Carpal bone anatomy measured by computer analysis of three-dimensional reconstructions of computed tomography images

The Three-Dimensional Relationship of the Axes of the Capitate and Third Metacarpal

PURPOSE

We quantified the morphology and angulation of the third metacarpal (MC3) relative to the capitate using three-dimensional computed tomography data to inform surgical procedures such as total wrist arthroplasty and wrist arthrodesis. Specifically, we report the three-dimensional location of the intersections of the long axis of MC3 axis with the capitate cortical surface, the sagittal and coronal angles between the MC3 and capitate axes, and the MC3 shaft angle in the sagittal plane. We tested the hypothesis that these metrics did not differ between women and men.

METHODS

Three-dimensional bone models of the capitate and MC3 were analyzed in 130 subjects (61M and 69F). Long axes of the MC3 and capitate were computed. The intersection of the metacarpal long axis with the cortical surface of the capitate, the angle between the metacarpal-capitate axes, and metacarpal shaft angle were calculated and compared between men and women.

RESULTS

The long axis of the MC3 intersected the capitate at two locations on the outer cortical surface of the capitate. The proximal intersection was located near the midportion of the capitate, whereas the distal intersection was typically located within the capitate-MC3 articulation. The angle between the axes of the capitate and MC3 in the sagittal plane was a mean of 15°, ranging from 5° to 23°. The mean sagittal MC3 shaft angle was 166° and ranged from 158° to 173°.There were only subtle differences in these metrics between the sexes.

CONCLUSIONS

The long axis of the MC3 penetrates the dorsal surface of the capitate about its midportion, but there is notable variation in this location as well as in the angular relationships.

CLINICAL RELEVANCE

Three-dimensional measurements of the relationships between the third metacarpal and the capitate may serve as an important reference for the placement of intramedullary wires, plates, devices, and prosthetics.

Bilateral lunotriquetral coalition: a dynamic four-dimensional computed tomography technical case report

Lunotriquetral coalitions are the most common form of carpal coalition wherein the cartilage between the lunate and triquetrum ossification centers failed to undergo apoptosis. This technical case report examines the arthrokinematics of bilateral lunotriquetral coalitions with dissimilar Minnaar types in one participant with one asymptomatic wrist and one wrist with suspected distal radioulnar joint injury. Static and dynamic (four-dimensional) CT images during pronosupination were captured using a photon-counting detector CT scanner. Interosseous proximity distributions were calculated between the lunotriquetral coalition and adjacent bones in both wrists to quantify arthrokinematics. Interosseous proximity distributions at joints adjacent to the lunotriquetral coalition demonstrate differences in median and minimum interosseous proximities between the asymptomatic and injured wrists during resisted pronosupination. Altered kinematics from lunotriquetral coalitions may be a source of ulnar-sided wrist pain and discomfort, limiting the functional range of motion. This case report highlights potential alterations to wrist arthrokinematics in the setting of lunotriquetral coalitions and possible associations with ulnar-sided wrist pain, highlighting anatomy to examine in radiographic follow-up. Furthermore, this case report demonstrates the technical feasibility of four-dimensional CT using photon-counting detector technology in assessing arthrokinematics in the setting of variant wrist anatomy.

Sex-Specific Size Analysis of Carpal Bones: Implications for Orthopedic Biomedical Device Design and Therapy Planning

Consideration of the individual carpal bone characteristics of the wrist plays a key role in well-functioning biomedical devices and successful surgical procedures. Although geometric differences and individual bone sizes have been analyzed in the literature, detailed morphologic descriptions and correlations covering the entire wrist reported in a clinical context are lacking. This study aimed to perform a comprehensive and automatic analysis of the wrist morphology using the freely available "Open Source Carpal Database" (OSCD). We quantified the size of each of the individual carpal bones and their combination. These sizes were extracted in n = 117 datasets of the wrist of the OSCD in anatomical directions and analyzed using descriptive statics and correlation analysis to investigate the morphological characteristics under sex-specific aspects and to provide regression plots and equations to predict individual carpal bone sizes from the proximal and distal row dimensions. The correlations in the proximal row were higher compared to the distal row. We established comprehensive size correlations and size rations and found that there exist statistical differences between sex, particularly of the scaphoid. The regression plots and equations we provided will assist surgeons in a more accurate preoperative morphological evaluation for therapy planning and may be used for future anatomically inspired orthopedic biomedical device designs.

Three-dimensional reconstruction of the hand from biplanar X-rays: Assessment of accuracy and reliability

BACKGROUND

Functional disorders of the hand are generally investigated first using conventional radiographic imaging. However, X-rays (two-dimensional (2D)) provide limited information and the information may be reduced by overlapping bones and projection bias. This work presents a three-dimensional (3D) hand reconstruction method from biplanar X-rays.

METHOD

This approach consists of the deformation of a generic hand model on biplanar X-rays by manual and automatic processes. The reference examination being the manual CT segmentation, the precision of the method was evaluated by a comparison between the reconstructions from biplanar X-rays and the corresponding reconstructions from the CT scan (0.3mm section thickness). To assess the reproducibility of the method, 6 healthy hands (6 subjects, 3 left, 3 men) were considered. Two operators repeated each reconstruction from biplanar X-rays three times to study inter- and intra-operator variability. Three anatomical parameters that could be calculated automatically from the reconstructions were considered from the bone surfaces: the length of the scaphoid, the depth of the distal end of the radius and the height of the trapezius.

RESULTS

Double the root mean square error (2 Root Mean Square, 2RMS) at the point/area difference between biplanar X-rays and computed tomography reconstructions ranged from 0.46mm for the distal phalanges to 1.55mm for the bones of the distal carpals. The inter-intra-observer variability showed precision with a 95% confidence interval of less than 1.32mm for the anatomical parameters, and 2.12mm for the bone centroids.

DISCUSSION

The current method allows to obtain an accurate 3D reconstruction of the hand and wrist compared to the traditional segmented CT scan. By improving the automation of the method, objective information about the position of the bones in space could be obtained quickly. The value of this method lies in the early diagnosis of certain ligament pathologies (carpal instability) and it also has implications for surgical planning and personalized finite element modeling.

LEVEL OF PROOF

Basic sciences.

The Effect of Derotational Kirschner Wires on Fracture Gap Reduction With Variable-Pitch Headless Screws

PURPOSE

We evaluated the impact of angled derotational Kirschner wires (K-wires) on fracture gap reduction with variable-pitch headless screws.

METHODS

Fully threaded variable-pitch headless screws (20 and 28 mm) were inserted into "normal" bone models of polyurethane blocks. In separate trials, derotational K-wires were inserted at predetermined angles of 0°, 15°, 30°, and 40° and compared with each other, with no K-wire as a control. Fluoroscopic images taken after each screw turn were analyzed. The optimal fracture gap closure, initial screw push-off, and screw back-out gap creation were determined and compared at various derotational K-wire angles.

RESULTS

Initial screw push-off due to screw insertion and screw back-out gap creation were not significantly affected by the angle of the derotational K-wire. With a 20-mm screw, only a 40° derotational K-wire led to significantly less gap closure compared with control and with 0°, 15°, and 30° derotational K-wires. It led to an approximately 60% decrease in gap closure compared with no K-wire. With the 28-mm screw, compared with no K-wire, 15° and 30° derotational K-wires led to statistically significant decreases in gap closure (approximately 25%), whereas a 40° derotational K-wire led to an approximately 60% decrease. With the 28-mm screw, the 40° derotational K-wire also led to a statistically significant smaller gap closure when compared with 0°, 15°, and 30° derotational K-wires.

CONCLUSIONS

A derotational K-wire placed in parallel to the planned trajectory of a headless compression screw does not affect fracture gap closure. With greater angulation of the derotational K-wire, the fracture gap is still closed, but less tightly.

CLINICAL RELEVANCE

Derotational K-wires can help prevent fracture fragment rotation during headless compression screw insertion. At small deviations from parallel (≤30°), fracture gap closure achieved by the screw is minimally affected. At greater angles (ie, 40°), fracture gap closure may be substantially reduced, preventing fracture compression.

Computer-based three-dimensional measurement of carpal alignment: measurement techniques and normal ranges

The three-dimensional carpal alignment was measured in the neutral wrist position in 121 asymptomatic volunteers using computer-based cone-beam CT analysis. Normal values and the reliability of the automated analysis are reported. An analysis software based on segmentation of CT images and mathematical modelling was used to determine several axis variants based on different landmarks and to calculate the intercarpal angles automatically. Twenty wrists were imaged twice to determine intra-observer reliability. Mean values using the preferred axis variants were: scapholunate angle 57° (SD 9°), radiolunate angle 2° (SD 10°), lunocapitate angle -14° (SD 9°). Using alternate axis variants notably changed the angles produced. The intra-observer reliability of the analysis was excellent (mean intraclass correlation coefficient 0.97, SD 0.03). Computer-based CT analysis enables highly reproducible and automated assessment of carpal alignment. This study provides a reference database for measurement techniques and normal carpal angle values in three-dimensional imaging.

Association between bone shape and the presence of a fracture in patients with a clinically suspected scaphoid fracture

Scaphoid fractures are difficult to diagnose with current imaging modalities. It is unknown whether the shape of the scaphoid bone, assessed by statistical shape modeling, can be used to differentiate between fractured and non-fractured bones. Therefore, the aim of this study was to investigate whether the presence of a scaphoid fracture is associated with shape modes of a statistical shape model (SSM). Forty-one high-resolution peripheral quantitative computed tomography (HR-pQCT) scans were available from patients with a clinically suspected scaphoid fracture of whom 15 patients had a scaphoid fracture. The scans showed no motion artefacts affecting bone shape. The scaphoid bones were semi-automatically contoured, and the contours were converted to triangular meshes. The meshes were registered, followed by principal component analysis to determine mean shape and shape modes describing shape variance. The first five out of the forty shape modes cumulatively explained 87.8% of the shape variance. Logistic regression analysis was used to study the association between shape modes and fracture presence. The regression models were used to classify the 41 scaphoid bones as fractured or non-fractured using a cut-off value that maximized the sum of sensitivity and specificity. The classification of the models was compared with fracture diagnosis on HR-pQCT. A regression model with four shape modes had an area under the ROC-curve of 72.3% and correctly classified 75.6% of the scaphoid bones (fractured: 60.0%, non-fractured: 84.6%). To conclude, fracture presence in patients with a clinically suspected scaphoid fracture appears to be associated with the shape of the scaphoid bone.

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.

Results of a prospective clinical study on the diagnostic performance of standard magnetic resonance imaging in comparison to a combination of 3T MRI and additional CT imaging in Kienböck's disease

PURPOSE

This prospective clinical study examined standard wrist magnetic resonance imaging (MRI) examinations and the incremental value of computed tomography (CT) in the diagnosis of Kienböck's disease (KD) with regard to reliability and precision in the different diagnostic steps during diagnostic work-up.

MATERIALS AND METHODS

Sixty-four consecutive patients referred between January 2009 and January 2014 with positive initial suspicion of KD according to external standard wrist MRI were prospectively included (step one). Institutional review board approval was obtained. Clinical examination by two handsurgeons were followed by wrist radiographs (step two), ultrathin-section CT, and 3T contrast-enhanced MRI (step three). Final diagnosis was established in a consensus conference involving all examiners and all examinations results available from step three.

RESULTS

In 12/64 patients, initial suspicion was discarded at step two and in 34/64 patients, the initial suspicion of KD was finally discarded at step three. The final external MRI positive predictive value was 47%. The most common differential diagnoses at step three were intraosseous cysts (n=15), lunate pseudarthrosis (n=13), and ulnar impaction syndrome (n=5). A correlation between radiograph-based diagnoses (step two) with final diagnosis (step three) showed that initial suspicion of stage I KD had the lowest sensitivity for correct diagnosis (2/11). Technical factors associated with a false positive external MRI KD diagnosis were not found.

CONCLUSION

Standard wrist MRI should be complemented with thin-section CT, and interdisciplinary interpretation of images and clinical data, to increase diagnostic accuracy in patients with suspected KD.

Comparison of clinical and radiologic treatment outcomes of Kienböck's disease

Purpose

The clinical outcomes of scaphotrapeziotrapezoid (STT) arthrodesis were compared to radial shortening osteotomy (RSO) to determine if any of the treatment methods was superior. The impact of RSO and vascularized bone grafts (VBG) on disease progression were measured based on X-rays to evaluate if a difference in Kienböck’s disease (KD) progression exists.

Methods

Out of 98 consecutive patients treated between 1991 and 2013, 46 had STT arthrodesis, 21 had RSO, 7 had VBG, and 3 had VBG and RSO. Patients treated with STT arthrodesis were compared to RSO regarding post-operative range of motion (ROM), wrist pain on the Numeric Rating Scale (NRS), grip strength, duration of incapacity for work, the Disabilities of the Arm, Shoulder, and Hand (DASH), and the Modified Mayo Wrist scores (MMWS). Radiographic assessment (Nattrass index, radioscaphoid angle, and Ståhl index) was performed to determine disease progression following RSO or VBG. Baseline patient characteristics were comparable in all treatment groups.

Results

There were no significant differences in post-operative ROM, wrist pain, grip strength, duration of incapacity, DASH score, or MMWS score following STT arthrodesis (n = 27) or RSO (n = 14). The Ståhl index, the Nattrass index, and the radioscaphoid angle suggested disease progression following RSO (n = 14) and/or VBG (n = 6) although the changes were not significant.

Conclusions

The study failed to demonstrate clinically relevant differences between STT arthrodesis compared to RSO. No evidence was found that decompression or revascularization, or the combination of the two, can reverse or halt the course of the disease.

Level of evidence

Therapy, level III, retrospective comparative study with prospectively collected data.

Reliability and validity of carpal alignment measurements in evaluating deformities of scaphoid fractures

PURPOSE

Several radiographic carpal alignment indices are used to evaluate the deformities of scaphoid fractures. The purpose of this study was to determine the reliabilities and validities of radiographic carpal alignment indices commonly used to evaluate deformities of scaphoid fractures.

METHODS

Thirty-six patients with a scaphoid fracture were evaluated. Five carpal alignment indices were assessed on lateral plain radiographs, namely, scapholunate angle, radioscaphoid angle, radiolunate angle, radiocapitate angle, and capitolunate angle. Three examiners measured these radiographic indices at two sessions, and intraobserver and interobserver reliabilities were determined and expressed as intraclass correlation coefficients. Discriminant validities of radiographic carpal alignment indicies between injured and uninjured wrists were evaluated. For convergent validity testing, the correlation between the radiographic carpal alignment indices and intrascaphoid angles (ISAs) or height-to-length (HL) ratios on CT longitudinal scans was assessed. Further, carpal alignment indices after surgical reconstruction were compared to the Mayo wrist score.

RESULTS

Scapholunate and radiolunate angles had the highest reliabilities, and radiocapitate angle had the lowest. Radiolunate angle had the highest discriminant validity followed by scapholunate, and capitolunate angles. In convergent validity testing, scapholunate angles and radiolunate angles correlated with ISA angles, and radiolunate and capitolunate angles correlated with HL ratios. Only the radiolunate angles correlated with the Mayo wrist scores.

CONCLUSIONS

Among radiographic carpal alignment measures, radiolunate angle is the most reliable and valid carpal alignment index for evaluating deformities of scaphoid fractures. Scapholunate and capitolunate angles could be used as an alternative, but have less validity.

Rotational stability for intercarpal fixation is enhanced by a 4-tine staple

PURPOSE

To compare the torsional stability of 6 fixation techniques for intercarpal fixation including a 4-tine, in-line staple.

METHODS

We chose the scapholunate interval as the test site for rotational stability for various constructs. We used 42 pairs of embalmed scaphoids and lunates for the comparisons and created 6 construct groups. Fixation of the scapholunate gap was performed with a 3-mm screw, 2 1.1-mm (0.045-inch) K-wires spaced 2 mm apart, or 2 1.1-mm K-wires spaced 5 mm apart. One member of each pair was fixed with either a standard 2-tine peripherally placed staple or a customized 4-tine staple. Each scapholunate construct was tested in torsion to failure on a biaxial materials testing machine.

RESULTS

In all cases, the 4-tine staple significantly increased rotational stability. The 2-tine staple resulted in statistically insignificant increases in rotational stability. With central fixation alone, K-wires separated by 5 mm showed the greatest resistance to torsion, and the 3-mm screw showed the least.

CONCLUSIONS

Use of an in-line, 4-tine staple provided increased rotational stability and may result in enhanced healing of intercarpal ligamentous reconstructions and arthrodeses.

CLINICAL RELEVANCE

A 4-tine staple compared with a standard staple provided superior rotational stability for intercarpal fixation.

Quantification of contralateral differences of the scaphoid: a comparison of bone geometry in three dimensions

The purpose of this study was to accurately quantify contralateral differences of the scaphoid in three-dimensional space to evaluate the feasibility of using the healthy contralateral bone as a reconstruction template in the preoperative planning of complex mal- or nonunions. Three-dimensional surface models of the left and right scaphoids were reconstructed from computed tomography images and compared in 26 individuals. Left-right differences were quantified with respect to volume, surface area, length, and surface-to-surface deviation. The average left-right differences in volume, surface area, and length were 95.4 mm(3) (SD 66.2 mm(3)), 32.7 mm(2) (SD 22.9 mm(32)), and 0.28 mm (SD 0.4 mm), respectively. The average surface-to-surface deviation between the sides was 0.26 mm (SD 0.2 mm). High statistical correlation (Pearson) between the left and the right side was found in all evaluated measures.

Short-term effects of self-mobilization with a strap on pain and range of motion of the wrist joint in patients with dorsal wrist pain when weight bearing through the hand: a case series

Dorsal wrist pain frequently occurs in weight bearing through the hand in patients with distal radius stress injuries, scaphoid impaction syndrome, and dorsal impingement. To improve the wrist extension motion, joint mobilization has been used. However, there is no report on the effects of mobilization on the range of motion (ROM) and pain onset in patients with dorsal wrist pain when weight bearing through the hand. This study determined the effects of self-mobilization with a strap (SMWS) while weight bearing through the hand on the ROM and force generated at the onset of pain (FGOP) and intensity in the wrist joints of patients with dorsal wrist pain. Fifteen patients (six men, nine women) with dorsal wrist pain during weight bearing through the hand were recruited from a workplace-based work-conditioning center. SMWS was applied during five visits for a 1-week period. Both passive and active wrist extension ROM, FGOP, and pain intensity (PI) while pushing down through the hand were measured before and after SMWS. Passive and active ROM of wrist extension and FGOP increased significantly after the five sessions over 1 week of SMWS (p < 0.05). PI decreased significantly after the five sessions of SMWS (p < 0.05). These results suggest that SMWS can be used to increase wrist extension ROM and decrease wrist pain in patients with dorsal wrist pain during weight bearing through the hand.

Bone alignment using the iterative closest point algorithm

Computer assisted surgical interventions and research in joint kinematics rely heavily on the accurate registration of three-dimensional bone surface models reconstructed from various imaging technologies. Anomalous results were seen in a kinematic study of carpal bones using a principal axes alignment approach for the registration. The study was repeated using an iterative closest point algorithm, which is more accurate, but also more demanding to apply. The principal axes method showed errors between 0.35 mm and 0.49 mm for the scaphoid, and between 0.40 mm and 1.22 mm for the pisiform. The iterative closest point method produced errors of less than 0.4 mm. These results show that while the principal axes method approached the accuracy of the iterative closest point algorithm in asymmetrical bones, there were more pronounced errors in bones with some symmetry. Principal axes registration for carpal bones should be avoided.

The length and position of the long axis of the scaphoid measured by analysis of three-dimensional reconstructions of computed tomography images

We established the maximum length and the position of the long axis of the scaphoid from three-dimensional reconstructions of spiral computed tomography in 30 pairs of wrists. The distance between two points on the three-dimensional scaphoid surface model were calculated using commercially available software and corresponding coordinates of the two points were documented. The mean length was 29.3 (SD 1.6) mm for men and 26.6 (SD 1.8) mm for women. The location of the distal point was at the centre of the scaphoid tuberosity, with the proximal point of the long axis located at the dorsal ridge of the scapholunate facet.

Modélisation du carpe osseux et biomécanique

Carpal morphology and orientation of carpal bones are usually studied on two-plane radiography. Those measurements depend on the incidence of X-ray and on the expertise of physician. A method that eliminates both should improve the accuracy of those measurements. The digital data from computed tomography scans can be use to describe carpal geometry. We defined biometric and angular parameters allowing the study of carpal morphology and bones orientation. From digital data from computed tomography scans software can obtain bone volume, inertia principal axis and volume of ellipsoid of inertia. Bone centroid location and principal axis orientation can be used to study bones orientation. 3D distances ratio between geometry centroid of carpal bones. The measurements allowed by this methodology are numerous. A study of a more consistent series of normal wrists will allow in the future for each quantitative parameter to define the normal range. A comparative study of normal wrists and pathology wrists should allow defining, for each pathology, the most judicious quantitative parameters.

Morphometry by computerized three-dimensional reconstruction of the human carpal bones during embryogenesis

Carpal skeleton shows drastic developmental changes during embryogenesis. At this stage, the cartilaginous matrices appear and later form models of the limb bones. The purpose of this study was to investigate the morphometry of carpal bones in humans during embryological development. We obtained digitalized histological serial sections of 18 human embryos and early fetuses from the Institute of Anatomy in Paris. Surfdriver and MSC.Patran software were used for three-dimensional reconstruction and morphometry. There was a strong correlation between the volume of the carpal cartilaginous structure and the size of the embryos (P<0.001) and an exponential correlation between the carpal volume and the percentage of volume presented by the proximal carpal row (P=0.005). According to inertia parameters, the geometry of carpal cartilaginous structure, initially plane, becomes curved during embryogenesis. Carpal bones growth follows non-homothetic transformation. The innovations in embryo reconstruction serve as new tool for scientific investigation. A hypothesis of carpal development is proposed.

A kinematic model of the wrist based on maximization of joint contact area

The wrist is a complex joint and the factors governing its behaviour are poorly understood. A hypothesis that the movement of the carpal bones could be predicted using a minimum energy principle was tested. Carpal bones were dissected from a cadaveric forearm and their shapes were laser-digitized to obtain three-dimensional computer models. A computer program was created to measure contact area between neighbouring articular surfaces and to maximize this quantity by adjusting the six degrees of freedom of the bone models. This procedure was performed for 1.0° increments of rotation applied to the capitate bone up to 20° of ulnar and 10° of radial deviation. The model correctly predicted certain aspects of the complex behaviour of the carpal bones. The results for the scaphoid in particular displayed characteristics in common with known behaviour of this bone. During 20° of unlar deviation and 10° of radial deviation, the bone demonstrated 11.3° of extension and 9.4° of flexion respectively. The novelty of the study lay in the fact that the model did not rely upon ligamentous constraints. The results are encouraging, considering the only information used by the algorithm was the shape of the articular surfaces.

Skeletal segments of the human pollical and hallucal rays: comparison and analysis of their intrinsic proportions

Since in humans, the first digital ray has a different functional significance in the hand and in the foot, the comparison of the pollical and hallucal rays seems interesting in order to evaluate the influence of specific evolutionary functional factors and biomechanical constraints. The objective of this study was to provide original and detailed data on the intrinsic proportions of the three segments of the human pollical and hallucal rays (metacarpal or metatarsal bone, proximal phalanx, and distal phalanx) in order to allow a quantitative comparison of their relative development. No similar data evaluated from three-dimensional approaches (volumetric or ponderal) seem to be available in the literature. The material consisted of 77 skeletons of the pollical ray and 77 skeletons of the hallucal ray of normal adult individuals. The ponderal approach was used. The first metapodial represented a mean of 57.17% for the pollical ray and 68.48% for the hallucal ray, whereas the phalanges respectively represented 42.83% and 31.52%. The intrinsic phalangeal proportions were almost identical for the pollex and for the hallux (respectively, 71.76% and 72.88% for the proximal phalanx; and 28.24% and 27.12% for the distal phalanx). Since these intrinsic proportions are the reflection of biological, functional and evolutionary constraints, these data seem of interest for the analysis of the functional significance of these rays, for the characterization of malformative syndromes in clinical practice, for reference in comparative morphology, and for the interpretation of hominid fossil bones.

Carpal bone size and scaling in men versus in women

PURPOSE

The purpose of this study was to quantify carpal bone size, to determine whether gender influences carpal size, and to determine whether small and large carpal bones differ in size only by simple isometric scaling.

METHODS

Cortical surfaces of all carpal bones in both wrists of 14 women and 14 men (ages 22-34 y) were reconstructed from computed tomography (CT) volume images. Carpal volume and bounding-box dimensions in 3 orthogonal directions were calculated and compared across genders. An average set of carpal bones were then scaled mathematically by a single factor in all directions (scaled isometrically) and compared across carpal bones of all sizes.

RESULTS

Although female carpal bones were significantly smaller than male carpal bones, individual carpal volume as a percentage of the volume of the entire carpus did not differ with gender. The 3 orthogonal bounding-box dimensions of the carpal bones scaled nearly isometrically from the smallest to the largest bones.

CONCLUSIONS

Across the wide range of wrist sizes studied the individual carpal volumes were a consistent percentage of carpus volume and this percentage did not differ with gender. Despite their complex shape the bounding dimensions of the carpal bones increased isometrically with increasing volume. The extensive database of dimensions provided in this study should be useful in the design and insertion of fixation systems and implants.

A morphological study of the scaphoid using a mathematical technique and comparative study of the three-dimensional measurements of the scaphoid

To guide reconstruction of scaphoid non-union, we attempted to create full-scale models of the scaphoid by three-dimensional computed tomography (3D CT) of the healthy side. In this study, we obtained 3D scans of 51 cadaveric hands and studied the difference in morphology between genders and between the left and right sides. The major axis length on a fixed plane and Fourier transformation curve were examined. Ten scaphoid images were also obtained with 3D CT before and after removal from the cadaveric hands. Our findings suggest good correlation between models produced using 3D CT images of the scaphoid alone, and this could serve as an accurate model if the magnification is corrected using the regression line. However, the model using 3D CT images of the intact wrist joint has a large margin of error and its use will not be practical.

An anatomical database of carpal bone measurements for intercarpal arthrodesis

During limited intercarpal fusion it is sometimes difficult to determine correct screw length and staple size. This is because of overlap, and the shape and orientation of the carpal bones on radiography. One hundred complete sets of dry cadaver carpal bones were measured to provide an anatomical database of carpal bone measurements. This should help prevent inadvertent overpenetration of fixation devices during surgery.

Relative weights of the human carpal bones: biological and functional interests

The relative carpal weights (Weight of each of the eight carpal bones/Weight of the complete carpus x 100) were studied in a series of 95 complete human adult carpi (dried bones). The greatest was the capitatum (19.92%; mean rank 1.16) and the smallest the pisiform (4.43%; mean rank 8.00). The scaphoideum and the hamatum presented very near values (17.19 and 15.81%; mean ranks 2.34 and 2.74), as did the lunatum and trapezium (12.56 and 12.52%; mean ranks 4.41 and 4.48), and the triquetrum and trapezoideum (9.21 and 8.36%; mean ranks 6.19 and 6.68). Within the proximal row, a regular radio-ulnar decrease was observed from the scaphoideum (39.58%) to the pisiform (10.20%). Within the distal row, a marked break existed between the trapezoideum (14.77%) and the capitatum (35.19%); the capitato-hamatal element represented 63.11% of the distal row. The distal row (mean 56.61%) was always a little heavier than the proximal row (mean 43.39%), resulting in a mean proximo-distal weight ratio of 0.77. A radio-ulnar decrease in the relative weights was observed from the radial to the ulnar carpal columns. The determination of the relative carpal weights is simple, reproducible, non-invasive, rapid, and inexpensive, and can be considered an interesting and valuable approach to the estimation of the relative carpal volumes. Relative carpal weights reveal the intrinsic proportions of the carpus and are the reflection of biological, functional and evolutionary constraints. Interesting relations appear with carpal growth and ossification, with functional characteristics, and with evolutionary processes.

In vivo kinematic behavior of the radio-capitate joint during wrist flexion-extension and radio-ulnar deviation

The capitate is often considered the "keystone" of the carpus, not simply because of its central and prominent position in the wrist, but also because of its mechanical interactions with neighboring bones. The purpose of this study was to determine in vivo three-dimensional capitate kinematics. Twenty uninjured wrists were investigated using a recently developed, non-invasive markerless bone registration (MBR) technique. Surface contours of the capitate, third metacarpal and radius were extracted from computed tomography images of seven wrist positions and the three-dimensional motions of the capitate and third metacarpal were calculated with respect to the radius in wrist flexion-extension and radio-ulnar deviation. We found that in vivo capitate motion does not simply occur about a single pivot point like a universal joint, as demonstrated by non-intersecting rotation axes for different capitate motions. The distance between flexion and ulnar deviation axes was 3.9+/-2.0 mm, and the distance between extension and ulnar deviation axes was 3.9+/-1.4 mm. Furthermore, capitate axes for males tended to be located more distally than axes for females. However, we believe that this result is related to subject size and not to gender. We also found that there is minimal relative motion between the capitate and third metacarpal during these in vivo wrist motions. These findings demonstrate the complexity of capitate kinematics, as well as the different mechanisms through which wrist flexion, extension, radial deviation and ulnar deviation occur.

An in vivo analysis of the motion of the peri-talar joint complex based on MR imaging

The purpose of this work is to characterize the three-dimensional (3-D) motion of the peritalar joint complex in vivo using magnetic resonance imaging (MRI). Each image data set utilized in this study is made of 60 longitudinal MR slices of the foot in each of eight positions from extreme pronation to extreme supination. We acquired and analyzed ten such data sets from normal subjects, seven data sets from pathological joints and two postoperative data sets. We segmented and formed the surfaces of the calcaneus, talus, cuboid and navicular from all data sets. About 30 geometrical parameters are computed for each joint in each position. The results present features of normal motion and show how normal and abnormal motion can be distinguished. They also show the consequences of surgery on the motion. This non- invasive method offers a unique tool to characterize and quantify the 3-D motion of the rearfoot in vivo from MR images.

Variations in the skeletal morphologic features of the wrist

Increased attention to and interest in the wrist and the field of hand surgery has brought about the discovery, rediscovery, and better description of variations in the skeletal morphologic features of the hand and wrist. In the second through fifth carpometacarpal joints, the fourth carpometacarpal articulation is the area of greatest variability. In the midcarpal joint, the scaphotrapeziotrapezoid and the capitolunate (hamate) articulations are areas of considerable variability in their skeletal morphologic features. New knowledge and awareness of variations in skeletal morphologic features in the carpus offer a better understanding and the opportunity to revisit various injury patterns and/or orthopaedic problems, and normal kinetics and kinematics to assess the effect and any differences that may be related to these different skeletal morphologic features.

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

Our present knowledge of the three-dimensional kinematic behavior of skeletal joints has been largely acquired with cadaveric models and use of invasive monitoring. In the wrist, the small size and complex motion of the carpal bones present a difficult challenge for implanted internal or external marker systems. This paper describes a technique for quantifying the three-dimensional kinematics of the wrist and carpal bones in vivo using noninvasive computed tomographic imaging. An error analysis employing a cadaveric specimen suggests that noninvasive carpal kinematics can be measured with an accuracy within 2 degrees of rotation and 1 mm of translation along a helical axis of motion. The in vivo application of this technique is illustrated with a single normal individual. Potential applications include the quantification of normal wrist motion, analysis of pathomechanics, and evaluation of surgical intervention. The technique is also applicable to other joints and imaging modalities.

Progressive patterns of degenerative arthritis in scaphoid nonunion demonstrated by three-dimensional computed tomography

Degenerative arthritis following scaphoid nonunion was studied in 28 patients (29 wrists) using X-ray computed tomography and three-dimensional computed tomography (3-DCT). Degenerative changes were observed in 18 wrists with plain radiography and 27 wrists with 3-DCT. 3-DCT imaging more readily revealed osteophyte formation in osteoarthritis than plain radiography. 3-DCT images showed degenerative changes in the distal fragment of the scaphoid earlier than plain radiography. We found three stages of osteophyte formation in the radioscaphoid joint using 3-DCT. In the first stage, a linear osteophyte formed along the most radial portion of the distal fragment of the scaphoid. In the second stage, the radial styloid became pointed. In the third stage, the osteophyte on the distal fragment enlarged and lay over the dorsum of the radioscaphoid joint and other intercarpal joints.

The carpal stretch test at the scapholunate joint

The purpose of this study was to evaluate the principle of the carpal stretch test. Eleven upper extremities from 6 fresh cadaver specimens and 40 normal wrists from 20 volunteers were used in this study. Changes in intercarpal distances (carpal interval ratio of the radioscaphoid, radiolunate, and lunocapitate joints) and step-off deformities at the scapholunate joint seen on the posteroanterior view of an x-ray film were analyzed with and without the carpal stretch test. In the cadaver wrists, the dorsal capsulotomy and radioscapholunate ligament (stage 1), the palmar half of the scapholunate interosseous ligament (stage 2), the dorsal half of the scapholunate interosseous ligament (stage 3), and the radioscaphocapitate ligament (stage 4) were sequentially sectioned. The carpal stretch test was completed in each stage. Each carpal interval ratio increased as each stage was added. Step-off deformities at the scapholunate joint were seen in 6 of 11 wrists in stage 2 and in 10 wrists in stages 3 and 4 with the carpal stretch test. In the normal wrists, neither gender nor wrist laxity (Garcia's criteria) not influenced the results of the carpal stretch test. The carpal stretch test may be helpful in identifying occult and/or dynamic scapholunate dissociation.

Carpal bone maturation during childhood and adolescence: assessment by quantitative computed tomography. Preliminary results

The aim of our study was to measure the volume of each carpal bone during childhood and adolescence by image processing from computed tomography (CT) scans, and to analyze the relationship between the eight carpal bones. Thirteen CT scans were performed in nine normal prepubertal, peripubertal and post-pubertal children, six boys and three girls, aged 5-14 years. Each scan was processed in order to extract the carpal bones. The volume was computed for each bone. There was a significant correlation between carpal bone volume and age (0.55 < r < 0.79), and a very strong correlation between the volume of a given carpal bone and the volume of all the others, whatever the age (0.87 < r < 0.99, p < 0.01). Image processing is a potentially useful method for assessing bone maturation. The constant ratio between carpal bone volumes indicates that these bones interact with each other in wrist bone maturation.