Most long-term follow-up studies report retrospective data, the quality of which remains limited due to their inherent biases. Prospective databases may overcome these limitations, however, feasibility and costs limit their application. To date there exists a paucity of evidence-based literature on which recommendations can be made for the ideal length of follow-up for spinal deformity research. Therefore, our aim was to evaluate the added value of follow-up of patients beyond 2 years following surgery for AIS. A database registry evaluating surgical outcomes for all consecutive AIS patients with post-op data-points of 6 months, 1 year, 2 year, and 5 year was analysed. Surgeon-reported complications, SRS-22 scores, and radiographic data were evaluated. Complications requiring surgical or medical intervention were compared between patients in whom complications developed within 2 years to those in which newly developed complications occurred between >2–5 years. 536 patients were analysed. SRS-22 scores significantly improved at 2 years post-op with no change at 5-year follow-up. Overall complication rate was 33.2% with majority occurring within 2 years (24.8%). The rate of complications occurring >2–5 years requiring intervention was significantly lower than those requiring intervention within 2 years of surgery (4.7% vs 9.7%, p=0.000), however was not negligible. The most common newly observed complication beyond 2 years was pain (1.9%), followed by surgical site infection (SSI) (1.3%) and implant issues (0.56%). There were no significant differences in the rates of crankshaft (p=0.48), implant issues (p=0.56), pseudarthrosis (p=0.19), and SSI (p=0.13) between the 2 time points. Although majority of complications following AIS surgery occurs within 2 years, a non-negligible rate of newly observed complications occur at >2–5 years post-op. Specifically crankshaft, pseudarthrosis, implant issues, and SSI have similar rates of occurrence at these 2 time points.
Natural history of AIS >30° in skeletally mature patients is poorly defined. Studies reporting rates and risk factors for progression are predominantly of large curves in immature patients. Our aim was to determine the rate of curve progression in AIS following skeletal maturity, any associated changes in SRS-22 scores, and identify any potential predictors of curve progression. Patients enrolled in a prospective, longitudinal, multicentre non-surgical AIS database were evaluated. All patients had minimum 2 year follow-up, idiopathic scoliosis >30°, and were skeletally mature. SRS-22 functional outcome scores and radiographic data were compared at baseline and 2-year follow-up. Patients were divided into 3 groups based on curve size: A=30°-39°, B=40°-49°, C= >50°. Curve progression was defined as any change in curve magnitude. There were 80 patients, majority females (93.8%) with a mean age of 16.5+/−0.16. Mean BMI was 21+/−0.31 with 15.1% overweight. Mean major cobb at baseline was 38.3°+/−0.88°. At 2 year follow-up 46.3% of curves had progressed an average 3.4°+/−0.38°. Of curves that progressed, patients in group A had the largest mean rate of progression followed by group B. SRS-22 scores on average declined significantly over 2 years in this cohort (4.23 to 4.08; p=0.002). Patients who progressed had on average a more significant decline in SRS outcome scores compared to those that did not (p=0.018, p=0.041 respectively), with the most significant change noted in the Self-Image domain (p=0.03). There was no significant difference in the change in SRS scores over 2 years based on curve size. Univariate analysis did not identify any factors predictive of curve progression in this cohort. Skeletally mature patients with AIS >30°may continue to have a risk of progression at a mean rate of 1.7°/yr and significant decline in SRS-22 outcome scores, in particular Pain and Self-Image, over time.
