BACKGROUND: This study compared the clinical and radiological outcomes of the single calcar screw plate and Polarus nail techniques for the treatment of the proximal humerus fractures. METHODS: Seventy-two patients diagnosed with displaced proximal humerus fracture were enrolled for the study. Of these, 50 patients underwent the locking plate surgery with a single calcar screw (plate group), whereas 22 patients underwent the Polarus nail surgery (nail group). The plate group was further divided into plate 1 group (with medial support), and plate 2 group (without medial support). The radiological and functional results of both groups were compared to the nail group. RESULTS: The α angle 1 year after surgery was significantly different between plate 1 and plate 2, and plate 2 and nail groups (p=0.041, p=0.043, respectively). The ratio that does not satisfy the reference value of γ angle was 2.8% in plate 1, 7.1% in plate 2 and 22.7% in nail group (p=0.007); there was a significant difference between plate 1 and nail group, and plate 2 and nail group (p=0.014, p=0.033, respectively). CONCLUSIONS: No significant differences were observed in the clinical results between locking plate and Polarus nail. However, in the plate 2 group and nail group, the rate of failure to maintain reduction during the 1-year period after surgery was statistically and significantly higher than the plate 1 group (level of evidence: level IV, case series, treatment study).
Humans ; Humeral Fractures ; Humerus* ; Reference Values

PURPOSE: This study is aimed to assess changes of stress distribution dependent on different connection lengths and placement of the fixture top relative to the ridge crest. MATERIALS AND METHODS: The internal-conical connection implant which has a hexagonal anti-rotation index was used for FEM analysis on stress distribution in accordance with connection length of fixture-abutment. Different connection lengths of 2.5 mm, 3.5 mm, and 4.5 mm were designed respectively with the top of the fixture flush with residual ridge crest level, or 2 mm above. Therefore, a total of 6 models were made for the FEM analysis. The load was 170 N and 30-degree tilted. RESULTS: In all cases, the maximum von Mises stress was located adjacent to the top portion of the fixture and ridge crest in the bone. The longer the connection length was, the lower the maximum von Mises stress was in the fixture, abutment, screw and bone. The reduction rate of the maximum von Mises stress depending on increased connection length was greater in the case of the fixture top at 2 mm above the ridge crest versus flush with the ridge crest. CONCLUSION: It was found that the longer the connection length, the lower the maximum von Mises stress appears. Furthermore, it will help prevent mechanical or biological complications of implants.
Dental Implant-Abutment Design ; Dental Stress Analysis ; Finite Element Analysis

The cesarean section has been considered as one of the most prime and most commonly performed operations in the obstetrics and gynecology field. In fact, all cesarean sections have depended upon the operator`s experience. However, there have been several cases reported on new technique of cesarean section in many developed countries, but not in Korea until we started the recent research. We have developed a new type of cesarean section named FAST(Finger Assisted Stretching Technique) through study on strength/weakness of other operation techniques as well as many other researches we conducted in the past plus our own experiences. To find the differences on the following subjects; operating time, postoperative complication, and recovery period. We compared and analyzed data from using new and traditional techniques. We selected 120 patients(group A using FAST: 45 patients, group B using traditional technique: 75 patients) as samples for this study. Together, they were all conducted cesarean section at Korea University, Guro Hospital between May 1993 and December 1995. Student-t-test and chi-square test were used for statistical analysis. We consider that below 0.05 for P value is statistically significant. The results of comparative study between two groups are; 1. There was no comparative difference on average age: group A: 29.6(range 23~39, S/D 7.1) group B: 31.1(range 24~38, S/D 5.4) 2. There was a significant difference on average operation times: group A: 15.4 min.(range 11~19, S/D 3.6) group B: 41.3 min.(range 23~50, S/D 19) 3. There was a significant difference on average amount of bleeding: group A: 580 ml(range 450~750, S/D 101) group B: 916 ml(range 800~1000, S/D 99) 4. There was a significant difference on the value of hemoglobin before and after operation group A: 0.8 g/dl(range 0.4~1.6, S/D 0.25) group B: 1.9 g/dl(range 0.9~2.6, S/D 0.21) 5. There was a significant difference on average period of hospitalization: group A: 3.7 days(range 3~4, S/D 0.7) group B: 6.4 days(range 5~8, S/D 0.6) 6. No one from group A experienced any infection, but 3 cases of wound infection and 2 cases of voiding difficulty were reported from group B. 7. 11 cases from group A and 16 cases from group B had laparotomy for some other reasons, later. There was no adhesion found in group A, but adhesions found in 2 cases from group B.
Cesarean Section* ; Developed Countries ; Female ; Fingers* ; Gynecology ; Hemorrhage ; Hospitalization ; Humans ; Korea ; Laparotomy ; Obstetrics ; Postoperative Complications ; Pregnancy ; Wound Infection

PURPOSE: The purpose of this study is to evaluate the effect of change in tibial posterior slope on contact force and ligament stress using finite element analysis. MATERIALS AND METHODS: A 3-dimensional finite element model for total knee arthroplasty was developed by using a computed tomography scan. For validation, the tibial translations were compared with previous studies. The finite element analysis was conducted under the standard gait cycle, and contact force on ultra-high molecular weight polyethylene (UHMWPE) and stresses on lateral and medial collateral ligaments were evaluated. RESULTS: The tibial translations showed similarity with previous studies. As the tibial posterior slope angle increases, the contact stress area increased and was well distributed, and the contact force on UHMWPE decreased overall. However, the maximum contact force in the case for 10degrees case was greater than those for others. The stresses on ligaments were the greatest and smallest in 0degrees and 10degrees cases, respectively. CONCLUSIONS: The higher tibial posterior slope angle leads to the lower contact stress and more extensive stress distribution overall in posterior-stabilized total knee arthroscopy. However, it does not absolutely mean the smallest contact force. The stresses on ligaments increased with respect to the smaller tibial posterior slope angle.
Arthroplasty ; Arthroscopy ; Collateral Ligaments ; Finite Element Analysis ; Gait ; Knee ; Ligaments ; Molecular Weight ; Polyethylene ; Polyethylenes ; Translations

Background: The use of newly developed mixed-dilution hemodiafiltration (HDF) can supplement the weaknesses of pre- and postdilution HDF. However, it is unclear whether mixed-HDF performs well compared to predilution HDF. Methods: We conducted a prospective, open-labeled, randomized controlled trial from two hemodialysis centers in Korea. Between January 2017 and September 2019, 60 patients who underwent chronic hemodialysis were randomly assigned at a 1:1 ratio to receive either predilution HDF (n = 30) or mixed-HDF (n = 30) for 6 months. We compared convection volume, changes in small- and medium-sized molecule clearance, high-sensitive C-reactive protein (hs-CRP) level, and dialysis-related parameters between the two dialysis modalities. Results: A mean effective convection volume of 41.0 ± 10.3 L/session in the predilution HDF group and 51.5 ± 9.0 L/session in the mixed-HDF group was obtained by averaging values of three time-points. The difference in effective convection volume between the groups was 10.5 ± 1.3 L/session. This met the preset noninferiority criteria, suggesting that mixed-HDF was noninferior to predilution HDF. Moreover, the β2-microglobulin reduction rate was greater in the mixed-HDF group than in the predilution HDF group, while mixed-HDF provided greater transmembrane pressure. There were no significant between-group differences in Kt/V urea levels, changes in predialysis hs-CRP levels, proportions of overhydration, or blood pressure values. Symptomatic intradialytic hypotension episodes and other adverse events occurred similarly in the two groups. Conclusion Use of mixed-HDF was comparable to predilution HDF in terms of delivered convection volume and clinical parameters. Moreover, mixed-HDF provided better β2-microglobulin clearance than predilution HDF.

We report three cases of coincidental cerebral aneurysm with pituitary tumor. In our hospital the incidence of such cases was 4.4% of 68 patients with pituitary tumors from March, 1970 to October, 1990. Cases No. 1 was a 47-year-old female suffering from progressive loss of visual acuity. Preoperative brain C-T scan and angiographies revealed unruptured posterior communicating aneurysm with pituitary tumor. Case No. 2 was a 39-year-old male suffering from headache after head trauma with acromegaly. Preoperative brain C-T scan and angiographies appeared unruptured anterior communicating aneurysm and pituitary tumor. Case No. 3 was a 62-year-old female suffering progressive loss of visual acuity and headache. Left middle cerebral artery aneurysm and pituitary tumor were found by preoperative brain C-T scan and angiographies. All cases were operated by transcranial route and performed tumor removal after primary clipping of aneurysm. Postoperatively remained tumor of all cases was treated by radiosurgery successfully.
Acromegaly ; Adult ; Aneurysm ; Angiography ; Brain ; Craniocerebral Trauma ; Female ; Headache ; Humans ; Incidence ; Intracranial Aneurysm* ; Male ; Middle Aged ; Pituitary Neoplasms* ; Radiosurgery ; Visual Acuity

PURPOSE: To assess the reproducibility and agreement of anterior chamber measurements between the Pentacam (PTC) and the Anterior segment optical coherence tomography (AOCT) in normal healthy eyes with open angle. METHODS: Prospective cross-sectional comparative case series. A total of 162 eyes of 81 healthy volunteers with normal open angle were included in this study. Anterior chamber angle (ACA) and anterior chamber depth (ACD) were measured with PTC and AOCT. Intra-observer variability and inter-methods agreement of both instruments for ACA and ACD were evaluated. RESULTS: Values of temporal and nasal ACA measured by two instruments were similar, and the results of ACD were also not significantly different between modalities (p>0.01). ACA and ACD measurements by PTC and AOCT showed good intra-observer and inter-method agreements (all >0.9). CONCLUSIONS: PTC and AOCT are presumed to be very useful for the anterior chamber angle examination. They may provide good images and quantitative data about the angle structures including ACA and ACD.
Adolescent ; Adult ; Anterior Chamber/*anatomy & histology ; Anterior Eye Segment ; Cross-Sectional Studies ; *Diagnostic Techniques, Ophthalmological ; Female ; Humans ; Male ; Observer Variation ; Photography/*methods ; Prospective Studies ; Reproducibility of Results ; Tomography, Optical Coherence/*methods ; Trabecular Meshwork/anatomy & histology ; Young Adult

PURPOSE: The purpose of this study was to evaluate and compare the biomechanical behavior of the lumbar spine after posterior decompression with the spinous process osteotomy (SPiO) technique or the conventional laminectomy (CL) technique using a finite element (FE) model. MATERIALS AND METHODS: Three validated lumbar FE models (L2-5) which represented intact spine and two decompression models using SPiO and CL techniques at the L3-4 segment were developed. In each model, the ranges of motion, the maximal von Mises stress of the annulus fibrosus, and the intradiscal pressures at the index segment (L3-4) and adjacent segments (L2-3 and L4-5) under 7.5 Nm moments were analyzed. Facet contact forces were also compared among three models under the extension and torsion moments. RESULTS: Compared to the intact model, the CL and SPiO models had increased range of motion and annulus stress at both the index segment (L3-4) and the adjacent segments under flexion and torsion. However, the SPiO model demonstrated a reduced range of motion and annulus stress than the CL model. Both CL and SPiO models had an increase of facet contact force at the L3-4 segment under the torsion moment compared to that of the intact model. Under the extension moment, however, three models demonstrated a similar facet contact force even at the L3-4 model. CONCLUSION: Both decompression methods lead to postoperative segmental instability compared to the intact model. However, SPiO technique leads to better segmental stability compared to the CL technique.
Biomechanical Phenomena ; Decompression, Surgical/*methods ; *Finite Element Analysis ; Humans ; Intervertebral Disc/physiopathology/surgery ; Laminectomy/*methods ; Lumbar Vertebrae/pathology/physiopathology/*surgery ; Male ; Middle Aged ; Models, Anatomic ; Osteotomy/*methods ; Range of Motion, Articular ; Stress, Mechanical ; Zygapophyseal Joint/pathology/physiopathology/surgery

PURPOSE: The purpose of this study was to investigate the effects of unilateral pedicle screw fixation on the fusion segment and the superior adjacent segment after one segment lumbar fusion using validated finite element models. MATERIALS AND METHODS: Four L3-4 fusion models were simulated according to the extent of decompression and the method of pedicle screws fixation in L3-4 lumbar fusion. These models included hemi-laminectomy with bilateral pedicle screw fixation in the L3-4 segment (BF-HL model), total laminectomy with bilateral pedicle screw fixation (BF-TL model), hemi-laminectomy with unilateral pedicle screw fixation (UF-HL model), and total laminectomy with unilateral pedicle screw fixation (UF-TL model). In each scenario, intradiscal pressures, annulus stress, and range of motion at the L2-3 and L3-4 segments were analyzed under flexion, extension, lateral bending, and torsional moments. RESULTS: Under four pure moments, the unilateral fixation leads to a reduction in increment of range of motion at the adjacent segment, but larger motions were noted at the fusion segment (L3-4) in the unilateral fixation (UF-HL and UF-TL) models when compared to bilateral fixation. The maximal von Mises stress showed similar patterns to range of motion at both superior adjacent L2-3 segments and fusion segment. CONCLUSION: The current study suggests that unilateral pedicle screw fixation seems to be unable to afford sufficient biomechanical stability in case of bilateral total laminectomy. Conversely, in the case of hemi-laminectomy, unilateral fixation could be an alternative option, which also has potential benefit to reduce the stress of the adjacent segment.
Biomechanical Phenomena ; *Computer Simulation ; Humans ; Lumbar Vertebrae/surgery ; Male ; Middle Aged ; *Models, Anatomic ; *Pedicle Screws ; *Range of Motion, Articular ; Software ; Spinal Fusion ; Stress, Mechanical

BACKGROUND/AIMS: Since comorbidities are major determinants of modality choice, and also interact with dialysis modality on mortality outcomes, we examined the pattern of modality choice according to comorbidities and then evaluated how such choices affected mortality in incident dialysis patients. METHODS: We analyzed 32,280 incident dialysis patients in Korea. Patterns in initial dialysis choice were assessed by multivariate logistic regression analyses. Multivariate Poisson regression analyses were performed to evaluate the effects of interactions between comorbidities and dialysis modality on mortality and to quantify these interactions using the synergy factor. RESULTS: Prior histories of myocardial infarction (p = 0.031), diabetes (p = 0.001), and congestive heart failure (p = 0.003) were independent factors favoring the initiation with peritoneal dialysis (PD), but were associated with increased mortality with PD. In contrast, a history of cerebrovascular disease and 1-year increase in age favored initiation with hemodialysis (HD) and were related to a survival benefit with HD (p < 0.001, both). While favoring initiation with HD, having Medical Aid (p = 0.001) and male gender (p = 0.047) were related to increased mortality with HD. Furthermore, although the severity of comorbidities did not inf luence dialysis modality choice, mortality in incident PD patients was significantly higher compared to that in HD patients as the severity of comorbidities increased (p for trend < 0.001). CONCLUSIONS: Some comorbidities exerted independent effects on initial choice of dialysis modality, but this choice did not always lead to the best results. Further analyses of the pattern of choosing dialysis modality according to baseline comorbid conditions and related consequent mortality outcomes are needed.
Cerebrovascular Disorders ; Comorbidity ; Dialysis* ; Heart Failure ; Humans ; Korea* ; Logistic Models ; Male ; Mortality* ; Myocardial Infarction ; Peritoneal Dialysis ; Renal Dialysis