Lumbar Scoliosis in Postmenopausal Women Increases With Age but Is Not Associated With Osteoporosis

Janet Rubin; Rebecca J. Cleveland; Alexander Padovano; David Hu; Maya Styner; James Sanders

Disclosures

J Endo Soc. 2021;5(5) 

In This Article

Abstract and Introduction

Abstract

Context: The contribution of lumbar scoliosis to osteoporosis is unknown.

Objective: This work aimed to determine the prevalence and relationship of lumbar scoliosis to osteoporosis in aging women.

Methods: A cross-sectional analysis used dual-energy x-ray absorptiometry (DXA) scans of randomly selected groups of postmenopausal women (64-68, 74–78, and 84–88 years; N = 300 each) in a university teaching hospital from 2014 to 2019. Lumbar Cobb angle was tested for an association to femoral neck (FN), total hip (TH), and spine T score, age, weight, and ethnicity. Logistic regression tested an association between scoliosis (Cobb angle > 10°) and osteoporosis (T score ≤ –2.5). Available sequential DXA scans (N = 51) were analyzed for changes in Cobb angle using a linear mixed model of these longitudinal data.

Results: Osteoporosis and Cobb angle both increased with age: from 22% and 4.4 (SD = 7.8) respectively in 64- to 68-year-olds to 32.9% and to 9.7 (SD = 9.2) in women age 84 to 88 years. The prevalence of clinically significant scoliosis rose from 11.5% in the youngest group, to 27.3% and 39.4% in the age 74 to 78 and 84 to 88 cohorts, respectively. Cobb angle increased 0.7° per year of follow-up. After adjusting for covariates, there was no significant association between T scores at any site (TH, FN, or spine) and Cobb angle.

Conclusion: Based on screening DXAs, the incidence and degree of lumbar scoliosis increases significantly in women between age 65 and 85 years. There was no association between the incidence of lumbar scoliosis and FN bone density.

Introduction

Despite the multitude of studies that guide the approach and treatment of postmenopausal osteoporosis, it is striking that an association with lumbar scoliosis—a common clinical entity afflicting the axial skeleton in the same age group[1]—has not been analyzed. During treatment of women for postmenopausal osteoporosis, studies reveal that lumbar spine bone mineral density (BMD) increases more rapidly than does hip density, and continues to increase in a sustained fashion when analyzed by serial dual-energy x-ray absorptiometry (DXA) exams.[2–5] However, quantification of BMD change at the lumbar spine is compromised in patients with spine deformities, particularly when an abnormal curvature in the coronal plane interferes with spine alignment,[6,7] and complicates monitoring of treatment. Moreover, that scoliosis may contribute to the appearance of vertebral fracture begs the question of whether scoliosis affects the diagnosis of osteoporosis.

Degenerative or de novo scoliosis in older adults is highly prevalent, estimated at 30% to 68% of adults.[1] Lumbar anatomical abnormalities are commonly recognized during review of bone density images from aging women, leading clinicians to discount spine DXA readings or to note that spine density is falsely elevated because of lumbar scoliosis or "sclerosis." Despite these truisms, few clinical studies in the bone field have attempted to quantify scoliosis, which, lacking an automated method, requires manual analysis. Moreover, individuals with scoliosis are routinely excluded from landmark osteoporosis trials that assess the efficacy of widely used pharmacologic therapies, exclusions based on imaging criteria, or diagnosis codes.[8–10] Frequent disqualification criteria includes patients with the presence of more than 2 nonevaluable lumbar vertebrae,[11] focal sclerosis in the spine,[4] or those designated as having bone diseases other than osteoporosis.[12]

Importantly, it is unclear if postmenopausal osteoporotic patients have a higher prevalence of scoliosis than expected in an age-matched population. The literature gives clinicians little idea whether current treatments to prevent spine fragility fractures are efficacious in patients with scoliosis, or if osteoporotic treatments have any effect on scoliosis.[13,14] Further, reliable distinctions between diagnosis of lumbar fractures due to osteoporosis and those due to adaptations to increasing lumbar curvature are currently lacking. In sum, the clinical ambiguity of spine BMD, which accompanies scoliotic spines,[15] results in a confounding both of diagnosis and therapeutic treatment decisions relating to osteoporosis.[16,17]

We here aimed to determine the relationship between postmenopausal osteoporosis and a lumbar spine curve consistent with clinical scoliosis as defined by a Cobb angle greater than or equal to 10°. Randomly selected DXA scans conducted in postmenopausal women were used to study the association of bone density at the spine, femoral neck (FN), and total hip (TH) with lumbar Cobb angle. We present here that our analysis failed to detect a significant relationship between osteoporosis and lumbar scoliosis.

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