Changes in tibial cortical dimensions and density associated with long-term locking plate fixation in goats

PURPOSE

Cortical porosis, secondary to either vascular injury or stress-shielding, is a comorbidity of fracture fixation using compression bone plating. Locking plate constructs have unique mechanics of load transmission and lack of reliance on contact pressures for fixation stability, so secondary cortical porosis adjacent to the plate has not been widely investigated. Therefore, this study aimed to assess the effects of long-term locking plate fixation on cortical dimensions and density in a caprine tibial segmental ostectomy model.

METHODS

Data was acquired from a population of goats enrolled in ongoing orthopedic research which utilized locking plate fixation of 2 cm tibial diaphyseal segmental defects to evaluate bone healing over periods of 3, 6, 9, and 12 months. Quantitative data included tibial cortical width measurements and three-dimensionally reconstructed slab density measurements, both assessed using computed tomographic examinations performed at the time of plate removal. Additional surgical and demographic variables were analyzed for effect on cortical widths and density, and all cis-cortex measurements were compared to both the trans-cortex and to the contralateral limbs.

RESULTS

The tibial cis-cortex was significantly wider and more irregular than the trans-cortex at the same level. This width asymmetry differed in both magnitude and direction from the contralateral limb. The bone underlying the plate was significantly less dense than the trans-cortex, and this cortical density difference was significantly greater than that of the contralateral limb. These cortical changes were independent of both duration of fixation and degree of ostectomy bone healing.

CONCLUSIONS

This study provides evidence that cortical bone loss consistent with cortical porosity is a comorbidity of locking plate fixation in a caprine tibial ostectomy model. Further research is necessary to identify risk factors for locking-plate-associated bone loss and to inform clinical decisions in cases necessitating long-term locking plate fixation.

Biopsy vs. peripheral computed tomography to assess bone disease in CKD patients on dialysis: differences and similarities

Results from bone biopsy and high-resolution peripheral quantitative computed tomography (HR-pQCT) were compared in 31 CKD patients. There was an agreement mainly for cortical compartment that may represent a perspective on the fracture risk assessment. HR-pQCT also provided some clues on the turnover status, which warrants further studies.

INTRODUCTION

Chronic kidney disease (CKD) patients are at high risk of bone disease. Although bone biopsy is considered the best method to evaluate bone disease, it is expensive and not always available. Here we have compared, for the first time, data obtained from bone biopsy and HR-pQCT in a sample of CKD patients on dialysis.

METHODS

HR-pQCT and dual-energy X-ray absorptiometry (DXA) were performed in 31 CKD patients (30 on dialysis). Biopsies were analyzed by quantitative histomorphometry, and classified according to TMV.

RESULTS

We have found an inverse correlation between radius cortical density measured by HR-pQCT, with serum, as well as histomorphometric bone remodeling markers. Trabecular density and BV/TV measured through HR-pQCT in the distal radius correlated with trabecular and mineralized trabecular bone volume. Trabecular number, separation, and thickness obtained from HR-pQCT and from bone biopsy correlated with each other. Patients with cortical porosity on bone histomorphometry presented lower cortical density at the distal radius. Cortical density at radius was higher while bone alkaline phosphatase was lower in patients with low turnover. Combined, these parameters could identify the turnover status better than individually.

CONCLUSIONS

There was an agreement between HR-pQCT and bone biopsy parameters, particularly in cortical compartment, which may point to a new perspective on the fracture risk assessment for CKD patients. Besides classical bone resorption markers, HR-pQCT provided some clues on the turnover status by measurements of cortical density at radius, although the significance of this finding warrants further studies.

Decreased bone cortical density at the forearm in subjects with subclinical peripheral arterial disease

The association between peripheral arterial disease (PAD) and low bone mass is controversial. In our study, peripheral quantitative computed tomography shows a reduction of cortical but not trabecular, bone mineral density (BMD) at the forearm, in patients with subclinical PAD.

INTRODUCTION

Some controversy exists regarding the association between peripheral arterial disease (PAD) and low bone mass. Previous studies have evaluated bone mineral density (BMD) in patients with subclinical PAD, with mixed results. Inconsistency of data may depend on the fact that most studies measured areal bone mineral density (aBMD) by Dual-energy-x ray absorptiometry (DXA). Because DXA cannot distinguish between cortical and trabecular compartments, we reasoned that a study aimed to establish whether these compartments were differentially affected by PAD status could give more information on the nature of this association.

METHODS

In this cross-sectional study, we used peripheral quantitative computed tomography (pQCT) to examine volumetric cortical and trabecular mineral density at the radius (vBMD) in a cohort of subjects with subclinical PAD as defined by ABI ≤0.90 and compared them with healthy subjects with no evidence of PAD.

RESULTS

Patients with subclinical PAD had significantly reduced cortical density (1101.0 ± 45.4 vs 1156.2 ± 51.3 mg/cm(3), p < 0.001) and cortical area (75.0 ± 20.9 vs 99.9 ± 18.2 mm(2), p < 0.001) than healthy subjects. Trabecular density (178.1 ± 47.9 vs 165.8 ± 29.6 mg/cm(3)) was not significantly different in the two groups.

CONCLUSION

Subclinical PAD induces a selective bone loss at the radius compartment, not identified by standard DXA, which seems to occur primarily at the cortical level.