Upper cervical spine instability in pseudoachondroplasia

Spinal Manifestations of Skeletal Dysplasia: A Practical Guide for Clinical Diagnosis

Skeletal dysplasias are a group of genetic conditions defined by atypical bone or cartilage growth and development. Skeletal abnormalities include short stature, limb deformity, joint contracture, and spinal deformity. Over 90% of disorders have a known genetic mutation that can definitively determine the diagnosis. As patients may present with a primary spinal concern, a careful clinical and radiographic evaluation can allow the physician to develop a working diagnosis to guide additional evaluation. Spinal manifestations include scoliosis and kyphoscoliosis, cervical instability, cervical kyphosis, thoracolumbar kyphosis, spinal stenosis, and atypical vertebral body morphology. An understanding of the affected conditions, prevalence, and natural history of these radiographic findings aids the orthopaedic surgeon in establishing a diagnosis and guides appropriate orthopaedic care.

Os odontoideum: A comprehensive review

Os odontoideum (OO) is a rare craniocervical anomaly that is characterized by a round ossicle separated from the C2 vertebral body. With a controversial etiology and unknown prevalence in the population, OO may be asymptomatic or present in patients with myelopathic and neurological symptoms. In this literature review, we aimed to investigate epidemiology, embryology, pathophysiology, clinical presentation, and the role of diagnostic radiography in OO. By providing an overview of different management strategies, surgical complications, and postoperative considerations for OO, our findings may guide neurosurgeons in providing proper diagnosis and treatment for OO patients. A literature review was conducted using the PubMed, EMBASE, and Scopus databases. A search using the query “os odontoideum” yielded 4319 results, of which 112 articles were chosen and analyzed for insights on factors such as etiology, clinical presentation, and management of OO. The presentation of OO varies widely from asymptomatic cases to severe neurological deficits. Asymptomatic patients can be managed either conservatively or surgically, while symptomatic patients should undergo operative stabilization. Although multiple studies show different techniques for surgical management involving posterior fusion, the diversity of such cases illustrates how treatment must be tailored to the individual patient to prevent complications. Conflicting studies and the paucity of current literature on OO highlight poor comprehension of the condition. Further understanding of the natural history of OO is critical to form evidence-based guidelines for the management of OO patients. More large-center studies are thus needed to promote accurate management of OO patients with optimal outcomes.

Anatomo-radiological importance and the incidence of os odontoideum in Turkish subjects: a retrospective study

PURPOSE

Os odontoideum is a rare anatomical and morphological variation of the odontoid process and associated with a range of symptoms such as spinal cord and vertebral artery injuries. This study aimed to evaluate the frequency of os odontoideum in Turkish cases by sagittal/coronal cervical magnetic resonance imaging (MRI) and computed tomography (CT) and analyze the relationship with age, gender and related symptoms.

METHODS

The incidence of os odontoideum was retrospectively diagnosed by sagittal/coronal cervical CT and MRI out of 16,122 subjects aged 20-70 years (mean 46) in the period between 2014 and 2018. The relationship of os odontoideum with age, gender, and symptoms was recorded.

RESULTS

The statistical analysis of the study was performed by the χ² test and two-way mixed ANOVA. Os odontoideum was detected in 18 (0.11%) (11 males; 7 females) out of 16,122 patients. The mean age was 47.5 ± 1.4 years in the females and 43.5 ± 2.5 years in the males (p < 0.05). 6 odontoideum were detected out of 6467 (3756 males, mean 48 ± 0.7, 2711 females, mean 46 ± 1.2) subjects by CT and 12 odontoideum were detected out of 9655 patients (5607 males and 4048 females) by MRI.

CONCLUSION

Neck pain was the most frequent symptom. The prevalence of os odontoideum especially round type is more frequent in older male patients over 40 years old with head and neck pain or atlantoaxial instability, and is less common in Turkish subjects when compared to various ethnic groups.

Orthopaedic manifestations of pseudoachondroplasia

PURPOSE

In 1959, Maroteaux and Lamy initially designated pseudoachondroplasia as a distinct dysplasia different from achondroplasia the most common form of skeletal dysplasia. Pseudoachondroplasia is caused by a mutation in the collagen oligomeric matrix protein gene (COMP) gene on chromosome 19p13.1-p12 encoding the COMP. The COMP gene mutations result in rendering the articular and growth plate cartilages incapable of withstanding routine biomechanical loads with resultant deformity of the joints. The purpose of the study was to characterize the typical orthopaedic findings in pseudoachondroplasia.

METHODS

The charts and radiographs of 141 patients with pseudoachondroplasia were analyzed. This cohort, to our knowledge, represents the largest group of patients describing the typical orthopaedic manifestations of pseudoachondroplasia.

RESULTS

Patients with pseudoachondroplasia have normal craniofacial appearance with normal intelligence. Short stature is not present at birth and generally appears by two to four years of age. The condition is a form of spondyloepiphyseal dysplasia and the long bones are characterized by dysplastic changes in the epiphysis, metaphysis and vertebral bodies. Radiographically the long bones have altered the appearance and structure of the epiphyses with small irregularly formed or fragmented epiphyses or flattening. The metaphyseal regions of the long bones show flaring, widening or 'trumpeting'. The cervical (89%) and thoracic and lumbar vertebrae show either platyspondyly, ovoid, 'cod-fish' deformity or anterior 'beaking'. Kyphosis (28%), scoliosis (58%) and lumbar lordosis (100%) are commonly seen. The femoral head and acetabulum are severely dysplastic (100%). The knees show either genu valgum (22%), genu varum (56%) or 'windswept' deformity (22%).

CONCLUSION

Most commonly these distortions of the appendicular and the axial skeleton lead to premature arthritis particularly of the hips and often the knees not uncommonly in the 20- to 30-year-old age group.

LEVEL OF EVIDENCE

III.

Upper cervical spine fusion in children with skeletal dysplasia

BACKGROUND

Skeletal dysplasias have been associated with upper cervical instability. Many patients are initially asymptomatic, but the instability may progress to subluxation and dislocation and complications thereof, including death. Surgery is hampered by petite osseous structures and low bone formation rate.

AIM

To review the outcomes of surgical fusion of upper cervical instability in children with rare skeletal dysplasias.

MATERIAL AND METHODS

A retrospective study of eight children with five different rare skeletal dysplasias needing upper cervical instrumented stabilization. Cases were evaluated for clinical, radiologic, and quality-of-life outcomes, with median follow-up time of 5 years.

RESULTS

Six patients underwent posterior, segmental cervical spine instrumentation and fusion (three C1/C2 fusions, three occipitocervical fusions), one anterior cervical instrumented spinal fusion, and one anteroposterior fusion. Autogenous bone grafting was used in all patients, and seven were immobilized using a halo body jacket. Nonunion in occipitocervical fusions was common in these patients (3/8 patients). Rib autograft from occiput to cervical spine with recombinant human BMP-2 was used to salvage nonunions.

CONCLUSIONS

Surgical fixation in the pediatric cervical spine is hampered by fragile posterior structures. A postoperative immobilization by halo vest for 4 months is customary. Selective anterior corpectomy and plate fixation is not recommended in pediatric patients with skeletal dysplasias.

LEVEL OF EVIDENCE

Level 4, Case Series.

Flexion-extension cervical spine MRI in children with skeletal dysplasia: is it safe and effective?

BACKGROUND

Skeletal dysplasias may be associated with cervical spinal instability or stenosis. Cervical spine flexion-extension plain radiographs in children with skeletal dysplasia are difficult to interpret. The purpose of this study was to review the indications, efficacy, and safety of performing flexion-extension magnetic resonance imaging (MRI) under sedation/anesthesia in these children.

METHODS

Retrospective, Institutional Review Board-approved review of 31 children with skeletal dysplasia who underwent 38 cervical spine flexion-extension MRI studies under sedation/anesthesia. Indications included abnormal neurological examination, suspected instability, stenosis, or inconclusive findings on flexion-extension radiographs. Studies were performed by the radiology technologist as directed by the radiologist with an anesthesiologist present. MRI was evaluated for odontoid hypoplasia, os odontoideum, cerebrospinal fluid effacement, cord compression, spinal cord changes, cervical canal narrowing in the neutral, flexion, and extension positions. Neurological examinations were recorded before and after MRI to assess safety.

RESULTS

The average age at MRI was 3 years, 2 months. In 6 patients whose plain radiographs showed C1-C2 or subaxial instability, flexion-extension MRI showed no cord compression. Nine patients with inconclusive plain radiographs had abnormal MRI findings. An os odontoideum not seen on plain radiographs was diagnosed in 3 patients on flexion-extension MRI. On the basis of the MRI findings, 14 patients underwent surgery, 9/14 had increased cord compression in flexion or extension compared with neutral, and observation was continued in 17 others. Patients who underwent surgery had significant cord compression on MRI. There were no significant changes in the neurological examinations after MRI.

CONCLUSIONS

Cervical spine flexion-extension MRI under sedation/anesthesia in children with skeletal dysplasia is safe under adequate supervision and is necessary to guide accurate medical and surgical decision making. Flexion-extension MRI is useful for identifying dynamic changes in canal diameter resulting in cord compression not seen on plain radiographs, and it is also useful for identifying patients with suspected plain film instability who may not have stenosis or cord compression on MRI.

STUDY DESIGN

Level IV-retrospective case series.

Review of cervical spine anomalies in genetic syndromes

STUDY DESIGN

Focused review of the literature.

OBJECTIVE

Assist spine specialists in diagnosis and treatment of cervical spine anomalies found in selected genetic syndromes.

SUMMARY OF BACKGROUND DATA

Cervical spine instability and/or stenosis are potentially debilitating problems in many genetic syndromes. These problems can be overlooked among the other systemic issues more familiar to clinicians and radiologists evaluating these syndromes. It is imperative that spine specialists understand the relevant issues associated with these particular syndromes.

METHODS

The literature was reviewed for cervical spine issues in 10 specific syndromes. The information is presented in the following order: First, the identification and treatment of midcervical kyphosis in Larsen syndrome and diastrophic dysplasia (DD). Next, the upper cervical abnormalities seen in Down syndrome, 22q11.2 Deletion syndrome, pseudoachondroplasia, Morquio syndrome, Goldenhar syndrome, spondyloepiphyseal dysplasia congenita, and Kniest dysplasia. Finally, the chin-on-chest deformity of fibrodysplasia ossificans progressiva.

RESULTS

Midcervical kyphosis in patients with Larsen syndrome and DD needs to be evaluated and imaged often to track deformity progression. Upper cervical spine instability in Down syndrome is most commonly caused by ligamentous laxity at C1 to C2 and occiput-C1 levels. Nearly 100% of patients with 22q11.2 deletion syndrome have cervical spine abnormalities, but few are symptomatic. Patients with pseudoachondroplasia and Morquio syndrome have C1 to C2 instability related to odontoid dysplasia (hypoplasia and os odontoideum). Morquio patients also have soft tissue glycosaminoglycan deposits, which cause stenosis and lead to myelopathy. Severely affected patients with spondyloepiphyseal dysplasia congenita are at high risk of myelopathy because of atlantoaxial instability in addition to underlying stenosis. Kniest syndrome is associated with atlantoaxial instability. Cervical spine anomalies in Goldenhar syndrome are varied and can be severe. Fibrodysplasia ossificans progressiva features severe, deforming heterotopic ossification that can become life-threatening.

CONCLUSION

It is important to be vigilant in the diagnosis and treatment of cervical spine anomalies in patients with genetic syndromes.

[Spinal problems in persons with skeletal dysplasias]

Most skeletal dysplasias are characterized by small stature. Less well known is the fact that most skeletal dysplasias are also associated with specific spinal problems or deformities. This article summarizes the various aspects of spinal problems in this patient population as well as the diagnostic strategies and current and new treatment options.