TEMPORAL BONE DYNAMICS, THE HARD WAY - FORMATION, GROWTH, MODELING, REPAIR AND QUANTUM TYPE BONE REMODELING IN THE OTIC CAPSULE - PREFACE

This review presents studies in which temporal bone dynamics were moni tored in undecalcified human and animal materials by combined microrad iolography and osteofluorochromic time labeling. The results are inter preted in accordance with modern concepts of spatial and temporal orga nization of bone behaviour in an attempt to contribute to a new basis for understanding the structure and function of the bony otic capsule. In postcartilaginous development, perilabyrinthine bone formed a sepa rate functional unit in which growth and modeling were absent. Consequ ently, all drift movements bypassed the bone present inside a narrow p erilabyrinthine zone, which in effect maintained a so-called drift bar rier enclosing the entire inner ear. In baseline bone remodeling and r epair-associated remodeling transients, secondary osteons were distrib uted centrifugally with respect to inner ear spaces, and the average o steonal size decreased towards the inner ear, suggesting a progressive inhibition of bone resorption towards inner ear spaces. No histologic al capsular component proved resistant to bone resorption during model ing and remodeling. Instead the dynamic behaviour of any moiety of cap sular bone appeared to depend on its spatial relation to the membranou s labyrinth rather than on histological characteristics. This spatial organization of perilabyrinthine bone development and turnover is resp onsible for the unique histology of capsular bone and may explain the accumulation of fatigue micro cracks which can be found in human peril a byrinthine bone. These findings suggests the role of inner ear tissu es a's a functional matrix in control of capsular bone dynamics even b eyond fetal life.