Infant Hip Dysplasia: Closed Reduction



Infant Hip Dysplasia: Closed Reduction





FUNDAMENTALS OF DEVELOPMENTAL DYSPLASIA OF THE HIP: TREATMENT BY CLOSED REDUCTION

Treatment of developmental dysplasia of the hip (DDH) between the ages of 0 and 6 months is typically performed using the Pavlik harness method or an abduction brace. One indication for a closed reduction of the hip is failure of these methods to achieve a concentric and stable reduction. Therefore, closed reduction of the hip has been the mainstay for the treatment of DDH in patients who failed bracing or in those presenting during the first year of life. Although closed reduction can be performed in older patients, the likelihood to obtain and maintain hip reduction by closed means decreases with increasing age. After the child starts to walk, the pathologic anatomy of the hip may not allow for a concentric reduction without surgery. The main pathologic factors and structures obstructing the reduction include the adduction contracture with limited hip abduction, an infolded acetabular labrum, hypertrophy of the acetabular roof cartilage (neolimbus), the hourglass constriction of the capsule by a tight iliopsoas tendon, excessive fibrofatty pulvinar, hypertrophy of the ligamentum teres, a tight anteromedial joint capsule, and increased thickness of the acetabular transverse ligament that restricts the introitus of the acetabulum. With increasing age, these obstacles to a concentric reduction may not allow the femoral head to seat deep in the acetabulum. Furthermore, acetabular remodeling after closed reduction is directly influenced by age, that is, older patients are more likely to grow with persistent acetabular dysplasia. Hence, closed reduction is preferably performed during the first year of life.

Although closed reduction of a dislocated hip may intuitively seem a simple and straightforward procedure, in reality, it requires attention to detail to avoid immediate complications, such as postoperative subluxation, and long-term complications, including osteonecrosis. The following principles should be considered:



  • Closed reduction of a dislocated hip should not be performed as a forceful maneuver.


  • The hip should be positioned in ≥90° flexion and gently abducted following the Ortolani maneuver.


  • The reduction should be easily felt as the femoral head enters the acetabulum.


  • The reduction should be stable. To determine the stability of the reduction, the safe zone or safe arc of motion as described by Ramsey et al1 should be assessed by comparing the maximum range of abduction to the degree of abduction where the hip redislocates. If the safe zone is wide (≥30°), the reduction is considered stable (Figure 2.1).


  • Wide abduction must be avoided because of the risk of osteonecrosis to the femoral head. We recommend immobilizing the hip in 10° to 20° less than the maximum abduction, with maximum abduction of 60°.


  • The morphology of the reduced hip should be assessed to determine the depth and stability of the reduction. The most common method to assess the morphology of the hip is an arthrogram performed at the time of the reduction (Figure 2.2). Alternatively, the hip may be assessed by magnetic resonance imaging (MRI) with or without contrast to evaluate the reduction and, when contrast is used, the perfusion of the femoral head or by ultrasonography. We rarely use computed tomography (CT) scan after closed reduction to assess hip morphology because of the radiation risk and because MRI is better at revealing the anatomy of the structures of interest.


  • A hip arthrogram is beneficial to help determine the relationship of the femoral head and the acetabulum
    before and after closed reduction. Several classification systems have been described to evaluate the hip arthrogram; however, we favor the grading scheme proposed by Tönnis (Figure 2.3). The arthrogram should be interpreted after the hip is reduced as follows:



    • The percentage or coverage of the femoral head by the acetabulum—at least two-thirds of the femoral head should be covered by the acetabulum.


    • The space between the superior labrum and the transverse acetabular ligament (introitus) should be larger than 20 mm. The femoral head should be under the superior labrum, which should not be completely infolded and over the transverse acetabular ligament.


    • The gap between the femoral head and the acetabular floor should be narrow. Although controversial, we recommend that no more than 4 mm of medial dye pooling should be considered for a closed reduction.


  • If gentle closed reduction is stable with a wide safe zone of stability and with adequate coverage of the femoral head on arthrogram, the patient is immobilized in a bilateral spica cast.


  • After the spica cast is applied, additional imaging is recommended to confirm a concentric reduction is maintained in the cast.






FIGURE 2.1. Illustration showing how to calculate the safe zone of reduction according to Ramsey et al.1 The safe zone or safe arc is calculated by assessing the maximum unforced abduction of the hip, represented here by 70°. Then, the hip is brought into adduction, and the degree of abduction with the hip dislocated is recorded; here, it is 20°. The safe zone or safe arc of motion is the range of abduction in which the hip maintains stability. It is, therefore, calculated by the maximum and forced abduction minus the degree of abduction at which the hip dislocates; 70° to 20° results in a wide zone of 50°. However, we take about 10° from each end, resulting in a safe zone between 30° and 60°, which is acceptable for closed reduction. Hips with a narrow zone of safety (<30°) are less likely to be stable after closed reduction. A popular method of increasing the safe zone is to perform an abduction tenotomy. The abductor tenotomy theoretically would increase the maximum and forced abduction and increase the safe zone of Ramsey.






FIGURE 2.2. Hip arthrogram of the pediatric patient for assessment of developmental dysplasia of the hip. A, Intraoperative fluoroscopy image of a previously closed reduced hip in a 7-month-old baby showing normalized parameters of hip arthrogram. In a normal arthrogram, more than two-thirds of the femoral head should be covered by the acetabular cartilage and the labrum. B, Schematic drawing showing the relevant structures outlined in the hip arthrogram: AC, acetabular cartilage; L, the labrum, is a triangular structure that covers the femoral head laterally; ZO, zona orbicularis; LT, ligamentum teres; TL+, transverse ligament + inferior labrum; FH, femoral head.







FIGURE 2.3. The Tönnis grading system for assessing the morphology of the hip on an arthrogram after closed reduction. A, Grade I: The femoral head is completely reduced and close to the ischial part of the acetabulum. B, Grade 2: The femoral head is below the labrum but sits more lateral because of the capsular constriction and narrowing of the introitus between the superior labrum and the transverse ligament and inferior labrum. A small amount of medial pooling of the contrast is observed between the femoral head and the acetabular fossa. C, Grade III: The femoral head cannot be positioned under the labrum and sits lateral to the acetabulum introitus. The labrum is typically inverted, and the capsule markedly constricted. White arrows point to the lateral aspect of the acetabular cartilage and labrum. Red arrows point to the medial dye pooling formed between the femoral head and the acetabular fossa. The yellow arrows point to the transverse acetabular ligament.

May 10, 2021 | Posted by in ORTHOPEDIC | Comments Off on Infant Hip Dysplasia: Closed Reduction

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