Aims. Appropriate acetabular component placement has been proposed for prevention of postoperative dislocation in total hip arthroplasty (THA). Manual placements often cause outliers in spite of attempts to insert the component within the intended safe zone; therefore, some surgeons routinely evaluate intraoperative pelvic radiographs to exclude excessive acetabular component malposition. However, their evaluation is often ambiguous in case of the tilted or rotated pelvic position. The purpose of this study was to develop the computational analysis to digitalize the acetabular component orientation regardless of the pelvic tilt or rotation. Methods. Intraoperative pelvic radiographs of 50 patients who underwent THA were collected retrospectively. The 3D pelvic bone model and the acetabular component were image-matched to the intraoperative pelvic radiograph. The radiological anteversion (RA) and radiological inclination (RI) of the acetabular component were calculated and those measurement errors from the postoperative CT data were compared relative to those of the 2D measurements. In addition, the intra- and interobserver differences of the image-matching analysis were evaluated. Results. Mean measurement errors of the image-matching analyses were significantly small (2.5° (SD 1.4°) and 0.1° (SD 0.9°) in the RA and RI, respectively) relative to those of the 2D measurements. Intra- and interobserver differences were similarly small from the clinical perspective. Conclusion. We have developed a computational analysis of acetabular component orientation using an image-matching technique with small measurement errors compared to visual evaluations regardless of the pelvic tilt or rotation. Cite this article: Bone Joint Res 2020;9(7):360–367

INTRODUCTION. Golf is considered low-impact sport, but concerns exist about whether golf swing can be performed in safe manner after THA. The purpose of this study was to clarify dynamic hip kinematics during golf swing after THA using image-matching techniques. METHODS. This study group consisted of eight right-handed recreational golfers with 10 primary THAs. Each operation was performed using a posterolateral approach with combined anteversion technique. Nine of ten polyethylene liners used had elevated portion of 15°. Continuous radiographic images of five trail and five lead hips during golf swing were recorded using a flat panel X-ray detector (Fig. 1) and analyzed using image-matching techniques (Fig. 2). The relative distance between the center of cup and femoral head and the minimum liner-to-stem distance were measured using a CAD software program. The cup inclination, cup anteversion, and stem anteversion were measured in postoperative CT data. Hip kinematics, orientation of components, and cup-head distance were compared between patients with and without liner-to-stem contact by Mann-Whitney U test. RESULTS. At the top of backswing, lead hips showed 26 ± 11° ER, and trail hips showed 24 ± 19° IR. At the end of follow-through, lead hips showed 24 ± 19° IR, and trail hips showed 24 ± 12° ER. The mean cup inclination and anteversion, stem anteversion, and combined anteversion were 40 ± 5°, 18 ± 11°, 33 ± 14°, and 50 ± 8°, respectively. The minimum liner-to-stem distance showed the smallest value of 3 ± 4 mm at the maximum ER. Bone-to-bone and bone-to-implant impingements were not observed in all hips at all phases. The liner-to-stem contact was observed in four hips with elevated liners (two trail and two lead hips; Fig 3). Patients with elevated liner-to-stem contact demonstrated significantly (p < .05) larger maximum ER and larger cup anteversion than patients without contact. The mean cup-head distance was 0.9 ± 0.5 mm of translation. No significant difference was found in the flexion/extension and adduction/abduction at the maximum ER, cup inclination, combined anteversion, and cup-head distance between patients with and without contact. DISCUSSION. Golf swing produced approximately 50° of axial rotations in both lead and trail hips after THA. The mean cup-head distances showed less than 1.0 mm, and there was no significant difference between patients with and without neck-liner contact. Therefore, we consider that dynamic stability without excessive hip rotations or subluxation was demonstrated during golf swing. Despite no evidence of component malpositioning, elevated liner-to-stem contact was observed in 40% of hips with significantly larger ER and cup anteversion. Because the liner-to-stem contact may be a concern with regard to the long-term prognosis following THA, further attention must be given to the anteversion of the components and the use of elevated liner at the time of surgery. To view tables/figures, please contact authors directly

Background:. The axis of the fibula in the sagittal plane are known as a landmark for the extramedullary guide in order to minimize posterior tibial slope measurement error in the conventional total knee arthroplasty (TKA). However, there are few anatomic studies about them. We also wondered if the fibula in the coronal plane could be reliable landmark for the alignment of the tibia. This study was conducted to confirm whether the fibula is reliable landmark in coronal and sagittal plane. Methods:. We evaluated 60 osteoarthritic knees after TKA using Athena Knee (SoftCube Co, Ltd, Osaka, Japan) 3-D image-matching software. Angle between the axis of the fibula (FA) and the mechanical axis (MA) in the coronal and sagittal plane were measured. Results:. The mean angle between the FA and MA was 0.86 ± 2.0° of varus in the coronal plane (range 6.0° of varus to 4.2° of valgus) and 2.6 ± 2.3° of posterior inclination in the sagittal plane (range 6.8° of posterior inclination to 2.8 of anterior inclination), respectively. The percentage of subjects in which FA was within 3° of the MA was 77% in the coronal plane and 58% in the sagittal plane, respectively. Conclusions:. The FA used as a landmark for the alignment of the tibia in the conventional TKA differed from MA relatively in this study, and not be used safely if the differences are considered

Progression of osteoarthritis (OA) of the knee is related to alignment of the lower extremity. Postoperative lower extremity alignment is commonly regarded as an important factor in determining favourable kinematics to achieve success in total knee arthroplasty (TKA) and high tibial osteotomy (HTO). An automated image-matching technique is presented to assess three-dimensional (3D) alignment of the entire lower extremity for natural and implanted knees and the positioning of implants with respect to bone. Sawbone femur and tibia and femoral and tibial components of a TKA system were used. Three spherical markers were attached to each sawbone and each component to define the local coordinate system. Outlines of the 3D bone models and the component computer-aided design models were projected onto extracted contours of the femur, tibia, and implants in frontal and oblique X-ray images. Threedimensional position of each model was recovered by minimizing the difference between the projected outline and the contour. The relative positions were recovered within −0.3 ± 0.5 mm and −0.5 ± 1.1° for the femur with respect to the tibia, −0.9 ± 0.4 mm and 0.4 ± 0.4° for the femoral component with respect to the tibial component, −0.8 ± 0.2 mm and 0.8 ±0.3° for the femoral component with respect to the femur, and −0.3 ± 0.2 mm and −0.5 ± 0.4° for the tibial component with respect to the tibia. Clinical applications were performed on 12 knees in 10 OA patients (mean age, 72.5 years; range, 62–87 years) to check change in the 3D mechanical axis alignment before and after TKA and to measure position of the implant with regard to bone. The femorotibial angle significantly decreased from 187.8° (SD 10.5) to 175.6° (SD 3.0) (p=0.01). The 3D weight-bearing axis was drawn from the centre of the femoral head to the centre of the ankle joint. It intersected significantly medial (p=0.01) and posterior (p=0.023) point at the proximal tibia before TKA. The femoral component rotation was 3.8° (SD 3.3) internally and the tibial component rotation was 14.1° (SD 9.9) internally. Compared with a CT-based navigation system using pre-and post-operative CT for planning and assessment, the benefit to patients of our method is that the post-operative CT scan can be eliminated

Flexion after total knee arthroplasty (TKA) has recently been improved by changing implant designs, surgical techniques and early postoperative rehabilitation protocols. Especially for Asian people, deep knee flexion is essential because of their life style. Small numbers of patients can achieve full flexion after TKA, however, most current prostheses are not designed to allow deep knee flexion safely. Furthermore, the kinematics involved in knee flexion greater than 90 degrees in cases of TKA is still unknown, even though fluoroscopic studies have shown the paradoxical anterior femoral translation in posterior cruciate retaining (CR) TKA with knee flexion up to 90 degrees. The purpose of this study was to determine the femoro-tibial contact pattern in deep knee flexion. The knee that had been operated upon was passively flexed from 90 degrees up to the maximum flexion under anesthesia soon after the surgery. Lateral roentgenograms of the knee were taken during flexion, and the three-dimensional kinematics was analyzed using image-matching techniques. Nine patients with CR type were included. The average maximum flexion angle was 131.8 °. The contact point moved posteriorly with deep knee flexion except for one patient. Five out of nine patients showed external rotation of the femoral condyle. Two patients showed internal rotation, and the other two exhibited no rotational movement. None of the patients showed dislocation or disengagement of the components. At the maximum flexion, the edge of the posterior flange of the femoral component contacted the polyethylene insert. This study was performed under non-weight-bearing conditions, but deep knee flexion is not usually performed in weight-bearing conditions. Most of the CR type showed posterior roll back during deep knee flexion. The design of the posterior flange of the femoral component should be changed to prevent damage to the polyethylene

Introduction. Increased long-term survival of TKA is becoming more important. Several studies have confirmed that optimal positioning and alignment of prosthetic components is crucial for the best long-term results. Therefore, the purpose of the current study was to compare the postoperative alignment and sizing of femoral prosthesis among patients performed by 3 different navigation systems. Methods. Twenty patients who underwent primary TKA (E. motion; B. Braun Aesculap, Tuttlingen, Germany) using a CT-free navigation system (OrthoPilot v 4.2) by modified gap technique were enrolled in this study. The results of this study group were retrospectively compared with those in a control group of 20 matched-paired posterior stabilized TKAs (Triathlon;Stryker; Mahwah, NJ, USA) which were using another CT-free navigation system (Stryker Navigation System) by measured technique and 20 matched-paired posterior stabilized TKAs (Press-fit Condylar prosthesis; DePuy, Tokyo, Japan) using CT-based navigation system (VectorVision) by measured technique. Several parameters were evaluated for each patient using Athena Knee (Softcube Co, Ltd. Osaka, Japan), 3-D image-matching software. The coronal component angles and sagittal component angles were measured in relation to mechanical axis (MA). In addition, axial femoral component angle was measured in relation to surgical epicondylar axis (SEA) and axial tibial component angle was measured in relation to Akagi line. Results. (Coronal plane alignment). The coronal femoral component angle (varus) was 1.3° ± 2.7° in the Orthopilot group, 1.1 ± 1.5° in the stryker group and 0.21° ± 2.2°in VectorVisioin group with no sigificant difference. The coronal tibial component angle (varus) was 0.7° ± 2.0° in the Orthopilot group, −0.50° ± 1.4° in the stryker group and −1.0° ± 1.2° in VectorVision group with no significant difference. (Sagittal plane alignment). The sagittal femoral component angle (flexion) was 2.7° ± 2.2° in the Orthopilot group, 3.3° ± 2.4° in the stryker group and −0.2° ± 2.9°in VectorVisioin group. The sagittal femoral component angle in VectorVison group is significantly smaller than that in the Orthopilot group and that in the Stryker group. The sagittal tibial component angle (posterior slope) was 4.7° ± 1.9° in the Orthopilot group, 2.6° ± 1.5° in the stryker group and 2.8° ± 1.4° in VectorVision group. The posterior slope was aimed at 5°in Orthopilot group and 3°in stryker group and VectorVision group. Accuracy among 3 groups is no significant difference. (Axial component angle). The axial femoral component angle (external rotation) was 2.2° ± 1.9° in the Orthopilot group, 1.2° ± 1.5° in the stryker group and −0.9° ± 2.0°in VectorVisioin group. The axial femoral component angle in Orthopilot group was significantly more external than that in the stryker group and that in the VectorVision group. The axial tibial component angle (external rotation) was 2.4° ± 5.0° in the Orthopilot group, 2.6° ± 5.5° in the stryker group and 2.0° ± 4.2° in VectorVision group with no differnence. Discussion and Conclusion. We performed primary TKA by 3 different navigation systems and analyzed alignment of component. Accurate alignment was obtained in all 3 different navigation systems. However surgeons should take into account the features in each navigation

Aims

This study aims to investigate the effects of posterior tibial slope (PTS) on knee kinematics involved in the post-cam mechanism in bi-cruciate stabilized (BCS) total knee arthroplasty (TKA) using computer simulation.

Objectives

The medially spherical GMK Sphere (Medacta International AG, Castel San Pietro, Switzerland) total knee arthroplasty (TKA) was previously shown to accommodate lateral rollback while pivoting around a stable medial compartment, aiming to replicate native knee kinematics in which some coronal laxity, especially laterally, is also present. We assess coronal plane kinematics of the GMK Sphere and explore the occurrence and pattern of articular separation during static and dynamic activities.