Evaluation of proximal junctional kyphosis in adolescent idiopathic scoliosis following pedicle screw, hook, or hybrid instrumentation.
Methods: Retrospective review. Objective: To compare the incidence of and risk factors for proximal junctional kyphosis (PJK) in adolescent idiopathic scoliosis (AIS) following posterior spinal fusion using hook, pedicle screw, or hybrid constructs.
Background: Proximal junctional kyphosis is a recently recognized phenomenon in adults and adolescents after AIS surgery. The postoperative effect on PJK with the use of hooks, hybrid constructs, or screws has not been compared in a multicenter study to date.
Methods: From a multicenter database, the preoperative and 2-year follow-up radiographic measurements from 283 patients with AIS treated with posterior spinal fusion using hooks (group 1, n = 51), hybrid constructs (group 2, n = 177), pedicle screws (group 3, n = 37), and pedicle screws with hooks only at the top level (group 4, n = 18) were compared.
Results: The average proximal level kyphosis at 2 years after surgery was 8.2 degrees (range -1 to 18) in the all screw constructs, representing a significant increase when compared with hybrid and all hook constructs, 5.7 degrees (P = 0.02) and 5.0 degrees (P = 0.014), respectively. Conversely, average postoperative T5-T12 kyphosis was significantly less (P = 0.016) in the screw group compared with the all hook group. Of potential interest, but currently not statistically significant, was the trend towards a decrease in proximal kyphosis in constructs with all pedicle screws except hooks at the most cephalad segment, 6.4 degrees . The incidence of PJK (assuming PJK is a kyphotic deformity greater than 15 degrees ) was 0% in group 1, 2.3% in group 2, 8.1% in group 3, and 5.6% in group 4 (P = 0.18). Patients with PJK had an increased body mass index compared with those who did not meet criteria for PJK (P = 0.013).
Conclusions: Adjacent level proximal kyphosis was significantly increased with pedicle screws, but the clinical significance of this is unclear. A potential solution is the substitution of hooks at the upper-instrumented vertebrae, but further investigation is required.