Reliability and accuracy of vertebral fracture assessment with densitometry compared to radiography in clinical practice

Abstract

Absorptiometry of the thoraco-lumbar spine at the time of bone densitometry to detect vertebral deformities consistent with fracture is now available. The performance of absorptiometry in clinical practice compared to radiography has not been fully established, especially in the presence of osteoarthritis or scoliosis. Our first objective was to compare absorptiometry to radiography for detection of vertebral deformity in elderly women who were referred for bone densitometry with or without scoliosis or disc space osteoarthritis excluded. Our second objective was to assess the effect of osteoarthritis and scoliosis on the inter-rater reliability of both technologies. The study group comprised two hundred five women age 65 and older referred for bone densitometry in a large multispecialty group practice. Lateral and antero-posterior (AP) absorptiometry images and lateral spine radiographs were obtained on all participants. The vertebrae on all images were evaluated for vertebral deformity by two observers according to the Genant semiquantitative criteria who were blinded to each other's readings. Disc spaces were evaluated on radiographs for osteoarthritis. Absorptiometry AP images were evaluated for scoliosis. In the absence of scoliosis, the sensitivity and specificity of absorptiometry for persons with one or more radiographic grade 2-3 deformities (>25% reduction of vertebral height) for the two readers were 87-93% and 93-95%, respectively. The inter-rater reliability of absorptiometry improved in the absence of moderate or severe disc space osteoarthritis. A strategy of absorptiometry with follow-up radiography only in those with scoliosis or apparent grade 2 deformity accurately identifies those with prevalent grade 2 or 3 deformity on radiography (accuracy 0.98 and kappa 0.86 for reader 1; accuracy 0.99 and kappa 0.92 for reader 2). Lateral and AP absorptiometry imaging of the spine with selective follow-up radiography accurately identifies elderly women with vertebral deformity consistent with moderate or severe fracture, but extra caution is necessary when evaluating vertebrae in the presence of adjacent disc space osteoarthritis.

Observer agreement in pediatric semiquantitative vertebral fracture diagnosis

“…The finding of lower interobserver agreement compared to intraobserver agreement is a standard result in most studies of observer variability, since besides the factors that lead to variability by an individual there are additional sources of inter-person inconsistencies (See Table 1). Our diagnostic agreement results are similar to those of a pediatric study using a different set of morphometric definitions that showed intraobserver κ of 0.47 to 1.0 for spine sub-regions and overlap those reported in the adult literature using the GSQ method (Table 1) [1][2][3][4][5][6][7][8][9]20]. Some of the causes for diagnostic variability may be the same as those noted for variability in readability, namely small body size and difficulty defining vertebral margins due to lower bone density [6,26].…”

“…In adults, small body size is a cause of impaired readability, suggesting another contributor to lower readability in younger subjects [6,8,[28][29][30]. Other possible causes of unreadability reported in adult vertebral fracture assessment and plain radiographic studies include patient movement, poor radiographic technique, obesity, and anatomical abnormalities of the spine including scoliosis [6,7,28]. Intraobserver agreement for determining readability in our study was moderate while interobserver agreement was moderate to substantial Intraobserver agreement for diagnosis of vertebral fracture was moderate to substantial while interobserver agreement was moderate.…”

“…There has been extensive investigation of vertebral fractures in adults over the past 20 years [1][2][3][4][5][6][7][8][9]. In contrast, the study of pediatric vertebral fracture is in its infancy, in part because these fractures are much less common in the general pediatric population than in adults, in part because of the lack of an accepted technique for diagnosis [10,11].…”

“…An important impetus to adult vertebral fracture research was the development of vertebral morphometry techniques that were subsequently shown to be clinically meaningful [12]. The predominant approach used in the field of adult osteoporosis is the modified Genant semi-quantitative method (GSQ method) [1][2][3][4][5][6][7][8][9]. This system has been used in many of the major drug trials and in clinical studies and has been recommended for use in routine clinical practice [13][14][15].…”

“…The reproducibility of the GSQ method in adult radiographic vertebral morphometry has been studied in depth, with results summarized in Table 1. Intra-and interobserver agreements range from fair (Cohen's kappa statistic (κ) from 0.21 to 0.40) to almost perfect (κ > 0.80) at both the individual vertebral level (determining whether individual vertebrae are fractured) and at the patient level (determining whether a patient has one or more vertebral fractures) [1][2][3][4][5][6][7][8][9]23]. As the reproducibility of the GSQ method in the pediatric population has not been described, we have evaluated observer agreement on vertebral readability and vertebral fracture diagnosis in a cohort of children with ALL, employing the same GSQ methodology and grading used in adults.…”