Complications following arthroscopic Bankart repair: a systematic review

BACKGROUND

Complications are rare after arthroscopic Bankart repair, and as a result, there is a lack of guidance over rates of complications that can be used to consent patients. The purpose of this study is to systematically review the literature to assess the complications after arthroscopic Bankart repair, other than recurrent instability.

METHODS

A literature search of MEDLINE, Embase, and the Cochrane Library was performed based on the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) guidelines. Clinical studies reporting on the complications after arthroscopic Bankart repair were included.

RESULTS

A total of 194 studies were included in the analysis, with 13,979 patients and 14,019 shoulders undergoing arthroscopic Bankart repair. The overall complication rate was 0.67%, with frozen shoulder being the most common complication occurring in 0.32%. Persistent pain occurred in 0.17%. The rates of nerve, hardware, and wound complications were 0.07%, 0.05%, and 0.03%, respectively.

CONCLUSION

The arthroscopic Bankart repair has a very low rate of complications. Frozen shoulder and persistent pain are the most frequently encountered complications.

Evaluation of information from artificial intelligence on rotator cuff repair surgery

Purpose

The purpose of this study was to analyze the quality and readability of information regarding rotator cuff repair surgery available using an online AI software.

Methods

An open AI model (ChatGPT) was used to answer 24 commonly asked questions from patients on rotator cuff repair. Questions were stratified into one of three categories based on the Rothwell classification system: fact, policy, or value. The answers for each category were evaluated for reliability, quality and readability using The Journal of the American Medical Association Benchmark criteria, DISCERN score, Flesch-Kincaid Reading Ease Score and Grade Level.

Results

The Journal of the American Medical Association Benchmark criteria score for all three categories was 0, which is the lowest score indicating no reliable resources cited. The DISCERN score was 51 for fact, 53 for policy, and 55 for value questions, all of which are considered good scores. Across question categories, the reliability portion of the DISCERN score was low, due to a lack of resources. The Flesch-Kincaid Reading Ease Score (and Flesch-Kincaid Grade Level) was 48.3 (10.3) for the fact class, 42.0 (10.9) for the policy class, and 38.4 (11.6) for the value class.

Conclusion

The quality of information provided by the open AI chat system was generally high across all question types but had significant shortcomings in reliability due to the absence of source material citations. The DISCERN scores of the AI generated responses matched or exceeded previously published results of studies evaluating the quality of online information about rotator cuff repairs. The responses were U.S. 10th grade or higher reading level which is above the AMA and NIH recommendation of 6th grade reading level for patient materials. The AI software commonly referred the user to seek advice from orthopedic surgeons to improve their chances of a successful outcome.

Evaluation of Online Artificial Intelligence-Generated Information on Common Hand Procedures

PURPOSE

The purpose of this study was to analyze the quality and readability of the information generated by an online artificial intelligence (AI) platform regarding 4 common hand surgeries and to compare AI-generated responses to those provided in the informational articles published by the American Society for Surgery of the Hand (ASSH) HandCare website.

METHODS

An open AI model (ChatGPT) was used to answer questions commonly asked by patients on 4 common hand surgeries (carpal tunnel release, cubital tunnel release, trigger finger release, and distal radius fracture fixation). These answers were evaluated for medical accuracy, quality and readability and compared to answers derived from the ASSH HandCare materials.

RESULTS

For the AI model, the Journal of the American Medical Association benchmark criteria score was 0/4, and the DISCERN score was 58 (considered good). The areas in which the AI model lost points were primarily related to the lack of attribution, reliability and currency of the source material. For AI responses, the mean Flesch Kinkaid Reading Ease score was 15, and the Flesch Kinkaid Grade Level was 34, which is considered to be college level. For comparison, ASSH HandCare materials scored 3/4 on the Journal of the American Medical Association Benchmark, 71 on DISCERN (excellent), 9 on Flesch Kinkaid Grade Level, and 60 on Flesch Kinkaid Reading Ease score (eighth/ninth grade level).

CONCLUSION

An AI language model (ChatGPT) provided generally high-quality answers to frequently asked questions relating to the common hand procedures queried, but it is unclear when or where these answers came from without citations to source material. Furthermore, a high reading level was required to comprehend the information presented. The AI software repeatedly referenced the need to discuss these questions with a surgeon, the importance of shared decision-making and individualized care, and compliance with surgeon treatment recommendations.

CLINICAL RELEVANCE

As novel AI applications become increasingly mainstream, hand surgeons must understand the limitations and ramifications these technologies have for patient care.

Clinical and Biomechanical Outcomes of Suture Button Fixation for Ligamentous Lisfranc Injury: A Systematic Review and Meta-analysis

Background

Flexible ligamentous fixation has increased in popularity for the treatment of ligamentous Lisfranc injury, but the optimal fixation strategy is unclear.

Purpose

To review the biomechanical, clinical, and radiographic results of ligamentous Lisfranc injuries treated with flexible fixation.

Study Design

Systematic review; Level of evidence, 4.

Methods

A systematic literature review was conducted according to the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. The PubMed/Medline and Google Scholar literature databases were queried for clinical and biomechanical (cadaveric) studies relating to flexible fixation of ligamentous Lisfranc injury. Outcomes of interest included patient-reported outcome scores, clinical/biomechanical results, radiographic alignment, and return to activity. Where appropriate, meta-analysis of the postoperative outcomes was performed.

Results

Of the 34 initial studies, 14 articles (243 feet) were included in the analysis. In the 11 clinical studies (216 patients), the mean postoperative American Orthopaedic Foot & Ankle Society score was 90.1 (n = 150; 6 studies) and the mean visual analog scale score was 1.5 (n = 137; 5 studies). The rate of return to activity was 100% (n = 35; 5 studies), and 100% of patients maintained radiographic alignment postoperatively (n = 62; 6 studies). No complications or subsequent hardware removals were reported. Of the 3 biomechanical studies (27 feet), 1 study found significantly greater change in diastasis under axial load between intact and postfixation ligaments with suture button versus screw fixation (+1.1 vs -0.1 mm; P < .05), another found no difference in the decrease in diastasis under axial load between the injured state and screw or suture button fixation (1.2 vs 1.0 mm; P = .5), and the third found no difference in displacement between intact and either screw or suture button fixation under either axial (intact vs screw: 1.0 vs 2.0 mm, P = .1; intact vs suture button: 0.6 vs 1.8 mm, P = .1) or abduction (intact vs screw: 1.5 vs 1.1 mm, P = .5; intact vs suture button: 1.3 vs 2.1 mm, P = .1) load.

Conclusion

Flexible fixation use in the treatment of ligamentous Lisfranc injury was found to have significant potential as a fixation option, as demonstrated by excellent clinical results. Biomechanical evidence was inconclusive but suggested a trend toward decreased diastasis in specimens fixed with screws compared with suture buttons.

Association Between Preoperative Multidimensional Psychological Distress and Physical Function After Surgery for Sports-Related Injury

Background

Psychological distress after orthopaedic surgery can lead to worse outcomes, including higher levels of disability and pain and lower quality of life. The 10-item Optimal Screening for Prediction for Referral and Outcome-Yellow Flag (OSPRO-YF) survey screens for multiple psychological constructs relevant to recovery from orthopaedic injury and may be useful to preoperatively identify patients who may require further psychological assessment and possible intervention after surgery.

Purpose/Hypothesis

To determine the association between the OSPRO-YF and physiological patient-reported outcomes (PROs). It was hypothesized that higher OSPRO-YF scores (indicating worse psychological distress) would be associated with worse PRO scores at time of return to sport.

Study Design

Case series; Level of evidence, 4.

Methods

This study evaluated 107 patients at a single, academic health center who were assessed at a sports orthopaedics clinic and ultimately treated surgically for injuries to the knee, shoulder, foot, or ankle. Preoperatively, patients completed the OSPRO-YF survey as well as the following PRO measures: Patient-Reported Outcomes Measurement Information System (PROMIS), Single Assessment Numeric Evaluation, numeric rating scale for pain; American Shoulder and Elbow Surgeons standardized shoulder assessment form for patients with shoulder injuries, the International Knee Documentation Committee score (for patients with knee injuries), and the Foot and Ankle Ability Measure (FAAM; for patients with foot or ankle injuries). At the time of anticipated full recovery and/or return to sport, patients again completed the same PRO surveys. Multivariable regression was used to evaluate the association between total OSPRO-YF score at baseline and PRO scores at the time of functional recovery.

Results

The baseline OSPRO-YF score predicted postoperative PROMIS Physical Function and FAAM Sports scores only. A 1-unit increase in the OSPRO-YF was associated with a 0.55-point reduction in PROMIS Physical Function (95% CI, -1.05 to -0.04; P = .033) indicating worse outcomes. Among patients who underwent ankle surgery, a 1-unit increase in OSPRO-YF was associated with a 6.45-point reduction in FAAM Sports (95% CI, -12.0 to -0.87; P = .023).

Conclusion

The study findings demonstrated that the OSPRO-YF survey predicts certain long-term PRO scores at the time of expected return to sport, independent of baseline scores.

The characteristics of opioid use in patients with proximal humerus fractures

BACKGROUND

Orthopaedic surgeons prescribe more opioid narcotics than any other surgical specialty. Proximal humerus fractures (PHF) often occur in the high-risk elderly population. The opioid epidemic has led to public policy aimed at reductions in opioid prescription. This study aimed to evaluate the impact that new legislation has had on opioid prescription patterns in patients who sustained proximal humerus fractures.

METHODS

A retrospective review of all patients who sustained PHF at a single academic institution from 1/1/2015-12/31/2019 was performed. A total of 762 proximal humerus fractures were identified and final analysis included 383 patients. Collected data included basic demographics and opioid prescriptions obtained through review of the electronic medical record. The North Carolina Strengthen Opioid Misuse Prevention act legislation that went into effect on July 1, 2017.

RESULTS

There was no difference in the number of pre- or postoperative opioid prescriptions provided with the new legislation. Our data showed a significant reduction in MeQs prescribed preoperatively pre-STOP act (188.1 MeQs) and post-STOP act (99.4 MeQs). There was also a significant difference in the amount of postoperative narcotics prescribed in the pre-STOP (972.6 MeQs) and post-STOP act (508.6 MeQs) groups (p < 0.01).

CONCLUSIONS

With the enactment of the STOP act in North Carolina, we have seen a significant reduction in the amount of narcotic prescribed after sustaining a proximal humerus fracture preoperatively and postoperatively. This data demonstrates the impact that implementation of state-wide regulatory changes in opioid prescribing policy has had for a common orthopedic condition.

A Current Concepts Review of Clavicle Injuries in Ice Hockey From Sternoclavicular to Acromioclavicular Joint

Clavicle injuries are common in ice hockey, and a number of high-profile fractures and dislocations have occurred in elite hockey players in recent years. Acromioclavicular joint injuries, clavicle fractures, and sternoclavicular joint injuries are some of the most frequent hockey-related injuries treated by orthopaedic surgeons, and familiarity with the management of these injuries and sport-specific considerations for treatment and recovery are critical. Injuries involving the clavicle can sometimes be life-threatening, and subtle findings on physical examination and radiographic studies can have profound implications for treatment. The recent literature pertinent to the diagnosis and treatment of clavicle-related injuries in ice hockey players was reviewed and compiled into a clinical commentary. For ice hockey players, the upper extremity was traditionally considered a relatively well-protected area. However, given the evolution of the game and its protective equipment, the upper extremity now accounts for the majority of youth ice hockey injuries, of which clavicle injuries comprise a significant proportion. Acromioclavicular joint injuries are the most common injury in this population, followed closely by clavicle fractures. Sternoclavicular joint injuries are rare but can be associated with serious complications. The treatment of these injuries often differs between athletes and the general population, and surgical indications continue to evolve in both groups. Although the evidence regarding clavicle injuries is ever-increasing and the treatment of these injuries remains controversial, clavicle injuries are increasingly common in ice hockey players. Rule and equipment changes, most notably the increased use of flexible boards and glass, have been shown to significantly decrease the risk of clavicle injuries. We also recommend compulsory use of shoulder pads, even at a recreational level, as well as continued enforcement and evolution of rules aimed at reducing the rate of clavicle injuries. Future research should focus on equipment design changes directed toward clavicle injury prevention, standardized return-to-play protocols, and studies weighing the risks and benefits of nonoperative management of controversial injuries, such as type III acromioclavicular joint dislocations and diaphyseal clavicle fractures.

The Impact of Body Checking on Youth Ice Hockey Injuries

Background

Body checking is a common cause of youth ice hockey injuries. Consequently, USA Hockey raised the minimum age at which body checking is permitted from the Pee Wee level (11-12 years old) to the Bantam level (13-14 years old) in 2011.

Purpose/Hypothesis

The purpose of this investigation was to determine the impact of body checking on the distribution of injuries reported in youth ice hockey players. We hypothesized that the elimination of body checking at the Pee Wee level would lower the frequency of serious injuries, particularly concussions.

Study Design

Descriptive epidemiology study.

Methods

Injury data from the National Electronic Injury Surveillance System (NEISS), a United States Consumer Product Safety Commission database, were analyzed for Pee Wee and Bantam players between January 1, 2008 and December 31, 2010 and again between January 1, 2013 and December 31, 2015. Data on the location of injury, diagnosis, and mechanism of injury were collected. The location of injury was categorized into 4 groups: head and neck, upper extremity, lower extremity, and core. Diagnoses investigated included concussions, fractures, lacerations, strains or sprains, internal organ injuries, and other. The mechanism of injury was broken down into 2 categories: checking and other.

Results

Between the 2008-2010 and 2013-2015 seasons, overall injuries decreased by 16.6% among Pee Wee players, with injuries caused by body checking decreasing by 38.2% (P = .012). There was a significant change in the distribution of diagnoses in the Pee Wee age group during this time frame (P = .007): strains or sprains, internal organ injuries, and fractures decreased in frequency, while the number of concussions increased by 50.0%. In the Bantam age group, recorded injuries decreased by 6.8%, and there was no change in the distribution of the location of injury, diagnosis, or mechanism of injury (P > .05).

Conclusion

There was an observed reduction in the total number, mechanism, and type of injuries when body checking was eliminated from the Pee Wee level. There was, however, an unexpected increase in the number of concussions.

Head, Neck, and Shoulder Injuries in Ice Hockey: Current Concepts

Ice hockey is a fast-paced contact sport that is becoming increasingly popular in North America. More than 1 million men, women, and juniors are playing hockey in the United States and Canada. With players colliding forcefully with one another and with the boards surrounding the ice, injury rates are among the highest in all of competitive sports. Physicians caring for a hockey team should be aware of the more common injuries, involving the head, the neck, and the shoulder. In this review, we discuss evaluation and treatment of these hockey injuries, return to play, and, where applicable, prevention strategies.

Diagnostic Algorithm for Residual Pain After Total Knee Arthroplasty

Although total knee arthroplasty is a successful and cost-effective procedure, patient dissatisfaction remains as high as 50%. Postoperative residual knee pain after total knee arthroplasty, with or without crepitation, is a major factor that contributes to patient dissatisfaction. The most common location for residual pain after total knee arthroplasty is anteriorly. Because residual pain has been associated with an un-resurfaced patella, this review includes only registry data and total knee arthroplasty with patella replacement. Some suggest that the pathogenesis of residual knee pain may be related to mechanical stimuli that activate free nerve endings around the patellofemoral joint. Various etiologies have been implicated in residual pain, including (1) low-grade infection, (2) midflexion instability, and (3) component malalignment with patellar maltracking. Less common causes include (4) crepitation and patellar clunk syndrome; (5) patellofemoral symptoms, including overstuffing and avascular necrosis of the patella; (6) early aseptic loosening; (7) hypersensitivity to metal or cement; (8) complex regional pain syndrome; and (9) pseudoaneurysm. Because all of these conditions can lead to residual pain, identifying the etiology can be a difficult diagnostic challenge. Often, patients with persistent pain and normal findings on radiographs and laboratory workup may benefit from a diagnostic injection or further imaging. However, up to 10% to 15% of patients with residual pain may have unexplained pain. This literature review summarizes the findings on the causes of residual pain and presents a diagnostic algorithm to facilitate an accurate diagnosis for residual pain after total knee arthroplasty.

Evaluation, management and prevention of lower extremity youth ice hockey injuries

Ice hockey is a fast-paced sport played by increasing numbers of children and adolescents in North America and around the world. Requiring a unique blend of skill, finesse, power and teamwork, ice hockey can become a lifelong recreational activity. Despite the rising popularity of the sport, there is ongoing concern about the high frequency of musculoskeletal injury associated with participation in ice hockey. Injury rates in ice hockey are among the highest in all competitive sports. Numerous research studies have been implemented to better understand the risks of injury. As a result, rule changes were adopted by the USA Hockey and Hockey Canada to raise the minimum age at which body checking is permitted to 13–14 years (Bantam level) from 11–12 years (Pee Wee). Continuing the education of coaches, parents and players on rules of safe play, and emphasizing the standards for proper equipment use are other strategies being implemented to make the game safer to play. The objective of this article was to review the evaluation, management and prevention of common lower extremity youth hockey injuries.

Severe Hand Osteoarthritis Strongly Correlates With Major Joint Involvement and Surgical Intervention

BACKGROUND

The presence of hand osteoarthritis (OA) increases the risk for developing OA in other major joints. Although genetic predisposition has been implicated in its causation, its exact role has yet to be established. The association of hand OA with symptomatic and asymptomatic major joints has not been previously studied.

METHODS

Hundred consecutive patients had a hand photo taken for visual documentation of the hand joints. Radiographs of hand and all major symptomatic joints were analyzed and classified using the Kellgren-Lawrence scale by 2 independent observers including an orthopedic radiologist.

RESULTS

Severe hand OA was present in 91% of the patients. Radiographic analysis showed that the hip was involved in 88% of the patients, of whom 85.2% (75) were symptomatic and 14.7% (13) were asymptomatic. Hip arthroplasty was required by 62.5% (55) of symptomatic hip patients. Knee involvement was present in 37% of the patients; all were symptomatic and 81.1% (30) of these required knee arthroplasty. Bilateral surgery was performed in 33% (28) and "2 joint (hip and knee)" surgery was performed in 6% (5). Spine involvement was present in 72% of the patients. There was a significant correlation between hand radiographic findings of OA and hip (r = 0.68; P = .03), knee (r = 0.58; P = .042), and spine (r = .39; P = .05) involvement.

CONCLUSION

There was a significant correlation between severe hand OA and hip, knee, and spine involvement. Severity of Hand OA can have a predictive value on multiple joint involvement and risk of surgical intervention. This study emphasizes the need to investigate the genetic predisposition in causation of OA.

Role of magnetic resonance imaging in the diagnosis of the painful unicompartmental knee arthroplasty

BACKGROUND

Unicompartmental knee arthroplasty (UKA) is a well established method for the treatment of single compartment arthritis; however, a subset of patients still present with continued pain after their procedure in the setting of a normal radiographic examination. This study investigates the effectiveness of magnetic resonance imaging (MRI) in guiding the diagnosis of the painful unicompartmental knee arthroplasty.

METHODS

An IRB-approved retrospective review identified 300 consecutive UKAs performed over a three years period with 28 cases of symptomatic UKA (nine percent) with normal radiographic images.

RESULTS

MRI examination was instrumental in finding a diagnosis that went undetected on radiographs. Based on MRI findings, 10 (36%) patients underwent surgery whilst 18 (64%) were treated conservatively.

CONCLUSION

This study supports the use of MRI as a valuable imaging modality for managing symptomatic unicompartmental knee arthroplasty.

LEVEL OF EVIDENCE

Case series.

Robotic-assisted femoral osteochondroplasty is more precise than a freehand technique in a Sawbone model

Robotic-assistance has the potential to improve the accuracy of bony resections, when performing femoral osteochondroplasty in the treatment of cam-type femoroacetabular impingement (FAI). The purpose of this study was to determine the accuracy of robotic-assisted femoral osteochondroplasty and compare this to a conventional open, freehand technique. We hypothesized that robotic-assistance would increase the accuracy of femoral head-neck offset correction in cam FAI. Sixteen identical sawbones models with a cam-type impingement deformity were resected by a single surgeon, simulating an open femoral osteochondroplasty. Eight procedures were performed using an open freehand technique and eight were performed using robotic-assistance, through the creation of a three-dimensional haptic volume. A desired arc of resection of 117.7° was determined pre-operatively using an anatomic plan. Post-resection, all 16 sawbones were laser scanned to measure the arc of resection, volume of bone removed and depth of resection. For each sawbone, these measurements were compared with the pre-operatively planned desired resection, to determine the resection error. Freehand resection resulted in a mean arc of resection error of 42.0 ± 8.5° compared with robotic-assisted resection which had a mean arc of resection error of 1.2 ± 0.7° (P < 0.0001). Over-resection occurred with every freehand resection with a mean volume error of 758.3 ± 477.1 mm³ compared with a mean robotic-assisted resection volume error of 31.3 ± 220.7 mm³ (P < 0.01). This study has shown that robotic-assisted femoral osteochondroplasty in the treatment of cam-type FAI is more accurate than a conventional, freehand technique, which are currently in widespread use.

Antifungal activity of salaceyin A againstColletotrichum orbiculare andPhytophthora capsici

The antifungal activities of novel salicylic acid derivatives, salaceyin A, 6-(9-methyldecyl) salicylic acid, and salaceyin B, 6-(9-methylundecyl) salicylic acid were evaluated against plant pathogenic fungi. Salaceyin A showed antifungal activity against Cladosporium cucumerinum, Colletotrichum orbiculare and Phytophthora capsici at 64 microg ml(-1) while salaceyin B was less effective. In vitro antifungal activities of the compounds were influenced by the experimental pH value of the MIC test medium wherein their antifungal activities were enhanced by increasingly acidic conditions. Salaceyin A showed potent in vivo control efficacy against Phytophthora blight in pepper plants. The disease was effectively suppressed at 500 microg ml(-1), which was comparable to the commercial fungicide, metalaxyl. Salaceyin A suppressed anthracnose development on cucumber leaves in a concentration dependent manner. The control efficacy of salaceyin A against C. orbiculare infection was similar to chlorothalonil when applied prior to pathogen inoculation. Since the salaceyins are derivatives of salicylic acid, a known important signal molecule critical to plant defenses against pathogen invasion, we investigated the possibility that exogenous application of the salaceyin A would activate a systemic acquired resistance against P. capsici infection and C. orbiculare development on pepper and cucumber plants respectively. The addition of 500 microg ml(-1) of salaceyin A to the plant root systems did not significantly decrease disease development in the hosts. We are led to conclude that the disease control efficacy of salaceyin A against the Phytophthora blight and anthracnose diseases, mainly originates from the direct interaction of the agent with the pathogens.

Methodology for characterizing distributions of incremental body burdens of 2,3,7,8-TCDD and DDE from breast milk in North American nursing infants

A clear picture of ranges of doses of breast-milk contaminants experienced by nursing infants in North America has not yet been described, resulting in a significant gap in our understanding of potential health risks to infants from those contaminants. While point estimates of incremental dose have appeared in the published literature, these do not account for the wide variability in exposures experienced by nursing infants. This research expands on the current state of understanding of breast-milk contaminant exposure by characterizing distributions, rather than point estimates, of dose. Distributions of milk intake by nursing infants were characterized to examine intake of 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) and dichlorodiphenyl dichloroethane (DDE). The results indicate that, despite the uncertainties inherent in modeling incremental body burdens of chemicals from nursing, estimating incremental infant body burdens of lipophilic chemicals from breastfeeding using point estimates may result in overly conservative estimates of the contribution of breastfeeding to long-term body burdens of those chemicals in children. To develop reliable estimates of incremental body burden from nursing, depuration via lactation and half-life in the infant should be considered. Further, incremental infant body burdens of lipophilic chemicals increase rapidly at the start of lactation, but decrease after approximately 5 to 6 mo; by 2 yr postpartum, incremental body burdens have decreased substantially. Given the benefits afforded to infants who breastfeed, and because breastfeeding does not necessarily lead to significantly increased long-term body burdens in infants, breastfeeding should be encouraged and promoted.

Development of a physiologically based pharmacokinetic model for risk assessment with 1,4-dioxane

A six compartment physiologically based pharmacokinetic (PB-PK) model was developed to describe the disposition of diethylene-1,4-dioxide (dioxane) and its principal metabolite beta-hydroxyethoxyacetic acid in rats, mice, and humans. The model was developed from experimentally measured partition coefficients (reported here for the first time) as well as pharmacokinetic data previously reported. The completed PB-PK model adequately described data from gavage and intravenous studies in rats, as well as inhalation studies in rats and humans. Substantial nonlinearities were observed in the kinetic behavior of dioxane under high exposure conditions (water concentrations greater than 0.1% dioxane and atmospheric concentrations greater than 300 ppm dioxane). The PB-PK model was subsequently used to prepare quantitative estimates of the "plausible upper bounds" on carcinogenic risk for human populations exposed to dioxane in air or water. Based on these quantitative estimates, it appears that human populations continuously exposed to 740-3700 ppb dioxane in air or 20,000-120,000 ppb dioxane in water would be unlikely to experience increased frequencies of tumors.

Mathematical models in quantitative assessment of carcinogenic risk

Regulatory guidelines have specified default assumptions for the calculation of upper bounds on potential carcinogenic risk. These default "science policy" assumptions are used in the absence of more appropriate biological information, but can, in theory, be overridden by compound-specific data. As a screening tool, the standard LMS procedure provides a useful yardstick for regulators to compare hazard potential across compounds and across exposure scenarios. This standard methodology does not estimate actual risk, however. When specific compounds are being considered for detailed evaluation, methodology for more accurately estimating the true risk is often available. Pharmacokinetic models can be used to more accurately define the high-dose to low-dose extrapolation as well as to provide insight into across route and across species extrapolations. "More central" estimates of the upper bound on risk can be derived, or decision analysis techniques can be used to define the probability distribution of risk estimates, as the assumptions are changed. These data give the risk manager more information as to the relevance of the upper bound, and should be presented in any risk estimate to provide a richer demonstration as to the true risk.

Incorporation of in vitro enzyme data into the physiologically-based pharmacokinetic (PB-PK) model for methylene chloride: implications for risk assessment

Physiologically-based pharmacokinetic (PB-PK) models provide a mechanism for reducing the uncertainty inherent in extrapolating the results of animal toxicity tests to man. This paper discusses a technique for incorporating data from in vitro studies of xenobiotic metabolism into in vivo PB-PK models. Methylene chloride is used as an example, and carcinogenic risk estimates incorporating PB-PK principles are presented.

Cytogenetic variability of lymphocytes from phenotypically normal men: influence of age, smoking, season, and sample storage

A cytogenetic study was conducted on cultured lymphocytes from a group of 60 male volunteers to determine the baseline of chromosomal aberrations in nonchemical workers. Only males were included in the study to avoid any sex effects on the results. Blood samples were collected from each man every 13 w (quarterly) over a period of 12 m. A single batch of culture medium was used for the entire study. The influence of storing the blood samples prior to culture, donor's age, cigarette smoking, and seasonal variation on lymphocyte mitotic index and chromosomal aberration yield was analyzed. A significant decrease in mitotic activity was observed in cultures from samples stored for 3 d at room temperature (22 +/- 1 degree C). Storing of samples at refrigerator temperature (4 +/- 1 degree C) for up to 3 d prior to culture did not affect lymphocyte growth. Although the mitotic index was found to be inversely proportional to the age of the donors, a significant influence of age on total cytogenetic aberrations was not detectable. A group of 15 smokers appeared to have higher number of chromosomal aberrations; however, the difference in mean mitotic activity between lymphocytes of the two groups was not statistically significant. No detectable seasonal influence was found on any chromosomal aberration category except in the number of chromatid gaps. The mitotic indices of the first quarter cultures, on the other hand, showed significant differences from the other three quarters. The chromosomal aberration baseline of the group was not strikingly different from the ones reported by other investigators.(ABSTRACT TRUNCATED AT 250 WORDS)

Behavioral effects of 0 and 0.05% blood alcohol in male volunteers

Five behavioral tests were evaluated to determine their sensitivity to the subtle central nervous system (CNS) depressant effects produced by ingestion of ethanol. Twenty-one adult male volunteers received 0 and 1.4 ml 100 proof vodka/kg body weight according to a "double-blind" crossover design. Behavioral tests were conducted between 15 and 65 minutes after ethanol ingestion, when blood alcohol concentrations (BAC's) were between 0.05 and 0.06%. Tests evaluated were Archimedes spiral, digit span memory, critical flicker fusion, stabilometry and tachistoscope. Multivariate analysis of variance (MANOVA) using composite scores representing the individual tests indicated that the battery as a whole was sensitive to ethanol effects. Repeated measures analysis of variance (ANOVA) on each test indicated that critical flicker fusion, stabilometry and tachistoscope contributed more to the overall sensitivity of the battery than did digit span memory and Archimedes spiral.

Analysis of sister chromatid exchanges in lymphocytes cultured from 71 healthy men

Sister chromatid exchanges (SCE) were analyzed in peripheral blood lymphocytes from a select group of 71 healthy men, 56 nonsmokers and 15 cigarette smokers. In addition to estimating baseline SCE, data were examined to seek relationships of SCE frequencies to age and smoking. The baseline value of 7.53 SCE per cell from the 56 nonsmokers was within the range (5.60 to 9.10 SCE/cell) reported for other human populations. No relationship was found between the mean SCE frequency per cell and age. However, a significant increase in the SCE mean value was observed in smokers as compared to nonsmokers. The results of this study are compared with those of other reports on SCE effects of age and smoking.

Validation of human behavioral tests using ethanol as a CNS depressant model

This study evaluated the sensitivity of a battery of tests proposed for use in determining the depressant effects of chemicals on human central nervous system (CNS) function. The first step in the development of such tests was to determine if the tests could detect the effects produced by a known CNS depressant, ethanol. Five behavioral tests, digit span memory, simple reaction time, tachistoscopic perception, flicker fusion and anticipation timing (velocity estimation) were evaluated to determine their sensitivity to the effects of ethanol at blood levels between 0.05-0.06%. Thirty-one adult male volunteers received 0 and 1.4 ml 100 proof vodka/kg body weight according to a double-blind crossover design. Tests were conducted before treatment and between 30 and 70 minutes after an ethanol or control drink was ingested. Multivariate analysis of variance (MANOVA), using composite scores representing the individual tests, indicated that the battery as a whole detected statistically significant ethanol effects. Repeated measures analysis of variance (ANOVA) comparing performance after drinking ethanol to control performance on each of the individual tests indicated a significant decrement in reaction time, tachistoscopic perception and anticipation timing.

Quantitative risk assessment: state-of-the-art for carcinogenesis

A critical evaluation of the use of statistical models in carcinogenic risk assessment is made with emphasis on the strengths and weaknesses of current practice. The objective is to bring together information from the fields of toxicology and statistics to develop a sound scientific basis for making risk decisions. It is emphasized that risk assessment is a complex, multifaceted process that is not easily quantified and, at present, must be based on qualitative as well as quantitative information. It is evident that dose-response modeling of tumor incidence data from animal studies is of limited value in estimating human risk associated with low-dose chemical exposures. The models take into account only one part of the complex process and have no accepted basis in biology. The key decision points, qualitative factors, and quantitative considerations are identified and discussed and a risk assessment framework that incorporates these inputs is presented. A model that incorporates the tumorigenic dose-response information as well as the qualitative and quantitative biological factors that affect the estimate of risk is proposed. It is concluded that much work needs to be done before a completely quantitative approach to risk assessment is to be useful; in particular pharmacokinetic modeling should be pursued more aggressively.

Insensitivity of tests for reproductive problems

Studies of reproductive capacity in rodents have been conducted for decades using a design which has had little refinement over the years. Most commonly, one or two litters from each of one through three generations are raised. The variability between studies, generations, groups, and animals often precludes the resolution of subtle toxicologic effects on reproductive parameters. Nonreproductive parameters yield more reliable data than reproductive parameters. Changes in design and additions to the protocol which will provide additional data are discussed. These include semen evaluation and the use of larger group sizes in reproduction studies.