It is very important for implanting tibial component to prevent bearing dislocation in Oxford UKA. One of the keys is accurate rotational position of tibia. But the problem remains what is accurate rotation of tibia in UKA. Oxford Signature decided the rotation of tibia component from MRI images. We measured the component rotation of tibia using CT after operation. Patients and Methods. 14 patients were operated by Oxford Signature and 11 patients were operated by Microplasty method. Patients were examined by CT 2 or 3 weeks later after operation. We compared component axis of tibia and A-P axis by best fit circle, Akagi's line. Results. In Oxford Signature group, component angle were 7.1 degree external rotation compared with A-P axis by best fit circle and were 3.6 degree external rotation compared with Akagi's line. In Microplasty group, component angle were 8.1 degree external rotation compared with A-P axis by best fit circle and were 3.8 degree external rotation compared with Akagi's line. Discussion. It is difficult to decide accurate position of tibial component for UKA. The A-P axis by best fit circle and Akagi's line are reliable methods for tibial axis in TKA. We examined component axis of Signature Oxford and Microplasty, these were same tendency toward external rotation

Total elbow arthroplasty (TEA) usage is increasing owing to expanded surgical indications, better implant designs, and improved long-term survival. Correct humeral implant positioning has been shown to diminish stem loading in vitro, and radiographic loosening in in the long-term. Replication of the native elbow centre of rotation is thought to restore normal muscle moment arms and has been suggested to improve elbow strength and function. While much of the focus has been on humeral component positioning, little is known about the effect of positioning of the ulnar stem on post-operative range of motion and clinical outcomes. The purpose of this study is to determine the effect of the sagittal alignment and positioning of the humeral and ulnar components on the functional outcomes after TEA. Between 2003 and 2016, 173 semi-constrained TEAs (Wright-Tornier Latitude/Latitude EV, Memphis, TN, USA) were performed at our institution, and our preliminary analysis includes 46 elbows in 41 patients (39 female, 7 male). Patients were excluded if they had severe elbow deformity precluding reliable measurement, experienced a major complication related to an ipsilateral upper limb procedure, or underwent revision TEA. For each elbow, saggital alignment was compared pre- and post-operatively. A best fit circle of the trochlea and capitellum was drawn, with its centre representing the rotation axis. Ninety degree tangent lines from the intramedullary axes of the ulna and humerus, and from the olecranon tip to the centre of rotation were drawn and measured relative to the rotation axis, representing the ulna posterior offset, humerus offset, and ulna proximal offset, respectively. In addition, we measured the ulna stem angle (angle subtended by the implant and the intramedullary axis of the ulna), as well as radial neck offset (the length of a 90o tangent line from the intramedullary axis of the radial neck and the centre of rotation) in patients with retained or replaced radial heads. Our primary outcome measure was the quickDASH score recorded at the latest follow-up for each patient. Our secondary outcome measures were postoperative flexion, extension, pronation and supination measured at the same timepoints. Each variable was tested for linear correlation with the primary and secondary outcome measures using the Pearson two-tailed test. At an average follow-up of 6.8 years (range 2–14 years), there was a strong positive correlation between anterior radial neck offset and the quickDASH (r=0.60, p=0.001). There was also a weak negative correlation between the posterior offset of the ulnar component and the qDASH (r=0.39, p=0.031), and a moderate positive correlation between the change in humeral offset and elbow supination (r=0.41, p=0.044). The ulna proximal offset and ulna stem angle were not correlated with either the primary, or secondary outcome measures. When performing primary TEA with radial head retention, or replacement, care should be taken to ensure that the ulnar component is correctly positioned such that intramedullary axis of the radial neck lines up with the centre of elbow rotation, as this strongly correlates with better function and less pain after surgery

INTRODUCTION. Recent studies indicated that the knee has a single flexion/extension axis but debated the location of this axis. The relationship of the flexion/extension axis in the coronal plane to the mechanical axis has received little attention. The purpose of this study was to investigate the relationship of the various axes and references with respect to the mechanical axis in the coronal plane. MATERIALS AND METHODS. Subjects were prospectively scanned into a Virtual Bone Database (Stryker Orthopaedics, Mahwah, NJ). Database is a collection of body CT scans from subjects collected globally. Only CT Scans that met the following qualifications were accepted: ≤1 mm voxels and had slice thickness that was equal to the spacing between the slices (≤ 1.0mm). For each CT Scan, a frontal plane was created through the 2 most posterior points of the medial/lateral condyles and the most posterior point of the trochanter. Then, a transverse plane was created perpendicular to the frontal plane and bisects the 2 most distal points on the medial/lateral condyles. Finally, a saggital plane was created that was perpendicular to the frontal and transversal planes. The following axes were identified: Mechanical Axis of the Femur (MAF) (line between the center of the femoral head and the center of the knee sulcus); Transepicondylar Axis Posterior Cylindrical Axis (PCA) (line between the Medial/Lateral Condylar Circle – best fit circle to three points identified on surface). Measurements made: Angle of MAF and the Joint-Line (Femoral Joint Angle), Angle of the MAF and the Transepicondylar Axis (Femoral TE Angle), and Angle of the MAF and the Posterior Cylindrical Axis (Femoral PC angle). Angles measuring 90° were neutral or perpendicular to the MAF. Angles measured <90° were valgus and >90° were varus. RESULTS. CT Scans from 519 knees were studied. The mean femoral joint angle was 86.1°±2.0°(Range:80.2°-92.2°). The mean TE angle was 88.8°±2.5°(Range:81.7°-98.4°). The mean Femoral PC angle was 87.9°±2.2°(Range:81.8°-94.0°). The average deviations from a neutral resection were 3.8°, 1.2° and 2.1° for the Femoral Joint Angle, Femoral TE Angle respectively. The mean Femoral Joint angle had the lowest variability, while the mean Femoral TE angle showed the largest. CONCLUSION. On average, the transepicondylar axis and the posterior cylindrical axis were approximately perpendicular to the mechanical axis in the coronal plane. Although surgeons do not align components in the coronal plane specifically to either axis, this data suggests that the average value is within the accepted ±3° range reported. The PCA values are closer to the values of the femoral joint line when compared to the TEA. The PCA may be a more reproducible landmark as it may be determined by either preoperative imaging or intraoperatively from instrumentation that references the distal/posterior surfaces. Further research is warranted

Aims

Recurrent dislocation is both a cause and consequence of glenoid bone loss, and the extent of the bony defect is an indicator guiding operative intervention. Literature suggests that loss greater than 25% requires glenoid reconstruction. Measuring bone loss is controversial; studies use different methods to determine this, with no clear evidence of reproducibility. A systematic review was performed to identify existing CT-based methods of quantifying glenoid bone loss and establish their reliability and reproducibility