Short-Term Morbidity After Posterior Fossa Decompression with Concurrent Occipitocervical Fusion in Pediatric Chiari I Patients—A Multi-Year NSQIP-P Analysis

Background: A subset of patients with Chiari I malformation carries craniovertebral junction anomalies such that posterior fossa decompression alone is insufficient to address ventral brainstem compression or craniocervical instability, and occipitocervical fusion is warranted. How often this occurs, and whether extended fusion carries added early morbidity are not established. We compared early outcomes between occipitocervical constructs ending at C2 and extended constructs in pediatric patients undergoing posterior fossa decompression. Methods: We identified patients undergoing posterior fossa decompression (CPT 61343) in the ACS NSQIP-Pediatric participant use files from 2016 through 2024. Cases with concurrent occipitocervical fusion were classified by construct extent into three mutually exclusive strata: fusion to C2 alone (OCF-2), fusion with a single additional subaxial interspace (OCF-3), and fusion with multiple subaxial interspaces (OCF-M). Thirty-day unplanned reoperation, unplanned readmission, and secondary outcomes were compared. Results: Among 9056 sampled PFD episodes, 100 (1.10%) included concurrent OCF: 61 constructs ended at C2 (OCF-2), and 39 extended below it (OCF-3, n = 20; OCF-M, n = 19). Age, sex, comorbidities, and preoperative risk factors were similar between groups. Reoperation occurred in 5.1% of patients with extended constructs and 8.2% of those with OCF-2 (RD −3.1%; 95% CI −13.4 to 9.6), and readmission in 5.1% and 4.9%, respectively (RD 0.2%; 95% CI −9.1 to 12.4). Across OCF-2, OCF-3, and OCF-M, no outcome showed a graded association with the number of fused levels. Conclusions: In this cohort of pediatric Chiari I patients, extending fixation below C2 was not associated with a detectable difference in early morbidity. Rates from this multi-institutional study may provide reference values for family counseling and expected event rates for future study design. Studies with long-term follow-up that capture radiological features are needed to address confounding by indication and better characterize the trade-offs of construct length.