# US 2023/0057541 A1 · Pivotal bone anchor assembly with bottom loaded shank head and resiliently expandable retainer > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2023/0057541 A1 - Document ID: US20230057541A1 - Status: Published application - Kind: A1 - Application number: 18/048,760 - Filed: 2022-10-21 - Published: 2023-02-23 - Earliest claimed: 2009-06-15 - Assignees: Roger P. Jackson - Inventors: Roger P. Jackson; James L. Surber - Web page: https://patentgrep.com/patent/US20230057541A1 ## CPC - A61B 17/702: {having a core or insert, and a sleeve, whereby a screw or hook can move along the core or in the sleeve} - A61B 17/68: Internal fixation devices {, including fasteners and spinal fixators, even if a part thereof projects from the skin (bone staples A61B17/0642)} - A61B 17/7008: {with parts of, or attached to, the longitudinal elements, bearing against an outside of the screw or hook heads, e.g. nuts on threaded rods (A61B17/7007 takes precedence)} - A61B 17/7032: {Screws or hooks with U-shaped head or back through which longitudinal rods pass} - A61B 17/7037: {wherein pivoting is blocked when the rod is clamped} - A61B 17/7076: {for driving, positioning or assembling spinal clamps or bone anchors specially adapted for spinal fixation} - A61B: DIAGNOSIS; SURGERY; IDENTIFICATION (usefulness limited to only animals A61D) ## Abstract A pivotal bone anchor assembly includes a receiver defining a cavity with an upper expansion region and a lower locking region, and a shank having a partial spherical head that is up-loadable into the cavity through a bottom opening. The assembly also includes a resiliently expandable retainer that is positionable within the upper expansion region with a discontinuous partial spherical internal surface and an inwardly facing surface above the discontinuous partial spherical internal surface, and a compression insert having a lower outwardly facing surface configured for side-to-side engagement with the inwardly facing surface and a downwardly facing partial spherical surface for frictionally engaging the head of the shank. The compression insert is positionable in overlapping engagement with the retainer within the receiver with the discontinuous partial spherical internal surface extending above and below a hemisphere of the head of the shank to capture the head within the retainer. ## Claims ### Claim 1 A pivotal bone anchor assembly for securing an elongate rod to a bone of a patient with a closure, the pivotal bone anchor assembly comprising: a receiver having a longitudinal axis, a lower body defining a cavity with a bottom opening, an upper expansion region, and a lower locking region, and a pair of upwardly extending arms with opposed interior surfaces that define an open channel to receive the elongate rod, the open channel communicating with the cavity to define a central bore, the interior surfaces of the open channel having a closure-mating structure formed therein, the central bore extending to a top of the receiver along the longitudinal axis; a shank having a partial spherical head with a hemisphere and an anchor portion extending distally from the head to attach to the bone, the head being up-loadable into the cavity of the receiver through the bottom opening; a retaining structure that is resiliently expandable and at least partially positionable within the upper expansion region prior to the shank and operable to capture the head of the shank, upon uploading of the head through the bottom opening, in spaced relationship from an internal surface of the cavity of the receiver, the retaining structure having a discontinuous partial spherical internal surface to engage the head of the shank and an inwardly facing surface above the discontinuous partial spherical internal surface; and a compression insert having an upwardly facing surface sized and shaped to engage the elongate rod, an upper exterior surface to slidably engage an internal surface of the central bore of the receiver, a lower outwardly facing surface configured for side-to-side engagement with the inwardly facing surface of the retaining structure above the discontinuous partial spherical internal surface, and a downwardly facing partial spherical surface to frictionally engage the head of the shank, wherein the compression insert is positionable within the central bore of the receiver prior to the shank and in overlapping engagement with the retaining structure, with the compression insert being prevented from moving upwardly within the central bore by at least partial overlapping engagement with at least one downwardly facing planar surface formed in the receiver; and wherein after the head of the shank is captured within the retaining structure, the discontinuous partial spherical internal surface extends above and below the hemisphere of the head of the shank. ### Claim 2 (depends on 1) The pivotal bone anchor assembly of claim 1, wherein the retaining structure is resiliently expandable in the upper expansion region to capture the head of the shank when uploaded through the bottom opening. ### Claim 3 (depends on 1) The pivotal bone anchor assembly of claim 1, wherein the retaining structure is non-pivotal with respect to the receiver when the assembly is in an unlocked configuration. ### Claim 4 (depends on 1) The pivotal bone anchor assembly of claim 1, wherein upward movement of the retaining structure during the uploading of the head of the shank is restricted by engagement between a top surface of an upper portion of the retaining structure and an overlapping surface of the compression insert. ### Claim 5 (depends on 1) The pivotal bone anchor assembly of claim 1, wherein the retaining structure includes at least one vertical gap defined by spaced apart end surfaces. ### Claim 6 (depends on 1) The pivotal bone anchor assembly of claim 1, wherein the retaining structure frictionally engages the head of the shank upon capture within the cavity of the receiver to allow for an unlocked but non-floppy angular positioning of the shank with respect to the receiver prior to a final locking of the pivotal bone anchor assembly. ### Claim 7 (depends on 1) The pivotal bone anchor assembly of claim 1, wherein the shank includes a central opening along a longitudinal axis thereof extending from a top end to a bottom end of the shank. ### Claim 8 (depends on 7) The pivotal bone anchor assembly of claim 7, wherein the top end of the shank incudes a central internal drive structure surrounded by an annular flat top surface. ### Claim 9 (depends on 1) The pivotal bone anchor assembly of claim 1 and further comprising the elongate rod and the closure, the closure having a helically wound guide and advancement structure formed into an outer sidewall surface and engageable with the closure-mating structure formed into the interior surfaces of the upwardly extending arms of the receiver to capture the elongate rod within the open channel. ### Claim 10 A pivotal bone anchor assembly for securing an elongate rod to a bone of a patient with a closure, the pivotal bone anchor assembly comprising: a receiver including a body and a pair of arms extending upwardly from the body, the body defining a cavity with a bottom opening in a bottom exterior of the body, the cavity including an expansion region and a locking region below the expansion region, the pair of arms including opposed interior surfaces that define an open channel above the cavity to receive the elongate rod, the open channel communicating with the cavity to define a central bore extending from the bottom opening to top surfaces of the pair of arms, the interior surfaces of the open channel including a closure-mating structure formed therein; a shank including a head and an anchor portion extending distally from the head to attach to the bone, the head being partially spherical, having a maximum diameter perpendicular to a longitudinal axis of the shank, and being up-loadable into the cavity of the receiver through the bottom opening; a retaining structure that is resiliently expandable and at least partially positionable within the expansion region prior to the shank and operable to capture the head of the shank, the retaining structure maintaining the head in spaced relationship from an internal surface of the cavity of the receiver upon the uploading of the head through the bottom opening and into the retaining structure, the retaining structure having an discontinuous internal surface to engage the head of the shank and an inwardly facing surface above the discontinuous internal surface, the discontinuous internal surface being partially spherical; and a compression insert having an upwardly facing surface, an upper exterior surface, a lower outwardly facing surface, and a downwardly facing partial spherical surface, the upwardly facing surface sized and shaped to engage the elongate rod, the upper exterior surface to slidably engage an internal surface of the central bore of the receiver, the lower outwardly facing surface configured for side-to-side engagement with the inwardly facing surface of the retaining structure above the discontinuous internal surface, and the downwardly facing partial spherical surface to frictionally engage the head of the shank, wherein the compression insert is positionable within the central bore of the receiver prior to the shank and in overlapping engagement with the retaining structure, the compression insert being prevented from moving upwardly within the central bore by at least partial overlapping engagement with at least one downwardly facing planar surface formed in the receiver; and wherein after the head of the shank is captured within the retaining structure, the discontinuous internal surface extends above and below the maximum diameter of the head of the shank when the longitudinal axis of the shank is coaxial with a longitudinal axis of the receiver. ### Claim 11 (depends on 10) The pivotal bone anchor assembly of claim 10, wherein the retaining structure is resiliently expandable in the expansion region to capture the head of the shank when uploaded through the bottom opening. ### Claim 12 (depends on 10) The pivotal bone anchor assembly of claim 10, wherein the retaining structure is non-pivotal with respect to the receiver when the assembly is in an unlocked configuration. ### Claim 13 (depends on 10) The pivotal bone anchor assembly of claim 10, wherein upward movement of the retaining structure during the uploading of the head of the shank is restricted by engagement between a top surface of an upper portion of the retaining structure and an overlapping surface of the compression insert. ### Claim 14 (depends on 10) The pivotal bone anchor assembly of claim 10, wherein the retaining structure includes at least one vertical gap defined by spaced apart end surfaces. ### Claim 15 (depends on 10) The pivotal bone anchor assembly of claim 10, wherein the retaining structure frictionally engages the head of the shank upon capture within the cavity of the receiver to allow for an unlocked but non-floppy angular positioning of the shank with respect to the receiver prior to a final locking of the pivotal bone anchor assembly. ### Claim 16 (depends on 10) The pivotal bone anchor assembly of claim 10, wherein the shank includes a central opening along the longitudinal axis of the shank extending from a top end to a bottom end of the shank. ### Claim 17 (depends on 16) The pivotal bone anchor assembly of claim 16, wherein the top end of the shank includes a central internal drive structure surrounded by an annular flat top surface. ### Claim 18 (depends on 10) The pivotal bone anchor assembly of claim 10, further comprising the elongate rod and the closure, the closure having a helically wound guide and advancement structure formed into an outer sidewall surface and engageable with the closure-mating structure formed into the interior surfaces of the upwardly extending arms of the receiver to capture the elongate rod within the open channel. ### Claim 19 A method of assembling a pivotal bone anchor assembly configured to secure an elongate rod to a bone of a patient, the method comprising: position a retaining structure that is resiliently expandable at least partially within an upper expansion region of a receiver, the retaining structure having a discontinuous partial spherical internal surface and an inwardly facing surface above the discontinuous partial spherical internal surface, the receiver having a longitudinal axis, a lower body defining a cavity with a bottom opening, the upper expansion region, and a lower locking region, and a pair of upwardly extending arms with opposed interior surfaces that define an open channel to receive the elongate rod, the open channel communicating with the cavity to define a central bore, the interior surfaces of the open channel having a closure-mating structure formed therein, the central bore extending to a top of the receiver along the longitudinal axis; position a compression insert within the central bore of the receiver in a side-to-side overlapping engagement with the retaining structure, with the compression insert being prevented from moving upwardly within the central bore by at least partial overlapping engagement with at least one downwardly facing planar surface formed in the receiver, the compression insert including an upwardly facing surface sized and shaped to engage the elongate rod, an upper exterior surface to slidably engage an internal surface of the central bore of the receiver, a lower outwardly facing surface configured for side-to-side engagement with the inwardly facing surface of the retaining structure above the discontinuous partial spherical internal surface, and a downwardly facing partial spherical surface; after the retaining structure is at least partially within the upper expansion region of the receiver and the compression insert is positioned in the central bore of the receiver, upload a head of a shank into the cavity of the receiver through the bottom opening of the receiver, the head of the shank being partially spherical with a hemisphere, the shank including an anchor portion extending distally from the head to attach to bone; and after the uploading of the head through the bottom opening, capture the head of the shank within the discontinuous partial spherical internal surface of the retaining structure and in spaced relationship from an internal surface of the cavity of the receiver, with the discontinuous partial spherical internal surface extending above and below the hemisphere of the head of the shank. ### Claim 20 (depends on 19) The method of claim 19, further comprising causing the downwardly facing partial spherical surface of the insert to frictionally engage the head of the shank.