Effectiveness of shorter femoral stems for hip replacement surgery, testing the biomechanics, using computer simulations, and comparing clinical outcomes between two types of short stems: one with a collar and one without

INTERVENTION: Total hip arthroplasty will be performed in patients with hip osteoarthritis and no hip surgery on the other side or hip dysplasia. The two stems compared will be a short‐collared stem and a short stem. Participants are randomized using Random.org. Clinically, our data will be collected prospectively including patient‐reported outcomes questionnaires (HOOS, Harris Hip Score, SF12, VAS), nutritional indexes, biochemical studies, clinical tests (Time Up and Go, 6m Walk Test), hand grip test and gait analysis pre‐ and postoperatively according to the literature. As far as the radiological results are concerned, a standard anteroposterior pelvis x‐ray will be performed pre‐operatively and at 3, 6, 12 and 24 months postoperatively, as well as a CT scan preoperatively. Regarding the biomechanical part, a finite element analysis model will be developed and the behavior of the two stems implanted will be modeled. A biomechanical experiment will be set utilizing a loading device to load composite implanted Sawbones under normal circumstances. Inductive miniature displacement transducers and digital image correlation will be used to measure subsidence and stress shielding accordingly. The data from the biomechanical experiment will be used to verify the finitel element analysis model. The verified model will be used to study the behaviour of the two stems regarding the stems’ subsidence and strain distribution (stress shielding). An interdisciplinary team of statisticians and clinicians will discuss and correlate the results of the biomechanical and clinical study. CONDITION: Total hip arthroplasty for hip osteoarthritis ; Surgery PRIMARY OUTCOME: 1. Patient‐reported outcomes reported preoperatively and at 3, 6, 12 and 24 months using:; 1.1. Hip pain and function measured using Forgoten Joint Score 12 (FJS‐12); 1.2. Hip pain and function measured using Hip Disability and Osteoarthritis Outcome Score (HOOS); 1.3. Hip pain and function measured using Harris Hip Score (HHS); 1.4. Pain measured using Visual Analogue Scale (VAS) ; 2. Quality of life measured using Western Ontario and McMaster Universities Arthritis Index (WOMAC) and 12‐Item Short Form Health Survey (SF‐12) preoperatively and at 3, 6, 12 and 24 months; 3. Stem subsidence measured using anteroposterior pelvis x‐ray at 1, 3, 6 and 12 months SECONDARY OUTCOME: 1. Gait analysis using VICON 2.4 preoperatively and at 1 and 6 months postoperatively; 2. Handgrip strength measured using a Jamar Hydraulic Hand Dynamometer at 3 ma Xrepetitions and capturing the best effort preoperatively INCLUSION CRITERIA: 1. Age 50 ‐ 80 years old 2. Primary hip osteoarthritis 3. Inflammatory hip arthritis 4. Hip avascular necrosis 5. Post‐traumatic arthritis