Abstract
Purpose
According to hip ultrasonography by Graf’s method, the type IIa hip has a certain degree of physiological delay in ossification of the bony acetabular roof. The aim of this case–control study was to evaluate the natural history of the type IIa hip.
Methods
Four hundred and thirty-one type IIa hips were identified in 312 of 1,690 ultrasonographically screened newborns with a mean age of 27 days. Parents were accurately informed about the prognosis of such a hip condition and invited for ultrasonographic re-examination at 6–7 weeks of age.
Results
Type IIa hip was more common in newborn girls than in boys (P < 0.001). Among 431 type IIa hips, 146 (34 %) missed the follow-up examination at 6–7 weeks of age. Among the completely followed 285 hips, 225 (79 %) developed into a normal hip at 6–7 weeks of age. Newborn boys’ hips had a higher rate of spontaneous normalization than girls’ hips at 6–7 weeks of age (P = 0.006). All but one type IIa(+) hip became type I without any treatment. According to our management protocol, 35 type IIa(−) hips and one type IIa(+) hip, which later became type IIb, underwent treatment. The rate of treatment was higher in newborn girls’ hips than in boys’ hips (P = 0.019).
Conclusions
As Graf type IIa hip is more common, has a lower rate of spontaneous normalization and higher rate of treatment in newborn girls than in boys, we recommend paying more attention the type IIa hip in newborn girls. The rate of missing the required follow-up is unacceptably high due to parents’ insensitivity regarding the type IIa hip.
Keywords: Developmental dysplasia of the hip, Hip ultrasonography, Graf type IIa hip
Introduction
Developmental dysplasia of the hip (DDH) has no single causative factor, but familial predisposition, prenatal and postnatal mechanical factors, racial predilection and gender (girls have 5–8 times higher incidence) are the well-known predisposing factors [1, 2]. Most of the authors agree that female newborns and newborns of either sex having a history of family members with DDH, breech presentation, torticollis, foot deformities or oligohydroamnios should have more careful newborn hip screening [1].
Hip ultrasonography (USG) provides early detection of DDH by visualizing both the bony and cartilaginous parts of the newborn hip joint [3]. The risk of missing the DDH diagnosis by hip USG is less than 0.1 % [4]. Graf initially described the use of infantile hip USG for the early diagnosis of DDH in the early 1980s [5], and his method has been the most widely used since then.
According to Graf’s method, bony roof (alpha) angle mainly determines the hip type. Cartilaginous roof (beta) angle, age of the patient and the course of the perichondrium are additional determining issues of ultrasonographic hip typing [3]. Graf type IIa hip is called a “physiologically immature hip” in which a certain degree of physiological maturation delay occurs in the bony acetabular roof. The alpha angle is between 50° and 59°, the beta angle is between 55° and 77°, and the patient is younger than 12 weeks of age [3]. There are two subtypes of type IIa hip; type IIa(+) and type IIa(−). The differentiation of type IIa(+) and type IIa(−) should be made at or after the 6th week. If the alpha angle is between 55° and 59° at 6 weeks of age, then it is defined as a type IIa(+) hip. Physiologic immaturation in such a hip is still within acceptable limits for the age [3]. On the other hand, if the alpha angle is between 50° and 54° at 6 weeks of age, then it is called a type IIa(−) hip. The maturation process of such a hip joint can be at risk [3].
Type IIa hip frequently has the potential of maturation until 12 weeks of age. However, at least one follow-up is needed in such a hip at 12 weeks of age at the latest, in order not to miss a failure in the expected maturation [3]. The risk of a true dysplastic hip development in a newborn with an initial Graf type IIa hip is about 10 % [4].
In the literature, the number of studies merely focusing on the natural history of type IIa hip is limited. The aim of this case–control study was to assess the natural history of the Graf type IIa hip as well as the effect of gender on the development of such a hip by using the data obtained from a newborn hip screening program.
Patients and methods
We have been performing ultrasonographic hip screening for 3–4 week-old babies born at our hospital since 2002. According to our screening protocol, we have been determining the risk factors for DDH, informing the parents about DDH within the first 48 h of life and inviting the babies for ultrasonographic examination at 3–4 weeks of age [6]. When we identify a type IIa hip at 3–4 weeks of age, we warn the parents that such a hip usually reaches normality by 12 weeks of age, but at least one ultrasonographic re-examination is needed at 6–7 weeks of age in order not to miss a possible failure in normal hip maturation that can lead to a true hip dysplasia. We do not apply any treatment modality at this stage. During the ultrasonographic re-examination at 6–7 weeks of age, we have three management alternatives. If a type I (normal) hip is present, we discontinue the follow-up. If a type IIa(+) hip is present, we call the baby for another ultrasonographic examination at 12 weeks of age. If a type IIa(+) does not turn into a type I hip at 12 weeks of age, then we immediately begin conservative treatment using Pavlik’s method [7]. If a type IIa(-) hip is present, we immediately start conservative treatment using Pavlik’s method [7]. We follow the treated hips by ultrasonographic examination at 4-week intervals and discontinue the treatment if the ultrasonographic examination reveals a type I hip. Following termination of the treatment, we perform regular radiographic follow-up at 6 months, 1 and 2 years of age, then biannually until skeletal maturity, in order not to miss possible complications, including avascular necrosis of the femoral head (AVN) and residual hip dysplasia, although the risk of such complications may be negligible in such hips.
The ethics board of our hospital initially approved the design and content of the study. We retrospectively investigated the medical records of all screened newborns between 1 July 2002 and 30 June 2008. We subsequently investigated the medical records of Graf IIa hips in detail and analysed the rates of missing the follow-up examination, spontaneous maturation and treatment rates of the hips as well as associated risk factors for DDH and clinical findings in such hips.
The Chi square test and the Fischer’s exact test were used for comparison of the frequencies between two groups and a P value less than 0.05 was considered significant.
Results
The total number of live-borns within the study period was 3,376 at our hospital; all of them were invited for ultrasonographic examination at 3–4 weeks of age. We were able to examine 3,380 hips of 1,690 newborns (1,706 hips of 853 girls and 1,674 hips of 837 boys) with a mean age of 27 days (range from 13 to 43 days) by ultrasonography using Graf’s method [3]. Among these hips, 2,917 were type I (86.3 %), 431 (12.7 %) type IIa, 12 type IIc (0.4 %), 18 type D (0.5 %) and 2 type IIIa (0.1 %) according to Graf’s classification [3]. Among the 321 newborns having unilateral or bilateral type IIa hip, 229 were girls and 92 were boys. Rate of type IIa hip was 2.7 times higher in newborn girls (316/1,706; 18.5 %) than in boys (115/1,674; 6.9 %) (P < 0.001). A risk factor for DDH was present in 44 newborns (13.7 %) having the type IIa hip. Positive family history and multiple pregnancy were the two most common risk factors (Table 1). Among 431 type IIa hips, 29 had positive clinical findings (6.7 %). Asymmetry of the inguinal/thigh folds was the most common clinical finding (Table 2).
Table 1.
Risk factors for DDH seen in 321 newborns with the type IIa hip
| No risk factor for DDH | 277 |
| DDH history in first degree relatives | 16 |
| Multiple pregnancy | 15 |
| Breech presentation at the third trimester | 8 |
| Foot deformity | 3 |
| Oligohydroamniosis | 2 |
Table 2.
Clinical examination results of 431 type IIa hips
| No clinical finding | 402 |
| Asymmetry of the thigh/inguinal folds | 18 |
| Limitation of abduction | 9 |
| Positive Barlow test | 2 |
As stated before, we invited all newborns having a type IIa hip at the initial ultrasonographic examination for control hip ultrasonography at 6–7 weeks of age. We observed that 146 hips (33.9 %) of 107 newborns missed the called follow-up examination. While gathering the data for this study, we contacted some of the parents of 107 babies who had no follow-up records and learned that the main cause of missing the ultrasonographic re-examination at 6–7 weeks of age was that parents had a high level of confidence based on the initial information given to them about the higher expected rate of spontaneous normalization of such hips at a certain time. This confidence kept them away from the control examinations. Missing follow-up rate of type IIa hip in newborn girls and in boys was similar (99/316; 31.3 %) vs. (47/115; 40.9 %) (P = 0.064).
Thus, 285 hips of 214 babies with a complete follow-up were included in the second part of the study. When the records of these 285 type IIa hips were assessed, it was seen that 225 (78.9 %) hips developed normally and became mature hips at 6–7 weeks of age (Table 3). However, the spontaneous normalization rate of type IIa hip in newborn boys was higher than that in girls at 6–7 weeks of age (P = 0.006) (Table 3).
Table 3.
Progression of completely followed type IIa hips at ultrasonographic re-examination
| Type I Hip | Type IIa(+) Hip | Type IIa(−) Hip | Total | |
|---|---|---|---|---|
| Girls | 162 (74.7 %) | 23 (10.6 %) | 32 (14.7 %) | 217 (100 %) |
| Boys | 63 (92.7 %) | 2 (2.9 %) | 3 (4.4 %) | 68 (100 %) |
| Total | 225 | 25 | 35 | 285 |
We immediately started treatment using Pavlik’s method in 35 type IIa(−) hips of 28 babies (25 girls, 3 boys). Among 25 type IIa(+) hips, all but one became type I at 12 weeks of age. One girl’s type IIa(+) hip became type IIb and was treated using Pavlik’s method. Thus, 36 hips of 29 babies (26 girls, 3 boys) required treatment. Among 29 treated babies, 4 (13.8 %) had a risk factor for DDH. Breech presentation was seen in two babies, positive family history in one and multiple pregnancy in one. Among 36 treated hips, 6 (16.7 %) had positive clinical findings. Asymmetry of the thigh/inguinal folds was present in five hips and limitation of abduction in one. In addition, type IIa hip in girls had a 3.5 times higher treatment rate than type IIa hip in boys (33/217; 15.2 vs. 3/68; 4.4 %) (P = 0.019).
All treated hips became normal within a 4-8 week time interval. AVN was not seen in any of these hips at the end of the second year following treatment.
Discussion
This case–control study investigated the development of the physiologically immature type IIa hip. The spontaneous normalization rate of type IIa hip until 6–7 weeks of age was about 80 % in the present series. However, based on the results of this study it is not possible to give the overall rate of spontaneous normalization in the type IIa hip at the end of 12 weeks, as we prefer to treat rather than to follow the type IIa(−) hip.
Failure in the maturation process of type IIa(+) hip is seldom seen. The spontaneous normalization rate of type IIa(+) hip until the age of 3 months is about 95 % [8]. This rate was 97.5 % in the present series, and the results of the present series revealed that the potential need for treatment in the type IIa(+) hip after the age of 3 months was very low. On the other hand, if a type IIa hip does not reach the minimum linear maturation rate, then it is called a type IIa(−) hip. The management of type IIa(−) hip is still controversial and such a hip always carries the risk of overtreatment or development of true hip dysplasia due to delay in the required treatment. About 85 % of type IIa(−) hips reach normality without any treatment at the end of 3 months [8]. In contrast, if the treatment of type IIc and worse hips is initiated after 6 weeks of age, then about one-fourth of such hips carry the risk of development of residual hip dysplasia [9]. Therefore, Graf recommends treating the type IIa(−) hip by an abduction orthosis in order not to miss the valuable time window for normal acetabular development [3, 10]. We have been following Graf’s suggestion concerning the routine treatment of the type IIa(−) hip for many years. In the present series, among the completely followed type IIa hips, 15.6 % became type IIa(−), so we began immediate treatment using Pavlik’s method at the age of 6–7 weeks. It is obvious that prospective controlled studies comparing the effects of wait-and-see regimen and abduction orthosis treatment on the long-term outcome of the type IIa(−) hip are needed.
It was previously reported that an experienced physician could always detect dislocated and subluxated hips (Graf types D, III and IV), but the risk of missing physiologically immature and pathologic hips (Graf types IIa and IIb) by physical examination was usually present [11]. Therefore, this study reinforces the significance of ultrasonographic newborn screening. The results of the present study have revealed that only 7 % of type IIa hips have apparent clinical findings. However, clinical examination may carry the risk of false positive or false negative findings. In addition, only 14 % of the newborns with unilateral or bilateral type IIa hip have a risk factor for DDH. Thus, we can suggest that the risk of missing a type IIa hip is considerably higher when only history and physical examination are taken into consideration for newborn hip screening.
The most important finding of the present study is that type IIa hip is more common and the rate of spontaneous normalization at 6–7 weeks of age is lower in newborn girls than in boys. A similar finding has recently been reported in another study [12]. Therefore, girls have a higher treatment rate than boys in type IIa hips of the present study. This is an expected finding as girls have a 5–8 times higher incidence of DDH than boys [2]. In addition, acetabular development in girls may be more deficient than that of boys during infancy. Based on the findings of the present study, we can suggest that the type IIa hip should be carefully followed, especially in newborn girls; in the existence of a type IIa(−) hip in a girl, immediate treatment is always safer than a wait-and-see regimen to lessen the rate of possible complications including residual hip dysplasia and AVN.
The rate of missing the compulsory follow-up in type IIa hip is about one-third in the present series; this ratio is remarkably high. We have observed that, after being informed about the benign nature of type IIa hips in most of the newborns, the parents commonly believe that their baby’s minor hip problem will be completely resolved without any additional tests or treatments. So, some preventive measures are needed to overcome the parents’ insensitivity for the re-examination of the type IIa hip at 6–7 weeks of age. The information concerning the importance of re-examination should be more precise to avoid parents’ unreasonably raised confidence in the natural history of such a hip.
We can conclude that Graf type IIa hip should be carefully handled in newborn girls, as its natural history is not as good in girls as in boys. Preventive measures are needed to influence the parents’ inconsiderateness regarding their babies’ type IIa hips.
Conflict of interest
None.
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