Protrusio (Inward migration of the socket)

Protrusio or medial migration of the socket can be of many types. Some are straight forward for the surgeon to manage. However there are some forms which can pose a formidable challenge to the surgery.

Protrusio with only medial migration :

In this example shown there is only medial migration of the hip.

This is managed by using bone graft from the head of femur (autograft).

The graft must be prepared in correct fashion ( min 5 mms size). This is impacted on the floor over which a pressfit hemispherical shell is fixed with good rim fit. It is mandatory to use augmentation screws in this condition.

Concept of judicious lateralization in protrusion:

With experience the surgeon builds up a feel of how much lateralization of the socket is best for that particular patient. This judicious lateralization gives the best functional result.

In the examples given below of protrusio done in other centres one can see that too much lateralization or no lateralization can result in very poor function.

Unacceptable medialization:

Unacceptable lateralization:

Judicious lateralization has been done in my patient given below. This gives excellent postoperative function:

More complex protrusio involves inward and upward displacement (proximo-medial migration or bottle neck protrusio)

This type of protrusio is a surgical challenge as the shape of the socket is that of small bottle with the neck of the bottle being the mouth of the bony socket.

Here, as the surgeon reams more the reamer gets loose in contrast to the usual situation of the reamer getting more tight as one goes inward. This technical complexity leads to a high failure rate of the socket if the surgeon does not have a specific plan and execute it precisely.

In the series of photos given below one can make out the defect of bone getting larger as the reamer goes more inward.

Management of bottle neck protrusio:

In the illustrated case femoral head autograft is used to bring the head out and down. Getting a good rim fit is difficult but it is mandatory to achieve to ensure long term success of the implant.

In this bottle neck protrusio a high hip centre technique is used judiciously. This technique must be employed if the hip has more of a vertical component than a medial component.

Rare example of Protrusio with Pathological Coxa vara:

In this rare case example there is pathological increase in offset. Here a metabolic cause has to be ruled out before tackling the protrusio. If one decreases this offset then there is a high chance of dislocation due to the laxity created. To offset this one has to use a large head.