Comparison of sagittal spinopelvic parameters in different types of double-level degenerative lumbar spondylolisthesis: a retrospective study

Background Degenerative lumber spondylolisthesis (DLS), a common orthopaedic disease causing low back pain, seriously affects daily life and work. Although sagittal spinopelvic parameters have been studied in single-level DLS patients, investigations into different types of double-level DLS are scarce. This study aims to analyse the demographic and radiological parameters of patients with different types of double-level DLS and compare their differences to provide a reference for guiding surgical treatment and restoring sagittal balance of DLS patients. Methods From January 2014 to January 2020, double-level DLS patients’ records were retrospectively reviewed and divided into three types: anterior, posterior, and combined; the anterior and combined types were studied. Two spin surgeons measured the sagittal spinopelvic parameters: C7 tilt, maximal thoracic kyphosis (TKmax), maximal lumbar lordosis (LLmax), pelvic incidence (PI), pelvic tilt (PT), and sacral slope (SS). Following descriptive analysis, demographic and radiographic data were compared between the anterior and combined types. Results Patients in the anterior type group (n = 40) were older (67.68 ± 6.66 vs. 61.72 ± 10.06 years, P = 0.031), and the proportion of females were significantly higher (90% vs. 50%, P = 0.001) than the combined group (n = 18). Both groups had different levels of chronic lower back pain, but the incidence of radiating leg pain and neurogenic claudication was significantly higher in the anterior type. Owestry disability index and visual analogue scale lower back scores were also higher in the anterior type. In the anterior type, C7 tilt (7.14 ± 2.15 vs. 5.41 ± 2.28, P = 0.007), LLmax (50.02 ± 14.76 vs. 36.96 ± 14.56, P = 0.003), PI (68.28 ± 9.16 vs. 55.53 ± 14.19, P < 0.001), PT (28.68 ± 7.31 vs. 19.38 ± 4.70, P < 0.001), and PT/PI (42.45 ± 11.22 vs. 36.04 ± 9.87, P = 0.041) were significantly higher. In the anterior type, PI correlated significantly positively with LLmax (r = 0.59) and SS (r = 0.71). LLmax and SS (r = 0.65) had a positive correlation. PT/PI and SS (r = -0.77) had a negative correlation. In the combined type, PI correlated positively with LLmax (r = 0.61) and SS (r = 0.88), and PT/PI correlated negatively with SS (r = -0.81). Conclusions In patients with double-level DLS, the sagittal spinopelvic parameters differ between the anterior and combined types. PI and LLmax were significantly higher in the anterior type, resulting in compensation by forward flexion and pelvic retroversion. Spinal surgeons should focus on correcting sagittal deformities, relieving postoperative clinical symptoms, and improving quality of life during fusion surgery, which is proven to guarantee long-term surgical results.