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Regional distribution of circulating microspheres in the femur of the rabbit
Abstract:
In an attempt to explain the distribution of lesions of caisson disease of bone in the human femur, the regional distribution of circulating microspheres which had been labelled with scandium-46 was studies in the femur of the rabbit. Microspheres with a diameter of 15 microns were equally distributed between the two ends of the bone and between the upper and lower halves of the shaft. However, microspheres with a diameter of 50 microns congregated in the upper end of the femur and in the lower half of the shaft, the two sites most commonly affected by caisson disease. A large percentage of the microspheres in the shaft, especially the larger spheres, were retained in the marrow. It is suggested that the microcirculation of the marrow may act as a filter and that the nature and distribution of its vessels determine the site of impaction of circulating emboli. This would explain why lesions of the shaft mainly affect the medulla of the bone and not the cortex.
Insights
Caisson disease bone lesions may be explained by microsphere distribution. Larger microspheres, like emboli, accumulate in specific femur regions, suggesting marrow microcirculation acts as a filter.
Area of Science:
- Orthopedic research
- Bone pathology
- Vascular biology
Background:
- Caisson disease (decompression sickness) causes bone lesions, particularly in the femur.
- The precise mechanism and location of these bone lesions remain incompletely understood.
- Understanding the vascular dynamics within bone may elucidate lesion distribution patterns.
Purpose of the Study:
- To investigate the regional distribution of circulating microspheres within the rabbit femur.
- To correlate microsphere distribution with known lesion sites of caisson disease.
- To propose a mechanism for the preferential localization of bone lesions.
Main Methods:
- Scandium-46 labeled microspheres of 15 and 50 microns in diameter were administered to rabbits.
- The regional distribution of these microspheres within the femur was analyzed.
- Microsphere retention within the bone marrow was quantified.
Main Results:
- Fifteen-micron microspheres showed even distribution throughout the femur.
- Fifty-micron microspheres preferentially accumulated in the upper femur and lower shaft.
- A significant percentage of larger microspheres were retained within the bone marrow.
Conclusions:
- The microcirculation of the bone marrow may function as a filter for circulating emboli.
- The vascular architecture of the marrow dictates the impaction sites of emboli.
- This mechanism explains why caisson disease lesions predominantly affect the bone medulla rather than the cortex.
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