The ASI method (Anterior Supine Intermuscular) is a minimally invasive technique for performing total hip arthroplasty. Its main characteristics are that it is performed with the patient in the supine position, using a limited anterior approach (direct anterior approach), through a small incision, without cutting muscles and tendons, and without applying external traction to the lower limb. The duration of the ASI procedure ranges from 45 to 60 minutes.
Small incision (5 - 6 cm)
A small incision is made on the anterior surface of the hip without cutting the muscles and tendons of the area.
Ideal for overweight patients
In contrast to other conventional methods, the ASI approach does not require preoperative weight loss.
Reduced Complications
The ASI method is also successfully used in revision hip arthroplasty procedures.
The ASI method allows precise control of the length of the leg during surgery, so that the risk of anisosceles (difference in the length of the two legs) is eliminated.
It allows the hip stability to be controlled during the surgery, so that the risk of dislocation later on is eliminated.
The use of radiological control during surgery ensures the perfect placement of the materials.
The technique is suitable for all body types. Increased body weight is not a factor, as the incision site by its nature has minimal subcutaneous fat.
The total time of the operation is shorter than the classical methods.
The patient is placed in the supine position on the operating table and receives either general or spinal anesthesia, depending on medical needs and preferences, as agreed with the anesthesiologist. Initially, a 5–6 cm incision is made on the anterior surface of the hip (starting approximately 2 cm below and lateral to the anterior superior iliac spine and directed toward the head of the fibula). The hip joint is accessed between the tensor fasciae latae and gluteus medius (laterally) and the sartorius and rectus femoris (medially), without damaging these muscles or their tendons. Next, the acetabulum (in the iliac bone) and the femur are prepared to receive the prosthetic components, while intraoperative clinical checks are performed for implant stability and leg length. This is followed by intraoperative radiographic evaluation, and finally, the definitive prostheses are implanted. The wound is closed in layers, with the skin closed using plastic surgery techniques. The patient is mobilized on the same day, walking with the aid of crutches or a walker. Discharge usually occurs on the first or second postoperative day, with instructions for anticoagulant and analgesic therapy.
Postoperatively, physical therapy is not required. Patients in good biological condition and with good bone quality can walk with full weight-bearing on the operated limb from the first day. Other patients gradually increase weight-bearing and can walk without aids after about one month. Wound dressings are changed daily during the first week and then every other day until day 20, when sutures are removed.
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The advantages of the ASI method are numerous and derive from its minimally invasive philosophy. It is performed through a small incision (5–6 cm) on the anterior surface of the hip, without cutting muscles or tendons. This minimizes pain, blood loss, and the need for transfusion, shortens hospitalization, and allows for faster mobilization and recovery. The cosmetic result is excellent. The minimal trauma and rapid recovery also help prevent complications often associated with older techniques, such as thrombosis, heavy bleeding, and respiratory problems.
The ASI method is ideal for overweight patients. Traditional approaches, with incisions on the lateral or posterior thigh, as well as their more modern variations, are often problematic in such patients due to fat accumulation in the gluteal region, which makes access to the hip more difficult. Larger incisions are required, leading to greater blood loss, increased pain, and slower recovery. For this reason, hip surgeons typically recommend significant preoperative weight loss, which is extremely difficult or even impossible for many patients. With ASI, these issues are overcome, as fat accumulation at the incision site is minimal. Preoperative weight loss is not required, and the rapid recovery helps prevent complications more common in overweight or obese patients compared to those of normal weight.
The ASI method is also successfully used in revision hip arthroplasty, which is technically a demanding procedure performed when the original prosthesis needs to be replaced (due to loosening, infection, fracture, etc.). Its minimally invasive philosophy helps reduce complications associated with these complex surgeries.
Leg Length Discrepancy
One of the most bothersome complications of total hip arthroplasty is leg length discrepancy, which may occur after implantation of the prosthesis. Although anterior approaches provide better intraoperative control of leg length compared to lateral or posterior approaches, some patients still experience postoperative discrepancies greater than one centimeter.
The Large Joint Clinic, under the direction of Dr. Ioannis Tsarouchas, has long addressed this issue by applying intraoperative clinical and radiological checks, ensuring that even minor discrepancies are corrected during surgery. The latest innovation of the clinic involves refining its intraoperative protocol through the use of specialized computer software that allows for precise measurement of leg length difference using digital radiographs during surgery. This new protocol has led to even better results in avoiding leg length discrepancy and further shortening the duration of the procedure. The clinic’s study on this method was recently published in the European Journal of Orthopaedic Surgery and Traumatology under the title: “A new method for intraoperative assessment of leg length, sizing and placement of the components in total hip replacement.”
The Large Joint Clinic is recognized as a pioneer in hip surgery utilizing the ASI method. Its most recent distinction was being selected as the only reference center in Greece and one of the few in Europe for training surgeons in the ASI technique. This recognition followed a thorough evaluation by representatives of Zimmer Biomet, based on the surgical team's application of the technique, the adequacy of hospital infrastructure, and the large number of successful procedures already performed (over 3,000 patients). Since February 2019, the clinic has hosted numerous visiting orthopedic surgeons from Greece and abroad for training in the ASI method.
The ASI method is the solution to the problems encountered with AMIS. In other words, since traction is not necessary for the operation, as the patient's legs are free, intraoperative control of the lower limbs' isoskeletal system is ensured and intraoperative fractures or other possible soft tissue complications are avoided. Finally, patients who have previously undergone total knee arthroplasty are not at any risk unlike the risks of the AMIS method already mentioned.
The technique of Total Hip Arthroplasty of minimal invasiveness with the ASI method is applied by Mr. Ioannis Tsarouchas, at the Athens Medical Center.
Orthopaedic Surgeons who wish to attend or even be trained in the ASI method, can contact the secretariat of Mr.Tsarouchas Ioannis:
See the animation for the
ASI technique
