Arthroscopic procedures seldom bring such presentations. It may be due to nerve compression due to positioning during the procedure which usually gets resolved in four to six weeks time. Consult with a physiotherapist who can check the nerve conduction with diagnostic electrical stimulation. A nerve conduction study may also be done to know the extent of innervation. Mobilisation of the thumb in normal range and stimulation will help in delaying any unwanted change. You may also consult with a neurologist for a second opinion.