Determination of Proximal Junctional Kyphosis in Adolescent Idiopathic Scoliosis Correction Fusion using Pedicle Screw Versus Hook Plus Screw Pedicle Instrumentation

Spinal instrumentation in idiopathic adolescent scoliosis (AIS) aims to correct spinal deformity, and maintain spinal stability. Proximal junctional kyphosis (PJK) is a relatively common postoperative complication. Posterior-only fusion using diverse instruments such as pedicle screw and hybrid hook plus screw is favored to correct spinal deformity. The current study aims to compare PJK incidence between pedicle screw versus hybrid hook plus screw. Methods: This non-randomized clinical trial has been conducted on 71 AIS patients undergone posterior-only spinal deformity fusion using pedicle screw only (n=42) or hook plus pedicle (n=29) implantation in 2015-20. The proximal thoracic (PT), main thoracic (MT), T5-T12 sagittal Cobb angles and proximal junctional angle (PJA) were evaluated through radiographies taken at baseline, immediately postoperative, within 6 and 18 months. PJK was defined as PJA >10 degrees.  Results: Using both pedicle screw only and hook plus pedicle have led to significant improvement in MT, PT, PJA and T5-T12 angles (P-value 0.05). Seventeen cases (23.9%) presented PJK among which 11 (26.2%) and 6 (20.7%) ones were in the predicle screw versus hook plus screw implantation groups, respectively (P-value=0.54). The comparison of PJA and T5-T12 Cobb angles revealed significant difference between the PJK versus non-PJK cases (P-value<0.05). Conclusion: AIS instrumentation was accompanied by satisfying outcomes using pedicle screw or hook plus screw. However, none of the applied instruments was superior over the other; PJK occurred in fewer cases undergone posterior-only approach of AIS correctional surgery using hook and screw.