ASI stands for Anterior Supine Intermuscular, a minimally invasive technique for total hip replacement in which the joint is reached through the natural plane between muscles, with the patient lying on the back. No muscle or tendon is detached, which is the reason patients recover so quickly.
The hip is approached from the front, through the interval between the tensor fasciae latae and the sartorius and rectus femoris. These muscles are separated rather than cut. Because the patient is supine, the surgeon can use intraoperative fluoroscopy to confirm cup inclination and anteversion, femoral offset and leg length against the opposite hip before the wound is closed. The result is accurate implant positioning with an intact soft-tissue envelope.
Preserving the abductor muscles and the posterior capsule has direct clinical consequences. Patients can usually stand and take their first steps within hours of surgery. Post-operative pain is lower and less opioid medication is required. The hip is stable from the outset, so the traditional restrictions after posterior-approach surgery — no crossing the legs, no bending past ninety degrees, no sleeping on the side — are largely unnecessary. Reported dislocation rates after anterior approaches are low, and the limp caused by abductor damage is avoided.
ASI is combined with a fast-track protocol: multimodal pain control, no routine drains or catheters, early feeding and mobilisation on the day of surgery. Most patients leave hospital within two to four days, walk without aids in two to four weeks and return to desk work in three to six weeks. Swimming and cycling are usually resumed at six to eight weeks. Detailed guidance is given in our hip replacement rehabilitation guide.
The technique is used for the great majority of primary total hip replacements, including patients with hip osteoarthritis, avascular necrosis of the femoral head, adult hip dysplasia and femoral neck fractures. Very high body mass index, severe deformity, previous hip surgery or complex revision cases may require a different approach; this is decided after clinical examination and imaging.
Modern uncemented titanium implants with highly cross-linked polyethylene or ceramic bearings have excellent long-term survival, and registry data show the majority of hips still functioning well twenty years after surgery. Implant choice depends on age, bone quality and activity level rather than on a single “best” brand.
The Major Joints Clinic at the Athens Medical Center is a reference and training centre for total hip replacement with the ASI method. Patients from Greece and abroad are assessed on the basis of recent imaging before travelling — contact the practice to arrange an appointment or a second opinion.
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