Effect of short stem alignment on initial fixation, stress transfer, and failure risk.

BACKGROUND: Short stems are advantageous for revision as they preserve autogenous bone. At present, the method of short-stem installation is determined based on the surgeon's experience. OBJECTIVE: To provide the guideline for installing a short stem, we aimed to investigate the alignment effect on the initial fixation of the stem, stress transfer, and the risk of failure numerically. METHODS: Models in which the caput-collum-diaphyseal (CCD) angle and flexion angle were hypothetically changed based on the two clinical cases of hip osteoarthritis were analyzed using the non-linear finite element method. RESULTS: The medial settlement of the stem increased in the varus model and decreased in the valgus model. With varus alignment, the stresses acting on the femur were high in the distal to the femoral neck. In contrast, the stresses in the proximal to the femoral neck tend to be higher with valgus alignment, although the difference in the femur stress between varus and valgus alignment was slight. CONCLUSION: Both initial fixation and stress transmission are lower when the device was placed in the valgus model than in the actual surgical case. In order to obtain initial fixation and suppress stress shielding, it is essential to extend the contact area between the medial portion of the stem and the femur along the bone axis, and to ensure adequate contact between the lateral portion of the stem tip and the femur.

Collarless Polished Tapered Stems of Identical Shape Provide Differing Outcomes for Stainless Steel and Cobalt Chrome: A Biomechanical Study.

Cemented polished tapered femoral stems (PTS) made of cobalt-chrome alloy (CoCr) are a known risk factor for periprosthetic fracture (PPF). The mechanical differences between CoCr-PTS and stainless-steel (SUS) PTS were investigated. CoCr stems having the same shape and surface roughness as the SUS Exeter® stem were manufactured and dynamic loading tests were performed on three each. Stem subsidence and the compressive force at the bone-cement interface were recorded. Tantalum balls were injected into the cement, and their movement was tracked to indicate cement movement. Stem motions in the cement were greater for the CoCr stems than for the SUS stems. In addition, although we found a significant positive correlation between stem subsidence and compressive force in all stems, CoCr stems generated a compressive force over three times higher than SUS stems at the bone-cement interface with the same stem subsidence (p < 0.01). The final stem subsidence amount and final force were greater in the CoCr group (p < 0.01), and the ratio of tantalum ball vertical distance to stem subsidence was significantly smaller for CoCr than for SUS (p < 0.01). CoCr stems appear to move more easily in cement than SUS stems, which might contribute to the increased occurrence of PPF with the use of CoCr-PTS.

A patient-cohort study of numerical analysis on sacroiliac joint stress distribution in pre- and post-operative hip dysplasia.

In acetabular dysplasia, the cartilaginous roof on the acetabular side does not fully cover the femoral head, which may lead to abnormal stress distribution in both the femoral head and pelvis. These stress changes may have implications to the adjacent sacroiliac joint (SIJ). The SIJ has a minimal range of motion and is closely coupled to the adjacent spine and pelvis. In consequence, the SIJ may react sensitively to changes in stress distribution at the acetabulum, with hypermobility-induced pain. The purpose of this study was to investigate the stress distribution of the SIJ in acetabular dysplasia, and to gain insight into the cause and mechanisms of hypermobility-induced pain at the SIJ. Finite element models of pre- and postoperative pelves of four patients with acetabular dysplasia were created and analyzed in double leg standing positions. The preoperative models were relatively inflare, the sacral nutation movement, SIJ cartilage equivalent stress, and the load on the surrounding ligaments decreased with increased posterior acetabular coverage. Acetabular morphology was shown to affect the SIJ, and improvement of the posterior acetabular coverage may help normalize load transmission of the pelvis and thus improve the stress environment of the SIJ in acetabular dysplasia.

Clinical Reasoning in Kampo Education for Teaching Kampo Beginners.

OBJECTIVES: Japanese traditional (Kampo) medicine has its own theories that are quite different from those of Western medicine. For many students and medical doctors, mastering it is a painstaking task. We examined the similarities in clinical reasoning between Western and Kampo medicine, and developed an easy-to-understand method to teach Kampo theories enabling physicians to make accurate diagnoses and choose suitable Kampo formulae. METHODS: We developed a teaching method for Kampo medicine along clinical reasoning for beginners and evaluate its availability and effectiveness in an actual team-based learning class. RESULTS: A Kampo diagnostic procedure similar to that in Western medicine was developed. In this method, some Kampo formulae, are chosen according to the chief complaint, concomitant symptoms, characteristics, and distribution and exacerbation factors. Subsequently, from a point of view of the chosen Kampo formulae, patients' signs and symptoms are matched to find the most suitable formula. Students chose the same suitable formula among 6 groups and gained confidence to choose the correct Kampo formulae. CONCLUSIONS: A new Kampo educational method was developed that raises students' and physicians' confidence in making diagnoses and prescribing Kampo medicines.

Vonoprazan versus conventional proton pump inhibitor-based triple therapy as first-line treatment against Helicobacter pylori: A multicenter retrospective study in clinical practice.

OBJECTIVE: Vonoprazan is a potassium-competitive acid blocker, a new type of acid-suppressing drug, and has recently become available for peptic ulcers, gastroesophageal reflux disease, and Helicobacter pylori (H. pylori) eradication. Its efficacy for H. pylori eradication has been reported. However, the evidence for its efficacy and feasibility remains limited. We aimed to compare the feasibility, effectiveness and safety of vonoprazan-based triple therapy with conventional proton pump inhibitor (PPI)-based triple therapy in multicenter clinical practice. METHODS: We performed a multicenter retrospective study on patients receiving first-line H. pylori eradication therapy between March 2013 and November 2015 with either vonoprazan-based triple therapy or conventional PPI-based triple therapy. RESULTS: A total of 2715 patients aged 63.0 ± 12.1 years (1412 [52.0%] males) were analyzed. Eradication rates were 87.2% (368/422) for vonoprazan-based therapy and 72.4% (1661/2293) for conventional PPI-based therapy (P < 0.01). Among the former group, there were 10 cases of diarrhea, six of nausea/vomiting, and five of rash, but the rates of these adverse events were similar to those in the conventional PPI group. CONCLUSION: Vonoprazan-based triple therapy is feasible, and has a higher rate for H. pylori eradication than conventional PPI as a first-line regimen.

Utility of single and double balloon endoscopy in patients with difficult colonoscopy: a randomized controlled trial.

AIM: To compare the utility of single-balloon colonoscopy (SBC) or double-balloon colonoscopy (DBC) for difficult colonoscopies. METHODS: Between August 2008 and June 2010, patients in whom total colonoscopy failed within 30 min of insertion were assigned randomly to undergo either SBC or DBC. No sedatives were used. After the endoscopy, all patients were asked to evaluate pain during the procedure on a 10-point analog scale (1 = no pain; 10 = worst imaginable pain) with a questionnaire. The study outcomes were the cecal intubation rate and time, endoscopic findings, complications, and pain score. RESULTS: The SBC and DBC groups included 11 and 10 patients, respectively. All but one SBC patient achieved total colonoscopy successfully. The cecal intubation times were 18 min (range: 10-85 min) and 12.8 min (range: 9.5-42 min) in the SBC and DBC groups, respectively (P = 0.17). No difference was observed in the prevalence of colon polyps between the SBC and DBC groups (45% vs 30%, P = 0.66). SBC showed advanced colon cancer in the ascending colon, which was inaccessible using conventional colonoscopy. The respective pain scores were 5 (1-10) [median (range)] and 5 (1-6) in the SBC and DBC groups (P = 0.64). No complications were noted in any patient. CONCLUSION: The utility of single- and double-balloon endoscopy for colonoscopy seems comparable in patients with incomplete colonoscopy using a conventional colonoscope.

[A case of coexisting malignant mesothelioma and squamous cell carcinoma of the lung].

We experienced a case of malignant mesothelioma with squamous cell carcinoma of the lung concurrently. A 40-year-old man presented with dyspnea. A massive pleural effusion was found by X-ray in the right side of his chest. Transcutaneous pleural biopsy yielded a diagnosis of malignant mesothelioma(IMIG cT4N0M0, Stage IV ). At the same time, his chest CT revealed tumor in the right hilar lesion. Transbronchial lung biopsy yielded a diagnosis of squamous cell carcinoma of the lung (cT3N0M0, Stage III B). Our diagnosis was double cancer, malignant mesothelioma and lung cancer. Chemotherapy with carboplatin, gemcitabine and radiation therapy was performed, but the patient died from deterioration of his systemic condition. We encountered a rare case of double cancer. More attention must be paid in making a diagnosis of malignant mesothelioma and lung cancer.

Single-balloon versus double-balloon endoscopy for achieving total enteroscopy: a randomized, controlled trial.

BACKGROUND: Balloon endoscopy has been accepted as an effective tool for examining the small intestine. Two types of balloon endoscopy, single and double, are commercially available. The difference in performance between these 2 types of balloon endoscopy has not yet been elucidated. OBJECTIVE: To compare the yield of single-balloon endoscopy (SBE) and double-balloon endoscopy (DBE). DESIGN: Single-center, randomized, controlled trial. SETTING: University hospital in Tokyo, Japan. PATIENTS: Patients with suspected small-bowel disease. INTERVENTIONS: SBE and DBE. MAIN OUTCOME MEASUREMENTS: Outcomes were the total enteroscopy rate, diagnostic yield, complication rate, and clinical outcomes. Analysis was done by intent to treat. RESULTS: The study started in April 2008 and was terminated in April 2010 because of an obvious disadvantage for the SBE group. Thirty-eight patients were enrolled in the study; 18 patients were assigned to the SBE group and 20 to the DBE group. The total enteroscopy rate was 0% in the SBE group and 57.1% in the DBE group (P = .002). In terms of complications, the DBE group had 1 patient with Mallory-Weiss syndrome, and the SBE group had 1 patient with hyperamylasemia. There was no difference in the overall diagnosis rate between the SBE and DBE groups (61.1% vs 50.0%, P = .49). There was no difference in therapeutic outcome between the SBE and DBE groups (27.8% vs 35.0%, P = .63). LIMITATIONS: Relatively small number of study patients. CONCLUSIONS: Total enteroscopy is more easily performed with DBE than with SBE.

Estimating the measuring sensitivity of unipolar and bipolar ECG with lead field method and FDM models.

New portable electrocardiogram (ECG) measurement systems are emerging into market. Some use nonstandard bipolar electrode montage and sometimes very small interelectrode distances to improve the usability of the system. Modeling could provide a straightforward method to test new electrode systems. The aim of this study was to assess whether modeling the electrodes' measuring sensitivity with lead field method can provide a simple tool for testing a number of new electrode locations. We evaluated whether the actual ECG signal strength can be estimated by lead fields with two realistic 3D finite difference method (FDM) thorax models. We compared the modeling results to clinical body surface potential map (BSPM) data from 236 normal patients and studied 117 unipolar and 42 bipolar leads. In the case of unipolar electrodes the modeled measuring sensitivities correlated well with the clinical data (r=0.86, N=117, p<0.05). In the case of bipolar electrodes the correlation was moderate (r=0.62 between Model 1 and clinical data, r=0.71 between Model 2 and clinical data, N=42 and p<0.05 for both). Based on this we can conclude that lead field analysis based on realistic thorax models provides a good initial prediction for designing new electrode montages and measurement systems.