11 Convergence insufficiency: are we making a difference in patients' lives or is it a waste of time!

Convergence insufficiency (CI) is a common condition that can impair visual performance and comfort during close visual work. This prospective study evaluated the effectiveness of interventions on clinical outcomes and quality-of-life using the adult strabismus quality-of-life questionnaire (AS20) in patients with CI.Data was extracted from a database collected at first consultation from 2015 to 2022. Demographics, interventions and outcomes of 84 patients with CI (mean age 47.0±24.9 years) were analysed.Orthoptic exercises were prescribed to 56% of patients, 32% received prisms, 15% received no treatment, with 3 discharged on the same day. At latest follow-up review, 22.6% were recommended to continue exercises, 28.6% had prisms, 1 underwent bimedial resection and 2 had botox. The median follow-up was 5.5(5.0-55)months, 88.1% were discharged with 29.8% following failure to attend and 9.5% deceased. Near-point of convergence (NPC) improved from a median of 15(6-50)cm to 10(6-30)cm. The median AS20 score at presentation were 100(30-100) and 47.5(0-100), and post-intervention were 100(80-100) and 77.5(12.5-97.5) for psychosocial and functional components, respectively.At the latest follow-up, the attendance failure rate was higher for exercises (36%) than for prisms (15%). Improvement was noted in NPC (33%) and mean AS20 scores was 9% higher psychosocially and 32.8% functionally, highlighting the benefits of intervention on patients' quality-of-life.This cohort provides valuable insights into the clinical management of CI, as evidenced by improvements in NPC and AS20 scores. However, the study also found that long-term compliance with treatment is intrinsically challenging, emphasising the importance of disease education.

Multimodal Mass Spectrometry Imaging of Rat Brain Using IR-MALDESI and NanoPOTS-LC-MS/MS

Multimodal mass spectrometry imaging (MSI) is a critical technique used for deeply investigating biological systems by combining multiple MSI platforms in order to gain the maximum molecular information about a sample that would otherwise be limited by a single analytical technique. The aim of this work was to create a multimodal MSI approach that measures metabolomic and proteomic data from a single biological organ by combining infrared matrix-assisted laser desorption electrospray ionization (IR-MALDESI) for metabolomic MSI and nanodroplet processing in one pot for trace samples (nanoPOTS) LC-MS/MS for spatially resolved proteome profiling. Adjacent tissue sections of rat brain were analyzed by each platform, and each data set was individually analyzed using previously optimized workflows. IR-MALDESI data sets were annotated by accurate mass and spectral accuracy using HMDB, METLIN, and LipidMaps databases, while nanoPOTS-LC-MS/MS data sets were searched against the rat proteome using the Sequest HT algorithm and filtered with a 1% FDR. The combined data revealed complementary molecular profiles distinguishing the corpus callosum against other sampled regions of the brain. A multiomic pathway integration showed a strong correlation between the two data sets when comparing average abundances of metabolites and corresponding enzymes in each brain region. This work demonstrates the first steps in the creation of a multimodal MSI technique that combines two highly sensitive and complementary imaging platforms. Raw data files are available in METASPACE (https://metaspace2020.eu/project/pace-2021) and MassIVE (identifier: MSV000088211).

Circulating tumor DNA guided adjuvant chemotherapy in stage II colon cancer (MEDOCC-CrEATE): study protocol for a trial within a cohort study

BACKGROUND

Accurate detection of patients with minimal residual disease (MRD) after surgery for stage II colon cancer (CC) remains an urgent unmet clinical need to improve selection of patients who might benefit form adjuvant chemotherapy (ACT). Presence of circulating tumor DNA (ctDNA) is indicative for MRD and has high predictive value for recurrent disease. The MEDOCC-CrEATE trial investigates how many stage II CC patients with detectable ctDNA after surgery will accept ACT and whether ACT reduces the risk of recurrence in these patients.

METHODS/DESIGN

MEDOCC-CrEATE follows the 'trial within cohorts' (TwiCs) design. Patients with colorectal cancer (CRC) are included in the Prospective Dutch ColoRectal Cancer cohort (PLCRC) and give informed consent for collection of clinical data, tissue and blood samples, and consent for future randomization. MEDOCC-CrEATE is a subcohort within PLCRC consisting of 1320 stage II CC patients without indication for ACT according to current guidelines, who are randomized 1:1 into an experimental and a control arm. In the experimental arm, post-surgery blood samples and tissue are analyzed for tissue-informed detection of plasma ctDNA, using the PGDx elio™ platform. Patients with detectable ctDNA will be offered ACT consisting of 8 cycles of capecitabine plus oxaliplatin while patients without detectable ctDNA and patients in the control group will standard follow-up according to guideline. The primary endpoint is the proportion of patients receiving ACT when ctDNA is detectable after resection. The main secondary outcome is 2-year recurrence rate (RR), but also includes 5-year RR, disease free survival, overall survival, time to recurrence, quality of life and cost-effectiveness. Data will be analyzed by intention to treat.

DISCUSSION

The MEDOCC-CrEATE trial will provide insight into the willingness of stage II CC patients to be treated with ACT guided by ctDNA biomarker testing and whether ACT will prevent recurrences in a high-risk population. Use of the TwiCs design provides the opportunity to randomize patients before ctDNA measurement, avoiding ethical dilemmas of ctDNA status disclosure in the control group.

TRIAL REGISTRATION

Netherlands Trial Register: NL6281/NTR6455 . Registered 18 May 2017, https://www.trialregister.nl/trial/6281.

Computer-Based Exercises in Anemia Diagnosis (PlanAlyzer)

PlanAlyzer is a microcomputer-based, event-driven system for instructional research in medical education. Aimed at the second year medical student, PlanAlyzer elicits and critiques a student´s approach to the diagnosis of a common medical disorder. In this paper we discuss the concept, development, implementation and formative evaluation of the PlanAlyzer system for the evaluation of anemia.

Abstract P2-02-20: Withdrawn

This abstract was withdrawn by the authors.

Collaborating to Compete: Blood Profiling Atlas in Cancer (BloodPAC) Consortium

The cancer community understands the value of blood profiling measurements in assessing and monitoring cancer. We describe an effort among academic, government, biotechnology, diagnostic, and pharmaceutical companies called the Blood Profiling Atlas in Cancer (BloodPAC) Project. BloodPAC will aggregate, make freely available, and harmonize for further analyses, raw datasets, relevant associated clinical data (e.g., clinical diagnosis, treatment history, and outcomes), and sample preparation and handling protocols to accelerate the development of blood profiling assays.

A Case of Early Neurosyphilis

INTRODUCTION

Neurosyphilis is an infection of the central nervous system by Treponema pallidum, which can occur after the initial syphilis infection. Although commonly associated with late stage disease, patients with early neurosyphilis may present with acute syphilitic meningitis, meningovascular syphilis, or uveitis.

CASE

A 28 year old man with a past medical history of HIV (CD4 364);, and recent diagnosis of uveitis presented to the Emergency Department with a positive RPR result. His visual acuity had been gradually declining over the past few months. He denied painless or painful ulcerating lesions on his penis, or scrotum, difficulty concentrating, dermatitis on the soles/palms, or difficulty with proprioception. Physical exam was notable for atrophic hyperpigmented polycyclic, annular plaques and patches along the hairline as well as several areas of confluent hyperpigmented polycyclic plaques and nodules on the patient's face, back, left arm, and right posterior leg. Fundoscopic exam revealed bilateral posterior uveitis and chorioretinitis. Evaluation of cerebrospinal fluid revealed a lymphocytic pleocytosis with a positive VDRL and FTA-ABS. Aqueous crystalline penicillin G was initiated for treatment of early neurosyphilis. Within six hours of beginning the infusion, the patient had a documented temperature of 101.8°F, heart rate of 128 beats per minute, blood pressure 142/84, with generalized malaise and headache. Fever and tachycardia resolved over the next 12 hours, with weakness and headache resolving within 1-2 days. His symptom complex was consistent with the Jarisch-Herxheimer reaction. Histopathology of skin biopsy of the back showed perivascular inflammation and rare spirochetes, consistent with secondary syphilis. The patient completed 14 days of aqueous crystalline penicillin G and was discharged after receiving the first of three benzathine penicillin injections.

DISCUSSION

The initial manifestations of syphilis in this patient were posterior uveitis and pruritic skin plaques. His diagnosis should be appropriately classified as secondary syphilis with concomitant symptomatic early neurosyphilis, requiring 14 days of aqueous crystalline penicillin G. This type of presentation is not specific to immunocompromised populations and must be considered even in the general population. Making the diagnosis of early neurosyphilis, regardless of stage, is critical, as it necessitates a longer duration of treatment. Furthermore, clinicians should be reminded of the profound immunologic reaction, Jarisch-Herxheimer, which may occur when treating any treponemal disease.

Study protocol for a natural experiment in a lower socioeconomic area to examine the health-related effects of refurbishment to parks including built-shade (ShadePlus)

INTRODUCTION

Parks in disadvantaged suburbs often have low quality and few amenities, which is likely to result in them being underutilised for recreation and physical activity. Refurbishment of parks, including shade, walking paths and other amenities, may have broad health-related benefits.

METHODS AND ANALYSIS

The study design, methods and planned analyses for a natural experiment examining the effects of refurbishments including built-shade added to parks in disadvantaged outer suburbs of Melbourne are described. Three intervention parks and three comparison parks matched for equivalence of park and neighbourhood characteristics were selected. Using mixed methods, the outcomes will be assessed during three consecutive spring-summer periods (T1: 2013-2014; T2: 2014-2015: T3: 2015-2016). Primary outcomes included: observed park use, physical activity and shade use. Self-reported social connectedness, community engagement and psychological well-being were assessed as secondary outcomes.

ETHICS AND DISSEMINATION

This study was approved by Cancer Council Victoria's Human Research Ethics Committee. Studies such as ShadePlus can improve understanding of the broader effects of park refurbishments (including physical activity levels and sun protection behaviours, as well as social connectedness and psychological well-being). The study findings will be disseminated through established urban planning and parks and recreation networks, peer review publications and conference presentations.

Improving the care of patients with severe open fractures of the tibia: the effect of the introduction of Major Trauma Networks and national guidelines

AIMS

The management of open lower limb fractures in the United Kingdom has evolved over the last ten years with the introduction of major trauma networks (MTNs), the publication of standards of care and the wide acceptance of a combined orthopaedic and plastic surgical approach to management. The aims of this study were to report recent changes in outcome of open tibial fractures following the implementation of these changes.

PATIENTS AND METHODS

Data on all patients with an open tibial fracture presenting to a major trauma centre between 2011 and 2012 were collected prospectively. The treatment and outcomes of the 65 Gustilo Anderson Grade III B tibial fractures were compared with historical data from the same unit.

RESULTS

The volume of cases, the proportion of patients directly admitted and undergoing first debridement in a major trauma centre all increased. The rate of limb salvage was maintained at 94% and a successful limb reconstruction rate of 98.5% was achieved. The rate of deep bone infection improved to 1.6% (one patient) in the follow-up period.

CONCLUSION

The reasons for these improvements are multifactorial, but the major trauma network facilitating early presentation to the major trauma centre, senior orthopaedic and plastic surgical involvement at every stage and proactive microbiological management, may be important factors.

TAKE HOME MESSAGE

This study demonstrates that a systemised trauma network combined with evidence based practice can lead to improvements in patient care.

Plastic surgical operative workload in major trauma patients following establishment of the major trauma network in England: A retrospective cohort study

INTRODUCTION

The introduction of major trauma centres (MTCs) in England has led to 63% reduction in trauma mortality.(1) The role of plastic surgeons supporting these centres has not been quantified previously. This study aimed to quantify plastic surgical workload at an urban MTC to determine the contribution of plastic surgeons to major trauma care.

METHODS

All Trauma Audit and Research Network (TARN)-recorded major trauma patients who presented to an urban MTC in 2013 and underwent an operation were identified retrospectively. Patients who underwent plastic surgery were identified and the type and date of procedure(s) were recorded. The trauma operative workload data of another tertiary surgical specialty and local historical plastics workload data from pre-MTC go-live were collected for comparison.

RESULTS

Of the 416 major trauma patients who required surgical intervention, 29% (n = 122) underwent plastic surgery. Of these patients, 43% had open lower limb fractures, necessitating plastic surgical involvement according to British Orthopaedic Association Standards for Trauma (BOAST) 4 guidance. The overall plastic surgery operative workload increased sevenfold post-MTC go-live. A similar proportion of the same cohort required neurosurgery (n = 115; p = 0.589).

DISCUSSION

This study quantifies plastic surgery involvement in major trauma and demonstrates that plastic surgical operative workload is at least on par with other tertiary surgical specialties. It also reports one centre's experience of a significant change in plastic surgery activity following designation of MTC status. The quantity of plastic surgical operative workload in major trauma must be considered when planning major trauma service design and workforce provision, and for plastic surgical postgraduate training.

What is the most reliable imaging modality for small colonic polyp characterization? Study of white-light, autofluorescence, and narrow-band imaging

BACKGROUND AND STUDY AIMS

In vivo optical diagnosis of small colorectal polyps has potential clinical and cost advantages, but requires accuracy and high interobserver agreement for clinically acceptability. We aimed to assess interobserver variability and diagnostic performance of endoscopic imaging modalities in characterizing small colonic polyps.

METHODS

High quality still images of 80 polyps < 1 cm were recorded using white-light endoscopy (WLE), autofluorescence imaging (AFI) and narrow-band imaging with and without magnification (NBI and NBImag). All images were assessed for quality, prediction of polyp histology, and vascular pattern intensity (with NBI) by nine experienced colonoscopists (four experts in advanced imaging) from five UK centers. Interobserver agreement (kappa statistic), sensitivity, specificity, and accuracy were calculated compared with histopathological findings.

RESULTS

Interobserver agreement for predicting polyp histology using NBImag was significantly better for experts (κ = 0.63, substantial) compared with nonexperts (κ = 0.30, fair; P < 0.001), and was moderate for all colonoscopists with WLE, AFI and NBI. Interobserver agreement for vascular pattern intensity using NBI was 0.69 (substantial) for experts and 0.57 (good) for nonexperts. NBImag had higher sensitivity than WLE (experts, 0.93 vs. 0.68, P < 0.001; nonexperts, 0.90 vs. 0.52, P < 0.001) and higher overall accuracy (experts, 0.76 vs. 0.64, P = 0.003; nonexperts 0.61 vs. 0.40, P < 0.001). AFI had worse accuracy than WLE for both expert colonoscopists (0.53 vs. 0.64, P = 0.02) and nonexperts (0.32 vs. 0.40, P = 0.04).

CONCLUSIONS

Of the imaging modalities tested, NBImag appeared to have the best overall accuracy and interobserver agreement, although not adequate for in vivo diagnosis. NBI and AFI did not have better sensitivity, specificity, or accuracy compared with WLE.

Clostridial typhlitis associated with topical antibiotic therapy in a Syrian hamster

A Syrian hamster that had been treated with topical antibiotic ointment for 10 days following injuries sustained during fighting was presented moribund. Postmortem and microscopic examinations revealed lesions consistent with clostridial typhlitis and enteritis. Anaerobic culture of caecal contents resulted in the isolation of two Clostridium species, and caecal contents contained Clostridium difficile enterotoxins. Based on these findings, a diagnosis of acute C. difficile enterotoxaemia was made. This report discusses the pathogenesis of C. difficile enterotoxaemia and the potential role of topical antibiotic ointment therapy in initiating the disease.

Acid-base accounting to predict post-mining drainage quality on surface mines

Acid-base accounting (ABA) is an analytical procedure that provides values to help assess the acid-producing and acid-neutralizing potential of overburden rocks prior to coal mining and other large-scale excavations. This procedure was developed by West Virginia University scientists during the 1960s. After the passage of laws requiring an assessment of surface mining on water quality, ABA became a preferred method to predict post-mining water quality, and permitting decisions for surface mines are largely based on the values determined by ABA. To predict the post-mining water quality, the amount of acid-producing rock is compared with the amount of acid-neutralizing rock, and a prediction of the water quality at the site (whether acid or alkaline) is obtained. We gathered geologic and geographic data for 56 mined sites in West Virginia, which allowed us to estimate total overburden amounts, and values were determined for maximum potential acidity (MPA), neutralization potential (NP), net neutralization potential (NNP), and NP to MPA ratios for each site based on ABA. These values were correlated to post-mining water quality from springs or seeps on the mined property. Overburden mass was determined by three methods, with the method used by Pennsylvania researchers showing the most accurate results for overburden mass. A poor relationship existed between MPA and post-mining water quality, NP was intermediate, and NNP and the NP to MPA ratio showed the best prediction accuracy. In this study, NNP and the NP to MPA ratio gave identical water quality prediction results. Therefore, with NP to MPA ratios, values were separated into categories: <1 should produce acid drainage, between 1 and 2 can produce either acid or alkaline water conditions, and >2 should produce alkaline water. On our 56 surface mined sites, NP to MPA ratios varied from 0.1 to 31, and six sites (11%) did not fit the expected pattern using this category approach. Two sites with ratios <1 did not produce acid drainage as predicted (the drainage was neutral), and four sites with a ratio >2 produced acid drainage when they should not have. These latter four sites were either mined very slowly, had nonrepresentative ABA data, received water from an adjacent underground mine, or had a surface mining practice that degraded the water. In general, an NP to MPA ratio of <1 produced mostly acid drainage sites, between 1 and 2 produced mostly alkaline drainage sites, while NP to MPA ratios >2 produced alkaline drainage with a few exceptions. Using these values, ABA is a good tool to assess overburden quality before surface mining and to predict post-mining drainage quality after mining. The interpretation from ABA values was correct in 50 out of 52 cases (96%), excluding the four anomalous sites, which had acid water for reasons other than overburden quality.

Minor effects of Helicobacter pylori on gastric secretion and dose of lansoprazole during long-term treatment in ZE and non-ZE acid hypersecretors

BACKGROUND

Helicobacter pylori infection may increase or decrease acid secretion and may augment proton pump inhibitor efficacy. Pepsin effects have not been reported. In Zollinger-Ellison syndrome (ZE) specifically, H. pylori has been reported to decrease acid.

AIM

To examine H. pylori effects on secretion and dose of medication in hypersecretors (basal acid output > 15 mmol/h) undergoing long-term treatment with individually optimized lansoprazole doses.

METHODS

Sixty-five patients (47 ZE and 18 non-ZE), treated for > 3 months to 10 years, were tested every 6 months with endoscopy, gastric analysis and serum gastrin.

RESULTS

Forty-three per cent were H. pylori-positive. Acid, pepsin and gastrin were not different between H. pylori-positive and H. pylori-negative patients before or during long-term lansoprazole treatment. Initially, H. pylori-positive patients required less lansoprazole than H. pylori-negative patients (68 +/- 6 vs. 96 +/- 8 mg/day), but after 3 years the doses converged (83 vs. 86 mg/day). The disappearance of H. pylori in 15 patients caused no significant changes in acid, pepsin, gastrin or lansoprazole dose in the following 4 years.

CONCLUSIONS

H. pylori had no significant initial or long-term physiological or potential clinical effects on acid or pepsin secretion or gastrin in these acid hypersecretors.

Long-term lansoprazole control of gastric acid and pepsin secretion in ZE and non-ZE hypersecretors: a prospective 10-year study

BACKGROUND

The majority of patients with Zollinger-Ellison syndrome require lifelong treatment with proton pump inhibitors.

AIMS

To determine the efficacy of lansoprazole control of acid and pepsin secretion over the long term in Zollinger-Ellison syndrome and non-Zollinger-Ellison syndrome hypersecretors.

METHODS

Sixty-three hypersecretors (basal acid output > 15 mmol/h), 46 Zollinger-Ellison syndrome and 17 non-Zollinger-Ellison syndrome, with a total history of 15.4 and 19.2 years, respectively, were entered into a long-term prospective study using lansoprazole. Sixty-one were studied every 3 months for 1 year and then every 3-6 months up to 10 years during lansoprazole treatment with endoscopy, serum gastrin and gastric analysis, measuring both basal and stimulated pH and acid and pepsin secretion. Doses were individually optimized and adjusted to keep the basal acid output at < 5 mmol/h in intact patients and < 1 mmol/h in antrectomized Zollinger-Ellison syndrome patients.

RESULTS

The dose of lansoprazole could not be predicted a priori from pre-treatment acid or pepsin output, serum gastrin, prior omeprazole dose or diagnosis or prior complications. The median dose was approximately 80 mg/day, with a wide range from 15 mg every other day to 360 mg/day, and generally stabilized by 12 months. However, as doses were adjusted over time for indications, almost half the patients required higher doses. With adjustments, the basal acid output was maintained in the target range in > 90% of intact patients and in 80% of antrectomized patients. Gastric juice pH increased from approximately 1.2 before therapy to > 3.4 during therapy. Serum gastrin in Zollinger-Ellison syndrome patients, after excluding five outliers, did not change over the course of therapy, but doubled in non-Zollinger-Ellison syndrome patients. There were no adverse events due to lansoprazole, and routine laboratory studies remained normal.

CONCLUSIONS

The dose of lansoprazole for hypersecretors cannot be predicted, and thus needs to be optimized empirically on an individual basis. With continued periodic adjustments, almost half the patients required increased doses, while safe dose reduction was possible in only one-quarter. When individually optimized, lansoprazole proved to be safe and effective in the control of secretion for the treatment of both Zollinger-Ellison syndrome and non-Zollinger-Ellison syndrome hypersecretors for up to 10 years.

Control of laser high-harmonic generation with counterpropagating light

Relatively weak counterpropagating light is shown to disrupt the emission of laser high-harmonic generation. Harmonic orders ranging from the teens to the low thirties produced by a 30-femtosecond pulse in a narrow argon jet are "shut down" with a contrast as high as 2 orders of magnitude by a chirped 1-picosecond counterpropagating laser pulse (60 times less intense). Alternatively, under poor phase-matching conditions, the counterpropagating light boosts harmonic production by similar contrast through quasiphase matching where out-of-phase emission is suppressed.

The role of family of origin food-related experiences in bulimic symptomatology

OBJECTIVE

With the goal of developing a model relating family of origin experiences to maladaptive cognitions to bulimic symptom formation, the authors developed a measure of family of origin food-related experiences called the Family History Inventory.

METHOD

A number (N = 662) of sixth to eighth-grade adolescents completed the inventory, eating and dieting expectancy measures, and the Bulimia Test-Revised (BULIT-R).

RESULTS

Fourteen scales were identified in the inventory. They emphasized family teasing about weight, negative maternal modeling regarding food, and family rules concerning eating. Eleven of the 14 scales correlated with the BULIT-R. Two superordinate factors called Family Teasing and Negative Maternal Modeling summarized 8 of the 14 subscales. Statistical tests were consistent with the hypothesis that eating and dieting expectancies mediate the influence of Family Teasing and Negative Maternal Modeling on bulimic symptomatology.

DISCUSSION

There was good evidence for the validity of the Family History Inventory. The theoretical implications of the mediation tests are discussed.

A functional polymorphism of the stromelysin gene (MMP-3) influences susceptibility to primary sclerosing cholangitis

BACKGROUND AND AIMS

We have investigated the influence of a biallelic polymorphism of the promoter region of stromelysin (matrix metalloproteinase 3) on susceptibility to primary sclerosing cholangitis (PSC). The 5A allele is associated with increased transcription, compared with wild-type (6A).

METHODS

An allelic association study was performed: in stage 1, 52 PSC patients (43 with inflammatory bowel disease [IBD]) and 99 healthy subjects (HS) were genotyped. In stage 2, 59 PSC patients (49 IBD), 84 patients with uncomplicated ulcerative colitis, and 72 HS were genotyped.

RESULTS

In stage 1, 5A carriage rate (90.4% vs. 72.7%; P = 0.012) and 5A allelic frequency (65.4% vs. 48.5%; P = 0.005) were increased, and 6A homozygosity was reduced in PSC (9.6% vs. 27.3%; P = 0.012). In stage 2, 5A allelic carriage was increased in PSC (93.2% vs. 76.4% in HS; P = 0.0092) and 6A homozygosity was reduced (6.8% vs. 23.8% in HS; P = 0.0092). Portal hypertension was associated with 5A homozygosity in PSC (P = 0.035; odds ratio [OR], 3.88). In the combined data set, 5A allelic frequencies (63.5% vs. 49.4%; P = 0.001; OR, 1.78) and 5A carriage rates (91.9% vs. 74.2%; P = 0.0002; OR, 3.92) were increased, and 6A homozygosity was reduced in PSC (8.1% vs. 25.7%; P = 0.0002; OR, 0.25). Overall, portal hypertension was associated with 5A homozygosity (P = 0.0192; OR, 3.12).

CONCLUSIONS

Stromelysin polymorphism may influence susceptibility and disease progression in PSC.

Effects of External Beam Irradiation on the TRAM Flap: An Experimental Model

The rat model of the transverse rectus abdominis musculocutaneous (TRAM) flap was used in the present study to determine the effects of external beam radiation on myocutaneous flap histology and pathophysiology. A total of 57 adult Sprague-Dawley rats underwent a TRAM procedure. A pilot study with 17 animals was first performed to determine proper radiation dosages, and the remaining 40 rats were then used in the definitive study. In half of the definitive study group, the flaps were subjected to fractionated doses of external beam radiation, whereas the other half served as controls. Six weeks after the last radiation dose, all animals were killed and the flaps were harvested for mechanical assessment and histopathologic evaluation. All TRAM flaps survived in both groups. The irradiated and nonirradiated flaps were minimally distinguishable in viscoelastic properties, as well as by histopathologic examination. Growth of the flap in the irradiated animals was significantly diminished (48 percent average surface area increase in irradiated flaps, versus 92 percent increase in nonirradiated flaps, p < 0.05). These findings suggest that the myocutaneous flap is relatively resistant to some of the known adverse affects of radiation on living tissues.