Posterolateral (Gibson) Approach

POSTEROLATERAL (GIBSON) APPROACH

USES

This approach is used for hip prostheses, for piriformis releases in cases where the sciatic nerve is being compressed by that muscle, and for resection of the greater trochanteric bursa.

ADVANTAGES

This approach provides excellent access to the hip joint itself, and probably gives the best access to that joint without requiring the release of significant muscles. It is also an internervous approach because the gluteal muscles innervated by the gluteal nerves are retracted superiorly. The sciatic innervated muscles are located posteriorly and medially, and the femoral innervated muscles anteriorly.

DISADVANTAGES

This approach has a slightly higher dislocation rate following prosthetic implant in the hip joint than does an anterior approach. There is also some risk of damage to the sciatic nerve, which is not the case with the anterior approach. Also, in children, there is risk to the blood supply to the femoral epiphysis, which largely comes through the capsule. The most critical blood vessels come in at the posterosuperior corner of the capsule. For this reason, the posterior approaches to the hip are generally avoided in children with an open growth plate at the hip.

STRUCTURES AT RISK

The major structure at risk with this approach is the sciatic nerve. It is imperative that this nerve not be damaged. The nerve is fairly far medial. If the approach to the hip joint is through the external rotators along their insertion into the greater trochanter, then the nerve will be protected by those muscles as they are retracted. The nerve is easy to identify because of the loose tissue around it and because it is large and runs longitudinally, whereas all the other structures in the area run transversely.

If the split between the gluteus maximus and medius is carried too far proximally, then the superior gluteal nerve can be damaged. This is the nerve supply to the gluteus medius and minimus, and tensor fascia lata. Damage to the nerve causes significant hip abductor weakness with resultant gait abnormalities.

TECHNIQUE

The incision starts 3 cm distal to the tip of the greater trochanter and just behind it, proceeds proximally in a curved posterosuperior fashion, and is carried through the subcutaneous tissue. The fascia lata and the gluteus maximus insertion are seen, and typically the fascia lata is split longitudinally distally for 4 or 5 cm in the region of the gluteus maximus insertion into it. The interval between the gluteus maximus and medius is developed and split proximally, so that the maximus can be retracted posteriorly and the medius and minimus retracted anteriorly.

After the gluteus maximus is retracted in a posterior direction, the greater trochanteric bursa is identified. This bursa needs to be resected off of the back of the greater trochanter and femoral neck area, to expose the external rotators. The piriformis is the easiest to identify because it has a discrete tendon. These rotators are then transected off of their insertion. There is typically a blood vessel in the inferior portion of the external rotators that needs to be cauterized. At that point, the hip capsule can be opened and the rest of the procedure completed.

TRICKS

The major trick to this exposure is getting the gluteus maximus released so that it can be moved posteriorly and then to hold the medius and minimus anteriorly. It is sometimes necessary to release part of the minimus to get to the superior aspect of the femoral neck. Typically, a periosteal elevator can be used to strip the soft tissues overlying the external rotators down. This wiping motion exposes them without risking damage to the sciatic nerve.

One of the other problems is identifying the proper place to split the muscles in the interval between the gluteus maximus and medius. Once the fascial portion of the gluteus maximus has been split, you can place your finger underneath the more muscular portion and feel for the thin part. That would be the correct location to make your split.

HOW TO TELL IF YOU ARE LOST

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