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Purpose: Acromioclavicular (AC) joint dislocation is commonly treated using a clavicle hook plate (HP). However, previous reports have indicated that acromial fractures may occur after HP fixation. The purpose of this study was to identify risk factors for acromial fractures. Methods: A retrospective study was conducted on 39 patients with AC joint dislocation who were treated using clavicle HP fixation in our hospital between 2006 and 2017. Related parameters, including Rockwood classification, hook angle, the degree of reduction, the coverage of the hook under the acromion, and the anteroposterior position of the hook under the acromion, were evaluated to identify risk factors for acromial fractures. Results: The mean age of the participants was 51.7 (range 19 - 81) years; 34 were men and 5 were women. Injury occurred on the right side in 18 patients and on the left side in 21. Injuries were categorized as follows: 24 were Rockwood type III, one was type IV, and 14 were type V. Four of the 39 patients (10%) experienced acromial fractures. Statistical analyses indicated that the degree of reduction at the final follow-up was moderately correlated with the Constant score. Posterior positioning of the hook was the only identified risk factor for acromial fractures. Hook angle and the degree of reduction at the time of surgery were not significantly associated with acromial fractures. Conclusions: Postoperative shoulder function was associated with the degree of reduction at the final follow-up, suggesting that anatomical reduction is recommended for AC joint dislocation. Posterior positioning of the hook is a risk factor for acromial fractures; however, clavicle HP fixation provides a positive outcome for AC joint dislocation. Therefore, careful positioning of the hook is required for preventing acromial fractures.

The efficacy of a computed tomography (CT)-based navigation system to accurately position the stem for intended alignment is unclear. In addition, the influence of stem design on the accuracy of insertion is unknown. We therefore retrospectively compared the accuracy and precision for the intended alignment of two different designs of femoral stem which were implanted with or without the navigation system. Forty-nine total hip arthroplasties (THAs) using a tapered wedge stem and 91 THAs using an anatomic stem were evaluated for the navigation group. Thirty-three THAs using the tapered wedge stem and 15 THAs using the anatomic stem were controls for the non-navigation group. Differences between postoperative measurement and preoperative planning were compared among the groups. In the navigation groups, accuracy (mean absolute difference) and precision (95% limits of agreement) of stem anteversion were 4.3° and ± 10.1° in the tapered wedge stem and 3.1° and ± 6.9° in the anatomic stem. In the non-navigation groups, these were 6.0° and ± 15.2° and 4.8° and ± 12.4°, respectively. The accuracy and precision in the navigation groups were significantly superior to those in the non-navigation group, and those in the anatomic stem group were significantly superior to those in the tapered wedge group. Using the CT-based navigation system, the accuracy and precision for intended stem anteversion were improved. When compared under guidance of navigation system, the accuracy and precision for intended stem anteversion in the anatomic stem were superior to those in the tapered wedge stem.

A computed tomography (CT)-based navigation system is one of the support tools to place implant with appropriate alignment and position in total hip arthroplasty (THA). To determine whether the higher performance of the navigation would further improve the accuracy of implant placement in the clinical setting, we retrospectively compared the navigation accuracy of two different versions of a navigation system. The newer version of the navigation system had an upgraded optical sensor with superior positional accuracy. Navigation accuracy, defined as differences between postoperative measurements on CT images and intraoperative records on the navigation system, of 49 THAs performed with the newer version of the navigation system was compared with that of 49 THAs performed with the older version. With the newer version, the mean absolute accuracy (95% limits of agreement) of implant alignment was 1.2° (± 3.3°) for cup inclination, 1.0° (± 2.4°) for cup anteversion, 2.0° (± 4.9°) for stem anteversion, and 1.1° (± 2.4°) for stem valgus angle. The accuracy of the implant position was 1.5 mm (± 3.1 mm), 1.3 mm (± 3.0 mm), and 1.5 mm (± 3.1 mm) for cup x-, y-, and z-axes, respectively, 1.6 mm (± 3.2 mm), 1.4 mm (± 2.9 mm), and 1.5 mm (± 2.7 mm) for stem x-, y-, and z-axes, respectively, and 2.4 mm (± 4.5 mm) for leg length discrepancy. The values for the newer version were significantly more accurate with less variation compared to those of the older version. With upgraded navigation performance, more accurate implant placement was demonstrated in the clinical setting.

Background Proper implant orientation is essential for avoiding edge-loading and prosthesis impingement in total hip arthroplasty. Although cup orientation is affected by a change in pelvic tilt after surgery, it has been unclear whether surgeons can prevent impingement and edge-loading by proper positioning by taking into account any change in pelvic alignment associated with alteration of hip range of motion. Methods We simulated implant orientation without edge-loading and prosthesis impingement, even with a change in pelvic tilt and associated change in hip range of motion after surgery, by collision detection using implant models created with computer-aided design. Findings If posterior pelvic tilting with a corresponding hyperextension change in hip range of motion after surgery remains within 10°, as occurs in 90% of cases, surgeons can avoid edge-loading and impingement by correctly orienting the implant, even when using a conventional prosthesis. However, if a 20° change occurs after surgery, it may be difficult to avoid those risks. Interpretation Although edge-loading and impingement can be prevented by performing appropriate surgery in most cases, even when taking into account postoperative changes in pelvic tilt, it may also be important to pay attention to spinal conditions to ensure that pelvic tilting is not extreme because of increasing kyphosis.

Major surgery in hemophilia patients has been facilitated by the development of coagulation concentrates. However, it is still difficult to manage bleeding during major surgery in patients with inhibitors to FVIII/IX. In addition, there have been few reports of major surgery in hemophilia B with high responding inhibitors. We report a 26-year-old hemophilia B patient with high responding factor IX inhibitor who demonstrated severe hemophiliac arthropathy in his left hip joint. Total hip arthroplasty was performed with a high dose of FIX followed by recombinant FVIIa. His inhibitor titer was decreased from 111 BU/ml to 1.0 BU/ml at surgery by avoiding the use of FIX concentrates. Thus, we could use high dose FIX for the management of surgical bleeding. Anamnestic response occurred on the 7th day after surgery and FIX concentrates were switched to recombinant FVIIa. The whole process was safely managed without any excess bleeding or adverse effects. The successful use of high dose FIX followed by recombinant FVIIa suggests that even major surgery could be safely performed in hemophilia B patients with a low titer of high responding inhibitors.

The supine functional pelvic plane is the recommended reference pelvic plane for acetabular cup planning in navigation-assisted total hip arthroplasty. However, it is unclear whether it can be used in patients with a large preoperative positional change in pelvic inclination (PC) from the supine to the standing position because it is unknown whether these patients have a different hip range of motion (ROM). We measured the anatomical hip ROM after implantation by computed tomography-based navigation in 91 patients and found it to be similar between those with a small PC (