Effect of nonablative laser energy on joint capsular properties: an in-vitro study using a rabbit model

Abstract

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...

Thermal-Assisted Capsular Shrinkage of the Glenohumeral Joint in Overhead Athletes: A 15- to 47-Month Follow-up

“…Recently the application of thermal energy as a means to selectively shrink the glenohumeral capsule using an arthroscopic procedure has been advocated. 4,[7][8][9]18 In our current study, we examined the functional outcomes of 130 overhead athletes undergoing TACS at a mean follow-up of 29 months (range, 15-47 months). The results of our study indicate superior outcomes to those which reported using open and arthroscopic stabilization procedures without TACS, 3,12,15,17,20,[22][23][24]29 and similar to those of Savoie and Field, 25 Lyons et al, 16 and Levitz et al, 14 which used TACS.…”

“…The rehabilitation program utilized in this study is based on the authors' clinical experience of over 700 patients treated with TACS between 1997 and 2003, the effects of mobilization on collagen tissue healing, 1,6,34,36 and the basic science of collagen tissue healing following thermal modification. [7][8][9]18,19,[27][28]34 The rehabilitation program follows a gradual progression of applied loads on the collagen tissue to restore range of motion as the strength and tensile properties of the collagen tissue gradually returns to the preoperative state. The use of immediate motion is based on the theory that gentle passive motion is beneficial to the restoration of the organization, alignment, and strength of collagen tissue.…”

“…Range of motion was progressed cautiously during the first 6 to 8 weeks secondary to the reduced tensile properties of the collagen tissue. [7][8][9]19 Our goal was to have 75°of ER at 90°of shoulder abduction at week 6, and 90°by week 8. Shoulder flexion should be to 180°by week 8.…”

“…4,[7][8][9]18 Thermal energy, in the form of heat, has been used in medicine dating back to Hippocrates. The authors of the current study 34 have previously discussed the basic science and clinical application of thermal-assisted capsular shrinkage (TACS) of the glenohumeral joint capsule.…”

“…The authors of the current study 34 have previously discussed the basic science and clinical application of thermal-assisted capsular shrinkage (TACS) of the glenohumeral joint capsule. Since the 1990s, thermal energy has been used to modify capsular tissue in orthopedics 4,[7][8][9]18 and may be applied using 2 types of probes: the Holium:YAG laser and the radiofrequency heat probe. Both methods of thermal delivery have been shown to achieve similar and predictable amounts of capsular shrinkage in the cadaveric and ovine model, depending on the temperature settings.…”