The term congenital hip disease was first used by Wedge and Wasylenko1,2 in 1979 to describe the wide spectrum of anatomic hip abnormalities seen at birth. Other authors subsequently described three radiographic types of the disease present after the neonatal period: 1) dysplasia, in which poor acetabular and femoral head development, with an intact Shenton's line, is found, 2) subluxation, in which Shenton's line is broken due to the proximal and lateral migration of the femoral head, without the latter over passing the upper edge of the acetabulum, and 3) dislocation, in which the femoral head is completely out of the acetabulum.3-5
In our previous studies of congenital hip disease in adult patients, we noted three distinct types of the disease: 1) dysplasia, in which the femoral head, despite some degree of subluxation, is contained within the original acetabulum, 2) low dislocation, in which the femoral head articulates with a false acetabulum that partially covers the true acetabulum, and 3) high dislocation, in which the femoral head has migrated superiorly and posteriorly and articulates with a hollow in the iliac wing, which may have the appearance of a false acetabulum.6,7 Acetabular deficiencies also have been noted7 in all three types.
This study examined the epidemiology and demographics of congenital hip disease in adults as well as the natural history of its three types: dysplasia, low dislocation, and high dislocation.
MATERIALS AND METHODS
From 1970-1996, a total of 468 adult patients (660 hips) with osteoarthritis were examined and underwent followup at regular intervals by the senior author. In a recent revaluation of the records of these patients, it was confirmed that in 356 (54%) hips, osteoarthritis was secondary to congenital hip disease; in 272 (41%) hips, idiopathic osteoarthritis was diagnosed; and in 32 (5%) hips, the diagnosis was uncertain.
Figure 1 : AP radiograph of a 30-year-old patient with osteoarthritis of the left hip secondary to dysplasia shows mild (stage II) osteoarthritis (A). Radiograph taken 1 7 years later shows advanced (stage III) osteoarthritis (B).
Figure 2: AP radiograph of a 35-year-old patient with a right dysplastic hip shows no osteoarthritic changes (stage I, prearthritic) (A). Radiograph taken 7 years after varus intertrochanteric osteotomy (B).
The total number of patients in our series with osteoarthritis secondary to congenital hip disease, 231 patients (356 hips), were used to obtain epidemiologic and demographic data. For the definition of the natural history of the disease, 157 patients (202 hips) who had received no previous treatment prior to their initial examination were separated from the total series. Of these untreated hips 102 were dysplastic, 42 had low dislocation, and 58 had high dislocation. For all of these hips, clinical data and long-term sequential radiographs during adulthood with an average follow-up of 17 years (range: 5-30 years) were available for study.
For the evaluation of the natural history, the following parameters were investigated:
* age at onset of symptoms (pain and limping),
* evolution of radiographic degenerative changes, and
* type of subsequent reconstructive surgery performed.
Epidemiologic and Demographic Data
Of the 356 hips (231 patients) with congenital hip disease, 170 (47.7%) hips were dysplastic, 85 (23.9%) had low dislocation, and 101 (28.4%) had high dislocation. Three hundred thirtyeight (95%) of the hips were in women. Left and right hips were equally involved in dysplasia and low dislocation, and left-to-right hip ratio was approximately 2:1 in high dislocation. Of all 231 patients, 125 (54%) had bilateral congenital hip disease, 17 (7%) had idiopathic osteoarthritis of the contralateral hip, and 89 (39%) had a normal contralateral hip.
In the 102 dysplastic hips that had received no previous treatment, no history of hip disease in childhood was recorded. The disease had been undiagnosed until the onset of symptoms at an average age of 34.5 years (range: 1 8-40 years). Dysfunction, moderate pain during exertion, and a mild limp were the initial symptoms.
Degenerative arthritis developed progressively in three stages following biomechanical patterns (Figure I).8"11 At stage I (prearthritic), the weightbearing surface of the acetabulum showed abnormal obliquity with the femoral head being spherical without osteophytes and cysts. Average age of patients at this prearthritic stage was 37. 1 years (range: 23-49 years).
At stage II, narrowing of the superolateral articular space, elliptical femoral head due to formation of the capital drop, and progressive subluxation were found. Average age of patients with stage II degenerative arthritis was 43.7 years (range: 34-50 years).
At stage III, the involved joint showed advanced degenerative arthritis. Large cysts and osteophytes were present both in the acetabulum and the femoral head. Subluxation of the femoral head was more prominent. Average age of patients at this stage of arthritis was 54.8 years (range: 34-75 years).
In 10 stage I hips, varus intertrochanteric osteotomy was performed, and in 4 stage II hips, valgus intertrochanteric osteotomy was performed (Figures 2 and 3). At final follow-up, all hips with stage UJ degenerative arthritis, except 16 that had not been operated on at all, had undergone total hip arthroplasty (THA) at an average age of 54.9 years (range: 34-75 years).
Patients with low dislocation (42 hips) who had received no previous treatment reported having a limp since early childhood and pain at an average age of 32.5 years (range: 17-50 years). Degenerative arthritis developed within the false acetabulum, following the same biomechanical patterns as in the dysplastic hips (Figure 4).
Three radiographic types of low dislocation according to the extent of the covering of the true acetabulum were recognized. In type I (13 hips, 31%), two thirds of the true acetabulum were covered by the false one; in type II (17 hips, 40%), one half of the true acetabulum was covered; and in type III (12 hips, 29%), one third of the true acetabulum was covered.
All hips with low dislocation, except two, had undergone THA by final follow-up. Average age of patients at the time of surgery was 51.4 years (range: 34-74 years).
Patients with high dislocation (58 hips) who had received no previous treatment also reported having a limp since early childhood. Limping was more severe in those patients with unilateral involvement. In 30 (52%) hips in which a false acetabulum was present, pain had started at an average age of 31.2 years (range: 18-40 years), while in 28 (48%) hips without a false acetabulum, pain had started at an average age of 46.4 years (range: 30-65 years).
In all patients with high dislocation, a 10°-25° valgus deformity of the ipsilateral knee was found; in unilateral cases, a coexisting thoracolumbar scoliosis was present, and in all patients with bilateral high dislocation, increased lordosis of the lumbar spine also was found. Degenerative arthritis had developed in all patients with a false acetabulum (Figure 5).
Figure 3: AP radiograph of a 42-year-old patient with a right dysplastic hip shows stage 11 osteoarthritic changes (A). Radiograph taken 12 years after a valgus intertrochanteric osteotomy (B).
Figure 4: AP radiograph of a 24-year-old patient with a type III low dislocation (one-third coverage of the true acetabulum) of the right hip (A). Radiograph taken 26 years later shows osteoarthritic changes within the false acetabulum (B).
In the 30 hips with a false acetabulum, THA was performed at an average age of 48.8 years (range: 23-63 years), while in 22 hips without a false acetabulum, THA was performed at an average age of 54.7 years (range: 37-68 years).12 Six hips without a false acetabulum have not been operated on yet.
There is little in the literature referring to the natural history of congenital hip disease. Stulberg and Harris13 studied the relationship between acetabular dysplasia and the development of osteoarthritis of the hip. Wedge and Wasylenko2 referred particularly to adult hips with no previous treatment to demonstrate the relationship between a patient's functional level and the development of osteoarthritis at the time of examination.
Cooperman et al14 conducted follow-up on 32 hips in adults with acetabular dysplasia for an average of 22 years to determine the natural history of this particular type of disease (dysplasia). Weinstein,5,15 in two classic articles, reviewed the literature on the normal growth and development of the hip joint, the etiology and epidemiology of congenital dislocation, and the natural history of complete dislocation, dysplasia and subluxation. Malvitz and Weinstein16 presented the long-term (15-53 years) functional and radiographic results of closed reduction in congenital dysplasia.
Figure 5: AP radiograph of a 20-year-old patient with bilateral high dislocation shows a false acetabulum in the right hip only (A). Radiograph taken at age 40 years shows osteoarthritis in the right hip with the false acetabulum only (B).
Classification of Congenital Hip Disease in Neonatal and Adult Life
Because of the use of different terms to describe the whole spectrum of the disease in infancy and failure to recognize different distinct types of it in adulthood, an understanding of the natural history becomes difficult. The most popular term used for all types of the disease is developmental dysplasia and dislocation. However, we consider the general term congenital hip disease and the radiographic classification of dysplasia, subluxation, and complete dislocation in infancy1,35 and dysplasia, low dislocation, and high dislocation in adult life6,7 as the most appropriate terms and classification (Table).
Serious confusion also derives from the use of the term subluxation in adult patients. Subluxation may be seen in a dysplastic hip as the disease progresses, while a hip with low dislocation is, by definition, subluxed. For this reason, subluxation is a misleading term in the description of an adult hip and should be avoided.7
Dysplasia is the most common type of congenital hip disease seen in adults. 17 In the present series, the incidence of dysplasia among adult patients with untreated congenital hip disease was 47.7%. The majority of dysplastic hips remain undiagnosed until the onset of early symptoms (slight pain and a limp), usually during the second or third decade of a patient's life.
Degenerative changes develop in three stages according to biomechanical patterns.81 ' Stage I is the "golden" time for a reconstructive varus intertrochanteric osteotomy or pelvic osteotomy, while in stage II, a valgus osteotomy is indicated (Figures 2 and 3). Dysplastic hips with stage III degenerative changes are best treated by THA.
Patients with low dislocation limp from infancy, but pain usually starts between the ages of 25 and 30. Degenerative changes develop within the false acetabulum and progress according to the same biomechanical principles as in dysplasia (Figure 4). Usually, between the ages of 45 and 50, patients with low dislocation need a THA. The effect of intertrochanteric osteotomy or pelvic osteotomy on low dislocation is uncertain.
The natural history of completely dislocated hips depends mainly on two factors: the unilaterality or bilaterali ty of the disease and whether a false acetabulum is present.5 In unilateral involvement, functional disability is greater. Limp is more severe from infancy, and early in adult life, patients complain of muscle fatigue pain, low back pain, and pain from the ipsilateral knee, which presents a progressively increasing valgus deformity. These patients need early treatment by THA.
The false acetabulum is not a constant finding in high dislocation, but when present, leads to the development of degenerative changes and early THA is necessary (Figure 5). When a false acetabulum is not present, the height of the dislocation, measured by the method of Crowe et al,18 increases gradually and causes pain mainly from muscle fatigue. We do not know why a false acetabulum is formed in some hips and not in others.
In this study, the natural history of congenital hip disease was assessed in patients who had received no previous treatment prior to their initial examination only as previous treatment alters the natural history of the disease (Figure 6).
Knowledge of the natural history of congenital hip disease facilitates the understanding of the potential development and progress of the disease, which differs among the three types. It can lead to a better understanding of the anatomical abnormalities found in the different types and thus facilitate preoperative planning and choice of the most appropriate therapeutic measures for adult patients.
Figure 6: AP radiographs of a patient who in infancy had a right hip with dysplasia and a left hip with subluxation. Closed reduction followed by the application of a hip-spica cast for both hips was the initial treatment at age 2 years. An intertrochanteric osteotomy was performed at age 12 years on the left hip. Radiograph before treatment at 2 years (A). Radiograph taken at 12 years shows the right hip is normal while the left hip is in subluxation (B). Radiograph taken at age 1 6 years (4 years post-osteotomy) shows the left hip remains unreduced (C). Radiograph taken at age 38 years shows the right hip is normal while the left hip has developed a type I low dislocation (two-thirds coverage of the true acetabulum) with osteoarthritic changes within the false acetabulum (D).
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2. Wedge JH, Wasylenko MJ. The natural history of congenita! disease of the hip. J Bone Joint Surg Br. 1979; 61:334-338.
3. Mubarak SJ. Developmental hip dysplasia and dislocation. Presented at: the 62nd annual meeting of the American Academy of Orthopaedic Surgeons; February 16-21. 1995; Orlando. Fla.
4. Wenger DR. Developmental hip dysplasia and dislocation. Presented at: the 62nd annual meeting of the American Academy of Orthopaedic Surgeons; February 16-21, 1995; Orlando, Fla.
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11. Pawels F. Biomechanical principles of varus/valgus intertrochanteric osteotomy in the treatment of Osteoarthritis of the hip. In: Schatzker J, ed. Intertrochanteric Osteotomy. Berlin, Germany: Springer- Verlag. 1984:3-23.
12. Hartofilakidis G. Stamos K, Karachalios Th. Treatment of high dislocation of the hip in adults with THA. J Bone Joint Surg Am. 1998: 80:510-517.
13. Stulberg SD, Harris WH. Acetabular dysplasia and the development of osteoarthritis of the hip. In: TAe Hip. Proceedings of the Second Open Scientific Meeting of the Hip Society. St Louis, Mo: CV Mosby; 1974:82-93.
14. Cooperman DR, Wallesten R, Stulberg SD. Acetabular dysplasia in the adult. Clin Orthop. 1983: 175:79-85.
15. Weinstein SL. Congenital hip dislocation. Long-range problems, residual signs and symptoms after successful treatment. Clin Orthop. 1992;281:69-74.
16. Malvitz TA, Weinstein SL. Closed reduction for congenital dysplasia of the hip. Functional and radiographic results after an average of 30 years. J Bone Joint Surg Am. 1994; 76:1777-1789.
17. Murphy SB, Ganz R, Muller ME. The prognosis in untreated dysplasia of the hip. A study of radiographic factors thai predict the outcome. J Bone Joint Surg Am. 1995; 77:985-989.
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Classification of Congenital Hip Disease in Neonatal and Adult Life