Do the benefits of hook-hybrid construct justify their use over all-pedicle screws constructs in maintaining postoperative curve correction for adolescent idiopathic scoliosis patients from an Asian population?

Study design: Retrospective study.

Objective: (1) Compare outcomes of all-pedicle screws (PS) and hook-hybrid (H) constructs in adolescent idiopathic scoliosis (AIS) patients; and (2) investigate whether BMI, height or pedicle size may modify the effect of the type of surgical construct on the extent of curve decompensation.

Methods: AIS patients who underwent surgical fixation with H or PS constructs at a single tertiary institution were reviewed. Patients with implant density of at least 70% and 2-year follow-up were included. Demographic and perioperative data collected were age, sex, height, BMI, implant density and pedicle diameter. Cobb's angles and curve correction were compared preoperatively, postoperatively and at follow-up.

Results: In total, 59 patients were included. H group had a lower pedicle size at the highest level of construct and at T4 compared to PS group. Postoperatively, H group (30.2° ± 11.7°) and PS group (32.1° ± 10.4°) had similar correction (mean diff. 2.0°, p = 0.516). At 2-year follow-up, H group (1.6° ± 3.5°) and PS group (0.1° ± 2.8°) had similar curve deterioration (mean diff. 1.5°, p = 0.079). Uni- and multivariate analyses revealed that BMI and height were not associated with curve deterioration at 2-year follow-up among the H and PS groups.

Conclusion: H constructs provided similar maintenance of curve correction at 2-year follow-up compared to PS constructs. BMI and Stature did not modify curve deterioration between both groups at follow-up. This study supports the use of H constructs when faced with difficult pedicle morphology associated with shorter stature as it provides comparable and satisfactory long-term maintenance of curve correction.

Level of evidence: Level III, retrospective cohort study.