Introduction: Kitchen elbow sign (KE-Sign) is a skin abnormality on the extensor side of the elbow and forearm that is often observed in patients with adult spinal deformity (ASD). The KE-Sign is a skin change that runs from the elbow to the forearm in patients with intractable low back pain in the standing position, and is caused by supporting oneself using the elbows in a standing position during housework. The KE-Sign is not specific to ASD patients, but may act as a surrogate marker of maintaining and continuing an independent lifestyle even with intractable low back pain due to sagittal plane imbalance if the population is limited to patients with ASD. Therefore, we hypothesized that the KE-Sign correlates with health-related quality of life (HRQOL) and can be used to predict surgical outcomes or patient satisfaction in ASD. This study aimed to investigate the significance of KE-Sign in surgical cases of ASD.

Methods: Overall, 114 patients with ASD treated with long spinal fusion were reviewed and divided into KE-Sign positive and negative groups. The preoperative and 1-year follow-up evaluations included radiographic parameters (C7 sagittal vertical axis [SVA], pelvic incidence [PI] and lumbar lordosis [LL]), the Oswestry Disability Index (ODI), visual analog scales (VASs) for low back pain, leg pain, and satisfaction, and Short Form 36 questionnaire (SF-36).

Statistics: To compare data between the KE-Sign positive and KE-Sign negative groups, Fisher’s exact test/chi-square test was used for proportional variables. Analysis of variance (ANOVA) was performed for continuous variables. First, baseline characteristics and postoperative outcomes at 1 year after surgery were compared between the two groups. Second, multi-regression analysis was performed to identify predictors of patient satisfaction and improvement in ODI as dependent variables, and sex, age, BMI, presence or absence of KE-Sign, preoperative C7 SVA, PI-LL, ODI (%), lumbar VAS, and component summary scales of SF-36 as independent variables.

Results: Preoperative characteristics showed no significant difference between both groups (Fig.1). Improvement in the ODI and VAS for satisfaction were significantly superior in the KE-Sign positive group (Fig.2). Multiple regression analysis showed that KE-Sign positivity and preoperative ODI score were the significant factors predicting the ODI improvement (Fig.3). Again, multiple regression analysis showed that age, KE-Sign positivity, and preoperative VASs of low back pain and leg pain were the significant factors in predicting the patient’s satisfaction at 1-year post-surgery (Fig. 4).

Conclusion: Both groups with and without KE-Sign showed similarly good recoveries of SVA, PI-LL, lumbar VAS, and component summary scales of SF-36 postoperatively. However, improvement in ODI (%) and the VAS for satisfaction were significantly superior in KE-Sign positive patients. Thus, the KE-Sign may be useful as a surrogate marker of increased postoperative satisfaction in ASD patients with respect to the preoperative inability to perform household chores.