A Genome-Wide Association Study of Respiratory Syncytial Virus Infection Severity in Infants.

BACKGROUND: Respiratory syncytial virus (RSV) is a significant cause of infant morbidity and mortality worldwide. Most children experience at least one 1 RSV infection by the age of two 2 years, but not all develop severe disease. However, the understanding of genetic risk factors for severe RSV is incomplete. Consequently, we conducted a genome-wide association study of RSV severity. METHODS: Disease severity was assessed by the ReSVinet scale, in a cohort of 251 infants aged 1 week to 1 year. Genotyping data were collected from multiple European study sites as part of the RESCEU Consortium. Linear regression models were used to assess the impact of genotype on RSV severity and gene expression as measured by microarray. RESULTS: While no SNPs reached the genome-wide statistical significance threshold (P < 5 × 10-8), we identified 816 candidate SNPs with a P-value of <1 × 10-4. Functional annotation of candidate SNPs highlighted genes relevant to neutrophil trafficking and cytoskeletal functions, including LSP1 and RAB27A. Moreover, SNPs within the RAB27A locus significantly altered gene expression (false discovery rate, FDR P < .05). CONCLUSIONS: These findings may provide insights into genetic mechanisms driving severe RSV infection, offering biologically relevant information for future investigations.

External Validation of the Discriminative Validity of the ReSVinet Score and Development of Simplified ReSVinet Scores in Secondary Care.

BACKGROUND: There is no consensus on how to best quantify disease severity in infants with respiratory syncytial virus (RSV) and/or bronchiolitis; this lack of a sufficiently validated score complicates the provision of clinical care and, the evaluation of trials of therapeutics and vaccines. The ReSVinet score appears to be one of the most promising; however, it is too time consuming to be incorporated into routine clinical care. We aimed to develop and externally validate simplified versions of this score. METHODS: Data from a multinational (the Netherlands, Spain, and United Kingdom) multicenter case-control study of infants with RSV were used to develop simplified versions of the ReSVinet score by conducting a grid search to determine the best combination of equally weighted parameters to maximize for the discriminative ability (measured by area under the receiver operating characteristic curve [AUROC]) across a range of outcomes (hospitalization, intensive care unit admission, ventilation requirement). Subsequently discriminative validity of the score for a range of secondary care outcomes was externally validated by secondary analysis of datasets from Rwanda and Colombia. RESULTS: Three candidate simplified scores were identified using the development dataset; they were excellent (AUROC >0.9) at discriminating for a range of outcomes, and their performance was not significantly different from the original ReSVinet score despite having fewer parameters. In the external validation datasets, the simplified scores were moderate to excellent (AUROC, 0.7-1) across a range of outcomes. In all outcomes, except in a single dataset for predicting admission to the high-dependency unit, they performed at least as well as the original ReSVinet score. CONCLUSIONS: The candidate simplified scores developed require further external validation in larger datasets, ideally from resource-limited settings before any recommendation regarding their use.

Single-cell immune profiling reveals markers of emergency myelopoiesis that distinguish severe from mild respiratory syncytial virus disease in infants.

Whereas most infants infected with respiratory syncytial virus (RSV) show no or only mild symptoms, an estimated 3 million children under five are hospitalized annually due to RSV disease. This study aimed to investigate biological mechanisms and associated biomarkers underlying RSV disease heterogeneity in young infants, enabling the potential to objectively categorize RSV-infected infants according to their medical needs. Immunophenotypic and functional profiling demonstrated the emergence of immature and progenitor-like neutrophils, proliferative monocytes (HLA-DRLow , Ki67+), impaired antigen-presenting function, downregulation of T cell response and low abundance of HLA-DRLow B cells in severe RSV disease. HLA-DRLow monocytes were found as a hallmark of RSV-infected infants requiring hospitalization. Complementary transcriptomics identified genes associated with disease severity and pointed to the emergency myelopoiesis response. These results shed new light on mechanisms underlying the pathogenesis and development of severe RSV disease and identified potential new candidate biomarkers for patient stratification.

Carpal Tunnel Release With Ultrasound Guidance: Intermediate-Term Clinical Outcomes and Magnetic Resonance Imaging Findings.

Purpose: The purpose of this study was to report intermediate-term outcomes following carpal tunnel release using ultrasound guidance and wide-awake local anesthesia no tourniquet, including a subset of patients with preoperative and postoperative magnetic resonance imaging (MRI). Methods: In this observational study, patients with carpal tunnel syndrome were treated with carpal tunnel release using ultrasound guidance and wide-awake local anesthesia no tourniquet in a procedure room at a single center. Main outcomes were complications; return to activity and work at 2 weeks; Quick Disabilities of the Arm, Shoulder, and Hand and Boston Carpal Tunnel Questionnaire scores through 6 months; and postoperative morphological changes of the transverse carpal ligament, median nerve, and carpal tunnel evaluated using MRI. Results: No complications were reported among 65 patients (68% women, 96 wrists). By 2 weeks, 97% of patients returned to normal activity and 100% returned to work. Statistically significant improvements in Boston Carpal Tunnel Questionnaire symptom severity scale, Boston Carpal Tunnel Questionnaire functional status scale, and Quick Disabilities of the Arm, Shoulder, and Hand scores occurred by the 2-week follow-up interval and persisted at 6 months (all P < .001). Pre- and postoperative MRI scans were available for 13 patients (17 wrists) at the 3-month mean follow-up. Complete transverse carpal ligament transection was documented in all wrists. Key MRI findings included a 22% increase in carpal tunnel cross-sectional area at the hamate (P < .001), a 52% increase in median nerve cross-sectional area at the hamate (P < .001), an 18% reduction in median nerve signal intensity (P = .002), a 38% reduction in the flattening ratio of the median nerve at the hamate (P < .001), a 33% reduction in the flattening ratio of the median nerve at the pisiform (P < .001), a 20% reduction in the flattening ratio of the carpal tunnel at the hamate (P < .001), and a palmar shift of the median nerve relative to the hamate in all cases. Conclusions: Carpal tunnel release using ultrasound guidance using wide-awake local anesthesia no tourniquet in a procedure room setting was safe, effective, and resulted in morphological changes that were consistent with carpal tunnel decompression as demonstrated by MRI. Type of study/level of evidence: Therapeutic IV.

Innovation for Orthopaedic Surgeons.

Entrepreneurship and innovation are cornerstones of the economy and move healthcare forward. Most physicians have little experience or knowledge in developing and commercializing novel concepts and ideas. It is important to focus on structured thinking concepts, fundraising, intellectual property, FDA regulations, and initial incorporation and teambuilding strategies. There are various aspects of creating ideas and moving them from notes scribbled on a napkin to a product or service, which can then be integrated into the economic fabric of the healthcare system. Surgeon founders and innovators can then share key aspects any surgeon should consider when becoming an entrepreneur.

Clinical and Viral Factors Associated With Disease Severity and Subsequent Wheezing in Infants With Respiratory Syncytial Virus Infection.

Respiratory syncytial virus (RSV) causes substantial morbidity and mortality in infants and young children worldwide. Here we evaluated host demographic and viral factors associated with RSV disease severity in 325 RSV-infected infants under 1 year of age from 3 European countries during 2017-2020. Younger infants had a higher clinical severity (ReSViNET) score and were more likely to require hospitalization, intensive care, respiratory support, and/or mechanical ventilation than older infants (<3 months vs 3 to <6 months and 3 to <6 months vs ≥6 months). Older age (≥6 months vs <3 months), higher viral load, and RSV-A were associated with a greater probability of fever. RSV-A and RSV-B caused similar disease severity and had similar viral dynamics. Infants with a more severe RSV infection, demonstrated by having a higher ReSViNET score, fever, and requiring hospitalization and intensive care, were more likely to have developed subsequent wheezing at 1 year of age. CLINICAL TRIALS REGISTRATION: NCT03756766.

Chronic Exertional Compartment Syndrome Caused by Functional Venous Outflow Obstruction.

OBJECTIVE: Investigate the theory that chronic exertional compartment syndrome (CECS) results from venous outflow obstruction due to functional muscular compression. Chronic exertional compartment syndrome occurs when increased pressure within a muscle compartment produces pain and/or neurologic symptoms. The exact etiology of CECS is unknown, leading to inconsistent diagnostic and treatment plans. STUDY DESIGN: Retrospective case series. SETTING: Private practice and sports medicine. PATIENTS: Two hundred eighty-four patients with exercise-induced lower leg pain. Twenty-two patients lost to follow-up. INTERVENTIONS: Leg vasculature was evaluated using stress computed tomography angiography (CTA) and MVP Flex to identify areas of functional venous compression. All patients then underwent targeted botulinum toxin treatment. Posttreatment follow-up imaging was performed using stress CTA in 197 patients. MAIN OUTCOME MEASURES: Presence of functional venous compression on stress CTA. Symptom reduction and normalization of venous flow after targeted botulinum toxin injections. RESULTS: Baseline imaging demonstrated CECS and functional venous obstruction with replication of symptoms in 260 of 284 patients [91.5% ± 3.2% (95% CI)]. Four weeks after treatment, 227 of 284 patients [79.9% ± 4.7% (95% CI)] described reduced/resolved symptoms with activity. One hundred fifty-five of the 197 patients [78.7% ± 5.7% (95% CI)] reimaged with stress CTA demonstrated resolved/reduced venous outflow obstruction. Twenty-two patients were lost to follow-up, and 35 patients had persistent symptoms. CONCLUSION: Chronic exertional compartment syndrome results from venous outflow obstruction due to functional muscular compression. Understanding the cause of CECS will allow the development of more precise and successful treatment plans. Based on our findings, treatment should be directed at the sites of venous compression.

A Systematic Review and Meta-analysis of Animal Studies Investigating the Relationship Between Serum Antibody, T Lymphocytes, and Respiratory Syncytial Virus Disease.

BACKGROUND: Respiratory syncytial virus (RSV) infections occur in human populations around the globe, causing disease of variable severity, disproportionately affecting infants and older adults (>65 years of age). Immune responses can be protective but also contribute to disease. Experimental studies in animals enable detailed investigation of immune responses, provide insights into clinical questions, and accelerate the development of passive and active vaccination. We aimed to review the role of antibody and T-cell responses in relation to RSV disease severity in animals. METHODS: Systematic review and meta-analysis of animal studies examining the association between T-cell responses/phenotype or antibody titers and severity of RSV disease. The PubMed, Zoological Record, and Embase databases were screened from January 1980 to May 2018 to identify animal studies of RSV infection that assessed serum antibody titer or T lymphocytes with disease severity as an outcome. Sixty-three studies were included in the final review. RESULTS: RSV-specific antibody appears to protect from disease in mice, but such an effect was less evident in bovine RSV. Strong T-cell, Th1, Th2, Th17, CD4/CD8 responses, and weak Treg responses accompany severe disease in mice. CONCLUSIONS: Murine studies suggest that measures of T-lymphocyte activity (particularly CD4 and CD8 T cells) may be predictive biomarkers of severity. Further inquiry is merited to validate these results and assess relevance as biomarkers for human disease.

Presumed Risk Factors and Biomarkers for Severe Respiratory Syncytial Virus Disease and Related Sequelae: Protocol for an Observational Multicenter, Case-Control Study From the Respiratory Syncytial Virus Consortium in Europe (RESCEU).

Respiratory syncytial virus (RSV) is the leading viral pathogen associated with acute lower respiratory tract infection and hospitalization in children < 5 years of age worldwide. While there are known clinical risk factors for severe RSV infection, the majority of those hospitalized are previously healthy infants. There is consequently an unmet need to identify biomarkers that predict host response, disease severity, and sequelae. The primary objective is to identify biomarkers of severe RSV acute respiratory tract infection (ARTI) in infants. Secondary objectives include establishing biomarkers associated with respiratory sequelae following RSV infection and characterizing the viral load, RSV whole-genome sequencing, host immune response, and transcriptomic, proteomic, metabolomic and epigenetic signatures associated with RSV disease severity. Six hundred thirty infants will be recruited across 3 European countries: the Netherlands, Spain, and the United Kingdom. Participants will be recruited into 2 groups: (1) infants with confirmed RSV ARTI (includes upper and lower respiratory tract infections), 500 without and 50 with comorbidities; and (2) 80 healthy controls. At baseline, participants will have nasopharyngeal, blood, buccal, stool, and urine samples collected, plus complete a questionnaire and 14-day symptom diary. At convalescence (7 weeks ± 1 week post-ARTI), specimen collection will be repeated. Laboratory measures will be correlated with symptom severity scores to identify corresponding biomarkers of disease severity. CLINICAL TRIALS REGISTRATION: NCT03756766.

Epidemiology and Immune Pathogenesis of Viral Sepsis.

Sepsis is a life-threatening organ dysfunction caused by a dysregulated host response to infection. Sepsis can be caused by a broad range of pathogens; however, bacterial infections represent the majority of sepsis cases. Up to 42% of sepsis presentations are culture negative, suggesting a non-bacterial cause. Despite this, diagnosis of viral sepsis remains very rare. Almost any virus can cause sepsis in vulnerable patients (e.g., neonates, infants, and other immunosuppressed groups). The prevalence of viral sepsis is not known, nor is there enough information to make an accurate estimate. The initial standard of care for all cases of sepsis, even those that are subsequently proven to be culture negative, is the immediate use of broad-spectrum antibiotics. In the absence of definite diagnostic criteria for viral sepsis, or at least to exclude bacterial sepsis, this inevitably leads to unnecessary antimicrobial use, with associated consequences for antimicrobial resistance, effects on the host microbiome and excess healthcare costs. It is important to understand non-bacterial causes of sepsis so that inappropriate treatment can be minimised, and appropriate treatments can be developed to improve outcomes. In this review, we summarise what is known about viral sepsis, its most common causes, and how the immune responses to severe viral infections can contribute to sepsis. We also discuss strategies to improve our understanding of viral sepsis, and ways we can integrate this new information into effective treatment.

Nonsurgical treatment of cystic adventitial disease of the popliteal artery caused by functional popliteal artery entrapment syndrome.

Lower extremity claudication in young men can be caused by popliteal artery entrapment and vascular pathology. The case reported here describes a young male wrestler who presented with unilateral calf pain with activity. Imaging studies at rest demonstrated cystic adventitial disease of the popliteal artery. Stress imaging showed severe functional popliteal artery entrapment. This patient was treated with an imaging-guided botulinum toxin injection of the muscles at the site of arterial compression. The patient was asymptomatic 6 weeks after treatment. Repeat stress imaging demonstrated complete resolution of the entrapment and nearly complete resolution of the popliteal artery cystic adventitial disease.

MRI detection of forearm soft tissue injuries with radial head fractures.

BACKGROUND: This study aims to evaluate the incidence of forearm soft tissue abnormalities associated with radial head fracture severity based on the Mason classification system. METHODS: Eighteen patients (age 18-45 years) were prospectively evaluated with elbow radiographs and magnetic resonance imaging (MRI) following longitudinal forearm trauma. MRI was performed within 10 days of the initial injury. Radiographs and MR images were evaluated in a blinded fashion by two musculoskeletal radiologists. RESULTS: Thirteen of 18 patients presented with Mason type I radial head fractures. In all patients with Mason type I fractures, the interosseous membrane (IOM) was intact. Two patients had Mason type II fractures with associated partial and compete tearing of the IOM and three patients had Mason type III fractures with complete tearing of the IOM. Edema was noted in the pronator quadratus in six of 13 type I injuries and seen in all type II and III injuries. No structural forearm soft tissue abnormalities were present in patients with Mason type I injuries. The presence of edema within the pronator quadratus correlated with distal forearm pain. CONCLUSIONS: The severity of radial head fracture correlates with longitudinal forearm injury evidenced by the presence of IOM tearing. The findings suggest patients with Mason type II or III fractures of the radial head should undergo further evaluation of the forearm for associated soft tissue injuries. Edema within the pronator quadratus was present following forearm trauma regardless of the severity of fracture and was related to symptomatic forearm pain.

Rotator cuff tears: association with acromion angulation on MRI.

OBJECTIVE: Using magnetic resonance imaging (MRI), evaluate the correlation of acromion angulation with thickening of the coracoacromial ligament (CAL) and narrowing of the subacromial space resulting in impingement upon the rotator cuff tendons. MATERIALS AND METHODS: Eighty-nine shoulder MRI studies performed on a 3T scanner were retrospectively analyzed by two blinded independent reviewers. Measurements of the acromion angle (delta angle), CAL thickness and distance between the CAL and humeral head were obtained. The data were categorized into two groups, delta angle less that and greater than 7.5°. The presence or absence of full thickness (FT) or near full thickness (NFT) rotator cuff tears was noted. RESULTS: In group 1, the acromion angle varied from -6.8 to 6.8° (1.7±3.5°) with a CAL thickness of 0.91±0.20 mm and a subacromial distance of 6.47±0.88 mm. Group 2 acromion angle varied from 7.6° to 46.8° (18.0°±8.1°) with a CAL of 1.77±0.51 mm and a subacromial distance of 4.52±0.82 mm. The difference in CAL thickness and subacromial distance were significantly different between the two groups (P<.001). In Group 1, 3 out of 51 patients had a FT or NFT tear of the rotator cuff compared to 20 out of 38 in Group 2 (P<.001). There was no significant interobserver variability. CONCLUSION: Steep acromion angulation is associated with CAL thickening and narrowing of the subacromial space. Patients with a steep acromion angle had a statistically increased incidence of rotator cuff tears.

Impaired contractile reserve in severe mitral valve regurgitation with a preserved ejection fraction.

BACKGROUND: Impaired contractile reserve in chronic MR results from load-independent, myocyte contractile abnormalities. AIMS: Investigate the mechanisms of contractile dysfunction in chronic mitral valve regurgitation (MR). METHODS: Mild MR was produced in eight dogs followed by pacing induced left ventricular (LV) dilatation over eight months. In-vivo LV dP/dt was measured at several pacing rates. Contractile function was measured in isolated LV trabeculae and myocytes at several stimulation rates and during changes in extracellular [Ca2+]. Identical studies were performed with six control dogs. RESULTS: Chronic MR resulted in a preserved ejection fraction with decreased dP/dt (p<0.01). LV trabeculae demonstrated significantly lower developed force and a negative force-frequency relation with chronic MR (p<0.05). Myocytes exhibited a negative shortening-frequency relationship in both groups with a greater decline with chronic MR (p<0.001) paralleled by decreases in peak [Ca2+](i) transients. Increases in extracellular [Ca2+] abrogated the defects in force generation in trabeculae from animals with chronic MR. CONCLUSION: Even with a preserved EF, chronic severe MR results in a significant reduction in intrinsic contractile function and reserve. Functional impairment was load-independent reflecting a predominant defect in calcium cycling rather than impaired peak force generating capacity due to myofibrillar attenuation.

Nondisplaced elbow fractures: A commonly occurring and difficult diagnosis.

PURPOSE: Determine the sensitivity and specificity of radiography in identifying nondisplaced elbow fractures after trauma. Our hypothesis is that nondisplaced fractures occur commonly following impact injuries and are difficult to diagnose with plain film imaging. METHODS: An in vitro double-blinded study of 16 cadaver arms was designed, simulating axial forearm trauma. Following injury, anteroposterior and lateral radiographs were obtained. Each specimen was dissected, and the injury described. A musculoskeletal radiologist, blinded to dissection results, examined the radiographs. RESULTS: Dissection revealed 39 fractures of 96 sites examined. A total of 14 fractures were nondisplaced, 7 involving the coronoid process. Radiographs identified 27 fractures. Of the 12 missed fractures, 11 were nondisplaced. Radiographic diagnosis of nondisplaced elbow fractures demonstrated a 21% sensitivity, 95% specificity, 50% positive predictive value, and 83% negative predictive value. CONCLUSIONS: Radiography for nondisplaced elbow fractures demonstrated limited success. Additional imaging studies may be required in suspected elbow injuries with initial negative radiographs.

Forearm interosseous membrane trauma: MRI diagnostic criteria and injury patterns.

OBJECTIVE: Define criteria for interosseous membrane (IOM) injury diagnosis using MRI, and characterize patterns of IOM disruption following forearm trauma. Our hypothesis is that most IOM injuries occur along the ulnar insertion, and MRI should be obtained following forearm trauma to assess IOM competency. DESIGN: Sixteen cadaver forearms were subjected to longitudinal impact trauma. Prior to and following injury, MR images were examined by a board-certified musculoskeletal radiologist using pre-defined criteria for determining IOM integrity. Each specimen was dissected and the viability/pattern of injury examined. The MRI and dissection results were compared using a double-blinded methodology. RESULTS: Eight of the 16 specimens demonstrated IOM trauma. Seven specimens demonstrated complete IOM disruption from the ulnar insertion, and one revealed a mid-substance tear with intact origin and insertion. The dorsal oblique bundle was disrupted in four specimens. MRI analysis identified IOM injury in seven of the eight forearms. The injury location was correctly identified in six specimens when compared to dissection observations. MRI determination of IOM injury demonstrated a positive predictive value of 100%, a negative predictive value of 89%, a sensitivity of 87.5% and a specificity of 100%. CONCLUSION: Our findings demonstrate the accuracy of MRI in identifying IOM disruption, and its ability to localize specific injuries in a clinically relevant model of forearm trauma. The injury patterns demonstrated most lesions occurred along the IOM's ulnar insertion, and in half of the injured specimens there was concomitant dorsal oblique bundle disruption.

Subvalvular alterations promote increased mitral valve regurgitation in progressive dilated cardiomyopathy.

BACKGROUND: Alterations in transmitral pressure, valve structure, subvalvular geometry, and abnormal myocardial function have all been implicated in the pathophysiology of functional/progressive mitral valve regurgitation (MR). In this study, we hypothesized that a relatively small structural lesion to the mitral valve apparatus predisposes to severe MR in the setting of progressive left ventricular dilation. While examining this hypothesis, an additional purpose of this study was to determine the extent of papillary muscle (PM) distortion and mitral annular dilation with increasing MR resulting from progressive dilated cardiomyopathy. METHODS AND RESULTS: Mild MR was produced via a limited, fixed structural lesion to the mitral valve apparatus of 8 dogs (20 to 22 kg). Incremental tachypacing induced left ventricular dilation over an 8-month period. The pacer was deactivated and the dogs followed for an additional 6 weeks. Echocardiographic measurements demonstrated significant cardiac remodeling (left ventricular end diastolic diameter) and MR progression with a 54% increase in left ventricular end diastolic diameter and a 44% increase in MR jet area (P < .05). Tachypacing induced decreases in left ventricular ejection fraction recovered nearly to baseline levels by 6 weeks after pacing cessation. Nevertheless, left ventricular dilation persisted and MR remained severe after pacing cessation. There was a significant increase in the short axis PM segment length and PM angular separation from baseline (6.28 +/- 0.83 versus 4.02 +/- 0.56 cm and 99.7 +/- 2.6 versus 90.1 +/- 3.2 deg, respectively, P < .05) with no change in mitral annulus circumference (8.71 +/- 0.70 versus 8.15 +/- 0.35 cm, P = NS). CONCLUSION: Progressive MR severity in nonischemic dilated cardiomyopathy resulted from changes in left ventricular shape and altered papillary muscle geometries and does not require mitral annulus dilation or a reduced left ventricular ejection fraction.

Forearm interosseous membrane imaging and anatomy.

OBJECTIVE: To determine the regional thickness variation of the interosseous membrane (IOM) along the forearm and validate magnetic resonance imaging of the IOM with laser micrometry. DESIGN AND PATIENTS: Axial thickness measurements of 12 cadaver forearms were obtained using magnetic resonance imaging (MRI) at radial, central, and ulnar locations. The specimens were dissected, and IOM thickness measured using a laser micrometer. MRI and laser measurements of the main and oblique IOM bundles were compared. An axial thickness profile was plotted versus forearm length, and radial, central, and ulnar positions were compared. RESULTS: The main bundle thickness was 2.18+/-0.20 mm using laser micrometry, which was not significantly different from MRI measurements (1.86+/-0.25 mm, p=0.11, power = 0.84). The dorsal oblique bundle thickness was not significantly different between measurement methods (2.93+/-0.77 mm and 3.30+/-1.64 mm using laser micrometry and MRI respectively, p=0.75, power = 0.04). Both methods demonstrated a progressive increase in thickness proximally within the forearm. MRI measurements demonstrated a significantly greater thickness increase in the radial location compared to the central location (slope = 2.26 and 1.05, r(2)=0.31 and 0.12 respectively, p<0.05). The ulnar slope was not significantly different from zero ( r(2)=0.02, p>0.05). CONCLUSION: Our findings describe the varying IOM anatomy using MRI, and determined the location of the clinically important IOM fiber bundles. This study confirms the accuracy of MR imaging of the IOM by comparison with a laser micrometer, and demonstrates the thickness variation along the forearm. This information may be used to identify changes in IOM anatomy with both acute IOM injury and chronic fiber attenuation.

Forearm and elbow injury: the influence of rotational position.

BACKGROUND: The purpose of this study was to develop an axial loading forearm fracture model and to determine the influence of forearm rotation on the fracture pattern. METHODS: Twenty-six cadaveric arms were thawed in saline solution. Pressure-sensitive film was sealed and was placed through a lateral arthrotomy into the radiocapitellar joint. The arm was potted at the proximal part of the humerus with the elbow in extension. Rotational range of motion was measured with use of a goniometer starting from a supinated position (0 degrees ). Specimens were placed in a vertical position at various angles of forearm rotation, and a 27-kg mass was raised to 90 cm and was dropped onto the distal part of the radius. The pressure film was removed and was analyzed to determine the radiocapitellar joint contact area following impact. Each arm was dissected, and the injury pattern was assessed. RESULTS: Both-bone forearm fractures (proximal radial fractures with concomitant distal ulnar fractures) occurred at 5 degrees +/- 2.6 degrees of rotation, isolated radial head fractures occurred at 44.4 degrees +/- 5.2 degrees of rotation, and Essex-Lopresti fractures (radial head fractures with tearing of the interosseous membrane) occurred at 70 degrees +/- 25.2 degrees of rotation. The distribution of Essex-Lopresti and radial head fractures was significantly different at a cutpoint of 54 degrees of forearm rotation (p = 0.009), and the distribution of radial head fractures and both-bone forearm fractures was significantly different at a cutpoint of 10 degrees of forearm rotation (p = 0.001). The percent contact area of the radial head varied with the injury pattern (p = 0.029). Marginal radial head fractures occurred at 46.7 degrees +/- 6.6 degrees of rotation with a contact area of 30.9% +/- 8.6%, while comminuted radial head fractures occurred at 74.4 degrees +/- 27.2 degrees of rotation with a contact area of 53.9% +/- 8.3%. CONCLUSION: The amount of forearm rotation at the time of axial load impact directly influenced the injury pattern. Furthermore, the radial head contact area and the fracture severity increased in pronation compared with supination.

Biochemical composition and histologic structure of the forearm interosseous membrane.

PURPOSE: The purpose of this study was to determine the structure and composition of the forearm interosseous membrane (IOM). METHODS: The IOM of 12 cadaver forearms was fixed in formalin. After fixation 5 individual IOM fiber bundles per arm were separated by dissection, excised, and processed with hematoxylin-eosin, trichrome, and Verhoff-vanGeison stains. Nine additional fresh forearms were dissected and 5 IOM fiber bundles per arm were analyzed using the hydroxyproline assay. Bundles were evaluated at ulnar, central, and radial locations. RESULTS: Histologic analysis of the IOM bundles obtained from the 12 fixed forearms showed an abundance of collagen in the main bundle central location (84% +/- 7.8%). A progressive increase in collagen was noted from distal to proximal bundles (r =.72). The hydroxyproline assay of collagen content of the main IOM bundle's central location from the 9 additional fresh forearms was 99.3% +/- 16.5%. There was no difference between bundles or location (power = 0.25 and 0.46). CONCLUSIONS: We found that the IOM possesses a large collagen content arranged in fibrillar structures surrounded by elastin. Collagen was abundant in the proximal bundles and decreased in the distal bundles.