Coxa Ltd.

Tampere, Finland

Coxa Ltd.

Tampere, Finland

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Reito A.,Coxa Ltd. | Puolakka T.,Coxa Ltd. | Paakkala A.,University of Tampere | Pajamaki J.,Coxa Ltd.
International Orthopaedics | Year: 2012

Purpose: Determination of the cup orientation after metal-on-metal hip resurfacing may provide important information in the postoperative follow-up. We present a mathematical method based on a previously described approach to assess the version and inclination of the cup in the metal-on-metal bearing without a separate software computation from plain radiographs. The aim of the study was to assess the intra- and inter-observer reliability of this method. Methods: Calculation of version and inclination were done twice for 20 hip resurfacings by four observers. Intra-observer reliability was estimated by mean error and correlation of the two sets of measurement for version and inclination. Bland-Altman plots, intra-class coefficient and mean error were used to assess the inter-observer reliability of the measurements. Results: Intra-observer correlation for version measurement ranged from 0.74 to 0.94. Correlation for inclination varied between 0.94 and 0.97. Upper and lower limits of agreement in Bland-Altman plots for version measurements between observers ranged from 4.1 to 7.2 degrees and from -3.2 to -8.3 degrees, respectively. For inclination measurements the upper and lower limits ranged from 3.1 to 5.3 degrees and from -2.7 to -6.0 degrees. Conclusions: Mean errors, correlation coefficients and 95% limits of agreement were on an acceptable level. We believe that this method is applicable for clinical use. © 2011 Springer-Verlag.


Aho A.J.,Coxa Ltd | Yli-Hankala A.,University of Tampere | Lyytikainen L.-P.,University of Tampere | Kamata K.,University of Tampere | Jantti V.,Seinajoki Central Hospital
Acta Anaesthesiologica Scandinavica | Year: 2013

Background Electroencephalogram (EEG)-based depth of anaesthesia monitoring is susceptible to contaminating electromyographic (EMG) activity. Many authorities have suggested that anaesthesiologists using these monitors should interpret the raw EEG waveform seen on the anaesthesia monitor. Methods In 34 patients anaesthetized with propofol using two doses of rocuronium (0.6 and 1.2 mg/kg), we studied whether the EMG arousal can be detected visually on the anaesthesia monitor. The Bispectral Index (BIS) and Entropy biosignals on the monitor were recorded with a video camera, and the one-channel EEG recorded by the Entropy strip was collected on a laptop computer. The recordings and the one-channel EEG were analyzed offline by two experts (anaesthesiologist and neurophysiologist), both with a long experience on anaesthesia-related EEG. Results EMG arousal existed in 14/34 and 13/33 patients in the BIS and Entropy biosignals, respectively. The anaesthesiologist detected EMG on the monitor in 7/14 patients with BIS (sensitivity 50%) and in 4/13 patients with Entropy (31%). The clinical neurophysiologist detected EMG in 6/14 (43%) patients with BIS and in 5/13 (38%) with Entropy. The specificity of the EMG analyses was 55 and 65% with BIS, and 85 and 90% with Entropy. EMG arousal was detected in BIS biosignal in 10/17 and 4/17 patients with 0.6 and 1.2 mg/kg doses of rocuronium (P = 0.04). Conclusions In contrast to many EEG phenomena, EMG activity cannot be accurately detected visually from the raw EEG on the anaesthesia monitor. Further development in the quality of the anaesthesia monitors is warranted. © 2012 The Acta Anaesthesiologica Scandinavica Foundation.


Aho A.J.,Coxa Ltd | Kamata K.,University of Tampere | Yli-Hankala A.,University of Tampere | Lyytikainen L.-P.,University of Tampere | And 2 more authors.
Acta Anaesthesiologica Scandinavica | Year: 2012

Sugammadex is designed to antagonize neuromuscular blockade (NMB) induced by rocuronium or vecuronium. In clinical practice, we have noticed a rise in the numerical values of bispectral index (BIS) and Entropy, two electroencephalogram (EEG) - based depth of anesthesia monitors, during the reversal of the NMB with sugammadex. The aim of this prospective, randomized, double-blind study was to test this impression and to compare the effects of sugammadex and neostigmine on the BIS and Entropy values during the reversal of the NMB. Methods Thirty patients undergoing gynecological operations were studied. Patients were anesthetized with target-controlled infusions of propofol and remifentanil, and rocuronium was used to induce NMB. After operation, during light propofol-remifentanil anesthesia, NMB was antagonized with sugammadex or neostigmine. During the following 5, the numerical values of BIS, BIS electromyographic (BIS EMG) and Entropy were recorded on a laptop computer, as well as the biosignal recorded by the Entropy strip. The Entropy biosignal was studied off-line both in time and frequency domain to see if NMB reversal causes changes in EEG. Results In some patients, administration of sugammadex or neostigmine caused a significant rise in the numerical values of BIS, BIS EMG and Entropy. This phenomenon was most likely caused by increased electromyographic (EMG) activity. The administration of sugammadex or neostigmine appeared to have only minimal effect on EEG. Conclusion The EMG contamination of EEG causes BIS and Entropy values to rise during reversal of rocuronium-induced NMB in light propofol-remifentanil anesthesia. © 2012 The Acta Anaesthesiologica Scandinavica Foundation.


Vaananen P.,Coxa Ltd. | Vaananen P.,University of Eastern Finland | Pajamaki I.,Coxa Ltd. | Pajamaki I.,Hatanpaa Hospital | And 5 more authors.
Journal of Bone and Joint Surgery - Series B | Year: 2010

We used a biodegradable mesh to convert an acetabular defect into a contained defect in six patients at total hip replacement. Their mean age was 61 years (46 to 69). The mean followup was 32 months (19 to 50). Before clinical use, the strength retention and hydrolytic in vitro degradation properties of the implants were studied in the laboratory over a two-year period. A successful clinical outcome was determined by the radiological findings and the Harris hip score. All the patients had a satisfactory outcome and no mechanical failures or other complications were observed. No protrusion of any of the impacted grafts was observed beyond the mesh. According to our preliminary laboratory and clinical results the biodegradable mesh is suitable for augmenting uncontained acetabular defects in which the primary stability of the implanted acetabular component is provided by the host bone. In the case of defects of the acetabular floor this new application provides a safe method of preventing graft material from protruding excessively into the pelvis and the mesh seems to tolerate bone-impaction grafting in selected patients with primary and revision total hip replacement. ©2010 British Editorial Society of Bone and Joint Surgery.


Aho A.J.,Coxa Ltd | Aho A.J.,University of Tampere | Kamata K.,University of Tampere | Jantti V.,Seinajoki Central Hospital | And 5 more authors.
British Journal of Anaesthesia | Year: 2015

Background Concomitantly recorded Bispectral Index® (BIS) and Entropy™ values sometimes show discordant trends during general anaesthesia. Previously, no attempt had been made to discover which EEG characteristics cause discrepancies between BIS and Entropy. We compared BIS and Entropy values, and analysed the changes in the raw EEG signal during surgical anaesthesia with sevoflurane. Methods In this prospective, open-label study, 65 patients receiving general anaesthesia with sevoflurane were enrolled. BIS, Entropy and multichannel digital EEG were recorded. Concurrent BIS and State Entropy (SE) values were selected. Whenever BIS and SE values showed ≥10-unit disagreement for ≥60 s, the raw EEG signal was analysed both in time and frequency domain. Results A ≥10-unit disagreement ≥60 s was detected 428 times in 51 patients. These 428 episodes accounted for 5158 (11%) out of 45 918 analysed index pairs. During EEG burst suppression, SE was higher than BIS in 35 out of 49 episodes. During delta-theta dominance, BIS was higher than SE in 141 out of 157 episodes. During alpha or beta activity, SE was higher than BIS in all 49 episodes. During electrocautery, both BIS and SE changed, sometimes in the opposite direction, but returned to baseline values after electrocautery. Electromyography caused index disagreement four times (BIS > SE). Conclusions Certain specific EEG patterns, and artifacts, are associated with discrepancies between BIS and SE. Time and frequency domain analyses of the original EEG improve the interpretation of studies involving BIS, Entropy and other EEG-based indices. Clinical trial registration.ClinicalTrials.gov:identifier NCT01077674. © 2015 The Author.


Lehtonen J.-M.,Tampere University of Technology | Torkki P.,Aalto University | Peltokorpi A.,Aalto University | Moilanen T.,Coxa Ltd
International Journal of Health Care Quality Assurance | Year: 2013

Purpose: Previous studies approach surgery scheduling mainly from the mathematical modeling perspective which is often hard to apply in a practical environment. The aim of this study is to develop a practical scheduling system that considers the advantages of both surgery categorization and newsvendor model to surgery scheduling. Design/methodology/approach: The research was carried out in a Finnish orthopaedic specialist centre that performs only joint replacement surgery. Four surgery categorization scenarios were defined and their productivity analyzed by simulation and newsvendor model. Findings: Detailed analyses of surgery durations and the use of more accurate case categories and their combinations in scheduling improved OR productivity 11.3 percent when compared to the base case. Planning to have one OR team to work longer led to remarkable decrease in scheduling inefficiency. Practical implications: In surgical services, productivity and cost-efficiency can be improved by utilizing historical data in case scheduling and by increasing flexibility in personnel management. Originality/value: The study increases the understanding of practical scheduling methods used to improve efficiency in surgical services. © Emerald Group Publishing Limited.


Reito A.,Coxa Ltd | Puolakka T.,Coxa Ltd | Pajamaki J.,Coxa Ltd
International Orthopaedics | Year: 2011

Hip resurfacings have been performed in our hospital since May 2001, and in this retrospective study, we analysed the clinical and radiological outcome of the first 144 prostheses (126 patients). One hundred and seven patients have visited our hospital for regular follow-up examination; 16 are not in regular follow-up and were sent a Harris Hip Score (HHS) questionnaire. Three patients live abroad. Mean follow-up was six years. One patient was lost during follow-up. Four prostheses have been revised. The six year cumulative survival rate was 96.7%. Two female patients required revision for aseptic lymphocyte-dominated vascular associated lesions (ALVAL) and two male patients due for femoral head necrosis. Both reoperated female patients had cup inclination <60°. Mean HHS in the follow-up was 95.3, and mean patient satisfaction 2.53 on a scale 0-3. Neck thinning <10% was seen in seven hips and impingement in 12 hips. © Springer-Verlag 2010.


Determination of the cup orientation after metal-on-metal hip resurfacing may provide important information in the postoperative follow-up. We present a mathematical method based on a previously described approach to assess the version and inclination of the cup in the metal-on-metal bearing without a separate software computation from plain radiographs. The aim of the study was to assess the intra- and inter-observer reliability of this method.Calculation of version and inclination were done twice for 20 hip resurfacings by four observers. Intra-observer reliability was estimated by mean error and correlation of the two sets of measurement for version and inclination. Bland-Altman plots, intra-class coefficient and mean error were used to assess the inter-observer reliability of the measurements.Intra-observer correlation for version measurement ranged from 0.74 to 0.94. Correlation for inclination varied between 0.94 and 0.97. Upper and lower limits of agreement in Bland-Altman plots for version measurements between observers ranged from 4.1 to 7.2 degrees and from -3.2 to -8.3 degrees, respectively. For inclination measurements the upper and lower limits ranged from 3.1 to 5.3 degrees and from -2.7 to -6.0 degrees.Mean errors, correlation coefficients and 95% limits of agreement were on an acceptable level. We believe that this method is applicable for clinical use.


PubMed | Coxa Ltd
Type: Journal Article | Journal: Acta anaesthesiologica Scandinavica | Year: 2012

Sugammadex is designed to antagonize neuromuscular blockade (NMB) induced by rocuronium or vecuronium. In clinical practice, we have noticed a rise in the numerical values of bispectral index (BIS) and Entropy, two electroencephalogram (EEG) - based depth of anesthesia monitors, during the reversal of the NMB with sugammadex. The aim of this prospective, randomized, double-blind study was to test this impression and to compare the effects of sugammadex and neostigmine on the BIS and Entropy values during the reversal of the NMB.Thirty patients undergoing gynecological operations were studied. Patients were anesthetized with target-controlled infusions of propofol and remifentanil, and rocuronium was used to induce NMB. After operation, during light propofol-remifentanil anesthesia, NMB was antagonized with sugammadex or neostigmine. During the following 5 min, the numerical values of BIS, BIS electromyographic (BIS EMG) and Entropy were recorded on a laptop computer, as well as the biosignal recorded by the Entropy strip. The Entropy biosignal was studied off-line both in time and frequency domain to see if NMB reversal causes changes in EEG.In some patients, administration of sugammadex or neostigmine caused a significant rise in the numerical values of BIS, BIS EMG and Entropy. This phenomenon was most likely caused by increased electromyographic (EMG) activity. The administration of sugammadex or neostigmine appeared to have only minimal effect on EEG.The EMG contamination of EEG causes BIS and Entropy values to rise during reversal of rocuronium-induced NMB in light propofol-remifentanil anesthesia.


PubMed | Coxa Ltd
Type: Journal Article | Journal: Acta anaesthesiologica Scandinavica | Year: 2013

Electroencephalogram (EEG)-based depth of anaesthesia monitoring is susceptible to contaminating electromyographic (EMG) activity. Many authorities have suggested that anaesthesiologists using these monitors should interpret the raw EEG waveform seen on the anaesthesia monitor.In 34 patients anaesthetized with propofol using two doses of rocuronium (0.6 and 1.2mg/kg), we studied whether the EMG arousal can be detected visually on the anaesthesia monitor. The Bispectral Index (BIS) and Entropy biosignals on the monitor were recorded with a video camera, and the one-channel EEG recorded by the Entropy strip was collected on a laptop computer. The recordings and the one-channel EEG were analyzed offline by two experts (anaesthesiologist and neurophysiologist), both with a long experience on anaesthesia-related EEG.EMG arousal existed in 14/34 and 13/33 patients in the BIS and Entropy biosignals, respectively. The anaesthesiologist detected EMG on the monitor in 7/14 patients with BIS (sensitivity 50%) and in 4/13 patients with Entropy (31%). The clinical neurophysiologist detected EMG in 6/14 (43%) patients with BIS and in 5/13 (38%) with Entropy. The specificity of the EMG analyses was 55 and 65% with BIS, and 85 and 90% with Entropy. EMG arousal was detected in BIS biosignal in 10/17 and 4/17 patients with 0.6 and 1.2mg/kg doses of rocuronium (P=0.04).In contrast to many EEG phenomena, EMG activity cannot be accurately detected visually from the raw EEG on the anaesthesia monitor. Further development in the quality of the anaesthesia monitors is warranted.

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