Childhood developmental dysplasia of the hip (DDH) is the result of many factors including a family history of dysplasia and a higher incidence in infants of families with joint laxity.1 Environmental factors such as breech delivery are also a major issue. Left untreated, hip dysplasia leads to stress loading of the acetabular rim and subsequent premature arthritis. The goal of orthopaedic management is to identify dysplasia at the earliest possible time and to apply treatment methods designed to normalize the hip, which includes treatment with a Pavlik harness or other device. Infants that present after age 6 months commonly require closed reduction plus hip spica immobilization followed by abduction bracing. Regular radiographic follow-up is performed with expectations for normal hip development. Unfortunately this desired course does not always occur, leaving some children with residual dysplasia despite good early treatment.2–4
Residual dysplasia often presents to a treating surgeon in more complex ways. The source of children who present to a surgeon with residual hip dysplasia can include:
- Children who have been previously treated with a recognized history (as described above).
- Children and adolescents with no known prior diagnosis or treatment who are found to have dysplasia on an incidental radiograph but have no symptoms.
- Patients who develop hip symptoms in their childhood or teenage years (no prior x-ray or knowledge of hip dysplasia. Radiographs demonstrate hip dysplasia).
Each of these patient types requires different kinds of surgical decision making.
Children with DDH treated in early childhood have 3 possible courses:
- The dysplasia can resolve completely—as documented by x-ray. Child has no symptoms.
- The dysplasia remains and is outside described radiographic limits, but the child is asymptomatic.
- The dysplasia remains and the child has hip pain.
The focus of this paper is on children and adolescents in group 2 who have residual dysplasia but who have no symptoms. Analysis and treatment of such patients remains controversial because traditionally surgery has not been offered for asymptomatic patients.
Physical Examination in Hip Dysplasia
The physical examination for children with hip dysplasia is notoriously unreliable. Very young children may demonstrate decreased hip abduction and children of all ages can have a limb length difference, although this is more common in children with complete hip dislocation (rather than dysplasia alone).
If the hip dysplasia is substantial, the child may walk with an abnormal gait with an abductor lurch. The Trendelenburg test can be positive, that is the pelvis tends to drop on the side opposite the affected hip. In cases of mild hip dysplasia in the modern child and adolescent, this test is often unreliable. A child who is athletic and has been using the dysplastic hip in sports and other vigorous activities often develops good strength in the abductor and gluteal muscles even though the hip is not perfectly seated.
Physical examination of passive hip motion should be analyzed, but is rarely asymmetric in an older child with unilateral hip dysplasia. The hip impingement test, commonly performed in teenagers and young adults to recreate symptoms, is difficult to interpret because there is no standard as to how much forced flexion one should apply to the hip in determining whether the test is positive.
Literature Review Including Radiographic Standards
Malvitz and Weinstein4 in a further follow-up of the patients studied by Lindstrom and colleagues clearly demonstrated that if a child has hip subluxation, the prognosis will be poor (Fig. 1). Whether 2, 8, or 12 years of age, hip subluxation with a break in Shenton line has a certain poor prognosis when children are followed over time. This elegant follow-up series suggest that dysplasia alone may be monitored until a child is 5 or 6 years of age, whereas dysplasia plus subluxation should be considered for an acetabuloplasty at a younger age.
Murphy et al,5 in their 1995 paper, noted that in long-term follow-up of adults, patients with a center-edge (CE) angle of <16 degrees had a poor prognosis and were reasonably certain of developing premature hip arthritis.
Terjesen6 presented a small series of children with DDH and with long-term follow-up provided concise advice. He noted that if the CE angle was >20 degrees, at long-term follow-up there was only a 5% chance of arthritis. If the child had dysplasia but no subluxation and a CE angle of 10 to 19 degrees, there was a 22% chance of arthritis. If the child had both dysplasia and subluxation, there was an 80% chance of arthritis. This study confirmed the findings of Malvitz and Weinstein.
Weinstein and colleagues have further followed the Iowa City cohort that was first reported in the mid-1970s. Their most recent follow-up, which is not yet published, has demonstrated that dysplasia plus subluxation has a very poor prognosis. They noted good anatomic and clinical results at early follow-up, with 59% of the hips having a Severin 1 or 2 (satisfactory). At 20- to 30-year follow-up of the same patients, only 47% (Severin 1 or 2) and at 40-year follow-up, only 33% of the hips had a satisfactory (Severin 1 or 2) outcome (AAOS ICL—San Francisco—February 2012).
The papers noted above suggest that if a child has significant residual dysplasia, particularly with subluxation, a corrective acetabuloplasty should be performed at a young age (Fig. 2). Lalonde and colleagues provided data as to what age this corrective surgery should be performed. They noted that children treated below the age of 8 years with an acetabuloplasty had a 95% chance of a satisfactory outcome. This contrasted with children treated from the age of 8 to 14 years (Fig. 3) who only had a 50% chance of a good long-term surgical outcome.7
Problems—Pain as Indicator for Surgery
Decision making regarding whether or not a child should have treatment of hip dysplasia has traditionally been dependent on determining whether a child has hip pain. With more educated North American families, where parents are very knowledgeable of the child’s radiographic results and very focused on every detail of a child’s activity, using hip pain to determine whether surgery should be performed becomes more difficult. There are 3 circumstances that the surgeon must deal with:
- A child with no knowledge of prior hip disease who presents with hip pain. X-rays are taken that show hip dysplasia. This turns out to be a relatively straight-forward circumstance. One can almost always deduce that the symptoms are secondary to dysplasia, which should be surgically corrected.
- A second more difficult circumstance includes a child who is being followed for known hip dysplasia but who has no complaints of pain, or who admits to having pain only when vigorously questioned. Such cases often include stoic children who know the consequences of reporting pain—it means surgery (and they want to avoid it).
- A third scenario includes a child, often with only mild dysplasia, whose parents, aware of the x-ray findings, ask the child almost daily whether their hip hurts. We sometimes see children who say they do not have hip pain, but with a parent who assures us that the child is symptomatic.
In introducing the 3 circumstances, it is difficult to make recommendations for both preschoolers and teenagers in the same section. Preschoolers with severe acetabular dysplasia are very likely not to have symptoms, whereas a teenager with severe acetabular dysplasia would almost certainly be symptomatic.
Considering the above, the treating orthopaedic surgeon has a difficult task in analyzing the probable natural history and advisability for corrective surgery for any child or adolescent that is being evaluated for hip dysplasia but has no symptoms. If the child has markedly abnormal acetabular indices, and particularly if there is a break in Shenton line suggesting hip subluxation, clearly one should proceed with a corrective acetabuloplasty.
In rare cases, a femoral osteotomy might be required as well, but usually not in a child with borderline hip dysplasia. The need for a combined femoral varus osteotomy along with an acetabuloplasty increases in a patient who has greater dysplasia. In children aged 4 to 10 years with moderate dysplasia but increased femoral anteversion and coxa valga, one can consider adding a femoral osteotomy. Similarly, in a teenager with severe dysplasia and significant coxa valga, as noted on the true anteroposterior (AP) view of the femur, one may need to add a femoral osteotomy to assure hip stability. The use of femoral osteotomy alone to treat hip dysplasia has long been questioned by Salter and colleagues and now is rarely performed for this purpose in North America.
Monitoring a child with asymptomatic hip dysplasia over time is appropriate and is safe in almost all young children until the age of 4 to 5 years. This provides time for spontaneous radiographic improvement that includes ossification of preossific cartilage in the superolateral rim of the acetabulum, which may be delayed in its appearance in children with residual hip dysplasia.8 In contrast, one must be cautious with this decision making, in that many of the patients in the Iowa series were not treated at a young age but instead monitored as this lateral ossification of preossific cartilage gradually appeared. The ring apophysis is the final ossification center to appear, completing formation of the bony acetabulum in the early teenage years.8
The early interpretation by Lindstrom et al3 suggested that irregular and delayed ossification within the lateral portion of the acetabular roof was a good sign and that the child would go on to develop a normal hip. Longer follow-up, however, demonstrated that in many cases this was not true and that the slow, late appearance of acetabular rim ossification may be a sign of acetabular rim stress rather than acetabular health. This new interpretation has led to more surgery being performed on children and adolescents who have continued radiographic abnormalities, even though they are asymptomatic. This is particularly advised for any child or adolescent who has both residual acetabular deficiency and a break in Shenton line (confirming hip subluxation).
When deciding about surgery, an orthopaedic surgeon should consider their skill and experience in performing corrective acetabular osteotomies. In the past, femoral osteotomies alone were performed for hip dysplasia with the reasoning that most surgeons could readily perform a femoral osteotomy because of their experience with pinning hips and other types of hip surgery performed in a general orthopaedic practice. Now that it is clear that femoral osteotomy alone rarely provides predictable correction of hip dysplasia, surgeons are directed toward acetabular osteotomies that are more difficult to perform. The treating orthopaedic surgeon should consider their ability to predictably perform a corrective acetabular procedure when analyzing the risk-benefit prospects for a child with residual dysplasia. This factor can be considered when deciding whether to treat or refer a patient.
- If a surgeon experienced with performing corrective acetabular osteotomies in childhood sees a patient who has symptoms and abnormal x-ray indices, he/she would likely proceed with corrective acetabular surgery.
- Similarly, an experienced surgeon, in seeing a patient who has no symptoms but who has very abnormal radiographic indices that would project a poor natural history would also proceed with a corrective acetabular osteotomy.
- A surgeon with little experience performing acetabular osteotomies in considering treatment for a child who has no symptoms, but has borderline radiographic indices, might choose to monitor the patient for several additional years for further spontaneous improvement of acetabular coverage. An experienced surgeon might also choose the same course.
- Finally, a less experienced surgeon who sees a child with no symptoms, but who has severely abnormal radiographic indices (that could be predicted to have a poor long-term prognosis based on literature data) should consider referring the patient to a center that has more experience in performing corrective acetabular osteotomies.
Age-related issues must also be considered. The decision making for a preschool child who can be treated with a simple procedure such as a Salter innominate osteotomy may be easier to make than for an asymptomatic teenager that would require a triple innominate osteotomy or a periacetabular procedure. There are some adult hip surgeons who feel that a periacetabular osteotomy should never be performed on an asymptomatic hip. This may be the case if there is no one available to perform such a procedure and the patient cannot be referred. In advanced treatment centers, however, the current literature suggests that such a patient should be considered for corrective surgery.
In summary, it is difficult to provide exact advice as to when a child with asymptomatic hip dysplasia should be treated with a corrective surgical acetabuloplasty. As more long-term studies become available, it would seem that any child who has significant hip subluxation above the age of 3 to 4 years should have surgical correction. Patients with significant dysplasia after the age of 5 to 6 years should likely also be surgically corrected, even if subluxation is not present.
Some might think that this philosophy could lead to overtreatment in the juvenile age group. Counter arguments include that procedures such as the Salter and Pemberton osteotomies, which can be readily performed up to the age of 10 years, are much easier to perform with predictable results. This is compared with a triple pelvic osteotomy or a Ganz periacetabular procedure, typically performed in the teenage or young adult years, when there is less potential for acetabular remodeling.
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