A twin Cessna pilot reported left main landing gear failure during landing resulting in a runway excursion into a snowbank.

Narrative

Aircraft was performing the first flight after maintenance (annual inspection). Pre-flight was extensive; no issues found. Systems check and run-up also extensive. Everything worked as it should; no problems noted. My plan was to depart runway XX and make one trip around the pattern with a full stop landing. At that time I would shut down and re-inspect the exterior of the aircraft. If everything looked good I would depart for a longer flight. On downwind abeam the touchdown point I lowered the landing gear. After gear extension I had an unsafe light and no green down and locked light for the left main landing gear. I then left the pattern and performed an emergency extension of the landing gear using the Cessna checklist. the left main gear still showed unsafe. At this point I called the airport manager on the CTAF frequency. He agreed to look at my gear during a flyby. He said that the gear was down but unable to verify if its locked. He also stated that the gear door was stuck halfway open and closed. With the manager standing by I returned to land; hoped for simply an indication problem but planned for a main gear failure. Failure it was; upon landing I felt the left gear give way. using the ailerons I held the wing of the ground as long as possible. After it contacted the ground differential braking stopped the aircraft mostly on the runway. The tip tank ended up settling on a snow bank and this greatly reduced the damage to the aircraft. The failure at this point appears to be caused by a failure of a threaded rod bearing end.