Aims

The Coronal Plane Alignment of the Knee (CPAK) classification is a simple and comprehensive system for predicting pre-arthritic knee alignment. However, when the CPAK classification is applied in the Asian population, which is characterized by more varus and wider distribution in lower limb alignment, modifications in the boundaries of arithmetic hip-knee-ankle angle (aHKA) and joint line obliquity (JLO) should be considered. The purposes of this study were as follows: first, to propose a modified CPAK classification based on the actual joint line obliquity (aJLO) and wider range of aHKA in the Asian population; second, to test this classification in a cohort of Asians with healthy knees; third, to propose individualized alignment targets for different CPAK types in kinematically aligned (KA) total knee arthroplasty (TKA).

Objective. Kinematically aligned total knee arthroplasty (TKA) is of increasing interest because this method may improve patient satisfaction. However, the biomechanics of kinematically aligned TKA remain largely unknown. Therefore, we analyzed whether the kinematic alignment method cause to increase the contact force on patellofemoral and tibiofemoral joints. Methods. A musculoskeletal computer simulation was used to determine the effects of kinematically or mechanically aligned TKA. Patellofemoral and tibiofemoral contact forces were examined for a mechanically aligned model and a kinematically aligned model using finite element analysis. Results. The peak contact stress on the patellofemoral joint in the kinematically aligned model was greater than that in the mechanically aligned model at 30° and 60°. Maximum peak contact stress was found at 30° flexion in the kinematically aligned model (73 MPa) and this was 221% higher than the stress in the mechanically aligned model (33 MPa). Similarly, peak contact stress of 33.0 MPa at 60° flexion occurred in the kinematically aligned model and this was 114% higher than that in the mechanically aligned model (29 MPa). The peak contact stress on the tibiofemoral joint in the kinematically aligned model was greater than that in the mechanically aligned model at 30°, 60° and 90° flexion. Maximum peak contact stress was found at 30° flexion in the kinematically aligned model (22 MPa) and this was 200% higher than the stress in the mechanically aligned model (11 MPa). Conclusions. Kinematically aligned TKA may have increased risks for implant longevity. Therefore, a strict surgical indication, including age and implant design, is needed to achieve excellent longevity after kinematically aligned TKA

Introduction. Most surgeons that have performed kinematically aligned TKA have noticed an overall better clinical outcome, better motion, better patient satisfaction, and a quicker recovery than their patients treated with mechanically aligned TKA. Materials and Methods. We prospectively followed all 128 knees who underwent primary total knee arthroplasty. The Lysholm knee score and VAS scale was recorded initially and 12months after the surgery. Independent T-test was used for statistical analysis at probability level of 95%. SPSS for Windows (Version 12, Chicago, Illinois) was used. Results. VAS score and passive ROM; Not significant difference statistically. But improved compared the preoperative and postoperative data. WOMAC score and HSS score; Significantly improved statistically. Discussion. Our data suggest that kinematic alignment may lessen the surgical stress experienced by the patient, reduce the pain, and increase function of knee. There is a need for more studies to clarify benefits of kinematic alignment technique. Kinematically aligned TKA restores function by aligning the femoral and tibial components to the normal or prearthritic joint lines of the knee. We prospectively followed all 128 knees who underwent total knee arthroplasty. We assessed postoperative function using the VAS, WOMAC, HSS score and passive ROM. HSS score and WOMAC score were significantly improved statistically

Aims

Nearly 99,000 total knee arthroplasties (TKAs) are performed in UK annually. Despite plenty of research, the satisfaction rate of this surgery is around 80%. One of the important intraoperative factors affecting the outcome is alignment. The relationship between joint obliquity and functional outcomes is not well understood. Therefore, a study is required to investigate and compare the effects of two types of alignment (mechanical and kinematic) on functional outcomes and range of motion.

The kinematic alignment (KA) approach to total knee arthroplasty (TKA) has recently increased in popularity. Accordingly, a number of derivatives have arisen and have caused confusion. Clarification is therefore needed for a better understanding of KA-TKA. Calipered (or true, pure) KA is performed by cutting the bone parallel to the articular surface, compensating for cartilage wear. In soft-tissue respecting KA, the tibial cutting surface is decided parallel to the femoral cutting surface (or trial component) with in-line traction. These approaches are categorized as unrestricted KA because there is no consideration of leg alignment or component orientation. Restricted KA is an approach where the periarthritic joint surface is replicated within a safe range, due to concerns about extreme alignments that have been considered ‘alignment outliers’ in the neutral mechanical alignment approach. More recently, functional alignment and inverse kinematic alignment have been advocated, where bone cuts are made following intraoperative planning, using intraoperative measurements acquired with computer assistance to fulfill good coordination of soft-tissue balance and alignment. The KA-TKA approach aims to restore the patients’ own harmony of three knee elements (morphology, soft-tissue balance, and alignment) and eventually the patients’ own kinematics. The respective approaches start from different points corresponding to one of the elements, yet each aim for the same goal, although the existing implants and techniques have not yet perfectly fulfilled that goal.

Objectives

Little biomechanical information is available about kinematically aligned (KA) total knee arthroplasty (TKA). The purpose of this study was to simulate the kinematics and kinetics after KA TKA and mechanically aligned (MA) TKA with four different limb alignments.