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Twisting [PATCHED]

Study design: A systematic review of the literature using Medline, Embase, CINAHL, Cochrane Library, and Occupational Safety and Health database, gray literature, hand-searching occupational health journals, reference lists of included studies, and experts. Evaluation of methodological quality using a modified Newcastle-Ottawa Scale for observational studies. Summary levels of evidence for each of the Bradford-Hill criteria for causality for each category of bending or twisting and type of LBP.


Methods: A systematic review was performed to identify, evaluate, and summarize the literature related to establishing a causal relationship, according to Bradford-Hill criteria, between occupational bending or twisting and LBP.

Results: This search yielded 2,766 citations. Ten high-quality studies reported on bending and LBP. Five were case-control studies and five were prospective cohort studies. There was conflicting evidence for association, with five studies demonstrating significant associations in the majority of their risk estimates, but no evidence for consistency. Seven studies assessed dose response, with four studies demonstrating a nonsignificant dose-response trend. Four studies were able to assess temporality, but only one demonstrated significant risk estimates. Biological plausibility was discussed by two studies. There was no available evidence for experiment. Seven high-quality studies reported on twisting and LBP. Two were case-control studies and five were prospective cohort studies. Three studies reported significant associations in the majority of their risk estimates, with no evidence for consistency. Three studies demonstrated a nonsignificant dose-response trend. Two studies were able to assess temporality, but only one study was able to demonstrate significant risk estimates. Two studies discussed biological plausibility. There was no available evidence for experiment.

Conclusions: A summary of existing studies was not able to find high-quality studies that satisfied more than three of the Bradford-Hill criteria for causation for either occupational bending or twisting and LBP. Conflicting evidence in multiple criteria was identified. This suggests that specific subcategories could contribute to LBP. However, the evidence suggests that occupational bending or twisting in general is unlikely to be independently causative of LBP.

The elastic properties of DNA are essential for its biological function. They control its bending and twisting as well as the induction of structural modifications in the molecule. These can affect its interaction with the cell machinery. The response of a single DNA molecule to a mechanical stress can be precisely determined in single-molecule experiments which give access to an accurate measurement of the elastic parameters of DNA.

A storm on December 1, 1951, caused the Golden Gate Bridge to twist and vibrate enough to cause some minor damage, so the Bridge was retrofitted from 1953 to 1954. The retrofit added new bracing across the bottom, connecting the two steel trusses that support the roadway deck. This change increased the Bridge's twisting, or torsional, stiffness.

How the Bridge Vibrates (all ages)This exhibit, in the visitor area at the San Francisco end of the Bridge, demonstrates four modes of vibration of the Bridge, including the twisting (wind flutter) mode.

Before & After the Torsional Resistance Retrofit from the Golden Gate Bridge, Highway and Transportation DistrictPrinceton University civil engineering professor Dr. Maria Garlock shows how this exhibit, designed by Elizabeth Deir, a student of hers, lets the visitor feel the difference in the torsional (twisting) stiffness of the original Bridge deck as compared to the deck after its wind engineering retrofit was implemented in the 1950s.

Background: Testicular torsion is surgical emergency. Prompt diagnosis and treatment of testicular torsion is essential for testicular viability. At surgical exploration, the spermatic cord is seen twisted a variable number of times around its longitudinal axis. There is scant data regarding the degree of twisting and its association with testis outcomes. The purpose of our study is to explore how the degree of torsion factors into testicular outcome using follow-up data.

Methods: We retrospectively reviewed the records of adolescent males who presented with testicular torsion to our institution, looking at duration of pain symptoms, degree of torsion documented in the operative note, procedure performed (orchiopexy versus orchiectomy), and follow-up clinic data for whether testicular atrophy after orchiopexy was present. A non-salvageable testis was defined as orchiectomy or atrophy. Receiver operator characteristics (ROC), multivariate, and logistic regression analyses were performed to determine the probability of a non-salvageable torsed testis based on time and degree of twisting.

Conclusions: We were able to derive separate formulas to determine the viability of the torsed testis based on symptom duration and degrees of twisting. Fifteen h of symptoms and 860 degrees of torsion gives testes a 50% salvage rate. Interestingly, we also found that about 1 out of every 4 testes undergoes atrophy after orchiopexy.

Testicular torsion is a surgical emergency affecting 1 in 4,000 boys below the age of 25, and accounting for up to 25% of acute scrotal disease in pediatrics (1). Although testicular torsion can occur at any age, it is most commonly seen in the adolescent population. Testicular torsion is defined as a twisting of the spermatic cord along a longitudinal axis, with resultant ischemia due to compromised blood flow to the testicle. Clinically, testicular torsion presents with an acute onset of scrotal pain, followed by scrotal swelling, nausea and vomiting. A high-riding testis in a transverse lie is often found on physical examination. These findings, in association with an absent cremasteric reflex, are highly suggestive of testicular torsion. The goal in managing testicular torsion is organ salvage. In order to maximize the chances of testicular survival, prompt diagnosis and treatment of testicular torsion is essential. Parameters associated with testis viability include duration of symptoms and the sonographic echotexture of the testis.

At surgical exploration, the spermatic cord is seen twisted a variable number of times around its longitudinal axis. There is scant data regarding the degree of twisting found at surgical exploration and its association with testis outcomes. Animal models have demonstrated a relationship between various testicular outcomes and degrees of twisting in the spermatic cord (5-8). In humans, Filho et al. demonstrated that the degree of testicular rotation has a multiplicative effect on the role of presentation delay in testicular torsion. Greater degree of testicular rotation is seen in patients undergoing orchidectomy vs. orchiopexy. However, testicular atrophy rates at follow-up were not measured (9). The purpose of our study is to further explore how the degree of torsion factors into testicular outcome. It is hypothesized that the greater number of twists of the spermatic cord would offer more obstruction of the vasculature and thus a lower salvage rate based on immediate intraoperative findings (orchiectomy) along with delayed atrophy of the testicle at follow-up.

Logistic regression analysis was then performed using the SAS JMP statistical analysis software platform (JMP, Version 13.1, SAS Institute Inc., Cary, NC, USA, 2016) to determine the predictive value of duration of pain and degree of twists for the probability of a non-salvageable testis at the time of surgical exploration. This was then used to estimate the probability of non-salvage for each patient based upon either the duration of pain or degree of twisting alone, with linear probability formulas generated for each variable.

We were also able to determine the clinical significance of the degree of twisting (separate from the duration of pain as the degree of twist did not significantly contribute to derive a formula which combined both variables) in ultimate testis viability during episodes of testicular torsion in the pediatric population, despite a low sensitivity on ROC analysis. When there is greater than one twist (more than 360 degrees) seen in the spermatic cord at scrotal exploration, there is a higher risk of non-salvage for the testis based on our data. Our study is also the first to derive separate formulas for duration and degree of twisting to determine the probability of a non-salvageable testis during torsion episodes. This probability can be calculated by our formulas, 4 + (3 duration in hours) and 7 + (0.05 degree of twisting). The clinical significance of these formulas can be helpful in patients counseling perioperatively and monitoring these testes during follow-up. For example, a testis that is twisted 360 degrees for 6 h will have a 25% and 22% chance of non-salvage based on degree and duration, respectively. However, the role these formulas play into the decision on whether to perform an orchiopexy versus orchiectomy at time of surgery largely depend on clinical judgement, the philosophy of the urologist in the management of a testis with equivocal viability, along with other intraoperative findings.

The limitations of the study are its retrospective nature and the relatively low number of patients with more than one month of follow-up as well as the degree of twisting dictated in the operative notes. Also, while our study was able to determine clinically helpful formulas using degree of twisting and duration of pain for testicular prognosis, we were unable to combine these variables into one formula to give one definitive probability of non-salvage. While more studies in humans are needed to truly determine the clinical relevance of twisting degree in relation to prognosis of testicular torsion, we must also look to other areas of torsion pathology to better enhance our knowledge in this common emergency room presentation in children.


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