Congenital and Developmental Abnormalities of the hip and Pelvis

Preoperative Traction

The role of preliminary traction in reducing the incidence of osteonecrosis and in improving reduction is controversial. Disagreement exists about whether skin or skeletal traction should be used, whether home or in-hospital traction is preferable, the amount of weight that should be used, the most beneficial direction of pull, and the duration of traction. Although controversial, some suggest that if traction decreases the risk of osteonecrosis even slightly it may be considered. However, a large retrospective study of over 300 children younger than 3 years of age failed to demonstrate any benefit of preoperative traction in improving the rate of successful closed reduction or in decreasing the rate of osteonecrosis. Although skin traction could be an option for some centers, skeletal traction is not indicated, and primary femoral shortening is now routinely used in older children. The objectives of traction or primary femoral shortening are to bring the laterally and proximally displaced femoral head down to and below the level of the true acetabulum to allow a gentler reduction with less risk of osteonecrosis.

Adductor Tenotomy

A percutaneous adductor tenotomy under sterile conditions can be performed for a mild adduction contracture. For a more severe adduction contracture or one of long duration, an open adductor tenotomy through a small transverse incision is preferable (see Technique 33.1).

Arthrography and Closed Reduction

Arthrography and gentle closed reduction are accomplished with the child under general anesthesia.

The interposition of soft tissue in the acetabulum may be suggested by lateralization of the femoral head. Because the radiograph of the hip in an infant or young child cannot yield all the information desired in diagnosing or treating DDH, arthrography is helpful in determining (1) whether mild dysplasia is present, (2) whether the femoral head is subluxated or dislocated, (3) whether manipulative reduction has been or can be successful, (4) to what extent any soft-tissue structures within the acetabulum may interfere with complete reduction of the dislocation, (5) the condition and position of the acetabular labrum (the limbus), and (6) whether the acetabulum and femoral head are developing normally during treatment. Because arthrograms are not always easy to interpret, the surgeon must be thoroughly familiar with the normal and abnormal signs they may reveal and with the technique of making arthrograms ( Video 30.1 ).

An arthrogram of the hip is beneficial in all children, regardless of age, who are given a general anesthetic for closed reduction, unless closed reduction is obviously impossible. It is most helpful to determine when manipulative reduction is unstable or when the femoral head is not concentrically seated within the acetabulum. The most important factor that determines outcome of closed treatment of developmental hip dislocation is the quality of the initial reduction. Proposed criteria for accepting a reduction are a medial dye pool of 5 mm or less and maintenance of reduction in an acceptable “safe zone.”

The use of image intensification in arthrography makes insertion of the needle much easier. The danger of damaging the articular surfaces and the possibility of injecting the contrast medium into areas other than the hip joint are decreased. This improves the safety of the procedure and decreases the likelihood of improper injection of the contrast material into an area that will obscure the surgeon’s view.

The findings of the clinical examination and of arthrography at the time of attempted closed reduction determine if the hip will be stable or may require open reduction. A clinical finding that usually indicates an acceptable closed reduction is the sensation of a “clunk” as the femoral head reduces in the true acetabulum. The “safe zone” concept of Ramsey, Lasser, and MacEwen can be used in determining the zone of abduction and adduction in which the femoral head remains reduced in the acetabulum. A wide safe zone (minimum of 20 degrees, preferably 45 degrees) ( Fig. 30.9 ) is desirable, and a narrow safe zone implies an unstable or unacceptable closed reduction. Forceful abduction to maintain a closed reduction is to be avoided, to decrease the likelihood of osteonecrosis. Osteonecrosis after closed reduction has been reported to be as high as 25% in some studies. A careful clinical evaluation of the reduction should be made before and after adductor tenotomy and before the arthrogram because, when the hip capsule is distended with dye, clinical examination becomes more difficult. An increase in the knee flexion angle (popliteal angle) is another indicator of a successful closed reduction.

Arthrography of the hip in Ddh

Application of a Hip Spica Cast

After confirmation of a stable reduction, a hip spica cast is applied with the hip joint in 95 degrees of flexion and 40 to 45 degrees of abduction. Salter advocated this “human position” as best for maintaining hip stability and minimizing the risk of osteonecrosis. Kumar described an easily reproducible and simple technique for applying a hip spica cast. Fiberglass can be used in place of plaster, but the technique is described in its original form. Although this technique is useful, good results can be obtained with modifications of the spica cast as described as long as the surgeon adheres to key principles: (1) the cast should be well-fitted and well-molded, particularly along the greater trochanter; (2) there should be appropriate space for toileting and hygiene to avoid cast soiling; (3) excessive abduction beyond the safe zone should be avoided but with enough hip flexion and abduction to maintain reduction.

Three-Dimensional Imaging After Closed Reduction

CT or MRI is useful in the postoperative period to assess reduction. These studies can be obtained under the same anesthetic as the closed reduction, or they can be delayed 24 to 28 hours to allow time for the child to become more active. A comparison of MRI and CT in the evaluation of reduction of DDH found sensitivity of 100% for both CT and MRI and specificity of 96% for CT and 100% for MRI. CT required less time (3 minutes) than MRI (10 minutes) and was less expensive but exposes the child to ionizing radiation. In contrast to routine radiography, a cast does not alter the image of an axial CT or MRI ( Figs. 30.12 and 30.13 ), but because of the radiation exposure of CT, the number of cuts should be limited. Fast MRI hip sequences have been proposed to allow for acquisition of MRI data without additional anesthesia. Long-term follow-up is recommended after successful closed reduction to monitor for resubluxation and acetabular remodeling. If stable closed reduction is achieved early in life, acceptable acetabular remodeling often results; however, if there is a delay in diagnosis and treatment of a dysplastic hip, the completeness of acetabular remodeling is not ensured, and additional surgical correction of acetabular dysplasia may be required.

Open Reduction

In children in whom efforts to reduce a dislocation without force have failed, open reduction is indicated to correct the interposed soft-tissue structures and to reduce the femoral head concentrically in the acetabulum. This surgical option is indicated by pathology rather than by age because open reduction may be required in children younger than 6 months and closed reduction occasionally can be successful in children 18 months of age. Open reduction can be performed through an anterior or medial approach; the choice depends on the experience of the surgeon and the particular dislocation.

Regardless of the approach chosen, open reduction of the dislocated and dysplastic hip should correct as many of the blocks to reduction as possible, which may include hourglass constricted capsule, iliopsoas tendon, hypertrophied limbus, inverted labrum, hypertrophied and elongated ligamentum teres, transverse acetabular ligament, and excess fibrofatty pulvinar. The surgeon should strive to correct all aspects of the deformity in a single surgical event because revision surgery often is challenging.

The anterior approach requires more anatomic dissection but provides greater versatility because the pathologic condition in the anterior and lateral aspects is easily reached and pelvic osteotomy can be performed through this approach if necessary.

The medial (Ludloff) approach utilizes the interval between the iliopsoas and the pectineus. This approach places the medial circumflex vessels at a higher risk and has been reported to be associated with a higher incidence of osteonecrosis (10% to 20%) in some studies and similar rates of osteonecrosis in others. Although the medial approach allows removal of the impediments to reduction, it does not allow capsulorrhaphy and is, therefore, generally recommended in infants 6 to 18 months old.

Anterior Approach

Medial Approach

Three-dimensional imaging should be considered after successful closed or open reduction. See the section, “Three-Dimensional Imaging After Closed Reduction” for a discussion on the timing, cost, anesthesia, and radiation considerations for the various options.

Concomitant Osteotomy

The use of a concomitant osteotomy of the ilium, acetabulum, or femur at the time of open reduction remains controversial. Innominate osteotomy, acetabuloplasty, proximal femoral varus derotation osteotomy, or femoral shortening osteotomy might increase the stability of open reduction. However, in younger children (<12 months), acetabular remodeling potential could render these procedures unnecessary. Conversely, inadequate remodeling after open reduction may necessitate a return to the operating room at a later date for a bony procedure.

Zadeh et al. used concomitant osteotomy at the time of open reduction to maintain stability of the reduction in which the following test of stability after open reduction was used.

• 1.

  Hip stable in neutral position—no osteotomy

• 2.

  Hip stable in flexion and abduction—innominate osteotomy

• 3.

  Hip stable in internal rotation and abduction—proximal femoral derotational varus osteotomy

• 4.

  “Double-diameter” acetabulum with anterolateral deficiency—Pemberton-type osteotomy

Aside from the need for osteotomy at the time of open reduction to maintain stability, there also are concerns about residual acetabular dysplasia. Better results have been reported in children younger than 30 months of age who were treated with combined open reduction and Salter osteotomy than in those treated with a staged procedure.

Concomitant osteotomy, particularly a femoral shortening osteotomy with or without derotation, should be done at the time of open reduction when necessary to maintain a safe, stable reduction. If open reduction is stable without an osteotomy, a bony procedure for residual deformity should be considered at the time of the open reduction in an older child (>18 months) and used with caution even in younger infants.

Teratologic Dislocations

A teratologic dislocation of the hip is one that occurs at some time before birth, resulting in significant anatomic distortion and resistance to treatment. It often occurs with other conditions, such as arthrogryposis, Larsen syndrome, myelomeningocele, and diastrophic dwarfism.

The anatomic changes in teratologic dislocations are much more advanced than the changes in a typical developmental hip dislocation in a child of the same age. The acetabulum is small, with an oblique or flattened shape; the ligamentum teres is thickened, and the femoral head is of variable size and may be flattened on the medial side ( Fig. 30.16 ). The hip joint is usually stiff and irreducible, and radiographs show superolateral displacement.

Most authors agree that closed reduction is ineffective and that open reduction is necessary, but indications for treatment are unclear. Most agree that unilateral dislocations should be treated more aggressively than bilateral dislocations, and the ambulatory potential of the patient is probably the most important consideration in deciding whether to treat bilateral dislocations. The difficulty of successfully treating teratologic dislocations is reflected in the results of Gruel et al., who found that of the 27 hips in their series, 44% had poor results and 70% had complications. Osteonecrosis occurred in 48% of hips, redislocation occurred in 19%, and subluxation occurred in 22%. Anterior open reduction and femoral shortening produced the best results with the fewest complications, whereas the worst results and most complications occurred in the hips treated by closed reduction.

Although multiple procedures may be required, good results can be obtained and a stable hip can be achieved in properly selected patients. Open reduction through a medial approach has been recommended for children 3 to 6 months old combined with surgical correction of congenital contractures of the knee and foot. In older children, primary femoral shortening and anterior open reduction, with or without pelvic osteotomy, is preferred.

Osteonecrosis

The most serious complication associated with treatment of DDH in early infancy is the development of osteonecrosis. Estimated rates of osteonecrosis vary widely, ranging from less than 5% to almost 50%. Proposed risk factors for osteonecrosis include open reduction with concomitant osteotomies, redislocation after surgical correction, or the need for secondary procedure after initial closed or open reduction. Although the rate of osteonecrosis after closed reduction is lower than after open reduction, the rate is still as high as 10% to 35% after closed treatment. Some authors have suggested that osteonecrosis is more frequent when reduction is done before the appearance of the ossific nucleus of the femoral head, whereas others have stated that waiting until the ossific nucleus appears does not seem to affect the development of osteonecrosis. Most recently, meta-analyses have indicated that the presence of the ossific nucleus provides little protective benefit against osteonecrosis after closed or open reduction, and Luhmann et al. found that delaying reduction of a dislocated hip until the appearance of the ossific nucleus more than doubled the need for future surgery. Despite a slight increase in the rate of osteonecrosis after reduction of hips without an ossific nucleus, they advocated early reduction to optimize development of the hip with the minimal number of operations.

Potential sequelae of osteonecrosis include femoral head deformity, acetabular dysplasia, lateral subluxation of the femoral head, relative overgrowth of the greater trochanter, and limb-length inequalities; osteoarthritis is a common late complication. Bucholz and Ogden and Kalamchi and MacEwen proposed classification systems based on morphologic changes in the capital femoral epiphysis, the physis, and the proximal femoral metaphysis ( Fig. 30.17 ). These classifications are useful in determining proper treatment and prognosis for a particular patient; however, the proper classification may not be identifiable on radiographs until the child is 4 to 6 years old. The prognostic ability of the Bucholz and Ogden classification system has been brought into question by an interrater reliability study; the authors concluded that a new classification scheme is needed. A simplification of the Kalamchi and MacEwen classification scheme has been proposed that combines groups II, III, and IV into a single group B. By classifying osteonecrosis cases into group A or group B, the authors were able to demonstrate that the type of reduction (closed with traction versus open without femoral shortening) was a factor in the development of osteonecrosis.

Treatment should be directed toward the clinical problems associated with each radiographic classification group. Many patients do not require any treatment during adolescence and young adulthood. In a few, femoral head deformity and acetabular dysplasia that predisposes the hip joint to incongruity and persistent subluxation can be treated with femoral osteotomy or appropriate pelvic osteotomy or both.

Children with osteonecrosis after treatment of developmental dislocation of the hip should be followed to maturity with serial orthoradiographs. Significantly better results have been reported in patients treated early (1 to 3 years after the ischemic insult) with innominate osteotomy than in patients treated later (5 to 10 years after the ischemic insult) and patients without pelvic osteotomy. Patients treated early also had less pain and fewer gait disturbances and required fewer additional procedures for limb-length inequality or greater trochanteric overgrowth. Early innominate osteotomy has been suggested to induce spherical remodeling of the femoral head, with a resultant congruous hip joint, whereas with later osteotomy the femoral head was already deformed, with little potential for remodeling. Significant limb-length inequality can be corrected by appropriate techniques, usually a well-timed epiphysiodesis. Symptomatic overgrowth of the greater trochanter can be treated in older patients with greater trochanteric advancement, which increases the abductor muscle resting length and increases the abductor lever arm ( Fig. 30.18 ).

Trochanteric Advancement