Soft tissue balance is important for good clinical outcome and good stability after TKA. Ligament balancer is one of the devices to measure the soft tissue balance. The objective of this study is to clarify the effect of the difference in the rotational position of the TKA balancer on medial and lateral soft tissue balance. This study included with 50 knees of the 43 patients (6 males, 37 females) who had undergone TKA with ADLER GENUS system from March 2015 to January 2017. The mean age was 71.1±8.1 years. All patients were diagnosed with medial osteoarthritis of the knee. All implants was cruciate substituted type (CS type) and mobile bearing insert. We developed a new ligament balancer that could be fixed to the tibia with keel and insert trial could be rotated on the paddle. We measured the medial and lateral soft tissue balance during TKA with the new balancer. The A-P position of the balancer was fixed on tibia in parallel with the Akagi line (A-P axis 0 group) and 20 degrees internal rotation (IR group) and 20 degrees external rotation (ER group). Soft tissue balance was measured in extension and 90 degrees of knee flexion on each rotational position. The mean angle of valgus and varus in IR group, 0 group and ER group were 4.6±2.2 degrees varus, 1.9±1.6 degrees varus and 0.4±2.4 degrees varus respectively in extension, and 5.5±3.0 degrees varus, 2.1±2.2 degrees varus and 0.7±3.2 degrees varus respectively in 90 degrees of knee flexion. There were significant differences between three groups in extension (p<0.0001) and flexion (p<0.0001). In other words, when the balancer was fixed on tibia with internal rotation against the Akagi line, the soft tissue balance indicated medial tightness. Conversely, when the balancer was fixed on tibia with external rotation against the Akagi line, the soft tissue balance showed lateral tightness. The insert trial significantly rotated to opposite side against the position of balancer fixed.Materials and Methods
Results
A full 3D postoperative analysis, i.e. a quantitative comparison between planned and postoperative positions of bone(s) and implant(s) in 3D, is necessary for a thorough assessment of the outcome of the surgery, as well as to provide information that could be used to optimize similar procedures in the future. In this work, we present a method of postoperative analysis based on a pair of X-ray images only, which reaches a level of accuracy that is comparable with the results obtained with a 3D postoperative image. The method consists in using 3D models of bones, segmented from 3D preoperative image (e.g. CT or MRI scans), and 3D models of implant, and aligning them independently to X-rays by matching contours manually drawn on the X-rays and projected contours. The result gives the relative postoperative position of bone and implant. The method was tested on a phantom consisting of commonly available femoral knee implant on a physical model of a femur (Sawbones®). Result was compared to the optical scan, considered as ground truth, of the implanted saw bone. Two studies were performed: inter-operator (six operators), and intra-operator (5 tests). In addition, the inter-operator study was repeated while asking all the operators to use the same pre-drawn contours. The results are presented by calculating the distance (anterior/posterior, proximal/distal, medial/lateral) between the centers of gravity, and the angles (varus/valgus, flexion/extension, external/internal rotations) of the implants from the X-ray based method and the ground truth. Results were also compared with the relative position of bone and implant extracted from a 3D CT postoperative image. Saw bone and implant were first segmented from this image. In order to determine the position of the implant, despite the metal artefacts in the CT images, the 3D model of the implant was registered on the segmented implant. All processing, including segmentation, registration of X-rays, and measurements, was performed using Mimics Innovation Suite 17.0 ®.Introduction
Methods
Previously, the Coonrad-Morrey elbow system has typically been performed using linked-type total elbow arthroplasty (TEA) implants. However, this implant have been reported to be associated with some problems, such as wearing down, loosening, the complexity of the necessary surgical techniques and inappropriate implant size for Asian people. The Discovery elbow system (Biomet Inc., Warsaw, US) has recently been developed and it has many advantages when compared to Coonrad-Morrey implant, but the treatment outcome for this system is unclear in patients with rheumatoid arthritis (RA). The aim of this study was to clarify the outcome of TEA using the Discovery elbow system.Background
Objectives
