 We expect that no major deviations in gait pattern occur later than 6 months after the intervention and therefore, a stable gait pattern is presented 6 months postoperatively. This expectation is made based on clinical experience, in which gait is often affected during these first 6 months after the intervention due to pain, a long non-weightbearing period of the leg in the postoperative phase and rehabilitation. After these six months no further deviations in gait pattern were expected and a stable, compensating gait pattern is observed and patients will be analysed between 6 months till 5 years postoperatively. 