Variability in Cobb angle measurements in children with congenital scoliosis

Variability in Cobb angle measurements using reformatted computerized tomography scans

STUDY DESIGN

Survey of intraobserver and interobserver measurement variability.

OBJECTIVE

To assess the use of reformatted computerized tomography (CT) images for manual measurement of coronal Cobb angles in idiopathic scoliosis.

SUMMARY OF BACKGROUND DATA

Cobb angle measurements in idiopathic scoliosis are traditionally made from standing radiographs, whereas CT is often used for assessment of vertebral rotation. Correlating Cobb angles from standing radiographs with vertebral rotations from supine CT is problematic because the geometry of the spine changes significantly from standing to supine positions, and 2 different imaging methods are involved.

METHODS

We assessed the use of reformatted thoracolumbar CT images for Cobb angle measurement. Preoperative CT of 12 patients with idiopathic scoliosis were used to generate reformatted coronal images. Five observers measured coronal Cobb angles on 3 occasions from each of the images. Intraobserver and interobserver variability associated with Cobb measurement from reformatted CT scans was assessed and compared with previous studies of measurement variability using plain radiographs.

RESULTS

For major curves, 95% confidence intervals for intraobserver and interobserver variability were +/-6.6 degrees and +/-7.7 degrees, respectively. For minor curves, the intervals were +/-7.5 degrees and +/-8.2 degrees, respectively. Intraobserver and interobserver technical error of measurement was 2.4 degrees and 2.7 degrees, with reliability coefficients of 88% and 84%, respectively. There was no correlation between measurement variability and curve severity.

CONCLUSIONS

Reformatted CT images may be used for manual measurement of coronal Cobb angles in idiopathic scoliosis with similar variability to manual measurement of plain radiographs.

The vertical expandable prosthetic titanium rib implant for the treatment of thoracic insufficiency syndrome associated with congenital and neuromuscular scoliosis in young children

Expansion thoracoplasty and vertical expandable prosthetic titanium rib (VEPTR; Synthes Spine Co., West Chester, Pennsylvania, USA) implantation is a new method for the treatment of thoracic insufficiency syndrome and congenital spinal deformity in children. The longitudinal rib implant expands the thorax and indirectly corrects spinal deformity, thus allowing spinal, thoracic and probably lung growth. VEPTR has been used since 1989 in San Antonio, USA, and was introduced to Europe in 2002. This paper describes the preliminary experience with the European patients. Fifteen children with progressive scoliosis had a VEPTR implantation at a mean age of 6 years (11 months to 12 years). Nine children had thoracic insufficiency syndrome due to unilateral unsegmented bars (n = 4), absent ribs (n = 1), hemivertebrae (n = 2) or bilateral fused ribs (n = 2). Six children had severe thoracolumbar scoliosis and pelvic obliquity due to neuromuscular scoliosis. After VEPTR implantation, families and patients reported improvement of the thoracic insufficiency syndrome and better sitting abilities in the neuromuscular patients, as well as radical cosmetic improvement. There were three complications (skin breakage, lumbar hook displacement, rib fracture) after performing fifteen primary VEPTR implantations and 13 expansion surgeries in eight patients. Our experience suggests that expansion thoracoplasty and VEPTR implantation is a safe and efficient method for the treatment of thoracic insufficiency syndrome in young children with severe scoliosis.

A new operative classification of idiopathic scoliosis: a peking union medical college method

STUDY DESIGN

A retrospective radiographic study on the type of surgically treated idiopathic scoliosis, with a prospective study on the reliability of the type-related fusion guide.

OBJECTIVES

To identify and classify surgically treated idiopathic scoliosis, and define its related fusion levels by a new classification system.

SUMMARY OF BACKGROUND DATA

Some classification methods for idiopathic scoliosis have been suggested. However, poor intraobserver reproducibility and interobserver reliability were experienced in these studies, and were not appropriate for guiding surgical planning.

METHODS

A total of 427 surgically treated idiopathic scoliosis cases were reviewed. Preoperative and postoperative standing anteroposterior, lateral, and preoperative supine side-bending radiograph were analyzed using the Scoliosis Research Society definition of scoliosis and curve apex. The resulting classification was tested for intraobserver reliability and interobserver reliability, and by 6 surgeons. Apical frequencies were determined for each type, and prospective surgical testing of the new type and its related fusion guide was performed.

RESULTS

Three major types and 13 subtypes were identified, of which the Peking Union Medical College type I accounted for 56.62%, type II 42.16%, and type III 1.22%. The interobserver reliability testing was 85% (kappa coefficient 0.832), while intraobserver reproducibility was 91% (kappa coefficient 0.898). Each type had its corresponding fusion levels. A prospective study of 152 cases was performed according to the classification. All of these cases were followed over 18 months, and no postoperative decompensation was noted.

CONCLUSION

The Peking Union Medical College classification of idiopathic scoliosis is one system to combine each type with its corresponding fusion level, and it had much higher interobserver reliability and intraobserver reproducibility than the King system. Further prospectivestudies would help to clarify and expand this system.

Measurement of fracture kyphosis with the Oxford Cobbometer: intra- and interobserver reliabilities and comparison with other techniques

STUDY DESIGN

Statistical analysis of 3 techniques for measuring thoracolumbar kyphosis secondary to fracture.

OBJECTIVES

To determine the reliability of using an Oxford Cobbometer and assess the most reliable measurement technique.

SUMMARY OF BACKGROUND DATA

The reproducibility of Cobb angles for the assessment of saggital plane deformity on spine radiographs has been shown to have significant variability in both intra- and interobserver error.

METHODS

Twenty-four lateral spine radiographs of patients with thoracic and lumbar vertebral fractures were measured on 2 separate occasions, in random order, by 4 blinded observers using the same Oxford Cobbometer and ruler.

RESULTS

Method 2, the angle from the inferior endplate of the vertebra above the fractured vertebra to the superior endplate of the vertebra below the fractured vertebra, had the greatest intraobserver and interobserver reliabilities (rho = 0.856-0.976 and rho = 0.95, respectively). The other 2 methods had lower reliabilities; however, all 3 methods were well above the statistically acceptable threshold of >0.8, and the intraobserver reliabilities with each observer was 99% overall. These reliabilities supersede results reported previously using the conventional Cobb technique. The absolute mean difference between readings and 95% limit of agreement also improves on previous data, 2 degrees and +/- 5.8 degrees , respectively.

CONCLUSIONS

Highest intraclass correlation coefficients were obtained using method 2. Using the Oxford Cobbometer to measure fracture kyphosis has higher reliability than the standard Cobb angle technique. It is easy and quick to use in a clinical setting.

Congenital scoliosis

Congenital scoliosis is caused by early embryologic errors in vertebral column formation. Defining the deformity, predicting the natural history, and applying the correct treatment can help ensure successful management. Most congenital spine anomalies can be classified, and many have a predictable natural history. Because the deformities are associated with other organ system anomalies in more than half of patients, the surgeon should look for cardiac, auditory, genitourinary, and renal anomalies. Intraspinal abnormalities are present in approximately one third of patients with congenital spine deformities. Curve progression is best documented by measuring identical landmarks on sequential radiographs. Magnetic resonance imaging is warranted when curve progression is established or when surgical intervention is planned. Management of progressive deformity is generally by early in situ fusion because orthotic treatment is rarely appropriate. Other surgical techniques include combined anterior and posterior epiphysiodesis, hemivertebra resection, and reconstructive osteotomies.

Scoliosis: evidence-based diagnostic evaluation

This article summarizes the evidence behind the imaging evaluation of scoliosis, which is primarily performed with plain radiographs and MR imaging. Issues related to the radiographic evaluation of spinal curvature include interobserver variability of scoliosis measurements and the radiologist's detection of unexpected findings. The effects of radiation exposure during scoliosis evaluation and strategies to minimize radiation dose are summarized. The use of MR imaging in idiopathic scoliosis is discussed, with special attention to imaging groups at higher risk for underlying pathology of the neural axis.

The crankshaft phenomenon after posterior spinal arthrodesis for congenital scoliosis: a review of 54 patients

STUDY DESIGN

Retrospective chart and radiographic reviews were conducted.

OBJECTIVE

To identify the incidence of and any possible risk factors for the crankshaft phenomenon after posterior spinal arthrodesis for congenital scoliosis.

SUMMARY OF BACKGROUND DATA

Studies have shown the crankshaft problem to be common after posterior arthrodesis for infantile and juvenile idiopathic scoliosis, but the few reports available show it to be much less common for congenital scoliosis.

METHODS

This study chose children fused before the pubertal growth spurt, all classified as Risser 0 and with open triradiate cartilages. These children were followed to the end of their growth (mean follow-up period 12 years). Several measurement parameters were used for evaluation.

RESULTS

The crankshaft problem, measured as a Cobb angle increase of more than 10 degrees, was seen in 15% of the 54 patients. There was a positive correlation with earlier surgery and larger (>50 degrees) curves. No other positive correlations could be identified.

CONCLUSIONS

Crankshafting was observed in 15% of the patients, more often with larger curves and earlier fusions.

Long-term results from in situ fusion for congenital vertebral deformity

STUDY DESIGN

Retrospective review of long-term outcome of fusion in situ for congenital vertebral anomaly with particular emphasis on cosmesis and the incidence of reoperation.

OBJECTIVE

Examination of the success rate of this procedure and of risk factors for failure.

BACKGROUND

Fusion in situ is the accepted prophylactic treatment to prevent deformity in congenital vertebral anomalies that have a high risk of progression or have been shown to be deteriorating.

METHODS

Records of patients who were at least 15 years of age at last examination were reviewed retrospectively. Consideration was given to cosmetic outcome and to the incidence of reoperation.

RESULTS

There were 43 patients in this category, 19 boys and 24 girls, who were at least 15 years of age when last seen. Reoperation had been performed in 11 cases (25.6%). The main finding was that, although the Cobb angle of the fused segment of spine remained constant after fusion, a curve sometimes developed in the whole spine, sometimes (but by no means always) centered on that fused segment. Cosmetic deformity continued to progress in a number of cases.

CONCLUSIONS

Localized fusion, whether posterior alone or anterior and posterior combined, was effective in preventing progression of the Cobb angle of the congenitally malformed area but did not control the overall deformity that developed or progressed with growth. Current concepts of the pathomechanism of deformity do not adequately explain the observations, and a more biologic approach is suggested.

Congenital spine deformities: scoliosis, kyphosis, and lordosis

By definition, congenital spine deformities-scoliosis, kyphosis, and lordosis-are due to abnormal vertebral development. Thus, affected children tend to have a curvature noted much earlier in life than typical patients with idiopathic scoliosis. This early development of the deformity has resulted in a tendency for the young child with congenital deformities to receive less than optimal care. These curves must not be allowed to progress. In many cases, early fusion is necessary, which is preferable to allowing severe curves to develop.

Congenital scoliosis caused by a unilateral failure of vertebral segmentation with contralateral hemivertebrae

STUDY DESIGN

The medical records and serial spine radiographs of 59 consecutive patients with congenital scoliosis caused by unilateral unsegmented bar with contralateral hemivertebrae were reviewed.

OBJECTIVES

To study the presentation, natural history, and treatment of these patients.

SUMMARY AND BACKGROUND DATA

This is the least common type of congenital scoliosis.

METHODS

The mean age at diagnosis was 4 years 1 month. Forty-three patients were observed without treatment for a mean of 6 years and 1 month. Prophylactic arthrodesis was performed in 10 patients before they were 5 years old. Thirty-five patients had a corrective procedure and arthrodesis after they were 5 years old.

RESULTS

Thoracolumbar curves had the worst prognosis. Without management all but two exceeded 50 degrees when the patients were 2 years old. All untreated curves exceeded 88 degrees. Midthoracic curves had only a slightly less severe prognosis, and all but one exceeded 40 degrees by the time the patient was 2 years old. All untreated curves exceeded 70 degrees. In eight of the 14 patients whose congenital curves had their apexes at T5, T6, or T7, a long secondary structural curve developed on the opposite side in the thoracolumbar region, and this contributed significantly to the overall deformity. Occult intraspinal anomalies were present in 24 patients (41%). Surgical treatment after the patient was 5 years old was not successful in producing significant correction of these severe rigid deformities.

CONCLUSION

These patients have the most rapidly progressive and severely deforming of all types of congenital scoliosis. All midthoracic, thoracolumbar, and lumbar curves require immediate prophylactic surgical treatment by anterior and posterior arthrodesis--preferably in the first year of life.

Radiology's Achilles' heel: error and variation in the interpretation of the Röntgen image

The performance of the human eye and brain has failed to keep pace with the enormous technical progress in the first full century of radiology. Errors and variations in interpretation now represent the weakest aspect of clinical imaging. Those interpretations which differ from the consensus view of a panel of "experts" may be regarded as errors; where experts fail to achieve consensus, differing reports are regarded as "observer variation". Errors arise from poor technique, failures of perception, lack of knowledge and misjudgments. Observer variation is substantial and should be taken into account when different diagnostic methods are compared; in many cases the difference between observers outweighs the difference between techniques. Strategies for reducing error include attention to viewing conditions, training of the observers, availability of previous films and relevant clinical data, dual or multiple reporting, standardization of terminology and report format, and assistance from computers. Digital acquisition and display will probably not affect observer variation but the performance of radiologists, as measured by receiver operating characteristic (ROC) analysis, may be improved by computer-directed search for specific image features. Other current developments show that where image features can be comprehensively described, computer analysis can replace the perception function of the observer, whilst the function of interpretation can in some cases be performed better by artificial neural networks. However, computer-assisted diagnosis is still in its infancy and complete replacement of the human observer is as yet a remote possibility.