Ablation of articular cartilage with an erbium:YAG laser: an ex vivo study using porcine models under real conditions-ablation measurement and histological examination.
OBJECTIVE
The use of an erbium:YAG laser in arthroscopic surgery has the advantage of a precise treatment of soft tissue. Due to the high absorption in water, the laser energy is perfectly matched to smoothing the hydrous, fibrillated articular cartilage surface. In minimal invasive surgery, the workspace is filled with aqueous liquids for enlargement. This appears contrary to the absorption characteristics of erbium:YAG laser radiation in water. The purpose of this study was to evaluate the ablated volume per pulse of cartilage lesions and the potential side effects including thermal damage and tissue necrosis.


METHODS
Twenty-four osteochondral specimens of porcine knee joints were irradiated with an Er:YAG laser completely submerged in water, with distances to the cartilage surface of 1, 3 and 5 mm and pulse durations of 75 and 100 microseconds. To keep a constant peak power of approximately 6 kW, pulse energies of 450 and 580 mJ were used at a pulse repetition rate of 15 Hz. After a histological preparation, ablated volumes, depths, and widths of the cuts were investigated. Additionally, laser protocols were correlated with different markers of cartilage tissue damage and apoptosis.


RESULTS
Ablation could be observed for every measurement. The influence of the distance showed a statistical significance (P < 0.001) for the volume, depth, and width of the cuts. For the pulse duration, statistical significance (P < 0.001) was found only for the volume and the depth. We observed no loss of proteoglycan or collagen type II. The total cell number, cell morphology, and number of apoptotic cells in an area close to the cutting edge and in a corresponding unaffected area of the same specimens revealed no differences regardless of the applied protocol.


CONCLUSIONS
The use of an Er:YAG laser demonstrates the successful application in liquid environments for cartilage removal without any damage of the surrounding tissue.
Medical Faculty, Department of Conservative Dentistry, Periodontology and Preventive Dentistry, RWTH Aachen University, Pauwelsstrasse 30, 52074 Aachen, Germany. jmeister@ukaachen.de
Jörg
J
Meister
René
R
Franzen
Karsten
K
Gavenis
Martin
M
Zaum
Sven
S
Stanzel
Norbert
N
Gutknecht
Bernhard
B
Schmidt-Rohlfing
D000818:Animals; D002358:Cartilage, Articular / Q000473:pathology / Q000528:radiation effects* / Q000601:surgery; D005269:Femur / Q000473:pathology / Q000528:radiation effects / Q000601:surgery; D007719:Knee Joint / Q000473:pathology / Q000528:radiation effects* / Q000601:surgery; D053685:Laser Therapy / Q000295:instrumentation*; D053844:Lasers, Solid-State; D023421:Models, Animal; D013552:Swine; D013582:Synovial Fluid; D046509:Tissue Culture Techniques; D014867:Water
D014867:Water