The aim of the present study is to explore the most efficient surgical approach in total hip replacement in short and long term when concerning strength, functionality and postoperative complications.

The objective is to register muscular strength, hip joint functionality/mobilisation and complications after total hip arthroplasty (THA) performed by the direct lateral approach (DLA), the posterior approach (PA) and the anterior approach (AA). The latter is a modified Smith-Petersen approach which follows the principles of minimally invasive surgery (MIS).

The primary working hypothesis is that due to a minimal dissection and reduced trauma in the muscles, patients will tolerate early hospital discharge better after the AA than the PA and the DLA. Patients in the AA group are also thought to be more active and maintain muscular strength and hip joint functionality/mobilisation better than patients in the lateral group.

With total hip replacement surgery, the orthopaedic surgeon's aim is not only pain relief for the patient, but also restoration of hip joint biomechanics resulting in a minimal functional deficit and maximal longevity of the implant. It is not exceptional that these patients still experience mild to moderate long-term impairments postoperatively. These impairments include pain, muscle weakness of the hip abductors, contracture of the hip, gait disorders, as well as weakness of hip extensors and flexors. These problems may in turn lead to complications such as joint instability and loosening of the implant.

MIS is defined as a surgical approach performed through a short skin and muscle incision to avoid injury to muscles and tendons. Following minimally invasive approach reduced muscle trauma has been found. Moreover clinical outcome improved, as the gluteus medius muscle can be spared more successfully. However, it is debated whether or not the overall results of MIS are superior, or even as good as the traditional hip replacement surgery in terms of component placing and time to revision of the prosthesis.

Inclusion Criteria:

• Patients scheduled for THA
• Diagnosis of primary osteoarthritis as the main cause for elective THA
• American Society of Anesthesiologists (ASA) score I, II, and stable III

Exclusion Criteria:

• Musculoskeletal diseases
• Current heart/pulmonary- or malignant diseases likely to influence the physical testing performance.