A device for measuring sternal bone connectivity using vibration analysis techniques.

OBJECTIVES: Stability of bone splitting sternotomy is essential for normal healing after open cardiac surgery. Mechanical vibration transmittance may offer a means for early detection of separation of bone (diastasis) in the sternotomy and prevent further complications. This article describes the technical implementation and validation of vibration analysis-based prototype device built for measuring sternal bone connectivity after sternotomy. METHODS: An in-house built measurement system, sternal vibration device, consisting of actuator, sensor, and main controller and signal acquisition unit was designed and manufactured. The system was validated, and three different test settings were studied in mockups (polylactide rods in ballistic gel) and in two human sternums: intact, stable wire fixation, and unstable wire fixation with a gap mimicking bone diastasis. The transmittance of vibration stimulus across the median sternotomy was measured. RESULTS: The validation showed that the force produced by the actuator was stable, and the sensor could be calibrated to precisely measure the acceleration values. The vibration transmittance response to material cut and sternotomy was evident and detectable in the 20 Hz to 2 kHz band. The transmittance decreased when the connectivity between the sternal halves became unstable. The trend was visible in all the settings. CONCLUSION: Technical solutions and description of validation process were given. The device was calibrated, and the vibration transmittance analysis differentiated intact and cut polylactide rod. In the sternum, intact bone, wire fixation with exact apposition, and with a gap were identified separately. Although further studies are needed to assess the accuracy of the method to detect different levels of diastases, the method appears to be feasible.

Vibration transmittance measures sternotomy stability - a preliminary study in human cadavers.

BACKGROUND: Stability is essential for the normal healing of a sternotomy. Mechanical vibration transmittance may provide a new means of early detection of diastasis in the sternotomy and thus enable the prevention of further complications. We sought to confirm that vibration transmittance detects sternal diastasis in human tissue. METHODS: Ten adult human cadavers (8 males and 2 females) were used for sternal assessments with a device constructed in-house to measure the transmittance of a vibration stimulus across the median sternotomy at the second, third, and fourth costal cartilage. Intact bone was compared to two fixed bone junctions, namely a stable wire fixation and an unstable wire fixation with a 10 mm wide diastasis mimicking a widely rupturing sternotomy. A generalized Linear Mixed Model with the lme function was used to determine the ability of the vibration transmittance device to differentiate mechanical settings in the sternotomy. RESULTS: The transmitted vibration power was statistically significantly different between the intact chest and stable sternotomy closure, stable and unstable closure, as well as intact and unstable closure (t-values and p-values respectively: t = 6.87, p < 0.001; t = 7.41, p < 0.001; t = 14.3, p < 0.001). The decrease of vibration transmittance from intact to stable at all tested costal levels was 78%, from stable to unstable 58%, and from intact to unstable 91%. The vibration transmittance power was not statistically significantly different between the three tested costal levels (level 3 vs. level 2; level 4 vs. level 2; level 4 vs. level 3; t-values and p-values respectively t = - 0.36, p = 0.723; t = 0.35, p = 0.728; t = 0.71, p = 0.484). CONCLUSIONS: Vibration transmittance analysis differentiates the intact sternum, wire fixation with exact apposition, and wire fixation with a gap. The gap detection capability is not dependent on the tested costal level. The method may prove useful in the early detection of sternal instability and warrants further exploration.

Symptoms of Sternal Nonunion Late after Cardiac Surgery.

Background A cohort of patients having symptoms of sternal nonunion late after sternotomy was studied to find out whether the complaints were related to true sternal nonunion or decreased bone density. Methods A survey was mailed to 2,053 cardiac surgical patients operated in our institution between July 2007 and June 2010. The patients were requested about symptoms referring to sternal instability. A group of symptomatic individuals as well as 1:1 age- and time-matched asymptomatic controls were examined with sternal palpation, ultrasound during standardized sternal pressure provocation, and computed tomography (CT). Results The number of patients replied in the survey was 1,918 (93.4%); 2.3% (44 patients) reported sensation of movement or clicking in sternum during body movements and during coughing. Symptomatic patients living within 200 km to the hospital (21) and their asymptomatic controls (21) were selected for further clinical and imaging studies. Mean period between the initial operation and the examinations was 36 (22-56) months. Sternal palpation pain was significantly associated with reported symptoms suggestive of sternal nonunion (odds ratio [OR] 22.0; 95% confidence interval [CI] 2.5-195); however, none of the patients had clinically unstable sternum or nonunion in the sternal imaging. The symptoms of sternal instability were more frequent in patients whose bone mineralization rate (as measured with T-scores) was higher. Conclusion Symptoms suggestive of sternal nonunion were experienced by 2.3%. However, their symptoms did not correlate with CT scans or provocation ultrasound although palpation pain was evident. Thus the pain is derived from nonmechanical etiologies. Higher bone mineralization rate correlated with abnormal symptoms of sternal wound.

Postoperative sternal stability assessed by vibration: a preliminary study.

PURPOSE: Mechanical stability of the postoperative sternum was assessed using novel analysis based on vibration response. DESCRIPTION: The response to controlled vibration in the 50 Hz to 1,500 Hz range was studied in 22 elective cardiac surgical patients with an accelerometer, recorded, and processed on a personal computer. Each patient had four measurement sessions. The mechanical transfer function of the sternum was estimated, and several descriptive factors were extracted from it to determine how they reflect changes occurring in the bone during the recovery from sternotomy. EVALUATION: Complete datasets were obtained from 14 patients. The most informative variable for the sternal healing was the P(600-1500) index, which reflects transmittance in the wide frequency band between 600 Hz and 1500 Hz. The index dropped after surgery, indicating a decrease in transmission. The postoperative measurements revealed a reverse trend in the same variable, which can be attributed to healing. CONCLUSIONS: Significant changes caused by the sternotomy and subsequent healing processes were observed using vibration measurement.

Genes involved in systemic and arterial bed dependent atherosclerosis--Tampere Vascular study.

BACKGROUND: Atherosclerosis is a complex disease with hundreds of genes influencing its progression. In addition, the phenotype of the disease varies significantly depending on the arterial bed. METHODOLOGY/PRINCIPAL FINDINGS: We characterized the genes generally involved in human advanced atherosclerotic (AHA type V-VI) plaques in carotid and femoral arteries as well as aortas from 24 subjects of Tampere Vascular study and compared the results to non-atherosclerotic internal thoracic arteries (n=6) using genome-wide expression array and QRT-PCR. In addition we determined genes that were typical for each arterial plaque studied. To gain a comprehensive insight into the pathologic processes in the plaques we also analyzed pathways and gene sets dysregulated in this disease using gene set enrichment analysis (GSEA). According to the selection criteria used (>3.0 fold change and p-value <0.05), 235 genes were up-regulated and 68 genes down-regulated in the carotid plaques, 242 genes up-regulated and 116 down-regulated in the femoral plaques and 256 genes up-regulated and 49 genes down-regulated in the aortic plaques. Nine genes were found to be specifically induced predominantly in aortic plaques, e.g., lactoferrin, and three genes in femoral plaques, e.g., chondroadherin, whereas no gene was found to be specific for carotid plaques. In pathway analysis, a total of 28 pathways or gene sets were found to be significantly dysregulated in atherosclerotic plaques (false discovery rate [FDR] <0.25). CONCLUSIONS: This study describes comprehensively the gene expression changes that generally prevail in human atherosclerotic plaques. In addition, site specific genes induced only in femoral or aortic plaques were found, reflecting that atherosclerotic process has unique features in different vascular beds.

Multiple pulmonary arteriovenous malformations presenting as an acute myocardial infarction.

Pulmonary arteriovenous malformations are rare, mostly asymptomatic vascular anomalies. These malformations cause direct right to left shunting of unoxygenated blood, resulting chronically in cyanosis, dyspnea, and exercise intolerance. The serious complications reported earlier have mainly been neurologic, for example, cerebrovascular accidents and brain abscesses and are most likely caused by paradoxical embolism. Detection of pulmonary arteriovenous malformations is challenging, and the emergency department personnel play an essential role. Once suspected, the diagnosis can be made promptly using standard imaging techniques and appropriate treatment may prevent serious complications. In this report, we describe a case of a 41-year-old man with acute anterior myocardial infarction, unexpectedly caused by emboli from pulmonary arteriovenous malformations. This rare etiology of acute myocardial infarction should be taken into consideration especially in cases with atypical presentation.