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Hip dysplasia (human)
Encyclopedia
Hip dysplasia, developmental dysplasia of the hip (DDH) or congenital dysplasia of the hip (CDH) is a congenital or acquired deformation or misalignment of the hip joint.
The use of the word congenital can also imply that the condition already exists at birth. This terminology introduces challenges, because the joint in a newborn is formed from cartilage
and still malleable, making the onset difficult to ascertain.
The newer term DDH also encompasses occult
dysplasia (e.g. an underdeveloped joint
) without dislocation and dislocation developing after the "newborn
" phase.
The term is not used consistently. In pediatric/neonatal orthopedics it is used to describe unstable/dislocatable hips and poorly developed acetabula. For adults it describes hips showing abnormal femur head or acetabular x-rays.
Some sources prefer the term "hip dysplasia" over DDH, considering it to be "simpler and more accurate", partly because of the redundancy created by the use of the terms developmental and dysplasia
.
TYPES OF DDH include subluxation,dysplasia,and dislocation.The main types are the result of either laxity of the supporting capsule or an abnormal acetabulum.
Hip dysplasia can range from barely detectable to severely malformed / dislocated.
The congenital
form, teratologic
or non-reducible dislocation occurs as part of more complex conditions.
The condition can be bilateral or unilateral:
If the joint is fully dislocated a false acetabulum often forms (often higher up on the pelvis) opposite the dislocated femoral head position.
In actetabular dysplasia the acetabulum
(socket) is too shallow or deformed. The center-edge angle is measured as described by Wiberg. In coxa vara
the femur head
grows at too narrow an angle to the shaft, in coxa valga
the angle is too wide.
A rare type, the "Beukes familial hip dysplasia" is found among Afrikaners that are members of the Beukes family. The femur head is flat and irregular. Sufferers develop osteoarthritis at an early age.
Rather than using the Wiberg angle because it makes it difficult to quantify the degree of dislocation they used 3 key elements to determine the degree of subluxation
: A reference line at the lower rim of the "teardrop", junction between the femoral head and neck of the respective joint and the height of the pelvis (vertical measurement). They studied anteroposterior pelvic x-rays and drew horizontal lines through the lower rim of a feature called "teardrop". The distance between this line and the middle lines of the junction between femur head and neck gave them a measure of the degree of femur head subluxation. They further established that a "normal" diameter of the femur head measures 20% of the height of the pelvis. If the middle line of the neck-head junction was more than 10% of the pelvis height above the reference line they considered the joint to be more than 50% dislocated.
The following types resulted:
An instability rate of 1:60 has been described, though this rate drops to 1:240 at one week. The condition is eight times more frequent in females than in males.
has been indicated.
A genetic factor is indicated by the trait running in families and increased occurrence in some ethnic populations (e.g. native Americans
, Lapps / Sami people
). A locus has been described on chromosome 13. Beukes familial dysplasia, on the other hand, was found to map to an 11-cM region on chromosome 4q35. With nonpenetrant
carriers not affected.
infants or use of a cradle board which locks the hip joint in an "adducted" position (pulling the knees together tends to pull the heads of the femur bone out of the sockets or acetabulae) for extended periods. Modern swaddling techniques allow some room for leg movement.
Further risk factors include breech birth
and firstborns. In breech position the femoral head tends to get pushed out of the socket. A narrow uterus also facilitates hip joint dislocation during fetal development and birth.
for early detection of hip dysplasia.
It can often be detected by a "click" or more precisely "clunk" in the hip (although not all clicks indicate hip dysplasia).
Two maneuvers commonly employed for diagnosis in neonatal exams are the Ortolani maneuver and the Barlow maneuver
.
The condition can be confirmed by ultrasound
and X-ray
. Ultrasound imaging yields better results defining the anatomy until the cartilage is ossified. When the infant is around 3 months old a clear roentgenographic image can be achieved. Unfortunately the time the joint gives a good x-ray image is also the point at which nonsurgical treatment methods cease to give good results. In x-ray imaging dislocation may be indicated if the Shenton's line (an arc drawn from the medial aspect of the femoral neck through the superior margin of the obturator foramen
) does not result in a smooth arc. However in infants this line can be unreliable as it depends on the rotation of the hip when the image is taken
Asymmetrical gluteal folds and an apparent limb-length inequality can further indicate unilateral hip dysplasia. Most vexingly, many newborn hips show a certain ligamentous laxity
, on the other hand severely malformed joints can appear stable. That is one reason why follow-up exams and developmental monitoring are important. Routine ultrasound screening has been discussed and rejected mainly because the small benefit would not justify the costs.
The Harris hip score (developed by William H. Harris MD, an orthopedist from Massachusetts) is one way to evaluate hip function following surgery. Other scoring methods are based on patients' evaluation like e.g. the Oxford hip score, HOOS and WOMAC
score. Children's Hospital Oakland Hip Evaluation Scale (CHOHES) is a modification of the Harris hip score that is currently being evaluated.
Other devices employed include the spica cast, particularly following surgical closed reduction. A few weeks in traction
can be used as part of a treatment plan.
and iliopsoas muscles
have to be treated surgically because they adapt to the dislocated joint position (contracture
).
Braces and splints are often used following either of these methods to continue treatment.
Although some children "outgrow" untreated mild hip dysplasia and some forms of untreated dysplasia cause little or no impairment of quality of life, studies have as yet been unable to find a method of predicting outcomes. On the other hand, it has often been documented that starting treatment late leads to complications and ends in poor results.
) or by seeding porous arthroplasty prosthesis with autologous fibroblasts or chondrocyte
progenitor cells to assist in firmly anchoring the artificial material in the bone bed.
of the hip at a comparatively young age. Dislocated load bearing surfaces lead to increased and unusual wear. Although there are studies that contradict these findings. (see ) Subsequent treatment with total hip arthroplasty
(hip replacement
) is complicated by a need for revision surgery (replacing the artificial joint) owing to skeletal changes as the body matures, loosening/wear or bone resorption.
Osteotomies
are either used in conjunction with arthroplasty
or by themselves to correct misalignment.
," Kerry Weaver
uses a crutch owing to congenital hip dysplasia. In season 12, she undergoes a hip replacement to cure her dysplasia when her previously untreated joint worsens.
Terminology
Some sources prefer "developmental dysplasia of the hip" (DDH) to "congenital dislocation of the hip" (CDH), finding the latter term insufficiently flexible in describing the diversity of potential complications.The use of the word congenital can also imply that the condition already exists at birth. This terminology introduces challenges, because the joint in a newborn is formed from cartilage
Cartilage
Cartilage is a flexible connective tissue found in many areas in the bodies of humans and other animals, including the joints between bones, the rib cage, the ear, the nose, the elbow, the knee, the ankle, the bronchial tubes and the intervertebral discs...
and still malleable, making the onset difficult to ascertain.
The newer term DDH also encompasses occult
Occult
The word occult comes from the Latin word occultus , referring to "knowledge of the hidden". In the medical sense it is used to refer to a structure or process that is hidden, e.g...
dysplasia (e.g. an underdeveloped joint
Joint
A joint is the location at which two or more bones make contact. They are constructed to allow movement and provide mechanical support, and are classified structurally and functionally.-Classification:...
) without dislocation and dislocation developing after the "newborn
Infant
A newborn or baby is the very young offspring of a human or other mammal. A newborn is an infant who is within hours, days, or up to a few weeks from birth. In medical contexts, newborn or neonate refers to an infant in the first 28 days after birth...
" phase.
The term is not used consistently. In pediatric/neonatal orthopedics it is used to describe unstable/dislocatable hips and poorly developed acetabula. For adults it describes hips showing abnormal femur head or acetabular x-rays.
Some sources prefer the term "hip dysplasia" over DDH, considering it to be "simpler and more accurate", partly because of the redundancy created by the use of the terms developmental and dysplasia
Dysplasia
Dysplasia , is a term used in pathology to refer to an abnormality of development. This generally consists of an expansion of immature cells, with a corresponding decrease in the number and location of mature cells. Dysplasia is often indicative of an early neoplastic process...
.
TYPES OF DDH include subluxation,dysplasia,and dislocation.The main types are the result of either laxity of the supporting capsule or an abnormal acetabulum.
Forms of the condition
The congenital
Congenital disorder
A congenital disorder, or congenital disease, is a condition existing at birth and often before birth, or that develops during the first month of life , regardless of causation...
form, teratologic
Teratology
Teratology is the study of abnormalities of physiological development. It is often thought of as the study of human birth defects, but it is much broader than that, taking in other non-birth developmental stages, including puberty; and other non-human life forms, including plants.- Etymology :The...
or non-reducible dislocation occurs as part of more complex conditions.
The condition can be bilateral or unilateral:
- If both hip joints are affected one speaks of "bilateral" dysplasia. In this case some diagnostic indicators like asymmetric folds and leg-length inequality do not apply.
- In unilateral dysplasia only one joint shows deformity, the contralateral side may show resulting effects. In the majority of unilateral cases the left hip has the dysplasia.
If the joint is fully dislocated a false acetabulum often forms (often higher up on the pelvis) opposite the dislocated femoral head position.
In actetabular dysplasia the acetabulum
Acetabulum
The acetabulum is a concave surface of the pelvis. The head of the femur meets with the pelvis at the acetabulum, forming the hip joint.-Structure:...
(socket) is too shallow or deformed. The center-edge angle is measured as described by Wiberg. In coxa vara
Coxa vara
Coxa vara is a deformity of the hip, whereby the angle between the ball and the shaft of the femur is reduced to less than 120 degrees. This results in the leg being shortened, and therefore a limp occurs. It is commonly caused by injury, such as a fracture...
the femur head
Femur head
The femur head is the highest part of the thigh bone . It is supported by the neck of the femur.The head is globular and forms rather more than a hemisphere, is directed upward, medialward, and a little forward, the greater part of its convexity being above and in front.Its surface is smooth,...
grows at too narrow an angle to the shaft, in coxa valga
Coxa valga
It is a deformity of the hip where the angle formed between the head and neck of the femur and its shaft is increased, usually above 135 degrees. It is caused by a slipped epiphysis of the femoral head.-See also:*Coxa vara*Genu valgum*Genu varum...
the angle is too wide.
A rare type, the "Beukes familial hip dysplasia" is found among Afrikaners that are members of the Beukes family. The femur head is flat and irregular. Sufferers develop osteoarthritis at an early age.
Crowe classification
In 1979 Dr. John F. Crowe et al. proposed a classification to define the degree of malformation and dislocation. Grouped from least severe Crowe I dysplasia to most severe Crowe IV. This classification is very useful for studying treatment results.Rather than using the Wiberg angle because it makes it difficult to quantify the degree of dislocation they used 3 key elements to determine the degree of subluxation
Subluxation
A subluxation may have different meanings, depending on the medical specialty involved. It implies the presence of an incomplete or partial dislocation of a joint or organ. The World Health Organization defines both the medical subluxation and the chiropractic subluxation...
: A reference line at the lower rim of the "teardrop", junction between the femoral head and neck of the respective joint and the height of the pelvis (vertical measurement). They studied anteroposterior pelvic x-rays and drew horizontal lines through the lower rim of a feature called "teardrop". The distance between this line and the middle lines of the junction between femur head and neck gave them a measure of the degree of femur head subluxation. They further established that a "normal" diameter of the femur head measures 20% of the height of the pelvis. If the middle line of the neck-head junction was more than 10% of the pelvis height above the reference line they considered the joint to be more than 50% dislocated.
The following types resulted:
| Class | Description | Dislocation >- | Crowe I |
Femur and acetabulum show minimal abnormal development. | >- | The acetabulum shows abnormal development. | >- | The acetabula is developed without a roof. A false acetabulum develops opposite the dislocated femur head position. The joint is fully dislocated. | >- | The acetabulum is insufficiently developed. Since the femur is positioned high up on the pelvis this class is also known as "high hip dislocation". | 100% dislocation |
Incidence
Determining the incidence can be difficult. In addition there is a wide margin in diagnostic results. A German study comparing two methods resulted in twice the usual rate for one method.An instability rate of 1:60 has been described, though this rate drops to 1:240 at one week. The condition is eight times more frequent in females than in males.
Causes
Hip dysplasia is considered to be a multifactorial condition. That means that several factors are involved in causing the condition to manifest. Cause is unknown but common in breech position or large fetal size.Congenital
Some studies suggest a hormonal link. Specifically the hormone relaxinRelaxin
Relaxin is a protein hormone first described in 1926 by Frederick Hisaw.The relaxin-like peptide family belongs in the insulin superfamily and consists of 7 peptides of high structural but low sequence similarity; relaxin-1 , 2 and 3 , and the insulin-like peptides, INSL3, INSL4, INSL5 and INSL6...
has been indicated.
A genetic factor is indicated by the trait running in families and increased occurrence in some ethnic populations (e.g. native Americans
Native Americans in the United States
Native Americans in the United States are the indigenous peoples in North America within the boundaries of the present-day continental United States, parts of Alaska, and the island state of Hawaii. They are composed of numerous, distinct tribes, states, and ethnic groups, many of which survive as...
, Lapps / Sami people
Sami people
The Sami people, also spelled Sámi, or Saami, are the arctic indigenous people inhabiting Sápmi, which today encompasses parts of far northern Sweden, Norway, Finland, the Kola Peninsula of Russia, and the border area between south and middle Sweden and Norway. The Sámi are Europe’s northernmost...
). A locus has been described on chromosome 13. Beukes familial dysplasia, on the other hand, was found to map to an 11-cM region on chromosome 4q35. With nonpenetrant
Penetrance
Penetrance in genetics is the proportion of individuals carrying a particular variant of a gene that also express an associated trait . In medical genetics, the penetrance of a disease-causing mutation is the proportion of individuals with the mutation who exhibit clinical symptoms...
carriers not affected.
Acquired
As an acquired condition it has often been linked to traditions of swaddlingSwaddling
Swaddling is an age-old practice of wrapping infants in swaddling cloths, blankets or similar cloth so that movement of the limbs is tightly restricted. Swaddling bands were often used to further restrict the infant...
infants or use of a cradle board which locks the hip joint in an "adducted" position (pulling the knees together tends to pull the heads of the femur bone out of the sockets or acetabulae) for extended periods. Modern swaddling techniques allow some room for leg movement.
Further risk factors include breech birth
Breech birth
A breech birth is the birth of a baby from a breech presentation. In the breech presentation the baby enters the birth canal with the buttocks or feet first as opposed to the normal head first presentation....
and firstborns. In breech position the femoral head tends to get pushed out of the socket. A narrow uterus also facilitates hip joint dislocation during fetal development and birth.
Diagnostics
Most countries have standard newborn exams that include a hip joint exam screeningScreening (medicine)
Screening, in medicine, is a strategy used in a population to detect a disease in individuals without signs or symptoms of that disease. Unlike what generally happens in medicine, screening tests are performed on persons without any clinical sign of disease....
for early detection of hip dysplasia.
It can often be detected by a "click" or more precisely "clunk" in the hip (although not all clicks indicate hip dysplasia).
Two maneuvers commonly employed for diagnosis in neonatal exams are the Ortolani maneuver and the Barlow maneuver
Barlow maneuver
The Barlow maneuver is a physical examination performed on infants to screen for developmental dysplasia of the hip. It is named for T.G. Barlow, 1962 at Hope Hospital Salford, Manchester....
.
The condition can be confirmed by ultrasound
Ultrasound
Ultrasound is cyclic sound pressure with a frequency greater than the upper limit of human hearing. Ultrasound is thus not separated from "normal" sound based on differences in physical properties, only the fact that humans cannot hear it. Although this limit varies from person to person, it is...
and X-ray
X-ray
X-radiation is a form of electromagnetic radiation. X-rays have a wavelength in the range of 0.01 to 10 nanometers, corresponding to frequencies in the range 30 petahertz to 30 exahertz and energies in the range 120 eV to 120 keV. They are shorter in wavelength than UV rays and longer than gamma...
. Ultrasound imaging yields better results defining the anatomy until the cartilage is ossified. When the infant is around 3 months old a clear roentgenographic image can be achieved. Unfortunately the time the joint gives a good x-ray image is also the point at which nonsurgical treatment methods cease to give good results. In x-ray imaging dislocation may be indicated if the Shenton's line (an arc drawn from the medial aspect of the femoral neck through the superior margin of the obturator foramen
Obturator foramen
The obturator foramen is the hole created by the ischium and pubis bones of the pelvis through which nerves and muscles pass.- General structure :...
) does not result in a smooth arc. However in infants this line can be unreliable as it depends on the rotation of the hip when the image is taken
Asymmetrical gluteal folds and an apparent limb-length inequality can further indicate unilateral hip dysplasia. Most vexingly, many newborn hips show a certain ligamentous laxity
Ligamentous Laxity
Ligamentous laxity is a term given to describe "loose ligaments."In a 'normal' body, ligaments are naturally tight in such a way that the joints are restricted to 'normal' ranges of motion. This creates normal joint stability...
, on the other hand severely malformed joints can appear stable. That is one reason why follow-up exams and developmental monitoring are important. Routine ultrasound screening has been discussed and rejected mainly because the small benefit would not justify the costs.
The Harris hip score (developed by William H. Harris MD, an orthopedist from Massachusetts) is one way to evaluate hip function following surgery. Other scoring methods are based on patients' evaluation like e.g. the Oxford hip score, HOOS and WOMAC
WOMAC
The Western Ontario and McMaster Universities Arthritis Index is a set of standardized questionnaires used by health professionals to evaluate the condition of patients with osteoarthritis of the knee and hip. It can be self-administered and was developed at Western Ontario and McMaster Universities...
score. Children's Hospital Oakland Hip Evaluation Scale (CHOHES) is a modification of the Harris hip score that is currently being evaluated.
Treatment
Given the very real possibility of a limp, constant and/or debilitating pain, complicated treatment and impaired mobility later in life, careful developmental monitoring and early intervention are indicated. The worst possible consequence of non treatment is developing early arthritis, sometimes even during teenage years. All treatment aims to delay the onset of arthritis, but no treatment is fully successful in avoiding it.Harnesses, casts, and traction
Early hip dysplasia can often be treated using a Pavlik harness (see photograph) or the Frejka pillow/splint in the first year of life with usually normal results. Cases of femoral head avascular necrosis have been reported with the use of the Pavlik harness, but whether these cases were due to improper application of the device or a complication encountered in the course of the disorder remains unresolved. Complications arise mainly because the sheet of the iliopsoas muscle pushes circumflex artery against the neck of the femur and decreases blood flow to the femoral head. That is the reason why the Frejka pillow is not indicated in all the forms of the developmental dysplasia of the hip.Other devices employed include the spica cast, particularly following surgical closed reduction. A few weeks in traction
Traction (orthopedics)
In orthopedic medicine, traction refers to the set of mechanisms for straightening broken bones or relieving pressure on the spine and skeletal system.There are two types of traction: skin traction and skeletal traction....
can be used as part of a treatment plan.
Surgery
In older children the hip abductorAbduction (kinesiology)
Abduction, in functional anatomy, is a movement which draws a limb away from the median plane of the body. It is thus opposed to adduction.-Upper limb:* of arm at shoulder ** Supraspinatus** Deltoid* of hand at wrist...
and iliopsoas muscles
Hip flexors
In human anatomy, the hip flexors are a group of skeletal muscles that act to flex the femur onto the lumbo-pelvic complex, i.e., pull the knee upward....
have to be treated surgically because they adapt to the dislocated joint position (contracture
Contracture
A muscle contracture is a permanent shortening of a muscle or joint.. It is usually in response to prolonged hypertonic spasticity in a concentrated muscle area, such as is seen in the tightest muscles of people with conditions like spastic cerebral palsy....
).
Braces and splints are often used following either of these methods to continue treatment.
Although some children "outgrow" untreated mild hip dysplasia and some forms of untreated dysplasia cause little or no impairment of quality of life, studies have as yet been unable to find a method of predicting outcomes. On the other hand, it has often been documented that starting treatment late leads to complications and ends in poor results.
Stem cells
One avenue of research is using stem cells. They are applied in grafting (bone graftingBone grafting
Bone grafting is a surgical procedure that replaces missing bone in order to repair bone fractures that are extremely complex, pose a significant health risk to the patient, or fail to heal properly....
) or by seeding porous arthroplasty prosthesis with autologous fibroblasts or chondrocyte
Chondrocyte
Chondrocytes are the only cells found in cartilage. They produce and maintain the cartilaginous matrix, which consists mainly of collagen and proteoglycans...
progenitor cells to assist in firmly anchoring the artificial material in the bone bed.
Hip replacement and osteotomy
Hip dysplasia is often cited as causing osteoarthritisOsteoarthritis
Osteoarthritis also known as degenerative arthritis or degenerative joint disease, is a group of mechanical abnormalities involving degradation of joints, including articular cartilage and subchondral bone. Symptoms may include joint pain, tenderness, stiffness, locking, and sometimes an effusion...
of the hip at a comparatively young age. Dislocated load bearing surfaces lead to increased and unusual wear. Although there are studies that contradict these findings. (see ) Subsequent treatment with total hip arthroplasty
Arthroplasty
Arthroplasty is an operative procedure of orthopedic surgery performed, in which the arthritic or dysfunctional joint surface is replaced with something better or by remodeling or realigning the joint by osteotomy or some other procedure.-Background:Previously, a popular form of arthroplasty was...
(hip replacement
Hip replacement
Hip replacement is a surgical procedure in which the hip joint is replaced by a prosthetic implant. Hip replacement surgery can be performed as a total replacement or a hemi replacement. Such joint replacement orthopaedic surgery generally is conducted to relieve arthritis pain or fix severe...
) is complicated by a need for revision surgery (replacing the artificial joint) owing to skeletal changes as the body matures, loosening/wear or bone resorption.
Osteotomies
Osteotomy
An osteotomy is a surgical operation whereby a bone is cut to shorten, lengthen, or change its alignment. It is sometimes performed to correct a hallux valgus, or to straighten a bone that has healed crookedly following a fracture. It is also used to correct a coxa vara, genu valgum, and genu varum...
are either used in conjunction with arthroplasty
Arthroplasty
Arthroplasty is an operative procedure of orthopedic surgery performed, in which the arthritic or dysfunctional joint surface is replaced with something better or by remodeling or realigning the joint by osteotomy or some other procedure.-Background:Previously, a popular form of arthroplasty was...
or by themselves to correct misalignment.
Cultural references
In the television program "ERER (TV series)
ER is an American medical drama television series created by novelist Michael Crichton that aired on NBC from September 19, 1994 to April 2, 2009. It was produced by Constant c Productions and Amblin Entertainment, in association with Warner Bros. Television...
," Kerry Weaver
Kerry Weaver
Dr. Kerry Weaver, portrayed by Laura Innes, was an fictional character on the NBC television series ER; she first appeared as a recurring character actor in season 2, and became a regular cast member in season 3. In January 2007, Innes left the show after 12 years and Kerry Weaver moved to...
uses a crutch owing to congenital hip dysplasia. In season 12, she undergoes a hip replacement to cure her dysplasia when her previously untreated joint worsens.
External links
- Hip Preservation Awareness, information and support for hip dysplasia, hip impingement, and related issues in the young adult (12-adult)
- International Hip Dysplasia Institute (IHDI)
- Hip Dysplasia Help
- Online orthopedic textbook http://www.wheelessonline.com
- Childrens Hospital Central California - Developmental Dysplasia of the Hip (DDH)
- United Kingdom Support group for DDH, Clubfoot and other lower limb disorders http://www.steps-charity.org.uk/links/4-15-developmental_dysplasia_of_the_hip_ddh.php