Ultracongruent insert design is a safe alternative to posterior cruciate-substituting total knee arthroplasty: 5-year results of a randomized controlled trial

Abstract

Purpose If substitution of the posterior cruciate ligament in total knee arthroplasty is necessary, there are two options available: posterior stabilized (PS) design with a post-cam mechanism or anterior-lipped ultracongruent (UC) inserts. UC inserts have the advantage that no femoral box is necessary and a standard femoral component can be used. The aim of this study was to compare the range of motion (ROM) and patient-reported outcome (PRO) after UC and PS fixed-bearing TKA. Better ROM in PS TKA and no difference in PRO between both designs was hypothesized. Methods A randomized controlled trial with 127 patients receiving a fixed-bearing UC or PS design of the same knee system was performed. Nine patients died and there were four revision surgeries. 107 patients completed the 5-year follow-up. Patient-reported outcome was assessed. Patellofemoral problems were evaluated using selected applicable questions of the Oxford Knee Score (getting up from a table, kneeling, climbing stairs). Results Surgical time was 10 min shorter in the UC group (p < 0.001). After 5 years, both groups demonstrated good knee function and health-related quality of life without significant differences between the groups. Both groups demonstrated a high satisfaction score and the majority of patients would undergo this surgery again. Patellofemoral problems were recognized more frequently in the PS group (p = 0.025). Conclusion Both designs demonstrated similar good results after 5 years. Stabilization with an anterior-lipped UC insert can be considered a safe alternative to the well-established PS design if cruciate substitution is necessary. Level of evidence 1.

Increased posterior translation but similar clinical outcomes using ultracongruent instead of posterior stabilized total knee arthroplasties in a prospective randomized trial

“…Previous studies have analysed knee kinematics with a navigation system, and showed less posterior tibial translation between 60° and 120° of flexion of the PS knees compared to the UC knees [4, 5, 8, 14, 17]. Despite the different kinematics, there were similar outcomes in the KSS, Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) and Forgotten Joint scores between PS and UC groups [13, 18]. In our study, the regular use of a patellar component could have prevented possible anterior knee pain in cases with increased posterior tibial translation.…”

A prospective comparison of total knee arthroplasty using ultra-congruent, condylar-stabilizing, and posterior-stabilized devices implanted with kinematic alignment: better 2-year outcomes with ultra-congruent

“…Both groups demonstrated equally good knee function, quality of life, and high satisfaction. Patellofemoral problems were more frequent in the PS group ( P = 0.025) [ 17 ]. In a report of the results from a large national registry, Dalton found that survivorship was better for a UC device versus a PS device: the cumulative revision at 18 years was 8.3% for UC, 9.2% for CR, and 8.9% for PS [ 3 ].…”

Similar outcomes including maximum knee flexion between mobile bearing condylar-stabilised and fixed bearing posterior-stabilised prosthesis: a case control study

“…Conversely, CS TKA features a deep dished polyethylene insert which has been proposed to lead to impingement of the femur on the posterior lip causing a subsequent reduction in flexion [18]. Several studies have examined ROM in CS designed TKA reporting variable results, but have not controlled for tibial slope or PCOR [18][19][20][21][22][23][24][25][26][27]. Both of these factors have been reported to influence flexion range at least in PS designed TKA [28].…”