MICROVASCULAR RESEARCH 37, 105-I 14 (1989) TECHNICAL REPORT A Horizontal lntravital Microscope-Plus-Bone Chamber System for Observing Bone Microcirculation H. WINET Department of Orthopaedics, University of Southern California and Orthopaedic Hospital, Los Angeles, California 90007 Received March 10, 1988 A horizontal intravital microscope has been built which utilizes the telescope optics format with infinity-corrected objectives. The intravital stage accomodates a rabbit into which a tibia1 bone chamber has been implanted. The chamber is itself an optical component and is considered an integral part of the system. Each animal is observed in supine position with its implanted leg held in an adjustable spring-loaded yoke which aligns the bone chamber in the optical axis. Long working-distance objectives and condensers allow for viewing of the slit-gap tissue in the bone chamber with both transmitted and epi-illumination; the latter being applied for fluorescence studies. A unique feature of the system is a transfer lens holder which can be relocated within the microscope tube. This adjustable lens holder allows for changing of transfer lenses, thereby freeing the investigator to utilize objective lenses with preferred numerical apertures for a given image size. Q 1989 Academic Press, Inc. INTRODUCTION Prior to the development of the tibia1 bone chamber by Branemark (1964) and his student Albrektsson (Albrektsson and Albrektsson, 1978) and McCuskey and McClugage (1971) there was no technique for chronic observation in situ and in vivo of neovascularization and microcirculation in bone comparable to the ear chamber technique. One limitation of these devices was their lack of a provision for permanently exposing the implant to allow for observation intervals less than 2 weeks. Moreover, the need to anesthetize the rabbit at each exposure-observation session seriously altered microcirculation thereby reducing the relevancy of its measurement. The titanium-quartz bone chamber described herein, together with its management protocol, allows for permanent exposure of the implant from W3 (the third week postimplantation) until at least W8. (No projects have yet required longer.) It may also be easily adapted for marrow observations. Another limitation of previous techniques is the design of the intravital microscope (IM). The Albrektsson system (Albrektsson and Albrektsson, 1978) is vertically oriented and requires that the rabbit lie on its side with its implanted leg bolted to a heavy metal plate. This arrangement places considerable shear stress on the bone-implant interface and creates a temporary compartment syndrome in 105 0026.2862/89 $3.00 Copyright 0 1989 by Academic Press, Inc. All rights of reproduction in any form reserved. Printed in U.S.A.