Hip Displacement in Spinal Muscular Atrophy: The Influences of Genetic Severity, Functional Level, and Disease-modifying Treatments.

PURPOSE: Hip displacement (HD) is common in spinal muscular atrophy (SMA), but neither genetic severity nor gross motor function level have been investigated as risk factors. Although disease-modifying agents (DMA) have improved function and overall health, their effects on the prevention of HD are unknown. The purpose of this study was to determine risk factors for HD development in SMA. METHODS: Retrospective cohort. Children with SMA presenting between January 2005 and August 2021, at least 1 hip radiograph, and a minimum 2-year follow-up were included. The primary outcome measure was the prevalence of HD (migration percentage ≥40%). Secondary outcomes included SMA type (I/II/III), survival motor neuron 2 copy number, Hammersmith Functional Motor Scale (HFMS, out of 66), ambulatory status (Functional Mobility Scale at 50 m), clinically relevant scoliosis (>40 degrees and/or surgery), and DMA treatment (>1-year duration, nusinersen/risdiplam/onasemnogene abeparvovec) as risk factors. Univariate and multivariate logistic regression analyses were performed. RESULTS: Eighty-two patients (52% female) with SMA type I (n=32, 39%), II (n=36, 44%), and III (n=14, 17%) met the inclusion criteria, with a final follow-up of 4.5 (SD: 2.7) years. Age at first hip radiograph was 3.4 (SD: 2.9) years. The prevalence of HD was 75.6%, with a mean age of onset of 4.6 (SD: 2.7) years. When stratified by SMA type, the prevalence/age of onset (mean, years) was 84%/3.1 (SD: 1.7), 80%/5.8 (SD: 2.3), and 36%/9.0 (SD: 4.3), respectively. HFMS score >23 was protective against HD by receiver operating characteristic analysis ( P =0.008). Significant risk factors by univariate analysis were SMA type I ( P =0.002) and II ( P =0.002), HFMS ≤23 ( P =0.01), nonambulatory status (Functional Mobility Scale at 50 m = 1, P =0.001), clinically relevant scoliosis ( P =0.01), and DMA treatment ( P =0.01). By multivariate analysis, only SMA type II ( P =0.04) and scoliosis ( P =0.04) were independent risk factors. CONCLUSIONS: The prevalence of HD in SMA is highly linked to disease severity. Identified risk factors can be used in the development of surveillance programs for early detection of HD in SMA, allowing for timely management. LEVEL OF EVIDENCE: Level III.

Scoliosis Development in Spinal Muscular Atrophy: The Influences of Genetic Severity, Functional Level, and Disease-Modifying Treatments.

BACKGROUND: Spinal muscular atrophy (SMA) is caused by abnormalities of the survival motor neuron (SMN) 1 gene, leading to deficiency in SMN protein and loss of spinal cord alpha motor neurons. Newer disease-modifying agents (DMA) targeting the involved genes, including nusinersen and gene replacement therapies, have improved gross motor and respiratory function, but their impact on scoliosis development has not been established. This study aimed to determine risk factors for scoliosis development in SMA, specifically genetic severity and DMA use. METHODS: In this retrospective cohort study, children with SMA and minimum 2-year follow-up were included. The primary outcome was the prevalence of clinically relevant scoliosis. Secondary outcomes included SMA type, SMN2 copy number, Hammersmith Functional Motor Scale (HFMS), ambulatory status [functional mobility scale at 50m (FMS 50 )], DMA use, and hip displacement as risk factors. Univariate/multivariate logistic regression analyses were performed to identify dependent/independent risk factors. RESULTS: One hundred sixty-five patients (51% female) with SMA types I-III met the inclusion criteria, with total follow-up of 9.8 years. The prevalence of scoliosis was 79%; age of onset 7.9 years. The major curve angle for the entire cohort at first assessment and final follow-up was 37 degrees (SD: 27 degrees) and 62 degrees (SD: 31 degrees) ( P <0.0001), respectively. Significant risk factors for scoliosis by univariate analysis were SMA type (I/II, P =0.02), HFMS (>23, P <0.001), nonambulatory status (FMS 50 =1, P <0.0001), DMA treatment ( P =0.02), and hip displacement ( P <0.0001). Multivariate analysis revealed that HFMS >23 ( P =0.02) and DMA ( P =0.05) treatment were independent (protective) risk factors. CONCLUSIONS: The development of scoliosis in SMA is high, with risk factors associated with proxy measures of disease severity, including SMA type, nonambulatory status, hip displacement, and most notably, gross motor function (by HFMS). DMA use and HFMS >23 were associated with a decreased risk of scoliosis development. Identified risk factors can be used in the development of surveillance programs for early detection of scoliosis in SMA. LEVEL OF EVIDENCE: Level III.

Tracheal Narrowing and Its Impact on Anesthesia Care in Patients With Morquio A (Mucopolysaccharidosis Type IVA): An Observational Study.

BACKGROUND: Recently, tracheal narrowing has been recognized as a significant comorbid condition in patients with Morquio A, also known as mucopolysaccharidosis IVA. We studied a large cohort of patients with Morquio A to describe the extent of their tracheal narrowing and its relationship to airway management during anesthesia care. METHODS: This is an observational study, collecting data retrospectively, of a cohort of patients with Morquio A. Ninety-two patients with Morquio A syndrome were enrolled, among whom 44 patients had their airway evaluated by computed tomography angiography and had undergone an anesthetic within a year of the evaluation. Our hypothesis was that the tracheal narrowing as evaluated by computed tomography angiography increases with age in patients with Morquio A. The primary aim of the study was to examine the degree of tracheal narrowing in patients with Morquio A and describe the difficulties encountered during airway management, thus increasing awareness of both the tracheal narrowing and airway management difficulties in this patient population. In addition, the degree of tracheal narrowing was evaluated for its association with age or spirometry parameters using Spearman's rank correlation. Analysis of variance followed by the Bonferroni test was used to further examine the age-based differences in tracheal narrowing for the 3 age groups: 1 to 10 years, 11 to 20 years, and >21 years. RESULTS: Patient age showed a positive correlation with tracheal narrowing ( rs= 0.415; 95% confidence interval [95% CI], 0.138-0.691; P = .005) with older patients having greater narrowing of the trachea. Among spirometry parameters, FEF25%-75% showed an inverse correlation with tracheal narrowing as follows: FEF25%-75% versus tracheal narrowing: ( rs = -0.467; 95% CI, -0.877 to -0.057; P = .007). During anesthetic care, significant airway management difficulties were encountered, including cancelation of surgical procedures, awake intubation using flexible bronchoscope, and failed video laryngoscopy attempts. CONCLUSIONS: Clinically significant tracheal narrowing was present in patients with Morquio A, and the degree of such narrowing likely contributed to the difficulty with airway management during their anesthetic care. Tracheal narrowing worsens with age, but the progression appears to slow down after 20 years of age. In addition to tracheal narrowing, spirometry values of FEF25%-75% may be helpful in the overall evaluation of the airway in patients with Morquio A.

Growth Modulation by Tension Band Plate in Achondroplasia With Varus Knee Deformity: Comparison of Gait Analysis Measurements.

BACKGROUND: Limited evidence exists concerning growth modulation by tension band plate (TBP) to correct varus deformity in patients with achondroplasia with limited growth due to FGFR3 gene mutation. We evaluated the efficacy of TBP in children with achondroplasia with genu varum and reported the static radiographic and dynamic motion data to determine parameters that impact the rate of deformity correction. METHODS: Patients with achondroplasia with genu varum who underwent TBP surgery for growth modulation were studied. Those with at least 1 year of follow-up with TBP were included. Radiographic parameters were measured. Growth velocity of femoral/tibial length was calculated separately. Patients were deemed successful or unsuccessful. Spearman correlation analysis and Student t test were used to describe statistical results. RESULTS: Twenty-two patients (41 limbs; 12 girls) fulfilled our criteria. Mean age at TBP surgery was 7.6±2.4 years. Thirty-six femoral TBP and 41 tibial TBP were in place for 24.5±9.7 months. Mean mechanical axis deviation, mechanical lateral distal femoral angle, and medial proximal tibial angle preoperatively were 30.1±7.6 mm, 97.2±6.4, and 80.3±4.3 degrees, and 11±15.6 mm, 87.4±5.9, and 84.7±5.3 degrees at last follow-up ( P <0.001). Fifteen limbs were successfully straightened; 4 limbs were in more varus than the initial deformity. Twenty-four limbs with TBP were still undergoing correction. In successful limbs, mean age at surgery was 6.5±1.7 years and duration of TBP was 29.9±7.8 months. In 4 unsuccessful limbs, mean age at surgery was 11.7±1.2 years. Analysis in the gait laboratory included physical examination with the measurement of knee varus and kinematic varus based on a posterior view static standing photograph. Photographic measurement of varus was higher than the radiographic measurement. CONCLUSIONS: Growth modulation by TBP surgery is a reliable and simple technique to correct genu varum in achondroplasia. An early age at TBP implementation (mean: 6.5 y) is crucial to successfully correct the varus knee deformity. Furthermore, we recommend early and regular surveillance of achondroplasia for progressive varus knee deformity. LEVEL OF EVIDENCE: Level IV-cohort study.

Collagen X Marker Levels are Decreased in Individuals with Achondroplasia.

Collagen X marker (CXM) is a degradation fragment of collagen type X. It is a real-time biomarker of height velocity with established norms. Plasma C-type natriuretic peptide (CNP) and NTproCNP levels have also been found to correlate with growth velocity in the general population and are elevated in individuals with achondroplasia compared with age- and sex-matched controls. Collagen X marker levels in people with fibroblast growth factor receptor 3 (FGFR3)-opathies have never been systematically measured. The objective of this study was to measure CXM in a population of dwarfism caused by FGFR3-opathies. Using the same cohort in which CNP and NTproCNP levels were previously measured, archived serum aliquots from 63 children with achondroplasia, six with hypochondroplasia, and two with thanatophoric dysplasia had CXM concentrations measured. Results were plotted against age- and sex-specific norms, and standard deviation scores were plotted for comparison between clinical diagnoses. CXM levels were significantly decreased (p < 0.0001) in children with achondroplasia compared with age- and sex-matched controls. Temporal patterns of change in CXM levels were sex-dependent. As the FGFR3 pathway was more constitutively active, CXM levels decreased. New tools are emerging to study impact of skeletal dysplasia on growth plate regulation and function.

Risk Factors for Rebound After Correction of Genu Valgum in Skeletal Dysplasia Patients Treated by Tension Band Plates.

BACKGROUND: Growth modulation using tension band plates (TBPs) is increasingly important for lower limb deformity correction in patients with skeletal dysplasia (SKD). Development of rebound deformity is a concern after TBP removal. Data regarding this complication are rare; therefore, we evaluated the prevalence and risk factors for rebound deformity in children with SKD undergoing correction of genu valgum using TBP. METHODS: All patients with SKD with genu valgum treated by TBP at the distal femur or/and proximal tibia at a single center were reviewed. Inclusion criteria were: (1) minimum 2-year follow-up after TBP removal or having revision surgery for rebound deformity and (2) implant removal age for girls 14 years and below and boys 16 years and below. Exclusion criteria were any femoral/tibial osteotomies during TBP treatment or follow-up. A change of ≥3 degrees of mechanical lateral distal femoral and/or medial proximal tibial angle was accepted as rebound deformity and analyzed statistically. RESULTS: Thirty-three patients (59 limbs; 52 femur and 29 tibia physes) met our criteria. Mean follow-up after implant removal was 43.7 months. Rebound deformities were seen in 43 limbs (39 femurs and 13 tibias). Boys had more rebound than girls; however, this was not influenced by body mass index. Femurs had more rebound than tibias. Patients in the rebound group were younger than the nonrebound group. Time from application to removal of TBP was shorter in the rebound versus nonrebound group. Overcorrected limbs had more rebound deformity than not overcorrected. The difference in growth velocity of lower limbs in the rebound versus nonrebound group was statistically significant. Patients with epiphyseal dysplasia had more rebound than metaphyseal dysplasia, but this was not statistically significant. CONCLUSION: Risk factors for developing a rebound deformity after correction of genu valgum using TBP in SKD included male sex, TBP surgery at a young age, short duration of TBP implantation, overcorrected extremity (mechanical axis deviation ≤1), and high percent growth velocity after TBP removal. LEVEL OF EVIDENCE: Level IV-retrospective study.

Elongation-Derotation-Flexion Casting Treatment of Early-Onset Progressive Scoliosis in Skeletal Dysplasia.

BACKGROUND: Early-onset scoliosis in children with skeletal dysplasia is progressive, contributing to cardiopulmonary restrictive disease. Serial elongation-derotation-flexion (EDF) casting, used in other etiologies of scoliosis to delay curve progression, may be beneficial in maximizing spine growth. Our hypothesis is serial EDF casting can be safely used as a temporary alternative to surgery, delaying progression and preserving growth, to treat scoliosis in skeletal dysplasia. METHODS: All patients with skeletal dysplasia treated at a single institution with serial EDF casting for scoliosis were reviewed retrospectively. Radiographic parameters: Cobb angle of major and minor curves, curve location, thoracic height, thoracolumbar height, space available for lung, and rib vertebra angle difference were measured before casting (C1), in first casting (C2), in last casting (C3), and out of last casting (C4). Peak inspiratory pressure (PIP) values were monitored and recorded during the casting application. RESULTS: Eleven patients met the inclusion criteria (mean 9.7 castings). The mean duration of EDF serial casting was 35 months. The mean major Cobb angles were 54 degrees° (C1), 30 degrees (C2), 37 degrees (C3), and 49 degrees (C4) with no statistically significant differences. The mean minor Cobb angles were 35 degrees (C1), 25 degrees (C2), 33 degrees (C3), and 51 degrees (C4) with no statistically significant differences. The mean thoracic heights were 130 mm (C1), 155 mm (C2), 173 mm (C3), and 160 mm (C4). The 19-mm mean difference between C2 and C3 represents spinal growth. The PIP-1, PIP-2, and PIP-3 mean values were 15, 27, and 18 cmH2O, respectively. Changes in PIP-1 and PIP-2 and PIP-2 and PIP-3 were statistically significant. CONCLUSION: Serial EDF casting can delay surgical scoliosis correction in children younger than 7 years with a diagnosis of skeletal dysplasia. Our study showed that serial casting controls progression of the major curve and allows longitudinal growth of the spine with possible expansion of lung volume for nearly 3 years. During cast application, PIP increased with molding and traction, and improved until windowing and trimming of the cast. LEVEL OF EVIDENCE: Level IV-retrospective study.

Tracheal narrowing in children and adults with mucopolysaccharidosis type IVA: evaluation with computed tomography angiography.

BACKGROUND: Mucopolysaccharidosis type IVA (MPS IVA) is characterized by progressive skeletal dysplasia and respiratory issues with difficult airway management during anesthesia. OBJECTIVE: To characterize tracheal abnormalities in children and adults with MPS IVA including interplay of the trachea, vasculature, bones and thyroid at the thoracic inlet. MATERIALS AND METHODS: Computed tomography (CT) angiograms of the chest were analyzed for trachea shape, narrowing and deviation at the thoracic inlet, course of vasculature, bone alignment and thyroid location. The tracheal cross-sectional area was measured at the cervical, thoracic inlet and intrathoracic levels. RESULTS: Thirty-seven patients (mean age: 18.1 years) were included. The mean tracheal cross-sectional area narrowing at the thoracic inlet was 63.9% (range: -2.1-96%), with a trend for increased tracheal narrowing in older children. The trachea was commonly deviated rightward posterior (22/37, 59%). T- or W-shaped tracheas had two times greater tracheal narrowing than D- or U-shaped tracheas (P<0.05). The brachiocephalic artery was tortuous in 35/37 (95%) with direct impingement on the trachea in 24/37 (65%). No correlation was observed between bony thoracic inlet diameter and tracheal narrowing. The thyroid was located in the thoracic inlet in 28/37 (76%) cases, significantly associated with tracheal narrowing (P=0.016). CONCLUSION: Narrowing, deviation and abnormal shape of the trachea at the thoracic inlet are common in children and adults with MPS IVA, with a trend toward increased narrowing with advancing age in children. A W- or T-shaped trachea is associated with focal tracheal narrowing. Crowding of the thoracic inlet, due to vascular tortuosity and thyroid position, appears to play a major role.

Intraoperative Neurological Monitoring in Lower Limb Surgery for Patients With Mucopolysaccharidoses.

BACKGROUND: There are reports of spinal cord injury (SCI) occurring after lower extremity (LE) surgery in children with mucopolysaccharidoses (MPS). Intraoperative neurological monitoring (IONM) has been adopted in some centers to assess real-time spinal cord function during these procedures. The aim of this investigation was to review 3 specialty centers' experiences with MPS patients undergoing LE surgery. We report how IONM affected care and the details of spinal cord injuries in these patients. METHODS: All pediatric MPS patients who underwent LE surgery between 2001 and 2018 were reviewed at 3 children's orthopaedic specialty centers. Demographic and surgical details were reviewed. Estimated blood loss (EBL), surgical time, positioning, use of IONM, and changes in management as a result of IONM were recorded. Details of any spinal cord injuries were examined in detail. RESULTS: During the study period, 92 patients with MPS underwent 252 LE surgeries. IONM was used in 83 of 252 (32.9%) surgeries, and intraoperative care was altered in 17 of 83 (20.5%) cases, including serial repositioning (n=7), aggressive blood pressure management (n=6), and abortion of procedures (n=8). IONM was utilized in cases with larger EBL (279 vs. 130 mL) and longer operative time (274 vs. 175 min) compared with procedures without IONM. Three patients without IONM sustained complete thoracic SCI postoperatively, all from cord infarction in the upper thoracic region. These 3 cases were characterized by long surgical time (328±41 min) and substantial EBL (533±416 mL or 30.5% of total blood volume; range, 11% to 50%). No LE surgeries accompanied by IONM experienced SCI. CONCLUSIONS: Patients with MPS undergoing LE orthopaedic surgery may be at risk for SCI, particularly if the procedures are long or are expected to have large EBL. One hypothesis for the etiology of SCI in this setting is hypoperfusion of the upper thoracic spinal cord due to prolonged intraoperative or postoperative hypotension. IONM during these procedures may mitigate the risk of SCI by identifying real-time changes in spinal cord function during surgery, inciting a change in the surgical plan. LEVEL OF EVIDENCE: Level III-retrospective comparative series.

Blood pressure in adults with short stature skeletal dysplasias.

Hypertension, compounded by obesity, contributes to cardiovascular disease and mortality. Data describing hypertension prevalence in adults with short stature skeletal dysplasias are lacking, perhaps due to poor fit of typical adult blood pressure cuffs on rhizomelic or contracted upper extremities. Through health screening research, blood pressure was measured in short stature adults attending support group meetings and skeletal dysplasia clinics. Blood pressure was measured with a commercially available, narrower adult cuff on the upper and/or lower segment of the arm. Height, weight, age, gender, diagnosis, exercise, and medications were collected. Subjects were classified as normotensive, prehypertensive, or hypertensive for group analysis; no individual clinical diagnoses were made. In 403 short stature adults, 42% were hypertensive (systolic >140, diastolic >90 OR taking antihypertensive medications). For every BMI unit and 1 kg weight increase in males, there was a 9% and an 8% increase, respectively, in the odds of hypertension versus normotension. In females, the increase was 10% and 6%, respectively. In those with achondroplasia, the most common short stature dysplasia, males (n = 106) had 10% greater odds of hypertension versus normotension for every BMI unit and kilogram increase. In females with achondroplasia (n = 128), the odds of hypertension versus normotension was 8% greater for each BMI unit and 7% for each additional kilogram. These data suggest a high population prevalence of hypertension among short stature adults. Blood pressure must be monitored as part of routine medical care, and measuring at the forearm may be the only viable clinical option in rhizomelic short stature adults with elbow contractures.

Best practice guidelines regarding diagnosis and management of patients with type II collagen disorders.

PURPOSE: Skeletal dysplasias comprise a heterogeneous group of inherited disorders of development, growth, and maintenance of the human skeleton. Because of their relative rarity and wide phenotypic variability, patients should be accurately identified, uniformly assessed, and managed by clinicians who are aware of their potential complications and possess the knowledge and resources to treat them effectively. This study presents expert guidelines developed to improve the diagnosis and management of patients with type II collagen skeletal disorders to optimize clinical outcomes. METHODS: A panel of 11 multidisciplinary international experts in the field of skeletal dysplasia participated in a Delphi process, which comprised analysis of a thorough literature review with subsequent generation of 26 diagnosis and care recommendations, followed by two rounds of anonymous voting with an intervening face-to-face meeting. Those recommendations with more than 80% agreement were considered as consensual. RESULTS: After the first voting round, consensus was reached to support 12 of 26 (46%) statements. After the panel discussion, the group reached consensus on 22 of 24 revised statements (92%). CONCLUSIONS: Consensus-based, expert best practice guidelines developed as a standard of care to assist accurate diagnosis, minimize associated health risks, and improve clinical outcomes for patients with type II collagen skeletal dysplasias.

Critical review of current MPS guidelines and management.

Mucopolysaccharidoses (MPS) are a group of lysosomal storage disorders that impair degradation of glycosaminoglycans (GAG). The specific GAGs that accumulate depend on the type of MPS, leading to unique characteristic clinical features. Development of guidelines for treatment of MPS has traditionally been multifaceted and largely based on palliative care. In the last three decades, hematopoietic stem cell transplantation and enzyme replacement therapy have been developed based on experimental and clinical studies. Guidelines have been established with the accumulation of the clinical data from natural history of the disease and therapeutic consequences, mainly sponsored by pharmaceutical companies. In recent years, committees in three countries, Australia (2015), Japan (2017), and Brazil (2018) have adopted guidelines for the treatment of MPS II, sponsored and authorized by each government. As novel treatments for MPS including substrate reduction therapy, pharmacological chaperone therapy, and gene therapy become clinically available, it is increasingly necessary to establish the optimal guideline for each type of MPS, considering multiple factors including therapeutic efficacy, adverse effects, age, disease stage, prognosis, feasibility and availability of access to treatment, and cost- performance. In this article, we discuss the historical guidelines for specific MPS types and the most recently adopted guidelines for MPS II and propose the development of future guidelines without conflict of interest and bias leading to mutual benefits to all parties including patients and families, professionals, tax payers, and governments.

Effect of enzyme replacement therapy on the growth of patients with Morquio A.

Mucopolysaccharidosis IVA (MPS IVA) is a degenerative systemic skeletal dysplasia, in which children exhibit marked short stature and become physically handicapped. This study evaluated the growth patterns of patients treated with enzyme replacement therapy (ERT), compared with those of untreated patients. Cross-sectional and longitudinal data of heights and weights were collected from 128 MPS IVA patients and compared with the growth charts of MPS IVA. Twelve patients (six males, six females) starting ERT before 5 years old were treated for at least 2 years. Six out of 12 patients (50%) with ERT over 2 years stopped growing between 94 and 98 cm (mean height of 95.1 ± 2.2 cm) from 5.0 years to 9.0 years of age (mean age of 6.2 ± 1.6 years). The other patients, except one attenuated case, exhibited a marked slow growth velocity from 3.6 years to 7.7 years. Treated and untreated patients with severe phenotype reached their final heights by ~10 years of age. Patients treated with ERT exhibited a reduced pubertal growth spurt analogous to their untreated counterparts, which contributes to the marked short stature associated with MPS IVA. Compared with the growth charts for untreated patients, patients treated with ERT did not show any significant increase in growth in any age group. Overall, ERT-treated patients do not experience growth improvement and continue to exhibit poor growth despite early ERT intervention before 5 years of age. These findings indicate that current intravenous ERT is ineffective at correcting abnormal growth in MPS IVA.

Prevalence of mental health conditions and pain in adults with skeletal dysplasia.

PURPOSE: We sought to examine the prevalence of depression and anxiety in adults with skeletal dysplasias, and to assess any correlations with pain. METHODS: Participation was via an anonymous REDCap survey, which consisted of sociodemographic questions followed by the brief pain inventory-short form (BPI-SF), patient health questionnaire-8 (PHQ-8), and generalized anxiety disorder-7 (GAD-7) questionnaires. These assessed pain, depression, and anxiety respectively. RESULTS: Of the 336 usable responses, 16.1% scored 10 or greater on the PHQ-8 consistent with current depression while 17.3% scored 10 or greater on the GAD-7 consistent with current anxiety. The majority of participants (76.2%) experienced pain, which was significantly associated with prior mental health diagnoses (p < 0.05). A total of 34% reported either a prior diagnosis of depression or scored 10 or greater on the PHQ-8, and 31% reported either a prior diagnosis of anxiety or scored 10 or greater on the GAD-7. CONCLUSIONS: This study identified a substantial percentage of individuals with mental health concerns as well as pain in the adult skeletal dysplasia population. Further research is warranted to investigate barriers to service or treatment of mental health disorders as well as pain management.

Comparison of Intended Lengthening of Magnetically Controlled Growing Rods: Ultrasound Versus X-Ray.

BACKGROUND: In the treatment of early onset scoliosis (EOS), there has been a trend to use magnetically controlled growing rods (MCGR) in order to reduce the number of surgeries. To confirm the amount of lengthening, spine radiographs were required. Recently, ultrasound (US) has been added to monitor lengthening of MCGR to avoid radiation exposure. Our aim was to determine whether US is as accurate as plain radiography (x-ray) in determining the amount of length achieved at individual MCGR lengthening episodes. METHODS: Retrospective study; inclusion criteria: EOS cases with dual MCGR with minimum 12 months follow-up. Intended lengthening IL (mm), lengthening on US (mm) and x-ray (mm) were documented from medical records for both right and left rods. Primary (no surgery before MCGR) and conversion (other types of instrumentation were replaced with MCGR) cases were reviewed separately. P-values determined with analysis of variance. RESULTS: Sixteen cases with 100 lengthening episodes met the inclusion criteria. Eleven were primary MCGR cases with 67 episodes. Mean follow-up was 19±5 months. Significant differences were found between IL (3.4±1 mm), US (2.7±1.9 mm), and x-ray (4.1±2.2 mm) (P<0.001). The difference between IL and x-ray was minimal, but statistically significant (P=0.046). US showed statistically lower values than both IL (P=0.001) and x-ray (P<0.001). The mean ratio of x-ray/IL, US/IL, and US/x-ray were 1.1, 0.75, and 0.84, respectively. Five conversion cases had 33 episodes. Mean follow-up was 21±2 months. Significant differences were found between IL (3.4±0.8 mm), US (1.3±0.8 mm), and x-ray (1.7±0.9 mm) (P<0.001) but there was no significant difference between US and x-ray (P=0.283). IL was significantly higher than both US (P< 0.001) and x-ray (P<0.001). The mean ratio of x-ray/IL, US/IL, and US/x-ray were 0.64, 0.41, and 1.1, respectively. CONCLUSIONS: US can provide confirmatory information of noninvasive lengthening of MCGR. However, US tended to underestimate the achieved length as measured by x-ray in primary cases. Conversion cases demonstrate better concordance between US and x-ray but in these cases less overall length was achieved at each lengthening episode. LEVEL OF EVIDENCE: Level III.

Valgus Hip Osteotomy in Children With Spondyloepiphyseal Dysplasia Congenita: Midterm Results.

BACKGROUND: Coxa vara has been frequently reported in spondyloepiphyseal dysplasia congenita (SEDC), and proximal femoral osteotomy has been described as a useful treatment. The aim of this study was to discuss the clinical, radiographic, and gait outcomes after valgus extension osteotomy of the proximal femur. Changes of lumbar lordosis, associated with coxa vara correction, are reported as well as the outcome differences between different ages. METHODS: Records of children with SEDC, who were followed at our institution between 2004 and 2014, were reviewed; and children had hip surgery were identified. Hip pain and passive range of motion, radiographic neck shaft angle (NSA), and Hilgenreiner trochanteric (H-T) angle, sagittal spinopelvic parameters, and gait data were recorded. Preoperative and last follow-up data were compared. Outcomes were also compared between 3 age groups. RESULTS: Of the 79 children with SEDC, 26 children (12 boys and 14 girls) had hip osteotomy in 48 hips. Mean age at surgery was 9.6 years and the mean follow-up was 5 years. Preoperative hip pain was noted in 30 hips. At the last follow-up, 3 hips were painful at the extreme range of motion. Passive range of motion, NSA, and H-T improved postoperatively. Although NSA was maintained over the follow-up, H-T deterioration was noted. Spinopelvic measurements changed significantly and gait data remained stable except pelvic tilt that reduced significantly after surgery. The changes of radiographic measurements in each age group were similar to the total group of patients. CONCLUSIONS: In children with SEDC, surgical correction of coxa vara, by proximal femoral valgus osteotomy, is an effective treatment that improves hip pain and range of motion in addition to the radiographic alignment of the proximal femur and the sagittal spinopelvic alignment. Children are expected to maintain their level of function after surgery and to have good results over the midterm regardless of their age at surgery. LEVEL OF EVIDENCE: Level IV-therapeutic study.

Cervical Spine Deformities in Children With Rhizomelic Chondrodysplasia Punctata.

BACKGROUND: Cervical spine deformity in rhizomelic chondrodysplasia punctata (RCDP) has been described with different findings reported in the literature. However, available literature provides limited data from a few cases with magnetic resonance imaging (MRI) of the cervical spine. Our report describes the MRI findings in a group of children with RCDP, aiming to reach a better understanding of this pathology. METHODS: An Institutional Review Board-approved RCDP Registry was created at our institution with the goal of identifying pertinent medical issues over the lifespan of individuals with RCDP. Records of children within the registry were evaluated, and magnetic resonance images obtained between 2004 and 2015, were available for review. The levels of spinal canal stenosis were recorded and the severity of the stenosis was decided based on adults' parameters. Cord compression and myelomalacia were confirmed on the axial images. Sagittal lumbar spine magnetic resonance images were also evaluated when available, and the presence of tethered cord and fatty filum was recorded. RESULTS: Twenty-six children (15 boys and 11 girls) were identified in the RCDP Registry. Eleven children (6 boys and 5 girls) had sagittal MRI of the cervical spine available for review. Age at the time of MRI study was variable (1 wk to 32 mo). All patients except 1 had stenosis of the cervical spinal canal. Myelomalacia of the cord was noted only in this patient. CONCLUSIONS: This study suggests that, in children with RCDP, cervical spinal stenosis and cord compression are a real risk, and children with this diagnosis should have monitoring for these issues. Tethered cord is also a possible finding that needs to be evaluated. Full sagittal spine MRI is necessary to detect the possible deformities at the cervical and lumbar levels.

Best practice guidelines regarding prenatal evaluation and delivery of patients with skeletal dysplasia.

BACKGROUND: Skeletal dysplasia comprises a heterogeneous and collectively common group of inherited disorders of development, growth, and maintenance of the human skeleton. There is potential for increased perinatal morbidity and mortality in pregnant women who themselves have skeletal dysplasia, and for affected fetuses where skeletal dysplasia is suspected in utero. OBJECTIVE: We sought to establish guidelines for perinatal health care professionals who should be aware of these risks, to optimize maternal and child health pregnancy outcomes through best prenatal and delivery management practices. STUDY DESIGN: A panel of 13 multidisciplinary international experts participated in a Delphi process, which comprised consideration of thorough literature review and a list of 54 possible care recommendations subject to 2 rounds of anonymous voting and a face-to-face meeting. Those recommendations with >80% agreement were considered as consensual. RESULTS: During the first round, consensus was reached to support 30 out of the 54 statements. After the panel discussion, the group reached consensus on 40 statements. These statements include guidelines for the evaluation and treatment of pregnant women with skeletal dysplasia and for the unborn child with or suspected to have skeletal dysplasia. CONCLUSION: Consensus-based best practice guidelines are provided as a minimum of standard care to minimize associated health risks, and improve clinical outcomes for patients with skeletal dysplasia.

Dynamic Lower Extremity Deformity in Children With Pseudoachondroplasia.

BACKGROUND: Pseudoachondroplasia is a diverse group of skeletal dysplasias with a common pathway of altered cartilage oligomeric matrix protein (COMP) production. This rhizomelic dwarfism is commonly associated with deformities of the lower extremities, accelerated osteoarthritis, and ligamentous laxity. One of the most common alignment problems is coronal knee angulation which combined with tibial torsion, results in a complex deformity. The outcome of surgical correction of these deformities is variable. METHODS: This study used 3-dimensional gait analysis to describe the kinematic deformities in 12 children (aged 3 to 15 y) and compared them to the static deformities measured on standing anteroposterior radiograph. RESULTS: Both gait analysis and radiographs showed large variability in the coronal deformities but strong correlation to each other. Gait analysis showed mean varus alignment of the knee to be 13.5±13.1 degrees; that mean is not statistically different from radiographs, which showed a mean varus of 16.2±17.1 degrees. The correlation coefficient between radiographic and kinematic measurement was 0.70. The kinematic internal tibial torsion measured an average 15±19 degrees, which was moderately correlated to knee varus (r=0.45, P<0.01). CONCLUSIONS: Measurements of varus-valgus alignment correlated well between gait analysis and radiographs. Tibial torsion correlated with varus. In the absence of gait analysis, anteroposterior standing leg length radiographs with the patella facing foreward can be used to assess deformity. As this study does not correlate these measurements to postoperative results, an appropriately powered prospective study and further investigation of biological effects of altered cartilage oligomeric matrix protein production are needed to explain the variable surgical outcomes. LEVEL OF EVIDENCE: Level IV-case series without control group).

Mucopolysaccharidosis IVA and glycosaminoglycans.

Mucopolysaccharidosis IVA (MPS IVA; Morquio A: OMIM 253000) is a lysosomal storage disease with an autosomal recessive trait caused by the deficiency of N-acetylgalactosamine-6-sulfate sulfatase. Deficiency of this enzyme leads to accumulation of specific glycosaminoglycans (GAGs): chondroitin-6-sulfate (C6S) and keratan sulfate (KS). C6S and KS are mainly produced in the cartilage. Therefore, the undegraded substrates are stored primarily in cartilage and in its extracellular matrix (ECM), leading to a direct impact on cartilage and bone development, and successive systemic skeletal dysplasia. Chondrogenesis, the earliest phase of skeletal formation, is maintained by cellular interactions with the ECM, growth and differentiation factors, signaling pathways, and transcription factors in a temporal-spatial manner. In patients with MPS IVA, the cartilage is disrupted at birth as a consequence of abnormal chondrogenesis and/or endochondral ossification. The unique skeletal features are distinguished by a disproportional short stature, odontoid hypoplasia, spinal cord compression, tracheal obstruction, pectus carinatum, kyphoscoliosis, platyspondyly, coxa valga, genu valgum, waddling gait, and laxity of joints. In spite of many descriptions of these unique clinical features, delay of diagnosis still happens. The pathogenesis and treatment of systemic skeletal dysplasia in MPS IVA remains an unmet challenge. In this review article, we comprehensively describe historical aspect, property of GAGs, diagnosis, screening, pathogenesis, and current and future therapies of MPS IVA.