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Minimal/limited access
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Anterolateral
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Single incision
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Intermuscular
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Readily extensile
The ultimate goal for arthroplasty surgeons is to provide patients with a state of the art total hip arthroplasty with excellent fixation and a durable bearing surface, allowing outstanding function that meets patient expectations. Recovery should be short and rehabilitation rapid so as to optimize transition through the entire experience.
Exposure is an important facet of the surgery and determines the extent to which the soft tissue envelope is compromised. If soft tissue damage can be kept to a minimum, then recovery and rehabilitation should be rapid. In the past, surgeons performed large exposures to aid component placement and protect neurovascular structures. Recently though, the concept of minimally invasive surgery has come to the fore. As a consequence, surgeons have had to re-evaluate the techniques they use and decide whether they adopt these new minimally invasive surgical techniques. There are many proposed advantages. However, it has yet to be proven that minimally invasive techniques will have the same impact in joint arthroplasty as they have had in other surgical applications. A number of minimally invasive surgical techniques have been described and a classification system has been advanced to clarify and simplify our understanding of this group of techniques. This classification defines whether the approach involves a single incision or multiple incisions, the type of approach or plane of entry into the hip (anterior, anterolateral, posterior, or combined), and finally, the method of deep dissection (either intermuscular or transmuscular).
In this chapter we describe the single-incision, anterolateral intermuscular technique for total hip arthroplasty. This anatomic approach was first described by Sayer in 1876 and was popularized by Watson-Jones for the management of fractures of the proximal femur in 1936. It was subsequently modified by Roettinger for its use in total hip arthroplasty. It is a single-incision intermuscular approach to the hip using the anterolateral interval between the posterior border of the tensor fascia lata and the anterior border of the gluteus medius and has recently been described in the literature.
This approach has many clear advantages. First, it is truly an intermuscular approach into the joint with no disruption of the abductor musculature and its associated morbidity. It allows good access to both the femur and the acetabulum to allow accurate placement of components and, with the use of specialized minimally invasive surgical instrumentation, avoids any potential damage to the abductor musculature during retraction. With minimal muscular disruption and a strong capsular repair, this approach is inherently stable and the risk of dislocation is minimized. Fluoroscopy is avoided as in other minimally invasive surgical techniques, and direct visualization allows precise component positioning.
INDICATIONS AND CONTRAINDICATIONS
As with all minimally invasive surgical techniques, cases selected during the learning phase should be straightforward until all nuances are mastered. Starting off with simple cases (i.e., patients with primary osteoarthritis and avascular necrosis with a low body mass index and slender build) is recommended. As experience is gained the surgeon should gradually progress to more difficult cases including traumatic osteoarthritis, protrusio acetabuli, patients with soft tissue contractures, and heavily muscled patients. Contraindications include patients with a significant leg length discrepancy that requires correction, marked acetabular/femoral dysplasia, significant contractures around the hip joint, or previous osteotomies and instrumentation. In these patients, trying to restore anatomic orientation through a minimally invasive surgical approach is fraught with difficulties and potential complications. Because of the inherent stability of the approach and minimal soft tissue disruption, trying to correct contractures and leg length discrepancies greater than 15 mm is difficult.
PREOPERATIVE PLANNING
Preoperative templating is performed on anteroposterior radiographs of the pelvis and on a lateral view of the hip. The specific objectives of preoperative planning include calculation of any leg length discrepancy and restoration of appropriate femoral offset, and determination of component sizes. Three important measurements are taken to aid intraoperative decision making for the femoral osteotomy and seating of the component ( Fig. 12-1 ). The first measurement is the distance from the saddle of the neck (the superior surface of the femoral neck at the base of the medial face of the greater trochanter) to where the definitive osteotomy is to be performed. The second measurement is the distance from the lesser trochanter to the medial point of the femoral osteotomy. The last measurement is from the tip of the greater trochanter to the shoulder of the prosthesis in its final location. Strict adherence to these measurements allows precise placement of components with minimal error and without compromising of stability.
TECHNIQUE
It is essential to put together a well-trained team that understands the nuances of this approach. The operation relies on choreography between the surgeon and the assistants. Preoperatively, all patients are seen by the anesthesiologist in a preadmission clinic and counseled as to the anesthesia protocol they will receive on the day of the operation. The majority of patients receive a spinal anesthetic, an adequate nerve block, proper sedation, adequate hydration, and prophylaxis for nausea during the perioperative period. They also receive a prophylactic dose of a third-generation cephalosporin if they do not have a history of allergy to this drug class.
A commercially available split table is used to position the patient, who is placed in a lateral decubitus position with the affected side up. The distal and posterior limbs of the table are removed, creating a posterior space into which the leg can be moved when mobilizing the femur. The patient is positioned anteriorly on the table in such a way that the buttock crease is at the point where the table splits with the lower leg resting on the anterior limb of the table. This ensures clearance of the leg without impingement on the table when positioning the patient for preparation of the femur in the posterior well. The pelvic clamps are applied so that the pelvis is rigidly held and does not move on manipulation. The surgeon stands anterior to the patient, and the one or two assistants are posterior. One assistant is assigned the job of “leg holder” and the other “the keeper of the medius” ( Fig. 12-2 ).
