Total knee arthroplasty (TKA) is a well-established procedure associated with excellent clinical results. We have previously reported that intraoperative knee kinematics correlate with the clinical outcome in mobile bearing TKA. In addition, the intraoperative knee kinematics pattern does not correlate with the degree of preoperative knee deformity in mobile bearing TKA. However, the relationship among preoperative knee deformity, intraoperative kinematics and clinical outcome in fixed bearing TKA has been unknown. The purpose of this study is to compare the relationship among preoperative knee deformity, knee kinematics after fixed bearing TKA and the clinical outcome including the subjective outcomes evaluated by the new knee society score (KSS). A cross-sectional survey of thirty-five consecutive medial osteoarthritis patients who had a primary TKA using a CT-based navigation system was conducted. All knees had a Kellgren-Lawrence grade of 4 in the medial compartment and underwent a primary posterior stabilized TKA (Genesis II, Smith&Nephew) between May 2010 and October 2012. In all cases, a computed tomography-guided navigation system (Brain LAB, Heimstetten, Germany) was used. All surgery was performed by the subvastus approach and modified gap technique. Intraoperative knee kinematics was measured using the navigation system after implantation and closure of the retinaculum and soft tissue except for the skin. Subjects were divided into two groups based on intraoperative kinematic patterns: a medial pivot group (M group, n=19)(Figure 1) and a non-medial pivot group (N group, n=16)(Figure 2). Subjective outcomes with the new KSS and clinical outcomes were evaluated. Statistical analysis to compare the two groups was made using unpaired a Student t test.Introduction
Materials and Methods
The effect of the implant posterior condylar offset has recently generated much enthusiasm among researchers. Some reports were concerned about the relationship between the posterior condylar offset and an extension gap. However, the posterior condylar offset was measured in a flexed knee position or in reference to femoral anatomy alone. Posterior femoral condylar offset relative to the posterior wall of the tibia (posterior offset ratio; POR) is possibly the risk of knee flexion contracture associated with posterior femoral condylar offset after TKA. However, there are no reports concerning the relationship between POR and flexion contracture in vivo. The aim of this study is to evaluate the relationship between the measurement of POR and flexion contracture of the knee in vivo. Twenty-seven patients who underwent a primary total knee arthroplasty (PFC Sigma RP-F) were participated in the study. The lateral femoro-tibial angle (lateral FTA) was measured using lateral radiographs obtained by two procedures. Two procedures are applied to obtain true lateral radiographs of the lower extremities. (1) Full-length true lateral radiographs on standing, (2) True lateral radiographs in the prone position (Fig. 1A). ‘Posterior offset ratio’ was defined as Fig. 1B. Significant differences among groups were assessed using two-tailed Student's t-tests. Spearman's correlation analysis was performed to evaluate the relationship between lateral FTA and posterior offset ratio of patients.Introduction
Methods
We have previously reported that patients who demonstrated medial pivot kinematics pattern after total knee arthroplasty (TKA) had better clinical results than that of non-medial pivot pattern. However, it is unclear how preoperative kinematics pattern affects postoperative knee kinematics. The aim of this study was to evaluate the relationship between preoperative and postoperative knee kinematics pattern in TKA. The present study consists of 38 patients with medial osteoarthritis who underwent a primary TKA using a CT-based navigation system from July 2010 to September 2012. All the operations were performed by a single surgeon using a subvastus approach and the same posterior cruciate ligament substituting type (PS type) of prosthesis (Genesis II™ total knee system, Smith & Nephew, Memphis, TN). The proximal tibia osteotomy and the distal femur osteotomy were set on the navigation system perpendicular to the mechanical axis in the coronal plane with 3° tibial posterior inclination in the sagittal plane. The coronal plane ligament imbalance was corrected until the gap imbalance was fewer than 2 mm. This gap balance was checked using a ligament balancer (Smith & Nephew) at 80 N in medial and lateral compartment of the knee. The navigation system was used to measure the flexion gap with the CAS ligament balancer (Depuy, Warsaw, IN, USA) at 90° knee flexion. The amount of external rotation on femoral osteotomy was adjusted by the navigation system with a balanced gap technique. The patella was resurfaced and a lateral release was not performed. Tibial A-P axis of the tibial tray was placed parallel to Akagi's line. We measured each kinematics pattern immediately after capsule incision (preoperative knee kinematics) and after implantation (postoperative knee kinematics) in TKA. Subjects were divided into two groups based on kinematics patterns: a medial pivot group (group M) and a non-medial pivot group (group N). A chi-square test was used for statistical analysis. P values less than 0.05 were considered significant.Introduction
Materials and Methods
