Anatomy of Distal Articular Surface of Hamate Bone, A Cadaveric Study.

Background: Hemi-hamate arthroplasty is one of the treatment options for dorsal proximal interphalangeal joint fracture dislocation. Many studies reported favorable outcomes. However, some long term studies demonstrated the degenerative change of PIP joint. The articular mismatch of the hemi-hamate autograft might play an important role of this complication. Methods: We studied the anatomy of distal articular surface of the hamate bone in embalmed hamate bones. The anatomy of distal articular surface and dimensions of the hamate bone were measured and recorded. Results: Seventy hamate bones were dissected out from embalmed cadavers and included in this study. The mean angle of the 4th metacarpal articulation was 85.54 degrees (SD = 3.53) and mean angle of the 5th metacarpal articulation was 95.51 degrees (SD = 3.57). The inter-articular ridge was approximately 5 degrees radial inclination. Conclusions: The inter-articular ridge of distal articular surface was approximately 5 degrees radial inclination. In order to minimize the graft mismatch, we recommend making the bone cut with the saw blade tilted to radial side 5 degrees to achieve better alignment of inter-articular ridge of the graft.

The Effect of Hamatum Curvature Angle on Carpal Tunnel Volumetry: A Mathematical Simulation Model.

In carpal tunnel volume measurements, the angle of the hamatum curvature is not considered a variable, and its effect on carpal tunnel volume has not been investigated. We hypothesize that a change in the anatomical angle of the hamatum curvature changes the carpal tunnel volume. To prove our hypothesis, we used a mathematical simulation model considering the carpal tunnel as a truncated cone. We reviewed the wrist CT scans of 91 adults (>18 years of age), including 51 men and 40 women. We measured the angle of the hamatum curvature in the CT scans. We measured cross-sectional areas at the outlet of the carpal tunnel at the level of the trapezium and hook of hamate (r1) and at the inlet at the level of the scaphoid and pisiform (r2) and the length (h) of the carpal tunnel. We attempted to calculate the effect of 2 degree by 2-degree changes in the angle of the hamatum curvature between the angles of 98° and 140° on the carpal tunnel volume. The mean angle of the hook of hamatum of the subjects was 122.55° ± 8.20° (range, 97.20° - 139.31°). No suitable cutoff point was found for the angle values. There was no difference between the gender groups according to the angle value. The data clearly show that there is a high correlation between carpal tunnel volume and the angle of hamatum curvature. The results of our study emphasize the importance of taking into account the anatomical features of the hamatum bone, especially the angle of curvature, which may play a predisposing role in idiopathic carpal tunnel syndrome.

The Use of the Proximal Hamate as an Autograft for Proximal Pole Scaphoid Fractures: Clinical Outcomes and Biomechanical Implications.

Scaphoid proximal pole fractures remain a surgical challenge because of high propensity for nonunion, osteonecrosis, and ultimately carpal collapse. Options for management of nonsalvageable proximal pole fractures include non-vascularized bone grafts, vascularized pedicled bone grafts, free vascularized bone flaps, and rib cartilage grafts. The proximal pole of the hamate can also serve as a replacement arthroplasty in the setting of proximal pole scaphoid nonunions with collapse, bone loss, and/or osteonecrosis. This novel graft addresses shortcomings of other graft choices by providing a local structural autograft solution with minimal donor site morbidity, correcting carpal collapse, reconstructing the scapholunate ligament, and mitigating the need for microvascular anastomosis.

Sliding Position of the Flexor Tendons Relative to the Hook of Hamate in CT Scans.

BACKGROUND: The aim of this study was to assess the height of nonunion formation injuring the ulnar-side finger flexor tendon, the positional relationship between the hook of the hamate and little finger flexor tendon was evaluated on CT scans. METHODS: The subjects were 20 healthy patients (40 hands) (14 males and 6 females, mean age: 28 years old). Their hands were imaged in extension and flexion of the fingers on CT. The position of the little finger flexor tendon was determined regarding the height of the hook of the hamate as 100%. RESULTS: The heights of the flexor digitorum profundus tendons were 46 ± 6% in extension and 44 ± 9% in flexion, and those of the flexor digitorum superficialis tendons were 87 ± 8% in extension and 91 ± 9% in flexion. CONCLUSIONS: Our study suggested that 40% of the base of the hook of the hamate does not contact with the flexor tendon, suggesting that flexor tendon injury is unlikely to occur in that region.

Evaluation of Articular Surface Similarity of Hemi-Hamate Grafts and Proximal Middle Phalanx Morphology: A 3D Geometric Morphometric Approach.

PURPOSE: Hemi-hamate arthroplasty has been described as a viable treatment option for unstable proximal interphalangeal joint fracture-dislocations. The procedure uses a dorsal distal hamate osteochondral graft to recreate the injured volar middle phalanx (MP) proximal base. The purpose of this study was to evaluate the similarity in shape of these articular surfaces using quantitative 3-dimensional methods. METHODS: Three-dimensional virtual renderings were created from laser scans of the articular surfaces of the dorsal distal hamate and the volar MP bases of the index, middle, ring, and little fingers from cadaveric hands of 25 individuals. Three-dimensional landmarks were obtained from the articular surfaces of each bone and subjected to established geometric morphometric analytical approaches to quantify shape. For each individual, bone shapes were evaluated for covariation using 2-block partial least-squares and principal component analyses. RESULTS: No statistically significant covariation was found between the dorsal distal hamate and volar MP bases of the middle, ring, or little digits. Whereas the volar MP bases demonstrated relative morphologic uniformity among the 4 digits both within and between individuals, the dorsal distal hamates exhibited notable variation in articular surface morphology. CONCLUSIONS: Despite the early to midterm clinical success of hemi-hamate arthroplasty, there is no statistically significant, uniform similarity in shape between the articular surfaces of the dorsal distal hamate and the volar MP base. In addition, there is wide variation in the articular morphology of the hamate among individuals. CLINICAL RELEVANCE: The lack of uniform similarity in shape between the dorsal distal hamate and the volar MP base may result in unpredictable outcomes in HHA. It is recommended that the variation in hamate morphology be considered while reconstructing the injured volar MP base in the procedure.

An Anthropometric Assessment of the Proximal Hamate Autograft for Scaphoid Proximal Pole Reconstruction.

PURPOSE: Fragmentation of the scaphoid proximal pole secondary to avascular necrosis presents a difficult reconstructive problem. This anthropometric study assesses the utility of the ipsilateral proximal hamate for complete osteochondral scaphoid proximal pole reconstruction. METHODS: Twenty-nine cadaveric specimens underwent computed tomography scanning and 3-dimensional reconstruction of the carpus and distal radius. Scaphoid height was measured and a third of its height was used to simulate resection of the proximal scaphoid pole and extent of hamate autograft required. The proximal scaphoid and hamate were divided into 6 sections, and compared using an iterative point-to-point distance algorithm. Average distance between the scaphoid and the hamate surfaces was determined. An interbone algorithm was used to assess radioscaphoid joint congruency and articular contact surface of the native scaphoid compared with the scaphoid reconstructed with hamate autograft. RESULTS: The mean height of scaphoid proximal pole excision and proximal hamate autograft height was 9.3 mm. Comparing the morphology of the native scaphoid and hamate autografts, the absolute distances were the largest in the volar radioscaphoid, dorsal radioscaphoid, and dorsal scaphocapitate segments. Without osteotomy, the hamate autograft may cause impaction in the dorsal-radial aspect of the distal radius. The hamate autograft also shifted the articular contact point of the radioscaphoid joint toward the dorsal-radial position. Nine hamate autografts were classified as poor-fitting. Poor-fitting specimens had a greater radial styloid to distal radioulnar joint distance. These specimens also had wider hamates and scaphoids in the radial-ulnar dimension and wider scaphoids in the volar-dorsal dimension. Lunate type did not correspond to anthropometric fit. CONCLUSIONS: The proximal hamate osteochondral graft was poor fitting in 31% of cases (9 of 29 specimens). Wrists with radial-ulnar hamate width less than 10 mm, radial-ulnar scaphoid width less than 10 mm, and volar-dorsal scaphoid width less than 16 mm demonstrate better anthropometric fit. CLINICAL RELEVANCE: This study provides an anthropometric assessment of the recently described proximal hamate autograft, a new bone graft option for proximal scaphoid pole reconstruction.

Variations in Hook of Hamate Morphology: A Cadaveric Analysis.

PURPOSE: The hook of the hamate is an anatomical structure that separates the ulnar border of the carpal tunnel from Guyon's canal and serves as a landmark for surgeons. The hook of the hamate is also subject to fracture from injury. We hypothesize that there are variations in the hook of the hamate in the general population. METHODS: One thousand pairs of hamates (2,000 hamates) from the Hamann-Todd Collection at the Cleveland Natural History Museum were analyzed. The height of the hook of the hamate and the total height of the hamate bone were measured using digital calipers. The hook height ratio was defined as the hook height divided by the total height of the hamate. Statistical analysis was performed using unpaired Student's t test to determine differences in sex and race. RESULTS: The mean hook height was 9.8 ± 1.4 mm (range, 2.5-15.9 mm), whereas the mean hook height ratio was 0.42 ± 0.04 (range, 0.15-0.56). There was a 3.1% (62/2,000) incidence of abnormally small hooks, which we classified as hypoplastic and aplastic. Of the hypoplastic hooks, 55% (24/44) were bilateral, whereas 44% (8/18) of the aplastic hooks were bilateral. The incidence of variation in size in the hook of the hamate was highest in white females (9.3%) and lowest in black males (1.4%). CONCLUSIONS: Abnormalities in hook of hamate anatomy are common in the general population, especially in white females. CLINICAL RELEVANCE: Knowledge of anatomic variation in the hook of the hamate may provide additional insight into surgeons' palpation of bony anatomy, interpretation of imaging studies, and use of the hook as a landmark during surgery.

Evaluation of the pulley function of the hamulus of the hamate for the flexor tendons.

PURPOSE: The aim of this study was to measure the curvature radii of the finger flexor tendons on CT acquired using tendon conditions to examine whether the hamulus of the hamate functions as a pulley of the flexor tendon. METHODS: The subjects were 20 healthy volunteers (40 hands) (14 males and 6 females, mean age: 27.5 years old). Their hands were imaged in extension and flexion of the fingers on CT. The curvature radii of the little and middle finger flexor tendons at the hamulus of the hamate were calculated. RESULTS: The curvature radii of the little and middle finger flexor tendons were 24.8 ± 7.3 and 327.1 ± 343.9 mm in finger extension, respectively, and 21.3 ± 5.3 and 265.1 ± 202.9 mm in finger flexion, respectively. The curvature radius of the little finger flexor tendon was significantly smaller than that of the middle finger flexor tendon in both finger extension and flexion (P < 0.01). CONCLUSIONS: Our study suggested that the hamulus of the hamate functions as a pulley for the little finger flexor tendon.

A simple method for bone age assessment: the capitohamate planimetry.

OBJECTIVES: To determine if the capitohamate (CH) planimetry could be a reliable indicator of bone age, and to compare it with Greulich-Pyle (GP) method. METHODS: This retrospective study included 391 children (age, 1-180 months). Two reviewers manually measured the areas of the capitate and hamate on plain radiographs. CH planimetry was defined as the measurement of the sum of areas of the capitate and hamate. Two reviewers independently applied the CH planimetry and GP methods in 109 children whose heights were at the 50th percentile of the growth chart. RESULTS: There was a strong positive correlation between chronological age and CH planimetry measurement (right, r = 0.9702; left, r = 0.9709). There was no significant difference in accuracy between CH planimetry (84.39-84.46 %) and the GP method (85.15-87.66 %) (p ≥ 0.0867). The interobserver reproducibility of CH planimetry (precision, 4.42 %; 95 % limits of agreement [LOA], -10.5 to 13.4 months) was greater than that of the GP method (precision, 8.45 %; LOA, -29.5 to 21.1 months). CONCLUSIONS: CH planimetry may be a reliable method for bone age assessment. KEY POINTS: • Bone age assessment is important in the work-up of paediatric endocrine disorders. • Radiography of the left hand is widely used to estimate bone age. • Capitatohamate planimetry is a reliable and reproducible method for assessing bone age.

A simple pre-operative imaging method to assess donor and recipient anatomy in hemi-hamate arthroplasty for proximal interphalangeal joint reconstruction.

PURPOSE: Post-traumatic arthritis is common in long-term follow-up of patients undergoing hemi-hamate arthroplasty (HHA). We hypothesize that anatomic mismatch could play a role in the development of arthritis. The purpose of this study is to establish a novel, computed tomography (CT)-based imaging technique for pre-operative assessment in HHA. With this technique, our group aims to identify digits with a high likelihood for anatomical mismatch between the donor graft and recipient interphalangeal joint. Using this technique to eliminate cases with high-likelihood of incongruent anatomy, we hypothesize the rates of arthritis could be reduced. METHODS: We conducted a retrospective review of upper extremity CT scans from 2007 to 2014 at our institution. Those studies meeting our inclusion criteria were exported to a clinical radiology software suite. Subsequently, angular and linear measurements of the hamate and potential recipient proximal interphalangeal joints were collected. Angular and linear comparisons were then made between the donor hamate graft and the individual recipient sites. Using pre-established cutoff values, matches were deemed to be inconsistent or consistent. RESULTS: The study included 31 CT scans. The rate of anatomical consistency was low; the small finger was most often consistent (38.7 %) and the index finger was least often consistent (12.9 %). Linear inconsistency was common in all joints besides the small finger; angular inconsistency was most prevalent in the index and long fingers. CONCLUSIONS: This novel use of CT scans as a tool for pre-operative HHA planning is a crucial first step in trying to reduce the observed rates of arthritis after HHA.

Exploring phylogenetic and functional signals in complex morphologies: the hamate of extant anthropoids as a test-case study.

Three-dimensional geometric morphometrics (3DGM) is a powerful tool for capturing and visualizing the "pure" shape of complex structures. However, these shape differences are sometimes difficult to interpret from a functional viewpoint, unless specific approaches (mostly based on biomechanical modeling) are employed. Here, we use 3DGM to explore the complex shape variation of the hamate, the disto-ulnar wrist bone, in anthropoid primates. Major trends of shape variation are explored using principal components analysis along with analyses of shape and size covariation. We also evaluate the phylogenetic patterning of hamate shape by plotting an anthropoid phylogenetic tree onto the shape space (i.e., phylomorphospace) and test against complete absence of phylogenetic signal using posterior permutation. Finally, the covariation of hamate shape and locomotor categories is explored by means of 2-block partial least squares (PLS) using shape coordinates and a matrix of data on arboreal locomotor behavior. Our results show that 3DGM is a valuable and versatile tool for characterizing the shape of complex structures such as wrist bones in anthropoids. For the hamate, a significant phylogenetic pattern is found in both hamate shape and size, indicating that closely related taxa are typically the most similar in hamate form. Our allometric analyses show that major differences in hamate shape among taxa are not a direct consequence of differences in hamate size. Finally, our PLS indicates a significant covariation of hamate shape and different types of arboreal locomotion, highlighting the relevance of this approach in future 3DGM studies seeking to capture a functional signal from complex biological structures.

The vascular basis of the hemi-hamate osteochondral free flap. Part 2: surgical anatomy and clinical application.

PURPOSE: The free vascularised hemi-hamate flap combines the utility of providing a small osteochondral portion of hamate for reconstruction, while providing a means of vascularisation to preserve articular cartilage after transfer. In Part 1 of this series, we highlighted the vascular approaches to such a technique. The current study investigates the bony architecture of the hamate, with particular emphasis on its utility for a range of osteochondral defects in the hand. METHODS: A morphometric assessment of the hamate as a potential osteochondral flap donor site for resurfacing digital phalangeal heads (either total or unicondylar) and/or bases was thus undertaken. This anatomic study was undertaken using in vivo imaging performed for a range of clinical indications, with computed tomographic angiography (CTA) and digital subtraction angiography (DSA) of the upper limb included. Bony and vascular measurements and relationships were recorded and assessed both quantitatively and qualitatively. A clinical case is presented, highlighting the application of these measurements. RESULTS: The mean digital artery diameter was 0.7 mm with a mean distance between digital artery and interphalangeal joint surface (i.e. pedicle length) of 1.18 mm. Mean hamate dimensions comprised a transverse width 16.62 mm, lateral width of 14.29 mm and ridge height of 1.43 mm. Measurements of the phalangeal bases, condyles and total phalangeal heads were recorded, and the optimal hamate harvest approaches demonstrated. Despite perceived differences, in all cases there was statistical similarity demonstrated between the fragments. CONCLUSION: The hemi-hamate osteochondral flap can be applied to a range of osteochondral defects in the hand and may offer new options to the hand surgeon.

The vascular basis of the hemi-hamate osteochondral free flap. Part 1: vascular anatomy and clinical correlation.

PURPOSE: The treatment of comminuted fractures of the proximal interphalangeal joint is highly challenging due to the complexities of joint bio-mechanics and stability. The hemi-hamate osteochondral auto-graft has been popularised in this role, able to replace articular loss and restore joint stability. Recent evaluation of their long-term follow-up however has shown the early development of osteoarthritis and potential early cartilage loss, which may be due to the non-vascularised nature of the graft. We offer a new technique that maintains vascularisation of the transferred hamate fragment, and investigate the anatomical vascular basis for the technique. METHODS: Dissection and angiographic studies of ten cadaveric specimens were undertaken, exploring the vascular anatomy of the dorsal hamate. A clinical case of hemi-hamate osteochondral free flap is presented, including preoperative, intraoperative and postoperative investigation of the relevant vasculature. RESULTS: Cadaveric studies demonstrated dorsal vascular supply to the hamate from the central of three dorsal carpal arches. The arch was supplied by the dorsal branch of the ulnar artery. Multiple supracapsular veins are present for use in flap venous drainage. This vascular pattern was found to be constant. A clinical case of hemi-hamate osteochondral free flap harvest demonstrated the same vascular anatomy intraoperatively. The digital artery was used as a recipient for microvascular anastomosis. Postoperative computed tomographic angiography and nuclear bone scan confirmed flap perfusion. CONCLUSIONS: The hemi-hamate osteochondral flap has a reliable anatomical vascular basis, and is clinically feasible as a technique for early vascularisation of the osteochondral fragment to sustain the transferred articular cartilage.

New wrist bones of Homo floresiensis from Liang Bua (Flores, Indonesia).

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.

Sex-related shape dimorphism in the human radiocarpal and midcarpal joints.

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.

Knuckle-walking in Sivapithecus? The combined effects of homology and homoplasy with possible implications for pongine dispersals.

Sivapithecus is a Miocene great ape from South Asia that is orangutan-like cranially but is distinctive postcranially. Work by others shows that the humerus resembles large terrestrial cercopithecoids proximally and suspensory hominoids distally, but most functional interpretations nevertheless situate Sivapithecus in an arboreal setting. We present a new quantitative analysis of the Sivapithecus capitate and hamate. Though the functional morphology of both bones suggests some degree of arboreality, the overall morphology is most similar to knuckle-walking African apes. Other features of the Sivapithecus humerus and hind limb are also functionally consistent with knuckle-walking, and we suggest that this locomotor behavior is a valid alternative functional interpretation of the postcranial morphology. We speculate that knuckle-walking in Sivapithecus would have evolved independently from African apes, perhaps for similar ecological reasons. The discovery of a possible pongine knuckle-walker challenges the hypotheses that (1) knuckle-walking evolved only once in hominoids and (2) knuckle-walking is too highly specialized to be the positional behavior from which human bipedalism evolved. The possibility of knuckle-walking in Sivapithecus may help to explain not only the curious combination of characters that typify the postcranium but also the unique postcranial morphology of extant Pongo. Furthermore, it may clarify the distribution of fossil pongines across many ecological zones in Eurasia in the Miocene and Pleistocene, as well as, independently, the spread of African apes across a diversity of environments in equatorial Africa.

Anatomy of the ulnar tunnel and the influence of wrist motion on its morphology.

PURPOSE: To examine the anatomy of the ulnar tunnel, with emphasis on the pisohamate arcade and pisohamate hiatus, and study the influence of wrist kinematics on the morphology of these structures. METHODS: Ten fresh-frozen cadaveric hands were dissected. The dimensions and relationships of the ulnar tunnel, pisohamate arcade, and pisohamate hiatus were recorded. The effect of 4 wrist positions on these dimensions and relationships was investigated. RESULTS: The ulnar tunnel has 3 compartments--proximal, middle, and distal relative to the pisiform-with variable morphologies, dimensions, and boundaries. In wrist neutral position, the length of the ulnar tunnel was 45 mm (range, 42 to 51 mm). The middle compartment was found to be the narrowest; the proximal, the widest, averaging 5.0 mm; and the pisohamate hiatus that separates the middle and distal compartments, highly dynamic. The length of the pisohamate arcade was 21.5 mm (range, 18.0 to 26.0 mm), and the length and width of the pisohamate hiatus were 11.0 mm (range, 9.8-11.5 mm) and 6.0 mm (range, 5.3 to 7.2 mm), respectively. During wrist extension, the ulnar nerve was under tension. Wrist flexion was the position that caused the most change in ulnar tunnel and pisohamate arcade and hiatus anatomy, causing the width of the proximal compartment to increase from 5.0 to 10.0 mm. During this motion, the shape of the pisohamate arcade changed from a C shape to linear, and the length increased to 24.5 mm (range, 19.3 to 28.5 mm). The pisohamate hiatus narrowed, its width decreased to 1.5 mm, and the deep branch of the ulnar nerve was somewhat compressed. CONCLUSIONS: The ulnar tunnel is a dynamic space with dimensions and relationships that are influenced by wrist motion. During ulnar tunnel surgery, all 3 compartments of the ulnar tunnel should be explored and decompressed, including the pisohamate hiatus, by releasing the pisohamate arcade.

[Anatomic study on hook of hamate bone].

OBJECTIVE: To study the hook of hamate bone by anatomy and iconography methods in order to provide information for the clinical treatment of injuries to the hook of hamate bone and the deep branch of ulnar nerve. METHODS: Fifty-two upper limb specimens of adult corpses contributed voluntarily were collected, including 40 antisepticized old specimens and 12 fresh ones. The hook of hamate bone and its adjacent structure were observed. Twenty-four upper limbs selected randomly from specimens of corpses and 24 upper limbs from 12 healthy adults were investigated by computed tomography (CT) three-dimensional reconstruction, and then related data were measured. The measurement results of 24 specimens were analyzed statistically. RESULTS: The hook of hamate bone is an important component of ulnar carpal canal and carpal canal, and the deep branch of ulnar nerve is located closely in the inner front of the hook of hamate bone. The flexor tendons of the forth and the little fingers are in the innermost side, closely lie next to the outside of the hook of hamate bone. The hamate bone located between the capitate bone and the three-cornered bone with wedge-shaped. The medial-, lateral-, and front-sides are all facies articularis. The hook of hamate bone has an approximate shape of a flat plate. The position migrated from the body of the hamate bone, the middle of the hook and the enlargement of the top of the hook were given the names of "the basis of the hook", "the waist of the hook", and "the coronal of the hook", respectively. The short path of the basement are all longer than the short path of the waist. The long path of the top of the hook is the maximum length diameter of the hook of hamate bone, and is longer than the long path of the basement and the long path of the waist. The iconography shape and trait of the hook of hamate bone is similar to the anatomy result. There were no statistically significant differences (P > 0.05) between two methods in the seven parameters as follows: the long path of the basement of the hook, the short path of the basement of the hook, the long path of the waist of the hook, the short path of the waist of the hook, the long path of the top of the hook, the height of the hook, of hamate bone, and the distance between the top and the waist of the hook. CONCLUSION: The hook of hamate bone can be divided into three parts: the coronal part, the waist part, and the basal part; fracture of the hamate bone can be divided into fracture of the body, fracture of the hook, and fracture of the body and the hook. Fracture of the hook of hamate bone or fracture union can easily result in injure of the deep branch of ulnar nerve and the flexor tendons of the forth and the little fingers. The measurement results of CT three-dimensional reconstruction can be used as reference value directly in clinical treatments.

Variations of capitate morphology in the wrist.

PURPOSE: This anatomical study details and categorizes variations in capitate morphology and associated structures in the human cadaveric wrist. METHODS: We dissected 107 cadaveric wrists. Capitate morphology, the presence of capitate and hamate ridges, the lunate types, and the width of the medial hamate facet of type II lunates and 4th carpometacarpal joint types were recorded. RESULTS: Three types of capitate were identified. The flat type (69/107, or 65%) was characterized by a horizontally oriented (radio-ulnar) lunate-capitate articulation and a longitudinally oriented (proximal-distal) scaphoid-capitate articulation. The flat type was associated with type I lunates or type II lunates with a smaller facet. The spherical type (23/107, or 22%) was associated with a concave articulation formed by the scaphoid and lunate articulations, with an indistinct border between the scaphoid and lunate facets. The width of the medial hamate facet of type II lunates in wrists with a spherical-type capitate was