Direct Lateral Approach Total Hip Arthroplasty

Indications

First described by McFarland and Osborne¹ in 1954, the direct lateral approach to the hip was popularized by Hardinge.² It is an extensile approach to the hip and can be utilized for many procedures, including hemiarthroplasty, hip resurfacing arthroplasty, total hip arthroplasty (THA), and revision hip arthroplasty. This approach is performed by reflecting the anterior portion of the gluteus medius and the vastus lateralis as a sleeve to expose the hip joint.

The direct lateral approach is preferred by many contemporary surgeons because it allows preservation of the posterior soft tissue structures, therefore decreasing the risk of hip instability and dislocation. Critics of the approach, however, believe that injury to the abductor mechanism can lead to limping and a Trendelenberg gait.

Research has shown that the direct lateral approach has a very low dislocation rate. Masonis et al³ examined 14 studies involving 13,203 primary THAs to evaluate the influence of approach on hip stability. They reported that with respect to surgical approach and dislocation, the combined dislocation rate for these studies was 1.27% for the transtrochanteric approach, 3.23% for the posterior approach (3.95% without posterior repair and 2.03% with posterior repair), 2.18% for the anterolateral approach, and 0.55% for the direct lateral approach. It is, therefore, the preferred approach in high-risk patients for whom dislocation is likely.

Preoperative Planning

Preoperative planning aids in the selection of the optimal surgical approach, implant style, and sizing. It is important to have good preoperative radiographs for analysis, including am anteropostrior radiograph of the pelvis and a lateral view of the hip. Radiographic analysis will allow identification of bony deformity and leg length discrepancy. In addition, acetabular sizing, optimal femoral stem fit, neck offset, and position of the femoral neck osteotomy can be planned. Contralateral hip anatomy, especially if normal, will help in recreating the femoral offset and leg length.

We recommend two measurements in the preoperative radiographs:

• Distance of the lateral neck osteotomy from the tip of the greater trochanter
• Distance of the medial neck osteotomy from the lesser trochanter

Accurate identification of bony landmarks and correct osteotomy position allow for precise placement of components with minimal error.

Positioning

The direct lateral approach can be performed with the patient in the supine or the lateral decubitus position. We prefer the supine position, as it allows for ease of positioning the patient on the operating room table and anatomic orientation of the patient's pelvis, which minimizes the potential for implant malposition and allows for easier leg length restoration.

Place the patient on the operating room table in the supine position. A standard table can be utilized, but we prefer to use an image table (OSI Jackson table) with a carbon fiber top to allow for intra-operative imaging (Figure 1). A small bump is placed under the pelvis (Figure 2). Care must be taken not to place the bump too distal or too proximal to prevent pelvic tilt. The patient is positioned as close to edge of the table as possible to allow the buttock to fall free by gravity.

Figure 1. Radiolucent Jackson table with pelvic bump and black roller bar

Figure 2. Bump under the pelvis. For proper positioning, two fingers of "cheek" at bottom and two fingers of hip overhanging edge of bed

A roller bar or sandbag is placed at the end of the bed. With the foot resting on the roller bar, the hip should be flexed to 45-60 degrees and the knee should be flexed to 90 degrees (Figure 3).

Figure 3. Roller bar or sandbag to allow hip flexion at 45 degrees and knee flexion at 90 degrees

A plastic, adhesive U-drape is taped to the patient to drape out the hip (Figure 4). The leg is draped free to allow manipulation of the entire limb. The lateral hip (including the trochanter and buttock) and the anterior thigh are included in the prep (Figure 5). An impervious stockinette is applied to the leg from toes to the upper thigh. Coban (3M, St. Paul, MN) is used to wrap the leg and secure the stockinette. Ioban (3M, St. Paul, MN) is utilized to isolate the skin in the surgical field.

Figure 4. Application of U-drape

Figure 5: Patient position ready for prep and drape. Note that the leg is draped entirely free.

Technique

Operating Room Personnel

It is imperative to assemble an appropriate surgical team to help in soft tissue retraction and exposure. Ideally, the assistants should be adequately trained in this approach to prevent inefficiency and complications. A minimum of two assistants is required to help the surgeon complete this procedure. One assistant is positioned on the side of the operative hip, and the other assistant is positioned across the other side of the table.

Skin and Superficial Dissection

The bony landmarks of the hip should be identified. Palpate and outline the greater trochanter (Figure 6). The incision is is started 2-4 cm proximal to the tip of the trochanter and extended distally in line with the femur. Extending the incision distally increases acetabular exposure, while extending the incision proximally, will increase femoral exposure. An incision length of 10-15 cm is adequate for most patients (Figure 7).

Figure 6. Outline the border of the greater trochanter

Figure 7. Incision is started 2-4cm proximal to the trochanter and in line with the femur

The skin and subcutaneous fat are incised down to the fascia. Take care to control bleeders encountered in the subcutaneous tissue (Figure 8). Hibs or rake retractors are utilized to retract this layer, exposing the underlying gluteus maximus fascia. The fascia is incised over the mid-trochanter in line with the femoral shaft (Figure 9). The gluteus maximus muscle is split along its fibers proximally. Retract the fascial sleeve, along with the gluteus muscle, to expose the abductor muscle (gluteus medius) beneath this layer.

Figure 8. Superficial dissection. Control bleeders with cautery.

Figure 9. Fascia is incised over the mid-trochanter in line with the femoral shaft

Deep Dissection

The anterior and posterior borders of the gluteus medius muscle are identified proximally (Figure 10a). The anterior third of the gluteus medius, the entire gluteus minimus, and the anterior half of the hip capsule are elevated as one flap, along with the anterior third of the vastus lateralis distally (Figure 10b). Care is taken to leave a cuff of tendon on the anterior border of the trochanter to allow for secure repair (see Wound Closure, below). This "flap" of muscle and capsule is elevated off the proximal femur using bovie cautery.

Figure 10a. Anterior and posterior borders of the gluteus medius muscle are identified proximally

Figure 10b. The anterior third of the gluteus medius, the entire gluteus minimus,and the anterior half of the hip capsule are elevated as one flap

The dissection is facilitated by external rotation and flexion of the leg. The assistant on the other side of the table gently rotates the limb by placing the leg in a "figure of 4" position (hip externally rotated; knee flexed). In this process, the flap is elevated from the bone until the hip joint is encountered. The labrum is incised at the proximal extent of the flap to aid in dislocation of the femur. A bone hook is then placed around the femoral neck anteriorly and the femoral head is dislocated by traction on the bone hook while externally rotating the leg.

A standard femoral neck osteotomy is performed (Figure 11). It is typically a line made from the medial neck 1 cm above the lesser trochanter to the saddle at the lateral neck. The femoral head is then removed from the surgical field, allowing exposure of the acetabulum.

Figure 11. Femoral neck cut is performed

Exposure of the Acetabulum

Three retractors are utilized to gain adequate exposure of the acetabulum:

• First, a Cobb elevator is utilized to develop the plane between the anterior wall of the acetabulum and the overlying anterior capsule. Finger palpation of the anterior wall of the acetabulum is initially performed and the anterior labrum is identified. A Cobb elevator is then placed anterior to the labrum, developing the plane between labrum and capsule. Care must be taken to ensure that the tip of the Cobb is directed posteriorly against bone to prevent injury to the neurovascular structures. Once this plane is developed, the Cobb elevator is replaced with a blunt Hohmann retractor.

• The second retractor is placed superior to the acetabulum. A sharp Cobra retractor is utilized to retract the gluteus muscle away from the surgical field. The tine of the Cobra is inserted into bone in the supero-lateral pelvis.

• A third retractor is place infero-posteriorly. A double-footed Mueller retractor is positioned against the ischium. Alternatively, a double-angled sharp, narrow Hohmann retractor can be utilized in patients with smaller anatomy in lieu of a double-footed Mueller retractor (Figure 12).

Figure 12. Acetabular exposure is achieved with a Hohmann retractor anteriorly, a sharp Cobra retrator superiorly, and a double-angled Hohmann postero-inferiorly

Once proper exposure of the acetabulum is achieved, the labrum is sharply excised (Figure 13). The fat within the cotyloid notch is removed to find the true floor of the acetabulum. It is imperative to visualize the entire anatomy of the acetabulum. With the patient in the supine position, the pelvis can be level to the floor to achieve proper orientation.

Figure 13. The labrum is resected sharply to expose the bony anatomy of the acetabulum

Acetabular Preparation

The acetabulum is reamed sequentially to the correct size (Figure 14). Start with a small-sized reamer and graduate to larger sizes to find the correct fit. Offset reamers are available but not necessary to obtain proper orientation of the acetabular component.

Figure 14. Sequential reaming of the acetabulum is performed

After reaming is completed, the final component is inserted using a straight inserter handle (Figure 15). We recommend 45 degrees of lateral opening and 10-15 degrees of anteversion. Intraoperative imaging is recommended while placing the acetabular component to ensure correct orientation. Once the final component is impacted, complete seating is verified through the insertion hole. If necessary, screws may be placed to augment the initial component fixation. The screws are placed in the postero-superior quadrant to avoid vessel injury. The appropriate-sized liner in impacted into place (Figure 16). We prefer a minimum of 6-7 mm of polyethylene. Make sure that the liner is "seated" within the acetabular component by checking the periphery of the shell.

Figure 15. Insert the acetabular component with straight inserter handle at 45 degrees of lateral opening and 15 degrees of anteversion

Figure 16. Insert the polyethylene liner with an impactor handle

Exposure of the Femur

The acetabular retractors are removed. The leg is positioned in a "figure of 4" position with the leg in external rotation and adduction. The knee is flexed and held in position by the assistant across the table. Two double-footed Mueller retractors are utilized for exposure. One retractor is placed on the medial aspect of the proximal femur (Figure 17). The second retractor is placed posterior to the greater trochanter. If properly placed, the retractors will prevent injury to the surrounding soft tissue and afford excellent exposure and access to the proximal femur.

Figure 17. Double footed utilized to gain exposure of the proximal femur

Femoral Preparation

Femoral preparation begins with removal of lateral cortical bone from the femoral neck cut. This can be achieved with a rongeur or box osteotome. A curette can be utilized to enter the medullary canal to act as a canal finder (Figure 18). A straight reamer is then utilized (Figure 19). Broaching is initiated with a starter rasp. Sequentially broaching is then completed, starting from the smallest broach until the correct size is reached (Figure 20). Intraoperative imaging can be utilized to determine size and orientation of the broach to ensure adequate fit.

Figure 18. Femur is entered with a currette

Figure 19. Starter reamer is utilized to open the medullary canal

Figure 20. Sequential broaching of the femur is performed until a good fit and stability are achieved

Trial reduction is performed with corresponding neck and head trials (Figure 21). The neck offset is determined from preoperative planning to match the patient's anatomy. Hip stability can be determined by soft tissue tension once the hip is reduced. To reduce the hip, gentle traction is placed on the leg while downward force is placed on the femoral head. The hip is flexed slightly and the hip is gently internally rotated as the femoral head is reduced into the shell.

Figure 21. Trial neck and head is applied to the last broach

Soft tissue tension is an important determinate of stability and leg length. The surgeon should ensure adequate tension of the reduced hip by avoiding excessive force in the reduction maneuver. The hip is taken through full range of motion, especially deep flexion (Figure 22a) and adduction (Figure 22b) and abduction with external rotation (Figure 22c) of the operative leg. By doing so, stability of the hip can be determined.

Figure 22a. Hip stability is checked with the leg in deep flexion

Figure 22b. Hip stability is checked with the leg in adduction, external and internal rotation

Figure 22c. Hip stability is checked with the leg in abduction, extension and external rotation

Leg length can be determined by bringing both legs together and directly palpating the medial malleolus (Figure 23). In addition, intraoperative imaging can be utilized to compare the operative hip to the opposite hip. Measuring the distance between the tear drop and lesser trochanter is performed and compared. The hip is dislocated with manual traction of the extremity combined with an anterolateral force on the proximal femur with the surgeon's finger or a bone hook.

Figure 23. Leg length can be checked by bringing the legs together at the end of the table and palpating the malleoli

The trial components are removed and the final femoral implant is inserted (Figure 24). We recommend inserting the final implant by hand (not attached to the inserter handle). Specialized curved femoral impactors are available to help with proper orientation of the femoral implant, but in most cases, a straight inserter handle is often adequate.

Figure 24. Insert femoral component freehand and then impact with the inserter handle. Femoral head is inserted onto the trunion with a head impactor.

The implant is then impacted into the femur with a laterally directed force to ensure that it is not placed in varus. Be sure that the orientation of the implant follows the space determined by the broach. The calcar must be visualized while the femoral component is impacted into place to avoid inadvertent fracture. The final head is impacted onto the trunion and the hip is reduced. Final intraoperative imaging can be performed at this point to check position and fit of the implant.

Wound Closure

The wound and the hip joint are irrigated thoroughly. A deep suction drain can be utilized but is not necessary. The anterior "flap" (gluteus medius, gluteus minimus, and anterior capsule) is returned to its anatomic position (Figure 25). Heavy, absorbable suture is utilized to repair the abductors onto the trochanter. The hip can be internally rotated to facilitate repair. The gluteus maximus fascia and the fascia lata are closed using interrupted, heavy, absorbable suture. The subcutaneous tissue is closed with interrupted absorbable suture. The skin is closed with skin staples.

Figure 25. Closure of the anterior abductor flap is achieved with absorbable heavy suture

Post-operative Management

Patients are allowed full weight-bearing post-operatively. Traditional hip precautions and limitations are not necessary. Patients are encouraged to start physical therapy as soon as possible. Walking aids, such as a walker, crutches, and a cane, are appropriate but are often discontinued within the first post-operative week. Patients are discharged to home within 48 hours of surgery; motivated patients may be discharged sooner. Outpatient physical therapy is instituted; inpatient rehabilitation is rarely necessary.

Pearls and Pitfalls

• Care must be taken with the initial dissection and exposure.
• Handling of the abductor mechanism must be gentle.
• Repair at the end of the procedure should be meticulous to prevent injury to the abductors and avoid failure of repair.

Complications

Approach-related Complication

• Damage to the gluteus medius

Access-related Complications

• Reaming and cup positioning
• Femoral perforation/fracture
• Stem positioning

Postoperative Complications

• Limp
• Pain over the incision
• Heterotopic ossification

Conclusion

The ultimate goal of THA is to provide pain-free function of the hip without complications. This includes excellent implant position and fixation with outstanding function that meets patient expectations. Recovery should be short and rehabilitation rapid. The direct lateral approach to hip is an extensile approach that can be utilized to meet these goals. The surgeon who is interested in this approach should commit time to learn the exposure and familiarize himself/herself with the anatomy to avoid complications.

References

1. McFarland B, Osborne G. Approach to the hip: a suggested improvement on Kocher's method. J Bone Joint Surg 1954; 36 (B): 364--7.
2. Hardinge K. The direct lateral approach to the hip. J Bone Joint Surg 1982; 64 B: 17--8.
3. Masonis J, Bourne, R. Surgical Approach, Abductor Function, and Total Hip Arthroplasty Dislocation. CORR 2002; 405:46-53.