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AimsThe aims of this study were to determine the change in pelvic sagittal alignment before, during, and after total hip arthroplasty (THA) undertaken with the patient in the lateral decubitus position, and to determine the impact of these changes on acetabular component position.Patients and MethodsWe retrospectively compared the radiological pelvic ratio among 91 patients undergoing THA. In total, 41 patients (46%) were female. The mean age was 61.6 years (sd10.7) and the mean body mass index (BMI) was 20.0 kg/m2(sd5.5). Anteroposterior radiographs were obtained: in the standing position preoperatively and at six weeks postoperatively; in the lateral decubitus position after trial reduction intraoperatively; and in the supine position in the post-anaesthesia care unit. Pelvic ratio was defined as the ratio between the vertical distance from the inferior aspect of the sacroiliac (SI) joints to the superior pubic symphysis and the horizontal distance between the inferior aspect of the SI joints. Changes in the apparent component position based on changes in pelvic ratio were determined, with a change of > 5° considered clinically significant. Analyses were performed using Wilcoxon’s signed-rank test, with p < 0.05 considered significant.ResultsIntraoperatively, in the lateral decubitus position, the pelvic ratio increased (anterior tilt) in 69.4% of cases, did not change significantly in 20.4%, and decreased (posterior tilt) in 10.2% of cases. When six-week postoperative radiographs were compared with preoperative radiographs, the pelvic ratio decreased in 44.9% of cases, did not change significantly in 42.3%, and increased in 12.8% of cases. This change in alignment correlated with a change in acetabular component version of > 5° in 79.6% of cases intraoperatively and 57.7% of cases at six weeks postoperatively.ConclusionChanges in pelvic sagittal pelvic position occur throughout THA that, if unaccounted for, introduce errors in acetabular component placement. The use of intraoperative imaging may help the appropriate placement of the acetabular component.Cite this article: Bone Joint J2019;101-B(6 Supple B):45–50.

AimsThe aim of this study was to compare the actual cost of a cemented and cementless total knee arthroplasty (TKA) procedure.Materials and MethodsThe cost of operative time, implants, cement, and cementing accessories were included in the overall cost of the TKA procedure. Operative time was determined from a previously published study comparing cemented and cementless implants of the same design. The cost of operative time, implants, cement, and cementing accessories was determined from market and institutional data.ResultsMean operative time for cemented TKA was 11.6 minutes longer for cemented TKA than cementless TKA (93.7 minutes (sd16.7) vs82.1 minutes (sd16.6); p = 0.001). Using a conservative published standard of $36 per minute for operating theatre time cost, the total time cost was $418 higher for cementing TKA. The cost of cement and accessories ranged from $170 to $625. Overall, the calculated cost of cemented TKA is $588 to $1043, depending on technique. The general increased charge for cementless TKA implants over cemented TKA implants was $366.ConclusionThe overall procedural cost of implanting a cementless TKA is less than implanting a cemented TKA. Cost alone should not be a barrier to using cementless TKA.Cite this article: Bone Joint J2019;101-B(7 Supple C):61–63