Assessment of the Bone Mineral Density and Microstructure of the Human Femoral Head according to Different Tip-apex Distances Can Guide the Treatment of Intertrochanteric Hip Fractures (original) (raw)
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Medical Physics, 2006
Microcomputed tomography ͑CT͒ produces three-dimensional ͑3D͒ images of trabecular bone. We compared conventional CT ͑CCT͒ with a polychromatic x-ray cone beam to synchrotron radiation ͑SR͒ CT with a monochromatic parallel beam for assessing trabecular bone microarchitecture of 14 subchondral femoral head specimens from patients with osteoarthritis ͑n =10͒ or osteoporosis ͑n =4͒. SRCT images with a voxel size of 10.13 m were reconstructed from 900 2D radiographic projections ͑angular step, 0.2°͒. CCT images with a voxel size of 10.77 m were reconstructed from 205, 413, and 825 projections obtained using angular steps of 0.9°, 0.45°, and 0.23°, respectively. A single threshold was used to binarize the images. We computed bone volume/ tissue volume ͑BV/TV͒, bone surface/bone volume ͑BS/BV͒, trabecular number ͑Tb.N͒, trabecular thickness ͑Tb.Th and Tb. Th * ͒, trabecular spacing ͑Tb.Sp͒, degree of anisotropy ͑DA͒, and Euler density. With the 0.9°angular step, all CCT values were significantly different from SRCT values. With the 0.23°and 0.45°rotation steps, BV/TV, Tb.Th, and BS/BV by CCT differed significantly from the values by SRCT. The error due to slice matching ͑visual site matching ±10 slices͒ was within 1% for most parameters. Compared to SRCT, BV/TV, Tb.Sp, and Tb.Th by CCT were underestimated, whereas Tb.N and Tb. Th * were overestimated. A Bland and Altman plot showed no bias for Tb.N or DA. Bias was −0.8± 1.0%, +5.0± 1.1 m, −5.9± 6.3 m, and −5.7± 29.1 m for BV/TV, Tb. Th * , Tb.Th, and Tb.Sp, respectively, and the differences did not vary over the range of values. Although systematic differences were noted between SRCT and CCT values, correlations between the techniques were high and the differences would probably not change the discrimination between study groups. CCT provides a reliable 3D assessment of human defatted bone when working at the 0.23°or 0.45°rotation step; the 0.9°rotation step may be insufficiently accurate for morphological bone analysis.
Bone mineral density Methods of measurement and its influence on primary stability of miniscrews
Objective: To verify whether bone mineral density (BMD) of cortical bone, trabecular bone, and total bone influence the primary stability of orthodontic miniscrews and to verify whether there is a correlation between the measurement of BMD by cone-beam computed tomography (CBCT) and central dual-energy x-ray absorptiometry (DEXA). Materials and Methods: Twenty bovine bone sections were extracted from the pubic and iliac bones from regions with cortical thicknesses of approximately 1 mm. The BMD of the total bone block was evaluated using two methods: CBCT and DEXA. The BMD of cortical, trabecular, and total bone in the region of interest (ROI) were also evaluated by CBCT. After scanning the bone blocks, 20 self-drilling miniscrews (INPH) 1.4 mm in diameter and 6 mm long were inserted into them. The peak implant insertion torque (IT) was registered. After this, the pull-out test (PS) was performed and the maximum force registered. The Pearson correlation test was applied to verify the correlations between variables. Results: The BMD of the total bone block verified by CBCT and DEXA showed a positive and strong correlation (r 5 0.866, P 5 .000). The BMD of the ROI for cortical bone influenced the IT (r 5 0.518, P 5 .40) and the PS of miniscrews (r 5 0.713, P 5 .001, ). However, the total bone BMD (verified by CBCT and DEXA) and trabecular bone BMD presented weak and not statistically significant correlations with primary stability. Conclusions: There was a positive correlation between total bone block BMD measured by DEXA and CBCT. The cortical BMD influenced the IT and PS. (Angle Orthod. 2012;82:62-66.) KEY WORDS: Bone density; Cone-beam computed tomography; Dual-energy x-ray absorptiometry; Miniscrew
Effects of a New Positioner on the Precision of Hip Bone Mineral Density Measurements
Journal of Bone and Mineral Research, 1997
In an attempt to reduce patient positioning errors, the authors tested the use of a new hip-specific positioning tool, OsteoDyne's Hip Positioner System (HPS). The HPS is an "A" frame splint designed to abduct both legs approximately 15°to hold them in full extension at the hips and knees and to lock the feet in a neutral position. Seventy volunteer women aged 35-82 years were randomly assigned in two age-matched groups (mean age 56 years). Each group underwent two consecutive femur dual X-ray absorptiometry (DXA) scans with intermediate repositioning using the HPS system and two others utilizing the standard hip positioner provided with Hologic and Lunar scanners. One technician performed all scans using a Hologic QDR 1000-Plus and Lunar DPX-Plus densitometer. One hundred and fifty volunteer women aged 50 -84 years (mean age, 64 years) were recruited in a multicenter study for the assessment of precision. Each subject underwent three consecutive femur DXA scans with intermediate repositioning using the HPS system. The coefficient of variation (CV) was significantly improved at the femoral neck by the use of the HPS with 0.7 versus 1.2 with the Hologic densitometer but only moderately altered at other sites. Similar results were found with the Lunar densitometer with improvement of precision at the femoral neck, 0.8 versus 1.8 with a similar trend but no significant difference at the other regions. No statistical difference was noted between the femoral neck BMD measured with the HPS system and with the standard positioners in either group. The mean precision of data obtained on the QDR 1000؉ was 0.8% (range 0.1-1.4) for the femoral neck BMD, 1.1% (range 0.1-3.0) for the trochanter BMD, 2.3% (range 0.2-5.2) for Ward's triangle BMD, and 0.8% (range 0.1-1.9) for the total femur BMD. The mean precision of data obtained on the QDR 2000 was 0.7% (range 0.1-2), 1% (range 0.1-4.9), 2.6% (range 0.3-5.7), and 0.7% (range 0.1-1.8), respectively. In conclusion, data obtained with the new OsteoDyne's HPS seem capable of reducing patient positioning errors for the hip measurement. Its use is likely to improve confidence in hip bone mineral density measurements
Directional Variation of Trabecular Bone in the Femoral Head, a μ-CT based Approach
Proceedings of the International Conference on Bioinformatics Models, Methods and Algorithms, 2013
The structural characteristics of bone are described by features of high complexity, defining the directional anisotropy of its mechanical properties. This phenomenon originates in the orientation of collagen fibers and osteons within the cortical tissue and the trabecular morphology of cancellous bone. the purpose of this study was the examination of the geometrical anisotropy of cancellous bone in the femoral head. 28 femoral heads, harvested during hip replacement of 17 women and 11 men, were studied in total. Cylindrical specimens of 11mm in diameter were extracted perpendicular to the fovea capitis femoris and subjected to micro Computed Tomography (μ-CT). a 11mm sphere was isolated from all samples and the cross-sectional area of the sphere was studied for 8 predefined regions, corresponding to planes perpendicular to principal loading directions of the hip joint. Significant topographical variations of trabecular bone structure in different subchondral regions were determined. in the superior region, the trabecular bone strength was the highest, while the inferior region exhibited the lowest bone strength and medial and lateral regions had intermittent magnitudes. No significant difference in anisotropy was found between male and female samples, although the absolute values were greater in males. The obtained results cohere with recent literature data of osteopenetration experiments in these directions.
Tip apex distance -Is it enough to predict implant failure in trochanteric fractures
IP Innovative Publication Pvt. Ltd., 2017
Introduction: The tip-apex distance (TAD) is the sum of the distances from the tip of lag screw to apex of the femoral head on both AP and lateral radiographs. A TAD of greater than 25 mm is considered to be an accurate predictor of lag screw cutout when dynamic hip screws are used to treat intertrochanteric hip fractures. The purpose of this study was to determine the factors affecting the clinical outcomes of trochanteric fractures treated surgically. Materials and Methods: This retrospective study included 124 patients. The TAD values of this cohort were analysed from post-operative radiographs. The fractures were classified according to severity and the post-operative reduction and their affection to cut out rates was determined. These were correlated with functional status and inability to achieve fracture union at a mean follow-up of 12 months. Results: Good reduction was obtained in 28 cases of type 1 fractures while all the fractures which had poor reduction were type 2 fractures. All type 1 fractures united at a mean of 12 months. Overall 14 patients experienced lag screw cutout , all of which were type 2 fractures. Discussion: The number of cutouts had direct correlation to the severity of fractures and the TAD. While using dynamic hip screws, surgeons should try to achieve a TAD less than 25 mm to avoid lag screw cutout. Though TAD plays a vital role in predicting implant failure in trochanteric fractures, quality of bone, fracture pattern, placement of screw etc also influence the outcome.
Review of methods to quantify lag screw placement in hip fracture fixation
2005
This review considers methods used to quantify lag screw placement within the femoral head following proximal femoral fracture. Implants used for fixation of femoral neck fractures can lead to unwanted outcomes in some patients. Cutting out of the screw within the femoral head has been shown to be the commonest cause of failure and is related to lag screw placement within the femur. Until now, there have been two methods published which quantify lag screw position within the femoral head. These are the concepts of 'Tip Apex Distance' and Parker's ratio method of lag screw placement. We shall discuss each one in turn and their implications in terms of fracture fixation failure.