BMI INCREASES AFTER ACL-RECONSTRUCTION IN ADOLESCENTS
Authors: Hanstein Regina , Kirschner Noah , Moloney Christine , Fornari Eric 
Published: March 2019

Background: The incidence of ACL injuries in the pediatric and adolescent patient population has increased over the last 20 years. ACL reconstruction is recommended to avoid osteoarthritis later in life. However, a 6-12 months rehabilitation with no or limited sports activity after surgery is required to protect the graft and graft fixation. The aim of this study was to determine, if this period of inactivity affects the BMI in an adolescent patient population and affects patient self-reported outcomes. Methods: A retrospective review of 115 patients between the ages of 12 and 21 years, who had undergone ACL reconstruction with hamstring or bone-patellar-bone autograft by a single orthopaedic surgeon between 2013 and 2017 was performed. 44 patients had records of height and weight pre- and post-operatively (6 months, 1 year, at most recent follow-up: average 2.09 years, range 1-5.25 years). BMI was calculated using the CDC BMI calculator for child & teen or adult, depending on the age of the patient. Based on this, patients were categorized as having a normal weight, being overweight or obese. Patient self-report outcomes - PediIKDC, Tegner-Lysholm and KOOSChild - were reviewed. Data was analyzed using Student’s t-test and Spearman correlation. Results: BMI did not change in the 6 months after ACL reconstruction, but was significantly higher 1 year after ACL reconstruction and at most recent follow-up compared to BMI at initial surgery (Table 1). Sub-analysis by gender revealed that males had a higher BMI at both timepoints, whereas females only showed an increase in BMI at most recent follow-up, but not at 1 year post-surgery. While 26.1% of male patients were obese at surgery, 54.2% were obese 6 months after ACL reconstruction and 40.9% at 1 year (Figure1). At most recent follow-up, the distribution of patients in the weight categories was similar to that at initial surgery. This trend was not seen in female patients. A selection-bias for overweight and obese patients in the follow-up period can be ruled out, as obesity or overweight were not related to complications after surgery. BMI weakly correlated with better outcomes for the KOOSChild Quality of Life domain at 6 months after surgery (r=0.450, p=0.031) and trended to be weakly correlated with the KOOSChild Symptom domain (p=0.071), KOOSChild Sport domain (p=0.076) and PediIKDC (p=0.061). No correlation between BMI and patient outcomes was found at 1 year after ACL reconstruction or at most recent follow-up. Conclusion: After ACL-reconstruction, adolescents gain weight, most likely due to limited activity during the rehabilitation phase. This weight gain was more pronounced in males than females. The increase in BMI lasted longer than the period of rehabilitation-related inactivity. Patients with higher BMI rated their Quality of Life better at 6 months. The activity restrictions might not have affected these patients usual life style, however, data on activity level before ACL injury was not available. [Table: see text][Figure: see text]