What does PAO do?
After PAO, the socket covers the femoral head more appropriately and the load is distributed over a larger area.
The posterior column of the pelvis remains intact. The pelvis stays stable and the birth canal is unchanged; vaginal delivery remains possible after PAO.
Assessment before surgery
Assessment starts with standing pelvic and axial hip X-rays. MRI helps us assess the cartilage and labrum. Together, these findings determine whether PAO is appropriate for you.
Who is suitable?
PAO can be suitable for hip dysplasia and acetabular retroversion when the cartilage is largely preserved and the joint is congruent, so that the head and socket fit together after correction.
If the cartilage is extensively worn or the joint severely deformed, reorientation offers little benefit. Hip replacement may then be the more appropriate recommendation. Cartilage condition matters more than age alone.
The Greifswald technique
We perform PAO through a 5–8 cm incision (depending on body size) in the groin, using a natural interval between muscles without cutting through them. The sartorius and rectus femoris remain attached; the iliopsoas is moved aside.
Four osteotomy steps
Four controlled bone cuts preserve the posterior pelvic column. The socket is then freed, rotated into the correct position and fixed with screws.
- Operating time: 30–45 minutes without additional procedures
- Getting up on the day of surgery
- Hospital stay: 3–5 days
- 1Ischium below the socket.
- 2Cutting the pubis above the obturator foramen.
- 3Cutting the ilium above the socket.
- 4Behind the socket to the ischial cut – the posterior pelvic column remains intact.
Additional procedures
We discuss any additional procedure with you before surgery.
- If cam impingement is also present, the femoral head–neck junction can be reshaped through the same approach.
- Significant rotational deformity of the femur can be corrected through a separate incision on the outer thigh. This is needed in approximately 5–10% of patients.
Aftercare
- Weeks 1–6
- Partial weight-bearing of 15 kg using forearm crutches; do not flex the hip beyond 90°.
- Weeks 1–8
- No active hip flexion or active leg lifting (clearance after 6–8 weeks).
- From week 3
- Once the wound has healed: exercise bike without resistance, with a high saddle; move the operated leg passively only.
- After 6 weeks
- Follow-up X-ray.
- From weeks 7–8
- Gradual progression to full weight-bearing.
- After 8–10 weeks
- Driving.
Inpatient rehabilitation is not routinely planned after PAO. If needed, it starts no earlier than around week 7. All timings are guidelines and depend on your clinical recovery and follow-up X-rays.
Risks
Every operation carries risks. In large centres, the reported rate of major complications after PAO is now around 1%, compared with around 6% approximately ten years ago. Higher rates may occur in centres performing few PAOs.
Temporary numbness on the outer thigh is common because of irritation of the lateral femoral cutaneous nerve. It usually resolves. Persistent burning pain is uncommon; please contact your surgeon promptly if it occurs.
With the minimally invasive technique, we now see virtually no heterotopic ossification, meaning new bone formation in the soft tissues.
Contact your surgeon directly with concerns after surgery. Your surgeon knows your hip and coordinates further care.
Frequently asked questions
+Is PAO a major operation?
Yes. It is a major pelvic procedure performed through a 5–8 cm groin incision (depending on body size), without cutting through muscle. Operating time is 30–45 minutes without additional procedures.
+Is there an age limit?
What matters is the condition of the cartilage, not your age. PAO can still make sense after 40. To assess this, we need a pelvic X-ray and an axial X-ray, ideally also an MRI.
+What is the difference between PAO and triple osteotomy?
In a triple osteotomy, the pelvis is cut further away from the joint. In a PAO, the back of the pelvic ring stays stable and the socket can be positioned more precisely. Today, PAO is the worldwide standard for adults.
+Can PAO also treat acetabular retroversion?
Yes, provided the cartilage is largely preserved and the joint remains congruent after correction.
+How big is the scar?
The incision is 5–8 cm long, depending on body size. It lies in the bikini area so the scar stays thin and can be easily covered.
+How long will I stay in hospital?
Usually 3–5 days. You can get up on the day of surgery.
+Will I be in a lot of pain?
The first days are uncomfortable, but modern pain management controls the pain well. With our minimally invasive approach, pain is much less than it used to be.
+Will I need a blood transfusion?
Very rarely. In Greifswald, only one transfusion has been needed in around 2,000 PAOs so far. Bleeding comes mainly from the bone and can cause a bruise that resolves on its own.
+When can I fully bear weight?
Initially, use crutches with 15 kg partial weight-bearing for six weeks. Following the six-week X-ray, full weight-bearing is introduced gradually from weeks 7–8, depending on your recovery. Weeks 1–8: no active hip flexion or leg lifting (clearance after 6–8 weeks).
+What must I avoid in the first 6 weeks?
Do not bend the hip beyond 90° and do not actively lift the leg. Active hip flexion is allowed only after 6–8 weeks. From week 3, once the wound has healed, you may use an exercise bike: no resistance, saddle set high, with the operated leg only moving passively.
+How should I sit after the operation?
Sitting is allowed from the first day. For the first 6 weeks, the hip should not bend beyond 90°. A high chair or a wedge cushion helps. Avoid low sofas and low car seats during this time.
+Will I need rehabilitation after PAO?
Inpatient rehabilitation is not routinely planned after PAO – at the earliest after about 7 weeks, if your recovery requires it.
+When can I go back to work?
With mainly seated work, usually after 6–8 weeks; with physically demanding work, later. We discuss this with you individually.
+Can I do sport again after PAO?
The aim of PAO is to preserve your own joint and prevent or significantly delay osteoarthritis. What activity is possible after healing depends on the condition of the cartilage, and we will discuss this with you personally.
+When is sex possible again?
Generally after about 6 weeks, when you feel comfortable. The hip should not bend beyond 90° as long as active flexion has not yet been cleared.
+Can I give birth after PAO?
Yes. The posterior pelvic column and birth canal remain unchanged, so vaginal delivery remains possible.
+Can both hips be operated on?
Yes, usually one after the other. We operate on the second side a few months after the first.
+How high is the risk of complications?
In large centres, serious complications now occur in about 1% of cases. Higher rates are likely in hospitals that perform few PAOs. Injury to the sciatic nerve (N. ischiadicus) or the femoral nerve (N. femoralis) is reported in about 2% in the literature, and in 0.4% in Greifswald. If a complication does occur, many patients still achieve a good result – it just takes a little longer.
+What if the outer thigh feels numb or burns?
Numbness on the outer thigh is common and usually resolves on its own. It is caused by irritation of the skin nerve on the side of the thigh (N. cutaneus femoris lateralis). Persistent burning or painful abnormal sensations are rare, but must be treated quickly. In that case, please contact us immediately.
+Do the screws have to be removed?
No, not necessarily. If they bother you, they can be removed in a small procedure once the bone has healed.
+How long does the result last?
With well-preserved cartilage, PAO can preserve your own joint for many years to decades. There is no guarantee. The earlier the operation, the better the outlook. With advanced cartilage damage, a hip replacement is often the better choice. We will discuss this honestly with you before surgery.
+Is a hip replacement still possible later?
Yes, without problems. PAO does not block the way to a hip replacement. Hip replacements after PAO achieve results just as good as without previous surgery. The corrected socket position can even make implantation easier, because there is more bone over the femoral head. If the screws are in the way, we remove them during the same operation. The anterior approach also remains possible.