Surgical Anatomy

McFarland and Osborne first described the modern lateral approach to the hip in 1954.1 This approach was popularised in 1982 by Hardinge.2 Whilst this approach was described originally for total hip arthroplasty, it is now commonly used both for total hip arthroplasty surgery in arthritis and hemiarthroplasty for intracapsular fracture of the neck of femur.

The lateral approach has a lower dislocation rate when compared to the posterolateral approach. This is especially important in arthroplasty for intracapsular femoral neck fracture. This is due to the fact that these patients have more range of movement at the hip preoperatively compared to patients with arthritis. Additionally, patients with dementia have difficulty complying with postoperative restrictions needed after posterior approaches.

The direct lateral approach bisects the thick periosteum covering the greater trochanter and preserves the continuity of the conjoined tendinous attachment of the gluteus minimus and medius proximally and the vastus lateralis distally. Its advantage is that it avoids the need for osteotomy of the greater trochanter while allowing access to the anterior and posterior hip joint because of the location of the midlateral incision.

There are two major neurological structures that are at risk in this approach.

The femoral nerve runs surprisingly laterally and may be injured by injudicious use of retractors placed over the anterior lip of the acetabulum.

The superior gluteal nerve runs in the gluteus medius about 4 to 5 cm superior and 2 cm posterior to the greater trochanter. Jacobs and Buxton3 identified two patterns of neural branching in cadaveric specimens. The most common pattern was a "spray pattern" in which the main trunk divides within 1 to 2 cm of the superior border of the piriformis muscle into numerous branches fanned out along the intermuscular plane between the gluteus medius and the gluteus minimus. A second pattern, the "transverse trunk pattern," was found in patients in whom the majority of the branching was peripheral. From these studies, a safe zone for the superior gluteal nerve was established which encompasses a band of the gluteus medius muscle approximately 5 cm wide immediately adjacent to the greater trochanter. The superior gluteal nerve is less likely to be damaged if surgical dissection is confined to this area.

The actual position of incision in the gluteus medius has been adapted over time. In the original description the gluteus medius was split into anterior two-thirds and posterior third. In the modified Hardinge4 approach only the anterior one-third of gluteus medius is reflected.

Positioning

The original description of the Hardinge approach describes positioning the patient supine with the greater trochanter lying at the edge of the table. This is reasonable, but the author

Total Hip Arthroplasty

prefers positioning the patient in the lateral position. In the lateral position the soft tissues will fall away from the operative field during the exposure. The operative leg must be draped entirely free so it can be maneuvered during the procedure. The lateral position requires the surgeon to employ one assistant to help position the leg during the procedure.

Incision and Approach

A straight lateral skin incision is made midway between the anterior and posterior dimensions of the greater trochanter and centered on the tip of the trochanter. The length is about 10-15 cm, dependent on the patient's habitus, the operative requirements and the surgeon's preference.

The skin is incised, along with the subcutaneous fat in the same line. The fascia lata is exposed and incised between the muscle bellies of the tensor fascia lata and the gluteus maximus to extend the full length of the surgical incision. The next structure seen is the trochanteric bursa. This structure is variable in its appearance. The bursa may be excised and the greater trochanter with the attached musculature visualized (Fig. 7.1).

At this point the anatomy should be delineated and a decision as to where the cut in the medius should be made. In the modified Hardinge4 the cut is in the line of the muscle fibers at the junction of the anterior 1/3 and posterior 2/3. A pair of mayo scissors is used to split open the muscle in the line of the fibers. Sharp dissection is used to incise and reflect the tendon of gluteus medius off its insertion into the greater trochanter in a crescent fashion, leaving a cuff of tendon on the bone to aid repair. The cut is continued distally into the most superior 1 cm of the vastus lateralis. Care is taken to observe and protect the inferior branch of the superior gluteal nerve as it courses between the gluteus medius and minimus muscles. Two areas of bleeding may be encountered. The ascending branch of the medial circumflex artery courses behind the trochanter, and the transverse branch of the lateral circumflex artery is found in the vastus lateralis. Both arteries are easily cauterized. Using the diathermy needle, a small portion of the vastus lateralis arising from the intertrochanteric line is separated, and the tendinous insertion of the anterior portion of the gluteus minimus and the ligament of Bigelow separated from their ridge on the anterior aspect of the neck of the femur. Adduction and external rotation of the limb helps to maintain tension on the flap and improves visualization of the dissection field. A sterile pouch is used on the assistant side of the table to receive the limb while the limb is adducted. The hip joint should now become visible in the base of the wound. Dislocation of the femoral head is achieved by full adduction and external rotation of the hip (Fig. 7.2). A bone hook may be used to help dislocation by applying a distraction on the femoral neck. An osteotomy of the femoral neck is performed as planned on the template and the femoral head is excised. Acetabulum is visualized by

Figure 7.1: Lateral approach to the hip demonstrating the incision centered on the greater trochanter. The fascia lata has been incised and retracted to expose the greater trochanter with attachments of gluteus medius proximally and vastus lateralis distally

The Lateral (Modified Hardinge) Approach to the Hip

Figure 7.2: Hip joint dislocated anteriorly by adducting and externally rotating the hip achieved by hanging the leg on the side of the table into a sterile pouch

Figure 7.3: Exposure of acetabulum can further be improved by retracting the inferior capsule with a Hohmann retractor inferior to the transverse ligament. The reflection of the gluteus medius, minimus tendon and capsule along with vastus lateralis anteriorly as one layer can be seen

retracting the femur posteriorly and bringing the leg back onto the table. For acetabular preparation, a Hohmann retractor is placed in the acetabular notch beneath the transverse acetabular ligament (Fig. 7.3). Posterior exposure is generally adequately achieved by externally rotating the leg and use of a soft tissue retractor. Rarely is a posterior rim retractor required. In total hip arthroplasty the acetabulum labrum may now be excised prior to reaming. In hemiarthroplasty the labrum may be spared or a radial cut may be necessary to extract the femoral head.

For femoral preparation the limb needs repositioning with the leg hanging on the side (Figs 7.4 to 7.7A and B).

Total Hip Arthroplasty

Figure 7.4: Exposure of the proximal femur

Figure 7.5: Demonstrating implantation of the femoral component

Figure 7.6: The prosthesis is reduced into the joint by gentle traction along the limb in slight adduction and flexion. The limb is brought back onto the table and stability confirmed prior to closure

The Lateral (Modified Hardinge) Approach to the Hip

Figures 7.7A and B: Pre and Postoperative radiographs demonstrating satisfactory alignment of components and restoration of limb length

Closure

The accurate closure of this approach is essential to ensure good hip abductor function post operatively. The author uses a heavy interrupted mattress absorbable suture to close the capsule separately and then perform a continuous suture to close the reflected medius and minimus flap to the retained cuff of tissue on the trochanter. To aid the closure the hip may be gently internally rotated. The fascia lata is repaired with a heavy absorbable suture to aid this closure the hip may be abducted. The fat layer and the skin are closed as per the surgeon's preference.

Postoperative Care

A pillow is placed between the patient's legs until they are awake in the recovery room. Brace and/or splint immobilization is not used. Ambulation with assistance is begun the next day. For the first 6 weeks, patients are instructed on crutch walking, progressing to full weight-bearing as tolerated. The only total hip precautions needed are to avoid excessive flexion of the hip and to avoid crossing the legs. Abduction exercises are allowed, with gravity removed initially. By 6 weeks, patients have advanced from crutches to a cane or have discarded walking aids. Abduction exercises are performed against gravity and with resistance, in addition to hip flexion and straight-leg raising exercises. Patients are allowed to drive a car and resume normal daily activities once they have regained good limb control usually at six weeks after operation

Advantages

• Provides good exposure of both the acetabulum and femur.

• Avoids the need for greater trochanteric osteotomy

• Used for both primary and revision arthroplasty.

• Improved access to proximal femur compared to anterior and anterolateral approaches.

  Complications

• Limp: May be due to direct damage to superior gluteal nerve or denervation of gluteus medius or dehiscence of repair in gluteus medius and minimus

  • Dislocation: Most likely anterior but may also be posterior if the acetabulum is retroverted.

  • Heterotopic ossification: Incidence is higher with lateral approaches but the severity is reduced with the modified Hardinge approach

    Total Hip Arthroplasty

  • Nerve Injury: The neurological structures at risk include the superior gluteal nerve with risk of denervation injury to gluteus medius and minimus, the femoral nerve and the sciatic nerve.

Results

Moskal and Mann4 reported their results using the direct lateral approach in 453 consecutive primary and revision total hip arthroplasties. They noted several advantages of the approach including its wide exposure and improved access to the femur when compared with the anterior and anterolateral approaches. This approach obviates the need for trochanteric osteotomy and its associated complications of nonunion, bursitis, pain, and wire breakage. However, a major postoperative complication was limp, with an incidence of 18%. The overall incidence of heterotopic ossification was 47%, with a slightly higher incidence in the revision group.

Mulliken et al5 reported on 712 total hip arthroplasties performed using the above modified direct lateral approach at a minimum 2-year follow-up (average, 3.6 years). They noted a 0.3% dislocation rate, a moderate to severe limp of 4% and 3% incidence of severe heterotopic ossification [Brooker6 grade III or IV].

Conclusion

The direct lateral approach offers the widest exposure of all the nontranstrochanteric approaches to the hip. Its major disadvantage is the increased incidence of postoperative abductor limp in addition to heterotopic ossification. Abductor weakness may be caused by detachment of the gluteus medius or by injury to the superior gluteal nerve. Anatomic studies of the course of the superior gluteal nerve have shown a safe zone of 3 to 5 cm from the tip of the greater trochanter. It is essential, however, to perform meticulous anatomic dissection and careful reattachment of the gluteus medius and gluteus minimus if abductor weakness is to be avoided. The repair is completed using drill holes if there is inadequate tendinous stump remaining. With repair and reattachment of the abductors and by keeping surgical dissection within the "safe zone,"3,7 the incidence of postoperative limp has been reported to be no higher with the direct lateral approach when compared with other approaches.

References

1. McFarland B, Osborne G. Approach to the hip: a suggested improvement on Kocher's method. J Bone Joint Surg [Br] 1954;36:364-7.

2. Hardinge K. The direct lateral approach to the hip. J Bone J Surg [Br] 1982;64(1):17-9.

3. Jacobs LGH, Buxton RA. The course of the superior gluteal nerve in the lateral approach to the hip. J Bone Joint Surg [Am] 1989;71:1239-43.

4. Moskal JT, Mann JW III. A modified direct lateral approach for primary and revision total hip arthroplasty. J Arthroplasty 1996;11:255-66.

5. Mulliken BD, Rorabeck MD, Bourne RB, et al. A modified direct lateral approach in total hip arthroplasty. J Arthroplasty 1998;13:737-47.

6. Brooker AF, Bowerman JW, Robinson RA, et al. Ectopic ossification following total hip replacement: Incidence and a method of classification. J Bone Joint Surg [Am] 1973;55:1629-32