Automatic identification of radius and ulna bone landmarks on 3D virtual models.

BACKGROUND: For bone morphology and biomechanics analysis, landmarks are essential to define position, orientation, and shape. These landmarks define bone and joint coordinate systems and are widely used in these research fields. Currently, no method is known for automatically identifying landmarks on virtual 3D bone models of the radius and ulna. This paper proposes a knowledge-based method for locating landmarks and calculating a coordinate system for the radius, ulna, and combined forearm bones, which is essential for measuring forearm function. This method does not rely on pre-labeled data. VALIDATION: The algorithm is validated by comparing the landmarks placed by the algorithm with the mean position of landmarks placed by a group of experts on cadaveric specimens regarding distance and orientation. RESULTS: The median Euclidean distance differences between all the automated and reference landmarks range from 0.4 to 1.8 millimeters. The median angular differences of the coordinate system of the radius and ulna range from -1.4 to 0.6 degrees. The forearm coordinate system's median errors range from -0.2 to 2.0 degrees. The median error in calculating the rotational position of the radius relative to the ulna is 1.8 degrees. CONCLUSION: The automatic method's applicability depends on the use context and desired accuracy. However, the current method is a validated first step in the automatic analysis of the three-dimensional forearm anatomy.

The effect of the interosseous ligament and selected antebrachiocarpal ligaments on rotation of the radius during extension of the carpus.

OBJECTIVE: To evaluate the effect of the interosseous ligament and selected antebrachiocarpal ligaments on the internal rotation of the radius relative to the ulna, during carpal extension. STUDY DESIGN: Cadaveric study. SAMPLE POPULATION: Twenty-four cadaveric canine forelimbs. METHODS: Twenty-four forelimbs were disarticulated at the elbow joint and the antebrachia were prepared for testing. The forelimbs were divided to 6 groups, defined by the order in which ligaments were transected. All specimens were tested intact and after transecting each of the ligaments with the order defined by the group. Rotation of the radius relative to the ulna, caused by extension of the carpus, was measured using a sensor connected to the radius. RESULTS: The mean(±sd) maximum internal rotation of the radius (5.94° ± (1.23°)) with all the ligaments intact was significantly greater (p < 0.012) than the mean(±sd) maximum internal rotation of the radius (3.13° (± 1.13°)) after transecting the interosseus ligament. Transecting the interosseous ligament subsequent to one of the other ligaments caused a decrease in internal radial rotation (p = 0.629), while, transecting the short radial collateral ligament caused an increase in radial rotation (p = 0.629). Transecting the palmar radiocarpal and ulnocarpal ligaments had no effect on radial rotation. CONCLUSION: The interosseous ligament was stretched with internal rotation of the radius due to carpal extension. Carpal flexion resulted in external rotation of the radius. This effect was lost when the interosseus ligament was transected. CLINICAL SIGNIFICANCE: Rotation of the radius is associated with carpal extension, and is likely an intrinsic part of forelimb biomechanics.

Kinematics of the Feline Antebrachiocarpal Joint from Supination to Pronation.

OBJECTIVE: Cats rely on their forelimb mobility for everyday activities including climbing and grooming. Supination and pronation of the forelimb in cats are considered to primarily involve the antebrachium, rather than the carpus. Therefore, our null hypothesis was that there would be no movement of the carpal bones (radial carpal bone, ulnar carpal bone and accessory carpal bone) relative to the ulna during supination and pronation. STUDY DESIGN: Eight feline cadaveric forelimbs were rotated from supination to pronation in a jig and computed tomography was performed in the neutral, supinated and pronated positions. The individual carpal bones were segmented from computed tomography images of the supinated and pronated scans in each of the eight specimens. A feline ulna coordinate system was established and used to quantify the translations and rotations between bones of the proximal carpal row and antebrachium. RESULTS: After the carpus was rotated from the initial supinated position into pronation, there was significant translation (x, y and z axes) and rotation (x and y axes) of the proximal row of carpal bones based on absolute magnitude values. Given the differences in translations and rotations of the proximal row of carpal bones, our null hypothesis was rejected. CONCLUSION: The proximal row of carpal bones translate and rotate independently from the ulna in the cat during pronation of the antebrachium. This may have future implications in the diagnosis and management of feline carpal injuries involving the antebrachiocarpal joint.

Age and gender related differences in load-strain response in C57Bl/6 mice.

We examined the changes in mechanical strain response of male and female mouse tibia and ulna, using axial compression tests, to assess age-related changes in tibiae and ulnae by a non-contact strain measurement technique called the digital image correlation (DIC) and the standard strain gage. A unique aspect of the study was to compare bones from the same animal to study variations in behavior with aging. This study was conducted using male and female C57Bl/6 mice at 6, 12 and 22 months of age (N=6-7 per age and sex) using three load levels. The DIC technique was able to detect a greater number of statistically significant differences in comparison to the strain gaging method. Male ulna showed significantly higher DIC strains compared to strains captured from strain gage at all three levels of load at 6 months and in the lowest load at 12 months. DIC measurements revealed that the ulna becomes stiffer with aging for both males and females, which resulted in 0.4 to 0.8 times reduced strains in the 22-month group compared to the 6 month group. Male tibia showed three-fold increased strains in the 22 months group at 11.5 N load compared to 6 months group (p<.05).

Force Distribution in the Canine Proximal Radio-Ulnar Joint on Extension of the Carpal Joint: A Cadaveric Study.

OBJECTIVE: The aim of this study was to measure the load on the lateral and medial aspects of the proximal radio-ulnar joint during extension of the carpus. STUDY DESIGN: This was an ex vivo biomechanical study. SAMPLE POPULATION: Twenty-two cadaveric Greyhound thoracic limbs were used. METHODS: Twenty-two paired thoracic limbs were used. The olecranon was attached to a custom jig with the foot resting on a stationary anvil. Load sensors were inserted into the proximal radio-ulnar joint, between the radial head and the lateral coronoid process, and between the radial head and the medial coronoid process. Specimens were tested under compression with measurements taken at 0, 4, 9 and 13.5 mm of axial displacement. Data collected at each point included forces on the specimen and medial and lateral coronoid processes as well as the angle of carpal joint extension. RESULTS: A linear mixed effects model relating load on the specimen and carpal joint extension angle had an R-squared value of 0.66, and load at the level of the medial coronoid process and angle of carpal extension had an R-squared value of 0.61. There was a significant difference in the loads measured on the lateral and medial coronoid processes at all angles (p < 0.0001). CONCLUSION: Extension of the carpus results in asymmetric loading of the proximal radio-ulnar joint. CLINICAL SIGNIFICANCE: The findings of this study show that loading of the medial coronoid process may be more complex than originally thought and supports the future investigation of novel management and therapeutic options for affected patients.

Impact of reference point selection on DXA-based measurement of forearm bone mineral density.

Few studies have systematically evaluated the technical aspects of forearm bone mineral density (BMD) measurement. We found that BMD remained stable regardless of the reference point; however, the ROI identified was not always consistent. Our study highlights the importance of using the same reference point for serial measurements of forearm BMD. BACKGROUND: Forearm fractures are clinically important outcomes from the perspective of morbidity, health care costs, and interruption of work. BMD of the forearm, as derived by dual-energy x-ray absorptiometry (DXA), is a better predictor of fracture at the forearm compared with BMD measured at other sites. However, very few studies have evaluated the technical aspects of selecting the ROI for forearm BMD measurement. This study aimed to compare the BMD values measured at the 1/3 radius site using three different reference points: the ulnar styloid process, the radial endplate, and the bifurcation of the ulna and radius. METHODOLOGY: Healthy Chinese patients participating in the control group of an ongoing study at Zhejiang Provincial People's Hospital were recruited for this study. For each patient, a DXA scan (GE Lunar Prodigy) of the forearm was performed and BMD values were separately calculated using each of the three reference points to identify the ROI. Pearson correlation coefficients were calculated to examine the correlation between the BMD measures derived from each reference point. The F test and independent t test were applied for more robust analysis of the differences in the variances and means. RESULTS: Sixty-eight healthy Chinese volunteers agreed to participate in this study. The root mean square standard deviation (RMS-SD) percentages of BMD values measured at the 1/3 radius site were 2.19%, 2.23%, and 2.20% when using the ulnar styloid process, radial endplate, and the bifurcation of the ulna and radius as the reference points, respectively. Pearson's correlation coefficients for all pairwise comparisons among these three groups were greater than 0.99. F tests and independent t tests showed p values ranging from 0.92 to 0.99. However, we observed that among 10% of patients, choosing an ROI at the ulnar styloid process led to an inability to accurately determine the BMD at the ultra-distal radius. CONCLUSIONS: Given equal ability to determine BMD at the 1/3 radius accurately, the radial endplate or the bifurcation of the ulna and radius should be preferentially selected as the reference point for routine forearm BMD measurements in order to avoid situations in which the ultra-distal radius BMD cannot be determined.

A geometric framework for the estimation of joint stiffness of the human wrist.

Estimating joint stiffness is of paramount importance for studying human motor control and for clinical assessment of neurological diseases. Usually stiffness estimation is performed using cumbersome instrumentations (e.g. robots), and by approximating robot joint angles and torques to the human ones. This paper proposes a methodology and an experimental setup to measure wrist joint stiffness in unstructured environments, with the twofold aim of: 1) providing a geometric framework in order to derive angular displacements and torques at the wrist Flexion/Extension (FE) and Radial/Ulnar Deviation (RUD) axes of rotation, using a subject specific kinematic model; 2) suggesting an experimental setup made of two portable sensors for motion tracking and one load cell, to allow for measurements in out-of-the-lab scenarios. We tested our method on a hardware mockup of wrist kinematics, providing a ground truth for estimated angles and torques at FE and RUD joints. The experimental validation showed average absolute errors in FE and RUD angles of 0.005 rad and 0.0167 rad respectively, and an average error of FE and RUD torques of 0.006 Nm and 0.003 Nm.

Evolution of the Ring Concept for the Forearm and Its Implication on Treatment: From Galeazzi, Monteggia, Essex-Lopresti, and Darrach to the Current Era.

Geometrically, rings distribute their stress along their arc instead of concentrating at any one point. The forearm ring is composed of the radius, ulna, proximal radioulnar joint, and distal radioulnar joint. The annular ligament, interosseous membrane, and triangular fibrocartilage complex link and stabilize the ring. Injuries to the forearm occur along a continuum with recognized patterns of ring disruption, including Galeazzi, Monteggia, and Essex-Lopresti injuries. The Darrach procedure causes a disruption to the forearm ring and can lead to painful convergence between the radius and distal ulnar stump. Injuries to the forearm ring are unstable. Management of forearm injuries is centered on the restoration of the anatomy and stability of the forearm ring. Forearm ring injuries and their treatment are discussed in this article.

Automated robot-assisted assessment for wrist active ranges of motion.

The measurement of wrist active range of motion (ROM) is essential for determining the progress of hand functional recovery, which can provide insight into quantitative improvements and enable effective monitoring during hand rehabilitation. Compared with manual methods, which depend on the experience of the therapist, the proposed robot-assisted assessment technique can measure active ROM of human wrists. The robot with a reconfigurable handle design allows for multiple wrist motions. Experiments were conducted with 11 human subjects to measure ROMs of human wrist flexion/extension and radial/ulnar deviation. Reliability analysis was conducted by calculating the intra-class correlation coefficients (ICC), standard error of measurement (SEM) and SEM%. Results showed high reliability (ICC2,1 ≥ 0.89, SEM ≤ 2.36°, SEM% ≤ 6.81%). Future will focus on adaptive joint self-alignment design between human users and robots to further improve its assessment accuracy.

Differences in the Rotation Axes of the Scapholunate Joint During Flexion-Extension and Radial-Ulnar Deviation Motions.

PURPOSE: To determine the location of the rotation axis between the scaphoid and the lunate (SL-axis) during wrist flexion-extension (FE) and radial-ulnar deviation (RUD). METHODS: An established and publicly available digital database of wrist bone anatomy and carpal kinematics of 30 healthy volunteers (15 males and 15 females) in up to 8 different positions was used to study the SL-axis. Using the combinations of positions from wrist FE and RUD, the helical axis of motion of the scaphoid relative to the lunate was calculated for each trial in an anatomical coordinate system embedded in the lunate. The differences in location and orientation between each individual axis and the average axis were used to quantify variation in axis orientation. Variation in the axis location was computed as the distance from the closest point on the rotation axis to the centroid of the lunate. RESULTS: The variation in axis orientation of the rotation axis for wrist FE and RUD were 84.3° and 83.5°, respectively. The mean distances of each rotation axis from the centroid of the lunate for FE and RUD were 5.7 ± 3.2 mm, and 5.0 ± 3.6 mm, respectively. CONCLUSIONS: Based on the evaluation of this dataset, we demonstrated that the rotation axis of the scaphoid relative to the lunate is highly variable across subjects and positions during both FE and RUD motions. The range of locations and variation in axis orientations in this data set of 30 wrists shows that there is very likely no single location for the SL-axis. CLINICAL RELEVANCE: Scapholunate interosseous ligament reconstruction methods focused on re-creating a standard SL-axis may not restore what is more likely to be a variable anatomical axis and normal kinematics of the scaphoid and lunate.

Quantitative assessment of distal radioulnar joint stability with pressure-monitor ultrasonography.

BACKGROUND: Diagnosing distal radioulnar joint (DRUJ) instability remains a challenge as it relies on physical examination. To quantitatively assess DRUJ stability, a pressure-monitor ultrasound system was developed. The objective of this study was to evaluate the force-displacement relationship of DRUJ in normal subjects. METHODS: Nine wrists of 9 asymptomatic volunteers were evaluated. The pressure-monitor ultrasound system was developed to apply pressure to the tissue with a pre-determined cycle and displacement of the transducer. Each subject was imaged sitting with the elbow flexed and forearm pronated. The dorsal surface of the distal radius and the center of the ulnar head were displayed at DRUJ level. The pressure toward palmar direction was applied to the distal ulna with different levels of transducer displacements, i.e., 1 mm, 2 mm, and 3 mm. The distance between the dorsal surface of the ulnar head and the dorsal surface of the distal radius was measured. The first measurement was performed at the initial position, and the second measurement was performed when the transducer pressed down the ulna to the degree that the ulnar head had shifted to the most palmar position. At the same time, the pressure to the transducer was measured. The changes of radioulnar distance (=the measurement at the most palmar position-the measurement at the initial position) and pressure, and pressure/distance ratio were compared among the different transducer displacements. RESULTS: The pressure was significantly increased as the transducer displacement became larger (P < 0.01). The changes of radioulnar distance were smaller in the 1 mm displacement condition compared to the 2 and 3 mm displacement conditions (P < 0.05). The pressure/distance ratio was larger in the 1 mm displacement condition compared to the 2 and 3 mm displacement conditions (P < 0.05). CONCLUSIONS: A method to assess DRUJ stability by measuring changes in radioulnar distance and force application was developed. It was found that the application of 2 mm displacement and 200 g force was the critical stress for the capsuloligamentous structures to start stabilizing DRUJ. This methodology and the indices may be clinically useful to investigate the mechanical properties of patients with DRUJ instability.

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

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

Reliability of Quantitative Assessment of Distal Radioulnar Joint Stability With Force-Monitor Ultrasonography.

The purpose of this study was to evaluate the reliability of ultrasound assessment of the displacement-force relationships for distal radioulnar joint (DRUJ) stability. Non-dominant wrists of 10 healthy male subjects were evaluated by force-monitor ultrasonography. This apparatus was developed to apply cyclic compression to the wrist with pre-determined transducer displacement conditions in the range of 0.1-3.0 mm. The subject's wrist was placed on the table with the forearm in the pronated position. The transducer was placed on the dorsal surface of the distal radius and ulna, perpendicular to the long axis of the forearm. The center of the ulnar head was at the DRUJ level. The distance between the dorsal surface of the distal radius and the ulnar head was measured at an initial and a pressed-down position. Changes in radioulnar displacement, force to the wrist and the displacement/force ratio were evaluated. The measurements were performed independently by two raters. The intra-class correlation coefficients (ICCs) for the radioulnar displacement were 0.76, 0.68, and 0.93, in the 1.0, 2.0, and 3.0 mm transducer displacement conditions, respectively. The ICCs for the force to the wrist were 0.18, 0.67, and 0.34, in different transducer displacement conditions, respectively. The ICCs for the displacement/force ratios were 0.68, 0.67, and 0.97, in different transducer displacement conditions, respectively. The highest ICC for the radioulnar displacement and the displacement/force ratio was observed in the 3.0 mm displacement condition. This assessment of displacement-force relationships may be useful to quantify DRUJ stability. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:2053-2060, 2019.

Contribution of Palmar Radiocarpal and Ulnocarpal Ligaments to the Stability of the Canine Antebrachiocarpal Joint.

OBJECTIVE: The aim of this study was to evaluate the contribution of the palmar radiocarpal ligament and the palmar ulnocarpal ligament to canine antebrachiocarpal joint stability. MATERIALS AND METHODS: The right carpus of four dog cadavers, free of musculoskeletal pathology, was stripped of muscle. Each specimen was placed into a custom-made joint testing machine and tested at 15° extension, and 0° and 15° flexion. A single motion tracking sensor was fixed to the metacarpal bones. All specimens were tested with all ligaments intact and after transection of the palmar radiocarpal and ulnocarpal ligaments. A range of weights between 0.2 and 2.0 kg was used to test the carpi in three directions (axial, medial/lateral and cranial/caudal) and two moments (pronation/supination and valgus/varus). RESULTS: No differences were found between the translations and rotations of the manus relative to the radius and ulna with the ligaments intact and the ligaments transected at any of the carpal angles tested, except at 15° of flexion. Increasing the angle of flexion resulted in a significant increase in cranial and caudal translation of the manus relative to the radius and ulna both in the intact and transected specimens. CLINICAL RELEVANCE: Antebrachiocarpal joint position plays a more important role in craniocaudal antebrachiocarpal joint stability than the palmar radiocarpal and ulnocarpal ligaments.

A new noninvasive mechanical bending test accurately predicts ulna bending strength in cadaveric human arms.

BACKGROUND: High error rates in the prediction of fragility fractures by bone mineral density have motivated searches for better clinical indicators of bone strength, and the high incidence of non-hip, non-spine fractures has raised interest in cortical bone. The aim of this study was to assess the accuracy of Cortical Bone Mechanics Technology™. CBMT is a new non-invasive 3-point bending technique for measuring the mechanical properties of cortical bone in the ulnas of living humans. METHODS: 35 cadaveric human arms were obtained from small women and large men ranging widely in age (17 < Age < 99 years) and body size (14 < BMI < 40 kg/m2). Noninvasive CBMT measurements of the flexural rigidity of the ulna bones within these arms (EICBMT) were compared to measurements of EI by Quasistatic Mechanical Testing in the ulnas excised from those arms (EIQMT). Ulna bending strength was also measured by QMT as the peak moment before fracture (Mpeak). The open source BoneJ plugin to ImageJ image processing software was used to calculate cortical porosity (CP) in micro-computed tomography images of a 2 mm length of the mid-shaft of each fractured ulna, and the interosseous diameter (IOD) of each ulna was also measured in those images. RESULTS: EICBMT measurements (13 < EICBMT < 97 Nm2) explained 99% of the variance in QMT measurements of ulna bending strength (11 < Mpeak < 90 Nm), but EICBMT was biased high by 30% (p < 0.0001) relative to EIQMT (11 < EIQMT < 69 Nm2). After correcting this bias, EICBMT and EIQMT measurements lay along the identity line (y = 1.00x, R2 = 0.99, SEE = 3.1 Nm2). Predictions of Mpeak by EICBMT were less accurate than predictions by EIQMT (both R2 = 0.99; SEECBMT = 5.9 Nm vs SEEQMT = 4.5 Nm, F = 2.92, p = 0.001), but EICBMT predictions were substantially more accurate than those by IOD (R2 = 0.79; SEEIOD = 10.6 Nm, F = 3.30, p < 0.001) and CP (R2 = 0.35; SEECP = 18.9 Nm, F = 10.45, p < 10-9). Predictions by EICBMT were also more accurate than predictions by arm donor height (R2 = 0.63; SEE = 14.3 Nm, F = 5.87, p < 10-6), body weight (R2 = 0.77; SEE = 11.1 Nm, F = 3.54, p < 0.001) and BMI (R2 = 0.64; SEE = 14.1 Nm, F = 2.39, p < 0.01). In forward stepwise multiple regression beginning with EICBMT, only age explained any additional variance in ulna bending strength (ΔR2 = 0.3%, F = 8.03, p = 0.008). CONCLUSION: Noninvasive CBMT measurements of ulna EI explain 99% of individual differences in QMT measurements of ulna bending strength in cadaveric human arms.

Distal Scaphoid Excision in Treatment of Symptomatic Scaphoid Nonunion: Systematic Review and Meta-analysis.

Background: Current treatment options for persistent scaphoid nonunion are limited to salvage procedures such as proximal row carpectomy (PRC) or 4-corner fusion (4CF). Several small studies have demonstrated that distal scaphoid excision may provide a simpler alternative with faster recovery. The purpose of this study was to determine the efficacy of distal scaphoid excision as a treatment option for symptomatic scaphoid nonunion. Methods: The MEDLINE and PubMed databases were searched for the use of distal scaphoid excision in scaphoid nonunions. Studies included reported on either the functional or patient-centered outcomes following distal scaphoid excision for symptomatic scaphoid nonunion. Results: Six articles described the outcomes of 70 patients with an average of 11.7 patients per study. Functional outcomes including flexion-extension arc, radial-ulnar deviation, and grip strength improved by an average of 98.95%, 58.96%, and 131.08%, respectively. Patient-derived outcomes included the Modified Mayo Wrist Score, which improved by 92.6%, and the Disabilities of the Arm, Shoulder and Hand, which improved by 137.17%. An average of 68.75% of patients experience complete relief of pain with 20.83% of patients experiencing pain with strenuous activity. The average postoperative visual analog scale (0-10) was 0.71. On average, 93.33% of patients returned to work with an average time of return being 6.89 weeks. Complete satisfaction was reported by 87.80% of patients. Complications included progression into 4CF or PRC and newly developed midcarpal arthritis. Conclusions: Given favorable outcomes, our analysis suggests that distal scaphoid excision may be a favorable, low-risk treatment for scaphoid nonunion without eliminating more extensive options such as 4CF and wrist arthrodesis.

Biomechanical Analysis of Capsular Repair Versus Arthrex TFCC Ulnar Tunnel Repair for Triangular Fibrocartilage Complex Tears.

Background: This study compares the effectiveness of a peripheral capsular repair with a knotless arthroscopic transosseous ulnar tunnel repair (TR) in restoring distal radioulnar joint (DRUJ) stability and stiffness in the setting of a massive triangular fibrocartilage complex (TFCC) tear. Methods: Eight matched pairs of fresh-frozen cadaveric forearms were tested. Each forearm was tested in supination and pronation using 3-dimensional (3D) optical tracking devices prior to any intervention. Each specimen then underwent a diagnostic wrist arthroscopy and sectioning of the TFCC's deep and superficial fibers. All specimens were then retested to assess instability secondary to the tear. The TFCC was repaired with either a peripheral capsular repair (CR) using three 2-0 polydioxanone sutures or a transosseous ulnar TR using a 2-0 FiberWire, and then retested (statistical significance; P < .05). Results: After TFCC arthroscopic sectioning, all specimens were unstable with a significant increase in translation and a significant decrease in stiffness. TFCC repair with TR resulted in displacement and stiffness similar to the native tissue. CR specimens were found to have significantly greater displacement and significantly decreased stiffness compared with the intact state. Conclusions: Arthroscopic sectioning of the TFCC resulted in DRUJ instability, as measured by stiffness and ulnar translation. TR effectively restored DRUJ stability and demonstrated no significant difference in postoperative stiffness or maximal displacement when compared with the intact specimen in pronation and supination. This study provides biomechanical evidence that an arthroscopic ulnar tunnel technique can restore stability to the DRUJ after a massive TFCC tear.

During forearm rotation the three-dimensional ulnolunate distance is affected more by translation of the ulnar head than change in ulnar variance.

Ulnolunate abutment has been thought to be aggravated by pronation because of an increase in ulnar variance. We hypothesized that the ulnolunate distance might be greater in pronation because the ulnar head is dorsally translated. Twenty-one three-dimensional reconstructions of computed tomographic scans of wrists taken in supination and pronation were investigated. The ulnolunate distance was measured in each position, and the change in ulnolunate distance from supination to pronation was calculated. The changes in ulnar variance from supination to pronation and the amount of translation of the ulnar head were measured directly by superimposing three-dimensional reconstructions. The mean ulnolunate distance in pronation was significantly greater than in supination. There was no significant correlation between the changes in ulnolunate distance and in the ulnar variance. The change in ulnolunate distance had a significant positive linear relationship with the amount of translation of the ulnar head. The change in ulnolunate distance during forearm rotation is determined by the amount of translation of the ulnar head rather than by change in ulnar variance. Level of evidence: IV.

Experimental assessment of biomechanical properties in human male elbow bone subjected to bending and compression loads.

This work discusses the biomechanical testing of 3 elbow bones, namely the humerus, ulna, and radius. There is a need to identify the mechanical properties of the bones at the organ level. The following tests were performed: 3-point bending, fracture toughness, and axial compression. Six sets of whole-bone samples of human male cadaveric humerus, ulna, and radius (age of donor: 35 to 56 years) were tested. The results were analyzed for statistical significance by 2-stage, repeated-measure analysis of variance (ANOVA). The difference between the bending strength of the humerus, ulna, and radius was statistically significant ( P = .001) when compared to one another. However, the fracture toughness and compressive strength were observed to be similar for the 3 bones. The knowledge of mechanical properties of elbow bones can aid in the design of elbow implants and upper limb protection systems, and also allow us to identify criteria for injury. Further, knowledge of the mechanical properties of the elbow bones can aid in calibrating simulations through finite elements analysis.

Finite-element analysis of the mouse proximal ulna in response to elbow loading.

Bone is a mechano-sensitive tissue that alters its structure and properties in response to mechanical loading. We have previously shown that application of lateral dynamic loads to a synovial joint, such as the knee and elbow, suppresses degradation of cartilage and prevents bone loss in arthritis and postmenopausal mouse models, respectively. While loading effects on pathophysiology have been reported, mechanical effects on the loaded joint are not fully understood. Because the direction of joint loading is non-axial, not commonly observed in daily activities, strain distributions in the laterally loaded joint are of great interest. Using elbow loading, we herein characterized mechanical responses in the loaded ulna focusing on the distribution of compressive strain. In response to 1-N peak-to-peak loads, which elevate bone mineral density and bone volume in the proximal ulna in vivo, we conducted finite-element analysis and evaluated strain magnitude in three loading conditions. The results revealed that strain of ~ 1000 µstrain (equivalent to 0.1% compression) or above was observed in the limited region near the loading site, indicating that the minimum effective strain for bone formation is smaller with elbow loading than axial loading. Calcein staining indicated that elbow loading increased bone formation in the regions predicted to undergo higher strain.