Growing rod for treating spinal deformities and method for using same

1 . An implantable growing rod assembly comprising:

a housing;

an internally threaded expansion tube mounted inside of the housing;

a fixed rod extending along a longitudinal axis away from the housing;

an expansion rod extendible from the housing along the longitudinal axis;

a bevel gear assembly disposed in the housing and adapted to translate the expansion rod along the longitudinal axis, the bevel gear assembly including a bevel output gear having a plurality of gear teeth arranged circumferentially about the longitudinal axis and rotatable about the longitudinal axis; and

a biased lock disposed in the housing and coupled to the bevel gear assembly, the biased lock including a locking bevel gear having a plurality of teeth arranged circumferentially around an axis which is lateral to the longitudinal axis and adapted to be coupled to the bevel output gear, the biased lock having a biased first position that prevents the bevel gear assembly from rotation and an unlocked second position configured to allow the bevel gear assembly to rotate to expand and collapse the expansion rod,

wherein the bevel gear assembly includes a bevel pinion gear having teeth at one end and arranged to rotate simultaneously with the locking bevel gear.

2 . The implantable growing rod assembly according to claim 1 , wherein the expansion rod comprises a threaded proximal end threadingly engaged with the internally threaded expansion tube.

3 . The implantable growing rod assembly according to claim 2 , wherein the expansion rod comprises a distal end adapted to extend outwardly from the housing.

4 . The implantable growing rod assembly according to claim 1 , wherein the bevel gear assembly is located in a housing cap between the housing and the fixed rod.

5 . The implantable growing rod assembly according to claim 4 , further comprising:

a first pinion bushing disposed between a bevel pinion gear and the housing; and

a second pinion bushing disposed between a lock gear and the housing.

6 . The implantable growing rod assembly of claim 5 , wherein the internally threaded expansion tube is formed of PEEK.

7 . The implantable growing rod assembly of claim 1 , further comprising:

a wave washer disposed between the housing and the lock and configured to exert an upward force on the lock to bias the lock towards the normally biased first position.

8 . The implantable growing rod assembly according to claim 1 , further comprising:

a keyed bushing disposed in the housing and wherein the expansion rod comprises a mating key located in the keyed bushing such that, as the expansion rod extends from the housing, the keyed bushing prevents the expansion rod from rotating.

9 . The implantable growing rod assembly according to claim 8 , wherein the keyed bushing includes four recesses, wherein the expansion rod includes four lobes configured to be disposed in corresponding ones of the four recesses to prevent rotation of the expansion rod relative to the keyed bushing, and wherein an outer surface of the keyed bushing includes a square shape to prevent rotation of the keyed bushing with respect to the housing.

10 . The implantable growing rod assembly according to claim 8 , wherein the keyed bushing includes an opening having a first dual-lobe shape, wherein the expansion rod includes two lobes corresponding to the first dual-lobe shape of the opening to prevent rotation of the expansion rod relative to the keyed bushing, and wherein an outer surface of the keyed bushing includes a second dual-lobe shape to prevent rotation of the keyed bushing with respect to the housing.

11 . An implantable growing rod assembly comprising:

a housing;

an internally threaded expansion tube mounted inside of the housing, wherein the internally threaded expansion tube is formed of PEEK;

a fixed rod extending along a longitudinal axis away from the housing;

an expansion rod extendible from the housing along the longitudinal axis;

a bevel gear assembly disposed in the housing and adapted to translate the expansion rod along the longitudinal axis, the bevel gear assembly including a bevel output gear having a plurality of gear teeth arranged circumferentially about the longitudinal axis and rotatable about the longitudinal axis; and

a biased lock disposed in the housing and coupled to the bevel gear assembly, the biased lock including a locking bevel gear having a plurality of teeth arranged circumferentially around an axis which is lateral to the longitudinal axis and adapted to be coupled to the bevel output gear, the biased lock having a biased first position that prevents the bevel gear assembly from rotation and an unlocked second position configured to allow the bevel gear assembly to rotate to expand and collapse the expansion rod,

wherein the bevel gear assembly includes a bevel pinion gear having teeth at one end and arranged to rotate simultaneously with the locking bevel gear.

12 . The implantable growing rod assembly according to claim 11 , wherein the expansion rod comprises a threaded proximal end threadingly engaged with the internally threaded expansion tube.

13 . The implantable growing rod assembly according to claim 12 , wherein the expansion rod comprises a distal end adapted to extend outwardly from the housing.

14 . The implantable growing rod assembly according to claim 11 , wherein the bevel gear assembly is located in a housing cap between the housing and the fixed rod.

15 . The implantable growing rod assembly according to claim 11 , further comprising:

a keyed bushing located in the housing and wherein the expansion rod comprises a mating key located in the keyed bushing such that, as the expansion rod extends from the housing, the keyed bushing prevents the expansion rod from rotating.

16 . The implantable growing rod assembly according to claim 15 , wherein the keyed bushing includes four recesses, wherein the expansion rod includes four lobes configured to be disposed in corresponding ones of the four recesses to prevent rotation of the expansion rod relative to the keyed bushing, and wherein an outer surface of the keyed bushing includes a square shape to prevent rotation of the keyed bushing with respect to the housing.

17 . The implantable growing rod assembly according to claim 15 , wherein the keyed bushing includes an opening having a first dual-lobe shape, wherein the expansion rod includes two lobes corresponding to the first dual-lobe shape of the opening to prevent rotation of the expansion rod relative to the keyed bushing, and wherein an outer surface of the keyed bushing includes a second dual-lobe shape to prevent rotation of the keyed bushing with respect to the housing.