Generalized osteopenia in adolescent idiopathic scoliosis--association with abnormal pubertal growth, bone turnover, and calcium intake?

STUDY DESIGN

A cross-sectional study in girls with adolescent idiopathic scoliosis (AIS) and healthy counterparts of similar age.

OBJECTIVES

To study the association of bone mass with anthropometric parameters, bone turnover, and calcium intake in 621 girls with AIS, aged 11-6-years, and compare the results with 300 healthy girls of similar age.

SUMMARY OF BACKGROUND DATA

Generalized low bone mass has been documented in AIS, yet the cause of low bone mineral density in AIS is unknown.

METHODS

Corrected height and arm span, bone mineral density and bone mineral content of proximal femur, lumbar spine, and distal tibia, and bone turnover markers (bone alkaline phosphatase [bALP] and deoxypyridinoline) were evaluated.

RESULTS

From age 13 years and older, the AIS group had longer anthropometric parameters (P < 0.05), generalized lower bone mass (P < 0.035), and 38.6% higher in bALP (P < 0.004) when compared with controls. A stronger inverse correlation between bALP and bone mass was noted in the AIS group. The bALP was positively correlated with bone area of tibia (P = 0.013) in the AIS group only. Deoxypyridonine of the AIS group was not different from the controls until age 15 years. The mean calcium intake of the AIS group was very low (only 361 mg/day), and calcium intake was significantly associated with bone mass in the AIS group. Low bone mass in AIS could be explained by faster anthropometric bone growth, higher bone turnover, and lower calcium intake in multiple regression analysis.

CONCLUSIONS

Results from the current study showed that an abnormally faster growth rate and higher bone turnover in the patient with AIS might lead to increased bone dimensions. Calcium intake in patients with AIS was very low and likely to be insufficient for normal bone mineralization. Therefore, low bone mass in AIS may result from abnormal bone mineralization qualitatively and quantitatively and, thus, fails to catch up with increased bone growth during the peripubertal period.