PS Knee Replacement

Posterior Stabilized (PS) Knee Replacement

A posterior stabilized knee replacement is a type of total knee replacement (TKA) where the posterior cruciate ligament (PCL) is removed and replaced with a post-cam mechanism in the implant. This mechanism prevents the femur from sliding too far back on the tibia during knee flexion and is a common alternative to cruciate-retaining TKA.

Key Features of PS TKA:

Cruciate Sacrifice:
Unlike cruciate-retaining TKA, the PS design involves removing the PCL during surgery.

Post-Cam Mechanism:
The core of the PS design is the interaction between the tibial post and the femoral cam. This mechanism engages as the knee bends, guiding femoral rollback and preventing posterior tibial subluxation.

Advantages of PS TKA:

• Improved Stability: The post-cam mechanism provides enhanced stability, particularly in preventing posterior tibial subluxation.
• Potential for Increased Range of Motion: PS designs can allow for greater range of motion compared to older TKA designs.
• Comparable Outcomes to CR-TKA: Long-term outcomes like pain relief, function, and survivorship are comparable to cruciate-retaining TKA.

Disadvantages of PS TKA:

• Bone Resection: More bone needs to be removed to accommodate the femoral box for the cam mechanism, which may be a concern for younger patients or future revisions.
• Tibial Post Fracture: Rare complication, especially in cases of high impact or certain implant designs.
• Potential for Stiffness: Some patients may experience postoperative stiffness (not unique to PS TKA).

When is PS TKA Used?

• Severe Osteoarthritis and Other Conditions: Commonly performed for advanced arthritis or cases like rheumatoid or psoriatic arthritis.
• PCL Compromised: Preferred when the posterior cruciate ligament is damaged or insufficient.
• Knee Balancing: Sometimes chosen for overall balancing when the PCL is unable to provide adequate support.

In summary:
Posterior stabilized knee replacement offers effective stability and function for patients with compromised PCL, though it requires careful consideration of bone resection and rare complications.