Evaluation of the Positioning of the Dynacup Cup "One C" Versus "Standard Dynacup" (DYNACUP)

The ceramic-ceramic friction pair is widely used today in total hip arthroplasty, including fourth-generation ceramics which show the lowest wear rate. These have considerably reduced the risk of head fracture compared to previous generations; however, the risk of insert rupture persists with rates similar to those of third generation ceramics. These ceramic fractures require complex revision surgery, which brings complications, exposing patients to the risk of third-body wear and tear related to persistent post-surgical debris. They are frequently due to an incorrect assembly of the ceramic causing intraoperative or early postoperative rupture. To fix this, manufacturers have developed pre-assembled cups in the factory. The Dynacup One C cup developed by Corin® corresponds to the pre-assembled version of the Dynacup cup, making it possible to eliminate the risk of anomaly during intraoperative assembly linked to the human factor and to offer patients with very small cups an adapted ceramic implant. A single study with a small sample compared the two implants (pre-assembled version [vs] modular version) clinically, radiologically and functionally without showing any significant difference. The lack of data in the literature comparing these two implants motivated us to conduct a randomized comparative study on a large sample of patients.

Patients eligible for a total hip arthroplasty with a ceramic-ceramic friction couple and scheduled for surgery will be included in this study after information and collection of written consent. After randomization, a preoperative radiograph with a calibration ball will be taken to plan the prosthesis and identify the characteristics of the operated hip. An x-ray of the pelvis with a 28 mm ball will be carried out the day after the intervention according to the same preoperative procedures in order to measure the postoperative radiographic parameters.

To Compare the positioning accuracy of the Dynacup One C (pre-assembled version) with that of the standard Dynacup.

Radiographic measurement of the position of the center of rotation of the final implant, its inclination and its anteversion, compared to the positioning planned before the intervention for the 2 types of implants.

Note the attempts at re-impactions for sensation of extrusion: after palpation with forceps of the bottom of the acetabulum (bone space - metal back for the standard Dynacups) or of its protruding periphery of the bone (for the pre-assembled versions) . ○ Note the operator's feeling before postoperative control X-ray on the good impaction of the acetabulum: at the bottom, doubtful or extrus.

Describe the rate of intraoperative complications according to the type of implant: Fracture of ceramics on impaction or assembly Fracture of the bony acetabulum or unplanned acetabular protrusion

Describe the rate of insufficient impaction of the acetabulum in the 2 versions Radiographic measurement of the space between the bottom of the prosthetic acetabulum and the bottom of the milled bone acetabulum (Space > 2mm = impaction defect) Radiographic analysis of postoperative front and side views by an independent evaluator

Look for predictive factors of insufficient impaction of the acetabular implant Depending on the type of implant According to the morphology of the arthritic hip: Type of indication and acetabular osteoarthritis: necrosis, upper lateral osteoarthritis, postero-internal osteoarthritis, global osteoarthritis or coxitis Acetabular morphology: osteophytosis, dysplasia, osteocondensation, protrusion, sheathing Femoral morphology: Dorr classification, cervico-diaphyseal angle.

Inclusion Criteria: Adult man and woman > 18 years old Indication for hip arthroplasty with a Dynacup One C or standard Dynacup cup Patient informed of the study and signed a consent form Exclusion Criteria: Refusal to participate in the study Indication of a friction couple other than ceramic-ceramic Contraindication or the technical impossibility of implanting an impacted acetabular component Pregnant or breastfeeding women. Minor patients aged < 18 years Subjects not affiliated to the national health insurance or to an equivalent insurance