2015 ISAKOS Biennial Congress ePoster #1435

Patellar Clunk Syndrome After Current High Flexion Total Knee Arthroplasty With Minimally Invasive Surgery

Masayoshi Okuda, MD, PhD, Yao, Osaka JAPAN
Katsuya Ito, MD, PhD, Yao, Osaka JAPAN
Yasuhito Tanaka, Prof., Kashihara, Nara JAPAN
Yoshiyuki Fujisawa, MD, Nara, Nara JAPAN

Ishinkai-Yao General Hospital , Yao, Osaka, JAPAN

FDA Status Not Applicable

Summary: We investigated causative factor of patellar clunk syndrome after high flexion total knee arthroplasty. A total of 163 patients using the NexGen LPS-Flex prosthesis were examined. Four knees were diagnosed with patellar clunk syndrome. The mean postoperative flexion angle was 147.5°.An excellent range of motion like this prosthesis can result in patellar clunk syndrome.

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Abstract:

Purpose

Patellofemoral pain, crepitus, and clunk syndrome are infrequent symptoms with occur after total knee arthroplasty. They are primarily associated with implantation of posterior-stabilized designs. These occurrences are the result of peripatellar fibrosynovial hyperplasia at the junction of the superior edge of the patella and the distal quadriceps tendon which becomes entrapped within the superior aspect of the intercondylar box of the femoral component during knee flexion. When the knee extends, a crepitant sensation occurs as the fibrosynovial tissue exits the intercondylar box. Second and third generation posterior-stabilized femoral components have typically been designed with a decreased intercondylar box ratio for a resultant decrease in the incidence of patellar clunk and crepitus. It has been proposed that the etiology of patella clunk syndrome is multi-factorial. We investigated the incidence of patellar clunk syndrome after current high flexion total knee arthroplasty with minimally invasive surgery and considered the causative factor of this syndrome.

Methods

A total of 163 patients( 124 women, 39 men; average age 73.4 years), in whom 185 consecutive fixed-bearing total knee artroplasties were performed using the NexGen LPS-Flex prosthesis( Zimmer, Warsaw, IN, America), were examined postoperatively to check for the presence of patellar clunk during knee extension. The patella had been resurfaced in all of the knees. Radiographic analysis was performed in patients who experienced patellar clunk.

Results

Four knees were diagnosed with patellar clunk syndrome( incidence 2.2%). The mean onset timing of symptoms was 8 months(range 5-12months), and the mean postoperative flexion angle was 147.5°(range 140°-155°). All of them were capable of high-level activity of daily living and deep flexion of the knees. Joint line changes, patella thickness, patellar height and tilting angle of patella were within the normal range.

Conclusions

Although the MIS approach resulted in increased knee flexion, this approach was indirectly associated with the increased incidence of patella clunk. The position of the box seemed to be one of the factors affecting patellar clunk syndrome. The modifications made to the NexGen LPS femoral component were a raised lateral flange, deepened trochlear groove, and a lengthened trochlear groove resulting in a more posteriorly positioned intercondylar box and a reduced intercondylar box ratio. The NexGen LPS-Flex prosthesis was considered to have no patellar clunk. Even, an excellent range of motion like this prosthesis can result in patellar clunk syndrome. Together with a lot of factors, achieving deep flexion may also be a relevant factor for patellar clunk syndrome.