Patients scheduled for THP (Total Hip Prosthesis) will be seen at the consultation the day before surgery, in the same hospital as the THP, or at an existing dedicated consultation scheduled for all THP patients. During these scheduled visits, they will be received in the gait analysis laboratory for a gait assessment (V1). Patients will be seen again at 6 months post-operatively for a second gait assessment (V2).

Patients scheduled for RTH (Hip Resurfacing) will be seen at the consultation the day before surgery, in the same hospital as the RTH, or at an existing dedicated consultation scheduled for all RTH patients. During these scheduled visits, they will be received in the gait analysis laboratory for a gait assessment (V1). Patients will be seen again at 6 months post-operatively for a second gait assessment (V2).

The severity of coxarthrosis is assessed on radiographs according to the Tönnis classification:

Grade Radiographic features 0 - No signs of osteoarthritis

1. - Slight narrowing of joint space

   • Slight lipping at joint margin
   • Slight sclerosis of the femoral head or acetabulum

2. - Small cysts in the femoral head or acetabulum

   • Increasing narrowing of joint space
   • Moderate loss of sphericity of the femoral head

3. - Large cysts

   • Severe narrowing or obliteration of joint space
   • Severe deformity of the femoral head
   • Avascular necrosis

The functional score consists of 10 items out of 100 points (best score = 100 points) assessing function, pain and mobility

Score on 3 items (pain, mobility and walking) rated on 18 points (18 = excellent results, 0 = worst result)

Activity score with 5 possibilities (1 = sedentary work and 5 = power work, competitive sport)

Activity score comprising 10 possibilities and assessing the intensity of physical activity (1= inactive or dependent patient, 10 = regular practice of high-impact sports)

This test consists in asking the patient to balance for as long as possible. A time of more than 30 seconds indicated a very low risk of falls. A time of less than 5 seconds indicates a very high risk of falls.

Pelvic incidence is a constant morphologic parameter that describes the "pelvic size" based on the angular relation between femoral heads and sacral plate for any given person

Spatial orientation of the pelvis in the sagittal plane is assessed by the sacral slope

Pelvic tilt is a position-dependent parameter defined as the angle created by a line running from the sacral endplate midpoint to the center of the bifemoral heads and the vertical axis.