Posterior Shift of Contact Point between Femoral Component and Polyethylene in the LCS Rotating Platform Implant under Weight Bearing Condition.
OBJECTIVE
To analyze the contact mechanics of the femoral component and polyethylene of the Low Contact Stress rotating platform (LCS-RP) in nonweight bearing and weight bearing conditions using full flexion lateral radiographs.


METHODS
From May 2009 to December 2013, 58 knees in 41 patients diagnosed with osteoarthritis and treated with total knee arthroplasty (TKA) were included in this study. TKA was performed using an LCS-RP knee prosthesis. Full flexion lateral radiographs in both weight bearing and nonweight bearing condition were taken at least one month postoperatively (average, 28.8 months). Translation of femoral component was determined by the contact point between the femoral component and polyethylene. Maximum flexion was measured as the angle between the lines drawn at the midpoint of the femur and tibia.


RESULTS
Posterior shift of the contact point in LCS-RP TKA was observed under weight bearing condition, which resulted in deeper flexion compared to LCS-RP TKA under nonweight bearing condition.


CONCLUSIONS
In the LCS-RP TKA, the contact point between the femoral component and polyethylene moved posteriorly under weight bearing condition, and the joint was more congruent and maximum flexion increased with weight bearing.
Department of Orthopaedic Surgery, Shim Jeong Hospital, Seoul, Korea.
Won Seok
WS
Oh
Department of Orthopedic Surgery, Seoul National University Bundang Hospital, Seongnam, Korea.
Yong Seuk
YS
Lee
Department of Orthopaedic Surgery, Gacheon University Gil Medical Center, Incheon, Korea.
Byung Kak
BK
Kim
Department of Orthopaedic Surgery, Gacheon University Gil Medical Center, Incheon, Korea.
Jae Ang
JA
Sim
Department of Orthopaedic Surgery, Gacheon University Gil Medical Center, Incheon, Korea.
Beom Koo
BK
Lee
Arthroplasty; Contact point; Knee; Osteoarthritis; Rotating platform