Periosteal and endosteal microcirculatory injury following excessive osteosynthesis.

INTRODUCTION: We examined the endosteal and periosteal circulations in a patient with fracture non-union who had undergone excessive osteosynthesis applications (two long plates had been placed medially and laterally on the left tibia extending from the proximal 2/7 to the distal 6/7 parts of the bone, while a tibial component of a total knee prosthesis with a long stem had been inserted at the same time). METHODS: Concomitant perfusion changes were determined in the anterolateral and anteromedial periosteal sheath of the non-united bone ends and intramedullary nearest the osteosynthesis materials during their surgical removal on re-operation. The blood flow in the periosteum and endosteum was recorded by a laser-Doppler flowmetric device using a novel approach. Control measurements were made at identical points of the right tibia. RESULTS: Considerably lower blood flow values were measured along the tibial periosteal region of the re-operated limb than on the contralateral side (the average perfusion unit (PU) was 76 vs. 106 PU, respectively). Perfusion values were markedly lower in the endosteal region (average values of approx. 30 PU) in the control tibia and were even more diminished in the re-operated tibial endosteum (average 9 PU). CONCLUSIONS: Our study was conducted to characterize the microcirculatory changes of a long bone in response to intramedullary implantation and to provide quantitative data on the insufficiency of local perfusion in a patient with fracture non-union. Our results highlight the association between local perfusion failure and the unfavorable outcome (i.e. fracture non-union), confirming that the vital aspects of the microcirculation should not be disregarded when aiming for mechanical stability. Microcirculatory measurements constitute a new area of improvement in planning the adequate treatment for fracture non-unions with an unclear aetiology. Further refinement of the laser-Doppler technique could have potential benefits for bone surgery and postoperative trauma care in the future.

[Experimental studies of microcirculatory changes in the bone]. / A csont mikrokeringési változásainak kísérletes vizsgálati lehetoségei.

INTRODUCTION/AIMS: Our aim was to characterize the periosteal microvascular reaction induced by the destruction of endosteal vasculature by reaming, and to monitor the time sequence of the events. We have also compared the microcirculatory effects of different implant materials that are most frequently employed in human endoprosthetics. MATERIALS AND METHODS: The right tibia of male Wistar rats was reamed by microsurgical means and implanted with titanium, steel-alloy or polyethylene nails. Intravital videomicroscopic examinations of the anteromedial and anterolateral surfaces of the tibial periosteum were performed to evaluate the changes in the overall vascular and capillary densities. Microscopic mechanical tests were used to assess the stability of the implants. In control groups, reaming without nailing was performed and the microvascular changes were examined 6 and 12 weeks after surgery. RESULTS: Reaming alone caused a significant increase in the vascular density of the anteromedial periosteum and a bilateral increase in capillary density. Vascular density at the anteromedial side was increased after all of the implant materials applied, while only polyethylene induced remarkable increases in the capillary and vascular densities at the anterolateral side. Furthermore, polyethylene did not bring about osseointegration. CONCLUSIONS: Enhanced periosteal angiogenesis could be demonstrated after 12 weeks following tibial reaming. The compensatory microvascular reactions evoked by destruction of endosteal microcirculation of long bones are not influenced by osseo-integrative implant materials, but materials of poor osseointegration properties induce considerable compensatory increases in the microvascular density of the periosteum.

Periosteal microvascular reorganization after tibial reaming and intramedullary nailing in rats.

BACKGROUND: Intramedullary reaming and nailing of long bones impairs the endosteal circulation, often causing necrosis of the inner region of the bone cortex. We hypothesized that compensatory hypertrophy of the periosteal microcirculation may develop in response to mechanical destruction of the endosteum, and that this may affect bone survival in these circumstances. In these studies, nailing was performed with materials that affect regeneration of the endosteum differently, and the effects on the tibial periosteal microvasculatory organization were examined. METHODS: In male Wistar rats, the right tibia was reamed and implanted with an inert titanium nail or a less osseointegrative polyethylene nail; the contralateral tibial endosteum was destroyed by reaming. Reaming without nailing or sham operation was performed on both extremities in two other groups of rats. Twelve weeks later, the anteromedial and anterolateral surfaces of the tibias were exposed by a microsurgical technique. The structural characteristics of the periosteal microcirculation (vessel density and distribution of vessel diameters) were determined by intravital videomicroscopy and computer-assisted analysis. The stability of the implants was assessed on the basis of grades 0-2 on a qualitative scale. RESULTS: Tibial reaming alone caused significant increases in overall blood vessel and capillary densities in the periosteum compared with those of the intact tibias. Implantation with a titanium nail resulted in firm embedding of the nail and caused changes in the periosteal vasculature similar to those after reaming alone. In contrast, implantation of a polyethylene nail was followed by the development of marked instability of the endomedullary implant and significant increases in the percentage of capillaries and the vessel density in the periosteum. CONCLUSIONS: Destruction of the endosteal microcirculation per se brings about an increase in periosteal vascular density, which is further augmented if implantation is performed with a material which delays regeneration of the endosteal circulation.

Periosteal microcirculatory action of chronic estrogen supplementation in osteoporotic rats challenged with tourniquet ischemia.

AIMS: Transient ischemia of osteoporotic bones during elective orthopedic surgery or fracture repair carries risks for serious complications, and estrogen loss or replacement has a potential to influence ischemia-reperfusion-induced inflammatory activation. To clarify this, we investigated the periosteal inflammatory changes in a clinically relevant time frame in ovariectomized rats, an experimental model of postmenopausal bone loss. Furthermore, the effects of chronic estrogen supplementation on the postischemic local and systemic inflammatory reactions were assessed. MAIN METHODS: Bilateral ovariectomy or sham operation was performed in 3-month-old female Sprague-Dawley rats. Five months later, estrogen replacement therapy with 17ß-estradiol (20 µg(-1) kg(-1) day(-1)) or vehicle treatment was initiated. The microcirculatory inflammatory consequences of 60-min total hindlimb ischemia followed by 180-min reperfusion were examined 11 months after ovariectomy and were compared with those in 3-month-old animals. KEY FINDINGS: The osteoporosis that developed 5 months after ovariectomy was significantly ameliorated by estrogen replacement therapy. Both in ovariectomized and in non-ovariectomized animals, ischemia-reperfusion elevated the neutrophil adherence ~3-fold in the postcapillary venules of the periosteum (intravital microscopy), with an ~50-60% increase in intravascular neutrophil activation (CD11b; FACS analysis), an enhanced TNF-α release (ELISA) and periosteal expression of ICAM-1 (the endothelial ligand of CD11b; immunohistochemistry). Exogenous 17ß-estradiol considerably reduced TNF-α release and the number of neutrophil-endothelial interactions in the periosteum, without affecting the CD11b and ICAM-1 expression changes. SIGNIFICANCE: Osteoporosis itself does not increase the magnitude of the limb ischemia-reperfusion-associated periosteal inflammatory reaction. Chronic estrogen supplementation, however, reverses osteoporosis and significantly ameliorates the microcirculatory consequences of transient ischemia.