ABSTRACT: Distraction osteogenesis is an established method of treatment of non-unions and limb length discrepancies. Despite improvements in surgical techniques and fixation devices there is still a considerable possibility of failure of the regenerate bone after frame removal. The hypothesis of the present experimental study was that a noninvasive bone strength marker, the strength-strain index (SSI) measured by peripheral quantitative computerized tomography (pQCT), could be significantly correlated with a biomechanical bone strength index, the maximum load at bone failure (F(max)), assessed in a three-point bending test. The right tibias of fifteen male New Zealand White rabbits were subjected to gradual lengthening using an external fixator. At the end of the consolidation phase (55th day) the animals were sacrificed and the lengthened tibiae were collected free of soft tissue, after removal of the lengthener, for immediate scanning and mechanical testing. The values of cortical bone mineral density, cortical bone area, and the corresponding SSIy, as measured by pQCT, were assessed for statistically significant correlation relative to the values of the F(max) and stiffness as evaluated by the three-point bending test were assessed. SSIy showed a statistically significant positive correlation with the maximum load (F(max)) with a correlation value R=0.846 (p<0.001), and it was a good predictor of F(max) since it was able to describe the 71.6% of variability of F(max)(R2=0.716). Furthermore, cortical bone area appeared to be highly correlated with F(max) (p<0.005), but it was a less efficient predictor of F(max) (R2=0.471). There was, also, a statistically significant correlation between SSIy and bone stiffness as assessed in the 3-point bending test (p<0.005). In conclusion, the present study reveals that the SSI can be used as a sensitive index of adequate consolidation of the regenerate bone, possibly able to reduce mechanical failure due to premature frame removal. In clinical relevance, the aforementioned hypothesis should be applied in studies of human populations and possible confirmation of its validity would establish pQCT as a valuable diagnostic tool not only in distraction osteogenesis but also in other techniques of bone healing.
Bone 07/2009; 45(3):512-6. · 4.02 Impact Factor
ABSTRACT: Bone changes are a prominent symptom of beta-thalassemias, related to expansion of bone marrow and reduction of bone density. Conventional treatment ameliorates bone changes and improves survival, thus increasing the morbidity of bone diseases in adulthood. Peripheral quantitative computer tomography (pQCT) was used recently to assess the changes in volumetric bone mineral density (vBMD) in various bone compartments.
Assessment of indices of bone density and structure in patients with thalassemia major (thal-major) and intermedia (thal-interm) on conventional therapy and in healthy adults.
45 patients with thal-major, 27 with thal-interm and 32 healthy individuals aged 21-42 years were studied by pQCT analysis. The vBMD total (tot), trabecular (trab) and cortical (cort), the bone mineral content (BMC), the cross sectional area (CSA), the cortical thickness (CRTHK) and the stress strain index (SSI) were assessed at the 4% site of the distal radius.
Tot, trab, and cort vBMD, BMC, and cortical thickness showed statistically significant differences among the three groups with significant reduction in thalassemics. No significant differences were found in the three groups with CSA and SSI. Impairment of bone density and structure in Greek thalassemics on proper treatment was not as severe as expected. A significant proportion of patients had bone density indices within the normal range and above the 10th percentile of normal.
Peripheral QCT analysis is a convenient method to study the regional changes of bone density in patients with thalassemia. These changes affect mainly the cortical compartment and are more pronounced in thalassemia intermedia.
Pediatric endocrinology reviews: PER 11/2008; 6 Suppl 1:127-31.
ABSTRACT: Primary hyperparathyroidism (PH) is characterized by inappropriate PTH elevation with or without hypercalcemia. Bone disease involves catabolic action at cortical sites, whereas cancellous sites and geometry might be relatively preserved.
Our objective was to examine the effect of PH on quantitative and qualitative bone characteristics using peripheral quantitative computed tomography at the tibia in postmenopausal women with PH and healthy controls.
We conducted a cross-sectional study at a tertiary referral center.
Fifty-two postmenopausal women with PH and 56 healthy controls, comparable for age and anthropometric measures, participated.
There was no intervention.
We assessed volumetric bone mineral density (vBMD), bone mineral content (BMC), cortical thickness, cortical and trabecular area, peri- and endosteal circumference, and polar stress strength index assessed by peripheral quantitative computed tomography of the left tibia at 4% (cancellous), 14% (transition zone), and 38% (cortical) from the distal end.
At 4%, there was a significant decrease of trabecular BMC and vBMD (P < 0.001), effect particularly evident in hypercalcemic patients, whereas trabecular area was comparable. At 38%, cortical BMC (P < 0.01), vBMD (P < 0.01), area (P < 0.05), and thickness (P < 0.001) were reduced in the PH group, particularly in hypercalcemic patients. Endosteal circumference increased (P < 0.001), whereas periosteal circumference was comparable, indicating cancellization of cortical bone. At 14%, polar stress strength index was significantly decreased (P < 0.01) in hypercalcemic patients, indicating impairment of bone mechanical properties.
Normocalcemic PH is characterized by catabolic actions at both cortical and cancellous sites (38 and 4%, respectively), an effect accentuated in hypercalcemic patients. Cortical geometric properties are adversely affected even in normocalcemic patients, whereas trabecular properties are generally preserved.
Journal of Clinical Endocrinology & Metabolism 06/2006; 91(5):1748-53. · 6.50 Impact Factor