Precision of dual energy x-ray absorptiometry in the upper extremities

Inter-arm bone mass and size asymmetries in children tennis players are maturity status specific: a 9-month study on the effects of training time across pubertal change and somatic growth

PURPOSE

Bone growth with exercise is best assessed by tennis-induced inter-arm asymmetries. Yet, the effects of training and maturation across puberty were unclear. This study explored arm bone growth across 9 months of training in 46 tennis players 7-14 years (25 boys, 21 girls).

METHODS

Bone mineral content (BMC) and bone area (BA) were measured from DXA scans. Pubertal status was assessed by Tanner stage (TS) and somatic growth by maturity offset (MO). Children were grouped as pre- (TS I-I), early (TS I-II), and mid/late pubertal (TS II-III).

RESULTS

Training time (TT) change in the three groups was 160-170, 190-230, and 200-220 h, respectively. Bone asymmetries were large in all groups (d > 0.8, P < 0.001): 5-18 g (9-21%) and 9-17 g (17-23%) in girls and boys, respectively, for BMC, and 5-15 cm2 (6-13%) and 9-15 cm2 (12-15%) in girls and boys (10-13%), respectively, for BA. BMC and BA change asymmetry peaked at pre-puberty in girls (56%, 46%) and at early puberty in boys (57%, 43%). Asymmetry gains varied with baseline asymmetry (41%) and change in TT (38%) and TS (17%) in BMC, and with baseline asymmetry (58%) and change in MO (17%) and TS (12%) in BA.

CONCLUSION

All bone asymmetries were substantial. Tennis-induced bone gains were higher at pre- to early puberty in girls and at early to mid/late puberty in boys. Training enhanced mostly bone mass and maturity status enhanced mostly bone size; sex was not bone-change modeling impactful. Implications are discussed considering certain limitations.

Optimization of a calibration phantom for quantitative radiography

OBJECTIVE

Dual energy radiography (DER) makes it possible to obtain separate images for soft-tissue and bony structures (tissue maps) based on the acquisition of two radiographs at different source peak-kilovoltage values. Current DER studies are based on the weighted subtraction method, which requires either manual tuning or the use of precomputed tables, or on decomposition methods, which make use of a calibration to model soft-tissue and bone components. In this study, we examined in depth the optimum method to perform this calibration.

METHODS

We used simulations to optimize the calibration protocol and evaluated the effect of the material and size of a calibration phantom composed of two wedges and its positioning in the system. Evaluated materials were water, PMMA and A-150 as soft-tissue equivalent, and Teflon, B-100 and aluminum as bone equivalent, with sizes from 5 to 30 cm. Each material combination was compared with an ideal phantom composed of soft tissue and bone. Our simulation results enabled us to propose four designs that were tested with the NOVA FA X-ray system with a realistic thorax phantom.

RESULTS

Calibration based on a very simple and inexpensive phantom with no strict requirements in its placement results in appropriate separation of the spine (a common focus in densitometry studies) and the identification of nodules as small as 6 mm, which have been reported to have a low rate of detection in radiography.

CONCLUSION

The proposed method is completely automatic, avoiding the need for a radiology technician with expert knowledge of the protocol, as is the case in densitometry exams. The method provides real mass thickness values, enabling quantitative planar studies instead of relative comparisons.

Natural Course of Local Bone Mineralization After Treatment of Benign or Borderline Bone Tumors and Cysts With a Composite Ceramic Bone Graft Substitute

After surgical bone tumor removal, filling of the bone defect is frequently performed using a bone graft or bone graft substitute. During follow-up, precise quantification of changes in bone mineral density, within the treated bone defect, is very difficult using conventional X-ray examinations. The objectives of this study were to characterize the pattern of resorption/biodegradation of a composite calcium sulfate/hydroxyapatite bone graft substitute and to quantify the bone defect healing with repeated dual-energy X-ray absorptiometry (DXA) measurements. Seventeen patients treated for 18 benign bone lesions, with subsequent defect filling using 2 variants of a composite ceramic bone graft substitute (CERAMENT™|BONE VOID FILLER or CERMAMENT™|G, BONESUPPORT AB, Lund, Sweden), were scanned postoperatively and after 2, 6, 12, 26, and 52 wk using DXA. After an initial increase in bone mineral density after implantation of the bone graft substitute, bone mineral density decreased in the bone defect region throughout the 52 wk: rapidly in the first 12 wk and slower in the remaining weeks. Despite this continuous decrease, bone mineral density remained, on average, 25% higher in the operated extremity, compared with the nonoperated extremity, after 52 wk. The observed pattern of reduction in bone mineral density is consistent with the anticipated resorption of calcium sulfate within the bone graft substitute during the first 12 wk after surgery. We believe the DXA technique provides a precise method for quantification of bone graft resorption, but for evaluation of new bone formation, 3-dimensional imaging is needed.

Propolis accelerates the consolidation phase in distraction osteogenesis

We evaluated the effect of propolis on new bone formation after distraction osteogenesis (DO). This study examined 3 groups: control group, P100, and P200. Rabbits underwent DO of the left mandible after an osteotomy between the first molar and the mental foramen. Bone mineral content and bone mineral density were evaluated using dual-energy x-ray absorption 1 and 4 weeks after the procedure. The volume of connective tissue and new bone and the number of capillaries were measured using stereologic analysis after the subjects were killed. Dual-energy x-ray absorption showed that the bone mineral content and bone mineral density were higher in the groups treated with propolis by week 4, and these parameters were higher in the P200 group. Stereologic analysis showed no significant differences in connective tissue volume and number of capillaries among the groups. New bone volume was lowest in the P200 group. We concluded that propolis accelerates bone formation and may shorten the consolidation phase with DO.

The measurement of bone mineral density of bilateral proximal humeri using DXA in patients with unilateral rotator cuff tear

We propose that the measurement of the bone mineral density (BMD) of the proximal humerus be standardized using the dual energy X-ray absorptiometry (DXA) in patients supposed to undergo rotator cuff repair surgery as well as those with the fracture of the proximal humerus as the BMD of the proximal humerus is decreased in these patients.

INTRODUCTION

We propose that the measurement of the BMD of the proximal humerus be standardized using the DXA in patients who are supposed to undergo rotator cuff repair surgery as well as those with the fracture of the proximal humerus.

METHODS

We conducted the prospective study in 213 patients with unilateral rotator cuff tear but without contralateral shoulder pain or disease. In these patients, we preoperatively measured the BMD of the bilateral proximal humeri with a repeat measurement in 20 patients. We predefined three regions of interest (ROIs) in the proximal humerus with the consideration of the rotator cuff repair surgery as well as proximal humeral fractures.

RESULTS

The measurement of the BMD of the proximal humerus using the DXA showed excellent reliability (intraclass correlation coefficient > .90). BMD values of all three ROIs in the affected shoulder were significantly lower than those in asymptomatic shoulder (all p < 0.05). In female patients, the BMD values of ROIs in bilateral shoulder were significantly lower than those in male patients (all p < 0.001). In multiple regressions, however, there were no significant correlations between other clinical characteristics, except for the gender, and the BMD of GT in the affected shoulder.

CONCLUSIONS

It is imperative that the bone quality of the proximal humerus be accurately evaluated prior to surgery in patients who are supposed to undergo rotator cuff repair using suture anchors as well as in those with proximal humeral fractures. This is because the BMD of the proximal humerus is decreased in these patients.

Stiffness and ultimate load of osseointegrated prosthesis fixations in the upper and lower extremity

Background

Techniques for the skeletal attachment of amputation-prostheses have been developed over recent decades. This type of attachment has only been performed on a small number of patients. It poses various potential advantages compared to conventional treatment with a socket, but is also associated with an increased risk of bone or implant-bone interface fracture in the case of a fall. We therefore investigated the bending stiffness and ultimate bending moment of such devices implanted in human and synthetic bones.

Methods

Eight human specimens and 16 synthetic models of the proximal femora were implanted with lower extremity prostheses and eight human specimens and six synthetic humeri were implanted with upper extremity prostheses. They were dissected according to typical amputation levels and underwent loading in a material testing machine in a four-point bending setup. Bending stiffness, ultimate bending moment and fracture modes were determined in a load to failure experiment. Additionally, axial pull-out was performed on eight synthetic specimens of the lower extremity.

Results

Maximum bending moment of the synthetic femora was 160.6±27.5 Nm, the flexural rigidity of the synthetic femora was 189.0±22.6 Nm². Maximum bending moment of the human femora was 100.4±38.5 Nm, and the flexural rigidity was 137.8±29.4 Nm². The maximum bending moment of the six synthetic humeri was 104.9±19.0 Nm, and the flexural rigidity was 63.7±3.6 Nm². For the human humeri the maximum bending moment was 36.7±11.0 Nm, and the flexural rigidity at was 43.7±10.5 Nm². The maximum pull-out force for the eight synthetic femora was 3571±919 N.

Conclusion

Significant differences were found between human and synthetic specimens of the lower and upper extremity regarding maximum bending moment, bending displacement and flexural rigidity. The results of this study are relevant with respect to previous finding regarding the load at the interfaces of osseointegrated prosthesis fixation devices and are crucial for the development of safety devices intended to protect the bone-implant interface from damaging loadings.

Proximal humeral fracture fixation: a biomechanical comparison of two constructs

BACKGROUND

Different options exist for stabilizing proximal humeral fractures. This study compared the mechanical stability of 2 common proximal humeral fixation plates in bending and torsion.

METHODS

Tests were conducted on 40 synthetic and 10 matched pairs of cadaveric humeri (evenly fixed with DePuy S3 proximal humeral plating system [DePuy Orthopaedics, Warsaw, IN, USA] and Synthes proximal humerus locking compression plate [Synthes, Paoli, PA, USA]). Half of the humeri were tested by cantilevered bending in flexion, extension, varus, and valgus for 100 cycles of ±5 mm of displacement at 1 mm/s before loading to failure in varus. The other half were tested in torsion for 100 cycles of ±8° of rotational displacement at 1°/s before loading to failure in external rotation.

RESULTS

Peak cyclic loads for synthetic constructs were higher for DePuy plates than Synthes plates in varus and valgus (P < .0001), but a difference was not detected in extension (P > .40) or flexion (P = .0675). Peak cyclic loads for cadaveric constructs showed a significant difference in extension and flexion (Synthes > DePuy, P < .0001) and in varus (DePuy > Synthes, P < .05) but not in valgus (P > .10). Bending stiffness during varus failure testing was higher for DePuy plates than Synthes plates (P < .0001) for synthetic constructs. Regarding torsion of synthetic and cadaveric constructs, DePuy plates experienced higher peak cyclic torques over all cycles in both directions (P < .0001). For synthetic constructs, DePuy plates showed higher torsional stiffness in external failure than Synthes plates (P < .0001).

CONCLUSIONS

The DePuy plate was stiffer than the Synthes plate with varus and valgus bending, as well as in torsion. The Synthes plate tended to be stiffer in flexion and extension.

Does osteoporosis increase complication risk in surgical fracture treatment? A protocol combining new endpoints for two prospective multicentre open cohort studies

Background

With an ever-increasing elderly population, orthopaedic surgeons are faced with treating a high number of fragility fractures. Biomechanical tests have demonstrated the potential role of osteoporosis in the increased risk of fracture fixation complications, yet this has not been sufficiently proven in clinical practice. Based on this knowledge, two clinical studies were designed to investigate the influence of local bone quality on the occurrence of complications in elderly patients with distal radius and proximal humerus fractures treated by open reduction and internal fixation.

Methods/Design

The studies were planned using a prospective multicentre open cohort design and included patients between 50 and 90 years of age. Distal radius and proximal humerus fractures were treated with locking compression 2.4 mm and proximal humerus internal locking plates, respectively. Follow-up examinations were planned for 6 weeks, 3 and 12 months as well as a telephone interview at 6 months. The primary outcome focuses on the occurrence of at least one local bone quality related complication. Local bone quality is determined by measuring bone mineral density and bone mineral content at the contralateral radius. Primary complications are categorised according to predefined factors directly related to the bone/fracture or the implant/surgical technique. Secondary outcomes include the documentation of soft tissue/wound or general/systemic complications, clinical assessment of range of motion, and patient-rated evaluations of upper limb function and quality of life using both objective and subjective measures.

Discussion

The prospective multicentre open cohort studies will determine the value of local bone quality as measured by bone mineral density and content, and compare the quality of local bone of patients who experience a complication (cases) following surgery with that of patients who do not (controls). These measurements are novel and objective alternatives to what is currently used.

Trial registration numbers

Clinical Trials.gov NCT01144208 and NCT01143675

Assessment of the bilateral asymmetry of human femurs based on physical, densitometric, and structural rigidity characteristics

The purpose of this study was to perform a comprehensive geometric, densitometric, biomechanical, and statistical analysis of paired femurs for an adult population over a wide age range using three imaging modalities to quantify the departure from symmetry in size, bone mineral density, and cross-sectional structural rigidities. Femur measurements were obtained from 20 pairs of cadaveric femurs. Dimensions of these anatomic sites were measured using calipers directly on the bone and plain radiographs. Dual energy X-ray absorptiometry was used to measure bone mineral density. Bone mineral content and axial and bending rigidities were determined from the CT imaging. No differences were observed between the geometric measurements, DXA based bone mineral density and axial and bending rigidities of left and right femurs (P>0.05 for all cases). Left and right proximal femurs are not significantly different based on geometric, densitometric, and structural rigidity measurements. However, absolute left-right differences for individual patients can be substantial. When using the contralateral femur as a control, the number of femur pairs required to assess significant changes in anatomic dimensions and structural properties induced by a tumor, infection, fracture, or implanted device can range from 3 to 165 pairs depending on the desired effect size or sensitivity (5% or 10% difference). This information is important both for femoral arthroplasty implant design and the use of the contralateral femur as an intra-subject control for clinical assessment and research studies. In addition, our statistical analysis provides sample size estimates for planning future orthopedic research studies.

Reproducibility of imaging human knee cartilage by delayed gadolinium-enhanced MRI of cartilage (dGEMRIC) at 1.5 Tesla

OBJECTIVE

The purpose of this study was to investigate the day-to-day reproducibility of the delayed gadolinium-enhanced MRI of cartilage (dGEMRIC) measurement at different knee joint surfaces in healthy subjects at 1.5 Tesla (T).

METHODS

The dGEMRIC experiment was repeated for 10 asymptomatic volunteers three times with an average interval of 5 days between scans. The measurement was performed from a single sagittal slice through the center of the lateral femoral condyle and from the center of the patella in the axial plane. Cartilage was manually segmented into superficial, deep and full-thickness regions of interests (ROIs) at different topographical locations of the femur, tibia and patella. The reproducibility was evaluated separately for each ROI as well as for the entire bulk cartilage in the slice of each joint surface.

RESULTS

The reproducibility at various ROIs expressed by root-mean-square average coefficient of variation (CV(RMS)) ranged between 4.7-12.9%. Thirty out of thirty-three ROIs showed a CV(RMS) less than 10%. Intraclass correlation coefficient (ICC) ranged between 0.45 and 0.98. The CV(RMS) and ICC for bulk dGEMRIC were 4.2% and 0.95 for femur, 5.5% and 0.87 for tibia, and 4.8% and 0.97 for patella.

CONCLUSIONS

The dGEMRIC technique showed good day-to-day reproducibility, on the average 8% for small deep or superficial segments, 7% for full-thickness ROIs and 5% for bulk ROIs covering all visible cartilage in a single joint surface. We conclude that dGEMRIC imaging at field strength 1.5 T can be used as a reliable instrument for the assessment of articular cartilage when staff has been carefully trained.

Differences in precision in bone mineral density measured by SXA and DXA: the NOREPOS study

The aims were to compare the precision (reliability) in single X-ray (SXA) and dual X-ray (DXA) absorptiometry, and to compare smallest detectable difference (SDD). An additional aim was to examine determinants for precision in bone mineral density (BMD). BMD was measured by SXA (DTX-100, Osteometer) in the forearm and by DXA (Lunar Expert) in the forearm and in the hip. Two measurements were performed at each site/method, and 195 of 207 participants had complete datasets. Participants were aged 47-49 and 71-74 years. The precision was estimated by Root Mean Square Standard Deviation (RMS SD) with 95% Confidence Interval (95%CI) and the corresponding coefficients of variation (CV%). Determinants (age, gender, BMD) were analysed by multiple linear regression with log (SD) and log (CV) as dependent variables. RMS SD tended to be largest in older women and in those with low BMD. RMS SD for SXA and DXA forearm was 4.6 (4.2-5.1) and 6.8 (6.1-7.4) and the corresponding CVs 1.0% and 1.4%. RMS SD for DXA hip was 11.0 (9.9-12.0) with CV 1.2%. To detect a 3% change in BMD one would need two repeated measurements by DXA in the distal forearm at each of two consultations, but only one measurement by SXA in the distal forearm and also only one measurement by DXA in the hip. Precision differed by type of densitometer affecting the number of repeated measurements needed to detect a given BMD difference.

A biomechanical comparison of locking plate and locking nail implants used for fractures of the proximal humerus

The aim of this study was to determine the biomechanical behavior of 2 different implants used in the fixation of proximal humeral fractures. The 2 implants in this study are specifically designed for the fixation of proximal humeral fractures, and both are based on the concept of fixed-angle locking screws. A reproducible 3-part fracture was created in paired human cadaveric bone and then fixed via the locking screw implants. Stress/strain curves for the bone-implant construct were created for loads applied in different directions to determine the relative stiffness below the yield point. After this, each construct was tested to failure with a valgus bending load. The locking nail implant provided a significantly stiffer construct to valgus, extension, and flexion cantilever bending loads below the failure threshold. The valgus load to failure was significantly higher for the nail. The mode of failure was different between implants.

[A new implant for proximal humeral fracture: experimental study of the basket plate]

PURPOSE OF THE STUDY

We conducted a comparative study of three ostheosynthesis systems for proximal humeral fractures. The conclusions led to the elaboration of a rigid extramedullary osteosynthesis implant. This novel implant allows specific fixation of the tuberosities via six adjustable and removable hooks organized like a basket. There are two versions, with and without a central cephalic locking screw. We report two static biomechanical studies conducted to analyze this material.

MATERIAL AND METHODS

The two studies were performed on fresh frozen cadaver specimens with known bone density and with an experimental model of a four-fragment fracture of the proximal humerus. The first tests were designed to measure axial pressure reproducing the physiological movement applying the most stress on the head of the humerus. This allowed a global analysis of the mechanical behavior of the implant and an assessment of the contribution of the central cephalic locking screw. The second series of tests were traction tests used to analyze the behavior of the tuberosities fixed with the hooks. We assess the assemblies by measuring the mechanical resistance: rigidity of the fixation was recorded in mm/100N. Pre- and post-procedure x-rays and photographs were obtained to allow a subjective assessment of fragment displacement.

RESULTS

The first series of tests demonstrated that the implant, with the central cephalic locking screw, presented good overall mechanical properties. The notion of better stability of the tuberosities obtained with the hooks, as seen during the first tests, was reinforced by the data from the second tests, although no statistically significant difference was demonstrated. We also noted that there was no statistically significant correlation between bone density and the slopes of the force-resistance curves.

DISCUSSION

This prototype implant has an overall mechanical resistance equivalent to the reference implant, with at least equivalent performance. Proof of the usefulness of the central locking screw was not established, even though improved tolerance to loading by better force distribution seemed apparent. The contribution of the hook basket was not demonstrated. Data from the observations do however suggest the expectations of the implant will be fulfilled. Tests conducted on a larger scale would probably demonstrate a difference. It is clear that the small number of implants used here limited the study. Comparison with data in the literature show that this new prototype is adapted to the mechanics of the proximal humerus. Resistant to physiological stress, the implant allows pendular movement and passive physical therapy during the early post-operative period.

Effect of long-term impact-loading on mass, size, and estimated strength of humerus and radius of female racquet-sports players: a peripheral quantitative computed tomography study between young and old starters and controls

Bone characteristics of the humeral shaft and distal radius were measured from 64 female tennis and squash players and their 27 age-, height-, and weight-matched controls with peripheral quantitative tomography (pQCT) and dual energy X-ray absorptiometry (DXA). The players were divided into two groups according to the starting age of their tennis or squash training (either before or after menarche) to examine the possible differences in the loading-induced changes in bone structure and volumetric density. The following pQCT variables were used: bone mineral content, total cross-sectional area of bone (TotA), cross-sectional area of the marrow cavity (CavA) and that of the cortical bone (CoA), cortical wall thickness (CWT), volumetric density of the cortical bone (CoD) and trabecular bone (TrD), and torsional bone strength index for the shaft (BSIt) and compressional bone strength index for the bone end (BSIc). These bone strength indices were compared with the DXA-derived areal bone mineral density (aBMD) to assess how well the latter represents the effect of mechanical loading on apparent bone strength. At the humeral shaft, the loaded arm's greater bone mineral content (an average 19% side-to-side difference in young starters and 9% in old starters), was caused by an enlarged cortex (CoA; side-to-side differences 20% and 9%, respectively). The loaded humerus seemed to have grown periosteally (the CavA did not differ between the sites), leading to 26% and 11% side-to-side BSIt differences in the young and old starters, respectively. CoD was equal between the arms (-1% difference in both player groups). The side-to-side differences in the young starters' bone mineral content, CoA, TotA, CWT, and BSIt were 8-22% higher than those of the controls and 8-14% higher than those of the old starters. Old starters' bone mineral content, CoA, and BSIt side-to-side differences were 6-7% greater than those in the controls. The DXA-derived side-to-side aBMD difference was 7% greater in young starters compared with that of the old starters and 14% compared with that in controls, whereas the difference between old starters and controls was 6%, in favor of the former. All these between-group differences were statistically significant. At the distal radius, the player groups differed significantly from controls in the side-to-side bone mineral content, TrD, and aBMD differences only: the young starters' bone mineral content difference was 9% greater, TrD and aBMD differences were 5% greater than those in the controls, and the old starters' TrD and aBMD differences were both 7% greater than those in the controls. In summary, in both of the female player groups, the structural adaptation of the humeral shaft to long-term loading seemed to be achieved through periosteal enlargement of the bone cortex, although this adaptation was clearly better in the young starters. Exercise-induced cortical enlargement was not so clear at the distal radius (a trabecular bone site), and the study suggested that at long bone ends, the trabecular density could be a modifiable factor to built a stronger bone structure. Conventional DXA-based aBMD measurement detected the intergroup differences in the exercise-induced bone gains, although, because it measured two dimensions of bone only, it seemed to underestimate the effect of exercise on the apparent bone strength, especially if the playing had been started during the growing years.

Effect of long-term impact-loading on mass, size, and estimated strength of humerus and radius of female racquet-sports players: a peripheral quantitative computed tomography study between young and old starters and controls

Bone characteristics of the humeral shaft and distal radius were measured from 64 female tennis and squash players and their 27 age-, height-, and weight-matched controls with peripheral quantitative tomography (pQCT) and DXA. The players were divided into two groups according to the starting age of their tennis or squash training (either before or after menarche) to examine the possible differences in the loading-induced changes in bone structure and volumetric density. The used pQCT variables were bone mineral content (BMC), total cross-sectional area (TotA) of bone, cross-sectional area of the marrow cavity (CavA) and that of the cortical bone (CoA), cortical wall thickness (CWT), volumetric density of the cortical bone (CoD) and trabecular bone (TrD), and torsional bone strength index (BSIt) for the shaft, and compressional bone strength index (BSIc) for the bone end. These bone strength indices were compared with the DXA-derived areal bone mineral density (aBMD) to assess how well the latter represents the effect of mechanical loading on apparent bone strength. At the humeral shaft, the loaded arm's greater BMC (an average 19% side-to-side difference in young starters and 9% in old starters) was caused by an enlarged cortex (CoA; side-to-side differences 20% and 9%, respectively). The loaded humerus seemed to have grown periosteally (the CavA did not differ between the sites) leading to 26% and 11% side-to-side BSIt difference in the young and old starters, respectively. CoD was equal between the arms (-1% difference in both player groups). The side-to-side differences in the young starters' BMC, CoA, TotA, CWT, and BSIt were 8-22% higher than those of the controls and 8-14% higher than those of the old starters. Old starters' BMC, CoA, and BSIt side-to-side differences were 6-7% greater than those in the controls. The DXA-derived side-to-side aBMD difference was 7% greater in young starters compared with that of the old starters and 14% compared with that in controls, whereas the difference between old starters and controls was 6%, in favor of the former. All these between-group differences were statistically significant. At the distal radius, the player groups differed significantly from controls in the side-to-side BMC, TrD, and aBMD differences only; the young starters' BMC difference was 9% greater, TrD and aBMD differences were 5% greater than those in the controls, and the old starters' TrD and aBMD differences were both 7% greater than those in the controls. In summary, in both of the female player groups the structural adaptation of the humeral shaft to long-term loading seemed to be achievedthrough periosteal enlargement of the bone cortex although this adaptation was clearly better in the young starters. Exercise-induced cortical enlargement was not so clear at the distal radius (a trabecular bone site), and the study suggested that at long bone ends also the TrD could be a modifiable factor to build a stronger bone structure. The conventional DXA-based aBMD measurement detected the intergroup differences in the exercise-induced bone gains, although, measuring two dimensions of bone only, it seemed to underestimate the effect of exercise on the apparent bone strength, especially if the playing had been started during the growing years.

Lateralized mineral content and density in distal forearm bones in right-handed men and women: relation of structure to function

To test whether handedness has an asymmetric effect on distal forearm bone mineral content (BMC) and bone mineral density (BMD), and whether there is an effect of sex on these variables, the mean BMCs and BMDs in bilateral distal forearms were compared in right-handed men and women. It was expected that the BMC and BMD would be higher on the right than the left side in right-handers. The present results were consistent with this working hypothesis. Namely, the right-BMCs were found to be significantly higher than left-BMCs for all regions of the bones studied. There were no sex differences either for the right-left BMCs or for the right-left BMDs. The results indicated that i) the relation of structure to function would also be valid outside the brain, ii) the mean BMCs, but not BMDs, were significantly higher in the right than the left arm at different distal forearm regions, and iii) there were no significant sex differences in the distal-forearm BMCs and BMDs.

Good maintenance of exercise-induced bone gain with decreased training of female tennis and squash players: a prospective 5-year follow-up study of young and old starters and controls

This prospective 5-year follow-up study of 64 adult female racquet sports players and 27 controls assessed the changes in the playing-to-nonplaying arm bone mineral content (BMC) differences to answer three questions: (1) Are training-induced bone gains lost with decreased training? (2) Is the bone response to decreased training different if the playing career has been started before or at puberty rather than after it? (3) Are the possible bone changes related to the changes in training? The players were divided into two groups according to the starting age of their tennis or squash playing. The mean starting age was 10.5 years (SD, 2.2) among the players who had started training before or at menarche (young starters; n = 36) while 26.4 years (SD, 8.0) among those players who had begun training a minimum of 1 year after menarche (old starters; n = 28). At baseline of the 5-year follow-up, the mean age of the young starters was 21.6 years (SD, 7.6) and that of old starters was 39.4 years (SD, 10.5). During the follow-up, the young starters had reduced the average training frequency from 4.7 times a week (2.7) to 1.4 times a week (1.3) and the old starters from 4.0 times a week (1.4) to 2.0 times a week (1.4), respectively. The 5-year follow-up revealed that despite reduced training the exercise-induced bone gain was well maintained in both groups of players regardless of their clearly different starting age of activity and different amount of exercise-induced bone gain. The gain was still 1.3-2.2 times greater in favor of the young starters (at the follow-up, the dominant-to-nondominant arm BMC difference was 22% [8.4] in the humeral shaft of the young starters versus 10% [3.8] in the old starters, and 3.5% [2.4] in controls). In the players, changes in training were only weakly related to changes in the side-to-side BMC difference (r(s) = 0.05-0.34, all NS), and this was true even among the players who had stopped training completely a minimum 1 year before the follow-up. In conclusion, if controlled interventions will confirm our findings that an exercise-induced bone gain can be well maintained with decreased activity and that the maintenance of the bone gain is independent of the starting age of activity, exercise can be recommended for preventing osteoporosis and related fractures.

Effect of distraction rate on biomechanical, mineralization, and histologic properties of an ovine mandible model

Craniofacial microsomia is a common congenital malformation. Ilizarov's method of distraction osteogenesis applied to the mandible has yielded promising results both experimentally and clinically. Because the technique is used predominantly in a pediatric population, length of treatment and compliance may be problematic. To date, the limits of distraction rate in the craniofacial skeleton have not been defined. This study was designed to investigate the effects of distraction rate, in a large animal model, on the mineralization, biomechanical, and histologic properties of lengthened mandibles. Clinically faster distraction rates would decrease the overall treatment time. Twenty-four animals were divided into four groups, with varying rates of distraction (1, 2, 3, and 4 mm/day). A uniaxial distractor at the angle of the mandible was used. The mandibles were lengthened to 24 mm and fixed for a period of 5 weeks, when the animals were killed. The specimens were analyzed with respect to mineralization using dual energy x-ray absorptiometry, biomechanical strength, through a modified three-point bending test, and histologic properties with hematoxylin and eosin stains. Biomechanical, mineralization, and histologic analyses of the samples indicated that group 1 (1 mm/day) samples were significantly superior (p<0.05) to those of group 4 (4 mm/day). Although bone formation was achieved in all groups, group 1 (1 mm/day) demonstrated the strongest biomechanical and histologic properties. Bone mineral density obtained using dual energy x-ray absorptiometry may be clinically useful as a reliable, noninvasive, and relatively cheap predictor for removal time of the fixator.

Cross-sectional assessment of age-related bone loss in men: the MINOS study

There are few data on osteoporosis in men, but cross-sectional studies have shown that age-related bone loss in men is of lower magnitude than in women. To elucidate some controversies related partially to methodological aspects, we measured bone mineral density (BMD) by dual-energy X-ray absorptiometry (DEXA) at various skeletal sites (spine, hip, and whole body using a Hologic QDR-1500 device; forearm using an Osteometer DTX 100 device) in a large cohort of 1040 men, aged 19-85 years. The final investigation was performed on 934 men, aged 19-85 years, after exclusion of 106 men with disease or treatment known to affect bone metabolism. Peak BMD was achieved at 25 and 29 years at the lumbar spine and hip, respectively, but only at 40 and 37 years at the distal forearm and whole body, respectively. The magnitude of bone loss between peak bone mass and 80 years of age was linear at most sites and averaged 13%-18%; that is, SD of 1.1-1.8 from peak BMD, except for Ward's triangle, which showed a marked bone loss of 43% (i.e., 2.5 SD), and for the lumbar spine. In the entire cohort, increase of the average lumbar spine BMD after the age of 55 years was related to the development of osteoarthritis, because, in men without severe arthritis, lumbar spine BMD continued to decrease. Height-adjusted partial correlations indicate that both the mineral content and the area of long bones of the limbs increased with age up to 50 years, followed by a significant decrease of BMD without change of bone surface. SD of mean BMD increased significantly with age at most skeletal sites. In summary, age-related change of BMD varied according to skeletal site in men with peak bone mass achieved earlier at sites rich in trabecular bone than at those rich in cortical bone. Bone loss varied according to skeletal site from 14% to 43%. The variability of BMD increased with age, which may reflect interindividual variability of age-related bone loss.

Osteoporosis in hemiplegic stroke patients as studied with dual-energy X-ray absorptiometry

OBJECTIVES

To compare bone mineral densities (BMDs) of the affected and unaffected limbs in stroke patients at multiple sites; to study longitudinal changes during a 3-month rehabilitation program; and to relate BMDs to demographic, impairment, and disability variables.

DESIGN

Descriptive study.

SETTING

Tertiary rehabilitation center.

PATIENTS

One hundred four consecutive hemiplegic inpatients, 69 men, age 56.5 +/- 13.2 yrs, 47 with left-sided brain lesion. Median days from onset to admission and median length of stay days were 83 and 105.5, respectively.

MAIN OUTCOME MEASURES

BMDs of proximal humerus, distal radius, femoral neck, and calcaneus bilaterally, and third lumbar vertebra, measured with dual-energy x-ray absorptiometry (DXA), were compared between affected and unaffected sides at admission and discharge.

RESULTS

Stroke Impairment Assessment Set (SIAS) motor scores, Functional Independence Measure (FIM) scores, grip strength, and awake/sleep heart rate counts (activity index) improved significantly at discharge. Affected/unaffected BMD ratios were 88.3% to 98.4% at admission and 79.6% to 98.8% at discharge, lowest for the humerus. Discharge/admission ratios were 89.1% to 97.8% for the affected and 97.4% to 100% for the unaffected side. All BMDs were intercorrelated (R = .438 to .873). They correlated significantly with age, body weight, grip strength, FIM scores, and activity index. Factors selected to explain BMD with multiple regression analysis differed according to the site and timing of the measurement.

CONCLUSIONS

BMDs of the affected side were lower and most marked in the humerus. Longitudinally, not only the affected but the unaffected BMDs decreased. Age, sex, duration of stroke, anthropometric measurements, motor paralysis, muscle strength, and activity level contributed differently to bone loss according to the site and timing of the measurement.

Changes in bone mineral content with decreased training in competitive young adult tennis players and controls: a prospective 4-yr follow-up

PURPOSE

The purpose of this 4-yr prospective follow-up study of male tennis players was to determine the changes in the playing-to-nonplaying arm differences in bone mineral content (BMC) and answer two questions: 1) Are training induced bone gains lost with decreased training? and 2) Are the possible bone changes related to the changes in training?

METHODS

Subjects were 13 former competitive male tennis players and their 13 controls. The players had started their playing career at the mean age of 11 yr. The initial comparisons between the playing and contralateral arms' BMC were done in 1992 (mean age 26 yr), and follow-up was performed 4 yr later. The players were competing at the national top level in the beginning of the study, and all had retired from the top tennis (mean) 2.3+/-0.6 yr before follow-up. Accordingly, they had reduced the average training frequency from 5.2 times a week to 2.6 times a week and the mean hours of training per week from 7.6 to 3.3.

RESULTS

The 1996 measurements revealed that on average the players' exercise-induced bone gain in the playing arm had not disappeared with time despite decreased average playing activity and that observed bone changes were not related to changes in training. The side-to-side BMC differences were largest in the humeral shaft (25% in 1992 and 26% 4 yr later) and the proximal humerus (19% and 18%). The radial shaft difference was 14% and the distal radius difference 13% in both 1992 and 1996. In controls, the side-to-side BMC differences were small, less than 5%, and they did not change by time.

CONCLUSIONS

In conclusion, this study suggests that bone gain obtained by regular tennis training does not disappear by time despite decreased playing activity. Regular exercise can be valuable for maximizing peak bone mass and thus contributing to prevention of osteoporosis and related fractures later in life.

Adhesive capsulitis of the shoulder (frozen shoulder) produces bone loss in the affected humerus, but long-term bony recovery is good

The objective of the study was to assess the short- and long-term effects of adhesive capsulitis (frozen shoulder) on the bone mineral density (BMD) of the affected extremity. BMD and clinical status of 22 patients (group A) with active-phase unilateral adhesive capsulitis and 31 patients (group B) with a previous adhesive capsulitis (average 9 years before the examination) were determined. BMD was measured from the proximal humerus, humeral shaft, radial shaft, ulnar shaft, and distal forearm of both upper extremities using dual-energy X-ray absorptiometry (DXA). In group A, the mean BMD of the affected extremity, as compared with that of the unaffected side, was significantly lower in the proximal humerus (-5.6%; p = 0.001) and humeral shaft (-3.0%; p = 0.008). The radial shaft, ulnar shaft, and distal forearm showed no significant side-to-side differences. In contrast, in group B, the affected-to-unaffected side BMD differences were small and statistically insignificant. Compared with the 31 patients in group B, the relative side-to-side BMD difference of the 22 patients with active-phase disease (group A) was significantly lower in the proximal humerus (-5.6% vs. -1.5%, p = 0.009). In the other sites, groups A and B showed no significant differences. In conclusion, this study indicates that adhesive capsulitis of the shoulder results in significant bone loss in the humerus of the affected extremity, but in the long term, capsulitis-induced bone loss shows good recovery.

Dual-energy X-ray absorptiometry in predicting mechanical characteristics of rat femur

Dual-energy X-ray absorptiometry (DXA), geometrical measurements, and mechanical testing of the rat femoral shaft and neck were performed on both femora of 51 Sprague-Dawley rats to: (i) determine the reproducibility of the DXA, geometrical, and biomechanical measurements of rat femora; (ii) determine linear and power-law (y=ax(b)) associations between the site-specific bone mineral variables and the actual mechanical characteristics of the given sites; (iii) develop, if sufficiently strong associations were found, appropriate prediction equations for the breaking load (F) and flexural rigidity (EI) of the femoral shaft and neck (only for F); and (iv) validate these equations in terms of accuracy of prediction. In the majority of the DXA measurements, the repeatability of the measurements was good, the CVrms varying between 1.2% and 3.9% in the bone mineral density (BMD) measurements and between 1.6% and 13.8% in the bone mineral content (BMC) measurements. DXA also proved accurate in length measurements of the rat femur (measurement error <1%). The manual (digimatic caliper-obtained) geometrical measurements of the rat femora were equally precise, the CVrms values varying between 0.2% and 5.0%. The repeatability of the biomechanical testings of these femora varied between 5.0% and 14.7%. Virtually all of the power-law and linear models explained more than 80% (at best 97%) of the variation in the F of the femoral shaft and neck, and the EI of the femoral shaft. Despite the high group-level correlations between the DXA-based predictions of bone strength and the actual breaking loads of the rat femora, and good precision of DXA, the ability of any DXA-based estimate to predict accurately the actual biomechanical characteristics of an individual bone remained relatively poor. In extreme cases, the prediction error could be tens of percent. Despite this we feel that bone strength-estimating equations can be used in the group-level analyses of experimental and clinical studies. Care must be taken, however, when choosing the most appropriate prediction method for a particular study.

Effect of long-term unilateral activity on bone mineral density of female junior tennis players

High peak bone mass in early adulthood is an important protective factor against osteoporotic fractures in later life, but little is known about the effects of exercise on growing bone. The purpose of this cross-sectional study was to determine at which state of maturity (Tanner stage), the areal bone mineral density (BMD) differences between the playing and nonplaying arms of junior tennis players become obvious, and to clarify in each developmental stage which training and background variables, if any, could explain the interindividual differences in bones' response to mechanical loading. Ninety-one 7- to 17-year-old female tennis players and 58 healthy female controls were measured. In each Tanner stage, differences in BMD in playing and nonplaying (dominant and nondominant) arms (proximal humerus, humeral shaft, and distal radius) and BMD of the lumbar spine and nondominant distal radius were compared between the controls and players. Within each Tanner stage of players, the associations between training and background variables and BMD differences were analyzed with Spearman rank correlation coefficients. In players, BMD differences between the playing and nonplaying arms were significant (P < 0.05- < 0.001) in all Tanner stages, with the mean difference ranging from 1.6 to 15.7%. In controls, these dominant-to-nondominant arm differences were clearly smaller (ranging from -0.2 to 4.6%), but significant at some measured sites. In comparison with the relative side-to-side arm differences between the players and controls (i.e., examination of the training effect), the mean difference was not obvious and significant until the adolescent growth spurt (i.e., the girls in Tanner stage III with a mean age of 12.6 years). In the lumbar spine, significant BMD differences between players and controls were not found until Tanner stage IV (mean age 13.5 years; 8.7%, P < 0.05) and V (mean age 15.5 years; 12.4%, P < 0.05). In a nonloaded site of the skeleton (nondominant distal radius), no significant BMD differences were found between the players and controls in any Tanner stage. In the correlation analysis, the Tanner I and II players (mean ages 9.4 and 10.8 years) showed no significant associations between any of the predictive variables and the side-to-side BMD differences, while in Tanner stages III, IV, and V, such associations could be found; the total amount of training hours during the playing career and the number of training sessions per week showed a significant and systematic correlation (rs ranging from 0.43 to 0.80) with the side-to-side BMD differences in several measured bone sites. In conclusion, this study suggests that in a majority of female junior tennis players, the benefit of unilateral activity on bone density does not become clearly evident until the adolescent growth spurt or Tanner stage III. The total amount of training during the player's career and the current training frequency (sessions per week) seem to best explain the training effect on bone tissue, leaving, however, room for speculation on the still unknown factors that modulate the loading response of a growing bone.

Reproducibility of dual-energy X-ray absorptiometry in the upper extremities in stroke patients

Bone mineral loss after stroke in affected extremities can increase the prevalence of fractures that interrupt the rehabilitation programme and lower the level of activity. In stroke rehabilitation, precise bone mineral measurement is needed in order to assess the risk of fractures. We defined five regions-of-interest of the upper extremity (proximal humerus, distal forearm, distal radius, distal ulna and hand) consistently, so that the position was comfortable for hemiplegic patients to maintain during the measurement. The aim of this study was to determine whether our method using dual-energy X-ray absorptiometry is useful in hemiplegic patients. Ten normal subjects and 15 hemiplegic patients were studied. In normal subjects the reproducibility of our method was evaluated by repeated measurements of both the right and left sides. In hemiplegic patients the reproducibility was evaluated by repeated measurements of the affected side. The coefficient of variation (CV) values were obtained for BMD (0.7-1.7%) and BMC (0.7-2.3%) in normal subjects, and BMD (1.3-2.1%) and BMC (1.7-5.4%) in hemiplegic patients. The CV for the side-to-side BMD and BMC ratios in the normal subjects ranged from 1.1% to 2.2% and from 1.8% to 3.1%, respectively. Our study shows that the reproducibility of our method is sufficient for application to hemiplegic patients.

Loss of bone mineral of the hip assessed by DEXA following tibial shaft fractures

We measured prospectively early changes (0-6 months) in bone mineral of the hip, the lumbar spine, and the tibia following tibial shaft fractures (n = 12), and in a cross-sectional study we evaluated the maximal amount of bone loss possible at the hip and tibia following long-term (average 3 years) impaired limb function as a consequence of complicated tibial shaft fractures [delayed union or nonunion (n = 7), chronic osteomyelitis (n = 5), decreased limb length (n = 1), or bone defect (n = 1)]. Bone mineral measurements were performed by dual energy X-ray absorptiometry. Following tibial shaft fractures, a significant decrease in bone mineral density (BMD) was seen at the hip reaching 7% [confidence limits (CL): -10.2%; -3.5%] and 14% (CL: -19.6; -7.8%) after 6 months for the femoral neck and greater trochanter, respectively. In the proximal tibia, bone mineral content (BMC) decreased and was 19% (CL: -27.4%; -9.9%) below the initial value after 6 months. BMD of the lumbar spine remained unchanged. In the cross-sectional study, BMC in the tibia of the injured legs was 43% (CL: -53.2%; -31.9%) below the value in the healthy contralateral legs, and BMD in the femoral neck and greater trochanter, respectively, was 22% (CL: -27.4%; -17.6%) and 24% (CL: -36.3%; -12.1%) below the values in the healthy contralateral legs. With respect to the expected age-related decay of bone mineral after peak bone mass, the loss of bone mineral of the hip and tibia associated with tibial shaft fractures may be considered of clinical importance with increased risk of sustaining a fragility fracture of the lower extremity later in life; and the complicated fractures may even represent a present risk of fracture.

Dimensions and estimated mechanical characteristics of the humerus after long-term tennis loading

This study evaluated the effects of long-term unilateral physical activity (tennis) on the playing arm humerus. Total lengths of both humeri, site-specific widths, and the bone mineral contents (BMC) at the proximal, middle, and distal parts of the bones were measured using dual-energy X-ray absorptiometry (DXA). Bone mineral apparent density (BMAD), cortical wall thickness (CWT), cross-sectional moment of inertia (CSMI), and section modulus (Z) were approximated from the DXA data for describing the bone's mechanical characteristics more concretely. The study population consisted of 67 healthy, competitive tennis players (17 young men with a mean age [+/- SD] of 25 +/- 5 years, 30 young women with a mean age of 19 +/- 3 years, and 20 older women with a mean age of 43 +/- 5 years) and 57 sedentary controls (16 young men with mean age of 25 +/- 5 years, 25 years, 25 young women with a mean age of 21 +/- 3 years, and 16 older women with mean age of 39 +/- 6 years). All the players had competitive playing histories greater than 4 years. The young male and female players had started their playing careers in childhood (men at the age of 10 +/- 3 years, women 9 +/- 2 years), while the older female players started the training at adulthood (29 +/- 6 years). The playing-to-nonplaying or dominant-to-nondominant arm differences in humeral length ranged from +0.2 to +1.4%, the difference being significant in young male players (+1.4%), young female controls (+1.1%), and older female players (+0.7%). When comparing players' relative side-to-side length differences with those of the controls, no significant differences were found. Significant side-to-side differences in humeral width were observed in all groups except male controls. Compared with the controls, the relative side-to-side width differences were significantly larger at the proximal humerus of the young male players (controls +1.2%, players +3.7%) and the distal humerus of young female players (controls -0.2%, players +1.6%). Compared with the controls, the players' relative side-to-side differences in BMC (range, +7.6 to +25.2%), BMD (+5.8 to +22.5%), BMAD (+5.5 to +20.4%), CWT (+6.9 to +45.2%), CSMI (+7.8 to +26.4%), and Z (+3.0 to +21.7%) were significantly larger in all measured humeral sites except BMAD in the distal humeri of the older female players. These relative side-to-side differences were clearly and significantly larger in the young players (+11.7 to +45.2%) than in the older players (+3.0 to +12.4%). In conclusion, long-term intensive tennis playing, especially if started in childhood or adolescence, clearly increases the humeral BMC, BMD, and CWT but seems to have only a minor effect on the width of this particular bone. In this respect, there seems to be no sex difference. However, along with the increases in mineral mass and density, the changes in bone width are important in increasing the bending stiffness and strength of the humerus. In older players, the relative side-to-side differences are at the same level or only slightly larger than those in their age-matched controls. This suggests that even intense physical loading of a mature bone is only marginally better in increasing the bone mass, bone density, and CWT of the target bone than the normal daily use of the dominant extremity.

Effects of unilateral strength training and detraining on bone mineral mass and estimated mechanical characteristics of the upper limb bones in young women

The aims of this study were to examine the effects of 12 months unilateral high-resistance strength training and 8-month detraining on bone mineral content (BMC), density (BMD) and estimated mechanical characteristics of upper limb bones, and also to estimate consequent loading induced strains on forearm bone shafts. Thirteen female physiotherapy students (mean 23.8 +/- 5.0 yrs, 166 +/- 7 cm, 64.4 +/- 7 cm, 64.4 +/- 13.3 kg) trained their left upper limbs with dumbbells on average 2.8 times per week for 12 months, followed by eight months detraining. Nineteen students served as controls (mean 25.7 +/- 5.2 yrs, 165 +/- 4 cm, 62.1 +/- 7.0 kg). BMC, BMD, and bone width and estimated cortical wall thickness (CWT) were measured at five different sites in both upper extremities (proximal humerus, humeral shaft, radial shaft, ulnar shaft, and distal forearm) using dual energy x-ray absorptiometry (DXA) scanner. In addition, cross-sectional moment of inertia (CSMI) was estimated from DXA data. The maximal isometric strength of the upper extremities was measured with an arm flexion-extension dynamometer. The training increased significantly the flexion strength by 14% (p = 0.001). During the detraining period, all measured strength values in the training group decreased in both limbs with respect to values after training. Despite the clear effect on muscular strength, no significant intergroup differences were observed in BMC, BMD, bone width, CWT, or CSMI values at any measured site after the training or detraining period. The estimated loading-induced strains remained within customary loading, and the change in strain level was only 15%. In conclusion, this study indicated that using high-resistance strength training may not provide an effective osteogenic stimulus for bone formation and geometric changes in upper limb bones of young, healthy, adult women. The interaction of bones and muscles may play an important and relatively unrecognized role in the development of bone strength, suggesting that the entire biomechanical environment should be carefully considered when evaluating the osteogenic efficiency of physical loading.

Late changes in bone mineral density of the proximal tibia following total or partial medial meniscectomy. A randomized study

The adaptive bone remodeling in the proximal tibia following medial meniscectomy was measured quantitatively by dual photon absorptiometry. Thirty-three patients who had undergone a meniscectomy (randomized to either total [n=19] or partial [n=14] meniscectomy) performed by open joint surgery approximately 12 years earlier were included in the study. Bone mineral density was measured in the previously injured legs and in the healthy contralateral legs in areas located medially and laterally in the cortical bone of the subchondral plates and below in the trabecular bone of the medial and lateral tibial condyles. The distribution of bone mineral within the proximal tibia showed a characteristic and significant pattern. In the trabecular bone of the healthy contralateral knees, bone mineral density was 15% higher in the medial tibial condyles compared with the values laterally; a total or partial meniscectomy increased this difference to 25%. With regard to the cortical bone of the subchondral plates, the bone mineral density in the healthy knees was 24.8-29.4% higher medially than laterally, whereas after total and partial meniscectomy the differences were, respectively, 37.7 and 41.4%. No significant differences in the distribution of bone mineral density, at either cortical or trabecular measuring sites, were found between totally and partially meniscectomized knees.

Estimation of various mechanical characteristics of human bones using dual energy X-ray absorptiometry: methodology and precision

The mechanical competence of bone is determined by its macroscopic geometric characteristics [size, shape, apparent density (BMAD), cortical thickness (CWT), cross-sectional area, trabecular architecture], intrinsic material properties (stiffness, strength), and loading conditions (mode, direction, rate) at a given skeletal site. The main objective of this study was to introduce precise methods for further analysis of dual energy X-ray absorptiometric (DXA) data and for estimating macroscopic mechanical characteristics of bone at several skeletal sites representing both the axial and appendicular skeleton. This study showed that using computational BMAD, CWT and dimensional parameters, different site-specific mechanical characteristics (stiffness and strength indices) of a typical long bone (a bone consisting of both the cortical shaft and trabecular metaphyses and epiphyses at both ends) can be approximated with a low precision error (generally < 2%). The efficacy of a study applying DXA may be further enhanced by applying relevant site-specific parameters (different parameters for bone ends and shafts) for evaluation, the parameters based on the anatomic ROIs. Evidently high-quality operator performance is a prerequisite for effective accomplishment of longitudinal studies, especially when small changes in bone characteristics are expected. It should be kept in mind that to some extent the inherent two-dimensional nature of the DXA measurement compromizes the potential efficacy of the presented methods since some simple assumptions had to be made regarding the geometry and structure of bone. Nevertheless, in this study the observed values were consistent with those found by other investigators. Further experimental studies are needed for direct site-specific validation of the proposed analytic methods.

Assessment of the skeletal status by peripheral quantitative computed tomography of the forearm: short-term precision in vivo and comparison to dual X-ray absorptiometry

In order to assess precision of peripheral quantitative computed tomography (pQCT), duplicate bone mineral density (BMD) measurements at the radius were performed in 20 healthy premenopausal, 20 healthy postmenopausal, and 20 osteoporotic postmenopausal women using a Stratec XCT-960 system. The short-term reproductibility in vivo for the total, trabecular, and cortical regions of interest (ROI) was expressed as the absolute precision error (standard deviation, SD) and as the relative precision error (SD/mean x 100, or coefficient of variation, CV, in %). Reproducibility in vivo was good in all volunteers but was influenced by the study group and the ROI. The precision error for trabecular BMD was 3 mg/cm3, or about 1.6%. This is large relative to the aging decrease of 0.22%/year, or to the difference (12 mg/cm3, or 7%) between osteoporotic women and postmenopausal controls. In order to compare pQCT to dual X-ray absorptiometry (DXA) at the forearm and at the lumbar spine (L1-L4), 40 premenopausal healthy controls, 40 postmenopausal healthy controls, and 35 postmenopausal osteoporotic women were assessed. DXA measurements performed at the ultradistal, middistal, 1/3, and total ROI of the radius showed only moderate correlations between r = 0.38--0.75, r = 0.27--0.64, and r = 0.38--0.53 for the comparison versus pQCT total BMD, versus pQCT trabecular BMD, and versus pQCT cortical BMD, respectively. Correlations of DXA at the lumbar spine and pQCT were between r = 0.18 and 0.44. DXA at radius and spine was able to discriminate between post- menopausal controls and osteoporotic women (p = 0.001--.004),but BMD measurements by pQCT did not show this ability (p = 0.15--0.52). However, two nonstandard pQCT parameters, namely the surface area of the cortical bone and the cortical BMC were factors that discriminated well between these two groups (p = 0.002, p = 0.005, respectively). These pQCT parameters also yielded the highest relative annual changes in pre- and post-menopausal control subjects. The measurement of cortical bone in the distal radius proved to be a good predictor of vertebral fracture status and was a good indicator of age-related skeletal change. Our data emphasize the importance of cortical measurements when using pQCT of the radius to assess osteoporosis.

A rotator cuff rupture produces permanent osteoporosis in the affected extremity, but not in those with whom shoulder function has returned to normal

Areal bone mineral density (BMD) and clinical status of 34 men treated surgically 9 years earlier for a rotator cuff rupture of the dominant side shoulder were determined. The BMD was measured at the lumbar spine (L2-L4) and the proximal humerus, humeral shaft, radial shaft, ulnar shaft, distal forearm, and hand of both extremities using a dual-energy X-ray absorptiometric (DXA) scanner. Thirty-four age-, height-, weight-, and profession-matched normal men (controls) were also measured. The patients' mean side-to-side BMD difference (dominant minus nondominant/nondominant x 100%) was significantly lower in the proximal humerus (patients -3.5% vs. controls +2.4%, p = 0.0002), humeral shaft (-2.6% vs. +1.6%, p = 0.0005), radial shaft (-0.4% vs. +1.9%, p = 0.0311), distal forearm (-0.2% vs. +2.4%, p = 0.0158), and hand (+2.3% vs. +4.0%, p = 0.0047). In the ulnar shaft, this difference was almost the same in the patients (-0.2%) and controls (+0.2%) (NS). Also, the lumbar spine BMD did not differ significantly between these groups (mean +/- SD = 1.098 +/- 0.148 g/cm2 in patients vs. 1.066 +/- 0.156 g/cm2 in controls). In patients, the relative BMDs of the injured extremity did not significantly associate with the size of the rupture; time delay between the injury and the surgery; type of surgery and postoperative treatment; postoperative immobilization time; follow-up time; patient's age, muscle strength or pain assessment; and subjective assessment of shoulder function. However, they strongly associated with the objective assessment of the shoulder function: the better the observed function of the shoulder, the less bone loss caused by the injury.(ABSTRACT TRUNCATED AT 250 WORDS)

Reduced bone mineral density in men with a previous femur fracture

This study determined the areal bone mineral density (BMD) from the lumbar spine (L2-4), right distal radius and ulna, and the femoral neck, trochanter area of the femur, distal femur, patella, proximal tibia, and calcaneus of both extremities in 29 men who had a femur shaft fracture 10 years earlier. For evaluation of the patients' BMDs in the spine and distal forearm, 29 age-, weight-, and height-matched normal men were also measured. Compared with normal men (mean +/- SD = 1.123 +/- 0.153), the spinal BMDs of the patients were significantly (p = 0.0054) lower (1.018 +/- 0.119, -9.3%). Distal radius and distal ulna showed no significant group differences. In patients, the mean BMD of the injured extremity (compared with the uninjured side) was significantly lower in the distal femur (-6.8%; p = 0.0000), patella (-5.4%; p = 0.0000), proximal tibia (-4.7%; p = 0.0000), and calcaneus (-2.2%; p = 0.0259). In the proximal femur, this value was at the same level (femoral neck 1.3%, NS) or higher (trochanter area 6.3%, p = 0.0002) than that in the uninjured extremity. The relative BMDs of the injured extremity did not associate with the fracture type, fracture location, age, muscle strength, follow-up time, or non-weight-bearing time but showed significant (r = 0.33-0.64) positive correlation with low pain assessment and high functional scores of the injured extremity.(ABSTRACT TRUNCATED AT 250 WORDS)

Quantifying the effect of hand preference on upper limb bone mineral and soft tissue composition in young and elderly women by dual-energy X-ray absorptiometry

The purpose of this study was to quantify the effect that hand preference has on upper limb bone mineral and soft tissue composition in healthy young and elderly women. Bone mineral content (BMC) in grams, bone mineral density (BMD) in g cm-2, fat-free soft tissue (FFST) in grams, fat tissue (g), and percent fat were determined by dual-energy X-ray absorptiometry (DXA) for dominant and non-dominant upper limbs as well as total body fat (%) in 25 young (26.6 +/- 4.3 years, mean +/- SD) and 35 elderly women (68.4 +/- 2.9 years). For both groups, the dominant upper limb had a greater BMC (P < 0.001), BMD (young, P < 0.001; elderly, P < 0.05), and FFST mass (P < 0.001), and a lower percent fat (young, P < 0.01; elderly, P < 0.05) than the non-dominant limb; however, there was no difference between limbs for total fat mass. BMC, BMD, and FFST in the dominant limb of young women were 7.1%, 1.8%, and 5.1% greater than the non-dominant limb, while for older women the differences were 5.3%, 1.0%, and 4.2%. Relative fat of the dominant limb was 3.0% and 1.3% less than the non-dominant limb for young and older women, respectively. Age did not affect the percent bone mineral or soft tissue difference. A higher bone mineral and FFST mass in the dominant limb is expected due to the greater activity demands placed upon these tissues. However, a larger bone and FFST mass increases the total mass of the dominant limb, resulting in a dilution of the fat tissue mass and hence a reduced fat percent for the limb. This study indicates that hand preference affects the tissue composition of the upper limb in both young and elderly women, resulting in an increased bone mineral and FFST mass with no change in absolute fat mass. Hand preference should be taken into account when upper limb bone mineral and/or soft tissue composition is assessed.

The site-specific effects of long-term unilateral activity on bone mineral density and content

This study assessed the site-specific effects of long-term tennis playing on the bone mineral density (BMD) and content (BMC) of upper extremities in male Finnish top-level players using a dual energy x-ray absorptiometric (DXA) scanner. In players (n = 20), the BMDs and BMCs were significantly higher in each bone of the playing right extremity (p < 0.05-0.001), the side-to-side difference being largest in the humeral shaft (BMD + 25.4%, BMC + 28.7%) and proximal humerus (BMD + 14.4%, BMC + 20.5%), and smallest in the ulnar shaft (BMD + 3.1%, BMC + 7.5%) and distal ulna (BMD + 6.3%, BMC + 7.8%). In sex-, age-, weight-, and height-matched controls (n = 20), the right-to-left differences were small ranging from 0.0% to + 6.4% (average +3%). The number of training sessions per week was the only variable in muscle strength and training history assessment which showed, in several anatomic sites, a significant correlation with the relative bone mineral variables (r = 0.460-0.627, p < 0.05-0.001). In conclusion, long-term unilateral tennis activity had a clearly positive effect on the BMD and BMC of the bones of the playing extremity. The effect was very site-specific, being greatest in the humerus and smallest in the ulna. The effect was always greater in BMC than BMD indicating that the excess mineral was used not only for condensation of the bone tissue, but also for enlargement of bone dimensions.(ABSTRACT TRUNCATED AT 250 WORDS)

Long-term unilateral loading and bone mineral density and content in female squash players

We examined 19 female Finnish national level squash players and 19 healthy female controls with a dual energy x-ray absorptiometric (DXA) scanner for the determination of the association between long-term unilateral activity and bone mineral density (BMD) and content (BMC) of the upper extremities. In players, the BMDs and the BMCs were significantly higher in each bone site of the playing extremity. The side-to-side difference was largest in the proximal humerus (BMD 15.6%, BMC 17.8%) and smallest in the ulnar shaft (BMD 5.6%, BMC 7.3%). In sex-, age-, weight-, and height-matched controls, the side-to-side differences were significantly smaller, ranging from 1.6% to 4.1%. The number of training years and elbow flexion strength correlated positively with the relative BMD and BMC in the humerus of the playing arm (r = 0.632-0.685). The starting age of training in turn correlated negatively (r = -0.483 to -0.577) with these bone parameters. Significantly larger side-to-side differences (average 22%) were found in players who had started their career before or during menarche than in those who had begun the training 1 year or more after the menarche (9%). These findings suggest that the bones of the playing extremity clearly benefit from active squash playing. The benefit is largest in humerus and smaller in the bone of the forearm. The benefit of playing is stronger if the athlete has started the training at or before menarche than after it.(ABSTRACT TRUNCATED AT 250 WORDS)

Precision of measurement by dual-energy X-ray absorptiometry of bone mineral density and content in rat hindlimb in vitro

Dual-energy x-ray absorptiometry (DXA) is a precise and effective method for measuring bone mineral density (BMD) and content (BMC) at various skeletal sites in the human, but its precision for measuring low BMD and BMC in tiny rat bones has scarcely been evaluated. The short-term precision of DXA (Norland XR-26) for eight regions of interest (ROI) was determined by measuring dissected, not totally defleshed hindlimbs from four rats of differently weights 10 times consecutively. The accuracy of the BMD (area) measurement was also evaluated. The following average precision values (coefficients of variation) with negligible reanalysis error were obtained for BMD and BMC measurements: 0.7 and 1.2% (total); 0.9 and 1.2% (femur); 1.3 and 2.8% (tibia); 1.3 and 2.1% (foot); 2.1 and 4.7% (proximal femur); 1.4 and 2.9% (femoral shaft); 1.8 and 5.6% (distal femur); and 2.7 and 7.6% (proximal tibia). As for the accuracy, BMD measured in tiny bones is likely to be markedly underestimated. We conclude that the standard DXA technique without additional modification for small animal measurements is a precise method for BMD and BMC measurements at multiple sites in rat hindlimb in vitro.

Osteoporosis in men with a history of tibial fracture

The long-term effects of bone fractures on bone mineral density (BMD) at various skeletal sites are poorly established, although a serious fracture, such as a tibia fracture, followed by long immobility and disuse may lead to permanently decreased BMD and, through this mechanism, may be a risk factor for osteoporotic fractures in later life. To determine whether such an injury leads to osteoporosis, we measured the areal BMD (g/cm2) from the lumbar spine (L2-4), right distal radius and ulna, and the femoral neck, distal femur, patella, proximal tibia, distal tibia, and calcaneus of both extremities in 14 men with a history of primarily nonunited (finally bone-grafted) shaft fracture of the tibia and 20 men with a history of primary union. For evaluation of the patients' BMD in the spine and distal forearm, 22 age-, weight-, and height-matched normal men were also measured. The average time of immobilization in a long plaster cast was 27 weeks in the former group of patients and 16 weeks in the latter. The measurements were performed an average of 9 years after the fracture using a dual-energy x-ray absorptiometric scanner. Compared with normal men (mean +/- SD = 1.116 +/- 0.160), the spinal BMDs were significantly lower in men with a history of a primary nonunion (0.979 +/- 0.100, -12.3%) and union (1.010 +/- 0.124, -9.5%). In distal radius and distal ulna, there were no significant differences between the three groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Dual energy X-ray absorptiometry is also an accurate and precise method to measure the dimensions of human long bones

The accuracy, as well as the in vitro and in vivo precision of width and length measurements of human humerus and femur from dual energy X-ray absorptiometry (DXA) images, was investigated. The measurement was based on the bone area inside a specified region determined by the bone edge detection software of the scanner. The accuracy and in vitro precision studies were performed using a bone-simulating aluminum phantom embedded in different amounts of water. The in vivo precision was determined by measuring both limbs twice in 10 subjects (for humerus) and in 9 subjects (for femur). The accuracy was not significantly affected by the amount of water, and varied from 0.6 to 1.2%. Similarly, the in vitro precision varied from 0.4 to 0.6%. The average in vivo precision of the width measurement ranged from 0.4% (humeral and femoral midshaft) to 0.9% (proximal humerus), not depending on the size of the measured bone. The precision of the length measurement was 0.3% for the humerus and 3.7% for the femoral neck. In conclusion, the standard DXA technique provides a reliable measurement of the width and length in human humerus and femur in vivo, and thus may be useful in evaluating the properties of these bones in conjunction with the standard bone mineral measurements. Specifically, studies evaluating the effects of various types of mechanical loading (exercise) on bone may greatly benefit from this possibility because not only the bone mineral content and density but also the bone geometry change due to loading.