79 - Factors Affecting Restoration of the Segmental Lordosis after Lateral Lumbar Interbody Fusion

Introduction: Lateral lumbar interbody fusion is one of widely performed by surgeons. The purpose of lateral lumbar interbody fusion is treatment of degenerative disease so that clinical and radiologic result is important. An adequate recovery of segmental lordosis is necessary to success outcomes. Insufficient restoration leads to significant problem to patients and surgeons. Factors related to lordosis were analyzed.

Objectives: This study was designed to analyze clinical, radiologic and operative factors that relate to the successful restoration of segmental lordosis after lateral lumbar interbody fusion

Methods: Patients, who underwent lateral lumbar interbody fusion (LLIF) and posterior pedicle screw instrumentation less than 3 levels, were analyzed to evaluate the change of segmental lordosis and its related factors. Multiple radiologic assessment and clinical outcomes were reviewed at preoperative, immediate postoperative, and postoperative 6 months, and 1 year. Radiologic evaluation includes presence of anterior osteophyte, olisthesis, facet hypertrophy, facet gap with fluid, cage subsidence, and vacuum change of disc. We also measured segmental lordosis, lumbar lordosis, dynamic segmental angle, central disc height, PI-LL mismatch. Clinical factors were reviewed such as age, osteoporosis, medical comorbidities. Operative factors were type of operating table during posterior surgery, addition of posterior column osteotomy (PCO), type, angle, and location of the interbody cage. Univariate and multiple logistic regression analyses were performed using R-EX.

Results: We analyzed 140 patients and 268 levels ranging from L1-S1. The average preoperative segmental lordosis was 9.3 degrees. The average segmental lordosis was 11.7 degrees immediately after surgery, and it gradually decreased to 11.0 at postoperative 6 months, and 10.9 at 1 year.
In univariate analysis, postoperative segmental lordosis was greater (OR 0.56, p < 0.001) when preoperative segmental lordosis was greater at immediate, 6 months and 1 year after surgery. Likewise, postoperative segmental lordosis was greater at L4-5 (OR 4.60, p < 0.001) and L5-S1 (OR 4.89, p < 0.013) than other levels. If a patient has a greater PI-LL mismatch, the immediate postoperative segmental angle was greater (OR 0.05, p=0.039). As age increases, postoperative segmental lordosis was significantly greater at 6 months (OR 0.07, p =0.049) and 1 year (OR 0.06, p =0.044).. The change of segmental lordosis was significantly smaller (OR -0.44, p < 0.001) when preoperative segmental lordosis was greater at immediate, 6 months and 1 year after surgery. Furthermore, the change was significantly greater at L4-5 (OR 5.00, p < 0.001) and L5-S1 (OR 4.89, p=0.014) than other levels.
In multiple logistic regression, the change of segmental lordosis showed an inverse correlation to preoperative segmental lordosis (OR -0.46, p < 0.001). Moreover, the change of segmental lordosis was significantly greater at L4-5 (OR 4.51, p < 0.001) and L5-S1 (OR 4.89, p=0.014) than other levels.

Conclusions: Preoperative segmental lordosis was a key factor to achieve adequate final segmental lordosis after LLIF. However, the greater preoperative segmental lordosis could result in a smaller correction of the segmental lordosis. Furthermore, the change of segmental lordosis was remarkable at L4-5, L5-S1, and surgeons should make good use of these characteristics.