Hip displacements and correctable scoliosis were prevalent in children with cerebral palsy registered in a Danish follow-up programme from 2010 to 2020.

AIM: We need a better understanding of non-surgical interventions for hip dislocations and scoliosis. This study estimated the cumulative incidence of problems among children with cerebral palsy and described the type and frequency of therapist-led interventions. METHODS: The study comprised 1482 children (58% male) aged 0-15 years, with a mean age of 3.6 years, who were registered in the Danish Cerebral Palsy Follow-up Programme from 2010 to 2020. We used the Kaplan-Meier estimator to examine the cumulative incidence of hip displacement, hip dislocation, correctable scoliosis and non-correctable scoliosis. The type and frequency of therapist-led interventions are reported descriptively. RESULTS: The cumulative incidence of hip displacement and hip dislocation were 15.8% and 3.5%, respectively, and 39.0% and 13.9% for correctable and non-correctable scoliosis. The most frequently reported type of therapist-led intervention was a joint range of motion exercise. We found that 60.5% with hip displacements and 43.8% with correctable scoliosis used a standing aid. A further 5.4% used a spinal orthosis to prevent deformity and 8.1% for stabilisation. CONCLUSION: Hip displacement and correctable scoliosis were prevalent in children with cerebral palsy, whereas the occurrence of hip dislocations and non-correctable scoliosis was low. The use of assistive aids was low.

The impact of the union of lesser trochanter fragments after intramedullary fixation of trochanteric femoral fractures: an X-ray based study.

BACKGROUND: Displacement of the lesser trochanter (LT) is not uncommon after managing intertrochanteric femoral fractures and the influence of nonunion of the LT-fragment on clinical outcomes remains controversial. This study aimed to investigate the relationship between the displacement distance and union of the LT-fragment and evaluate the influence of LT-fragment nonunion on hip function and complications. METHODS: This retrospective study included patients with intertrochanteric fractures and displaced LT treated with intramedullary fixation at Wenzhou Hospital of Integrated Traditional Chinese and Western Medicine from June 2015 to July 2017. The patients were grouped as union and nonunion of the LT-fragment at 1 year. The LT-fragment displacement distance of LT was measured by the anterior-posterior radiographs. RESULTS: Thirty-one and 22 patients showed union and nonunion at 1 year, respectively. The nonunion group had a higher postoperative complication rate than the union group (59% vs. 29%, P = 0.047), especially mechanical complications (45% vs. 6%, P = 0.001). There was no significant difference in hip function between the two groups (P > 0.05). The receiver operating characteristic (ROC) curve revealed an area under the curve of 0.933 of displacement ratio. Patients with a displacement ratio > 0.35 were more likely to have nonunion of the LT-fragment. CONCLUSIONS: The displacement ratio might be a reliable predictor of LT-fragment union. The incidence of postoperative complications might increase with LT-fragment nonunion.

The effectiveness of adding guided growth to soft tissue release in treating spastic hip displacement.

BACKGROUND: Guided growth at the proximal femur using one transphyseal screw corrects coxa valga and improves hip displacement in cerebral palsy. This study aimed to validate the effects of adding guided growth (GG) to soft tissue release (STR), in terms of decreasing the migration percentage (MP), compared to those with soft tissue alone. METHODS: This retrospective study comprised patients with cerebral palsy who underwent soft tissue release alone (Group STR) or soft tissue release plus guided growth (Group GG) for hip displacement (mean age, 8.1 years; mean follow-up, 4.9 years). Difference in the MP and rate of controlling MP <40% at 2 years postoperatively and rate of revision surgeries at 5 years postoperatively were compared between the groups. RESULTS: The two groups were comparable in age, side, and gross motor function level, but Group GG (n = 24) had more severe hip displacement preoperatively than did Group STR (n = 64). Group GG had a significantly greater 2-year decrease in the MP (-14.8% vs. -11.8%, p < 0.05) than did Group STR. Among patients with a pre-operative MP >50%, the rate of MP <40% was greater in Group GG (73%) than in Group STR (41%). Revision surgeries, mainly repeated guided growth and soft tissue release, were comparable between the groups. CONCLUSIONS: This is the first comparative study to support adding guided growth to soft tissue release, as it results in greater improvements in hip displacement than that with soft tissue release alone. Non-ambulatory patients or severe hip displacement with MP 50%-70% could benefit from this less aggressive surgery by controlling the MP under 40% without femoral osteotomy.

Avascular necrosis of the femoral head in patients with cerebral palsy after hip surgery-incidence and impact on quality of life.

PURPOSE: This study investigated the incidence of AVN in patients with cerebral palsy who underwent a hip reconstruction surgery (soft tissue release, femur and pelvic osteotomies) and its impact on quality of life. METHODS: Retrospective study, with clinical and radiographic analysis of 104 patients (128 hips) GMFCS IV and V with a minimum two year follow-up. Reimers migration percentage, the amount of abduction, acetabular index, and the neck-shaft angle were collected before and after surgery. Modified Tönnis classification was used to analyze the hips before surgery, and the Bucholz and Ogden classification was used to identify hips with AVN. Function and quality of life were investigated with the CPCHILD questionnaire after surgery. RESULTS: The mean age of participants at surgery was 120.1 months (72-184), and it was not related with AVN (p = 0.946). AVN signs were observed in 62 hips (48.5%). The mean pre-op Reimers value was 68.7% (16-100) in normal hips and 83.1% (0-100) in hips with AVN (p = 0.003). All hips considered as Tönnis IV before surgery developed AVN (p = 0.006). The amount of abduction did not differ between hips that developed AVN and those that did not (p = 0.313). Patients who developed AVN had lower scores of quality of life (p = 0.023) and comfort (p = 0.025) according to the CPCHILD questionnaire. CONCLUSION: We observed a relationship between the greater pre-operative severity according to the Reimers index and the modified Tonnis classification and the development of AVN.

Hip displacement in Wolf-Hirschhorn syndrome: Report on three cases and review of associated musculoskeletal pathologies.

Wolf-Hirschhorn syndrome is a rare genetic disease caused by a chromosomal deletion of the distal short arm of Chromosome 4. It is associated with multisystem abnormalities, including delayed growth, characteristic facial features, epilepsy, and skeletal abnormalities. We report three patients who developed hip displacement, and describe the occurrence of delayed and nonunion in patients who underwent corrective proximal femoral osteotomy for hip displacement. We also performed a literature review identifying common musculoskeletal presentations associated with the condition. Patients with Wolf-Hirschhorn Syndrome are at risk of hip displacement (subluxation), and we would advocate annual hip surveillance in this patient group.

More than an X-ray: Experiences and perspectives of parents of children with cerebral palsy when engaging in hip surveillance.

AIM: We explored the experiences of parents of children with cerebral palsy (CP) when engaging in hip surveillance for their child and aimed to identify the barriers and facilitators they encounter. METHODS: We conducted a pragmatic qualitative study through five focus groups conducted with 23 parents and primary care givers of young people with cerebral palsy. A semi-structured topic guide was used to facilitate discussion. Recordings were transcribed verbatim and transcripts analysed using content analysis. RESULTS: Six major categories emerged: (i) hip surveillance is a shared responsibility; (ii) knowledge is empowering; (iii) hip surveillance should be proactive rather than reactive; (iv) consistency and support from health professionals is valuable; (v) good communication is crucial; and (vi) challenges associated with having an X-ray may not be appreciated. Participants made recommendations related to: service model enhancements, information provision and improving both communication and the experience of having an X-ray. CONCLUSION: Despite having a good understanding of the need and importance of hip surveillance for their child, several barriers to parent engagement exist. Findings will inform the implementation of a family-centred model for hip surveillance and may be relevant to those undertaking or planning the implementation of hip surveillance in other areas.

Association between pelvic obliquity and scoliosis, hip displacement and asymmetric hip abduction in children with cerebral palsy: a cross-sectional registry study.

BACKGROUND: Pelvic obliquity (PO) is common in individuals with cerebral palsy (CP). The prevalence of PO in a population of children with CP and its associations with scoliosis, hip displacement and asymmetric range of hip abduction were analysed. METHODS: Over a 5-year period all pelvic radiographs from the Swedish surveillance programme for CP and the recorded data for scoliosis and hip abduction in children from southern Sweden at Gross Motor Function Classification System (GMFCS) levels II-V were analysed. PO and hip displacement calculated as migration percentage (MP) were measured on supine pelvic radiographs and compared with presence of scoliosis and side difference in hip abduction. Statistical analyses comprised chi-squared and binominal testing. RESULTS: In total, 337 children were analysed, of whom 79 had a PO of ≥5°. The proportion of children with PO increased from 16% in GMFCS level II to 34% in level V. Scoliosis combined with PO was reported in 38 children, of whom 34 (89%, 95% confidence interval [CI] 80-99%) had the convexity opposite to the high side of the PO. Asymmetric abduction with PO was reported in 45 children, of whom 40 (89%, CI 79-99%) had reduced abduction on the high side of the PO. Asymmetric MP of ≥5% with PO was seen in 62 children, of whom 50 had higher MP on the high side of the PO (81%, CI 71-90%). Children in GMFCS levels II-IV more often had isolated infra-pelvic association with PO (47% versus 19% in GMFCS V, P = 0.025), while combined supra- and infrapelvic association was more common in GMFCS level V (65% versus 30% in GMFCS II-IV, P = 0.004). Isolated infrapelvic or no association was seen in 74% of children ≤10 years of age while 76% of children ≥11 years old had suprapelvic or combined supra- and infrapelvic association with PO (P < 0.001). CONCLUSIONS: There was a strong association between the high side of the PO and the side of scoliosis, highest MP, and lowest range of abduction when PO was measured in supine position. PO was more often associated with infrapelvic factors. PO was seen in young children indicating the need for early awareness of this complication.

Health professionals' experiences and barriers encountered when implementing hip surveillance for children with cerebral palsy.

AIM: This study aimed to explore health professionals' experiences of implementing hip surveillance for young people with cerebral palsy (CP) and to identify any barriers they encounter. METHODS: A cross-sectional web-based survey of health professionals supporting children with CP was conducted. Responses were analysed through mixed methods. Responses to items presented as ordinal scales were analysed using descriptive statistics, and open-ended responses through a qualitative approach to identify themes. RESULTS: A total of 32 paediatricians, 2 rehabilitation specialists and 50 physiotherapists completed the survey, with respondents working within both hospital- and community-based settings. Barriers most frequently reported were inconsistency in radiology practice and reporting (35%), parent engagement (32%), limited communication between clinicians (31%), lack of clarity in lines of responsibility (27%) and forgetting to undertake surveillance (26%). Four major themes were identified through qualitative analysis: (i) recognition of the importance of clinical guidelines to hip surveillance; (ii) the value of each role in the team around a child; (iii) the challenge of sharing responsibility; and (iv) the importance of communication in facilitating collaboration. CONCLUSIONS: Barriers can be encountered at each phase of the hip surveillance process, but there are also factors that act as facilitators. Locally, the results will inform the development of an enhanced state-wide approach to hip surveillance for all children with CP. The identified barriers do not appear unique to the local context, and the findings may be transferable to other settings. Awareness of the potential barriers and facilitators would be valuable to those implementing hip surveillance in other areas.

The head shaft angle is associated with hip displacement in children at GMFCS levels III-V - a population based study.

BACKGROUND: An increased Head Shaft Angle (HSA) has been reported as a risk factor for hip displacement in children with cerebral palsy (CP) but opinions differ in the literature. The purpose of this study was to re-evaluate the relationship between HSA and hip displacement in a different population of children with CP. METHODS: The Cerebral Palsy Integrated Pathway Scotland surveillance programme includes 95% of all children with CP in Scotland. The pelvic radiographs from 640 children in GMFCS levels III-V were chosen. The most displaced hip was analysed and the radiographs used were those taken at the child's first registration in the database to avoid the potential effects of surveillance on subsequent hip centration. A logistic regression model was used with hip displacement (migration percentage [MP] ≥40%) as outcome and HSA, GMFCS, age and sex as covariates. RESULTS: The MP was ≥40% in 118 hips with a mean HSA of 164° (range 121-180°) and < 40% in 522 hips with a mean HSA of 160° (range 111-180°). The logistic regression analysis showed no significant influence of age and sex on MP in this population but a high GMFCS level was strongly associated with hip displacement. An increased HSA was also associated with hip displacement, a 10° difference in HSA for children adjusted for age, sex, and GMFCS gave an odds ratio of 1.26 for hip displacement equal or above 40% (p = 0.009) and hips with HSA above 164.5 degrees had an odds ratio of 1.96 compared with hips with HSA below 164.5 degrees (p = 0.002). CONCLUSION: These findings confirm that HSA is associated with hip displacement in children in GMFCS levels III-V.

[Use of dual mobility cups for revision hip arthroplasty]. / Einsatz von Dual-Mobility-Pfannen beim Hüftprothesenwechsel.

The dual mobility cup (DMC) is an increasingly important tool not only in primary but also in revision total hip arthroplasty to prevent dislocation and eventually reduce postoperative complication rates. Various studies have shown survival rates with DMCs of up to 100% with an average dislocation rate of less than 1.5% after primary hip arthroplasty and a follow-up of 10 years. In revision surgery, survival rates of up to 99% were reported with dislocation rates between 0 and 10% after an average of 5 years after implantation. This article is intended to provide an overview of the principle and function of DMCs. Furthermore, indications as well as complications are presented.

[Spontaneous reposition of a hip prosthesis after atraumatic dislocation]. / Spontanreposition einer Hüft-TEP nach atraumatischer Luxation.

Traumatic dislocations of a hip prosthesis are not uncommon, and spontaneous repositions are well documented as well. To the best of our knowledge, however, there has been no report of a spontaneous reposition of a dislocated hip prosthesis head on the stem taper. We present such a rare case.

Progression of Hip Displacement during Radiographic Surveillance in Patients with Cerebral Palsy.

Progression of hip displacement is common in patients with cerebral palsy (CP). We aimed to investigate the rate of progression of hip displacement in patients with CP by assessing changes in radiographic indices according to Gross Motor Function Classification System (GMFCS) level during hip surveillance. We analyzed the medical records of patients with CP aged < 20 years who underwent at least 6 months interval of serial hip radiographs before any surgical hip intervention, including reconstructive surgery. After panel consensus and reliability testing, radiographic measurements of migration percentage (MP), neck-shaft angle (NSA), acetabular index (AI), and pelvic obliquity (PO) were obtained during hip surveillance. For each GMFCS level, annual changes in radiographic indices were analyzed and adjusted for affecting factors, such as sex, laterality, and type of CP. A total of 197 patients were included in this study, and 1,097 radiographs were evaluated. GMFCS classifications were as follows: 100 patients were level I-III, 48 were level IV, and 49 were level V. MP increased significantly over the duration of hip surveillance in patients with GMFCS levels I-III, IV, and V by 0.3%/year (P < 0.001), 1.9%/year (P < 0.001), and 6.2%/year (P < 0.001), respectively. In patients with GMFCS level IV, NSA increased significantly by 3.4°/year (P < 0.001). Our results suggest that periodic monitoring and radiographic hip surveillance is warranted for patients with CP, especially those with GMFCS level IV or V. Furthermore, physicians can predict and inform parents or caregivers regarding the progression of hip displacement in patients with CP.

[Resection at symptomatic cam impingement. Use of a minimally invasive antero-lateral approach]. / Offene Offsetkorrektur bei symptomatischem Cam-Impingement. Therapie über einen minimalinvasiven anterolateralen Zugang.

BACKGROUND: Surgical treatment of femoroacetabular impingement (FAI) is nowadays achieved by either open surgical hip dislocation or hip arthroscopy. However, drawbacks of both procedures include the invasiveness of the open procedure and a high learning curve to successfully perform arthroscopic treatment. In our institution, we established a minimally invasive, arthroscopically assisted, antero-lateral approach for the correction of cam type FAI. OBJECTIVES: The goal of the study was to describe the surgical technique and highlight the short-term clinical outcome in a consecutive series of patients operated between 2011 and 2014 in our institution. MATERIALS AND METHODS: In total, 77 patients were included in this study. The patients were allocated to two groups (Toennis = 0: Group I; Toennis 1 and 2: Group II). Clinical and radiographic follow up was obtained at 6 and 12 weeks postoperatively. Clinical outcome was assessed using the Hip-Outcome-Score. RESULTS: The mean age of patients in Group I was 25 (16-48) years and in Group II 38 (17-50) years respectively. Internal rotation (IR) in 90° flexion increased by 11 degrees from pre- to postoperatively in Group I (p < 0.001) and by 14° in Group II (p < 0.001). The Hip Outcome Score revealed the ability to perform sports with reduced pain at three months follow up. Subjectively, all patients benefitted in terms of pain and hip function in both groups (p < 0.001). There were no complications with long-term morbidity during the perioperative course. CONCLUSION: Arthroscopically assisted cam resection using a minimally invasive anterolateral approach is a safe technique for the treatment of FAI. At short term follow up, nearly all operated patients seem to benefit in terms of pain and hip function. The influence of progression of osteoarthritis still has to be shown.

Hip displacement in children with cerebral palsy: surveillance to surgery - a current concepts review.

This review brings together a multidisciplinary, multinational team of experts to discuss the current state of knowledge in the detection and treatment of hip displacement in cerebral palsy (CP), a global public health problem with a high disease burden. Though common themes are pervasive, different views are also represented, reflecting the confluence of traditional thinking regarding the aetiology and treatment of hip displacement in CP with emerging research that challenges these tried-and-true principles. The development of hip displacement is most closely related to gross motor function, with radiographic surveillance programs based on the Gross Motor Function Classification System (GMFCS), the goal being early detection and timely treatment. These treatments may include non-operative methods such as abduction bracing and Botulinum Neurotoxin A (BoNT-A), but outcomes research in this area has been variable in quality. This has contributed to conflicting opinions and limited consensus. Soft tissue lengthening of the hip adductors and flexors has traditionally been employed for younger patients, but population-based studies have shown decreased survivorship for this treatment when performed in isolation. Concerns with the identification of hip displacement in very young children are raised, noting that early reconstructive surgery has a high recurrence rate. This has prompted consideration of viable minimally invasive alternatives that may have better success rates in very young children with CP, or may at least delay the need for osteotomies. Recent reports have implicated the role of abnormal proximal femoral growth and secondary acetabular dysplasia as a primary cause of hip displacement, related to ambulatory status and abductor function. As such, guided growth of the proximal femur has emerged as a possible treatment that addresses this purported aetiology, with promising early results.

Prevalence and Regional Differences in Migrated Hips in Danish Children with Cerebral Palsy from 2008 to 2021-A Comparison of Ambulant vs. Non-Ambulant Children.

PURPOSE: This study aims to assess the incidence of hip displacement and dislocation (denominated as hip migration) among ambulant and non-ambulant Danish children with cerebral palsy (CP) by estimating their cumulative incidence of migrated hips. A secondary objective is to compare the prevalence across different Danish regions. METHODS: Data were obtained from the Danish Cerebral Palsy Follow-Up Program (CPOP) from the years 2008 to 2021. This population-based cohort study included 1388 children with CP (58% male; 42% female) as subjects; aged 0-15 years; with an average age of 5.4 years at their last follow-up. The children were categorized according to their Gross Motor Function Classification System (GMFCS) level into ambulators (GMFCS I-III) and non-ambulators (GMFCS IV-V). The Kaplan-Meier estimator was employed to calculate the cumulative incidence of migrated hips from birth until the date of their last radiographic follow-up. Differences between ambulatory and non-ambulatory children and regional differences were assessed with the Log-rank test. RESULTS: Median radiological follow-up for ambulators was 51 months and 94 months for non-ambulators. The cumulative incidence of hip dislocation was 0.3% (95% CI: 0-0.8%) and 22.0% (95% CI: 9.2-34.8%) for ambulators and non-ambulators, respectively (p < 0.0001), whereas the incidence of hip displacement was 21.1% (95% CI: 16.3-25.9%) and 76.7% (95% CI: 68.6-84.7%) for ambulators and non-ambulators, respectively (p < 0.0001). There were no significant regional differences in the incidence of hip dislocation among ambulators, but there were significant differences for non-ambulators. Moreover, significant regional differences were detected in hip displacement for both ambulators and non-ambulators. CONCLUSIONS: The prevalence of hip migration in Danish children with CP is significantly higher among non-ambulators, who are at an increased risk of hip migration compared to their ambulant counterparts. However, the low frequency of radiographic follow-up for ambulators might cause the incidence of hip migration to be underestimated. This study highlights the necessity of continued targeted surveillance and interventions in Danish non-ambulators.

Reliability and Accuracy of Ultrasound Measurement of Hip Displacement in Children with Cerebral Palsy.

OBJECTIVE: Hip migration percentage (MP) measured on anteroposterior pelvis radiographs is the gold standard to assess the severity of hip displacement in children with cerebral palsy (CP). Repeated exposure of these children to ionizing radiation under a hip surveillance program is undesirable. Recently, a semi-automatic approach to measure MPUS on ultrasound (US) images was validated in a phantom study. This pilot in vivo study applied the previous phantom method and aimed to determine the reliability and accuracy of the MPUS. METHODS: Thirty-four children (23 boys and 11 girls) aged 8.9 ± 3.1 y old and diagnosed with CP were recruited. A total of 59 hips were scanned once, while 43 of these were scanned twice to evaluate the test-retest reliability. Two raters (R1 and R2) manually measured MPUS; procedures included selecting images of interest, cropping a region of interest and removing soft tissues on hip US images. Custom software was developed to measure MP automatically after the manual pre-image processing. RESULTS: The intra-class correlation coefficients (ICC2,1) for the test-retest (R1), intra-rater (R1) and inter-rater (R1 vs R2) reliabilities were 0.90, 0.94 and 0.82, respectively. The standard error of measurement of MPUS for all three evaluations was ≤3.0%. The mean absolute difference between MPUS and MPX-ray and the percentage of MPUS within clinical acceptance error of 10% for R1 and R2 were (R1: 6.2% ± 4.9%, 84.7%) and (R2: 7.6% ± 6.1%, 73.7%), respectively. CONCLUSION: This study demonstrated that US scans were repeatable and MPUS could be measured reliably and accurately.

Optimal configurations of an electromagnetic tracking system for 3D ultrasound imaging of pediatric hips - A phantom study.

Tracking the position and orientation of a two-dimensional (2D) ultrasound scanner to reconstruct a 3D volume is common, and its accuracy is important. In this study, a specific miniaturized electromagnetic (EM) tracking system was selected and integrated with a 2D ultrasound scanner, which was aimed to capture hip displacement in children with cerebral palsy. The objective of this study was to determine the optimum configuration, including the distance between the EM source and sensor, to provide maximum accuracy. The scanning volume was aimed to be 320 mm × 320 mm × 76 mm. The accuracy of the EM tracking was evaluated by comparing its tracking with those from a motion capture camera system. A static experiment showed that a warm-up time of 20 min was needed. The EM system provided the highest precision of 0.07 mm and 0.01° when the distance between the EM source and sensor was 0.65 m. Within the testing volume, the maximum position and rotational errors were 2.31 mm and 1.48°, respectively. The maximum error of measuring hip displacement on the 3D hip phantom study was 4 %. Based on the test results, the tested EM system was suitable for 3D ultrasound imaging of pediatric hips to assess hip displacement when optimal configuration was used.

A National Observational Study From 2010 to 2021 of the Trends in the Timing of Hip Surgery in Children With Cerebral Palsy: Is Surgery Being Performed Earlier?

Background Hip instability is a concern in pediatric cerebral palsy (CP) patients, with approximately one-third developing hip displacement. This may lead to pain, functional limitations, and decreased quality of life. Due to the progressive nature of hip displacement in CP, earlier surgical interventions may be beneficial. However, any shifts in practice to earlier surgical intervention, on a national scale, is not well described. The purpose of this study was to determine the recent trends in the surgical timing of hip interventions in children with CP. Methods A retrospective study was conducted using the PearlDiver Mariner all-payer claims database (PearlDiver Technologies, Colorado Springs, Colorado, United States). CP patients aged 10 years and younger were identified between 2010 and 2021. Hip surgeries including open reduction, adductor tenotomy, and pelvic osteotomy were identified. Patients were stratified by their age on the date of surgery and the year of the procedure. Linear regression analysis was conducted for temporal trends. Further, the compounded annual growth rate (CAGR) was calculated. Results A total of 309,677 CP patients were identified. For those aged one to four years old, the percentage undergoing hip surgery increased from 10.2% in 2010 to 19.4% in 2021. In the five- to 10-year-old age group, the surgery rate peaked at 14.9% in 2016 and steadily declined to 11.5% in 2021. The overall CAGR from 2010 to 2021 was +6.03% for the one- to four-year-old group and +0.88% for the five- to 10-year-old group. Linear regression demonstrated a significant association between year and the percentage of operations for patients ages one to four (R2=0.792, p<0.001), but not ages five-10 (R2=0.019, p=0.704). Conclusions Rates of surgical hip procedures in one- to four-year-old CP patients have been increasing since 2010, whereas the rate in five- to 10-year-old CP patients has been decreasing since 2016. Recently, CP patients may be undergoing hip surgery at younger ages.

Ultrasound Imaging of Hip Displacement in Children With Cerebral Palsy.

OBJECTIVE: An approach to estimation of hip displacement on ultrasound (US) images is described. Its accuracy is validated through numerical simulation, an in vitro study with 3-D-printed hip phantoms and pilot in vivo data. METHODS: A diagnostic index, migration percentage (MP), is defined by the ratio of acetabulum-femoral head distance to femoral head width. The acetabulum-femoral head distance could be measured directly on hip US images, while the femoral head width was estimated from the diameter of a best-fit circle. Simulation was performed to evaluate the accuracy of circle fitting with noiseless and noisy data. Surface roughness was also considered. Nine hip phantoms (three different sizes of femur head × three MP values) and 10 US hip images were used in this study. RESULTS: The maximum diameter error was 16.1 ± 8.5% when the roughness and noise were 20% of the original radius and 20% of the wavelet peak, respectively. In the phantom study, the percentage errors of MPs between the 3-D-design US and X-ray US were 0.3%-6.6% and 0.0%-5.7%, respectively. From the pilot clinical trial, the mean absolute difference between the X-ray-US MPs was 3.5 ± 2.8% (1%-9%). CONCLUSION: This study indicates that the US method can be used to evaluate hip displacement in children.

Definition of hip displacement and dislocation by acetabular dysplasia in children with cerebral palsy.

Purpose: The acetabulum interacts with the femoral head in daily activities and may exhibit structural changes in the presence of hip disorders. This study aims to redefine hip disorders in children with cerebral palsy by structural characteristics of the acetabulum in relation to the degree of the migration percentage. Methods: The clinical and radiographic data of 70 patients (36 males, 34 females; mean age 8.2 years) with spastic cerebral palsy were retrospectively analyzed. The acetabular structure was measured by the acetabular index on reconstructed three-dimensional computerized tomography for precision of measurement. Any significant change in acetabular index measured on the reconstructive computerized tomography related to every 10% increment of migration percentage was regarded as clinically significant in hip disorders. Results: The acetabular index measured on the reconstructive computerized tomography showed an increasing trend with the increment of migration percentage. The most significant acetabular index measured on the reconstructive computerized tomography change occurred between the 20%-29% and 30%-39% migration percentage groups (p < 0.001), suggesting that a migration percentage of 30% is the starting point of hip disorder. A significant increase in the posterolateral acetabular index measured on the reconstructive computerized tomography occurred in migration percentages >50%, indicating posterolateral acetabular dysplasia. Hips with migration percentages from 80% to 100% had consistent acetabular indexes measured on the reconstructive computerized tomography values, suggesting complete dislocation and no more contact and interaction between the femoral head and acetabular fossa. Conclusion: Structural characteristics in the acetabulum reflect hip dysfunction and potentially classify hip disorders. Results suggest the migration percentage 30% as a starting point of hip disorder and 80% as a turning point of hip dislocation in children with cerebral palsy. Level of evidence: level IV, diagnostic study.