The data needed for regulatory submissions based on the current pace of the study, will not be available in the foreseeable future.

This study is a Prospective, Multicenter, Single-Arm, Cohort post-market study to evaluate the accuracy of acetabular implant position using the robotic-arm surgical assistant (ROSA® Hip System).

Consecutive patients who meet all of the inclusion criteria and none of the exclusion criteria will be eligible for participation in the study, and will be pre-screened for participation in the informed consent process.

The primary objective of this study is to assess the accuracy of acetabular implant position by evaluating the percentage of participants who are within the range of the Callanan safe zones for Acetabular Inclination (30 - 45 degrees). A patient is considered a success if their intra-operative and/or post-operative full pelvis fluoroscopic or radiographic images show the postoperative acetabular inclination to be within this safe zone range.

Secondary Objectives include the evaluation of safety and efficacy of this system and will include the assessment of common adverse events, physical exam findings, radiologic results, and patient reported outcome measures.

Data collection will occur at the following intervals: Pre-operative, Operative, 3-months, 1-year, and 2-years. Enrollment for the study is anticipated to last approximately 18 months. Allowing for 24 months of follow-up, the total estimated study time to final-patient final-visit will be approximately 42 months.

Inclusion:

1. Age 18 - 80 years
2. Body mass index ≤40 (BMI = kg/m2)
3. Patient is willing and able to provide informed consent
4. Patient qualifies for primary THA, via an anterior approach, due to osteoarthritis or avascular necrosis of the hip based on Investigator's clinical judgment
5. Independent of study participation, patient is a candidate and meets the indications and none of the contraindications for use with the ROSA Hip System

Exclusion:

1. Has undergone an orthopaedic procedure of the spine or lower extremity, or is currently participating in a pain management clinical study of any joint, within the last 6 months or planned within the next 6 months
2. Patients receiving simultaneous bilateral hip arthroplasties are excluded from participation in this study; as well as any participants with staged bilateral arthroplasties within 6 months of each other
3. Active infection, sepsis, osteomyelitis
4. Patient is at a high risk for dislocation including those with long-segment spinal fusions (>3 levels) and neuromuscular disorders
5. Inflammatory (rheumatoid or psoriatic arthritis) or post-traumatic arthropathy, or any other degenerative joint disease not consistent with osteoarthritis
6. Would, in the Investigator's opinion, be unwilling or unable to comply with the postoperative follow-up schedule
7. Patient is considered a member of a vulnerable population (pregnant, prisoner, mentally incompetent, etc.)
8. Previous hardware in the proximal femur or acetabulum from a prior orthopaedic procedure