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Concept: Scaphoid bone

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Previous research has revealed significant size differences between human male and female carpal bones but it is unknown if there are significant shape differences as well. This study investigated sex-related shape variation and allometric patterns in five carpal bones that make up the radiocarpal and midcarpal joints in modern humans. We found that many aspects of carpal shape (76% of all variables quantified) were similar between males and females, despite variation in size. However, 10 of the shape ratios were significantly different between males and females, with at least one significant shape difference observed in each carpal bone. Within-sex standard major axis regressions (SMA) of the numerator (i.e., the linear variables) on the denominator (i.e., the geometric mean) for each significantly different shape ratio indicated that most linear variables scaled with positive allometry in both males and females, and that for eight of the shape ratios, sex-related shape variation is associated with statistically similar sex-specific scaling relationships. Only the length of the scaphoid body and the height of the lunate triquetrum facet showed a significantly higher SMA slope in females compared with males. These findings indicate that the significant differences in the majority of the shape ratios are a function of subtle (i.e., not statistically significant) scaling differences between males and females. There are a number of potential developmental, functional, and evolutionary factors that may cause sex-related shape differences in the human carpus. The results highlight the potential for subtle differences in scaling to result in functionally significant differences in shape. Anat Rec, 2013. © 2012 Wiley Periodicals, Inc.

Concepts: Human, Male, Female, Wrist, Carpus, Lunate bone, Trapezoid bone, Scaphoid bone

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Scaphocapitate fracture syndrome is rare, complex injury. We report an unusual presentation of scaphocapitate fracture syndrome, involving fracture of the scaphoid and capitate associated with volar dislocation of the lunate and scaphoid and the proximal fragment of the capitate in a 30-year-old male after a motor vehicle accident. Computed tomography was found to be helpful for achieving the correct diagnosis. Open reduction and internal fixation was performed. The scaphoid fracture was fixed using a headless compression screw, and the volar displaced proximal fragment of the capitate was reduced to its original position, but could not be fixed because of severe comminution. This case cautions that the capitate fragment should not be excised even when it cannot be fixed due to comminution.

Concepts: Tram accident, Lunate bone, Scaphoid bone

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The carpals from the Homo floresiensis type specimen (LB1) lack features that compose the shared, derived complex of the radial side of the wrist in Neandertals and modern humans. This paper comprises a description and three-dimensional morphometric analysis of new carpals from at least one other individual at Liang Bua attributed to H. floresiensis: a right capitate and two hamates. The new capitate is smaller than that of LB1 but is nearly identical in morphology. As with capitates from extant apes, species of Australopithecus, and LB1, the newly described capitate displays a deeply-excavated nonarticular area along its radial aspect, a scaphoid facet that extends into a J-hook articulation on the neck, and a more radially-oriented second metacarpal facet; it also lacks an enlarged palmarly-positioned trapezoid facet. Because there is no accommodation for the derived, palmarly blocky trapezoid that characterizes Homo sapiens and Neandertals, this individual most likely had a plesiomorphically wedge-shaped trapezoid (like LB1). Morphometric analyses confirm the close similarity of the new capitate and that of LB1, and are consistent with previous findings of an overall primitive articular geometry. In general, hamate morphology is more conserved across hominins, and the H. floresiensis specimens fall at the far edge of the range of variation for H. sapiens in a number of metrics. However, the hamate of H. floresiensis is exceptionally small and exhibits a relatively long, stout hamulus lacking the oval-shaped cross-section characteristic of human and Neandertal hamuli (variably present in australopiths). Documentation of a second individual with primitive carpal anatomy from Liang Bua, along with further analysis of trapezoid scaling relative to the capitate in LB1, refutes claims that the wrist of the type specimen represents a modern human with pathology. In total, the carpal anatomy of H. floresiensis supports the hypothesis that the lineage leading to the evolution of this species originated prior to the cladogenetic event that gave rise to modern humans and Neandertals.

Concepts: Human, Hominidae, Wrist, Neanderthal, Carpus, Lunate bone, Trapezoid bone, Scaphoid bone

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The scaphoid is the most commonly fractured carpal bone. The presence of a concomitant hook of hamate fracture is of particular relevance given that it is often occult on routine wrist/scaphoid radiographs and that hook of hamate fractures are prone to symptomatic non-union, resulting in chronic ulnar wrist pain. Prompt diagnosis and immobilisation/fixation may minimise such complications. Our study is aimed at assessing the frequency of concomitant hook of hamate fractures in patients with scaphoid fractures.

Concepts: Wrist, Carpus, Lunate bone, Trapezoid bone, Scaphoid bone

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To systematically review the literature on the performance of ultrasound in diagnosing radiographically occult scaphoid fracture.

Concepts: Scaphoid fracture, Scaphoid bone

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The association of scaphoid or other carpal bone fractures with distal radius fractures is frequently reported, whereas few studies have described pisiform malalignment associated with distal radius fractures. The purpose of this study was to investigate the frequency and characteristics of pisiform malalignment associated with distal radius fractures.

Concepts: Wrist, Distal radius fracture, Carpus, Lunate bone, Scaphoid bone, Triquetral bone, Pisiform bone, Hamate bone

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Background  Scaphoid fractures in the pediatric population are rare. The majority of nondisplaced fractures tend to unite; however, there is an increased risk of nonunion in proximal pole fractures. Limited evidence exists in their outcomes, owing to the scarcity of the fracture pattern. Case Description  A 13-year-old boy who presented late after developing a traumatic proximal pole scaphoid fracture developed nonunion. He was treated conservatively owing to it being asymptomatic and developed union at 18 months. Literature Review  No previous case of proximal pole pediatric scaphoid fractures with established nonunion that has developed union with conservative management has been described. Clinical Relevance  The authors highlight a unique case of an established proximal pole scaphoid nonunion in a child progressing to union with nonoperative intervention. Owing to its rarity and difficulty in obtaining research, we recommend consideration of nonoperative management of asymptomatic nondisplaced proximal pole fractures in children.

Concepts: Bone fracture, Fracture, United States, United Kingdom, Conservatism, Scaphoid fracture, Scaphoid bone, Nonunion

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Background  Ideal internal fixation of the scaphoid relies on adequate bone stock for screw purchase; so, knowledge of regional bone density of the scaphoid is crucial. Questions/Purpose  The purpose of this study was to evaluate regional variations in scaphoid bone density. Materials and Methods  Three-dimensional CT models of fractured scaphoids were created and sectioned into proximal/distal segments and then into quadrants (volar/dorsal/radial/ulnar). Concentric shells in the proximal and distal pole were constructed in 2-mm increments moving from exterior to interior. Bone density was measured in Hounsfield units (HU). Results  Bone density of the distal scaphoid (453.2 ± 70.8 HU) was less than the proximal scaphoid (619.8 ± 124.2 HU). There was no difference in bone density between the four quadrants in either pole. In both the poles, the first subchondral shell was the densest. In both the proximal and distal poles, bone density decreased significantly in all three deeper shells. Conclusion  The proximal scaphoid had a greater density than the distal scaphoid. Within the poles, there was no difference in bone density between the quadrants. The subchondral 2-mm shell had the greatest density. Bone density dropped off significantly between the first and second shell in both the proximal and distal scaphoids. Clinical Relevance  In scaphoid fracture ORIF, optimal screw placement engages the subchondral 2-mm shell, especially in the distal pole, which has an overall lower bone density, and the second shell has only two-third the density of the first shell.

Concepts: Fracture, Skeletal system, Poles, Scaphoid fracture, Scaphoid bone, Polish language

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To review the incidence of union of patients with proximal pole scaphoid fracture nonunions treated using a 1,2 intercompartmental supraretinacular artery (1,2 ICSRA) vascularized graft and a small compression screw.

Concepts: Diseases and disorders, Distraction osteogenesis, Scaphoid fracture, Scaphoid bone, Nonunion

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Treatment of scaphoid fractures has been focused mainly on achieving union, with less attention to restoring normal scaphoid shape and orientation. Malalignment of one carpal bone will disrupt the kinetics of the entire wrist. The dorsal intercalated segment instability deformity associated with scaphoid waist nonunion is a nondissociative form of carpal instability. It has to be reduced in the treatment of scaphoid waist nonunions to avoid kinetic problems that will lead to arthritic changes. Computerized tomography scanning has become indispensable to visualize the humpback deformity clearly. Different techniques may be used to restore the normal anatomy of scaphoid, from non-vascularized graft to arthroscopic bone grafting, and also the option of vascularized bone grafting.

Concepts: Wrist, Carpal tunnel, Carpus, Lunate bone, Trapezoid bone, Scaphoid bone