Serum Vitamin D Level and Bone Mineral Density Among Adolescent Idiopathic Scoliotic Patients

INTRODUCTION

Adolescent idiopathic scoliosis (AIS) is the commonest type of pediatric scoliosis with prevalence about 1% to 3% ¹. It takes place in persons from 10 to 18 years of age. Typically, idiopathic scoliosis means an unexplained etiology of a particular syndrome, congenital and neuromuscular disorder ².

Etiology of AIS may involve Genetic and non-genetic causes ³. Bone mineral density (BMD) is one of the non-genetic causes, as bone content plays a vital role in distorting osseous mechanical strength. The incidence of AIS with osteoporosis is believed to reduce the intensity of the bone by about 20-38 percent ⁴.

Vitamin D has a vital role in preserving a good, mineralized bone. It aids in the absorption of calcium and vitamin D-deficient patients may have problems in developing new bones and retaining bone intensity ⁵.

Many recent researches have indicated that the start and development of AIS could be caused by a decline in BMD, and some researches have attempted to correlate vitamin D with AIS ⁶. Considering that serum vitamin D level has a positive correlation with the BMD of the hip ^7,8  and negative correlation with the Cobb angle ⁹ , vitamin D insufficiency or deficiency is speculated to has effects on AIS etiopathogenesis Exploration of vitamin D associations with AIS can help us understand spinal deformity pathogenesis in the AIS ¹⁰. The purpose of this research is to measure vitamin D and BMD in adolescent scoliosis.

PATIENTS AND METHODS

A prospective, non-interventional study for 112 subjects diagnosed with idiopathic scoliosis and a Cobb angle > 10^o aged from 10 - 18 years old had been recruited from Al-Azhar University hospitals during the period from 1 March 2020 to 1 March 2021.

Our study was approved by a local ethical committee. A written informed consent was achieved from the parents of all the participants.

Exclusion criteria:

Age less than 10 or more than 18 years.

Causes of secondary scoliosis (congenital, neuromuscular, or traumatic).

Postural scoliosis, metabolic or endocrine diseases.

Patients with fracture history.

Methods:

All participants subjected to full history, examination, serum vitamin D, Cobb angle, Beighton scale for Joint hypermobility [11], spinal and bilateral femoral neck BMD, trabecular bone score (TBS), serum calcium, phosphorus, parathyroid hormone, and alkaline phosphatase (ALP).

Serum 25-hydroxyvitamin D (25(OH)D) were assessed using electrochemiluminescence immunoassay (Roche, USA). Regarding to the producer, normal 25(OH)D is ≥75 nmol/L and low levels are < 75 nmol/L. Cobb angle was achieved by estimating the largest spinal curve, taken from the upper-end vertebra until the lower-end vertebra, on x-ray. BMD of the lumbar spine (L1–L4) and the proximal femur (neck, Ward’s triangle, and greater trochanter) were assessed by dual-energy X-ray absorptiometry (DEXA; Hologic, Discovery, QDR series, GE Medical, Milwaukee, WI, USA).

Statistical analysis:

The Statistical package for Social Science (IBM Corp. Released 2011. IBM SPSS Statistics for Windows, Version 21.0. Armonk, NY: IBM Corp.) was used. The Mean and standard deviation (mean ± SD) were used to describe the parametric numerical data. The frequency and percentage were used to describe the non-numerical data. Pearson's correlation test was used to determine the correlation between 25(OH)D and the other study variables.

RESULTS

A total of 112 participants, their mean of age 15.81 years and BMI mean was 19.63 kg/m². The majority of patients was females (63.4%). Seventy-four (66.1%) of our patients had vitamin D deficiency. The mean Cobb angle was 24.63° (table 1).

Considering bone density, mean of femoral neck BMD 0.73g/cm², greater trochanter BMD 0.64 g/cm², ward's triangle BMD 0.63 g/cm² andlumbar spine BMD 0.82 g/cm². Mean of trabecular bone score was 0.99. Also, mean of beighton scale was 5.33. Mean of lumbar and hip Z-score was -1.531 and -1.362 (table 2). Osteopenia present in 39% and osteoporosis in 25% of AIS patients by lumbar spine Z-score and by hip Z-score, osteopenia present in 53% and osteoporosis in 12% of AIS patients (Figure 1).

Regarding to laboratory results, mean of 25-OH-D3 was 15.30 ng/ml, ca 5.92 mg/dl, phosphorus 4.32 mg/dl, ALP 170 IU/L and PTH 47.90 pg/ml (table 3).

There is negative significant association between 25(OH)D and cobb angel (p value < 0.001) and positive significant association between 25(OH)D, calcium and BMD of hip (p value= 0.001 and 0.019, respectively) while no significant correlation was found between 25(OH) D and BMD of lumbar spine (table 4).

Table 1: Distribution of patients regarding demographic and clinical data

TBS: trabecular bone score

Table 2: Distribution of studied patients regarding bone density investigation

Fig. 1: Z-score of the hip and lumbar spine of studied patients

ALP: Alkaline phosphatase, PTH: parathyroid hormone

Table 3: Distribution of studied patients regarding laboratory investigation

Pearson’s correlation test.                                          *p value is significant

Table 4: Correlation between 25-OH-D3 and cobb angle, calcium, and BMD.

                      Fig. 2: Measurement of Cobb angle. (12)

Fig. 3: Plain X-ray whole spine A-P and lateral view in standing position (Cobs Angle 19.8). and DEXA imaging of the same patient showing Z-score at L1-4 -2.6.