SUMMARY. A retrospective cohort study of 19 patients of EOS who underwent MCGR rod instrumentation with subsequent serial distractions, measured using ultrasonography. The degree of distraction achieved during each session were analyzed and subgroup analysis done. HYPOTHESIS. The degree of distraction/ distractibility of the MCGR rod is closely linked to the etiology of EOS. The degree of distraction achieved at each session progressively diminishes with successive distractions. STUDY DESIGN. Retrospective cohort study. INTRODUCTION. MCGR rods have gained popularity as an alternative to traditional growing rods for the treatment of Early-onset scoliosis (EOS), serially distracting with an aim to mimic the normal spinal growth, which can be achieved in an outpatient setting using external remote controller. The use of ultrasound as a tool to measure the degree of distraction achieved has been validated previously. However the association between the etiological diagnosis of EOS and the degree of distraction achieved has not been studied previously. METHODS. We performed a retrospective cohort study of 19 patients with EOS of varying etiologies who underwent MCGR rod instrumentation at our institution since 2016. Their hospital records were analyzed to assess the demographics, distraction interval and the degree of distraction achieved at each session. RESULTS. 19 patients (12 females and 7 males) were included in the study. The average age of the study population was 7 years (4–13 years). The average follow up was 2.1 years (1–4). The following were the etiological diagnoses: Idiopathic EOS(8), Neuromuscular scoliosis(5), Syndromic(5), Congenital(1). The average interval between each distraction was 109.8days (88.2–140.6). The overall mean distraction was 1.66mm (0.6–3.427). The mean distraction achieved for the concave rod was 1.69mm (0.6–3.03) as against 1.59mm (0.2–3.427) for the convex rod. The degree of distraction achieved per session was the greatest in patients with neuromuscular scoliosis 2.79mm (0.94–4.62), while it was the least in Congenital scoliosis 0.99mm (0.8–2.93). The degree of distraction in Syndromic and Idiopathic scoliosis groups were 2.19mm (0.1–4.2) and 1.50mm (0.2–4.45) respectively. The mean distraction achieved during the first session after MCGR instrumentation was 2.82mm (0.4–9.8) as against 1.98mm (0.1–4.2) and 1.18mm (0.2–2.3), achieved during the 5. th. and 10. th. distractions respectively. CONCLUSIONS. The average distraction of the MCGR rod achieved per session depends upon the etiological diagnosis of EOS. Neuromuscular curves are the most amenable to MCGR distractions, while the congenital curves are the least. The degree of distraction achieved progressively diminishes with each successive distractions. The distraction achieved slumps to 70% of the initial distraction by the 5. th. session and further declines to 41% of the initial distraction by the 10. th. session. TAKE HOME MESSAGE. The distractibility of the MCGR rod is closely linked to the etiology of EOS. MCGR rods are most effective in cases of neuromuscular scoliosis, while least effective in congenital scoliosis. The law of diminishing returns holds true even with MCGR rods

A combination of hemivertebrae and diastematomyelia is rare. We have identified 12 such patients seen during a period of 11 years in the orthopaedic, spinal and neurosurgical units in Nottingham and analysed their treatment and outcome.