = .62). Radiographers working with MSK radiography had more correct positioning assessments than radiographers who did not routinely obtain radiographs of the MSK system (p = 0.0003).

CONCLUSION

Results indicated that MSK radiographers are more consistent in assessment of the need for a retake in lateral wrist radiographs and more able to correctly judge positioning compared to non-MSK radiographers.

IMPLICATIONS FOR PRACTICE

Constant focus on image quality may lead to increased awareness and adherence to image criteria. Improved image quality will in turn improve the diagnostic value for the benefit of the patients potentially leading to better outcomes.

Dorsal Tilt of the Distal Radius Fracture Changes With Forearm Rotation When Measured on Radiographs

Purpose

This study examined the impact of pronation and supination on the reliability of the radiographically measured values of dorsal tilt, radial inclination (RI), and ulnar variance (UV) in cadaveric forearms with artificially created distal radius fractures.

Methods

We prepared 21 human cadaveric forearms (11 right and 10 left) for radiostereometric analysis (RSA) by insertion of tantalum markers. Distal radius fractures were created midway between the marker segments. Radiographs and RSA images were taken at different degrees of supination and pronation. The precise degree of forearm rotation was calculated using RSA software. Two observers (H.B.T. and T.T.) independently measured tilt, RI, and UV on all radiographs in a blinded and randomized fashion. Univariate linear regression analyses were used to determine the relationship between forearm rotation and the measured radiographic values.

Results

The radiographically measured value of tilt was significantly impacted by forearm rotation. Supinating or pronating the forearm by 10° decreased and increased, respectively, the radiographic value of dorsal tilt by approximately 3°.

Conclusions

This study showed that the positioning of the fractured forearm during the radiographic procedure significantly impacted subsequent radiographic measurements of tilt. Dorsal tilt measurements increased (ie, fracture displacement measured more dorsal) with pronation and decreased (ie, fracture displacement measured more toward neutral, with less dorsal tilt) with supination of the forearm. However, measurements of RI (p = 0.12 and p = 0.55 for observer 1 and 2) and UV (p = 0.34 and p = 0.17, observer 1 and 2) were not significantly impacted by rotation.

Clinical relevance

Treatment of a distal radius fracture is, at least to some extent, based on radiographic quantification of fracture deformity. Therefore, unreliable measurements may adversely influence clinical decision making.

Computer-based three-dimensional measurement of carpal alignment: measurement techniques and normal ranges

The three-dimensional carpal alignment was measured in the neutral wrist position in 121 asymptomatic volunteers using computer-based cone-beam CT analysis. Normal values and the reliability of the automated analysis are reported. An analysis software based on segmentation of CT images and mathematical modelling was used to determine several axis variants based on different landmarks and to calculate the intercarpal angles automatically. Twenty wrists were imaged twice to determine intra-observer reliability. Mean values using the preferred axis variants were: scapholunate angle 57° (SD 9°), radiolunate angle 2° (SD 10°), lunocapitate angle -14° (SD 9°). Using alternate axis variants notably changed the angles produced. The intra-observer reliability of the analysis was excellent (mean intraclass correlation coefficient 0.97, SD 0.03). Computer-based CT analysis enables highly reproducible and automated assessment of carpal alignment. This study provides a reference database for measurement techniques and normal carpal angle values in three-dimensional imaging.

The effect of forearm rotation on radiographic measurements of the wrist: an experimental study using radiostereometric analyses on cadavers

Background

Although dorsal/palmar tilt, radial inclination (RI), and ulnar variance (UV) are measurements commonly performed in wrist radiographs, the impact of forearm rotation on those measurements during the radiographic procedure is uncertain. Our aim was to determine the impact of supination and pronation on the reliability of measurements of tilt, RI, and UV.

Methods

Tantalum markers were inserted into the distal radius of 21 unfractured cadaver forearms. The forearms were radiographed in different degrees of supination and pronation. The exact degree of rotation was calculated with radiostereometric analyses. Tilt, RI, and UV were measured by two independent readers in a random and anonymised fashion. Association between forearm rotation and radiographic measurements was examined using linear regression.

Results

Forearm rotation significantly impacted the radiographically measured tilt. One degree of supination and pronation respectively increased and decreased palmar tilt with 0.68° and 0.44°, observers 1 and 2, respectively. As opposed to observer 1, observer 2 found that RI was significantly impacted by rotation with a slope of 0.08. Ulnar variance was not significantly impacted by rotation with linear regression slopes of 0.01° (95% confidence interval [CI] − 0.02–0.05, p = 0.490) and 0.02° (95% CI − 0.02–0.07; p = 0.288), observer 1 and observer 2, respectively.

Conclusion

In unfractured forearms, the radiographically measured tilt was significantly affected by rotation. Palmar tilt increased with supination and decreased with pronation. Rotation significantly affected radial inclination, although of a magnitude that is probably not clinically relevant. No significant impact on UV was found.

Radiographic measurements of the normal distal radius: reliability of computer-aided CT versus physicians' radiograph interpretation

We examined the reliability of a computer-aided cone-beam CT analysis of radiographic parameters of 50 normal distal radii and compared it with interobserver agreement of measurements made by three groups of physicians on two-dimensional plain radiographs. The intra-rater reliability of the computer-aided analysis was evaluated on 33 wrists imaged twice by cone-beam CT. The longitudinal axis, anterior tilt, radial inclination and ulnar variance were measured. The reliability of computer-aided analysis was excellent (intraclass correlation coefficient (ICC) 0.94-0.96) while the interobserver agreement of two-dimensional radiograph interpretation was good (ulnar variance, ICC 0.80-0.84) to poor (anterior tilt and radial inclination, ICC 0.20-0.42). We conclude that computer-aided cone-beam CT analysis was a reliable tool for radiographic parameter determination, whereas physicians demonstrated substantial variability especially in interpreting the angular parameters.

Computer-aided 3D analysis of anatomy and radiographic parameters of the distal radius

INTRODUCTION

This study applied mathematical modeling to examine the anatomy of the distal radius; to define the radiographic parameters in a 3D imaging modality; and to report their normal ranges in the uninjured radius.

MATERIALS AND METHODS

A series of 50 cone-beam computed tomography (CBCT) scans of uninjured radii were analyzed using computer-aided image processing. The radius shape model was used to determine the optimal location for measuring the longitudinal axis. With the axis determined, the volar tilt and radial inclination angles and the areas of the articular facets and their reference points were analyzed.

RESULTS

The optimal location for determining the longitudinal axis was between 28.8 and 53.3 mm proximally from the articular surface. The mean radial inclination angle was 21.8°. The mean volar tilt angle via the most distal tips of the volar and dorsal rims was 13.0°; along the lunate and scaphoid facets it was 9.1° and 11.2°, respectively. The scaphoid facet was larger than the lunate facet and 25% of it was convex.

CONCLUSIONS

Computer-aided CBCT image processing offers an advanced tool to record 3D geometry and the radiographic parameters of the osseous structures of the wrist. Analysis of the distal radius' anatomy showed that the longitudinal axis was affected by its measurement location and subsequently also affected the determination of the angular parameters. We also report the variation of the volar tilt along the articular surface and the shapes and sizes of the articular facets.

Are adult carpal angle measurements applicable to the pediatric population in the trauma setting?

OBJECTIVE

The aim of this study is to assess the applicability of standard adult carpal angle measurements, specifically the scapholunate and capitolunate angles, in the assessment of the pediatric wrist.

MATERIALS AND METHODS

The study cohort comprised male and female children who underwent a wrist radiograph for the evaluation of suspected wrist injuries following trauma. A gender- and indication-matched adult cohort was also assessed. To ensure an accurate carpal angle measurement, only individuals with a sufficiently ossified carpus and an adequately positioned lateral wrist radiograph were included.

RESULTS

Carpal angle measurements were performed on the lateral wrist radiographs of 256 individuals between the ages of 5 and 17 years (mean 11.2 years, SD ± 2.5 years) and 256 individuals between the ages of 18 and 40 years (mean 28.8 years, SD ± 6.2 years). The mean pediatric scapholunate angle was 47° (SD ± 8) and the mean pediatric capitolunate angle was 11° (SD ± 7). The mean adult scapholunate and capitolunate angles were 48° (SD ± 8°) and 10° (SD ± 6°) respectively. No statistically significant difference was observed between the scapholunate or capitolunate angle measurements in the two groups (p = 0.26 and p = 0.36).

CONCLUSION

The study data supports the applicability of standard adult carpal angle values to the pediatric population provided the carpus is sufficiently ossified.

Magnetic resonance imaging investigation of radio-lunate relations: use in assessing distal radial fracture reduction

Reformatted magnetic resonance imaging scans of 27 normal wrists were examined in incremental degrees of rotation around the central axis of the radial shaft to 30° in both directions from true lateral. A line was superimposed on the outer border of the radial dorsal cortex and continued distally to the carpal region. Measurements were made from the superior pole of the lunate to this line. This distance did not change significantly with rotation. This allows a quick and accurate way of assessing distal radial fracture reduction from poorly taken lateral radiographs. In addition, the relevant landmarks are not obscured by implants or casts.

LEVEL OF EVIDENCE

III, diagnostic study.

Computer-assisted 3D planned corrective osteotomies in eight malunited radius fractures

In corrective osteotomy of the radius, detailed preoperative planning is essential to optimising functional outcome. However, complex malunions are not completely addressed with conventional preoperative planning. Computer-assisted preoperative planning may optimise the results of corrective osteotomy of the radius. We analysed the pre- and postoperative radiological result of computer-assisted 3D planned corrective osteotomy in a series of patients with a malunited radius and assessed postoperative function. We included eight patients aged 13–64 who underwent a computer-assisted 3D planned corrective osteotomy of the radius for the treatment of a symptomatic radius malunion. We evaluated pre- and postoperative residual malpositioning on 3D reconstructions as expressed in six positioning parameters (three displacements along and three rotations about the axes of a 3D anatomical coordinate system) and assessed postoperative wrist range of motion. In this small case series, dorsopalmar tilt was significantly improved (p = 0.05). Ulnoradial shift, however, increased by the correction osteotomy (6 of 8 cases, 75 %). Postoperative 3D evaluation revealed improved positioning parameters for patients in axial rotational alignment (62.5 %), radial inclination (75 %), proximodistal shift (83 %) and volodorsal shift (88 %), although the cohort was not large enough to confirm this by statistical significance. All but one patient experienced improved range of motion (88 %). Computer-assisted 3D planning ameliorates alignment of radial malunions and improves functional results in patients with a symptomatic malunion of the radius. Further development is required to improve transfer of the planned position to the intra-operative bone.

Level of evidence IV.

Effect of wrist position on the measurement of carpal indices on the lateral radiograph

The purpose of this study was to find out whether the carpal indices measured on lateral radiographs with a slightly malpositioned wrist are the same as those measured in the true neutral position. Lateral radiographic views of 25 wrists were taken with 5° intervals from 20° of flexion to 20° of extension. Most carpal indices measured in the flexed or extended position were significantly different from the wrist in zero flexion-extension, except scapholunate angle at 5° of extension and scaphocapitate angle at 5° and 10° of flexion. Starting from the flexed position, there was an average of -4.0° change in radioscaphoid angle, -1.0° in scapholunate angle, -1.0° in scaphocapitate angle, +3.0° in radiolunate angle, and +2.0° in lunocapitate angle for each 5° of extension with linear trends. The results from this study suggest that even minimal degrees of flexion-extension can affect the measurements of carpal indices on lateral radiographs.

Positioning evaluation of corrective osteotomy for the malunited radius: 3-D CT versus 2-D radiographs

The authors retrospectively investigated the postoperative position of the distal radius after a corrective osteotomy using 2-dimensional (2-D) and 3-dimensional (3-D) imaging techniques to determine whether malposition correlates with clinical outcome. Twenty-five patients who underwent a corrective osteotomy were available for follow-up. The residual positioning errors of the distal end were determined retrospectively using standard 2-D radiographs and 3-D computed tomography evaluations based on a scan of both forearms, with the contralateral healthy radius serving as reference. For 3-D analysis, use of an anatomical coordinate system for each reference bone allowed the authors to express the residual malalignment parameters in displacements (Δx, Δy, Δz) and rotations (Δφx, Δφy, Δφz) for aligning the affected bone in a standardized way with the corresponding reference bone. The authors investigated possible correlations between malalignment parameters and clinical outcome using patients' questionnaires. Two-dimensional radiographic evaluation showed a radial inclination of 24.9°±6.8°, a palmar tilt of 4.5°±8.6°, and an ulnar variance of 0.8±1.7 mm. With 3-D analysis, residual displacements were 2.6±3 (Δx), 2.4±3 (Δy), and -2.2±4 (Δz) mm. Residual rotations were -6.2°±10° (Δφx), 0.3°±7° (Δφy), and -5.1°±10° (Δφz). The large standard deviation is indicative of persistent malalignment in individual cases. Statistically significant correlations were found between 3-D rotational deficits and clinical outcome but not between 2-D evaluation parameters. Considerable residual malalignments and statistically significant correlations between malalignment parameters and clinical outcome confirm the need for better positioning techniques.

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.

What are the radiological predictors of functional outcome following fractures of the distal radius?

The fracture most commonly treated by orthopaedic surgeons is that of the distal radius. However, as yet there is no consensus on what constitutes an 'acceptable' radiological position before or after treatment. This should be defined as the position that will predict good function in the majority of cases. In this paper we review the radiological indices that can be measured in fractures of the distal radius and try to identify potential predictors of functional outcome. In patients likely to have high functional demands, we recommend that the articular reconstruction be achieved with less than 2 mm of gap or step-off, the radius be restored to within 2 mm of its normal length, and that carpal alignment be restored. The ultimate aim of treatment is a pain-free, mobile wrist joint without functional limitation.