Spring-mediated cranial vault expansion (SMC) has become a primary treatment modality at our institution to correct scaphocephalic head shape in the setting of isolated sagittal craniosynostosis (CS). Spring-mediated cranioplasty is associated with minimal procedural morbidity and reliable clinical efficacy, although long-term outcomes are not well elucidated. Herein we describe our institutional experience and lessons learned with SMC. We hypothesize that SMC performed in young infants offers durable scaphocephalic correction as measured by cephalic index (CI) at the 1, 3, and 5-year postoperative timepoints.Patients with isolated sagittal CS who underwent SMC at our institution during an 8-year period were retrospectively studied. The primary outcome measure was long-term head shape determined by CI at the 1, 3, and 5-year postoperative timepoints. Secondary outcomes included patient and spring factors associated with change in CI, including age and spring force. All statistical tests were 2-tailed with P < 0.05 denoting significance.In total, 88 patients underwent SMC at a median age of 3.3 months with a median preoperative CI 69 (interquartile range: [66, 71]). The postoperative CI increased to 73 [71, 76] at postoperative day 1. At 1 month, the CI increased by 8.6 to 77 (P < 0.0001) and appeared to reach a plateau at 3 months (76, [74, 78]) without further improvement (P < 0.10). At 5 years, CI remained stable without relapse (76, [75, 81], demonstrating an 8.9 increase from preoperative CI. Age at time of spring placement and change in CI were inversely related (P < 0.005). Total spring force directly correlated with increased change in postoperative CI at the 6-month postoperative timepoint (P < 0.02).In summary, SMC offers durable correction of scaphocephaly as measured by CI for patients with isolated sagittal CS at the 5-year postoperative timepoint. The cranial expansion observed 1-month post-spring implantation may serve as a proxy for long-term CI.