Measures Of Bone Quality Research Articles

BEHAVIOR OF IMPLANT STABILITY DURING IMPLANT TREATMENT: IN VIVO STUDY

Implant stability is essential parameters that indicate the success of the implant treatment. However, the relation between implant stability, osseointegration and also remodeling process during that period is still unclear. This study was to evaluate the behavior of implant stability during implant treatment period.To investigate the behavior of the implant stability and its relation with quality and quantity of the bone during implant treatment, eight dental implant patients have been involved. Series of monitoring stages were conducted. The implant stability for each stage were measured using Resonance Frequency Analysis (RFA) devise and the behavior of quality and quantity of the bone during treatment have been monitored by using CBCT data. The phases of monitoring are divided into 3 phases; phase 1 is immediately after implant insertion, phase 2 is immediately after crown installation (4 month after implant insertion), and phase 3 is 1 month after crown installation (5 month after implant insertion). The results were tabulated and analyzed using statistical software namely SPSS 20.5 to examine the correlation between basic measurement of bone quality and quantity and ISQ. The results show that during 4 month after implant insertion period, the density of bone around the implant are decrease, this period was predicted as remodeling process. After 5 moth since implant insertion, the density start to increase. This phase possibly indicated the starting phase of osseointegration process. In addition, the ISQ for each patient was increased significantly. The primary implant stability was correlated with the space availability and bone quantity and quality, the result shows that the implant stability is proportional with the height of the mandibular and cortical thickness and inversely with width of mandibular. The highest correlation with the primary implant stability is the product of cortical thickness with the height of mandibular. There is a significant correlation between implant stability (ISQ) with dimension of site implant and density of bone.

METODE DE EVALUARE A OSTEOINTEGRĂRII IMPLANTURILOR DENTARE

The stability of dental implants is a prerequisite for osseointegration. Osseointegration is the process that involves the formation of bone around the dental implant, resulting in increased stability and its integration in the organism. Therefore, successful osseointegration contributes to a functionally optimal treatment. There is a need for a clinical method capable of measurement of bone quality at the time and following implant placement, to measure the degree of osseointegration and the ability of the implants to distribute loads to the surrounding bone. Research to date focuses on finding an ideal method to assess the osseointegration of dental implants in order to improve and broaden the clinical indications of dental implant systems. This paper aims to supply information about current methods used to assess the osseointegration of dental implants. In this regard, a literature review was conducted. Full-text scientific articles relevant to the chosen topic, written in English or whose text could be accessed in English were included.

Quantitative Ultrasound Measurements of Bone Quality in Female Adolescents With Idiopathic Scoliosis Compared To Normal Controls

ObjectiveThe aims of this study were to compare the speed-of-sound (SOS) between adolescent idiopathic scoliosis (AIS) patients and controls using quantitative ultrasound examination and to further analyze the relationship between the SOS and curve type, curve magnitude, maturation status and Risser's sign in AIS patients compared to controls. MethodsSeventy-eight female AIS patients and 58 healthy female controls 10 to 16 years of age were recruited to participate. Quantitative ultrasound measurements were performed at the non-dominant distal end of the radius. The standard method for estimating the SOS and z-score was used. Comparisons were made between the SOS values and z-score in AIS patients and age-matched Asian adolescents. ResultsThe SOS values of the patients were significantly lower than the controls (P < .01). The percentage of cases with low bone quality was 25% in the entire AIS sample. The prevalence of low bone quality in AIS patients was 20.5%. However, there were no correlations between the SOS and types of scoliosis (P > .05). The SOS values among different severity groups were significant, particularly between the 10° to 19° and 20° to 39° groups as well as between 10° to 19° and ≥40° groups. However, there was no significant correlation between the SOS and Cobb angles. Significant correlations were also found between the pre- and post-menarchy status in patients. There was a significant difference in the SOS values for different Rissers’ signs (P < .05). ConclusionsCompared to nonscoliotic controls, subjects with AIS had a generally lower SOS, indicating lower bone quality. The age, Risser’s sign, or maturation status, may have an effect on the bone quality; however, the curve type and magnitude do not affect the bone quality. The results of this study indicate that slower bone maturation may affect the bone quality in adolescents with AIS.

Multiscale Predictors of Femoral Neck In Situ Strength in Aging Women: Contributions of BMD, Cortical Porosity, Reference Point Indentation, and Nonenzymatic Glycation.

The diagnosis of fracture risk relies almost solely on quantifying bone mass, yet bone strength is governed by factors at multiple scales including composition and structure that contribute to fracture resistance. Furthermore, aging and conditions such as diabetes mellitus alter fracture incidence independently of bone mass. Therefore, it is critical to incorporate other factors that contribute to bone strength in order to improve diagnostic specificity of fracture risk. We examined the correlation between femoral neck fracture strength in aging female cadavers and areal bone mineral density, along with other clinically accessible measures of bone quality including whole-bone cortical porosity (Ct.Po), bone material mechanical behavior measured by reference point indentation (RPI), and accumulation of advanced glycation end-products (AGEs). All measurements were found to be significant predictors of femoral neck fracture strength, with areal bone mineral density (aBMD) being the single strongest correlate (aBMD: r = 0.755, p < 0.001; Ct.Po: r = -0.500, p < 0.001; RPI: r = -0.478, p < 0.001; AGEs: r = -0.336, p = 0.016). RPI-derived measurements were not correlated with tissue mineral density or local cortical porosity as confirmed by micro-computed tomography (μCT). Multiple reverse stepwise regression revealed that the inclusion of aBMD and any other factor significantly improve the prediction of bone strength over univariate predictions. Combining bone assays at multiple scales such as aBMD with tibial Ct.Po (r = 0.835; p < 0.001), tibial difference in indentation depth between the first and 20th cycle (IDI) (r = 0.883; p < 0.001), or tibial AGEs (r = 0.822; p < 0.001) significantly improves the prediction of femoral neck strength over any factor alone, suggesting that this personalized approach could greatly enhance bone strength and fracture risk assessment with the potential to guide clinical management strategies for at-risk populations.

Circulating Lipocalin 2 Levels Predict Fracture-Related Hospitalizations in Elderly Women: A Prospective Cohort Study.

Lipocalin 2 (LCN2) or neutrophil gelatinase-associated lipocalin (NGAL) is expressed in a wide range of cells and pathological states. Mounting evidence suggests lipocalin 2 may be an important regulator of bone homeostasis. Recently it has been suggested LCN2 is a novel mechanoresponsive gene central to the pathological response to low mechanical force. We undertook a prospective study of 1009 elderly women over 70 years of age to study the association between circulating LCN2 and potential associated variables, including estimated glomerular filtration rate, physical activity, and baseline measures of hip bone density and heel bone quality. Osteoporotic fractures requiring hospitalizations were identified from the Western Australian Data Linkage System. Over 14.5 years, 272 (27%) of women sustained an osteoporotic fracture-related hospitalization; of these, 101 were hip fractures. Circulating LCN2 levels were correlated with body mass index and estimated glomerular filtration rate (r = 0.249, p < 0.001 and r = -0.481, p < 0.001, respectively) that modified the association with hip and heel bone measures. Per standard deviation increase in LCN2, there was a 30% multivariable-adjusted increase in the risk of any osteoporotic fracture (hazard ratio [HR] = 1.30, 95% confidence interval [CI] 1.13-1.50, p < 0.001). In participants with elevated LCN2 levels above the median (76.6 ng/mL), there was an 80% to 81% increase in the risk of any osteoporotic or hip fracture (HR = 1.81, 95% CI 1.38-2.36, p < 0.001 and HR = 1.80, 95% CI 1.16-2.78, p = 0.008, respectively). These associations remained significant after adjustment for total hip bone mineral density (p < 0.05). In conclusion, we have demonstrated that circulating LCN2 levels predict future risk of osteoporotic fractures requiring hospitalization. Measurement of LCN2 levels may improve fracture prediction in addition to current fracture risk factors in the elderly, particularly in those with impaired renal function.

Combined Measures of Dynamic Bone Quality and Postural Balance—A Fracture Risk Assessment Approach in Osteoporosis

We evaluated functional measures of neuromuscular integrity and bone's resistance to fracture as a combined tool in discriminating osteoporosis patients with and without fractures. Functional aspects of neuromuscular integrity were quantified with a noninvasive measure of static and dynamic functional postural stability (FPS), and fracture resistance was obtained with bone shock absorption in patients with osteoporosis aged 65–85 and compared our measures with dual-energy X-ray absorptiometry and Fracture Risk Assessment Tool (FRAX [World Health Organization Collaborating Center for Metabolic Bone Diseases, Sheffield, UK]) in women with osteoporosis, some with and some without vertebral fractures. Patients with vertebral fracture showed larger static FPS (postural sway excursion) in the mediolateral and anterior-posterior directions, suggesting poorer balance. Most of the variables of dynamic FPS showed significant differences between fracture and no-fracture groups (e.g., the fracture group took significantly longer during turning, implying poorer dynamic balance control). Also, compared with healthy control subjects, all 4 dynamic FPS responses for osteoporosis patients with and without fracture were significantly poorer, suggesting potential risk for falls. In summary, patients with osteoporosis who have vertebral fractures (compared with patients with similarly low bone mineral density and other nonfracture risk fractures) have not only lower bone shock absorption damping (ζ) but also increased postural imbalance.

Positive association between serum silicon levels and bone mineral density in female rats following oral silicon supplementation with monomethylsilanetriol.

SummaryObservational (epidemiological) studies suggest the positive association between dietary silicon intake and bone mineral density may be mediated by circulating estradiol level. Here, we report the results of a silicon supplementation study in rats that strongly support these observations and suggest an interaction between silicon and estradiol.IntroductionEpidemiological studies report strong positive associations between dietary silicon (Si) intake and bone mineral density (BMD) in premenopausal women and indicate that the association may be mediated by estradiol. We have tested this possibility in a mixed-gender rodent intervention study.MethodsTissue samples were obtained from three groups of 20-week-old Sprague Dawley rats (five males and five females per group) that had been supplemented ad libitum for 90 days in their drinking water with (i) <0.1 mg Si/L (vehicle control), (ii) 115 mg Si/L (moderate dose) or (iii) 575 mg Si/L (high dose). All rats received conventional laboratory feed, whilst supplemental Si was in the form of monomethylsilanetriol, increasing dietary Si intakes by 18 and 99 %, for the moderate- and high-dose groups, respectively.ResultsFasting serum and tissue Si concentrations were increased with Si supplementation (p < 0.05), regardless of gender. However, only for female rats was there (i) a trend for a dose-responsive increase in serum osteocalcin concentration with Si intervention and (ii) strong significant associations between serum Si concentrations and measures of bone quality (p < 0.01). Correlations were weaker or insignificant for tibia Si levels and absent for other serum or tibia elemental concentrations and bone quality measures.ConclusionsOur findings support the epidemiological observations that dietary Si positively impacts BMD in younger females, and this may be due to a Si-estradiol interaction. Moreover, these data suggest that the Si effect is mediated systemically, rather than through its incorporation into bone.Electronic supplementary materialThe online version of this article (doi:10.1007/s00198-014-3016-7) contains supplementary material, which is available to authorized users.

Is it worthwhile to measure bone quality in patients with adolescent idiopathic scoliosis?

Is it worthwhile to measure bone quality in patients with adolescent idiopathic scoliosis?

Reference point indentation is not indicative of whole mouse bone measures of stress intensity fracture toughness

Bone fragility is a concern for aged and diseased bone. Measuring bone toughness and understanding fracture properties of the bone are critical for predicting fracture risk associated with age and disease and for preclinical testing of therapies. A reference point indentation technique (BioDent) has recently been developed to determine bone's resistance to fracture in a minimally invasive way by measuring the indentation distance increase (IDI) between the first and last indentations over cyclic indentations in the same position. In this study, we investigate the relationship between fracture toughness KC and reference point indentation parameters (i.e. IDI, total indentation distance (TID) and creep indentation distance (CID)) in bones from 38 mice from six types (C57Bl/6, Balb, oim/oim, oim/+, Phospho1−/− and Phospho1 wild type counterpart). These mice bone are models of healthy and diseased bone spanning a range of fracture toughness from very brittle (oim/oim) to ductile (Phospho1−/−). Left femora were dissected, notched and tested in 3-point bending until complete failure. Contralateral femora were dissected and indented in 10 sites of their anterior and posterior shaft surface over 10 indentation cycles. IDI, TID and CID were measured. Results from this study suggest that reference point indentation parameters are not indicative of stress intensity fracture toughness in mouse bone. In particular, the IDI values at the anterior mid-diaphysis across mouse types overlapped, making it difficult to discern differences between mouse types, despite having extreme differences in stress intensity based toughness measures. When more locations of indentation were considered, the normalised IDIs could distinguish between mouse types. Future studies should investigate the relationship of the reference point indentation parameters for mouse bone in other material properties of the bone tissue in order to determine their use for measuring bone quality.

Cortical bone water changes in ovariectomized rats during the early postoperative period: Objective evaluation using sweep imaging with Fourier transform.

To evaluate the cortical bone signal-to-noise ratio (SNR) in ovariectomized (OVX) rats during the early postoperative period as a method to measure bone quality using the sweep imaging with Fourier transform (SWIFT) technique. Twelve-week-old female Sprague-Dawley rats (n = 64) were divided into sham and OVX groups. Preoperative tetracycline was immediately administered subcutaneously to distinguish new cortical bone area, and tibial samples were collected at 2, 4, 8, and 12 weeks postoperatively. Magnetic resonance imaging (MRI) was performed using proton density-weighted imaging (PDWI) and SWIFT to obtain cross-sectional images of the tibial diaphysis. The cortical bone SNR was calculated. Bone histomorphometry was performed. Histomorphometry findings showed that the new bone area was significantly greater at 8 and 12 weeks postoperatively in the OVX group (P < 0.05) while the porosity area decreased gradually in both groups (P < 0.001). The difference of SNR receiving PDWI did not reach statistical significance (P = 0.057). The SWIFT technique showed that the SNR was significantly higher at 8 and 12 weeks postoperatively in the OVX group (P < 0.05) and was correlated with the new bone area (R(2) = 0.430). The SWIFT findings suggest that the SWIFT technique may depict early changes in cortical bone quality.

Could the bone mineral density (T-score) be correlated with the Raman spectral features of keratin from women's nails and be used to predict osteoporosis?

Osteoporosis is a disease with great importance in current public health due to the associated risk of fracture; therefore, a rapid and accurate diagnosis becomes increasingly important. Recent literature has described a possible relationship between the changes in the organic phase of bone and the changes in nail keratin measured through Raman spectroscopy, aiming at the development of a standard for measuring bone quality and fracture risk both rapid and accurately. This work evaluated the correlation between the bone mineral density (BMD) scores of women with and without osteoporotic disease with the changes in the Raman spectra of the nail keratin, by assessing the intensity of the peak at 510 cm(-1) (S-S bridge) and the scores of principal component analysis (PCA), correlated with the values of BMD measured at the lumbar and hip. Raman spectra of ex vivo fingernails of 213 women were obtained by means of a dispersive Raman spectrometer (830 nm, 300 mW, in the spectral range between 400 and 1,800 cm(-1)). Peak intensities at ∼510 cm(-1) (assigned to the keratin S-S bridge) were measured, and the scores of first principal component loading vectors were calculated. Results showed no differences in the mean Raman spectra of nails of groups with and without osteoporosis. No correlation was found between the BMD scores and both the intensities of the 510 cm(-1) peak and the scores of the first four principal component vectors. Results suggest that BMD and fracture risk could not be assessed by the nail keratin features.

Higher glucocorticoid secretion in the physiological range is associated with lower bone strength at the proximal radius in healthy children: importance of protein intake adjustment.

Whether higher production of glucocorticoids (GCs) within the physiological range may already be affecting bone status in healthy children is unknown. Because dietary protein intake affects both bone and GCs, we examined the association of urinary measures of glucocorticoid status and cortical bone in healthy non-obese children, after particularly controlling for protein intake. Proximal forearm bone parameters were measured by peripheral quantitative computed tomography (pQCT). Subjects studied (n = 175, 87 males, aged 6 to 18 years) had two 24-hour urine samples collected: the first sample at 1 year before bone measurement, and the second sample at the time of bone measurement. Major urinary GC metabolites were measured by mass spectrometry and summed to assess daily adrenal GC secretion (∑C21). Urinary free cortisol (UFF) and cortisone (UFE) were summed to assess potentially bioactive free GCs (UFF + UFE). After controlling for several covariates and especially urinary nitrogen (the biomarker of protein intake) cortisol secretion ∑C21 was inversely associated with all analyzed pQCT measures of bone quality. ∑C21 also predicted a higher endosteal and lower periosteal circumference, explaining both a smaller cortical area and (together with lower BMD) a lower strength-strain-index (SSI). UFF + UFE, UFE itself, and a urinary metabolite-estimate of 11beta-hydroxysteroid dehydrogenase type1 (11beta-HSD1) activity showed corresponding reciprocal associations (p < 0.05) with BMD and bone mineral content, but not with SSI and bone geometry variables. In conclusion, higher GC levels, even within the physiological range, appear to exert negative influences on bone modeling and remodeling already during growth. Our physiological data also suggest a relevant role of cortisone as the direct source for intracrine-generated cortisol by bone cell 11beta-HSD1.

No. 240 Is It Worthwhile to Measure Bone Quality in Patients With Adolescent Idiopathic Scoliosis

Aim The aims of this study were to compare bone quality (speed-of-sound, SOS and z-scores) between female adolescent idiopathic scoliosis (AIS) patients and controls using quantitative ultrasound examination, and further to analyze the relationship between bone strength and maturation, severity and type of scoliosis in AIS patients measured by the same technique along the long axis of the distal radius.

Internal Magnetic Field Gradients in Heterogeneous Porous Systems: Comparison Between Spin-Echo and Diffusion Decay Internal Field (DDIF) Method

Two techniques used for evaluating internal magnetic field gradient (G i), spin-echo (SE) and diffusion decay internal field (DDIF), were investigated at 9.4 T and compared in porous systems characterized by different pores size ranging from 4 to 96 μm with magnetic susceptibility difference between solid and liquid phase, $$\Delta \chi$$ ≈ 1.6 ppm. Since diffusion of a fluid in a solid porous matrix plays a role in both SE and DDIF methods, we investigated these two different methods by highlighting their dependence on characteristic parameters and length scales used to describe diffusion behavior of fluids in porous systems. Therefore, G i behavior as a function of the dephasing length (l g), diffusion length (l d) and pores size (l s) was obtained. Moreover G i was evaluated by using both free diffusion and measured apparent diffusion coefficient of water, to quantify diffusion effect in different porous samples. This study gives more insight into the physical dynamics process to explain contrast mechanisms recently exploited by DDIF and SE applications for cancellous bone quality measurements.

A Transformative Risk Assessment Approach for Osteoporosis Fracture-Combined Measures of Dynamic Bone Quality and Postural Balance

A Transformative Risk Assessment Approach for Osteoporosis Fracture-Combined Measures of Dynamic Bone Quality and Postural Balance

SP0202 How to Measure Bone Quality in Daily Practice?

In recent years a number of new imaging techniques have been developed in order to evaluate components of bone quality in-vivo, in particular advanced three-dimensional Quantitative Computer Tomography (QCT), high...

Qualitative Ultrasound Comparisons Between Pre-Pubertal Normally Active Girls versus Competitive Jump Rope Participants

Jumping rope (JR) is known to enhance Os Calcis Stiffness Index (OCSI) in postpubertal girls; however the effects in prepubescent girls are unknown.Purpose:Qualitative Ultrasound (QUS) indices were compared between competitive JRs (N = 19) and normally active (NA, N = 18) girls 9–12 years old.Methods:Heel QUS, height, weight, percent body fat (bioelectrical impedance), and Tanner Sex Stage (self-report) were measured.Results:JR were significantly younger and had less body fat than NA (p &lt; .01). No other between group differences were found. OCSI was not different between groups even after correcting for fat mass (p &gt; 0.3). Broadband attenuation (BUA) was correlated with Tanner stage (R &gt; .40; p = .01).Conclusion:QUS of the heel bone is more related to pubertal status than to JR participation in young girls. Prepubertal girls who perform high intensity jumping have similar bone quality measures as normally active girls.

Comparison of immature porcine and human bone mineral density about the knee

Background: Orthopaedic hardware pull-out studies frequently utilize various animal models to assess axial and multiplanar loading of bone. Biomechanical models and techniques for testing are common; however, bone quality measures frequently are not provided in published studies. Bone mineral density (BMD) and bone mineral content (BMC) are used for assessment of bone quality. The authors sought to determine whether immature porcine knees would be an appropriate model for human graft and hardware pull-out studies. Our hypothesis was that immature cadaver porcine knees (ICPK) would be less dense than those of healthy adult human distal femurs and proximal tibias and thus an inadequate model for human graft and hardware pull-out studies. Methods: This was an in vivo and in vitro comparative laboratory study of BMD and BMC between two human knee groups and ICPK. Eleven ICPK 3 mo in age (body mass 25.0±3.3 kg) were used. Human Group 1 consisted of 18 collegiate athletes with a mean age of 19.2±0.86 yr (body mass 76.1±14.4 kg). Human group 2 included 10 people with a mean age of 34.4±9.3 yr (body mass 79.3±5.9 kg). BMD and BMC were measured using a Lunar 10655/Prodigy DEXA Scanner and software. ANOVA tested differences among the three groups, and post hoc testing assessed differences between the groups. Results: Differences in BMD were shown among the three groups for distal femur (ICPK-0.91±0.11 g/cm2; HG1-1.17±0.34 g/cm2; HG2-1.2±0.32 g/cm2 [P=0.037]), and proximal tibia (ICPK-0.94±0.12 g/cm2; HG1-1.41±0.22 g/cm2; HG2- 1.26±0.17 g/cm2 [P=0.001]). Statistical differences were found among the three groups for femoral BMC (ICPK-3.51±1.25 g; HG1-7.5±3.06 g; HG 2-11.59±5.40 g [P=0.001]) and tibial BMC (ICPK-4.58±2.00 g; HG1-9.64±3.92 g; HG2-13.07±5.37 g [P=0.001]). Conclusions: BMD and BMC in the distal femur and proximal tibia of an immature pig are significantly less than that of an adult human. Testing of graft pull-out using an immature porcine model involving the bones about the knee may not be accurately extrapolated to humans. We believe our work illuminates the need for bone quality assessment and documentation with BMD and BMC when performing or comparing pull-out studies.

Skeletal robustness and bone strength as measured by anthropometry and ultrasonography as a function of physical activity in young adults

During the last 10 years, skeletal robustness in children has generally decreased. The reasons for this phenomenon, as well as its outcomes, are undetermined so far. The present study explores the association between anthropometric skeletal measurements, bone quality measurements, and physical activity in young adults. 118 German young men (N = 68; 19-25 years old) and women (N = 50; 19-24 years old) were investigated by anthropometric methods (i.e., height, weight, shoulder, elbow breadth, and pelvic breadth) and quantitative ultrasound measurement (QUS). Strength and stability of Os calcis have been determined by speed of sound (in m/s) and broadband ultrasound attenuation (in dB/Mhz); individual physical activity was analyzed by a pedometer and by questionnaire. The results show a correlation between sports hours per week and bone quality index in males. But no correlation exists between anthropometric data and QUSs for either sexes, as well as no correlation between total steps per day and internal bone quality or external bone dimensions. These results are discussed in the context of generally decreasing physical activity, the outcomes of prevention programs as well as evolutionary adaptation of human phenotypic plasticity in a changing environment.

Effects of semi-group housing and floor type on pododermatitis, spinal deformation and bone quality in rabbit does

The most common housing system for reproduction rabbits, individual cage housing on a wire floor, is increasingly scrutinized because of its potential detrimental impact on animal welfare. We compared three types of housing: (1) individual cage housing on a wire floor (3952 cm2/doe, maximum roof height 63 cm, one 1000 cm2 plastic footrest/doe), (2) semi-group housing on a wire floor (5000 cm2/doe, roofless, one 1000 cm2 plastic footrest/doe) and (3) the same semi-group housing, but with a fully plastic slatted floor. In all housing systems, does had free access to an elevated platform. In the semi-group housing pens, four does were housed communally during 21 days of the reproduction cycle (to allow more space for locomotion and to increase opportunities for social contact), and individually during the other 21 days of the cycle (to minimize doe–doe and doe–kit aggression that peaks around kindling). In all, 24 Hycole does were included per system. The does entered the experiment at 203 days of age (after their first parity). The experiment consisted of four reproductive cycles, ending at 369 days of age. Pododermatitis was scored in cycles 1, 2 and 4. At the end of the 4th cycle the does were euthanized and X-rays were taken to assess spinal deformation. Tibia and femur length, width and cortical thickness were determined and bone strength was assessed using a shear test, as a measure of bone quality. Although severe pododermatitis was absent, the prevalence of plantar hyperkeratosis (hair loss and callus formation) at the end of the 4th cycle was much greater on the wire floor (65% and 68% for semi-group housing and individual cages, respectively) than on the plastic floor (5%, P<0.0001), even though the wire floors were equipped with a plastic footrest known to decrease hyperkeratosis. In contrast to our expectations, semi-group housing did not affect the prevalence of spinal deformations (P>0.10), but in line with our expectations bone quality was affected favourably by semi-group housing. The tibial cortex (and to a lesser extent the femoral cortex) was thicker in semi-group housing than in individual cages (1.45, 1.46 and 1.38 mm for semi-group housing on wire, semi-group housing on plastic and individual housing on wire, respectively, P=0.045). What this increase in cortical thickness means in terms of doe welfare requires further study, as it may reflect an increase in activity resulting either from increased space for locomotion, or from fleeing aggressive pen mates.