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.

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.

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.

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.

Automated objective robot-assisted assessment of wrist passive ranges of motion.

The measurement of wrist passive ranges of motion (ROMs) can provide insight into improvements and allow for effective monitoring during a rehabilitation program. Compared with conventional methods, this study proposed a new robotic assessment technique for measuring passive ROMs of the wrist. The robotic system has a reconfigurable handle structure that allows for multi-dimensional applications of wrist motions. The assessment reliability of this robotic system was analysed on 11 subjects for measuring wrist extension/flexion and radial/ulnar deviation. Preliminary data demonstrated its potential with intraclass correlation coefficient (ICC2,1) all greater than 0.857 and standard error of measurement (SEM) less than 3.38°. Future work will focus on the standardization of the assessment protocol of this robotic system for assessment purposes, paving the way for its clinical application.

Assessment of radial and ulnar torsion profiles with cross-sectional magnetic resonance imaging. A study of volunteers.

BACKGROUND: We determined whether the torsion profiles of the radius and ulna could be reliably assessed with cross-sectional magnetic resonance imaging and whether these torsion profiles were comparable on the two sides of volunteers. METHODS: We assessed magnetic resonance imaging cross sections of the left and right forearms of twenty-four asymptomatic volunteers. The torsion profile of the ulna was defined as the angle formed between a line tangential to the volar cortical surface of the distal part of the humerus and a line connecting the center of the ulnar head and the center of the ulnar styloid. Use of paired proximal and distal landmarks resulted in five different methods of assessment of the radial torsion profile. Intrarater and interrater reliabilities and side-to-side variability were assessed. RESULTS: This method of assessment of the ulnar torsion profile had intraclass and interclass coefficients of 0.95 and 0.91, respectively. A method previously described by Bindra et al. had the best combined intrarater and interrater reliabilities for assessment of the radius. The mean differences between the right and left sides of the volunteers were the lowest with the use of these two methods; nevertheless, the maximum side-to-side difference was > 30 degrees with techniques. CONCLUSIONS: Torsion-profile assessment with cross-sectional magnetic resonance imaging had high intrarater and interrater reliabilities. However, individual side-to-side variations in the radial and ulnar profiles are important considerations. CLINICAL RELEVANCE: Cross-sectional magnetic resonance imaging is currently the only available method to quantify rotational malunion of the radius and ulna. Its low side-to-side reliability warrants comparison between the imaging results and the clinical findings. A side-to-side difference in the rotation profile may serve as a reason to perform an axial osteotomy when the results of the clinical and magnetic resonance imaging assessments are consistent with each other.

Assessment of forearm volumetric bone mineral density from standard areal densitometry data.

The common bone density measurement procedures produce areal bone mineral density data (BMD) alone. Volumetric bone density is thought to offer a different diagnostic perspective and is usually measured by peripheral quantitative computed tomography. We developed a calculation procedure for radial and ulnar volumetric densities based on single X-ray absorptiometry. The study consisted of 418 healthy Bulgarian females (ages 20 83 yr). Forearm bone density was measured on a DTX-100 densitometer at the 8-mm distal site, and the total volumetric bone densities of radius and ulna were calculated. The accuracy error determined on cadaveric bones was 10 14%. The in vivo precision error was 1.0 1.1%. Age-matched reference curves for volumetric BMD (vBMD) were built. Peak values were registered in the age 30 34 group: 0.403 (radius) and 0.469 g/cm(3) (ulna). Ulnar volumetric density exceeded the radial one, representing an interesting finding to be further investigated. For the age 70 74 group, vBMD was reduced by approx 30% compared with the age 30 34 group. Our data confirmed the fact that volumetric density was much less affected by age and menopause. Correlations between forearm vBMD and axial BMD were moderate. The proposed calculation procedure could become an extra option in forearm bone densitometry to be applied in pediatric populations or adults of extremely large or small body size.

Assessment of ulnar variance: a radiological investigation in a Dutch population.

OBJECTIVE: A radiological study was performed to evaluate ulnar variance in 68 Dutch patients using an electronic digitizer compared with Palmer's concentric circle method. Using the digitizer method only, the effect of different wrist positions and grip on ulnar variance was then investigated. Finally the distribution of ulnar variance in the selected patients was investigated also using the digitizer method. DESIGN AND PATIENTS: All radiographs were performed with the wrist in a standard zero-rotation position (posteroanterior) and in supination (anteroposterior). Palmer's concentric circle method and an electronic digitizer connected to a personal computer were used to measure ulnar variance. The digitizer consists of a Plexiglas plate with an electronically activated grid beneath it. A radiograph is placed on the plate and a cursor activates a point on the grid. Three plots are marked on the radius and one plot on the most distal part of the ulnar head. The digitizer then determines the difference between a radius passing through the radius plots and the ulnar plot. RESULTS AND CONCLUSIONS: Using the concentric circle method we found an ulna plus predominance, but an ulna minus predominance when using the digitizer method. Overall the ulnar variance distribution for Palmer's method was 41.9% ulna plus, 25.7% neutral and 32.4% ulna minus variance, and for the digitizer method was 40.4% ulna plus, 1.5% neutral and 58.1% ulna minus. The percentage ulnar variance greater than 1 mm on standard radiographs increased from 23% to 58% using the digitizer, with maximum grip, clearly demonstrating the (dynamic) effect of grip on ulnar variance. This almost threefold increase was found to be a significant difference. Significant differences were found between ulnar variance when different wrist positions were compared.

Right versus left symmetry of ulnar variance. A radiographic assessment.

One hundred skeletally mature healthy volunteers underwent standardized bilateral posteroanterior radiographs in unloaded (static) and loaded (dynamic) conditions to determine the symmetry of ulnar variance. The mean age was 32 +/- 9 years (range, 19-61 years), with 58 women and 42 men. Ulnar variance was measured to the closest 0.5 mm using the method of perpendiculars. Three separate measurements were made of each radiograph in a blinded fashion by the same investigator. An intraobserver standard deviation of 0.21 was used to calculate a 95% tolerance interval of 0.7 mm (rounded up to 1 mm) as a measure of significance. The average static ulnar variance was -0.13 +/- 1.5 mm on the left and -0.29 +/- 1.6 mm on the right. The average dynamic ulnar variance was 0.93 +/- 1.5 mm on the left and 0.82 +/- 1.5 mm on the right. When compared individually, there was a greater than or equal to 1 mm side to side difference in 37% of volunteers under static and 38% under dynamic conditions. There were no significant correlations between ulnar variance measurements and patient age, gender, race, or handedness. Use of the normal wrist radiograph as a baseline for static radial length measurements is valid in only 63% of cases.

Anteroposterior and lateral spinal DXA for the assessment of vertebral body strength: comparison with hip and forearm measurement.

Spinal bone mineral density (BMD) is traditionally measured by dual-energy X-ray absorptiometry (DXA) in the anteroposterior (AP) projection which includes both the vertebral body and the posterior elements in the measurement. The posterior elements, however, contribute little to the compressive strength of the spine. It has therefore been suggested that spinal BMD measured in the lateral projection, including only the vertebral body in the measurement, might be more appropriate for the prediction of fracture risk. To date little clinical evidence has been presented to support this assumption. To address the issue, we measured vertebral, hip and forearm BMD in situ in 14 human cadavers and remeasured BMD in vitro in excised vertebrae. Lateral spinal measurements were performed in the decubitus position. Fracture force and other biomechanical measures were determined for 32 vertebrae in a mechanical testing machine and compared with BMD values in situ and in vitro. Correlations of BMD with vertebral fracture force were r = 0.48/0.51 (in situ/in vitro) for the AP spinal measurements, r = 0.45/0.71 (in situ/in vitro) for the lateral spinal measurements, and r = 0.64 and r = 0.53 for total hip and forearm measurements in situ, respectively. Thus, despite an apparent diagnostic advantage in vitro, lateral spinal BMD measurement was not superior to AP measurement when performed in situ. This observation corresponds well with previous clinical findings and is probably due to the larger accuracy error in the lateral than in the AP projection resulting from a lower ratio of bone to soft tissue. The high correlation between hip BMD and vertebral fracture force suggests that hip measurement may prove as useful for vertebral fracture risk assessment as spinal measurement in any projection, especially in the elderly with a high prevalence of degenerative changes in the spine.

In vivo assessment of forearm bone mass and ulnar bending stiffness in healthy men.

The cross-sectional bending stiffness EI of the ulna was measured in vivo by mechanical resistance tissue analysis (MRTA) in 90 men aged 19-89 years. MRTA measures the impedance response of low-frequency vibrations to determine EI, which is a reflection of elastic modulus E and moment of inertia I for the whole ulna. EI was compared to conventional estimates of bone mineral content (BMC), bone width (BW), and BMC/BW, which were all measured by single-photon absorptiometry. Results obtained from the nondominant ulna indicate that BW increases (r = 0.27, p = 0.01) and ulnar BMC/BW decreases (r = -0.31, p < or = 0.005) with age. Neither BMC nor EI declined with age. The single best predictor of EI was BW (r2 = 0.47, p = 0.0001), and further small but significant contributions were made by BMC (r2 = 0.53, p = 0.0001) and grip strength (r2 = 0.55, p = 0.0001). These results suggest that the resistance of older men to forearm fracture is related to age-associated changes in the moment of inertia achieved by redistributing bone mineral farther from the bending axis. We conclude that the in vivo assessment of bone geometry offers important insights to the comprehensive evaluation of bone strength.

Noninvasive assessment of ulnar bending stiffness in women.

The load-carrying capacity of cortical bone is closely related to its geometry and to its fundamental material properties, including mineral content (BMC). Together these determine the bending stiffness EI, where I is the cross-sectional moment of inertia and E is Young's modulus of elasticity. To assess the relationship of BMC and bone width (BW) to EI in healthy women, we used mechanical response tissue analysis (MRTA), a noninvasive method that involves analysis of tissue responses to ulnar vibration. A total of 48 healthy women were enrolled into an older (64 +/- 1y, n = 25) and a younger (25 +/- 0.6y, n = 23) group. BMC and BW of the dominant ulna were measured by single-photon absorptiometry (SPA). EI was determined by MRTA. BMC (0.75 +/- 0.02 versus 0.63 +/- 0.02 g/cm), BMC/BW (0.75 +/- 0.02 versus 0.63 +/- 0.02 g/cm2), and EI (27.7 +/- 1.3 versus 21.3 +/- 1.1 N.m2) were significantly greater (p less than 0.005) in the young subjects. BW did not change with age (1.00 +/- 0.01 versus 1.01 +/- 0.01 cm). In young women, simple correlations of BMC and BW with EI were both significant. By multiple regression analysis only BW independently predicted EI (EI = -0.35 + 39.1 x BMC, R2 = 0.52). In older women BMC and BW correlated with EI, but in multiple regression only BMC was significant (EI = -34.5 + 62.1 x BW; R2 = 0.45). When this analysis of older women included only those whose BMC values were within 2 SD of the young mean, BMC remained the only significant predictor of EI.(ABSTRACT TRUNCATED AT 250 WORDS)