Noninvasive technique for measuring in vivo three-dimensional carpal bone kinematics

Development and stability analysis of carpal kinematic metrics from 4D magnetic resonance imaging

OBJECTIVE

To develop MRI-derived carpal kinematic metrics and investigating their stability.

METHODS

The study used a 4D MRI method to track scaphoid, lunate, and capitate movements in the wrist. A panel of 120 metrics for radial-ulnar deviation and flexion-extension was created using polynomial models of scaphoid and lunate movements relative to the capitate. Intraclass correlation coefficients (ICCs) analyzed intra- and inter-subject stability in 49 subjects, 20 with and 29 without wrist injury history.

RESULTS

Comparable degrees of stability were observed across the two different wrist movements. Among the total 120 derived metrics, distinct subsets demonstrated high stability within each type of movement. For asymptomatic subjects, 16 out of 17 metrics with high intra-subject stability also showed high inter-subject stability. The differential analysis of ICC values for each metric between asymptomatic and symptomatic cohorts revealed specific metrics (although relatively unstable) exhibiting greater variability in the symptomatic cohort, thereby highlighting the impact of wrist conditions on the variability of kinematic metrics.

CONCLUSION

The findings demonstrate the developing potential of dynamic MRI for assessing and characterizing complex carpal bone dynamics. Stability analyses of the derived kinematic metrics revealed encouraging differences between cohorts with and without wrist injury histories. Although these broad metric stability variations highlight the potential utility of this approach for analyzing carpal instability, further studies are necessary to better characterize these observations.

Carpal kinematics and morphological correlates of wrist ulnar deviation mobility in nonhuman anthropoid primates

OBJECTIVES

Primates employ wrist ulnar deviation during a variety of locomotor and manipulative behaviors. Extant hominoids share a derived condition in which the ulnar styloid process has limited articulation or is completely separated from the proximal carpals, which is often hypothesized to increase ulnar deviation range of motion. Acute angulation of the hamate's triquetral facet is also hypothesized to facilitate ulnar deviation mobility and mechanics. In this study, we test these longstanding ideas.

METHODS

Three-dimensional (3D) carpal kinematics were examined using a cadaveric sample of Pan troglodytes, Pongo sp., and five monkey species. Ulnar styloid projection and orientation of the hamate's triquetral facet were quantified using 3D models.

RESULTS

Although carpal rotation patterns in Pan and Pongo were uniquely similar in some respects, P. troglodytes exhibited overall kinematic similarity with large terrestrial cercopithecoids (Papio and Mandrillus). Pongo, Macaca, and Ateles had high wrist ulnar deviation ranges of motion, but Pongo did this via a unique mechanism. In Pongo, the triquetrum functions as a distal carpal rather than part of the proximal row. Ulnar styloid projection and wrist ulnar deviation range of motion were not correlated but ulnar deviation range of motion and the triquetrohamate facet orientation were correlated.

CONCLUSIONS

Increased ulnar deviation mobility is not the function of ulnar styloid withdrawal in hominoids. Instead, this feature probably reduces stress on the ulnar side wrist or is a byproduct of adaptations that increase supination. Orientation of the hamate's triquetral facet offers some potential to reconstruct ulnar deviation mobility in extinct primates.

The Intercalated Segment: Does the Triquetrum Move in Synchrony With the Lunate?

PURPOSE

To quantify the relative motion between the lunate and triquetrum during functional wrist movements and to examine the impact of wrist laxity on triquetral motion.

METHODS

A digital database of wrist bone anatomy and carpal kinematics for 10 healthy volunteers in 10 different positions was used to study triquetral kinematics. The orientation of radiotriquetral (RT) and radiolunate rotation axes was compared during a variety of functional wrist movements, including radioulnar deviation (RUD) and flexion-extension (FE), and during a hammering task. The motion of the triquetrum relative to the radius during wrist RUD was compared with passive FE range of motion measurements (used as a surrogate measure for wrist laxity).

RESULTS

The difference in the orientation of the radiolunate and RT rotation axes was less than 20° during most of the motions studied, except for radial deviation and for the first stage of the hammering task. During wrist RUD, the orientation of the RT rotation axis varied as a function of passive FE wrist range of motion.

CONCLUSIONS

The suggestion that the lunate and triquetrum move together as an intercalated segment may be an oversimplification. We observed synchronous movement during some motions, but as the wrist entered RUD, the lunate and triquetrum no longer moved synchronously. These findings challenge the assumptions behind models describing the mechanical function of the carpals.

CLINICAL RELEVANCE

Individual-specific differences in the amount of relative motion between the triquetrum and lunate may contribute to the variability in outcomes following lunotriquetral arthrodesis. Variation in triquetral motion patterns may also have an impact on the ability of the triquetrum to extend the lunate, affecting the development of carpal instability.

The biomechanics of osteoarthritis in the hand: Implications and prospects for hand therapy

BACKGROUND

The unique anatomy of the human hand makes it possible to carefully manipulate tools, powerfully grasp objects, and even throw items with precision. These apparent contradictory functions of the hand, high mobility for manual dexterity vs high stability during forceful grasping, imply that daily activities impose a high strain on a relatively instable joint. This makes the hand susceptible to joint disorders such as osteoarthritis. Both systemic (eg, genetics, hormones) and mechanical factors (eg, joint loading) are important in the development of osteoarthritis, but the precise pathomechanism remains largely unknown. This paper focuses on the biomechanical factors in the disease process and how hand therapists can use this knowledge to improve treatment and research.

CONCLUSION

Multiple factors are involved in the onset and development of osteoarthritis in the hand. Comprehension of the biomechanics helps clinicians establish best practices for orthotics intervention, exercise, and joint protection programs even in de absence of clear evidence-based guidelines. The effect and reach of hand therapy for OA patients can be expanded substantially when intervention parameters are optimized and barriers to early referrals, access reimbursement, and adherence are addressed. Close and early collaboration between hand therapists and primary care, women's health, rheumatology, and hand surgery providers upon diagnosis, and with hand surgeons pre and postoperatively, combined with advances in the supporting science and strategies to enhance adherence, appear to be a promising way forward.

Dynamic tracking of scaphoid, lunate, and capitate carpal bones using four-dimensional MRI

A preliminary exploration of technical methodology for dynamic analysis of scaphoid, capitate, and lunate during unconstrained movements is performed in this study. A heavily accelerated and fat-saturated 3D Cartesian MRI acquisition was used to capture temporal frames of the unconstrained moving wrist of 5 healthy subjects. A slab-to-volume point-cloud based registration was then utilized to register the moving volumes to a high-resolution image volume collected at a neutral resting position. Comprehensive in-silico error analyses for different acquisition parameter settings were performed to evaluate the performance limits of several dynamic metrics derived from the registration parameters. Computational analysis suggested that sufficient volume coverage for the dynamic acquisitions was reached when collecting 12 slice-encodes at 2.5mm resolution, which yielded a temporal resolution of and 2.6 seconds per volumetric frame. These acquisition parameters resulted in total in-silico errors of 1.9°±1.8° and 3°±4.6° in derived principal rotation angles within ulnar-radial deviation and flexion-extension motion, respectively. Rotation components of the carpal bones in the radius coordinate system were calculated and found to be consistent with earlier 4D-CT studies. Temporal metric profiles derived from ulnar-radial deviation motion demonstrated better performance than those derived from flexion/extension movements. Future work will continue to explore the use of these methods in deriving more complex dynamic metrics and their application to subjects with symptomatic carpal dysfunction.

Four-dimensional CT analysis of carpal kinematics: An explorative study on the effect of sex and hand-dominance

Wrist pathology is often diagnosed by using the contralateral wrist as a comparison of baseline motion and strength. However, recent range of motion studies suggest that females have different carpal motion patterns compared to males and that the dominant carpal bones have different motion patterns. The purpose of this study is to evaluate the effect of sex and hand dominance on in vivo kinematics of the scaphoid, lunate and capitate using four-dimensional computed tomography (4D-CT) analysis in healthy uninjured volunteers. In this prospective study, both wrist of 20 uninjured Caucasian volunteers (11 men and 9 women) were assessed using 4D-CT during active flexion-extension and radial-ulnar deviation. A linear mixed model was used to compare the carpal motion patterns. Sex had no influence on carpal kinematics. Hand-dominance in males did have a significant effect on carpal kinematics. During flexion-extension of the male wrist, more radial-ulnar deviation of the lunate, scaphoid and capitate of the non-dominant hand was seen. During radial-ulnar deviation of the male wrist, radial-ulnar deviation and pro-supination of the lunate was more in the dominant hand. This study provides a better understanding of carpal kinematics and the effect of sex and hand-dominance on the scaphoid, lunate and capitate in uninjured wrists.

Carpal Kinematics in Madelung Deformity

PURPOSE

Various skeletal and soft tissue abnormalities have been identified in Madelung deformity and have been hypothesized to play a causal role in its progressive symptomatology; however, our pathological understanding of these changes remains limited. In this study, we biomechanically assessed the Madelung deformity wrist, using 4-dimensional computed tomography imaging.

METHODS

Nine Madelung deformity wrists (5 patients; age, 24 ± 5 y) and 18 healthy wrists (9 volunteers; age, 28 ± 3 y) underwent 4-dimensional imaging during flexion-extension motion and radioulnar deviation. Carpal kinematics and radiocarpal joint parameters were quantified and compared.

RESULTS

In Madelung deformity wrists, significantly decreased rotation was seen in the lunate (-4.6°) and the triquetrum (-4.8°) during flexion-extension motion. During radioulnar deviation, significant decreases were visible in lunate bone translation (-0.7 mm), triquetrum bone translation (-0.6 mm), and triquetrum bone rotation (-1.9°). Patients had significantly decreased articulating surface areas of the scaphoid (1.4 ± 0.2 cm² versus 1.6 ± 0.2 cm²) and lunate (1.2 ± 0.4 cm² versus 1.5 ± 0.3 cm²) fossa, and significantly increased radioscaphoid (1.3 ± 0.1 mm versus 1.2 ± 0.1 mm) and radiolunate (1.6 ± 0.2 mm versus 1.3 ± 0.3 mm) joint space thicknesses.

CONCLUSIONS

There is a decreased mobility of the lunate and triquetrum bones in Madelung deformity.

CLINICAL RELEVANCE

Four-dimensional imaging could be used in future studies that investigate the effect of surgical ligament release on carpal kinematics and subsequent wrist mobility.

Quantifying in vivo scaphoid, lunate, and capitate kinematics using four-dimensional computed tomography

OBJECTIVE

We aimed to establish a quantitative description of motion patterns and establish test-retest reliability of the four-dimensional CT when quantifying in vivo kinematics of the scaphoid, lunate, and capitate.

MATERIALS AND METHODS

We assessed in vivo kinematics of both wrists of 20 healthy volunteers (11 men and 9 women) between the ages of 20 and 40 years. All volunteers performed active flexion-extension and radial-ulnar deviation with both wrists. To test for reliability, one motion cycle was rescanned for both wrists approximately 15 min after the first scan. The coefficient of multiple correlation was used to analyze reliability. When two motion patterns are similar, the coefficient of multiple correlation tends towards 1, whereas in dissimilar motion patterns, it tends towards 0. The root mean square deviation was used to analyze the total motion patterns variability between the two scans.

RESULTS

Overall, mean or median coefficient of multiple correlations were higher than 0.86. The root mean square deviations were low and ranged from 1.17° to 4.29°.

CONCLUSION

This innovative non-invasive imaging technique can reliably describe in vivo carpal kinematics of uninjured wrists in healthy individuals. It provides us with a better understanding and reference values of carpal kinematics of the scaphoid, lunate, and capitate.

The use of 4D-CT in assessing wrist kinematics and pathology

The wrist is a complex joint involving many small bones and complicated kinematics. It has, therefore, been traditionally difficult to image and ascertain information about kinematics when making a diagnosis. Although MRI and fluoroscopy have been used, they both have limitations. Recently, there has been interest in the use of 4D-CT in imaging the wrist. This review examines the literature regarding the use of 4D-CT in imaging the wrist to assess kinematics and its ability to diagnose pathology. Some questions remain about the description of normal ranges, the most appropriate method of measuring intercarpal stability, the accuracy compared with established standards, and the place of 4D-CT in postoperative assessment.

Cite this article: Bone Joint J 2019;101-B:1325–1330.

A principal component analysis-based framework for statistical modeling of bone displacement during wrist maneuvers

We present a method for the statistical modeling of the displacements of wrist bones during the performance of coordinated maneuvers, such as radial-ulnar deviation (RUD). In our approach, we decompose bone displacement via a set of basis functions, identified via principal component analysis (PCA). We utilized MRI wrist scans acquired at multiple static positions for deriving these basis functions. We then utilized these basis functions to compare the displacements undergone by the bones of the left versus right wrist in the same individual, and between bones of the wrists of men and women, during the performance of the coordinated RUD maneuver. Our results show that the complex displacements of the wrist bones during RUD can be modeled with high reliability with just 5 basis functions, that captured over 91% of variation across individuals. The basis functions were able to predict intermediate wrist bone poses with an overall high accuracy (mean error of 0.26 mm). Our proposed approach found statistically significant differences between bone displacement trajectories in women versus men, however, did not find significant differences in those of the left versus right wrist in the same individual. Our proposed method has the potential to enable detailed analysis of wrist kinematics for each sex, and provide a robust framework for characterizing the normal and pathologic displacement of the wrist bones, such as in the context of wrist instability.

Feasibility of a New Desktop Motion Analysis System with a Video Game Console for Assessing Various Three-Dimensional Wrist Motions

Background

The restriction of wrist motion results in limited hand function, and the evaluation of the range of wrist motion is related to the evaluation of wrist function. To analyze and compare the wrist motion during four selected tasks, we developed a new desktop motion analysis system using the motion controller for a home video game console.

Methods

Eighteen healthy, right-handed subjects performed 15 trials of selective tasks (dart throwing, hammering, circumduction, and winding thread on a reel) with both wrists. The signals of light-emitting diode markers attached to the hand and forearm were detected by the optic receptor in the motion controller. We compared the results between both wrists and between motions with similar motion paths.

Results

The parameters (range of motion, offset, coupling, and orientations of the oblique plane) for wrist motion were not significantly different between both wrists, except for radioulnar deviation for hammering and the orientation for thread winding. In each wrist, the ranges for hammering were larger than those for dart throwing. The offsets and the orientations of the oblique plane were not significantly different between circumduction and thread winding.

Conclusions

The results for the parameters of dart throwing, hammering, and circumduction of our motion analysis system using the motion controller were considerably similar to those of the previous studies with three-dimensional reconstruction with computed tomography, electrogoniometer, and motion capture system. Therefore, our system may be a cost-effective and simple method for wrist motion analysis.

Three-dimensional kinematics of the canine carpal bones imaged with computed tomography after ex vivo axial limb loading and palmar ligament transection

OBJECTIVE

To describe normal antebrachiocarpal joint kinematic motion during axial loading and to describe the effect of palmar radiocarpal ligament (PRL) and palmar ulnocarpal ligament (PUL) transection on this motion.

SAMPLE POPULATION

Ten forelimbs from 5 adult greyhound cadavers.

METHODS

Limbs were placed in a custom jig and computed tomography images of limbs were obtained in neutral and extended positions. The translation and rotation of the intermedioradiocarpal bone (RCB), ulnar carpal bone, and accessory carpal bone were described relative to the radius through rigid body motion analysis. Kinematic and load analysis was repeated after sequential transection of the PRL and the PUL.

RESULTS

Sagittal plane extension with a lesser component of valgus motion was found in all evaluated carpal bones. RCB supination was also detected during extension. Compared with the normal intact limb, transection of either or both the PRL and the PUL did not influence mean translation or rotation data or limb load. However, the transection of the PRL and the PUL increased the variance in rotation data compared with intact limb.

CONCLUSION

This study describes normal antebrachiocarpal kinematics as a foundation for determining carpal functional units. During axial loading, the PRL and the PUL may function to guide consistent motion in extension and flexion as well as pronation and supination.

CLINICAL SIGNIFICANCE

Three-dimensional carpal kinematic analyses may improve our understanding of carpal injury and facilitate the development of novel treatments techniques.

Measurement of Carpal Alignment Indices Using 3-Dimensional Computed Tomography

PURPOSE

This study aimed to establish normal values for wrist carpal alignment measured by 3-dimensional computed tomography (CT) and to show the inter- and intraobserver reliability of this measurement compared with simple radiography.

METHODS

The study utilized 3-dimensional CT and simple radiography of wrist joints in 30 asymptomatic volunteers. The wrist position was standardized using a custom-designed positioning device. Three independent observers measured carpal alignment parameters including distal radius articular angle, radiolunate angle, radioscaphoid angle, radiocapitate angle, radius-third metacarpal angle, scapholunate angle, lunocapitate angle, and lunate-third metacarpal angle.

RESULTS

Based on 3-dimensional CT measurement, the mean values of these parameters were: 12.9° ± 1.8° for the distal radius articular angle; 1.2° ± 3.8° for the radiolunate angle; 54.2° ± 5.6° for the radioscaphoid angle; 1.9° ± 2.2° for the radiocapitate angle; -1.0° ± 2.5° for the radius-third metacarpal angle; 52.9° ± 6.9° for the scapholunate angle; 0.7° ± 4.1° for the lunocapitate angle; -2.3° ± 4.6° for the lunate-third metacarpal angle. All parameters showed high inter- and intraobserver reliability in the 2 modalities.

CONCLUSIONS

The normal values and ranges for carpal alignment angles were evaluated by using 3-dimensional CT. We could obtain high reliability in 3-dimensional CT as well as plain radiograph for the measurement of carpal alignment.

TYPE OF STUDY/LEVEL OF EVIDENCE

Diagnostic II.

Does Wrist Laxity Influence Three-Dimensional Carpal Bone Motion?

Previous two-dimensional (2D) studies have shown that there is a spectrum of carpal mechanics that varies between row-type motion and column-type motion as a function of wrist laxity. More recent three-dimensional (3D) studies have suggested instead that carpal bone motion is consistent across individuals. The purpose of this study was to use 3D methods to determine whether carpal kinematics differ between stiffer wrists and wrists with higher laxity. Wrist laxity was quantified using a goniometer in ten subjects by measuring passive wrist flexion-extension (FE) range of motion (ROM). In vivo kinematics of subjects' scaphoid and lunate with respect to the radius were computed from computed tomography (CT) volume images in wrist radial and ulnar deviation positions. Scaphoid and lunate motion was defined as "column-type" if the bones flexed and extended during wrist radial-ulnar deviation (RUD), and "row-type" if the bones radial-ulnar deviated during wrist RUD. We found that through wrist RUD, the scaphoid primarily flexed and extended, but the scaphoids of subjects with decreased laxity had a larger component of RUD (R2 = 0.48, P < 0.05). We also determined that the posture of the scaphoid in the neutral wrist position predicts wrist radial deviation (RD) ROM (R2 = 0.46, P < 0.05). These results suggest that ligament laxity plays a role in affecting carpal bone motion of the proximal row throughout radial and ulnar deviation motions; however, other factors such as bone position may also affect motion. By developing a better understanding of normal carpal kinematics and how they are affected, this will help physicians provide patient-specific approaches to different wrist pathologies.

Kinematics of the anthropoid os centrale and the functional consequences of scaphoid-centrale fusion in African apes and hominins

In most primates, the os centrale is interposed between the scaphoid, trapezoid, trapezium, and head of the capitate, thus constituting a component of the wrist's midcarpal complex. Scaphoid-centrale fusion is among the clearest morphological synapomorphies of African apes and hominins. Although it might facilitate knuckle-walking by increasing the rigidity and stability of the radial side of the wrist, the exact functional significance of scaphoid-centrale fusion is unclear. If fusion acts to produce a more rigid radial wrist that stabilizes the hand and limits shearing stresses, then in taxa with a free centrale, it should anchor ligaments that check extension and radial deviation, but exhibit motion independent of the scaphoid. Moreover, because the centrale sits between the scaphoid and capitate (a major stabilizing articulation), scaphoid-centrale mobility should correlate with scaphocapitate mobility in extension and radial deviation. To test these hypotheses, the centrale's ligamentous binding was investigated via dissection in Pongo and Papio, and the kinematics of the centrale were quantified in a cadaveric sample of anthropoids (Pongo sp., Ateles geoffroyi, Colobus guereza, Macaca mulatta, and Papio anubis) using a computed-tomography-based method to track wrist-bone motion. Results indicate that the centrale rotates freely relative to the scaphoid in all taxa. However, centrale mobility is only correlated with scaphocapitate mobility during extension in Pongo-possibly due to differences in overall wrist configuration between apes and monkeys. If an extant ape-like wrist characterized early ancestors of African apes and hominins, then scaphoid-centrale fusion would have increased midcarpal rigidity in extension relative to the primitive condition. Although biomechanically consistent with a knuckle-walking hominin ancestor, this assumes that the trait evolved specifically for that biological role, which must be squared with contradictory interpretations of extant and fossil hominoid morphology. Regardless of its original adaptive significance, scaphoid-centrale fusion likely presented a constraint on early hominin midcarpal mobility.

Influence of Scan Resolution, Thresholding, and Reconstruction Algorithm on Computed Tomography-Based Kinematic Measurements

Radiographic data, including computed tomography (CT) and planar X-ray, is increasingly used for human and animal kinematic studies. There is a tendency toward using as high-resolution imaging as possible. Higher resolution imaging is one factor (in conjunction with the reconstruction algorithm), which may increase the precision of reconstructed three-dimensional (3D) surface models in representing true bone shape. However, to date no study has tested the effects of scan resolution, threshold, and 3D model reconstruction algorithm on the accuracy of bone kinematic results. The present study uses a novel method to do this where canine tarsal bones were positioned on a radiolucent Lego™ board and scanned before and after undergoing known translations and/or rotations. The digital imaging and communications in medicine (DICOM) images were acquired using two different CT scanning resolutions and processed using three different segmentation threshold levels and three different reconstruction algorithms. Using one bone as the reference bone, an iterative closest point (ICP) algorithm was used to register bones to a global co-ordinate system and allow measurement of other bone kinematics in terms of translations and rotations in and around the x-, y-, and z-axes. The measured kinematics were compared to the “known” kinematics, which were obtained from the Lego™ board's manufacturing standards and tolerances, to give accuracy error metrics for all bones. The results showed error in accuracy of measured kinematics was at subvoxel levels (less than 0.5 mm). Despite altering the volume and surface area of the 3D bone models, variation in resolution, segmentation threshold and reconstruction algorithm had no significant influence upon the accuracy of the calculated tarsal bone kinematics.

In vivo kinematics of the thumb during flexion and adduction motion: Evidence for a screw-home mechanism

The thumb plays a crucial role in basic hand function. However, the kinematics of its entire articular chain have not yet been quantified. Such investigation is essential to improve our understanding of thumb function and to develop better strategies to treat thumb joint pathologies. The primary objective of this study is to quantify the in vivo kinematics of the trapeziometacarpal (TMC) and scaphotrapezial (ST) joints during flexion and adduction of the thumb. In addition, we want to evaluate the potential coupling between the TMC and ST joints during these tasks. The hand of 16 asymptomatic women without signs of thumb osteoarthritis were CT scanned in positions of maximal thumb extension, flexion, abduction, and adduction. The CT images were segmented and three-dimensional surface models of the radius, scaphoid, trapezium, and the first metacarpal were created for each thumb motion. The corresponding rotations angles, translations, and helical axes were calculated for each sequence. The analysis shows that flexion and adduction of the thumb result in a three-dimensional rotation and translation of the entire articular chain, including the trapezium and scaphoid. A wider range of motion is observed for the first metacarpal, which displays a clear axial rotation. The coupling of axial rotation of the first metacarpal with flexion and abduction during thumb flexion supports the existence of a screw-home mechanism in the TMC joint. In addition, our results point to a potential motion coupling between the TMC and ST joints and underline the complexity of thumb kinematics. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:1556-1564, 2017.

Three-Dimensional Analysis of Acute Scaphoid Fracture Displacement: Proximal Extension Deformity of the Scaphoid

BACKGROUND

Our goal was to analyze the movement of acute scaphoid waist fracture fragments and adjacent bones in a common coordinate system. Our hypothesis was that the distal scaphoid fragment flexes and pronates and the proximal fragment extends.

METHODS

Computed tomography (CT) scans of patients diagnosed with an acute scaphoid waist fracture were evaluated using a 3-dimensional (3D) model. The scans of 57 nondisplaced and 23 displaced fractures were compared with a control group of 27 scans showing no pathological involvement of the wrist. Three anatomical landmarks were labeled on the distal and proximal fragments of the scaphoid, the lunate, and the trapezium. Each set of labels formed a triangle representing the bone or fragment. Four landmarks were labeled on the distal radial articular surface and used to create a common coordinate system. The position of each bone or fragment was calculated in reference to these coordinates.

RESULTS

The displaced fracture group showed significant extension, supination, and volar translation of the proximal scaphoid fragment when compared with the other groups. The lunate tended toward a supinated position, which was not statistically significant. The distal scaphoid fragment and the trapezium showed no movement.

CONCLUSIONS

In acute displaced scaphoid fractures, it is the proximal fragment that displaces and should be reduced.

CLINICAL RELEVANCE

The typical "humpback" deformity is actually a "proximal extension" deformity, the consequence of displacement of the proximal fragment of the scaphoid (with the lunate). Manipulating only the proximal fragment (with the lunate) may be technically easier and more effective than manipulating both fragments.

Carpal Kinematics and Kinetics

The complex interaction of the carpal bones, their intrinsic and extrinsic ligaments, and the forces in the normal wrist continue to be studied. Factors that influence kinematics, such as carpal bone morphology and clinical laxity, continue to be identified. As imaging technology improves, so does our ability to better understand and identify these factors. In this review, we describe advances in our understanding of carpal kinematics and kinetics. We use scapholunate ligament tears as an example of the disconnect that exists between our knowledge of carpal instability and limitations in current reconstruction techniques.

Three-Dimensional Carpal Kinematics after Carpal Tunnel Release

BACKGROUND

Carpal tunnel release (CTR) has been shown to change carpal arch morphology. However, the effect of CTR on the three-dimensional kinematics of the carpal bones has not been demonstrated.

PURPOSE

This study examined whether release of the transverse carpal ligament (TCL) would alter the three-dimensional kinematics of the carpus, specifically the bony attachments of the TCL.

METHODS

The in vitro kinematics of the carpus was studied in five fresh-frozen cadaveric wrists before and after CTR using three-dimensional computed tomography. The specimens were evaluated in three positions: neutral, 60 degrees of flexion, and 60 degrees of extension.

RESULTS

The data indicate that carpal arch width increases significantly in all positions after CTR as measured between the trapezium and hamate. Second, the trapezium-hamate distance increases in both a translational and rotational component after CTR. Additionally, the pisiform rotates away from the triquetrum after CTR.

CONCLUSIONS

Carpal kinematics is significantly altered with a CTR, especially on the ulnar side of the wrist.

CLINICAL RELEVANCE

Although the kinematic changes are small, they may be clinically significant and potentially responsible for pillar pain or postoperative loss of grip strength.

Registration-Based Morphometry for Shape Analysis of the Bones of the Human Wrist

We present a method that quantifies point-wise changes in surface morphology of the bones of the human wrist. The proposed method, referred to as Registration-based Bone Morphometry (RBM), consists of two steps: an atlas selection step and an atlas warping step. The atlas for individual wrist bones was selected based on the shortest ℓ2 distance to the ensemble of wrist bones from a database of a healthy population of subjects. The selected atlas was then warped to the corresponding bones of individuals in the population using a non-linear registration method based on regularized ℓ2 distance minimization. The displacement field thus calculated showed local differences in bone shape that then were used for the analysis of group differences. Our results indicate that RBM has potential to provide a standardized approach to shape analysis of bones of the human wrist. We demonstrate the performance of RBM for examining group differences in wrist bone shapes based on sex and between those of the right and left wrists in healthy individuals. We also present data to show the application of RBM for tracking bone erosion status in rheumatoid arthritis.

Functional kinematics of the wrist

The purpose of this article is to review past and present concepts concerning functional kinematics of the healthy and injured wrist. To provide a context for students of the wrist, we describe the progression of techniques for measuring carpal kinematics over the past century and discuss how this has influenced today's understanding of functional kinematics. Next, we provide an overview of recent developments and highlight the clinical relevance of these findings. We use these findings and recent evidence that supports the importance of coupled motion in early rehabilitation of radiocarpal injuries to develop the argument that coupled motion during functional activities is a clinically relevant outcome; therefore, clinicians should develop a framework for its dynamic assessment. This should enable a tailored and individualized approach to the treatment of carpal injuries.

The effect of wrist surgery on the kinematic consistency of joint axis reconstruction in a static posture

Three-dimensional analysis of wrist motion is a growing focus in orthopedic research, however, our understanding of its validity (accuracy and reliability) remains limited. Nine human cadavers were tested to estimate wrist joint axes alignment in a postural static pose. The objective was to investigate a rater's ability to reliably align three skin- tracked wrist joint coordinate system (WJCS) definitions across baseline and reconstructive wrist states (intact, mid-carpal arthrodesis, and proximal-row carpectomy). Two WJCSs (legacy, anatomic) were based on palpated bony landmarks and the third (functional) was based on both landmarks and passive flexion-extension motion. A coordinate frame based on the anatomic definition was tracked with bone pins and served as a reference. Each WJCS was tested in each wrist state and in three forearm position (45° pronation, neutral, 45° supination). The angular offset about each axis of the WJCS frames were calculated with respect to the reference in flexion-extension, radial-ulnar deviation, and pronation-supination for every iteration. Reliability and root mean square deviation values were analyzed across wrist states. Our data suggest that no WJCS is uniformly more reliable than another. The functional WJCS definition was most consistent across intact and post-operative states for pronation-supination offset, but this was dependent on rater interpretation. It still however offers the practical benefit of requiring fewer landmarks.

A technique for quantifying wrist motion using four-dimensional computed tomography: approach and validation

Accurate quantification of subtle wrist motion changes resulting from ligament injuries is crucial for diagnosis and prescription of the most effective interventions for preventing progression to osteoarthritis. Current imaging techniques are unable to detect injuries reliably and are static in nature, thereby capturing bone position information rather than motion which is indicative of ligament injury. A recently developed technique, 4D (three dimensions + time) computed tomography (CT) enables three-dimensional volume sequences to be obtained during wrist motion. The next step in successful clinical implementation of the tool is quantification and validation of imaging biomarkers obtained from the four-dimensional computed tomography (4DCT) image sequences. Measures of bone motion and joint proximities are obtained by: segmenting bone volumes in each frame of the dynamic sequence, registering their positions relative to a known static posture, and generating surface polygonal meshes from which minimum distance (proximity) measures can be quantified. Method accuracy was assessed during in vitro simulated wrist movement by comparing a fiducial bead-based determination of bone orientation to a bone-based approach. The reported errors for the 4DCT technique were: 0.00-0.68 deg in rotation; 0.02-0.30 mm in translation. Results are on the order of the reported accuracy of other image-based kinematic techniques.

In Vivo changes in the lengths of carpal ligaments after mild dorsal angulation of distal radius fractures

The need for surgical correction in patients with malunion with mild dorsal angulation after a distal radius fracture is controversial. We specifically investigated in vivo changes in the lengths of carpal ligaments in a group of patients with mild-degree dorsal angulation following a distal radial fracture. We obtained computed tomography scans of both wrists in eight patients, whose distal radius on one side had united with dorsal angulation from 10° to 20°. The three-dimensional images of the carpus were reconstructed and the lengths of wrist ligaments were measured based on known anatomical landmarks. Compared with the contralateral uninjured side, the dorsal radiocarpal ligament and ulnotriquetral ligament were substantially lengthened (p < 0.05) and the long radiolunate ligament was substantially shortened (p < 0.05) at most wrist positions except extension. However, five other ligaments that we measured did not show significant differences in length compared with those of the uninjured side (p > 0.05). The lengths of some ligaments are substantially altered even by mild dorsal angulation of the distal radius, while the lengths of most other ligaments are not substantially affected.

In Vivo length changes of the proximal interphalangeal joint proper and accessory collateral ligaments during flexion

PURPOSE

To investigate the length changes in proper collateral ligament (PCL) and accessory collateral ligament (ACL) during flexion of the proximal interphalangeal (PIP) joint in vivo and how portions of the PCL and ACL stabilize the PIP joint.

METHODS

We obtained computed tomography scans of the index, middle, and ring fingers of one hand from 6 volunteers at 0°, 30°, 60°, 90°, and full flexion of the PIP joint. Radial and ulnar PCL and ACL were measured and analyzed with computer modeling.

RESULTS

The data showed that during flexion the average length of the dorsal portion of the radial and ulnar PCL increased significantly and reached a maximum at 90°. The volar portion of the radial and ulnar PCL and the distal portion of the radial and ulnar ACL shortened continuously from extension to full flexion.

CONCLUSIONS

The proximal and middle portions of each ACL are nearly isometric, the dorsal portion of each PCL becomes taut only in flexion, and the volar portion of PCL and the distal portion of ACL become taut only in extension. The current findings indicate that the dorsal portion of PCL is the most stabilizing structure during flexion of the PIP joint, and that the volar portion of PCL and the distal portion of ACL provide the crucial lateral stability to the joint at extension.

CLINICAL RELEVANCE

The results may provide information relevant to the ligaments of PIP joint reconstruction and rehabilitation.

Development of an anatomical wrist joint coordinate system to quantify motion during functional tasks

The purpose of this study was to develop a three-dimensional (3D) motion analysis based anatomical wrist joint coordinate system for measurement of in-vivo wrist kinematics. The convergent validity and reliability of the 3D motion analysis implementation was quantified and compared with manual and electrogoniometry techniques on 10 cadaveric specimens. Fluoroscopic measurements were used as the reference. The 3D motion analysis measurements (mean absolute difference [MAD] = 3.6°) were significantly less different (P < .005) than manual goniometry (MAD = 5.7°) but not (P = .066, power = 0.45) electrogoniometry (MAD = 5.0°) compared with fluoroscopy. The intraclass correlation coefficient (ICC[2,1]) was highest for 3D motion analysis compared with manual and electrogoniometry, suggesting better reliability for this technique. To demonstrate the utility of this new wrist joint coordinate system, normative data from 10 healthy subjects was obtained while throwing a dart.

Global point signature for shape analysis of carpal bones

We present a method based on spectral theory for the shape analysis of carpal bones of the human wrist. We represent the cortical surface of the carpal bone in a coordinate system based on the eigensystem of the two-dimensional Helmholtz equation. We employ a metric--global point signature (GPS)--that exploits the scale and isometric invariance of eigenfunctions to quantify overall bone shape. We use a fast finite-element-method to compute the GPS metric. We capitalize upon the properties of GPS representation--such as stability, a standard Euclidean (ℓ(2)) metric definition, and invariance to scaling, translation and rotation--to perform shape analysis of the carpal bones of ten women and ten men from a publicly-available database. We demonstrate the utility of the proposed GPS representation to provide a means for comparing shapes of the carpal bones across populations.

A novel method to replicate the kinematics of the carpus using a six degree-of-freedom robot

Understanding the kinematics of the carpus is essential to the understanding and treatment of wrist pathologies. However, many of the previous techniques presented are limited by non-functional motion or the interpolation of points from static images at different postures. We present a method that has the capability of replicating the kinematics of the wrist during activities of daily living using a unique mechanical testing system. To quantify the kinematics of the carpal bones, we used bone pin-mounted markers and optical motion capture methods. In this paper, we present a hammering motion as an example of an activity of daily living. However, the method can be applied to a wide variety of movements. Our method showed good accuracy (1.0-2.6°) of in vivo movement reproduction in our ex vivo model. Most carpal motion during wrist flexion-extension occurs at the radiocarpal level while in ulnar deviation the motion is more equally shared between radiocarpal and midcarpal joints, and in radial deviation the motion happens mainly at the midcarpal joint. For all rotations, there was more rotation of the midcarpal row relative to the lunate than relative to the scaphoid or triquetrum. For the functional motion studied (hammering), there was more midcarpal motion in wrist extension compared to pure wrist extension while radioulnar deviation patterns were similar to those observed in pure wrist radioulnar deviation. Finally, it was found that for the amplitudes studied the amount of carpal rotations was proportional to global wrist rotations.

Four-dimensional computed tomography and trigger lunate syndrome

BACKGROUND

A 22-year-old man with no history of trauma and normal plain films, ultrasound, and magnetic resonance imaging presents with several months of increasingly severe pain and clicking in the right wrist. He is clinically diagnosed with midcarpal instability and undergoes a 4-dimensional computed tomography scan of his wrist for further evaluation.

METHODS

The motion of the subject's lunate was evaluated through a full arc of flexion and extension as well as radial and ulnar deviation. A comparison was made with the lunate of an asymptomatic patient demonstrating the same motions.

RESULTS

The symptomatic lunate demonstrated early smooth motion, followed by cessation of motion, and then again followed by smooth catch up motion. The asymptomatic patient demonstrated smooth lunate motion throughout the study.

DISCUSSION

The lunate motion, with an abrupt cessation and recommencement of flexion/extension, was consistent with a triggering phenomenon. This trigger lunate motion abnormality, although consistent with the "clunking" sensation often described during the physical examination, has not been previously recognized radiographically as a feature of midcarpal instability.

Four-dimensional real-time cine images of wrist joint kinematics using dual source CT with minimal time increment scanning

PURPOSE

To validate the feasibility of real time kinematography with four-dimensional (4D) dynamic functional wrist joint imaging using dual source CT.

MATERIALS AND METHODS

Two healthy volunteers performed radioulnar deviation and pronation- supination wrist motions for 10 s and 4 s per cycle in a dual source CT scanner. Scan and reconstruction protocols were set to optimize temporal resolution. Cine images of the reconstructed carpal bone of the moving wrist were recorded. The quality of the images and radiation dosage were evaluated.

RESULTS

The 4D cine images obtained during 4 s and 10 s of radioulnar motion showed a smooth stream of movement with good quality and little noise or artifact. Images from the pronation-supination motion showed noise with a masked surface contour. The temporal resolution was optimized at 0.28 s.

CONCLUSION

Using dual source CT, 4D cine images of in vivo kinematics of wrist joint movement were obtained and found to have a shorter scan time, improved temporal resolution and lower radiation dosages compared with those previously reported.

Three-dimensional analysis of cervical spine segmental motion in rotation

INTRODUCTION

The movements of the cervical spine during head rotation are too complicated to measure using conventional radiography or computed tomography (CT) techniques. In this study, we measure three-dimensional segmental motion of cervical spine rotation in vivo using a non-invasive measurement technique.

MATERIAL AND METHODS

Sixteen healthy volunteers underwent three-dimensional CT of the cervical spine during head rotation. Occiput (Oc) - T1 reconstructions were created of volunteers in each of 3 positions: supine and maximum left and right rotations of the head with respect to the bosom. Segmental motions were calculated using Euler angles and volume merge methods in three major planes.

RESULTS

Mean maximum axial rotation of the cervical spine to one side was 1.6° to 38.5° at each level. Coupled lateral bending opposite to lateral bending was observed in the upper cervical levels, while in the subaxial cervical levels, it was observed in the same direction as axial rotation. Coupled extension was observed in the cervical levels of C5-T1, while coupled flexion was observed in the cervical levels of Oc-C5.

CONCLUSIONS

The three-dimensional cervical segmental motions in rotation were accurately measured with the non-invasive measure. These findings will be helpful as the basis for understanding cervical spine movement in rotation and abnormal conditions. The presented data also provide baseline segmental motions for the design of prostheses for the cervical spine.

In vivo kinematics of the scaphoid, lunate, capitate, and third metacarpal in extreme wrist flexion and extension

PURPOSE

Insights into the complexity of active in vivo carpal motion have recently been gained using 3-dimensional imaging; however, kinematics during extremes of motion has not been elucidated. The purpose of this study was to determine motion of the carpus during extremes of wrist flexion and extension.

METHODS

We obtained computed tomography scans of 12 healthy wrists in neutral grip, extreme loaded flexion, and extreme loaded extension. We obtained 3-dimensional bone surfaces and 6-degree-of-freedom kinematics for the radius and carpals. The flexion and extension rotation from neutral grip to extreme flexion and extreme extension of the scaphoid and lunate was expressed as a percentage of capitate flexion and extension and then compared with previous studies of active wrist flexion and extension. We also tested the hypothesis that the capitate and third metacarpal function as a single rigid body. Finally, we used joint space metrics at the radiocarpal and midcarpal joints to describe arthrokinematics.

RESULTS

In extreme flexion, the scaphoid and lunate flexed 70% and 46% of the amount the capitate flexed, respectively. In extreme extension, the scaphoid extended 74% and the lunate extended 42% of the amount the capitates extended, respectively. The third metacarpal extended 4° farther than the capitate in extreme extension. The joint contact area decreased at the radiocarpal joint during extreme flexion. The radioscaphoid joint contact center moved onto the radial styloid and volar ridge of the radius in extreme flexion from a more proximal and ulnar location in neutral.

CONCLUSIONS

The contributions of the scaphoid and lunate to capitate rotation were approximately 25% less in extreme extension compared with wrist motion through an active range of motion. More than half the motion of the carpus when the wrist was loaded in extension occurred at the midcarpal joint.

CLINICAL RELEVANCE

These findings highlight the difference in kinematics of the carpus at the extremes of wrist motion, which occur during activities and injuries, and give insight into the possible etiologies of the scaphoid fractures, interosseous ligament injuries, and carpometacarpal bossing.

In vivo changes in contact regions of the radiocarpal joint during wrist hyperextension

PURPOSE

Distal radius and scaphoid fractures commonly occur after a fall with the hand outstretched and wrist hyperextended. We investigated contact characteristics of the radiocarpal joint in neutral position, hyperextension, and hyperextension combined with radial deviation in vivo.

METHODS

Eight volunteers without a known history of wrist injury were enrolled. We obtained computed tomography scans with 3-dimensional reconstructions of the subjects' right wrists in neutral, hyperextension, and hyperextension with 10° of radial deviation. The contact regions of the radiocarpal joint were mapped. The direction and distance of changes in the contact region centers were recorded and analyzed.

RESULTS

From neutral position to hyperextension, the contact of the scaphoid substantially shifted from the middle to the dorsal part of the articular surface of the radius in 5 of the 8 wrists. With these wrists further deviated radially, the contact shifted to the surface over the radial styloid. In the other wrists, the contact of the scaphoid remained in the center of the radial articular surface. In all wrists, the contact of the radius on the scaphoid shifted from the proximal lateral surface of the scaphoid to the proximal dorsal surface of the scaphoid, and the contact of the radius on the lunate shifted dorsally.

CONCLUSIONS

During wrist hyperextension, the contact of the scaphoid on the distal radius exhibited 2 possible types of changes: either shifting from the mid-portion to the dorsal ridge of the articular surface of the radius or remaining at the center of the articular surface. Combined wrist hyperextension with radial deviation caused the scaphoid to contact the radius over the radial styloid. The contact of the radius on the scaphoid shifted from proximal lateral to proximal dorsal scaphoid, and that on the lunate shifted dorsally.

CLINICAL RELEVANCE

This study provided in vivo mechanical findings to improve our understanding of the mechanism of hyperextension injuries of carpus.

Elongation of the dorsal carpal ligaments: a computational study of in vivo carpal kinematics

PURPOSE

The dorsal radiocarpal (DRC) and dorsal intercarpal (DIC) ligaments play an important role in scapholunate and lunotriquetral stability. The purpose of this study was to compute changes in ligament elongation as a function of wrist position for the DRC and the scaphoid and trapezoidal insertions of the DIC.

METHODS

We developed a computational model that incorporated a digital dataset of ligament origin and insertions, bone surface models, and in vivo 3-dimensional kinematics (n = 28 wrists), as well as an algorithm for computing ligament fiber path.

RESULTS

The differences between the maximum length and minimum length of the DRC, DIC scaphoid component, and DIC trapezoidal component over the entire range of motion were 5.1 ± 1.5 mm, 2.7 ± 1.5 mm, and 5.9 ± 2.5 mm, respectively. The DRC elongated as the wrist moved from ulnar extension to radial flexion, and the DIC elongated as the wrist moved from radial deviation to ulnar deviation.

CONCLUSIONS

The DRC and DIC lengthened in opposing directions during wrist ulnar and radial deviation. Despite complex carpal bone anatomy and kinematics, computed fiber elongations were found to vary linearly with wrist position. Errors between computed values and model predictions were less than 2.0 mm across all subjects and positions.

CLINICAL RELEVANCE

The relationships between ligament elongation and wrist position should further our understanding of ligament function, provide insight into the potential effects of dorsal wrist incisions on specific wrist ranges of motion, and serve as a basis for modeling of the wrist.

In vivo triquetrum-hamate kinematics through a simulated hammering task wrist motion

BACKGROUND

The shape and kinematics of the triquetrum-hamate joint have been the subject of continued research, as its articulation provides wrist stability and motion. The purpose of this study was to measure the in vivo articulation of the triquetrum-hamate joint as the wrist moves along an important functional wrist motion, the dart thrower's path.

METHODS

The right wrist of six male and six female volunteers (average age [and standard deviation], 24.8 ± 3.8 years) were imaged with computed tomography in five positions along a simulated hammering task. Three-dimensional kinematics of the third metacarpal, triquetrum, hamate, and radius were analyzed with use of the rotation axis and the path of contact areas.

RESULTS

As the wrist ulnar-flexed with respect to the radius, the triquetrum translated 3.7 ± 1.7 mm distally on the hamate. Approximately midway through this distal course, when the triquetrum appeared to engage the distal ridge of the hamate, the triquetrum began translating volarly. Total volar translation was 2.6 ± 1.1 mm. As the wrist ulnar-flexed, there was also a decrease in the distance and variability in the location of the triquetrum-hamate rotation axis from the hamate centroid: it decreased from 11.7 ± 4.1 mm to 3.3 ± 1.4 mm (p < 0.0001).

CONCLUSIONS

Our findings support the concept that the triquetrum rotates on the convex ellipsoid surface of the hamate and that the helicoidal description of the triquetrum's motion on the hamate may be an oversimplification.

A 4D statistical model of wrist bone motion patterns

Direct imaging of ligament damage in the wrist remains a challenge. Still, such damage can be assessed indirectly through the analysis of changes in wrist pose and motion pattern. For this purpose we built a statistical reference model that describes healthy motion patterns. We show that such a model can also be used to detect and quantify pathologies. A model that only describes the global translations and rotations of the carpal bones is insufficiently accurate due to size and shape variations of the bones. We present a local statistical motion model that minimizes the influence of size and shape differences by analyzing the coordinate differences of pairs of points on adjacent bone surfaces. These differences are determined in a set of 14 healthy example wrists imaged in a range of poses by means of 4D-RX imaging. The distribution of the differences as a function of the pose form the local statistical motion model (LSMM). Translations of 2 mm and rotations of 20° with respect to the healthy example wrists are detected as outliers in the point pair distributions. An evaluation involving wrists with a damaged ligament between scaphoid and lunate shows that not only joint space widenings can be detected, but also shifts of congruent bone surfaces. The LSMM is also used to perform a virtual reconstruction of the most likely healthy wrist after a simulated perturbation of bones. The reconstruction precision is shown to be about 1 mm. Therefore, the presented 4D statistical model of wrist bone movement may become a valuable clinical tool for diagnosis and surgical planning.

Does close proximity robot motion tracking alter gait?

Dynamic fluoroscopic imaging and three-dimensional model-image registration techniques provide detailed joint kinematic measurements for motions constrained to small volumes of space. Several groups are working to mount radiographic imaging hardware onto mobile platforms to provide these same imaging capabilities for observation of unrestricted activities. These dynamic radiographic imaging systems could provide accurate skeletal kinematics during a wide range of clinically relevant, daily activities. However, the premise that people move naturally when followed by a dynamic imaging system has not been evaluated. The goal of this study was to determine if a close-up robot tracking system affects natural free-speed gait. 14 healthy adults were recruited to walk through the workspace of a dynamic radiographic imaging system. Randomized walking trials were performed with and without the dynamic imaging system tracking the motions of the subject's left knee. With- and without-robot trials were compared using detailed temporal-spatial and frequency analysis of kinematic and kinetic parameters. On average, participants increase their stride length by 0.9 cm. There also were slight increases in unexplained variation in ankle flexion/extension and ground reaction forces compared to baseline measurements. The statistically significant differences indicate that, on average, people tried to move faster through the workspace of the dynamic radiographic imaging system while it was actively tracking their motion. These differences are small and potentially clinically irrelevant.

In vivo length and changes of ligaments stabilizing the thumb carpometacarpal joint

PURPOSE

To investigate the lengths and changes of selected ligaments stabilizing the thumb carpometacarpal (CMC) joint during thumb motion in vivo.

METHODS

We obtained serial computed tomography scans of the thumb CMC joints of 6 healthy volunteers during thumb flexion, abduction, and opposition. We reconstructed the 3-dimensional structures of the bones of the thumb CMC joint using customized software and modeled the paths of fibers of 5 principal ligaments--deep anterior oblique (beak), dorsoradial, posterior oblique, intermetacarpal, and dorsal intermetacarpal--at each of the CMC joint positions studied. We estimated the virtual lengths of these ligaments in neutral position, flexion, abduction, and opposition of the CMC joint by measuring the distances between the origin and the insertion of individual ligaments, and statistically analyzed the length changes.

RESULTS

The estimated length of the CMC joint ligaments underwent significant changes during thumb motion in vivo. Thumb flexion led to the greatest changes in ligament lengths. During flexion, all the ligaments lengthened significantly (p < .05 or p < .01), except for the beak ligament, which shortened significantly (p < .001). The lengths of the ligaments changed similarly during thumb abduction and opposition, except for the dorsoradial ligament. In both motions, the posterior oblique and dorsal intermetacarpal ligaments lengthened and the beak ligament shortened significantly (p < .05 or p < .01). During the 3 thumb motions, the beak ligament underwent marked shortening, while the other measured ligaments lengthened to varied extent.

CONCLUSIONS

The estimated lengths of principal ligaments stabilizing the CMC joint change substantially during thumb motions in vivo. Thumb flexion causes the greatest changes of the ligament lengths; abduction and opposition result in similar changes in the ligament lengths. The beak ligaments shorten while the other ligaments lengthen. This in vivo study suggests that thumb motions expose the CMC joint ligaments to different tensions at these thumb positions, and that the ligaments are under lower tension during thumb opposition and abduction than during flexion.

In vivo length changes of carpal ligaments of the wrist during dart-throwing motion

PURPOSE

The dart-throwing motion is an important movement pattern during most wrist actions. The aim of this study was to investigate length changes in the wrist ligaments in different positions of the dart-throw motion in vivo.

METHODS

We obtained computed tomography scans of the wrists of 6 volunteers at 5 positions of the wrist during the dart-throw motion: 20° of radial deviation with 60° of extension; 10° of radial deviation with 30° of extension; the neutral position of the carpus; 20° of ulnar deviation with 30° of flexion; and 40° of ulnar deviation with 60° of flexion. We reconstructed the 3-dimensional carpal and distal radioulnar joint structures with customized software and computed changes in length of 8 palmar and dorsal wrist ligaments.

RESULTS

From wrist radial deviation with extension to ulnar deviation with flexion, the radioscaphocapitate, long radiolunate, ulnocapitate, and ulnotriquetral ligaments decreased significantly in length but the dorsal radiocarpal ligament and the dorsal intercarpal (DIC) ligament inserting on the trapezoid lengthened significantly; the ulnolunate ligament and the DIC ligament inserting on the scaphoid were shortest in neutral position.

CONCLUSIONS

At wrist radial extension, the radioscaphocapitate, long radiolunate, ulnocapitate, and ulnotriquetral ligaments are lengthened and under increased tension. At wrist ulnar flexion, the dorsal radiocarpal ligament and the DIC ligament inserting on the trapezoid are lengthened and under increased tension. The ulnolunate ligament and the DIC ligament inserting on the scaphoid are the shortest and under the least tension in neutral position. These findings will help us understand the biomechanics of the carpus during the dart-throwing motion.

Scaphoid and lunate movement in different ranges of carpal radioulnar deviation

PURPOSE

We aimed to investigate scaphoid and lunate movement in radial deviation and in slight and moderate ulnar deviation ranges in vivo.

METHODS

We obtained computed tomography scans of the right wrists from 20° radial deviation to 40° ulnar deviation in 20° increments in 6 volunteers. The 3-dimensional bony structures of the wrist, including the distal radius and ulna, were reconstructed with customized software. The changes in position of the scaphoid and lunate along flexion-extension motion (FEM), radioulnar deviation (RUD), and supination-pronation axes in 3 parts--radial deviation and slight and moderate ulnar deviation--of the carpal RUD were calculated and analyzed.

RESULTS

During carpal RUD, scaphoid and lunate motion along 3 axes--FEM, RUD, and supination-pronation--were the greatest in the middle third of the measured RUD (from neutral position to 20° ulnar deviation) and the smallest in radial deviation. Scaphoid motion along the FEM, RUD, and supination-pronation axes in the middle third was about half that in the entire motion range. In the middle motion range, lunate movement along the FEM and RUD axes was also the greatest.

CONCLUSIONS

During carpal RUD, the greatest scaphoid and lunate movement occurs in the middle of the arc--slight ulnar deviation--which the wrist frequently adopts to accomplish major hand actions. At radial deviation, scaphoid and lunate motion is the smallest.

In-vivo kinematic analysis of forearm rotation using helical axis analysis

BACKGROUND

Controversy still exists regarding the location and nature (static or dynamic) of the forearm joint axis. This might be due to inconsistent results from in-vitro data and less precise methods of analysis. We present the first in-vivo kinematic analysis of normal forearm joint rotation described by helical axis analysis.

METHODS

Data obtained from computed tomography images of both forearms of five healthy volunteers was used to calculate finite helical axis parameters from transformation matrices. Four positions were analyzed: maximum pronation, maximum supination, 60 degrees pronation, and 60 degrees supination. Kinematic analysis focused on the motion of the radius around the ulna.

FINDINGS

The forearm axis as defined by finite helical axis extended from the radial head between its kinematic center and the proximal radioulnar joint, to the dorsal region of the ulnar head at the distal radioulnar joint. The axis was found to be variable.

INTERPRETATIONS

Helical axis analysis has precisely defined the nature and location of the forearm axis. This new information of forearm kinematics defined by finite helical analysis, may be useful in implant design, and in guiding surgeons in their reconstruction of instabilities of the distal and proximal radioulnar joint.

Studying primate carpal kinematics in three dimensions using a computed-tomography-based markerless registration method

The functional morphology of the wrist pertains to a number of important questions in primate evolutionary biology, including that of hominins. Reconstructing locomotor and manipulative capabilities of the wrist in extinct species requires a detailed understanding of wrist biomechanics in extant primates and the relationship between carpal form and function. The kinematics of carpal movement, and the role individual joints play in providing mobility and stability of the wrist, is central to such efforts. However, there have been few detailed biomechanical studies of the nonhuman primate wrist. This is largely because of the complexity of wrist morphology and the considerable technical challenges involved in tracking the movements of the many small bones that compose the carpus. The purpose of this article is to introduce and outline a method adapted from human clinical studies of three-dimensional (3D) carpal kinematics for use in a comparative context. The method employs computed tomography of primate cadaver forelimbs in increments throughout the wrist's range of motion, coupled with markerless registration of 3D polygon models based on inertial properties of each bone. The 3D kinematic principles involved in extracting motion axis parameters that describe bone movement are reviewed. In addition, a set of anatomically based coordinate systems embedded in the radius, capitate, hamate, lunate, and scaphoid is presented for the benefit of other primate functional morphologists interested in studying carpal kinematics. Finally, a brief demonstration of how the application of these methods can elucidate the mechanics of the wrist in primates illustrates the closer-packing of carpals in chimpanzees than in orangutans, which may help to stabilize the midcarpus and produce a more rigid wrist beneficial for efficient hand posturing during knuckle-walking locomotion.