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NeoQuest April 2023: Limb Abnormality in a Term Neonate

April 5, 2023

A term infant was born to a 28-year-old primigravid woman. The pediatrician noted the findings demonstrated in Figure 1 and was able to easily place the left lower extremity into a neutral position. The upper extremities and right lower extremity appeared well-developed with normal range of motion. The Barlow maneuver was negative for both hips. A left lower extremity radiograph was negative for a fracture.


Figure 1: Presentation of infant’s bilateral lower extremities in the delivery room. From: Babbar S, Lala R, Pollack R. Extramural delivery and limb hyperextension. Neoreviews. 2023;24(4):e243–2451

What additional study is indicated to evaluate for the condition most commonly associated with this presentation?

  1. Bilateral upper extremity radiographs
  2. Hip ultrasonography
  3. Low-dose cranial computed tomography
  4. Magnetic resonance imaging of the brain and spine

Explanation:

Answer: B. Hip ultrasonography

The physical exam findings in Figure 1 are consistent with a diagnosis of congenital dislocation of the knee (CDK). CDK, also known as genu recurvatum, is a rare congenital anomaly that occurs in approximately 1 in 100,000 infants.2 The etiology of CDK is unknown.3 Proposed etiologies of CDK include fetal molding due to oligohydramnios, breech positioning, anterior cruciate ligament abnormalities, or contracture of the quadriceps.4 CDK can occur as an isolated finding.  However, it may also be associated with other musculoskeletal (including arthrogryposis multiplex, talipes equinovarus, developmental dysplasia of the hip) or genetic syndromes (including Larsen syndrome).2,4 CDK complicated by arthrogryposis multiplex, Larsen Syndrome, or spinal dysraphism is typically associated with poor treatment outcomes.4

The diagnosis of CDK is based on physical exam findings of a hyperextended knee present at birth. The presence and number of transverse anterior skin grooves of the affected limb is also important to note, as these findings correlate with the timing of the dislocation and prognosis.2 A greater number of anterior skin grooves correlates with a more recent in utero dislocation, portending a more favorable prognosis (Figure 2).5 The absence of anterior skin grooves likely indicates a more prolonged duration of dislocation, which may lead to a more severe deformity.5


Figure 2: A neonate with a right congenital knee dislocation. Transverse anterior skin grooves (circled area) suggest a more recent in utero dislocation. From: Falcão I, Almeida A, Carvalho C, Campos A, Neiva-Araújo, L. Female newborn with extreme hyperextension of right kneeNeoreviews. 2018;19(3):e196–e200

An initial radiograph of the affected limb should be obtained to confirm the diagnosis of CDK and to evaluate for other musculoskeletal abnormalities.2,4,5 Dynamic radiographs showing the anteroposterior and lateral views of the knee in maximum flexion and extension may be helpful in determining the severity of the dislocation and guiding further management (Figure 3).2,4


Figure 3: Dynamic radiographs of a neonate with a right congenital knee dislocation. Lateral views showing knee subluxation with maximal manipulation in both hyperextension (top circled area) and flexion (bottom circled area). From: Falcão I, Almeida A, Carvalho C, Campos A, Neiva-Araújo, L. Female newborn with extreme hyperextension of right kneeNeoreviews. 2018;19(3):e196–e200

Several classification systems exist to grade CDK based on physical exam features and radiographic measurements of the affected limb.2,4 One commonly used classification system, proposed by Mehrafshan et al., is based on the reducibility and stability of the affected joint at birth prior to treatment (Table 1):2

Table 1: CDK types based on reducibility and stability of the joint. Based on material from Mehrafshan M, Wicart P, Ramanoudjame M, Seringe R, Glorion C, Rampal V. Congenital dislocation of the knee at birth – part 1: clinical signs and classification. Orthop Traumatol Surg Res. 2016;102(5):631–633

Developmental dysplasia of the hip (DDH) in one or both hips is the most common anomaly associated with CDK.3,6 Maneuvers to screen for DDH, such as the Barlow and Ortolani test, may be negative on initial exam.7 Thus, newborns diagnosed with CDK should have hip ultrasonography (Option B) performed after birth to evaluate for DDH even if the hip exam is normal.1,2,7 Overall, DDH is much more common than CDK, with an approximate incidence of 1 in 1000 infants.7

Bilateral upper extremity radiographs (Option A) may be helpful in cases of CDK where there is a high clinical suspicion for an associated musculoskeletal or genetic syndrome.6 In this scenario, the infant’s bilateral upper extremities and right lower extremity were well-developed with normal range of motion, and thus, radiographs are not indicated. Arthrogryposis is a congenital condition characterized by multiple joint contractures, which are in fixed and abnormal positions due to the shortening or thickening of the infant’s muscles, tendons, or ligaments.8 The causes of arthrogryposis are diverse and include genetic mutations, neuromuscular disorders, or fetal exposure to teratogens in utero.8 Limb radiographs of patients with arthrogryposis can demonstrate abnormal joint alignment and bony abnormalities, although routine radiographs are not required to establish this diagnosis.8

Bilateral upper extremity radiographs may also be helpful in the evaluation of genetic conditions associated with CDK, including Larsen syndrome. Physical exam findings of Larsen syndrome vary widely and can include multiple joint dislocations, joint contractures, and atypical craniofacial features.8,12 The joint dislocations and contractures typically affect the elbows, hips, knees, and ankles.12 When a diagnosis of Larsen syndrome is suspected, bilateral upper extremity radiographs may reveal several bony anomalies as seen in Figure 4. Genetic testing may be indicated in patients who present with other physical exam anomalies in addition to CDK. Larsen syndrome is caused by an autosomal dominant mutation in the filamin B (FLNB) gene that encodes for the filamin B protein.9


Figure 4: Long bone radiographs with upper and lower extremity bony anomalies in an infant with Larsen syndrome including: rhizomelic shortening of the distal humerus (A), hypoplastic phalanges (B), and knee dislocation (C). From: Ambat MT, Villanos MT, Prasad D. Newborn with multiple congenital joint dislocationsNeoreviews. 2013;14(1):e49–e53

Low-dose cranial computed tomography (Option C) can aid in evaluating an infant with craniosynostosis. Specifically, it can measure the thickness of the skull, assess the shape and location of the suture lines, and guide preoperative planning for surgical correction.10 Because the infant presents with a musculoskeletal syndrome consistent with CDK, cranial computed tomography would not be helpful in further evaluation.

Magnetic resonance imaging (MRI) of the brain and spine (Option D) is not useful in the evaluation of CDK.  However, this combined imaging may be obtained to evaluate an infant with a suspected diagnosis of spinal dysraphism to assess for intracranial anomalies such as a Chiari II malformation and associated spinal cord abnormalities such as a tethered cord or syringomelia.13 Spinal dysraphism, such as a myelomeningocele, can be associated with CDK but is rare and not as common as DDH in CDK.3,4 Cases of CDK and myelomeningocele may also present with concurrent talipes equinovarus, or club foot (Figure 5).2  Cases of CDK associated with myelomeningocele typically result in poorer therapeutic outcomes.4


Figure 5: An infant with bilateral talipes equinovarus. Note that the feet are adducted, supinated, and in varus positioning. From: Woolnough R, Dhawan A, Dow K, Walia JS; Are patients with Loeys-Dietz syndrome misdiagnosed with Beals syndrome? Pediatrics. 2017;139(3):e20161281

Did you know?
CDK should be treated prior to managing an associated dislocated or dysplastic hip. Spontaneous reduction of the dislocated hip may occur following corrective treatment for CDK.11 Management options range from nonsurgical approaches consisting of reduction and serial casting to surgical correction requiring several soft tissue release procedures.3,5

What imaging findings would be expected in an infant suspected to have skeletal dysplasia?
To find the answer, please refer to the following article: Langston SJ, Krakow D, Chu A. Revisiting skeletal dysplasias in the newborn. Neoreviews. 2021;22(4):e216–e229

April NeoQuest Authors
Angelina June MD, MD, University of Virginia Children’s Hospital
Faith Kim, MD, Columbia University Medical Center/NewYork-Presbyterian Children’s Hospital of New York

References:

  1. Babbar S, Lala R, Pollack R. Extramural delivery and limb hyperextension. Neoreviews. 2023;24(4):e243–245
  2. Mehrafshan M, Wicart P, Ramanoudjame M, Seringe R, Glorion C, Rampal V. Congenital dislocation of the knee at birth – part 1: clinical signs and classification. Orthop Traumatol Surg Res. 2016;102(5):631–633
  3. Gleason CA, Juul SE, White KK, Bouchard M, Goldberg MJ. Torsional and angular deformities of the lower extremities. In: Avery’s Diseases of the Newborn. Philadelphia, PA: Elsevier; 2018
  4. Abdelaziz TH, Samir S. Congenital dislocation of the knee: a protocol for management based on degree of knee flexion. J Child Orthop. 2011;5(2):143–149
  5. Rampal V, Mehrafshan M, Ramanoudjame M, Seringe R, Glorion C, Wicart P. Congenital dislocation of the knee at birth – part 2: impact of a new classification on treatment strategies, results and prognostic factors. Orthop Traumatol Surg Res. 2016;102(5):635–638
  6. Ellsworth B, Dawkins B, Hidalgo Perea S, Green D. Management of congenital dislocation of the knee: current concept review. J Pediatr Orthopaed, Soc No Am.2021;3(3)
  7. Shaw BA, Segal LS; Section on Orthopaedics. Evaluation and referral for developmental dysplasia of the hip in infants. Pediatrics. 2016;138(6):e20163107
  8. Bamshad M, Van Heest AE, Pleasure D. Arthrogryposis: a review and update. J Bone Joint Surg Am. 2009 Jul;91(Suppl 4):40–6
  9. Zhang D, Herring JA, Swaney SS, McClendon TB, et al. Mutations responsible for Larsen syndrome cluster in the FLNB protein. J Med Genet. 2006;43(5):e24
  10. Montoya JC, Eckel LJ, DeLone DR, et al. Low-dose CT for craniosynostosis: preserving diagnostic benefit with substantial radiation dose reduction. AJNR Am J Neuroradiol. 2017;38(4):672–677
  11. B K AR, Singh KA, Shah H. Surgical management of the congenital dislocation of the knee and hip in children presented after six months of age. Int Orthop. 2020;44(12):2635–2644
  12. Ambat MT, Villanos MT, Prasad D. Newborn with multiple congenital joint dislocations. Neoreviews. 2013;14(1):e49–e53
  13. Kumar J, Afsal M, Garg A. Imaging spectrum of spinal dysraphism on magnetic resonance: a pictorial review. World J Radiol. 2017;9(4):178–190
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