Following landing at Melbourne Aerodrome from Adelaide on 20th October 2009, the crew of a Boeing 737-8FE aircraft, registration VHVUI, reported that the aircraft was difficult to taxi, requiring more power and steering input than usual. A subsequent visual inspection revealed the number-4 wheel to be oriented at an angle with respect to the axle and, following disassembly, it was discovered that the inner wheel hub and bearing mount had broken away from the wheel assembly.