Background Data: The classic treatment of severe rigid adolescent idiopathic scoliosis (AIS) was performed by combined anterior and posterior surgery which carries higher morbidity to the patient. Recently, posterior only surgery using all
pedicle screws has been used for treatment of severe AIS with many advantages over combined approaches.
Purpose: To evaluate the safety and effectiveness of high density pedicle screws through posterior only approach in correction of severe cases of adolescent idiopathic scoliosis (AIS) with curves > 70o. Study Design: Prospective cohort study. Patients and Methods: Between 2012 and 2014, fourteen patients were surgically treated for severe AIS with curves > 70o and were prospectively followed up for a minimum of 1 year (Range 1-4 years). Clinical outcomes were evaluated using SRS- 22 questionnaire. All patients were classified according to Lenke et al classification.
Major and minor curves Cobb angle as well as sagittal parameters were measured on whole spine X-rays. Side bending films were used to assess curve flexibility. High density pedicle screws and multiple Ponte osteotomies were used in all patients. Five patients required asymmetrical pedicle subtraction osteotomy due to very rigid curve. Results: This study included 14 patients (8 females, 6 males).The mean age at time of surgery was 17.4 years (range 14-24 years). The mean correction rate for the coronal Cobb angle of the major and minor curves was 73.7% (80.4o preoperative
and 21.7o postoperative) and 68.7% (51.5o preoperative and 19.63o postoperative)  respectively. The mean thoracic kyphosis angle was 44.2o preoperatively, 28.55o postoperatively and 28.1o at latest follow up. The mean SRS-22 questionnaire scores improved significantly from 2.8 preoperatively to 3.7 at the final follow up (P>0.001). No cases of pseudarthrosis, metal failure or neurological deficits were encountered. One patient with asymmetrical PSO developed hemothorax that was managed with chest tube insertion and follow up. Conclusion: High density pedicle screws through posterior only approach is a safe and effective method in treatment of severe AIS. It can achieve coronal curve correction comparable to combined anterior and posterior approaches without the morbidity of combined approaches. It also restores the sagittal profile leading to good functional outcomes and better quality of life. (2014ESJ073)