Clinical application of SPHARM-PDM to quantify temporomandibular joint osteoarthritis

Abstract

The severe bone destruction and resorption that can occur in osteoarthritis of the temporomandibular joint (TMJ) is associated with significant pain and limited joint mobility. However, there is no validated method for the quantification of discrete changes in joint morphology in early diagnosis or assessment of disease progression or treatment effects. To achieve this, the objective of this cross-sectional study was to use simulated bone resorption on cone-beam CT (CBCT) to study condylar morphological variation in subjects with temporomandibular joint (TMJ) osteoarthritis (OA). The first part of this study assessed the hypothesis that the agreement between the simulated defects and the shape analysis measurements made of these defects would be within 0.5mm (the image's spatial resolution). One hundred seventy-nine discrete bony defects measuring 3mm and 6mm were simulated on the surfaces of 3D models derived from CBCT images of asymptomatic patients using ITK-Snap software. SPHARM shape correspondence was used to localize and quantify morphological differences of each resorption model with the original asymptomatic control. The size of each simulated defect was analyzed and the values obtained compared to the true defect size. The statistical analysis revealed very high probabilities that mean shape correspondence measured defects within 0.5mm of the true defect size. 95% confidence intervals (CI) were (2.67, 2.92) and (5.99, 6.36) and 95% prediction intervals (PI) were (2.22, 3.37) and (5.54, 6.82), respectively for 3mm and 6mm simulated defects. The second part of this study applied shape correspondence methods to a longitudinal sample of TMJ OA patients. The mapped longitudinal stages of TMJ OA progression identified morphological variants or subtypes, which may explain the heterogeneity of the clinical presentation. This study validated shape correspondence as a method to precisely and predictably quantify 3D condylar resorption.

Figure 1

Spectrum of joint morphology in a cross-sectional study.

Figure 2

Workflow used for statistical shape analysis.

Figure 3

Description of shape correspondence procedures.

Figure 4

a) Defect generation in ITK Insight SNAP b) Final result, 3C defect left condyle.

Figure 5

Example of measurements in a 3C left condyle.

Figure 6

Semitransparent overlays of average models for each observer (blue and purple) show no significant differences.

Figure 7

Surface to surface registration between different time point models allow for accurate longitudinal bone resorption measurement in the condylar area. A. Pre-surgery models compared with models generated after splint removal do not show relevant condylar remodeling. B. One year post surgery models present condylar resorption. C. More marked changes are found when comparing one year post and two years post sugery models. D. Condylar changes from pre surgery to screening two years post surgery.

Figure 8

A. Right lateral views of jaw surface models from pre-surgery through recall 2 years postsurgery (1 year post orthodontics). B. Frontal view of condylar morphology prior to surgery through recall C. Registration and overlay of condylar changes between pre-surgery (transparent mesh lines) and 2 year postsurgery (surface models). D. Registration and overlay show progression of condylar changes between 1 year postsurgery (transparent mesh lines) and 2 year postsurgery (surface models).

Figure 9

Close up views of the longitudinal follow-up of changes in the right condyle in figure 9. The findings for this patient reveal bone resorptive changes approximately four times larger than other cases in our TMJ OA asymptomatic database (data not included on this paper). A. Frontal view of condylar morphology prior to surgery, at splint removal, 1 year postsurgery and 2 years postsurgery. B-E. Absolute distances and difference vectors B. Presurgery subtracted from splint removal. C. Splint removal subtracted from 1 year postsurgery; D. One year postsurgery subtracted from 2 years postsurgery; E. Presurgery subtracted from 2 years post surgery; F. Visualization of changes using signed distances, where bone formation is shown in red, 5mm of bone resorption in the superior and articular surfaces in blue.

Figure 10

Close up views of the longitudinal follow-up of changes in the left condyle in figure 10. The findings for this patient reveal bone resorptive changes approximately four times larger than other cases in our TMJ OA asymptomatic database (data not included on this paper). A. Frontal view of condylar morphology prior to surgery, at splint removal, 1 year postsurgery and 2 years postsurgery. B-E. Absolute distances and difference vectors B. Presurgery subtracted from splint removal. C. Splint removal subtracted from 1 year postsurgery; D. One year postsurgery subtracted from 2 years postsurgery; E. Presurgery subtracted from 2 years postsurgery F. Visualization of changes using signed distances, where bone formation is shown in red, 4mm of bone resorption in the superior and articular surfaces in blue.