The goal of this randomized controlled trial is to measure the periprosthetic bone mineral density changes around a 3D-printed highly-porous titanium acetabular cup used in primary total hip arthroplasty compared to a standard hydroxyapatite/titanium plasma-sprayed acetabular cup up to 2-year follow-up.

In joint arthroplasty, the need to use devices with highly-porous structures even more close to cancellous bone, arises from the need of optimal implant primary stability and osseointegration to guarantee long term longevity of the prosthetic implant.

After decades of clinical use of highly-porous tantalum (Trabecular Metal) acetabular components in total hip arthroplasty with excellent results, new highly-porous titanium structures have been developed and introduced in the market thanks to the additive manufacturing technology.

This study aims to investigate how bone remodeling occurs after primary total hip arthroplasty around a highly-porous trabecular-irregular acetabular cup, 3D-printed with selective laser melting, in comparison with a standard hydroxyapatite/titanium plasma-sprayed cup with the same design. The null hypothesis, which the study aims to reject, is that there is no difference in bone mineral density changes between highly-porous and traditional plasma-sprayed cups.

Overall 50 patients will be enrolled to be 1:1 randomized for receiving the investigational cup or the control cup in two centers.

Periprosthetic bone mineral density will be measured by DEXA (Dual-Energy X-ray Absorptiometry) around the acetabular cup according to four ROI (Region Of Interest). DEXA scans will be taken at different time-points up to 2-year follow-up. DEXA scan taken before patient discharge will be used as baseline.

Patients will be assessed also for clinical and radiological results, with focus on osseointegration signs of the acetabular cup.

Inclusion Criteria:

• Patient candidated to undergo unilateral cementless primary total hip arthroplasty with Jump System Traser® cup or Jump System HAX-Pore® cup by Permedica Orthopaedics (study sponsor).
• Patient with primary or secondary hip osteoarthritis;
• Patient who has given informed consent;

Exclusion Criteria:

• Male patients younger than 40 years or older than 85 years;
• Female patients younger than 50 years or older than 85 years;
• Childbearing;
• Patients not indicated for receiving the investigational devices;
• Patients not indicated for receiving cementless metaphyseal short femoral stems by Permedica Orthopaedics as the "Exacta RS" or "Exacta S" brand;
• Patients with rheumatoid arthritis, avascular osteonecrosis, severe hip dysplasia (grade III-IV according to Crowe classification), Perthes disease, Paget disease, femoral neck fracture, pelvic fracture or sequelae of previous surgical procedures or trauma to the ipsilateral hip;
• Patients with bone disorders;
• Patients with diabetes;
• Patients under PTH (parathyroid hormone), corticosteroid, or osteoporosis pharmacological therapy;
• Patients with disabling disease in the contralateral limb;
• Patients with BMI > 30 or < 18;
• Patients not willing to follow the study protocol;
• Patients incapable to understand the study protocol;
• Patients addicted to alcohol or drugs;
• Patients already enrolled in other clinical investigations;