Influence of posterior tibial slope on postoperative outcomes after postero-stabilized and condylar-stabilized total knee arthroplasty.

Purpose: To compare clinical outcomes and surgical times of two different types of total knee arthroplasty(TKA), postero-stabilized(PS) and condylar-stabilized(CS), in relation to posterior tibial slope(PTS) values and the deviation of these values from the surgical technique.

Methods: 168 patients undergoing TKA surgery between 2016 and 2020 met our inclusion criteria. For each case, gender, age at surgery, operating time, type of implant and preoperative PTS(preop-PTS) and postoperative PTS(postop-PTS) measurements were collected; difference(∆PTS) between preop-PTS and postop-PTS was also calculated. Short Form 12 Mental and Physical scores(SF-12 M and P) and functional Knee Society Score(fKSS) were collected preoperatively and at a minimum of 12 months postoperatively. Four subgroups were thus created in relation to PS or CS system and postop-PTS value(≤ 5°and > 5°).

Results: Of the 168 patients, 96 had a PS system and 72 CS system. Performing a CS-TKA took less time than a PS-TKA(p < 0.05). SF-12P showed better results(p < 0.05) in CS-TKA group than PS-TKA, probably because of the younger age of CS-TKA patients(p < 0.05). In the PS > 5° all examined postoperative scores were better(p < 0.05) than PS ≤ 5°, while only fKSS was better(p < 0.05) in CS > 5° than CS ≤ 5°. No significant difference(p > 0.05) in terms of postoperative outcomes between the PS > 5° and CS > 5° was noted, whereas only SF-12P was better in the CS ≤ 5° compared with PS ≤ 5°. Highest values of SF-12 M and fKSS were obtained in the PS ≤ 5°, in which postop-PTS was closer to technique.

Conclusion: When performing a PS-TKA, the best result was obtained with a postop-PTS > 5°, but comparable outcomes between the two systems were evident with postop-PTS > 5°. It is crucial to come as close as possible to the indications reported in surgical technique regardless ∆PTS.