Differences in the setting of acetabular component alignment guides between the supine and lateral positions for total hip arthroplasty

The acetabular component orientation in total hip arthroplasty is of critical importance to clinical results. Although navigation systems and surgical robots have been introduced, most surgeons still use acetabular component alignment guides. This study aimed to compare the accuracy between modern acetabular component alignment guides for the lateral position and those for the supine position. Thirteen alignment guides for the lateral position and 10 for the supine position were investigated. All the lateral position alignment guides indicated cup alignment in operative definition, and the supine position alignment guides indicated cup alignment in radiographic definition. For lateral position alignment guides, the anteversion actually indicated by the alignment guide itself was smaller than that indicated by the manufacturer by a mean of 6° (maximum, 9°), and the inclination actually indicated by alignment guides themselves was larger than that by the manufacturer (p < 0.01) by a mean of 2° (maximum, 4°). For supine position alignment guides, the inclination and anteversion indicated by the alignment guide itself were identical with those indicated by the manufacturer. The current study showed that the angles actually indicated and those stated by manufacturers were not identical for lateral position alignment guides.

A Method Combining the Use of an Application and a Dedicated Pelvic Positioner for Acetabular Cup Insertion

Background: We developed a mobile device application and dedicated pelvic positioner with the aim of improving the acetabular cup placement accuracy in patients undergoing total hip arthroplasty (THA). The function of the application was to display the intra-operative cup angle. The accuracy and clinical usefulness of this combined method was verified through comparison with the conventional alignment guide method.Methods: In total, 60 patients who underwent cementless THA were included in this study. We compared the cup alignment when using this combined method with that when using the conventional alignment guide method. The absolute value error between the intra- and post-operative angles of inclination and anteversion of the cup was calculated.Results: The absolute value error of inclination was 2.4° ± 2.1° in the study group and 4.0° ± 3.3° in the control group (P = 0.107). The absolute value error of anteversion was 2.8° ± 2.6° in the study group and 7.4° ± 5.3° in the control group (P < 0.001).Conclusion: Using the application and pelvic positioner is simple and can be introduced at a low cost. The more accurate measurement of the intra-operative cup angle using this combined method has improved the cup insertion accuracy compared with that of the conventional alignment guide method.

The Adjustment of the Rotational Alignment of the Distal End of the Extramedullary Guide to the Anteroposterior Axis of the Proximal Tibia in Total Knee Arthroplasty

The optimal placement within 3 degrees in coronal alignment was reportedly achieved in only 60 to 80% of patients when using an extramedullary alignment guide for the tibial side in total knee arthroplasty (TKA). This probably occurs because the extramedullary alignment guide is easily affected by the position of the ankle joint which is difficult to define by tibial torsion. Rotational direction of distal end of the extramedullary guide should be aligned to the anteroposterior (AP) axis of the proximal tibia to acquire optimal coronal alignment in the computer simulation studies; however, its efficacy has not been proven in a clinical setting. The distal end of the guide can be overly displaced from the ideal position when using a conventional guide system despite the alignment of the AP axis to the proximal tibia. This study investigated the effect of displacement of the distal end of extramedullary guide relative to the tibial coronal alignment while adjusting the rotational alignment of the distal end to the AP axis of the proximal tibia in TKA. A total of 50 TKAs performed in 50 varus osteoarthritic knees using an image-free navigation system were included in this study. The rotational alignment of the proximal side of the guide was adjusted to the AP axis of the proximal tibia. The position of the distal end of the guide was aligned to the center of the ankle joint as viewed from the proximal AP axis (ideal position) and as determined by the navigation system. The tibial intraoperative coronal alignments were recorded as the distal end was moved from the ideal position at 3-mm intervals. The intraoperative alignments were 0.5, 0.9, and 1.4 degrees in valgus alignment with 3-, 6-, and 9-mm medial displacements, respectively. The intraoperative alignments were 0.7, 1.2, and 1.7 degrees in varus alignment with 3-, 6-, and 9-mm lateral displacements, respectively. In conclusion, the acceptable tibial coronal alignment (within 2 degrees from the optimal alignment) can be achieved, although some displacement of the distal end from the ideal position can occur after the rotational alignment of the distal end of the guide is adjusted to the AP axis of the proximal tibia.

Active focus stabilization for fluorescence microscopy by tracking actively generated infrared spots

Maintaining focus during time-lapse experiments remains an important challenge in optical microscopy. In this paper we present an automated focusing system for fluorescence microscopy that can be used in time-lapse experiments. We provide software for flexibly operating the autofocus system and a complete alignment guide. The system is evaluated using a time-lapse experiment with temperature variations on Tetraspeck beads.

Accuracy of acetabular cup placement using an angle-adjusting alignment guide with laser pointer in total hip arthroplasty

Purpose: To evaluate cup-positioning accuracy in total hip arthroplasty (THA) using a novel angle-adjusting alignment guide with laser pointer and determine whether level of surgical experience affects accuracy of cup placement or not. Methods: We included 117 hips in 104 patients who underwent THA using the novel guide. We retrospectively reviewed 44 hips in 40 patients who underwent THA before the novel guide was introduced. We compared differences in cup angles between the novel guide group and the conventional guide group as well as the discrepancies in targeted angles between the experienced surgeon group and the inexperienced surgeon group. Results: There were 114/117 hips (97.4%) within the Lewinnek safe zone in the novel guide group and 32/44 hips (72.7%) within the safe zone in the conventional guide group. There were significantly fewer outliers in the novel guide group ( p < 0.001). In the experienced surgeon group, the mean absolute errors in inclination and anteversion were 2.0 ± 1.7° and 2.1 ± 2.3°, respectively; which were not significantly different from those in the inexperienced surgeon group (2.3 ± 2.1° and 2.8 ± 2.3°, respectively). Conclusion: The novel angle-adjusting alignment guide with laser pointer is a simple tool that provides better accuracy of cup position than that obtained using conventional guides. Accurate cup placement is possible using the novel guide, regardless of surgeons’ experience.