Single center, pilot, randomized, controlled clinical trial to assess metabolic and morphological images between two types of cemented stem prostheses in patients undergoing total hip arthroplasty surgery during a 2-year follow up period.

Single center, pilot, controlled clinical trial to assess metabolic and morphological images of patients undergoing total hip arthroplasty surgery randomized to the thick layer technique (Exeter hip stem model) or to the "French paradox" technique (Müller straight stem model).

Participants will be performed a plain radiography and a SPECT-CT at 3, 6, 12 and 24 months of the intervention. SPECT-CTs will be performed in addition to the usual medical care complementary imaging exams. The SPECT will require the administration of the 99mTechnetium-methylene diphosphonate (99mTc-MDP) radiopharmaceutical (useful to assess bone metabolism) and its combination with a CT scan (SPECT-CT) allows a combined metabolic and morphological study.

Inclusion Criteria:

• patients ≥ 18 years-old
• both genders
• patients undergoing a primary total hip arthroplasty surgery with implantation of a cemented prosthesis (Exeter hip stem model or Müller straight stem model)
• patients with a diagnosis of hip osteoarthritis, operated by the Orthopedic Surgery and Traumatology Department at the Bellvitge University Hospital
• patients who signed the written informed consent.

Exclusion Criteria:

• patients allergic to 99mTc-MDP radiopharmaceutical
• patients with claustrophobia
• patients with a background of an active septic process
• patients with a postoperative septic complication
• patients periprosthetic fracture or misalignment of the prosthetic component
• patients who have a total hip prosthetic implanted due to a subcapital femoral fracture

After assignment to interventions (Exeter V40 cemented femoral stem or Müller THA), participant and surgeon team will be aware of the type of cemented stem prosthesis allocated. Since after randomization this is an open-label study, emergency unblinding does not apply. Data analysts will be blinded.

Personal patient data will be coded and dissociated, so that the patient to whom they correspond is not recognizable. Consecutive numbers will be assigned as they are enrolled in the study, and these numbers (or codes) will be used in the eCRF, rather than personal data.