Functional adaptation through changes in regional biochemical characteristics during maturation of equine superficial digital flexor tendons.

OBJECTIVE: To quantify and compare biochemical characteristics of the extracellular matrix (ECM) of specimens harvested from tensional and compressive regions of the superficial digital flexor tendon (SDFT) of horses in age classes that include neonates to mature horses. SAMPLE POPULATION: Tendon specimens were collected on postmortem examination from 40 juvenile horses (0, 5, 12, and 36 months old) without macroscopically visible signs of tendonitis. PROCEDURE: Central core specimens of the SDFT were obtained with a 4-mm-diameter biopsy punch from 2 loaded sites, the central part of the mid-metacarpal region and the central part of the mid-sesamoid region. Biochemical characteristics of the collagenous ECM content (ie, collagen, hydroxylysylpyridinoline crosslink, and pentosidine crosslink concentrations and percentage of degraded collagen) and noncollagenous ECM content (percentage of water and glycosaminoglycans, DNA, and hyaluronic acid concentrations) were measured. RESULTS: The biochemical composition of equine SDFT was not homogeneous at birth with respect to DNA, glycosaminoglycans, and pentosidine concentrations. For most biochemical variables, the amounts present at birth were dissimilar to those found in mature horses. Fast and substantial changes in all components of the matrix occurred in the period of growth and development after birth. CONCLUSIONS AND CLINICAL RELEVANCE: Unlike cartilage, tendon tissue is not biochemically blank (ie, homogeneous) at birth. However, a process of functional adaptation occurs during maturation that changes the composition of equine SDFT from birth to maturity. Understanding of the maturation process of the juvenile equine SDFT may be useful in developing exercise programs that minimize tendon injuries later in life that result from overuse.

Palmar grasp behavior in full-term newborns in the first 72 hours of life.

BACKGROUND: The palmar grasp behavior is one of the items of an infant's routine neurological tests. Its exacerbated presence after the fifth month of age or absence in the first day after birth is an important sign of neuro-sensorimotor disorders. This study aimed to describe the palmar grasp behavior of full-term newborns in the first 72 h of life. METHODS: This nonrandomized cross-sectional developmental study included 219 typical newborns aged 12-2 4h, 25-48 h and 49-72 h. Three measurements were performed with newborns in the supine position, recording the palmar grasp time and strength. Statistical analysis was applied with significant level of p<0.05. RESULTS: Higher palmar grasp strength was observed in newborns aged 49-72 h compared to newborns aged 12-24 h and 25-48 h (F=7.42, p=0.01). There was significant difference in palmar grasp strength between hands (F=6.55, p=0.01), only in 12-24h, with greater strength in the left hand (t=-2.43, p=0.01), and difference in palmar grasp between strength (F=18.7, p=0.01) with greater strength in females (t=-5.40, p=0.01) only at the age 48-72 h. CONCLUSIONS: It was concluded that the palmar grasp behavior modifies in the first 72 h of life.

Metacarpophalangeal pattern profiles: Q-score for ages from birth to 7 years.

The metacarpophalangeal pattern profile (MCPP) analysis is a widely used method of standardization of bone length measurements to quantify congenital skeletal dysplasia of the hands. A main source of inaccuracy is the prominent scatter in the values of the standard deviation (S.D.) of the reference length, which is used in the calculation of the standardized values (Z-scores). Other sources of error, especially when bone length measurements of younger children are evaluated, are the rather large variability in the age of appearance of the epiphyses of the different bones, and the use of tabulated reference data which are available only at one-year intervals. We have devised another method of standardization of bone length measurements, by calculating the Q-score. Its advantages are that no S.D. values are needed and that more accurate results are obtained. Moreover the interpretation of the Q-scores is more straightforward than the interpretation of the Z-scores. Q-scores for 3 patients with Sotos syndrome are presented. Use of the MCPP in the form of the Q-score, will probably make it an even stronger tool than before.

Carpo-metacarpal growth disturbance and the assessment of carpal narrowing in children with juvenile rheumatoid arthritis.

Second metacarpal length (M2), radio-metacarpal length (RM), and intermetacarpal width (W) were measured on 96 radiographs in 52 children with polyarticular juvenile rheumatoid arthritis (JRA), and compared with body height and skeletal maturation in order to: (1) differentiate between processes resulting in retardation of bone growth and those producing delay in skeletal maturation; (2) assess the severity and progression over time of such retardation; and (3) assess the impact of retardation of the second metacarpal on the assessment of carpal narrowing in children with JRA. All measurements were converted into z scores (the units of standard deviation above or below the normal mean for each measurement) based on published norms. Retardation of M2 (mean z scores -0.91) began earlier and was more severe compared with retardation of height (mean z score -0.25). This disproportion widened with increasing duration of disease. That this primarily represents a disturbance in M2 growth rather than a secondary effect due to altered maturation is suggested by the bone ages being normal (mean z score 0.14) and the absence of premature closure of the metacarpal physes. Z scores for RM/W (mean -3.53) were at least 1 Z more negative than for corresponding measurements of RM/M2 (mean -2.41) in 47 (90.4%) children and the mean difference between the z scores for RM/W was -1.12. This discrepancy between RM/W and RM/M2 was eliminated by correcting for the reduction in M2.

Fractures, physical activity, and growth velocity in adolescent Belgian boys.

The relationship of fractures to physical activity and growth velocity in stature and metacarpal II bone dimensions was investigated in adolescent Belgian boys. Peak fracture incidence occurred between 12 and 14 yr of age and preceded the age at peak height velocity. The peak fracture rate occurred during mid adolescence (+/- 2 SD of the age at peak height velocity) and was twice as high as the rates before and after this period. The majority of fractures occurred during active participation in sports and general physical activities. The age at peak growth velocity for metacarpal cortical thickness, an indirect measure of bone mineral content, was about 6 months later than the ages at peak height velocity and peak growth velocity for metacarpal length. Peak fracture incidence occurred during a period when the amount of time spent in sports physical activity was low compared with later years. A lag in cortical bone thickness and mineralization, relative to linear skeletal growth, and unknown factors associated with active participation in sports, rather than an increase in the amount of physical activity, appear to be the predominant factors associated with the increased fracture incidence in Belgian boys during the growth spurt.

Ontogeny and limb bone scaling in two New World Marsupials, monodelphis domestica and Didelphis virginiana.

This study examines the growth of two species of marsupials who share common ancestry and are born at the same neonatal size of a little less than 1 g. Despite this similarity at birth, adult size of these two species differs by about 50 times, with the smaller species believed to be the more ancestral. We quantified the growth in the limb bones (humerus, femur, ulna, tibia, metacarpal, and metatarsal) beginning around 40 days of age until adult size was reached. Results indicate that the larger species grows at a higher rate of growth as well as for a longer period of time to reach its larger adult size. Despite these differences in growth, there were few differences observed in the scaling over time of length to width in the various limb bones that were measured. The two species, although different in their adult size and the patterns of growth, maintain the same length to width proportions in each limb bone. The biggest difference between species in scaling was observed in the bones of the hands and feet, which may suggest adaptation to size and/or locomotor performance as body size increases. Despite variation in size, these heterochronic patterns do not affect the shape among adults or over evolutionary time.

Experimental forward mandibular displacement in sheep.

In order to investigate growth modifications of the temporomandibular joint (TMJ) during dentofacial orthopaedic treatment, specific functional appliances have been used experimentally to prompt the mandible into a protrusive position in various animal models. The purpose of this study was to test the effectiveness of a functional appliance specially designed for sheep and to evaluate the sheep as a model for dentofacial orthopaedic research. Eight, 4-month-old, castrated male Merino sheep were randomly assigned to experimental or control groups, with four in each group. Cast functional appliances were fabricated for the animals in the experimental group. The treatment period was 15 weeks. Dental casts, endosseous implant markers and cephalograms were used to analyse the displacement of the mandible. Undemineralised sagittal sections of TMJ were used to evaluate the tissue responses induced by the appliances. The weight of the animals was measured monthly to monitor their growth. The growth of the metacarpus was also measured. During the experimental period, the animals maintained their weight within the normal range and grew normally. The appliance displaced the mandible to a downward and forward position. The adaptive responses in the TMJ induced by the appliances included changed anteroposterior shape of the condylar process, anteriorly thickened condylar cartilage, and a thickened compact bone layer along the anterior surface of the posterior wall of the glenoid fossa. The sheep coped well with the experimental procedures and the appliance used was demonstrably effective in inducing adaptive responses in the TMJ. Consequently, it is believed that the sheep is an appropriate animal model to study growth modifications in the TMJ region.

Can some physical therapy and manual techniques generate potentially osteogenic levels of strain within mammalian bone?

BACKGROUND AND PURPOSE: Although physical therapy techniques are used to alleviate pain and stiffness in joint injuries, whether these methods are capable of affecting bone is unknown. For example, can these techniques potentially influence bone formation or resorption? To begin exploring this possibility, this study investigated the ability of 4 manual techniques to generate levels of compressive strains that presumably can stimulate bone metabolism. SUBJECTS: Six 3,4 metacarpals from three 3-year-old Merino ewes were used. METHODS: A rosette strain gauge was implanted onto the dorsomedial cortex of each ovine 3,4 metacarpal. Four different manual procedures were applied on 2 occasions on each metacarpal in vivo and ex vivo. Mean peak principal compressive strains were calculated for each technique. RESULTS: Levered bending produced greater mean peak compressive strains than almost all other manual procedures tested in vivo or ex vivo. CONCLUSION AND DISCUSSION: Manual levered bending created levels of compressive strain similar in magnitude to those created by mechanical devices used in previous animal experiments to induce new bone formation (osteogenesis). This animal model appears to be suitable for investigating the effects of manually applied procedures on bone and may establish whether manual techniques can stimulate bone formation.

Effects of treadmill exercise on cortical bone in the third metacarpus of young horses.

The effects of exercise and relative inactivity on cortical bone were compared in young horses. Two groups were used; one was given a 14-week programme of exercise (n = 6) and the other kept as unexercised controls (n = 6). The first nine weeks of exercise involved trotting and cantering (2 to 4 km d-1 at speeds up to 12 m s-1) on a treadmill set at an incline of 3 degrees. Over the next five weeks the horses were trained at near maximal speeds (that is, up to 14.5 m s-1) with no incline of the treadmill. At the end of the programme marked differences in cortical porosity and distribution of subperiosteal osteogenesis at the mid-shaft of the third metacarpal bone were found between the groups. Histomorphometrical examination of the dorsal cortex showed minimal bone remodelling in the exercised horses, but extensive modelling as evidenced by the large amount of subperiosteal bone formation. In contrast, the unexercised horses had significantly more bone remodelling and less formation of subperiosteal bone. The histomorphometric and microradiographic findings provided an explanation for changes in the non-invasive bone measurements that occurred during training. Bone mineral content of the mid-metacarpus was found to increase more in the exercised than the unexercised horses despite a lower overall growth in bodyweight. In those horses that completed the full training programme, ultrasound speed increased significantly by the end of the training programme. It remained unchanged in the horse that did not complete the full exercise programme and decreased slightly in the unexercised horses. The difference in ultrasound speed between the groups was considered to reflect differences in intracortical bone porosity, endosteal bone formation and alterations in skin thickness. The stiffness of cortical bone increased significantly in the exercised horses but remained unaltered in the unexercised horses.

Restricted energy and elevated calcium and phosphorus intake for boars during growth. 1. Feedlot performance and bone characteristics.

Eighty crossbred boars were utilized in a 2 X 2 factorial arrangement of two energy levels (ad libitum and 75% ad libitum) and two Ca/P levels (100 and 150% of National Research Council daily requirement) to determine the effect of varying growth rate and Ca/P intake on performance and bone characteristics throughout the growth phase. Boars were fed the diets beginning postweaning at 5 wk of age and continuing until necropsy at 10 +/- 2-d intervals between 80 and 220 d of age, inclusive. Body weight of limit-fed boars was 72% that of ad libitum-fed boars. Daily gain and feed per gain ratio favored boars fed the 150% Ca/P levels. Although limit-feeding enhanced the development of longer, thicker and heavier metacarpals earlier in the growth period (between 80 and 150 d of age), there was little difference between limit-fed and ad libitum-fed boars at 220 d of age when values were corrected for differences in body weight. Mechanical bone characteristics, which were greater for ad libitum-fed than for limit-fed boars at the same age, were not different when values were corrected for body weight. Boars fed 150% Ca/P levels had heavier and thicker walled metacarpals that had greater bone strength than boars fed 100% Ca/P levels, with the magnitude of the difference not as great at 220 d of age and when values were corrected for body weight. Generally, boars fed the ad libitum-150% Ca/P diet had the heaviest and strongest bones. Ether extract, ash and Ca and P content of ash were generally higher for ad libitum-fed vs limit-fed and 150 vs 100% Ca/P diets at 80 and 150 d of age, but were not different at 220 d. Metacarpal weight, size, thickness, strength and ash content increased with age with a small decline in the rate of increase. Ether extract decreased with age. There was a very small increase in the Ca content of ash and a very small decrease in the P content with age, resulting in a slightly wider Ca:P ratio in older boars.

Endocrine and histologic correlates of the dynamics of the metacarpal growth plate in growing rams.

The objective was to study control of mature size by characterizing metacarpal growth plate closure in relation to relevant bone growth-regulating hormones in two breeds exhibiting distinct differences in mature frame size. Thirty-four Suffolk and 34 Dorset ram lambs were slaughtered in pairs within breed at birth, weaning and monthly intervals until 420 d and then bimonthly to 600 d. Plasma growth hormone was depressed to undetectable levels due to the high-energy, ad libitum-fed diet. Plasma insulin-like growth factor-I (IGF-I) rose over the growth period from 116 ng/ml (newborn Suffolk) to a high of 451 ng/ml (420-d Dorset); it appeared to peak at approximately 400 d and then declined to a stable level. Dorsets consistently exhibited higher IGF-I levels. The thyroid hormones exhibited no apparent age association. An age-associated rise was detected for testosterone, but not for estradiol. Mature metacarpal lengths were estimated to be 147.2 and 127.4 mm for Suffolks and Dorsets, respectively. Ninety-five percent of mature length was attained in Suffolks by 226 d and in Dorsets by 165 d. Growth plates, however, did not begin to appear closed until 390 d and closure was not complete in all animals until 480 d, suggesting that metacarpal growth rate was dissociated temporally from growth plate closure. Although growth plate closure likely is controlled by the endocrine system, there were no apparent relationships between circulating hormones and growth plate width, age at closure or zonal divisions within the growth plate, suggesting that the growth plate experiences a very different hormonal environment than what can be measured in the circulating blood.

Effects of testosterone on skeletal growth in lambs as assessed by labeling index of chondrocytes in the metacarpal bone growth plate.

The effects of testosterone on the epiphyseal growth plate of metacarpal bones of growing sheep were evaluated in 20 rams, 20 wethers, and 20 wethers receiving subcutaneous testosterone replacement therapy. Two animals from each testosterone treatment group were slaughtered at 14-d intervals from 49 to 133 d, and then at 28-d intervals until 217 d, for a total of 10 slaughter ages. Immediately after slaughter, the cannon bones were dissected of extraneous tissue, weighed, and their lengths measured. Growth plates from the metacarpal bones were isolated and explants were cultured for 24 h in medium containing [3H]thymidine. After autoradiography, labeling index was calculated as the ratio of labeled to total nuclei in the resting and proliferative zones of the growth plate. Testosterone increased (P < .03) weight and length of the metacarpal bone. Increased bone length due to testosterone was associated, in part, with a higher (P < .05) labeling index in chondrocytes of the proliferative zone of the growth plate. Labeling indices in the resting zone chondrocytes of rams were higher near the time of puberty. Accelerated growth followed by cessation of growth occurs concurrently with puberty in males of several species and is accompanied by an increase in the blood concentration of testosterone. Testosterone may mediate this accelerated growth by first increasing bone growth and then depleting the source of stem cells in the cartilage growth plate, the site where growth in length of long bones occurs.

Bone ossification and carcass characteristics of wethers given silastic implants containing estradiol.

Administration of growth promotants with estrogenic activity via hastening closure of the growth plate could have an economic impact on lambs because closure results in ovine carcasses being classified as yearlings. Twelve wether lambs approximately 12 mo old were given silastic implants filled with estradiol-17 beta and allotted randomly to be slaughtered 30, 60, 90, or 220 d after implantation to determine time of growth plate closure in relation to date of implanting. Seven comparable wethers not implanted served as controls. Four wethers implanted at 2 mo of age and slaughtered 220 d later also were included. Implanted wethers had serum concentrations of estradiol averaging 13.9 pg/ml over the 220-d implant period; controls averaged 2.7 pg/ml. Estradiol implants increased carcass maturity scores but fat deposition was not altered. Growth plate widths decreased (P less than .05) as wethers grew older and implants were in place for longer periods of time. Metacarpal growth plates in 12-mo-old lambs were completely ossified 220 d after implanting, but control wethers and wethers implanted at 2 mo maintained growth plate widths. Neither metacarpal nor metatarsal bone lengths differed (P less than .05) between control and implanted wethers. Growth plate ossification was not complete until 570 d of age in implanted lambs, even though bone length had stopped increasing by 408 d. Therefore, even though estradiol and other growth stimulants with estrogenic activity increase rate of ossification of the metacarpal growth plate, bone length or mature size is not limited.(ABSTRACT TRUNCATED AT 250 WORDS)

Quantitative analysis of long-bone growth in the horse.

Long-bone growth at the distal ends of the radial bones, the distal ends of the 3rd metacarpal bones, the distal ends of the 3rd metatarsal bones, and the proximal ends of the proximal phalangeal bones (of thoracic and pelvic limbs) was quantitatively analyzed in 9 Thoroughbred-Quarter Horse foals from birth to 2 years of age. Metal growth markers were surgically implanted in the bones of the animals at 2 to 4 days of age. Radiographs of the bones were made on the day of surgical manipulation, the next day, and then once a week for 8 months, and once a month thereafter for an additional 18 months. On each radiograph, the intervals between the growth markers were measured and plotted, and these accumulated growth data were subjected to statistical analyses. Growth curves, cumulative growth, and relative growth rates were determined. The ages of radiographic growth plate closure also were determined. Total bone growth observed in these foals was proportionately greater than that observed in a similar study of Shetland-Welsh ponies, probably indicating a breed difference. The most rapid growth rate at the 5 anatomic sites in the foals occurred from birth to 10 weeks of age; however, in the distal part of the radius, there was a continuous, though declining growth rate until 60 weeks of age, whereas in the distal ends of the 3rd metacarpal and metatarsal bones and the proximal end of the proximal phalanges growth ceased abruptly and nearly plateaued after 10 weeks of age.(ABSTRACT TRUNCATED AT 250 WORDS)

Necropsy survey of metacarpal fusion in the horse.

Paired metacarpi obtained at necropsy from 100 horses ranging in age from term fetus to 35 years were examined to estimate the prevalence and sites of metacarpal fusion. Metacarpal fusion was seen in 192 of 200 metacarpi, and 78% of all horses 2 years or older had 2 or more fusions. Fusion of the second metacarpal bone to the third metacarpal bone was significantly (P < 0.001) more common than was fusion of the fourth to the third metacarpal bone. Fusions appeared for the most part in pairs and were bilaterally symmetric. Rooney-Prickett type-A carpometacarpal joint configurations (in which there is no measurable articulation between the third carpal and second metacarpal bones) were rare in this population, and Rooney-Prickett type-B configurations (in which there is a measurable articulation between the third carpal and second metacarpal bones) were observed in 98.5% of metacarpi. Medial metacarpal fusion was positively correlated with age, occupation, and proportion of the proximal projection of the carpometacarpal distal joint surface that was taken by the second metacarpal bone. Lateral metacarpal fusion was positively correlated with age and the proportion of the proximal projection of the carpometacarpal distal joint surface taken by the fourth metacarpal bone. Horses in performance careers (racing, race training, or show ring occupations) had an earlier development of the first 2 fusions than did horses in other or unknown occupations; development of the third and fourth fusions were not significantly different between occupation groups. The rate of metacarpal fusion per horse-year appeared to be at least 10 times higher than a clinically evident rate. A variety of gross morphologic features was observed in the fusions from this sample, some of which were small, subtle, and possibly difficult to detect in vivo. It is hypothesized that many instances of metacarpal fusion may be a result of functional adaptation of the metacarpus to increased or changed loading conditions, rather than a response to isolated traumatic events.

Correlation between antler and long bone relative bone mass and circulating androgens in white-tailed deer (Odocoileus virginianus).

The relationship between serum androgen concentrations and relative density changes in the antlers and long bones of male deer was determined. Four male white-tailed deer were sampled 2 times a week during the antler-growing period. Serum androgen values were determined by radioimmunoassay, and relative bone mass (RBM) coefficients were determined by radiograph densitometry. As circulating androgen concentrations increased over the antler-growing period, the RBM coefficients of the antler increased from a mean of 18.5 (+/- 1.96 SD) to a mean of 57.7 (+/- 2.74) at 2 weeks after "rubout." Concurrently, the RBM coefficients of the metacarpus decreased from a mean of 52.0 (+/- 1.92) to a mean of 46.4 (+/- 1.86). There were positive correlation between increasing androgen concentrations and increasing antler RBM and negative correlation between androgens and decreasing metacarpus RBM. Antler RBM coefficients continued to increase after rubout, but metacarpus RBM did not change after rubout. Two castrated deer were injected subcutaneously with 1 g of testosterone and sampled every other day. Similar but smaller changes occurred in RBM values of the metacarpus and developing antler.

Mechanical correlations derived from segmental histologic study of the equine superficial digital flexor tendon, from foal to adult.

OBJECTIVE: To assess histologic variations of the equine superficial digital flexor tendon (SDFT) according to site and to horse age and activity, and to correlate these data with reported segmental mechanical results. SAMPLE POPULATION: Superficial digital flexor tendons isolated from 42 horses 0.5 hour to 23 years old. PROCEDURE: 7 segments of each SDFT were delimited and submitted for conventional histologic examination. Each segment was examined and graded for fiber undulation, cellularity, number and size of interfascicular connective spaces (ICS), presence or absence of focal and diffuse chondroid metaplasia, and differentiation of the dorsal (DB) and palmar (PB) borders of the tendon. RESULTS: Fiber undulation and cellularity significantly decreased with age. The proximal and middle metacarpal segment fibers were significantly less undulated and their ICS were smaller than those of the other segments, especially in old horses. Focal chondroid metaplasia developed from 5 years onward, mainly in the sesamoidean segments. Diffuse chondroid metaplasia was characteristic of the digital region in horses > 6 years old. The DB of the metacarpodigital region tended to differentiate into fibrocartilage in association with age. The PB was generally differentiated as nonfascicular dense connective tissue. Activity induced a decrease in the number and size of the ICS. CONCLUSIONS: The lesser undulation of the proximal and middle metacarpal segments fibers can be correlated to their mechanical behavior (stress-strain curve) and relative weakness within the SDFT. Focal chondroid metaplasia and fibrocartilage on the DB are normal features, related to the compression stresses undergone by the sesamoidean region of the tendon.

Segmenting radiographs of the hand and wrist.

The work presented in this paper concerns the development of computer-based techniques for the segmentation of hand-wrist radiographs and in particular those obtained for the TW2 method for the assessment of skeletal maturity (bone age). The segmentation method is based on the concept of regions and it consists of region growing and region merging stages. A bone extraction stage follows, which labels regions as either bone or background using heuristic rules based on the grey level properties of the scene. Finally, a technique is proposed for the segmentation of bone outlines which helps in identifying conjugated bones.

Observations on growth plates in limbs of foals.

Observations were made which may be related to growth plate disorders. They included irregularity and thickening of the growth plate bridging of the plate by bony spicules, distortion of the plate adjacent to foci of fusion, and metaphyseal lipping. These observations are very similar to those found in "epiphysitis." The question had to be asked, where these normal foals or did they have sub-clinical "epiphysitis"?

Comparison of mandibular growth with other variables during puberty.

The purpose of this investigation was to compare growth characteristics of the mandible during puberty with growth characteristics of the hyoid bone, cervical vertebrae, hand bones and standing height. Data were compiled from serial lateral cephalometric roentgenograms, hand-wrist roentgenograms and body height records of 33 Japanese girls between 9 and 14 years old. Records were updated annually. The mandibular growth rate differed from the other growth rates. The timing of maximum growth velocity of the mandible varied more widely than the timing of maximum growth velocity of the other parameters measured, and the total amount of mandibular growth did not correlate to any other measurement. The timing and magnitude of circumpubertal growth acceleration of various components of the body vary within a certain range of difference. However, the amount and timing of mandibular growth seems to be more variable than the other areas studied.