Expanders for rod retraction
In one embodiment, an expander set includes a first and second expander. The first expander includes an outer surface having a first engagement feature and a groove and the second expander includes an inside surface having a second engagement feature adapted to engage with the first engagement feature. The inside surface of the second expander is shaped to correspond to a portion of the outer surface of the first expander. Additionally, the groove on the outer surface of the first expander is sized and shaped to accommodate a rod of a retraction system such that when the first expander is advanced within the retraction system, the rod remains within the groove. When the first and second expanders are engaged with one another, they define an oblong cross-section.
1 . An expander comprising:
an elongate rod positioned within a void defined between a first portion and a second portion that each extend between a proximal end and a distal end to enclose the elongate rod;
a first spring secured to:
(i) the elongate rod at a first block, and
(ii) the second portion at a second block, so as to be biased outwardly in response to longitudinal movement of the elongate rod;
a second spring secured to:
(iii) the elongate rod at a third block, and
(iv) the second portion at a fourth block so as to be biased outwardly in response to longitudinal movement of the elongate rod;
whereby moving the elongate rod longitudinally causes the first and third blocks to move towards the second and fourth blocks thus biasing the first and second springs outwardly into engagement with the first portion so as to urge the first portion away from the second portion thereby enlarging the void defined between the first portion and the second portion.
2 . The expander of claim 1 wherein an outer surface of each of the first portion and the second portion define a plurality of elongate grooves each being suitable to receive one of a plurality of elongate rods of a retractor system.
3 . The expander of claim 1 , wherein the first and second blocks each comprise a protrusion extending inwardly toward the void located between the first portion and the second portion.
4 . The expander of claim 1 , wherein the first spring is connected to the first portion at a location between the first block and the second block.
5 . The expander of claim 1 , wherein the second spring is connected to the first portion at a location between the third block and the fourth block.
6 . The expander of claim 1 , further comprising the upper and lower portions having an unbiased outer surface with a radius of 10 mm.
7 . An expander comprising:
a central member positioned within a region defined between an upper portion and a lower portion so as to extend between a proximal end and a distal end;
a knob located at the proximal end of the central member configured to be moved in a proximal direction;
a first spring secured to:
(i) the central member at a first block, and
(ii) the lower portion at a second block, so as to be biased outwardly in response to proximal urging of the knob;
a second spring secured to:
(iii) the central member at a third block, and
(iv) the lower portion at a fourth block so as to be biased outwardly in response to proximal urging of the knob;
whereby moving the knob proximally causes the central member to move in the proximal direction so that the first and third blocks move towards the second and fourth blocks thus biasing the first and second springs outwardly into engagement with the upper portion so as to move the upper portion away from the lower portion thereby enlarging the region defined between the upper portion and the lower portion.
8 . The expander of claim 7 wherein an outer surface of each of the upper portion and the lower portion each a plurality of elongate grooves each suitable to receive and engage one of a plurality of elongate rods of a retractor system.
9 . The expander of claim 7 , wherein the first and second blocks each comprise a protrusion extending inwardly toward the region located between the upper portion and the lower portion.
10 . The expander of claim 7 , wherein the first spring is connected to the upper portion at a location between the first block and the second block.
11 . The expander of claim 7 , wherein the second spring is connected to the upper portion at a location between the third block and the fourth block.
12 . The expander of claim 7 , further comprising a compressed position of the upper and lower portions having an outer surface with a radius of 10 mm.
13 . A method for creating a portal in a body of a patient comprising:
(a) advancing a retractor including a plurality of rods into the body of the patient;
(b) inserting an expander into the retractor, the expander comprising a movable central member positioned within a region defined between an upper portion and a lower portion so as to extend between a proximal end and a distal end, an outer surface of each of the upper portion and the lower portion defining a plurality of elongate grooves each suitable to receive and engage one of the plurality of rods;
a first spring secured to:
(i) the central member at a first block, and
(ii) the lower portion at a second block, so as to be biased outwardly in response to proximal urging of the central member;
a second spring secured to:
(iii) the central member at a third block, and
(iv) the lower portion at a fourth block so as to be biased outwardly in response to proximal urging of the central member;
(c) moving the central member proximally so that the first and third blocks move towards the second and fourth blocks thus biasing the first and second springs outwardly into engagement with the upper portion thereby moving the upper portion away from the lower portion so that grooves on the outer surfaces engage corresponding rods causing the rods to move apart from one another increasing a size of a portal defined by an area between the rods.
14 . The method of claim 13 , further comprising a cylindrical tube having a smooth outer surface corresponding to an inner surface of the expander.
15 . The method of claim 13 , further comprising a tissue retaining ring having an oblong shape and an opening therein sized so that a plurality of expanders are disposable within the opening, an outer surface of the tissue retaining ring including a second groove located in alignment with the first groove of the first expander such that a rod engageable with the first groove is also engageable with the second groove when the tissue retaining ring is inserted over the expanders.
16 . The method of claim 15 , wherein the tissue retaining ring further comprises a recess on an inner surface defining the opening, the recess shaped to accommodate the securement of a ring configured to generate light.
17 . The method of claim 13 , wherein the first and second blocks each comprise a protrusion extending inwardly toward a void located between the first portion and the second portion.
18 . The method of claim 13 , wherein the first spring is connected to the first portion at a location between the first block and the second block.
19 . The method of claim 13 , wherein the second spring is connected to the first portion at a location between the third block and the fourth block.
20 . The method of claim 13 , further comprising the upper and lower portions having an outer surface with a radius of 10 mm.