Non-invasive adjustable distraction system
A spinal distraction system includes a distraction rod having a first end and a second end, the first end being configured for affixation to a subject's spine at a first location, the distraction rod having a second end containing a recess having a threaded portion disposed therein. The system further includes an adjustable portion configured for affixation relative to the subject's spine at a second location remote from the first location, the adjustable portion comprising a housing containing a magnetic assembly, the magnetic assembly affixed at one end thereof to a lead screw, the lead screw operatively coupled to the threaded portion. A locking pin may secure the lead screw to the magnetic assembly. An o-ring gland disposed on the end of the housing may form a dynamic seal with the distraction rod.
1. A spinal distraction system comprising:
a distraction rod having a first end configured for affixation to a subject's spine at a first location and a second end containing a recess having a threaded portion disposed therein; and
an adjustable portion configured for affixation to a subject's spine at a second location remote from the first location and comprising a housing coaxially containing at least a portion of a magnetic assembly affixed at one end thereof to a lead screw via a locking pin passing transversely through the lead screw and the magnetic assembly defining an interface between the magnetic assembly and the lead screw, the lead screw operatively coupled to the threaded portion of the distraction rod;
wherein upon a rotation of the lead screw and the magnetic assembly about a longitudinal axis, the lead screw is configured to communicate with the threaded portion of the distraction rod to move the distraction rod relative to the adjustable portion and change an axial length of the spinal distraction system, with the interface between the locking pin and the lead screw configured to allow the lead screw to pivot relative to the magnetic assembly, allowing the lead screw to align with the threaded portion and prevent jamming of the lead screw against the threaded portion.
2. The spinal distraction system of claim 1 , wherein the locking pin comprises heat treated stainless steel.
3. The spinal distraction system of claim 2 , wherein the locking pin maintains structural integrity up to tensile loads of 124 lbs.
4. The spinal distraction system of claim 3 , wherein the locking pin maintains structural integrity up to tensile loads of 350 lbs.
5. The spinal distraction system of claim 1 , wherein the magnetic assembly comprises a first cup and a second cup, the first cup comprising a receptacle having an aperture dimensioned to receive the locking pin.
6. The spinal distraction system of claim 5 , further comprising a bearing disposed about the receptacle and within the housing of the adjustable portion.
7. The spinal distraction system of claim 5 , wherein the receptacle is dimensioned to permit angular displacement of the lead screw relative to a longitudinal axis of the magnetic assembly.
8. The spinal distraction system of claim 1 , wherein the magnetic assembly comprises at least one rotatable magnet.
9. The spinal distraction system of claim 1 , the housing comprising a stop configured to limit advancement of the lead screw within the housing.
10. The spinal distraction system of claim 1 , wherein the magnetic assembly comprises a cylindrical magnet having a first length contained within a cavity formed between first and second cups, wherein the cavity has a length that is longer than the first length.
11. A spinal distraction system comprising:
a distraction rod having a first end configured for affixation to a subject's spine at a first location and a second end containing a recess having a threaded portion disposed therein;
an adjustable portion configured for affixation to a subject's spine at a second location remote from the first location and comprising a housing coaxially containing at least a portion of a magnetic assembly affixed at one end thereof to a lead screw by an interface comprising a locking pin passing transversely through the lead screw and the magnetic assembly, the lead screw operatively coupled to the threaded portion of the distraction rod; and
a recess disposed in an interior portion of the housing, the recess having at least one O-ring therein dimensioned to form a fluid tight seal between the housing and the distraction rod;
wherein upon a rotation of the lead screw and the magnetic assembly about a longitudinal axis, the lead screw is configured to communicate with the threaded portion of the distraction rod to move the distraction rod relative to the adjustable portion and change an axial length of the spinal distraction system, with the interface between the magnetic assembly and the lead screw configured to allow the lead screw to pivot relative to the magnetic assembly, allowing the lead screw to align with the threaded portion and prevent jamming of the lead screw against the threaded portion.
12. The spinal distraction system of claim 11 , wherein the at least one O-ring has a compression value that ranges from about 13% to about 18%.
13. The spinal distraction system of claim 11 , wherein the at least one O-ring is coated with a lubricant.
14. The spinal distraction system of claim 11 , wherein the fill volume of the recess containing the at least one O-ring is less than 75%.
15. The spinal distraction system of claim 11 , wherein an interior of the housing has a positive pressure with respect to an external environment.
16. The spinal distraction system of claim 11 , wherein the magnetic assembly comprises at least one rotatable magnet.
17. The spinal distraction system of claim 11 , wherein the fluid tight seal comprises an air tight seal.
18. The spinal distraction system of claim 13 , wherein the lubricant comprises silicone oil.
19. The spinal distraction system of claim 11 , wherein the at least one O-ring comprises ethylene propylene diene M-class rubber (EPDM).
20. The spinal distraction system of claim 11 , further comprising an external adjustment device and wherein the lead screw is configured to rotate in a first direction to increase a distraction force or distance and configured to rotate in a second, opposing direction to decrease a distraction force or distance.