The effect of denosumab on pedicle screw fixation: a prospective 2-year longitudinal study using finite element analysis

Abstract

Background Pedicle screw loosening is a major complication following spinal fixation associated with osteoporosis in elderly. However, denosumab is a promising treatment in patients with osteoporosis. The effect of denosumab on pedicle screw fixation is unknown. Therefore, we investigated whether denosumab treatment improves pedicle screw fixation in elderly patients with osteoporosis. Methods This was a 2-year prospective open-label study. From February 2015 to January 2016, we included 21 patients with postmenopausal osteoporosis who received initial denosumab treatment. At baseline, 12 months, and 24 months, we measured volumetric bone mineral density (BMD) using quantitative computed tomography (QCT) and performed CT-based finite element analysis (FEA). Finite element models of L4 vertebrae were created to analyze the bone strength and screw fixation. Results BMD increased with denosumab treatment. FEA revealed that both pullout strength of pedicle screws and compression force of the vertebra increased significantly at 12 and 24 months following denosumab treatment. Notably, pullout strength showed a stronger correlation with three-dimensional volumetric BMD around pedicle screw placement assessed by QCT (r = 0.83, at 24 months) than with two-dimensional areal BMD assessed by dual energy X-ray absorptiometry (r = 0.35, at 24 months). Conclusion To our knowledge, this is the first study to reveal that denosumab treatment achieved strong pedicle screw fixation with an increase in BMD around the screw assessed by QCT and FEA; therefore, denosumab could be useful for osteoporosis treatment during spinal surgery in elderly patients with osteoporosis.

What’s New in Osteoporosis and Fragility Fractures

“…A prospective study utilized quantitative CT at baseline and 12 and 24 months in postmenopausal women with osteoporosis receiving denosumab and utilized finite element models of L4 to analyze bone strength and pedicle screw pullout. Their results showed improved BMD and pullout strength at 12 and 24 months compared with baseline 51 .…”

Evaluating bone quality and asymmetrical aplasia of the thoracic vertebral body in Lenke 1A adolescent idiopathic scoliosis using hounsfield units

“…reported that HU value measured on CT was an independent predictor for pedicle screw loosening, and lower HU value was significantly correlated with higher risk of screw loosening ( 49 , 50 ). Another study showed that anti-osteoporosis treatment could achieve strong pedicle screw fixation effectively with an increase in bone mineral density around the screw assessed by QCT ( 51 ).Our results found lower bone quality in the convex vs. the concave side in the AV, AV ± 1, and AV ± 2 regions of the structural curve in AIS patients, suggesting that surgeons should exercise increased vigilance when selecting pedicle screw dimensions, a thicker and longer pedicle screw should be better to provide stronger holding force for internal fixation on the convex side during surgery when the width and length were suitable.…”

Implantatversagen nach Instrumentierungen bei Osteoporose: Ursachen und Behandlungskonzepte

“…Mittlerweile findet auch zunehmend Denosumab, als Anti-RANKL-Antikörper, Anwendung in der Osteoporose-Therapie. In einer Kombination aus medikamentöser klinischer und chirurgischer Finite Element Analyse zeigte Denosumab eine verbesserte Schraubenbiomechanik [13]. Klinische Studien existieren auch in Kombination mit Teripraratid mit guten Ergebnissen für die Osteoporose, jedoch fehlenden Aussagen für spinale Operationen.…”