Vol. 14, Issue 3 May 2014

Case Management: Periacetabular Osteotomy for Hip Dysplasia

Contributing Author: Todd McKinley, MD


Indiana University School of Medicine is accredited by the Accreditation Council for Continuing Medical Education to provide continuing medical education for physicians.


Indiana University School of Medicine designates this enduring material for a maximum of 1.0 AMA PRA Category 1 Credits™. Physicians should claim only the credit commensurate with the extent of their participation in the activity.


In accordance with the Accreditation Council for Continuing Medical Education (ACCME) Standards for Commercial Support, educational programs sponsored by Indiana University School of Medicine (IUSM) must demonstrate balance, independence, objectivity, and scientific rigor. All faculty, authors, editors, and planning committee members participating in an IUSM-sponsored activity are required to disclose any relevant financial interest or other relationship with the manufacturer(s) of any commercial product(s) and/or provider(s) of commercial services that are discussed in an educational activity.


Statements of Disclosure of Relevant Financial Relationships have been obtained from Todd McKinley, MD. Dr. McKinley has disclosed that he has received consulting fees from Bioventus.


After reading this article, the reader should be able to:

  • Discuss the pathophysiology and etiology of developmental dysplasia of the hip (DDH).
  • Summarize the risk factors for and symptoms and diagnosis of DDH.
  • Identify the goal of surgery in adults with DDH.
  • Describe the periacetabular osteotomy (PAO) procedure and its advantages.
  • Assess PAO with respect to complications and short- and long-term outcomes.
  • Date of original release: May 2014 

    Date of expiration: May 2015

    Note: While it offers CME credits, this activity is not intended to provide extensive training or certification in the field. 

    Case Study

    A 35-year-old woman presents with a two-year history of intensifying right hip pain that is deep and diffuse, often extending into the groin, top of the thigh, and the buttocks. She reports that pain is exacerbated with activity and becomes activity-limiting as the day goes on. A recreational runner who has participated in marathons, she can no longer run because of pain. On physical examination, significant tenderness is noted in both hips with provocative maneuvers. Plain radiographs demonstrate bilateral hip dysplasia and early changes consistent with hip osteoarthritis. 

    Overview of Hip Dysplasia

    Developmental dysplasia of the hip (DDH) refers to an underdeveloped or shallow, upwardly sloping acetabulum with decreased coverage of the femoral head, typically the superior and posterior aspects, although significant anterior uncovering may occur. Varying degrees of proximal femur abnormalities may also be present, primarily excessive femoral neck anteversion or incomplete formation of the femoral head. Malpositioning in utero and limited fetal mobility, which subject the developing hip to mechanical forces that direct the femoral head away from the central portion of the acetabulum, have been implicated in the etiology of DDH. A spectrum of disorders may result, ranging from hip instability, joint subluxation, and frank dislocation in infants and young children to dysplasia and secondary osteoarthritis in adolescents and adults. Up to 90 percent of persons younger than 50 years with osteoarthritis of the hip have underlying structural problems,1 and half of these cases are attributable to DDH.2

    Risk factors for DDH include breech presentation, linked to a 40 percent increased risk,3 and family history, with children (particularly daughters) of affected fathers having 12 times the risk of developing the condition themselves.4 Nonetheless, the majority of patients with DDH have no identifiable risk factors.5 Females account for more than 80 percent of cases, the left side is predominantly affected, and the deformity is bilateral in 20 percent of individuals.

    Symptoms and Diagnosis

    When DDH is identified in infancy, most babies can be successfully treated with a Pavlik harness or an alternative abduction device.

    However, the condition generally goes undiagnosed until adolescence or young adulthood, when it becomes symptomatic and increasingly affects lifestyle. The onset of pain is usually slow and progressive, commonly involving the groin, lower back, and/or buttocks and radiating from the back to the front of the hip. Symptoms are often activity-related and may be exacerbated by rising from a seated position, climbing in or out of a car, descending stairs, or rotating the hip and are often associated with an anterior labral tear and adjacent articular cartilage damage. Pain may also begin acutely after a period of heightened activity, such as race-training. Pregnancy and weight gain may cause a dysplastic hip to deteriorate.

    The standing anteroposterior (AP) pelvis radiograph remains the most valuable tool for diagnosing dysplasia, used to assess femoral head coverage by the acetabular cartilage and acetabular version.
    The lateral center edge angle, formed by a vertical line through the center of the femoral head and a line connecting the femoral head center with the lateral edge of the acetabulum, is a surrogate for assessing superior coverage. This angle is considered normal when it measures more than 25 degrees, borderline between 20 and
    25 degrees, and dysplastic below 20 degrees (Figures 1a and 1b). The acetabular index measures the slope of the sourcil (acetabular dome) to a horizontal line. In a normal hip, the sourcil is nearly horizontal, the acetabulum faces downward, and the acetabular index does not exceed 8 degrees (Figures 1a and 1b). The extrusion index is a two-dimensional measurement calculated using a vertical line drawn from the femoral head through the lateral-most aspect of the acetabulum. Normally, no more than 10 to 15 percent of the femoral head should extrude to this line (Figures 1c and 1d). Finally, the posterior wall, which is also visualized on the AP X-ray, should cover at least half of the femoral head (Figures 1c and 1d).

    Figure 1. AP pelvis X-rays of normal and dysplastic hips Figure 1a. Normal hip with a lateral center edge angle of 37 degrees and an acetabular index of 1 degree.
    Figure 1b. Dysplastic hip with decreased coverage of the superior femoral head (lateral center edge angle of 17 degrees) by an upsloping acetabulum (acetabular index of 24 degrees).

    Case Study (cont.)

    The patient does extremely well after surgery, reaching all postoperative milestones ahead of schedule, and her hip is completely pain-free eight months after the procedure. Three years after the first operation, she undergoes PAO on her left hip because of steadily increasing pain and experiences similarly excellent results. 

    Surgical Treatment

    “The goal of surgery in symptomatic adult patients with acetabular structural changes consistent with hip dysplasia is restoration of hip anatomy as close to normal as possible to reduce pain, improve function, and prevent or delay the development of osteoarthritis,” explains Todd McKinley, MD, staff surgeon with IU Health Physicians Orthopedics & Sports Medicine and professor of orthopedic surgery at Indiana University School of Medicine. “The limited longevity of prosthetic joint replacement in younger patients and the relatively high incidence of bilateral DDH have led orthopedic surgeons to preferentially perform joint-preserving osteotomies to achieve femoral head coverage and improve joint congruity.”

    A number of reconstructive pelvic osteotomies for adults with DDH and non-arthritic hips have been described. The Bernese periacetabular osteotomy (PAO), developed by Reinhold Ganz and colleagues in 1983,6 has become the preferred technique in many centers in North America and Europe because of its balance between low complications and, in experienced hands, the ability to provide optimal correction.

    Periacetabular Osteotomy

    “PAO is a technically complex operation with the potential to considerably improve the natural history of the dysplastic hip,” says Dr. McKinley. “Surgery involves making a series of hexagonal cuts around the acetabulum (Figure 2) to reorient it so that it more completely covers the femoral head (Figure 3). The procedure does not deepen the socket but rotates it to increase the load-bearing surface area while maintaining or improving joint stability. The goal is to increase socket coverage on the superior and posterior aspects of the femoral head.”

    Compared with other acetabular reorientation osteotomies, the Bernese PAO has several advantages. First, surgery is performed through a single incision, and all cuts are made from the inner aspect of the pelvis, which preserves the abductors. Second,

    the osteotomy leaves the posterior column of the pelvis intact, retaining pelvic stability and allowing early patient mobility.
    Third, because of the proximity of the osteotomy to the joint, the dimensions of the pelvic ring and outlet are unchanged, making subsequent vaginal childbirth safe. Lastly, proximity to the joint allows for significant surgical correction of the bony mechanics in multiple planes—medially, laterally and anteriorly, as needed.

    “PAO is performed under general anesthesia and is often combined with epidural anesthesia,” describes Dr. McKinley. “A benefit of epidural anesthesia is that the catheter can be left in place to provide postoperative pain relief. Patients may opt to predonate a unit of autologous blood and receive it back the morning after surgery. Occasionally, arthroscopy is performed at the time of PAO to evaluate the articular cartilage and repair or debride the acetabular labrum.” 

    Figure 1c. Normal hip with an extrusion index of 7 percent; the posterior wall covers nearly 75 percent of the femoral head (dashed line).
    Figure 1d. Dysplastic hip with an extrusion index of 31 percent; the posterior wall covers <50 percent of the femoral head (dashed line).

    Case Study (cont.)

    PAO is discussed with the patient, and she elects to undergo the procedure on her right hip. Surgery is performed under combined general and epidural anesthesia. The acetabulum is exposed, and bone cuts through the pelvis are made medial to, below, above, and behind the socket to detach it from the pelvis. The acetabulum is rotated into optimal position and fixed to the pelvis with three screws. An X-ray demonstrates excellent coverage of the femoral head. (Figure 4). The hip joint is opened, and a labral tear is repaired to the rim of the acetabulum. The incision is closed immediately below the skin surface, avoiding the need to remove stitches postoperatively. 

    After surgery, the patient is transferred to the orthopedic floor. Narcotic pain medication is administered through the epidural catheter. Her hospital stay is uneventful, and she is discharged to home on day 3. She is instructed to continue narcotic analgesia for three to four weeks and to use crutches until her follow-up visit. Seven weeks post-PAO, she is evaluated, and weight-bearing is allowed. She chooeses to work with a physical therapist to assist with her rehabilitation. 

    Figure 2. Periacetabular osteotomy PAO is performed through four bone cuts. The first cut is made medial to the acetabulum, after which the ischium is cut below the acetabulum.
    Next, a saw is used to make the roof cut above the joint. Lastly, the roof cut is connected to the ischial cut with another cut made posterior to the joint, thereby freeing the acetabulum from the pelvis.
    Figure 3. Acetabular cuts and repositioning Postoperative three-dimensional CT scan
    demonstrating an acetabulum rotated over the femoral head to optimize hip joint cartilage contact mechanics.

    Complications and Outcomes

    The risks and complications of PAO are generally related to the learning curve.7 In experienced hands, the risks are very low, and major nerve injuries are rare. Lateral femoral cutaneous nerve trauma is common and may result in short-term paresthesias and numbness on the outside of the thigh. Infrequently, painful neuralgia or neuromas in the thigh have been reported. The incidence of vascular complications is low.

    With regard to outcomes, PAO has consistently been shown to provide durable pain relief and functional improvement. Intermediate to long-term follow-up in 139 patients showed 10-year hip joint survival rates of 94 percent in patients younger than 40 years at the time of surgery and 81 percent in those 40 years.8 After 15 years, survival rates for the two groups were 87 percent and 71 percent, respectively.

    “Patients who have no or minimal osteoarthritis at PAO have the best long-term results,” says Dr. McKinley. “For those with significant arthritis at operation, outcomes are less predictable." 

    Figure 4. Perioperative radiograph showing proper positioning of the femoral head. Radiograph shows excellent reorientation of the femoral head resulting in: 1) lateral edge angle of 35 degrees, 2) acetabular index of 5 degrees, 3) extrusion index <10 percent, and 4) posterior wall coverage ~75 percent.

    PAO: One Patient's Perspective

    Individuals described in Advanced Praxis case studies are not identified, but in this instance, Dr. McKinley asked that we contact his patient to get her perspective on PAO. She agreed, and the following is a synopsis of her story, as told to our medical writer.

    Jenifer Secrist is a 41-year-old mother of two young sons who lives in Iowa City, Iowa, where she teaches high school biology. She started having “low back problems” at age 12. A four- sport athlete during high school, she experienced ongoing pain that periodically prevented her from practicing and playing. Over the next several years, she sought care from a number of specialists and received several diagnoses, but the pain persisted. By her mid-thirties, the pain had become so debilitating she had to give up long-distance running and could no longer get down on the ground to play with her children. A physician recommended a series of steroid injections that ultimately provided little relief. However, a hip X-ray obtained before one of the injections prompted an MRI evaluation that showed a labral tear and hip dysplasia. She was referred to Dr. McKinley and diagnosed with bilateral DDH. He recommended a right hip PAO, and although the procedure sounded “daunting,” she agreed because it offered her the best chance to “regain her life.”

    Eight weeks following surgery, Jenifer discarded her crutches and resumed coaching softball. Six months after that, “I felt like I had been given my life back,” she reports. “I could once again play with my children and go running (short-distances).”

    Today, with two PAOs completed, Jenifer coaches her son’s baseball team, plays volleyball, kick-boxes, and regularly does five-mile runs— although she admits that Dr. McKinley would prefer she choose less intense forms of exercise. In addition to teaching, she runs a non-profit organization called One Nation Education and has recently returned from Haiti where, together with her older son, they helped build a house for a hurricane victim. 

    Todd McKinley, MD

    Professor of Orthopedic Surgery Indiana University School of Medicine
    IU Health Physicians Orthopedics & Sports Medicine

    Dr. McKinley received his medical degree from the University of Minnesota Medical School in Minneapolis; completed a residency in orthopedic surgery at the University of California Davis Medical Center in Sacramento, where he also did a research fellowship; and completed a fellowship in orthopedic traumatology at the University of Maryland in Baltimore. His primary area of research involves the pathomechanical etiology of post-traumatic arthritis. Additionally, he has initiated a multidisciplinary investigation of the pathomechanisms and interventions for multiply-injured patients.

    The author of more than 50 peer-reviewed medical journal articles, Dr. McKinley teaches and lectures extensively in the United States and abroad and serves as a consultant reviewer for six specialty journals. He is the recipient of numerous research grants, and a portion of his ongoing research activities is supported by the National Institutes of Health and the Department of the Army.

    Prior to coming to IU School of Medicine, Dr. McKinley was a professor of orthopedic surgery at the University of Iowa Hospitals and Clinics in Iowa City, where he received the outstanding teaching award in 2010. In 1998, Dr. McKinley was a finalist candidate in the NASA mission specialist astronaut selection process. 

    1. Clohisy JC, Dobson MA, Robison JF, et al. Radiographic structural abnormalities associated with premature, natural hip-joint failure. J Bone Joint Surg Am. 2011;93 Suppl 2:3-9.

    2. Sanchez-Sotelo J, Berry DJ, Trousdale RT, Cabanela ME. Surgical treatment of developmental dysplasia of the hip in adults: II. Arthroplasty options. J Am Acad Orthop Surg. 2002;10(5):334-344

    3. Imrie M, Scott V, Stearns P, Bastrom T, Mubarak SJ. Is ultrasound screening for DDH in babies born breech sufficient? J Child Orthop. 2010;4(1):3-8.

    4. Stevenson DA, Mineau G, Kerber RA, Viskochil DH, Schaefer C, Roach JW. Familial predisposition to developmental dysplasia of the hip. J Pediatr Orthop. 2009;29(5):463-466

    5. Patel H, Canadian Task Force on Preventive Health C. Preventive health care, 2001 update: screening and management of developmental dysplasia of the hip in newborns. CMAJ. 2001;164(12):1669-1677.

    6. Ganz R, Klaue K, Vinh TS, Mast JW. A new periacetabular osteotomy for the treatment of hip dysplasias. Technique and preliminary results. Clin Orthop Relat Res. 1988(232):26-36

    7. Matheney T, Kim YJ, Zurakowski D, Matero C, Millis M. Intermediate to long-term results following the Bernese periacetabular osteotomy and predictors of clinical outcome. J Bone Joint Surg Am. 2009;91(9):2113-2123.

    8. Ito H, Tanino H, Yamanaka Y, Minami A, Matsuno T. Intermediate to long-term results of periacetabular osteotomy in patients younger and older than forty years of age. J Bone Joint Surg Am. 2011;93(14):1347-1354.