if it is a pneumatic system, the gas cylinder can be replaced, most chairs end with that piece damaged after 3 years
but maybe for some time you should avoid that chair and just sit on something different? what are you doing while you recover?
The chair I'm now using doesn't have a gas cylinder but is height adjustable through a screw in the lower platform. The main body of the chair is a molded contour butt bucket, with a rolled front over which the cushioning also rolls. The main part of the chair can also recline, but as a complete unarticulated unit, with a separate foot/leg rest that is now under the desk, so I can raise my feet or lean back as separate or combined actions.
I had one of those pneumatic height controlled chars in the past. It was quite comfortable and shaped much like the present chair. The cylinder didn't fail, but the welded plate that holds the cylinder did. My mother was sitting on the chair at the time it failed, and the cylinder came right up through the chair bottom.
Imagine, if you will, the expression on her face, and the whoop that accompanied it, when suddenly poked from below by that which was neither a pistol in a pocket, nor someone just happy to see her. She was not amused,. I was near hysterical with laughter.