Stem Extension Line (USTAR II System)

The Stem Extension Line (USTAR II System) is a knee and hip joint prosthesis system used to treat patients with severe bone loss and deformity from failed arthroplasty, trauma, tumor resection, or ligament deficiencies. It includes cemented and cementless components for knee and hip reconstruction in cases requiring massive resection and transplantation or revision surgery.

The device introduces two new size variations to the cleared USTAR II System: a cemented curved stem (RHS, non-coated, Ø17×200 mm) and tibial stems with lengths from 30 mm to 150 mm and diameters from Ø9 to Ø24. The design, materials, geometrical characteristics, locking mechanism, manufacturing process, and compatibility are identical to the predicate device; only the specifications differ.

Stem fatigue analysis per ISO 7206-4; mechanical strength analysis of tibial baseplate per ASTM F1800 and ISO 21536:2023.

Substantial equivalence is established because the subject device has identical intended use, design, materials, principle of operation, fixation method, surface coating, geometry design, locking mechanism, and sterilization method as the predicate USTAR II System (K190100). Design control activities validated that the new stem size specifications meet required acceptance criteria with no new risks compared to the predicate, based on mechanical analyses using the same methods as the prior submission.