Posterior approach to the acetabulum (Kocher-Langenbeck)

Introduction

The posterior approach to the acetabulum, also known as the Kocher-Langenbeck approach, provides access to the posterior wall of the acetabulum and its posterior column. It also allows for direct visualization of the dorsocranial part of the acetabulum, either through the fracture gap or via a capsulotomy.

Indications for Use

The posterior approach to the acetabulum is used for:

1. Total hip arthroplasty (THA)
2. Hemiarthroplasty of the hip
3. Removal of loose bodies
4. Dependent drainage of the septic hip
5. Fractures of the posterior wall and posterior column
6. Simple transverse fractures (with the patient in a prone position):
   • Fractures must be less than 15 days old.
   • The fracture line is located at or below the acetabular roof.
   • No significant anterior displacement.

The Kocher-Langenbeck approach is the simplest of all acetabular approaches, and significant blood loss is typically not a concern.

Patient Positioning

Lateral Position

• Indicated for posterior wall and posterior lip fractures (skeletal traction may be needed in lateral positioning).
• Allows for dislocation of the femoral head.
• Position of choice for joint arthroplasty.
• Allows the gluteal tissue to fall away from the surgical field.

Prone Position

• Used for transverse fractures (bend the knee to prevent overstretching the sciatic nerve).
• The femoral head is held in a reduced position throughout the procedure.
• Improves access to the quadrilateral surface.
• Provides better access to the cranial and anterior parts of posterior wall fractures.

Landmarks and Incision

• Landmarks:
  • The greater trochanter.
• Incision:
  • Make a longitudinal incision centered over the greater trochanter, extending from just below the iliac crest to 10 cm below the tip of the greater trochanter.

Internervous Plane

• In the posterior approach to the acetabulum, there is no true internervous plane.
• The gluteus maximus, which is split in line with its fibers, does not experience significant denervation as it receives its nerve supply far proximal to the split.

Superficial Dissection

• Deepen the incision through the subcutaneous fat.
• Incise the fascia lata in line with the skin incision in the lower half of the wound, and extend this incision superiorly along the anterior border of the gluteus maximus muscle.
• Retract the split edges of the fascia to expose the piriformis muscle and the short external rotators of the hip.
• Partial detachment of the gluteus maximus insertion from the femur facilitates mobilization of this muscle.

Deep Dissection

• Internally rotate the leg to stretch the short external rotators and the piriformis, and release these muscles at their insertion into the femur.
• Using the short external rotator muscles as a cushion, carefully insert a retractor into the greater sciatic notch (apply no significant pressure on this retractor, as this can cause sciatic nerve palsy).
• Insert a second retractor into the lesser sciatic notch to expose the posterior column in its entirety.
• The posterior capsule of the hip is exposed (it is often torn or detached in trauma).
• If the posterior capsule is intact and direct inspection of the joint is required, perform a T-shaped capsulotomy (be careful to avoid damaging the labrum when incising the capsule).
• The inner surface of the acetabulum can only be visualized by distracting the femoral head (this can be achieved through skeletal traction or with the help of a Schanz screw placed in the femoral head).
• Posterior lip fractures of the acetabulum can be adequately visualized and addressed at this stage.
• If you require a more extensive exposure of the posterior column, perform an osteotomy of the greater trochanter.
• Divide the greater trochanter from posterior to anterior, removing a 5 mm bone fragment. The gluteal muscles are attached to the superior part of this fragment, and the vastus lateralis to the inferior part.
• Using a sharp retractor, gradually turn over the trochanter with its attached muscles across the anterior surface of the femur. The small remaining attachment of the gluteus medius to the intertrochanteric crest must now be released.
• If mobilizing the fragment is difficult, it may sometimes be necessary to partially release the piriformis insertion.
• If you need access to the anterior surface of the hip joint capsule, flex the hip and externally rotate it. Mobilize the insertion of the gluteus minimus from the retroacetabular surface along the superior capsule to its femoral insertion along the anterior side of the trochanter.
• If further exposure of the anterior joint capsule is required, mobilize the proximal part of the vastus intermedius from the femur to allow access to the anterior hip joint capsule.
• This trochanteric fragment can be easily reattached with screws during closure.
• Note that trochanteric osteotomies in acetabular surgery are associated with heterotopic bone formation.

Approach Extension

Proximal Extension:

• The posterior approach to the acetabulum (Kocher-Langenbeck approach) can be extended distally down to the level of the knee.
• Either split the vastus lateralis or elevate it from the lateral intermuscular septum to expose the lateral surface of the entire femoral shaft.

Distal Extension:

• The posterior approach to the acetabulum (Kocher-Langenbeck approach) cannot be meaningfully extended proximally.

Dangers

Structures at risk during the posterior approach to the acetabulum (Kocher-Langenbeck approach) include:

1. Sciatic nerve:
   • Extend the hip and bend the knee to prevent injury.
   • Minimize the risk of injury by carefully and gently retracting the short external rotators (obturator internus) posteriorly to protect the sciatic nerve from traction.
2. Inferior gluteal artery.
3. First perforating branch of the profunda femoris artery.
4. Femoral vessels.
5. Superior gluteal artery and nerve.

References

• Book "Surgical Exposures in Orthopaedics" – 4th Edition
• Campbell's "Operative Orthopaedics", 12th Edition