Sedation reversal trends at outpatient ambulatory endoscopic center vs in-hospital ambulatory procedure center using a triage protocol.

BACKGROUND: Routine outpatient endoscopy is performed across a variety of outpatient settings. A known risk of performing endoscopy under moderate sedation is the potential for over-sedation, requiring the use of reversal agents. More needs to be reported on rates of reversal across different outpatient settings. Our academic tertiary care center utilizes a triage tool that directs higher-risk patients to the in-hospital ambulatory procedure center (APC) for their procedure. Here, we report data on outpatient sedation reversal rates for endoscopy performed at an in-hospital APC vs at a free-standing ambulatory endoscopy digestive health center (AEC-DHC) following risk stratification with a triage tool. AIM: To observe the effect of risk stratification using a triage tool on patient outcomes, primarily sedation reversal events. METHODS: We observed all outpatient endoscopy procedures performed at AEC-DHC and APC from April 2013 to September 2019. Procedures were stratified to their respective sites using a triage tool. We evaluated each procedure for which sedation reversal with flumazenil and naloxone was recorded. Demographics and characteristics recorded include patient age, gender, body mass index (BMI), American Society of Anesthesiologists (ASA) classification, procedure type, and reason for sedation reversal. RESULTS: There were 97366 endoscopic procedures performed at AEC-DHC and 22494 at the APC during the study period. Of these, 17 patients at AEC-DHC and 9 at the APC underwent sedation reversals (0.017% vs 0.04%; P = 0.06). Demographics recorded for those requiring reversal at AEC-DHC vs APC included mean age (53.5 ± 21 vs 60.4 ± 17.42 years; P = 0.23), ASA class (1.66 ± 0.48 vs 2.22 ± 0.83; P = 0.20), BMI (27.7 ± 6.7 kg/m2 vs 23.7 ± 4.03 kg/m2; P = 0.06), and female gender (64.7% vs 22%; P = 0.04). The mean doses of sedative agents and reversal drugs used at AEC-DHC vs APC were midazolam (5.9 ± 1.7 mg vs 8.9 ± 3.5 mg; P = 0.01), fentanyl (147.1 ± 49.9 µg vs 188.9 ± 74.1 µg; P = 0.10), flumazenil (0.3 ± 0.18 µg vs 0.17 ± 0.17 µg; P = 0.13) and naloxone (0.32 ± 0.10 mg vs 0.28 ± 0.12 mg; P = 0.35). Procedures at AEC-DHC requiring sedation reversal included colonoscopies (n = 6), esophagogastroduodenoscopy (EGD) (n = 9) and EGD/colonoscopies (n = 2), whereas APC procedures included EGDs (n = 2), EGD with gastrostomy tube placement (n = 1), endoscopic retrograde cholangiopancreatography (n = 2) and endoscopic ultrasound's (n = 4). The indications for sedation reversal at AEC-DHC included hypoxia (n = 13; 76%), excessive somnolence (n = 3; 18%), and hypotension (n = 1; 6%), whereas, at APC, these included hypoxia (n = 7; 78%) and hypotension (n = 2; 22%). No sedation-related deaths or long-term post-sedation reversal adverse outcomes occurred at either site. CONCLUSION: Our study highlights the effectiveness of a triage tool used at our tertiary care hospital for risk stratification in minimizing sedation reversal events during outpatient endoscopy procedures. Using a triage tool for risk stratification, low rates of sedation reversal can be achieved in the ambulatory settings for EGD and colonoscopy.

Outcomes of colon self-expandable metal stents for malignant vs benign indications at a tertiary care center and review of literature.

BACKGROUND: Endoscopic placement of a self-expandable metal stent (SEMS) is a minimally invasive treatment for use in malignant and benign colonic obstruction. However, their widespread use is still limited with a nationwide analysis showing only 5.4% of patients with colon obstruction undergoing stent placement. This underutilization could be due to perceived increase risk of complications with stent placement. AIM: To review long- and short-term clinical success of SEMS use for colonic obstruction at our center. METHODS: We retrospectively reviewed all the patients who underwent colonic SEMS placement over a eighteen year period (August 2004 through August 2022) at our academic center. Demographics including age, gender, indication (malignant and benign), technical success, clinical success, complications (perforation, stent migration), mortality, and outcomes were recorded. RESULTS: Sixty three patients underwent colon SEMS over an 18-year period. Fifty-five cases were for malignant indications, 8 were for benign conditions. The benign strictures included diverticular disease stricturing (n = 4), fistula closure (n = 2), extrinsic fibroid compression (n = 1), and ischemic stricture (n = 1). Forty-three of the malignant cases were due to intrinsic obstruction from primary or recurrent colon cancer; 12 were from extrinsic compression. Fifty-four strictures occurred on the left side, 3 occurred on the right and the rest in transverse colon. The total malignant case (n = 55) procedural success rate was 95% vs 100% for benign cases (P = 1.0, NS). Overall complication rate was significantly higher for benign group: Four complications were observed in the malignant group (stent migration, restenosis) vs 2 of 8 (25%) for benign obstruction (1-perforation, 1-stent migration) (P = 0.02). When stratifying complications of perforation and stent migration there was no significant difference between the two groups (P = 0.14, NS). CONCLUSION: Colon SEMS remains a worthwhile option for colonic obstruction related to malignancy and has a high procedural and clinical success rate. Benign indications for SEMS placement appear to have similar success to malignant. While there appears to be a higher overall complication rate in benign cases, our study is limited by sample size. When evaluating for perforation alone there does not appear to be any significant difference between the two groups. SEMS placement may be a practical option for indications other that malignant obstruction. Interventional endoscopists should be aware and discuss the risk for complications in setting of benign conditions. Indications in these cases should be discussed in a multi-disciplinary fashion with colorectal surgery.

Spectrum of Drug Resistance in Musculoskeletal Tuberculosis.

BACKGROUND: Very few studies report resistance pattern exclusively in musculoskeletal tuberculosis (MSK-TB). METHODS: This study of 100 pus samples from patients of MSK-TB with active disease in whom Mycobacterium tuberculosis (MTB) was detected by cartridge-based nucleic acid amplification test (CBNAAT), revealed the pattern of resistance among newly diagnosed and previously treated cases. Liquid culture and drug susceptibility testing (DST) using MGIT 960 was done for 11 anti-tubercular drugs. RESULTS: Among these 100 cases; 22% were AFB positive; MGIT 960 detected MTB in 58.33% (35/60) new cases and 30.0% (12/40) previously treated cases. Five new and 10 previously treated cases had drug resistance and 12 were detected rifampicin resistance (Rif-R) by CBNAAT. Among new cases MGIT-DST detected mono-INH resistant in 2.86% (1/35), mono-STR resistant in 2.86% (1/35), MDR-TB in 5.7% (2/35) and pre-XDR in 2.9%(1/35).Among previously treated cases Rif-R was found in 10% (4/40) where MTB was not detected by MGIT and MGIT-DST detected mono-INH resistant in 8.33% (1/12); MDR-TB in 8.33% (1/12) and pre-XDR in 33.3%. There were no cases of XDR-TB. CONCLUSION: High disease burden of various type drug resistance were seen more commonly in previously treated cases and was not uncommon in new cases of MSK-TB. Both CBNAAT and DST are essential for detecting resistance pattern in MSK-TB.

Prospective Comparison of Moderate Conscious Sedation and Anesthesia Assistance for the Performance of Endoscopic Retrograde Cholangiopancreatography (ERCP).

Objectives: Recent trends have favored the use of anesthesia personnel more frequently for advanced endoscopic procedures. We hypothesize a selective sedation approach based on patient and procedural factors using either moderate conscious sedation (MCS) or general anesthesia (GA) will result in similar outcomes and safety with significant cost savings. Methods: A 12-month prospective study of all adult endoscopic retrograde cholangiopancreatography (ERCPs) performed at a tertiary medical center was enrolled. Technical success, cannulation rates, procedural related complications, procedure time, and cost were compared between MCS and GA. Results: A total of 876 ERCPs were included in the study with 74% performed with MCS versus 26% with GA. The intended intervention was completed successfully in 95% of cases with MCS versus 96% cases with GA (p = 0.59). Cannulation success rates with MCS were 97.5 versus 97.8% with GA (p = 0.81). Overall, adverse event rates were similar in both groups (MCS: 6.6% vs. GA: 9.2%, p = 0.21). Mean procedure time was less for MCS versus GA, 18.3 and 26 minutes, respectively (p < 0.0001). Selective use of MCS vs. universal sedation with GA resulted in estimated savings of $8,190 per case and $4,735,202 per annum. Conclusions: Preselection of ERCP sedation of moderate conscious sedation versus general anesthesia based upon patient risk factors and planned therapeutic intervention allows for the majority of ERCPs to be completed with MCS with similar rates of technical success and improvement in resource utilization and cost savings compared to performing ERCPs universally with anesthesia assistance.

Trends in Wait Time for Colorectal Cancer Screening and Diagnosis 2013-2016.

OBJECTIVES: Colorectal cancer (CRC) screening has increased in the United States during the past 20 years, resulting in an increased demand for colonoscopy. We tested the hypothesis that such increase resulted in longer wait times for colonoscopy and influenced CRC diagnosis. METHODS: A total of 36,623 consecutive colonoscopies performed at the University of Wisconsin from April 8, 2013, until December 31, 2016, were included in the analysis. Wait times for colonoscopy were stratified by consecutive 6-month periods and indications of screening/surveillance vs diagnostic colonoscopy. RESULTS: Despite unchanged number of endoscopists, more colonoscopies were performed in 2015-2016 than in 2013-2014 (20,897 vs 15,726, respectively, P = 0.004). The mean wait time for colonoscopy increased from 68 days in 2013-2014 to 111 days in 2015-2016 (P < 0.0001), with most change affecting screening/surveillance colonoscopy. In 170 patients with a newly diagnosed CRC, the wait time did not significantly change between 2013-2014 and 2015-2016 (21 vs 27 days, respectively, P = 0.2206). DISCUSSION: An increase in screening/surveillance colonoscopies resulted in a substantial rise in the number of procedures between 2013 and 2016. This increase was associated with longer wait times for screening/surveillance but not diagnostic colonoscopy. Longer wait times did not result in later CRC stage at diagnosis.

A Prospective, Randomized Comparison of Duodenoscope Reprocessing Surveillance Methods.

Duodenoscope use in healthcare facilities has been associated with transmission of multidrug resistant pathogens between patients. To assist healthcare facilities in monitoring the quality of their duodenoscope reprocessing procedures and limit patient risk of infection, the Centers for Disease Control and Prevention (CDC) deployed voluntary interim duodenoscope sampling and culturing surveillance protocols in 2015. Though the interim methods were widely adopted, alternative surveillance protocols were developed and implemented at individual institutions. Here, we compared two sampling methods-the 2015 CDC interim protocol and an alternative protocol developed by the University of Wisconsin Hospitals and Clinics (UWHC). We hypothesized that the UWHC protocol would detect a higher incidence of bacterial contamination from reprocessed duodenoscopes. A total of 248 sampling events were performed at UWHC. The CDC protocol (n = 129 sampling events) required culturing samples collected from each duodenoscope after brushing its terminal end and flushing its lumen with sterile water. The UWHC protocol (n = 119 sampling events) required culturing samples collected from each duodenoscope after swabbing its elevator, immersing its terminal end into broth and flushing its lumen with saline. With the CDC method, 8.53% (n = 11) of the duodenoscopes sampled were positive for bacterial growth with 15 isolates recovered. Using the UWHC method, 15.13% (n = 18) of cultures were positive for bacterial growth with 20 isolates recovered. The relative risk of identifying a contaminated duodenoscope using the CDC interim method, however, was not different than when using the UWHC protocol. Mean processing time (27.35 and 5.11 minutes, p < 0.001) and total cost per sample event ($17.87 and $15.04) were lower using the UWHC method. As the UWHC protocol provides similar detection rates as the CDC protocol, the UWHC method is useful, provided the shorter processing time and lower cost to perform.

A Rare Case of Endometrial Cancer Metastatic to the Sigmoid Colon and Small Bowel.

Metastatic endometrial cancer to the small bowel or colon has been described but is quite rare. We present a case of metastatic endometrial cancer with synchronous metastases to the colon and jejunum identified three years after surgical treatment of early stage endometrial cancer.

Laparoscopic-assisted ERCP and EUS in patients with prior Roux-en-Y gastric bypass surgery: a dual-center case series experience.

BACKGROUND: Patients with Roux-en-Y gastric bypass (RYGB) develop pancreatobiliary issues after surgery. Endoscopic management via the conventional route with endoscopic retrograde cholangiopancreatography (ERCP) and endoscopic ultrasound (EUS) is quite limited due to the altered anatomy. Laparoscopic-assisted ERCP (LA-ERCP) via the excluded stomach has been highly successful. Reported use of laparoscopic-assisted EUS (LA-EUS) is extremely rare. METHODS: A retrospective review was conducted at two tertiary referral centers for cases that involved laparoscopic-assisted ERCP and EUS. Patient demographic data were collected along with data regarding procedure, indication, complications and length of stay. RESULTS: A total of 16 cases involving 15 patients were identified: 11 cases of LA-ERCP and five cases of combined LA-EUS plus LA-ERCP were performed. Four patients had previously undergone failed endoscopy via the conventional route (27 %). There was a 100 % biliary/pancreatic cannulation and intervention rate. There were no endoscopic-related complications. Therapeutic interventions included laparoscopic cholecystectomy, lysis of adhesions, biliary and pancreatic sphincterotomy, biliary and pancreatic stent placement, stone removal including mechanical lithotripsy and EUS biopsy and diagnosis of pancreatic cancer. Average discharge was on postoperative day 3.4. However, 50 % were discharged after 1 day. CONCLUSIONS: LA-ERCP and combined LA-EUS plus LA-ERCP are safe and highly successful diagnostic and therapeutic modalities for a wide variety of pancreatobiliary ailments in RYGB patients.

Comparison of Capsule Endoscopy Findings to Subsequent Double Balloon Enteroscopy: A Dual Center Experience.

Background. There has been a growing use of both capsule endoscopy (CE) and double balloon enteroscopy (DBE) to diagnose and treat patients with obscure gastrointestinal blood loss and suspected small bowel pathology. Aim. To compare and correlate sequential CE and DBE findings in a large series of patients at two tertiary level hospitals in Wisconsin. Methods. An IRB approved retrospective study of patients who underwent sequential CE and DBE, at two separate tertiary care academic centers from May 2007 to December 2011, was performed. Results. 116 patients were included in the study. The mean age ± SD was 66.6 ± 13.2 years. There were 56% males and 43.9% females. Measure of agreement between prior capsule and DBE findings was performed using kappa statistics, which gave kappa value of 0.396 with P < 0.001. Also contingency coefficient was calculated and was found to be 0.732 (P < 0.001). Conclusions. Our study showed good overall agreement between DBE and CE. Findings of angioectasia had maximum agreement of 69%.

Endoscopic ultrasound in the evaluation of pancreatic neoplasms-solid and cystic: A review.

Pancreatic neoplasms have a wide range of pathology, from pancreatic adenocarcinoma to cystic mucinous neoplasms. Endoscopic ultrasound (EUS) with or without fine needle aspiration (FNA) is a helpful diagnostic tool in the work-up of pancreatic neoplasms. Its utility in pancreatic malignancy is well known. Over the last two decades EUS-FNA has become a procedure of choice for diagnosis of pancreatic adenocarcinoma. EUS-FNA is highly sensitive and specific for solid lesions, with sensitivities as high as 80%-95% for pancreatic masses and specificity as high as 75%-100%. Multiple aspects of the procedure have been studied to optimize the rate of diagnosis with EUS-FNA including cytopathologist involvement, needle size, suctioning and experience of endoscopist. Onsite pathology is one of the most important elements in increasing diagnostic yield rate in EUS-FNA. EUS-FNA is valuable in diagnosing rare and atypical pancreatic neoplasms including neuroendocrine, lymphoma and metastatic disease. As more and more patients undergo cross sectional imaging, cystic lesions of the pancreas are becoming a more common occurrence and EUS-FNA of these lesions can be helpful for differentiation. This review covers the technical aspects of optimizing pancreatic neoplasm diagnosis rate, highlight rare pancreatic neoplasms and role of EUS-FNA, and also outline the important factors in diagnosis of cystic lesions by EUS-FNA.

Modelling hollow organs for impact conditions: a simplified case study.

This study compares the performances of three numerical approaches [Lagrangian (LAG), arbitrary Lagrangian-Eulerian (ALE) and control volume (CV)] for modelling the response of a short cylindrical pipe representing a portion of the intestines subjected to large and rapid compressions. While not being able to simulate sustained fluid flow, the LAG approach provided similar results as the ALE for moderate levels of compression. However, it was the stiffest approach for larger levels and had numerical issues for extreme compressions. While the ALE did not have these issues, its computing cost was very high, which would be problematic for large models. The CV approach had the lowest computing cost and seemed promising for larger compressions. However, its response was the softest and further investigations are needed to define its dependency to modelling parameters.

Influence of previous night call and sleep deprivation on screening colonoscopy quality.

OBJECTIVES: There are few studies evaluating the influence of sleep deprivation on endoscopic outcomes. To evaluate the effect of a previous night call on the quality of screening colonoscopies performed the following day. METHODS: Average-risk patients undergoing screening colonoscopies were included. Quality metrics were retrospectively compared between two groups of post-call colonoscopies and colonoscopies performed by the same individuals not on call the night before: those performed by gastroenterologists who were only on call the night prior and those performed by gastroenterologists who performed emergent on-call procedures the night prior. RESULTS: Between 1 July 2010 and 31 March 2012, 447 colonoscopies were performed by gastroenterologists who were on call only the night prior, 126 colonoscopies were performed by gastroenterologists who had completed on-call emergent procedures the night prior, and 8,734 control colonoscopies were completed. There was a lower percent of patients who were screened with adenomas detected in procedures performed by endoscopists who had performed emergent on-call procedures the night prior compared with the controls (30 vs. 39%, respectively; P=0.043). The mean withdrawal time for these colonoscopies was significantly longer than that for the control procedures (15.5 vs. 14.0 min; P=0.025). For the colonoscopies performed by endoscopists who were on call only the night prior, there was no significant difference in the percent of patients screened with adenomas detected compared with controls (42 vs. 39%, respectively; P=0.136). CONCLUSIONS: (1) Despite longer withdrawal times, being on call the night prior and performing an emergent procedure lead to a significant 24% decrease in the adenoma detection rates. (2) It is imperative for screening physicians to be aware of the influence of sleep deprivation on procedural outcomes and to consider altering their practice accordingly.

Observations on pedestrian pre-crash reactions during simulated accidents.

Pedestrian protection systems, both active and passive systems, are being introduced in the EU and Japan to comply with regulatory requirements. Their designs are specific and, in general, reflect an accident scenario of the pedestrian being struck on the side by a vehicle traveling at a maximum travel speed of 40 kph. The present study is an effort to quantify the effects of pedestrian reaction prior to an accident and identify characteristics that may help minimize or prevent the pedestrian to vehicle interaction. Accident situations were simulated with volunteers using a non-impacting methodology. Fifty one reactions from 23 volunteers of two age groups were observed. Most of the volunteers were found to run, step-back or stop in fright in a dangerous situation. Volunteer speed was an important parameter which could help in differentiating these reactions. Age related differences were also observed, both for reaction strategy and reaction times. While the majority of young subjects ran, elderly stopped as often as they run. Volunteers' posture at the time of impact was found to be highly variable irrespective of the type of reactions. The exception was when a volunteer stopped/braced in apparent fright and raised their arms to form a triangle covering their face and their head. Results of the present study may be helpful when selecting or evaluating the benefit of pedestrian safety strategies by allowing the inclusion of information about types of reaction, pedestrian speed, reaction time and age differences in the scenarios. In addition, pedestrian pre-crash postures and muscle activities could be utilized for evaluating/improving the passive safety systems and active models.

Endoscopic ultrasound fine-needle aspiration characteristics of primary adenocarcinoma versus other malignant neoplasms of the pancreas.

BACKGROUND: Endoscopic ultrasound (EUS) with fine-needle aspiration (FNA) is often used to assist in the evaluation of pancreatic lesions and may help to diagnose benign versus malignant neoplasms. However, there is a paucity of literature regarding comparative EUS characteristics of various malignant pancreatic neoplasms (primary and metastatic). OBJECTIVE: To compare and characterize primary pancreatic adenocarcinoma versus other malignant neoplasms, hereafter referred to as nonprimary pancreatic adenocarcinoma (NPPA), diagnosed by EUS-guided FNA. METHODS: The present study was a retrospective analysis of a prospectively maintained database. The setting was a tertiary care, academic medical centre. Patients referred for suspected pancreatic neoplasms were evaluated. Based on EUS-FNA characteristics, primary pancreatic adenocarcinoma was differentiated from other malignant neoplasms. The subset of other neoplasms was defined as malignant lesions that were 'NPPAs' (ie, predominantly solid or solid/cystic based on EUS appearance and primary malignant lesions or metastatic lesions to the pancreas). Pancreatic masses that were benign cystic lesions (pseudocyst, simple cyst, serous cystadenoma) and focal inflammatory lesions (acute, chronic and autoimmune pancreatitis) were excluded. RESULTS: A total of 230 patients were evaluated using EUS-FNA for suspected pancreatic mass lesions. Thirty-eight patients were excluded because they were diagnosed with inflammatory lesions or had purely benign cysts. One hundred ninety-two patients had confirmed malignant pancreatic neoplasms (ie, pancreatic adenocarcinoma [n=144], NPPA [n=48]). When comparing adenocarcinoma with NPPA lesions, there was no significant difference in mean age (P=0.0675), sex (P=0.3595) or average lesion size (P=0.3801). On average, four FNA passes were necessary to establish a cytological diagnosis in both lesion subtypes (P=0.396). Adenocarcinomas were more likely to be located in the pancreatic head (P=0.0198), whereas masses in the tail were more likely to be NPPAs (P=0.0006). Adenocarcinomas were also more likely to exhibit vascular invasion (OR 4.37; P=0.0011), malignant lymphadenopathy (P=0.0006), pancreatic duct dilation (OR 2.4; P=0.022) and common bile duct dilation (OR 2.87; P=0.039). CONCLUSIONS: Adenocarcinoma was more likely to be present in the head of the pancreas, have lymph node and vascular involvement, as well as evidence of pancreatic duct and common bile duct obstruction. Of all malignant pancreatic lesions analyzed by EUS-FNA, 25% were NPPA, suggesting that FNA is crucial in establishing a diagnosis and may be helpful in preoperative planning.

Fiscal analysis of establishment of a double-balloon enteroscopy program and reimbursement.

BACKGROUND & AIMS: As double-balloon enteroscopy (DBE) programs continue to be established, further research is needed to assess their financial impact. We evaluated actual financial outcomes and compared them with estimated return on investment (ROI) projections for DBE. METHODS: We retrospectively compared the predicted and actual financial results for outpatients referred for DBE at an academic tertiary referral center. RESULTS: The ROI analysis was based on a 5-year time frame. The analysis projected a net present value of $64,623 and an internal rate of return of 24.6%. The projected first-year volume was 52 outpatient cases; however, the actual experience was 20 outpatient cases. The predicted percent margin for these outpatient cases was 16.6%; the actual margin was 24.4%. After 37 months, 52 outpatient cases were completed, and the actual percent margin was 4.6%. Payer type had a significant influence on the financial outcomes when projected activity and actual activity were compared. CONCLUSIONS: Institutions interested in establishing a DBE program should be aware of the financial implications of program establishment, which can be evaluated in a return on investment analysis. Payer mix significantly influences DBE reimbursement and collection rates.

Outcomes of sphincter of oddi manometry when performed in low volumes.

Background. Sphincter of Oddi manometry is a highly specialized procedure associated with an increased risk of procedural complications. Published studies have typically been performed in large volume manometry centers. Objective. To examine the outcomes and complication rate of SOM when performed in small volumes. Design. Retrospective analysis at a tertiary care referral hospital that infrequently performs Sphincter of Oddi manometry. Patient records were reviewed for procedural details, patient outcomes, and complications after sphincter of Oddi manometry. Results. 36 patients, 23 (23 type II sphincter of Oddi dysfunction (SOD), 13 type III SOD) underwent sphincter of Oddi manometry and were followed up for mean of 16 months. Nine Type II patients (90%) with elevated basal sphincter pressures noted symptom improvement after sphincterotomy compared with only 3 patients (43%) of the patients with normal basal pressures. In type III SOD, 7 patients had elevated basal SO pressure and underwent sphincterotomy. Three patients (43%) improved. There were six (16%) procedure-related complications. There were four cases of post ERCP pancreatitis (11%), all of which were mild. Conclusion. In low numbers, sphincter of Oddi manometry can be performed successfully and safely by experienced biliary endoscopists with results that are comparable to large volume centers.

Effect of active muscle forces on knee injury risks for pedestrian standing posture at low-speed impacts.

OBJECTIVES: The objective of the present study is to investigate the effect of muscle active forces on lower extremity injuries for various impact locations and impact angles for a freely standing pedestrian. METHODS: FE simulations have been performed using a validated lower extremity FE model with active muscles (A-LEMS). In all, nine impact orientations have been studied. For each impact orientation, three different pre-impact conditions of a freely standing pedestrian, representing a cadaver, and an unaware and an aware braced pedestrian, have been simulated. Stretch-based reflexive action was included in the simulations for an unaware pedestrian. RESULTS: Strains in knee ligaments and knee joint kinematics have been compared in each impact orientation to assess the effect of muscle activation. It is observed that strain in knee ligaments is dependent on impact locations and angles and the MCL is the most vulnerable ligament. Further, due to muscle effects, except when the impact is on the knee, peak strain values in all the ligaments are lower for an unaware pedestrian than either for a cadaver or for a fully braced pedestrian. CONCLUSIONS: It is concluded that active muscle forces significantly affect the knee kinematics and consequently reduce strains in knee ligaments.