Abstract. Objectives. Hip instability following total hip arthroplasty in treatment of intracapsular neck of femur fractures is reported at 8–11%. Utilising the principle of a small articulation to minimize the problems of wear coupled with a large articulation, dual-mobility total hip arthroplasty prostheses stabilise the hip further than conventional fixed-bearing designs. The aim of this study is to compare the rate of dislocation and complication between standard fixed-bearing and dual-mobility prostheses for the treatment of intracapsular neck of femur fractures. Methods. A four-year retrospective review in a large district general hospital was completed. All cases of intracapsular neck of femur fractures treated with total hip arthroplasty were identified through the theatre logbooks. Patient's operative and clinical notes were retrospectively reviewed to collect data. Results. A total of 91 patients underwent total hip arthroplasty for intracapsular neck of femur fracture in the four-year period. 61.5% were dual-mobility design versus 28.5% had fixed-bearing implants. There were no statistical differences between patient group characteristics. Choice of implant was dependent on surgeon preference. There was a 0.0% dislocation rate in the dual-mobility group versus 8.6% in the fixed-bearing prosthesis group. All dislocations occurred in patients who underwent total hip arthroplasty with 36.0mm fixed-bearing prosthesis via posterior surgical approach. There was no statistical difference in mortality between both groups. Conclusion. There was an increasing trend of towards the use of dual-mobility prosthesis for fractured neck of femur within this department with excellent outcomes. Dual-mobility designs provide reduced dislocation rates in total hip arthroplasty in intracapsular neck of femur fractures compared to standard fixed-bearing designs at this institution. The authors recommend that all orthopaedic staff consider the use of dual-mobility prostheses in suitable patients and ensure trainees are suitably trained in use of dual-mobility designs. Declaration of Interest. (b) declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported:I declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project

In total knee replacement (TKR), neutral mechanical alignment (NMA) is targeted in prosthetic component implantation. A novel implantation approach, referred to as kinematic alignment (KA), has been recently proposed (Eckhoff et al. 2005). This is based on the pre-arthritic lower limb alignment which is reconstructed using suitable image-based techniques, and is claimed to allow better soft-tissue balance (Eckhoff et al. 2005) and restoration of physiological joint function. Patient-specific instrumentation (PSI) introduced in TKR to execute personalized prosthesis component implantation are used for KA. The aim of this study was to report knee kinematics and electromyography (EMG) for a number lower limb muscles from two TKR patient groups, i.e. operated according to NMA via conventional instrumentation, or according to KA via PSI. 20 patients affected by primary gonarthrosis were implanted with a cruciate-retaining fixed-bearing prosthesis with patella resurfacing (Triathlon® by Stryker®, Kalamazoo, MI-USA). 17 of these patients, i.e. 11 operated targeting NMA (group A) via convention instrumentation and 6 targeting KA (group B) via PSI (ShapeMatch® by Stryker®, Kalamazoo, MI-USA), were assessed clinically using the International Knee Society Scoring (IKSS) System and biomechanically at 6-month follow-up. Knee kinematics during stair-climbing, chair-rising and extension-against-gravity was analysed by means of 3D video-fluoroscopy (CAT® Medical System, Monterotondo, Italy) synchronized with 4-channel EMG analysis (EMG Mate, Cometa®, Milan, Italy) of the main knee ad/abductor and flexor/extensor muscles. Knee joint motion was calculated in terms of flex/extension (FE), ad/abduction (AA), and internal/external rotation (IE), together with axial rotation of condyle contact point line (CLR). Postoperative knee and functional IKSS scores in group A were 78±20 and 80±23, worse than in group B, respectively 91±12 and 90±15. Knee motion patterns were much more consistent over patients in group B than A. In both groups, normal ranges were found for FE, IE and AA, the latter being generally smaller than 3°. Average IE ranges in the three motor tasks were respectively 8.2°±3.2°, 10.1°±3.9° and 7.9°±4.0° in group A, and 6.6°±4.0°, 10.5°±2.5° and 11.0°±3.9° in group B. Relevant CLRs were 8.2°±3.2°, 10.2°±3.7° and 8.8°±5.3° in group A, and 7.3°±3.5°, 12.6°±2.6° and 12.5°±4.2° in group B. EMG analysis revealed prolonged activation of the medial/lateral vasti muscles in group A. Such muscle co-contraction was not generally observed in all patients in group B, this perhaps proving more stability in the knee replaced following the KA approach. These results reveal that KA results in better function than NMA in TKR. Though small differences were observed between groups, the higher data consistency and the less prolonged muscle activations detected using KA support indirectly the claim of a more natural knee soft tissue balance. References