Pelvis radiographs in children with cerebral palsy: effects of patient positioning on calculating migration percentages.

BACKGROUND: Hip displacement in children with cerebral palsy (CP) is monitored by measuring migration percentage on anteroposterior pelvis radiographs. However, proper positioning for radiography in children with spasticity is difficult. The reliability and accuracy of migration percentage as a function of patient positioning is unknown. OBJECTIVE: To determine the effects of patient positioning on migration percentage measurements in children with CP. MATERIALS AND METHODS: We identified children with CP (≤18-year-old) with pelvis CT and anteroposterior pelvis radiograph obtained <6 months apart (10/2018-11/2021). Digitally reconstructed radiographs were generated from each pelvis CT, to simulate nine different patient positions: neutral; 10° and 20° lordosis and kyphosis; and 10° and 20° right rotation and left rotation. Two radiologists measured migration percentages from the simulated and real pelvis radiographs. We used Spearman's rho to assess inter-rater reliability, and Wilcoxon signed rank test to determine statistical significance. RESULTS: We studied sixty-three children (male=41; median age=8 years; range=4-18 years). The two radiologists' migration percentage measurements were highly correlated with each other across all simulated and real radiographs (Spearman's rho=0.86-0.99, P<0.01). For both readers and hips, migration percentages measured from real radiographs were significantly different from those measured from neutral simulated radiographs (P<0.01), with median absolute difference=5-6 percentage points (PP) and interquartile range (IQR)=9-12 PP. When comparing migration percentage measurements from neutral simulated radiographs to those in kyphosis/lordosis and right/left rotations, median absolute differences were 2-4 PP (IQR=3-8 PP) and 4-15 PP (IQR=6-17 PP), respectively. CONCLUSION: Inter-rater reliability of measured migration percentages is high, but accuracy decreases with patient positional changes.

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.

Beyond Words: Embracing Migration Percentage as the Universal Measurement for Hip Displacement in Children With Cerebral Palsy by Radiologists and Orthopedic Surgeons.

INTRODUCTION: Migration percentage (MP) is the standard radiographic measurement to quantify hip displacement in cerebral palsy (CP) hip surveillance programs. We aim to evaluate the use of MP and other descriptors of hip displacement in radiographic impressions by radiologists and orthopedic surgeons before and after the introduction of hip surveillance guidelines at our institution. METHODS: CP patients who underwent hip surveillance imaging at our institution in 2016 were retrospectively identified, and their radiographic impressions were collected between 2016 and 2019. Only patients with radiology and orthopedic impressions for the same image were included. The inclusion of MP was documented and compared between the two groups before and after the hip guidelines were implemented in 2018. We also examined the use of other qualitative descriptors for hip displacement within the impressions. Fisher's Exact test was used for statistical significance (p<0.05).  Results: Two hundred and fifty-one radiographs were analyzed. One radiology (0.40%) and 33 orthopedic impressions (13.15%) incorporated MP (p<0.001). No statistical significance was found between the inclusion of MP before and after 2018 in the radiology group. In contrast, the orthopedic group showed a significant increase in MP inclusion following guideline implementation, rising from 12 to 21 incidences (p=0.013). Descriptors for hip displacement were more commonly utilized than MP for both orthopedic surgeons and radiologists.  Conclusion: MP is underutilized in radiologic and orthopedic impressions in hip surveillance programs. Extensive education for both specialties regarding MP is crucial for the successful management of hip displacement in CP hip surveillance programs.

Effect of hip CPM on gross motor function and development of the hip joint: a single-center randomized controlled study on spastic cerebral palsy children with hip dysplasia.

Objective: To investigate the effectiveness of hip continuous passive motion (hCPM) on hip development at skeletal maturity and gross motor function for spastic cerebral palsy children with hip dysplasia. Methods: Prospective case-control research of hCPM with goal-directed training versus merely goal-directed training. On the basis of goal-directed training, the hCPM group used the hip joint CPM instrument (the external fixator was connected to the power device to make the hip joint carry out continuous passive movement) for 40-60 min, twice a day, and five times a week, and received continuous training for 8 weeks simultaneously. The control group received only goal-directed training for 8 weeks. Functional outcomes pertaining to the affected hip joints were assessed via gross motor function measure (GMFM), migration percentage (MP), acetabular index (AI), and Harris hip functional score (HHS) at the time of enrollment and the end of the intervention. Results: The case-control research included 65 participants (mean age = 46.20 months, SD = 17.09 months; Gross Motor Function Grading System level: III = 41, IV = 24) who were randomly selected to either the hCPM (n = 45) or the control group (n = 20). No differences were found in baseline (acquisition phase) GMFM, MP, AI, or HHS (t = -1.720, P = 0.090; t* = 1.836, P* = 0.071; t# = -1.517, P# = 0.139; t* = -1.310, P* = 0.195; t# = -1.084, P# = 0.097; t = -1.041, P = 0.301). At the 8-week follow-up, GMFM, MP, AI, and HHS significantly improved over baseline in the hCPM group (hCPM group: t = 18.59, 20.172*, 40.291#, 16.820*, 32.900#, 28.081; P < 0.001). Between-group differences at 8-week follow-up times points favored the hCPM group for GMFM (t = -2.637, P = 0.011), MP (t* = 2.615, P* = 0.014; t# = 3.000, P# = 0.006), AI (t* = 2.055, P* = 0.044; t# = 2.223, P# = 0.030), HHS (t = -4.685, P < 0.001) (*: left side; #: right side). Conclusion: Spastic cerebral palsy children with hip dysplasia achieved meaningful functional improvement after 8 weeks of goal-directed training with hCPM therapy.

Risk factors for hip displacement in cerebral palsy: A population-based study of 121 nonambulatory children.

Purpose: The aim was to evaluate which clinical and radiographic variables are independent (true) risk factors for hip subluxation in nonambulatory children below 5 years of age with cerebral palsy. Methods: Patients were recruited from a population-based hip surveillance program. Inclusion criteria were birth during 2002-2006, age below 5 years, and gross motor function classification system levels III-V. In all, 121 children (71 boys) met these criteria. Gross motor function classification system was level III in 29 patients, level IV in 28, and level V in 64. Anteroposterior radiographs at diagnosis and during follow-up were assessed, and only the worst hip of each patient was used for the analyses. The mean age at the initial radiograph was 2.5 years (range: 0.7-4.9 years), and the mean follow-up time was 4.0 years (range: 0.5-11.8 years). Results: At the last follow-up, 67 children had a clinically significant hip displacement, defined as migration percentage ≥40%. Univariable regression analysis defined these risk factors: gross motor function classification system level V, spastic bilateral cerebral palsy, initial migration percentage, yearly rate of migration percentage progression, and initial acetabular index. When these variables were analyzed with multivariable regression in 107 patients with initial migration percentage <50% and follow-up ≥1.0 year, the independent risk factors were initial migration percentage (p = 0.003) and yearly rate of migration percentage progression (p < 0.001). Conclusion: The parameters that need to be assessed in hip surveillance in children below 5 years of age are initial migration percentage and rate of migration percentage progression. Acetabular index and femoral head-shaft angle might be useful later for decision-making regarding choice of treatment. Level of evidence: Level II, development of diagnostic criteria.

Imaging Parameters of Hip Dysplasia in Cerebral Palsy: A Systematic Review.

Background: Cerebral Palsy is the leading cause of childhood physical disability globally. The motor disorders of CP are often associated with musculoskeletal anomalies, of which hip displacement is the second most common abnormality after abnormalities of foot and ankle. Various radiological parameters have been described in the literature which detects and quantifies hip dysplasia, with MP being the current gold standard. This study aims to review these radiological indicators of hip dysplasia in children with cerebral palsy from the published literature. Methods: A literature search using PubMed, Embase, and Google Scholar was done on 15th June 2021 focusing on surveillance of hip dysplasia in cerebral palsy. The studies to be included were to have used anyone or more radiological parameter for detection of hip dysplasia with the use of any of the radiological methods. Results: The initial search yielded 1184 results. After the screening of the abstracts and full texts, a final of 30 studies was included for this systematic review. The majority of the studies were graded as Level 3 evidence (16/30), followed by Level 2 studies (14/30). X-ray was the most common modality of detection of dysplasia followed by CT scan, ultrasonography, and arthrogram. The reproducibility of the various parameters shows good to excellent intraclass coefficients. Conclusions: Parameters other than MP can be used to screen hips in CP. This would be useful in patients in whom either the lateral acetabular edge is not discernible on a plain anteroposterior radiograph or there are issues in the positioning of the patient. Additional views and structures can be visualized which can lead to improved screening and planning. Further investigations are required to appreciate the full potential of these parameters and how they can be better utilized.

A retrospective cohort study about hip luxation in non-ambulatory cerebral palsy patients: The point of no return.

Purpose: The migration percentage is a widely used criterion for surgery in displaced hips. Literature suggests that no hip can spontaneously improve if the migration percentage exceeds 45%, in a mixed population of cerebral palsy children. The aim of the present article was to identify the point of no return of the migration percentage in a selected sample of non-ambulatory cerebral palsy children, being the most exposed to hip luxation. Methods: This single-center retrospective cohort study included patients with spastic or dyskinetic cerebral palsy, Gross Motor Function Classification System level IV or V, age 0-18, having at least three pelvic radiographies, excluding radiographies relative to hips having previously undergone surgery. The following information was collected: sex, cerebral palsy subtype, Gross Motor Function Classification System level, presence of drug-resistant epilepsy, migration percentage, age at assessment, use of walking or standing assistive devices, previous botulinum injection, oral or intrathecal baclofen, and hip pain. Data were analyzed at the level of the individual hips. Descriptive statistics were presented. Receiver operating characteristic curve analysis was conducted to investigate which value of the migration percentage could be adopted as the "point of no return": that is, the cutoff value beyond which no migration percentage reduction, by more than 5%, could be expected. Results: The optimal cutoff value was identified as migration percentage ≥50%, with a sensitivity of 84.5% and a specificity of 100% (p-value <0.001). Conclusion: Based on the present study, migration percentage ≥50% is the "point of no return" for Gross Motor Function Classification System IV-V cerebral palsy patients, representing the cutoff value beyond which no spontaneous cerebral palsy reduction may be expected, unless addressing surgery. Level of evidence: level II-retrospective study.

Migration of Trivalent Praseodymium from Tombarthite Sewage by Microtubule Ultrafiltration Reactor with Organophosphorus in Fuel Oil.

A microtubule ultrafiltration reactor (MUFR), with an organophosphorus system containing a sewage section with buffer liquid acetic acid and an enrichment section with aqua fortis liquid and organophosphorus dissolved in fuel oil, has been studied for praseodymium(III) migration. Many factors of praseodymium(III) migration using MUFR need to be explored, including hydrogen ion molarity (or pH), cinit of praseodymium(III), the different ionic strengths of rare-earth mine sewage, the volume ratio of organophosphorus fuel oil and aqua fortis liquid (O/A), aqua fortis' molarity, organophosphorus' molarity, and the effects of different acid liquids in the enrichment section on praseodymium(III) migration with MUFR. The virtues of MUFR compared to conventional migration were explored. The effects of the hydrodynamic properties (stability and flow velocity) and UF system parameters (internal diameter of the microtubule, tubule shell thickness, void ratio), etc., on the mass migration performance of the MUFR process for praseodymium(III) migration were also studied. The experimental results show that the best migration prerequisites of praseodymium(III) were obtained as follows: an aqua fortis molarity of 4.00 mol/L, an organophosphorus molarity of 0.200 mol/L, an O/A of 0.6 in the enrichment section, and a pH value of 4.80 in the sewage section. The ionic strength of rare-earth mine sewage had no obvious effect on praseodymium(III) migration. When the cinit of praseodymium(III) molarity was 1.58 × 10-4 mol/L, the migration percentage of praseodymium(III) reached 95.2% in 160 min.

Hip surgery and radiology reporting for children with cerebral palsy prior to initiation of a hip surveillance program.

PURPOSE: Hip displacement impacts quality of life for many children with cerebral palsy (CP). While early detection can help avoid dislocation and late-stage surgery, formalized surveillance programs are not ubiquitous. This study aimed to examine: 1) surgical practices around pediatric hip displacement for children with CP in a region without formalized hip surveillance; and 2) utility of MP compared to traditional radiology reporting for quantifying displacement. METHODS: A retrospective chart review examined hip displacement surgeries performed on children with CP between 2007-2016. Surgeries were classified as preventative, reconstructive, or salvage. Pre- and post-operative migration percentage (MP) was calculated for available radiographs using a mobile application and compared using Wilcoxon Signed Ranks test. MPs were also compared with descriptions in the corresponding radiology reports using directed and conventional content analyses. RESULTS: Data from 67 children (115 surgical hips) were included. Primary surgery types included preventative (63.5% hips), reconstructive (36.5%), or salvage (0%). For the 92 hips with both radiology reports and radiographs available, reports contained a range of descriptors that inconsistently reflected the retrospectively-calculated MPs. CONCLUSION: Current radiology reporting practices do not appear to effectively describe hip displacement for children with CP. Therefore, standardized reporting of MP is recommended.

Hip Displacement in Cerebral Palsy: The Role of Surveillance.

INTRODUCTION: Hip displacement is common in cerebral palsy (CP) and is related to the severity of neurological and functional impairment. It is a silent, but progressive disease, and can result in significant morbidity and decreased quality of life, if left untreated. The pathophysiology of hip displacement in CP is a combination of hip flexor-adductor muscle spasticity, abductor muscle weakness, and delayed weight-bearing, resulting in proximal femoral deformities and progressive acetabular dysplasia. Due to a lack of symptoms in the early stages of hip displacement, the diagnosis is easily missed. Awareness of this condition and regular surveillance by clinical examination and serial radiographs of the hips are the key to early diagnosis and treatment. HIP SURVEILLANCE PROGRAMMES: Several population-based studies from around the world have demonstrated that universal hip surveillance in children with CP allows early detection of hip displacement and appropriate early intervention, with a resultant decrease in painful dislocations. Global hip surveillance models are based upon the patients' age, functional level determined by the Gross Motor Function Classification system (GMFCS), gait classification, standardized clinical exam, and radiographic indices such as the migration percentage (MP), as critical indicators of progressive hip displacement. CONCLUSION: Despite 25 years of evidence showing the efficacy of established hip surveillance programmes, there is poor awareness among healthcare professionals in India about the importance of regular hip surveillance in children with CP. There is a need for professional organizations to develop evidence-based guidelines for hip surveillance which are relevant to the Indian context.

Is the Gothic Arch a reliable radiographic landmark for migration percentage in children with cerebral palsy?

INTRODUCTION: Reimers migration percentage (MP) is the gold standard for measuring hip displacement in children with cerebral palsy (CP). Hip surveillance registries proposed using the top of the Gothic arch (GA) as a modification in patients with acetabular dysplasia because the classical method (CM) described by Reimers may underestimate hip migration. The aim of this study is to assess the inter- and intra-observer reliability of the modified method (MM) versus the CM and identify their effect on the MP. METHODS: We performed a retrospective review of 50 children with CP, who had a hip radiograph at our institution between 1st April 2014 and 28th February 2018. All hip radiographs were carefully selected to show the presence of a GA. Four observers measured the MP using the CM and MM for each patient. Interclass coefficient was used to estimate inter- and intra-observer reliability. RESULTS: Inter-observer reliability was excellent for the CM with ICC 0.96 (95% CI 0.94 to 0.97) and good for the MM, ICC 0.78 (95% CI 0.51 to 0.89) p < 0.001. Intra-observer reliability was excellent for both methods raging from ICC 0.94 to 0.99 for the CM and ICC 0.89 to 0.95 for the MM. The mean MP was 19% for the CM and 28% for the MM (p < 0.001). CONCLUSION: The CM is more reliable than the MM to measure hip migration in children with CP. If the CM is used and acetabular dysplasia with a GA are present on the hip radiograph, then a 9% hip migration underestimation should be considered on decisions for both referral and surgical management. LEVEL OF EVIDENCE: II.

Postural asymmetry in non-ambulant adults with cerebral palsy: a scoping review.

PURPOSE: Non-ambulant adults with cerebral palsy are vulnerable to development of postural asymmetry and associated complications. The primary aim of this scoping review was to identify postural deformities in non-ambulant adults with cerebral palsy. MATERIALS AND METHODS: Comprehensive searches were undertaken in EMBASE, CINAHL, AMED, Cochrane, Psych INFO, and Joanna Briggs (1986-Jan 2017), supplemented by hand searching. Two reviewers independently extracted data using a customised tool focusing on study design, participant characteristics, postural descriptors, measurement tools, and interventions. RESULTS: From 2546 potential records, 17 studies were included. Variability in populations, reporting methodology, and measurement systems was evident. Data suggest more than 30% of this population have hip migration percentage in excess of 30%, more than 75% experience "scoliosis", and more than 40% demonstrate pelvic obliquity. Estimates ranged from 14% to 100% hip and 32% to 87% knee contracture incidence. Conservative interventions were infrequently and poorly described. CONCLUSION: Many non-ambulant adults with cerebral palsy experience postural asymmetry associated with windswept hips, scoliosis, pelvic obliquity, and limb contracture. Options for non-radiographic monitoring of postural asymmetry should be identified, and conservative interventions formally were evaluated in this population. Implications for rehabilitation The common postural asymmetries of windswept hips, scoliosis, pelvic obliquity, and limb contracture require standardised clinical measurement. Radiography is most commonly used to monitor postural asymmetry in this population, but standardised positioning is not applied and may not be feasible indicating a need for alternate methods and rigorous documentation. The Posture and Postural Ability Scale may be considered for use in the management of body shape in adults with CP.

A single-center retrospective review of factors influencing surgical success in patients with cerebral palsy undergoing corrective hip surgery.

PURPOSE: To identify factors associated with success of corrective bony hip surgery among patients with cerebral palsy (CP). METHODS: A retrospective review was conducted of medical records of patients diagnosed with CP and hip displacement who underwent surgery from 2004 to 2016 at the authors' institution and who had a one-year minimum follow-up. Patient age, sex, Gross Motor Function Classification System (GMFCS) level, surgical procedure(s), type and extent of CP, presence of preoperative and postoperative hip pain, and hip migration percentages (MPs) were recorded. Surgical success was defined as a postoperative MP ⩽ 30% and no hip pain at final follow-up. RESULTS: Thirty-eight patients (55 hips) met the inclusion criteria. Mean age at surgery was 10.2 years (range, 2-24 years). Mean MP (standard deviation) improved from 64 ± 29% preoperatively to 22 ± 30% at a mean 1.7-year follow-up (p< 0.001). The absence of preoperative hip pain (p= 0.014), surgery after age 5 (p= 0.041), and a milder preoperative MP (p< 0.001) were significantly associated with surgical success. CONCLUSION: In patients with CP and hip displacement, early preventative correction of hip displacement after age 5 may improve clinical outcomes, though future studies are needed to provide more definitive clinical direction.

Migration percentage and odds of recurrence/subsequent surgery after treatment for hip subluxation in pediatric cerebral palsy: a meta-analysis and systematic review.

PURPOSE: This meta-analysis aims to systematically assess and quantitatively pool the best clinical evidence for migration percentage (MP) and odds ratio (OR) for recurrence/reoperation following treatment for hip subluxation in children with cerebral palsy (CP), including Botulinum Toxin A (BNT-A), soft-tissue lengthening and osteotomies. METHODS: Pubmed, EMBASE and Cochrane were systematically searched from between 1 January 1953 and 11 January 2017 inclusive for studies reporting resubluxation/reoperation rates, and/or MP following treatment for hip subluxation in children with CP. The primary outcome was odds of resubluxation/reoperation. The secondary outcome was change in MP. Studies were graded for quality using the Newcastle Ottawa Scale. This meta-analysis was performed and reported in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. RESULTS: A total of 14 studies were included in analysis of odds of resubluxation/reoperation and 24 studies were included in analysis of MP. The OR for resubluxation/reoperation was lower for combined osteotomies compared with femoral (OR = 0.49; 95% confidence interval (CI) 0.25 to 0.98) and for femoral osteotomy compared to soft-tissue procedures (OR = 0.20; 95% CI 0.07 to 0.61). There was no difference in odds of recurrence/reoperation between pelvic and femoral osteotomies (OR = 2.27; 95% CI 0.37 to 13.88). Combined osteotomies provided the greatest improvement in MP, while BoNT-A showed no improvement in MP. CONCLUSION: Resubluxation/reoperation rates are high; management with osteotomies is preferred to soft-tissue procedures alone in preventing resubluxation/reoperation. This meta-analysis is limited by the observational nature and small sample sizes of many of the included studies, with their inherent risk of bias and lack of homogeneity of patient characteristics at baseline. It is possible that with larger and higher quality studies, the results and conclusions of this analysis may be altered.

Relationship between lumbar spine development and hip development in children with spastic cerebral palsy / 中国组织工程研究

BACKGROUND:Most scholars now believe that children with cerebral palsy who have severe spinal deformities in early childhood(<15 years of age)may have a higher risk of progression of spinal deformities,which may result from imbalances in movement due to pelvic tilt,pain,etc. OBJECTIVE:To investigate the relationship between lumbar spine development and hip joint development in children with spastic cerebral palsy. METHODS:A retrospective analysis was performed in 102 children with spastic cerebral palsy admitted at Dongzhimen Hospital Affiliated to Beijing University of Chinese Medicine from January 2014 to December 2021.All admitted children had X-rays of the pelvic position and the lumbar lateral position.Anteroposterior X-ray of the pelvis was performed to measure femoral head migration percentage,central edge angle,neck-shaft angle,and acetabular index.The sagittal Cobb angle,sacral slope,arch-top distance,and lumbar lordosis index were measured by the lateral X-ray of the lumbar spine.Correlation of the two sets of indicators was further analyzed.All children were divided into normal group,risk group,hip subluxation group and total hip dislocation group according to their femoral head migration percentage,and the differences in lumbar spine indexes between groups were evaluated. RESULTS AND CONCLUSION:Pearson correlation analysis showed that the femoral head migration percentage was moderately positively correlated with sagittal Cobb angle and arch-top distance,and weakly positively correlated with lumbar lordosis index;the central edge angle was moderately negatively correlated with the arch-top distance and weakly negatively correlated with the sagittal Cobb angle;the neck-shaft angle was weakly positively correlated or not correlated with the sagittal Cobb angle and lumbar lordosis index;and the acetabular index was weakly positively correlated with the sagittal Cobb angle and arch-top distance.No statistically significant correlation was found between the remaining indicators.According to the femoral head migration percentage,the children were divided into four groups,including 25 cases in the normal group,41 cases in the risk group,27 cases in the hip subluxation group,and 9 cases in the total hip dislocation group.The sagittal Cobb angle was significantly increased in the risk group,the hip subluxation group and the total hip dislocation group compared with the normal group,showing an increasing trend group by group,and there were significant differences between groups(P<0.05).Compared with the normal group,the lumbar lordosis index in the risk group and the hip subluxation group increased significantly,and there were significant differences between groups(P<0.05).There was an increase trend in the lumbar lordosis index of the total hip dislocation group compared with the normal group.Compared with the normal group,the arch-top distance in the hip subluxation group and the total hip dislocation group increased significantly(P<0.05),and there was a stepwise increasing trend.There was no significant difference in sacral slope between groups.To conclude,the development of the lumbar spine in children with cerebral palsy is closely related to the development of the pelvic hip joint,and the most obvious relationship is between lumbar lordosis and hip dislocation.

Evaluation of errors in measurements of infantile hip radiograph using digitally reconstructed radiograph from three-dimensional MRI.

PURPOSE: Plain hip radiograph is commonly used for the diagnosis of infantile acetabular dysplasia. Many infants are unable to maintain adequate position during radiography. Besides, the infantile hip is much smaller and has a higher cartilage component in the acetabulum and proximal femur compared with the adult hip. In this study, we developed a digitally reconstructed radiograph synthesized from magnetic resonance imaging (MRI) and investigated errors of hip radiographic measurements in different pelvic positions. PATIENTS AND METHODS: MRI of both hips was performed in 10 patients (mean age 3.9 years). Three-dimensional (3D) bone models were created from MRI data. We tilted 3D pelvic bone models between 10° anteversion and retroversion and through 10° rotation on the affected and contralateral sides using 3D axes. Following this, we created digitally reconstructed radiographs in each pelvic position and calculated the acetabular index (AI), center-edge angle (CEA), migration percentage (MP), and teardrop distance (TDD). RESULTS: AI tended to increase with pelvic retroversion and did not change with pelvic rotation. CEA tended to decrease with pelvic retroversion and rotation on the contralateral side. MP increased with pelvic retroversion and rotation on the contralateral side. TDD did not change significantly with pelvic tilt and rotation. CONCLUSIONS: Radiographic measurements of hip in infants were highly influenced by pelvic movement. AI was influenced by pelvic tilt; CEA and MP were influenced by both pelvic tilt and rotation. We need to keep in mind that infantile hip radiographs could have about ±5° errors in AI and CEA.

Reliability and efficiency of three methods of calculating migration percentage on radiographs for hip surveillance in children with cerebral palsy.

PURPOSE: Hip surveillance programmes for children with cerebral palsy (CP) utilize the migration percentage (MP) measurement to initiate referrals and recommend treatment. This study assesses the reliability and efficiency of three methods of MP measurement on anteroposterior (AP) pelvis radiographs. METHODS: A total of 20 AP pelvis radiographs (40 hips) of children with CP were measured by three raters on two occasions using three methods: digital measurement (DM) on a Picture Archiving and Communication System monitor, computer-aided measurement (CA) using a digital templating tool and mobile device application measurement (MA) using a freely available MP measurement tool. For each method, the time required to complete the MP measurement of both hips on each AP pelvis radiograph was measured. Intra-class correlation coefficient (ICC) was used to determine reliability, and analysis of variance was used to compare groups. RESULTS: All three methods of determining MP showed excellent inter-rater and intra-rater reliability (ICC 0.976 to 0.989). The mean absolute difference in MP measurement was not significant between trials for a single rater (DM 2.8%, CA 1.9%, MA 2.2%) or between raters (DM 3.6%, CA 2.9%, MA 3.6%). The mean time to complete MP measurement was significantly different between methods, with DM = 151 seconds, CA = 73 seconds and MA = 80 seconds. CONCLUSION: All three MP measurement methods were highly reliable with clinically acceptable measurement error. The time required to measure a hip surveillance radiograph can be reduced by approximately 50% by utilizing a computer-based or mobile application-based MP measurement tool.

Avascular necrosis in children with cerebral palsy after reconstructive hip surgery.

PURPOSE: Progressive hip displacement is one of the most common orthopaedic pathologies in children with cerebral palsy (CP). Reconstructive hip surgery has become the standard treatment of care. Reported avascular necrosis (AVN) rates for hip reconstructive surgery in these patients vary widely in the literature. The purpose of this study is to identify the frequency and associated risk factors of AVN for reconstructive hip procedures. METHODS: A retrospective analysis was performed of 70 cases of reconstructive hip surgery in 47 children with CP, between 2009 and 2013. All 70 cases involved varus derotation osteotomy (VDRO), with 60% having combined VDRO and pelvic osteotomies (PO), and 21% requiring open reductions. Mean age at time of surgery was 8.82 years and 90% of patients were Gross Motor Function Classification System (GMFCS) 4 and 5. Radiographic dysplasia parameters were analysed at selected intervals, to a minimum of one year post-operatively. Severity of AVN was classified by Kruczynski's method. Bivar- iate statistical analysis was conducted using Chi-square test and Student's t-test. RESULTS: There were 19 (27%) noted cases of AVN, all radio- graphically identifiable within the first post-operative year. The majority of AVN cases (63%) were mild to moderate in severity. Pre-operative migration percentage (MP) (p = 0.0009) and post-operative change in MP (p = 0.002) were the most significant predictors of AVN. Other risk factors were: GMFCS level (p = 0.031), post-operative change in NSA (p = 0.02) and concomitant adductor tenotomy (0.028). CONCLUSION: AVN was observed in 27% of patients. Severity of displacement correlates directly with AVN risk and we suggest that hip reconstruction, specifically VDRO, be performed early in the 'hip at risk' group to avoid this complication.

An independent assessment of reliability of the Melbourne Cerebral Palsy Hip Classification System.

PURPOSE: Neuromuscular (NM) hip dysplasia is common in patients with cerebral palsy (CP). Traditionally, migration percentage (MP) has been used to measure the severity of NM hip dysplasia; however, the MP has some limitations. The purpose of this study is to determine the intra- and inter-reliability of the Melbourne Cerebral Palsy Hip Classification System in the typical paediatric population of patients with CP. METHODS: A total of 65 anteroposterior pelvis radiographs in patients (age range 12 years to 21 years) with CP spanning all grades (I to VI) of the classification system were identified and collected for analysis in this institutional review board approved study. Four paediatric orthopaedic surgeons and one orthopaedic surgical resident classified each radiograph according to the Melbourne system. Then, at least four weeks later, the raters repeated the process with a re-randomised order of radiographs. Statistical analysis was performed using the intraclass correlation coefficient (ICC) where < 0 denotes poor agreement and > 0.8 indicates almost perfect agreement. RESULTS: The interobserver reliability was found to be excellent with the ICC of 0.853 (0.813 to 0.887) and 0.839 (0.795 to 0.877). The intraobserver reliability was also found to be excellent with the ICC in the range of 0.838 to 0.933 among the raters. Subgroup analysis indicated no differences in the reliability of observers based on clinical experience. CONCLUSION: This study independently demonstrates that the Melbourne Cerebral Palsy Hip Classification System for NM hip dysplasia in patients with CP can be reliably used for communication among various healthcare providers and research and epidemiological purposes.