Increased Risk of Adjacent Segment Spondylolisthesis or Instability Following L5-S1 Versus L4-S1 Fixation for L5-S1 High-Grade Dysplastic Spondylolisthesis in Children.

OBJECTIVE

High-grade dysplastic spondylolisthesis (HGDS) is a relatively rare condition mainly involving the L5/S1 segment of the spine and occurring in children and adolescents. Whether surgical fixation should be L5-S1 monosegmental or extended up to L4 remains controversial. This study aimed to compare clinical outcomes and the risk of adjacent segment spondylolisthesis between L5-S1 monosegmental fixation and L4-S1 double-segmental fixation for pediatric HGDS.

METHODS

This is a retrospective control study Pediatric patients diagnosed with HGDS between March 2007 and October 2022 at our hospital were followed up, and their data were analyzed. The study involved 39 HGDS patients (average slip, 70.0%) divided into two groups: the L5-S1 monosegmental reduction and fusion group (L5 group, 16 patients) and the L4-S1 double-segmental reduction and fusion group (L4 group, 23 patients). Radiographic parameters and patient-reported outcomes were collected before surgery and at follow-up and compared between the two groups. Additionally, the prevalence of adjacent segment spondylolisthesis and instability (ASS/ASI) was compared between the groups at the last follow-up. Independent sample t-tests were employed to compare normally distributed data between the two groups. Paired sample t-tests were employed to compare preoperative data with postoperative data. The chi-square test was utilized to compare rates.

RESULTS

The average age was (12.5 ± 2.3) years. The L4 group had a greater slip percentage (77.6% vs. 59.2%; p < 0.001), a smaller Dub-LSA (60.3° vs. 69.7°; p = 0.022), and a higher slip grade (p = 0.002) than the L5 group, indicating more severe spondylolisthesis in the L4 group. Clinical parameters, namely the visual analog scale, Oswestry disability index, and Japanese Orthopedic Association-29 score, did not significantly differ between the two groups. The L5 group had a higher rate of ASS/ASI than the L4 group (6/16, 37.5% vs. 0/23, 0%; p = 0.002). Of all the ASS/ASI patients, one underwent a second surgery due to L4 spondylolisthesis 2 years after the primary surgery. The remaining five exhibited no symptoms or mild symptoms.

CONCLUSIONS

For pediatric HGDS, both L5-S1 monosegmental fixation and L4-S1 fixation can achieve satisfactory outcomes. However, there is a higher risk of ASS/ASI following L5-S1 fixation than following L4-S1 fixation.