114 Bulletin • Hospital for Joint Diseases Volume 61, Numbers 3 & 4 2003-2004 Abstract This study performed the first in vitro histological analysis of the effects of bipolar thermal energy on human menis- cal tissue. Sixteen fresh human menisci were mounted on a cutting block and placed in a water bath simulating an arthroscopic environment. Each specimen was divided into four sections and randomized to one of four treatment op- tions: 1. thermal ablation with a bipolar multielectrode 3 mm Covac wand (power 3 setting); 2. thermal ablation with a bipolar multielectrode 3 mm Covac wand (power setting 7); 3. resection with a scalpel blade; and 4. resection with a motorized 4.5 full-radius resector. Six micron sections were cut and stained with Hematoxylin and Eosin and Masson’s trichrome stain. Menisci were evaluated for the contour of the cut edge: straight, jagged, frayed, or combined. The zone of thermal necrosis and zone of thermal alteration were determined by examining the differential staining of the connective tissue and measuring the affected area. Menisci treated with the bipolar thermal probe were noted to have a smoother contoured edge in comparison to motorized cutters. The zone of thermal penetration for the Arthrocare power setting 3 averaged 0.18 mm (range: 0.09 to 0.20; SD 0.04) and for Arthrocare power setting 7 averaged 0.33 mm (range: 0.26 to 0.36; SD 0.03). The difference in thermal penetration between Arthrocare power settings 3 and 7 was 0.15 mm. This was statistically significant at p < 0.0001 (95% CI: 0.11 to 0.19 mm). The zone of thermal penetration was non-existent for the shaver and scalpel groups. This study provides the first histological description of the effects of bipolar radiofrequency energy on meniscal tissue. It demonstrates that there is intrasubstance thermal penetration and alteration of the meniscal tissue. Its clinical significance is unclear and further in vivo studies are needed to address its clinical applicability. T he recent resurgence of electrosurgery for arthroscopic partial meniscectomies has been fueled by the development of bipolar electrodes (i.e., Covac™ wand, Arthrocare, Sunnyvale, CA; VAPR™ Flexible Side Effect Electrode, Mitek Surgical Products, Inc, Westwood, MA). Prior to the advent of these probes, the unipolar confguration, consisting of a small treatment electrode and a large grounding pad attached to the patient’s leg, was the type conventionally used in arthroscopy. 1-4 The current passed through the patient’s body from the electrode to the grounding pad, which was often a signifcant distance away. This resulted in current scattering, decreased current, and an increased demand for energy resulting in penetration of the meniscus and surrounding tissue. 5 The bipolar confguration has both electrodes (treatment electrode and ground pad) in the probe tip. The current passes through the tissue and back to the probe tip without passing through the rest of the patient. Theoretically, this increases the current density at the treatment site allowing increased cutting effciency, decreased damage to other local tissue, and decreased thermal penetration. 6 The ablation is achieved as charged particles in the conducting fuid (0.9% normal saline) are accelerated toward the meniscus secondary to the voltage gradient created between the conductive media and the tissue. 5 These charged particles are able to cause the dissociation of the molecular bonds within meniscal tissue resulting in volumetric removal. Due to the short range of these accelerated particles, the dissociative process is theoretically confned to the surface layer of the target, The Effects of Radiofrequency Bipolar Thermal Energy on Human Meniscal Tissue Laith M. Jazrawi, M.D., Andrew Chen, M.D., Drew Stein, M.D., Christian S. Heywood, M.D., Adam Bernstein, M.D., German Steiner, M.D., and Andrew Rokito, M.D. Laith M. Jazrawi, M.D., Andrew Chen, M.D., Drew Stein, M.D., Christian S. Heywood, M.D., Adam Bernstein, M.D., German Steiner, M.D., and Andrew Rokito, M.D., are in the NYU-Hospi- tal for Joint Diseases, Department of Orthopaedic Surgery, New York, New York. Correspondence and reprint requests: Laith M. Jazrawi, M.D., NYU-Hospital for Joint Diseases, Department of Orthopaedic Surgery, 301 East 17th Street, NewYork, NewYork 10003.