The long-term results of shoulder hemiarthroplasty in irreducible four-part fracture-dislocation of the proximal humerus without rotator cuff tear arthropathy.

PURPOSE: Although there are concerns about nonunion of the greater tuberosity or shoulder weakness, hemishoulder arthroplasty (HSA) is a viable treatment option for irreducible four-part proximal humerus fractures-dislocation without rotator cuff tear arthropathy. This study aims to analyze the long-term radiological and functional outcomes of HSA. METHODS: This study enrolled 36 patients who underwent HSA due to irreducible four-part proximal humerus fracture-dislocation without rotator cuff tear arthropathy between March 2005 and May 2020. The exclusion group included 10 reverse total shoulder arthroplasty patients. The mean age and mean follow-up period were 68.6 years old and 48.6 months, respectively. Radiological assessments, such as vertical and horizontal greater tuberosity position, greater tuberosity healing, and implant position, were evaluated. Clinically, American Shoulder and Elbow Surgeons Score (ASES), Constant-Murley Score (CMS), and range of motion were evaluated. RESULTS: The greater tuberosity union rate was 55.6% (n = 20), with 44.4% (n = 16) experiencing nonunion, malunion, and bone resorption. The mean vertical and horizontal greater tuberosity positions showed significant difference at last follow-up compared to immediate postoperation. The retroversion of the implant was 23.8 ± 4.61°, and the acromio-humeral interval was 7.6 ± 1.34 mm. The mean last follow-up ASES and CMS were 39.5 ± 4.03 and 55.4 ± 10.41, respectively. The mean active forward flexion, abduction, internal rotation, and external rotation were 100.9 ± 15.04°, 92.5 ± 14.47°, 44.2 ± 12.83°, and 42.5 ± 15.32°, respectively. CONCLUSION: In long-term follow-up, the greater tuberosity was superiorly migrated and externally rotated. Active forward flexion and abduction in the last follow-up were significantly limited. However, in terms of pain relief, a satisfactory result was seen.

Results of the Use of Bioabsorbable Magnesium Screws for Surgical Treatment of Mason Type II Radial Head Fractures.

Background: In Mason classification type II radial head fractures, compared to plate fixation, fixation with cannulated headless screws and absorbable pins has been reported to provide more favorable postoperative outcomes, including less postoperative limitation in range of motion. The fact that radial head fractures are less prone to weight-bearing during fracture union further supports the use of absorbable screws as a suitable alternative treatment option in radial head fractures. This study aimed to perform fixation through open reduction using bioabsorbable magnesium screws for Mason type II radial head fractures and to report radiographic and clinical results. Methods: Among patients who visited the orthopedic department from April 2017 to August 2021, 22 with surgical indications were selected for participation. Radiographic tests were conducted at 2 weeks, 4 weeks, 8 weeks, 12 weeks, 6 months, and over 1 year after surgery to confirm the degree of bone union, reduction loss, and degree of H2 gas production. The Disabilities of the Arm, Shoulder and Hand (DASH) score, Mayo Elbow Performance Score (MEPS), hand grip power, and range of joint motion were measured at the 6-month follow-up to evaluate the clinical efficacy of the operation. Results: Bone union was confirmed in all 22 cases, and the mean time to union was 10.2 weeks. DASH score was 22.27 on average and no patients complained of significant discomfort after the surgery. The mean MEPS was 91.1. The hand grip power of the affected hand was similar to that of the unaffected hand, being 1.19% weaker on average. These differences reached statistical significance (p = 0.002). The range of elbow joint motion was measured: mean flexion, 146.1°; mean extension, 1.4°; mean pronation, 88.2°; and mean supination, 87.9°. Conclusions: In treating Mason type II radial head fractures, the use of bioabsorbable screws made of magnesium showed satisfactory results in radiographic and clinical evaluations. Magnesium bioabsorbable screws can maintain sufficient stability at the fracture site and have the advantage of avoiding secondary operation for the removal of internal fixation devices.

Filtering of Discrete-Time Switched Neural Networks Ensuring Exponential Dissipative and $l_{2}$ - $l_{\infty }$ Performances.

This paper studies delay-dependent exponential dissipative and l2 - l∞ filtering problems for discrete-time switched neural networks (DSNNs) including time-delayed states. By introducing a novel discrete-time inequality, which is a discrete-time version of the continuous-time Wirtinger-type inequality, we establish new sets of linear matrix inequality (LMI) criteria such that discrete-time filtering error systems are exponentially stable with guaranteed performances in the exponential dissipative and l2 - l∞ senses. The design of the desired exponential dissipative and l2 - l∞ filters for DSNNs can be achieved by solving the proposed sets of LMI conditions. Via numerical simulation results, we show the validity of the desired discrete-time filter design approach.

Myocardial mechanics in a rat model with banding and debanding of the ascending aorta.

BACKGROUND: Aortic banding and debanding models have provided useful information on the development and regression of left ventricular hypertrophy (LVH). In this animal study, we aimed to evaluate left ventricular (LV) deformation related to the development and regression of LVH. METHODS: Minimally invasive ascending aorta banding was performed in rats (10 Sprague Dawley rats, 7 weeks). Ten rats underwent a sham operation. Thirty-five days later, the band was removed. Echocardiographic and histopathologic analysis was assessed at pre-banding, 35 days of banding and 14 days of debanding. RESULTS: Banding of the ascending aorta created an expected increase in the aortic velocity and gradient, which normalized with the debanding procedure. Pressure overload resulted in a robust hypertrophic response as assessed by gross and microscopic histology, transthoracic echocardiography [heart weight/tibia length (g/m); 21.0 ± 0.8 vs. 33.2 ± 2.0 vs. 26.6 ± 2.8, p < 0.001]. The circumferential (CS) and radial strains were not different between the groups. However, there were significant differences in the degree of fibrosis according to the banding status (fibrosis; 0.10 ± 0.20% vs. 5.26 ± 3.12% vs. 4.03 ± 3.93%, p = 0.003), and global CS showed a significant correlation with the degree of myocardial fibrosis in this animal model (r = 0.688, p = 0.028). CONCLUSION: In this animal study, simulating a severe LV pressure overload state, a significant increase in the LV mass index did not result in a significant reduction in the LV mechanical parameters. The degree of LV fibrosis, which developed with pressure overload, was significantly related to the magnitude of left ventricular mechanics.