Introduction

Metal-on-metal hip resurfacing arthroplasty has re-emerged as a viable alternative to traditional total hip arthroplasty for selected patients. Improvements in design technology and in the metallurgy of metal-on-metal bearings have helped solve many of the problems associated with the first generation of metal-on-polyethylene hip resurfacing, such as massive bone loss with cemented acetabular components and high wear rates associated with larger femoral head sizes. Current hip resurfacing systems make use of a hybrid design, with a press-fit acetabular component and a cemented femoral component. Early and midterm results have been favorable and comparable with traditional total hip arthroplasty, although femoral neck fractures continue to be a concern, with osteonecrosis as a leading cause.

The most commonly used approach for hip resurfacing is the posterior approach. This is an extensile approach that provides excellent visualization of the acetabulum as well as of the posterosuperior femoral head–neck junction. However, it has been well documented that the blood flow to the femoral head is compromised, thus putting the area at risk for an osteonecrotic event. Other approaches that are currently being used are the direct lateral approach, surgical dislocation as described by Ganz, and the anterior Hueter approach, each of which preserves the extraosseous blood supply to the femoral head. Since 2006, we have adopted the anterior Hueter approach with the use of an orthopedic traction table, because it represents the only true internervous surgical approach to the hip, with excellent preservation of the soft-tissue envelope.

Indications

• Young patients

Men less than 65 years old

Women less than 55 years old

Relative contraindications

Absolute contraindications

Clinical history

The clinical history of advanced hip arthritis is straightforward, especially for younger patients with no other source of distracting pain (e.g., back pain). Intra-articular hip pain is typically reproducible and felt in the groin area with activity.

Physical examination

The goal of the physical examination is to confirm the clinical history. Pain in the groin area should be reproduced by passively moving the hip joint, which is usually limited with regard to flexion and internal rotation. If the patient has no groin pain with flexion, adduction, and internal rotation, other causes (e.g., back, extra-articular hip pathology) must be sought. True and functional leg-length discrepancies should be carefully assessed.

Imaging and diagnostic studies

Our hip series for evaluating the patient with osteoarthritis of the hip includes a supine anteroposterior pelvic view that is centered on the hips and that shows the proximal femur down to the diaphysis as well as cross-table lateral views, Dunn views, or both (Figure 34-1). These two radiographs are scrutinized to analyze for structural abnormalities (e.g., insufficient femoral head–neck offset), the integrity of the joint space, and periarticular bone. In the rare case of a patient with radiographic osteoarthritis of the hip joint without a typical clinical history or physical examination, we perform an intra-articular anesthetic injection to determine whether the patient’s symptoms are a result of the radiographic hip degeneration.

Figure 34–1 A 42-year-old patient with advanced left hip osteoarthritis. The inset is a cross-table lateral view that assesses the femoral head–neck offset.

Surgical technique

Although the anterior Hueter approach can be performed without a special surgical table, our main experience is with the use of a specialty orthopedic traction table (Figure 34-2). We do not exclude patients on the basis of body mass index or underlying deformity.

Figure 34–2 An orthopedic traction table (Delacroix Device, Maquet-Dynamed, Paris, France) used for anterior-approach total hip arthroplasty. Note the capacity to extend the operated limb with the patient in the supine position.

Patient Positioning (Figure 34-3)

The patient is placed supine on the operative table. The operative leg is placed into a leg-holding device that allows for controlled positioning in three dimensions during surgery. The leg is not draped free but rather attached to the foot holder to allow for traction, internal and external rotation, flexion, extension, abduction, and adduction. Slight internal rotation of the operative leg allows for the better surface delimitation of the interval between the tensor of the fascia lata and the sartorius. The contralateral lower limb is set in 15 degrees of internal rotation and in neutral flexion, extension, abduction, and adduction; it is also placed under tension to serve as a radiographic control for the operated side.

Figure 34–3 The patient in the supine position. The incision is centered at the tip of the greater trochanter; it is 2 cm to 3 cm longer than the incision that is used when performing a total hip replacement.

Exposure

The incision is placed 1 cm to 2 cm posterolateral and 2 cm distal to the anterosuperior iliac spine. The incision is extended distally and posterolaterally toward a line that connects to the fibular head for a total of 6 cm to 10 cm. The subcutaneous tissue is divided with the use of electrocautery until the aponeurosis of the tensor of the fascia lata is identified. The latter is incised longitudinally with a No. 10 blade, with all muscle fibers preserved. Blunt finger dissection is then performed between the medial aspect of the muscle belly (which can sometimes be bipennate) and the aponeurosis. At this point, retractors are placed in between the muscle and its sheath to expose the rectus femoris and the fat that overlies the hip capsule. With the use of electrocautery, this fat is removed to expose the capsule. After incising the fascia over the rectus femoris, blunt dissection is performed to expose the lateral circumflex vessels, which are then ligated and cut. These vessels can bleed briskly, and they deserve attention. Some of the lateral aspects of the rectus femoris and the iliocapsularis muscle can be elevated to maximize the exposure of the hip capsule. It is recommended to release the reflected head of the rectus femoris to facilitate the exposure of the acetabulum. At this point, the capsulotomy is performed with the use of electrocautery from inferomedial to superolateral, and a second transverse capsular incision is made from inferomedial to lateral, leaving a laterally based capsular flap attached to the proximal femur. In some cases, it is preferable to excise the lateral capsular flap to facilitate the delivery of the proximal femur (Figure 34-4). A large cobra retractor is then placed around the proximal femur to retract the tensor muscle laterally, and a blunt Hohmann retractor is placed at the inferomedial femoral neck.

Figure 34–4 A view of the hip joint after capsulotomy.

Femoral Head Preparation

A femoral neck elevator is placed medially on the neck and held by a scrubbed surgical assistant on the opposite side of the patient. A large cobra retractor is placed to gently retract the tensor of the fascia lata laterally. A pointed Hohmann retractor is applied superiorly under the greater trochanter, and the leg is then brought into extension without any traction. The leg is then further externally rotated to 180 degrees. In large male patients, it may be necessary to release the anterior portion of the tensor muscle off of the iliac crest. The femoral head is then sized with the use of femoral head gauges (Figure 34-5). A smooth pin is advanced through the femoral head and into the middle of the femoral neck in about 5 degrees to 10 degrees of valgus relative to the native femoral neck shaft angle, which usually ends up being about 140 degrees (Figure 34-6). A spin-around gauge that corresponds with the femoral implant size is used to ensure the clearance of the femoral head–neck junction. The gauge should hug the inferomedial neck and clear the anterior aspect of the neck. Proximal femur preparation can follow, with the reamers chosen in accordance with preoperative templating and intraoperative findings. We usually recommend starting at least one size larger than the planned size and completing the first cylindrical reaming with osteotomes to provide overall better visualization for the final preparation. The final sequence of femoral head preparation will then vary from one manufacturer to another in terms of stem hole and chamber head (Figure 34-7). It is extremely important to ensure that the trial component can seat fully on the prepared femoral head; marking the endpoint where it should go may be useful.

Figure 34–5 The sizing of the femoral head with the use of a spherometer gauge (Wright Medical Technology, Memphis, TN) allows for the confirmation of the templating as well as the assessment of the head–neck offset anteriorly.

Figure 34–6 A smooth pin positioned in the middle of the femoral neck or in a slight valgus orientation of 5 degrees to 10 degrees. The proper visualization of the superior head–neck junction may be difficult, but ensuring that the component will be along the inferomedial neck will avoid notching.

Figure 34–7 Femoral head reaming according to sizing.

Acetabular Preparation

After the femoral head has been reamed definitively, the acetabulum is prepared in accordance with the size chosen on the femoral side. The retractors are taken out, no traction is applied, the rotation is freed up, and the leg is brought into neutral flexion and extension, which leaves the proximal femur to fall posterior to the socket. A long, pointed Hohmann retractor is first placed on the anteromedial lip of the acetabulum to retract the medial soft tissues away, and a second one is placed posteriorly, with the tip on the mid-posterior rim (Figure 34-8). A long knife is then used to debride the socket, and osteophytes are removed with a curved osteotome. Reaming commences with the use of tools that are three sizes smaller than those required for the planned definitive component. Offset reamer handles are critical. The reamers are usually brought in from a superior direction, slightly levering on the femoral neck. Attention is paid to maximize the bony contact between the reamers (Figure 34-9) and the bone, because most resurfacing shells do not have screw holes to supplement a poor press-fit fixation. To prevent soft-tissue damage, we suggest manually inserting and removing each reamer into and from the socket and to attach and detach the reamers to power in situ.

Figure 34–8 Acetabular view after femur preparation. Performing a medial capsulotomy is critical to ensure proper visualization.

Figure 34–9 During acetabular reaming, one has to be careful to not have the reamer handle being pushed anteriorly by the femoral neck, which could compromise the anterior wall.

Acetabular Cup Insertion

The tendency is to place the cup in a too-anteverted and vertical position because of soft-tissue interference with the cup inserter. Image intensification or intraoperative x-rays help to ensure proper component positioning. Cup positioning can be assessed by finger palpating the rim to see how closely it matches the see-through gauge. In the coronal plane (i.e., the acetabular component abduction angle), the guide rod should be parallel to a line drawn between the two anterosuperior iliac spines. Acetabular version is then judged from the patient’s longitudinal axis. After proper impaction, component stability is tested with a punch applied manually all around the cup’s periphery to detect any movement. Any remaining overhanging osteophytes can be removed at this point with a curved osteotome to prevent impingement. We often leave some overhanging acetabular rim to minimize the irritation of the iliopsoas tendon. We aim for a cup abduction angle of 45 degrees, with 20 degrees of anteversion (Figure 34-10).

Figure 34–10 Acetabular cup impaction to ensure the proper version and cup abduction angle. The version is referenced off of the floor and the abduction angle, with the guide being parallel to a line that joins the two anterosuperior iliac spines.

Postoperative rehabilitation

Patients typically leave the hospital on postoperative day 2. We let patients perform 50% weight bearing with crutches for 4 weeks to allow for femoral neck remodelling. In bilateral cases, we ask the patients to walk with the aid of a walker for the same period of time. Venous thromboembolism prophylaxis is given for 4 weeks. Transfer to a rehabilitation center is rarely necessary in the population of patients who have undergone resurfacing unless there are social issues. Outpatient physiotherapy is not prescribed routinely, because it has been shown to have no effect at 3 months postoperatively. We see every patient for follow up appointments at 6 weeks, 6 months, and then annually thereafter.

Clinical results

To date, we have performed about 80 hip resurfacing procedures with the use of the anterior Hueter approach and an orthopedic traction table. Four patients have undergone bilateral procedures in the same setting. The mean age of the group is 48 years (range, 29 to 62 years) with the majority (more than 80%) being male (Figure 34-11). In terms of implant positioning, there was a tendency to have more acetabular components in the range of 45 degrees to 55 degrees of abduction, although none of the components was placed in more than 55 degrees of abduction. The femoral component has a tendency toward a slight valgus orientation and an anterior translation. Distally extending the skin incision for 1 cm or 2 cm can help to prevent the conflict between the cup impactor. The anterior translation of the femoral component is probably related to the more difficult access to the posterior femoral neck that occurs with the Hueter approach. Although we are still early in our experience, patients so far have demonstrated excellent recovery with minimal pain.

Figure 34–11 Postoperative radiography that demonstrates the optimal implant positioning of metal-on-metal hip resurfacing.

(Conserve Plus, Wright Medical Technology, Memphis, TN.)

Complications

We have noted that the majority of patients do complain of paresthesias of the anterolateral thigh as a result of injury of the lateral femoral cutaneous nerve. There have been no infections or deep venous thromboses in this group. No femoral neck fractures occurred in any patient in this study, and no complications were related to the orthopedic traction table. We have had one revision of an acetabular component as a result of an initial loss of fixation at 4 weeks. The patient was revised to a thick-shell acetabular component and maintained as a hip resurfacing.

Conclusion

Despite the increasing popularity of resurfacing, most published reports are from implant designers or leading experts in hip resurfacing arthroplasty (Table 34-1). Further long-term studies of this implant as well as reports from independent centers and national registries will help to support generalized use in the orthopedic community. Early published results appear to indicate that hip resurfacing arthroplasty is a viable alternative to total hip arthroplasty for the young active adult. In terms of surgical approach selection, we would urge surgeons to start using the approach that they are most at ease with and to consider the anterior Hueter approach as a strong alternative to preserve femoral head vascularity and to facilitate recovery.