Changes in knee shape and geometry resulting from total knee arthroplasty. (January 2018)

• Record Type: Journal Article
• Authors: Akbari Shandiz, Mohsen; Boulos, Paul; Saevarsson, Stefan Karl; Ramm, Heiko; Fu, Chun Kit (Jack); Miller, Stephen; Zachow, Stefan; Anglin, Carolyn
• Is Part Of: Proceedings of the Institution of Mechanical Engineers. Volume 232:Number 1(2018:Jan.)
• Page Start: 67
• Page End: 79
• Publication Date: 2018-01
• Subjects: Total knee arthroplasty -- knee shape -- knee geometry -- femoral component rotation -- joint line distance -- patellofemoral distance -- patellar thickness -- 3D-3D registration -- 2D-3D registration; Biomedical engineering -- Periodicals; Medical instruments and apparatus -- Periodicals; 610.28
• DOI: 10.1177/0954411917743274
• Languages: English
• ISSNs: 0954-4119

Abstract

Changes in knee shape and geometry resulting from total knee arthroplasty can affect patients in numerous important ways: pain, function, stability, range of motion, and kinematics. Quantitative data concerning these changes have not been previously available, to our knowledge, yet are essential to understand individual experiences of total knee arthroplasty and thereby improve outcomes for all patients. The limiting factor has been the challenge of accurately measuring these changes. Our study objective was to develop a conceptual framework and analysis method to investigate changes in knee shape and geometry, and prospectively apply it to a sample total knee arthroplasty population. Using clinically available computed tomography and radiography imaging systems, the three-dimensional knee shape and geometry of nine patients (eight varus and one valgus) were compared before and after total knee arthroplasty. All patients had largely good outcomes after their total knee arthroplasty. Knee shape changed both visually and numerically. On average, the distal condyles were slightly higher medially and lower laterally (range: +4.5 mm to −4.4 mm), the posterior condyles extended farther out medially but not laterally (range: +1.8 to −6.4 mm), patellofemoral distance increased throughout flexion by 1.8–3.5 mm, and patellar thickness alone increased by 2.9 mm (range: 0.7–5.2 mm). External femoral rotation differed preop and postop. Joint line distance, taking cartilage into account, changed by +0.7 to −1.5 mm on average throughout flexion. Important differences in shape and geometry were seen between pre-total knee arthroplasty and post-total knee arthroplasty knees. While this is qualitatively known, this is the first study to report it quantitatively, an important precursor to identifying the reasons for the poor outcome of some patients. Using the developed protocol and visualization techniques to compare patients with good versus poor clinical outcomes could lead to changes in implant design, implant selection, component positioning, and surgical technique. Recommendations based on this sample population are provided. Intraoperative and postoperative feedback could ultimately improve patient satisfaction.