Proximal Carpals Research Articles

Morphology and ontogeny of carpus and tarsus in stereospondylomorph temnospondyls.

Skeletal development is well known in temnospondyls, the most diverse group of Paleozoic and Mesozoic amphibians. However, the elements of carpus and tarsus (i.e., the mesopodium) were always the last bones to ossify relative to the other limb bones and with regard to the rest of the skeleton, and are preserved only in rare cases. Thus, in contrast to the other parts of the limb skeleton, little is known about the ontogeny and sequence of ossification of the temnospondyl carpus and tarsus. We intended to close this gap by studying the ontogenies of a number of Permo/Carboniferous stereospondylomorphs, the only temnospondyls with preserved growth series in which the successive ossification of carpals and tarsals can be traced. Studying the degree of mesopodial ossification within the same species show that it is not necessarily correlated with body size. This indicates that individual age rather than size determined the degree of mesopodial ossification in stereospondylomorphs and that the largest individuals are not necessarily the oldest ones. In the stereospondylomorph tarsus, the distal tarsals show preaxial development in accordance with most early tetrapods and salamanders. However, the more proximal mesopodials exhibit postaxial dominance, i.e., the preaxial column (tibiale, centrale 1) consistently started to ossify after the central column (centralia 2-4, intermedium) and the postaxial column (fibulare). Likewise, we observed preaxial development of the distal carpals in the stereospondylomorph carpus, as in most early tetrapods for which a statement can be made. However, in contrast to the tarsus, the more proximal carpals were formed by preaxial development, i.e., the preaxial column (radiale, centrale 1) ossified after the central column (centralia 2-4, intermedium) and before the postaxial column (ulnare). This pattern is unique among known early tetrapods and occurs only in certain extant salamanders. Furthermore, ossification proceeded from distal to proximal in the central column of the stereospondylomorph carpus, whereas the ossification advanced from proximal to distal in the central column of the tarsus. Despite these differences, a general ossification pattern that started from proximolateral (intermedium or centrale 4) to mediodistal (distal tarsal and carpal 1) roughly in a diagonal line is common to all stereospondylomorph mesopodials investigated. This pattern might basically reflect the alignment of stress within the mesopodium during locomotion. Our observations might point to a greater variability in the development of the mesopodium in stereospondylomorphs and probably other early tetrapods than in most extant tetrapods, possibly mirroring a similar variation as seen in the early phases of skeletogenesis in salamander carpus and tarsus.

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

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. 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. 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. 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.

Patterns of internal bone structure and functional adaptation in the hominoid scaphoid, lunate, and triquetrum

AbstractThe morphology of the proximal carpals (scaphoid, lunate, triquetrum) are linked to the range of motion (ROM) at the radiocarpal and midcarpal joints. While the relationship between ROM and habitual locomotor mode is well established, it has yet to be investigated whether relative patterns of internal bone architecture reflect the kinematics and kinetics at the proximal row. As internal bone is known to model its structure to habitually incurred forces, internal architecture has the potential to provide insight into how joints have been loaded during the lifetime of an individual. Using a broad sample of extant great apes and humans (n = 177 total bones), this study investigates whether relative differences in the bone volume to total volume (BV/TV) and degree of anisotropy (DA) across the scaphoid, lunate and triquetrum correlate with the presumed force transfer and biomechanics of the hominoid wrist. Results reveal that broad patterns in BV/TV and DA differentiate hominoids by their predominant locomotor mode. The human pattern suggests the lunate may be the most highly strained bone within the proximal row. Both knuckle‐walking taxa (Gorilla, Pan) exhibited similar architectural patterns suggesting they are adapted to resist similar forces in this region of the wrist. The relatively high DA across all Pongo carpals suggests it may have more stereotypical wrist loading than commonly assumed. Finally, the distinctly low DA in the triquetrum across all taxa suggests force transfer via the synapomorphic triangular fibrocartilage complex may leave a distinctive signature in the internal bone architecture that requires further investigation.ObjectivesFunctional adaptation in the trabecular and cortical bone of individual wrist bones has been investigated across hominoid species but functional conclusions remain limited. This study examines whether relative patterns in internal bone architecture across multiple carpal bones can be correlated to the known or assumed kinetics and kinematics of the wrist joint in extant hominoids.Materials and MethodsThis study applied a whole‐bone methodology to quantify the internal architecture (cortical and trabecular bone) of the scaphoid, lunate, and triquetrum of suspensory (Pongo sp.), knuckle‐walking (Pan paniscus, Pan troglodytes, Gorilla sp.) and bipedal (Homo sapiens) hominoids (n = 177 total bones).ResultsH. sapiens showed unique patterns in both measured parameters: a decrease in degree of anisotropy (DA) from the scaphoid to the triquetrum with higher bone volume to total volume (BV/TV) in the lunate relative to the other bones. Knuckle‐walking taxa had similar patterns in both parameters: highest mean DA in the lunate and lowest in the triquetrum while significantly higher BV/TV was recorded the triquetrum. Pongo exhibited the same DA pattern as knuckle‐walking taxa but a distinct pattern of continual decrease in BV/TV from scaphoid to triquetrum.DiscussionRelative differences in the internal bone structure across multiple carpals differentiated locomotor modes in extant hominoids. The triquetrum and lunate are particularly understudied but their importance to differentiating locomotor mode indicates further research is warranted. Establishing patterns across more carpal joints in primates should be a research priority as they will provide critical context to interpreting fossil species represented by single or few carpal elements.

Vascularized Bone Graft to the Lunate Combined with Shortening of the Capitate and Radius for Treatment of Advanced Kienböck Disease After a Follow-Up for More Than 10 Years

PurposeThis study aimed to report the outcomes of patients with stage III Kienböck disease after treatment with a vascularized bone graft (VBG) to the lunate combined with capitate shortening osteotomy (CS) after a more than 10-year follow-up.MethodsA VBG to the lunate was combined with CS in 10 patients with stage III Kienböck disease (6 patients with stage IIIA and 4 with stage IIIB). We performed VBG, CS, and radial shortening osteotomy (RS) on 7 patients. Among them, 4 had undergone RS previously. The passive wrist extension angle and wrist flexion angle, grip strength (GS), carpal height ratio, Stahl index, visual analog scale of wrist pain, and Mayo modified wrist score were assessed before surgery and at the final follow-up.ResultsThe flexion angle decreased markedly after surgery, when GS increased in all 10 patients. Radiographic examinations revealed that the carpal height ratio decreased in 9 of 10 patients, whereas the Stahl index increased in 8 patients and remained unchanged in 2. The oldest 3 of 7 patients who underwent VBG, CS, and RS exhibited fusion of the proximal carpals except the pisiform. The mean visual analog scale decreased from 27.6 before surgery to 5.7 afterward. The Mayo modified wrist score improved in 9 patients after surgery and remained unchanged in one.ConclusionsIn stage III Kienböck disease, VBG to the lunate combined with CS relieved wrist pain and increased GS and lunate height but was followed by severely restricted wrist motion. Fusion of the proximal carpals developed in 3 of 7 patients who received VBG with CS and RS.Type of study/level of evidenceTherapeutic Ⅳ.

The manus of Tetracynodon (Therapsida: Therocephalia) provides evidence for survival strategies following the Permo-Triassic extinction

We present a comprehensive qualitative and quantitative study of the manus of a new therocephalian specimen referable to Tetracynodon from the Early Triassic of South Africa. We examined 18 specimens, representing at least 12 genera, including basal therocephalians (Lycosuchidae and Scylacosauridae) and eutherocephalians (Akidnognathidae, Whaitsioidea and Baurioidea). A temporal range of 23 million years through the Permo-Triassic (Wordian to Anisian) was surveyed. A principal component analysis of the therocephalian manus indicates that (1) metacarpals II, III, and IV acted as a module of which the medial and lateral elements (metacarpals I and V) were independent from each other; and (2) the proximal carpals, ulnare, and radiale lengths show contrasting variation in their measurements (e.g., groups with longer ulnares tend to have shorter radiales). The manus of Permian and Triassic taxa occupy separate regions in morphospace. This segregation pattern suggests selection for a manus with slender, elongated second to fourth metacarpals during and after the Permo-Triassic mass extinction. We show a heterogeneous condition of the fifth distal carpal bone. Although usually interpreted as fused to the fourth distal carpal or absent, the fifth distal carpal was present as a cartilaginous element in Tetracynodon. Strong and proportionally long unguals in relation to length of digits III and IV, wide and stocky basal phalanges, and short non-ungual phalanges strongly suggest that Tetracynodon was a scratch-digger. This supports the proposition that burrowing was an important behavioral strategy of terrestrial taxa during and after the Permo-Triassic mass extinction.

Functional carpal anatomy

The analysis of the carpal mechanism requires detailed examination of the anatomy of the wrist. The multiple joints within the wrist form a complex structure capable of transmitting significant loads to the upper extremity while providing a mobile base for the precision movements of the hand. This duality is accomplished through a fine interplay between the carpal bones and an arrangement of highly specific ligamentous structures, a system loaded by balanced muscle forces. The carpal joint can be approached as a mechanism consisting of kinematic chains. In these chains, the proximal carpals function as intercalated segments. Intercarpal displacements are linked to one another and are based upon the mutual attuning of carpal bone geometry, joint contacts, and ligamentous interconnections. The study of these mechanisms is crucial for understanding the pathophysiology of carpal instability.

Patterns of carpal development among anuran amphibians.

The unity and diversity of developmental processes in the vertebrate limb have singular importance in the interpretation of evolutionary hypotheses of tetrapod diversification. In anurans, the intraordinal diversity of forelimbs seems to be related to the fusion of distal carpals, whereas proximal carpals are invariable. However, there are different ontogenetic pathways involved in the differentiation of proximal carpals. This study presents a comparative analysis of early developmental features in one archeobatrachian and 23 neobatrachian species representing five families and explores the variability in the differentiation of carpal cartilages. We found new evidence supporting the presence of an embryonic intermedium that incorporates with the ulnare. Difference between the pipid Xenopus and the neobatrachians is interpreted as a change in the rate of differentiation of Distal Carpal 5 that does not affect the developmental pattern of digits. The developmental variability exhibited by the intermedium, radiale, and Element Y is combined in patterns that converge on the same adult carpal morphology among neobatrachians; these patterns appear to contain potentially useful phylogenetic information.

A new genus of ichthyosaur from the Late Triassic Pardonet Formation of British Columbia: bridging the Triassic Jurassic gap

Both the genus Shastasaurus and the family Shastasauridae have long been hard to define due to the fragmentary nature of the type specimens. Consequently, recent interpretations of the genus have been based almost entirely on Shastasaurus neoscapularis from the Late Triassic Pardonet Formation of British Columbia. Two new specimens of this taxon, from Pink Mountain, British Columbia, demonstrate that it does not belong in the genus Shastasaurus. This paper describes the new specimens, and refers the species to Metashastasaurus gen nov. Post-cranially, the skeleton of Metashastasaurus resembles that of shastasaurids, differing primarily only in the shape of the scapula and fibula. However, the skull has a unique combination of characters, including large diamond-shaped frontals that enter the supratemporal fenestrae, and very narrow posterior extensions of the nasals, which contact the postfrontals. It also differs from the skull of Shastasaurus in the presence of both a parietal ridge and postparietal shelf. This is a combination of derived characters previously known only in Jurassic forms. The front limb has four proximal carpals and four digits, indicating that previous reconstructions were based on incomplete material. Shastasaurus pacificus Merriam 1895, the type species of the genus Shastasaurus, must be considered a nomen dubium, making the genus Shastasaurus invalid. Until this problem is clarified, the use of the generic name Shastasaurus should be restricted to Merriam's type specimens, of which only Shastasaurus alexandrae and Shastasaurus osmonti are based on adequate material.

The Carpal Joint

The carpal joint can be approached as a mechanism consisting of kinematic chains. In these chains, the proximal carpals function as intercalated segments. Intercarpal displacements are linked to one another and are based upon the mutual attuning of carpal bone geometry, joint contacts, and ligamentous interconnections.

Kinematic behavior of the human wrist joint: a roentgen-stereophotogrammetric analysis.

Using a roentgen-stereophotogrammetric measurement system, the three-dimensional kinematic characteristics of each carpal bone in two human wrist joints were obtained as the hands were moved in vitro through dorsopalmar flexion and through radioulnar deviation, both in the supinated and pronated positions of the hand. The results were described in terms of Euler rotation angles and showed that in flexion, the distal carpal bones may be considered as one fixed group while the proximal carpals may not. For the deviation motion, quite different rotational excursions for the carpal bones were observed, therefore, none of the two rows may be assumed acting as rigid groups. In both of the hand motions performed, all carpal bones moved synchronously and uniformly. These results demonstrate that accurate measurements of three-dimensional carpal-bone motions are feasible by using an adequately refined roentgen-stereophotogrammetric system. The detailed and precise kinematic information obtained can serve as a database for future developments of functional wrist-joint models, and will provide more insight into carpal-bone behavior, useful in clinical diagnosis and surgical reconstruction procedures.

Fractures of the distal radius and ulna and dislocation of the proximal carpals.

The wrist is commonly injured in falls on the outstretched hand, the character of the injury depending to a considerable extent upon the brittleness of the bones and the relative strength of the muscles and tendons upon which the forces of stress are exerted. In general, such falls tend to produce fractures of the radius and ulna in children and also in weak or elderly individuals. The same stresses in strong adults are prone to result in carpal dislocation or fracture of the scaphoid. The inherent toughness and elasticity of juvenile bones favor greenstick fracture. The brittle cortex and trabecular fragility of senile bones predispose to comminution, impaction, and T-fractures. There are endless varieties of fractures of the wrist, most of which are too well known to radiologists to justify extensive discussion here. A few are exemplified in Figure 1. We prefer descriptive adjectives to proper names in the identification of fractures. Examination The importance of adequate clinical and radiological study cannot be overemphasized. Multiple views, special views, and fine-detail technics are imperative. The use of a good magnifying lens is recommended. Films of the contralateral wrist are frequently helpful, particularly in children when the secondary centers of ossification may present problems. The radiologist should examine clinically all patients referred for radiological study. Frequently, a few well chosen questions will resolve diagnostic difficulties. We prefer to question and examine the patient after having seen the “wet films.” This is also an advantageous time for ordering special views, improving technics, and securing films of the contralateral wrist if indicated. Limitations Unrecognized Fractures: In spite of all the above precautionary measures, one may fail to demonstrate an abnormality which is clinically suspected. In such cases it is wise to treat the wrist as though it were fractured and to re-examine it in a week or ten days. This applies not only to scaphoid injuries (which are outside my province) but also to injuries of the bones and epiphyses of the forearm. Figure 2 illustrates such a “missed” fracture which was clearly demonstrated fourteen days later. Misdiagnosis of Fracture: Occasionally, sesamoid-like accessory ossicles are found in the wrist, and one is faced with the problem of differentiation between accessory bone and fracture. More than twenty carpal accessories have been described (6, 7). Although they may be mistaken for chip or avulsion fractures, careful attention to contour and reference to a chart such as is shown in Figure 3 should be helpful. The bilateral accessory pisiform bones of the nine-year-old child shown in Figure 4 has might simulate fractures of the ulnar styloids. Double ulnar styloid centers have been described (1) but are not readily confused with fractures. Double ossification centers occur infrequently in the wrist.

The primitive carpus

AbstractThere is as yet no proof that the prepollex and postminimus ever occurred as actual digits. Romer's discovery of previous confusion of the preaxial with the postaxial fin border of Sauripterus allows a more accurate interpretation of primitive conditions. The latter involved essential asymmetry. The carpal cartilages of the Sauripterus type offin must have split into transverse rows. When the radius and ulna had become of equal length there was redistribution of the most proximal carpals, thus displacing elements in the other rows. It seems that eventually the original first carpale assumed the position and function of a first metacarpal, while the original fifth metacarpale assumed the position and function of a fifth carpale.