Aim of the present investigation is to analyse the amount of muscle trauma in relation to the surgical approach and to the individual postoperative functional recovery. The investigation will compare the MIS (minimally invasive surgery) anterior approach with the MIS anterolateral approach to the hip.

The surgical approach to the hip is reportedly an important factor influencing implant stability and postsurgical muscle functioning. Reviewing the literature, controversial studies towards minimally invasive hip surgery can be found. Currently, none of the approaches can be considered superior, but the trend is towards minimally invasive techniques, as it is generally accepted that muscle trauma and damage of the periarticular structures should be minimized. However, a surgical approach that causes no damage to surrounding muscle is unrealistic. Whether the muscle is stretched, transacted or partially torn, injury will occur.

Aim of the present investigation is to analyse the amount of muscle trauma in relation to the surgical approach and to the individual postoperative functional recovery. The investigation will compare the MIS anterior approach with the MIS anterolateral approach to the hip. The investigators questioned, which technique would be the less invasive? Pain and functional performance will be measured using the Harris Hip Score, the Western Ontario McMaster, and the UCLA (University of California) Activity Score. Subject quality-of-life will be determined by evaluation the Short-Form 36 Health Survey. Standard radiographs of the hip are required to be captured before surgery and at 3, 6 and 12 months postoperatively. MRI scans will be performed to evaluate tendon defects, fatty atrophy and changes in the muscle cross-sectional area. Next, the patients will be referred for hip sonography, performed by a radiologist who is experienced in imaging of the musculoskeletal system who will be unaware of the clinical examination results of the patients. Moreover gait analyses will be performed preoperatively, 3 and 12 months after surgery. Pre- and postoperative standard blood tests and specific serum trauma markers will be obtained.

Inclusion Criteria:

• unilateral, noninflammatory end-stage osteoarthritis of the hip
• willingness and ability to cooperate in the required post-operative therapy
• willingness and ability to provide written informed consent
• age 50-80 years

Exclusion Criteria:

• inflammatory arthropathies
• prior hip surgery
• prior infection of the hip
• severe morbidity
• severe osteoporosis
• inability to tolerate general anesthesia
• no contraindications to MRI e.g. pacemakers, claustrophobia
• neuromuscular disorder, vascular disorder or other conditions that could contribute to prosthesis instability, prosthesis fixation failure, or complications in postoperative care
• known alcohol or drug abuse
• unwillingness to participate