Analysis of proximal femur DXA scans in growing children: Comparisons of different protocols for cross-sectional 8-month and 7-year longitudinal data

Dual-energy X-ray absorptiometry (DXA) is a widely used method for measuring bone mineral in the growing skeleton. Because scan analysis in children offers a number of challenges, we compared DXA results using six analysis methods at the total proximal femur (PF) and five methods at the femoral neck (FN), In total we assessed 50 scans (25 boys, 25 girls) from two separate studies for cross-sectional differences in bone area, bone mineral content (BMC), and areal bone mineral density (aBMD) and for percentage change over the short term (8 months) and long term (7 years). At the proximal femur for the short-term longitudinal analysis, there was an approximate 3.5% greater change in bone area and BMC when the global region of interest (ROI) was allowed to increase in size between years as compared with when the global ROI was held constant. Trend analysis showed a significant (p < 0.05) difference between scan analysis methods for bone area and BMC across 7 years. At the femoral neck, cross-sectional analysis using a narrower (from default) ROI, without change in location, resulted in a 12.9 and 12.6% smaller bone area and BMC, respectively (both p < 0.001), Changes in FN area and BMC over 8 months were significantly greater (2.3 %, p < 0.05) using a narrower FN rather than the default ROI, Similarly, the 7-year longitudinal data revealed that differences between scan analysis methods were greatest when the narrower FN ROI was maintained across all years (p < 0.001), For aBMD there were no significant differences in group means between analysis methods at either the PF or FN, Our findings show the need to standardize the analysis of proximal femur DXA scans in growing children.

Strength indices of the proximal femur and shaft in prepubertal female gymnasts

Introduction/Purpose: The role of impact loading activity on bone mass is well established; however, there are little data on the effects of exercise on bone geometry and indices of bone strength. The primary purpose of this study was to compare indices of bone strength at the proximal femur (PF) between elite premenarcheal gymnasts (N = 30) and age-matched controls (N = 30). Methods: Structural properties of the proximal femur were derived from the hip analyses program and included measurement of subperiosteal width, endosteal diameter, cross-sectional area, bone mineral density, cross-section moment of inertia (CSMI), and section modulus (Z). These parameters were measured for two regions of the PF: the narrow neck (NN), and the shaft (S). In addition, a strength index (S-SI) was calculated at the shaft by dividing the Z at the shaft by the femur length. A secondary purpose was to compare bone mineral content (BMC) values at the total body, lumbar spine, and three sites at the PF (neck, trochanter, and total) between the groups. All dependent values were compared adjusting for height and weight using an ANCOVA procedure and for relative lean body mass post hoc. Results: The gymnasts had significantly greater size-adjusted strength indices (CSMI, Z, and SI) at the NN and S. Gymnasts also had significantly greater size-adjusted BMC at all sites investigated. However, these differences disappeared when adjusted for relative lean body mass. Conclusion: When adjusted for body size, gymnasts had significantly greater indices of both axial strength and bending strength at the NN region of the PF and S, as well as a greater bone SI at the femoral shaft. These differences may be related to greater relative lean body mass attained in gymnastics training.

Change in lean body mass Is a major determinant of change in areal bone mineral density of the proximal femur: A 12-year observational study

Our objective was to assess the contribution of lean body mass (LBM) and fat body mass (FBM) to areal bone mineral density (aBMD) in women during the years surrounding menopause. We used a 12-year observational design. Participants included 75 Caucasian women who were premenopausal, 53 of whom were available for follow-up. There were two measurement periods: baseline and 12-year follow-up. At both measurement periods, bone mineral content and aBMD of the proximal femur, posterior-anterior lumbar spine, and total body was assessed using dual-energy X-ray absorptiometry (DXA). LBM and FBM were derived from the total-body scans. General health, including current menopausal status, hormone replace therapy use, medication use, and physical activity, was assessed by questionnaires. At the end of the study, 44% of the women were postmenopausal. After controlling for baseline aBMD, current menopausal status, and current hormone replacement therapy, we found that change in LBM was independently associated with change in aBMD of the proximal femur (P = 0.001). The cross-sectional analyses also indicated that LBM was a significant determinant of aBMD of all three DXA-scanned sites at both baseline and follow-up. These novel longitudinal data highlight the important contribution of LBM to the maintenance of proximal femur bone mass at a key time in women's life span, the years surrounding menopause.

The effect of water fluoridation on the bone mineral density of young women [Saskatoon study]

Introduction: Osteogenic effects of therapeutic fluoride have been reported; however, the impact of exposure to low level water fluoridation on bone density is not clear. We investigated the effect of long-term exposure to fluoridated water from growth to young adulthood on bone mineral density (BMD). Methods: BMD was measured in 24 healthy women from Regina (fluoride 0.1 mg/L) and 33 from Saskatoon (fluoride 1.0 mg/L), with no differences between groups for height, weight, lifestyle or dietary factors. Results: Saskatoon women had significantly higher mean BMD at total anterior-posterior lumbar spine (APS) and estimated volumetric L3 (VLS), with no difference at total body (TB) or proximal femur (PF). Conclusion: Exposure to water fluoridation during the growing years may have a power impact on axial spine bone density in young women.

The management of elderly patients with femoral fractures - A randomised controlled trial of early intervention versus standard care

Objective: To determine the effect of an early intervention program in an acute care setting on the length of stay in hospital of elderly patients with proximal femoral fractures. Setting: Acute orthopaedic ward of a large teaching hospital. Design and Participants: A randomised controlled trial comparing 38 intervention patients with 33 Standard Care patients. Intervention: Early surgery, minimal narcotic analgesia, intense daily therapy and close monitoring of patient needs via a multidisciplinary approach versus routine hospital management. Main outcome measures: Length of stay (LOS); deaths; level of independent functioning. Results: Mean LOS was shorter in the Intervention group than in the Standard Care group (21 days v. 32.5 days; P<0.01). After adjusting for other factors that could affect LOS (e.g. age, sex, pre-trauma functional levels, pre-trauma comorbidity and postsurgical complications), the Intervention program was significantly predictive of shorter LOS (P=0.01). The Intervention group did not experience greater numbers of deaths, deterioration in function or need for social support than the Standard Care group. Conclusion: This early intervention program in an acute care setting results in significantly shorter length of hospital stay for elderly patients with femoral fractures.

Regional and total body bone mineral density in elite collegiate male swimmers

Back,ground To examine the role of long-term swimming exercise on regional and total body bone mineral density (BMD) in men. Methods. Experimental design: Cross-sectional. Setting: Musculoskeletal research laboratory at a medical center, Participants:We compared elite collegiate swimmers (n=11) to age-, weight-, and height-matched non-athletic controls (n=11), Measures: BMD (g/cm(2)) of the lumbar spine L2-4, proximal femur (femoral neck, trochanter, Ward's triangle), total body and various subregions of the total body, as well as regional and total body fat and bone mineral-free lean mass (LM) was assessed by dual-energy X-ray absorptiometry (DXA, Hologic QDR 1000/W). Results. Swimmers, who commenced training at 10.7+/-3.7 yrs (mean+/-SD) and trained for 24.7+/-4.2 hrs per week, had a greater amount of LM (p<0.05), lower fat mass (p<0.001) and percent body fat (9.5 vs 16.2 %, p<0.001) than controls. There was no significant difference between groups for regional or total body BRID, In stepwise multiple regression analysis, body weight was a consistent independent predictor of regional and total body BMD, Conclusions. These results suggest that long-term swimming is not an osteogenic mode of training in college-aged males. This supports our previous findings in young female swimmers who displayed no bone mass benefits despite long-standing athletic training.

A six-year longitudinal study of the relationship of physical activity to bone mineral accrual in growing children: The University of Saskatchewan bone mineral accrual study

To investigate the influence of physical activity on bone mineral accrual during the adolescent years, we analyzed 6 years of data from 53 girls and 60 boys. Physical activity, dietary intakes, and anthropometry were measured every 6 months and dual-energy X-ray absorptiometry scans of the total body (TB), lumbar spine (LS), and proximal femur (Hologic 2000, array mode) were collected annually. Distance and velocity curves for height and bone mineral content (BMC) were fitted for each child at several skeletal sites using a cubic spline procedure, from which ages at peak height velocity (PHV) and peak BMC velocity (PBMCV) were identified. A mean age- and gender-specific standardized activity (Z) score was calculated for each subject based on multiple yearly activity assessments collected up until age of PHV. This score was used to identify active (top quartile), average (middle 2 quartiles), or inactive (bottom quartile) groups. Two-way analysis of covariance, with height and weight at PHV controlled for, demonstrated significant physical activity and gender main effects (but no interaction) for PBMCV, for BMC accrued for 2 years around peak velocity, and for BMC at 1 year post-PBMCV for the TB and femoral neck and for physical activity but not gender at the LS (all p < 0.05). Controlling for maturational and size differences between groups, we noted a 9% and 17% greater TB BMC for active boys and girls, respectively, over their inactive peers 1 year after the age of PBMCV. We also estimated that, on average, 26% of adult TB bone mineral was accrued during the 2 years around PBMCV.

Gender differences in bone geometry during the adolescent growth spurt

To investigate whether there are gender differences in the bone geometry of the proximal femur during the adolescent years we used an interactive computer program ?Hip Strength Analysis? developed by Beck and associates (Beck et al., Invest Radiol. 1990,25:6-18.) to derive femoral neck geometry parameters from DXA bone scans (Hologic 2000, array mode). We analyzed a longitudinal data-set collected on 70 boys and 68 girls over a seven year period. Distance and velocity curves for height were fitted for each child utilizing a cubic spline procedure and the age of peak height velocity (PHV) was determined. To control for maturational differences between children of the same chronological age and between boys and girls, section modulus (Z) an index of bending strength, cross sectional area of bone (CSA), sub-periosteal width (SPW), and BMD values at the neck and shaft of the proximal femur were determined for points on each individual?s curve at the age of PHV and one and two years on either side of peak. To control for size differences, height and weight were introduced as co-variates in the two-way analyses of variance looking at gender over time measured at the maturational age points (-2, -1, age of PHV, +1, +2). The following figure presents the results of the analyses on two variables, BMD and Z at neck and shaft regions:After the age of peak linear growth (PHV), independent of body size, there was a gender difference in BMD at the shaft but not at the neck. Section modulus at both sites indicated that male bones became significantly stronger after PHV. Underlying these maturational changes, male bones became wider (SPW) after PHV in both the neck and shaft and enclosed more material (CSA) at all maturational age points at both regions. These results call into question the emphasis on using BMD as a measure of skeletal integrity in growing children

The Saskatchewan Pediatric Bone Mineral Accrual Study: Bone mineral acquisition during the growing years

To investigate bone mineral accretion in growing children, the Saskatchewan Pediatric Bone Mineral Accrual Study was initiated in 1991. The study involves the collection of dietary and physical activity information along with anthropometric growth and maturity measurements every 6 months and dual-energy X-ray absorptiometer (DXA) bone scans of the whole body, AP lumbar spine and proximal femur taken annually, The study has now finished its 6th year and 68 males and 72 females from an original sample of 228 elementary schoolchildren are still involved, To investigate how bone mineral at clinically important sites proceeds in relation to maturation we developed distance and velocity growth curves for height and bone mineral content (BMC) for the AP lumbar spine, the femoral neck and the whole body, In both boys and girls, over 35% of total body and AP spine bone mineral and over 27% of the bone mineral at the femoral neck was laid down during the 4-year adolescent period surrounding peak linear growth velocity. The clinical significance of these values can be appreciated by consideration of the fact that as much bone mineral will be laid down during these 4 adolescent growing years as most people will lose during all of adult life.

Altered loading patterns and femoral bone mineral density in children with unilateral Legg-Calve-Perthes disease

Maximization of bone accrual during the growing years is thought to be an important factor in minimizing fracture risk in old age. Mechanical loading through physical activity has been recommended as a modality for the conservation of bone mineral in adults; however, few studies have evaluated the impact of different loading regimes in growing children. The purpose of this study was to compare bone mineral density (BMD) in weight-bearing and non-weight-bearing limbs in 17 children with unilateral Legg Calve Perthes Disease (LCPD). Children with this condition have an altered weight-bearing pattern whereby there is increased mechanical loading on the noninvolved normal hip and reduced loading on the involved painful hip. Thus, these children provide a unique opportunity to study the impact of differential mechanical loading on BMD during the growing years while controlling for genetic disposition. BMD at four regions of the proximal femur (trochanter, intertrochanter, femoral neck, total of the regions) was measured using dual energy x-ray absorptiometry (DXA), and the values were compared between the involved and noninvolved sides of the children with LCPD. The BMD of both sides also were compared with normative values based on both chronological and skeletal age data. A significantly higher BMD was found on the noninvolved side over the involved side for all regions (P

The ratio of messenger RNA levels of receptor activator of nuclear factor kappa B ligand to osteoprotegerin correlates with bone remodeling indices in normal human cancellous bone but not in osteoarthritis

skeletal disease. Bone remodeling is initiated by osteoclastic resorption followed by osteoblastic formation of new bone. Receptor activator of nuclear factor KB ligand (RANKL) is a newly described regulator of osteoclast formation and function, the activity of which appears to be a balance between interaction with its receptor RANK and with an antagonist binding protein osteoprotegerin (OPG). Therefore, we have examined the relationship between the expression of RANKL, RANK, and OPG and indices of bone structure and turnover in human cancellous bone from the proximal femur. Bone samples were obtained from individuals with osteoarthritis (OA) at joint replacement surgery and from autopsy controls. Histomorphometric analysis of these samples showed that eroded surface (ES/BS) and osteoid surface (OS/BS) were positively associated in both control (p < 0.001) and OA (p < 0.02), indicating that the processes of bone resorption and bone formation remain coupled in OA, as they are in controls. RANKL, OPG, and RANK messenger RNA, (mRNA) were abundant in human cancellous bone, with significant differences between control and OA individuals. In coplotting the molecular and histomorphometric data, strong associations were found between the ratio of RANKL/OPG mRNA and the indices of bone turnover (RANKL/OPG vs. ES/BS: r = 0.93, p < 0.001; RANKL/OPG vs. OS/BS: r = 0.80, p < 0.001). These relationships were not evident in trabecular bone from severe OA, suggesting that bone turnover may be regulated differently in this disease. We propose that the effective concentration of RANKL is related causally to bone turnover.

Surgical outcomes of a randomized prospective trial involving patients with a proximal femoral fracture

Background: An orthopaedic management/patient-focused care unit (OMPFCU) involving a dedicated orthopaedic-geriatrics liaison team was established at the Royal Brisbane Hospital in 1994 in an effort to safely accelerate rehabilitation of patients with proximal femoral fractures. Methods: The surgical outcomes of the patients were monitored in order to determine whether accelerated rehabilitation had any significant adverse effects on the surgical outcomes, measured by mortality, readmission to hospital, deep wound infection, fracture union delay, mobility and the revision surgery rate. Results: No significant difference was recorded in mortality and morbidity, deep wound infection and revision surgery rates between patients in the Royal Brisbane Hospital OMPFCU and those in standard care in the orthopaedic surgery wards. Conclusion: Accelerated rehabilitation for patients with a proximal femoral fracture in a major teaching hospital can be accomplished safely.