OBJECTIVE To determine the effectiveness of posterior spinal fixation in maintaining the stability of spine and to determine mortality in 6 months after posterior spinal fixation. METHODS Quasi experimental study. METHODS Department of Orthopaedics, Jinnah Postgraduate Medical Centre, Karachi and Department of Orthopaedics, Postgraduate Medical Institute, Hayatabad Medical Complex, Peshawar, from April 2006 to April 2009. METHODS Fifty patients with unstable thoracolumbar spinal fractures from T7 - L4 were included. All the patients were operated by posterior approach using pedicle screws and rods. Effectiveness of the fixation was measured at 6 months postoperatively in terms of relief of pain and improvement in mobility using Oswestry disability index, range of motion of spine using Schobar Test/sign, reduction in deformity by measuring Cobb angle, local kyphosis angle (LKA), thoracolumbar angle, anterior and posterior vertebral heights (AVH and PVH respectively), evidence of union was made using plain radiographs and by computer assisted measurement using " OSIRIS " software. The data was then analyzed using SPSS software version 13 and presented in the form of tables and charts. RESULTS Twenty-eight patients were operated within first week. In 38 patients, 4 screws were used and in 12 patients, 8 screws were used with 2 rods. Pain and disability showed improvement, with mean 71.98% score pre-operatively to 44.96% mean at last visit (p = 0.001). Mean range of motion increased 0.5 - 2 cms postoperatively in all directions (p = 0.001). Mean kyphosis angle, Cobb angle and thoracolumbar angle improved postoperatively. Anterior and posterior vertebral body heights increased postoperatively with resultant decrease in anterior vertebral body compression. Ninety six percent patients showed signs of postoperative union on last visit and only 3 people died of unrelated causes till last visit. CONCLUSIONS Posterior spinal fixation with pedicle screws and rods is an effective surgical technique in maintaining stability of spine by improvement in pain and mobility, range of motion of spine, correction of deformity and bone union.