Incidence and Risk Factors for Proximal and Distal Junctional Kyphosis Following Surgical Treatment for Scheuermann Kyphosis

STUDY DESIGN: Retrospective case review at a single center. OBJECTIVE: To analyze the incidence and risk factors associated with proximal junctional kyphosis (PJK) and distal junctional kyphosis (DJK) in patients undergoing instrumented spinal fusion for Scheuermann kyphosis. SUMMARY OF BACKGROUND DATA: Previously reported risk factors for junctional kyphosis include improper end vertebrae selection, curve correction greater than 50%, or excessive junctional soft tissue dissection. METHODS: Clinical and radiographic data on 67 patients (mean age 37) from a single center treated with instrumented fusion for Scheuermann kyphosis were reviewed. All patients had complete radiographic data with a minimum 5-year follow-up (mean: 73 months). Abnormal PJK was defined by a proximal junctional angle greater than 10 degrees and at least 10 degrees greater than the corresponding preoperative measurement. DJK was similarly defined between the caudal endplate of the lower instrumented vertebra to the caudal endplate that was 1 vertebra below. RESULTS: The incidence of PJK as defined above was seen in 20 patients (30%). The development of PJK was associated with failure to incorporate the proximal end vertebra (15 patients), disruption of junctional ligamentum flavum (3 patients), or combination of both (2 patients). The most common cause of inappropriate end vertebra selection was poor visualization of the upper thoracic vertebra.DJK occurred in 8 patients (12%) and 7 of them had fusion short of including the first lordotic disc. CONCLUSION: The incidence of PJK can be minimized by the appropriate selection of the upper end vertebra to be fused and avoiding disruption of the junctional ligamentum flavum. The development of DJK can be minimized by incorporation of the first lordotic disc into the fusion construct.