Tim Schrader and J. Anthony Gonzales, Jr.
DEFINITION
The Pemberton8 (FIG 1A–C) and Dega1,2 (FIG 1D–F) osteotomies are performed for acetabular dysplasia that is either part of a developmental disorder or an acquired disorder due to muscle imbalance in neuromuscular conditions.
These are reshaping procedures that alter the shape of the acetabulum and increase its volume.7,12
They are used primarily to increase anterior acetabular coverage but can be altered to provide more lateral coverage.
ANATOMY
The acetabulum develops at the confluence of the growth centers of the ilium, ischium, and pubis.
Normal growth of the acetabulum requires not only that all of these growth centers remain open and function normally but also that the femoral head remains concentrically reduced and stable within the acetabulum.
If the growth centers are damaged, either from pathologic conditions or iatrogenically, or if the femoral head is not stable within the acetabulum, normal growth is unlikely to occur and hip dysplasia develops.
PATHOGENESIS
Because of an abnormality in the growth centers of the acetabulum, abnormal periosteal growth, or abnormal positioning of the femoral head, the acetabulum does not develop properly.
FIG 1 • A–C. Pemberton osteotomy depicted on a bone model viewed from anteriorly (A), from inside the pelvis medially (B), and from outside the pelvis laterally (C). The osteotomy starts at the anteroinferior iliac spine (AIIS) and extends posteriorly following the insertion of the capsule. It then turns caudally and bisects the posterior column to the level of the triradiate cartilage. D–F. Dega osteotomy depicted on bone model viewed from anteriorly (D), from inside the pelvis medially (E), and from outside the pelvis laterally (F). As for the Pemberton, the Dega osteotomy starts at the AIIS and extends posteriorly following the insertion of the capsule. However, it then stops about 1 cm from the sciatic notch on the lateral surface. The medial surface is cut just above the horizontal limb of the triradiate cartilage. The more of the medial surface that is left intact, the more lateral coverage the osteotomy provides.
Even with a concentric reduction of the femoral head, the prior period of abnormal growth may prevent the acetabulum from achieving a normal configuration at maturity. The older the child is at the time of reduction, the more likely an osteotomy will be necessary.
NATURAL HISTORY
Many patients with acetabular dysplasia develop subluxation or dislocation of the femoral head. This can lead to early arthritis in the middle adult years.
The degree of subluxation does not necessarily correlate with the time to onset of symptoms or the degree of arthritic changes.
PATIENT HISTORY AND PHYSICAL FINDINGS
Hip dysplasia can be diagnosed clinically in newborns and young infants owing to instability of the hip.
Patients with a history of hip dysplasia are typically followed radiographically until adulthood to ensure normal acetabular development.
Older children without a prior history of developmental hip dysplasia are typically diagnosed with radiographs based on clinical suspicion, especially when significant risk factors are present.
Risk factors include breech position, female, first-born, and oligohydramnios. Developmental hip dysplasia is associated with other “packaging disorders.”
Patients sometimes present in childhood with a limp, hip pain, limb-length discrepancy, or asymmetric hip abduction, particularly those with underlying neuromuscular conditions.
Routine screening for hip dysplasia in neuromuscular conditions with radiographs is widely performed.
Examinations and tests to perform include:
Ortolani test: Positive if a clunk is felt as a dislocated hip reduces.
Barlow test: Positive if a clunk is felt as a reduced hip dislocates.
Hip abduction: In a normal hip, abduction should be more than 60 degrees and symmetric. This may be the only abnormal sign in infants. A difference of 10 degrees or more is significant.
Galeazzi sign: A difference in thigh length is a positive result. A positive Galeazzi sign can indicate a dislocated hip, a short femur, or a congenital hip deformity.
Abnormal skin folds can occur in normal children but may also indicate asymmetric hip abduction.
Limp with ambulation, Trendelenburg sign, or limp associated with limb-length discrepancy may be the only abnormal sign in older children.
IMAGING AND OTHER DIAGNOSTIC STUDIES
Dynamic hip ultrasound can be used to detect hip dysplasia in very young infants (under 6 months of age).
Plain radiographs, including an anteroposterior (AP) view of the pelvis and false profile views, typically can be used to make the diagnosis in older children.
Radiographic parameters, including the acetabular index, lateral center–edge angle, anterior center–edge angle, the position of the sourcil, and the line of Shenton, should be evaluated (FIG 2).
FIG 2 • A. Preoperative AP pelvic radiograph of a child with bilateral hip dislocations. B. Preoperative AP pelvic radiographs of a child with right hip dysplasia. This child had undergone a closed reduction and adductor tenotomy at 12 months of age. The hip is now located, but acetabular dysplasia persists and did not improve over a year of observation. Changes consistent with avascular necrosis are present in the right femoral epiphysis.
Dislocation is detected by lack of contact between the acetabulum and femoral head.
Subluxation is detected by a break in the line of Shenton.
Acetabular dysplasia can be detected by a decrease in the lateral center–edge angle or an increased acetabular index on the AP pelvic radiograph or a decrease in the anterior center–edge angle on the false profile view.
A pelvic radiograph with the legs abducted and internally rotated can give some idea about the ability of the hip to reduce, with either increased acetabular coverage or a femoral osteotomy.
A CT scan can provide a closer look at anterior and lateral coverage.
DIFFERENTIAL DIAGNOSIS
Slipped capital femoral epiphysis
Legg-Calvé-Perthes disease
Congenital coxa vara
Proximal femoral focal deficiency
NONOPERATIVE MANAGEMENT
Infants are typically treated with full-time braces, such as the Pavlik harness.
Young children can be treated with a closed reduction and cast immobilization.
The initial treatment for primary acetabular dysplasia without hip instability or residual acetabular dysplasia following treatment for instability is observation.
As long as the acetabular index continues to improve and the hip remains concentrically reduced, observation can be continued.
If hip subluxation develops or the acetabular index fails to improve over a 12-month period, operative treatment is indicated.
Neuromuscular patients with a migration index less than 25% can be observed as long as their abduction remains greater than 45 degrees. Patients with migration indexes over 50% generally will benefit from surgical treatment of their dysplasia, which can include a femoral or pelvic osteotomy.
SURGICAL MANAGEMENT
The Pemberton and Dega osteotomies are used to treat acetabular dysplasia with anterior and lateral deficiencies.
They are used when more than 10 degrees of acetabular index correction is needed.
They are also used to augment the reduction during open reduction in a patient with severe acetabular dysplasia.
Mubarak's variation of the Dega osteotomy incorporates a lateral ilium cut that goes all the way to the sciatic notch.
It includes a bicortical cut into the sciatic notch with a rongeur.
The inner wall of the ilium is cut only anteriorly between the anterosuperior and anteroinferior iliac spines (ASIS and AIIS) and posteriorly at the sciatic notch.
Preoperative Planning
Hip and knee contractures should be carefully evaluated preoperatively so they can be addressed during the surgical procedure.
With neuromuscular patients, the femoral head may be deformed. An open capsulotomy to look at the articular cartilage may prove to be beneficial.
If there is significant articular cartilage damage, particularly laterally from the hip capsule, a resection arthroplasty may be indicated as opposed to a reduction.
The primary area of acetabular deficiency needs to be determined to plan the osteotomy.
The triradiate cartilage should be open because the osteotomy hinges on this cartilage. Generally this osteotomy can be performed up to 10 years of age.
Hip mobility must be good, especially abduction and internal rotation.
A concentric reduction of the femoral head in the acetabulum before the osteotomy is an absolute prerequisite. This can be assessed preoperatively with an abduction internal rotation hip radiograph or can be assessed intraoperatively after a capsulotomy or varus proximal femoral osteotomy.
Positioning
Patients are positioned supine on a radiolucent table with a bump under the lumbosacral spine to provide about 30 degrees of elevation of the ipsilateral hip (FIG 3).
A fluoroscopic evaluation should be done at this time to ensure adequate radiographic visualization.
The entire limb is prepared from the lower rib cage to midline.
Approach
A standard anterolateral approach using the interval between the tensor fascia lata and sartorius is used.
FIG 3 • Patient positioning. A bump is placed under the lumbosacral area, and the entire lower extremity is draped free.
TECHNIQUES
INCISION AND SUPERFICIAL EXPOSURE
Two different skin incisions have been described (TECH FIG 1A).
The concave Smith-Peterson incision is curvilinear along the iliac crest and then extends along the anterior thigh; it is expansile and can be used to perform a concomitant femoral osteotomy.
The “bikini” oblique incision is more cosmetically appealing and offers the experienced surgeon adequate exposure. A separate lateral incision is used with the bikini incision in case a femoral osteotomy is planned. To prevent injury to the neurovascular structures below the fascia, care must be taken with the oblique incision medial to the ASIS.
Either skin incision is deepened to expose the iliac crest and the interval between the sartorius and tensor fascia lata.
The deep fascia is incised next on top of the tensor fascia lata muscle to avoid injury to the lateral femoral cutaneous nerve (TECH FIG 1B).
The tensor–sartorius interval is deepened until the rectus femoris is encountered. The interval is then developed proximally up to the ASIS. The direct head of the rectus attached to the AIIS is identified. It can be released and reattached at the end of the osteotomy or left attached.
TECH FIG 1 • A. Skin incisions. There are two alternatives for the skin incision. The more extensile Smith-Petersen concave incision (red line) can be used for a concurrent femoral osteotomy, but it often leaves an unsightly scar. The more limited “bikini” incision (black line) provides plenty of exposure, leaves an appealing scar, and can be combined with a lateral incision for concurrent femoral osteotomies. B. Superficial exposure. The iliac apophysis has been exposed by elevating the overlying abdominal musculature. The tensor–sartorius interval has been opened. The interval is opened over the tensor musculature to protect the lateral femoral cutaneous nerve. The nerve is on top of the pickup.
PEMBERTON OSTEOTOMY
Deep Exposure
The exposure is important in this osteotomy. Before any cuts are made the surgeon should be able to clearly see the inner and outer portions of the iliac wing to the sciatic notch posteriorly and the entire hip capsule anteriorly.
The outer table of the ilium can be exposed either by splitting the iliac apophysis or by dissecting just below the apophysis, in which case the apophysis is then taken off as an entire piece to minimize injury to this growth area.
The outer and inner tables are exposed in a subperiosteal fashion to the sciatic notch.
Chandler retractors are placed into the sciatic notch from medial and lateral to protect the neurovascular bundle (TECH FIG 2).
The reflected head of the rectus is then released and followed posteriorly. It acts as a guide to the border of the hip capsule.
TECH FIG 2 • Deep exposure. The medial and lateral portions of the iliac wing have been exposed by splitting the apophysis. The Chandler retractors are in the sciatic notch. The capsule has been exposed. The direct head of the rectus is tagged with the suture.
Creating the Osteotomy
The first cut is made on the outer table starting 1 to 1.5 cm above the AIIS and extending posteriorly and parallel to the joint capsule.
About 0.5 to 1 cm from the sciatic notch, the osteotome should be turned and directed distally down the ischium to the level of the ischial limb of the triradiate cartilage (TECH FIG 3A).
The last portion of this cut is made in a blind fashion with fluoroscopic guidance, and care must be taken to avoid cutting into the sciatic notch, the hip joint, or the triradiate cartilage.
The osteotome should remain midway between the capsular attachment and the sciatic notch, splitting the posterior column in half to the level of the triradiate cartilage.
The inner cut is started at the same point as the outer cut on the anterior surface, and the cut is generally at the same level as the outer cut running parallel to it (TECH FIG 3B).
Osteotomy Variation
If more lateral coverage is needed, the inner cut is moved more distal and shortened to make a more oblique osteotomy.
This changes the fulcrum of rotation from straight posterior to more posteromedial, giving more lateral coverage as the fragment is levered downward (TECH FIG 4).
Separating the Bone
A special curved osteotome (TECH FIG 5A) is inserted into the osteotomy to connect the two cuts. This osteotome is advanced by hand.
Once the osteotome is at the level of the triradiate cartilage (TECH FIG 5B), the acetabular roof is gently levered down (TECH FIG 5C).
TECH FIG 3 • A. Lateral wall cut. The Chandler retractor is in the sciatic notch and the osteotome is used to cut the lateral cortex. The cut has started between the anterosuperior and anteroinferior iliac spines (ASIS and AIIS) and is extending parallel to the joint. The posterior portion of this osteotomy will be made in a blind fashion. B. Medial wall cut. The Chandler retractor is in the sciatic notch and the osteotome is used to cut the medial cortex. The cut has started at the same location as the lateral wall cut, between the ASIS and the AIIS, and is extending in the same direction as the lateral wall cut.
TECH FIG 4 • Variations in the Pemberton osteotomy. The inner and outer iliac wing cuts determine the amount of coverage based on their direction. A,B. If more anterior coverage is required, then the inner cut is more transverse. C,D. If more lateral coverage is required, then the osteotomy is inclined laterally and both cuts begin a little farther away from the capsule.
TECH FIG 5 • A. Pemberton osteotome. The special curved Pemberton osteotome is necessary to connect the inner and outer wall cuts and make the sharp posterior curve. B. Connecting the cuts. A special curved osteotome is necessary to make the sharp curve of the osteotomy posteriorly. The osteotome is advanced by hand, connecting the inner and outer wall cuts made previously. The osteotome is advanced to the level of the triradiate cartilage. The dotted line represents the anterosuperior iliac spine autograft fragment that can be used to hold the osteotomy open. C. Levering down the osteotomy. The osteotomy is levered downward with the osteotome. A lamina spreader can also be used with caution. In this patient, a femoral shortening osteotomy and open reduction have been performed and sutures are in place allowing for a capsulorrhaphy once Pemberton osteotomy has been completed.
TECH FIG 6 • A. Anterosuperior iliac spine (ASIS) autograft bone wedge. An osteotome is used to harvest the ASIS autograft bone wedge. The height of the wedge is determined by the amount the osteotomy will be levered downward. B. Graft placement. An autograft bone wedge from the ASIS or an allograft wedge can be used. The graft is inserted in an anterior-to-posterior direction and should be stable after it is impacted. Internal fixation is seldom necessary. C. AP postoperative pelvic radiograph of a left Pemberton osteotomy in a spica cast. An open reduction, capsulorrhaphy, and femoral shortening osteotomy have also been performed.
Graft Placement and Closure
Once the roof is in the desired position (usually an opening of 1 to 2 cm anteriorly), bone wedges are placed in the opening to hold the osteotomy open. Allograft or a wedge of the ASIS can be used.5
An autograft wedge of the ASIS can be harvested with a straight cut of the ilium (TECH FIG 6A).
The graft is usually placed from anterior to posterior. A gouge may be used to make a trough in the iliac wing and the acetabular fragment for the graft to rest in (TECH FIG 6B).
Internal fixation is usually not necessary.
The apophysis and muscles are then reattached with suture, and the skin is closed in routine fashion.
A hip spica cast is then applied (TECH FIG 6C).
DEGA OSTEOTOMY
Exposure
As for the Pemberton osteotomy, the outer table of the ilium can be exposed either by splitting the iliac apophysis or by dissecting just below the apophysis, in which case the apophysis is then taken off as an entire piece to minimize injury to this growth area.
The outer table is exposed in a subperiosteal fashion to the sciatic notch. Although it is not necessary to expose the inner table for a Dega osteotomy, it does aid in orientation and adds little to the morbidity of the procedure (TECH FIG 7).
A Chandler retractor is placed into the sciatic notch from the lateral side to protect the neurovascular bundle.
The reflected head of the rectus is then released and followed posteriorly. It acts as a guide to the border of the hip capsule.
TECH FIG 7 • Deep exposure. The iliac apophysis has been slit and the inner and outer walls of the ilium have been exposed by subperiosteal elevation. Sponges have been placed posteriorly along the inner and outer ilium to aid in retraction.
Creating the Osteotomy
A curvilinear osteotomy is performed on the outer wall starting just above the AIIS to a point 1 to 1.5 cm in front of the sciatic notch.
Guidewires can be inserted at the most cephalad portion of the osteotomy, directed toward the inner wall just above the triradiate cartilage. They are placed under radiographic guidance on the obturator oblique view. They serve as a guide for the chisel when the osteotomy is made.
Like exposing the inner table, guidewires are not necessary but aid in orientation and add little to the morbidity of the operative procedure (TECH FIG 8A).
Next, an osteotome is used to cut the ilium medially and inferiorly in line with the guidewire down through the inner wall (TECH FIG 8B). If the inner table has been exposed, this can be confirmed with direct visualization. The posterior third of the inner wall should be left intact to act as a fulcrum for rotation.
The less inner wall that is cut, the more lateral the coverage that will be obtained with rotation (TECH FIG 8C–E).
The thinner the roof fragment, the deeper the coverage and less redirection you have.
The cortex is then levered down with a wide osteotome to provide the desired coverage.
TECH FIG 8 • A. Guidewire placement. Three Kirschner wires have been placed along the outer ilium. They are placed under fluoroscopic guidance on an obturator oblique view. They enter the lateral ilium about 1 cm cephalad to the joint capsule and are directed to exit the medial ilium just above the triradiate cartilage. B. Making the osteotomy cut. An osteotome is inserted along the lateral ilium about 1 cm above the hip capsule and directed medially and inferiorly. In this case, guidewires have been placed and the osteotome is inserted parallel to the wires. The osteotomy starts between the anterosuperior and anteroinferior iliac spines and extends to within 1 cm of the sciatic notch. C. Variations in the osteotomy cuts. The osteotome is directed inferomedially. The steeper the acetabular slope preoperatively, the higher the osteotomy will need to start laterally. The amount of lateral and anterior coverage is determined by how much of the posterior medial inner wall is left intact. D. If more of the medial wall is left intact, then the fulcrum of rotation will move more anterior and more lateral coverage will be obtained. E. If more of the medial wall is cut, then the fulcrum of rotation will move posteriorly and more lateral coverage will be obtained.
TECH FIG 9 • The Mubarak variation is shown in an anterior and lateral projection. The osteotomy extends anteriorly from the anteroinferior iliac spine posteriorly to the sciatic notch 0.5 to 1.0 cm above the hip capsule. The osteotomy is bicortical only in the area of the iliac spines and the sciatic notch. The sciatic notch cut can be made with a Kerrison rongeur. Osteotomes are then used to cut toward the triradiate cartilage between the hip joint and the medial wall. Once the cut has been extended to the triradiate cartilage, the acetabular fragment is levered downward. If the anterior and posterior cuts are not bicortical, then the fragment may not displace adequately.
Mubarak Variation
Mubarak's osteotomy 6 is a variation of the Dega osteotomy that incorporates a lateral ilium cut that goes all the way to the sciatic notch (TECH FIG 9).
It includes a bicortical cut into the sciatic notch with a rongeur.
The inner wall of the ilium is cut only anteriorly between the ASIS and AIIS and posteriorly at the sciatic notch.
The outer ilium is exposed down to AIIS anteriorly and the sciatic notch posteriorly. The inner wall is exposed only enough to take the upper ilium and ASIS for bone graft.
Two points are identified, one about 0.5 to 1 cm above the acetabulum and one within the sciatic notch. Bicortical cuts are made at each spot.
A Kerrison rongeur can be used to make the posterior cut safely.
A curvilinear cut is made in the outer cortex to connect the two points.
The osteotome is directed down to the triradiate cartilage but does not enter the cartilage. It is used to lever the roof down 1 to 1.5 cm, and once the bone is levered down, bone graft wedges are used to hold it open.
Graft Placement and Closure
Triangular bone wedges are used to hold the osteotomy open (TECH FIG 10A). Allograft wedges can be used. Autograft wedges from the iliac crest or from a concurrent femoral shortening osteotomy can also be used.
The wedges are inserted in a lateral-to-medial direction. It is important to place the largest piece of graft where the most coverage is desired (TECH FIG 10B).
Internal fixation is usually not necessary.
The apophysis and muscles are then reattached with suture and the skin is closed in routine fashion.
A hip spica cast is then applied (TECH FIG 10C,D).
TECH FIG 10 • A. Triangular pieces of autograft or allograft bone can be used as wedges. The size of the wedge depends on the amount the osteotomy is mobilized and the remaining gap left. B. Autograft bone wedges from the anterosuperior iliac spine or allograft can be used. The grafts are inserted in a lateral-to-medial direction. The largest wedge is inserted in the area where the largest amount of coverage is desired. The grafts should be stable after they are impacted. Internal fixation is seldom necessary. C. Postoperative AP pelvic radiograph of a right Dega osteotomy in a spica cast (same child as shown in Fig 2B). Allograft bone has been used. D. An AP pelvic radiograph of the same child 12 months postoperatively. The line of Shenton is now intact, the allograft has incorporated nicely, and the femoral epiphysis remains round.
POSTOPERATIVE CARE
Patients are almost exclusively treated with a hip spica cast for 6 to 12 weeks. If this is a staged procedure, the patient should be left in half of the spica cast while the second procedure is being done.
Radiographs are obtained to make sure graft displacement has not occurred.
Once good radiographic healing has been demonstrated, progressive weight bearing over 4 weeks can be started.
Children are followed until maturity to detect avascular necrosis and ensure adequate acetabular coverage.
Physical therapy is typically not needed to regain mobility after immobilization.
OUTCOMES
The Pemberton osteotomy provides excellent long-term acetabular correction in children, particularly those under age 4.3,8,9,13,14
The osteotomy has also been effective in patients with neuromuscular dysplasia.11
The Dega osteotomy has been successfully used in the treatment of developmental dysplasia of the hip and neuromuscular dysplasia.
Several studies have found excellent results in younger children (under age 6), with results in older children less reliable.4,10
COMPLICATIONS
Stiffness
Subluxation or dislocation
Closure of triradiate cartilage
Chondrolysis
Avascular necrosis of the femoral head
REFERENCES
· Dega W. Osteotomis trans-iliakalna w leczeniu wrodzonej dysplazji biodra. Chir Narzadow Ruchu Ortho Pol 1974;39:601–613.
· Dega W, Krol J, Polakowski L. Surgical treatment of congenital dislocation of the hip in children; a one-stage procedure. J Bone Joint Surg Am 1959;41A:920–934.
· Faciszewski T, Kiefer GN, Coleman SS. Pemberton osteotomy for residual acetabular dysplasia in children who have congenital dislocation of the hip. J Bone Joint Surg Am 1993;75A:643–649.
· Grudziak JS, Ward WT. Dega osteotomy for the treatment of congenital dysplasia of the hip. J Bone Joint Surg Am 2001;83A:845–854.
· Kessler JI, Stevens PM, Smith JT, et al. Use of allografts in Pemberton osteotomies. J Pediatr Orthop 2001;21:468–473.
· Mubarak SJ, Valencia FG, Wenger DR. One-stage correction of the spastic dislocated hip: use of pericapsular acetabuloplasty to improve coverage. J Bone Joint Surg Am 1992;74A:1347–1357.
· Ozgur AF, Aksoy MC, Kandemir U, et al. Does Dega osteotomy increase acetabular volume in developmental dysplasia of the hip? J Pediatr Orthop B 2006;15:83–86.
· Pemberton PA. Pericapsular osteotomy of the ilium for the treatment of congenital subluxation and dislocation of the hip. J Bone Joint Surg Am 1965;47A:65–86.
· Pemberton PA. Pericapsular osteotomy of the ilium for the treatment of congenitally dislocated hip. Clin Orthop Relat Res 1974;98:41–54.
· Reichel H, Hein W. Dega acetabuloplasty combined with intertrochanteric osteotomies. Clin Orthop Relat Res 1996;323: 234–242.
· Shea KG, Coleman SS, Carroll K, et al. Pemberton pericapsular osteotomy to treat a dysplastic hip in cerebral palsy. J Bone Joint Surg Am 1997;79A:1342–1351.
· Slomczykowski M, Mackenzie WG, Stern G, et al. Acetabular volume. J Pediatr Orthop 1998;18:657–661.
· Vedantam R, Capelli AM, Schoenecker PL. Pemberton osteotomy for the treatment of developmental dysplasia of the hip in older children. J Pediatr Orthop 1998;18:254–258.
· Wada A, Fujii T, Takamura K, et al. Pemberton osteotomy for developmental dysplasia of the hip in older children. J Pediatr Orthop 2003;23:508–513.