At our national explant retrieval unit, we identified an unusual pattern of backside-deformation on polyethylene (PE) inserts of contemporary total-knee-replacements (TKRs). The PE backside's margins were inferiorly deformed in TKRs with central-locking trays. We reported that this backside-deformation appeared to be linked to tray debonding. Moreover, recent studies have shown high-rate of tray debonding in PS NexGen TKRs. Therefore, we hypothesised that backside deformation on PS inserts may be more than on CR inserts. We used peer-reviewed techniques to analyse changes in the bearing (wear rate) and backside surfaces (deformation) of PE inserts using coordinate measuring machines [N=61 NexGen (CR-39 and PS-22) TKRs with non-augmented-trays]. Multiple regression was used to determine which variable had the greatest influence on backside-deformation. The amount of cement cover on trays was quantified as a %of the total surface using Image-J software.Abstract
Introduction
Methodology
Traditional TKR designs exhibit abnormal and unpredictable kinematics: with posterior subluxation in extension and anterior slide with flexion. These can contribute to restricted knee flexion and reduced quadriceps efficiency. Newer designs attempt to provide “guided motion” with the aim of mimicking normal knee kinematics. The Journey (Smith & Nephew) BCS TKR incorporates both an anterior and a posterior cam/post mechanism while Triathlon PS TKR (Stryker) incorporates a posterior cam/post mechanism. This study compares the in-vivo kinematics of these two designs and compares it with normal knee. Knee kinematics of 10 patients with Journey-BCS TKR and 11 patients with Triathlon PS TKR; all with excellent clinical outcome (average age: 65) were analysed. Patients underwent fluoroscopic assessment of the knee during a step-up and deep knee bend exercise. 2D fluoroscopic images were recorded. Data was analysed for patella tendon angle (PTA) and contact points using a 3D model fitting technique. This data was compared to normal knee kinematics (n=20).Introduction
Methods
To examine the short term patient assessed functional results of the Journey BCS ¯(Smith & Nephew) and Triathlon ¯(Stryker Orthopaedics, Mahwah, NJ) total knee replacements when compared to the Scorpio ¯(Stryker) total knee replacement using a multi-surgeon case control design in a single centre. From September 2006 to August 2008 a total of 135 Journey and 97 Triathlon total knee replacements (TKR) were performed. 105 patients with Journey and 90 patients with Triathlon implants were available for follow-up at a minimum of 1 year, with an average of 2 years. Age and sex matched controls were obtained from our pool of patients who had had Scorpio TKR's. The same surgeons using the same approach operated on patients in both groups. All implants were posterior stabilised and all underwent patella resurfacing. All patients were seen pre-operatively and followed up post operatively in a physiotherapist led joint review clinic to assess range of motion (ROM) as well as function using the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), Oxford Knee Score (OKS) and the High Activity Arthroplasty Score (HAAS - used post operatively only).OBJECTIVE
METHODS
