Abstract
Background:
The incidence of developmental dysplasia of the hip (DDH) in Japanese newborns has reduced drastically following a primary prevention campaign initiated around 1972 to 1973; this perinatal education campaign promoted maintaining the hips of newborns in the naturally flexed-leg position. The purpose of the present study was to describe the life course epidemiology of hip osteoarthritis (OA) in adolescent and adult patients and to assess its association with exposure to the primary prevention campaign for DDH.
Methods:
We included new patients with hip OA diagnosed from January 1, 2022, to December 31, 2022, at 12 core hospitals (8 special-function hospitals and 4 regional medical care support hospitals). The trend in the percentage of hips with a history of DDH treatment in childhood was estimated with use of a centered moving average using the birth year of the patient. We compared the prevalence of severe subluxation (Crowe type II, III, or IV) between patients with secondary hip OA due to hip dysplasia who were born in or before 1972 and those who were born in or after 1973.
Results:
Overall, 1,095 patients (1,381 hips) were included. The mean age at the time of the survey was 63.5 years (range, 15 to 95 years). A total of 795 patients (1,019 hips; 73.8% of hips) were diagnosed with secondary OA due to hip dysplasia. Approximately 13% to 15% of hips among patients born from 1963 to 1972 had a history of DDH treatment in childhood; however, the percentage decreased among patients born in or after 1973. The prevalence of severe subluxation (Crowe type II, III, or IV) among patients born in or after 1973 was 2.4%, which was significantly less than that among patients born in or before 1972 (11.1%; odds ratio, 0.20; p < 0.001).
Conclusions:
As of 2022, secondary hip OA due to hip dysplasia is still responsible for most new cases of adolescent and adult hip OA seen in core hospitals in Japan. However, the perinatal education campaign initiated 50 years ago, which utilized a population approach and advocated for maintaining the hips of newborns in the naturally flexed-leg position, may have improved the environmental factors of DDH, as indicated by the apparently reduced need for treatment of DDH in childhood and the associated severe subluxation. This may result in a reduced need for challenging hip surgery later in life.
Level of Evidence:
Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.
Hip osteoarthritis (OA) is one of the most common and most disabling conditions affecting the older population; most adult patients with hip OA in Japan have hip dysplasia, a disease concept that indicates radiographic findings of mechanical instability1. Shifting the efforts of hip OA research and public health intervention to primary prevention2 may greatly improve the current management paradigm. However, among the risk factors for hip OA in adults, only a few are known as modifiable factors, such as body weight3. A reevaluation of hip OA as having a sequential pathology from newborns to older adults might effectively reveal modifiable behavioral changes in the earlier life stage4.
Developmental dysplasia of the hip (DDH) is a disease characterized by hip dislocation or subluxation and acetabular morphological abnormalities observed in infants and children5. The incidence of DDH is racially different and is reportedly high in Japanese6, Singaporean5, Native American7, and Turkish populations8, and in Sami populations in Scandinavia9. In the Japanese population prior to 1965, dislocation was present in approximately 1.1% to 3.5% of all newborns6, and severe subluxation was present among adults10 (Fig. 1).
Fig. 1.
Radiograph demonstrating a once-typical case of hip osteoarthritis (OA) in Japan. The radiograph shows the hips of a female patient born in 1964 who had a history of DDH treatment in childhood. She began experiencing hip pain in her mid-40s and first visited a core hospital at 58 years old. We diagnosed both hips as having secondary OA due to hip dysplasia; the left hip showed Crowe type-II subluxation.
Hip dislocation was common worldwide half a century ago11,12. The Japanese people had a tradition of forcibly maintaining the legs of a newborn in an extended position with use of a diaper6,13, as is done through swaddling in some regions of China14; this position was confirmed to cause dislocated hips in animal models15. However, around 1972 to 1973, Ishida and Yamamuro6,13 initiated a program to educate obstetricians, midwives, health nurses, and pregnant women that the hips of newborns should be in the naturally flexed-leg position, as the primary prevention of DDH, and that this position promotes acetabular development. Manufacturers of diapers, diaper covers, and baby clothes were advised on the proper design of clothing that allows newborns’ hips and knees to move freely. This campaign, which utilized a population approach16, was extended nationwide in Japan6,17, and reports have shown that DDH has since drastically reduced6,13,18.
The perinatal education campaign for preventing DDH via a population approach might be associated with the epidemiology of hip OA in adolescence and adulthood; however, to our knowledge, no studies have reported this perspective. The purpose of the present study was to describe the life course epidemiology of hip OA in adolescents and adults and to investigate its association with past exposure to the perinatal education campaign for the primary prevention of DDH.
Materials and Methods
Study Design
Following approval from our institutional review board, patient recruitment for this multicenter, cross-sectional study was conducted from January 1, 2022, to December 31, 2022. We utilized a life course approach, which investigates the long-term effects of physical and social exposures in the fetal period, childhood, adolescence, and early adulthood on adult disease risk4. An opt-out patient consent procedure was utilized to obtain the routine medical care information of the patients. This study was conducted per the tenets of the Medical Research Involving Human Subjects Act and the principles of the Declaration of Helsinki. This paper was structured according to the STROBE (Strengthening the Reporting of Observational Studies in Epidemiology) statement19. We enrolled participants from 12 core hospitals (8 special-function hospitals and 4 regional medical care support hospitals) located in various prefectures of Japan, subsequently recruiting >1,000 patients with hip OA who first reported to the core hospitals in 2022 (Fig. 2).
Fig. 2.
Flow diagram showing the patient-selection process for the analysis. The prefectures in gray indicate the location of the 12 core hospitals (8 special-function hospitals and 4 regional medical care support hospitals) that participated in the study.
Patient Selection
New patients ≥15 years old who visited any of the 12 core hospitals with a chief concern related to hip pain were assessed for eligibility. Following prior studies1,20, we included patients diagnosed with hip OA on the basis of clinical and radiographic findings of hip pain, no history of inflammation, and joint space narrowing. We also included patients with hip pain without joint space narrowing who had abnormal joint morphology such as hip dysplasia21-23. Patients with a history of previous hip surgery on the affected side were excluded because of difficulties in morphological evaluation.
Radiographic Assessment of Hip OA
The stage of OA was assessed with use of the Kellgren-Lawrence grade24. The minimum joint space width25 was measured and utilized as supportive information because it could be increased in conditions such as hip OA following Legg-Calvé-Perthes disease26.
Primary Outcome: Descriptive Epidemiology
Prevalence of Hip OA Subclassifications by Patient Age
The hip OA subclassification was determined with use of an algorithm based on the progress of the arthropathy, patient history, radiographs (supine hip anteroposterior and lateral or Lauenstein views), and magnetic resonance imaging for specific patients (Fig. 3). Hip OA etiology was subclassified into 9 types: rapidly destructive coxopathy, Legg-Calvé-Perthes disease, slipped capital femoral epiphysis, trauma, skeletal dysplasia, hip dysplasia, femoroacetabular impingement (FAI), subchondral insufficiency fracture (SIF) of the femoral head, and primary OA.
Fig. 3.
Diagnostic criteria of the hip OA subclassification. This algorithm was shared with the 12 core hospitals before January 1, 2022. The final diagnoses were determined by a conference at each facility; therefore, a reliability assessment was not performed. If the diagnosis was inconclusive, a consensus meeting was held among members of the collaborating institutions. OA = osteoarthritis, RDC = rapidly destructive coxopathy, LCPD = Legg-Calvé-Perthes disease, SCFE = slipped capital femoral epiphysis, DDH = developmental dysplasia of the hip, LCEA = lateral center-edge angle, ARO = acetabular roof obliquity, FAI = femoroacetabular impingement, MRI = magnetic resonance imaging, SIF = subchondral insufficiency fracture.
Hip dysplasia was diagnosed according to the criteria by Nakamura et al.27: a Sharp angle of ≥45°, a lateral center-edge angle (LCEA) of ≤20°, or an acetabular roof obliquity (ARO) of ≥15°. These 3 angles were measured using the lateral acetabular rim as described by Wiberg12,28, with the reference line passing through the bilateral acetabular teardrops on the anteroposterior view.
FAI29 was diagnosed according to the Japanese Hip Society criteria30. Pincer-type FAI was diagnosed in patients with an LCEA of ≥40°, an LCEA of ≥30° and an ARO of ≤0°, or an LCEA of ≥25° and a positive crossover sign. Cam-type FAI was diagnosed in patients with an LCEA of ≥25° and 1 of the following: an alpha angle of ≥55°, a head-neck offset ratio of <0.14, a positive pistol grip deformity, or a positive herniation pit. SIF of the femoral head, caused by osteoporosis and resultant femoral head collapse, has also been proposed as an etiology of secondary OA31.
Secondary Outcomes
Patients with a History of DDH Treatment in Childhood
If primary prevention successfully prevents DDH, a patient would not need to receive any treatment for DDH in childhood. All patients included in the primary analysis were surveyed for their history of DDH treatment in childhood. We utilized information from the patient’s self-reported history of DDH treatment before 15 years of age (i.e., before the closure of the epiphyseal line). Given the likelihood of recall bias and the fact that orthotic treatment is usually applied to both sides, we considered a patient to have undergone treatment if there was a history of treatment on either side.
Severe Subluxation Among Patients with Hip Dysplasia
We assumed that severe subluxation is a result of the failure of both primary and secondary prevention. Therefore, we utilized the Crowe classification10, the most commonly utilized classification system for dysplastic hips in adult patients32, to evaluate subluxation in patients with secondary hip OA due to hip dysplasia. We defined severe subluxation as Crowe type II, III, or IV. The measurements were made on the radiographic anteroposterior view and were classified on the basis of the amount of subluxation: Crowe type I, <50% subluxation; Crowe type II, 50% to 75%; Crowe type III, 75% to 100%; and Crowe type IV, >100%.
Statistical Analysis
We determined the prevalence of secondary OA due to hip dysplasia among new patients with hip OA at the core hospitals. Patients were grouped according to their age at the time of the visit (15 to 29, 30 to 39, 40 to 49, 50 to 59, 60 to 69, 70 to 79, and ≥80 years old) based on their year of birth4. The number of patients in the assessment groups and the percentage of the total study population were then described for each group. A Fisher exact test was performed for categorical variables, and a Kruskal-Wallis test was performed for continuous variables compared among multiple groups. The intra- and interobserver reliability of the radiographic measurements are presented in Appendix Supplementary Table 1.
To smooth the data and to estimate the trend regarding the percentage of hips with a history of DDH treatment in childhood, we utilized a centered moving average33 (see Appendix Supplementary Table 2), a method that is commonly utilized for data smoothing, especially for time series data.
Patients with secondary hip OA due to hip dysplasia were divided into those born in or before 1972 and those born in or after 1973, and the prevalence of severe subluxation, defined as Crowe type II, III, or IV, was investigated. The prevalence of severe subluxation was compared between groups with use of a Fisher exact test. The odds ratio and 95% confidence interval were calculated. All analyses were conducted with use of R (version 4.0.5; The R Foundation) and RStudio (version 2023.06.0). The level of significance was set at p < 0.05.
Results
Overall, 1,157 patients (1,458 hips) were assessed for eligibility. A total of 1,095 patients (1,381 hips) were included in the analysis after excluding patients with a history of previous surgery on the same side (57 patients [69 hips]), patients with rheumatoid arthritis (2 patients [2 hips]), patients with an infectious disease (1 patient [1 hip]), and patients with insufficient data (5 patients [5 hips]). The mean age (and standard deviation) was 63.5 ± 14.7 years (range, 15 to 95 years), and the most common age range at the time of the initial visit was 70 to 79 years (406 hips; 29.4%), followed by 60 to 69 years (401 hips; 29.0%; Table I). Overall, 795 patients (1,019 hips; 73.8% of hips) were diagnosed with secondary OA due to hip dysplasia. However, this percentage varied among age groups (p < 0.001). When the cohort was stratified by age and year of birth, the prevalence of hip dysplasia was highest (87.4%) in the group 40 to 49 years old and the prevalences of primary OA and SIF were both highest in the group ≥80 years old. The prevalence of hip dysplasia was 71.5% (894 of 1,251 hips) among hips with OA without a history of DDH treatment in childhood and 96.2% (125 of 130 hips) among those with such a history (Table I).
TABLE I.
Descriptive Epidemiology of New Patients with Hip OA Among 12 Core Hospitals in 2022*
| Overall | Patient Age in 2022 (Patient Birth Year) | P Value | |||||||
|---|---|---|---|---|---|---|---|---|---|
| ≤29 Years Old (1993-2007) | 30-39 Years Old (1983-1992) | 40-49 Years Old (1973-1982) | 50-59 Years Old (1963-1972) | 60-69 Years Old (1953-1962) | 70-79 Years Old (1943-1952) | ≥80 Years Old (1927-1942) | |||
| No. of hips | 1,381 | 60 | 35 | 103 | 247 | 401 | 406 | 129 | |
| Age at visit† (yr) | 63.5 ± 14.7 | 21.5 ± 4.7 | 35.0 ± 2.9 | 45.4 ± 2.9 | 55.2 ± 2.8 | 64.9 ± 2.8 | 73.8 ± 2.7 | 84.2 ± 3.3 | <0.001‡ |
| Age at onset† (yr) | 57.0 ± 17.6 | 17.9 ± 6.1 | 30.8 ± 6.8 | 38.9 ± 10.3 | 47.0 ± 11.5 | 58.6 ± 10.0 | 67.6 ± 10.6 | 78.3 ± 11.3 | <0.001‡ |
| Sex (no. [%] of hips) | 0.100 | ||||||||
| Male | 236 (17.1) | 17 (28.3) | 5 (14.3) | 12 (11.7) | 34 (13.8) | 70 (17.5) | 72 (17.7) | 26 (20.2) | |
| Female | 1,145 (82.9) | 43 (71.7) | 30 (85.7) | 91 (88.3) | 213 (86.2) | 331 (82.5) | 334 (82.3) | 103 (79.8) | |
| BMI† (kg/m2) | 23.8 ± 4.3 | 20.3 ± 2.5 | 23.1 ± 4.2 | 23.7 ± 5.0 | 25.2 ± 5.4 | 24.2 ± 4.1 | 23.5 ± 3.6 | 22.9 ± 3.7 | <0.001‡ |
| Side (no. [%] of hips) | 0.175 | ||||||||
| Right | 784 (56.8) | 26 (43.3) | 20 (57.1) | 64 (62.1) | 132 (53.4) | 225 (56.1) | 245 (60.3) | 72 (55.8) | |
| Left | 597 (43.2) | 34 (56.7) | 15 (42.9) | 39 (37.9) | 115 (46.6) | 176 (43.9) | 161 (39.7) | 57 (44.2) | |
| Hemilateral (no. [%] of hips) | 809 (58.6) | 26 (43.3) | 17 (48.6) | 51 (49.5) | 125 (50.6) | 235 (58.6) | 263 (64.8) | 92 (71.3) | <0.001‡ |
| History of DDH treatment in childhood (no. [%] of hips) | <0.001‡ | ||||||||
| Yes | 130 (9.4) | 6 (10.0) | 3 (8.6) | 16 (15.5) | 40 (16.2) | 36 (9.0) | 28 (6.9) | 1 (0.8) | |
| No | 1,251 (90.6) | 54 (90.0) | 32 (91.4) | 87 (84.5) | 207 (83.8) | 365 (91.0) | 378 (93.1) | 128 (99.2) | |
| Subclassification (no. [%] of hips) | <0.001‡ | ||||||||
| Secondary OA due to hip dysplasia | 1,019 (73.8) | 50 (83.3) | 26 (74.3) | 90 (87.4) | 207 (83.8) | 316 (78.8) | 276 (68.0) | 54 (41.9) | |
| Primary OA | 187 (13.5) | 0 (0.0) | 2 (5.7) | 3 (2.9) | 13 (5.3) | 39 (9.7) | 82 (20.2) | 48 (37.2) | |
| Secondary OA due to FAI | 67 (4.9) | 7 (11.7) | 7 (20.0) | 6 (5.8) | 11 (4.5) | 16 (4.0) | 15 (3.7) | 5 (3.9) | |
| Secondary OA due to SIF | 51 (3.7) | 0 (0.0) | 0 (0.0) | 2 (1.9) | 3 (1.2) | 16 (4.0) | 19 (4.7) | 11 (8.5) | |
| Other§ | 47 (3.4) | 3 (5.0) | 0 (0.0) | 2 (1.9) | 11 (4.5) | 12 (3.0) | 12 (3.0) | 7 (5.4) | |
| Unclassifiable | 10 (0.7) | 0 (0.0) | 0 (0.0) | 0 (0.0) | 2 (0.8) | 2 (0.5) | 2 (0.5) | 4 (3.1) | |
OA = osteoarthritis, BMI = body mass index, DDH = developmental dysplasia of the hip, FAI = femoroacetabular impingement, SIF = subchondral insufficiency fracture.
Values are given as the mean ± standard deviation.
Significant, p < 0.05.
Included rapid destructive coxopathy, trauma, Legg-Calvé-Perthes disease, slipped capital femoral epiphysis, and skeletal dysplasia.
Overall, 9.4% of hips (130 of 1,381) or 9.5% of patients (104 of 1,095) had a history of DDH treatment in childhood. According to the 20-year centered moving average, approximately 13% to 15% of hips among patients born from 1963 to 1972 (aged 50 to 59 years at the time of the survey) had a history of DDH treatment in childhood, representing a plateau; however, around the boundary birth years of 1972 and 1973, the trend changed and the percentage of hips with a history of DDH treatment decreased (Fig. 4). A similar trend was observed when the width of the centered moving average was set to 10 years (see Appendix Supplementary Figure 1).
Fig. 4.
Histogram showing the number of hips with new hip OA (gray bars) and the number of such hips with a history of DDH treatment in childhood (black bars) by birth year. A line for the 20-year centered moving average was utilized to estimate the trend in the percentage of hips with a history of DDH treatment in childhood across birth years.
In total, 795 patients (1,019 hips) with secondary OA due to hip dysplasia were included in the final analysis (Table II; see also Appendix Supplementary Table 3). The prevalence of severe subluxation (i.e., Crowe type II, III, or IV) was 2.4% (4 of 166 hips) among patients born in or after 1973, which was significantly less than the 11.1% (95 of 853 hips) among patients born in or before 1972 (odds ratio, 0.20; p < 0.001; Table III). Histograms of the number of hips by patient birth year and Crowe classification showed that there were only 4 hips with Crowe type II among patients born in or after 1973 and no cases of Crowe type III or IV (Fig. 5).
Fig. 5.
Histograms showing the number of hips with secondary hip OA due to hip dysplasia, by Crowe classification and birth year.
TABLE II.
Descriptive Epidemiology of New Patients with Secondary Hip OA Due to Hip Dysplasia*
| Overall | Patient Age in 2022 (Patient Birth Year) | P Value | |||||||
|---|---|---|---|---|---|---|---|---|---|
| ≤29 Years Old (1993-2007) | 30-39 Years Old (1983-1992) | 40-49 Years Old (1973-1982) | 50-59 Years Old (1963-1972) | 60-69 Years Old (1953-1962) | 70-79 Years Old (1943-1952) | ≥80 Years Old (1931-1942) | |||
| No. of hips | 1,019 | 50 | 26 | 90 | 207 | 316 | 276 | 54 | |
| Age at visit† (yr) | 61.6 ± 14.3 | 21.5 ± 4.7 | 34.9 ± 3.1 | 45.4 ± 2.9 | 55.1 ± 2.8 | 64.8 ± 2.8 | 73.7 ± 2.7 | 83.4 ± 2.9 | <0.001‡ |
| Age at onset† (yr) | 54.6 ± 16.9 | 18.0 ± 6.2 | 30.0 ± 7.6 | 40.1 ± 8.1 | 46.5 ± 11.9 | 57.9 ± 10.0 | 67.0 ± 9.8 | 75.5 ± 14.5 | <0.001‡ |
| Sex (no. [%] of hips) | <0.001‡ | ||||||||
| Male | 130 (12.8) | 10 (20.0) | 1 (3.8) | 6 (6.7) | 14 (6.8) | 39 (12.3) | 46 (16.7) | 14 (25.9) | |
| Female | 889 (87.2) | 40 (80.0) | 25 (96.2) | 84 (93.3) | 193 (93.2) | 277 (87.7) | 230 (83.3) | 40 (74.1) | |
| BMI† (kg/m2) | 23.9 ± 4.4 | 20.4 ± 2.6 | 23.6 ± 4.5 | 24.0 ± 5.2 | 25.1 ± 5.3 | 24.3 ± 4.3 | 23.4 ± 3.5 | 22.9 ± 3.8 | <0.001‡ |
| Side (no. [%] of hips) | 0.356 | ||||||||
| Right | 579 (56.8) | 22 (44.0) | 14 (53.8) | 56 (62.2) | 113 (54.6) | 176 (55.7) | 167 (60.5) | 31 (57.4) | |
| Left | 440 (43.2) | 28 (56.0) | 12 (46.2) | 34 (37.8) | 94 (45.4) | 140 (44.3) | 109 (39.5) | 23 (42.6) | |
| Hemilateral (no. [%] of hips) | 552 (54.2) | 22 (44.0) | 11 (42.3) | 43 (47.8) | 97 (46.9) | 167 (52.8) | 172 (62.3) | 40 (74.1) | <0.001‡ |
| History of DDH treatment in childhood (no. [%] of hips) | <0.004‡ | ||||||||
| Yes | 125 (12.3) | 6 (12.0) | 2 (7.7) | 16 (17.8) | 39 (18.8) | 35 (11.1) | 26 (9.4) | 1 (1.9) | |
| No | 894 (87.7) | 44 (88.0) | 24 (92.3) | 74 (82.2) | 168 (81.2) | 281 (88.9) | 250 (90.6) | 53 (98.1) | |
| KL grade (no. [%] of hips) | <0.001‡ | ||||||||
| Grade 1 | 134 (13.2) | 44 (88.0) | 15 (57.7) | 32 (35.6) | 19 (9.2) | 13 (4.1) | 11 (4.0) | 0 (0.0) | |
| Grade 2 | 111 (10.9) | 5 (10.0) | 4 (15.4) | 30 (33.3) | 38 (18.4) | 21 (6.6) | 11 (4.0) | 2 (3.7) | |
| Grade 3 | 206 (20.2) | 1 (2.0) | 4 (15.4) | 13 (14.4) | 44 (21.3) | 83 (26.3) | 52 (18.8) | 9 (16.7) | |
| Grade 4 | 568 (55.7) | 0 (0.0) | 3 (11.5) | 15 (16.7) | 106 (51.2) | 199 (63.0) | 202 (73.2) | 43 (79.6) | |
| LCEA† (deg) | 16.1 ± 11.8 | 14.4 ± 6.8 | 12.2 ± 8.0 | 11.8 ± 14.0 | 16.1 ± 13.6 | 16.0 ± 11.8 | 17.9 ± 10.8 | 18.8 ± 7.9 | <0.001‡ |
| ARO† (deg) | 20.4 ± 8.4 | 16.2 ± 5.5 | 19.0 ± 8.6 | 20.2 ± 9.9 | 21.2 ± 8.3 | 21.4 ± 8.6 | 19.7 ± 7.7 | 20.3 ± 8.7 | 0.002‡ |
| Sharp angle† (deg) | 44.9 ± 5.3 | 46.9 ± 4.6 | 48.5 ± 3.7 | 47.3 ± 5.1 | 45.2 ± 5.7 | 44.7 ± 5.4 | 43.7 ± 4.8 | 43.6 ± 5.0 | <0.001‡ |
| MJS† (mm) | 1.20 ± 1.70 | 4.19 ± 1.20 | 3.54 ± 2.13 | 2.96 ± 1.83 | 1.17 ± 1.57 | 0.74 ± 1.19 | 0.63 ± 1.25 | 0.28 ± 0.66 | <0.001‡ |
| Crowe classification (no. [%] of hips) | 0.160 | ||||||||
| Type I | 920 (90.3) | 50 (100) | 25 (96.2) | 87 (96.7) | 183 (88.4) | 285 (90.2) | 241 (87.3) | 49 (90.7) | |
| Type II | 78 (7.7) | 0 (0.0) | 1 (3.8) | 3 (3.3) | 19 (9.2) | 26 (8.2) | 25 (9.1) | 4 (7.4) | |
| Type III | 15 (1.5) | 0 (0.0) | 0 (0.0) | 0 (0.0) | 4 (1.9) | 2 (0.6) | 9 (3.3) | 0 (0.0) | |
| Type IV | 6 (0.6) | 0 (0.0) | 0 (0.0) | 0 (0.0) | 1 (0.5) | 3 (0.9) | 1 (0.4) | 1 (1.9) | |
OA = osteoarthritis, BMI = body mass index, DDH = developmental dysplasia of the hip, KL = Kellgren-Lawrence, LCEA = lateral center-edge angle, ARO = acetabular roof obliquity, MJS = minimum joint space width. Hip dysplasia was diagnosed in cases in which 1 of the following criteria was met: a Sharp angle of ≥45°, an LCEA of ≤20°, or an ARO of ≥15°.
Values are given as the mean ± standard deviation.
Significant, p < 0.05.
TABLE III.
Prevalence of Severe Subluxation Among New Patients with Secondary Hip OA Due to Hip Dysplasia (1,019 Hips), by Age Group*
| Patient Birth Year (Age in 2022) | No. of Hips | No. of Hips with Severe Subluxation | Prevalence | Odds Ratio (95% CI) | P Value |
|---|---|---|---|---|---|
| Born in or before 1972 (50-91 years old) | 853 | 95 | 11.1% | 1, reference | |
| Born in or after 1973 (15-49 years old) | 166 | 4 | 2.4% | 0.20 (0.05-0.53) | <0.001† |
Severe subluxation was defined as Crowe type II, III, or IV. OA = osteoarthritis, CI = confidence interval.
Significant, p < 0.05.
Discussion
The prevalence of secondary hip OA due to hip dysplasia was 73.8% in our cohort, and hip dysplasia was the most frequent cause of hip OA in new patients at core hospitals. The perinatal education campaign regarding the primary prevention of DDH was a success over the life course of the patients because it was associated with a decrease in the percentage of hips with a history of DDH treatment in childhood and a decrease in the prevalence of severe subluxation among new patients with hip OA at core hospitals.
In 2010, the percentage of Japanese patients with hip OA who had a history of DDH treatment in childhood was 28%1; this percentage decreased to 9.5% in 2022, as demonstrated in the present study. Furthermore, severe subluxations were rare among patients with secondary hip OA due to hip dysplasia who were born after 1973. Hip preservation surgery in patients with hip OA with severe subluxation can be challenging34, and special techniques such as bone grafting and shortening osteotomies are required for total hip arthroplasty in such patients35. Therefore, the prevention campaign initiated half a century prior to the present study may have contributed to expanding the treatment options available to the patient, which may further be associated with a decrease in patients requiring difficult surgery techniques or a decrease in the incidence of complications. Appropriate medical resource allocation to prevent DDH in newborns has the potential to prevent hip dislocation in newborns in the short term and to be cost-effective in the long term, emphasizing the importance of preventive medicine.
Genome-wide screening has revealed that familial hip OA is associated with acetabular dysplasia36, and a recent genome-wide association study and transcriptome analysis found an association between the ferroptosis signaling pathway and DDH37. In an epidemiological study using data from the Rochester Epidemiology Project, LaPrade et al. found that only 156 (8%) of 1,893 patients <50 years of age with hip pain had hip dysplasia38. A previous study found that 78% of Japanese patients with hip OA had congenital hip disease or hip dysplasia, whereas only 9 of 199 Caucasian American patients had hip dysplasia39. Reportedly, the mean LCEA in the Japanese population (31° in male and female individuals) was significantly lower than that in the British population (36° in male individuals and 37° in female individuals)40. Skirving and Scadden reported that the acetabulum tended to be deeper in African neonates than in Caucasian neonates, as assessed by dissection41. A study comparing 1,062 male and 1,146 female hips of healthy Japanese infants found that the acetabular angles were slightly larger in female infants than in male infants at any stage before 6 months of age42. These differences in the morphology and etiology of hip OA between patients of different races and sexes suggest that genetic factors may influence the incidence of DDH, and DDH may therefore not be completely preventable through newborn care alone.
In 2023, the Japanese population had the highest life expectancy worldwide according to the World Health Organization43; however, the impact of a rapidly aging society on the epidemiology of hip OA in Japan has yet to be investigated. In 2010, Jingushi et al.1 reported that the mean age of new patients with hip OA was 58 years and that patients in their 50s constituted the age group with the most patients. In the present study, the mean patient age was 63.5 years and patients in their 70s made up the largest age group; the increase in age among patients in our study is consistent with the aging population in Japan44. Our findings indicate that the prevalence of secondary hip OA due to hip dysplasia decreased from 81%1 to 73.8%; this change could be explained by the increasing number of patients in their 70s and 80s with primary OA and SIF. A histopathological analysis revealed that SIF, caused by osteoporosis, was observed in 6.3% of patients (460 of 7,349) in the U.S. who were preoperatively diagnosed with hip OA45, emphasizing that we also need to focus on specific pathologies in older adults in an aging society.
The present study has limitations. First, because of the cross-sectional design, the causal inferences regarding whether the primary DDH prevention campaign reduced the incidence of secondary hip OA due to hip dysplasia in the Japanese population could not be studied. Second, the study population included new patients at core hospitals, which introduced a selection bias toward patients from general clinics who may need specialized treatment. Additionally, some patients with radiographic features of OA were asymptomatic at the time of the study but may develop symptoms later. Moreover, although the sample was obtained from a wide geographic area in Japan, it was not from across the whole country, which may have introduced another selection bias. Third, the critical years of the campaign, 1972 to 1973, were derived from results observed in Fushimi Ward, Kyoto Prefecture6,13, and the time frame of the campaign may have differed in other regions of Japan. Additionally, we could not identify the specific number of patients or communities who received the education. Fourth, in the present study, the impact of infant screening was not discussed5; this secondary prevention of DDH by means of screening for high risk16 likely also plays an important role in the life course epidemiology of hip OA. Fifth, although we could not confirm the reliability of self-reported DDH treatment in childhood, we believe that misclassification would be unlikely to differ across the age groups. It stands to reason that whether or not the family told the child about the DDH treatment would be a greater reason for misreporting the treatment history than forgetting having been told because of older age46.
Despite these limitations, to the best of our knowledge, the present study is the first to examine the association of life course epidemiology with a campaign for disease primary prevention initiated half a century ago while taking advantage of the characteristics of Japan—that is, a large population and a relatively small influx of people from other regions, as Japan is an island nation with a unique language.
In conclusion, as of 2022, patients with secondary hip OA due to hip dysplasia still make up most new adolescent and adult patients with hip OA seen in core hospitals in Japan, possibly due to genetic factors. However, the perinatal education campaign initiated 50 years ago, which utilized a population approach to raise awareness of maintaining the hips of newborn in the naturally flexed-leg position, may have improved the environmental factors associated with DDH, as indicated by the apparently reduced need for treatment of DDH in childhood and the associated severe subluxation. This may result in reducing the need for challenging hip surgery later in life.
Appendix
Supporting material provided by the authors is posted with the online version of this article as a data supplement at jbjs.org (http://links.lww.com/JBJS/H970).
Acknowledgments
Note: The helpful contributions to this manuscript by Stephen Lyman, PhD (support in writing, methods, and statistical analysis), Atsuko Ueda (Research Assistant), and Editage (English language editing) are gratefully acknowledged.
Members of the Japanese Hip OA Consortium include Ryosuke Yamaguchi, MD, PhD; Goro Motomura, MD, PhD; Satoshi Hamai, MD, PhD; Shinya Kawahara, MD, PhD; Daisuke Hara, MD, PhD; Hyonmin Choe, MD, PhD; Takuaki Yamamoto, MD, PhD; Hajime Seo, MD, PhD; Taiki Matsunaga, MD, PhD; Satoshi Shin, MD; Makoto Fukui, MD; Toru Ichiseki, MD, PhD; Yutaka Kuroda, MD, PhD; Toshiyuki Kawai, MD, PhD; Yaichiro Okuzu, MD, PhD; Koichiro Kawano, MD, PhD; Reima Sueda, MD; Satoshi Hagio, MD; Satoru Harada, MD, PhD; Yuya Takakubo, MD, PhD; and Takeshi Sameshima, MD.
Footnotes
Taishi Sato, MD, PhD, and Satoshi Yamate, MD, contributed equally to this work.
A list of the Japanese Hip OA Consortium members is included as a note at the end of the article
Investigation performed at the Department of Orthopaedic Surgery, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
Disclosure: This work was supported by the Japan Society for the Promotion of Science (KAKENHI) (grant JP23K08654). The Article Processing Charge for open access publication was funded by the Japan Society for the Promotion of Science (KAKENHI) (grant JP23K08654). The Disclosure of Potential Conflicts of Interest forms are provided with the online version of the article (http://links.lww.com/JBJS/H969).
Contributor Information
Taishi Sato, Email: sato.taishi.075@m.kyushu-u.ac.jp.
Satoshi Yamate, Email: yamate.satoshi.073@s.kyushu-u.ac.jp.
Takeshi Utsunomiya, Email: takeshiu0625@gmail.com.
Yutaka Inaba, Email: yute0131@yokohama-cu.ac.jp.
Hiroyuki Ike, Email: hike@yokohama-cu.ac.jp.
Koichi Kinoshita, Email: kinopfukuoka@yahoo.co.jp.
Kenichiro Doi, Email: m05066kd@gmail.com.
Tsutomu Kawano, Email: tsutomu417@gmail.com.
Kyohei Shiomoto, Email: grungust@hotmail.com.
Toshihiko Hara, Email: le6t-hr@asahi-net.or.jp.
Kazuhiko Sonoda, Email: skazuhik@gmail.com.
Ayumi Kaneuji, Email: kaneuji@kanazawa-med.ac.jp.
Eiji Takahashi, Email: eiji@kanazawa-med.ac.jp.
Tomohiro Shimizu, Email: simitom@wg8.so-net.ne.jp.
Daisuke Takahashi, Email: rainbow-quest@pop02.odn.ne.jp.
Yusuke Kohno, Email: y-kohno@ortho.med.kyushu-u.ac.jp.
Tamon Kabata, Email: tamonkabata@yahoo.co.jp.
Daisuke Inoue, Email: daisuke_i_0909@yahoo.co.jp.
Shuichi Matsuda, Email: smat522@kuhp.kyoto-u.ac.jp.
Koji Goto, Email: kgoto@med.kindai.ac.jp.
Taro Mawatari, Email: mawtaro@gmail.com.
Shoji Baba, Email: shojibaba0929@yahoo.co.jp.
Michiaki Takagi, Email: mtakagi@ameria.org.
Juji Ito, Email: indigo.cross@gmail.com.
Collaborators: Ryosuke Yamaguchi, Goro Motomura, Satoshi Hamai, Shinya Kawahara, Daisuke Hara, Hyonmin Choe, Takuaki Yamamoto, Hajime Seo, Taiki Matsunaga, Satoshi Shin, Makoto Fukui, Toru Ichiseki, Yutaka Kuroda, Toshiyuki Kawai, Yaichiro Okuzu, Koichiro Kawano, Reima Sueda, Satoshi Hagio, Satoru Harada, Yuya Takakubo, and Takeshi Sameshima
References
- 1.Jingushi S, Ohfuji S, Sofue M, Hirota Y, Itoman M, Matsumoto T, Hamada Y, Shindo H, Takatori Y, Yamada H, Yasunaga Y, Ito H, Mori S, Owan I, Fujii G, Ohashi H, Iwamoto Y, Miyanishi K, Iga T, Takahira N, Sugimori T, Sugiyama H, Okano K, Karita T, Ando K, Hamaki T, Hirayama T, Iwata K, Nakasone S, Matsuura M, Mawatari T. Multiinstitutional epidemiological study regarding osteoarthritis of the hip in Japan. J Orthop Sci. 2010. Sep;15(5):626-31. [DOI] [PubMed] [Google Scholar]
- 2.Leavell HR, Clark EG. Preventive medicine for the doctor in his community: an epidemiologic approach. 3rd ed. McGraw-Hill; 1965. [Google Scholar]
- 3.Murphy NJ, Eyles JP, Hunter DJ. Hip osteoarthritis: etiopathogenesis and implications for management. Adv Ther. 2016. Nov;33(11):1921-46. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 4.Kuh D, Ben-Shlomo Y, Lynch J, Hallqvist J, Power C. Life course epidemiology. J Epidemiol Community Health. 2003. Oct;57(10):778-83. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 5.Ang KC, Lee EH, Lee PY, Tan KL. An epidemiological study of developmental dysplasia of the hip in infants in Singapore. Ann Acad Med Singap. 1997. Jul;26(4):456-8. [PubMed] [Google Scholar]
- 6.Yamamuro T, Ishida K. Recent advances in the prevention, early diagnosis, and treatment of congenital dislocation of the hip in Japan. Clin Orthop Relat Res. 1984. Apr;(184):34-40. [PubMed] [Google Scholar]
- 7.Rabin DL, Barnett CR, Arnold WD, Freiberger RH, Brooks G. Untreated congenital hip disease. a study of the epidemiology, natural history, and social aspects of the disease in a Navajo population. Am J Public Health Nations Health. 1965. Feb;55(Suppl 2):1-44. [PMC free article] [PubMed] [Google Scholar]
- 8.Adanir O, Zorer G. Comparison of four parameters to assess acetabular dysplasia and acetabular dysplasia rates in primary hip osteoarthritis patients: A study in Turkish population. J Orthop Surg (Hong Kong). 2018. May-Aug;26(2):2309499018768032. [DOI] [PubMed] [Google Scholar]
- 9.Dezateux C, Rosendahl K. Developmental dysplasia of the hip. Lancet. 2007. May 5;369(9572):1541-52. [DOI] [PubMed] [Google Scholar]
- 10.Crowe JF, Mani VJ, Ranawat CS. Total hip replacement in congenital dislocation and dysplasia of the hip. J Bone Joint Surg Am. 1979. Jan;61(1):15-23. [PubMed] [Google Scholar]
- 11.Wilkinson JA. Prime factors in the etiology of congenital dislocation of the hip. J Bone Joint Surg Br. 1963;45-B(2):268-83. [Google Scholar]
- 12.Wiberg G. Studies on dysplastic acetabula and congenital subluxation of the hip joint: with special reference to the complication of osteoarthritis. Acta Chir Scand. 1939;83(suppl 58):5-135. [Google Scholar]
- 13.Ishida K. Prevention of the development of the typical dislocation of the hip. Clin Orthop Relat Res. 1977. Jul-Aug;(126):167-9. [PubMed] [Google Scholar]
- 14.Xu N, Xia B, Tao H, Sun K, Liu Q, Chen W, Wang D, Gao H, Guo Y, Liu Y, Gao J, Teng J, Li T, He Q, Wu Z. Epidemiological investigation and ultrasonic diagnosis of developmental dysplasia of the hip in Chinese infants: A large multi-center cohort study. Medicine (Baltimore). 2022. Jan 14;101(2):e28320. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 15.Michelsson JE, Langenskiöld A. Dislocation or subluxation of the hip. Regular sequels of immobilization of the knee in extension of young rabbits. J Bone Joint Surg Am. 1972. Sep;54(6):1177-86. [PubMed] [Google Scholar]
- 16.Rose G. Sick individuals and sick populations. Int J Epidemiol. 1985. Mar;14(1):32-8. [DOI] [PubMed] [Google Scholar]
- 17.The Japanese Pediatric Orthopaedic Association. Congenital Dislocation of the Hip: Onkochishin (Developing New Ideas Based on Study of the Past). Read at the 31st Annual Meeting of the Japanese Pediatric Orthopaedic Association; 2020. Dec 3-5; online conference. [Google Scholar]
- 18.Loder RT, Skopelja EN. The epidemiology and demographics of hip dysplasia. ISRN Orthop. 2011. Oct 10;2011:238607. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 19.von Elm E, Altman DG, Egger M, Pocock SJ, Gøtzsche PC, Vandenbroucke JP; STROBE Initiative. The Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) statement: guidelines for reporting observational studies. Lancet. 2007. Oct 20;370(9596):1453-7. [DOI] [PubMed] [Google Scholar]
- 20.Reijman M, Hazes JM, Koes BW, Verhagen AP, Bierma-Zeinstra SM. Validity, reliability, and applicability of seven definitions of hip osteoarthritis used in epidemiological studies: a systematic appraisal. Ann Rheum Dis. 2004. Mar;63(3):226-32. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 21.Takatori Y, Ito K, Sofue M, Hirota Y, Itoman M, Matsumoto T, Hamada Y, Shindo H, Yamada H, Yasunaga Y, Ito H, Mori S, Owan I, Fujii G, Ohashi H, Mawatari T, Iga T, Takahira N, Sugimori T, Sugiyama H, Okano K, Karita T, Ando K, Hamaki T, Hirayama T, Iwata K, Matsuura M, Jingushi S; Investigation Group into Coxarthrosis and Acetabular Dysplasia in Japan. Analysis of interobserver reliability for radiographic staging of coxarthrosis and indexes of acetabular dysplasia: a preliminary study. J Orthop Sci. 2010. Jan;15(1):14-9. [DOI] [PubMed] [Google Scholar]
- 22.Kanezaki S, Nakamura S, Nakamura M, Yokota I, Matsushita T. Curtain osteophytes are one of the risk factors for the poor outcome of rotational acetabular osteotomy. Int Orthop. 2017. Feb;41(2):265-70. [DOI] [PubMed] [Google Scholar]
- 23.Aoki H, Nagao Y, Ishii S, Masuda T, Beppu M. Acetabular and proximal femoral alignment in patients with osteoarthritis of the dysplastic hip and its influence on the progression of disease. J Bone Joint Surg Br. 2010. Dec;92(12):1703-9. [DOI] [PubMed] [Google Scholar]
- 24.Kellgren JH, Lawrence JS. Radiological assessment of osteo-arthrosis. Ann Rheum Dis. 1957. Dec;16(4):494-502. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 25.Iidaka T, Muraki S, Oka H, Kodama R, Tanaka S, Kawaguchi H, Nakamura K, Akune T, Yoshimura N. Radiographic measurements of the hip joint and their associations with hip pain in Japanese men and women: the Research on Osteoarthritis/osteoporosis Against Disability (ROAD) study. Osteoarthritis Cartilage. 2017. Dec;25(12):2072-9. [DOI] [PubMed] [Google Scholar]
- 26.Vijayan S, Mehta O, Jacob G, Siddesh ND, Shah H, Joseph B. The fate of the joint space in Legg-Calvé-Perthes’ disease. Skeletal Radiol. 2013. Mar;42(3):341-5. [DOI] [PubMed] [Google Scholar]
- 27.Nakamura S, Ninomiya S, Nakamura T. Primary osteoarthritis of the hip joint in Japan. Clin Orthop Relat Res. 1989. Apr;(241):190-6. [PubMed] [Google Scholar]
- 28.Wiberg G. Shelf operation in congenital dysplasia of the acetabulum and in subluxation and dislocation of the hip. J Bone Joint Surg Am. 1953. Jan;35-A(1):65-80. [PubMed] [Google Scholar]
- 29.Ganz R, Leunig M, Leunig-Ganz K, Harris WH. The etiology of osteoarthritis of the hip: an integrated mechanical concept. Clin Orthop Relat Res. 2008. Feb;466(2):264-72. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 30.Japanese Hip Society FAI Working Group. Diagnosis of femoroacetabular impingement. Hip Joint. 2015;41:1-6. [Japanese]. [Google Scholar]
- 31.Yamamoto T. Subchondral insufficiency fractures of the femoral head. Clin Orthop Surg. 2012. Sep;4(3):173-80. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 32.Jawad MU, Scully SP. In brief: Crowe’s classification: arthroplasty in developmental dysplasia of the hip. Clin Orthop Relat Res. 2011. Jan;469(1):306-8. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 33.Nhita F, Saepudin D, Adiwijaya K, Wisesty UN. Comparative study of moving average on rainfall time series data for rainfall forecasting based on evolving neural network classifier. In: 2015 3rd International Symposium on Computational and Business Intelligence. 2015. p 112-6. [Google Scholar]
- 34.Nakashima Y, Ishibashi S, Kitamura K, Yamate S, Motomura G, Hamai S, Ikemura S, Fujii M. 20-year hip survivorship and patient-reported outcome measures after transpositional osteotomy of the acetabulum for dysplastic hips. Bone Joint J. 2022. Jul;104-B(7):767-74. [DOI] [PubMed] [Google Scholar]
- 35.Sanchez-Sotelo J, Berry DJ, Trousdale RT, Cabanela ME. Surgical treatment of developmental dysplasia of the hip in adults: II. Arthroplasty options. J Am Acad Orthop Surg. 2002. Sep-Oct;10(5):334-44. [DOI] [PubMed] [Google Scholar]
- 36.Mabuchi A, Nakamura S, Takatori Y, Ikegawa S. Familial osteoarthritis of the hip joint associated with acetabular dysplasia maps to chromosome 13q. Am J Hum Genet. 2006. Jul;79(1):163-8. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 37.Mori Y, Ueno K, Chiba D, Hashimoto K, Kawai Y, Baba K, Tanaka H, Aki T, Ogasawara M, Shibasaki N, Tokunaga K, Aizawa T, Nagasaki M. Genome-wide association study and transcriptome of Japanese patients with developmental dysplasia of the hip demonstrates an association with the ferroptosis signaling pathway. Int J Mol Sci. 2023. Mar 6;24(5):5019. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 38.LaPrade MD, Melugin HP, Hale RF, Leland DP, Bernard CD, Sierra RJ, Trousdale RT, Levy BA, Krych AJ. Incidence of hip dysplasia diagnosis in young patients with hip pain: a geographic population cohort analysis. Orthop J Sports Med. 2021. Mar 5;9(3):2325967121989087. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 39.Hoaglund FT, Shiba R, Newberg AH, Leung KY. Diseases of the hip. A comparative study of Japanese Oriental and American white patients. J Bone Joint Surg Am. 1985. Dec;67(9):1376-83. [PubMed] [Google Scholar]
- 40.Yoshimura N, Campbell L, Hashimoto T, Kinoshita H, Okayasu T, Wilman C, Coggon D, Croft P, Cooper C. Acetabular dysplasia and hip osteoarthritis in Britain and Japan. Br J Rheumatol. 1998. Nov;37(11):1193-7. [DOI] [PubMed] [Google Scholar]
- 41.Skirving AP, Scadden WJ. The African neonatal hip and its immunity from congenital dislocation. J Bone Joint Surg Br. 1979. Aug;61-B(3):339-41. [DOI] [PubMed] [Google Scholar]
- 42.Yamamuro TCS. A Radiological Study on the development of the Hip Joint in Normal Infants. J Jpn Orthop Assoc. 1975;49:421-39. [Google Scholar]
- 43.World Health Organization. Life expectancy at birth (years). Accessed 2023 Jul 18. https://www.who.int/data/gho/data/indicators/indicator-details/GHO/life-expectancy-at-birth-(years).
- 44.Yamate S Hamai S Lyman S Konishi T Kawahara S Yamaguchi R, et al. Clinical evaluation of hip joint diseases: total hip arthroplasty to support patients’ quality of life. Journal of Joint Surgery and Research. 2023;1(1):18-25. [Google Scholar]
- 45.Yamamoto T, Iwamoto Y, Schneider R, Bullough PG. Histopathological prevalence of subchondral insufficiency fracture of the femoral head. Ann Rheum Dis. 2008. Feb;67(2):150-3. [DOI] [PubMed] [Google Scholar]
- 46.Smith JP. Reconstructing childhood health histories. Demography. 2009. May;46(2):387-403. [DOI] [PMC free article] [PubMed] [Google Scholar]