On September 5, 2002, at 0640 central daylight time, a Fokker 100, N1473K, operated by American Airlines, Fort Worth, Texas, sustained minor damage when the number two main landing gear wheel separated from the axle during takeoff from Minneapolis-St. Paul International Airport (MSP), Minneapolis, Minnesota. Visual meteorological conditions prevailed at the time of the incident. The scheduled passenger flight was operating under the provisions of 14 CFR Part 121 on an instrument flight rules (IFR) flight plan. The flightcrew and passengers reported no injuries. The flight made an uneventful landing at Chicago O'Hare International Airport (ORD) at 0735. A company mechanic stated that during a walk-around inspection he noted the #1 and #2 main landing gear tires needed to be replaced. The #1 & #2 tires are on the left main landing gear assembly; with the #1 tire being outboard of the #2 tire. The mechanic reported, "We removed & replaced #2 main landing gear [tire], with nothing unusual during the tire change." The mechanic stated the #1 main landing gear tire was then replaced and "nothing unusual" was encountered during that tire change. During takeoff the #2 wheel separated from the left main landing gear assembly and was found near the end of runway 12L. The axle nut/spacer assembly was found with the wheel. The axle nut lock-bolts were found installed in the axle nut/spacer assembly with safety wire connecting the lock-bolts to the axle nut. The lock-bolts were not damaged. The interfacing threads between the axle nut/spacer assembly and the axle were not stripped and the treads were not worn. A demonstration of a wheel installation and a review of the installation procedures were performed at the request of the NTSB. In order for the lock-bolts to engage the axle keyslot, the axle nut/spacer assembly had to be properly torqued and wheel bearings seated.