Characterization of the mid-coronal plane method for measurement of radiographic change in knee joint space width across different levels of image parallax.

OBJECTIVE: Radiographic measurement of the change in knee joint space width (ΔJSW) is often affected by image parallax, which causes an apparent exaggeration of JSW due to projectional differences. This issue with parallax (quantified by intermargin distance) can in part be addressed with a novel mid-coronal plane (MCP) measurement method. The objectives of the study were to determine 1) accuracy and 2) reproducibility of the MCP method, and 3) compare the MCP method to that used in the Osteoarthritis Initiative (OAI) for different categories of parallax. METHODS: Posteroanterior radiographs (n = 70) with known JSW were digitally reconstructed from CT images of cadaver knees and used to determine the accuracy of ΔJSW using the MCP method for parallax categories of None, Mild/Moderate, and Severe. Reproducibility was determined from pairs of clinical radiographs selected from the OAI (n = 170). The MCP method was also compared to the OAI methodology. Both reproducibility and agreement were characterized by Bland-Altman analysis and intraclass correlation coefficients (ICC). RESULTS: The MCP method was accurate to 0.11 mm in cases with no parallax, and 0.18 mm across all categories of parallax for medial and lateral compartments. Reproducibility of the MCP method was graded "excellent" (ICC 0.98, 95% CI [0.98, 0.99]). The MCP results agreed very well with the OAI (ICC 0.92, 95% CI [0.89, 0.94]), with mean absolute differences between methods increasing with increasing parallax. CONCLUSION: The MCP method is an accurate, reproducible alternative to the OAI method for multi-center clinical trials where subject and X-ray beam positioning may be variable.

Worksite nutrition supports and sugar-sweetened beverage consumption.

OBJECTIVE: This study examined the link between worksite environmental supports for nutrition behaviours and sugar-sweetened beverage (SSB) consumption and offers insight into potential intervention points for reducing SSB consumption and combatting overweight and obesity. METHODS: Perceived worksite supports for healthy nutrition and self-reported SSB consumption were analysed for 2,015 working adults in the state of Missouri using a subset of questions from the Supports at Home and Work for Maintaining Energy Balance (SHOW-ME) study. RESULTS: Employees' use of vending facilities and the availability of water coolers/water bottles was significantly associated with increased SSB consumption, while use of cafeterias was significantly associated with decreased SSB consumption. Symbols or signs to identify healthy alternatives were significantly associated with sports drink consumption. CONCLUSIONS: This study supports previous work indicating the worksite as a necessary environment for nutrition interventions. When choices (vending and cafeteria) are provided, employees report making healthier decisions. For worksites without cafeterias, alternatives should be explored including mobile food trucks and farmer's markets.

The effect of retained intramedullary nails on tibial bone mineral density.

BACKGROUND: Intramedullary nailing has become a standard treatment for adult tibial shaft fractures. Retained intramedullary nails have been associated with stress shielding, although their long-term effect on decreasing tibial bone mineral density is currently unclear. The purpose of this study was to determine if retained tibial intramedullary nails decrease tibial mineral density in patients with successfully treated fractures. METHODS: Patients treated with statically locked intramedullary nails for isolated, unilateral tibia shaft fractures were studied. Inclusion required that fracture had healed radiographically and that the patient returned to the pre-injury activity level. Data on patient demographic, fracture type, surgical technique, implant, and post-operative functional status were tabulated. Dual energy X-ray absorptiometry was used to measure bone mineral density in selected regions of the affected tibia and the contralateral intact tibia. Image reconstruction software was employed to ensure symmetry of the studied regions. FINDINGS: Twenty patients (mean age 43; range 22-77 years) were studied at a mean of 29 months (range 5-60 months) following intramedullary nailing. There was statistically significant reduction of mean bone mineral density in tibiae with retained intramedullary nails (1.02 g/cm(2) versus 1.06 g/cm(2); P=0.04). A significantly greater decrease in bone mineral density was detected in the reamed versus non-reamed tibiae (-7% versus +6%, respectively; P<0.05). INTERPRETATION: The present study demonstrates a small, but statistically significant overall bone mineral density decrease in healed tibiae with retained nails. Intramedullary reaming appears to be a factor potentiating the reduction of tibia bone mineral density in long-term nail retention.

The use of a virtual three-dimensional model to evaluate the intraosseous space available for percutaneous screw fixation of acetabular fractures.

We created virtual three-dimensional reconstruction models from computed tomography scans obtained from patients with acetabular fractures. Virtual cylindrical implants were placed intraosseously in the anterior column, the posterior column and across the dome of the acetabulum. The maximum diameter which was entirely contained within the bone was determined for each position of the screw. In the same model, the cross-sectional diameters of the columns were measured and compared to the maximum diameter of the corresponding virtual implant. We found that the mean maximum diameter of virtual implant accommodated by the anterior columns was 6.4 mm and that the smallest diameter of the columns was larger than the maximum diameter of the equivalent virtual implant. This study suggests that the size of the screw used for percutaneous fixation of acetabular fractures should not be based solely on the measurement of cross-sectional diameter and that virtual three-dimensional reconstructions might be useful in pre-operative planning.

Posterior annular strains during discography.

Discography is commonly used in the workup of back disorders. The clinical utility of the test is controversial, and little is known about mechanical changes that may occur in the disc during this exam. To quantify three-dimensional deformations of the posterior annulus during discography, and to examine some of the covariates that influence the deformations, displacements of the lumbar posterior annulus were measured during discographic injection for three different spinal positions. Disc bulge and annular strains were calculated from the displacements. The combined effect of disc pressurization, spine position, and location on the disc (lateral versus midline) explained much of the variation in the measured bulges and strains (r(2) = 0.56). Disc pressurization or spine position alone did not always have a significant effect on strains, and the strains and bulges were often influenced by the interactions between position of the spine, location of the disc, and pressurization. In clinical studies of discography, these results suggest that patient position during the examination should be standardized.

Cancer vaccines: an update.

This review summarizes the most recent findings and the future directions in designing cancer vaccines. The newest tumor-associated antigens and the most promising approaches to cancer vaccine development are discussed. We categorized them as follows: peptide vaccines, recombinant viral vaccines, DNA vaccines, dendritic cell-based immunotherapy, and the use of heat shock proteins and adjuvants. We focus on their advantages and disadvantages in addition to clinical potential.

Sensitivity and specificity of dural sac and herniated disc dimensions in patients with low back-related leg pain.

Narrow spinal canals or herniated discs can be associated with leg pain. However, it is not known whether quantitative measurements of the spinal canal or herniated disc are sensitive and specific for low back-related leg pain. The size and cross-sectional area of the dural sac and any herniated discs were measured from magnetic resonance imaging examinations of 22 asymptomatic individuals and 44 patients with sciatica. The sensitivity and specificity of these measurements were determined. In this small population of patients, a dural sac anteroposterior (AP) diameter of 10.2 mm at the L3-4, L4-5, or L5-S1 vertebral levels was 74% sensitive and 74% specific for leg pain. Based on measurements in symptomatic patients, a herniated disc with an AP diameter of approximately 3 mm was over 95% sensitive and 95% specific. However, if the AP diameters of herniated discs in symptomatic patients were compared with similar measurements in asymptomatic controls, the most sensitive and specific threshold value was 6.8 mm. These findings must be confirmed in a larger population before they are applied clinically. J. Magn. Reson. Imaging 2000;12:439-443.

Postfracture instability of vertebrae with simulated defects can be predicted from computed tomography data.

STUDY DESIGN: Structural properties of vertebrae with simulated defects were measured from computed tomography data. Relations between structural properties and postfracture stability were tested using linear regressions. OBJECTIVES: To determine whether the postfracture stability of lumbar and thoracic vertebrae can be predicted from noninvasive, prefracture measurements of structural properties. SUMMARY OF BACKGROUND DATA: Sensitive and specific guidelines are needed that can predict fracture risk and spinal stability after pathologic fractures. Such guidelines may help determine whether treatment is needed to prevent neurologic complications. Simple measurements made from computed tomography data can predict the load-bearing capacity of intact vertebrae and vertebrae with simulated and actual metastatic defects. It is not known whether these same measurements can also predict postfracture stability. METHOD: Simulated metastatic defects were created in human three-vertebrae segments from the lumbar and thoracic spine. Axial rigidity was calculated from quantitative computed tomography data, and failure load and postfracture stability were measured. RESULTS: Postfracture stability was linearly correlated with both failure load (r2 = 0.3-0.6) and axial rigidity (r2 = 0.3-0.6). CONCLUSIONS: The postfracture stability of three-vertebrae segments with simulated defects was modestly related to noninvasively measured, prefracture structural properties.

Magnetic resonance imaging measurements of bone density and cross-sectional geometry.

Magnetic resonance imaging (MRI) is commonly used in the assessment of the musculoskeletal system and associated pathology. The ability of MRI to measure the signals from water and lipid protons enables quantitative measurements of bone porosity. The goal of this investigation was to demonstrate that the density and cross-sectional geometry of whole bones can be noninvasively measured using MRI. Ten trabecular specimens cored from whale vertebrae were used to compare apparent bone density measured directly, and using a quantitative MRI algorithm. Bone density and several cross-sectional geometric properties were also measured using MRI in the distal tibia of 14 volunteers. The MRI measurements were compared with measurements made using quantitative-computed tomography (QCT). A proton density sequence was used for all MRI studies. A porosity phantom was included in the MRI examinations and used to convert the MRI signal intensity to bone volume fraction. Bone density and cross-sectional bone geometry were calculated from the bone volume fractions by assuming constant tissue properties. The apparent density of trabecular bone cores measured directly and using quantitative MRI were linearly related (r(2) = 0.959; P < 0. 01). A strong linear relation also existed between MRI and QCT measurements of ash density (r(2) = 0.923; P < 0.01) and cross-sectional geometric properties (r(2) = 0.976-0.992; P < 0.01). MRI data can be used to measure bone density and cross-sectional geometry of whole bones if a proton density sequence is used to homogenize differences in marrow composition and a porosity phantom is used for slice-specific volume fraction calibration.

Use of percutaneous transpedicular external fixation pins to measure intervertebral motion.

STUDY DESIGN: Direct measurement of intervertebral motion was compared to motion determined by measuring the position of the exposed ends of the external fixation pins. OBJECTIVES: To verify the accuracy of this technique, so that this protocol can be used to study intervertebral motion in the clinical setting. SUMMARY OF BACKGROUND DATA: The transpedicular external fixation test has been shown to be a test that can predict the outcome of spinal fusion. In patients who are candidates for this test, intervertebral motion can be calculated from motion at the external ends of these pins. METHODS: Six fresh cadaveric spinal segments from L2 to L5 were instrumented with titanium Schanz screws. Reflective markers were placed on the tips of the pins, and intervertebral motion was measured using a noncontacting camera system. Computed tomography data were used to determine the position of the vertebra relative to the reflective markers. Intervertebral distances were calculated and compared with direct measurements obtained using a three-dimensional digitizing arm. RESULTS: There was an excellent correlation (r2 = 0.931) between the directly measured intervertebral motions and those that were indirectly calculated from measurements of motion at the end of the Schanz screws. CONCLUSIONS: Intervertebral motion can be measured by monitoring motion of the ends of transpedicular external fixation pins. Motion of anatomic landmarks on the vertebrae can be calculated from the pin end's motion if computed tomography data are used to determine the geometric relation between the vertebrae and the external fixation pins. This validation study supports the use of this method in clinical investigations of intervertebral motion in patients with low back pain and external fixation.

Quantitative assessment of the midcarpal shift test.

The subjective, clinical midcarpal shift test was compared with a quantitative measurement of carpal volar/dorsal translation versus ulnar deviation using a mechanical testing system. Testing was performed on 19 healthy volunteers (mean age, 33 years) and 3 patients (four wrists; mean age, 23 years) who had been diagnosed with ulnar midcarpal instability, a nondissociative form of carpal instability. During physical examination, each subject's wrist was graded I to V using the previously described classification of the degree of laxity and clunk observed with the midcarpal shift test. Each subject was also evaluated using a quantitative mechanical testing system that simulates the subjective clinical test. The testing system measures displacement of the distal carpal row, more specifically, the capitate, as the wrist is moved from neutral to ulnar deviation under a constant axial load of 44 N directed volarly at the head of the capitate. Reflective markers were attached to the skin above the proximal and distal ends of the third metacarpal and at the point where the 44-N load was applied to the carpus. Motion of the markers was used to calculate ulnar deviation and dorsal/volar translation of the carpus. The maximum slope of the carpal translation versus ulnar deviation curve was measured for each subject and compared with the results of the clinical midcarpal shift test. Higher maximum slopes were seen in subjects with the higher grades of carpal laxity. There were also differences with regard to the point at which the clunk occurred; the higher the clinical grade of laxity, the greater the ulnar deviation of the wrist at the point at which the clunk was observed. These differences were not significant, however. These data confirm the validity of the clinical test and establish its usefulness as a diagnostic indicator of midcarpal nondissociative carpal instability. The mechanized test also may be useful as a biomechanical marker, enabling the results of ligament sectioning to be effectively compared with defined clinical laxity.

Planning acetabular redirection osteotomies based on joint contact pressures.

Acetabular redirection osteotomy can be used to relieve pain, improve function, and extend the life of dysplastic hip joints. To understand better the factors that may determine the acetabular reorientation that minimizes pressures, joint contact pressures were calculated by computer assisted methods in 70 dysplastic and 12 normal hips (82 patients). Calculated pressures were consistent with pressures estimated and measured by other investigators. Contact areas were 26% smaller, and contact pressures were 23% higher, in the dysplastic hips compared with the normal hips. When the acetabula were reoriented to minimize contact pressures for an activity such as the midstance phase of gait, then contact pressures were elevated for dissimilar activities such as stair ascent. Contact pressures in the dysplastic hips were reduced when the acetabula were rotated in the frontal plane to increase lateral coverage or rotated in the sagittal plane to increase anterior coverage. In most of the dysplastic hips, contact pressures were reduced twice as much when the acetabulum was rotated in the frontal and the sagitta' planes. Computer assisted methods to quantify joint contact pressures can be used to assess potential candidates for reconstruction, plan acetabular redirection surgery, and possibly may improve the long term success of acetabular redirection osteotomy.

Density predicts the activity-dependent failure load of proximal femora with defects.

OBJECTIVE: To determine whether the load-bearing capacity of human proximal femora with metastatic defects can be predicted from the bone mineral content. DESIGN: The bone mineral content (BMC) of the total proximal femur was measured by dual-energy X-ray absorptiometry (DXA). The femurs were loaded so as to simulate stair ascent or external rotation. PATIENTS: Simulated lytic defects were created using specialized cutting tools in the intertrochanteric region of 32 human cadaveric femora. Bone density measurements were made before and after creating defects. RESULTS: A linear relation could be used to predict failure load from BMC or bone mineral density. The slope of the linear relation was greater for loads representing external rotation than for loads representing stair ascent. The linear relations suggest that the BMC measurements account for both the density of the host bone and the amount of bone removed by the defect. CONCLUSIONS: The data suggest that between 70% and 80% of the variation in failure load of human femora with lytic metastatic defects can be predicted from the BMC and that relations between BMC and failure load are sensitive to the type of loading. Combined with information on the loads associated with the activities of daily living, these data may be used to help identify patients in whom prophylactic stabilization might prevent a pathologic fracture.

Radiographic verification of pedicle screw pilot hole placement using Kirshner wires versus beaded wires.

STUDY DESIGN: Kappa statistics were used to compare the accuracy of two different techniques for verifying pedicle screw pilot hole placement in cadaveric vertebrae. OBJECTIVE: To determine whether clinicians radiographically detect misplaced pedicle screw holes with greater sensitivity and specificity when beaded wires rather than straight Kirschner wires are used. SUMMARY OF BACKGROUND DATA: Pedicle screws commonly are used in orthopedic surgery to obtain and maintain spinal stability. Pedicle screws are reportedly misplaced at a rate of 20% to 40%. Radiographic verification is commonly used to place pedicle screw pilot holes, but this technique is known to be less than 100% accurate. Computer-assisted techniques may allow more accurate screw placement, but these techniques require expensive equipment. METHODS: Pedicle screw pilot holes were drilled into 12 human lumbar and thoracic vertebrae. Some of the holes were misplaced deliberately so that they violated the pedicle walls. Lateral and posteroanterior radiographs of the vertebrae were evaluated by 13 experienced orthopedic spine surgeons and 3 inexperienced observers. At different times, the observers were shown radiographs depicting Kirschner wires or beaded wires placed in the pilot holes. Observers indicated whether they thought the pedicle screw pilot hole violated the pedicle. RESULTS: The sensitivity and specificity of using posteroanterior or lateral radiographs to detect misplaced pedicle screws were increased when beaded wires were placed in the pilot holes. CONCLUSIONS: Radiographic evaluation of beaded wires placed in pedicle screw pilot holes can be both sensitive and specific for misplaced screws. The highest sensitivity and specificity were found using posteroanterior radiographs.

Use of computed tomography image processing for mapping of human cervical facet surface geometry.

Vertebral facets transmit a significant percent of spinal loading, provide translational, rotational, and axial stability for the spine, and are responsible for the coupling between lateral bending and rotational motions. The shape and the orientation of vertebral facets vary with level and are influenced by degenerative processes. These variations may play an important role in many cases of neck pain, back pain, and instability. To determine whether the shape and orientation of cervical facets can be accurately measured from computed tomography (CT) data, the surfaces of 39 human cervical facets were non-invasively digitized from reconstructed three-dimensional CT data and then invasively digitized using a hand-held three-dimensional probe before and after bleaching away the cartilage. Digitized data describing the facet surfaces were fit to both plane and spherical surfaces. For the adult cervical vertebrae that we measured, the presence of cartilage had no significant effect on the measured shape or orientation of the facets. The orientation of the facet surfaces measured from CT data was within 11 deg of that measured using the hand-held probe. Quantitative measurements of facet shape (flat or spherical) and surface irregularity were similar between CT and hand digitized surfaces. These results suggest that individual facet geometries can be accurately quantified using non-invasive CT examinations. Non-invasively determined variations in facet geometries may assist in the diagnosis of back pain, neck pain and instability.

The internal bony architecture of the sacrum.

STUDY DESIGN: Radiographic and direct quantitative measurements were made of the cortical and the trabecular anatomy of the sacrum. OBJECTIVES: To define the trabecular patterns and the cortical thickness of the sacrum. SUMMARY OF BACKGROUND DATA: The sacrum is a frequent site of internal fixation. In previous anatomic studies, investigators have focused on specific dimensional measurements of the sacrum, whereas others have described the anatomic course of the anterior sacral neurovascular or visceral structures. Computed tomographic imaging also has been used to quantify the sacral trabecular bone density. The internal architecture of the sacrum has yet to be described in detail. METHODS: Seventeen cadaveric sacra were studied by computed tomographic imaging and then were sectioned at 3-mm intervals in the axial or sagittal plane. The cortical thickness of each section was measured under microscopic visualization. The sections were radiographed with high-resolution imaging to delineate their trabecular patterns. RESULTS: The trabecular bone was densest adjacent to the endplates. The sacral body trabeculae were arranged in a cruciate pattern, and bony atrophy occurred in a systematic fashion. An alar void was a consistent finding in all specimens with definable boundaries. The cortical thickness was uniform throughout the surface of each specimen. The computed tomographic images correlated with the anatomy observed in the cadaveric sections. CONCLUSION: The internal bony architecture of the sacrum has several consistent features. The relatively uniform cortical thickness seen in each sacral specimen may have clinical significance in the internal fixation of this region.

A motion analysis of the cervical facet joint.

STUDY DESIGN: The stability of motion segments of human cervical spines was sequentially tested as portions of the vertebral anatomy were removed or cut. Isolated, individual facet joints were then similarly studied. OBJECTIVES: To define the laxity of isolated cervical facet joints and the relative contribution of the different components of the vertebral anatomy to the overall stability of the cervical spine. SUMMARY OF BACKGROUND DATA: Facet joints are known to be important in determining cervical stiffness and mobility. This is the first known study in which the biomechanical behavior of isolated cervical facet joints has been documented. METHODS: From five fresh frozen human cervical spines, three C3-C4 and five C5-C6 motion segments were dissected and potted. Rotations and translations in response to 10 bending or twisting moments were recorded by tracking the motion of a testing plate fixed to the superior vertebrae using an articulated arm digitizer. Each motion segment was tested five times, with sequential dissections performed as follows: intact; after removal of the anterior longitudinal ligament intervertebral disc, and posterior longitudinal ligament; after cutting the interspinous ligament; after isolation of the left facet joint; and after isolation of the right facet joint. Each testing sequence involved applying low and high forces 10 cm from the center of the testing plate in each of 10 testing directions. After completion of rotational testing, landmarks on the superior vertebral body and facet joints were digitized to calculate vertebral translations. RESULTS: Isolated facet joints allowed up to 19 degrees of flexion, 14 degrees of extension, 28 degrees of lateral bending, and 17 degrees of rotation. Coupled motions were less in isolated facet joints compared with those in intact vertebral bodies. Isolated facet joints allowed up to 9 mm of translation between superior and inferior surfaces. CONCLUSIONS: Isolated cervical facet joints are highly mobile in comparison with their motions within the constraints of intact motion segments; gliding motions of the isolated facet to near dislocation is possible before the facet capsule constrains motion. Cervical coupled motions are a result of an intact vertebral ring and a combination of the two facet joints. The vertebral ring with facet joints and capsules all intact is necessary for lateral bending stability and rotational stability in the cervical spine.

Predicting failure of thoracic vertebrae with simulated and actual metastatic defects.

Indications for operative treatment in spinal metastatic disease depend on estimates of vertebral loadbearing capacity. There are no noninvasive diagnostic tools for estimating vertebral loadbearing capacity in the presence of a metastatic lesion. Thus, relationships between vertebral failure load and measurements from computed tomography data were investigated to determine if measurements that account for defect size and bone density can predict loadbearing capacity better than can defect size alone. Cylindrical defects were created in thoracic vertebrae of 20 anatomic specimen spinal segments, with 10 other segments serving as controls. Five vertebrae with actual metastatic defects also were tested. Vertebrae were scanned using quantitative computed tomography, and the defect size and the axial rigidity of the midvertebral cross section were calculated using an image analysis program. The spinal segments were tested to failure using a combination of axial compression and anterior flexion. Linear regressions between axial rigidity and absolute failure load showed a high positive correlation, but there was no correlation between defect size and failure load. Axial rigidity may prove useful as a noninvasive assessment of vertebral loadbearing capacity in patients with spinal metastatic disease.

Noninvasive measurement of distal radius instability.

Except for subjective clinical criteria, there is no formal definition of distal radius fracture instability in the literature. The purposes of this ex vivo biomechanical study were (1) to provide an objective mechanical definition of fracture instability and (2) to demonstrate a noninvasive method that allows for direct measurement of instability. The following 3 questions are addressed: (1) Can the stability of distal radius fractures be measured using computed tomography (CT)? (2) Are the stability measurements reproducible? (3) How does external fixation change stability? A CT technique is described that was used to measure displacement of fracture fragments and measure the compliance of ex vivo distal radius fractures before and after external fixation. Validation studies of the CT technique revealed a mean coefficient of variation of 0.38. There was a linear relationship between measured and known displacements for all 3 orthogonal planes (coefficient of determination 0.99; p < .01). There was significant fracture displacement with loads as small as 20 N. The slope of the load-displacement curve (structural compliance) provided a quantitative measure of fracture instability. Fracture compliance decreased up to 69% after application of an external fixator.

Method-based differences in the automated analysis of the three-dimensional morphology of trabecular bone.

The three-dimensional (3D) morphology of trabecular bone is frequently quantified using computer programs. However, there are no standardized implementations of morphology programs and many variations are possible. Even though programs may use the same basic method, results can be significantly different because of differences in implementation. Morphology data from different laboratories therefore may not be comparable. The method of directed secants, with parallel plate assumptions, is commonly used to quantify 3D morphology. We examined the effect of several variations in the implementation of this method on measurements of trabecular plate number (Tb.N), trabecular thickness, and trabecular spacing. Three-dimensional micromagnetic resonance images of 10 bovine trabecular bone specimens were analyzed using several variations of the directed secant method. An analysis of covariance with repeated measures suggested that variations in the algorithm used to count test line intersections, variations in the criteria used to classify a test coordinate as bone or marrow, and variations in the number of test grid rotations had significant effects on Tb.N (p < 0.0001). The largest difference in Tb.N (52%) was due to the method used to count test line intersections with the bone-marrow interface. Variations in the classification algorithm and variations in the number of test line grid rotations resulted in a 6% difference in Tb.N. The spacing of the test line grids did not affect Tb.N (p = 0.28), and all differences were independent of volume fraction (p = 0.67). These data show that there can be significant differences in trabecular bone morphology measurements due only to the method used for the measurements. To facilitate comparisons between laboratories, we have made validated computer programs to measure trabecular bone morphology available over the Internet.