Selection of distal fusion level in terms of distal junctional kyphosis in Scheuermann kyphosis. A comparison of 3 methods

Abstract

Objective: The aim of this study was to investigate the effect of distal fusion level selection on the distal junctional kyphosis (DJK) in Scheuermann kyphosis (SK) patients who underwent posterior fusion. Methods: Thirty-nine SK patients who underwent posterior fusion with a minimum follow-up of 3 years were retrospectively evaluated. According to the distal fusion level, patients were divided into 3 groups. Group S; lowest instrumented vertebra (LIV) was the sagittal stable vertebra (SSV), Group F; LIV was the first lordotic vertebra (FLV) and, Group L; LIV was the lower end vertebra (LEV). DJK was evaluated according to distal level selection. Results: Thoracic kyphosis (TK) decreased from 73.3° (SD ± 7.9°) to 39° (SD ± 8.7°) postoperatively, with a mean correction rate of 46% (SD ± 13) (p < 0.0001). In 11 patients, FLV and SSV was the same vertebra. In remaining 28 patients, 10 patients were in Group S, 15 patients were in Group F and 3 patients were in Group L. In Group S, none of them developed DJK, however, DJK was observed 9 of 15 patients in Group F. DJK was developed in all cases in Group L. There is a statistically higher risk for developing DJK when FLV or LEV was selected as LIV (p < 0.05). Conclusion: Selecting SSV for the distal fusion level has been found to be effective for preventing DJK. Selecting distal fusion level proximal to SSV will increase the risk of DJK which may become symptomatic and require revision surgery. Level of evidence: Level IV, therapeutic study. Keywords: Scheuermann kyphosis, Distal junctional kyphosis, Sagittal stable vertebra, First lordotic vertebra, Lower end vertebra