The purpose was to determine the lifetime risk of re-operation due to specific complications related to dual mobility using re-operation as a competing risk, excluding loosening, periprosthetic fracture, and infection. 1503 mono-block dual mobility total hip arthroplasty (DM-THAs). Defining the re-operation when anesthesia (for dislocation) and revision when the implant changed. Surgery (801 for primary, 702 for revision with 201 for recurrent dislocation and 501 for loosening) performed between 1990 and 2020 in average 81-year-old (range 50–102) patients, with 522 living patients at 10 years follow-up. During the first month, outer dislocation (60 cases; 4%) was the cause re-operation (1% among primary and 6 % among revisions). Twenty-four intra-prosthetic dislocations (IPD) were an iatrogenic consequence of a failed closed reduction (reduction maneuver dissociating the inner head) with 1.6% revision. Between 1 month and 1 year, 22 new outer dislocations, while 25 of the 60 “first month” dislocations had recurrent dislocation. Fifteen other IPDs as iatrogenic consequences were observed. At one year, the cumulative revision was 3% (49 of 82 dislocations). Between 1- 10-year FU, 132 other dislocations, and 45 other revisions for dislocations were observed. Corrosion was another cause of revision (37 cases): between the cobalt-chromium shell and the femoral neck (23 hips), or 14 crevice corrosion between the trunnion and the metal head (trunnion damage). In summary, at 10-year: dislocation first cause of re-operation (214 anesthesia, 14%), while among 131 revisions (8.9 %) the 55 iatrogenic intra-prosthetic dislocations were the first revision cause before 39 recurrent dislocations and 37 corrosions. The 522 patients followed ten years or more had a 15% risk revision due to DM specific complications during their lifetime and 10% more risk associated with loosening (6%), periprosthetic fracture (2%) and infection (2%)

Aims

Dual mobility (DM) implants have been shown to reduce the dislocation rate after total hip arthroplasty (THA), but there remain concerns about the use of cobalt chrome liners inserted into titanium shells. The aim of this study was to assess the clinical outcomes, metal ion levels, and periprosthetic femoral bone mineral density (BMD) at mid-term follow-up in young, active patients receiving a modular DM THA.

The hip joint capsular ligaments (CL) passively restrain extreme range of motion (ROM) by wrapping around the native femoral head, and protect against impingement, edge loading wear and dislocation. This study compared how ligament function was affected by device (hip resurfacing arthroplasty, HRA; dual mobility total hip arthroplasty, DM-THA; and conventional THA, C-THA), with and without CL repair. It was hypothesized that ligament function would only be preserved when native anatomy was preserved: with restoration of head-size (HRA or DM-THA) and repair. Eight normal male cadaveric hips were skeletonised, retaining the hip capsule. CL function was quantified by measuring ROM by internally (IR) and externally rotating (ER) the hip in six functional positions, ranging from full extension with abduction to full flexion with adduction (squatting). Native ROM was compared to ROM after posterior capsulotomy and HRA, and C-THA and DM-THA, before and after surgical CL repair. ROM increased most following C-THA (max 62°), then DM-THA (max 40°), then HRA (max 19°), indicating later engagement of the capsule and reduced biomechanical function with smaller head-size. Dislocations also occurred in squatting after C-THA and DM-THA. CL-repair following HRA restored ROM to the native hip (max 8°). CL-repair following DM-THA reduced ROM hypermobility in flexed positions only and prevented dislocation (max 36°). CL-repair following C-THA did not reduce ROM or prevent dislocation. When HRA was combined with repair, native anatomy was preserved and ligament function was restored. For DM-THA with repair, ligament function depended on the movement of the mobile bearing resulting in near-native function in some positions, but increased ROM when ligaments were unable to wrap around the head/neck. Following C-THA, the reduced head-size resulted in inferior capsular mechanics in all positions as the ligaments remained slack, irrespective of repair. Choosing devices with anatomic head-sizes (resurfacing or dual-mobility) and repairing the capsular ligaments may protect against instability in the early postoperative period

Aims

In the native hip, the hip capsular ligaments tighten at the limits of range of hip motion and may provide a passive stabilizing force to protect the hip against edge loading. In this study we quantified the stabilizing force vectors generated by capsular ligaments at extreme range of motion (ROM), and examined their ability to prevent edge loading.

Aims

The rate of dislocation when traditional single bearing implants are used in revision total hip arthroplasty (THA) has been reported to be between 8% and 10%. The use of dual mobility bearings can reduce this risk to between 0.5% and 2%. Dual mobility bearings are more expensive, and it is not clear if the additional clinical benefits constitute value for money for the payers. We aimed to estimate the cost-effectiveness of dual mobility compared with single bearings for patients undergoing revision THA.