Mpact Constrained Liner

The Mpact Constrained Liner is an acetabular preassembled liner made of UHMWPE with an incorporated bipolar head, used in uncemented total hip arthroplasty for patients at high risk of hip dislocation. It is intended for primary or revision patients with history of prior dislocation, bone loss, soft tissue laxity, neuromuscular disease, or intraoperative instability, and should only be used in patients with limited functional demand due to its smaller range of motion compared to standard components.

The device shares general design, bipolar head design, range of sizes, range of motion, locking mechanism, materials, biocompatibility, device usage, packaging, and sterilization method with predicate devices. Minor differences exist in thickness measures (larger in the subject device) and shelf-life, neither of which pose safety or performance risks.

EN ISO 21535 (hip-joint replacement implants), ASTM F2582-20 (dynamic impingement testing), ASTM F1820-22 (modular acetabular device disassembly forces), ISO 14242-1 (hip prosthesis wear testing), ASTM F732 (polymeric material wear testing), ISO 11737-3 (bacterial endotoxin testing), USP <151> (pyrogenicity in rabbits), and European Pharmacopoeia §2.6.14.

The Mpact Constrained Liner is substantially equivalent because it incorporates the same fundamental design principles, materials (UHMWPE with bipolar head), and intended use as the predicate devices (Trident Constrained Acetabular Insert and R3 Constrained Liner). Although thickness measures differ, they are larger and thus safer. The shelf-life is shared with other cleared Medacta devices with equivalent manufacturing materials and production processes. Performance testing confirms acceptable range of motion, wear characteristics, and mechanical integrity comparable to predicates.