Abstract
BackgroundImmobilization and associated periods of inactivity can cause osteopenia, the physiological response of the bone to disuse. Mechanical loading plays an essential role in maintaining bone integrity. Skeletal fractures represent one cause of reduction of the physical activity (PA) level in adolescents. The purpose of this study was to quantify the reduction of PA in adolescents with limb fractures during the cast immobilization period compared with healthy controls.MethodsTwo hundred twenty adolescents were divided into three groups: those with upper limb fractures (50 cases); lower limb fractures (50 cases); and healthy cases (120 cases). Patients and their healthy peers were matched for gender, age, and seasonal assessment of PA. PA level was assessed during cast immobilization by accelerometer. Time spent in PA in each of the different intensity levels - sedentary, light, moderate, and vigorous - was determined for each participant and expressed in minutes and as a percentage of total valid time.ResultsReduction in PA during cast immobilization was statistically significant in patients with limb fractures compared to healthy controls. The total PA count (total number of counts/min) was significantly lower in those with upper and lower limb fractures (-30.1% and -62.4%, respectively) compared with healthy controls (p < 0.0001 and p = 0.0003, respectively). Time spent in moderate-to-vigorous PA by patients with upper and lower limb injuries decreased by 36.9% (p = 0.0003) and 76.6% (p < 0.0001), respectively, and vigorous PA was reduced by 41.4% (p = 0.0008) and 84.4% (p < 0.0001), respectively.ConclusionsPA measured by accelerometer is a useful and valid tool to assess the decrease of PA level in adolescents with limb fractures. As cast immobilization and reduced PA are known to induce bone mineral loss, this study provides important information to quantify the decrease of skeletal loading in this patient population. The observed reduction of high intensity skeletal loading due to the decrease in vigorous PA may explain osteopenia due to disuse, and these data should be kept in mind by trauma practitioners to avoid any unnecessary prolongation of the cast immobilization period.
Highlights
Immobilization and associated periods of inactivity can cause osteopenia, the physiological response of the bone to disuse
Patients with limb fractures were paired with healthy controls according to gender, age (± 0.5 years), and seasonal assessment, as the latter may have an impact on the physical activity (PA) level
PA measured by accelerometer is a useful and valid tool to assess the decrease of PA levels in adolescents with limb fractures
Summary
Immobilization and associated periods of inactivity can cause osteopenia, the physiological response of the bone to disuse. Exercise exerts a positive effect on bone growth, if the activity has been initiated before puberty or in the early pubertal [13,14,15,16,17,18]. Based on this evidence, it is recommended that physical activity for children include activities generating relatively high ground-reaction forces, such as jumping, skipping, running, and possibly strengthening exercises [5]. It is recognized that immobilization and associated periods of inactivity can cause osteopenia [19,20,21], the physiological response of the bone to disuse. The objective of our study was to quantify the reduction of PA levels during cast immobilization in this patient population
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