What is Periacetabular Osteotomy (PAO) Surgery?

///What is Periacetabular Osteotomy (PAO) Surgery?

Periacetabular Osteotomy (PAO) is a surgical treatment for hip dysplasia that involves repositioning the acetabulum (socket) into a location that best covers the femoral head.   “Periacetabular” means around the acetabulum. “Osteotomy” means to cut bone. Simply put, the PAO cuts the bone around the acetabulum that joins the acetabulum to the pelvis. Once the acetabulum is detached from the rest of the pelvis by a series of carefully controlled cuts, it is rotated (or “reoriented”) to a position that provides better coverage of the femoral head, thereby improving the stability of the hip joint and unloading the peripheral soft tissues.   The socket fragment is then secured with screws.

This “reorientation” unloads the peripheral articular cartilage and acetabular labrum such that they are no longer subject to the force concentration associated with the shallow socket.  The shallow, upsloping roof that incompletely covered the femoral head is brought over the head to provide normal coverage and also brings the roof to a horizontal position. This improves the coverage of the femoral head, decreases the instability associated with dysplasia, and unloads the peripheral labrum and articular cartilage.  These changes optimize the mechanics of the hip such that the soft tissues no longer are subject to damaging forces.

Periacetabular Osteotomy.  Pre-operatively (left) the socket is shallow, covering only part of the femoral head.  It is upward sloping, and the force of weightbearing concentrated to the periphery rather than distributed throughout the acetabulum.

After PAO surgery, the socket has been repositioned to optimize coverage of the head, and the peripheral labrum and articular cartilage no longer experience the loaded stress.

Individual cases of dysplasia however present with their own unique morphologies, and the osteotomies must be tailored to solve these unique problems.  The femur may  be abnormally shaped and benefit from a combined femoral osteotomy, for example.  Commonly, the femoral neck is excessively long and straight (Coxa Valga).  Alternatively, the femoral neck may be too short (Coxa Breva) or the femoral head insufficiently round (CAM deformity).

A. Coxa Vara, Coxa Breva. The femoral neck is short and the angle low. An osteotomy to lengthen the neck and open the angle would be indicated at PAO.

Normal proximal femur, requiring no additional surgery at the time of the PAO performed to address the acetabular dysplasia.

C. Coxa Valga. The femoral neck angle is too high, contributing to the force concentration on the shallow socket. Surgery to decrease the neck angle is indicated.

If there is an abnormality of the proximal femur that threatens the intra-articular tissues after the socket has been reoriented, a combined Proximal Femoral Osteotomy may be required.   Below is an example of a patient with a dysplastic acetabulum, but also a femoral deformity common to Legg-Calve-Perthes Disease.  A combined Periacetabular Osteotomy and Proximal Femoral Osteotomy was performed to optimize the hip mechanics.

Below is an example of a patient with a dysplastic acetabulum, but also a femoral deformity common to Legg-Calve-Perthes Disease.  A combined Periacetabular Osteotomy and Proximal Femoral Osteotomy was performed to optimize the hip mechanics.  The femoral plate was ultimately removed.

Often, the abnormal mechanics associated with hip dysplasia have cause labral injury and cartilage damage.  In the majority of cases, the surgeon will evaluate the labrum at the time of the surgery (either by open means or with Arthoscopic Assisted PAO surgery) and perform labral surgery as indicated depending on the damage.  The articular cartilage may be injured and be treated also.

A. The acetabular labrum is often detached and injured at the time of reorientation osteotomy.

B. This MRI of a patient with acetabular dysplasia is compelling for injury to the acetabular labrum.

C. Injury was identified at the chondrolabral junction in this patient with a hpertropic acetabular labrum arthroscopically during this combined procedure.

Why is Osteotomy Preferable to Total Hip Replacement?

Over the past 5 years, there has been a renewed and growing interest in adult hip osteotomy. Osteotomy was used more frequently as a treatment for adult hip problems before the advent of Charnley’s low friction arthroplasty (the first successful artificial hip joint) in the 1960’s. The encouraging early good results regarding function and pain relief after Charnley total hip replacement in young patients led many surgeons to abandon osteotomy.

However, despite good initial results of total hip replacement, the long-term follow up of these patients has shown increased problems, especially in the young active population. Osteolysis (bone loss) can cause loosening of the hip prosthesis (artificial hip) when patients outlive the longevity of their artificial hip.  This is particularly important in young patients, who are active and will cycle their hips move over many years.  Hip replacement revision surgery for failed THA presents significant problems, particular for the patients with osteolsis.  Failure of THA requiring revision surgeries in active young to middle aged adults have underscored the importance of preserving the hip rather than replacing it.

Osteotomy should not be thought of as an inferior second choice to total hip replacement that the young patient with early arthritis must undergo because he or she is too young for total hip replacement. The results after PAO, which preserves the patient’s own hip, justify its use, and the long-term results can be better than what the patient could have obtained from a hip replacement. The patient’s own hip is a living tissue with self-maintenance capabilities, whereas deterioration with time is inevitable for an artificial part. The sensory capabilities of the joint are preserved, and the patient can continue to remain as active as symptoms or lack thereof permits. The patient with a total hip replacement, however, must always be cautioned regarding possible hip dislocation and the substantial complication portfolio associated with implant based replacement surgeries.

What should you expect after surgery?

Surgery is performed at the St. Thomas Midtown Center.  You will be evaluated by our Medical Hospitalist or Pediatric Hospitalist partners before surgery, and these physicians will see you each day and contribute to your non-orthopaedic care while you are in the hospital.  Surgery lasts 4-8 hours, depending on the unique surgical plan developed for the individual patient.

An epidural catheter will be placed by the anesthesiologist and continued for the first two days after surgery.  This greatly improves pain control immediately after surgery, and decreases total narcotic pain utilization. After it is discontinued, oral medications become the mainstay of pain control.  Most patients continue to utilize narcotic pain medications

The usual hospital stay is five to seven days and depends on how rapidly pain subsides and physical therapy progresses. You will have a Foley catheter in your bladder for at least one night, have compressive devices on your legs to prevent blood clots, and be treated with a multi-modal analgesic program to address post-surgical pain.

St. Thomas Midtown Nursing team.  These nurses truly enjoy caring for patients after complex hip and pelvis surgery.  They are specialized in orthopaedic patient care, and the floor only has patients that have had orthopaedic surgery.Our patients after PAO surgery commonly visit the team at the time of their return clinical visits.

Surgical drains will be removed 1-2 days after surgery.  Occassionaly patients require a blood transfusion.

Your incision will most likely be closed without sutures nor staples requiring removal, and will be sealed with a glue.

If you have chosen to obtain a “Game Ready” device, it will be applied at the time of surgery, and you will be trained to apply it and adjust it while in the hospital.

You will work with Physical therapy 2x a day and be encouraged to ambulate (with restrictions) as much as possible, starting the day after the surgery. Weighbearing is restricted to 30lbs on the operative side for 8 weeks after surgery to allow the osteotomy sites to begin healing.  Most commonly patients utilize a walker for 3 weeks, and then transition to crutches.  There are some restrictions on the range of motion after the surgery, including limitations to active flexion and flexion beyond 90 degrees.  If labral surgery is performed, there may be rotational restrictions also.  A continuous passive motion machine is utilized, allowing safe and controlled motion starting the day after the surgery.

*Each surgery is individualized, and therefore the specific restrictions and precautions for each patient will be different for each patient.  We will spend a lot of time with you after surgery ensuring that you understand your unique protocols before you leave the hospital.

When Will I be Discharged?

Patients are discharged once pain is controlled with oral medications and physical therapy goals are met.  In general, this takes 5-7 nights of stay in the hospital.

At discharge, pain medication is prescribed as well as an anticoagulant to prevent blood clots. Some degree of pain after discharge is natural, which may increase or decrease on different days, but the general trend should be toward decreasing pain. Some patients may sense an occasional “click” or “pop” in or around the hip. Numbness and a tingling sensation is common around the incision area. Patients experiencing new, severe pain or having ANY wound drainage, redness or seperation should call NHI (615-284-5800) regardless of the time or day to discuss with the oncall practitioner.  *Concerns should NOT be sent by email.

When Do I Return to the Nashville Hip Institute?

Follow-up outpatient visits are necessary to monitor progress by X-ray and physical examination, and to graduate patients to the next phases of rehabilitation. The first follow-up visit is usually scheduled about 6 weeks after surgery with Morgan Schlundt, the Physician Assistant. The second visit is at 3 months.

At 8 weeks after the surgery, the patient is allowed to be full weight bearing and work toward discontinuing use of the crutches (which usually takes 2-4 weeks).

Ultimately, your postoperative course depends on return of muscle strength. Working with a trained physical therapist adept in treating hip dysplasia is critical.  You should develop a relationship with the therapist before surgery, and many patients benefit from working with therapists as part of the “pre-hab” strengthening program.  These therapists will be critical in your post-surgical rehabilitation, particularly once weight-bearing is allowed after 8 weeks.

You will be asked to visit us 6 weeks after surgery (or see your local surgeon who might be coordinating your care locally), again at 3 months, at 6 months, and at 1 year and 2 years for routine follow-up.  After the second year, we schedule appointments at 2 year intervals.

A minority of patients request removal of one or more screws that were used to fix the PAO, and this can be performed as an outpatient procedure that does not interrupt a patient’s continued full function.  Patients who have undergone some femoral osteotomies at the time of PAO often require secondary metal removal for symptomatic implants.

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