Alternatives to Periacetabular Osteotomy (PAO) for Adult Acetabular Dysplasia

1. Alternatives to Periacetabular Osteotomy (PAO) for Adult Acetabular Dysplasia Cara Beth Lee, MD Michael B. Millis, MD Director, Center for Hip Preservation, Department of Orthopedics, Virginia Mason Medical Center, Seattle, Washington Hip and Pelvis Clinic , Chonbuk University Hospital , Jeonju, Korea . E-mail: hugo999@naver.com

2. Introduction • Salter • Instability in the dysplastic hip is caused by inadequate anterior and lateral femoral head coverage • Modification of Salter’s osteotomy technique have led to improvements in correcting the components of the dysplastic hip • In the US, periacetabular osteotomy is currently the most commonly used reorientation procedure for adult acetabular dysplasia

3. Periacetabular osteotomy • PAO is single surgical approach • has ability to obtain a large, multiplanar correction • preserves the acetabular blood supply • maintains posterior column integrity • conserves the true pelvis • With modification of original technique, additional advantage • Rotational acetabular osteotomy • Triple Pelvic Osteotomy • Chiari Pelvic Osteotomy

4. Rotational Acetabular Osteotomy • Using specially curved osteotomies that follow its circumference • Approximately 1.5 cm proximal to the acetabular roof • Wagner’s method uses an extensive anterior iliofemoral approach to expose the pelvis • Type I correction • Acetabular fragment is rotated anteriorly and laterally to improve coverage, and bone graft is placed proximal to the overhanging acetabular bone • Type II • Iliac crest graft is inserted into the osteotomy site, which allows the fragment to be moved distally up to 2 cm to increase leg length • Type III • Require metallization of the acetabular fragment

5. Rotational Acetabular Osteotomy • The RAO is combined with a complete cut of ilium, similar to a Chiari osteotomy • Proximal ilium is shifted laterally while the distal acetabular fragment moves medially • All three variations are stabilized with internal fixation • Joint capsule remains intact

6. Rotational Acetabular OsteotomyAdvantages and Disadvantages • Advantages • Major correction without altering the shape of the true pelvis • Childbirth is unaffected • Disadvantages • Proximity of the osteotomy to the joint • Vascularity to the acetabulum is at risk • Fragment can be difficult to stabilize for early weight bearing • Risk of fracture into the hip joint

7. Rotational Acetabular OsteotomyResult • Good success rate • Schramm et al 20-year follow-up of 22 patients • Kaplan-Meier survivorship : 86% at 20 years, with conversion to total hip arthroplasty as the end point • Nakamura et al • 80% good-to-excellent long-term result in 112 hips with minimal or no arthorosis at the time of surgery • Even advanced OA secondary to acetabular dysplasia, decrease pain at 8- to 12-year follow-ups • A minimum of 2.5mm of joint space is recommended to consider RAO • Risk factors for progressive osteoarthritis • Under correction and persistent lateralization of the femoral head

8. Triple Pelvic Osteotomy • Divide the pelvis form just proximal to the AIIS transversely to the sciatic notch • With the pubic symphysis as a hinge, distal fragment rotated anteriorly and laterally to increase femoral head coverage • Initially developed to treat persistent dislocation and subluxation in children

9. Triple Pelvic Osteotomy Advantages and Disadvantages • Key advantage • Ability to metalize the joint • Achieve an much larger correction than other innominate osteotomies • Patient with persistent subluxation and dislocation • Unlike RAO, PAO, safe for patient with open triradiate cartilage, if performed with extraperiosteal dissection of the superior pubic ramus • Disadvantage • Lacks intrinsic stability because both columns of the pelvis are disrupted • Large gaps at the osteotomy sites can result in nonunion • Alters the morphology of the true pelvis – impede childbirth

10. Triple Pelvic OsteotomyResult • Van Hellemondt et al • 42 of 48 hip (88%) preserved at an average of 15 years after TPO • Merle d’Aubigne and Postel functional scores, 64% of hips were rated good to excellent • 31 of 41 hips (76%) had no osteoarthritis at the time of surgery showed no OA over the 15 year interval • Peters et al • 60 hips with acetabular dysplasia • 49 of 50 patients (98%) were satisfied with the procedure at a mean follow-up of 9 years • 16 of the 60 osteotomies (27%) were considered failures – need to convert to a total hip arthroplasty or the presence of intractable hip pain • When nonunion occurs, patients are less satisfied with the procedures

11. Chiari Pelvic Osteotomy • With advances in reorienting osteotomy, considered a salvage augmentation procedure • Indicated for a dysplastic hip with incongruity or to supplement coverage in an acetabulum with small weight-bearing zone • Anterior iliofemoral approach and involves division of the ilium from just inferior to the AIIS and curving in a semicircle to exit posteriorly through the sciatic notch

12. Chiari Pelvic Osteotomy • Osteotomy is directed approximately 15’ laterally to medially to allow medial displacement of the distal fragment • Lateralized ilium serves as the augmented bony coverage of the femoral head with the capsule interposed • In the initial series, patients were immobilized in an abduction spica cast for 4 weeks • Now accomplished with internal fixation

13. Chiari Pelvic OsteotomyAdvantages and Disadvantages • Abducts the distal fragment which results in a more vertical orientation of the true acetabulum and may be beneficial in unstable hips with anterolateral impingement • Hip joint reaction forces are decreased, mechanical environment of the hip is improved because of the increased weight-bearing area and medialization of the femoral head • achieve adequate coverage of the femoral head by the iliac shelf

14. Chiari Pelvic OsteotomyAdvantages and Disadvantages • Primary disadvantage • femoral head articulates with the capsule and labrum rather than the native articular cartilage • Capsule may undergo metaplasia to form fibrocartilage • Labral pathology is common • Labral tear and detachment • Abductor weakness with a persistent Trendelenburg sign can occur • Alters the true pelvis and narrows the birth canal

15. Chiari Pelvic OsteotomyResults • Positive with consistent pain improvement • Windhager et al • 236 hips in 208 patients • 21 of 236 hips (9%) had revision procedures (19 THA, 2 arthrodesis)at a mean 15 years after the osteotomy • Fifty-four percent of the hips had good-to-excellent result based on measures of pain, walking distance, Trendelenburg sign, range of motion • 60% of patients were able to walk unlimited distance • Kotz et al • 38 of 70 native hips(54%) in 66 patients were preserved at a mean follow-up of 32 years • 32 hips were converted to THA, average of 26 years after the Chiari procedure

16. Summary • Pelvic osteotomies are complex, technically demanding procedures • Offer mechanical correction and symptom improvement in properly • Chiari osteotomy is reserved for • dysplastic hips with an incongruent articulation • Acetabular weight-bearing surface is exceedingly small and requires augmentation • Reorientation osteotomies • Congruent dysplasia and minimal arthrosis • PAO • Single surgical approach • Large multiplanar correction among other advantages • RAO, TPO • All of the techniques can achieve major corrections • Good results at long-term follow-up

17. Summary • Disadvantages of a triple pelvic osteotomy • Instability from disruption of both columns of the pelvis • Alters true pelvis and can lead higher nonunion rate • RAO maintains the true pelvis but requires abductor muscle dissection - Prolonged limp or Trendelenburg sign • Acetabular fragment osteonecrosis and intra-articular fracture in sclerotic bone • At Boston Children’s Hospital • Adult patients with symptomatic acetabular dysplasia are managed with PAO • Skeletally immature patients are treated with a triple pelvic osteotomy • RAO has been widely used in Japan with good long-term success • Chiari pelvic osteotomy • rare patient who requires augmentation rather than reorientation of the dysplastic acetabulum

18. Summary