Quantification of long-term nonlinear stress relaxation of bovine trabecular bone

The reliability of computational models in orthopedic biomechanics depends often on the accuracy of the bone material properties. It is widely recognized that the mechanical response of trabecular bone is time-dependent, yet it is often ignored for the sake of simplicity. Previous investigations into the viscoelastic properties of trabecular bone have not explored the relationship between nonlinear stress relaxation and bone mineral density. The inclusion of this behavior could enhance the accuracy of simulations of orthopedic interventions, such as of primary fixation of implants. Although methods to quantify the viscoelastic behavior are known, the time period during which the viscoelastic properties should be investigated to obtain reliable predictions is currently unclear. Therefore, this study aimed to: 1) Investigate the duration of stress relaxation in bovine trabecular bone; 2) construct a material model that describes the nonlinear viscoelastic behavior of uniaxial stress relaxation experiments on trabecular bone; and 3) implement bone density into this model. Uniaxial compressive stress relaxation experiments were performed with cylindrical bovine femoral trabecular bone samples (n = 16) with constant strain held for 24 h. Additionally, multiple stress relaxation experiments with four ascending strain levels with a holding time of 30 min, based on the results of the 24-h experiment, were executed on 18 bovine bone cores. The bone specimens used in this study had a mean diameter of 12.80 mm and a mean height of 28.70 mm. A Schapery and a Superposition model were used to capture the nonlinear stress relaxation behavior in terms of applied strain level and bone mineral density. While most stress relaxation happened in the first 10 min (up to 53 %) after initial compression, the stress relaxation continued even after 24 h. Up to 69 % of stress relaxation was observed at 24 h. Extrapolating the results of 30 min of experimental data to 24 h provided a good fit for accuracy with much improved experimental efficiency. The Schapery and Superposition model were both capable of fitting the repeated stress relaxation in a sample-by-sample approach. However, since bone mineral density did not influence the time-dependent behavior, only the Superposition model could be used for a group-based model fit. Although the sample-by-sample approach was more accurate for an individual specimen, the group based approach is considered a useful model for general application.

The Effect of Patient-Related Factors on the Primary Fixation of PEEK and Titanium Tibial Components: A Population-Based FE Study

Polyetheretherketone (PEEK) is of interest as implant material for cementless tibial total knee arthroplasty (TKA) components due to its potential advantages. One main advantage is that the stiffness of PEEK closely resembles the stiffness of bone, potentially avoiding peri-prosthetic stress-shielding. When introducing a new implant material for cementless TKA designs, it is essential to study its effect on the primary fixation. The primary fixation may be influenced by patient factors such as age, gender, and body mass index (BMI). Therefore, the research objectives of this finite element (FE) study were to investigate the effect of material (PEEK vs. titanium) and patient characteristics on the primary fixation (i.e., micromotions) of a cementless tibial tray component. A total of 296 FE models of 74 tibiae were created with either PEEK or titanium material properties, under gait and squat loading conditions. Overall, the PEEK models generated larger peak micromotions than the titanium models. Differences were seen in the micromotion distributions between the PEEK and titanium models for both the gait and squat models. The micromotions of all tibial models significantly increased with BMI, while gender and age did not influence micromotions.

The effect of periprosthetic bone loss on the failure risk of tibial total knee arthroplasty

The effect of long-term periprosthetic bone loss on the process of aseptic loosening of tibial total knee arthroplasty (TKA) is subject to debate. Contradicting studies can be found in literature, reporting either bone resorption or bone formation before failure of the tibial tray. The aim of the current study was to investigate the effects of bone resorption on failure of tibial TKA, by simulating clinical postoperative bone density changes in finite element analysis (FEA) models and FEA models were created of two tibiae representing cases with good and poor initial bone quality which were subjected to a walking configuration and subsequently to a traumatic stumbling load. Bone failure was simulated using a crushable foam model incorporating progressive yielding. Repetitive loading under a level walking load did not result in failure of the periprosthetic bone in neither the good nor poor bone quality tibia at the baseline bone densities. When applying a stumble load, a collapse of the tibial reconstruction was noticed in the poor bone quality model. Incorporating postoperative bone loss led to a significant increase of the failure risk, particularly for the poor bone quality model in which subsidence of the tibial component was substantial. Our results suggest bone loss can lead to an increased risk of a collapse of the tibial component, particularly in case of poor bone quality at the time of surgery. The study also examined the probability of medial or lateral subsidence of the implant and aimed to improve clinical implications. The FEA model simulated plastic deformation of the bone and implant subsidence, with further validation required via mechanical experiments.

The sensitivity of the stiffness and thickness of a titanium inlay in a cementless PEEK femoral component to the micromotions and bone strain energy density

Polyetheretherketone (PEEK) has been proposed as alternative material for total knee arthroplasty implants due to its low stiffness, which may reduce stress-shielding. In cementless fixation, a proper primary fixation is required for long-term fixation. Previous research showed that the lower stiffness of a cementless PEEK femoral component results in larger micromotions at the implant-bone interface compared to a cobalt-chrome femoral component. A titanium inlay on the PEEK implant surface may improve the primary fixation while maintaining the favourable stiffness properties. Therefore, the effect of thickness and stiffness of a titanium inlay on the primary fixation and stress-shielding was investigated. A finite element model of the femur and femoral component was created with five titanium inlay variants. The micromotions and strain energy density (SED) were quantified as outcome measures. The distal thin - proximal thick variant showed the largest resulting micromotions (51.2 µm). Relative to the all-PEEK femoral component, the addition of a titanium inlay reduced the micromotions with 30 % to 40 % without considerably affecting the stress-shielding capacity (strain energy difference of 6 % to 10 %). Differences in micromotions (43.0-51.2 µm) and SED between the variants were relatively small. In conclusion, the addition of a titanium inlay could lead to a reduction of the micromotions without substantially affecting the SED distribution.

The application of an isotropic crushable foam model to predict the femoral fracture risk

For biomechanical simulations of orthopaedic interventions, it is imperative to implement a material model that can realistically reproduce the nonlinear behavior of the bone structure. However, a proper material model that adequately combines the trabecular and cortical bone response is not yet widely identified. The current paper aims to investigate the possibility of using an isotropic crushable foam (ICF) model dependent on local bone mineral density (BMD) for simulating the femoral fracture risk. The elastoplastic properties of fifty-nine human femoral trabecular cadaveric bone samples were determined and combined with existing cortical bone properties to characterize two forms of the ICF model, a continuous and discontinuous model. Subsequently, the appropriateness of this combined material model was evaluated by simulating femoral fracture experiments, and a comparison with earlier published results of a softening Von-Mises (sVM) material model was made. The obtained mechanical properties of the trabecular bone specimens were comparable to previous findings. Furthermore, the ultimate failure load predicted by the simulations of femoral fractures was on average 79% and 90% for the continuous and discontinuous forms of the ICF model and 82% of the experimental value for the sVM material model. Also, the fracture locations predicted by ICF models were comparable to the experiments. In conclusion, a nonlinear material model dependent on BMD was characterized for human femoral bone. Our findings indicate that the ICF model could predict the femoral bone strength and reproduce the variable fracture locations in the experiments.

A Patient-Specific Fracture Risk Assessment Tool for Femoral Bone Metastases: Using the Bone Strength (BOS) Score in Clinical Practice

Patients with femoral metastases are at risk of fracturing bones. It is important to prevent fractures in order to maintain mobility and quality of life. The BOne Strength (BOS) score is based on a computed tomography (CT)-based patient-specific finite element (FE) computer model that objectively calculates bone strength. In this pilot study, the added clinical value of the BOS score towards treatment-related decision making was assessed. In December 2019, the BOS score was implemented in four radiotherapy centers. The BOS scores and fracture risks of individual patients were calculated and returned to the physician to assist in treatment decisions. The physicians filled out a questionnaire, which was qualitatively analyzed. A follow-up to identify fractures and/or death was performed after six months. Until June 2021, 42 BOS scores were delivered (20 high, 9 moderate, and 13 low fracture risk). In 48%, the BOS score led to an adaptation of treatment plans. Physicians indicated that the BOS score provided objective insight into fracture risk, was reassuring for physicians and patients, and improved multidisciplinary discussions and shared decision making. In conclusion, the BOS score is an objective tool to assess fracture risk in femoral bone metastases and aids physicians and patients in making a more informed decision regarding the most appropriate treatment.

Dual-functional porous and cisplatin-loaded polymethylmethacrylate cement for reconstruction of load-bearing bone defect kills bone tumor cells

Malignant bone tumors are usually treated by resection of tumor tissue followed by filling of the bone defect with bone graft substitutes. Polymethylmethacrylate (PMMA) cement is the most commonly used bone substitute in clinical orthopedics in view of its reliability. However, the dense nature of PMMA renders this biomaterial unsuitable for local delivery of chemotherapeutic drugs to limit the recurrence of bone tumors. Here, we introduce porosity into PMMA cement by adding carboxymethylcellulose (CMC) to facilitate such local delivery of chemotherapeutic drugs, while retaining sufficient mechanical properties for bone reconstruction in load-bearing sites. Our results show that the mechanical strength of PMMA-based cements gradually decreases with increasing CMC content. Upon incorporation of ≥3% CMC, the PMMA-based cements released up to 18% of the loaded cisplatin, in contrast to cements containing lower amounts of CMC which only released less than 2% of the cisplatin over 28 days. This release of cisplatin efficiently killed osteosarcoma cells in vitro and the fraction of dead cells increased to 91.3% at day 7, which confirms the retained chemotherapeutic activity of released cisplatin from these PMMA-based cements. Additionally, tibias filled with PMMA-based cements containing up to 3% of CMC exhibit comparable compressive strengths as compared to intact tibias. In conclusion, we demonstrate that PMMA cements can be rendered therapeutically active by introducing porosity using CMC to allow for release of cisplatin without compromising mechanical properties beyond critical levels. As such, these data suggest that our dual-functional PMMA-based cements represent a viable treatment option for filling bone defects after bone tumor resection in load-bearing sites.

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Dual-functional porous PMMA cements are developed by introducing CMC as both pore generator and drug vehicle for cisplatin.

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PMMA-based cements containing ≥3% CMC release sufficient amounts of chemotherapeutically active cisplatin.

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PMMA-based cements containing ≤3% CMC retain sufficient mechanical properties for bone reconstruction at load-bearing sites.

Development of a crushable foam model for human trabecular bone

Finite element (FE) simulations can be used to evaluate the mechanical behavior of human bone and allow for quantitative prediction of press-fit implant fixation. An adequate material model that captures post-yield behavior is essential for a realistic simulation. The crushable foam (CF) model is a constitutive model that has recently been proposed in this regard. Compression tests under uniaxial and confined loading conditions were performed on 59 human trabecular bone specimens. Three essential material parameters were obtained as a function of bone mineral density (BMD) to develop the isotropic CF model. The related constitutive rule was implemented in FE models and the results were compared to the experimental data. The CF model provided an accurate simulation of uniaxial compression tests and the post-yield behavior of the stress-strain was well-matched with the experimental results. The model was able to reproduce the confined response of the bone up to 15% of strain. This model allows for simulation of the mechanical behavior of the cellular structure of human bone and adequately predicts the post-yield response of trabecular bone, particularly under uniaxial loading conditions. The model can be further improved to simulate bone collapse due to local overload around orthopaedic implants.

Association between olfactory function and quality of life in patients with olfactory disorders: a multicenter study in over 760 participants

BACKGROUND

This cross-sectional, multi-centric study aimed to investigate the differences in quality of life among patients with olfactory dysfunction (OD) of different origin, and to identify factors associated with olfactory-related quality of life (QOL).

METHODS

Seven hundred sixty-three adults were recruited from 8 Smell & Taste clinics in Germany, Switzerland, and Austria. Olfactory-related QOL was assessed by the Questionnaire of Olfactory Disorders (QOD). Olfactory function was assessed with the "Sniffin' Sticks" test; self-assessment was performed with visual analog scales.

RESULTS

Patients with post-infectious and post-traumatic OD showed poorer olfactory-related QOL than patients with sinonasal and idiopathic OD. The olfactory-related QOL was positively associated with the "Sniffin' Sticks" test score, self-assessed olfactory function, disease duration, and age, with younger olfactory dysfunction patients showing lower QOL. Female patients presented with poorer olfactory-related QOL. In addition, the results showed that self-assessment of olfactory function explained more of the variance in olfactory-related QOL than olfactory function evaluated by the Sniffin’ Sticks test.

CONCLUSIONS

In addition to the psychophysical testing results, several factors such as disease cause, disease duration, sex, or self- assessed olfactory dysfunction should be taken into account when assessing the individual severity of the smell loss.

P1767Prevalence and clinical significance of sleep-disordered breathing in patients with hypertrophic cardiomyopathy

Background

Despite major advances in knowledge on hypertrophic cardiomyopathy (HCM) at the genetic and molecular levels, the understanding of essential clinical aspects remains limited. The aim of this study is to identify the prevalence and clinical significance of Sleep-disordered Breathing (SDB) in a large patient population.

Methods

201 patients (78 women, age 64±15 years) with HCM were screened for obstructive (OSA) or central (CSA) sleep-disordered breathing using multichannel cardiorespiratory polygraphy. Additionally, patients received a spiroergometric examination and echocardiography. SDB was defined as apnea-hypopnea index (AHI) ≥5/h and OSA/CSA differentiated after the majority of events.

Results

SDB was documented in 60% of all patients. OSA was diagnosed in 71 patients (35.3%) and CSA in 44 (21.9%) patients. SDB requiring treatment was found in 106 (52.7%) patients. In patients with AHI ≥15/h NYHA class was increased (2.1 vs. 2.39, p=0.04) and maximal O2 uptake during exercise was lower (20.1 vs. 16.1 p<0.001). Also left atrial diameter was significantly larger (46.9 mm vs. 50.41 mm, p=0.01) and rate of atrial fibrillation was increased (0.5 vs. 0.72 p=0.03). CSA pts had a larger left atrial diameter compared to pts with OSA (52.13 mm vs. 47.82 mm, p=0.02).

Conclusion

There is a high prevalence of SDB in HCM patients. Patients with moderate to severe SDB showed increased atrial fibrillation incidence and reduced cardiopulmonary performance. Whether the SDB has an independent prognostic relevance in patients with HCM needs to be elucidated.

Case-specific non-linear finite element models to predict failure behavior in two functional spinal units

Current finite element (FE) models predicting failure behavior comprise single vertebrae, thereby neglecting the role of the posterior elements and intervertebral discs. Therefore, this study aimed to develop a more clinically relevant, case-specific non-linear FE model of two functional spinal units able to predict failure behavior in terms of (i) the vertebra predicted to fail; (ii) deformation of the specimens; (iii) stiffness; and (iv) load to failure. For this purpose, we also studied the effect of different bone density-mechanical properties relationships (material models) on the prediction of failure behavior. Twelve two functional spinal units (T6-T8, T9-T11, T12-L2, and L3-L5) with and without artificial metastases were destructively tested in axial compression. These experiments were simulated using CT-based case-specific non-linear FE models. Bone mechanical properties were assigned using four commonly used material models. In 10 of the 11 specimens our FE model was able to correctly indicate which vertebrae failed during the experiments. However, predictions of the three-dimensional deformations of the specimens were less promising. Whereas stiffness of the whole construct could be strongly predicted (R²  = 0.637-0.688, p < 0.01), we obtained weak correlations between FE predicted and experimentally determined load to failure, as defined by the total reaction force exhibiting a drop in force (R²  = 0.219-0.247, p > 0.05). Additionally, we found that the correlation between predicted and experimental fracture loads did not strongly depend on the material model implemented, but the stiffness predictions did. In conclusion, this work showed that, in its current state, our FE models may be used to identify the weakest vertebra, but that substantial improvements are required in order to quantify in vivo failure loads. © 2018 The Authors. Journal of Orthopaedic Research® Published by Wiley Periodical, Inc. on behalf of Orthopaedic Research Society. J Orthop Res 36:3208-3218, 2018.

A combined experimental and finite element approach to analyse the fretting mechanism of the head-stem taper junction in total hip replacement

Fretting corrosion at the taper interface of modular hip implants has been implicated as a possible cause of implant failure. This study was set up to gain more insight in the taper mechanics that lead to fretting corrosion. The objectives of this study therefore were (1) to select experimental loading conditions to reproduce clinically relevant fretting corrosion features observed in retrieved components, (2) to develop a finite element model consistent with the fretting experiments and (3) to apply more complicated loading conditions of activities of daily living to the finite element model to study the taper mechanics. The experiments showed similar wear patterns on the taper surface as observed in retrievals. The finite element wear score based on Archard’s law did not correlate well with the amount of material loss measured in the experiments. However, similar patterns were observed between the simulated micromotions and the experimental wear measurements. Although the finite element model could not be validated, the loading conditions based on activities of daily living demonstrate the importance of assembly load on the wear potential. These findings suggest that finite element models that do not incorporate geometry updates to account for wear loss may not be appropriate to predict wear volumes of taper connections.

Experimental Measurement of the Static Coefficient of Friction at the Ti-Ti Taper Connection in Total Hip Arthroplasty

The modular taper junction in total hip replacements has been implicated as a possible source of wear. The finite-element (FE) method can be used to study the wear potential at the taper junction. For such simulations it is important to implement representative contact parameters, in order to achieve accurate results. One of the main parameters in FE simulations is the coefficient of friction. However, in current literature, there is quite a wide spread in coefficient of friction values (0.15 - 0.8), which has a significant effect on the outcome of the FE simulations. Therefore, to obtain more accurate results, one should use a coefficient of friction that is determined for the specific material couple being analyzed. In this study, the static coefficient of friction was determined for two types of titanium-on-titanium stem-adaptor couples, using actual cut-outs of the final implants, to ensure that the coefficient of friction was determined consistently for the actual implant material and surface finish characteristics. Two types of tapers were examined, Biomet type-1 and 12/14, where type-1 has a polished surface finish and the 12/14 is a microgrooved system. We found static coefficients of friction of 0.19 and 0.29 for the 12/14 and type-1 stem-adaptor couples, respectively.

[Chemosensory Evoked Changes of Breathing Pattern During Propofol-induced Sedation]

BACKGROUND

The affective valence of an olfactory stimulus will be encoded in its respiratory response. Unpleasant odors shorten the inhalation of the first stimulated breaths in wakefulness and sleep. The aim of the present study was to assess the effekt of intravenous anesthetic propofol on the chemosensory evoked changes of breathing pattern.

MATERIAL AND METHODS

13 ASA 1/2 patients got intranasal chemosensory stimuli (H2S and CO2) by flow-olfactometer during "deep" (EEG-based bispectral analysis, BIS:≤60) and "moderate" (BIS>60) propofol-induced sedation with preserved spontaneous breathing. The duration of the in- and exhalation was analyzed for 5 breaths before and for 2 breaths after the onset of stimulation.

RESULTS

During deep sedation respiratory reactions were observed only by CO2 irritation. During moderate sedation respiratory responses were evoked by H2S stimuli, too. In moderate sedation extensions of the inhalations of the first breath after both the unpleasant pure olfactory H2S stimuli and the trigeminal stimuli were more frequent than reductions.

CONCLUSION

Olfactory stimuli change the breathing only during moderate sedation, trigeminal stimuli during deep and moderate propofol-induced sedation. In opposite to both wakefulness and sleep the duration of inhalation is often extended by H2S-stimuli during moderate sedation.

[Global and Spatial Gustatory Function after Proven Unilateral Transsection of the Chorda Tympani]

BACKGROUND

A transection of the chorda tympani results in loss of spatial gustatory function on the ipsilateral tongue. Most patients do not notice anymore this alteration. The cause is unclear. Do adjacent gustatory areas become more sensitive or is the gustatory perception rather independent of the size of stimulated area?

METHODS

51 patients with proven unilateral transection of the chorda tympani and 51 healthy subjects were tested for gustatory recognition thresholds. The methods used were the "three-drops-choice-technique" by Henkin to evaluate the whole mouth taste (global taste examination) and the "spatial taste test" to evaluate the local gustatory function on 4 areas of the tongue. The taste solutions were sweet, sour, salty and bitter with increasing concentrations.

RESULTS

The global gustatory function of the patients and of the control group did not differ in either the 4 taste qualities but the composite score was increased within the group of patients. Most patients did not realize that. The spatial taste examination showed reduction of taste perception on 3 of the 4 gustatory areas of the tongue in the patients. The decreased gustatory function on the area of the transected chorda remained unchanged over time. The taste attenuation on the ipsilateral back area and the contralateral front area improved over time.

CONCLUSION

Transection of chorda tympani also leads to an attenuation of spatial gustatory function in adjacent areas. Therefore, adjacent areas cannot be taken as reference. Instead, taste function has to be compared to the results of healthy probands.

[The regularity of the breathing pattern of both sitting and reclining adults is not different]

BACKGROUND

A prestimulatory regular breathing is required for the respiration-olfactometry. In a sitting position, just about every second prestimulatory breathing sequence fulfilled this requirement checking off -line. It should be examined whether breathing in reclining position is more regular.

METHODS

The coefficients of variation of the time parameters of breathing in reclining and sitting position during 30 min were determined and compared.

RESULTS

Breathing regularity did not increase in reclining position with 48 healthy persons (age group 1: 18 to 30 years, n = 24, 18 women; age group 2: > 55 years, n = 24, 13 women). The age and gender had no eff ect on the proportion of regular breathing. With 7 persons, the yield of 5 on each other following regular breaths was inadequate. Additionally one person excluded from our study was not able to breathe regularly without interruptions.

CONCLUSION

The respiration-olfactometry cannot be performed in each person. It is not more successful in reclining than in sitting position.

Parotidectomy and submandibulectomy for benign diseases in Thuringia, Germany: a population-based study on epidemiology and outcome

Although salivary gland surgery for benign diseases is an integral part of clinical routine of head and neck surgeons, there is not many population-based data published on incidence and efficiency of this surgery. Parotidectomy was performed in 180 patients and submandibulectomy in 97 patients for benign diseases in eight otorhinolaryngology and two maxillofacial surgery departments in Thuringia, Germany, in 2005. All patients were analysed regarding patients' characteristics, therapy, complications and further course of disease. Predominant indications were epithelial tumours for parotidectomy (79 %) and sialolithiasis for submandibulectomy (50 %). The most frequent tumour types were pleomorphic adenoma (46 %) and Warthin tumours (29 %). Pleomorphic adenoma was significantly more frequent in female patients and Warthin tumours in male patients and smokers. The incidence of parotidectomy, i.e. the surgical rate, was 7.8/100,000 habitants and of submandibulectomy 4.1/100,000 habitants. One hundred and seventy-eight tumours including 154 epithelial tumours resulted in an incidence of 7.6/100,000 habitants for all treated tumours and of 6.6/100,000 for epithelial tumours, respectively. The majority of parotid cases were treated by lateral parotidectomy (79 %). Relevant complications were observed in 22 % of patients. After parotidectomy and submandibulectomy a postoperative facial palsy was observed in 28 and 2 % of cases, respectively. Only 1 % was permanent. During a mean follow-up time of 9.6 months, 3 % of parotidectomy patients developed a Frey's syndrome needing treatment and 0.8 % developed a tumour recurrence. This population-based analysis shows that salivary gland surgery is performed in higher incidence than expected, effectively and with low-risk in daily routine of head and neck surgeons.

[Sleep-disordered breathing and cardiac arrhythmias]

Sleep-disordered breathing (SDB) is an important comorbidity in patients with cardiac arrhythmias. Previous studies confirmed associations between supraventricular and ventricular arrhythmias and SDB. In heart failure patients, SDB was also found independently associated with a shorter event-free survival to the occurrence of malignant ventricular arrhythmias requiring appropriate cardioverter-defibrillator therapy. In obstructive sleep apnea, repetitive hypoxemia, mechanical stress (wall tension), arousals from sleep, and activation of the sympathetic nervous system promote cardiac arrhythmias. Pathophysiological concepts for the link between Cheyne-Stokes respiration and malignant arrhythmias are not fully understood and require further research. In addition, large-scale, randomized, controlled trials are awaited to prove whether adequate treatment of SDB is associated with a risk reduction for the occurrence of arrhythmias, in general, and malignant ventricular arrhythmias, in particular, in these patients.

[Health services research on paranasal sinus surgery in Thuringia: epidemiologic key data and outcome]

BACKGROUND

Although modern minimal-invasive paranasal sinus surgery is an integral part of clinical routine of otorhinolaryngologic surgeons, there are no population-based data on incidence and efficiency of this surgery published.

MATERIAL AND METHODS

1,582 patients underwent paranasal sinus surgery in the 8 Thuringian departments of otorhinolaryngology in 2005. All patients were analysed regarding patients' characteristics, therapy, complications and further course of disease.

RESULTS

The incidence of paranasal sinus surgery was 46/100,000 for women and higher for men with 72/100,000. Median age was 48 years. Chronic sinusitis was the main reason for surgery (94%; including 33% with nasal polyps) and was performed dominantly as endoscopic sinus surgery (96%). Surgery was performed bilaterally in 75% of the cases and as primary surgery. In most cases at least 2 paranasal sinuses per side were approached. Relevant complications were observed in 4% of patients. During the follow-up time of 45-51 months a recurrence was observed in 9% of cases. Using a multivariate regression analysis, revision surgery, allergic subject and diagnosis of a malignant tumor were significant independent risk factors to predict a recurrence. Older age and longer time of surgery were significant independent risk factors for a complication.

CONCLUSION

This population based analysis is showing that modern paranasal sinus surgery is performed in high incidence, effectively and with low-risk on a large scale in daily routine of rhinologic surgeons.

Differences in anosmic and normosmic group in bimodal odorant perception: a functional- MRI study

So-called bimodal odorants are able to stimulate the intranasal trigeminal system at relatively low concentrations. Using them as stimuli, the current study focused on the interaction between the olfactory and trigeminal systems at a cerebral level. In the experiment, menthol was used at two concentrations, low and high, and these were delivered to two groups of subjects, a healthy control group and an anosmic group who were unable to perceive smells. A computer-controlled olfactometer based on principles of air-dilution was used to deliver the stimuli, while the brain functions were assessed by a functional magnetic resonance imaging (fMRI) technique. SPM5 was used for data analysis. The results showed that normosmic subjects exhibited activation in the anterior cingulate cortex (ACC) and posterior cingulate cortex (PCC), prefrontal cortex (PFC), and cerebellum. Whilst anosmic subjects activated the same area inside the anterior cingulate; moreover a cluster of activation was found in the left parahippocampal gyrus. In controls, an effect of stimulus intensity was localized between the anterior cingulated, the medial frontal gyrus and the cerebellum; such areas could not be found in anosmic subjects. These results suggest that the olfactory system modifies trigeminally mediated information causing an evident effect in the differentiation between stimulus intensities.