Orthopedic growing devices

An expandable rod system comprising:

• a first rod portion having an internal cavity;
• a second rod portion sealingly positioned within the internal cavity of the first rod portion, and moveable in a first axial direction relative to the first rod portion;
• an osmotic chamber for receiving an osmotic agent to facilitate movement of the second rod portion to expand the rod system;
• a semi-permeable membrane fluidly connected to the osmotic chamber for allowing water flow across the semi-permeable membrane and into the osmotic chamber;
• a lock assembly engageable with the second rod portion to prevent the second rod portion from moving in a second axial direction, the lock assembly including a tapered ramped portion and a bearing member, when the rod system is in a locked configuration, the bearing member is wedged in the tapered ramped portion and bears on the second rod portion to lock the second rod portion relative to the first rod portion;
• and
• an access hole to permit access of an instrument through the access hole such that when the bearing member is wedged in the tapered ramped portion, the instrument may dislodge the bearing member from the tapered ramped portion.