External fixation
External fixation techniques for immobilizing joints or fractured bones are described herein. An external fixation system may include one or more clamp assemblies connected to one or more rod assemblies at polyaxial joints. Each rod assembly may be length adjustable, and may include a one-way locking mechanism to provisionally lock the length of the rod assembly, and additional locking mechanisms to permanently lock the length of the rod assembly. The system may be deployed pre-assembled as a unit to immobilize a joint or fracture. Another external fixation system further includes a spanning member extending transverse to the rod assemblies. Two or more external fixation systems may be deployed in a stacked configuration on one set of bone pins to immobilize two joints and/or fractures. The systems may be provided in kits including guiding instrumentation, bone pins and pin clamping assemblies for connecting the bone pins to the external fixation systems.
1. An external fixation system, the system comprising:
a first clamp assembly including a spherical clamping surface;
a second clamp assembly;
a first rod assembly secured to and extending between the first clamp assembly and the second clamp assembly, the first rod assembly including a first tubular member and a second tubular member received in the first tubular member, the first rod assembly including a spherical portion; and
a one-way locking mechanism which limits axial translation between the first tubular member and the second tubular member, the one-way locking mechanism having an unlocked configuration and a locked configuration;
wherein the spherical clamping surface is configured to at least partially surround the spherical portion and form a polyaxial joint between the first clamp assembly and the first rod assembly;
wherein the external fixation system has a length measured between the first clamp assembly and the second clamp assembly;
wherein when the one-way locking mechanism is in the unlocked configuration the second tubular member can freely translate relative the first tubular member to increase or decrease the length of the external fixation system; and
wherein when the one-way locking mechanism is in the locked configuration the second tubular member can freely translate relative to the first tubular member to increase the combined length of the external fixation system but is prevented from translating relative to the first tubular member to decrease the length of the external fixation system.
2. The external fixation system of claim 1 , comprising a second rod assembly secured to and extending between the first clamp assembly and the second clamp assembly, wherein the first clamp assembly is identical to the second clamp assembly, and wherein the first rod assembly is identical to the second rod assembly.
3. The external fixation system of claim 1 , wherein the second tubular member can axially translate in a first direction to increase the length of the external fixation system and in a second direction opposite the first direction to decrease the length of the external fixation system.
4. The external fixation system of claim 1 , wherein in the locked configuration the one-way locking mechanism engages the first rod assembly to prevent the length of the external fixation system from decreasing.
5. The external fixation system of claim 4 , wherein the one-way locking mechanism comprises a collar encircling the second tubular member, wherein, in the locked configuration, the collar binds against the second tubular member to prevent translation of the second tubular member in the second direction.
6. The external fixation system of claim 1 , wherein the one-way locking mechanism is a first locking mechanism, the system comprising a second locking mechanism to further prevent the second tubular member from any motion of the second tubular member relative to the first tubular member.
7. The external fixation system of claim 6 , comprising a third locking mechanism which engages the first and second tubular members.
8. The external fixation system of claim 1 , wherein the first clamp assembly comprises a locking screw, wherein tightening the locking screw compresses the spherical clamping surface around the spherical portion to lock the position of the first rod assembly relative to the first clamping assembly.
9. The external fixation system of claim 8 , comprising a second rod assembly comprising a second spherical portion, wherein the first clamping assembly comprises a second spherical clamping surface, the second spherical portion received within the second spherical clamping surface to form a polyaxial joint between the first clamp assembly and the second rod assembly, wherein tightening the locking screw simultaneously locks the positions of the first and second rod assemblies relative to the first clamping assembly.
10. The external fixation system of claim 1 , comprising a first bone pin, wherein the first clamping assembly houses a first fixation plate and a second fixation plate, wherein the first bone pin passes through the first fixation plate and the second fixation plate, and the first and second fixation plates are deformable to bind against the first bone pin and fix the position of the first bone pin relative to the first clamping assembly.
11. The external fixation system of claim 1 , comprising a removable tab attached to the one-way locking mechanism, wherein the removable tab holds the one-way locking mechanism in the unlocked configuration, wherein removal of the tab from the one-way locking mechanism converts the one-way locking mechanism to the locked configuration.
12. An external fixation system, the system comprising:
a first clamp assembly;
a second clamp assembly;
a first rod assembly secured to and extending between the first clamp assembly and the second clamp assembly, the first rod assembly including:
a first tubular member and a second tubular member received in the first tubular member; and
a first locking mechanism, the first locking mechanism comprising a clamp encircling the first tubular member, wherein the clamp is compressible about the first tubular member to compress the first tubular member around the second tubular member to prevent any motion relative to the first tubular member; and
a second locking mechanism which limits axial translation between the first tubular member and the second tubular member, the second locking mechanism being a one-way locking mechanism having an unlocked configuration and a locked configuration;
wherein the external fixation system has a length measured between the first clamp assembly and the second clamp assembly;
wherein when the one-way locking mechanism is in the unlocked configuration the second tubular member can freely translate relative the first tubular member to increase or decrease the length of the external fixation system; and
wherein when the one-way locking mechanism is in the locked configuration the second tubular member can freely translate relative to the first tubular member to increase the combined length of the external fixation system but is prevented from translating relative to the first tubular member to decrease the length of the external fixation system.
13. An external fixation system, the system comprising:
a first clamp assembly;
a second clamp assembly;
a first rod assembly secured to and extending between the first clamp assembly and the second clamp assembly, the first rod assembly including a first tubular member and a second tubular member received in the first tubular member;
a first locking mechanism which limits axial translation between the first tubular member and the second tubular member, the first locking mechanism being a one-way locking mechanism having an unlocked configuration and a locked configuration;
a second locking mechanism to further prevent the second tubular member from any motion of the second tubular member relative to the first tubular member; and
a third locking mechanism which engages the first and second tubular members, the third locking mechanism including a plug received in the second tubular member, wherein drawing the plug within the second tubular member expands a portion of the second tubular member to fit tightly within the first tubular member;
wherein the external fixation system has a length measured between the first clamp assembly and the second clamp assembly;
wherein when the one-way locking mechanism is in the unlocked configuration the second tubular member can freely translate relative the first tubular member to increase or decrease the length of the external fixation system; and
wherein when the one-way locking mechanism is in the locked configuration the second tubular member can freely translate relative to the first tubular member to increase the combined length of the external fixation system but is prevented from translating relative to the first tubular member to decrease the length of the external fixation system.