Zimmer Biomet’s Freedom Constrained Liner offers a high level of
constraint for joint stability without the trade-off of having to
sacrifice range of motion. A versatile implant system tailored to meet
patients’ needs, the Freedom system has performed well in clinical
trials, resisting dislocation in the early term when patients are most prone.1-3
Freedom Constrained Acetabular Liners feature:
- 36mm head for range of motion up to 114° to reduce risk of
impingement and further dislocation3
- Pre-assembled constraining ring to maximize lever-out force of
the head and allow for easy assembly in-situ1-2
- Multiple liner configurations to meet the demands of chronic
- Clinically proven locking
mechanism2,4,5 used with G7 and RingLoc®
The first generation of constrained liners relied almost exclusively
on a metal constraining ring to provide stability and prevent
dislocation. Zimmer Biomet’s Freedom Constrained Liner System takes
this design two steps further to a new level of tri-mode stabilization:
1. Modular Head Equatorial Flats
Circumferential flats along the head permit easier reduction and
provide an extremely strong construct that actively counters the
distractive forces that can lead to hip dislocation.
2. Titanium Constraint Ring
The traditional titanium constraint ring supplements the liner’s
inherent stability by increasing resistance to lever-out under high
3. Hydraulic Stabilization
Tightly controlled manufacturing tolerances recreate a natural fluid
membrane between the head and liner, resulting in a “suction effect”
that further minimizes the possibility of dislocation1
Product Feature References:
- Berend, K,, et al. A Constrained Device with Increased Range
of Motion Prevents Early Dislocation.Clinical Orthopedics and
Related Research. 447: 705, 2006.
- Tradonsky, Set al.
Performance Characteristics of Twopiece Acetabular Cups Series II.
Scientific Exhibit. 62nd Annual AAOS Meeting. 1996.
on file at Biomet. Bench test results not necessarily indicative of
- Fehring,T. et al. Motion at the
Modular Acetabular Interface: A Competitive Study. Scientific
Exhibit. 62nd Annual AAOS Meeting.1996.
- The Danish Hip
Arthroplasty Register, 2011 Annual Report, confirms 15-year
survivorship at 98.1% for the Ranawat-Burstein RingLoc cup