Postoperative TTTG is not associated with PROMs at 12 months following TKA with unrestricted kinematic alignment: An observational case series

Purpose The purpose of this retrospective cohort study was to evaluate changes in tibial tuberosity trochlear groove distance (TTTG) among patients who received total knee arthroplasty (TKA) with unrestricted kinematic alignment, and to determine whether these changes are correlated with patient-reported outcome measures (PROMs) and patient satisfaction at a minimum follow-up of 12 months. Methods The initial cohort of 63 patients (71 knees) received augmented reality (AR)-assisted TKA with unrestricted kinematic alignment between January 2024 and September 2024. Patients completed pre- and post-operative questionnaires for the Oxford Knee Score (OKS; worst, 0; best, 48), the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC Total; best, 0; worst, 96; WOMAC Pain; best, 0; worst, 20; WOMAC Stiffness; best, 0; worst, 8; WOMAC Function; best, 0; worst, 68;), and the Forgotten Joint Score (FJS; best, 100; worst, 0). Patients also rated their level of satisfaction on a 7-point Likert Scale (“Very unsatisfied”; “Unsatisfied”; “Somewhat unsatisfied”; “Neutral”; “Somewhat satisfied”; “Satisfied”; “Very satisfied”). Knees were classified according to their postoperative TTTG using a threshold of <15 mm versus ≥15 mm. Exploratory multivariable analyses were used to assess the association between postoperative TTTG and postoperative as well as the net change in PROMs, adjusting for age, body mass index (BMI), sex, and baseline score. Results Of the initial cohort of 63 patients (71 knees), three did not provide informed consent, three had missing data, two had patellar resurfacing, and two were lost to follow-up. Of the final cohort of 53 patients (61 knees), 50 knees had a TTTG <15 mm, whereas 11 had a postoperative TTTG ≥15 mm. Multivariable analyses revealed no association between continuous postoperative TTTG and postoperative OKS, WOMAC or FJS after adjusting for age, BMI, sex and baseline score. Exploratory multivariable analyses did revealed significant negative associations between postoperative TTTG ≥15 mm and net improvement in WOMAC Total (ß = −8.4; p = 0.046), and Function (ß = −6.9; p = 0.025). Conclusion This single-centre, single-surgeon retrospective study revealed no associations between postoperative TTTG and patient satisfaction or PROMs at 12 months following TKA using unrestricted kinematic alignment. Although TTTG ≥15 mm was associated with reduced net improvement in WOMAC Total and Function, the 15 mm threshold and its potential association with postoperative PROMs need validation in larger cohort studies. Level of evidence IV Clinical trial registration Not applicable.