Objective: The study aimed to investigate the incidence of painful proximal junctional kyphosis (PJK) after posterior fusion surgery in patients with adolescent idiopathic scoliosis (AIS) and their clinical results. Materials and Methods: A total of 220 patients diagnosed with AIS (180 females and 40 males) were reviewed retrospectively. PJK was defined as the development of kyphosis more than 10 degrees between the upper instrumented end vertebra and the proximal adjacent vertebra. Visual analogue score (VAS) and the Scoliosis Research Society (SRS)-24 questionnaire were used for clinical evaluations. Thoracic kyphosis (TK) and lumbar lordosis (LL) were measured on the sagittal spinal radiograph pre and postoperatively. Computed tomography (CT) and magnetic resonance imaging (MRI) were performed on patients with pain and worst disability scores. Results: The mean age was 15±2.4 years and the mean follow-up period was 24.27±11.69 months. PJK was detected in 20 of the 220 patients. TK changed from 35.5º±13.6º to 25º±7.3º postoperatively (p=0.001) while on observation, LL decreased from 53º±10º to 44.4º±7.8º postoperatively (p=0.001). The average score of the VAS average score was 3.2 (3-8), the mean SRS-24 pain was 2.5 and the self-image score was 4.1 in patients with PJK. In three of the 20 patients with PJK, the pain was severe (VAS=8), SRS-24 pain was on average 5 and the self-image score was three in patients who had disc penetration. CT and MRI evaluations in these three patients manifested severe disc degeneration and disc space collapse caused by pedicle screw penetration through the endplate and disc. Conclusion: Upper disc penetration with pedicle screw at the upper instrumented end vertebra leads to symptomatic disc degeneration and development of PJK. The proper placement and perfect trajectory of the most proximal pedicle screw is crucial and mandator
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