Finding and defining the ideal patellar resection plane in total knee arthroplasty

• Published in: Journal of biomechanics 2009-10, Vol.42 (14), p.2307-2312
• Main Authors: Anglin, C, Fu, C, Hodgson, A.J, Helmy, N, Greidanus, N.V, Masri, B.A
• Format: Article
• Language: English
• Subjects: Algorithms; Arthroplasty, Replacement, Knee - methods; Asymmetry; Female; Gender; Humans; Joint surgery; Knee; Knee Joint - diagnostic imaging; Knee Joint - surgery; Male; Patella; Patella - diagnostic imaging; Patella - surgery; Patellar resection; Physical Medicine and Rehabilitation; Radiographic analysis; Radiographic Image Interpretation, Computer-Assisted - methods; Radiography, Interventional - methods; Reproducibility of Results; Sensitivity and Specificity; Surgery, Computer-Assisted - methods; Symmetry; Tendons; Total knee arthroplasty; Treatment Outcome
• ISSN: 0021-9290; 1873-2380
• DOI: 10.1016/j.jbiomech.2009.06.021

Abstract Asymmetric resection of the patella during total knee arthroplasty (TKA) correlates with anterior knee pain, bony impingement and patellar maltracking. Despite this, there is no consensus regarding the desired landmarks; the cut is often done freehand; and there has been no quantitative comparison of proposed resection planes. The objectives of this study were to: determine the intra- and inter-surgeon repeatability of two radiographic resection definitions (medial–divot, MD, and medial–lateral extents, MLE); calculate two additional definitions from the radiographic patellar circumferences (parallel to the anterior surface, ANT, and perpendicular to the anteroposterior tangent points, PERP); compare the clinical resection line to the previous four definitions before and after introducing the MD method clinically; and identify distinguishing features of patellae with better vs. worse resection angles. We hypothesized that the MD method would improve repeatability both radiographically and clinically, that the different radiographic definitions would produce comparable angles, and that we could identify distinguishing features. For the radiographic study, three surgeons drew lines on 40 preoperative X-rays plus 9 interspersed repetitions of 3 of these X-rays. For the clinical study, we compared the patellar resection angle for 20 patients immediately before and after implementing the new method. Given that the clinical goal is to have equal distances from the resection surface to the anterior surface, we compared all results to the ANT definition as the theoretically ideal definition. Confirming the first hypothesis, intra-surgeon repeatability (10 repetitions of 3 X-rays) and inter-surgeon repeatability (3 surgeons×40 X-rays) were both significantly better using the new MD method compared to the MLE method ( p