This study examined healing of 1.0 mm diameter defects in rabbit knee articular cartilage for as long as 14 weeks after creation of the defects by either laser or drilling. The purpose of the research was to determine the effects of laser debridement of cartilage on the intrinsic biomechanical properties of the repair tissue. We therefore imitated chondral shaving and subchondral abrasion of cartilage by creating partial-thickness and full-thickness cartilage defects of standardized size with both excimer laser and drilling. Light and scanning electron microscopic examinations of the repair tissue showed that healing of osteochondral defects created by laser may be delayed compared with defects created by drilling, for at least 6 weeks postoperatively. Even though there initially was a considerable delay in healing in the laser group, neither laser nor drilling had any appreciable effects on the mechanical properties of the repair tissue, as demonstrated by biomechanical testing at 14 weeks. Specifically, the repair cartilage in the defects in the laser group had the following material properties (mean +/- SD): aggregate modulus, 0.40 +/- 0.24 MPa; Poisson's ratio, 0.37 +/- 0.08; permeability, 3.72 +/- 4.28 x 10(-15) m4/N.s; and thickness, 0.20 +/- 0.06 mm. The corresponding values for the defects in the drilling group were 0.39 +/- 0.23 MPa, 0.34 +/- 0.09, 3.82 +/- 3.44 x 10(-15) m4/N.s, and 0.22 +/- 0.09 mm. The repair tissue from both types of defects was pooled, and the values were compared with those for contralateral (control) tissue.(ABSTRACT TRUNCATED AT 250 WORDS)
Excimer laser is used for cartilage debridement, although the resulting cell damage is yet unclear. For examination of cartilage survival after treatment, we used short-term tissue cultures of human joint cartilage. Specimens were treated with a XeCl-Excimer laser using different laser parameters, pulse energies, and repetition rates. Following treatment, discs were cultured for 8 days prior to examination. In contrast to the 20 microns damage zone as instant visible effect in histomorphologic examinations, we found a 0.3 mm zone in which approximately 50% of cartilage cells had morphological signs of damage on light microscopic examinations. Autoradiography revealed that cartilage cells in an 0.5-0.7 mm area surrounding the laser craters had no collagen synthesis. This examination indicates that cell damage of excimer laser is higher than expected from prior studies.
Worm reeflets discribed here are composed of parallel and straight, curved, or bifurcated tub es, which are up to 10 cm long and have an average diameter of 1.4 mm. Their walls are composed of microgranular calcite and are multilamellar. The reef-builders settled on soft bottoms within the tidal or uppermost zone. They tolerated high water turbulence and a certain rate of sedimentation. Dead parts of the reef were recolonlzed by a new population. The reefs stabilized the sediment, produced biogenic debris, and offered new ecological niches for endo-and epilithic organlsms. They mark a regional ecologlcal event at the Oligocene/Miocene boundary. Diplochaetetes mexicantlS as weil D. longituhtls demonstrate e10se relationships to a modern skeletal-forming polychaete \Vorm, Dodecar/(I. Dlplochaetetes Is definltly not a selerosponge and demonstrates a convergence with the chaetetid basal skeletons of sponges and favositld corals. REsUME ful suggestions. Dr.E. Gierlowski-Kordesch, Berlin, helped with English correctlons and critlcal readlng of the manuscript. The present study was supported financially by DMD. To all above-766mentioned persons and Institutions, we experss our sincere thanks. Geobios 11 0 22, fase. 6 PI.
Background und Objective: The aim of the present study was to clarify which of the presently available continuous-wave laser systems are best suited for application in stapes surgery. Study DesignlMuterhZs and Methods: Isolated human stapes and bovine compact-bone platelets were used to investigate the connections between the parameters of various laser systems and their effects on bone tissue. The purpose was to optimize the laser parameters required to achieve a perforation measuring 500 pm to 600 pm in diameter. Three different laser systems were applied: the argon and COz laser in continuous wave (cw) mode and the COz laser in superpulse mode. Results: The suitability of the argon laser for stapedotomy is doubtful in view of the lower absorption coefficient of the stapes for the argon beam and the considerable influence which the degree of pigmentation of the irradiated medium exerts on its effect with the resultant poor reproducibility of the perforation diameter. The beam of the CO, laser is far better absorbed at the footplate than that of the argon laser. This results in higher effectivity, lower thermic side effects, and better reproducibility of the perforation. The two modes of the CO, laser do not show any appreciable differences. Conclusion.-The experimental results presented indicate that the C02 laser in cw and superpulse mode is the most suitable of the systems now clinically applied in stapes surgery. 0 1996 Wiley-Liss, Inc.
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