Role of Dynamic Ultrasound Scan in Detection of Hip Instability and Changing Management Plan

DDH was first described by Hippocrates (460-370 B.C) who reported it to be caused by congenital and injury to the mother’s womb, and Ambroise Pare found that it could be hereditary. Clinical screening is a common practice internationally for infant hips however its dependent on experience. There are numerous techniques used for the examination of infant hips using ultrasonography.

Developmental Hip dysplasia (DDH) is a group of disorders that ranges from unstable hip to total dislocation.

DDH is commonly found in infants with musculoskeletal birth defects with an occurrence in children of up to 11.5/1,000 live births estimated using meta-analysis procedures and numerous logistic regressions [1]. Some of the factors that increase the risks for DDH are positive family history, breech presentation and the oligohydramnios [2]. In infants DDH is asymptomatic and some of the early symptoms are abnormal walking, limping, waddling when the child is learning to walk however late detection can lead to pain and early osteoarthritis. Overall, the prevalence of 1% to 1.5% in infants is reported by Alfonso with 0.005% incidence in males and 0.013 in females [3]. The hip ultrasonography is performed both statically and dynamically and is acknowledged as an early diagnostic technique for DDH.

In order to assess the neonatal hips using the static ultrasound imaging, Graf’s method is widely used in most places [4]. In this method, the infant’s hip morphological assessment helps to assess the angle of the roof of the acetabulum (alpha angle) which is classified using the hips into being mature, immature, or dysplastic, however it is not considered as an effective tool for early neonatal diagnosis.

Ortolani method is the clinical test used to spot unstable hips whereby the dislocated femoral head is relocated by a sudden palpable clunk into the acetabulum by holding the infant’s hip although the accuracy is dependent on skills and experience of the operators [2, 5].

In 1988, Harcke [6] first reported the dynamic ultrasound for hip examination. In previous literatures, lateral dynamic ultrasound (LDUS) & anterior dynamic ultrasound (ADUS) are the two techniques that are widely used for evaluating hip mobility [7]. Our objective is to study the role of dynamic ultrasound in screening while simultaneously reviewing the management plans for developmental dysplasia of the hip with a view to reduce the progression of true DDH in infants.

The detailed study was carried out during November 2021 to January 2023 including a total of 942 hips examination of infants with a suspicion of DDH aging 6 weeks to six months in Helena Governmental Specialized Rehabilitation Center of Children with Special Needs/ Iraq Government/Kurdistan Region/ Erbil City. The following infants were excluded in the study:

• infants with neuromuscular disorder
• myelodysplasia or arthrogryposis.

We also conducted a validation study by taking referrals from orthopedic specialists and outpatient pediatricians. After taking consent we logged patient data and assessed the presence of risk factors (family history as first degree relatives, breech presentation during third trimester or at birth, and first-born child). Both genders were examined. Once the validation study statistically proved the technique to be followed, we performed the ultrasound using a GE Versana Premier ultrasound system with a linear probe 12 L to check each patient bilaterally during static and dynamic scans.

The infant was positioned to lay on its side (15–20° flexion) or with the hip placed in 35 degrees of flexion to see the hip in a coronal view. Overall approach included coronal lateral neutral at rest (static morphological test for Graf Types and obtaining the ACI -acetabular coverage index). The coronal lateral flexion was obtained by adduction (stress) to calculate ACI and stability assessment for cases Graf Types I through IId, while Harcke [6] method (transverse abduction-adduction scan) is used for reducibility, which is only applicable to advanced cases of DDH [Type III and IV].

Modified Graf Method: the hip joint was classified by U/S; the coronal section at rest yielding the following Types:

1. Graf Type I (normal hip joint).
2. Graf Type IIa: age <3 m (representing physiological immaturity).
3. Graf Type IIb: age >3 months (regarded as delayed maturity).
4. Graf Type IIc: (dysplastic hip).
5. Graf Type IId: (dysplastic hip)
6. Graf Type III: (partially dislocated hip).
7. Graf Type IV: (frank total hip dislocation).

• (β) Alpha angle normal value >60
• (β) Beta angle normal value<55

A) Dynamic Scan included two Methods as given below:

1. Moren-Terjesen’s femoral head coverage method using 3 categories: at rest, coronal lateral, neutral is used to obtain the percentage of acetabular coverage index [ACI] as d/D [normal value>50%]. In the same position, we applied adduction stress while the hip in 90-degree flexion, to drive the femoral head out of position with the least amount of force [without harming the baby], we then obtained acetabular coverage index[ACI] during stress (Figure 1 A and B). The terminology we used to classify stability are:

1. Laxity if the ACI is >50% at rest but mildly reduced <50% on stress.
2. Subluxable if ACI is <50% at rest and further reduced on stress but not dislocated.
3. Dislocatable if ACI is <50% or normal at rest but the head is completely dislocated on stress.