Evert Smith performs minimally invasive hip surgery (MIS) on a regular basis as he believes that the smaller incision and keyhole approach disrupts surrounding hip muscles far less than the conventional approaches in hip surgery. He was the first orthopaedic surgeon to perform MIS in the South West region.
This technique has been refined by Erik de Witt and Michael Nogler. Standard incisions from around 20 – 30cm (8 – 12 inches) to around 10cm (4 inches) are now performed with MIS.
- Smaller incision (scar)
- Less muscle blood loss
- Less post–operative pain
- Quicker rehabilitation
- Shorter hospital stay
- Quicker return to work and functional activities
- Skin damage
- Muscle damage
- Leg length discrepancy
- Superficial nerve injuries
- Component malposition
- Extended learning curve for surgeon
- Long-term outcome unknown
MIS Detail: Two Incisions
This approach uses two small incisions and requires radiographic screening in the operating theatre in order for the surgeon to insert the cementless acetabular cup and femoral stem. The MIS—2 incision approach is made through an anterior (front) skin incision. The hip is exposed through the inter-muscular plane. The capsule is divided allowing for removal of the arthritic head and neck and insertion of the acetabular cup. The cup position is assessed with the aid of fluoroscopy.
The second posterior (back) incision is made in line with the femoral canal. The gluteus maximus muscle is split and a plane is developed between the deep muscles of the hip.
Exaggerated statements have been made about this surgical approach, especially the fact that surgeons do not disrupt or incise muscles when performing such surgery. However, the MIS—2 incision approach has been shown to have a high incidence of complications, namely that of mal-positioning of components, neurovascular injuries and fractures.
MIS Detail: Single Incision—Anterior (front) Approach
This is a true muscle sparing approach to the hip as it avoids any incision to the muscles in the front of the hip joint. The incision is centred between the anterior superior iliac spine (the prominent anterior [front] part of the pelvis) and the greater trochanter.
The patient is positioned flat on their back and draped so that the legs are free and mobile. Leg lengths can usually be more accurately assessed when the patient is in a supine position.
The incision is performed in line with the tensor fascia lata muscle.
The tensor fascia lata muscle is identified and the plane between this muscle and the rectus femoris muscle is identified and exposed.
Retractors are positioned medial and lateral to the femoral neck. The hip capsule is split and the femoral neck resection is performed. The arthritic head and neck of the femur are removed to allow insertion of the acetabular cup into the acetabular socket.
The acetabulum is visualised with the help of a funnel formed by the MIS retractors. The specially designed retractors protect both soft tissue and skin in order to allow access to the acetabular socket. The MIS off-set acetabular reamers allow the surgeon to ream the worn socket and likewise the off–set acetabular shell impactor allows the surgeon to set the acetabular cup in an optimum position. A liner of choice can then be seated in the acetabular shell.
A musculotendinous and soft tissue release is performed in the trochanteric fossa. The resected femoral neck is delivered into the surgical wound. This is facilitated by crossing the operative leg under the contra–lateral leg in a figure four position.
A trial femoral component is inserted into the femoral canal and the hip joint can then be tested for stability and leg length before insertion of the final femoral component and femoral head.
Closure of the surgical wound is performed by interrupted sutures to the fascia, subcutaneous layers and skin.
MIS Detail: Single Incision—Posterior (back) Approach
This approach avoids incision of the gluteus medius muscle. The patient is placed in the lateral decubitus position.
The incision is centred over the posterior third of the greater trochanter and buttock. The fascia is incised in line with the fibres of gluteus maximus muscle.
The piriformis muscle is spared while the external rotators are incised to expose the hip capsule. The femoral neck is incised and the arthritic femoral head and neck are removed allowing for insertion of the acetabular cup into the acetabular socket.
The acetabulum is visualised with the help of a funnel formed by the MIS retractors. The specially designed retratcors protect both soft tissue and skin in order to allow access to the acetabular socket. The MIS off–set acetabular reamers allow the surgeon to ream the worn socket and likewise the off-set acetabular shell impactor allows the surgeon to set the acetabular cup in an optimum position.
The resected femoral neck is delivered into the surgical wound. The trial femoral component is inserted into the femoral canal and the hip joint can then be tested for stability and leg length before insertion of the final femoral component and femoral head in the optimum position. A liner of choice can then be seated in the acetabular shell.
Closure of the wound is performed in the standard manner.