Morphometric assessment and virtual resection of the patellae on three dimensional CT-based models using computer assisted technology

Objective To assess patellar morphology and determine the reliability of the subchondral method (resecting the patella at the level of the subchondral bone of the lateral facet) for patellar resection in total knee arthroplasty (TKA) using computer assisted technology. Methods Computer tomography examinations were performed in 200 volunteers (100 males, 100 females). The CT scan images were imported into the Mimics software for generating 3D patellar models. Furthermore, comprehensive assessment of patellar morphology and virtually resurfacing the patella were conducted with the three-dimensional models. An anthropometric analysis of variance was used with the models to detect differences between genders both before and after resecting the patellae. Results There was good intraand inter-observer reliability regarding the dimensional measurements in this study (Intra-class correlation coefficient, ICC >0.75). Significant gender differences in the patellar width, height, thickness and length of articulating fact were found (P <0.05). The average patellar width/thickness ratio was 1.95±0.11, regardless of gender, and there was a good correlation between the patellar width and thickness (Male r=0.67, P=0.00; Female r=0.63, P=0.00). After virtual resection, the mean thickness of resected patellae was 9.59±1.53 mm. The resected thickness in male and female group was 10.21±1.53 mm and 8.98±1.27 mm, respectively. It was found that 89% female patellae were resected between 8 and 11 mm and 82% of male patellae were resected between 9 and 12 mm. Conclusion CT based 3D computer assisted technology is an accurate and efficient tool in evaluating the anthropometric patellar dimensions. The anthropometric dimensions of this study could provide basic data for guiding surgical management of the patella in TKA. Key words: Patella; Osteotomy; Arthroplasty, replacement, knee; Anatomy