Three-dimensional evaluation of skeletal deformities of the pelvis and lower limbs in ambulant children with cerebral palsy

doi:10.1016/j.gaitpost.2016.06.029

Gait & Posture

Volume 49, September 2016, Pages 102-107

https://doi.org/10.1016/j.gaitpost.2016.06.029 Get rights and content

Highlights

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Skeletal abnormalities are known to affect the posture of children with CP.
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Skeletal parameters were evaluated in 3D using biplanar X-rays.
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Ambulatory CP without surgical history was enrolled along with TD subjects.
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3D acetabular parameters were described for the first time in children.
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Pelvic and lower limb parameters were altered in children with CP.

Abstract

Skeletal abnormalities, affecting posture and walking pattern, increase with motor impairment in children with cerebral palsy (CP). However, it is not known whether these skeletal malalignments occur in children with slight motor impairment. Our aim was to evaluate skeletal malalignment at the level of the pelvis and lower limbs in ambulant children with CP, with slight motor impairment, using a low dose biplanar X-ray technique.

Twenty-seven children with spastic CP (mean age: 10.9 ± 4 years, 7 Hemiplegia, 20 Diplegia, GMFCS levels I:17, II:10), with no previous treatments at the hips and knees, underwent EOS^® biplanar X-rays. A control group consisting of 22 typically developing children was also included. Three-dimensional reconstructions of the pelvis and lower limbs were performed in order to calculate 11 radiological parameters related to the pelvis, acetabulum and lower limbs.

Pelvic incidence and sacral slope were significantly increased in children with CP compared to TD children (48° ± 7° vs. 43° ± 8°, 42° ± 7° vs. 38° ± 5°, respectively, p = 0.003). Acetabular parameters did not significantly differ between the two groups. Femoral anteversion and neck shaft angle were significantly increased in children with CP (25° ± 12° vs. 14° ± 7°, p < 0.001; 134° ± 5° vs. 131° ± 5°, p = 0.005 respectively). No difference was found for tibial torsion.

This study showed that even slightly impaired children with CP have an anteverted and abducted femur and present positional and morphological changes of the pelvis in the sagittal plane. The orientation of the acetabulum in 3D seems to not be affected when children with CP present slight motor impairment.

Introduction

Cerebral Palsy (CP) is a neurological disorder that can cause muscle spasticity. The increased muscle tone of patients with CP is known to affect their posture and walking pattern [1]. Skeletal malalignments of the lower limbs are often encountered in children with CP in the three planes [2], [3], [4] and are mainly caused by spasticity, abnormal posture, delays in gaining independent walking as well as gait alterations [5].

Previous studies have reported that skeletal malalignments of the lower limbs increase with motor impairment [2], [6]. These studies have described only a few femoral parameters (neck shaft angle and femoral parameters) in different groups of CP that differed by their motor impairment but did not compare their results to those of control groups [2], [7]. Moreover, it is not known whether these skeletal malalignments occur even in children with slight motor impairment.

Other studies have reported skeletal abnormalities of the hip and acetabulum in children with CP, such as hip dysplasia or acetabular deficiencies [8], [9]. It was suggested that these abnormalities, which had been reported in severely affected children with CP, were mainly due to abnormal weight-bearing on the lower limbs. Since slightly impaired children with CP also present abnormal weight-bearing, it would be interesting to elucidate whether their acetabular parameters are affected as well.

The assessment of skeletal malalignments is important in surgical decision-making for children with CP [10], and is usually based on physical examination [11], two-dimensional X-Ray imaging [12] and three-dimensional (3D) gait analysis [13]. However, torsional abnormalities, such as abnormal femoral anteversion (FA) or tibial torsion (TT), require measurements in 3D.

Three-dimensional computed tomography (CT) is a reliable tool to measure FA and TT [10]. This technique has been used to measure these parameters in children with CP [6]. However, the use of this technique is limited by the high exposure to radiation [14] and the fact that its accuracy is affected by positional variables [10], which are difficult to control in children with CP. For these reasons, 3D CT scan is not routinely used to assess lower limb skeletal abnormalities in children with CP.

Low dose biplanar X-rays have been previously found to be a fast and reliable tool for the measurement of skeletal malalignments in the standing position [15], [16], [17]. This technique allows quantification of subject-specific skeletal parameters based on 3D reconstruction of the pelvis and lower limbs [16], [18] and could be a viable alternative to CT in daily practice.

The aim of this study was to investigate whether ambulant children with CP, with slight motor impairment, present skeletal deformities at the pelvis and lower limbs, using the low dose biplanar X-ray technique.

Section snippets

Population

This is an IRB approved cross-sectional case-control review of a consecutive series of children with CP who underwent full body low dose biplanar radiographs using EOS^® system (EOS Imaging, Paris France), in the setting of their pre-treatment evaluation.

Twenty-seven children with spastic CP (17 boys, 10 girls) were included. Motor impairment was defined according to GMFCS E&R levels [19]. Children with a history of previous orthopedic interventions (botulinum toxin, casting, surgery), other

Comparison between TD and CP children

Comparison of age, weight and height (Table 1) between the two groups showed no significant differences (p = 0.355, p = 0.441 and p = 0.129 respectively). Mean values of the radiological parameters for the TD and CP children are reported in Table 3.

The mean value of the pelvic incidence (PI) was significantly increased in the CP population compared to TD (48° ± 7° vs. 43° ± 8° respectively, p = 0.003, d = 0.66). A significantly more vertical sacral plate was found in children with CP compared to the control

Discussion

In this study, a comparison of 3D postural and morphological skeletal parameters of both pelvis and lower limbs, between TD and ambulant children with CP presenting GMFCS levels I and II, was performed using the EOS^® biplanar X-ray system. The children with CP included in this study had neither medical nor surgical history. This is the first study that calculated the acetabular parameters in CP and TD groups. While no differences were found for the acetabular parameters and tibial torsion, the

Conclusion

In conclusion, this study showed that even slightly impaired ambulant children with CP present an anteverted and abducted femur. The orientation of the acetabulum and the tibial torsion were not found to be affected; however morphological and postural changes at the pelvis in the sagittal plane were noted. The low dose biplanar X-ray technique could be routinely used in daily practice in order to assess in 3D pelvic and lower limb deformities in children with CP. The quantification of these

Conflict of interest

None.

Acknowledgments

This study was funded by the research council of the University of Saint-Joseph (grant FM244) and the CEDRE Project (grant 11SCIF44/L36). Both institutions did not interfere in any part of this study.

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For the legs, significant differences (p < 0.05) appeared between the XLH patients and the control group in the neck-shaft angle, femur/tibia length ratio and HKS. Among the 70 legs in the XLH group, 23 were in genu varum, 25 were in genu valgum and 22 were straight. There were significant differences between the genu varum and genu valgum subgroups in the femoral mechanical angle and the HKS. A strong correlation was found between the femoral mechanical angle and femorotibial angle (r² = 0.73) and between the femoral mechanical angle and HKS (r² = 0.69) The sacral slope and acetabular anteversion were significant different from the reference values.
Quantitative radiological parameters derived from 3D reconstructions show that the deformities in XLH patients are (1) mainly in - but not limited to - the femoral shaft; (2) highly variable from one person to another. Some of these radiological parameters may be useful for the diagnosis and monitoring of XLH patients.
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Thus, children with CP undergo regular orthopaedic follow-up to prevent, diagnose and treat musculoskeletal disorders, with the long-term aim of improving activity and participation [4]. The degree of bone deformity has been found correlated with the severity of the motor impairment [5–7]. Ambulant children with CP may have excessive femoral torsion (Fem.Tor) [5–9], excessive neck shaft angle (NSA) [5–7] and lack of tibial torsion (Tib.Tor) [9,10].
Changes in lower-extremity bone morphology are potential mid- to long-term secondary consequences of cerebral palsy (CP), affecting activity. Little is known about the 3-D morphology of lower-extremity bones in children with CP and the association with gait deviations. The main aim of this study was to describe and compare 3-D lower-extremity bone morphology in ambulant children with unilateral or bilateral CP. Secondary aims were to determine whether certain bone parameters were related to the unilateral or bilateral CP and to quantify the association between bone parameters and gait deviations. Among 105 ambulant children with CP (aged 3 to 17 years), 48 had bilateral CP (Bilat-CP) and 57 had unilateral CP (Unilat-CP); the unaffected limb of children with Unilat-CP was used as control limbs. Fifteen bone parameters were calculated by EOS® biplanar radiography, and the Gait Deviation Index (GDI) was calculated by 3-D gait analysis. Data were compared by descriptive and comparative statistical analysis (Anova, principal component analysis [PCA] and focused-PCA). Mean (SD) neck shaft angle was significantly greater for Unilat-CP than control limbs (134.9° [5.9] vs. 131.3° [5]). Mean mechanical tibial angle was significantly smaller (85.8° [6.7] vs. 89° [4.6]) and mean femoral torsion was significantly greater (29.4° [1.6] vs. 19.1° [11.8]) for Bilat-CP than control limbs. On PCA of the main determinants of 3-D bone morphology, bone shape was more complex with Bilat-CP, with changes in all 3 dimensions of space, than Unilat-CP and control limbs. Few bone parameters were correlated with the GDI in any limbs. In ambulant children with CP, femoral and tibial growth are not affected by the condition. The unilateral or bilateral nature of CP must be considered during treatment to prevent bone deformities and bone morphology affecting gait quality.
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Lower extremity malalignment can be corrected by femoral derotation osteotomy (FDO) or tibial derotation osteotomy (TDO) with good outcomes in both short and long term follow-up studies even with some debate on the recurrence in young population under 10 years of age [7–9]. When planning for osteotomy, it is essential to measure the degree of torsion [10]. Physical examination, gait analysis and computed tomography scanning (CT) are commonly used to measure femoral or tibial torsion (TT) [11].
The purpose of study was to analyze correlations between bony torsions measured by Staheli’s rotation profile, computed tomography (CT) torsional study, and gait analysis in patients with cerebral palsy (CP).
The study group comprised of 26 children with CP (spastic diplegia, Gross Motor Function Classification System (GMFCS) 1–2, mean age 12.6 years) with torsional deformities. All subjects were assessed by examining: 1) rotational profile [internal rotation (IR) and external rotation (ER)], 2) CT torsional profile [femoral anteversion (FAV) and tibial torsion (TT)], and 3) gait analysis [mean hip rotation (HR) and mean knee rotation (KR)]. Statistical analysis was performed using the Pearson correlation test.
In the femur, there was good correlation between FAV and Staheli’s rotational profile of IR and ER (Pearson correlation coefficient (PC = 0.69, 0.52, p < 0.05)). ER correlated very strongly with mean HR during gait (PC = 0.8, p < 0.05). There was, however, poor correlation between HR and IR (p > 0.05), and between HR and FAV (p > 0.05).
In the tibia, mean KR correlated well with thigh-foot angle (TFA) (PC = 0.72) and CT tibia torsion (TT) (PC = 0.62). TT also correlated with TFA (PC = 0.62).
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¹: Laboratory of Biomechanics and Medical Imaging, Campus of Innovation and Sport, University of Saint-Joseph, Damascus Street, P.O. Box 1104-2020 Beirut, Lebanon.

²: Institut de Biomécanique Humaine Georges Charpak, Arts et Métiers ParisTech, 151 Boulevard de l’Hôpital, 75013 Paris, France.

³: Department of Orthopaedic Surgery, Hotel-Dieu de France Hospital, Alfred Naccache Avenue, Achrafiyeh, Beirut, Lebanon.

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Full length articleThree-dimensional evaluation of skeletal deformities of the pelvis and lower limbs in ambulant children with cerebral palsy

Highlights

Abstract

Introduction

Section snippets

Population

Comparison between TD and CP children

Discussion

Conclusion

Conflict of interest

Acknowledgments

Orthop. Clin. North Am.

Annales de Readaptation et de Medecine Physique

Eur. J. Radiol.

Eur. J. Radiol.

Orthop. Traumatol.

Gait Posture

An update on the treatment of gait problems in cerebral palsy

J. Pediatr. Orthop. Part B

Proximal femoral geometry in cerebral palsy: a population-based cross-sectional study

J. Bone Joint Surg. Br.

Evaluation of rotational gait abnormality in the patients cerebral palsy

J. Pediatr. Orthop.

Measuring anteversion and femoral neck-shaft angle in cerebral palsy

Dev. Med. Child Neurol.

Morphometric analysis of the femur in cerebral palsy: 3-dimensional CT study

J. Pediatr. Orthop.

Femoral anteversion and neck shaft angle in children with cerebral palsy

Clin. Orthop. Relat. Res.

The natural history of hip development in cerebral palsy

Dev. Med. Child Neurol.

Hip surveillance in Tasmanian children with cerebral palsy

J. Paediatr. Child Health

Femoral anteversion in children with cerebral palsy

J. Bone Joint Surg.

The Consensus Statement on Hip Surveillance for Children with Cerebral Palsy: Australian Standards of Care

J. Pediatr. Rehabil. Med.

Full length article
Three-dimensional evaluation of skeletal deformities of the pelvis and lower limbs in ambulant children with cerebral palsy