Neonatal Laxity

Neonatal laxity is the mildest form of instability of the newborn hip. As the name implies, this label should be used only for children younger than 30 days of age.8,14 This form of instability is often not detectable by clinical examination alone.14 Even in the hands of experienced clinicians, this mild form of instability may not produce characteristic physical findings or signs.14 Neonatal laxity is best appreciated on ultrasound examination. During the stress maneuvers, the femoral head is noted to displace from the acetabulum slightly but not to the degree expected with subluxation. This determination is dependent upon the skill and experience of the ultrasonographer and is highly subjective.15 If this degree of instability is nearly impossible to detect clinically, how is it being detected in the absence of a universal ultrasound screening program? In most clinical settings, the ultrasound is ordered after a suspicious finding on a clinical examination or in the presence of significant risk factors either in the infant or the family.

By correctly timing the ultrasound evaluation, false-positive tests can be minimized.4 If the clinical examination is normal but pathology is still suspected, the ultrasound examination should be delayed for a minimum of 4 weeks.4 During this time, many insignificant, self-limited cases of minor instability will resolve, and further referral can be avoided.4 If the ultrasound is performed in the first few days of life, a large percentage of these patients will have positive findings, necessitating a referral and follow-up ultrasound in 2 to 3 weeks.4 As no formal intervention is recommended during the first few weeks of an infants’ life; it is simply more logical to defer the testing until more than 4 weeks of age. If the physical examination detects actual clinical instability, immediate evaluation is indicated.


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When this form of newborn laxity persists into the fifth or sixth week of age, treatment with a Pavlik harness should be considered.16 A significant proportion of these patients whose neonatal laxity persists may go on to complete spontaneous resolution. Unfortunately, quality clinical studies are not available to help guide treatment decisions in this situation. Therefore intervention is recommended.16 The Pavlik harness is generally used for 6 continuous weeks with the expectation that virtually all patients will normalize.17

Subluxation

When the femoral head can be significantly displaced from the acetabulum but not wholly dislocated, it is classified as subluxed.18 How much laxity must one have to be classified as subluxed? This is where the subjective aspects of this continuum are most apparent. The determination of subluxation is entirely dependent upon the experience of the ultrasonographer.18 Subluxation at any age is at risk to persist. Therefore management with a Pavlik harness is recommended. The harness is worn full time for 6 weeks; a follow-up ultrasound is conducted as a small number of patients may fail treatment.17 If the subluxation persists in a patient managed with compliant harness wear, another form of management must be considered.

In some cases, soft tissue found within the acetabulum will not allow the femoral head to seat into the socket completely.18 In this situation, an injection arthrogram under general anesthesia is generally performed to detect any blocks to reduction and determine the limb position that produces a concentric reduction.19 The child is then placed into a double hip spica cast to immobilize the limb in this most reduced position.19 It should be emphasized that this treatment is not often required, as the Pavlik harness is most effective in resolving subluxation in the early infant period.

Dislocatable Hip

In this classification, the hip is reduced into the acetabulum at rest (although not necessarily a fully concentric reduction) but shows considerable laxity and can be manually dislocated during the provocative Barlow maneuver. The limb is grasped by the examiner’s hand while the pelvis is stabilized by the opposite hand. The limb is brought into adduction, and pressure is applied over the knee along the limb’s axis, producing a posterior force on the femoral head. The hip is held in flexion. The femoral head is felt to dislocate posteriorly over the rim of the acetabulum during the maneuver. When the posterior force is relaxed, the femoral head is noted to return to the acetabulum. By definition, the femoral head is reduced at rest.

All patients with a positive Barlow test require treatment with a Pavlik harness.19 The harness is worn full time and ultrasound is obtained at 2-week intervals.19,20 The instability should diminish with treatment, but some mild instability may persist for a few weeks. It is recommended that the infant wear the harness for 6 weeks following an ultrasound documenting stability.17 If instability is not improving after the initial 6 weeks of therapy, a block to concentric reduction should be suspected. In this situation, arthrogram and spica casting may be required.19

Dislocated Reducible Hip

At rest, the hip is dislocated beyond the rim of the acetabulum. The Galeazzi sign will be positive; with the hips flexed to 45 to 50 degrees and knees at 90 degree with the patient supine, the apparent knee heights above the examination table will not be the same. An evident limb length discrepancy may be found in the supine position. Most often, the posterior skin creases or folds will be asymmetric. While asymmetric skin folds can indicate that a patient may have DDH, it is possible to have asymmetric folds in an infant with normal hips.19 In the newborn period (4-6 weeks of age), limb abduction is usually not limited; however, with advancing age, the unreduced hip leads to contracture of the adductor tendons and eventually limited abduction on the involved side.19,21

When the Ortolani maneuver is performed, the femoral head can be felt to reduce into the acetabulum. The limb is held while the pelvis is stabilized. The limb is slowly abducted while pressure is placed behind the greater trochanter to pull the limb anteriorly as it is abducted. The femoral head will reduce into the acetabulum giving a positive Ortolani sign. When the limb is released, it will passively return to the dislocated position.19

Management begins with the Pavlik harness.5,17 In many cases, the patient will show a reduction of the hip shortly after placement of the harness but, in some cases, it will take 1 or 2 weeks. Patients in this category who fail Pavlik harness treatment will require an arthrogram and casting; in some cases, patients may require open surgical reduction to remove impediments to reduction.5,19,20

Dislocated Nonreducible Hip

In this classification, the hip is dislocated out of the acetabulum (positive Galeazzi sign, limited abduction, and asymmetric skin creases); however, during the Ortolani maneuver, the femoral head will not return to the acetabulum. In an infant less than 6 weeks of age, this is a concerning finding and requires ruling out teratologic dislocation (discussed in the next section). The reducible dislocation will become nonreducible (generally within 3 months); thus, the patient will be classified as a late DDH case. As these patients are more than 3 months of age at the time of diagnosis, failure rates for the Pavlik harness will be higher.22,23

Teratologic Dislocation

Patients with this classification of hip dysplasia have a dislocation of the hip that is associated with other severe systemic conditions. Teratologic dislocations are seen with genetic or developmental syndromes such as arthrogryposis, genetic translocations and trisomy, and spinal dysraphism (spina bifida).8,20 The patients will have additional clinical malformations and the dislocations are often significantly stiff at the time of birth. This category of dislocations cannot be managed with nonsurgical methods.24 In most cases, the additional medical and surgical conditions take precedence over the management of the hip dislocations. Major surgical reconstructions are generally required to return the femoral heads to the acetabula. A complete discussion of the management of these most severely dislocated hips is beyond the scope of this review.

Stages of Management of Developmental Dysplasia of the Hip

Management of DDH can be divided into stages (Figure). The first stage (and arguably the most important) is the diagnosis stage. Early diagnosis markedly simplifies the management of DDH and improves the prognosis for the patient. Late diagnosis and treatment of DDH dramatically increase the chances that total recovery will not be achieved without the need for complex reconstructive surgery.

The second stage is the reduction stage. The hip must be replaced into the acetabulum. The reduction must be maintained until the third and final stage of stability is achieved. In the stability stage, acetabulum development is observed to confirm that acetabular dysplasia (lack of complete and deep coverage of the femoral head) resolves. This stage requires periodic radiographic evaluation of the patient, who is most always clinically normal.

Acetabulum development will require follow-up by the specialist. This will most often require periodic radiographs for at least the first 2 years of life. Patients with DDH  also must receive long-term, periodic follow-up. Residual acetabular dysplasia rarely causes symptoms until at least the early teenage years yet can lead to considerable early degenerative osteoarthritis of the hip.19 The need for early total joint arthroplasty of the hip is often related to untreated residual acetabular dysplasia.19,25 Patients, parents, and primary care providers must be told of the need for long-term follow-up until the patient reaches skeletal maturity.




Figure. Initial evaluation and management of developmental dysplasia of the hip.
aIncluding one or more of the following: asymmetric skin folds, positive Ortolani, positive Barlow, positive Galeazzi
bBreech position at birth or family history of developmental dysplasia of the hip.

Summary

The introduction of ultrasound imaging for the evaluation and treatment of DDH has markedly reduced delays in DDH diagnosis. Unfortunately, the extreme sensitivity of this modality has led to a significant increase in the referral of patients who would likely resolve their subclinical instability without medical intervention. Using the proposed algorithm will result in more efficient utilization of consultant resources without increasing the risk of missing a case of instability requiring referral. The early management of the newborn with hip instability using the proposed algorithm requires skill in infant hip ultrasonography. The utility of standard radiography in children less than 3 months of age is low. The primary care provider should be familiar with the physical evaluation of the newborn patient and the appropriate use of ultrasound examination in cases of both abnormal physical findings and patients with significant risk factors.

Amanda P. Stanton, PA-C, is a lead physician assistant with the Division of Colon and Rectal Surgery at Mayo Clinic Florida and assistant professor at Mayo Clinic College of Medicine and Science in Jacksonville, Florida. 

Hannah Hoppe, BHS, is a 2021 graduate of the Physician Assistant Program at Duquesne University in Pittsburgh, PA.

Bradley Richey, MS, BS, is a fourth-year medical student at the University of Central Florida College of Medicine in Orlando, Florida.

Robert P. Stanton, MD, FACS, is on staff in the Department of Pediatric Orthopedic Surgery at Nemours Children’s Hospital, Orlando, FL.


aImage reprinted from Colta RC, Stoicanescu C, Nicolae M, Oros S, Burnei G. Hip dysplasia screening – epidemiological data from Valcea County. J Med Life. 2016;9(1):106-111.

References

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