Dislocations have impact on quality of life, but it is difficult to quantify this impact for each patient. The Quality-of-Life Time Trade-Off assesses the percentage of a patient's remaining life that the patient would be willing to trade for perfect health [1]. This technique has been used for non-unions [2], but never proposed for dislocation.

154 patients (with 3 recurrent dislocations) undergoing revision were asked to choose between living with their associated dislocation risk or trading a portion of their life expectancy for a period of perfect health without dislocation, thus determining their Quality-of-Life score. This score may range from 0.1 (willing to trade nine years among 10) to 1.0 (unwilling to trade any years). Additionally, patients were assessed on their willingness to trade implant survival time for a reduced risk of dislocation, considering various implant options that might offer lower (but not necessary) survival time before revision than the theoretical best (for the surgeon) “standard” implant, thus determining a “Survival Implant Quality” score.

Patients diagnosed with 3 hip dislocations have a low health-related quality of life. The score of our “dislocation” cohort was average 0.77 with patients willing to trade average 23% of remaining lifespan for perfect health (range 48% to 12%). This score is below that (0.88) of illnesses type-I diabetes mellitus [3] and just higher than tibial non-union (0.68) score [2]. The mean “Survival Implant Quality” score of our recurrent dislocation cohort was 0.71 (range 0.59 to 0.78) which means that patients accept to trade average 3 years (range 2 to 4 years) among 10 theoretical years of survival of the implant.

Hip dislocation has a devastating impact that can be quantified for each patient when discussing revision and choice of implants for instability.

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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%).

The variables involved in a robotic THA can exceed 52: many parameters as pelvic orientation with CT scan, templating, offset, and leg-length, acetabular reaming, femoral osteotomy, mapping the anatomy; predefining safe zones, robotic execution, femoral head size, thickness of PE etc. with several variables for each parameter, with a total number of variables exceeding 52. This familiar number is the number of cards in a standard deck. The number of possible combinations (factorial 52! = 10^67) to shuffle the cards (and may be to perform a THA) is greater than the number of atoms on earth! Thinking that artificial intelligence and robotics can solve these problems, some surgeons and implant manufacturers have turned to artificial intelligence and robotics.

We asked two questions:1) can robot with artificial intelligence really process 52 variables that represent 10^67 combinations? 2) the safety of the technology was ascertained by interrogating Food and Drug Administration (FDA) database about software-related recalls in computer-assisted and robotic arthroplasty [1], between 2017 and 2022.

1)

The best computers can only calculate around 100 thousand billion combinations (10^14), and with difficulty: it takes more than 100 days to arrive at this number of digits (10^14) after the decimal point for the number π (pi). We can, therefore, expect the robot to be imperfect.

Hip surgeon is as intelligent as a robot and almost twice as safe.

Symptomatic and non-symptomatic hip osteonecrosis related to sickle cell disease (SCD) has a high risk of progression to collapse and total hip arthroplasty (THA) in this disease has a high rate of complications. We asked question about the benefit of performing an IRM to detect and treat with cell therapy an early (stage I or II) contralateral osteonecrosis.

430 consecutive SCD adult (32 years, 18 to 51) patients (225 males) with bilateral osteonecrosis (diagnosed with MRI) were included in this study from 1990 to 2010. One side with collapse was treated with THA and the contralateral without collapse (stage I or II) treated with cell therapy. The volume of osteonecrosis was measured with MRI. For cell therapy, the average total number of mesenchymal stem cells (MSCs) counted as number of colony forming units-fibroblast injected in each hip was 160,000 ± 45,000 cells (range 75,000 to 210,000 cells).

At the most recent FU (20 years, range 10 to 30), among the 430 hips treated with cell therapy, 45 hips (10.5%) had collapsed and had required THA at 10 years (range 5 to 14 years) and 380 hips (88%) were without collapse and asymptomatic (or with few symptoms) with a decrease percentage of necrosis on MRI from 45% to 11%. Among the 430 contralateral THA, 96 (22.3%) had required one revision, 28 had a re-revision, and 12 a third re-revision with aseptic loosening (85% of revisions) and/or infection (6% of revisions). Hips undergoing cell therapy were approximately three times less likely to undergo revision or re-revision surgery (p < 0.01) as compared with hips undergoing a primary THA.

THA is the usual treatment of collapsed ON in patients with SCD. In this population, it is worth looking with MRI for an early stage on the contralateral hip and performing (when necessary) bone marrow cell implantation during the same anesthesia as for arthroplasty.

We questioned about bearing surface and infection in two populations of patients who had bilateral THA with different bearings performed in the same hospital by the same surgical team from the year 1981 to the year 2010 (mean followup 15 years; 7 to 35).

1) first population (mean age 32 years): 325 patients (650 hips) with sickle cell disease (SCD) with two different bearing on each side. 116 patients had Metal on PE (MoP) on one side and Ceramic on PE (CoP) on the contralateral; 106 patients had (CoP) and Ceramic on Ceramic (CoC); 103 patients had MoP and CoC. 2) matched control population (same age, same period) of 820 patients without co-morbidities: 354 patients had MoP and CoP; 237 had CoP and CoC; 229 had MoP and CoC.

Among the 2290 hips, 3 early (less than 12 months) unilateral infections (2 in the controls, 1 in the SCD), and 59 late unilateral infections: 23 (1.4%) in 1640 THAs control, versus 36 (5.5%) in the SCD 650 THAs (P < 0.0001) during the observation period of 35 years.

In control group with the Kaplan-Meier analysis, increase infections over time but different (p=0.02) for each bearing surfaces, respectively from 0% at one year to 0.4% revision (2 cases) at most recent follow-up for 466 CoC hips, from 0% to 1.1% (7 cases) for 591 CoP hips, and from 0.3% to 2.4% (14 cases) for 583 MoP hips.

In sickle cell disease group MoP hips had higher risk of infection (26 among 219) when compared with CoP (9 among 222; p=0.002), and CoC (1 among 209 hips; p=0.0004); with increase over time from 1% at one year to 4% with CoP, and from 1% to 11.8% with MoP.

When contralateral hip of same patient is control, PE components are more prone to infection than those involving ceramic-on-ceramic.

It is unknown whether the risk of periprosthetic femoral fracture is the same in patients with two different bearing surfaces, ceramic on ceramic (CoC) and ceramic on polyethylene (CoP).

We retrospectively reviewed selected 126 patients (252 hips) with bilateral THA (one ceramic-ceramic, AL/AL and the contralateral ceramic-polyethylene, AL/PE) who had THA performed between from 1981 to 1985 for osteonecrosis. Surgery was performed in patients who were average 50 years (range 30–60) old. The stem was always cemented and the same for both sides. The alumina head was 32 mm in diameter. The acetabular component was a polyethylene cup or an alumina cup and was always cemented. The mean follow-up for living patients was 35 years (range 32 to 36), and the mean follow-up for patients who had died was 23 years range 15 to 30).

14 periprosthetic fractures occurred in 252 hips after THA, representing an overall prevalence of 5.5% for hips and 11% for patients. Periprosthetic fractures increased in number with followup: 3 patients (3%) sustained fractures within 10 years of their primary implantation, 7 within 20 years, 10 within 30 years, 14 (11%) within 35 years. The risk of fracture was influenced (p=0.01) by the bearing surfaces at the time of prosthetic implantation, low (1%) for ceramic on ceramic (1/14 fractures; 1/126 hips), higher (10%) for ceramic on PE (13/14; 13/126).

When the contralateral hip of the same patient is the control, the long-term risk of periprosthetic fracture on the side with PE cup is greater (10%) than on the side with ceramic/ceramic bearing.

Although alumina has been used in orthopaedic surgery since the 1970s, the long-term clinical results of zirconia have not been well documented in vivo. We studied hips with these two different ceramics during the same period and with a minimum follow-up of ten years. Because the size of the alumina and zirconia heads was different, hips with 32 mm alumina heads and those with 28 mm zirconia heads were compared with control hips with stainless-steel heads of the same size. Our aim was to compare the two ceramics.

There was an increased linear rate of penetration of the femoral heads into the liner between years five and 12 for the zirconia and the stainless-steel groups. This was severe in the zirconia group (0.4 mm/year compared with 0.13 mm/year for the stainless-steel group). During the same 12-year period there was, however, no significant change in the rate of wear in the alumina group (0.07 mm/year). The mean wear at the most recent follow-up was 1360 mm³ for the 28 mm zirconia group, 683 mm³ for the 28 mm stainless-steel group, 755 mm³ for the 32 mm alumina group and 1314 mm³ for the 32 mm stainless-steel group. The monoclinic content rose on the surface of three zirconia heads which were retrieved at revision. This change was associated with an increase in the surface roughness. A change in the roundness with an increase in the sphericity deviation was also observed both in the articular and non-articular parts of the femoral heads. The increase in rate of wear in the zirconia group was only evident after eight years and may be linked to a long-term biodegradation of zirconia in vivo, associated with the altered roughness and roundness which was observed on the retrieved heads.

We tested the accuracy of MRI for the precise quantification of the volume of osteonecrosis in 30 hips (stage III). The values were compared with direct anatomical measurements of the femoral heads obtained after total hip replacement. When the area of osteonecrosis was determined visually, and manually outlined on each slice, the accuracy of the measurement of volume was satisfactory, and the mean absolute deviation between MRI and anatomical measurements was similar to that between two MRI data sets. For ten of the hips which were measured by MRI, both before and after collapse, the volume did not appear to change significantly. Our findings suggest that the volume of osteonecrosis can be determined with accuracy by MRI, both before and after collapse.