Abstract
We conducted a prospective randomized clinical study to determine if osteonecrosis occurs after arthroscopic laser surgery. 8 The patients with cartilage problems in their knee joints were treated with arthroscopic surgery using either laser or conventional instruments. Laser wavelength was 2.1 μm, and pulse duration was 250 μsec. Power settings for Holmium:YAG laser were 0.5–1.5 J/pulse and 5–25 Hz. Total energy used for these procedures was 1–2 kJ. During surgery, the laser probe was used at an angle of ≥30 degrees and at a distance of ≥1 mm. Magnetic resonance imaging (MRI) was performed for all patients preoperatively and postoperatively (in the 3rd, 6th, and 13th months).
No patient had abnormal signals in the MRI (as a sign of articular cartilage damage or osteonecrosis) following arthroscopic laser surgery. Postoperative MRI showed signal changes that might have been consistent with osteonecrosis in a small or moderately sized area of the femoral condyle in four patients in the laser group and in two patients in the conventional instrument group. However, these patients had the same signal changes in their preoperative MRIs.
Holmium laser is a pulsed laser; it delivers its energy in pulses. For this reason, tissue heating is reduced; the degree of thermal damage to the treated and adjacent tissues is limited in joints. 2,9
We also conducted experimental studies to evaluate the histological alternations after irradiation of the meniscus and cartilage using Holmium:YAG laser. 10,11 Meniscus and cartilage specimens were obtained during total knee replacements. Half of them, in a saline immersion, were exposed to Holmiun:YAG laser irradiation. The other half of the meniscus and cartilage specimens served as the control group. Laser wavelength was 2.1 μm, and pulse duration was 250 μsec.
In meniscus specimens, power settings were 1–1.5 J/pulse and 10–15 Hz. Total laser energy used in these procedures was 2, 3.5, and 6 kJ. During the procedures, the handpiece was placed perpendicular to and in contact with the surface. Histological evaluation with an electron microscope demonstrated no significant abnormal histological finding when lower laser energy was used (<3 kJ). But at higher laser energy levels (>3 kJ), separation of the gap between collagen fibers was obviously seen on electron microscopic evaluation of the meniscus specimens. The structure and continuity of collagen fibers seemed to be demolished, and this led to an increase in the gap between collagen fibers. A three-dimensional dispersion in the striation and abolition of transverse striation of collagen fibers was observed in this group.
In cartilage specimens, power settings were 0.2–1 J/pulse and 10–15 Hz. Total laser energy used in these procedures was 1.5 kJ. During the procedures, the handpiece was used at an angle of 30 degrees and at a distance of 1 mm. There was no abnormal histological finding with electron microscopic evaluation. The ultrastructure of the cartilage was preserved in both the control and laser groups. Collagen fibers and chondrocytes with oval nucleus and uniform chromatin were normal.
In conclusion, it is not the laser that causes osteonecrosis, but the laser surgeon, who is not using the laser properly. When a higher energy level is required, conventional instruments should be preferred for the treatment of meniscal lesions. Laser should be reserved for the posteriorly located or smaller meniscal pathologies. When laser is used in optimal dosage (optimal joule and Hertz) with optimal technique (keeping the handpiece at an appropriate angle and distance) and overtreatment is avoided, laser does not cause any damage to the treated and adjacent tissues.