CONGENITAL DISLOCATION OF HIP
Congenital dislocation of the hip (CDH) varies greatly in incidence among different peoples and in different regions. It is more common in girls than in boys in the ratio of about 5:1; and it is ten times as common after breech deliveries as cephalic, but with the girl-to-boy ratio reduced to 2:1. It is more common in dizygotic twins, in the first-born girl, and in those born during winter months than in their opposites. Except for teratologic dislocations, as in some instances of proximal focal femoral deficiency, prenatal and perinatal relaxation of the capsule of the hip joint appears to be the primary cause of this of-ten disabling condition that can be recognized in the newborn. Limitation of abduction by restrictive clothing or by actual binding of the legs in adduction, a practice still common in various cultures, may be responsible for postnatal onset of dislocation as late as the latter half of the first year. Dysplasia of the acetabulum (indicated by increased acetabular angle), elongation of the capsule, femoral antever-sion, and contracture of the periarticular muscles are all secondary complications of primary hypotonia of the capsule and consequent malposition of the cartilaginous femoral head (Figs 2-102 and 2-103). Morphologic and histochemical studies of joint capsule and ligamentum teres biopsies during open reduction of CDH have demonstrated changes that were believed to be secondary to the mechanical stresses caused by the dislocation. The high incidence of CDH in girls suggested a hormonal factor (Andren) but no conclusive support for this has appeared. Thieme and colleagues measured the urinary estrogen content in 16 patients with CDH and 19 matched controls during the first 6 days of life and found no significant differences.
Initially, radiographic identification of congenital dislocation of the hip was made in late childhood. In 1925, Hilgenreiner described early radiographic diagnosis in infants by measurement of acetabular an-gles (Fig 2-104). The method was considered objective and was accepted with enthusiasm even after 1956 when Coleman and Caffey, independently, challenged the validity of the "standards" for acetabular angles. It was pointed out that the number of patients previously evaluated was inadequate for a meaningful statistical value for the measurements. Furthermore, in practice, values reported as normal averages were used as limiting values between normal and abnormal. Caffey's study of over 600 infants indicated that radiographic examination, apart from demonstrating gross dislocation or malformation, had little to offer in the diagnosis of CDH in the newborn period. Nevertheless, radiographic methods (Andren and von Rosen) for identification of CDH has enjoyed considerable popularity among orthopedists even though strict adherence to the positioning standards is seldom accomplished. At present, US has become the procedure of choice for the diagnosis of congenital hip dislocation in the newborn and young infant (Zieger and Schulz). MRI and CT imaging have been used successfully, but are too elaborate for routine screening.
The monumental studies of CDH in the newborn by Andren and von Rosen, and by Palmen, indicated that a reliable, simple indication of CDH in the newborn period is clinical examination. The Ortolani maneuver, which detects the return of a dislocated femoral head to its acetabular cavity, coupled with the "subluxation provocation" maneuver (Palmen, Coleman), which recognizes dislocatability under appropriate physical stresses, have been utilized by trained examiners in studies of almost 500,000 children in Sweden and in over 62,000 children born during 1 year in Yugoslavia. In these and similar studies, all infants with positive tests were treated with devices maintaining constant, gentle abduction and external rotation of the hips for approximately 6 weeks, with the net result that gross dislocations and other sequelae of CDH in childhood have been virtually eliminated in infants so treated. Infants immobilized in plaster casts may develop necrosis of the femoral head ossification centers in the originally healthy femur as well as in the dislocated femur during treatment for unilateral CDH (Gore). Rarely, Perthes disease develops several years after apparently successful, uncomplicated closed reduction.
It is advisable to reexamine all infants during well-baby visits for clinical signs of hip abnormality up to the time of ambulation, as both Palmen, and Brecelj and associates, found that a small number of children, clinically and radiologically normal as newborns, may develop distinct dislocation by the second half of the first year. Closed reduction is still feasible with positional treatment in such cases, but for longer periods of time than in the newborn. In patients diagnosed late, especially those unresponsive to attempted closed reduction, arthrography may be helpful by demonstrating contraction of the capsule or interposition of the capsule and labrum between the head and the acetabular cavity preventing reduction. CT can demonstrate the exact location of the structures and can evaluate anterior or posterior malposition of the head, even through a plaster cast.
The application of US to the diagnosis of congenital dislocation of the hip has provided a noninvasive, nonionizing, repeatable, and sensitive method for evaluation of equivocal clinical signs of hip abnormality. The technique of Graf and his standards are used by many ultrasonographers with very satisfying results. Infants up to the age of 1 year can be examined satisfactorily with the usual 5-MHz transducers; in newborns, a 7.5-MHz transducer is recommended.
The cartilage components of the hip joint as well as the capsule and the margins of the bony structures can be visualized (Fig 2-105). US has been found to be 100% sensitive and highly specific for monitoring the position of the femoral head and the acetabular cavity in patients under treatment with the popular Pavlik harness.
Occasionally, newborn infants will have limitation of abduction and external rotation of the hip without clear-cut dislocation. Radiographs are normal except for adduction of the affected femur; the pelvis tends to be rotated and a true AP projection is difficult to obtain. It has been suggested that the adductor muscles on the affected side are "tight" be-cause of the fetal position. Spontaneous resolution is the rule. Bowyer and associates reported a similar clinical finding, not present at birth, in older infants during the first year of life. Radiologic findings in these infants include acetabular angles greater on the affected than on the normal side, retardation of epiphyseal development of the ipsilateral femoral head, pelvic obliquity, and rotational deformity of the pelvis in the transaxial plane. Plagiocephaly was present in almost all cases. The authors believed that these features are due to postnatal postural habits and are self-correcting. None of 98 patients they examined had "clicks" (i.e., positive Ortolani or Palmen maneuver s).
Radiographic features similar to those described for CDH (shallow acetabuli with highly angled roofs, lateral and cephalic displacement of the upper end of the femur, and small ossification center for the head) can be observed occasionally in congenital cretins. With improved tone and extension of ossification into the radiolucent cartilage of the acetabular roof following appropriate therapy, spontaneous resolution of the "dislocation" can occur. Recurrent dislocation has been observed in a 26-month-old girl with congenital indifference to pain.
Acquired traumatic dislocation of the hip is rare; about four fifths of the cases occur in boys. Two thirds of them have complete recovery, and very few develop late coxa plana. Acquired nontraumatic dislocation may develop in neuromuscular disease (Fig 2-106) and is frequent in cerebral palsy. It can develop fairly rapidly in pyarthrosis of the hip; in such cases, clinical signs of infection and swelling of soft tissues may point to the proper diagnosis. Traumatic epiphyseal separation of the femoral head or fracture of the femoral neck in very young infants may simulate congenital dislocation as the head and neck are still cartilaginous and not visible radiographicaly. With clinical or radiologic signs of abnormal orientation of the upper end of the femur and the adjacent acetabular cavity, this possibility must be entertained, especially when they are associated with a history of abnormal presentation and difficult delivery, or of other trauma tic episodes.
Congenital dislocation of the hip (CDH) varies greatly in incidence among different peoples and in different regions. It is more common in girls than in boys in the ratio of about 5:1; and it is ten times as common after breech deliveries as cephalic, but with the girl-to-boy ratio reduced to 2:1. It is more common in dizygotic twins, in the first-born girl, and in those born during winter months than in their opposites. Except for teratologic dislocations, as in some instances of proximal focal femoral deficiency, prenatal and perinatal relaxation of the capsule of the hip joint appears to be the primary cause of this of-ten disabling condition that can be recognized in the newborn. Limitation of abduction by restrictive clothing or by actual binding of the legs in adduction, a practice still common in various cultures, may be responsible for postnatal onset of dislocation as late as the latter half of the first year. Dysplasia of the acetabulum (indicated by increased acetabular angle), elongation of the capsule, femoral antever-sion, and contracture of the periarticular muscles are all secondary complications of primary hypotonia of the capsule and consequent malposition of the cartilaginous femoral head (Figs 2-102 and 2-103). Morphologic and histochemical studies of joint capsule and ligamentum teres biopsies during open reduction of CDH have demonstrated changes that were believed to be secondary to the mechanical stresses caused by the dislocation. The high incidence of CDH in girls suggested a hormonal factor (Andren) but no conclusive support for this has appeared. Thieme and colleagues measured the urinary estrogen content in 16 patients with CDH and 19 matched controls during the first 6 days of life and found no significant differences.
Initially, radiographic identification of congenital dislocation of the hip was made in late childhood. In 1925, Hilgenreiner described early radiographic diagnosis in infants by measurement of acetabular an-gles (Fig 2-104). The method was considered objective and was accepted with enthusiasm even after 1956 when Coleman and Caffey, independently, challenged the validity of the "standards" for acetabular angles. It was pointed out that the number of patients previously evaluated was inadequate for a meaningful statistical value for the measurements. Furthermore, in practice, values reported as normal averages were used as limiting values between normal and abnormal. Caffey's study of over 600 infants indicated that radiographic examination, apart from demonstrating gross dislocation or malformation, had little to offer in the diagnosis of CDH in the newborn period. Nevertheless, radiographic methods (Andren and von Rosen) for identification of CDH has enjoyed considerable popularity among orthopedists even though strict adherence to the positioning standards is seldom accomplished. At present, US has become the procedure of choice for the diagnosis of congenital hip dislocation in the newborn and young infant (Zieger and Schulz). MRI and CT imaging have been used successfully, but are too elaborate for routine screening.
The monumental studies of CDH in the newborn by Andren and von Rosen, and by Palmen, indicated that a reliable, simple indication of CDH in the newborn period is clinical examination. The Ortolani maneuver, which detects the return of a dislocated femoral head to its acetabular cavity, coupled with the "subluxation provocation" maneuver (Palmen, Coleman), which recognizes dislocatability under appropriate physical stresses, have been utilized by trained examiners in studies of almost 500,000 children in Sweden and in over 62,000 children born during 1 year in Yugoslavia. In these and similar studies, all infants with positive tests were treated with devices maintaining constant, gentle abduction and external rotation of the hips for approximately 6 weeks, with the net result that gross dislocations and other sequelae of CDH in childhood have been virtually eliminated in infants so treated. Infants immobilized in plaster casts may develop necrosis of the femoral head ossification centers in the originally healthy femur as well as in the dislocated femur during treatment for unilateral CDH (Gore). Rarely, Perthes disease develops several years after apparently successful, uncomplicated closed reduction.
It is advisable to reexamine all infants during well-baby visits for clinical signs of hip abnormality up to the time of ambulation, as both Palmen, and Brecelj and associates, found that a small number of children, clinically and radiologically normal as newborns, may develop distinct dislocation by the second half of the first year. Closed reduction is still feasible with positional treatment in such cases, but for longer periods of time than in the newborn. In patients diagnosed late, especially those unresponsive to attempted closed reduction, arthrography may be helpful by demonstrating contraction of the capsule or interposition of the capsule and labrum between the head and the acetabular cavity preventing reduction. CT can demonstrate the exact location of the structures and can evaluate anterior or posterior malposition of the head, even through a plaster cast.
The application of US to the diagnosis of congenital dislocation of the hip has provided a noninvasive, nonionizing, repeatable, and sensitive method for evaluation of equivocal clinical signs of hip abnormality. The technique of Graf and his standards are used by many ultrasonographers with very satisfying results. Infants up to the age of 1 year can be examined satisfactorily with the usual 5-MHz transducers; in newborns, a 7.5-MHz transducer is recommended.
The cartilage components of the hip joint as well as the capsule and the margins of the bony structures can be visualized (Fig 2-105). US has been found to be 100% sensitive and highly specific for monitoring the position of the femoral head and the acetabular cavity in patients under treatment with the popular Pavlik harness.
Occasionally, newborn infants will have limitation of abduction and external rotation of the hip without clear-cut dislocation. Radiographs are normal except for adduction of the affected femur; the pelvis tends to be rotated and a true AP projection is difficult to obtain. It has been suggested that the adductor muscles on the affected side are "tight" be-cause of the fetal position. Spontaneous resolution is the rule. Bowyer and associates reported a similar clinical finding, not present at birth, in older infants during the first year of life. Radiologic findings in these infants include acetabular angles greater on the affected than on the normal side, retardation of epiphyseal development of the ipsilateral femoral head, pelvic obliquity, and rotational deformity of the pelvis in the transaxial plane. Plagiocephaly was present in almost all cases. The authors believed that these features are due to postnatal postural habits and are self-correcting. None of 98 patients they examined had "clicks" (i.e., positive Ortolani or Palmen maneuver s).
Radiographic features similar to those described for CDH (shallow acetabuli with highly angled roofs, lateral and cephalic displacement of the upper end of the femur, and small ossification center for the head) can be observed occasionally in congenital cretins. With improved tone and extension of ossification into the radiolucent cartilage of the acetabular roof following appropriate therapy, spontaneous resolution of the "dislocation" can occur. Recurrent dislocation has been observed in a 26-month-old girl with congenital indifference to pain.
Acquired traumatic dislocation of the hip is rare; about four fifths of the cases occur in boys. Two thirds of them have complete recovery, and very few develop late coxa plana. Acquired nontraumatic dislocation may develop in neuromuscular disease (Fig 2-106) and is frequent in cerebral palsy. It can develop fairly rapidly in pyarthrosis of the hip; in such cases, clinical signs of infection and swelling of soft tissues may point to the proper diagnosis. Traumatic epiphyseal separation of the femoral head or fracture of the femoral neck in very young infants may simulate congenital dislocation as the head and neck are still cartilaginous and not visible radiographicaly. With clinical or radiologic signs of abnormal orientation of the upper end of the femur and the adjacent acetabular cavity, this possibility must be entertained, especially when they are associated with a history of abnormal presentation and difficult delivery, or of other trauma tic episodes.
