Difficulties with bearing dislocation and breakage using a movable bearing total knee replacement system

Area of Science:

• Orthopedic Surgery
• Biomedical Engineering
• Materials Science

Background:

• The New Jersey low contact stress system was developed to address loosening and wear in conventional knee replacements.
• It utilizes movable high-density polyethylene bearings between metallic femoral and tibial components.

Purpose of the Study:

• To evaluate the long-term efficacy and failure rates of the New Jersey low contact stress knee system.
• To compare the outcomes of cemented versus cementless fixation in this specific knee arthroplasty system.

Main Methods:

• A two-phase study evaluating cemented and cementless fixation of the New Jersey system.
• Cemented components were implanted in 40 knees (1981-1984) and followed for an average of seven years.
• Cementless components were implanted in 16 knees (1984-1986) and followed for an average of five years.

Main Results:

• The cemented group experienced a 10% failure rate (loosening, dislocation, infection).
• The cementless group had a 31% failure rate, primarily due to bearing fracture and knee pain.
• Bearing failures were linked to subluxation, particularly when the anterior cruciate ligament was compromised.

Conclusions:

• The New Jersey system demonstrated significant failure rates in both cemented and cementless configurations.
• Bearing subluxation and subsequent failure are critical concerns, especially in knees with compromised anterior cruciate ligaments.
• Further investigation into bearing design and fixation methods is warranted for improved outcomes in total knee arthroplasty.