Vanessa R. Yingling

Quantification of trabecular bone mass and orientation using Gabor wavelets

Bone strength is dependent on both its mass and architecture. In this study, a tool was developed that incorporates metrics associated with both of these features. To accomplish this, textural features of trabecular bone were extracted from stained bone images using Gabor wavelets. Gabor wavelets are 2-D spatial filters that are both frequency and orientation tunable. A texture feature vector was constructed that consists of localized texture energies along different orientations at different scales. The texture feature characterizes the spatial (regional) distributions of the constituent bone lattice in terms of their size, shape and orientation. Results indicated that wavelet analysis provides the insight of the frequency composition that can be localized to the pizel level. Bone mass can be discriminated by the averaged texture energy across all orientations. Dominant bone lattice orientation can be determined by the orientation with the maximal value of the averaged texture energy across all scales. A measure of anisotropy can be quantified by the span between the maximum texture energy and the minimum texture energy. This methodology has the potential to provide a tool for quantifying both bone mass and bone structural anisotropy.

THE EFFECTS OF DELAYED PUBERTY ON THE GROWTH PLATE

Background: Many athletes are beginning intense training before puberty, a time of increased bone accrual when up to 25% of total bone mineral accrual occurs. Female athletes experiencing late or delayed pubertal onset may have open epiphyseal plates that are vulnerable to injury. This investigations purpose was to determine whether a delay in puberty (primary amenorrhea) affects the growth plate immediately postpuberty and at maturity. Methods: Forty-eight female Sprague-Dawley rats (23 d old) were randomly assigned to 4 groups (n=12); short-term control (C-ST), long-term control (C-LT), short-term GnRH antagonist (G-ST), and long-term GnRH antagonist (G-LT). At 25 days of age, daily gonadotropin-releasing hormone antagonist (GnRH-a) injections were administered delaying pubertal onset. Left tibias were analyzed. Stained frontal slices of proximal tibia (5 µm thick) were analyzed in hypertrophic, proliferative, and reserve zones for total height, zone height, and cell/column counts. All procedures were approved by Institutional Animal Care and Use Committee at Brooklyn College. Results: Growth plate height was 19.7% wider in delayed puberty (G-ST) group and at maturity was 27.9% greater in G-LT group compared with control (C-LT) (P<0.05). No significant differences were found in short-term or long-term growth plate zone heights or cell/column counts between groups (P>0.05). Growth plate zone height normalized to total height resulted in 28.7% larger reserve zone in the short-term GnRH-a group but the proliferative zone was 8.5% larger in the long-term group compared with the control group (P<0.05). Normalized to growth plate height a significant decrease was found in column counts in proliferative zones of the short-term and long-term GnRH-a groups. Conclusions: Current data illustrate that delayed puberty using GnRH-a injections results in significant growth plate height and decreases proliferative column counts and zone height, thus potentially contributing to decreases in bone mass at maturity. Clinical Relevance: Growth plate height increases indicate increased potential for growth and bone accrual. However, previous models report decreased bone volume following delayed puberty via GnRH-a injections that may have detrimental effects in the long term.

Hypothalamic Suppression during Adolescence Varies by Bone Envelope

PURPOSE The purposes of this study were to suppress estradiol levels in adolescent (postpubertal rats) using gonadotropin-releasing hormone antagonist (GnRH-a) injections and to determine the changes in bone structure and mechanical strength. METHODS In an Institutional Animal Care and Use Committee-approved study, female rats at 23 d of age were assigned to a baseline group (BL65; n = 10) sacrificed on day 65, a control group (Control; n = 15) sacrificed on day 90, or an experimental group (AMEN; n = 9) sacrificed on day 90 that received daily injections of GnRH-a for a 25-d period from 65 to 90 d of age (2.5 mg·kg(-1) per dose). RESULTS Body weights were similar on day 65; however, the AMEN group was significantly heavier than the Control group (17%, P = 0.001) on day 90. In the AMEN rats relative to the Control group, plasma estradiol levels were reduced by 36% (P = 0.0001) and plasma insulin-like growth factor 1 levels were 24% higher (P = 0.003). In the femur, there was no change in periosteal bone apposition or total cross-sectional area. The marrow area increased by 13.7% (P = 0.05) resulting in a 7.8% decrease in relative cortical area (P = 0.012), and endocortical bone formation rate increased by 39.4% (P = 0.04). Trabecular volume and number decreased by 51.5% (P = 0.0003) and 49.5% (P = 0.0003), respectively. The absolute peak moments of the tibiae and femurs were unchanged in the AMEN group relative to the Control group, but these were reduced by 8.8% (P = 0.03) and 7.5% (P = 0.09), respectively, when normalized by body weight. CONCLUSIONS Suppression of estradiol by 25 d of GnRH-a administration to 65-d-old (postpubertal) rats reduced trabecular volume and number by about 50%, increased endocortical bone turnover, and reduced relative cortical thickness without changing tibial and femoral total area. These changes in bone structure were associated with no change in absolute mechanical strength possibly because of increases in body weight or in insulin-like growth factor 1 concentrations.

The reliability of vertical jump tests between the Vertec and My Jump phone application

Background The vertical jump is used to estimate sports performance capabilities and physical fitness in children, elderly, non-athletic and injured individuals. Different jump techniques and measurement tools are available to assess vertical jump height and peak power; however, their use is limited by access to laboratory settings, excessive cost and/or time constraints thus making these tools oftentimes unsuitable for field assessment. A popular field test uses the Vertec and the Sargent vertical jump with countermovement; however, new low cost, easy to use tools are becoming available, including the My Jump iOS mobile application (app). The purpose of this study was to assess the reliability of the My Jump relative to values obtained by the Vertec for the Sargent stand and reach vertical jump (VJ) test. Methods One hundred and thirty-five healthy participants aged 18–39 years (94 males, 41 females) completed three maximal Sargent VJ with countermovement that were simultaneously measured using the Vertec and the My Jump. Jump heights were quantified for each jump and peak power was calculated using the Sayers equation. Four separate ICC estimates and their 95% confidence intervals were used to assess reliability. Two analyses (with jump height and calculated peak power as the dependent variables, respectively) were based on a single rater, consistency, two-way mixed-effects model, while two others (with jump height and calculated peak power as the dependent variables, respectively) were based on a single rater, absolute agreement, two-way mixed-effects model. Results Moderate to excellent reliability relative to the degree of consistency between the Vertec and My Jump values was found for jump height (ICC = 0.813; 95% CI [0.747–0.863]) and calculated peak power (ICC = 0.926; 95% CI [0.897–0.947]). However, poor to good reliability relative to absolute agreement for VJ height (ICC = 0.665; 95% CI [0.050–0.859]) and poor to excellent reliability relative to absolute agreement for peak power (ICC = 0.851; 95% CI [0.272–0.946]) between the Vertec and My Jump values were found; Vertec VJ height, and thus, Vertec calculated peak power values, were significantly higher than those calculated from My Jump values (p < 0.0001). Discussion The My Jump app may provide a reliable measure of vertical jump height and calculated peak power in multiple field and laboratory settings without the need of costly equipment such as force plates or Vertec. The reliability relative to degree of consistency between the Vertec and My Jump app was moderate to excellent. However, the reliability relative to absolute agreement between Vertec and My Jump values contained significant variation (based on CI values), thus, it is recommended that either the My Jump or the Vertec be used to assess VJ height in repeated measures within subjects’ designs; these measurement tools should not be considered interchangeable within subjects or in group measurement designs.