Congenital Hip Dysplasia
What do female babies, left hips, and breech presentations all have in common?
Congenital Hip Dysplasia, aka CHD, CDH, DDH
by Allan Strongwater, M.D.
Congenital Dislocation of the hip
Developmental Dysplasia of the hip
Developmental Dislocation of the hip
The hip joint is a spherical ball in socket joint comprised of bone from the pelvis, contributed to by the Ilium, Ischium and Pubic bones forming the socket, called the acetabulum. The ball portion of the hip joint is the head of the proximal femur. The acetabulum and femoral head are, in large part, covered by articular cartilage forming the weight bearing, gliding surface of the joint. The skeletally immature pediatric hip contains a number of growth plates (physes), absent in the adult, that allow for increases in size and changes in shape of the joint during the growth period. The physis is located between the metaphysis and the epiphysis of the bone. The physis is comprised primarily of special growth cartilage cells carefully aligned in vertical columns like stacks of coins. During growth, the bone elongates by adding cells to each of the columns. If the columnar alignment of the cartilage is disrupted, growth in the affected physis may stop, slow or grow in a deformed manner. The delicate structure of the physis can be injured in a number of ways, including by direct (fracture through the physis) and indirect trauma (due to excessive compressive loads), and from various infective organisms, particularly staphylococcus aureus and streptococcus. Several neoplastic processes of both the benign and malignant type can be identified targeting the pediatric hip. Several, rare inborn genetic disorders like Gaucher’s disease and fibrous dysplasia can affect hip development.
When observing a radiograph of the pediatric hip, multiple growth plates, physes, may be visible in and around the hip, depending upon the projected view of the image. In addition to the visual differences between bone and cartilage, cartilage of the physis is mechanically much less strong, especially resisting shear force. The physis is therefore susceptible to injury of both acute and chronic forms of trauma resulting in types of injury not seen in adults, such as slipped capital femoral epiphysis, transphyseal fracture or avulsion fractures of the lesser trochanter, greater trochanter and ischial apophysis.
As we review some of the specific common congenital and acquired afflictions of the immature hip it is important to keep the structural differences between skeletally immature and mature hip in focus as it will help clarify the etiology of the pathology discussed.
This InReview will limit discussion to Congenital Hip Dysplasia. A broader discussion, “A Summary of some Common Congenital and Acquired Afflictions of the Immature Hip” will be presented in FibonacciMD in the near future.
In the newborn and peri-natal period, the greatest concern regarding the hip is the presence or absence of congenital dislocation of the hip (CDH). This serious problem has been referred to by several names: developmental dislocation of the hip (DDH) or congenital hip dysplasia (CHD). In all cases the pathology refers to abnormal seating of the femoral head within the acetabulum and spans the gamut from the femoral head being completely out of the acetabulum (no or minimal contact between the articular surfaces of the femoral head and acetabulum) to merely not being concentrically located in the acetabulum (referred to as subluxated or non-concentric). The unstable hip also falls into the category of CDH. The unstable hip is initially located within the acetabulum but can be dislocated out of the acetabulum with little force by the examiner performing a Barlow maneuver.
The optimal time to identify CDH is shortly after birth. If detected early in life and appropriately treated, complete cure with no disability is possible in most cases. Delay in diagnosis may result in less satisfactory outcome with more complicated treatment. In many cases, if the dislocated hip is not diagnosed in the first few months of life, it may remain undiscovered until the child starts to walk at which time the toddler will demonstrate a notable limp on the affected lower extremity.
Causes and Risk Factors
CDH tends to be more common in female babies, in the left hip, with breech presentation, and with a positive family history of CDH. The precise cause of congenital hip dislocation is unknown however there are clearly defined risk factors including: oligohydramnios, multiple fetuses, previous pregnancy resulting in a baby with hip dislocation, female baby, first born, and breech presentation.
Signs and Symptoms
In the perinatal period, before 6 weeks of age, the most reliable finding on examination is a positive Ortolani sign. This is a palpable clunk as the dislocated hip pops back into the acetabulum when the hips are flexed and abducted. The Barlow is the pop of the hip moving out of the acetabulum when the hip is moved from a position of flexion and abduction to adduction. If either of these maneuvers are positive, the baby requires treatment.
Careful history and examination are indicated. Several physical findings may be apparent on careful examination of the infant including:
A limb length inequality with the affected dislocated hip on the short side as the femoral head usually migrates proximal, lateral and posteriorly. Shortening of the thigh segment on the affected side is referred to as a positive Galeazzi sign.
Thigh skin fold asymmetry with extra skin folds on the affected side, due to shortening.
Positive Ortolani or Barlow signs, a low frequency palpable clunk as the femoral head moves in and out of the acetabulum (this is not an audible click) as the hip is moved from flexion adduction to flexion abduction when axial compression is applied. These signs are often associated with either hip dislocation or instability of the joint.
Sometimes a sense of telescoping can be palpated on gentle push pull of the affected limb especially if the femoral head is completely out of the acetabulum.
Finally, an important sensitive indicator of CDH is the presence of asymmetric range of hip abduction. When dislocated or subluxated, the center of rotation of the hip joint moves out of the acetabulum resulting in tightening of medial musculotendinous structures which restrict the range of abduction motion of the affected joint. In cases of bilateral CDH symmetric reduced range of hip abduction may obscure proper diagnosis. Uncommonly, the femoral head represented as a hard mass can be palpated in the buttock of the affected hip. Certain neuromuscular afflictions that result in abnormal muscle tone in the womb predispose to the development of CDH most commonly myelomeningocele. Later in childhood, myelomeningocele, cerebral and other neuromuscular afflictions may lead to late dislocation or subluxation of the developing hip, even as late as the adolescent years. Children with neuromuscular afflictions require more careful and frequent evaluation of hip development.
Diagnostic Evaluation and Differential Diagnosis
Diagnostically there are several tools available to objectively evaluate the immature hip. In the peri-natal period and up to approximately six months of age, real-time high-resolution ultrasound is the most accurate non-invasive means to evaluate the anatomy and stability of the hip as the Ortolani and Barlow maneuvers can be performed under direct visualization of the joint to ensure concentric reduction and stability of the femoral head in the acetabulum. Additionally, the anatomy and configuration of the hip can be measured. In the age group between birth and six months of age radiographs of the hip are relatively contraindicated for the routine workup of CDH.
Beyond six months of age the capital femoral epiphysis is sufficiently ossified to make ultrasonic imaging more difficult and therefore less reliable. Once the ossific nucleus of the capital femoral epiphysis is well formed radiographs or CT scan may prove more useful. The most definitive tool to evaluate hip joint stability, congruence of reduction, and intra-articular anatomy is the contrast enhanced arthrogram. Hip joint arthrography should not be undertaken without consideration of all other modalities as the study requires infant sedation and although is of low risk, it is not without complications.
In uncommon cases MRI has been used to evaluate the infant hip and surrounding structures. Although MRI is a non-invasive modality it usually requires sedation of the infant and young child.
DDH should be differentiated from congenital or developmental coxa vara, perinatal fracture, and proximal focal femoral deficiency.
Staging and Further Stratifications
A variety of systems have been described to classify the degree of DDH, most are based on the degree of displacement of the femoral head from the true acetabulum and or the degree of deformity of the acetabulum, or both.
Pearl to Know
Restriction of hip abduction is strongly suspicious for DDH.
Asymmetric thigh skin folds is suspicious but not diagnostic of DDH.
Treatment and Recommended Follow-Up
The precise treatment algorithm for CDH is very complex and highly branched depending on such factors as age of the child, degree of dislocation, duration of dislocation, anatomy of the proximal femur and acetabulum, including any deformity due to previous unsuccessful treatment, any underlying affliction which may be driving the hip dislocation, and integrated with results of various tests that may have been performed. For these reasons, the precise treatment of any specific case is beyond the scope of the current text. The text is intended to provide a general outline of potential treatment strategies. Suffice it to say CDH diagnosed early in life that demonstrates a positive Ortolani and/or Barlow can usually be treated with some form of brace or cast that holds the hip in a position of stable reduction such that the femoral head is contained in the acetabulum. A commonly used brace for the treatment of CDH is the Pavlik harness. Other devices include: Frejka pillow, Von Rosen splint, or universal hip abduction orthosis. The harness is considered a dynamic brace in that range of motion of the lower extremities is allowed but constrained to certain arcs thereby thought to allow the infant to “kick” the hip into reduction. The Pavlik harness requires precise application as potentially serious complications can arise from its use. Periodic adjustment of the Pavlik harness is necessary to accommodate infant growth. CDH in the peri-natal age group can usually be treated for a period of four to six weeks of bracing. The hip must be stable to discontinue immobilization treatment. Rehabilitation of the afflicted hip may be necessary to obtain normal range of motion. Careful follow up to beyond one year of age is recommended.
Individuals in which the Ortolani and/or Barlow signs are absent, or the femoral head cannot be reduced into the acetabulum with brace treatment alone require further evaluation of the anatomy of the joint, beyond ultrasonography. Most commonly an arthrogram of the hip, under sedation or anesthesia, is performed and immediately followed by whatever treatment modality is best indicated by the information gleaned from the arthrogram. Hips in this category have usually failed simple closed reduction treatment and may require traction and/or surgical intervention to obtain a concentric reduction of the femoral head into the acetabulum. Traction is applied to the affected lower extremity with the hip and knee in some degree of flexion. The goal is to manually pull, over time, the femoral head distally to the level of the true acetabulum to facilitate closed or open joint reduction followed by brace or cast to hold the hip in a concentrically reduced position.
Children who demonstrate anatomic anomalies of the hip, usually seen beyond six months of age may require surgical correction. Anatomic anomalies in and around the hip that require open reduction may include an “hourglass” constriction of the hip joint capsule which prevents reduction of the femoral head through the constricted capsule into the true acetabulum. Capsular contracture may occur with or without iliopsoas tendon contracture which further obstructs movement of the femoral head medially into the true acetabulum. In those individuals in which the femoral head has been dislocated for a substantial period of time, the acetabulum often becomes deformed, or the hip adductor muscles become contracted and need to be corrected. Finally, the femur itself may have malrotation, excessive femoral anteversion leading to hip instability requiring surgical derotation osteotomy.
Each child with CDH requires followup care and monitoring until the hip joint development is deemed normal or growth has ceased. Children who at the time of skeletal maturity do not have normal hip development will generally develop hip pain in their fourth or fifth decade of life and require additional hip surgery up to and including total hip replacement surgery.
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ABOUT THE AUTHOR
Allan Strongwater, M.D.
Allan Strongwater was originally educated as an Electrical Engineer. He is now a semi-retired pediatric orthopaedic surgeon who did his surgical training at Yale and his pediatric surgery at Newington Children’s Hospital (University of Connecticut). He has held numerous positions including Chairman of Orthopaedic Surgery and Musculoskeletal Services, Orthopaedic Surgery Residency Program Director, Chief of Pediatric Orthopaedic Surgery and Chairman of Bioengineering. Most recently he has returned to the engineering world as Senior Vice President of Medical Informatics and now he has joined IMIT as Chief Technology Officer.
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initial post 1/24/2022