A statistics primer. Statistical terminology--Part 2.
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Biomedical subjects
Publications and source records attributed to M L Greenfield.
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Anterior cruciate ligament injury rates are four to eight times higher in women than in men. Because of estrogen's direct effect on collagen metabolism and behavior and because neuromuscular performance varies during the menstrual cycle, it is logical to question the menstrual cycle's effect on knee injury rates. Of 40 consecutive female athletes with acute anterior cruciate ligament injuries (less than 3 months), 28 (average age, 23 +/- 11 years) met the study criteria of regular menstrual periods and noncontact injury. Details concerning mechanism of injury, menstrual cycle, contraceptive use, and previous injury history were collected. A chi-square test was used to compute observed and expected frequencies of anterior cruciate ligament injury based on three different phases of the menstrual cycle: follicular (days 1 to 9), ovulatory (days 10 to 14), and luteal (day 15 to end of cycle). A significant statistical association was found between the stage of the menstrual cycle and the likelihood for an anterior cruciate ligament injury (P = 0.03). In particular, there were more injuries than expected in the ovulatory phase of the cycle. In contrast, significantly fewer injuries occurred in the follicular phase. These hormones may be a factor in the knee ligament injury dilemma in women.
SUMMARY: Slipped capital femoral epiphyses (SCFEs) can be idiopathic or atypical (associated with renal failure, radiation therapy, and endocrine disorders). The demographics of 433 children (285 idiopathic, 148 atypical) with 612 SCFEs were studied to define predictors of atypical SCFEs. Multiple logistic regression analysis showed that age and weight were predictors. For two patients of equal weight, those younger than 10 or older than 16 years of age were 4.2 times more likely to have an atypical SCFE; for two patients of equal age, those <50th percentile weight were 8.4 times more likely. The age-weight test was defined as negative when age younger than 16 years and weight > or = 50th percentile and positive when beyond these boundaries. The probability of a child with a negative test result having an idiopathic SCFE was 93%, and the probability of a child with a positive test result having an atypical SCFE was 52%. An evaluation of the child's age and weight is useful when considering the cause of an SCFE.