Department of Orthopaedic Surgery

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Pediatric Orthopaedics

PAO: A Patient's Perspective

M. Brady, M.D. (a PAO patient of Dr. Diab as a medical student, now a physician)

What is a PAO?
The hip is a ball (the head of femur, or thigh bone) and socket (acetabulum, which is formed by the pelvis).  A PAO is an operation to correct deformity of the hip, in which the acetabulum does not cover the head of femur properly.  In this situation, the force across the hip joint produced by body weight during standing, walking and running is not evenly distributed and becomes concentrated abnormally.  This wears away the cartilage that lines the hip joint, resulting in osteo-arthritis.  Osteo-arthritis refers to degeneration of a joint such that a patient experiences pain, then stiffness then ultimately inability ot use the joint at all.
The most common cause of deformity of the hip is hip dysplasia.  There are other causes, such as Legg-Calvé-Perthes disease.  In a PAO, bone (osteo-) is cut (-tomy) around (peri-) the socket (-acetabular) in order to put it in a better position to cover the head of the femur.  The most common type of PAO is the type developed in Berne, Switzerland (hence the name Bernese PAO) 1.  The PAO is a joint-preserving operation, by contrast with a hip arthroplasty, which replaces the hip with a metal and plastic joint.  The PAO is much better for a teenager or young adult (< 50 years of age) than a hip replacement2.

Considerations before operation.

In addition to the physical examination, the surgeon will use imaging studies as  part of the evaluation. These include X-rays, and variably computed tomography (CT) as well as magnetic resonance imaging (MRI).  The most important factors determining the long term outcomes (how well you do) after a PAO are the severity and type of the hip deformity, as well as the degree of osteoarthritis.  Osteo-arthritis may be assessed on X-rays (for example narrowing of the joint) and/or MRI (for example a tear in the labrum, which is the cartilage rim of the acetabulum).  The best results are in patients who have the least osteo-arthritis.  Some patients may have too much osteo-arthritis to benefit from PAO2.  For patients who need a PAO on both hips, the time between operations will depend on recovery from the first surgery, but typically is 6-12 months.  The second side always is easier than the first, because you know what to expect and are less anxious.

You will have a pre-operative visit with the surgeon, typically the week before operation, to go over everything again and to sign the consent forms for operation and blood transfusion.  You will be given an opportunity to donate blood ahead of the operation, or ask designated donors to do so on your behalf.

What does the surgeon do during a PAO?
The acetabulum is repositioned so that it covers or fits the head of femur properly – “putting the hat on top of the head,” as my doctor says.
A single oblique incision is made on the front of the hip, starting above the bony prominence of the hip and ending in the groin crease.  Muscles, blood vessels, and nerves are retracted to expose the joint.  The joint may be opened for inspection of the labrum.  If the labrum is torn, it may be repaired (a clean tear) or trimmed (an irregular or degenerative tear).  The hip joint is then repaired and closed.  The physician will use a bone-cutting tool called an osteotome (resembles a chisel for wood work) to make a series of cuts around (peri-) the acetabulum. The acetabulum, now freed from the rest of the pelvis, is rotated over the head of femur to normalize as much as possible the coverage of the head of femur and thereby correct the weight-bearing load of the joint.  Long screws are inserted to hold the acetabulum in place while it heals.  Over the next 3-6 months, the acetabulum heals in its new place.  Sometimes, if the acetabulum has to be moved a long distance (in cases of severe hip deformity), bone graft is applied to some of the cut surfaces to enhance healing.  The surgical technique of the PAO is continually evolving and each surgeon may practice slight variations on the surgical procedure.  Specifics of the operation, such as the length of the incision, the number of screws inserted, whether or not the screws are removed, and post-operative care, will depend on the surgeon.

What can I expect on surgery day?

When you arrive at the hospital, you will be taken to a pre-operative room on the surgery floor.  The anæsthesiology team will discuss anæsthesia options with you.  An IV will be started and you may be given medication to reduce your anxiety before being taken into the operating room.  Some patients are candidates for epidural anæsthesia, which bathes the nerves of the pelvis and lower limbs directly with pain and numbing medication.  An epidural anæsthetic is administered under general anesthesia.  You probably will not remember falling asleep because the anæsthesiologist gives you drugs that make you forget (so you are less traumatized by the experience!).  Before the surgeon begins, a nurse will insert a catheter into the bladder, which will remain for a few days after the operation.  In this way, you won’t have to get up to urinate, which is a big help as you will be very sore for the first couple of days.  The operation lasts about 4-6 hours.  During the operation, your vital signs will be continually monitored.  If too much blood is lost, you will receive a transfusion.

When you wake from the operation, you should not be in excessive pain because of the medicine being administered through the IV and/or epidural.  The anæsthesiology team will continually check on your pain and nausea level to make you comfortable.  Patients are monitored for a few hours in the recovery unit before being taken to a hospital room.

What will recovery be like during my hospital stay?
Patients stay in the hospital for about 3-5 days.  Patients experience variable amounts of post-operative nausea, in large part because of the pain medications they take.  Pain management is monitored by the anæsthesiology team during your hospital stay.  In the first 2-3 days, you will have a patient-controlled anæsthesia device, in which you can self-administer extra medicine into the epidural or IV line by clicking a button.  After that, you will be switched to pain medications that you take by mouth.  No matter how well your pain is controlled, your hip still may hurt.  The hip, buttock, entire thigh, groin and foot may be swollen and bruised, sometimes for a few weeks.

The surgeon will check your nerves by asking you to move your leg in certain directions, and your blood flow by checking pulses in your leg and how swollen you are.  You will be helped out of bed on the first post-operative day with the assistance of a physical therapist.  This is important for many reasons.

  1. Movement pumps blood through the veins in your legs, thereby reducing the risk of a blood clot (which can be very dangerous).
  2. Movement helps you move your bowels, which will be slowed not only by inactivity but also by pain medications.  Constipation is very uncomfortable when you are in pain after a big operation.
  3. Movement will help your lungs inflate more completely, reducing the risk of pneumonia.
  4. Movement prevents bed sores.

You will use a walker and/or crutches, and will be taught how to place your foot on the ground, relax your muscles, but not put any weight through you leg on the operated side.
Your blood level will be checked daily: if your blood pressure gets too low or if the blood levels (hæmoglobin and hæmatocrit) dip below safe levels, you may receive a transfusion.  By the third day after operation, IV pain medications will be off and the catheter in your bladder will be removed.  At this point, you will use a bed-side commode or a bed-pan. It may take a day or so to regain full control of your bladder muscles.  You may be given a laxative and stool softener to help reduce constipation.
Physical and occupational therapists will visit each day to teach the safest way to get in and out of bed and to use walking aids.  Learning how to use the toilet, sit, and stand with pain and restrictions feels unnatural and takes time getting used to.  The therapists will also assist in preparation for going home.  The occupational therapists will arrange for equipment you can bring home – such as walker, crutches, bed-side commode, and possibly a wheelchair.  If there are stairs at your home, the physical therapists will teach you the correct way to use stairs with crutches.
You will be discharged from the hospital to home when

  1. You are able to urinate by yourself after the catheter in your bladder is removed.
  2. You are comfortable on oral pain medications.
  3. You are able to move around independently, with assistive devices and the obvious restrictions that you will be taught.
  4. Your surgeon obtains X-rays of your pelvis to make sure that nothing has shifted after you have been mobilized and body-weight forces have been applied to your hip.

What will recovery be like when I go home?

Patients cannot bear weight on the operated side for 6-8 weeks after operation.  The recovery period sounds overwhelming, especially for the active parent or student, but it can be done.  Reading this document in advance will help you make the proper accommodations so that the recovery is smoother and you can return to your normal routine sooner.
It is important that patients arrange a support system with friends and family for the recovery period. Some patients may have access to more assistance than others, but during the first few weeks of recovery, it will be difficult to take care of yourself – getting up from a lying or sitting position, eating, using the bathroom, and bathing are activities with which you will need help.  Sleeping positions may also take some getting used to – at first you will only be able to sleep on your back.  After a few weeks (when pain subsides), you may be able to roll onto your unoperated side.  Having several different sized pillows for positioning is helpful.

Pain will be managed as needed with prescription pain medication.  During each recovery milestone, such as moving from a walker to crutches, physical therapy, and beginning to bear weight again, it may be necessary to adjust medication intake.  Since narcotic pain medications cause constipation, a stool softener and/or laxative pills may be taken while using the medication.  Urinating can also be difficult for several days after operation due to internal swelling.  Burning sensation during urination or unexpected voiding may occur.  A bed-side commode or an elevated toilet seat will make using the bath-room much easier.
You will see your surgeon the week after operation.  The incision cannot get wet until then, when your surgeon will inspect it to make sure it is dry and healing well.  If the wound is inflamed or is draining fluid, it may be infected and the surgeon will act accordingly (wound infection after such an operation is rare).  Until then, you can get creative as far as how to bathe – using wash-cloths or covering the incision well and using a shower hose while sitting on a shower chair are options.  After the dressing is removed, you may choose to crutch into a shower and stand, carefully balancing your weight on the unoperated leg.
Patients will graduate from a walker to crutches when the pain of swinging the pelvis subsides.  It is important to get up and walk around several times each day to maintain strength in both legs.  Patients’ arms and wrists may hurt because they are not accustomed to using walking aids.  The foot on the unoperated side of the body that bears all the weight may also cramp and be sore from overuse.  Strengthening arms and legs in the months before operation can make recovery much easier.  The operated leg will weaken from lack of use, so moving around and trying to be active will make walking on that leg easier later.  For the first 6-8 weeks after operation, you will focus on moving your hip so that you don’t become stiff – you will need someone to help you with this, as the pain may inhibit you from doing this on your own.
You may notice other changes in your hip, such as clicking and popping of the hip for weeks after operation as the muscles and other tissues around the joint which were dissected during the operation heal.  A frequent consequence of operation is the nerve that provides sensation to the skin of the front of the thigh goes to sleep because it is in the way and gets squeezed as it is retracted for most of the operation (several hours).  You may notice numbness or uncomfortable sensation here when touched, but this typically resolves within about 2 years.

Slowly, you will regain strength and range of motion in the operated leg.  At 6-8 weeks after operation, you will have an X-ray and see the surgeon, who will decide if your bone has healed enough to begin weight bearing on the operated side.  You should wean yourself off pain medications so that you are not taking any by this visit.  You will be advised to increase motion exercises for your hip, as well as to begin strengthening exercises (especially of your quadriceps, hip flexor and hip abductors), often with the assistance of a physiotherapist.

The time it takes to return to a work or school routine will vary from patient to patient.  The earliest is 4-6 weeks after operation for those with a desk job or who plan to attend class.  You can not drive until you can move your hip independently and quickly, and until you can apply force through your leg normally.  This is necessary not to drive a car in a straight line, but to be prepared if you need to perform an emergency manœuvre.  This takes about 12 weeks after operation.

Through physical therapy and becoming active again, you will re-learn how to walk on the operated leg.  It takes months after surgery to regain strength and a normal way of walking.  Initially, you will waddle toward the operated side as you walk.  Don’t let this get you down: it is the result of weakness of the hip abductor muscles (the physiotherapist will teach you about this), and it will go away.  You may use one crutch or a cane until you can walk without an aid, which happens by the three month mark for most patients.

A final note.  The PAO does not change the size of the birth canal, so women are able to carry a pregnancy normally and to deliver vaginally.  If you plan to become pregnant, you may start trying at 12 weeks after operation.  This is the basic follow up time, during which X-rays are essential to the post-operative assessment (and you can not risk fœtal exposure to radiation from X-rays).  Your obstetrician/gynecologist should be made aware of your condition.

Ask your surgeon to put you in contact with patients who have undergone a PAO and are willing to share their experience with you.  A PAO is a big operation, and talking to others ahead of time will give you important information to help ease the anxiety that you may feel.

Further reading.

  • Ganz R, Klaue K, Vinh TS, Mast JW. A new periacetabular osteotomy for the treatment of hip dysplasias. Clin Orthop 1988; 232: 26-36..
  • Sharifi E, Sharifi H, Morshed S, Bozic K, Diab M.  Cost utility of peri-acetabular osteotomy compared with total hip arthroplasty.  J. Bone Joint Surg. Am. 90:1447-1456, 2008.