130 Chapter 7 for the insertion). The median (95% RI) AP thickness in asymptomatic individuals for the midportion region was 4.9 mm (3.8–6.9) and 3.7 mm (2.8–4.8) for the insertional region. Age and height had the largest influence on tendon thickness, with older age and higher height being associated with increased values for tendon thickness (Table 2). In the bivariate analysis, male sex was found to be positively correlated with tendon thickness but this effect was not significant in the multiple quantile regression model (Table 2). The results of the multiple quantile regression model (n=492, R2=0.22 for the midportion and R2=0.16 for the insertion) with the relevant parameters is provided in Table 2. The data for the 8 participants who opted not to disclose their sex were excluded from the multiple quantile regression analysis. Table 2. Estimates (95%CI, p-value) of the effect of the parameters on maximum Achilles tendon thickness derived from the multiple quantile regression analysis adjusted for age, height (cm), BMI and sex. Examples on how to employ the normative equations based on two fictional patients are provided in the lower part of the table. * Sex: male = 0, female = 1 ** Values are median (mm) with 95% RI (2.5th percentile, 97.5th percentile). Abbreviations; BMI: Body Mass Index Variable Parameter estimated in the Midportion region Parameter estimated in the Insertional region Intercept -2.1 (-3.7, -0.35) -0.34 (-1.6, 0.9) Age 0.021 (0.017, 0.025, p=0.000) 0.010 (0.007, 0.012, p<0.001) Height 0.032 (0.023, 0.041, p<0.001) 0.018 (0.012, 0.025, p<0.001) BMI 0.028 (0.010, 0.045, p=0.003) 0.022 (0.009, 0.036, p=0.001) Sex 0.054 (-0.11, 0.22, p=0.553) -0.050 (-0.18, 0.78, p=0.446) Normative equation* Intercept + age + height + BMI + sex Example A Female, 23 years, 20 kg/m2, 165 cm Example B Male, 58 years, 28 kg/m2, 186 cm Tendon thickness (midportion)** -2.1 + 0.021 x (age) + 0.032 x (height) + 0.028 x (BMI) + 0.054 x (sex) A: 4.3 (3.1-5.5) mm -2.1 + 0.021 x (23) + 0.032 x (165) + 0.028 x (20) + 0.054 x (1) B: 5.9 (4.6-7.9) mm -2.1 + 0.021 x (58) + 0.032 x (186) + 0.028 x (28) + 0.054 x (0) Tendon thickness (insertion)** -0.34 + 0.010 x (age) + 0.018 x (height) + XX x (BMI) + XX x (sex) A: 3.2 (2.7-4.1) mm -0.34 + 0.010 x (23) + 0.018 x (165) + 0.022 x (20) – 0.050 x (1) B: 4.2 (3.3-5.6) mm -0.34 + 0.010 x (58) + 0.018 x (186) + 0.022 x (28) – 0.050 x (0) Estimates of normative median (95% RI) values for tendon thickness of the midportion and insertional region are presented in Table 3.
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