The Forgotten Joint Score-12 is a patient-reported outcome scale to assess joint awareness in hips during various activities of daily living. It uses a 5-point Likert response format, consists of 12-questions and the raw score is transformed to range from 0 (worst) to 100 (best) points. High scores indicate good outcome, i.e. a high degree of being able to forget about the affected joint in daily life. The FJS has a low ceiling effect and especially discriminates between good, very good and excellent outcome after THA and TKA. In its validation study it showed high internal consistency and discriminated well between patient groups known to show different outcome.

The Short Form 12 is a 12-item questionnaire used to assess generic health outcomes from the patient's perspective. The SF-12 results in two summary scores: the physical and mental components summary (PCS and MCS) scores. This score is calculated using norm-based methodology and population mean scores. Both PCS and MCS have a population mean score of 50 with an standard deviation of 10.

The EuroQol 5-dimension is a standardised instrument with five items for use as a measure of self-reported general health. Applicable to a wide range of health conditions and treatments, it provides a simple descriptive profile and a single index value for health status. This index for the UK population is on a scale of -0.594 to 1, where 1 represents perfect health and 0 represents death, with a utility of less than 0 being worse than death. It is one of the most frequently used measures to gain quality of life scores for analysis in health economy as utility weights for calculating quality of life adjusted life years (QALYs) can be obtained

Global hip pain severity will be assessed using an 11 point (0-10) numerical rating scale (NRS), where 0 represents no pain and 10 the worst possible pain. The validity and sensitivity of the NRS has been well documented. As it has been suggested that using multiple measurements of pain status as opposed to a single value of 'current pain' may provide more realistic and meaningful measurements of pain intensity, separate assessments will be made of 'worst pain' and 'perceived mean daily pain' as has been specifically recommended for use in OA clinical trials.

Satisfaction questions are reported using a 5-point Likert response format hip (very satisfied, satisfied, unsure, dissatisfied or very dissatisfied). Specifically, questions will ask patients as to their

1. overall satisfaction with their operated hip
2. how well the surgery relieves pain in the operated joint
3. how well surgery increases the ability to perform regular activities of daily living and to perform heavy work or sport activities

Plain radiographs will be obtained for assessment of fixation of the device evaluating radiolucent lines (mm), cup abduction angle (degrees), anteversion (degrees) and cup-centre-edge angle (degrees). Plain radiographs will be divided into the three acetabular zones according to those defined by DeLee and Charnley. Radiolucent lines will be defined as less then 2mm, more than this will be defined a lysis. Lysis in all three acetabular zone will define a loose cup. Acetabular component inclination and version will be calculated from anteroposterior radiographs of the hip and/or hip and pelvis using established and validated techniques. The safe zones for acetabular component positioning were assessed using the commonly adopted parameters defined by Lewinnek et al. (inclination of 30° to 50° and anteversion of 5° to 25°) and Callanan et al. (inclination of 30° to 45° and anteversion of 5° to 25°).