Aims. Intraoperative 3D navigation (ION) allows high accuracy to be achieved in spinal surgery, but poor workflow has prevented its widespread uptake. The technical demands on ION when used in patients with adolescent idiopathic scoliosis (AIS) are higher than for other more established indications. Lean principles have been applied to industry and to health care with good effects. While ensuring optimal accuracy of instrumentation and safety, the implementation of ION and its associated productivity was evaluated in this study for AIS surgery in order to enhance the workflow of this technique. The aim was to optimize the use of ION by the application of lean principles in AIS surgery. Methods. A total of 20 consecutive patients with AIS were treated with ION corrective spinal surgery. Both qualitative and quantitative analysis was performed with real-time modifications. Operating time, scan time, dose length product (measure of CT radiation exposure), use of fluoroscopy, the influence of the reference frame, blood loss, and neuromonitoring were assessed. Results. The greatest gains in productivity were in avoiding repeat intraoperative scans (a mean of 248 minutes for patients who had two scans, and a mean 180 minutes for those who had a single scan). Optimizing accuracy was the biggest factor influencing this, which was reliant on incremental changes to the operating setup and technique. Conclusion. The application of lean principles to the introduction of ION for AIS surgery helps assimilate this method into the environment of the operating theatre. Data and stakeholder analysis identified a reproducible technique for using ION for AIS surgery, reducing operating time, and radiation exposure. Cite this article: Bone Joint J. 2020;102-B(1):5–10

Purpose and Background. Both overall spine shape and the size and shape of individual vertebrae undergo rapid growth and development during early childhood. Motor development milestones such as age of walking influence spine development, with delayed ambulation linked with spinal conditions including spondylolysis. However, it is unclear whether associations between motor development and spine morphology persist into older age. Therefore, these associations were examined using data from the MRC National Survey of Health and Development, a large nationally-representative British cohort, followed up since birth in 1946. Methods and Results. Statistical shape modelling was used to characterise spinal shape (L5-T10) and identify modes of variation in shape (SM) from dual energy x-ray absorptiometry images of the spine taken at age 60–64 years (N=1327 individuals; 51.8% female). Associations between walking age in months (reported by mothers at 2 years) and SMs were examined with adjustment for sex, birthweight, socioeconomic position, height, lean mass and fat mass. Later onset of independent walking was weakly associated with greater lordosis (SM1; P=0.05) and more uniform antero-posterior vertebral size along the spine (SM6, P=0.07). Later walking age was also associated with smaller relative anterior-posterior vertebral dimensions (SM3) among women whereas the opposite was found for men (P <0.01 for sex interaction). Conclusions. Spinal morphology in early old age was associated with the age that individuals began walking independently in childhood, potentially due to altered mechanical loading. This suggests that motor development may have a persisting effect on clinically-relevant features of spine morphology throughout life. Conflict of interest: None. Funded by the UK Medical Research Council (Grant MR/L010399/1) which supported FRS, SGM and AVP

Introduction. Despite extensive research, the cause of adolescent idiopathic scoliosis (AIS) is still largely unclear. Girls with AIS tend to be taller and leaner, and have a lower body-mass index (BMI) and lower bone mass, than do healthy girls. Recent MRI studies have shown the presence of relative anterior spinal overgrowth in girls with AIS. The lower bone mineral status and BMI could be related to dysfunctional central regulation pathway of growth, bodyweight, and bone metabolism. Following several interesting reports on the role of leptin in regulation of the above pathway in animals and human beings, our recent study has shown a low leptin concentration in girls with AIS girls compared with healthy adolescents. This finding leads to our new hypothesis that abnormal leptin bioavailability could be associated with the lower bodyweight, lower bone mineral density, and relatively disproportional endochondral skeletal growth in AIS. This study aimed to investigate the leptin bioavailability in girls with AIS. Methods. 53 girls with AIS and 27 healthy girls (aged 11–16 years) were recruited in this preliminary study. Clinical and anthropometric data were obtained. Blood samples were obtained for ELISA of leptin and soluble leptin receptor (sOB-R). Independent Student's t test and multivariate regression were used in group comparison. Results. The AIS group had significantly lower BMI and longer arm span than did controls. Additionally, girls with AIS had significantly higher soluble leptin receptor concentrations (22·1 ng/mL [□}6·9] vs 17·8 ng/mL [4·4]; p<0·01). However, the leptin concentration (7·6 ng/mL [□}5·3] vs 8·7 ng/mL [□}6·0]) and the leptin/sOB-R ratio (0·38 [□}0·28] vs 0·56 [□}0·47]) were similar to that of the controls. In girls with AIS, the leptin, sOB-R, and the leptin/sOB-R ratio correlated well with bodyweight and BMI. After adjustment for BMI, sOB-R in girls with AIS was significantly higher than in controls (r=0·37, p=0·042). Conclusions. This preliminary report showed that the soluble leptin receptor could be abnormal in girls with AIS. Leptin and sOB-R are related to bodyweight. sOB-R is a major modulator of leptin concentration in circulation, the abnormality of which may lead to the retention of leptin in the circulation and thus abnormal regulatory effect. In this study, girls with AIS had lower BMI and longer arm span, which may reflect the possible change resulting from abnormal leptin bioavailability. Further longitudinal study with larger sample size would be useful to help to understand the long-term effect of the low leptin and high sOB-R in girls with AIS on their bodyweight and skeletal development. It is also noteworthy to study the mechanism of increased sOB-R in AIS