Background:
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Childhood and adolescence is a critical time for bone mass accrual which helps prevent adult osteoporosis. During this time, many adolescents engage in sports, which provides them with numerous health benefits. However, as trends in sport specialization and participation in year-round sports have increased over the past decade, the number of pediatric overuse injuries, including bone stress injuries, have increased, accounting for approximately 46-54% of all sports injuries. Bone stress injuries can range from stress reactions to stress fractures. There is limited evidence reporting on the various locations of middle and lower body bone stress injuries and recovery times in the pediatric population. The purpose of this study was to describe various locations of middle and lower body bone stress injuries and to identify differences in time to recovery in the pediatric population.

Methods:
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A retrospective review of subjects diagnosed with a lumbar spine or lower body bone stress injury presenting to a pediatric sports medicine clinic over a two-year period was performed. Subjects were included if they were between the ages of 7-18 years old, presented to clinic within three years from symptom onset, and their diagnosis was confirmed via X-ray or MRI. Subjects were categorized into groups by location of their bone stress injury (femur, fibula, foot, lumbar spine, tibia, and tibia/fibula). Medical records were reviewed for demographics, injury characteristics, sport, imaging, treatment, and outcomes when available. Bone stress injury locations were compared using a Kruskal-Wallis test for continuous variables and a chi-square test for categorical variables. When the sample was small, a Fisher's exact test was used.

Results:
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Of 134 eligible subjects, 84 (62.7%) were female and 50 (37.3%) were male with a mean age of 14.37 years (range=7-18) and mean BMI of 21.93 kg/m⁁2. 127 (94.8%) subjects participated in sports, including gymnastics (15.2%), football (11.6%), running/cross-country (11.6%), and soccer (10.9%). The most common location of bone stress injury was lumbar spine (n=71, 53.0%), followed by foot (n=27, 20.2%) and tibia (n=16, 11.9%). 117 (87.3%) subjects were diagnosed via radiographs and 88 (65.7%) required further imaging via MRI to confirm diagnosis. CT was obtained in only 4 (3%) subjects. No significant differences in gender, sport, level of competition, imaging type, or treatment type were noted between bone stress injury groups.

While various treatment modalities were implemented, physical therapy was prescribed in 99 (73.9%) subjects and bracing was prescribed in 38 (28.4%). 32 (23.9%) subjects were taking supplements prior to treatment or were prescribed them for their bone stress injury, which included vitamin D and calcium. 62 (46.3%) subjects were taking nonsteroidal anti-inflammatory drugs prior to treatment or were prescribed them by the physician for their bone stress injury.

Across all bone stress injury groups, the mean time from symptom onset to initial presentation was 80.76 days. The lumbar spine group had the longest time to presentation (103.99 days), followed by tibia (81.13 days) and femur (80.73 days, p=0.047) (Figure 1A).

Follow-up information was available on 116 (86.6%) subjects. Mean time from diagnosis to recovery across all groups was 88.26 days. Bone stress injuries of the tibia had the longest recovery time (127.27 days), followed by lumbar spine (92.23 days) and femur (89 days, p=0.018) (Figure 1B).

Conclusion/Significance:
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The lumbar spine was the most common location for middle and lower body bone stress injuries in this pediatric population, followed by foot and tibia. Tibia bone stress injuries took the longest time to heal.

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