Vertebroplasty with self-locking hexagonal metal implants shows comparable primary and secondary stiffness to PMMA cement augmentation techniques in a biomechanical vertebral compression fracture model

Abstract

With the growing incidence of vertebral compression fractures in elderly patients having a fair overall health condition, minimal-invasive treatment techniques are getting in focus of surgical therapy. Cement augmentation is widely performed and its complications and mechanical limitations are well described. Implants avoiding the side effects of cement augmentation while reaching the same level of stability would be desirable. The primary and secondary stability of a new augmentation method with self-locking hexagonal metal implants were investigated and compared with the performance of established augmentation options. 18 fresh-frozen human spinal specimens (Th12-L2/L3-L5) were tested with pure moments of 7.5 Nm in a six-degree-of-freedom spine simulator to investigate primary and secondary stability of three augmentation techniques: (1) vertebroplasty, (2) PMMA filled cavity and (3) hexagonal metal implants. An increasing three-step cyclic loading model was included. Elastic displacement and height loss under loading did not show significant differences between the three test groups. Investigation of primary and secondary stability evenly demonstrated comparable results for all techniques indicating an insufficiency to stabilise the fracture with higher load cycles. The newly introduced method for augmentation with the metal implant Spine Pearls achieved comparable results to bone cement based techniques in a biomechanical in vitro study. Midterm and longterm reduction preservation and ingrowth of the implants have to be proven in further studies.

Cement Augmentation in a Thoracolumbar Fracture Model

“…The ROM values and stiffness measurements achieved in this study are comparable with those described in previous publications, 8,25 with no differences between the 2 augmentation techniques. Accurate information about segmental stability may be limited with this method, particularly because the cyclic loading protocol involved continuous loading of the discs, causing progressive fl uid loss.…”

A 20-Year Review of Biomechanical Experimental Studies on Spine Implants Used for Percutaneous Surgical Repair of Vertebral Compression Fractures

“…Cubes are bundles of hexagonal hollow tubes that are fabricated from brass, steel, or titanium which crudely simulate the porous architecture of cancellous bone, thereby eliminating or reducing the need for cement, providing a scaffold for cancellous bone regeneration, and reducing the stress concentrations associated with VP, KP, stents, jacks, and coils (Figure 2(h)) [38][39][40][41]. These "porous" cubes are inserted into the vertebra through 1 or both reamed or drilled pedicles or, alternatively, through the hollow canal of a pedicle screw.…”

“…The Cube Method. Only 3 biomechanical evaluations of "porous" cube implants have been published to date [38,40,41]. The only commonality in experimental protocol was the use of a traditional VP and/or KP as the control group.…”

“…Cube Implant Studies. Few investigations to date experimentally analyzed "porous" multitube cube devices from a biomechanical standpoint [38,40,41]. One of these studies primarily examined the influence of cube shape and material on bone stress distribution [38], which was followed up with a computational biomechanics analysis that looked at the effects of tube diameter and thickness [39].…”

Local osteo-enhancement of osteoporotic vertebra with a triphasic bone implant material increases strength—a biomechanical study

“…Twenty-one fresh frozen human cadaver vertebra (Th11-L2) from consenting informed donors were included in the study ( Table 1). The bone mineral density (BMD) of each vertebra was measured using a qCT scan (LightSpeed VCT 16, GE Healthcare, Chicago, USA) with a calibration phantom (European Forearm Phantom, QRM GmbH, Möhrendorf, Germany) [10]. For BMD measurement, the average of three circular regions of interest placed in the trabecular area of three slices evenly distributed across the height of each vertebral body was taken.…”