ABSTRACTS 149

tion. The joint was again decompressed. After a similar time span another intraarticular clot had formed. A repeat arthroscopic inspection and doc- umentation was performed after saline solution.

Both solutions showed blood clot formation and collection throughout the joint. Cleansing of the joint showed blood-clot adherence to surgically in- cised or exposed surfaces of synovium, articular cartilage, and meniscus. There was blood clot at- tached to naturally existing areas of degenerative articular cartilage.

There were some differences in blood-clot forma- tion between Ringer’s lactate and normal saline so- lutions. There was a greater amount of blood-clot formation after normal saline. There was a greater number of transarticular bands of blood clot after normal saline solution than after Ringer’s lactate.

This study indicates that Ringer’s lactate solution should be selected in nondegenerative joints and for anterior cruciate ligament surgery to minimize in- traarticular clot formation, the probable precursor to transarticular adhesion formation. A normal sa- line solution should be used when desire for clot formation exists, as in meniscal repair and after ar- throscopic debridement procedures in degenerative knee joint. There probably is no necessity for ex- tracorporal fibrin clot formation and a reimplanta- tion during meniscal repair surgery because blood clot forms at the repair site in 5-7 min. The imme- diate postarthroscopic blood-clot formation and at- tachment after articular cartilage debridement probably explains the subsequent articular cartilage repair process seen at subsequent second-look ar- throscopy.

The Use of the Contact Nd:YAG Laser in Arthro- scopic Surgery. Drew V. Miller, Stephen J. O’Brien, Anne M. Kelly, Stephen V. Fealy, Steven P. Arnoc- zky, Russell F. Warren, and Edward F. DiCarlo. New York, New York, U.S.A.

We evaluated the effects of the contact Nd:YAG laser on articular cartilage and meniscal tissue as compared with electrocautery. In addition, the ef- fect of laser energy to enhance meniscal repair was studied.

To assess depth of damage, the menisci, tibia1 plateaus, and femoral condyles of seven canine ca- daver knees were subjected to uniform pulse dura- tions of laser energy with 75 g of pressure at watt- ages varying from 1 to 25.

Twenty-four New Zealand white rabbits then un-

derwent bilateral knee arthrotomies and articular cartilage lesions were made on the femoral condyles with the laser in one group and with the electrosur- gical meniscectomy probe in another. Similar pulse durations and wattage variations were used. Scalpel lesions on the contralateral knee served as controls.

Next, 16 rabbits underwent bilateral medial and lateral meniscectomies through the avascular zone. Laser and electrocautery meniscectomies were per- formed on opposite knees with scalpel meniscecto- mies as controls. One-second pulses of 20 W were used for both laser and electrocautery.

In an additional eight rabbits, medial meniscal re- pairs were performed on scalpel incisions through the avascular zone. The left medial meniscal defect was exposed to laser energy of 10 W with a l-s pulse before repair. All rabbits above were killed at 1 day and 2, 6, and 12 weeks. Histologic analysis, which included depth of damage and assessment of healing response, was performed.

Vertical depth of damage was comparable be- tween the laser and electrocautery, with the laser penetrating subchondral bone at lower wattages. However, defects created by the laser showed a small margin of necrosis (co.2 mm) and a vigorous healing response characterized at 6 weeks by chon- drocyte proliferation, increased vascularity, and re- pair with hyaline cartilage with nearly complete healing by 12 weeks. The electrocautery defects showed a significant lateral margin of necrosis (0.7- 1.8 mm) at increasing wattages that increased with time. By 12 weeks, there was little evidence of heal- ing at ~20 W, and a limited response with partial tilling with fibrocartilage at lower wattages.

Laser meniscectomies showed characteristic re- modeling with Iibrocartilage-like tissue by twelve weeks, which in some cases was indistinguishable from normal meniscal tissue. Electrocautery menis- cectomies, however, showed irregular margins with a lack of regeneration.

Laser energy was not shown to enhance meniscal repair; by 3 weeks, both groups appeared histolog- ically identical.

In addition to its small size, variety of tips, and its suitability for arthroscopy in a saline medium, the contact Nd:YAG laser offers promising advantages over electrocautery. Less articular cartilage dam- age and greater healing potential were seen at each wattage level, and laser meniscectomies allowed for a normal and perhaps enhanced response to subto- tal meniscectomy. It does not appear that low-level laser energy enhances meniscal repair.

Arthroscopy. Vol. 5, No. 2, 1989