The operation of periacetabular osteotomy is designed
to move the socket (acetabulum) of the hip joint so that
it covers more of the femoral head (ball). The aim is to
improve the biomechanics of the hip joint and reduce the
high stresses that start to cause damage and arthritis
because of the shallow acetabulum. Sometimes it is
recommended that an arthroscopy of the hip is undertaken
sometime prior to the PAO. This allows the changes
within the hip joint to be accurately assessed and and
frequently procedures can be performed to the cartilage
to optimize the outcome of the PAO.
The operation is usually performed either under a spinal
anaesthetic with sedation, or a general anaesthetic with
an epidural in place. The surgery itself usually takes
about 2 hours. The incision is curved over the outside
of the pelvic bone and is typically 10-12cm in length.
The operation involves a series of bone cuts around the
acetabulum, freeing it from the pelvis and allowing it
to be moved to a new position. The new position of the
joint is checked with X-rays at the time of surgery and
once the optimal position for the hip has been achieved,
it is fixed in place with 3 or 4 screws.
After the surgery, patients are mobilized out of bed
with the aid of the physiotherapists the day after the
operation. Pain is initially controlled with a self
administered morphine pump (PCA – patient controlled
analgesia). The aim is to get safe on crutches only
putting a small amount of weight through the leg. On the
third or fourth day following surgery exercises are
started in the hydrotherapy pool. Hospital stay is
usually 5 to 8 days.
The aim of the surgery is to improve the pain coming from the hip. It is also anticipated that the risk of the development or progression of arthritis will be reduced in the long term, however, this depends a lot on how much arthritis damage has already occurred to the joint before surgery.
Risks and complications
Clearly, a periacetabular osteotomy is not a small procedure.
However, with appropriate experience it can be performed
through a relatively small incision with a low risk of
complications and with a predictable end result.
Bleeding. Because the pelvic bone has a very good blood supply
and is surrounded by a lot of blood vessels there is the
potential for significant bleeding to occur. During the
surgery itself, a cell saver is used which allows blood lost
in the wound to be given back to the patient during the
operation. It is rather rare for patients to require a blood
transfusion.
Nerve and blood vessel injury. Because the acetabulum is surrounded by a lot of important nerves and blood vessels there is a small risk of damage to one of these serious structures. This could lead to some weakness in the lower leg. The overall risk of a major complication such as this is in the region of 2%.
Deep vein thrombosis and pulmonary embolus. During the recovery you will be treated with blood thinning injections and thromboembolic deterrant stockings to reduce this risk (2%).
Wound infections. These may occur about 1% of the time and may require antibiotics or further surgery to deal with them.
Failure of the osteotomy to unite. Because the pelvic bone has such a good blood supply and muscle cover, it would be very unusual for the osteotomy not to unite. If this were to happen then further surgery may be needed to stimulate the bone to heal.
Numbness around the wound and thigh. Because of the location of the incision for this operation and because of the anatomy of specific small sensory nerves, there is always some numbness over the upper outer aspect of the thigh. This area gradually gets smaller with time. Rarely the numbness may affect the outer aspect of a major portion of the thigh extending down to the knee but it would be unusual for it to persist to this extent.
Arthritis. In time the joint may become arthritic and this depends on the extent of damage before surgery and how shallow the acetabulum is. Although the aim is to make the hip look as normal as possible, it still won’t be a normal hip and therefore the stresses through it may result in the development of arthritis at some stage.
Rehabilitation following PAO
After discharge from hospital it is very helpful to
continue with hydrotherapy for 6 weeks after the operation,
usually 2-3 times per week. This allows strength and range of
movement to be worked on while weight bearing through the hip
is restricted. It is worth investigating prior to surgery
whether a hydrotherapy facility is available local to you so
that this can be organized in advance.
After 6 weeks patients are reviewed and a repeat X-ray taken
to ensure that the bone is healing satisfactorily. At this
point half body weight is allowed through the leg using 2
crutches for 1 week and then full weight bearing is allowed
graduating onto 1 crutch. The exercise programme in this phase
of the recovery concentrates more on strengthening the muscles
around the hip in particular the hip abductors (gluteus medius
and minimus). These muscles need to be strong to avoid any
limping when taking full weight through the leg. Patients
usually find they can return to most activities 10-12 weeks
after surgery and to impact exercise and sports after 6
months.
In general there are no restrictions with activity level after
a PAO, but the kinds of sports undertaken should take into
account any arthritic damage that may have taken place prior
to the osteotomy.
content written by Johan Witt Hip othopaedic and trauma surgeon
