Postoperative Weight Loss and its Impact on Outcomes in Patients with Adolescent Idiopathic Scoliosis after Spinal Fusion Roslyn Tarrant1,2, Mary Nugent3, Padraig Sheeran4, David Moore3, Pat Kiely3,5 1Dept. of Clinical Nutrition, OLCHC; 2National Children’s Research Centre; 3Dept. of Orthopaedic Surgery/4Dept. Of Anaesthetics, OLCHC; 5Blackrock Clinic, Co. Dublin BACKGROUND METHODS Abnormal anthropometry including comparably lower weight and body mass index (BMI) in the adolescent idiopathic scoliosis (AIS) population is increasingly recognised. Studies from Greece, Poland, Spain and Ireland1 report that approx. one quarter of patients with AIS are considered clinically underweight preoperatively – it is still unknown whether these altered anthropometric features are a symptom of AIS, or related to abnormal spinal growth. The impact of preoperative weight and BMI on outcomes in patients with AIS has been previously examined1. This is the first study to quantify postoperative weight loss, and assess its clinical impact on outcomes in these already very thin patients following posterior spinal fusion (PSF). In all, 77 consecutive and eligible patients with AIS who underwent PSF were prospectively followed up from hospital admission (Jan 2010-April 2012), until return to postoperative function2. Pre- & postoperative anthropometric measurements were collected (weight, height and BMI) and unintentional weight loss from admission to hospital discharge recorded. The primary outcome was impact of clinically severe involuntary weight loss during the hospital stay, defined as ‘>10% loss of initial body weight from admission to hospital discharge’3, on clinical outcomes. The effect of clinically severe weight loss >10% was analysed in relation to radiographic, nutritional, biochemical, socio-demographic and perioperative complication data, as well as length of hospitalisation and timing of return to function (including return to preoperative weight). RESULTS Mean age of the cohort was 15 yrs; 93.5% were female. Clinically severe postoperative weight loss >10% was identified in almost one third of patients (n = 22; 30.6%). A significantly increased superficial wound infection incidence was the only clinical outcome under analysis associated with >10% weight loss (13.6% vs. 2%, P = 0.047) (Table 1). A non-significant trend towards an increased hospital readmission rate, as well as overall minor and major perioperative complications in patients who lost >10% body weight was also observed. Table 1 Associations between % weight loss ≤ 10% vs. > 10% during the hospital stay, and selected characteristics and outcomes* Parameter ≤ 10% (n = 50) > 10% (n = 22) P Value Weight on admission (kg), mean (SD) 51.8 (11) 51.3 (8.8) NS Weight at discharge (kg), 48.9 (11) 44.1 (7.9) 0.05 Preoperative primary curve degree, mean (SD) 63.1 (14.9) 60.4 (9.7) No. of fused vertebrae, median (IQR) 11 (10-13) 12 (10-13.3) Postoperative PN feeding, n (%) 6 (12) 1 (4.5) Minor perioperative complication rate, n (%) 35 (70) 18 (81.8) Minor complications, n (%) Gastrointestinal (ileus) Blood product transfusion Superficial wound infection 21 (42) 1 (2) 13 (59.1) 3 (13.6) 0.047 Major perioperative complication rate, n (%) 2 (4) 2 (9.1) Length of hospitalisation (days), median (IQR) 9 (8-11) 9.5 (8-11) Albumin at discharge (g/L), 28 (4) 25 (4.6) Hospital readmission rate, n (%) Reported time to achieving preoperative weight after surgery (wks), median (IQR) 8 (4-19) 21 (16-24) <0.0001 CONCLUSIONS This study demonstrates that clinically severe postop. weight loss >10%, identified in 30.6% of this cohort, was associated with a sig. increased wound infection incidence. Severe postoperative weight loss >10% may be a potentially valuable marker of wound infection risk in this patient group – a novel finding that requires confirmation in future studies. Early detection and prevention of severe postoperative weight loss may prove particularly beneficial to modifying wound infection risk in the AIS population. Abbreviations: SD, standard deviation; IQR, interquartile range; wks, weeks; PN, parenteral nutrition; SMA, superior mesenteric artery; NS, non-significant. References: 1Tarrant et al., (2014) Low body mass index in AIS: relationship with pre- and postsurgical factors. Spine 39; 140-148; 2Tarrant et al., (2014) Timing and predictors of return to short-term functional activity in AIS after posterior spinal fusion: a prospective study. Spine (unpublished); 3Blackburn et al., (1977) Nutritional & metabolic assessment of the hospitalised patient. JPEN 1:111-22. *SPSS® 19.0 software was used for data analysis. Comparison between groups was performed using Pearson Chi-squared test for categorical data. The Independent t-test & Mann-Whitney U test were used for comparison of mean values between groups.