Therefore, femoral offset restoration is essential to improve function and longevity of hip arthroplasty. CT-scan is more accurate than plain radiography to assess femoral offset. Hip resurfacing decreases offset without effect on function. Modular neck and computer assistance may improve intraoperative calculation and reproduction of femoral offset. Increasing offset with a standard cemented design may decrease long-term fixation. Level IV: Retrospective or historical series.

Component impingement is frequently observed in cups after removal, but is rarely found as a direct indication for revision, except in case of hard-on-hard friction couples (polyethylene being the most impingement-tolerant material). Systematic use of extended head flanges and elevated antidislocation rims is not to be recommended, especially in case of excessive ROM. A good head/neck ratio should be sought, notably by increasing the head diameter in less impingement-tolerant hard-on-hard friction couples. Although not identified as a risk factor in the present study, implant orientation should be checked; computer-assisted surgery can be useful in this regard, for adaptation to the patient's individual range-of-motion cone.

level IV. Retrospective study.

PurposeThe purpose of the study was to compare clinical and radiological results between kinematic alignment (KA) and mechanical alignment (MA) with a posterior-stabilized (PS) total knee arthroplasty (TKA) with a post-cam mechanism at a minimum follow-up of 3 years. The authors hypothesized a higher risk of aseptic loosening when performing KA using PS TKA. Methods A retrospective monocentric single surgeon case control study was performed comparing 100 matched patients who had TKA performed using a MA philosophy to 50 patients receiving TKA with a KA technique between January 2016 and October 2017. All patients had the same knee prosthesis (GMK primary posterior-stabilized, Medacta ® , Switzerland). Patient speciic cutting blocks were used in both groups and a restricted KA (rKA) was aimed in the KA group. A hybrid cementation technique was performed. The new Knee Society Score (KSS) and radiological assessment were collected preoperatively and at the inal follow-up. Comparisons between groups were done with the T test or Fisher exact test. Global survival curves were estimated with Kaplan-Meier model. Signiicance was set at p < 0.05. Results Mean follow-up was 42.9 months ± 3.6 (range 37.6-46.7) and 53.3 months ± 4.1 (range 45.5-59.8) for rKA and MA groups. Postoperatively, no signiicant diferences were found for clinical scores between both groups. Radiological assessment found similar postoperative Hip-Knee-Ankle angle for rKA and MA groups (178° versus 179° respectively, NS). At last follow-up, a signiicant higher survivorship was found for the MA group compared to the rKA group (97 versus 84%; p < 0.001) for aseptic loosening revision as the endpoint. Conclusion An increased risk of tibial implant loosening was found with rKA compared to MA using a posterior-stabilized TKA with a post-cam system at short-term follow-up. Caution should be taken when choosing the TKA design while performing rKA. Level of evidence Retrospective case-control study, Level IV.