Saiph Knee System. Technical Dossier

Transcription

1 Saiph Knee System Technical Dossier

2 Developed in collaboration with an international surgical team Professor Justin P Cobb Chair in Orthopaedic Surgery Imperial College Hospital, London Professor Fares S Haddad Director, Institute of Sport and Surgical Specialties University College London Hospitals, London Dr Andrew J Shimmin Specialist Hip and Knee Surgeon Melbourne Orthopaedic Group, Melbourne Mr Adrian Fairbank Consultant Orthopaedic Surgeon Parkside Hospital, Wimbledon Mr Gilbert T Railton Consultant Orthopaedic Surgeon The Elective Orthopaedic Centre, Epsom Associate Professor William L Walter Chairman Department Orthopaedic Surgery Mater Hospital, Sydney Further acknowledgement to Professor Piers J Yates Fremantle Hospital and University of Western Australia Patents UK Patent Number / USA Patent Number UK Patent Number / USA Patent Number Manufactured by MatOrtho Limited 13 Mole Business Park Randalls Road Leatherhead Surrey KT22 7BA United Kingdom T: +44 (0) info@matortho.com For more information visit: MatOrtho Limited All rights reserved. No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopy, recording or any information storage and retrieval system. 2 Saiph Knee System Technical Dossier

3 Introduction The Saiph Knee was developed in collaboration with an international panel of surgeons, with the aim of improving patient outcomes and satisfaction. It is the latest in a series that has evolved over 40 years, using clinical experience gained since 1968 with the first condylar knee replacement at the Royal London Hospital [1,2]. The tibiofemoral bearing design is based on the principle of medial rotation, which mimics the function of the normal healthy knee [3-5]. It comprises a prominent spherical medial condyle, similar to a ball-in-socket joint, which stabilises the medial condyle throughout flexion. The lateral side is a conforming cylinder that permits some laxity and can be thought of as a stabilising outrigger. The patellofemoral design has a trochlear groove that aids more normal patellar tracking [6], positioned laterally to the midline throughout flexion to reflect the natural position of the patella. The deep trochlear groove and smooth single radius allow for increased conformity and stability of the patella during flexion. This combination of asymmetric tibiofemoral and patellofemoral articulations provides a superior blend of stability and mobility and is associated with improved high-end function [7] and low revision rates [8]. Saiph Knee System Technical Dossier 3

4 Evolution of the Saiph Knee design Freeman-Swanson Knee The world s first total condylar knee replacement, using the collateral ligaments to stabilise the joint, was performed in 1968 [1,2]. The knee was a metal-on-polyethylene roller-in-trough design with flattened anterior medial and lateral surfaces to protect the fixation interfaces from rotational forces. This knee was released to market as the Freeman-Swanson Knee in ICLH Knee The ICLH was introduced in 1977 to improve on clinical experience with the Freeman-Swanson Knee. New features included a range of sizes to improve tibial fixation, a patellofemoral bearing to reduce anterior knee pain, and an intercondylar cut-out to enable removal of cement associated with third-body wear. A key development for the ICLH was an instrumented soft-tissue balancing technique, which distinguished this series from an alternative design that relied on a central stabilising post [9]. Freeman-Samuelson (FS) Knee The FS Knee was first used in 1980 and introduced a trochlear groove with a saddle-shaped patella component to prevent patellar subluxation and metal-backed tibia fixation with a central stem. With aseptic loosening as the criterion for failure, the FS Knee had a reported 96% 10-year survivorship [10] and in 2007 the Swedish Arthroplasty Register recorded that the device maintained a significantly lower revision rate than its benchmark [11]. Medial Rotation Knee In 1994, the Medial Rotation Knee was introduced with the aim of improving stability and function. Initially named the FS1000 (because of the functional contact area), stability was built around the medial condyle with a deep spherical dish. The cylindrical lateral condyle was retained to dissociate rotational forces from the fixation interfaces. The trochlear floor was widened and lateralised to accommodate the larger medial condyle and to encourage more natural patellar tracking and the successful cementless saddle-shaped patella was retained. The knee is a clinical success; the tibiofemoral and patellar kinematic profiles are similar to the normal knee [4-6], it has exceptionally low revision rates in the UK [8] and patients report superior high-end functional activity [7]. Saiph Knee The Saiph Knee was developed with an international panel of widely-experienced surgeons to further improve clinical outcomes and patient satisfaction, and was first used in It features the same tibiofemoral and patellafemoral articulating designs, now with a more anatomical profile, and introduces a wider range of sizes, proportional articulating geometry and increased lateral rollback for improved range of motion. The system also features a new range of instrumentation. MatOrtho s surgeon-led post-market surveillance programme has shown that, in the first three years of use, the Saiph Knee rivals the market-leading survivorship rates of its predecessor. Functional and patient-reported clinical studies are ongoing. 4 Saiph Knee System Technical Dossier

5 Design of the tibiofemoral articulation Medial condyle The Saiph Knee features a spherical ball-and-socket geometry on the medial condyle. This design provides a unique level of stability with full congruency maintained throughout flexion and internal tibial rotation mm Lateral condyle The lateral geometry is designed to permit limited rollback in flexion whilst acting as a stabilising outrigger. With the Saiph Knee, 10 of unrestricted rotation about the medial condyle has been introduced to enhance the natural kinematics of the flexed knee. d 1 d 2 High flexion High flexion is permitted with the conforming design preventing anterior slide of the femur, normal rotation and a slight closing radius with low profile posterior tibial geometry. Patients prefer medial rotation The principle of the Saiph Knee tibio-femoral bearing has been demonstrated to exhibit near-normal knee kinematics [4,5] and is associated with patient preference, with reasons given citing the more stable feeling of Medial Rotation TKA [12] Normal Knee [1] Medial Rotation TKA [2] Saiph Knee System Technical Dossier 5

6 Design of the patellofemoral articulation The design of the trochlear groove is key to the success of the patellofemoral articulation [14,16,17]. The Saiph Knee has two distinct features to address this: Wide, lateralised trochlear groove The Saiph Knee features a wide lateralised trochlear groove to allow the patella to track from the midline in extension, laterally into flexion. This design principle has been demonstrated to exhibit near normal knee kinematics [6] and with the Medial Rotation Knee there has been no reported incidence of patella clunk or malalignment. 3mm 3mm Smooth, single radius flexion arc With a smooth single radius flexion arc that extends distally (it is not shortened by an intercondylar box-cut), the patella is designed to track smoothly throughout the range of motion, preventing anterior knee pain, clunking and crepitus associated with alternative designs [18]. 10 Mean Patellar Displacement (mm) Degree of Flexion Full Normal Knee TKR with lateralised trochlea TKR with central trochlea 6 Saiph Knee System Technical Dossier

7 Fixation Femoral fixation The Saiph Knee femoral component features two pegs to aid correct positioning and provide an interference fit. The pegs are not cemented. The distal femur retains the proven stippled cement pockets for cement interdigitation with almost 20 years clinical history, enhanced for the Saiph Knee with opposing anterior and posterior cement pockets. Tibial fixation The tibial tray features an anatomically positioned stem and two outlying pegs, linked by a web to provide rotational stability. The pegs and stem provide an interference fit and are not cemented. The base of the tray retains the stippled pockets for cement interdigitation, proven to provide secure fixation with the increased constraint of the tibiofemoral bearing design [15]. Patellar fixation The cementless saddle-shaped inset patella is press-fit and able to self-align once implanted, ensuring maximum contact during articulation. The cementless patella has been shown to accommodate natural rotation even after seven years in situ [13]. The Saiph Knee now also features a conventional cemented patella, which can be implanted inset or onset to the prepared patella surface. Saiph Knee System Technical Dossier 7

8 Component sizing Based on clinical experience and anthropological studies, the Saiph Knee features an increased range of sizes, with proportional articulating geometry and with a low-profile trochlear groove and anterior ridge. Femoral and tibial components can be cross-matched as shown in the Saiph Knee size compatibility chart. ML ML AP AP Table 1 - Femur Size ML AP* * In neutral flexion Table 2 - Tibia Size ML AP A B C D E F Product range The Saiph Knee provides a solution to all primary TKA requirements. Component type Femur Primary surgery Complex Primary Pegged Femur (CoCr) Tibia Short Stem (CoCr) Tibial Inserts (UHMWPE) All-Polyethylene Tibia (UHMWPE) Patella Cemented Patella Button (UHMWPE) Cementless fixation Cementless Saddle Button (UHMWPE) 8 Saiph Knee System Technical Dossier

9 Indications Severely painful and/or disabled joint resulting from osteoarthritis, traumatic arthritis, rheumatoid arthritis or a failed previous implant. Contraindications Active local or systemic infection, severe osteoporosis or severe neurological, vascular or muscular compromise such that knee replacement is inappropriate. Severe bone loss or collateral ligament instability. References 1. Freeman and Swanson (1972) JBJS; 54-B(1): Freeman et al. (1978) JBJS; 60-B(3): Iwaki et al. (2000) JBJS; 82-B: Monoot et al. (2009) KSSTA; 17: Moonet et al. (2010) The Knee; 17: Rhee et al. (2012) JBJS; 94-B (Suppl. IX): Hossain et al. (2011) CORR; 469(1): National Joint Registry for England and Wales, 9th Annual Report (2012) 9. Robinson (2005) J Arth; 20(1) Suppl. 1: Robertsson et al. (2000) JBJS; 82-B(4): Swedish Arthroplasty Register (2008) 12. Pritchett et al. (2011) J Arth; 26(2): Valdivia et al. (2002) J Arth; 17(1): Kulkarni et al. (2000)J Arth; 15(4): Mannan et al. (2009) JBJS; 91-B: Eckhoff et al. (1996) J Arth; 11(2): Amis et al. (2005) CORR; 436: Pollock et al. (2002) JBJS; 84-A(12): Saiph Knee System Technical Dossier 9

10 Saiph Knee size compatibility chart Primary size should be taken from the femur measurement Femoral Component Tibial Component Tibial Insert* Cementless Patella Cemented Patella 1 A A 2 B B 3 4 B B C C D D 16mm 20mm Small sizes: Large sizes: Small sizes: Large sizes: C D E C D E 24mm Small sizes: Large sizes: E F E F 28mm Small sizes: Large sizes: *18/20mm optional 10 Saiph Knee System Technical Dossier

11 Notes Saiph Knee System Technical Dossier 11

12 MatOrtho Limited 13 Mole Business Park Randalls Road Leatherhead Surrey KT22 7BA United Kingdom T: +44 (0) For more information visit: Part No. ML H issue 7