Significance of various risk factors for proximal junctional kyphosis and instability of instrumentation in surgical treatment for adult spinal deformities

Objective. To analyze the significance of the influence of various risk factors on the development of proximal junctional kyphosis (PJK) and instability of instrumentation.Material and Methods. The results of surgical treatment of 382 patients with scoliotic deformities of the lumbar spine of type I and IIIb according to Aebi were analyzed. Patients were operated on through the posterior approach using the TLIF-PLIF technique with extended rigid transpedicular instrumentation. Potential risk factors influencing the development of proximal junctional kyphosis and instability of instrumentation were analyzed.Results. It was found that only three risk factors significantly affect the development of PJK: correction of lumbar lordosis more than 30° (p = 0.036) increases the likelihood of its development by 1.5 times, osteoporosis (p = 0.001) – by 2.5 times, and proximal junctionalangle ≥10° (p = 0.001) – by 3.5 times. Three factors showed a statistically significant effect on the incidence of instrumentation instability: correction of lumbar lordosis more than 30° (p = 0.034) increases the likelihood of its occurrence by 1.7 times, osteoporosis (p = 0.018) – by 1.8 times, and deviation of the sagittal vertical axis by more than 50 mm (p = 0.001) – by 3.3 times.Conclusion. The most significant risk factors for the occurrence of PJK and instability of instrumentation are osteoporosis, correction of lumbar lordosis more than 30°, an increase in the proximal junctional angle ≥10°, and an anterior deviation of sagittal vertical axis more than 50 mm. Consideration of these factors in the preoperative period, as well as during surgery, can decrease likelihood of the occurrence of PJK and instability of instrumentation.