Provided is an accumulator that may store energy within a pressurized inflatable nail to compensate for small changes or losses in a system volume. Alternatively, the accumulator may be external to a pressurized inflatable nail and attached to the nail after the nail is implanted. The accumulator may be comprise a piston or a pressurized bladder. The energy may be stored in a spring, compressed air, or other pressure source. The accumulator may stabilize a system pressure by supplying fluid to the closed system. Alternatively, the accumulator may stabilize a system pressure by replacing the volume of the lost fluid.
