Shipyards are very interested in improving their working environment and resolving environmental pollution issues by replacing mechanical cleaning technologies used before and after painting processes with laser cleaning technology. Because epoxy paint is thickly coated, with a thickness of 200 μm or greater, it is difficult to remove using both laser cleaning and mechanical cleaning technologies. Therefore, this study tried to obtain effective cleaning results by controlling the process parameters when removing the thick epoxy coating using a Q-switching fiber laser cleaning system with an average power of 100 W developed by our research team. The pulse duration time of the laser is 150 ns. Additionally, in order to determine whether the cleaning was sufficient, the difference in laser-induced plume/plasma was compared. By controlling the beam scanning patterns, line overlap rate, and pulse overlap rate, it was possible to obtain effective cleaning results without introducing removal deviation. In addition, the NOP increased when the laser beam overlap rate increased. This increased the amount of heat input to the material and reduced the number of scans required to remove the epoxy paint. As a result of the plume/plasma analysis, less plume/plasma was generated as the paint was removed if the epoxy paint remained on the surface. On the other hand, when all of the paint was removed, a higher brightness of plume/plasma generated by evaporation of the bare metal was observed.

Background Surgical fixation using hook plates is widely used in the treatment of acromioclavicular (AC) joint dislocations. The purpose of this study was to evaluate the incidence and shape of subacromial erosions after removal of the hook plate in type 5 AC joint dislocations. Further, we evaluated the effect of the shape of the subacromial erosion on the rotator cuff. Methods We retrospectively reviewed 30 patients who underwent hook plate fixation for type 5 AC joint dislocations at our hospital between December 2010 and December 2018. Patients with a follow-up of at least 1 year were included. Clinical outcomes were assessed using the final follow-up Constant-Murley, Korean Shoulder, and visual analog scores. To ensure that the appropriate reduction was well maintained, the coracoclavicular distances of the injured and contralateral sides were evaluated at the last follow-up. Computed tomography was performed to investigate the presence and shape of the subacromial erosion after hook plate removal at 4 months after surgery. Ultrasonography was performed to investigate the presence of rotator cuff lesions at the last follow-up. Clinical and radiological outcomes were compared between groups divided according to the presence and types of subacromial erosions. Results Subacromial erosion was observed in 60% of patients (18/30): 13, 2, and 3 simple groove, cave, and marginal protrusion types, respectively. Four patients showed reduction loss at the final follow-up. There were no significant differences in clinical and radiological outcomes between the groups with and without subacromial erosion. Moreover, there were no significant differences between groups according to the types of subacromial erosion. There were no rotator cuff lesions, such as partial tears, in the injured shoulders. Conclusions Hook plate fixation may induce subacromial erosions. However, the subacromial erosions caused by the hook plate did not affect the clinical outcomes of type 5 AC joint dislocations. Moreover, regardless of its shape, the subacromial erosion did not affect the clinical outcomes nor cause rotator cuff lesions after plate removal.

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Although various surgical techniques have been reported for the treatment of advanced Kienböck’s disease (Lichtman stage IIIB and above), the ap- propriate operative treatment is still being debated. This study compared the clinical and radiological outcomes of combined radial wedge and shortening osteotomy (CRWSO) and scaphocapitate arthrodesis (SCA) in the treatment of advanced Kienböck’s disease (above type IIIB) with a minimum of 3 years of follow-up. We analyzed the data from 16 and 13 patients who underwent CRWSO and SCA, respectively. The average follow-up period was 48.6±12.8 months. Clinical outcomes were evaluated using the flexion-extension arc, grip strength, Disabilities of the Arm, Shoulder, and Hand Questionnaire (DASH), and Visual Analogue Scale (VAS) for pain. The following radiological parameters were measured: ulnar variance (UV), carpal height ratio (CHR), radioscaphoid angle (RSA), and Stahl index (SI). Osteoarthritic changes in the radiocarpal and midcarpal joints were evaluated using computed tomography (CT). Clinically, both groups showed significant improvements in the grip strength, DASH, and VAS at final follow-up. However, regarding the flexion-extension arc, the CRWSO group showed a significant improvement, while the SCA group did not. Radiologically, compared to the preoperative values, the CHR results improved at final follow-up in the CRWSO and SCA groups. There was no statistically significant difference in the degree of CHR correction between the 2 groups. By the final follow-up visit, none of the patients in either group had progressed from Lichtman stage IIIB to stage IV. Considering restoration of wrist joint range of motion, CRWSO may be a good alternative for limited carpal arthrodesis for advanced Kienböck’s disease.

In the shipbuilding and marine industry, laser cleaning is considered an eco-friendly technology because it can significantly reduce the generation of secondary waste when removing the paint and oxide layer on a steel surface during ship repair work. Accordingly, various studies are being conducted worldwide for the application of laser cleaning. However, studies on the removal of various types of paint used on ships for anticorrosion and cosmetic effects and on the control of the scanning mode of laser cleaning application parts, such as square and circular, are limited. Therefore, in this study, the effects of the scanning mode and major process parameters were analyzed for four types of specimen coated with different paints and with various thicknesses. Consequently, it was possible to remove the paint on the steel surface completely by using handheld-type laser cleaning equipment with an average power of 100 W. In addition, the working time was reduced and the cleaning performance was improved by determining the scanning mode suitable for the laser cleaning application part and the optimal process parameters for each specimen.