mXACT Total Prosthesis Offcenter, mXACT Total Prosthesis Center and mXACT PRO Total Prosthesis Kit

The mXACT Total Prosthesis devices are passive middle ear implants (ossicular replacement prostheses) designed to restore sound transmission from the tympanic membrane to the oval window by replacing the ossicles. They are implanted in patients with congenital or acquired ossicular chain defects or inadequate hearing from previous middle ear surgery, provided the stapes footplate is present and functional. The devices are single-use, sterile implants intended for use by qualified ENT surgeons.

The MED-EL devices use medical-grade titanium construction with a cannulated stem for stability on the stapes footplate and are available in fixed (Offcenter and Center variants) or adjustable (PRO variant with snap-mechanism) functional lengths ranging from 3.0–7.0 mm. Key differences from predicates include a slit-headplate design allowing optional bending and a snap-closing mechanism for length adjustment, versus the predicate's plastic deformation headplate. All devices share identical headplate dimensions, shaft staging, biocompatibility, and MRI conditional compatibility at 1.5T, 3.0T, and 7.0T.

Testing followed EN ISO 10993 (biocompatibility), EN ISO 11137-1 and 11137-2 (sterilization validation with gamma irradiation to <10⁶ SAL), EN ISO 11607 (shelf-life and packaging validation), ASTM F2119, F2052, and F2182 (MRI environment compatibility), and mechanical testing.

The devices are substantially equivalent because they treat the same ossicular chain defects using identical intended use, method of attachment (cannulated stem placement on stapes footplate), materials (medical-grade titanium), and similar design principles as the predicate devices. Clinical data from 92 patients showed 53.3% achieving postoperative air-bone gap closure ≤20 dB, comparable to the state-of-the-art benchmark of 48.3–57.4%, with low adverse event rates (4 total in 102 patients, including only 1 device dislocation and 3 revision surgeries). The snap-closing headplate mechanism represents an improvement over the predicate's requirement for special surgical closing tools, confirmed through non-clinical testing, thus raising no new safety or effectiveness concerns.