Development and assessment of 3-dimensional computed tomography measures of proximal humeral bone density: a comparison to established 2-dimensional measures and intraoperative findings in patients undergoing shoulder arthroplasty

Abstract

Background The purpose of this study was to develop novel three-dimensional (3D) measures of bone density from computed tomography (CT) scans and to compare them with validated two-dimensional (2D) radiographic assessments of bone density. Patient demographic data were also analyzed to see if there were any predictors of bone density (age, sex, etiology). Methods The study group consisted of 290 consecutive patients undergoing primary shoulder arthroplasty surgery (total anatomic, reverse, and hemiarthroplasty). All underwent preoperative CT imaging. Three 3D CT measurements (metaphysis cancellous, metaphysis cortical, and proximal diaphysis) were developed and automated into software. The developed 3D measurements were compared with validated 2D measures (Tingart and Gianotti Index). Patient demographic data were correlated with these measurements. The difference between the size of the final sounder and of the final stem was calculated as Delta. Results There was moderately strong correlation between Tingart and Gianotti measures (0.674, P < .001), as well as between 3D metaphysis cancellous measurements and Tingart (0.645, P < .001). Decreased bone density was highly correlated with female sex. Tingart (area under the curve [AUC]: 0.87, 95% confidence interval [CI]: 0.82-0.91) and 3D metaphysis cancellous (AUC: 0.78, 95% CI: 0.72-0.84) had the highest correlation. These were significantly more than other measures of bone density ( P < .01). Decreased bone density measured with Tingart also had moderate correlation with advanced age (AUC: 0.67, 95% CI: 0.6-0.73), but less so for etiology (AUC: 0.62, 95% CI: 0.55-0.69). The 3D metaphysis cancellous measure had lower correlation with age (AUC: 0.59, 95% CI: 0.52-0.66) and etiology (AUC: 0.59, 95% CI: 0.52-0.65). The highest correlation with Delta (the difference between the final sounder and the stem size) was with the 3D metaphysis cancellous measure (AUC: 0.67, 95% CI: 0.59-0.73), followed by Tingart (AUC: 0.647, 95% CI: 0.57-0.671). A multiple regression model to predict Delta demonstrated the stronger prediction using 3D metaphysis cancellous (analysis of variance F-ratio of 42.6, P < .001) than Tingart (35.9, P < .001). Conclusion This study demonstrates that automated measures of bone density can be obtained from 3D CT scans. Of the three novel 3D measurements of bone density, the humeral metaphysis cancellous measurement was most correlated to the known 2D measures and most correlated to the intraoperative assessment of bone density (delta).

Preoperative metaphyseal cancellous bone density is associated with intraoperative conversion to stemmed total shoulder arthroplasty

“…This 3-dimensional (3D) CT measurement of metaphyseal cancellous bone density has previously been correlated with both validated 2-dimensional measures of proximal humerus bone density, in addition to intraoperative assessment of bone density using a diaphyseal sounder. 2 In that study, other 3D measurements of proximal humeral bone density were also calculated, but were not found to be as correlated. Similarly, in our study, although other measurements of proximal humeral bone density were performed, none were found to be as strongly correlated with stem usage.…”

“…Cortical index and thickness were calculated, and bone densities of the proximal diaphysis, cancellous metaphysis, and cortical metaphysis were obtained by averaging Hounsfield units (HU) across anatomically defined regions using previously validated techniques. 2 …”

Can we predict the humerus stem component size required to achieve rotational stability in metaphyseal stability concept?

“…The same two levels were also used to measure the humerus proximal diaphysis cortical thickness described by Blakeney et al, 2 V bone and V cancellous were defined as the humerus volume (in mm 3 ) between level 1 and level 2 where the corresponding Hounsfield units in the CT scan were higher than 220 and lesser than 220, respectively. Assuming a cylinder shape of the humeral outer and inner cortices between level 1 and level 2, with a fixed height h = 20 mm , the corresponding cortical thickness was measured as 2 :

Figure 2 Humerus regions used for measuring geometry and bone density.

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“…A second set of measures described by Blakeney et al 2 was focused on bone density characteristics. Humerus metaphysis cancellous and cortical bone densities were measured in the metaphyseal region between the surgical neck and the anatomical neck ( Fig.…”

“…Investigating local bone density measurement in the proximal humerus, Blakeney et al demonstrated that known 2-dimensional radiographic and novel 3-dimensional (3D) measurements of bone density can reproducibly be measured from computed tomography (CT) scans. 2 …”