Beyond the pedicle screw–a patent review

Abstract

Purpose This review provides an overview of the patent literature on posteriorly placed intrapedicular bone anchors. Conventional pedicle screws are the gold standard to create a fixation in the vertebra for spinal fusion surgery but may lack fixation strength, especially in osteoporotic bone. The ageing population demands new bone anchors that have an increased fixation strength, that can be placed safely, and, if necessary, can be removed without damaging the surrounding tissue. Methods The patent search was conducted using a classification search in the Espacenet patent database. Only patents with a Cooperative Patent Classification of A61B17/70 or A61B17/7001 concerning spinal positioners and stabilizers were eligible for inclusion. The search query resulted in the identification of 731 patents. Based on preset inclusion criteria, a total of 56 unique patents on different anchoring methods were included, reviewed and categorized in this study. Results Five unique fixation methods were identified; (1) anchors that use threading, (2) anchors that utilize a curved path through the vertebra, (3) anchors that (partly) expand, (4) anchors that use cement and (5) anchors that are designed to initiate bone ingrowth. Of the anchor designs included in this study, eight had a corresponding commercial product, six of which were evaluated in clinical trials. Conclusion This review provides insights into worldwide patented intrapedicular bone anchors that aim to increase the fixation strength compared to the conventional pedicle screw. The identified anchoring methods and their working principles can be used for clinical decision-making and as a source of inspiration when designing novel bone anchors.

Novel Polyethylene Terephthalate Screw Sleeve Implant: Salvage Treatment in a Case of Spine Instability after Vertebroplasty Failure

“…Therefore, we adopted a screw implant system. Different strategies, i.e., mechanical devices such as intrapedicular bone anchors, are being tested to improve screw pull-out strength [ 2 ]. However, such devices are quite expensive and require storage space and specific training in order to implant them correctly.…”

“…Osteoporosis is a condition that causes the bone to lose structural integrity by decreasing its mineral density and altering the bone formation/resorption mechanism [ 1 ], which results in increased susceptibility to fractures [ 2 ]. Osteoporosis-related vertebral fractures also occur in the spine and may require cement augmentation using vertebroplasty (VP) or surgical fixation with hardware (i.e., pedicle screws and rods) [ 2 ].…”

“…Osteoporosis is a condition that causes the bone to lose structural integrity by decreasing its mineral density and altering the bone formation/resorption mechanism [ 1 ], which results in increased susceptibility to fractures [ 2 ]. Osteoporosis-related vertebral fractures also occur in the spine and may require cement augmentation using vertebroplasty (VP) or surgical fixation with hardware (i.e., pedicle screws and rods) [ 2 ]. As the screw strength in the osteoporotic bone is impaired due to the loss of trabecular bone, several techniques have been developed to improve fixation, such as augmentation with bone cement to increase screw stability in osteoporotic vertebral bodies [ 1 , 2 ].…”

“…Osteoporosis-related vertebral fractures also occur in the spine and may require cement augmentation using vertebroplasty (VP) or surgical fixation with hardware (i.e., pedicle screws and rods) [ 2 ]. As the screw strength in the osteoporotic bone is impaired due to the loss of trabecular bone, several techniques have been developed to improve fixation, such as augmentation with bone cement to increase screw stability in osteoporotic vertebral bodies [ 1 , 2 ]. Furthermore, population aging requires new solutions for increasing a fixation strength that can be applied safely and, if necessary, removed without damaging the surrounding tissue [ 2 ].…”

Biomechanical analysis of detachable duet screw to resist intraoperative screw loosening.

“…Furthermore, the persistence of physiological stress across the unfused segment, resulting from delayed union or pseudarthrosis, has the potential to exacerbate the loosening or failure of the instrumentation subsequent to spinal surgery [6] . Previous research has indicated that the ability of the screw to resist axial pull-out primarily relies on its holding strength within the cortical bone of the pedicle [2,7] .…”