Association between carpal height ratio and ulnar variance in normal wrist radiography.

INTRODUCTION: The wrist joint is a complex anatomical structure, and various radiographic parameters are utilized to assess its normal alignment and orientation. Among these parameters are carpal height ratio (CHR) and ulnar variance (UV). Previous literature has indicated that factors such as age and gender may influence these parameters; However, there is a lack of studies investigating these differences specifically in the Middle East or Jordan. Additionally, no prior research has explored the relationship between UV and CHR. Therefore, the objective of this study is to investigate these critical radiological parameters and their associations. METHODOLOGY: A cross-sectional study design was employed, wherein a total of 385 normal wrist X-rays were reviewed, and CHR and UV were measured. Intra-observer and inter-observer reliability assessments were conducted to ensure the consistency and accuracy of measurements. Additionally, the association between UV and CHR was measured and plotted for further analysis. RESULTS: In our study, the mean CHR was 0.5 (range: 0.4 to 1.5), and the mean UV was - 0.3 mm (range: -5.8 mm to 4.1 mm). We found a significant negative correlation between CHR and age (p < 0.05). No significant gender differences were observed in UV and CHR. Additionally, a weak positive correlation was found between UV and CHR (Pearson correlation coefficient = 0.13, p = 0.01; adjusted R2 = 0.014, p = 0.02). CONCLUSION: Age correlated significantly with a decline in carpal height ratio. Additionally, ulnar variance had a week positive yet significant correlation with carpal height ratio. LEVEL OF EVIDENCE: Cross-sectional study, Level III.

The accuracy of Cameriere methods in Turkish children: chronological age estimation using developing teeth and carpals and epiphyses of the ulna and radius.

The aim of the present study was to develop a specific formula by measuring the developing teeth, carpal bones, and epiphyses of the ulna and radius to determine the chronological age in Turkish children. The left developing permanent mandibular teeth were evaluated, and the number of teeth with closed apex was recorded. The distance between the inner sides of open apex/apices was measured by using the ImageJ program and divided by the tooth length. The sum of the normalized open apices was also calculated. The carpal area (Ca), covering the epiphyses of ulna and radius and the carpal bones, was measured on the X-rays of left hand. The areas of each carpal bone and epiphyses of the ulna and radius were measured, and these measurements were added together to obtain the bone area (Bo). The Bo/Ca ratio between the total area of carpal bones and the carpal area was calculated to normalize the measurements. The accuracy of the equations formulated by Cameriere was evaluated, and a new regression equation was developed accordingly. The new formula showed no statistically significant difference between the chronological and the estimated age for females, males, and total sample. The new formula, which hit the age with 72.80% accuracy, was more successful in predicting chronological age than other adjusted regression equations. The new regression model, created for the Turkish children by using both developing teeth and hand-wrist bones, was considerably successful in estimating the chronological age.

Imaging evaluation of traumatic carpal instability.

PURPOSE: To review the epidemiology, pertinent wrist anatomy, classification system, and emergent imaging evaluation of carpal instability with a focus on radiographic assessment of instability. METHODS: A review of current literature on carpal instability was performed with summary presentation of carpal instability epidemiology, carpal anatomy, imaging evaluation, and classification with imaging evaluation focused on diagnosis in the emergency setting. RESULTS: Carpal instability is a common pathology in falls on outstretched hand and is likely underdiagnosed due to instability being occult or demonstrating subtle malalignment on static imaging of the wrist. While there is a complex network of intrinsic and extrinsic ligaments contributing to carpal instability, a detailed knowledge of these ligaments is not necessary for radiologists to make an accurate diagnosis in the emergency setting, as identification and classification of carpal instability is based on identification of carpal malalignment patterns on radiography as opposed to identification of specific ligament injuries on advanced imaging. The Mayo classification is the most widely used classification system, which divides carpal instability into four categories: dissociative, non-dissociative, complex, and adaptive. Understanding this classification system allows radiologists to successfully classify almost all carpal instability injuries they will encounter, even in the setting of unusual or rare instability patterns. CONCLUSION: In working with the treating clinician, it is essential that the emergency radiologist is comfortable with identifying and classifying carpal instability. This will ensure prompt treatment of seemingly benign injuries and those that require intervention, surgical or otherwise, improving the likelihood of a good outcome.

A new radiographic view of the scaphotrapeziotrapezoid joint-a cadaveric study.

BACKGROUND: The scaphotrapeziotrapezoid joint (STTJ) has a complex osseous and ligamentous anatomy. Precise radiographic assessment is paramount when assessing osteoarthritic, post-traumatic, or post-operative patients. There has been no described technique to image the STTJ without any wrist movement, unobscured by the rest of the carpus. The aim of this study was to define an optimal radiographic method to assess the STTJ while maintaining the wrist in neutral position. METHODS: Computer tomography 3-D reconstructions of three uninjured wrists were initially used to determine an approximate beam angle. Serial radiographs of 12 cadaveric wrists were taken. The forearms were positioned in varying degrees of pronation and supination. The beam angle was concurrently adjusted to varying degrees of caudal tilt. From the images obtained, we assessed if the adjacent carpus obscured the view of the STTJ. RESULTS: Optimal STTJ imaging was in the semi-pronated wrist position with the X-ray beam tilted caudal. We found that the STTJ was best visualized at 48° supination from a fully pronated wrist and a caudal beam angle of 22°. CONCLUSIONS: The described wrist and beam orientation can aid in achieving an unobstructed view of the STTJ with little technical effort. This can aid in imaging ambulatory patients where symptoms prevent using other imaging techniques as well as patients in the operating room where imaging timing can be critical.

Anatomical relationship of palmar carpal bone landmarks used in locating the lunate and capitate during palpation: A cadaveric investigation.

STUDY DESIGN: Descriptive in situ cadaveric study. INTRODUCTION: Performing accurately directed examination and treatment to the wrist requires clinicians to orient to carpal bone structures. PURPOSE OF THE STUDY: To examine the anatomical relationships that exist within the wrist-hand complex and identify the accuracy of surface anatomy mapping strategies for localizing anatomical landmarks using a palmar approach. METHODS: Twenty-three embalmed cadavers were dissected using standardized procedures. Metal markers were placed in the most prominent palmar landmark of key carpal structures. Relationships between the most prominent palpation landmarks and the carpal bones of interest were visualized using fluoroscopy. RESULTS: The most successful methods of palmar capitate localization included the midpoint of a line from trapezium tubercle to pisiform; the midpoint of a line from scaphoid tubercle to hamate hook; or the intersection (cross) of these 2 diagonal lines, with successful capitate identification 100% (23/23) of the time. The most successful method for locating the lunate included the midpoint of a line from the radial styloid process to the ulnar styloid process, which identified the lunate in 100% (23/23) of cases. DISCUSSION: The results of this cadaveric anatomical relationship study support the use of the midpoint of a line from pisiform to trapezium tubercle, the midpoint of a line from scaphoid tubercle to hamate hook, or a combination (cross) of these lines to locate the capitate from a palmar approach. In addition, the anatomical relationships examined in this study support the use of the midpoint of a line from the radial styloid process to ulnar styloid process to locate the lunate from a palmar approach. Knowledge of these anatomical relationships may improve the clinician's confidence in locating the capitate and lunate during intercarpal examination, special testing, and treatment. CONCLUSION: Results of this study provide information of the anatomical relationships of the carpal bones from a palmar approach, giving clinicians a foundation for proper orientation to the carpal bones during clinical examination and intervention. Further research is needed to evaluate the reliability and accuracy of these methods for surface palpation on live patients.

New Neandertal wrist bones from El Sidrón, Spain (1994-2009).

Twenty-nine carpal bones of Homo neanderthalensis have been recovered from the site of El Sidrón (Asturias, Spain) during excavations between 1994 and 2009, alongside ∼2500 other Neandertal skeletal elements dated to ∼49,000 years ago. All bones of the wrist are represented, including adult scaphoids (n = 6), lunates (n = 2), triquetra (n = 4), pisiforms (n = 2), trapezia (n = 2), trapezoids (n = 5), capitates (n = 5), and hamates (n = 2), as well as one fragmentary and possibly juvenile scaphoid. Several of these carpals appear to belong to the complete right wrist of a single individual. Here we provide qualitative and quantitative morphological descriptions of these carpals, within a comparative context of other European and Near Eastern Neandertals, early and recent Homo sapiens, and other fossil hominins, including Homo antecessor, Homo naledi, and australopiths. Overall, the El Sidrón carpals show characteristics that typically distinguish Neandertals from H. sapiens, such as a relatively flat first metacarpal facet on the trapezium and a more laterally oriented second metacarpal facet on the capitate. However, there are some distinctive features of the El Sidrón carpals compared with most other Neandertals. For example, the tubercle of the trapezium is small with limited projection, while the scaphoid tubercle and hamate hamulus are among the largest seen in other Neandertals. Furthermore, three of the six adult scaphoids show a distinctive os-centrale portion, while another is a bipartite scaphoid with a truncated tubercle. The high frequency of rare carpal morphologies supports other evidence of a close genetic relationship among the Neandertals found at El Sidrón.

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.

Carpal bones of Nacholapithecus kerioi, a Middle Miocene Hominoid From Northern Kenya.

OBJECTIVES: The carpal bones of the middle Miocene hominoid Nacholapithecus kerioi are described based on new materials. MATERIALS AND METHODS: The materials comprise a trapezoid, three capitates, two hamates, a centrale, a lunate, a triquetrum, and a pisiform, collected during the 2001 and 2002 field seasons from Nachola, Kenya. We also describe a pisiform recently assigned to the type specimen of N. kerioi, KNM-BG 35250. RESULTS: In the Nacholapithecus wrist, the ulnar styloid process articulates with both the triquetrum and pisiform, and the triquetrum facet on the hamate is relatively proximodistally oriented in dorsal view. The Nacholapithecus capitate possesses a moderate distopalmar hook-like process and separated radial articular facets for the trapezoid and the second metacarpal due to the carpometacarpal ligament attachment that is absent in the Proconsul capitate. DISCUSSION: The carpal anatomy of Nacholapithecus is similar to that of the early Miocene hominoid Proconsul. However, Nacholapithecus wrist anatomy appears to exhibit slightly more emphasized stability. Am J Phys Anthropol 160:469-482, 2016. © 2016 Wiley Periodicals, Inc.

Influence of Exercise and Intra-articular Site on Canals in Articular Calcified Cartilage of Equine Third Carpal Bones.

The third carpal bone (C3) responds to exercise by adaptive modeling of bone and articular calcified cartilage along the dorsal load path. Canals penetrating articular calcified cartilage, thought to contain vascular tissue, are reported in numerous species. Their significance remains unclear. Our objective was to determine if the number of canals was significantly different in strenuously exercised and control young horses and in a site of intermittent high loading compared to sites sustaining lower habitual loads. Volumetric bone mineral density in the radial facet of C3 of strenuously exercised and gently exercised (control) 19-month-old thoroughbred horses (n= 6/group) was determined by peripheral quantitative computed tomography. The hyaline cartilage was corroded to expose the surface of articular calcified cartilage. The number of canals penetrating the articular calcified cartilage surface in en face scanning electron microscopy images was compared in 4 regions. Volumetric bone mineral density of C3 was significantly greater (P= .004) in strenuously exercised horses. There were 2 morphologically distinct groups of canals and significantly fewer (P= .006) large canals in the dorsal than in the palmar aspect of C3 in control but not in exercised horses. Roughly circular depressions in the articular calcified cartilage surface around apparently forming canals were visible in some samples and have not been previously described in the literature. The canals may be evidence of chondroclastic activity reaching the interface of hyaline and calcified cartilage. Further work is needed to elucidate the relationships between presence of canals and the responses to exercise and to joint disease.

The effect of magnification on sonographically measured nerve cross-sectional area.

INTRODUCTION: The primary aim of this investigation was to determine whether use of write-zoom magnification affects sonographically determined cross-sectional area (CSA) of peripheral nerves. METHODS: CSAs of the median (MN) and posterior interosseous (PIN) nerves were measured in 22 limbs from 11 asymptomatic volunteers using both standard imaging and write-zoom magnification. CSA measurements were repeated on the same images 1 week later. RESULTS: The average CSA of write-zoomed images for the MN was significantly larger at both measurement sessions (week 1: 11.1 mm(2) write-zoom vs. 10.0 mm(2) standard, P = 0.019; week 2: 11.8 mm(2) vs. 10.4 mm(2), P = 0.023). Similar differences were noted for the PIN (week 1: 2.3 mm(2) vs. 1.9 mm(2), P = 0.002; week 2: 2.5 mm(2) vs. 1.9 mm(2), P = 0.001). CONCLUSIONS: Write-zoom magnification may significantly increase the measured CSA of peripheral nerves. These changes appear to be more substantial when smaller nerves are measured.

Accuracy of MRI skeletal age estimation for subjects 12-19. Potential use for subjects of unknown age.

INTRODUCTION: In forensic practice, there is a growing need for accurate methods of age estimation, especially in the cases of young individuals of unknown age. Age can be estimated through somatic features that are universally considered associated with chronological age. Unfortunately, these features do not always coincide with the real chronological age: for these reasons that age determination is often very difficult. Our aim is to evaluate accuracy of skeletal age estimation using Tomei's MRI method in subjects between 12 and 19 years old for forensic purposes. MATERIAL AND METHODS: Two investigators analyzed MRI images of the left hand and wrist of 77 male and 74 female caucasian subjects, without chronic diseases or developmental disorders, whose age ranged from 12 to 19 years. Skeletal maturation was determined by two operators, who analyzed all MRI images separately, in blinded fashion to the chronological age. Inter-rater agreement was measured with Pearson (R (2)) coefficient. One of the examiners repeated the evaluation after 6 months, and intraobserver variation was analyzed. Bland-Altman plots were used to determine mean differences between skeletal and chronological age. RESULTS: Inter-rater agreement Pearson coefficient showed a good linear correlation, respectively, 0.98 and 0.97 in males and females. Bland-Altman analysis demonstrated that the differences between chronological and skeletal age are not significant. Spearman's correlation coefficient showed good correlation between skeletal and chronological age both in females (R (2) = 0.96) and in males (R (2) = 0.94). CONCLUSIONS: Our results show that MRI skeletal age is a reproducible method and has good correlation with chronological age.

Value of MRI of the hand and the wrist in evaluation of bone age: preliminary results.

PURPOSE: To evaluate bone age determination using MRI of the hand and wrist. MATERIALS AND METHODS: A total of 179 (78 female and 101 males, 11 to 16 years old) subjects of 252 normal volunteers met entrance criteria. A low field open magnet (0.2 Tesla) was used for this study; coronal T1-weighted images with a slice thickness of 1.3mm were acquired. Two blinded radiologists evaluated the studies and the following elements were considered: the appearance of cartilage, vacuolization of cartilage, provisional calcification, progression of ossification, and complete ossification. Correlation between chronologic age and MR bone age was determined by means of simple linear regression analysis. RESULTS: Strong correlation between MR skeletal age and chronological age was observed for both investigators, Pearson correlation R2 = 0.9 for each. CONCLUSION: Determination of bone age with MRI is feasible and shows good interobserver reproducibility. Data from this study may be useful to develop an atlas of skeletal development and bone age.

Carpal angles as measured on CT and MRI: can we simply translate radiographic measurements?

OBJECTIVE: To determine the reliability of carpal angles measured on CT and MRI compared to radiography and assess if these measurements are interchangeable. MATERIALS AND METHODS: Our institutional ethic research committee approved this study. For this retrospective study, two independent observers measured the scapholunate (SL), capitolunate (CL), radiolunate (RL), and radioscaphoid (RS) angles on 21 sets of exams, with each set including a radiograph, CT, and MRI of the same wrist. Inter- and intra-observer agreements were evaluated with the intraclass correlation coefficient (ICC). Linear mixed models and two-way contingency tables were used to determine if the angles measured on cross-sectional modalities were significantly different from those obtained on radiography. RESULTS: Inter-observer agreement was strong (ICC >0.8) for all angles, except for the RL angle measured on MRI (ICC 0.68). Intra-observer agreement was also strong for all angles, except for the CL angle measured on CT (ICC 0.66). SL angles measured on CT and MRI were not statistically different from those measured on radiographs (p = 0.37 and 0.36, respectively), unlike CL, RL, and RS angles (p < 0.05). Accuracy between modalities varied between 76 and 86% for the SL angle and ranged between 43 and 76% for the other angles. CONCLUSIONS: CL, RL, and RS angles showed large intermodality variability. Therefore, their measurements on CT or MRI could potentially lead to miscategorization. Conversely, our data showing no significant difference between modalities, SL angle could be measured on CT and MRI to assess wrist instability with a lower risk of error.

Carpal variability and asymmetry in limb reduced Western lesser sirens (Siren nettingi).

Trait functionality can act as a constraint on morphological development. Traits that become vestigialized can exhibit unstable developmental patterns such as fluctuating asymmetry (FA) and variation in populations. We use clearing and staining along with morphometric analyzes to compare FA and allometry of limbs in Western lesser sirens (Siren nettingi) to Ouachita dusky salamanders (Desmognathus brimleyorum). Our results describe new carpal phenotypes and carpal asymmetry in our sample of S. nettingi. However, we found no significant evidence of limb length asymmetry in S. nettingi. The degree of relative limb asymmetry correlates inversely with body size in both of our samples. This work provides strong evidence of increased mesopodal variation within a population of S. nettingi. Our work provides a basis for further study of a broader range of morphological traits across salamanders.

Distal forelimb radiographic bone morphology in Thoroughbred foals during the first 10 months post-partum. Part 1: Carpus.

BACKGROUND: The risk of carpal injury in racehorses may be related to the morphology, yet whether carpal morphologies are set from birth or change through growth remains unclear. OBJECTIVE: To quantify carpal bone changes through growth. METHOD: Twenty privately owned Thoroughbred foals born between January 2022 and May 2023 were radiographed bimonthly from birth to 10 months of age. Imprint training was used to take radiographs safely without chemical restraints. Fifteen individual and 11 relative angular carpal parameters were measured using ImageJ on dorsopalmar radiographs of the carpus at zero degrees of vertical and horizontal rotation. Associations with age (growth), sex and the differences between left and right limbs were analysed separately using a linear mixed effects model. RESULTS: Six individual carpal parameters changed with age (radial carpal joint [RCJ], Prx.dor. radial carpal [Cr], Prx.Cu, Dis.dor. third carpal [C3], Dis.pal.C3 and Dis.pal. intermediate carpal), and one was influenced by side, that is higher in the left carpus (Dis.pal.Cr). Seven relative parameters changed with age, and one relative parameter was influenced by side, that is higher in the left (Ra.met-RCJ). The proximo-dorsal bone surface angle of Cr and disto-dorsal bone surface angle of C3 became flatter over time, which may be associated with the re-direction of the load towards the sagittal carpal plane. Sex did not influence any of the carpal parameters, nor did the combined effect of age, side of the limb and sex. CONCLUSION: Specific individual and relative angular carpal parameters changed significantly over time and some differed between the left and right limb, whereas other parameters did not change. The steeper carpal bone angles achieved proximally with the parameters that did change may improve stability by redirecting the load more medially through the carpus and the proximal and distal bones.

The carpal insertions of the transverse carpal ligament.

PURPOSE: To quantitatively define the anatomic insertions of the transverse carpal ligament (TCL) to the carpals. METHODS: We dissected 5 fresh-frozen cadaver limbs, isolating the TCL. The ligament insertion sites into bone were clearly marked and photographed. We then used computer software to measure the area of insertion into the individual carpals. RESULTS: The TCL had consistent insertion sites into the scaphoid, trapezium, pisiform, and hamate. The average insertion of the TCL on the scaphoid was 6 × 6 mm (proximal to distal × radial to ulnar maximum distance), trapezium 13 × 6 mm, pisiform 9 × 6 mm, and hamate 11 × 5 mm. The area of ligament insertion on the scaphoid was 29 mm(2), trapezium was 42 mm(2), pisiform was 38 mm(2), and hamate was 40 mm(2). The perimeter of the ligament insertion on the scaphoid was 21 mm, trapezium was 28 mm, pisiform was 25 mm, and hamate was 29 mm. CONCLUSIONS: The TCL has a broad but definable footprint on the trapezium and scaphoid on the radial side and the hamate and the pisiform on the ulnar side of the carpal tunnel. The distal carpal insertion sites are longer and oblong, whereas the proximal insertion sites are more circular. CLINICAL RELEVANCE: Precise knowledge of TCL attachment sites may allow the surgeon greater confidence and safety during procedures that involve its release, such as carpal tunnel release, trapeziectomy, hook of hamate excision, or Guyon canal release.

Carpal tunnel syndrome - anatomical and clinical correlations.

Carpal tunnel syndrome (CTS) is the most common and widely known of the entrapment neuropathies in which the body's peripheral nerves are compressed. Common symptoms of CTS involve the hand and result from compression of the median nerve within the carpal tunnel. In general, CTS develops when the tissues around the median nerve irritate or compress on the nerve along its course through the carpal tunnel, however often it is very difficult to determine cause of CTS. Proper treatment (conservative or surgical) usually can relieve the symptoms and restore normal use of the wrist and hand.

Carpal arch space increased by volar force applied to the skin surface above the carpal tunnel.

BACKGROUND: Carpal arch space augmentation can help decompress the median nerve. The augmentation can be achieved by mechanical manipulations utilizing the biomechanics of the tunnel structure. The purpose of this study was to expand the carpal arch in vitro by applying volar forces on the surface of the wrist. METHODS: The mechanism was implemented in eight cadaver hands by attaching a volar force transmitter to the palmar surface of the wrist and pulling the transmitter volarly at six force levels (0, 3, 6, 9, 12, and 15 N). Ultrasound images of the cross section at the distal carpal tunnel were collected for morphological analysis. FINDINGS: The carpal arch height, width, and area were significantly altered by the volarly applied force (P < 0.001). The arch height and area were increased but the arch width was decreased by the force. Pearson's correlation coefficient showed that there was a positive correlation between the arch height and force magnitude; and between the arch area and force magnitude. A negative correlation existed between the arch width and force magnitude (P < 0.001). The magnitude of change of the arch height, width, and area was increased as the force magnitude increased. INTERPRETATION: This study demonstrated that applying external forces on the wrist skin to increase the carpal arch space was feasible. The magnitude of the force influenced its effect on altering the carpal arch. Study limitations include small sample size and inclusion of male specimens. Future in vivo work is needed for clinical translation feasibility.

Modularity of the wrist in extant hominines.

Wrist shape varies greatly across primates and previous studies indicate that the numerous morphological differences among them are related to a complex mixture of phylogeny and function. However, little is known about whether the variation in these various anatomical differences is linked and to what extent the wrist bones vary independently. Here, we used 3D geometric morphometrics on a sample of extant hominines (Homo sapiens, Pan troglodytes, Gorilla gorilla, and Gorilla beringei), to find the model that best describes the covariation patterns among four of the eight carpals (i.e., capitate, lunate, scaphoid, and trapezium). For this purpose, 15 modular hypotheses were tested using the Covariance Ratio. Results indicate that there is a covariation structure common to all hominines, which corresponds to stronger covariation within each carpal as compared to the covariation between carpals. However, the results also indicate that that there is a degree of codependence in the variation of some carpals, which is unique in humans, chimpanzees, and gorillas, respectively. In humans there is evidence of associated shape changes between the lunate and capitate, and between the scaphoid and trapezium. This covariation between lunate and capitate is also apparent in gorillas, while chimpanzees display the greatest disassociation among carpals, showing low covariation values in all pairwise comparisons. Our analyses indicate that carpals have an important level of variational independence which might suggest a high degree of independent evolvability in the wrists of hominines, and that although weak, the structure of associated changes of these four carpals varies across genera. To our knowledge this is the first report on the patterns of modularity between these four wrist bones in the Homininae and future studies might attempt to investigate whether the anatomical shape associations among carpals are functionally related to locomotion and manipulation.

Carpal kinematics in quadrupedal monkeys: towards a better understanding of wrist morphology and function.

The purpose of this study is to provide new data on carpal kinematics in primates in order to deepen our understanding of the relationships between wrist morphology and function. To that end, we provide preliminary data on carpal kinematics in seven species of quadrupedal monkeys that have not been previously investigated in this regard (cercopithecoids, n = 4; ceboids, n = 3). We radiographed wrists from cadavers at their maximum radial and ulnar deviations, as well as at maximum flexion and extension. We took angular measurements to quantify the contribution of the mobility of the two main wrist joints (antebrachiocarpal and midcarpal) with respect to total wrist mobility. We also recorded qualitative observations. Our quantitative results show few clear differences among quadrupedal monkeys for radioulnar deviation and flexion-extension: all the primates studied exhibit a greater midcarpal mobility (approximately 54-83% of the total range of motion) than antebrachiocarpal mobility; however, we identified two patterns of carpal kinematics that show the functional impact of previously recognised morphological variations in quadrupedal monkeys. Firstly, qualitative results show that the partition that divides the proximal joint of the wrist in ceboids results in less mobility and more stability of the ulnar part of the wrist than is seen in cercopithecoids. Secondly, we show that the olive baboon specimen (Papio anubis) is characterised by limited antebrachiocarpal mobility for extension; this effect is likely the result of a radial process that projects on the scaphoid notch, as well as an intraarticular meniscus. Because of these close relationships between carpal kinematics and morphology in quadrupedal monkeys, we hypothesise that, to some extent, these functional tendencies are related to their locomotor hand postures.