[The influence of laser irradiation of low-power density on an experimental cartilage damage in rabbit knee-joints: an in vivo investigation considering macroscopic, histological and immunohistochemical changes]. / Der Einfluss von Laserlichtbestrahlung niedriger Leistungsdichte auf einen experimentellen Knorpelschaden im Kniegelenk des Kaninchens: eine in vivo-Untersuchung unter Berücksichtigung makroskopischer, histologischer und immunhistochemischer Veränderungen.

In a total of 45 rabbits, knee-joint arthrosis was induced according to the Hulth & Telhag model. Depending on the post-operative survival time, the cartilage was investigated macroscopically, histologically and immunohistochemically (within a period of 10 days to 8 months). Thereafter, the influence of laser irradiation at a wavelength of 692.6 nm and energy densities of 1 and 4 J/cm2 on the cartilage morphology seven days following the exposure was examined. After joint instability surgery it was found out that the cartilage changes in the main stress area (MSA) and in regions outside the main stress area (ROMSA) progressed differently. Various qualitative and semi-quantitative changes were found for collagens I, II, IV and V, and for the glycoproteins fibronectin and tenascin. Immunohistochemically, there was a growing expression of collagen I in the apical layers, collagen II showed a stronger pericellular expression, and collagen IV showed, after an initial growth of the pericellular expression, a reduced territorial expression and a stronger apical-interterritorial expression in the osteoarthrotic cartilage. For fibronectin, the cellular expression turned out to grow in the ROMSA. In the MSA it decreased, but at the same time the interterritorial expression grew. For Tanascin, there was a decrease of the interterritorial expression in the radial zone while the pericellular and interterritorial expression of the apical layers of the osteoarthrotic cartilage grew. Lasing proved to significantly influence the osteoarthrotically changed cartilage when applied at an energy density of 1 J/cm2, i.e., the morphological changes had not yet progressed to the extent the control group had. Both the chondrocyte density and the glucosaminoglycan content turned out to be higher. When lasing was applied at higher energy densities, no significant difference among the control groups was found. Thus, it could be demonstrated in vivo that an arthrotic process decelerates through the influence of laser light of low-energy densities.

Intralesional cryosurgery enhances the involution of recalcitrant auricular keloids: a new clinical approach supported by experimental studies.

To explain the mechanism of action of a novel intralesional cryoprobe, thermal behavior measurements, and histological studies were performed in swine muscle specimens after intralesional cryosurgery ex vivo. Slow cooling (20 degrees C/min) and thawing (25 degrees C/min) rates, end temperature of -30 degrees C, produced 8 mm wide diffuse coagulative-type necrosis and a 3 mm-wide transition zone around the cryoprobe. In contrast, contact cryosurgery showed fast cooling and thawing rates (80 degrees C/min) and an end temperature of -100 degrees C. Efficacy and safety of the intralesional cryoprobe was further assessed in ten recalcitrant auricular keloids in nine Caucasian patients. There was a 67.4 +/- 23 percent reduction of scar volume at the end of the 18-month follow-up period after a single intralesional treatment (p < 0.005). Significant reduction of hardness, elevation, and redness as well as itching, pain, and tenderness was documented. The histomorphometric analysis, including spectral and fractal analysis, as well as assessment of the fast Fourier transform algorithm, showed parallel alignment and reorganization of the collagen fibers in the treated scar similar to that in the normal dermis. A long hold time in the deep scar core caused minimal damage to the superficial tissue, including melanocytes. There was no evidence of permanent hypopigmentation, active bleeding, infection, or recurrence. The major advantages of the intralesional cryoprobe, including the marked efficacy of a single treatment, may have a major importance in the clinical application of cryosurgery in the treatment of keloids and of other lesions localized deep in the skin.

Principles of lasers and biophotonic effects.

In this review, we discuss how, due to a variety of different interactions between laser radiation and biological tissue, the laser has become an established instrument in most medical fields. Depending on the interaction time and the effective power density, three types of laser tissue interaction can be distinguished: photochemical effects, photothermal effects, and photomechanical and photoionizing effects. After a description of the physical mechanisms, the typical parameters, and the medical applications of these effects, a review of the laser types used in medicine is given. For percutaneous laser disc decompression (PLDD), lasers in the near-infrared region (Nd:YAG, Ho:YAG, and diode lasers) and with visible green radiation (frequency doubled Nd:YAG, called "KTP laser") were reported to be effective.