13 Direct Anterior Approach to Total Hip Arthroplasty
Anterior approach hip replacement has been popularized over the decade, in part because of a potential early postop functional benefit over other approaches. It is an approach that uses intermuscular planes to access and replace the hip joint, which results in comparatively less muscle damage. However, anterior hip replacement is a technically challenging procedure during the learning phase, and takes dedication to master. Specialized instrumentation, implants, and techniques have been developed to make the procedure easier. The surgery is performed in the supine position, rather than the lateral decubitus position of more traditional approaches. Fluoroscopy is also commonly used during the procedure to aid in component sizing and positioning. The procedure can be made easier to learn by understanding and studying the step-by-step progression of the surgery.
The direct anterior approach used in hip arthroplasty has been described by Smith-Petersen, but also by Heuter and others. 1 This approach has a steep learning curve, and takes about 50 cases to master the technique. Complications are more common at the start of the learning curve, and one must be aware of the potential pit-falls of this approach. 2 However, despite the learning curve, this approach does have potential benefits in early recovery and function to the patient, but long-term benefits are controversial. 3 , 4
Surgical table. A regular table with a foot extension that allows for fluoroscopy of the hip and a break in the bed at the hip joint; or a specialized table designed for the procedure.
Surgical instruments. Specialized instruments are available to aid in performing the procedure; shorter femoral stems are helpful, and it should be noted that femoral head sizes larger than 36 mm can be harder to reduce.
Surgical team. A consistent, experienced operating room team is very helpful as this procedure is more of a team approach than others.
Patient position. Supine tape is used from the umbilicus to the contralateral side of the bed to bring any pannus out of the way of the proposed incision.
Patient considerations. This approach is technically more challenging in patients with a large pannus or those who are very muscular.
Patient exam. Recommend a motor exam including the quadriceps, tibialis anterior, extensor halluces longus, and planter flexors; a sensory exam of the lateral femoral cutaneous, the femoral/saphenous, and the deep/superficial peroneal and tibial nerves; and a vascular exam of dorsalis pedis and posterior tibial arteries.
Mark the relative start point for the incision about 2-cm distal and 2-cm lateral to the ASIS.
Use fluoroscopy to mark the femoral neck, and the lateral border of the greater trochanter.
Center the 10-cm longitudinal incision on the femoral neck marking, along the lateral border of the femur, and extending a little extra proximally is common to gain more access to the femur. Running the incision a little lateral on the distal aspect can aid in acetabular preparation and insertion.
Make a sharp incision and dissection down to the tensor fascia. Hemostasis is really helpful in the subcutaneous tissue and any perforators out of the tensor fascia. Identify the tensor laterally by looking for the fibers that run obliquely and laterally away from the hip joint. Try to feel the interval and stay lateral to that interval. Incise the tensor fascia with a knife (▶Fig. 13.1).
Lift the fascia medially, and use finger to dissect the muscle away from the remaining centimeter or so of medial fascia, and bring finger down to the deep fascia. Retract muscle gently laterally and then identify the circumflex vessels. These vessels are proximal, and are almost always present and identifiable. If not seen, consider being in the wrong interval or too distal. Sometimes, they are a bit hidden and a little dissection bluntly will bring them into view. Cauterize these vessels well. Then, cut them and perforate the deep fascia to open up the interval to the anterior capsule (▶Fig. 13.2).
Place retractors superior and inferior to the hip capsule. Place additional retractor under the rectus anteriorly and into the joint or over the anterior wall. Incise the capsule, or excise a portion of the anterior capsule. Incise the inferior capsule off the calcar a bit. Try to get up to the labrum and excise at least the anterior portion.
Some surgeons use a large screw in the femoral head and traction and external rotation at this point to dislocate the head, then relocate it to just to break up the ligamentum. It is not required, but it is helpful.
Mark the neck cut with fluoroscopy, and then mark a second cut about a centimeter proximally. Make the proximal cut, making sure the head is dissociated from the cut. Make the neck cut, and make sure the cut is complete. Do not cut into the acetabulum or too deep as posterior structures are close. Remove the neck fragment with a Steinman pin. Tilt the head into external rotation to see more of the joint surface and insert the Steinman pin into the head and remove with force. Retractors may have to be removed to relieve tension, but take care to protect the tensor muscle as too forceful removal can cut the muscle fibers. Traction on the leg can be helpful.