My physician wants me to have fusion surgery. After surgery, will I be able to use the stairs?
Usually, walking up and down the stairs after surgery is not a problem. Your surgeon will probably want you to limit your bending, lifting, and twisting, however, to allow the fusion to heal properly. You will be given additional instructions and guidelines before and after your spine surgery to ensure a good recovery.
Activity and exercise-related guidelines to consider after your spinal fusion procedure

Walking is the best exercise after surgery and you need to walk daily. You should gradually increase the distance you walk and, if the weather permits, you may walk outside. Make sure you have someone walking with you to prevent falls.
You should be able to gradually increase the distance until you can walk about one mile within 1-2 months after surgery. Women must avoid high heels for the first month after surgery and you should not engage in any other exercise until instructed by your physician.
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Source: https://www.cedars-sinai.edu/