Single-Incision Direct Anterior Approach for Total Hip Arthroplasty

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CHAPTER SYNOPSIS

Minimally invasive single-incision direct anterior approach surgery is completed by an 8- to 10-cm incision. The incision is positioned more laterally to protect the lateral femoral cutaneous nerve. Access to the joint capsule is achieved through the septum between the tensor fasciae latae and gluteus medius and the rectus femoris of the quadriceps femoris muscle and the sartorius. The approach requires specialized instruments for proper viewing and implantation of the hip joint. The anterior approach does not require any detachments of muscle insertions or muscle dissection. The direct anterior approach spares the abductor muscles and therefore minimizes the risk of gluteal insufficiency.

IMPORTANT POINTS:

1

Ideal candidates have a body mass index less than 30 kg/m ²and moderately developed subcutaneous tissue and muscles.
2

Contraindications to the procedure include significant femoral bone deformity.
3

The intermuscular portal consists of the tensor fasciae latae, gluteus medius, and rectus femoris and sartorius.
4

A localized light source at the acetabular exposure is helpful.
5

Complications include lateral femoral cutaneous nerve injury.

CLINICAL/SURGICAL PEARLS:

1

The surgical table can be broken at the level of the hip joint to hyperextend both legs; an additional arm board supports the abducted leg.
2

The starting point of the incision is located 3 cm distal and lateral to the anterior superior iliac spine. This lateral skin incision protects the branches of the lateral femoral cutaneous nerve.
3

At the intermuscular portal, the fat layer defines the Smith-Peterson interval.
4

If the retractor is placed perpendicularly to the ilioinguinal band and kept under the iliopsoas muscle, injuries of the femoral nerve or the vascular bundle can be avoided.
5

The use of four specially curved retractors reduces pressure on soft tissue and optimizes the surgical area. The ascending branches of the lateral circumflex vessels must be ligated or cauterized. An offset reamer handle and cup impactor are necessary for correct acetabular preparation and implant placement.
6

Use a micro-saw or a standard power tool with a long, small saw blade for the double osteotomy; the saddle is the starting point.

CLINICAL/SURGICAL PITFALLS:

Skin Incision, lateral femoral cutaneous nerve, Intermuscular Portal femoral nerve vascular bundle.

INTRODUCTION

Total hip arthroplasty (THA) is considered one of the most successful surgical procedures because it relieves pain, restores mobility, and improves quality of life for patients with previously incapacitating arthritis. The success of operative treatment depends on a quick recovery of limb function, safety and reproducibility of the procedure, and alleviation of associated pain. The concept of minimally invasive surgery (MIS) was introduced to orthopedics in the 1970s by Watanabe in association with arthroscopy. MIS is defined as a surgical technique performed through a short skin incision to minimize injury to muscles and bones. “Minimally invasive” does not necessarily mean “short scar”; it refers to minimal damage to soft tissues, particularly muscles and their insertions. Every injury to a muscle or its attachment is associated with decreased muscle strength and impaired proprioception. Muscle protection translates into accelerated rehabilitation that, in turn, enables the patient to be discharged sooner and possibly start rehabilitation faster. In a standard surgical approach, size of the incision is dictated by the requirements during the surgery; with minimally invasive techniques the size of the surgical approach is much more of a fixed parameter. MIS approaches include the posterior, anterolateral, direct anterior, and two-incision approach.

During recent years the orthopedic community has witnessed an immense preoccupation with MIS, particularly for THA. Although long-term results of MIS THA are unknown at this point, short-term benefits have been reported by some studies, advocating that MIS THA reduces intraoperative blood loss, reduces perioperative pain, results in faster recovery, shortens hospital stay, and provides better incision cosmetics. Other studies refute the beneficial merits of MIS THA, reporting higher complications and worse cosmetic appearance for the incision. In addition, the learning curve connected with MIS is steep, and mastering the skill frequently is an ongoing process. Also, confounding factors such as patient selection, patient and family education, accelerated rehabilitation, and better pain control may play an important role in influencing the outcome of minimally invasive THA.

The anterior approach best follows the principles of MIS because implantation of a hip prosthesis is possible with minimal damage to muscles or their insertions. This approach was first described by Robert Judet in 1947 as a modification of the Smith-Peterson approach. Judet used an orthopedic table with indirect traction applied to both feet; traction applied to the lower limbs combined with traction and simultaneous external rotation and hyperextension in the hip joint of the treated limb facilitate hip joint dislocation. Current modifications of the technique do not require an orthopedic table and traction to the lower limbs. The procedure can now be performed on a flat-top table. Hyperextension is obtained before for the femoral preparation by manipulation of the table to break at the level of the pelvis and hyperextend the legs. The direct anterior approach is an inter-nervous plane surgical approach. Access to the joint capsule is achieved through the septum between the tensor fasciae latae and gluteus medius (superior gluteal nerve) and the rectus femoris of the quadriceps femoris muscle and the sartorius (femoral nerve).

Appropriate instruments significantly facilitate prosthesis implantation and, more importantly, reduce the risk of complications. The procedure also is facilitated by a fiber-optic light source attached to retractors.

INDICATIONS AND CONTRAINDICATIONS

Indications for using the minimally invasive technique include moderate degenerative changes in the hip joint of various etiologies requiring total hip replacement. The ideal patient is a flexible, nonmuscular patient with a valgus femoral neck and good femoral offset. Not every surgeon can perform the minimally invasive procedure because it requires excellent manual skills and knowledge of anatomy as well as experience in performing conventional hip joint surgery so that the operator can appropriately widen the approach if need be. An efficient and experienced operating team, including the assistants and adjunct personnel, also is of great importance. Initially only slim patients with a body mass index less than 30 kg/m ²(below degree I obesity) with moderately developed subcutaneous tissue and muscles around the joint should undergo the procedure. As experience develops, the surgeon can expand this approach to virtually all patients. However, the procedure should not be used in the presence of significant femoral bone deformity. Muscular patients make the exposure much more difficult, which is true for all approaches to the hip. The lack of appropriate instrumentation also is considered a contraindication. The direct anterior approach requires the availability of specific curved, angulated, or offset instruments.

The direct anterior approach can be used for revision surgery as well. However, distal exposure for the femur requires that the incision be curved laterally to prevent injury to the femoral nerve and vessels. A partial release of the tensor fasciae latae muscle’s origin gives straight access to the femur. Lateral access to the femur can be achieved by a dorsolateral extension of the incision or a second lateral incision dorsal to the lateral vastus muscle. In revision THA the direct anterior approach is particularly useful for isolated simple acetabular revisions.

SURGICAL TECHNIQUE

Positioning and Draping

A standard operating table is used; it can be broken at the level of the hip joint to hyperextend both legs. The patient is placed in the supine position and the operative leg is draped. The supine position promises a stable pelvis and allows easy leg length measurement. The opposite leg is supported by an additional arm board attached to the table. This should make hyperabduction of the opposite leg during femoral exposure easier. The authors drape only the operated leg but other surgeons drape both legs, which allows crossing the operated leg under the opposite leg during the surgical exposure of the femur.

Skin Incision

The position of the skin incision is found by palpating the anterior superior iliac spine from below. From this point, measure 3 cm laterally and 3 cm distally to find the starting point and orient the incision along the longitudinal axis of the tensor fasciae latae. Keep the initial incision small (8 to 10 cm), but do not hesitate to extend it as needed ( Fig. 23-1 ). Lengthen distally to increase acetabular exposure and proximally to increase exposure of the femur. The site of the incision is located much more laterally than the site of the incision in the original Smith-Peterson approach. Another method for finding the incision site is to draw a line between the anterior superior iliac spine and the greater tuberosity. The proximal extent of the incision starts on this line approximately halfway between the two landmarks. The incision should angulated gradually toward the greater tuberosity rather than go straight distally. In the area of the incision, vessels perforating the iliotibial band can be found and should be cauterized.