In total knee arthroplasty (TKA), the effectiveness of the mechanical alignment (MA) within 0°±3° has been recently questioned. A novel implantation approach, i.e. the kinematic alignment (KA), emerged recently, this being based on the pre-arthritic lower-limb alignment. In KA, the trans-cylindrical axis is used as the reference, instead of the trans-epicondylar one, for femoral component alignment. This axis is defined as the line passing through the centres of the posterior femoral condyles modeled as cylinders. Recently, patient specific instrumentation (PSI) has been introduced in TKA as an alternative to conventional instrumentation. This provides a tool for preoperative implant planning also via KA. Particularly, KA using PSI seems to be more effective in restoring normal joint kinematics and muscle activity. The purpose of this study was to report preliminarily joint kinematic and electromyography results of two patient groups operated via conventional MA or KA, the latter using PSI. Twenty patients recruited for TKA were implanted with Triathlon® prosthesis (Stryker®-Orthopaedics, Mahwah, NJ-USA). Seventeen patients, eleven operated targeting MA using the convention instrumentation (group A) and six targeting KA (group B) using PSI (Stryker®-Orthopaedics), were assessed at 6 month follow-up clinically via IKSS and biomechanically. Knee kinematics during stair-climbing, chair-rising, and extension-against-gravity were evaluated using three-dimensional mono-planar video-fluoroscopy (CAT® Medical-System, Monterotondo, Italy) synchronised with electromyography (Wave-Wireless, Cometa®, Milan, Italy). Component pose was reconstructed to calculate knee flexion/extension (FE), ad/abduction (AA), internal/external-rotation (IE), together with the rotation of the contact-line (CLR), i.e. line connecting the medial (MCP) and lateral (LCP) tibio-femoral contact points. MCP and LCP antero-posterior translations were calculated and reported in percentage (%) of the tibial base-plate length.INTRODUCTION
PATIENT AND METHODS
In Total Knee Arthroplasty (TKA), the neutral overall limb alignment (NOLA), i.e. the mechanical alignment of the lower limb within 0°±3°, is targeted for achieving good clinical/functional results. The kinematic overall limb alignment (KOLA), which uses the axis through the centres of the femur posterior condyles modelled as cylinders, represents a novel approach for achieving better soft tissue balance. Patient-specific instrumentation (PSI) is nowadays offered as an effective technology in TKA to obtain better lower limb alignments than those via conventional guides (CON). Although relevant results are still inconsistent, the benefits claimed include shorter operative time, reduced surgical instrumentation, and accurate preoperative planning. The aim of this study was to report the preliminary clinical and radiological results of TKA patients operated via NOLA-PSI and KOLA-PSI. Comparisons between them and with the results obtained via NOLA-CON were performed. A four-centre randomised study on 144 patients has been designed to assess these three techniques. In each centre, 36 patients are planned to be operated, 12 per technique. Currently, in our centre 18 patients have been operated so far: 6 via NOLA-CON (Group A), 3 via NOLA-PSI (Group B), and 9 via KOLA-PSI (Group C). All patients were implanted with a cruciate-retaining TKA (Triathlon®, Stryker®-Orthopaedics, Mahwah, NJ-USA) with patella resurfacing, those in PSI groups according to Otismed® imaging protocol. This includes pre-operative MRI scans at the hip, knee and ankle joints. Clinical evaluations were performed pre-operatively, at 45 days, and 3, 6 and 12 months post-operatively using the knee and functional IKSS (International Knee Society Score). At 45 days post-operatively a weight-bearing long leg radiograph was performed to measure possible differences between planned and implanted component alignment in patients operated via NOLA groups (A and B) and via KOLA group (C).INTRODUCTION
PATIENTS AND METHODS
