Abstract Purpose Traditional management of hyperextension deformity in total knee arthroplasty (TKA) involves routine under‐resection of distal femoral bone to lower the joint line and close the extension gap. This study aimed to assess how a robotic functional alignment (FA) workflow with pre‐resection gap assessment managed hyperextending knees to achieve balance compared to controls. Methods A retrospective analysis of a prospective registry was performed using a single implant/robotic platform, two surgeons, between 2016 and 2023. 100 hyperextending TKA patients with hyperextension of 5° or more were compared to a control group of 1881 patients with 0°–10° of fixed flexion contracture. Results The hyperextension group had a greater maximum flexion ROM (137° vs. 132°) compared to controls. All four mean start‐of‐case gaps (medial and lateral in flexion and extension) were larger for the hyperextension patients by 0.7–1.2 mm. The femoral joint line was not routinely distalised by a clinically significant amount in the hyperextension patients (0.3 mm difference in means; 0.6 mm vs. 0.3 mm. The hyperextension cohort had relative tibial under‐resection (4.8 mm vs. 5.4 mm; p 0.05) and forgotten joint score (FJS, p > 0.05). Two patients had hyperextension recurrence at 1‐year review, measured at –2° and –5°. Conclusions Hyperextending arthritic knees may not require routine distalisation of the femoral joint line to achieve balance and close the extension gap. These knees have a global laxity that can often be effectively managed with predominantly tibial sided changes. Level of Evidence Therapeutic Level III, retrospective comparative study.
Lambers et al. (Mon,) studied this question.