Gradual change in knee extension following total knee arthroplasty using ultracongruent inserts

• Published in: The knee 2019-08, Vol.26 (4), p.905-913
• Main Authors: Lee, Sung-Sahn, Kim, Joo Hwan, Heo, Jae-Won, Moon, Young-Wan
• Format: Article
• Language: English
• Subjects: Arthroplasty (knee); Clinical outcomes; Extension angle; Flexion contracture; Joint surgery; Knee; Multiple regression analysis; Navigation systems; Patient satisfaction; Prostheses; Radiography; Recurvatum; Studies; Surgery; Total knee arthroplasty; Ultracongruent insert
• ISSN: 0968-0160; 1873-5800
• DOI: 10.1016/j.knee.2019.06.001

Total knee arthroplasty (TKA) using an ultracongruent (UC) insert is widely performed. Lack of the posterior cruciate ligament or post-cam mechanism is a concern in terms of range of motion. The flexion angle of UC TKA had been well investigated; however, natural history and correlation factors of the postoperative extension angle have not been well documented. This study aimed to investigate time-dependent changes in extension after TKA using UC inserts, and to evaluate factors that correlated with the postoperative extension angle. This study reviewed 388 gap-balanced UC TKAs (331 patients) without hyperextension at navigation and performed between November 2010 and December 2014. The extension angle (a positive number indicates hyperextension) was measured on full-extension lateral radiographs. The extension angles from five days post-operation to final follow-up were investigated. Factors correlated with the postoperative extension angle were evaluated using multiple regression analysis. Mean follow-up duration was 46.2 months. Until two years, the extension angle gradually increased; mean angles at five days/six months/one year/two years/and final follow-up were: −9.2°/−2.6°/0.6°/1.0°/1.0°, respectively. Female sex (β = −0.15, P = 0.002) and pre-operative hyperextension (β = 0.31, P