ANATOMIC FACTORS ASSOCIATED WITH OSTEOCHONDRAL ALLOGRAFT MATCHING FOR TROCHLEAR CARTILAGE DEFECTS: A COMPUTER-SIMULATION STUDY
Figure 1 - Anatomic measurements for all trochlear specimens performed on computed tomography imaging, including (A) lateral radius of curvature, (B) central radius of curvature, (C) trochlear width, (D) trochlear length, and (E) medial and lateral facet width.
Background:
Articular step-off between the donor and recipient in osteochondral allograft transplant has been shown to alter contact pressures. Currently, commercial allograft donor selection is primarily based on simple anatomic parameters such as trochlear length, trochlear width, and tibial width.
Purpose:
To identify anatomic factors associated with optimal graft matching by using a 3-dimensional simulation model.
Study Design:
Descriptive laboratory study.
Methods:
Computed tomography images of 10 cadaveric trochlear specimens were obtained to generate 3-dimensional models. Circular defects were created virtually in the recipient trochleae at both superolateral (18.0 mm and 22.5 mm) and central (18.0 mm, 22.5 mm, 30.0 mm) locations. The donor models were virtually projected onto the defect models, and the most optimal graft from any location of the donor specimen was selected. Cartilage incongruity, subchondral bone incongruity, and peripheral articular step-off were calculated for each graft-defect combination. Linear regression models were generated to identify predictors of incongruity, step-off, and the effect of sulcus and sagittal angle mismatch. Akaike information criterion–driven stepwise regression models were generated to identify multivariate predictors.
Figure 2 - (A) Schematic representations of simulated defect locations and sizes at the trochlea. Inset shows cartilage and subchondral bone surface models. Red points indicate the defect orientation by a clock face. (B) The matching algorithm: best-fit virtual grafts harvested from 9 other trochleae to match defect model, followed by measurement of incongruity and articular step-off.
Figure 3 - Definition of sulcus angle ∠3C9 and sagittal angle ∠12C6 in defect or graft cartilage surface model. C, center of the model.
Figure 5 - Linear regression models with 95% confidence bands demonstrating the effect of (A) sulcus and (B) sagittal angle mismatch on graft proudness separated by defect size. Larger defects demonstrated sequentially greater effects per degree of mismatch on step-off. adj, adjusted.
Results:
Ideal matches were found for 100% of superolateral defects but for only 15% to 53% of central defects, depending on the defect size. Multivariate stepwise regression identified laterality (odds ratio [OR], 0.54; P = .081), sulcus angle (OR, 0.79; P < .001), sagittal angle (OR, 0.83; P = .001), lateral radius of curvature (OR, 0.81; P < .001), and medial facet width (OR, 0.86; P = .155) as predictors of ideal graft matching. In central defects with proud grafts, increasing sagittal angle and sulcus angle resulted in significantly (P < .001) increased articular step-off, which became sequentially larger with defect size.
Conclusion:
Sagittal angle, sulcus angle, and lateral radius of curvature mismatch should be used to determine optimal donor allografts, especially in the setting of large (30-mm) central defects. Increasing sulcus angle and sagittal angle mismatch correlated with increasing step-off in proud grafts, whereas sulcus angle and sagittal angle inconsistently correlated with step-off in recessed grafts.
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Published September 22, 2022 in the American Journal of Sports Medicine (Volume 50 - Issue 13).