Strontium Prevents the Progression of Thoracic Kyphosis

Background: Thoracic kyphosis (a frequent feature in the elderly and in post menopausal osteoporosis) can be caused by vertebral fractures. This exaggerated curvature of the spine is also related to degenerative changes including intervertebral disc space narrowing, deformities of the anterior part of the vertebrae and reduced spinal muscles strength. An increase over time in thoracic kyphosis has been associated with impairment in global health due to increased body sway and risk of falls, impairments in pulmonary function, presence of esophagial hiatal hernia, and an increase in risk of mortality in older women.

Objectives: The objective of this study was to assess the effect on thoracic kyphosis progression over a 3-year treatment with strontium ranelate, a treatment against osteoporosis that reduces the risk of vertebral, nonvertebral and hip fractures.

Methods: This study was performed in women with postmenopausal osteoporosis from SOTI 1 and TROPOS 2 studies, aiming to demonstrate the efficacy of strontium ranelate against vertebral and non-vertebral fractures. Patients underwent lateral radiographs of the thoracic and lumbar spine at baseline and annually over 3 years (standardized procedures). The level of thoracic kyphosis was reflected by a kyphosis index, defined on lateral thoracic radiographs as the ratio BD/AC (AC= line from the anterior superior edge of T4 to the anterior inferior edge of T12; BD= perpendicular line from the furthest superior or inferior posterior point of T7, T8 or T9 vertebrae to AC line) expressed as a %. The highest the KI, the more severe the thoracic kyphotic curvature.

Results: The population consisted of 4055 women with postmenopausal osteoporosis (2038 patients randomised to strontium ranelate and 2017 randomised to placebo). Baseline characteristics were similar: mean age 73.5; Spine BMD T-score (L2-L4): -3.06; Femoral neck T-score: -2.97; KI: 25.4. Over 3 years, there was a significant increase from baseline in kyphotic index for all patients. However, this increase was significantly lower (p=0.003) in patients treated with strontium ranelate: +3.71±7.69% than in the placebo group:+4.70±7.32%.
The same calculations were repeated after exclusion of patients having either prevalent or incident thoracic vertebral fractures. In this subset of 1193 patients (634 in the strontium ranelate group and 559 in the placebo group), the change in the strontium ranelate group was still lower than in the placebo group (+ 2.72±7.17% versus 4.34±6.54%, respectively).



Conclusion: These prospective results demonstrate that thoracic kyphosis increases over time in postmenopausal women with osteoporosis. Strontium ranelate decreased the progression of this thoracic kyphosis over 3 years, regardless of the presence or not of vertebral fractures. This new effect of strontium ranelate possibly reflects additional benefit on spinal components besides its efficacy in decreasing vertebral fractures.

References: 1 Meunier PJ et al. N Engl J Med 2004; 2 Reginster J.Y et al. JCEM 2005

Ann Rheum Dis 2008;67(Suppl II):541
http://www.abstracts2view.com/eular/view.php?nu=EULAR08L_SAT0344