Abstract
Background:
Hip displacement (HD), common in cerebral palsy (CP), is reportedly less prevalent for spastic hemiplegia. Patients with a Winter-Gage-Hicks (WGH) type IV gait pattern are believed at increased risk of HD, but true prevalence is unknown. This study aimed to analyze the rates of HD according to the sagittal plane-based WGH classification and identify associated risk factors.
Methods:
Patients with hemiplegic CP, ≥1 instrumented gait analysis (IGA), hip surveillance radiograph(s), and minimum 2-year follow-up were included. The primary outcome was presence of an “unsuccessful hip” defined as a migration percentage ≥30% and/or undergoing reconstructive osteotomies for HD. Secondary outcome variables included WGH type, previous surgery, sex, scoliosis, epilepsy, ventriculoperitoneal shunt, gastrostomy tube, and IGA-derived hip kinematics.
Results:
Included were 144 patients (39.6% female), classified as Gross Motor Function Classification System I (45.1%) or II (54.9%), mean follow-up 9.6 ± 4.6 years. Seventeen patients (11.8%) had an unsuccessful hip outcome (age 11.6 ± 3.6 years). Stratified by WGH type, unsuccessful hip outcome rates were I: 9.5% (2/21), II: 9.4% (6/64), III: 6.7% (2/30), and IV: 24.1% (7/29); age at onset was not different between WGH types (p = 0.8). Multivariate analysis identified hip internal rotation (odds ratio [OR]: 4.7, confidence interval [CI]: 1.2-18.1, p = 0.02) and hip adduction (OR: 5.2, CI: 1.2-22.1, p = 0.02) as significant independent risk factors.
Conclusion:
The rates of HD in spastic hemiplegia were higher than expected for all WGH types, particularly IV. A high index of suspicion and regular hip surveillance radiographs is required for patients with hip internal rotation and adduction, starting during preadolescence.
Level of Evidence:
III-Retrospective cohort observational study. See Instructions for Authors for a complete description of levels of evidence.
Introduction
Hip displacement (HD) is common in cerebral palsy (CP), particularly for those classified as Gross Motor Function Classification System (GMFCS) levels Ⅳ and Ⅴ1. The risk of HD for patients with hemiplegia, typically GMFCS I and II, has been reported to be low and linked to improved functional ambulation associated with more typical hip development2,3. Despite this assertion, HD can be a problem in hemiplegia, with radiographic surveillance programs in Australia, Canada, and Sweden listing the most severe subtype, Winters-Gage-Hicks (WGH) type IV, as being at risk, particularly during the adolescent growth spurt (Fig. 1)2-6. Given limited evidence, guidelines for the frequency of radiographs for patients with hemiplegia were based on expert opinion and consensus, with WGH IV emphasized in hip surveillance programs7.
Fig. 1.
Representative sagittal kinematic gait patterns depicting the WGH classification (top). See text for descriptions. Adapted from Winters et al., 19878. The WGH gait patterns are further illustrated by line drawings for clarity, adapted from Rodda and Graham, 20019 (bottom). ROM = range of motion, and WGH = Winters-Gage-Hicks.
The severity of functional impairment in hemiplegia is traditionally described according to the WGH classification derived from sagittal plane kinematics obtained with instrumented gait analysis (IGA) (Fig. 1)8,9. Type I involves a drop foot throughout swing with ankle dorsiflexion past neutral in stance. Type II involves excessive ankle plantarflexion and normal range of motion (ROM) at the knee. Type III involves similar features as type II with limited ROM of the knee, particularly reduced flexion during swing. Type IV includes the features of type III in addition to reduced hip extension during terminal stance.
Identifying coronal and transverse plane deformities as commonly seen during hemiplegic gait, Rodda et al. modified the WGH IV classification by adding descriptors for hip adduction and internal rotation9. However, the authors made no comment regarding the impacts of these deformities on the development of HD. Others have surmised that hip internal rotation and/or adduction may be contributors to HD; however, studies specifically investigating these factors are currently unavailable3,10.
The study aimed to analyze the rates of HD according to the commonly referenced WGH classification and to identify risk factors that can inform radiographic surveillance protocols. These data will provide much-needed evidence to fill an essential gap in the literature regarding our understanding of HD development in spastic hemiplegia.
Methods
This study was an Institutional Review Board–approved retrospective cohort study conducted at a tertiary-level children’s hospital with a Commission for Motion Laboratory Accreditation–accredited gait laboratory (https://cmlainc.org). Inclusion criteria were children with spastic CP, hemiplegic topographic pattern, at least 1 IGA, at least 1 hip surveillance radiograph (without prior hip surgery), and a minimum 2-year follow-up. Patients with bilateral involvement, unclassifiable WGH type, incomplete hip surveillance radiographs, a non-CP neuromuscular diagnosis (e.g., hereditary spastic paraplegia), or surgical procedures for HD before initial IGA were excluded. Patients were determined to have unilateral CP through a gait analysis assessment, including a comprehensive physical examination by a highly experienced physical therapist, confirmed by the absence of spasticity (by Modified Ashworth Scale), normal selective motor control, and the absence of static contractures on the less affected side. In determining the WGH type, the first IGA was utilized.
The primary outcome was the development of an “unsuccessful hip” defined as a migration percentage (MP) ≥30% or requiring hip soft-tissue procedures (e.g., adductor, iliopsoas, proximal hamstrings releases) and/or reconstructive osteotomies for the treatment of HD (i.e., varus derotational osteotomy (VDRO), pelvic acetabuloplasty) rather than for gait correction alone. The choice of MP ≥ 30% was used in the definition of an “unsuccessful hip” based on this threshold being associated with a “hip at risk” of further progression in prior studies11,12. In addition, hips with MP ≥ 30% have been reported to have a higher risk of femoral head deformity, arthritic changes, and pain after this threshold13-15. The MP was determined using HipScreen software (https://www.hipscreen.org; Shriners Hospital for Children, Sacramento, CA), a reliable measurement tool that uses digitized anteroposterior pelvis surveillance radiographs16. For cases where dedicated anteroposterior pelvis radiographs were not available, alternative radiographs were used if the view of the pelvis was unobstructed: 68.1% anteroposterior pelvis, 12.5% anteroposterior scoliosis, 13.2% lower extremity alignment, and 6.2% abdominal.
Secondary outcomes included WGH type (determined by IGA combined with physical examination; Fig. 1), age, sex, clinically relevant scoliosis (≥40° or requiring spinal fusion), epilepsy, ventriculoperitoneal shunt use, presence of gastrostomy tube, previous lower extremity surgery before IGA, kinematic (including hip extension maximum in stance phase, internal rotation, and adduction mean in stance phase), and kinetic (hip abduction peak moment) features. Kinematic and kinetic measures were defined as “excessive” if they were outside of 1 standard deviation from our laboratory norms. All radiographic and gait analysis parameters were collected and measured under the supervision of a senior pediatric orthopaedic surgeon with extensive experience in IGA interpretation and in diagnosing and treating HD in CP.
Chi-square analysis was used to compare categorical variables. Univariate and multivariate logistic regression modeling were used to identify risk factors for an unsuccessful hip outcome. All statistical analyses used SPSS, version 30 (IBM Corp., Armonk, NY).
Results
Two-hundred and twenty-two children were initially identified from our institutional database, with 144 (64.9%) meeting the inclusion criteria (n = 57 [39.6%] female). A patient flow diagram detailing those excluded is presented in Figure 2. The mean ages at initial IGA for the unsuccessful and successful hip groups were 10.1 ± 3.7 and 8.7 ± 3.8, respectively. The final follow-up duration for the entire cohort was 9.6 ± 4.6 years, not significantly different between unsuccessful and successful hip outcome groups (10.1 ± 5.5 vs. 9. 5 ± 4.5 years, respectively; p = 0.6).
Fig. 2.
Patient flow diagram.
When stratified by WGH type, 21 (14.6%) patients were classified as type I, 64 (44.4%) as type II, 30 (20.8%) as type III, and 29 (20.1%) as type IV. By GMFCS, 65 (45.1%) patients were classified as level I and 79 (54.9%) as level II. As for comorbidities, 52 (36.1%) patients had epilepsy, 15 (10.4%) had hydrocephalus with ventriculoperitoneal shunt, 9 (6.3%) had a gastrostomy tube, 4 (2.8%) had clinically relevant scoliosis, and 1 (0.7%) had an intrathecal baclofen pump. There were no significant differences in demographic parameters between the unsuccessful and successful hip groups (Table I).
TABLE I.
Demographics Analysis of Risk Factors by Hip Outcome
| Parameters | Total | Successful Hip (%) | Unsuccessful Hip (%) | p |
|---|---|---|---|---|
| Sex | ||||
| Female | 57 | 52 (40.2) | 5 (29.4) | 0.436 |
| Male | 87 | 75 (59.8) | 12 (70.6) | |
| Ethnicity | ||||
| White | 102 | 91 (71.7) | 11 (64.7) | 0.660 |
| African American | 25 | 21 (16.5) | 4 (23.5) | |
| Asian | 4 | 3 (2.4) | 1 (5.9) | |
| Hispanic or Latino | 4 | 4 (3.1) | 0 (0.0) | |
| Others | 9 | 8 (6.3) | 1 (5.9) | |
| Laterality | ||||
| Left | 48 | 44 (34.6) | 4 (23.5) | 0.424 |
| Right | 96 | 83 (65.4) | 13 (76.5) | |
| Motor type | ||||
| Spastic | 137 | 121 (95.3) | 16 (94.1) | 0.593 |
| Mixed* | 7 | 6 (4.7) | 1 (5.9) | |
| WGH type | ||||
| Type I | 21 | 19 (15.0) | 2 (11.8) | 0.183 |
| Type II | 64 | 58 (45.7) | 6 (35.3) | |
| Type III | 30 | 28 (22.0) | 2 (11.8) | |
| Type IV | 29 | 22 (17.3) | 7 (41.2) | |
| GMFCS level | ||||
| Ⅰ | 65 | 59 (46.5) | 6 (35.3) | 0.445 |
| Ⅱ | 79 | 68 (53.5) | 11 (64.7) | |
| History of lower limb surgeries before GA | ||||
| Yes | 17 | 14 (11.0) | 3 (17.6) | 0.426 |
| No | 127 | 113 (89.0) | 14 (82.4) | |
| Epilepsy history | ||||
| Yes | 52 | 48 (37.8) | 4 (23.5) | 0.294 |
| No | 92 | 79 (62.2) | 13 (76.5) | |
| Intrathecal baclofen use | ||||
| Yes | 1 | 0 (0.0) | 1 (5.9) | 0.118 |
| No | 143 | 127 (100.0) | 16 (94.1) | |
| History of hydrocephalus with ventriculoperitoneal shunt | ||||
| Yes | 15 | 13 (10.2) | 2 (11.8) | 0.691 |
| No | 129 | 114 (89.8) | 15 (88.2) | |
| Clinically relevant scoliosis | ||||
| Yes | 4 | 4 (3.1) | 0 (0.0) | 1 |
| No | 140 | 123 (96.9) | 17 (100.0) | |
| Gastrostomy tube | ||||
| Yes | 9 | 8 (6.3) | 1 (5.9) | 1 |
| No | 135 | 119 (93.7) | 16 (94.1) | |
| Tracheostomy history | ||||
| No | 144 | 127 (100.0) | 17 (100.0) | NA |
| Total | 144 | 127(100.0) | 17(100.0) | NA |
GA = gait analysis, GMFCS = Gross Motor Function Classification System, NA = not available, and WGH = Winter-Gage-Hicks.
Refers to clinical features of more than one motor type, usually spastic and dyskinetic18.
The age at commencement of hip radiographic surveillance for the entire cohort was 6.2 ± 4.8 years, significantly older for the unsuccessful vs. successful hip groups (9.7 ± 4.7 vs. 5.7 ± 4.6, respectively; p = 0.003). The MP at first radiograph was significantly higher in the unsuccessful vs. successful groups (25.3 ± 10.9 vs. 12.4 ± 8.6, respectively; p < 0.001). The age at cessation of radiographic hip surveillance for the entire cohort was 13.3 ± 3.9 years, not different between unsuccessful and successful hip outcome groups (12.8 ± 3.0 vs. 13.4 ± 4.1 years; p = 0.6). The MP at last radiograph was significantly higher in the unsuccessful vs. successful groups (34.6 ± 6.6 vs. 15.9 ± 6.3, respectively; p < 0.001), with ranges 28 to 51% and 0 to 27%, respectively.
An unsuccessful hip outcome was identified for 17 (11.8%) patients, with 12 (8.3%) patients having hip reconstruction and 5 (3.5%) having an MP ≥ 30% by final follow-up. Of the 17 patients in the unsuccessful hip group, 16 had an MP ≥ 30% at last preoperative radiograph, 1 had an MP = 28% that was progressive and underwent VDRO of the proximal femur. The age at diagnosis of an unsuccessful hip was 11.6 ± 3.7 years, with a mean MP of 32 ± 4%. Stratified by WGH type, unsuccessful hip outcome rates were I: 9.5% (2/21 patients), II: 9.4% (6/64 patients), III: 6.7% (2/30 patients), and IV: 24.1% (7/29 patients), with age at onset not different between WGH types (I: 13.5 ± 2.1, II: 11.7 ± 5.7, III: 10.0 ± 1.4, and IV: 11.4 ± 2.1 years; p = 0.8).
By kinematics, for the entire cohort, 29 (20.1%) patients demonstrated excessive hip flexion, 71 (49.3%) excessive internal hip rotation, and 12 (8.3%) excessive hip adduction during stance phase of gait. The mean (± standard deviation) for each of these kinematic parameters was 30.6 ± 8.2, 13.9 ± 9.0 and 11.9 ± 4.4°, respectively. The prevalence of excessive hip adduction in WGH type I (3, 14.3%) and IV (6, 20.7%) was higher than for II (3, 4.7%) or III (0, 0.0%) (p = 0.009). The prevalence of excessive internal hip rotation gradually increased as the WGH type progressed—I: 6 (28.6%), II: 30 (46.9%), III: 15 (50.0%), and IV: 20 (69.0%) (p = 0.004). A reduced hip abduction moment was identified in 47 (32.6%) patients. The prevalence of an abnormal hip abduction moment gradually increased as WGH type progressed—I: 2 (10.0%), II: 21 (37.5%), III: 8 (30.8%), and IV: 16 (66.7%) (p = 0.001).
By chi-square testing, excessive hip flexion (p = 0.030), internal rotation (p = 0.004), and adduction (p = 0.006) were risk factors for an unsuccessful hip. For the unsuccessful vs. successful hip groups, excessive hip internal rotation was identified in 19.7% vs. 4.1%, respectively (p = 0.004); excessive hip adduction in 41.7% vs. 9.1%, respectively (p = 0.006); and excessive hip flexion in 24.1% vs. 8.7%, respectively (p = 0.03). Further details regarding IGA parameters are presented in Table II.
TABLE II.
Kinematic and Kinetic Outcomes on IGA
| IGA Parameters | Total (N) | Successful Hip N (%) |
Unsuccessful Hip N (%) |
p |
|---|---|---|---|---|
| Hip flexion | ||||
| Yes | 29 | 22 (17.3) | 7 (41.2) | 0.030* |
| No | 115 | 105 (82.7) | 10 (58.8) | |
| Hip internal rotation | ||||
| Yes | 71 | 57 (44.9) | 14 (82.4) | 0.004* |
| No | 73 | 70 (55.1) | 3 (17.6) | |
| Hip adduction | ||||
| Yes | 12 | 7 (5.5) | 5 (29.4) | 0.006* |
| No | 132 | 120 (94.5) | 12 (70.6) | |
| Reduced abduction moment | ||||
| Yes | 47 | 38 (34.9) | 9 (52.9) | 0.123 |
| No | 79 | 71 (65.1) | 8 (47.1) | |
| Total | 144 | 127 (100.0) | 17 (100.0) | NA |
IGA = Instrumented Gait Analysis, and NA = not available.
Denotes statistical significance (p < 0.05).
In the unsuccessful group, surgery for HD was performed in 12 (8.3%) patients, stratified by WGH type—I: 0 (0.0%), II: 3 (25.0%), III: 2 (16.7%), and IV: 7 (58.3%). Of these, all 12 had hip reconstruction (VDRO and/or pelvic osteotomy ± soft-tissue releases) and none had nonreconstructive (i.e., soft tissue) hip surgery alone. For those undergoing hip reconstruction, 5 had VDRO alone and 7 had VDRO plus acetabuloplasty.
There were 17 patients (of 144, 12%) with non–hip-related lower extremity surgeries before the first IGA: 14 in the successful hip group and 3 in the unsuccessful hip group. Of these, 16 patients had plantar flexor lengthenings, 4 had hamstring lengthenings, 3 had rectus femoris transfer, 4 had tibialis posterior tendon recession or transfer, and 2 had tibial derotational osteotomy. With respect to femoral derotational osteotomies for gait correction and not for the treatment of HD after the first IGA, there was 1 patient in the unsuccessful group at age 5 years and 11 patients in the successful group at mean age 12.3 ± 3.6 years.
By univariate logistic regression analysis, hip flexion (odds ratio [OR] 3.34, p = 0.027), internal hip rotation (OR 5.73, p = 0.008), and hip adduction (OR 7.14, p = 0.003) were found to be significant risk factors for an unsuccessful hip outcome (Table III). Multivariate logistic regression analysis demonstrated that only excessive internal hip rotation (OR 4.7, p = 0.024) and hip adduction (OR 5.21, p = 0.025) were independent risk factors for an unsuccessful hip outcome.
TABLE III.
Univariable and Multivariable Logistic Regression Analyses of Risk Factors for an Unsuccessful Hip Outcome
| Univariable | Multivariable | |||
|---|---|---|---|---|
| Variables | OR (95% CI) | p | OR (95% CI) | p |
| Sex | ||||
| Female | Reference | |||
| Male | 1.66 (0.55-5.01) | 0.37 | ||
| Ethnicity | ||||
| White | Reference | |||
| African American | 1.58 (0.46-5.44) | 0.47 | ||
| Asian | 2.76 (0.26-28.86) | 0.40 | ||
| Others | 1.03 (0.12-9.07) | 0.98 | ||
| Motor type | ||||
| Spastic | Reference | |||
| Mixed | 1.26 (0.14-11.15) | 0.84 | ||
| WGH type | ||||
| Type I | Reference | |||
| Type II | 0.98 (0.18-5.28) | 0.98 | ||
| Type III | 0.68 (0.088-5.2) | 0.68 | ||
| Type IV | 3.02 (0.56-16.33) | 0.20 | ||
| Laterality | ||||
| Left | Reference | |||
| Right | 1.72 (0.53-5.60) | 0.37 | ||
| GMFCS | ||||
| Ⅰ | Reference | |||
| Ⅱ | 1.59 (0.55-4.56) | 0.39 | ||
| History of lower limb surgeries | ||||
| Yes | 1.73 (0.44-6.77) | 0.43 | ||
| No | Reference | |||
| Epilepsy history | ||||
| Yes | 0.51 (0.16-1.64) | 0.26 | ||
| No | Reference | |||
| History of hydrocephalus with ventriculoperitoneal shunt | ||||
| Yes | 1.17 (0.24-5.69) | 0.85 | ||
| No | Reference | |||
| Gastrostomy tube | ||||
| Yes | 0.93 (0.11-7.93) | 0.95 | ||
| No | Reference | |||
| Hip flexion | ||||
| Yes | 3.34 (1.15-9.74) | 0.027* | 1.75 (0.51-5.97) | 0.373 |
| No | Reference | |||
| Hip internal rotation | ||||
| Yes | 5.73 (1.57-20.93) | 0.008* | 4.70 (1.23-18.07) | 0.024* |
| No | Reference | |||
| Hip adduction | ||||
| Yes | 7.14 (1.96-26.00) | 0.003* | 5.21 (1.23-22.12) | 0.025* |
| No | Reference | |||
| Reduced abduction moment in initial GA | ||||
| Yes | 2.10 (0.75-5.89) | 0.16 | ||
| No | Reference | |||
| Age at initial GA | 1.09 (0.96-1.24) | 0.18 | ||
| Body mass index | 0.91 (0.79-1.05) | 0.18 | ||
| Follow-up duration (yr) | 1.03 (0.92-1.15) | 0.63 | ||
CI = confidence interval, GA = gait analysis, GMFCS = Gross Motor Function Classification System, NA = not available, OR = odds ratio, and WGH = Winter-Gage-Hicks.
Denotes statistical significance (p < 0.05).
Discussion
Patients with spastic hemiplegia typically ambulate without assistive devices (i.e., GMFCS I and II), conferring a protective effect against the development of HD17. Although the development of HD in hemiplegia is relatively low compared with nonambulatory CP, risk stratification by gait pattern, specifically by WGH classification, had not been comprehensively established. These data are required to inform hip surveillance programs, which currently provide recommendations based mainly on expert opinion and consensus.
A study pooling data from 4 CP registers in Australia identified 42 patients classified as WGH IV, with 6 (14%) developing HD (i.e., MP ≥ 30%)5. Although this study identified 967 patients with hemiplegia, they did not stratify the risk of HD by WGH types I to III, only WGH IV. The authors stated that “…children with hemiplegia, regardless of WGH type, do not demonstrate progressive HD at younger ages…[but was] primarily seen in…WGH type IV.” A recent narrative review stated a persistent lack of evidence to support surveillance guidelines for hemiplegia. Still, it reiterated that most children function at GMFCS level I or II and “…rarely, if ever, suffer hip dislocation”7.
Another population-based study from Sweden found that no patient with unilateral spastic CP developed dislocation in their hip surveillance program3. This study, however, evaluated frank dislocation, likely underreporting the incidence of HD as per a more commonly accepted definition (i.e., MP ≥ 30%). From a Norwegian cohort of 335 children with CP, Terjesen identified 127 children with hemiplegia, 3% developing hip subluxation (MP = 33%-39%), and none with an MP ≥ 40%10. Despite this finding, with only 2.1 years of follow-up and a young age range (6 months to 7 years), the development of HD may not yet be detected given its typical emergence during the adolescent growth spurt.
By contrast, this study of 144 patients had a final follow-up of almost 10 years, with WGH stratification confirmed by IGA. Over this longer follow-up period, we determined a substantially higher prevalence of HD overall, at 12%. At 24%, the prevalence of HD was highest for WGH IV; however, we also found relatively high rates for WGH I-III, up to 10%. In accordance with current consensus, our study identified the age at onset of HD to be 11.6 years (i.e., preadolescent/adolescent stage), which may be linked to rapid growth during this period.
Anatomic factors that position the hip in a provocative position during this phase may predispose the hip to subluxate. Presedo et al. stated that the “predominating limb position is the most important element in defining the hip joint reaction force vector direction and magnitude”18. Specifically, an adducted hip increases this force, directing the femoral head toward the posterosuperior acetabulum, resulting in dysplasia. Accordingly, we found hip adduction to be an independent risk factor for HD, irrespective of WGH type.
In addition to hip adduction, excessive internal hip rotation was an independent risk factor, but the reasons are unclear. In a modeling study by Miller et al., femoral torsion had little influence on the hip force environment19. Despite this, we found increased internal hip rotation in all WGH types, worsening with ascending joint levels: from 28.6% in type I to 69% in type IV. These findings were corroborated by Riad et al., who reported increased hip internal rotation in WGH I and II (WGH III and IV were not represented)20.
Based on the low incidence of HD determined for hemiplegia (1%) in the Victorian CP Register, Soo et al. recommended a single hip radiograph at 6 to 8 years as a screening test1. This is consistent with the age at commencement of radiographic surveillance in this study (mean 6 years). Unlike the Victorian cohort, we found a significantly higher rate of HD at 12%, prevalent across WGH types. This may result from our increased number of hip radiographs over a period long enough to detect the later onset of HD, at a mean age of 11.6 years. Given the mean age at diagnosis of HD in this study was 11.6 with a standard deviation of approximately 4 years, we suggest that more regular radiographic hip surveillance for children with hemiplegic CP (all WGH types) should be considered, particularly for those with internal hip rotation and/or hip adduction during gait. This surveillance should commence at age 7 years and then annually, with cessation at triradiate cartilage closure (i.e., skeletal maturity). Consistent with the findings of Lindgren et al., if the MP ≥ 28% at triradiate cartilage closure, then at least biannual hip surveillance radiographs should be continued until 18 years12.
Given the influence of transverse and coronal plane kinematic deviations on the risk of developing HD in hemiplegia, the utility of the WGH classification may no longer be sufficient. The identification of hip adduction and internal rotation as independent risk factors of HD would suggest that this classification might be further modified to include these aspects, regardless of sagittal gait pattern.
The limitations of this study include its retrospective nature, not being population-based, and its sample size, with wide confidence intervals associated with hip internal rotation and adduction. In particular, the requirement for IGA as an inclusion criterion may have introduced selection bias. Unfortunately, we were unable to evaluate pelvic obliquity as a risk factor for HD, as most radiographs were taken in a supine position. In addition, a substantial number of radiographic measures used were from radiographs other than from standardized anteroposterior pelvis supine hip radiographs, due to the decreased emphasis on hip surveillance for children with hemiplegic CP. Despite this, radiographic hip measures from scoliosis films have been previously shown to be reliably correlated to anteroposterior pelvis radiographs21. The strengths of this study include its almost 10-year follow-up and the use of IGA for stratification by WGH type.
In conclusion, the rates of HD in spastic hemiplegia were higher than expected for all WGH types, particularly IV (24%). Notably, the rates for WGH I-III (∼7-10%), previously thought to have negligible risk of HD, were surprising. Regardless of WGH type—solely a sagittal plane classification—patients with increased hip internal rotation (transverse plane) and adduction (coronal plane) were at highest risk of HD. A high index of suspicion and regular hip surveillance radiographs is required for patients with these risk factors, starting in the preadolescent phase.
Institutional Review Board Statement
The study was reviewed by the Institutional Review Board of Nemours Children’s Health and deemed exempt (protocol code 2230714 approved 8/30/2024).
Informed Consent Statement
Patient consent was waived due to retrospective study, and all data were deidentified.
Data Availability Statement
Data are available by request from the corresponding author.
Acknowledgments
Note: The authors acknowledge Jobayer Hossain for statistical support consultation on this study. The authors also acknowledge the assistance of Editorial Services of Nemours Children’s Health. Publication made possible in part by support from the Nemours Grants for Open Access from Library Services.
Footnotes
This research received no external funding.
Jason J. Howard discloses podcast payments from Scholar Rock Inc. and paid educational talk from Orthopediatrics Corp., both are past and unrelated to the study. The remaining authors declare no conflicts of interest.
Investigation performed at Nemours Children's Health, Wilmington, DE
Disclosure: The Disclosure of Potential Conflicts of Interest forms are provided with the online version of the article (http://links.lww.com/JBJSOA/B131).
Contributor Information
Zhe Yuan, Email: Jerry.Yuan@nemours.org.
Alexander Aretakis, Email: alexanderaretakis@gmail.com.
Chris Church, Email: chris.church@nemours.org.
M. Wade Shrader, Email: wade.shrader@nemours.org.
Freeman Miller, Email: freeman.miller@nemours.org.
Anuj Gupta, Email: anuj.toto123@gmail.com.
Arianna Trionfo, Email: arianna.trionfo@nemours.org.
Jason J. Howard, Email: jason.howard@me.com.
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Associated Data
This section collects any data citations, data availability statements, or supplementary materials included in this article.
Data Availability Statement
Data are available by request from the corresponding author.