Characterization and rate of symptomatic adjacent-segment disease after index lateral lumbar interbody fusion: a single-institution, multisurgeon case series with long-term follow-up.

OBJECTIVE The rate of symptomatic adjacent-segment disease (ASD) after newer minimally invasive techniques, such as lateral lumbar interbody fusion (LLIF), is not known. This study aimed to assess the incidence of surgically significant ASD in adult patients who have undergone index LLIF and to identify any predictive factors. METHODS Patients who underwent index LLIF with or without additional posterior pedicle screw fixation between 2010 and 2012 and received a minimum of 2 years of postoperative follow-up were retrospectively included. Demographic and perioperative data were recorded, as well as radiographic data and immediate perioperative complications. The primary endpoint was revision surgery at the level above or below the previous construct, from which a survivorship model of patients with surgically significant symptomatic ASD was created. RESULTS Sixty-seven patients with a total of 163 interbody levels were included in this analysis. In total, 17 (25.4%) patients developed surgically significant ASD and required additional surgery, with a mean ± SD time to revision of 3.59 ± 2.55 years. The mean annual rate of surgically significant ASD was 3.49% over 7.27 years, which was the average follow-up. One-third of patients developed significant disease within 2 years of index surgery, and 1 patient required surgery at the adjacent level within 1 year. Constructs spanning 3 or fewer interbody levels were significantly associated with increased risk of surgically significant ASD; however, instrument termination at the thoracolumbar junction did not increase this risk. Surgically significant ASD was not impacted by preoperative disc height, foraminal area at the adjacent levels, or changes in global or segmental lumbar lordosis. CONCLUSIONS The risk of surgically significant ASD after LLIF was similar to the previously reported rates of other minimally invasive spine procedures. Patients with shorter constructs had higher rates of subsequent ASD.