Selectively lockable ball and socket joint
A ball and socket joint assembly is disclosed that includes a body defining a cavity, a collet disposed in the cavity to receive a ball of a connector, and an actuator shaft coupled to the collet for rotating and translating the collet in the cavity. The cavity has a distal opening to accept the ball and an engagement feature extending into the cavity. The collet has an outer diameter larger than the opening in the body when the ball is disposed in the collet, and the collet has a corresponding engagement feature around at least a portion of the outer surface for receiving the engagement feature and converting rotation of the compression member into translation of the compression member along a proximal-distal axis of the body. The collet is compressed against the opening of the cavity when the collet is advanced distally against the opening.
1. A ball and socket joint assembly comprising:
a housing defining a cavity and a distal opening to the cavity, the distal opening having a diameter larger than a diameter of a spherical portion of a connector and less than a diameter of an inner wall of the cavity proximal to the distal opening, the housing comprising an engagement feature extending into the cavity;
a compression member disposed in the cavity, a distal end of the compression member comprising a collet configured to accept the spherical portion of the connector, the collet defining an outer diameter that is configured to be larger than the diameter of the distal opening in the housing when the spherical portion is disposed in the collet, and the compression member comprising an outer surface defining a corresponding engagement feature around at least a portion of the outer surface for receiving the engagement feature of the housing; and
wherein the engagement feature of the housing and the corresponding engagement feature of the compression member are configured to define a first configuration in which the compression member is free to translate along a longitudinal axis of the housing and a second configuration in which rotation of the compression member causes translation of the compression member to compress the collet against the distal opening of the cavity.
2. The assembly of claim 1 , wherein, after inserting the spherical portion of the connector into the collet, rotation of the compression member in a first direction and engagement between the engagement feature of the housing and the corresponding engagement feature of the compression member advances the compression member distally, and, when advanced distally, the collet engages the distal opening of the cavity and locks the collet about the spherical portion.
3. The assembly of claim 1 , wherein the cavity defines an outwardly tapered inner wall region extending proximally from the distal opening.
4. The assembly of claim 1 , wherein a distal end of the compression member defines a plurality of resilient fingers each having a tapered exterior surface configured to interface with the outwardly tapered inner wall region of the cavity when the compression member is advanced distally, the outwardly tapered inner wall region constricting the plurality of resilient fingers.
5. The assembly of claim 1 , wherein the engagement feature is a cam pin and the corresponding engagement feature comprises an angled locking channel sized and shaped to receive the cam pin.
6. The assembly of claim 5 , wherein the angled locking channel defines a variable pitch to provide a variable mechanical advantage during rotation of the compression member with respect to the cam pin, when the cam pin is disposed in the angled locking channel.
7. The assembly of claim 5 , wherein the angled locking channel comprises one or more divots or straight sections at one or more circumferential locations, each divot or straight section defining a predetermined level of friction between the collet and the distal opening of the housing.
8. The assembly of claim 1 , wherein the outer surface of the compression member further comprises an axial channel for receiving the engagement feature of the housing and allowing the compression member to translate freely along the longitudinal axis in the cavity, and the corresponding engagement feature of the compression member extends from the axial channel and is angled proximally from the axial channel.
9. The assembly of claim 8 , comprising a spring disposed in the housing, the spring being coupled to the housing and the compression member for biasing the compression member towards the distal opening.
10. The assembly of claim 8 , wherein the spring is configured to urge the collet against the distal opening and impart a drag force on the spherical portion for resisting polyaxial movement of the spherical portion about the collet.
11. The assembly of claim 8 , wherein the spring is configured to urge the collet against the distal opening and impart a retaining force on the spherical portion.
12. The assembly of claim 1 , wherein the engagement feature of the housing comprises a threaded portion of the inner wall of the cavity, and the corresponding engagement feature of the compression member comprises a corresponding threaded portion of the outer wall of the compression member, wherein the compression member is in threaded engagement with the housing.
13. The assembly of claim 1 , wherein the collet is configured to passively secure the spherical portion of the connector without engaging the distal opening of the housing.
14. The assembly of claim 1 , wherein the collet is configured to extend distally beyond a maximum diameter location of the spherical portion of the connector.
15. The assembly of claim 1 , wherein the collet defines a distal opening having an inner diameter less than a maximum inner diameter of the collet.
16. The assembly of claim 1 , further comprising an actuator shaft coupled to the compression member and configured to rotate the compression member in the cavity.
17. A surgical instrument, comprising:
a retractor body configured to couple to an implantable anchor; the retractor body comprising a first coupling feature and a second coupling feature;
a first tissue manipulating implement comprising a first connector having a spherical portion coupled to the first coupling feature of the retractor body and capable of polyaxial movement relative thereto; and
a second tissue manipulating implement comprising a second connector having a spherical portion coupled to the second coupling feature of the retractor body and capable of polyaxial movement relative thereto;
wherein each of the first and second tissue manipulating implements couples to the corresponding coupling feature via the ball and socket joint assembly of claim 1 , wherein each of the first and second coupling features comprises the housing of the ball and socket joint assembly.
18. The instrument of claim 17 , wherein each of the first and second connectors comprises an extension post coupled to the first or second tissue manipulating implements.
19. A method of assembling a surgical instrument, the method comprising:
inserting a spherical portion of a connector into a collet of a compression member disposed within a cavity of a body, the connector being attached to a body of a surgical retractor, the spherical portion passing through a distal opening to the cavity that has a diameter larger than a diameter of the spherical portion of a connector and less than a diameter of an inner wall of the cavity proximal to the opening;
rotating the compression member with respect to an engagement feature of the body that extends into the cavity, the engagement feature interfacing with the compression member such that the rotation of the compression member urges the compression member distally in the cavity; and
continuing to rotate the compression member until an outer surface of the collet is compressed against the opening of the cavity and an inner surface of the collet is compressed around the spherical portion to retain the spherical portion in the collet.
20. The method of claim 19 , wherein inserting the spherical portion into the collet includes urging the compression member proximally against a spring force, wherein the spring force urges the compression member distally towards the opening after the inserting.