Distinctive Polyethylene Damage in Rotating-Platform Total Knee Arthroplasty: A Comparative Retrieval Study in...

Area of Science:

• Orthopedic Surgery
• Biomedical Engineering
• Materials Science

Background:

• Mobile-bearing rotating-platform total knee arthroplasty (TKA-RP) may be sensitive to asymmetric flexion gaps.
• Improper balancing can lead to polyethylene insert instability in TKA-RP.
• A distinct polyethylene damage pattern associated with TKA-RP clinical failure was investigated.

Purpose of the Study:

• To identify a characteristic polyethylene insert damage pattern in TKA-RP associated with clinical instability.
• To correlate observed damage patterns with biomechanical predictions of dynamic instability.

Main Methods:

• Analysis of nine TKA-RP revisions for symptomatic flexion instability (clinical cohort).
• Random selection of 30 TKA-RPs from a revision retrieval database (registry cohort).
• Inspection and categorization of polyethylene inserts using the modified Hood method.

Main Results:

• Seven of nine clinical cohort inserts showed postero-lateral polyethylene damage, from minor wear to gross deformation.
• Eight of 30 registry cohort inserts exhibited similar postero-lateral damage patterns.
• Instability symptoms were reported by nine registry patients; similar damage was seen in eight.

Conclusions:

• A distinctive postero-lateral polyethylene damage pattern was observed in 15 of 18 TKA-RP inserts with clinical instability.
• This damage suggests posterior condyle subluxation over the insert's peripheral wall.
• Aseptic loosening did not prevent the occurrence of this hallmark damage pattern.