The effects of femoral component design on the patello-femoral joint in a PS total knee arthroplasty

Abstract

without need of reoperation for any reason was 98 % at 3 years minimum follow-up; two reoperations were done for removal of fibromatous intra-articular tissue ("Clunk syndrome"). There were no revisions for septic or aseptic loosening of the components. The mean rOM improved from 104° preoperatively to 115° (97°-132°) postoperatively: postoperative flexion was 120° or more in 58 % of the knees. Severe anterior knee pain was present in 9 % of patients. radiographic evaluation showed 90 knees with a tibio-femoral anatomical axis between 8° and 2° of valgus (±3° from the intraoperative goal). CT evaluation of 30 consecutive knees showed that the femoral component positioning in relationship to the trans-epicondylar axis had only 2.80° of external rotation (±2.10°) with respect to a planned external rotation of 3°. This difference was statistically significant. Conclusions Although the pFC Sigma pS system provides good and predictable results for tricompartmental arthritis of the knee, anterior mechanism complications still represent a reason for dissatisfaction in a substantial group of patients.

Analysis of differences in bone removal during femoral box osteotomy for primary total knee arthroplasty

“…Because of these patellofemoral problems, the PFC-Sigma femoral component was re-designed, becoming available in 2009 under the name PFC Sigma PS (DePuy). The principal modifications regarding the PS housing design included a "J curve" femoral design, a new femoral box and smoother trochlear groove edges: these design changes provided a better patellar route during ROM (5). The Sigma PS implant shows an in vivo posterior post-cam engagement at an average of 93º of flexion (14).…”

“…Femoral box osteotomy in primary tKa several potential disadvantages of PS designs with respect to other CR implants, and these include tibial post wear and breakage (4), increased incidence of anterior knee pain (5), and implant instability, especially during the flexion phase (6). One of the main disadvantages of PS designs (compared with CR implants) is also linked to the amount of bone removed during femoral osteotomy to create the housing of the PS mechanism (box osteotomy).…”

Primary posterior stabilized total knee arthroplasty: analysis of different instrumentation

“…Because of these patello-femoral issues, the PFC Sigma femoral component was redesigned, becoming available in 2009 under the name PFC Sigma PS (DePuy Orthopaedics Inc., Warsaw, IN, USA). The new principal modifications regarding the PS housing design included a ‘J curve’ femoral design, a new femoral box, and smoother trochlear groove edges: these design changes provided a better patellar route during ROM [5]. The Sigma PS implant shows an in vivo posterior cam-post engagement at an average of 93° [16].…”

“…A decrement in patello-femoral contact pressure in PS TKA designs when compared to CR designs is another potential advantage [3]. There are several potential disadvantages in the use of PS designs with respect to other CR implants, including tibial post wear and breakage [4], increased incidence of anterior knee pain [5], and implant instability especially during the midflexion phase [6]. …”

No reduced patellar loading with latest-generation cruciate-retaining total knee arthroplasty—a comparative study of Attune and Press-Fit Condylar®

“…Anterior knee pain (AKP) and poor range of motion are two of the most commonly experienced problems after total knee arthroplasty (TKA) [1,2]. Patellofemoral problems resulting in patellar overloading are often responsible for AKP [2,3].…”