Bone Mineral Density After Spinal Fusion Surgery for Adolescent Idiopathic Scoliosis at a Minimum 20-Year Follow-up

Abstract

Study design: A retrospective, long-term follow-up study.

Objective: We investigated the incidence and risk factors for osteopenia at a minimum of 20 years after spinal instrumented fusion for adolescent idiopathic scoliosis (AIS).

Summary of background data: Surgically treated AIS patients may be likely to have osteopenia in adulthood because the association between AIS and osteopenia has been well documented. However, the long-term results of AIS surgery on BMD have not been evaluated.

Methods: Twenty-one (19 women; mean age, 45.3 years) of 45 consecutive patients with AIS who underwent spinal instrumented fusion surgery between 1973 and 1994 consented to inclusion in the current analysis. Based on their T scores for bone mineral density (BMD) of the left hip, participants were divided into an osteopenia/osteoporosis group (group P, T score < -1.0) and a normal group (group N, T score ≥ -1.0). Z scores of the left hip were used for analyses of the association between bone mineral status and individual factors.

Results: Eleven participants (52.4%) were categorized into group P. Mean body weight (kg) at survey (46.6 vs. 56.8) and mean body mass index (BMI) at both surgery (17.2 vs. 19.5) and survey (18.7 vs. 23.2) were significantly lower in group P than in group N (p < .05). Moreover, body weight at survey (Spearman rank correlation coefficient, r_S = 0.49), as well as BMI at both surgery (r_S = 0.67) and survey (r_S = 0.61) demonstrated positive correlations with the Z-score (p < .05).

Conclusion: More than half of the participants had osteopenia or osteoporosis, and both preoperative and postoperative low BMI were risk factors for osteopenia in adulthood.

Level of evidence: Level IV.

Keywords: Body mass index; Body weight; Bone metabolism; Osteopenia; Osteoporosis.