Bernese Periacetabular Osteotomy

Chapter 75

Bernese Periacetabular Osteotomy

Travis H. Matheney and Michael B. Millis

DEFINITION

Hip dysplasia is the most common etiology of coxarthrosis, often leading to arthroplasty long before joint replacement can be considered a lifetime solution.3
Surgical realignment of the congruous dysplastic acetabulum can improve or eliminate symptoms for years, sometimes indefinitely, in a majority of appropriately selected patients, even in those with some degree of preoperative arthro-sis.1,3,4,6–8
Age limits for this procedure are adolescence (closed triradiate cartilage) to an indefinite upper age limit (limited by preoperative arthrosis and other considerations that might make arthroplasty a better choice).

ANATOMY
The acetabulum lies between the anterior and posterior columns of the pelvis.
The most common area of acetabular deficiency in developmental dysplasia of the hip (DDH) is anterior and lateral.
The Bernese periacetabular osteotomy (PAO) differs from the triple osteotomy primarily by maintaining the integrity of the posterior column of the pelvis.
The Bernese PAO uses five steps to divide the acetabular fragment from the remainder of the pelvis, allowing multipla-nar reorientation.
Important bony landmarks include:
- Iliopectineal eminence (which marks the medialmost extent of the acetabulum)
- Infracotyloid groove (just distal to the acetabulum, where the obturator externus tendon lies; this is the site of the anterior ischial osteotomy)
- Anterosuperior iliac spine (ASIS)
- Apex of the greater sciatic notch
- Ischial spine
The posterior column is triangular and thickest just posterior to the acetabulum; it becomes much thinner closer to the sciatic notch. For this reason, the optimal plane for the posterior column is angled obliquely to the medial cortex and perpendicular to the lateral cortex of the ischium–posterior column.

PATHOGENESIS
Genetic and developmental causes exist for “developmental dysplasia.”
Neuromuscular: Charcot-Marie-Tooth disease and spastic diplegia
Posttraumatic: injuries to the triradiate cartilage; aggressive excision of the limbus in the infant hip

NATURAL HISTORY
There is a clear correlation between acetabular dysplasia and osteoarthrosis of the hip.

The more severe the acetabular dysplasia and any subluxation, the earlier the onset of symptoms from arthrosis.
Murphy et al5 found that every patient with a lateral cen-ter–edge angle less than 16 degrees developed osteoarthritis by age 65.

PATIENT HISTORY AND PHYSICAL FINDINGS
Key portions of the history include:
- Personal or family history or treatment of DDH
- History of other hip disorders, including Legg-Calvé-Perthes
- Trauma
- Skeletal dysplasias
- History of cerebral palsy
- Birth order and weight
- Description of pain or mechanical symptoms, including location, duration, activity limitation, giving way, “click-ing,” “catching,” and “popping”
Physical examination should include gait, limb length, assistive devices, and strength.
Specific hip tests include the following:
- Trendelenburg test: Demonstrates weakness in abductors.
- Anterior apprehension test: A positive result is a subjective noting of “apprehension” or instability by the patient.
- Anterior impingement test (pain with passive hip flexion, adduction, and internal rotation): Test of anterior labral pathology, not just a tear.
- Bicycle test for abductor fatigability.
- Range of motion (ROM): Dysplastic hips may demonstrate a relative increase in flexion due to anterior acetabular uncoverage. Decreased ROM with pain may indicate arthrosis.
  
  IMAGING AND OTHER DIAGNOSTIC STUDIES
Radiography includes weight-bearing anteroposterior (AP) views of bilateral hips (FIG 1A), false profile of hips (FIG 1B), and AP views of the hips in maximal abduction and internal rotation (von Rosen view; FIG 1C). These studies allow assessment of lateral and anterior coverage of the femoral head as well as congruency of the hip joint. Additionally noted will be presence of hinge abduction, which is a relative contraindication to PAO.
Radiographic parameters include the following:
- Lateral center–edge angle of Wiberg measured from AP view of the hip (lower limits of normal about 25 degrees; see Fig 1A)
- Anterior center–edge angle of Lequesne and de Seze (lower limits of normal 20 degrees measured on the false profile view; see Fig 1B)
- Tönnis acetabular roof angle measured on the AP view of the hip (upper limits of normal 10 to 15 degrees; FIG 1D)

1559

A B C

FIG 1 • A. AP view of pelvis and hips. Lateral center–edge angle of Wiberg is marked on right hip. B. False profile view of right hip. Anterior center–edge angle of Lequesne and de Seze is marked. The anterior edge is marked to the edge of the sourcil. C. Von Rosen AP view of pelvis with hips in maximal abduction and internal rotation. This is used to assess congruency and mimic the appearance of the hip after reorienting acetabular osteotomy. D. AP view of

D pelvis and hips. The Tönnis acetabular roof angle is marked on the right hip.

Crossover sign (anterior wall shadow crossing posterior wall shadow on AP view of the pelvis)
Assessment of the line of Shenton for breaks indicative of femoral head subluxation
Computed tomography (CT) scan of both hips with three-dimensional reconstruction as well as with axial slices through the femoral condyles may be of assistance in preoperatively assessing the amount and direction of correction required as well as the potential need for proximal femoral osteotomy.
Magnetic resonance imaging (MRI) of involved hips with radial sequences centered at the femoral head allows assessment of articular and labral cartilage.
- Delayed gadolinium-enhanced MRI of cartilage (dGEMRIC) is a recently developed technique that assesses the mechanical damage to the articular cartilage. It has been demonstrated to be a better preoperative predictor than plain radiographs in determining outcome after PAO.2
  
  NONOPERATIVE MANAGEMENT
Activity and job modification may be of benefit in delaying or mitigating arthritic symptoms.
Physical therapy may be of some benefit in increasing ROM and strength. To date, there are no data to suggest that a specific therapy regimen can affect the onset of arthritis in the dysplastic hip.

SURGICAL MANAGEMENT
Indication: Symptomatic, congruous acetabular dysplasia (closed triradiate cartilage) with lateral and anterior center–edge angles 18 degrees or less
Contraindications: Tönnis osteoarthrosis grade 2 or more (subchondral cysts, significant joint space narrowing); severe limitation of motion secondary to arthrosis; active joint infection

Preoperative Planning
Radiographs and MRI are evaluated to assess the following:
- Degree and character of dysplasia
- Amount and direction of correction required to normalize the Tönnis acetabular roof angle (0 to 10 degrees), correct subluxation, and improve mechanical stability
Proximal femoral deformity may also require treatment at time of PAO.
Presence of acetabular articular or labral lesions (seen on MRI) should also be taken into consideration, as treatment either arthroscopically (before the osteotomy) or intraopera-tively through limited arthrotomy may be required for best long-term results.
- Isolated treatment of a labral lesion in the presence of acetabular dysplasia is contraindicated. Simultaneous acetabular realignment must be considered.
- The torn acetabular labrum is usually associated with other structural abnormality within the hip (femoral acetabular impingement or DDH), which may also require correction for best results.9
Partial weight-bearing technique is taught preoperatively in preparation for postoperative mobilization.

Positioning
The patient is positioned supine on a radiolucent table.
The operative extremity is prepared and draped free up to the costal margin; the surgeon should be certain to prepare and drape posteriorly to at least the posterior third of the ilium and medially to the umbilicus.
- Analgesia: We typically use an epidural for perioperative pain management; it is removed by postoperative day 3. However, this is not mandatory.
  
  Approach
- The standard longitudinal anterior Smith-Petersen incision and approach to the hip provides the appropriate access (FIG 2A).
- As an alternative, an ilioinguinal (bikini) incision may be A
  
  used followed by a similar deep approach (FIG 2B). This incision typically provides a better cosmetic result but can limit access for the anterior ischial osteotomy. Therefore, we recommend the standard anterior incision for larger and more muscular patients.
  
  FIG 2 • A. Hip with traditional Smith-Petersen incision marked.
  
  B. Hip with bikini-type incision marked. B
  
  SUPERFICIAL DISSECTION
- The skin is incised into subcutaneous tissue.
- The fascia over the external oblique and gluteus medius is identified and incised posterior to the ASIS and the plane between the two muscles is developed to expose the periosteum over the iliac crest.
- The periosteum is sharply divided over the iliac crest and subperiosteal dissection carried out over the inner table of the ilium. This space is packed with sponges for hemostasis.
- Entry into the tensor fascia lata–sartorius interval is initially accomplished via the compartment of the proximal tensor fascia lata to avoid injury to the lateral femoral
  
  cutaneous nerve. The tensor fascia lata is bluntly elevated off the intermuscular septum and the compartment floor is identified proximally until the anterior ilium is palpated.
  
  TECHNIQUES
Once hemostasis is attained, the ASIS is predrilled with a 2.5-mm drill and the anterior 1 × 1 × 1-cm portion is os-teotomized to facilitate the medial dissection and later repair.
- Alternatively, the sartorius can be taken off with just a thin wafer of bone that will be sewn back in place at the end instead of with a screw.
Subperiosteal dissection is continued to the anteroinfe-rior iliac spine (AIIS).

DEEP DISSECTION
- Flexion and adduction of the hip facilitates the deep in-trapelvic and superior ramus dissection.
- The reflected head of the rectus femoris is divided at its junction with the direct head (TECH FIG 1A,B).
- The direct head and underlying capsular iliacus are ele-
  
  vated as a unit and reflected distally and medially off the underlying joint capsule.
The iliacus, sartorius, and abdominal contents are reflected medially.
The psoas sheath is opened longitudinally, and the

Iliopsoas and sartorius (retracted)

Rectus femoris (cut)

Ilioinguinal vs. iliofemoral incision

Iliac crest

A

Gluteus medius

Acetabular capsule

Gluteus minimus

B

TECH FIG 1 • A. Deep dissection through anterior hip interval. The direct and indirect heads of the rectus femoris have been cut. B. Surgical exposure of the anterior hip capsule (arrow). The iliac crest is marked in the left half of the wound before subperiosteal dissection of the iliacus. (continued)

TECHNIQUES

TECH FIG 1 • (continued) C,D. Intraoperative fluoroscopic AP views of the right hip. Lane bone lever is used to first palpate the outer and inner

C D aspects of the anterior ischium.

psoas tendon is retracted medially to allow access to the superior pubic ramus medial to the iliopectineal eminence.
- The interval between the medial joint capsule and the iliopsoas tendon is created and sequentially dilated
  
  using the tip of a long-handled Mayo scissor, then further by Lane bone levers, with the tips of each pal-pating the anterior ischium at the infracotyloid groove.
  - Proper placement of the scissor and bone levers can be confirmed with the image intensifier (TECH FIG 1C,D).
    
    OSTEOTOMIES
    
    Anterior Ischial Osteotomy
    - With the hip flexed 45 degrees and slightly adducted, a 30-degree forked, angled bone chisel (Synthes, USA; in 15- or 20-mm blade widths) is carefully inserted through the previously created interval between the medial capsule and psoas tendon to place its tip in contact with the superior portion of the infracotyloid groove of the anterior ischium, just superior to the obturator externus tendon (TECH FIG 2A–C).
    - Staying proximal to the obturator externus tendon helps to protect the nearby medial femoral circumflex artery.
  The medial and lateral aspects of the ischium should be gently palpated with the chisel. Proper chisel placement (about 1 cm below the inferior acetabular lip) is confirmed on AP and oblique projections with the image intensifier (TECH FIG 2D).
The osteotome is impacted in a posterior direction to a depth of 15 to 20 mm in a posterior direction and through both medial and lateral cortices of the ischium (TECH FIG 2E).
Care should be taken not to drive the osteotome too deeply through the lateral cortex, as the sciatic nerve is nearby.

Iliopsoas

B

Acetabular capsule

A C

TECH FIG 2 • A. Surgical exposure and placement of osteotome for ischial cut. The osteotome is placed medial to the joint capsule and lateral to the iliopsoas. B,C. Bone models demonstrating the planned position of the osteotome for the ischial cut: Ganz angled chisel (B) and Mast curved chisel (C). (continued)

TECHNIQUES

TECH FIG 2 • (continued) D,E. Intraoperative fluoroscopic AP view of right hip with Ganz 30-degree osteotome (D) at the anterior ischium and false profile view of right hip with Mast curved chisel (E) seated into anterior ischium. The sciatic notch and ischial spine are outlined in black. Proper direction of this cut should also be con-

D E firmed on fluoroscopic false profile view.

Superior Pubic Ramus Osteotomy
- The hip is kept flexed and adducted to relax the anterior soft tissues.
- The psoas tendon and medial structures are gently retracted medially (TECH FIG 3A).
- After circumferential subperiosteal dissection of the ramus, either a spiked Hohmann retractor or a large-gauge Kirschner wire is impacted into the superior aspect of the ramus at least 1 cm medial to the iliopectineal eminence (TECH FIG 3B).
- Blunt Hohmann retractors, Rang retractors, or Lane bone levers are placed anteriorly and posteriorly as well as inferior to the ramus to protect the obturator nerve and artery.
- The osteotomy is perpendicular to the long axis of the ramus when viewed from above but oblique from distal-medial to proximal-lateral when viewed from the front
  
  and may be carried out either by passing a Gigli saw around the ramus and sawing upward away from the retractors or by impacting a straight osteotome just lateral to the spiked Hohmann or Kirschner wire. In the former method, the Gigli saw is passed with the aid of a Satinsky vascular clamp.
  - The key to this osteotomy is to stay medial to the iliopectineal eminence and avoid entering the medial acetabulum (TECH FIG 3C).
Arthrotomy and intracapsular inspection: At a point before all osteotomies are completed, an arthrotomy may be performed to identify and treat intra-articular lesions such as a torn labrum or impingement lesions of the femoral head and neck.
- This is closed loosely with simple, interrupted absorbable suture before proceeding with the remainder of the osteotomies.
  
  Superior liopectinea
  
  B
  
  A
  
  TECH FIG 3 • A. Anterior approach. The superior pubic ramus is exposed and the iliopsoas is retracted medially. B. Bone model demonstrating the superior ramus osteotomy. The Lane bone levers are placed on either side of the ramus and a Kirschner wire is placed as a retractor. The iliopectineal eminence is marked with a circle. C. Intraoperative fluoroscopic false profile view of hip. A small Hohmann retractor is placed under the abductors
  
  aiming toward the apex of the sciatic notch. C
  
  TECHNIQUES
  
  TECH FIG 4 • Bone model demonstrating the saw cut of the ilium aiming toward a point about 1 cm above the iliopectineal line.
  
  Supra-acetabular Iliac Osteotomy
  - A 1.5- to 2-mm subperiosteal window is started beneath the anterior abductors just distal to the ASIS without disturbing the abductor origin.
  - The leg is slightly abducted and extended to allow atrau-matic subperiosteal dissection using a narrow elevator posteriorly toward, but not into, the apex of the greater sciatic notch.
  - A narrow, long, spiked Hohmann retractor is placed in this window. Correct placement is confirmed with image intensifier; in the lateral projection the spike of the Hohmann should point toward the apex of the sciatic notch (TECH FIG 3C).
The iliacus is retracted medially with a reverse Hohmann with its tip on the quadrilateral surface.
Under direct vision the iliac osteotomy is performed with an oscillating saw and cooling irrigation in line with the Hohmann retractor until reaching a point about 1 cm above the iliopectineal line (well anterior to the notch). This end point of the iliac saw cut represents the posterosuperior corner of the PAO. This corner is also the starting point of the posterior column osteotomy, which will be midway between the sciatic notch and posterior acetabulum (TECH FIG 4).
At this point, a single Schanz screw on T-handled chuck is inserted into the acetabular fragment distal and parallel to the iliac saw cut, well above the dome of the acetabulum, into a hole predrilled with a 3.2-mm drill.

Posterior Column Osteotomy
The leg is once again flexed and adducted to relax the medial soft tissues.
A reverse blunt Hohmann retractor is placed medially with the tip on the ischial spine. Dissection into the sciatic notch is neither necessary nor recommended.
The osteotomy is made through the medial cortex with a long, straight 1.5-cm osteotome. It extends from the posterior end of the iliac saw cut, passing over the iliopectineal line, through the medial quadrilateral plate, parallel to the anterior edge of the sciatic notch on iliac oblique fluoroscopy, and is directed toward the ischial spine (TECH FIG 5A).
This osteotomy must extend at least 4 cm below the iliopectineal line to avoid entry into the acetabulum when completing the final (posteroinferior) infra-acetabular osteotomy. This posterior cut is made first through the medial, then second through the lateral wall of the ischium.
- The ischium is wider here than at its anterior extent. If pictured from above, it resembles a triangle with the narrower apex at the anterior edge of the sciatic notch. Therefore, the surgeon should not
  
  B C
  
  TECH FIG 5 • A. Bone model demonstrating the division of the posterior column. B,C. The incorrect (B) and the correct (C) angles of the osteotome for division of the posterior column. The dotted line indicates the relative position of the acetabulum and lateral aspect of the ischium. The proper angle of the osteotome is away from the sciatic notch about
  
  A 10 to 15 degrees. (continued)
  
  D
  
  TECH FIG 5 • (continued) D. Intraoperative fluoroscopic false profile view of the right hip. Division of the posterior column is performed here. The borders of the osteotomy (acetabulum anteriorly and sciatic notch posteriorly) should be clearly visible to avoid intra-articular or intranotch extension of the osteotomy.
  
  place the osteotome perpendicular to the medial quadrilateral plate. Instead, the free medial edge of the osteotome should be tipped 10 to 15 degrees away from the sciatic notch to create a more true coronal-plane osteotomy, perpendicular to the lateral cortex of the posterior column (TECH FIG 5B,C).
  
  TECHNIQUES
Correct angulation and positioning are once again confirmed by the image intensifier (TECH FIG 5D).

Completion Osteotomy
The final osteotomy is a completion osteotomy of the posteroinferomedial corner of quadrilateral plate connecting the anterior and posterior ischial cuts.
A 30-degree long-handled chisel is used to connect these two prior osteotomies (TECH FIG 6).
A key point: the blade is placed to connect the prior cuts and the osteotome face should not be more than 50 degrees off the quadrilateral plate. This will prevent accidentally aiming anteriorly into the acetabulum.

TECH FIG 6 • A. Bone model of right pelvis demonstrating the final cut with a bent osteotome to connect the anterior ischial and posterior column osteotomies. B. Intraoperative fluoroscopic false profile view showing proper positioning of

A B the osteotome.

ACETABULAR DISPLACEMENT
- A 1-inch straight Lambotte chisel is placed into the supra-acetabular iliac saw cut to both confirm completion of the lateral cortex osteotomy and protect the cancellous bone above the acetabulum during displacement.
- The tines of a Weber bone clamp are placed onto the superior ramus portion of the acetabular fragment in such a way as to place its handle anterior and in contact with the Schanz screw (TECH FIG 7A).
- A lamina spreader is placed into the iliac osteotomy between the posterosuperior intact ilium and the Lambotte chisel anteriorly.
- While gently opening the lamina spreader, the Schanz screw and Weber clamp are used to mobilize the acetabular fragment. It is important to ascertain whether the posterior and anterior osteotomies are complete; otherwise, the fragment will not freely rotate and the common outcome will be distal and lateral displacement as you hinge on the lateral, intact cortices. These cuts can
be inspected with a narrow or broad 30-degree chisel (TECH FIG 7B).
Once the fragment is completely free, it may be positioned to obtain the desired correction. As previously noted, the most common deficiency is anterior and lateral. Therefore, the most commonly used maneuvers are to lift the acetabular fragment slightly toward the ceiling, creating an initial displacement, followed by a three-step movement of lateral, distal, and internal rotation.
- When performed properly, the posteroinferior corner of the acetabular fragment should be impacted slightly into the superior intact iliac cut and the prominent superior tip of the acetabular fragment should be roughly in line with the superior intact iliac crest (TECH FIG 7C).

The radiographic “teardrop” and its relation to the femoral head after fragment positioning should be ele-

TECHNIQUES

A B C

TECH FIG 7 • A. Bone model showing placement of Schanz screw (far left) and large bone-holding clamp for manipulation of acetabular fragment. The bone clamp is placed anterior to the Schanz screw. B. Intraoperative fluoroscopic false profile view of right hip. Seen here is displacement of the acetabular fragment with a lamina spreader (top) and use of an angled chisel from medial to lateral to find areas where the osteotomies are not complete. C. Sawbones model showing acetabular fragment placement. The posteroinferior corner of the fragment is impacted into the superior iliac wing and its prominent anterior spike is roughly in line with the intact iliac crest.

vated and tilted laterally commensurate with the amount of lateral correction.

It is commonly necessary to medialize the acetabular fragment a little once the desired anterolateral cover-

age is obtained to recreate the proper position of the femoral head in relation to the medial pelvis. This will maintain proper biomechanical position of the femur in relation to the pelvis.

ACETABULAR FIXATION

Once the desired acetabular position is obtained, 3/32-inch smooth Kirschner wires (the approximate diameter of a 2.5-mm drill) are placed proximal to distal through the ilium and into the fragment in a divergent pattern.

At this point we perform a final fragment position check in the AP and false profile views (TECH FIG 8A,B).

Importantly, in the false profile view, we check the anterior femoral head coverage in full extension and

at 100 degrees of flexion (TECH FIG 8C). In the former view, the sourcil should be roughly horizontal, the femoral head should be well covered, and the line of Shenton should be intact. The false profile view is to confirm that we have neither overcovered the femoral head nor created impingement from a femoral-sided deformity.

A B C

TECH FIG 8 • A,B. Intraoperative fluoroscopic AP and false profile of the right hip. Preliminary check of fragment position. It is important to obtain at least one view including the sacrococcygeal joint over and about 2 cm above the pubic symphysis. This aids in confirming proper final positioning of the acetabular fragment. C. Intraoperative fluoroscopic false profile view of the right hip with the hip maximally flexed. This confirms that the surgeon has not overcovered the femoral head, thus creating femoroacetabular impingement. (continued)

TECH FIG 8 • (continued) D,E. Intraoperative fluoroscopic AP and false profile views of right hip. The sourcil is now horizontal with adequate-appearing femoral head coverage in both views. The femoral head is medial-ized appropriately.

ilium if required for stability (especially in patients who are ligamentously lax or have a neuromuscular condition or poor bone quality). We prefer not to use this screw unless necessary, as it is our practice to remove these screws once bony healing is confirmed for screw head irritation or in case MRI is to be performed at a later point.

TECHNIQUES

WOUND CLOSURE

copiously.

iliac crest. This is accomplished by predrilling holes in the

iliac crest to facilitate passage of heavy, absorbable su-

tures to reattach the abductor, iliacus, and external

by using a 3.5-mm, partially threaded cancellous screw

oblique musculature.

and washer or by being sewn back with heavy, ab-

sorbable suture through thinner wafer.

If there is less than 90 degrees of flexion on palpation or radiograph, it may be necessary to either reposition the fragment or address femoral-sided deformity.

The Kirschner wires are measured for depth and length and then replaced with either 3.5-mm or 4.5-mm cortical screws.
The image intensifier is used to confirm extra-articular placement of all screws (TECH FIG 8D,E).
An additional “home run” screw may be placed anterior to posterior from the AIIS posteriorly into the inferior

The anterior iliac prominence of the acetabular fragment is trimmed and used for bone graft.
Gelfoam is placed along osteotomy sites to assist with hemostasis.

All sponges are removed and wounds are irrigated

Careful attention is paid to proper, tight closure over the

Suction drains are placed under the iliacus.

The ASIS osteotomy (if performed) is reattached either

The remainder of the wound is closed in layers.

PEARLS AND PITFALLS

Patient selection

Pubic osteotomy Ischial osteotomy

Iliac osteotomy

Incomplete osteotomies

Schanz screw placement

Appropriate patient selection is paramount.
Risk factors for failure include older age, poor congruency, decreased joint space (less than 2 mm), and advanced arthrosis.
Presence of a labral tear preoperatively may also be an indicator of degeneration, more than may be apparent on plain radiographs.
The hip should be flexed 40 to 50 degrees for making the pubis osteotomy, which takes tension off the iliopsoas and improves access to the brim of the pelvis.
If the medial joint is entered while attempting to gain access for the ischial cut, the surgeon can open the psoas sheath and try a second approach dissecting through the floor of the sheath. This technique can be helpful in re-establishing an extra-articular dissection to the ischium.
Straying too medial risks injury to the neurovascular bundle.
In general, given true supine positioning of the pelvis and patient, the iliac wing osteotomy will be roughly directed perpendicular to the floor. This sighting technique gives a second visual reference, which, in combination with intraoperative imaging, will aid in proper positioning of the osteotomy.
Connecting the inferior ischial (infracotyloid) osteotomy and the posterior ischial cuts may require a medial-to-lateral osteotome cut through their medial junction. This is most commonly necessary when the lateral portion of these osteotomies is incomplete and the finding is an inability to freely move the acetabular fragment at the initial completion of all planned osteotomies.
The Schanz pin (screw) should be placed nearly in line with and 1 to 1.5 cm below the iliac wing osteotomy. In poorer-quality bone, it may be necessary to place the screw closer to the acetabular subchondral bone. Additionally, the acetabular fragment should be mobilized by using both the Schanz pin and the bone clamp holding the pubic portion of the free fragment.

POSTOPERATIVE CARE

Sitting is permitted on postoperative day 2.
Partial weight bearing is reviewed by a physical therapist once the epidural catheter is removed on postoperative day 2 or 3.
Weight bearing is progressed from partial to full, typically by 6 to 8 weeks with radiographic healing and return of abductor strength.
Range of motion is limited to 90 degrees of flexion, 10 degrees from full extension, and 10 degrees of adduction, abduction, and rotation for the first 6 weeks.
Resistive exercises are avoided for 3 months.
Patients older than 16 years are given either low-molecular-weight heparin or warfarin for 4 to 6 weeks.
Nonsteroidal anti-inflammatories are avoided.

OUTCOMES
Outcomes are generally good to excellent in the appropriately selected patient.
Hips with minimal arthrosis (more than 2 mm of joint space and no significant subchondral changes) in younger (less than 35 years old) patients have demonstrated significant improvement in Harris hip and Merle D’Aubigne scores that can last at least 20 years.1,3,4,6–8
Hips with moderate to advanced arthrosis in older patients can still show significant improvement in symptoms. However, their symptom relief may be shorter-lived, requiring conversion to either a surface replacement or total hip arthroplasty.

COMPLICATIONS
Sciatic or lateral femoral cutaneous nerve palsy
Postoperative wound hematoma requiring return to operating room
Wound infection
Nonunion of pubic ramus
Heterotopic ossification
Vascular injury
Intra-articular osteotomy
Malalignment of fragment leading to insufficient correction or overcorrection

REFERENCES

Clohisy JC, Barrett SE, Gordon JE, et al. Periacetabular osteotomy for the treatment of severe acetabular dysplasia. J Bone Joint Surg Am 2005;87A:254–259.
Cunnigham T, Jessel R, Zurakowski D, et al. Delayed gadolinium-enhanced magnetic resonance imaging of cartilage to predict early failure of Bernese periacetabular osteotomy for hip dysplasia. J Bone Joint Surg Am 2006;88A:1540–1549.
Ganz R, Leunig M, Leunig-Ganz K, et al. The etiology of osteoarthritis of the hip: an integrated mechanical concept. Clin Orthop Relat Res 2008;466:264–272.
Millis MB, Kim YJ. Rationale of osteotomy and related procedures for hip preservation: a review. Clin Orthop Relat Res 2002;405:108–121.
Murphy SB, Ganz R, Muller M. The prognosis in untreated dysplasia of the hip. J Bone Joint Surg Am 1995;77A:985–989.
Peters CL, Erickson JA, Hines JL. Early results of the Bernese periacetabular osteotomy: the learning curve at an academic medical center. J Bone Joint Surg Am 2006;88A:1920–1926.
Steppacher SD, Tannast M, Ganz R, et al. Mean 20-year followup of Bernese periacetabular osteotomy. Clin Orthop Relat Res 2008;466: 1633–1644.
Trousdale RT, Ekkernkamp A, Ganz R. Periacetabular and in-tertrochanteric osteotomy for the treatment of osteoarthrosis in dysplastic hips. J Bone Joint Surg Am 1995;77A:74–85.
Wenger DE, Kendell KR, Miner MR, et al. Acetabular labral tears rarely occur in the absence of bony abnormalities. Clin Orthop Relat Res 2004;426:145–150.