The biomechanical and functional relationships of the proximal radioulnar joint, distal radioulnar joint, and interosseous ligament

Reliability and Validity Analysis of the Distal Radioulnar Joint Ballottement Test

PURPOSE

Triangular fibrocartilage complex injuries can cause distal radioulnar joint (DRUJ) instability, which can be evaluated clinically with the DRUJ ballottement test. However, the reliability and validity of the test are unclear. This study aimed to analyze the reliability and validity of the test using a tracking device on healthy participants and patients with triangular fibrocartilage complex injuries.

METHODS

In this cross-sectional study, three orthopedic hand surgeons performed the DRUJ ballottement test using a technique of holding the carpal bones to the radius on 25 healthy participants (50 hands; 10 men and 15 women; mean age, 33 years; range, 20-51 years) and eight patients with triangular fibrocartilage complex injuries (16 hands; six men and two women; mean age, 43 years; range, 27-59 years). We used a three-dimensional electromagnetic tracking device to quantify the movement of the DRUJ and verify the reliability and validity of the test.

RESULTS

The intrarater and interrater intraclass correlation coefficients for DRUJ movement were 0.77 and 0.61, respectively, and the kappa coefficient for grading of DRUJ instability was 0.79. The correlation coefficient between DRUJ movement measured using the tracking device and instability judged clinically was 0.77. A comparison of healthy participants and the patients showed significantly greater DRUJ movement in the patients.

CONCLUSIONS

The test showed substantial intrarater and interrater reliability for assessing DRUJ movement and instability. The significant positive correlation between DRUJ movement and instability indicates the concurrent validity of the test. Moreover, the test showed discriminative validity in identifying mild or moderate DRUJ instability.

CLINICAL RELEVANCE

The DRUJ ballottement test using the holding technique has a relatively high diagnostic accuracy and can be used to assess DRUJ instability.

The optimal tension for the reconstruction of the distal radioulnar ligaments

PURPOSE

This study aimed to investigate the optimal tension for the reconstruction of the distal radioulnar ligaments (DRULs) in the treatment of the distal radioulnar joint (DRUJ) instability.

METHODS

A total of eight human cadaver upper extremities were used. First, the Tekscan sensor film system was used to measure the contact characteristics of the intact DRUJ. Following this, the DRULs were resected, and the measurement was repeated. The DRULs were then reconstructed according to Adams' procedure, and the contact forces under different initial tension were compared with that of the intact group to obtain the optimal tension. At that point, the contact force of the DRUJ was close to normal. The reliability of the obtained tension was verified by translational testing, which reflected the stability of the DRUJ.

RESULTS

In the neutral position, the contact force, area, and pressure inside DRUJ were 0.51 ± 0.10 N, 64.08 ± 11.58 mm², and 8.33 ± 2.42 kPa, respectively. After the DRULs were resected, they were 0.19 ± 0.02 N, 41.75 ± 5.01 mm², and 4.86 ± 1.06 kPa, respectively. The relationship between the tension and contact force was linear regression (Y = 0.0496x + 0.229, R² = 0.9575, P < 0.0001). According to the equation, when the tension was 3.64-7.68 N, the contact force was close to normal. There was no statistical difference in the stability of the reconstructed DRUJ under this tension compared with the intact group (P = 0.08).

CONCLUSION

By comparing the contact forces under different reconstruction tensions with the normal value, we obtained the optimal tension, which can provide the theoretical basis for the clinical treatment of chronic DRUJ instability.

Analysis and validation of a 3D finite element model for human forearm fracture

Most researchers have performed finite element (FE) analysis of the human forearm fracture by exploring the strength and load transmission of the bones. However, few studies concentrated a complete simulation of the whole forearm complex including ligaments. This paper aims to investigate the load transmission through the bones, contact stress at the joints and strain in the ligaments by using an elaborate FE model, further validating the fracture condition for human forearm. The interosseous ligament was separated into three regions based on the distance to the proximal and distal ends. The FE simulation results were slightly more or less than a previous experimental data in the literature, but generally provided a close approximation of the bone and ligament behaviors. Compared with the experiment results under different loading conditions, maximum contact stress at the proximal radio ulnar joint (PRUJ) and distal radio ulnar joint (DRUJ) of the simulations was higher with an average of 13.4%, and peak strain in the interosseous ligament (IOL) was lower with an average of 11.0%. Under 10 kg load, the maximum stress in the radius (2.25 MPa) was less than double the value in the ulna (1.43 MPa). Finally, the FE model has been validated with the onset and location of the Colles' fracture in the literature. This study will provide a great benefit in terms of surgical and medical applications related to forearm fracture that require an extensive knowledge of the behavior of the bones and ligaments under various loading conditions.

Biomechanical evaluation of interference screw fixation techniques for distal radioulnar ligament reconstruction: a cadaveric experimental study

INTRODUCTION

In the reconstruction of distal radioulnar ligaments (DRULs), interference screws can be used for antegrade or retrograde fixation of grafts to the ulna. However, the biomechanics of interference screw fixation are currently unknown. This study aimed to determine the biomechanical effects of these two fixations on the distal radioulnar joint (DRUJ) in a cadaveric model and to investigate the appropriate initial tension.

MATERIALS AND METHODS

A total of 30 human cadaver upper extremities were used, and the DRULs were reconstructed according to Adams' procedure. First, eight specimens were randomly divided into two groups: antegrade and retrograde, followed by translational testing and load testing. Then, the other eight specimens were divided into the two groups above, and the contact mechanics, including forces, areas, and pressures, were measured. Finally, to investigate the appropriate initial tension, the remaining 14 specimens were fixed with interference screws under different tensions in an antegrade way, and the translational testing was repeated as before.

RESULTS

In the neutral position, antegrade fixation exhibited less translation than retrograde fixation (7.21 ± 0.17 mm versus 10.77 ± 1.68 mm, respectively). The maximum failure load was 70.45 ± 6.20 N in antegrade fixation, while that in retrograde fixation was 35.17 ± 2.95 N (P < 0.0001). Antegrade fixation exhibited a larger increase in contact force than retrograde fixation (99.72% ± 23.88% versus 28.18% ± 10.43%) (P = 0.001). The relationship between tension and displacement was nonlinear (Y = - 1.877 ln(x) + 7.94, R² = 0.868, P < 0.0001).

CONCLUSIONS

Compared with retrograde fixation, the antegrade fixation of interference screws may be a more reliable surgical technique, as it shows a higher failure load and stability. In addition, to avoid the risk of potential arthritis caused by anterograde fixation, we propose an equation to determine the appropriate initial tension in DRUL reconstruction.

The reliability of clinical assessment of distal radioulnar joint instability

Accurate assessment of distal radioulnar joint (DRUJ) stability is increasingly recognized as an important part of clinical examination of the wrist. The ability of 30 specialist UK hand surgeons to clinically determine the stability of four volunteers' wrists was assessed. Volunteers' wrist stability had previously been confirmed with a validated measurement rig. Use of the wrist ballottement test as the primary examination technique yielded a positive predictive value of 81%, a negative predictive value of 55%, a specificity of 94% and a sensitivity of only 24%, for the detection of DRUJ instability. No correlation between background speciality (orthopaedic versus plastic surgery), nor years of clinical experience was found. Clinical assessment of DRUJ instability among experienced clinicians appears unreliable and instability is typically under recognized. Previous research to date using this clinical assessment method as a parameter of success is therefore brought into question.Level of evidence: IV.

Radiocapitellar joint pressures following transradial amputation increase during elbow motion

This study aimed to compare the contact area, mean pressure, and peak pressure of the radiocapitellar joint (RCJ) in the upper limb after transradial amputation with those of the normal upper limb during elbow flexion and forearm rotation. Testing was performed using ten fresh-frozen upper limbs, and the transradial amputation was performed 5 cm proximal to the radial styloid process. The specimens were connected to a custom-designed apparatus for testing. A pressure sensor was inserted into the RCJ. The biomechanical indices of the RCJ were measured during elbow flexion and forearm rotation in all specimens. There was no significant difference in the contact area between the normal and transradial amputated upper limbs. However, in the upper limbs after transradial amputation, the mean pressure was higher than that in the normal upper limbs at all positions of elbow flexion and forearm rotation. The peak pressure was significantly higher in the upper limbs after transradial amputation than in the normal upper limbs, and was especially increased during pronation at 45° of elbow flexion. In conclusion, these results could cause cartilage erosion in the RCJ of transradial amputees. Thus, methods to reduce the pressure of the RCJ should be considered when a myoelectric prosthesis is developed.

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.

Computer-Aided Assessment of Displacement and Reduction of Distal Radius Fractures

This study aims to investigate displacements and reductions of distal radius fractures using measurement indices based on the computer-aided three-dimensional (3D) radius shape model. Fifty-two distal radius fracture patients who underwent osteosynthesis were evaluated with pre- and post-operative distal radius 3D images. In the 3D images, three reference points, i.e., the radial styloid process (1), sigmoid notch volar, and dorsal edge (2) (3) were marked. The three-dimensional coordinates of each reference point and the barycentric coordinates of the plane connecting the three reference points were evaluated. The distance and direction moved, due to the reductions for each reference point, were (1) 12.1 ± 8.1 mm in the ulnar-palmar-distal direction, (2) 7.5 ± 4.1 mm in the ulnar-palmar-proximal direction, and (3) 8.2 ± 4.7 mm in the ulnar-palmar-distal direction relative to the preoperative position. The barycentric coordinate moved 8.4 ± 5.3 mm in the ulnar-palmar-distal direction compared to the preoperative position. This analyzing method will be helpful to understand the three-dimensional direction and the extent of displacements in distal radius fractures.

Stabilization of the distal radioulnar joint by reconstructing the interosseous membrane's distal oblique bundle: Cadaver study

INTRODUCTION

The distal radioulnar (DRU) ligaments play a key role in stabilizing the DRU joint. Ligament reconstruction in this area is an accepted treatment. However, another structure may also be a significant DRUJ stabilizer-the distal oblique bundle (DOB) of the interosseous membrane (IOM). Recent studies have described DOB reconstruction methods, which should be compared to DRU ligament reconstruction.

METHODS

Twelve upper limbs were used. First, a descriptive anatomy study was done to determine the prevalence and features of the DOB (insertions, thickness, and relationship with DRU ligaments). Second, biomechanical testing was done with the wrist in neutral position, supination, and pronation. Distal radius translation was evaluated first on an intact wrist then evaluated again after creating bidirectional instability. Lastly, the same tests were repeated after DRU reconstruction using the Adams-Berger technique and DOB reconstruction using the Riggenbach technique.

RESULTS

The DOB was present in 50% of specimens and was bilateral. Reconstructing the DOB stabilized the wrist to the same degree as the Adams-Berger technique in neutral and pronation (8% residual major instability). Stability was harder to achieve in supination (25% major instability). It was better at controlling posterior radial translation than anterior translation (3% versus 14% major instability).

CONCLUSION

DOB reconstruction appears to be a reliable and less invasive treatment option for DRUJ instability since it is extra-articular. However, the wrist's position and the direction of radial translation seem to alter the stabilization's effectiveness.

LEVEL OF EVIDENCE

IV; Cadaver study.

Evaluation of CT-MR image registration methodologies for 3D preoperative planning of forearm surgeries

Computerized surgical planning for forearm procedures that considers both soft and bony tissue, requires alignment of preoperatively acquired computed tomography (CT) and magnetic resonance (MR) images by image registration. Normalized mutual information (NMI) registration techniques have been researched to improve efficiency and to eliminate the user dependency associated with manual alignment. While successfully applied in various medical fields, the application of NMI registration to images of the forearm, for which the relative pose of the radius and ulna likely differs between CT and MR acquisitions, is yet to be described. To enable the alignment of CT and MR forearm data, we propose an NMI-based registration pipeline, which allows manual steering of the registration algorithm to the desired image subregion and is, thus, applicable to the forearm. Successive automated registration is proposed to enable planning incorporating multiple target anatomical structures such as the radius and ulna. With respect to gold-standard manual registration, the proposed registration methodology achieved mean accuracies of 0.08 ± 0.09 mm (0.01-0.41 mm range) in comparison with 0.28 ± 0.23 mm (0.03-0.99 mm range) associated with a landmark-based registration when tested on 40 patient data sets. Application of the proposed registration pipeline required less than 10 minutes on average compared with 20 minutes required by the landmark-based registration. The clinical feasibility and relevance of the method were tested on two different clinical applications, a forearm tumor resection and radioulnar joint instability analysis, obtaining accurate and robust CT-MR image alignment for both cases.

Biomechanical analysis of simultaneous distal and proximal radio-ulnar joint instability

BACKGROUND

Simultaneous dislocation of the proximal and distal radio-ulnar joints without bony injuries has been reported, but the mechanism remains unclear. We investigated concurrent proximal and distal radio-ulnar joint instability after sequential sectioning of the annular ligament, triangular fibrocartilage complex, and quadrate ligament.

METHODS

We performed this biomechanical study with six fresh-frozen cadaveric upper extremities. Proximal and distal radio-ulnar joint displacement was measured using an electromagnetic tracking device during passive mobility testing with anterior, lateral, and posterior loads on the radial head with pronation, supination, and neutral rotation. Measurements were statistically analyzed using the generalized linear mixed model.

FINDINGS

Proximal radio-ulnar joint instability was significantly greater after sectioning of the annular (lateral: 1.4%, P < .05; posterior: 0.7%, P < .05) and quadrate (lateral: 43.7%, P < .05; posterior: 29.5%, P < .05) ligament. Distal radio-ulnar joint instability was significantly greater in every sequential stage (final stage: anterior: 24.1%, P < .05; lateral 21.0%, P < .05; posterior: 31.3%, P < .05). Finally, significant simultaneous instability of the joints was observed after sectioning of the annular ligament, triangular fibrocartilage complex, and quadrate ligament, and neutral rotation potentially induced gross instability.

INTERPRETATION

Our ligament injury model induced simultaneous proximal and distal radio-ulnar joint instability without bony or interosseous membrane injury, probably induced by severe soft tissue injury. Proximal radio-ulnar joint instability may influence distal radio-ulnar joint instability from pivoting of the interosseous membrane. Our findings will help surgeons evaluate the magnitude of soft tissue injury and plan surgery for patients with simultaneous proximal and distal radio-ulnar joint instability.

Digitalization of the IOM: A comprehensive cadaveric study for obtaining three-dimensional models and morphological properties of the forearm's interosseous membrane

State-of-the-art of preoperative planning for forearm orthopaedic surgeries is currently limited to simple bone procedures. The increasing interest of clinicians for more comprehensive analysis of complex pathologies often requires dynamic models, able to include the soft tissue influence into the preoperative process. Previous studies have shown that the interosseous membrane (IOM) influences forearm motion and stability, but due to the lack of morphological and biomechanical data, existing simulation models of the IOM are either too simple or clinically unreliable. This work aims to address this problematic by generating 3D morphological and tensile properties of the individual IOM structures. First, micro- and standard-CT acquisitions were performed on five fresh-frozen annotated cadaveric forearms for the generation of 3D models of the radius, ulna and each of the individual ligaments of the IOM. Afterwards, novel 3D methods were developed for the measurement of common morphological features, which were validated against established optical ex-vivo measurements. Finally, we investigated the individual tensile properties of each IOM ligament. The generated 3D morphological features can provide the basis for the future development of functional planning simulation of the forearm.

Effect of soft tissue injury and ulnar angulation on radial head instability in a Bado type I Monteggia fracture model

The effects of soft tissue damage and ulnar angulation deformity on radial head instability in Monteggia fractures are unclear. We tested the hypothesis that radial head instability correlates with the magnitude of ulnar angular deformity and the degree of proximal forearm soft tissue injury in Bado type I Monteggia fractures.We performed a biomechanical study in 6 fresh-frozen cadaveric upper extremities. Monteggia fractures were simulated by anterior ulnar angulation osteotomy and sequential sectioning of ligamentous structures. We measured radial head displacement during passive mobility testing in pronation, supination, and neutral rotation using an electromagnetic tracking device. Measurements at various ligament sectioning stages and ulnar angulation substages were statistically compared with those in the intact elbow.Radial head displacement increased with sequential ligament sectioning and increased proportionally with the degree of anterior ulnar angulation. Annular ligament sectioning resulted in a significant increase in displacement only in pronation (P < .05). When the anterior ulnar deformity was reproduced, the radial head displaced least in supination. The addition of proximal interosseous membrane sectioning significantly increased the radial head displacement in supination (P < .05), regardless of the degree of anterior ulnar angulation.Our Monteggia fracture model showed that radial head instability is influenced by the degree of soft tissue damage and ulnar angulation. Annular ligament injury combined with a minimal (5°) ulnar deformity may cause elbow instability, especially in pronation. The proximal interosseous membrane contributes to radial head stability in supination, regardless of ulnar angulation, and proximal interosseous membrane injury led to significant radial head instability in supination.

Establishing Safe Extra-articular Parameters for Cortical Button Distal Fixation During Ulnar Collateral Ligament Reconstruction

BACKGROUND

A variety of methods exist for fixation during ulnar collateral ligament (UCL) reconstruction on the ulna for the overhead throwing athlete. Current biomechanical evidence suggests that cortical button fixation may fail at a higher load and under more cycles than interference screw fixation alone, while also minimizing the risk of fracture. A safe angle for placement of this cortical button has not yet been determined.

PURPOSE

To define a safe angle for cortical button deployment during UCL reconstruction to avoid violation of the proximal radioulnar joint (PRUJ).

STUDY DESIGN

Descriptive laboratory study.

METHODS

Measurements on 100 cadaveric ulna bones, 50 women and 50 men, were obtained referencing the entry point for ulnar fixation, which is 1 cm distal to the ulnar humeral joint line along the medial UCL ridge. Ulnar width at the entry point and distance to the PRUJ were obtained to calculate safe distal angulation, while distance from the entry point to the posterior ulnar crest ulnarly and distance from the PRUJ to the posterior ulnar crest radially were obtained to calculate safe posterior angulation. Ten bony measurements on the same group of specimens were performed by 3 authors to establish an interobserver reliability. Means, quartiles, and outliers were obtained for the calculated angles. Finally, recommended angles of entry were determined to be approximately 1 interquartile range above the upper limit.

RESULTS

The mean distal angle of entry that was obtained was 11.32° (SD, ±4.80°; 95% CI, 10.37°-12.27°; P < .001). Three upper limit outliers were discovered: 24.20°, 23.4°, and 21.1°. The mean posterior angle of entry was 40.44° (SD, ±6.18°; 95% CI, 39.22°-41.67°; P < .001). There were no outliers for the posterior angle of entry. Interobserver reliabilities were strong for the 4 measurements.

CONCLUSION

To be safely outside of the PRUJ utilizing a cortical button construct, we recommend 30° distal angulation and 60° posterior angulation for ulnar fixation during UCL reconstruction. Both parameters are 1 quartile above the highest calculated angle of entry.

CLINICAL RELEVANCE

These data define safe parameters for distal fixation during UCL reconstruction and highlight a clear entry point for reference.

Computed Tomography Analysis of the Radial Notch of the Ulna

PURPOSE

The anatomy of the radial head and capitellum has been extensively studied; however, the anatomy of the radial notch of the ulna (RNU) has received little attention. This imaging-based anatomic study characterizes the morphology of the RNU.

METHODS

Ninety-eight cadaveric arms (57 male, 72 ± 14 y) were imaged with computed tomography, and 3-dimensional reconstructions of the proximal ulna were constructed. The anteroposterior and proximal-distal dimensions of the RNU as well as the radius of curvature at standardized levels were measured in 2-mm increments. The orientation of the RNU was also determined.

RESULTS

The proximal-distal and anteroposterior dimensions of the RNU were 12 ± 2 mm (range, 7-16 mm) and 18 ± 3 mm (range, 12-24 mm), respectively. The average radius of curvature of the RNU was 15 ± 0 mm (range, 15-16 mm). The radius of curvature did not change significantly when comparing the proximal and distal aspect of the RNU. The RNU was rotated 33° ± 2° (range, 31° to 38°) externally relative to the transverse plane of the ulna. The average depth of the RNU at its deepest point was 2.2 ± 0.4 mm (range, 1.5-2.7 mm). The depth decreased from proximal to distal, being most shallow distally. The depth changed by an increase of the radius of curvature, as well as by rotation in the frontal plane.

CONCLUSIONS

The RNU anatomy was variable, generally extending laterally from proximal to distal. This suggests that a radial head implant should taper from proximal to distal to optimize contact at the RNU.

CLINICAL RELEVANCE

The present study investigates the detailed anatomy of the radial notch of the ulna using computed tomography scans. The data might help improve the design of prosthetic components.

The Effect of Dorsal Angulation on Distal Radioulnar Joint Arthrokinematics Measured Using Intercartilage Distance

Background  The effects of dorsal angulation deformity on in vitro distal radioulnar joint (DRUJ) contact patterns are not well understood. Purpose  The purpose of this study was to utilize intercartilage distance to examine the effects of forearm rotation angle, distal radius deformity, and triangular fibrocartilage complex (TFCC) sectioning on DRUJ contact area and centroid position. Methods  An adjustable implant permitted the creation of simulated intact state and dorsal angulation deformities of 10, 20, and 30 degrees. Three-dimensional cartilage models of the distal radius and ulna were created using computed tomography data. Using optically tracked motion data, the relative position of the cartilage models was rendered and used to measure DRUJ cartilage contact mechanics. Results  DRUJ contact area was highest between 10 and 30 degrees of supination. TFCC sectioning caused a significant decrease in contact area with a mean reduction of 11 ± 7 mm ² between the TFCC intact and sectioned conditions across all variables. The position of the contact centroid moved volarly and proximally with supination for all variables. Deformity had a significant effect on the location of the contact centroid along the volar-dorsal plane. Conclusion  Contact area in the DRUJ was maximal between 10 and 30 degrees of supination during the conditions tested. There was a significant effect of simulated TFCC rupture on contact area in the DRUJ, with a mean contact reduction of 11 ± 7 mm ² after sectioning. Increasing dorsal angulation caused the contact centroid to move progressively more volar in the sigmoid notch.

Arthrokinematics of the Distal Radioulnar Joint Measured Using Intercartilage Distance in an In Vitro Model

PURPOSE

Current techniques used to measure joint contact rely on invasive procedures and are limited to statically loaded positions. We sought to examine native distal radioulnar joint (DRUJ) contact mechanics using nondestructive imaging methods during simulated active and passive forearm rotation.

METHODS

Testing was performed using 8 fresh-frozen cadaveric specimens that were surgically prepared by isolating muscles involved in forearm rotation. A wrist simulator allowed for the evaluation of differences between active and passive forearm rotation. Three-dimensional cartilage surface reconstructions were created using volumetric data acquired from computed tomography. Using optically tracked motion data, the relative position of the cartilage models was rendered and used to measure DRUJ cartilage contact mechanics. The effects of forearm movement method and rotation angle on centroid coordinate data and DRUJ contact area were examined.

RESULTS

The DRUJ contact area was maximal at 10° supination. There was more contact area in supination than pronation for both active and passive forearm rotation. The contact centroid moved volarly with supination, with magnitudes of 10.5 ± 2.6 mm volar for simulated active motion and 8.5 ± 2.6 mm volar for passive motion. Along the proximal-distal axis, the contact centroid moved 5.7 ± 2.4 mm proximal during simulated active motion. These findings were statistically significant. The contact centroid moved 0.2 ± 3.1 mm distal during passive motion (not significant).

CONCLUSIONS

It is possible to examine cartilage contact mechanics of the DRUJ nondestructively while undergoing simulated, continuous active and passive forearm rotation. The contact centroid moved volarly and proximally with supination. There were higher contact area values in supination compared with pronation, with a peak value at 10° supination.

CLINICAL RELEVANCE

This study documented normal DRUJ arthrokinematics using a nondestructive in vitro approach. It further reinforced the established biomechanical and clinical literature on contact patterns at the native DRUJ during forearm rotation.

Biomechanical study of isolated radial head dislocation

Background

Isolated radial head dislocation is a rare injury with an unclear pathomechanism, and the treatment is controversial. The purpose of the present study was to investigate the biomechanical contributions of the annular ligament, quadrate ligament, interosseous membrane, and annular ligament reconstructions to proximal radioulnar joint stability.

Methods

Five fresh frozen cadaveric upper extremities were amputated above the elbow and solidly fixed on a customized jig. Radial head dislocation was reproduced by sequential sectioning of ligamentous structures and passive mobility testing. Radial head displacement during mobility testing was measured with an electromagnetic tracking device in three forearm rotation positions. The data were compared among different sectioning stages and between two types of simulated ligamentous reconstruction.

Results

Lateral displacement of the radial head significantly increased in the neutral forearm rotation after annular ligament sectioning (46 ± 10%, p < 0.05). After quadrate ligament sectioning, we found significant posterior (67 ± 36%, p < 0.05) and lateral (74 ± 24%, p < 0.01) displacement in neutral forearm rotation and pronation. Significant radial head displacement was found in all directions and in all forearm positions after sequential sectioning of the proximal half of the interosseous membrane. Anatomical annular ligament reconstruction stabilized the proximal radioulnar joint except for anterior laxity in neutral forearm rotation (15 ± 6%, p < 0.05). The radial head with Bell Tawse procedure was significantly displaced in all directions.

Conclusion

The direction of radial head instability varied depending on the degree of soft tissue sectioning and specific forearm rotation. Anterior radial head dislocation may involve more severe ligament damage than other types of dislocation. Anatomical annular ligament reconstruction provided multidirectional radial head stability.

Rehabilitation of distal radioulnar joint instability

Distal radioulnar joint (DRUJ) instabilities are common and often combined with other injuries of the interosseous membrane and/or the proximal radioulnar joint. Once they are diagnosed and the treatment is chosen, physiotherapists have limited choices due to the lack of validated protocols. The benefits of proprioception and neuromuscular rehabilitation have been brought to light for the shoulder, knee and ankle joints, among others. However, no program has been described for the DRUJ. The purpose of this article is to study the muscular elements responsible for active DRUJ stability, and to propose a proprioceptive rehabilitation program suited to this condition.

Ultrasound imaging of the distal radioulnar joint: a new method to assess ulnar radial translation in forearm rotation

A cross-sectional reliability study was conducted with 23 normal participants to establish normal values, and the repeatability and validity of distal radioulnar joint translation measurements using ultrasound imaging. Static transverse images of maximal supination, neutral and maximal pronation were examined to assess translation, using a method consistent with the rheumatoid arthritis subluxation ratio. Translation while gripping a 1 kg weight in supinated and pronated positions was then compared with non-gripping translation. There was significantly more ulnar radial translation found with pronation than supination, when compared with neutral. Gripping in pronation did not produce statistically significant changes in translation, whereas the changes produced by gripping in supination were significant. Internal consistency was deemed very high and the rheumatoid arthritis subluxation ratio values measured using ultrasound imaging were consistent with previously documented values measured by computerized tomography. This study demonstrated that translational movement of the distal radioulnar joint can be reliably detected in healthy participants using ultrasound imaging. This may reduce dependency on other imaging modalities to diagnose distal radioulnar joint instability.

LEVEL OF EVIDENCE

2.

Distal radioulnar joint: functional anatomy, including pathomechanics

The distal radioulnar joint allows the human to rotate the forearm to place the hand in a desired position to perform different tasks, without interfering with the grasping function of the hand. The ulna is the stable part of the forearm around which the radius rotates; the stability of the distal radioulnar joint is provided by the interaction between ligaments, muscles and bones. The stabilizing structures are the triangular fibrocartilage complex, the ulnocarpal ligament complex, the extensor carpi ulnaris tendon and tendon sheath, the pronator quadratus, the interosseous membrane and ligament, the bone itself and the joint capsule. The purpose of this review article is to present and illustrate the current understanding of the functional anatomy and pathomechanics of this joint.

Minimally invasive stabilization of the distal radioulnar joint: a cadaveric study

This study describes a minimally invasive procedure for stabilization of the distal radioulnar joint, using a suture-button construct placed percutaneously in the direction of the distal oblique bundle in the distal interosseous membrane. In five cadaveric specimens, placement of the suture-button suspension system reduced dorsal displacement of the radius in an unstable distal radioulnar joint to baseline values, both in neutral position and in pronation and supination. These results indicate the possibility of minimally invasive treatment for distal radioulnar joint instability.

Suture button reconstruction of the central band of the interosseous membrane in Essex-Lopresti lesions: a comparative biomechanical investigation

Surgical reconstruction of the interosseous membrane may restore longitudinal forearm stability in Essex-Lopresti lesions. This study aimed to compare the longitudinal stability of the intact forearm with a single-bundle and a double-bundle reconstruction of the central band of the interosseous membrane using digital image correlation with a three-dimensional camera system. Single and cyclic axial loading of eight fresh-frozen forearm specimens was carried out in the intact state, after creation of an Essex-Lopresti lesion, after a single-bundle and after a double-bundle reconstruction of the central band using a TightRope^® (Arthrex GmbH, Munich, Germany) construct. Instability significantly increased after creation of an Essex-Lopresti lesion. The stability of intact specimens was similar to both reconstruction techniques. The results of this study suggest that TightRope^® reconstruction of the central band restores longitudinal forearm stability. However, the single-bundle technique may be less reliable than double-bundle reconstruction.

LEVEL OF EVIDENCE

Basic Science Study.

[Treatment of traumatic ulnar styloid impaction syndrome by Sauvé-Kapandji procedure]

Objective

To evaluate the effectiveness of Sauvé-Kapandji procedure in the treatment of traumatic ulnar styloid impaction syndrome.

Methods

Between June 2010 and January 2013, 12 patients with traumatic ulnar styloid impaction syndrome were treated by Sauvé-Kapandji procedure. There were 4 men and 8 women, with an average age of 58.9 years (range, 50-69 years). The disease was caused by traffic accident in 1 case, and by falling from height in 11 cases. All patients had dislocation of the distal radioulnar joint, and 7 patients also had old fractures of the distal radius. The main clinical symptoms were pain and limited activity of the wrist joint, and the disease duration was 2-4 months (mean, 3.5 months). The visual analogue scale (VAS) was 6.2±1.4. The clinical outcomes were assessed by VAS, range of motion (ROM) of the wrist, grip strength, Evans score, and X-ray film of wrist joint during follow-up.

Results

All patients obtained healing of incision by first intention and were followed up 37-73 months (mean, 58.4 months); no complication of infection, blood vessel injury, or nerves injury occurred. VAS was 1.2±1.0 at the final follow-up, showing significant difference when compared with preoperative one ( t=9.950, P=0.000). The ROM of the affected wrist joint in flexion, extension, ulnar deviation, forearm pronation and supination were improved, but the ROM of the affected side were significantly less than those of normal side ( P<0.05). No significant difference was found in the grip strength and Evans score between the affected side and normal side ( t=-0.885, P=0.386; t=-1.969, P=0.062). According to Evans scores, the results were excellent in 8 cases, good in 3 cases, and fair in 1 case, with an excellent and good rate of 91.7%. Postoperative radiographs showed bony healing in all patients, with the average healing time of 3.5 months (range, 3-6 months). The instability of proximal ulna occurred in 3 cases.

Conclusion

Sauvé-Kapandji procedure is a reliable remedy method for traumatic ulnar styloid impaction syndrome, with favorable improvement in wrist pain and forearm rotation. However, the surgical indications for Sauvé-Kapandji procedure should be strictly controlled.

Patients with triangular fibrocartilage complex injuries and distal radioulnar joint instability have reduced rotational torque in the forearm

A total of 20 patients scheduled for wrist arthroscopy, all with clinical signs of rupture to the triangular fibrocartilage complex and distal radioulnar joint instability, were tested pre-operatively by an independent observer for strength of forearm rotation. During surgery, the intra-articular pathology was documented by photography and also subsequently individually analysed by another independent hand surgeon. Arthroscopy revealed a type 1-B injury to the triangular fibrocartilage complex in 18 of 20 patients. Inter-rater reliability between the operating surgeon and the independent reviewer showed absolute agreement in all but one patient (95%) in terms of the injury to the triangular fibrocartilage complex and its classification. The average pre-operative torque strength was 71% of the strength of the non-injured contralateral side in pronation and supination. Distal radioulnar joint instability with an arthroscopically verified injury to the triangular fibrocartilage complex is associated with a significant loss of both pronation and supination torque.

LEVEL OF EVIDENCE

Case series, Level IV.

Interosseous membrane reconstruction with a suture-button construct for treatment of chronic forearm instability

BACKGROUND

The purpose of this study was to report outcomes of interosseous membrane (IOM) reconstruction with a suture-button construct for treatment of chronic longitudinal forearm instability.

METHODS

We performed a retrospective review with prospective follow-up of patients who underwent ulnar shortening osteotomy and IOM reconstruction with the Mini TightRope device from 2011 through 2014. Bivariate statistical analysis was used for comparison of preoperative and postoperative Quick Disabilities of the Arm, Shoulder, and Hand (QuickDASH) scores, range of motion, grip strength, and ulnar variance. Complications and patient satisfaction were also recorded.

RESULTS

Ten patients (mean age, 45.3 years) satisfied inclusion criteria: 8 treated for post-traumatic sequelae of Essex-Lopresti-type injuries, 1 for forearm instability secondary to previous elbow surgery, and 1 for instability secondary to trauma and multiple elbow surgeries. Surgeries were performed an average of 28.6 months from initial injury. At mean follow-up of 34.6 months after surgery, significant improvement was observed in elbow flexion-extension arc (+23° vs. preoperatively; P = .007), wrist flexion-extension arc (+22°; P = .016), QuickDASH score (-48; P = .000), and ulnar variance (-3.3 mm; P = .006). Three patients required additional surgery: 1 revision ulnar shortening osteotomy for persistent impingement, 1 revision ulnar osteotomy and Mini TightRope removal for lost forearm supination, and 1 fixation of a radial shaft fracture after a fall.

CONCLUSION

IOM reconstruction using a suture-button construct is an effective treatment option for chronic forearm instability.

Anatomic Relationships of the Distal and Proximal Radioulnar Joints Articulating Surface Areas and of the Radius and Ulna Bone Volumes - Implications for Biomechanical Studies of the Distal and Proximal Radioulnar Joints and Forearm Bones

Background

Previous work from this laboratory has evidenced the biomechanical role of forearm osseoligamentous structures in load transfer of applied forces. It has shown that forces transmitted across the distal radioulnar joint (DRUJ) and proximal radioulnar joint (PRUJ) are similar, though not identical, under axial loading conditions. The purpose of the study was to assess the articulating surface areas of the radioulnar joints and the volumes of the forearm bones addressing the hypothesis that there may be anatomic adaptations that reflect the biomechanical function of the integrated forearm unit.

Methods

The articulating surface areas of PRUJ and DRUJ were assessed using a laser scanner in 24 cadaver forearms. The articulating joint surfaces were additionally delineated from standardized photographs assessed by three observers. The surface areas of matched pairs of joints were compared on the null hypothesis that these were the same within a given forearm specimen. An additional 44 pairs of matched forearm bone volumes were measured using water displacement technique and again compared through statistical analysis (paired sample t-test and Bland–Altman analysis).

Results

The findings of this study are that the articulating surface areas of the DRUJ and PRUJ as well as the bone volumes are significantly different and, yet, strongly correlated. The paired sample t-test showed a significant difference between the surface areas of the DRUJ and PRUJ (p < 0.05). The PRUJ articulating surface area was marginally larger than the DRUJ with a PRUJ:DRUJ ratio of 1.02. Paired sample t-test showed a significant difference between the two bone volumes (p < 0.01) with a radius to ulna bone volume ratio of 0.81. When the olecranon was disregarded, radius volume was on average of 4% greater than ulna volume.

Conclusion

This study demonstrates and defines the anatomical relationships between the two forearm bones and their articulating joints when matched for specimen. The data obtained are consistent with the theory of integrated forearm function generated from published biomechanical studies.

The Effect of Radial Head Hemiarthroplasty Geometry on Proximal Radioulnar Joint Contact Mechanics

PURPOSE

To compare the joint contact area and peak contact stress of different radial head (RH) hemiarthroplasty articular profiles for the proximal radioulnar joint (PRUJ) to the native radial head with the hypothesis that the side radius and side angle closest to the native mating ulnar articular profile would provide the best contact mechanics.

METHODS

Finite element models generated from the computed tomography geometry of 14 native elbows (73 ± 17.5 years) were subjected to 12 different RH profiles having varying side radii (flat [r = ∞ mm], 16.25, 8.12, and 4.50 mm) and side angles (0°, 5°, and 10°) under a constant compressive 20-N medial load. Contact areas and peak contact stresses were computed and compared with the native joint.

RESULTS

On average, RH implants significantly reduced PRUJ contact area by 55% ± 16% and increased peak contact stress by 337% ± 241% compared with the native RH. The prosthesis side radius had significant effects on both contact area and stress, but side angle did not. The 16.25-mm radii produced the largest contact areas, and the 4.50-mm radius model generated the smallest contact areas. As the side radius was decreased, peak contact stress was reduced as the contact migrated toward the center of the native ulnar articulation, although the 8.12-mm radius achieved the lowest peak contact stress.

CONCLUSIONS

Whereas RH hemiarthroplasty side radius can affect both contact area and peak contact stress, the magnitude of the effect on contact area is relatively small compared with that of the peak contact stress. Furthermore, although a flat RH side profile with a side angle of 5° more closely matched the side profile of the native ulnas used in the present study, the optimal profile was found to be a smaller radius of 8.12 mm.

CLINICAL RELEVANCE

Optimizing PRUJ contact mechanics after metallic RH hemiarthroplasty may contribute to better clinical outcomes by reducing the potential for native cartilage degeneration.

In-vivo three-dimensional measurement of distal radioulnar joint translation in normal and clinically unstable populations

Assessment of distal radioulnar joint instability is clinically difficult and subjective. The distal radioulnar joint is postulated to 'tighten' in ulnar/radial deviation and pronation/supination. Using a rig, we measured mean distal radioulnar joint translation in neutral forearm rotation and neutral wrist radial and ulnar deviation, as well as extremes of wrist radial and ulnar deviation and forearm rotation. We tested the rig on ten cadaver forearms to validate the measurements we made. We tested 50 normal adults and 50 patients with clinical distal radioulnar joint instability. Distal radioulnar joint stability in men and women and on contralateral sides were comparable. Distal radioulnar joint translation decreased significantly with wrist radial and ulnar deviation and forearm pronation and supination, matching clinical practice and further validating the rig. The data in normal patients is comparable with previous computed tomography-based studies. Translation in all positions was statistically increased within the clinical instability group and did not cross-over with the normal ranges. Distal radioulnar joint translation is a physically measurable phenomenon. Our device appears to be a valid test of distal radioulnar joint translation, establishing normal data in vivo.

LEVEL OF EVIDENCE

III.

The transverse force experienced by the radial head during axial loading of the forearm: A cadaveric study

BACKGROUND

When designing a radial head replacement, the magnitude and direction of forces applied across the proximal radio-ulnar joint (PRUJ) and the radiocapitellar joint must be included. These designs often focus on axial loads transmitted to the radial head by the capitellum; however, the radial head also bears a significant transverse force at the PRUJ. Load transmission by the central band of the interosseous ligament induces a force component in a lateral direction perpendicular to the axis of the limb, which is borne by the articular surfaces of the proximal and distal radio-ulnar joints. The objective of this study is to establish the relationship between distally applied axial forces and proximal transverse reaction forces.

METHODS

Five cadaveric, human forearms with intact interosseous membranes were used to measure the magnitude of transversely-directed forces experienced by the radial head during axial loading of the forearm at the lunate fossa. A Mark-10 test stand applied a gradual and continuous axial load on the articular surface of the distal radius. A Mark-10 force gauge measured the resultant transverse force experienced by the radial head in the proximal radioulnar joint. Classical mechanics and static force analysis were applied in order to predict lateral force values that would occur when the interosseous ligament is treated as the major load transmitter between the radius and ulna.

FINDINGS

Acquired data show that the radial head bears a force in the transverse direction that averages 18% (SD 3.89%) in magnitude of the axial force applied at the wrist. This figure is in close accordance with the predicted value of 22% that was calculated by way of free-body plotting.

INTERPRETATION

Physiologic forearm loading results in a clinically significant transverse force component transmitted through the interosseous ligament complex. The existence of transverse forces in the human forearm may explain clinical problems seen after radial head resection and suggest that radial head implants be designed to sustain substantial transverse forces.

LEVEL OF EVIDENCE

Basic science study, anatomical.

Intraoperative Physical Examination for Diagnosis of Interosseous Ligament Rupture-Cadaveric Study

PURPOSE

To study the intraobserver and interobserver reliability of the diagnosis of interosseous ligament (IOL) rupture in a cadaver model.

METHODS

On 12 fresh frozen cadavers, radial heads were cut using an identical incision and osteotomy. After randomization, the soft tissues of the limbs were divided into 4 groups: both IOL and triangular fibrocartilage (TFCC) intact; IOL disruption but TFCC intact; both IOL and TFCC divided; and IOL intact but TFCC divided. All incisions had identical suturing. After standard instruction and demonstration of radius pull-push and radius lateral pull tests, 10 physician evaluators with different levels of experience examined the cadaver limbs in a standardized way (elbow at 90° with the forearm held in both supination and pronation) and were asked to classify them into one of the 4 groups. Next, the same examiners were asked to re-examine the limbs after randomly changing the order of examination.

RESULTS

The interobserver reliability of agreement for the diagnosis of IOL injury (groups 2 and 3) was fair in both rounds of examination and the intraobserver reliability was moderate. The intra- and interobserver reliabilities of agreement for the 4 groups of injuries among the examiners were fair in both rounds of examination. The sensitivity, specificity, accuracy, positive, and negative predictive values were all around 70%. The likelihood of a positive test corresponding with the presence of IOL rupture (positive likelihood ratio) was 2.2. The likelihood of a negative test correctly diagnosing an intact IOL was 0.40.

CONCLUSIONS

In cadavers, intraoperative tests had fair reliability and 70% accuracy for the diagnosis of IOL rupture using the push-pull and lateral pull maneuvers. The level of experience did not have any effect on the correct diagnosis of intact versus disrupted IOL.

CLINICAL RELEVANCE

Although not common, some failure of surgeries for traumatic elbow fracture-dislocations is because of failure in timely diagnosis of IOL disruption.

The Effect of Elbow Extension on the Biomechanics of the Osseoligamentous Structures of the Forearm

PURPOSE

To investigate the hypothesis that elbow extension alters the biomechanics of forearm rotation including force transmission in the distal and proximal radioulnar joints (DRUJ and PRUJ) and the interosseous ligament (IOL).

METHODS

A cadaver model with a custom-designed jig was used to measure forearm pronosupination ranges, transmitted forces and contact areas across the PRUJ and DRUJ, and tension in the 3 main components of the IOL's central band. Testing with applied loads was undertaken throughout pronosupination with the elbow fully flexed (n = 15) and fully extended (n = 11).

RESULTS

Elbow extension-flexion affected the range of forearm pronosupination, shifting the arc of rotation such that the forearm supinated maximally with the elbow flexed and pronated maximally with the elbow extended. Elbow extension also increased transmitted forces across the DRUJ and PRUJ while also increasing contact areas within the DRUJ and PRUJ. Elbow extension significantly increased tension in the central band of the IOL when the forearm was maximally pronated.

CONCLUSIONS

Maximum supination occurred with the elbow flexed. Maximum pronation occurred with it extended. Elbow position altered forearm biomechanics, including force transmission across the PRUJ and DRUJ and transmitted tension in the IOL.

CLINICAL RELEVANCE

The interplay of osseoligamentous forearm structures is such that we would anticipate surgical alteration of any one of them to have effects upon function of the others.