Representative pre-clinical studies, including the optimization of vertebroplastic/ kyphoplastic cement augmentation for vertebral body defects, should be performed in large animal models. This study aimed at the systematic characterization of an in vivo large animal model using strictly minimally-invasive, lumbar, ventrolateral vertebroplasty.
Lumbar defects [diameter 5 mm; depth approx. 14 mm] were generated using a ventrolateral percutaneous approach in old, osteopenic, female sheep (40 Merino sheep; 6 – 9 years; 68 - 110 kg). L1 remained untouched, L2 contained an empty defect, and L3 a defect injected with a brushite-forming calcium phosphate cement (CPC). Trauma/functional impairment, surgical techniques, reproducibility, bone defects, cement filling, and functional cement augmentation were assessed by intraoperative incision-to-suture time and x-ray, postoperative trauma/impairment scores, and ex vivo osteodensitometry, micro-CT, histomorphometry, and biomechanical testing.
Minimally-invasive vertebroplasty showed a short operation time (28 ± 2 min; mean ± standard error of the mean) and x-ray exposure (1.59 ± 0.12 min), marginal local trauma (score 0.00 ± 0.00 at 24 h), fast postoperative recovery (2.95 ± 0.29 h), and rapid decrease of the postoperative impairment score to 0 (3.28 ± 0.36 h). Reproducible defect creation and cement filling was documented by intraoperative x-ray and ex vivo conventional/micro-CT. Vertebral cement augmentation and osteoconductivity of the CPC was validated by osteodensitometry, micro-CT, histology/static histomorphometry, fluorescence histomorphometry, and compressive strength measurements.
This minimally-invasive, ventrolateral, lumbar vertebroplasty model in aged, osteopenic sheep shows short operation times, rapid postoperative recovery, and high experimental reproducibility and may thus represent a good basis for standardized evaluation of future studies on vertebral augmentation with resorbable and osteoconductive CPC.