THE FORMATION OF HETEROTOPIC OSSIFICATION AFTER TRAUMATIC BRAIN INJURY - A BIOPSY STUDY WITH ULTRASTRUCTURAL ANALYSIS

Heterotopic bone with different maturation stages was obtained from se ven patients with spasticity secondary to traumatic brain injury. The specimens were studied under light and electron microscopy to determin e the nature and sequence of formation of heterotopic ossification (HO ). The findings revealed that immature heterotopic bone was made up of well-ordered collagen fibers with speckles of calcification distribut ed throughout the collagen network. No osteoid was observed in any spe cimen. Inflammation appears to be a secondary process beginning after the initial stages of calcification. The appearance of osteoblasts and osteoclasts with remodeling of the immature bone occurs as a very lat e process. These findings provide a new insight into the nature of HO and may influence future treatments.