The uncemented Symax hip stem is developed through optimization of the uncemented Omnifit hip stem. The Symax stem design combines an anatomical anteverted proximal geometry with a straight distal section. The proximal part is coated with a biomimetic hydroxyapatite (HA) coating for improved osseointegration to enhance load transfer and to minimize proximal bone loss. The distal part is treated with an anodization surface treatment in order to prevent distal bone apposition, which is expected to prevent distal loading and reduce proximal stress shielding. Aim of this study is to report mid-term clinical performance and evaluate whether the radiographic features are in line with the design principles of the Symax hip in an international clinical study with 5 years of follow-up.

Inclusion Criteria:

• Patients requiring uncemented primary total hip arthroplasty (osteoarthritis, avascular necrosis and/or post-traumatic arthritis), age between 18-70 years, BMI less or equal to 35.

Exclusion Criteria:

• Patients with bilateral hip complaints, impaired cognitive function and use of medication or illness influencing bone metabolism.