Should the position of the patellar component replicate the vertical median ridge of the native patella?
BACKGROUND
In total knee arthroplasty (TKA), the position of the patellar component can affect patellar tracking. However, the patellar component cannot always replicate the original high point of the patella because of anatomical variance. This study investigated whether altering the highest point of the patella can affect outcomes of primary TKA, especially in patients having a patella with a far-medialized median ridge.


METHODS
A retrospective review was performed for 177 knees (143 patients) treated with primary TKA between July 2011 and March 2014. Group 1 (34 knees) had the patellar component displaced over three millimeters from the median ridge, while Group 2 (143 knees) had the patellar component placed on the original median ridge position. The one-year follow-up outcomes were reviewed, including: patellar tilt angle, Knee Society Score, Feller Patellar Score, and modified Kujala Anterior Knee Pain Score.


RESULTS
Mean (±standard deviation) displacement of the patellar component in Group 1 was 3.97±0.97mm lateral to the original position of the median ridge, with a significant decrease in lateral patellar tilt angle (P<0.001). Lateral patellar tilt showed a positive correlation with the medialization of the patellar component (P<0.001, r=0.401). Ability to rise from a chair was better in Group 1 (P=0.025). There were no other between-group differences in other clinical outcomes.


CONCLUSIONS
There should be no need for the patellar component to replicate the original highest point of the native patella in primary TKA.
Department of Orthopaedic Surgery, Hanyang University College of Medicine, 222 Wangsimni-ro, Seongdong-gu, Seoul, Republic of Korea.
Rae Hyeong
RH
Lee
Department of Orthopaedic Surgery, Hanyang University College of Medicine, 222 Wangsimni-ro, Seongdong-gu, Seoul, Republic of Korea.
Hae Won
HW
Jeong
Department of Orthopaedic Surgery, Hanyang University College of Medicine, 222 Wangsimni-ro, Seongdong-gu, Seoul, Republic of Korea.
Jin Kyu
JK
Lee
Department of Orthopaedic Surgery, Hanyang University College of Medicine, 222 Wangsimni-ro, Seongdong-gu, Seoul, Republic of Korea. Electronic address: chhchoi@hanyang.ac.kr.
Choong Hyeok
CH
Choi
D000368:Aged; D000369:Aged, 80 and over; D019645:Arthroplasty, Replacement, Knee; D005260:Female; D006801:Humans; D007720:Knee Prosthesis; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000150:complications / Q000000981:diagnostic imaging / Q000601:surgery*; D010329:Patella / Q000000981:diagnostic imaging*; D011859:Radiography; D016059:Range of Motion, Articular; D020127:Recovery of Function; D012189:Retrospective Studies; D016896:Treatment Outcome
Patellar component; Patellar tracking; Total knee arthroplasty