The purpose of this study was to evaluate the effect of temperature on shrinkage and the histologic properties of glenohumeral joint capsular tissue. Six fresh-frozen cadaveric shoulders were used for this study. Seven joint capsule specimens were taken from different regions from each glenohumeral joint and assigned to one of seven treatment groups (37 degrees, 55 degrees, 60 degrees, 65 degrees, 70 degrees, 75 degrees, 80 degrees C) using a randomized block design. Specimens were placed in a tissue bath heated to one of the designated temperatures for 10 minutes. Specimens treated with temperatures at or above 65 degrees C experienced significant shrinkage compared with those treated with a 37 degrees C bath. The posttreatment lengths in the 70 degrees, 75 degrees, and 80 degrees C groups were significantly less than the pretreatment lengths. Histologic analysis revealed significant thermal alteration characterized by hyalinization of collagen in the 65 degrees, 70 degrees, 75 degrees, and 80 degrees C groups. This study demonstrated that temperatures at or above 65 degrees C caused significant shrinkage of glenohumeral joint capsular tissue. These results are consistent with histologic findings, which revealed significant thermal changes of collagen in the 65 degrees, 70 degrees, 75 degrees, and 80 degrees C groups. To verify the validity of laser application for shrinkage of joint capsule, studies designed to compare these findings with the effects of laser energy must be performed.
The purpose of this in vivo study was to analyze the short-term tissue response of joint capsule to monopolar radiofrequency energy and to compare the effects of five power settings at 65 degrees C on heat distribution in joint capsule. In 12 mature Hampshire sheep, the medial and lateral aspects of both stifles were treated with monopolar radiofrequency energy under arthroscopic control in a single uniform pass to the synovial surface. The radiofrequency generator power settings were 0, 10, 15, 20, 25, and 30 watts (N = 8/group). The electrode tip temperature was 65 degrees C. Histologic analysis at 7 days after surgery revealed thermal damage of capsule at all radiofrequency power settings. The lesion's cross-sectional area, depth, vascularity, and inflammation were commensurate with radiofrequency power. Tissue damage was indicated by variable inflammatory cell infiltration, fusion of collagen, pyknosis of fibroblasts, myonecrosis, and vascular thrombosis, whereas synovial hyperplasia, fibroblast proliferation, and rowing of sarcolemmal nuclei demonstrated regenerative processes. This study revealed that radiofrequency power settings and heat loss through lavage solution play a significant role in heat distribution and morphologic alterations in joint capsule after arthroscopic application of monopolar radiofrequency energy.
Recent scientific studies evaluating laser energy for tissue welding and thermokeratoplasty have demonstrated that the application of laser energy at non-ablative levels can alter collagen's structural and biochemical properties. A recent pilot study has demonstrated that the non-ablative application of holmium: yttrium-aluminum-garnet (Ho:YAG) laser energy to the joint capsule of patients with glenohumeral instability shrank the joint capsule, stabilizing the shoulder in the majority of the patients treated. Based on the collective findings of these studies, we hypothesized that thermal modification of dense collagenous tissues such as joint capsule, ligament, and tendon can be achieved by applying non-ablative laser energy. The purpose of this study was to evaluate the effect of laser energy at non-ablative levels on joint capsular mechanical, biochemical, histological, and ultrastructural properties in an in vitro rabbit model. Joint capsular tissues harvested from rabbit femoropatellar joints were treated by one of three power settings (5 watts (SW), 10 watts (lOW), 15 watts (15W)) or served as control in a randomized block design. Laser energy was applied using a Ho:YAG laser in 4 transverse passes across the tissue at a velocity of 2 mm/sec with the handpiece set at 1 .5 mm from the synovial surface in a 3TC tissue bath. Forty-eight specimens (n=12) were mechanically tested to determine tissue shrinkage, stiffness and viscoelastic properties. Twenty-four specimens (n=6) were processed for biochemical analysis to evaluate type I collagen content and non-reducible crosslinks. Twenty-four specimens (n=6) were processed for histological examination and transmission electron microscopy for ultrastructural analysis.Laser treatment significantly shortened the tissue by 9% (SW), 26% (lOW), and 38% (15W). Joint capsular stiffness decreased significantly in the lOW (77% decrease) and 15W (90% decrease) groups. Laser energy application did not significantly alter the viscoelastic properties of the tissue and the biochemical parameters evaluated, including type I collagen content and non-reducible crosslinks. Histological analysis revealed thermal alteration of collagen (fusion) and fibroblasts (pyknosis), with each subsequently higher laser energy causing significantly greater morphologic change over a larger area. Transmission electron microscopy revealed alteration of collagen ultrastructure, with significantly increased fibril crosssections for each of the treated groups compared to control. The fibrils began to lose their distinct edges and their periodical cross-striations at subsequently higher energy densities. This study demonstrated that laser energy at non-ablative levels can significantly alter joint capsular length and its structural properties. Ultrastructurally, laser energy caused disruption of the regular collagen organization. The results of this study suggested that the effects of laser energy were secondary to thermal denaturation of collagen with heat stable crosslinks maintained. To further clarif...
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