# Surgical Approaches to the Hip: Posterior, Anterolateral, and Direct Anterior

## Introduction

The surgical approach to the hip joint is one of the most consequential decisions in hip arthroplasty and fracture surgery. Each approach offers distinct advantages and limitations regarding visualization, implant positioning, soft tissue damage, recovery, and complication profile. A thorough understanding of the relevant anatomy and technical nuances of each approach is fundamental to orthopedic surgical training.

## Posterior Approach (Moore or Southern Approach)

### Anatomical Basis

The patient is positioned in the lateral decubitus position. The incision is centered over the greater trochanter, curving posteriorly along the femoral shaft. The gluteus maximus is split in line with its fibers (internervous plane between the superior and inferior gluteal nerves). The short external rotators (piriformis, obturator internus, superior and inferior gemelli) are divided to access the posterior capsule. The sciatic nerve lies posterior to the short external rotators and must be protected throughout.

### Advantages

The posterior approach provides excellent visualization of the acetabulum and femur, is extensile (can be extended distally for fracture work), preserves the abductor mechanism (gluteus medius and minimus), and is familiar to most surgeons as the most commonly taught approach worldwide.

### Disadvantages

The historical dislocation rate of 2 to 5% is higher than anterior approaches, though modern capsular repair significantly reduces this. There is approximately a 1% risk of sciatic nerve injury, and meticulous repair of the posterior capsule and short external rotators is required.

### Technical Pearls

The piriformis and posterior capsule should be repaired as a single sleeve using transosseous tunnels or suture anchors. Internal rotation of the hip during retractor placement increases sciatic nerve stretch and should be avoided. The inferior gluteal artery lies at the inferior border of the piriformis and can bleed significantly if injured.

## Anterolateral Approach (Watson-Jones / Modified Hardinge)

### Anatomical Basis

The patient is positioned in the lateral decubitus or supine position. The approach utilizes the interval between the tensor fasciae latae (superior gluteal nerve) and the gluteus medius (superior gluteal nerve). The Watson-Jones approach is truly internervous, while the Hardinge modification splits the anterior third of the gluteus medius. The anterior capsule is exposed after elevating the gluteus medius and minimus off the greater trochanter.

### Advantages

This approach offers a lower dislocation rate compared to the traditional posterior approach, good visualization of the acetabulum, and versatile positioning (lateral or supine).

### Disadvantages

The Hardinge modification carries a risk of abductor damage potentially causing a Trendelenburg gait. The superior gluteal nerve enters the gluteus medius approximately 5 cm proximal to the greater trochanter tip, so dissection must not extend beyond this point. Femoral exposure is more limited than with the posterior approach.

### Technical Pearls

When using the Hardinge modification, the gluteus medius split should not extend more than 3 to 4 cm proximal to the trochanter tip. Complete release of the anterior capsule is necessary for adequate acetabular visualization. The abductor sleeve must be repaired meticulously at closure to prevent postoperative limp.

## Direct Anterior Approach (Smith-Petersen / Hueter)

### Anatomical Basis

The patient is positioned supine on a standard or specialized table (such as the Hana table). This approach utilizes the true internervous interval between the tensor fasciae latae (superior gluteal nerve) and the sartorius/rectus femoris (femoral nerve). The ascending branch of the lateral femoral circumflex artery crosses the surgical field and requires ligation. The lateral femoral cutaneous nerve is at risk during superficial dissection.

### Advantages

This approach is muscle-sparing, with no muscles detached or split. It has a lower dislocation rate, particularly in the early postoperative period. Supine positioning allows intraoperative fluoroscopy for real-time assessment of component position and leg length. Some studies associate it with faster early recovery and shorter hospital stay.

### Disadvantages

The learning curve is steep, with higher complication rates during the initial surgeon experience (first 50 to 100 cases). The risk of lateral femoral cutaneous nerve injury (lateral thigh numbness) reaches 15 to 30%. Femoral exposure is difficult, especially in muscular or obese patients. There is a higher risk of femoral component malpositioning (varus) and proximal femoral fracture during the learning curve. Extensibility is limited.

### Technical Pearls

Adequate release of the superior capsule is critical for femoral exposure. A specialized table with leg positioning capability greatly facilitates femoral preparation. Fluoroscopy should be used to confirm cup position, stem alignment, and leg length intraoperatively. Offset broach handles and curved instrumentation designed for this approach should be considered.

| Feature | Posterior (Moore) | Anterolateral (Watson-Jones/Hardinge) | Direct Anterior (Smith-Petersen) |
|---------|-------------------|--------------------------------------|----------------------------------|
| Position | Lateral decubitus | Lateral or supine | Supine |
| Internervous plane | Sup/inf gluteal nerves (glut max split) | TFL / glut med (sup gluteal nerve) | TFL (sup gluteal) / sartorius (femoral) |
| Muscles cut | Short external rotators | Glut med split (Hardinge) or none (W-J) | None (muscle-sparing) |
| Dislocation rate | 2-5% (reduced with capsule repair) | 1-3% | < 1-2% |
| Key nerve at risk | Sciatic | Superior gluteal | Lateral femoral cutaneous (15-30%) |
| Fluoroscopy | Not routine | Not routine | Routine (real-time leg length/cup position) |
| Extensibility | Excellent | Moderate | Limited |
| Learning curve | Standard | Standard | Steep (50-100 cases) |
| Best for | Most THA; fracture work; revision | Primary THA | Primary THA in experienced hands |

## Approach Selection in Clinical Practice

No single approach is universally superior; surgeon experience and training are the most important determinants of outcome. The posterior approach remains the most commonly used worldwide and is the most extensile. The direct anterior approach offers early functional advantages but requires dedicated training and may increase complications during the learning curve. For revision surgery, the posterior approach offers the best extensibility. For patients at high dislocation risk, anterior-based approaches or dual-mobility constructs may be advantageous.

## Clinical Pearls

The superior gluteal nerve is the critical structure limiting proximal dissection in the anterolateral approach; the gluteus medius split should never extend more than 5 cm from the trochanter tip. Posterior capsule and short external rotator repair reduces the dislocation rate of the posterior approach to levels comparable with anterior approaches. The direct anterior approach learning curve is real and significant, with higher complication rates in the first 50 to 100 cases being well documented. Approach selection should be driven by surgeon training, experience, and the specific clinical scenario rather than marketing or patient demand.

## References
1. Masonis JL, Bourne RB. Surgical approach, abductor function, and total hip arthroplasty dislocation. *Clin Orthop Relat Res*. 2002;(405):46-53.
2. Meermans G, Van Doorn J, Herregodts S, et al. The use of the direct anterior approach in total hip arthroplasty: a comparison of complication rates between the initial learning curve and the experienced surgeon. *Acta Orthop Belg*. 2018;84(1):1-8.
3. Pellicci PM, Bostrom M, Poss R. Posterior approach to total hip replacement using enhanced posterior soft tissue repair. *Clin Orthop Relat Res*. 1998;(355):224-228.
4. Post ZD, Orozco F, Diaz-Ledezma C, et al. Direct anterior approach for total hip arthroplasty: indications, technique, and results. *J Am Acad Orthop Surg*. 2014;22(9):595-603.