Artificial Disc System

What is this patent about?

’567 is related to the field of artificial intervertebral discs, specifically those designed for posterior insertion into the lumbar spine. The background highlights the limitations of existing anteriorly placed discs, including vascular injury risks, retrograde ejaculation in males, and restrictions on placement levels due to anatomical constraints. Prior art disc designs often involve a core surrounded by a container, with materials ranging from rubber to metal, each with trade-offs between motion preservation, shock absorption, and long-term durability. The patent addresses the need for a safer, more versatile disc replacement option.

The underlying idea behind ’567 is to create a total artificial disc that can be inserted from the posterior, thus avoiding the risks associated with anterior placement. The design incorporates expandable plates that can be adjusted in both height and width to ensure a secure fit within the intervertebral space. A key element is the use of a removable core that allows for customized sizing and unhindered flexibility of motion after the plates are anchored to the vertebral endplates. The concept also includes features to prevent core extrusion, such as ball limiters or raised edges.

The claims of ’567 focus on a total artificial disc comprising first and second substantially parallel plates configured to occupy a space defined by vertebral endplates, each of the first and second substantially parallel plates having a vertebral-facing surface, an opposite surface, and a perimeter surface extending around a perimeter of the first or second substantially parallel plates between the vertebral-facing surface and the opposite surface, wherein the opposite surfaces of the first and second substantially parallel plates are formed as concave surfaces; a mobile core disposed between the first and second substantially parallel plates, the mobile core having a generally circular perimeter core rim, the mobile core being positioned against the concave surface of the opposite surfaces of each of the parallel plates, the mobile core configured to permit the vertebral endplates to move relative to one another, a dimension of the mobile core in a horizontal plane being substantially less than a dimension of the first and second substantially parallel plates such that each of first and second substantially parallel plates extend beyond the mobile core in each direction of the horizontal plane; a first plurality of anchors formed as right-angled lateral protrusions positioned on the vertebral-facing surface of the first substantially parallel plate, wherein the first plurality of anchors are positioned within a center portion of the vertebral-facing surface and are configured to engage with one of the vertebral endplates, and the first plurality of anchors arranged to form at least one line of anchors across the center portion of the vertebral-facing surface, the first plurality of anchors positioned so that a right-angled side of each anchor in the at least one line of anchors is oriented in a same direction across the vertebral-facing surface; and a second plurality of anchors positioned about at least a portion of a perimeter of the vertebral-facing surface of the first substantially parallel plate, each of the second plurality of anchors positioned at and extending to an edge of the first substantially parallel plate; wherein each anchor of the second plurality of anchors has an exterior surface that extends continuously from the perimeter surface of the first substantially parallel plate.

In practice, the disc is inserted posteriorly after a discectomy. The plates are then expanded using a specialized tool, and traction spikes on the outer surfaces of the plates engage with the vertebral endplates to provide secure fixation. Once the plates are anchored, the expansion tool is removed, and a ball-shaped core of appropriate size is inserted between the plates. The core allows for natural spinal movement while the ball limiters or raised edges prevent it from being expelled from between the plates. The posterior insertion method can be performed using open microscopic or minimally invasive techniques.

The key differentiation from prior approaches lies in the posterior insertion technique, which avoids the risks associated with anterior access. The design also incorporates unique features like the bi-functional screws for height and width adjustment, and the oblique orientation of the traction spikes for enhanced endplate penetration and resistance to extrusion. The use of a removable core allows for customized fitting , and the ball limiters or raised edges provide an additional safety mechanism to prevent core displacement. This combination of features aims to provide a safer, more versatile, and more durable artificial disc replacement option.