Background. Temporary hemiepiphysiodesis using 8 plate guided growth has gained widespread acceptance for the treatment of paediatric angular deformities. This study aims to look at outcomes of coronal lower limb deformities corrected using temporary hemiepiphysiodesis over an extended period of follow up. Methods. A retrospective analysis was undertaken of 56 children (92 legs) with coronal plane deformities around the knee which were treated with an extraperiosteal 2 holed titanium plate and screws between 2007 and 2015. Pre and post-op long leg radiographs and clinic letters were reviewed. Results. The mean age was 11.9 years (range 3 to 16) with a mean angular deformity of 12.3 degrees (5.1 to 33.5). The mean rate of correction was 0.8 degrees per month. Isolated distal femur correction occurred at a mean rate of 0.6 degrees per month (0.2 to 1.4) and isolated tibia at a rate of 0.5 degrees per month (0.0 to 1.7). Children treated with concurrent treatment of both femur and tibia corrected at a rate of 1.4 degrees per month (0.1 to 2.7). Similar rates of correction occur in children aged 10 and over compared to those younger than 10 (0.8 degrees per month compared to 0.7). We also saw similar rates of correction with extended follow up. The average rate of correction over the first 9 months post op was 0.8 degrees compared to 0.6 degrees over the following 10 months. Conclusion. This study is the largest long term follow up of 8 plate hemiepiphysiodesis which highlights the rate of correction in all age groups. Implications. With this knowledge surgeons can make a more informed decision regarding placement of hemiepiphysiodesis plates and length of time required for correction of angular deformities. It may also lead to consideration of alternative, more powerful techniques if the rate of correction is insufficient. Conflict of Interest: None declared

Purpose. Angular deformity in the lower extremities can result in pain, gait disturbance, cosmetic deformity and joint degeneration. Up until the introduction of guided growth in 2007, which has since become the gold standard, treatment for correcting angular deformities in skeletally immature patients had been either an osteotomy, a hemiepiphysiodesis, or the use of staples. Methods. We reviewed the surgical records and diagnostic imaging in our childrens hospital to identify all patients who had guided growth surgery since 2007. All patients were followed until skeletal maturity or until their metalwork was removed. Results. 113 patients, with 147 legs were assessed for eligibility. Three were excluded for various reasons including inadequate follow-up or loss of records. Of the 144 treated legs which met the criteria for final assessment 32 (22.2%) were unsuccessful, the other 112 (77.8%) were deemed successful at final follow up. Complications were few, but included infection in one case and metal failure in another. Those with a pre-treatment diagnosis of idiopathic genu valgum/genu varum had a success rate of 83.6%. Conclusions. In our hands, guided growth had a seventy-eight percent success rate when all diagnosis were considered. Those procedures that were unlikely to be successful included growth disturbances due to mucopolysaccharide storage disease (28% failure rate), Blounts disease (66.6% failure rate) and achondroplasia (37.5% failure rate). If you exclude those three diagnoses, success rate for all other conditions was 81.4%. We continue to advocate the use of guided growth as a successful treatment option for skeletally immature patients with limb deformity