Einrichtung einer Checkliste für die Identifizierung von Patienten mit postoperativen spinaler Implantat Infektionen

Introduction. The incidence of postoperative spinal implant infections (PSII) has been reported to be up to 20%. Many PSIIs are caused by low virulent pathogens and thus the diagnosis rate of PSII is relatively low. There is no scientific consensus regarding the diagnostic criteria for PSII. This study therefore aimed to compare PSII patients with patients without evidence of infection. Based on the results, we aimed at formulating a comprehensive checklist with all important diagnostic parameters to help surgeons identify patients with an increased risk prior to revision surgery. Method. A retrospective study was carried out. Patients with evidence of peri-implant infections after spinal revision surgery were identified. Patients without PSII (control group: matched according to age, gender and surgical indications) were included. Digital and physical patient files were examined for collecting of clinical, radiological, laboratory, intraoperative and microbiological findings in both groups. The parameters collected were identified based on the recommendations of the Center for Disease Control and prevention, the International Consensus Meeting Criteria, and the Infectious Diseases Society of America. The paired t-test and Wilcoxon test were used to compare the two groups according to the dependence of the variables. Results. In total, 61 patients with PSII and 61 controls were included. Patients with PSII showed a significantly higher incidence of local skin findings (P = 0.008) and a raised body temperature (P = 0.003). In addition, significant risk factors for the occurrence of PSII were the presence of a port catheter (P = 0.002), positive blood culture (P = 0.008), and urinary tract infections (P = 0.032). Furthermore, patients with PSII showed a lower rate of implant failure (P = 0.031) and pain at rest or in motion (P = 0.006; P = 0.002). In summary, routine laboratory parameters showed a low sensitivity in the diagnosis of PSII. The histological analysis showed a low sensitivity of 48.84%, yet a good specificity of 100%. The microbiological culture of peri-implant tissue also showed a good specificity of 94.23%, but a moderate sensitivity of 68.63%. The sonication showed both a high sensitivity and specificity (92.45% and 95.08%). Conclusion. Individual risk factors for the occurrence of peri-implant infections already exist before the revision surgery. In summary, radiological analysis, laboratory findings and the presence of pain have been regarded as secondary to the presence of PSII. Suspicious skin findings, raised body temperature, the presence of a port catheter, blood and urinary tract infections could lead to an increased risk of peri-implant spinal infections. Considering these risk factors, sonication should be chosen to exclude a peri-implant infection due to it having the highest sensitivity and specificity. Based on the present results, a preoperative checklist for patients before spinal revision interventions was drawn up.Einleitung. Die Inzidenz postoperativer spinaler Implantat Infektionen (PSII) wurde mit bis zu 20% angegeben. Bisher gibt es keine konsensbasierten Kriterien für die Diagnose von PSII. Ziel dieser Studie ist es, Patienten mit dem Nachweis einer PSII mit Patienten ohne Infektionsnachweis zu vergleichen. Darauf basierend wird eine Checkliste mit diagnostischen Parametern entworfen, um Patienten mit einem erhöhten PSII Risiko präoperativ zu identifizieren. Methodik. Eine retrospektive Studie wurde durchgeführt. Patienten mit dem Nachweis einer PSII nach Wirbelsäulenrevisionseingriffen wurden retrospektiv identifiziert und mit einer nach Alter, Geschlecht und Indikation gepaarten Kontrollgruppe ohne PSII verglichen. Es wurden klinische, radiologische, laborchemische, intraoperative und mikrobiologische Befunde erhoben. Die verwendeten Parameter wurden auf der Basis der Empfehlungen vom Center for Disease Control and Prevention, der International Consensus Meeting Criteria und der Infectious Diseases Society of America ausgewählt. Der gepaarte t-Test und der Wilcoxon Test wurden entsprechend der Abhängigkeit der Variablen zum Vergleich der beiden Gruppen herangezogen. Ergebnisse. Es wurden 61 Patienten mit PSII zu 61 Patienten in der Kontrollgruppe gematched. Patienten mit PSII zeigten eine signifikant erhöhte Inzidenz eines lokal suspekten Hautbefundes (P = 0,008), eine erhöhte Körpertemperatur (P = 0,003), das Vorhandensein eines Portkatheters (P = 0,002), einen Erregernachweis in der Blutkultur (P = 0,008) und eine Harnwegsinfektion (P = 0,032). Patienten mit einer PSII zeigten eine niedrigere Rate an Implantatversagen (P = 0,031) und Schmerzen in Ruhe bzw. Bewegung (P = 0,006; P = 0,002). Zusammengefasst zeigten die Parameter des Routinelabors eine geringe Sensitivität in der Diagnostik von PSII. Die histologische Analyse hatte eine geringe Sensitivität von 48,84% und eine gute Spezifität von 100%. Die mikrobiologische Kultur von periimplantärem Gewebe hatte ebenfalls eine gute Spezifität von 94,23%, jedoch eine moderate Sensitivität von 68,63%. Die Sonikation zeigte sowohl eine hohe Sensitivität als auch Spezifität (92,45% und 95,08%). Schlussfolgerung. Einzelne Risikofaktoren für das Auftreten von peri-implantären Infektionen können bereits vor dem Revisionseingriff identifiziert werden. Suspekte Hautbefunde, eine erhöhte Körpertemperatur, das Vorhandensein eines Portkatheters, ein Erregernachweis in Blutkulturen und eine Harnwegsinfektion konnten als Risikofaktoren für peri-implantäre spinale Infektionen identifiziert werden. Radiologische und laborchemische Befunde, sowie vermehrte Schmerzen sind für die Diagnostik einer PSII als nachrangig zu betrachten. Die Sonikation sollte aufgrund der höchsten Sensitivität und Spezifität zum Ausschluss einer peri-implantären Infektion gewählt werden. Auf der Grundlage dieser Ergebnisse wurde eine präoperative Checkliste für Patienten vor Wirbelsäulenrevisionseingriffen entworfen

Acetabular cup position differs in spinopelvic mobility types: a prospective observational study of primary total hip arthroplasty patients

Introduction: Spinopelvic mobility was identified as a contributing factor for total hip arthroplasty (THA) instability. The influence of spinopelvic function on acetabular cup positioning has not yet been sufficiently investigated in a prospective setting. Therefore, our study aimed (1) to assess cup inclination and anteversion in standing and sitting based on spinopelvic mobility, (2) to identify correlations between cup position and spinopelvic function, (3) and to determine the influence of the individual spinal segments, spinal sagittal balance, and spinopelvic characteristics on the mobility groups. Materials and methods: A prospective study assessing 197 THA patients was conducted with stereoradiography in standing and sitting position postoperatively. Two independent investigators determined cup anteversion and inclination, C7-Sagittal vertical axis, cervical lordosis (CL), thoracic kyphosis (TK), lumbar lordosis (LL), sacral slope, pelvic tilt (PT), anteinclination (AI), and pelvic femoral angle (PFA). Spinopelvic mobility is defined based on increment PT = PTstanding - PTsitting as increment PT = 10-30 degrees normal, and increment PT > 30 degrees hypermobile. Pearson coefficient represented correlations between the cup position and spinopelvic parameters. Results: Significant differences were demonstrated for cup anteversion (stiff/hypermobile 29.3 degrees/40.1 degrees; p < 0.000) and inclination (stiff/hypermobile 43.5 degrees/60.2 degrees; p < 0.000) in sitting, but not in standing position. increment (standing/sitting) of the cup anteversion (stiff/neutral/hypermobile 5.8 degrees/12.4 degrees/19.9 degrees; p < 0.000) and inclination (stiff/neutral/hypermobile 2.3 degrees/11.2 degrees/18.8 degrees; p < 0.000) revealed significant differences between the mobility groups. The acetabular cup position in sitting, was correlated with lumbar flexibility ( increment LL) and spinopelvic mobility. Significant differences were detected between the mobility types and acetabular orientation (AI sit:stiff/hypermobile 47.6 degrees/65.4 degrees; p < 0.000) and hip motion ( increment PFA:stiff/hypermobile 65.8 degrees/37.3 degrees; p < 0.000). Assessment of the spinal segments highlighted the role of lumbar flexibility ( increment LL:stiff/hypermobile 9.9 degrees/36.2 degrees; p < 0.000) in the spinopelvic complex. Conclusion: The significantly different acetabular cup positions in sitting and in the increment between standing and sitting and the significantly altered spinopelvic characteristics in terms of stiff and hypermobile spinopelvic mobility underlined the consideration for preoperative functional radiological assessment. Identifying the patients with altered spinopelvic mechanics due to a standardized screening algorithm is necessary to provide safe acetabular cup positioning. The proximal spinal segments appeared not to be involved in the spinopelvic function

Influence of operative timing on the early post-operative radiological and clinical outcome after kyphoplasty

Purpose: To clarify the relationship between operative timing and the early post-operative radiological and clinical outcome after kyphoplasty. Methods: We conducted a retrospective cohort study including patients who underwent kyphoplasty of a single vertebra. Patients were divided into three groups (acute [< 2 weeks], subacute [2–6 weeks] or chronic [6–51 weeks]) based on the interval between fracture and surgery. The relative vertebral body height (VBH) and local kyphotic angle (LKA) of the fractured vertebra (measured on plain radiographs) as well as pain and use of analgesics were compared pre- and post-operatively (day 2) and between the groups. Results: A total of 230 patients (100 with acute, 91 with subacute and 39 with chronic fractures) with fractures from T4 to L5 were included. In all groups, there was a significant post-operative improvement in the anterior (8.9–12.9%) and middle (10.7–13.4%) VBH (all groups: p < 0.001), LKA (acute: 3.8°, p < 0.001; subacute: 4.3°, p < 0.001; chronic: 1.7°, p = 0.046) and pain. The use of analgesics significantly decreased post-operatively in the acute and subacute groups, but did not significantly change in the chronic group. Patients from acute (p = 0.042) and subacute (p = 0.027) groups showed significantly better post-operative correction of the LKA than the chronic group. Conclusion: Kyphoplasty is effective for vertebral height restoration as well as pain relief for both acute, subacute and chronic fractures. However, the achievable correction of the fracture-related local kyphosis decreases significantly after 6 weeks. Therefore, we recommend making a final decision about conservative vs. operative treatment within 6 weeks to ensure better height restoration in surgically treated patients

Spinopelvic mobility is influenced by pre-existing contralateral hip arthroplasty: a matched-pair analysis in patients undergoing hip replacement

Background: Spinopelvic mobility gained increased attention as a contributing factor for total hip arthroplasty (THA) instability. However, it is unknown how a pre-existing THA affects spinopelvic mobility. Therefore, a propensity-score-matched analysis of primary THA patients comparing the individual segments of spinopelvic mobility between patients with pre-existing THA and no-existing THA was conducted. Consequently, the study aimed to discuss (1) whether patients with a pre-existing THA have altered spinopelvic mobility compared to the control group and (2) if spinopelvic mobility changes after THA. Methods: A prospective observational study enrolled 197 elective primary THA patients, including N = 44 patients with a pre-existing unilateral THA. Using propensity-score matching adapted for age, sex, and BMI, N = 44 patients without a pre-existing THA were determined. The patients received stereoradiography in standing and relaxed sitting position pre- and postoperatively. Assessed parameters were lumbar lordosis (LL), pelvic tilt (PT), and pelvic femoral angle (PFA). Key parameters of the spinopelvic mobility were defined as lumbar flexibility ( increment LL = LLstanding - LLsitting), pelvic mobility ( increment PT = PTstanding - PTsitting) and hip motion ( increment PFA = PFA(standing) - PFA(sitting)). Pelvic mobility was classified as stiff ( increment PT = 10 degrees-30 degrees) and hypermobile ( increment PT > 30 degrees). The Wilcoxon rank sum test for dependent samples was used. Results: Pelvic mobility was significantly increased in the pre-existing THA group ( increment PT 18.2 degrees +/- 10.7) compared to the control group ( increment PT 7.7 degrees +/- 8.0; p < 0.001) preoperatively and postoperatively (pre-existing: 22.2 degrees +/- 9.3; control: 17.0 degrees +/- 9.2, p = 0.022). Lumbar flexibility was significantly increased in the pre-existing THA group ( increment LL 21.6 degrees +/- 11.8) compared to the control group ( increment LL 12.4 degrees +/- 7.8; p < 0.001) preoperatively and postoperatively (pre-existing: 25.7 degrees +/- 11.0; control: 19.0 degrees +/- 10.2; p = 0.011). The contribution of stiff pelvic mobility is distinctly smaller in the pre-existing THA group (25%) than in the control group (75%) preoperatively. Conclusions: Pre-existing THA is associated with significantly enhanced pelvic mobility and lumbar flexibility. Accordingly, we identified the patients without a pre-existing THA as risk candidates with higher likelihood for pathological spinopelvic mobility. This information will assist arthroplasty surgeons in deciding which THA candidates require preoperative radiological screening for pathologic spinopelvic mobility

Does obesity affect acetabular cup position, spinopelvic function and sagittal spinal alignment? A prospective investigation with standing and sitting assessment of primary hip arthroplasty patients

Background: Total hip arthroplasty (THA) instability is influenced by acetabular component positioning, spinopelvic function and sagittal spinal alignment. Obesity is considered as a risk factor of THA instability, but the causal relationship remains unknown. This study aimed to investigate the influence of BMI on (1) spinopelvic function (lumbar flexibility, pelvic mobility and hip motion), (2) sagittal spinal alignment pre- and postoperatively and (3) acetabular cup position postoperatively in primary THA patients in a prospective setting. Methods: One hundred ninety patients receiving primary total hip arthroplasty were enrolled in a prospective cohort study and retrospectively analysed. All patients received stereoradiography (EOS) in standing and relaxed sitting position pre-and postoperatively. C7-sagittal vertical axis (C7-SVA), lumbar lordosis (LL), pelvic incidence (PI), pelvic tilt (PT), anterior plane pelvic tilt (APPT), and pelvic femoral angle (PFA) were assessed. Key parameters of the spinopelvic function were defined as lumbar flexibility ( increment LL = LLstanding - LLsitting), pelvic mobility ( increment PT = PTstanding - PTsitting) and hip motion ( increment PFA = PFA(standing) - PFA(sitting)). Pelvic mobility was further defined based on increment PT as stiff, normal and hypermobile ( increment PT 30 degrees). The patients were stratified to BMI according to WHO definition: normal BMI >= 18.5-24.9 kg/m(2) (n = 68), overweight >= 25.0-29.9 kg/m(2) (n = 81) and obese >= 30-39.9 kg/m(2) (n = 41). Post-hoc analysis according to Hochberg's GT2 was applied to determine differences between BMI groups. Results: Standing cup inclination was significant higher in the obese group compared to the normal BMI group (45.3 degrees vs. 40.1 degrees; p = 0.015) whereas standing cup anteversion was significantly decreased (22.0 degrees vs. 25.3 degrees; p = 0.011). There were no significant differences for spinopelvic function key parameter lumbar flexibility ( increment LL), pelvic mobility ( increment PT) and hip motion ( increment PFA) in relation to BMI stratified groups. The obese group demonstrated significant enhanced pelvic retroversion compared to the normal BMI group (APPT - 1.8 degrees vs. 2.4 degrees; p = 0.028). The preoperative proportion of stiff pelvic mobility was decreased in the obese group (12.2%) compared to normal (25.0%) and overweight (27.2%) groups. Spinal sagittal alignment in C7-SVA and PI-LL mismatch demonstrated significantly greater imbalance in the obese group compared to the normal BMI group (68.6 mm vs. 42.6 mm, p = 0.002 and 7.7 degrees vs. 1.2 degrees, p = 0.032, respectively) The proportion of patients with imbalanced C7-SVA was higher in the obese (58.5%) than in the normal BMI group (44.1%). Conclusions: The significantly increased spinal sagittal imbalance with altered pelvic mechanics is a potential cause for the reported increased risk of THA dislocations in obese patients. Consequently, the increased spinal sagittal imbalance in combination with normal pelvic mobility need to be taken into account when performing THA in obese patients

A data-driven based decomposition?integration method for remanufacturing cost prediction of end-of-life products

Remanufacturing cost prediction is conducive to visually judging the remanufacturability of end-of-life (EOL) products from economic perspective. However, due to the randomness, non-linearity of remanufacturing cost and the lack of sufficient data samples. The general method for predicting the remanufacturing cost of EOL products is very low precision. To this end, a data-driven based decomposition–integration method is proposed to predict remanufacturing cost of EOL products. The approach is based on historical remanufacturing cost data to build a model for prediction. First of all, the remanufacturing cost of individual EOL product is arranged as a time series in reprocessing order. The Improved Local Mean Decomposition (ILMD) is employed to decompose remanufacturing cost time series data into several components with smooth, periodic fluctuation and use this as input. BP neural network based on Particle Swarm Optimization (PSO-BP) algorithm is utilized to predict the cost of each component. Finally, the predicted components are added to obtain the final prediction result. To illustrate and verify the feasibility of the proposed method, the remanufacturing cost of DH220 excavator is applied as the sample data, and empirical results show that the proposed model is statistically superior to other benchmark models owing to its high prediction accuracy and less computation time. And proposed method can be utilized as an effective tool to analyze and predict remanufacturing cost of EOL products

Effects of Surface Roughness on Windage Loss and Flow Characteristics in Shaft-Type Gap with Critical CO₂

To investigate the effects of surface roughness on windage loss and flow characteristics in a shaft-type gap, the skin friction coefficient (Cf) and flow versus Reynolds number (Re) at different surface roughness (Ra) and radius ratio (η) values were investigated. The results showed that Cf decreased as Re increased, and the rate of decrease was constant at low Re but reduced at high Re. The growing relative deviations between the coefficients of smooth and rough walls with Ra indicated that Cf was influenced by rough walls when Re > 102. Moreover, Cf and the variation rate increased with η and were easily influenced by Ra for larger η at low Re, since the interaction between wall roughness and fluid influences windage loss. In addition, the flow field implied the flow had transitioned to Taylor-Couette flow, Taylor vortexes occurred when Re > 102, and the number of vortexes increased with increasing Ra and were reduced with increasing η. The velocity was divided into three regions and the pressure rose from the rotational to stationary walls, but decreased with growing η as a whole. This paper improves the research exploring windage loss and will help design smaller supercritical CO2 power devices

Effects of Surface Roughness on Windage Loss and Flow Characteristics in Shaft-Type Gap with Critical CO2

To investigate the effects of surface roughness on windage loss and flow characteristics in a shaft-type gap, the skin friction coefficient (Cf) and flow versus Reynolds number (Re) at different surface roughness (Ra) and radius ratio (&eta;) values were investigated. The results showed that Cf decreased as Re increased, and the rate of decrease was constant at low Re but reduced at high Re. The growing relative deviations between the coefficients of smooth and rough walls with Ra indicated that Cf was influenced by rough walls when Re &gt; 102. Moreover, Cf and the variation rate increased with &eta; and were easily influenced by Ra for larger &eta; at low Re, since the interaction between wall roughness and fluid influences windage loss. In addition, the flow field implied the flow had transitioned to Taylor-Couette flow, Taylor vortexes occurred when Re &gt; 102, and the number of vortexes increased with increasing Ra and were reduced with increasing &eta;. The velocity was divided into three regions and the pressure rose from the rotational to stationary walls, but decreased with growing &eta; as a whole. This paper improves the research exploring windage loss and will help design smaller supercritical CO2 power devices

Action mechanism of axial flow on windage loss in open shaft‐type gap with CO2

Abstract The windage loss in rotor‐stator gap has an important effect on rotating machinery, especially with higher rotational speed and fluid density. However, the mechanism of axial flow on windage loss in open shaft‐type gap is hardly studied in most literature. To clarify it, the influences of axial Reynolds number Reu and rotational Reynolds number Reω on skin friction coefficient Cf are investigated, and flow characteristics are analyzed with different gap geometry, radius ratio η. First, the results reveal that the Cf remains constant when Reu is less than 2.8 × 104 and increases rapidly as Reu when Reu ≥ 2.8 × 104, which indicates that the effect of axial velocity u on Cf is negligible for low Reu. The positive relative deviation Δ suggests that the axial flow makes windage loss and Cf rise. Besides, a larger number of Taylor vortexes fill with gap when the effect of the centrifugal force is larger than that of the inertial force, but they gradually disappear as Reu. Subsequently, the Cf and Δ increase as η, highlighting that the effect of u on windage loss and Cf is more prominent for larger η. The fact that vorticity near walls is larger than that at the center of gap reveals that windage loss arises from the interaction between walls and fluid rather than the dissipation with fluid itself. Finally, the model of Cf in shaft‐type gap is proposed in different Reω ranges based on numerical results, and the maximum sum of squares error of 1.02 × 10−5 and minimal R2 of 0.969 satisfy the requirement of fitting accuracy and indicate that the fitting model can accurately predict Cf. The conclusions significantly help predict windage loss in open shaft‐type gap with axial flow, and further improve the design for generators of supercritical CO2 turbine‐alternator‐compressor unit