Decreased extrusion of calcium phosphate cement versus high viscosity PMMA cement into spongious bone marrow – an ex vivo and in vivo study in sheep vertebrae.
Spine J. 2016 Aug 2;
Authors: Xin L, Bungartz M, Maenz S, Horbert V, Hennig M, Illerhaus B, Günster J, Bossert J, Bischoff S, Borowski J, Schubert H, Jandt KD, Kunisch E, Kinne RW, Brinkmann O
BACKGROUND CONTEXT: Vertebroplasty/kyphoplasty of osteoporotic vertebral fractures bears the risk of pulmonary cement embolism (3.5-23%) due to leakage of commonly applied acrylic polymethylmethacrylate (PMMA) cement to spongious bone marrow or outside of the vertebrae. Ultraviscous cement and specific augmentation systems have been developed to reduce such adverse effects. Rapidly setting, resorbable, physiological calcium phosphate cement (CPC) may also represent a suitable alternative.
PURPOSE: To compare the intravertebral extrusion of CPC and PMMA cement in an ex vivo/in vivo study in sheep.
STUDY DESIGN/SETTING: Prospective experimental animal study METHODS: Defects (diameter 5 mm; 15 mm depth) were created by a ventrolateral percutaneous approach in lumbar vertebrae of female Merino sheep (2-4 years) either ex vivo (n = 17) or in vivo (n = 6), and injected with: i) CPC (L3); ii) CPC reinforced with 10% poly(l-lactide-co-glycolide (PLGA) fibers (L4); or iii) PMMA cement (L5; Kyphon HV-R(®)). Controls were untouched (L1) or empty defects (L2). The effects of the cement injections were assessed in vivo by blood gas analysis and ex vivo by computed tomography (CT), micro-CT (voxel size: 67 µm), histology, and biomechanical testing.
RESULTS: Following ex vivo injection, micro-CT documented significantly increased extrusion of PMMA cement in comparison to CPC (+/- fibers) starting at a distance of 1 mm from the edge of the defect (confirmed by histology); this was also demonstrated by micro-CT following in vivo cement injection. In addition, blood gas analysis showed consistently significantly lower values for the fraction of oxygenized hemoglobin/total hemoglobin (FO2Hb) in the arterial blood until 25 min following injection of the PMMA cement (p ? 0.05 versus CPC; 7, 15 min). Biomechanical testing following ex vivo injection showed significantly lower compressive strength and Young’s modulus than untouched controls for the empty defect (40% and 34% reduction, respectively) and all 3 cement-injected defects (21-27% and 29-32% reduction, respectively), without significant differences among the cements.
CONCLUSIONS: Due to comparable compressive strength, but significantly lower cement extrusion into spongious bone marrow than PMMA cement, physiological CPC (+/- PLGA fibers) may represent an attractive alternative to PMMA for vertebroplasty/kyphoplasty of osteoporotic vertebral fractures in order to reduce the frequency/severity of adverse effects.
PMID: 27496285 [PubMed – as supplied by publisher]