The principal objective of this study is to compare mean 2-year subsidence of the ACTIS femoral stem using model-based RSA against published migration patterns for hip stems of a similar design. Secondary objectives include comparison of migration per surgical approach, quantifying changes in functional and health status of subjects following surgery, and assess occurrences of complications and adverse events.

This is a multi-centre, sequential enrollment trial of patients undergoing primary total hip arthroplasty. Patients will be recruited at three Canadian Centres to receive the ACTIS femoral hip stem via 3 different surgical approaches.

Model-based RSA will identify migration of the implant with respect to the femoral bone during the first 2 post-operative years. Patient health and functional outcomes will be recorded at pre- and post-operative intervals to quantify improvement as a result of the surgery and trajectory of recovery. Adverse events and clinical complications in each study group will be captured and compared. Select surgical, hospital and rehabilitation data will be collected to measure health economic outcomes relating to the surgery.

Inclusion Criteria:

• Symptomatic osteoarthritis of the hip indicating primary total hip arthroplasty
• Aged 21 years or older
• Patients willing and able to comply with follow-up requirements and self-evaluations
• Ability to give informed consent
• Body mass index ≤45 kg/m2

Exclusion Criteria

• Active or prior infection
• Medical condition precluding major surgery
• Medical condition with less than 2 years life expectancy
• Overhanging pannus (for anterior approach cohort only)
• Prior surgery of the hip involving implantation of hardware (i.e., hemiarthroplasty, internal fixation, pelvic reconstruction near the acetabulum requiring removal)
• Skin condition on the area of incision
• Multi-level lumbar spine fusion
• Ankylosing spondylolithesis
• Shortening osteotomy through the femur