Hip Axis Research Articles

Association of neck strength with upper femoral geometry and bone mineral density in postmenopausal women

Background: Hip fracture is a severe health burden in the elderly population. In order to prevent, it is to evaluate the bone strength by establishing the relation between bone mineral density (BMD), neck strength, and geometry. Materials and Methods: The subjects under study were 100 postmenopausal women who visited bone clinic of Bharat Scan Centre. After recording general profile such as age, body mass index (BMI), geometric measures such as hip axis length (HAL), neck shaft angle (NSA), and neck width (NW) were measured from digital X-ray. For the same individuals, BMD was measured using dual energy X-ray absorptiometry (DXA) scan. From the DXA print out neck strength was calculated using the formula = sectional modulus/HAL. Results: The correlation test was analyzed among BMD, neck strength, anthropometric, and geometric factors using Statistical packages for social services (SPSS) software. BMD is inversely related with age and positively correlated with height, weight, and BMI. HAL, NSA, and NW had a weaker association with BMD. Age, BMD, and NSA had a negative relation with neck strength. HAL and NW had a positive relation with neck strength. Conclusion: Noninvasive means of associating neck strength with BMD and geometry will provide improved estimates for fracture risk beyond any other invasive method of assessing bone mineral properties.

Validation of a six degree-of-freedom robotic system for hip in vitro biomechanical testing

Currently, there exists a need for a more thorough understanding of native hip joint kinematics to improve the understanding of pathological conditions, injury mechanisms, and surgical interventions. A biomechanical testing system able to accomplish multiple degree-of-freedom (DOF) movements is required to study the complex articulation of the hip joint. Therefore, the purpose of this study was to assess the repeatability and comparative accuracy of a 6 DOF robotic system as a testing platform for range of motion in vitro hip biomechanical analysis. Intact human cadaveric pelvises, complete with full femurs, were prepared, and a coordinate measuring machine collected measurements of pertinent femoral and pelvic bony landmarks used to define the anatomic hip axes. Passive flexion/extension path and simulated clinical exam kinematics were recorded using a 6 DOF robotic system. The results of this study demonstrate that the 6 DOF robotic system was able to identify hip passive paths in a highly repeatable manner (median RMS error of <0.1mm and <0.4°), and the robotically simulated clinical exams were consistent and repeatable (rotational RMS error ≤0.8°) in determining hip ranges of motion. Thus, a 6 DOF robotic system is a valuable and effective tool for range of motion in vitro hip biomechanical analysis.

Choosing the tool for osteoporosis risk prediction.

Predicting fracture risk is a major challenge because it allows the prevention of major osteoporotic fracture in high-risk populations. With the aging of the population, this matter will become of even greater importance. In recent years, novel clinical, biochemical, and imaging tools have been developed to improve the assessment of fracture risk. The present review summarizes novel clinical strategies, Dual energy X-ray absorptiometry (DXA)-derived tools, imaging techniques, and biochemical markers that have been developed recently to improve fracture risk prediction. DXA and clinical fracture risk prediction tools are preferential markers of fracture risk. Clinical fracture risk alone might be used if DXA facilities are unavailable. The fracture risk assessment tool may be used in osteoporosis consultation in many countries. Other tools may be used soon after more studies are performed, particularly trabecular bone score, quantitative ultrasound, bone turnover markers. Specific factors for example falls, hip axis length, vertebral fracture assessment could be used in individual patients. This may significantly improve the clinical decision-making.

Adjusting Hip Fracture Probability in Men and Women Using Hip Axis Length: the Manitoba Bone Density Database

Most studies report that longer hip axis length (HAL) is associated with increased hip fracture risk in women, but comparable data in men are sparse. Using a registry of all dual-energy X-ray absorptiometry (DXA) results for Manitoba, Canada, we identified 4738 men and 50,420 women aged 40 yr and older with baseline hip DXA results, HAL measurements, and Fracture Risk Assessment Tool (FRAX) hip fracture probability computed with femoral neck bone mineral density (BMD). Population-based health service records were assessed for a subsequent hospitalization with a primary diagnosis of hip fracture. During mean 6.2 yr of follow-up, 70 men and 1020 women developed incident hip fractures. Mean HAL was significantly greater in those with vs without incident hip fractures (men 123.0 ± 7.6 vs 121.3 ± 7.4 mm, p = 0.050; women 106.9 ± 6.2 vs 104.6 ± 6.2 mm, p < 0.001). When adjusted for age and femoral neck BMD, each millimeter increase in HAL increased hip fracture risk by 3.6% in men (p = 0.022) and 4.6% in women (p < 0.001); this association was unaffected by sex (p value for interaction = 0.477). When adjusted for log-transformed FRAX hip fracture probability, each millimeter increase in HAL increased hip fracture risk by 3.4% in men (p = 0.031) and 4.8% in women (p < 0.001); this association was again unaffected by sex (p interaction = 0.409). A bilinear adjustment applicable to both men and women was developed: relative increase in hip fracture probability 4.7% for every millimeter that HAL is above the sex-specific average, relative decrease in hip fracture probability 3.8% for every millimeter that HAL is below the sex-specific average. We concluded that greater DXA-derived HAL is associated with increased incident hip fracture risk in both men and women, and this risk is independent of BMD and FRAX probability.

Proximal femur geometry assessed by hip structural analysis in hip fracture in women.

In the pathogenesis of hip fracture, proximal femur geometry plays a key role as well as decreased bone density. The hip structural analysis (HSA) processes dual energy X-ray absorptiometry (DXA) images containing information on the geometry closely related to the strength of the proximal femur. The objective of this study was to investigate bone mineral density (BMD) and mechanical properties of the proximal femur in a group of women with a previous contralateral hip fragility fracture compared to women without history of hip fracture. In a population of postmenopausal women, we evaluated bone density by DXA and bone geometry using the HSA parameters (femoral strength index, cross-sectional moment of inertia, cross-sectional area, section modulus, and buckling ratio) including hip axis length (HAL) and neck shaft angle. Of a total of 62 postmenopausal women, twenty-six with a history of hip fracture had a mean femoral neck BMD significantly lower in comparison with 36 women in the control group (0.703 versus 0.768 g/cm(2), p = 0.0347). There was a statistically significant difference between groups also for HAL (106.75 mm in fracture group versus 100.93 mm in control group, p = 0.0015). Our results demonstrated that all the geometrical parameters resulted worst into the group of patients with history of hip fracture, even though only the HAL was significantly lower in control subjects. In our opinion HSA is useful to characterize the risk of hip fracture in postmenopausal women, providing additional data on the spatial distribution of bone mass strongly related to bone strength.

Bone Mineral Density, Spinal and Micro-Architecture (TBS Data) and Body Composition in the Older Ukranian Women with Vertebral Fragility Fractures

Bone mineral density (BMD) measured by dual-energy X-ray absorptiometry is the current imaging procedure of choice to assess fracture risk. However, BMD is only one of the factors that explain bone strength or resistance to fracture. Other factors include bone microarchitecture and macroarchitecture. We now have the ability to assess some of these non-BMD parameters from a dual-energy X-ray absorptiometry image. Available measurements include various measurements of hip geometry including hip structural analysis, hip axis length, and neck-shaft angle. At the 2015 Position Development Conference, the International Society of Clinical Densitometry established official positions for the clinical utility of measurements of hip geometry. We present the official positions approved by an expert panel after careful review of the recommendations and evidence prepared by an independent task force. Each question addressed by the task force is presented followed by the official position with the associated medical evidence and rationale.

Fracture Risk Prediction by Non-BMD DXA Measures: the 2015 ISCD Official Positions Part 1: Hip Geometry

Bone mineral density (BMD) measured by dual-energy X-ray absorptiometry is the current imaging procedure of choice to assess fracture risk. However, BMD is only one of the factors that explain bone strength or resistance to fracture. Other factors include bone microarchitecture and macroarchitecture. We now have the ability to assess some of these non-BMD parameters from a dual-energy X-ray absorptiometry image. Available measurements include various measurements of hip geometry including hip structural analysis, hip axis length, and neck-shaft angle. At the 2015 Position Development Conference, the International Society of Clinical Densitometry established official positions for the clinical utility of measurements of hip geometry. We present the official positions approved by an expert panel after careful review of the recommendations and evidence prepared by an independent task force. Each question addressed by the task force is presented followed by the official position with the associated medical evidence and rationale.

Hip axis length is a FRAX- and bone density-independent risk factor for hip fracture in women.

Bone mineral density (BMD) measurement from dual-energy X-ray absorptiometry (DXA) is widely used to assess skeletal strength in clinical practice, but DXA instruments can also measure biomechanical parameters related to skeletal shape. The objective of the study was to determine whether DXA-derived hip geometry measures provide information on fracture prediction that is independent of hip fracture probability determined from the fracture risk assessment tool (FRAX) algorithm. This was a retrospective registry study using BMD results for Manitoba, Canada. Women aged 40 years and older with baseline hip DXA, derived hip geometry measures, and FRAX scores (n = 50 420) participated in the study. Hospitalized hip fracture (n = 1020) diagnosed during 319 137 person-years of follow-up (median 6.4 y) was measured. Among the hip geometry measures, hip axis length (HAL) showed a consistent association with hip fracture risk when adjusted for age [hazard ratio (HR) 1.30 per SD increase, 95% confidence interval (CI) 1.22-1.38], and this was unaffected by further adjustment for BMD or FRAX score. Adjusted for FRAX score with BMD, there was a significant effect of increasing HAL quintile on hip fracture risk (linear trend P < .001); relative to quintile 1 (referent), the HR increased from 1.43 (95% CI 1.12-1.82) for quintile 2, 1.61 (95% CI 1.27-2.04) for quintile 3, 1.85 (95% CI 1.47-2.32) for quintile 4, and 2.45 (95% CI 1.96-3.05) for quintile 5. There was a modest but significant improvement in net reclassification improvement (1.5%) and integrated discrimination improvement (0.7%) indices. The effect of HAL was particularly strong among younger, nonosteoporotic women (FRAX adjusted HR 1.70 per SD increase, 95% CI 1.48-1.94). DXA-derived hip geometry measurements are associated with incident hip fracture risk, but many do not confer significant independent predictive information. HAL was found to predict hip fractures when adjusted for BMD or FRAX score and may be of clinical value in refining hip fracture risk.

Kinematics of Elite Unilateral Below-elbow Amputee Treadmill-running - A Case Study

Although scientists have already shown interest in the contribution of upper body movements (e.g. arm swing) to the biomechanics of running and walking, no study so far has investigated the influence of upper limb impairment on running or walking, respectively. Nevertheless, the International Paralympic Committee partly bases its classification system for athletes with unilateral through or above wrist impairment on research done with able-bodied subjects nearly three decades ago. Hence, in this study a high caliber male middle distance runner (age: 26 yrs., height: 183cm, weight: 67kg; personal bests: 400m: 0:48.45min, 800m: 1:50.92min, multiple medal winner at Paralympic Games, currently being classified as a T47 due to a missing right forearm from just a few centimeters below the elbow on) performed several trials without and with additional weight (0.5kg, cu worn just proximal to the elbow joint) on the impaired arm at running speeds of 12, 16, 20 and 24km/h on a treadmill. Concurrently a full-body motion analysis using a ten infrared camera Vicon motion analysis system was performed. Stance phase duration, arm swing velocity and angle between hip and shoulder axis were analyzed. It could be shown, that without weight stance phase duration for the right leg was highly significantly (alpha = 95%) longer at all running speeds than for the left leg, that arm swing velocity was faster for the right (impaired) arm. The hip-shoulder angle, however, did not show any significant difference for right or left side. Running with additional weight changed stance phase duration differences between left and right (not significantly), reduced the velocity differences between the impaired and sound limb (not significantly) and changed the rotation between hip and shoulder (significantly). The results of this study indicate that a missing upper limb affects running kinematics more clearly as hitherto assumed.

2P1-M01 装着者と一致する腰と脚の関節軸を有し1台のモータで重量物の支持運搬を補助するパワーアシストスーツの開発

2P1-M01 装着者と一致する腰と脚の関節軸を有し1台のモータで重量物の支持運搬を補助するパワーアシストスーツの開発

STUDY ON NECK SHAFT ANGLE AND FEMORAL LENGTH OF SOUTH INDIAN FEMURS

Address for Correspondence: Shaik Hussain Saheb, Assistant Professor, Department of Anatomy, JJM Medical College, Davangere, Karnataka 577004, India. E-Mail: anatomyshs@gmail.com Access this Article online Quick Response code Web site: 1Assistant Professor, Department of Orthopedics, JJM Medical College, Davangere, Karnataka, India *2 Assistant Professor, Department of Anatomy, JJM Medical College, Davangere, Karnataka, India. Background: Femoral nek anteversion describes the angle subtended by the femoral neck with reference to the transcondylar plane of the distal end of the femur and is usually 15° to 45°. This along with the neck shaft angle, hip axis length, femoral neck width influence the risk of femoral neck fracture. Femoral neck anteversion angle has to be taken into consideration when reduction and fixation is selected as a method of treatment. Objectives: The objectives of present study to find out the measurements of Neck shaft angle, Femoral Length and Neck Length of femur. Materials and Methods: In present study have used 250 femurs from different colleges in south India. The following measurements were conducted Neck shaft angle, Femoral Length and Neck Length of femur. Results: The results of present study are the length of femur was 446.2+26.39mm, right femur was 446.6+26.66mm and left femur was 445.8+26.12mm, the Neck Length femur was 36.3+4.2mm, right femur was 36.1+4.1mm and left femur was 36.4+4.3m. the neck shaft angle of femur was 137.10 , right femur was 137.30 and left femur was 136.90. Conclusion: There is no significance difference between right and left femur measurements. Orthopaedists and Radiologists use the normal range and means of the neck shaft angle in the diagnosis and treatment of the disease of the hip. The angle is increased in congenital subluxation and dislocation of the hip, poliomyelitis, cerebral palsy and idiopathic scoliosis and decreased in the congenital coxavara , post traumatic coxa vara due to malunited femoral neck and inter trochanteric fractures.

Growth and aging of proximal femoral bone: a study with women spanning three generations.

Osteoporotic hip fracture is a serious clinical event associated with high morbidity and mortality. Understanding femoral growth patterns is important for promoting bone health in the young and preventing fractures in later life. In this study, growth patterns of areal bone mineral density (aBMD) and geometric properties of the proximal femur were measured by dual-energy X-ray absorptiometry. They were studied in 251 girls from premenarche (11.2 ± 0.7 years) to late adolescence (18.3 ± 1.1 years) and compared with their premenopausal mothers (n = 128, aged 44.9 ± 4.1 years) and postmenopausal grandmothers (n = 128, aged 70.0 ± 6.3 years). Hip axis length (HAL) was the first to reach peak growth velocity (-10.5 months before menarche), followed by neck diameter (ND) and neck cross-sectional area (CSA), (-7.1 and -4.1 months before menarche, respectively). Both neck-shaft angle (NSA) and aBMD of neck and total hip peaked at menarche. At 18 years (7-year follow-up), girls already had higher femoral neck aBMD but similar HAL and NSA compared with their mothers. Grandmothers had the longest HAL, narrowest NSA, widest ND but lowest aBMD and CSA. Hip strength index (HSI), an index of femoral neck strength during a fall, dropped rapidly after menarche in girls but thereafter remained relatively constant. Grandmothers had lower HSI than either mothers or girls. In conclusion, differences in proximal femoral bone mass and structure in adulthood are largely established before menarche, indicating that heritable factors are responsible for most of the individual variance. The development of geometric properties precedes aBMD in puberty, resulting in relatively constant hip strength after menarche. This asynchronous growth leads to adaptation of bone strength to the imposed loads, avoiding fractures in a biologically efficient manner. Both deterioration of aBMD and inadequate compensatory change in bone geometry after menopause contribute to the increased fracture risk later in life.

Is coxa valga a predictor for the severity of knee osteoarthritis? A cross-sectional study.

In the present study, we aimed to evaluate the affect of the variations in hip anatomy and pelvic geometry on the severity of knee OA. Idiopathic knee OA patients fulfilling the clinical criteria of American College of Rheumatology for OA were enrolled in the study. Several measurements regarding the hip and pelvis were performed on pelvic radiographs. Each knee was graded according to the Kellgren and Lawrence (KL) radiographic system (0-4) along with a categorization in accordance with the medial tibiofemoral joint space widths (JSW). The study group consisted of 111 subjects. The inner and outer pelvic diameters were getting wider as the JSW grade increased. Likewise, among the hip measurements, femoral head, neck and shaft diameters and hip axis lengths were linked with KL grade. There were significant differences in neck-shaft angle (NSA) between groups of JSW with a highest NSA in JSW grade 3. The optimal cut-off value for NSA in predicting the severity of knee OA was 134.4°. Furthermore, NSA beyond 134.4° was found to increase the risk of severe knee OA eightfold. Variations in pelvic geometry and hip anatomy are associated with the severity of knee OA. People with NSA of above 134.4° have eightfold increased risk of developing severe knee OA. Pelvic radiographies could be evaluated at younger ages-particularly in people with high genetic predispositions-to identify the individuals at high risk and in turn, to tailor the preventive measures to these subjects.

Including a Hip Axis Length Assessment Can Justify Altering a T-Score Based Treatment Strategy

Including a Hip Axis Length Assessment Can Justify Altering a T-Score Based Treatment Strategy

Sacrum pubic incidence and sacrum pubic posterior angle: two morphologic radiological parameters in assessing pelvic sagittal alignment in human adults.

The morphology and position of pelvis are critical in regulating the biomechanical organization of spine-pelvis-leg in the sagittal plane. Several radiological parameters have been developed to present the sagittal morphology of the pelvis such as pelvic incidence (PI) and Jackson's angle (PRS1). In addition, the femoral sacral posterior angle (FSPA) was developed for patients with a dome-shaped deformity in the upper plate of the sacrum. The identification of hip axis, which was represented by the line connecting the centers of femoral heads in normal subjects, was important for these parameters measurement. However, in subjects with fused hip joint or deformed femoral heads, the accurate localization of hip axis become imprecise. Herein, the upper edge of the pubic symphysis, which is easy to identify on the lateral X-ray film, was selected as an alternative landmark of the hip axis, and two morphologic parameters, the sacrum pubic incidence (SPI) and sacrum pubic posterior angle (SPPA), were proposed accordingly. The present study aimed to understand the reliability of these two parameters and their value in predicting PI, PRS1 and FSPA. Upright standing spine and pelvis radiographs of 60 normal adults (30 male and 30 female) with an average age of 38.5 years were obtained. Two independent observers then measured the following radiological parameters on the films: PI, PRS1, FSPA, SPI, SPPA, sacral slope, pelvic tilt and lumbar lordosis. The SPI is the angle between the line perpendicular to the superior plate of the first sacral vertebra at its midpoint and the line connecting this point to the upper edge of the pubic symphysis, while the SPPA is the angle between the line extending from the posterior upper edge of the sacrum to the upper edge of the pubic symphysis and the posterior side of the first sacral vertebral body. The intra-observer and inter-observer reliabilities of the parameters were analyzed using intraclass correlations. The correlations between parameters were analyzed by Pearson's correlation coefficients. Regression analysis was carried out to establish formulas to predict the values of PI, PRS1 and FSPA using the SPI and SPPA. A p < 0.05 was considered statistically significant. The SPI was 64.4° ± 9.5° and 68.3° ± 9.4°, and the SPPA was 77.7° ± 7.5° and 78.7° ± 9.4° in males and females, respectively. These radiological parameters showed excellent intra- and inter-observer reliabilities, with an intraclass correlation >0.8. No gender differences were identified in these morphologic and positional radiological parameters. The SPI demonstrated strong correlation with PI and PRS1 (R (2) > 0.9, p < 0.001). In addition, strong correlation was also found between SPPA and FSPA (R (2) > 0.9, p < 0.001). Furthermore, both SPPA and FSPA showed close correlations with the other morphologic and positional parameters. Linear regression analysis established equations to predict PI and PRS1 using SPI and to predict FSPA by SPPA with significantly high reliability. Both SPI and SPPA are reliable parameters for determining the morphology of the pelvis. The SPI is precise in predicting PI and PRS1, while SPPA is reliable in predicting FSPA. The SPI and SPPA will allow further study on lateral spinal-pelvic alignment in patients with hip joint abnormalities.

Femoral neck shaft angle width is associated with hip-fracture risk in males but not independently of femoral neck bone density

To investigate the specificity of the neck shaft angle (NSA) to predict hip fracture in males. We consecutively studied 228 males without fracture and 38 with hip fracture. A further 49 males with spine fracture were studied to evaluate the specificity of NSA for hip-fracture prediction. Femoral neck (FN) bone mineral density (FN-BMD), NSA, hip axis length and FN diameter (FND) were measured in each subject by dual X-ray absorptiometry. Between-mean differences in the studied variables were tested by the unpaired t-test. The ability of NSA to predict hip fracture was tested by logistic regression. Compared with controls, FN-BMD (p < 0.01) was significantly lower in both groups of males with fractures, whereas FND (p < 0.01) and NSA (p = 0.05) were higher only in the hip-fracture group. A significant inverse correlation (p < 0.01) was found between NSA and FN-BMD. By age-, height- and weight-corrected logistic regression, none of the tested geometric parameters, separately considered from FN-BMD, entered the best model to predict spine fracture, whereas NSA (p < 0.03) predicted hip fracture together with age (p < 0.001). When forced into the regression, FN-BMD (p < 0.001) became the only fracture predictor to enter the best model to predict both fracture types. NSA is associated with hip-fracture risk in males but is not independent of FN-BMD. The lack of ability of NSA to predict hip fracture in males independent of FN-BMD should depend on its inverse correlation with FN-BMD by capturing, as the strongest fracture predictor, some of the effects of NSA on the hip fracture. Conversely, NSA in females does not correlate with FN-BMD but independently predicts hip fractures.

Ancestral differences in femoral neck axis length: Possible implications for forensic anthropological analyses

In forensic anthropological contexts, very few methods of estimating ancestry from the postcranial skeleton are available. The cranium is widely recognized to show the greatest ancestral variation, and is often regarded by forensic anthropologists as the only reliable bone for estimating ancestry from unidentified skeletal remains. Several studies have demonstrated ancestral variation in aspects of the femur, but none have shown significant predictive power for discriminating multiple groups, and have therefore not gained wide acceptance by forensic anthropologists. Skeletal health experts (particularly bone densitometrists), however, have long recognized a relationship between proximal femur geometry (especially hip axis length) and osteoporosis-related fracture risk. Moreover, fracture risk has been noted to vary between ancestral groups. Here, we investigate whether measurements that are related to fracture risk might also be used to estimate ancestry from unidentified skeletal remains. Specifically, we investigate ancestral differences in femoral neck axis length (FNAL) and find significant differences between European, Asian and African groups in both women and men. FNAL was largest in European groups followed by African and then Asian groups. The greatest discriminating power was found between European and Asian groups, but was also significant between European and African groups. These differences may have utility in estimating ancestry in forensic anthropological contexts.

Kinematic analysis of a side volley in soccer

The purpose of this study was to analyze kinematic variables of side volley in elite soccer players, as well as examining kinematic variables adjustment in relation to the change of velocity and height of incoming ball. Thirty professional soccer players participated in this study. The experimental protocol implied kicking the ball towards the subject at three different velocities and three different heights. The analysis included a total of the following seven dependent variables: Maximum linear velocity of the foot, the knee and the hip (V_FOOT_max, V_KNEE_max, V_HIP_max), Maximum knee and hip joint angular velocities (W_KNEE_max, W_HIP_max), Distance between the foot and the hip at impact with the ball (D_hip.foot_tk), and Angle between the shoulder and hip axis and the hip and foot axis at impact with the ball (α_SHF_tk). Also, for the purpose of descriptive kinematic analysis, the variables of changed angles and hip and knee joint angular velocities were used in different phases of side volley performance, as well as the variables of changed linear velocity of the foot, the knee and the hip. The variables of side volley kinematics were measured with the 3D kinematic analysis system (Qualisys). The effects of the ball height and velocity, and their interaction, on dependent kinematic variables were tested by using the statistical method of two-way analysis of variance with repeated measures (two-way ANOVA). The velocity and height of the incoming ball had a significant effect on V_ FOOT_max in the sense that, as ball velocity grew, V_FOOT_max increased as well, while as ball height increased, V_FOOT_max dropped. A similar effects of the ball velocity and ball height was observed for V_ HIP_max, but is observed only a tendency towards statistical significance. Also, it was observed that increased speed of the incoming ball affected increase of D_hip.foot_tk, as well as α_SHF_tk, while values of W_HIP_max were decreased. The statistical analysis revealed that changes in the mechanical conditions in which side volleys were performed such as a different velocity/height of the incoming ball affected the modulation of the velocity of the farthermost proximal and distal ends of the kinetic chain/hip and foot joints, while the knee joint function was primarily to fine-tune the distance between the subjects' position and the ball.

Hilus pulmonis as the center of gravity for AS thoracolumbar kyphosis

The sagittal vertical axis (SVA) is a meaningful measurement and widely used for evaluating sagittal balance, and is considered a design standard for surgery, including most ankylosing spondylitis (AS) kyphotic deformity planning. However, recent research indicates that the C7 plumb line is actually not the center of gravity (CG) line. Therefore, whether there is a better radiological marker as the CG of the trunk for AS thoracolumbar kyphosis remains unknown. This research is to investigate a radiological marker for the CG of the trunk in lateral radiographs for AS thoracolumbar kyphosis. The center of gravity of an irregular object can be obtained by hanging or supporting it in different points and directions, and the CG will be on the point of intersection. According to this principle of mechanics, we could use the pre- and post-operative hip axis vertical lines to locate the CG of the trunk. We evaluated 38 AS-fixed thoracolumbar kyphotic patients with pedicle subtraction osteotomies. Full-length, free-standing lateral radiographs, including the spine and pelvis, were available for all patients. Pre- and post-operative radiological parameters were measured, including SVA, horizontal distance between hip axis and C7 (HDHC), horizontal distance between hip axis and T5 (HDHT5), horizontal distance between hip axis and T9 (HDHT9), and horizontal distance between hip axis and hilus pulmonis (HDHH). Pre- and post-operative radiological parameter changes were compared by paired samples t tests. The intraclass correlation coefficient (ICC) was used to determine the intra- and interobserver reliabilities of HDHH. Pre-operative SVA, HDHC, HDHT5, HDHT9, and HDHH values were, respectively, 21.1, 12.7, 3.5, -3.8, and 2.7 cm, and their post-operative values were, respectively, 9.1, 4.2, -2.1, -5.6, and 0.9 cm. Changes in SVA, HDHC, HDHT5, and HDHT9 were significant (p < 0.05), while the change in HDHH was not (p > 0.05). The ICC for overall interobserver reliability was 0.958 (p < 0.001), and it was 0.963 (p < 0.001) for overall intraobserver reliability. The hilus pulmonis fell approximately on the hip axis both pre- and post-operatively. It was a better marker as the center of gravity of the trunk for deformity planning for AS thoracolumbar kyphosis.

Increased pelvic incidence may lead to arthritis and sagittal orientation of the facet joints at the lower lumbar spine

BackgroundCorrect sagittal alignment with a balanced pelvis and spine is crucial in the management of spinal disorders. The pelvic incidence (PI) describes the sagittal pelvic alignment and is position-independent. It has barely been investigated on CT scans. Furthermore, no studies have focused on the association between PI and facet joint (FJ) arthritis and orientation. Therefore, our goal was to clarify the remaining issues about PI in regard to (1) physiologic values, (2) age, (3) gender, (4) lumbar lordosis (LL) and (5) FJ arthritis and orientation using CT scans.MethodsWe retrospectively analyzed CT scans of 620 individuals, with a mean age of 43 years, who presented to our traumatology department and underwent a whole body CT scan, between 2008 and 2010. The PI was determined on sagittal CT planes of the pelvis by measuring the angle between the hip axis to an orthogonal line originating at the center of the superior end plate axis of the first sacral vertebra. We also evaluated LL, FJ arthritis and orientation of the lumbar spine.Results596 individuals yielded results for (1) PI with a mean of 50.8°. There was no significant difference for PI and (2) age, nor (3) gender. PI was significantly and linearly correlated with (4) LL (p = < 0.0001). Interestingly, PI and (5) FJ arthritis displayed a significant and linear correlation (p = 0.0062) with a cut-off point at 50°. An increased PI was also significantly associated with more sagitally oriented FJs at L5/S1 (p = 0.01).ConclusionPI is not correlated with age nor gender. However, this is the first report showing that PI is significantly and linearly associated with LL, FJ arthritis and more sagittal FJ orientation at the lower lumbar spine. This may be caused by a higher contact force on the lower lumbar FJs by an increased PI. Once symptomatic or in the event of spinal trauma, patients with increased PI and LL could benefit from corrective surgery and spondylodesis.