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Total hip arthroplasty (THA) for fibrous-fused hips is technically demanding. This study aimed to evaluate the precision and accuracy, as well as the rate of conversion of robotic-assisted THA in such difficult patients. We retrospectively analyzed 67 patients (84 hips) who underwent THA with fibrous-fused hips between August 2018 and June 2021 at our institution. Demographics, acetabular cup positioning, leg-length discrepancies, and postoperative Harris hip scores were recorded for all patients. Thirty-six patients (44 hips) who underwent robotic-assisted THA and 31 patients (40 hips) who underwent manual THA were enrolled in this study. The robot accurately executed the preoperative plan, and there were no statistically significant differences between the preoperative planned anteversion, inclination, and postoperative measurements. In the robotic group, the percentage of acetabular cups in the safe zone was significantly higher than in the manual group (87.2 versus 55%, respectively, P =.042). The rate of conversion to manual THA for various reasons in the robotic-assisted THA group was 11.4% (5/44). Compared with manual THA, the mean increase in operative time for conversion from robotic-assisted to manual THA was 24 min (P <.001). In patients who have fibrous-fused hips, preoperative planning can be accurately executed by robotic-assisted technology. Compared with manual THA, robotic-assisted THA had a remarkable advantage in improving the frequency of achieving cup positioning within the target zone. Overall, robotic-assisted technology was helpful in such difficult cases, and the approximately 11.4% of cases converted to manual THA are reminders that surgeons should be thoroughly prepared preoperatively. [ABSTRACT FROM AUTHOR]

Background: The purpose of this study is to measure acetabular cup position and wear of the highly crosslinked polyethylene liner in the supine and standing position for patients at a minimum of 10 years after the operation.Methods: A total of 38 patients were recruited at a mean of 12.5 years after the operation. All patients received a single acetabular cup design with a highly crosslinked liner and a 28-mm cobalt-chromium femoral head. Patients underwent supine and standing radiostereometric examinations in which the X-ray sources and detectors were positioned to obtain an anterior-posterior and cross-table lateral radiograph. Acetabular cup position and the three-dimensional wear rate were measured from the radiographs, and outcome scores were recorded for each patient.Results: Anteversion significantly increased (P < .0001) a mean of 12° from supine (15.1° ± 10.4°) to standing (27.2° ± 10.5°) position. Inclination also significantly increased (P = .001) a mean of 2° from supine (44.4° ± 6.8°) to standing (46.3° ± 7.7°) position. There was no difference (P = .093) in wear rate between supine (0.067 ± 0.070 mm/y) and standing (0.073 ± 0.074 mm/y) positions. There were no correlations between cup orientation and wear rate in either position.Conclusion: Highly crosslinked polyethylene is a forgiving bearing material. Although adherence to the traditional acetabular position target zone is recommended, ensuring hip stability and consideration of the patient's functional position are also important objectives to consider for the acetabular position. [ABSTRACT FROM AUTHOR]

This retrospective study measured the change of the acetabular component orientation between supine and standing radiographs in 113 THA patients and identified the associated anatomical parameters that may help direct pre-operative planning. The mean change of the acetabular component inclination and version from supine to standing was 4.6° and 5.9° respectively ( P < 0.0001), with 49 (43%) hips showing inclination change > 5° and 69 (53%) hips showing version change > 5°. Twelve (43%) of 28 ‘malpositioned’ cups became ‘well-positioned’ and 26 (31%) of 85 ‘well-positioned’ cups became ‘malpositioned’ upon standing. Changes in inclination were associated with leg length discrepancy and pelvic obliquity; and changes in version were associated with pelvic tilt and pelvic incidence. Standing position and patient factors should be considered when defining “optimal” acetabular orientation. [ABSTRACT FROM AUTHOR]

Abstract: After periacetabular osteotomy (PAO), some patients develop osteoarthritis with need of a total hip arthroplasty (THA). We evaluated the outcome of THA following PAO and explored factors associated with inferior cup position and increased polyethylene wear. Follow-up were performed 4 to 10years after THA in 34 patients (38 hips) with previous PAO. Computer analysis evaluated cup position and wear rates. No patient had dislocations or revision surgery. Median scores were: Harris hip 96, Oxford hip 38 and WOMAC 78. Mean cup anteversion and abduction angles were 22o (range 7°–43°) and 45° (range 28°–65°). Outliers of cup abduction were associated with persisting dysplasia (CE <25°). THA after PAO can produce excellent clinical results. Persisting acetabular dysplasia following PAO may lead surgeons to place the acetabular component in excessive cup abduction, and this tendency should be recognized at the time of the PAO. [Copyright &y& Elsevier]

Abstract: Proper acetabular cup orientation is essential in total hip arthroplasty. The purpose of this study was to evaluate the accuracy of a particular imageless computer navigation system in determining cup position. Thirty-nine computer-navigated total hip arthroplasty intraoperative measurements of cup abduction and anteversion were compared with those from follow-up radiographs. Sensitivity, specificity, accuracy, prevalence-adjusted positive value (PPV), and negative predictive value were calculated for both navigation and radiographs. Navigation measurements had high specificity and PPV when assessing cup abduction and anteversion (specificity >90%, PPV >94%). In contrast, the system was not very effective in detecting suboptimal cup position (sensitivity abduction, 50%; anteversion, 33%). Intraoperative navigation readings in the safe zone have high probability of indicating correct placement. However, confirmation of suboptimal cup position intraoperatively requires additional diagnostic methods. [Copyright &y& Elsevier]

Abstract: The purpose of this study was to evaluate the results of bilateral total hip arthroplasties (THAs) with special regard to angle of cup position in patients with bilaterally ankylosed hips. Twenty-four ankylosed hips were converted to THAs in 12 patients. Their mean age was 36 years and they were followed up for more than 3 years (average, 11 years). The mean Harris hip score increased from 55.4 to 82.3 points. Osteolysis and loosening were found in 3 and 2 hips, respectively. Eleven cups of 24 hips (46%) were outside the safe ranges of Lewinnek. Overall outcome after bilateral conversion of bilaterally ankylosed hips to THA was favorable, but the fused position of the contralateral limb had the tendency to define the direction of the malposition of the acetabular cup. [Copyright &y& Elsevier]