Computer Navigation Assisted Restricted Kinematic Alignment Improves Short-Term Outcomes in Total Knee Arthroplasty: An Ambispective Cohort Study.

OBJECTIVES
Mechanical alignment (MA)-total knee arthroplasty (TKA) has been challenged due to the excessive soft tissue release and the evidence of the clinical outcomes of computer assisted navigation is still limited. The aim of this ambispective cohort study was to: (i) investigate whether computer assisted navigation is capable to achieve restricted kinematic alignment (rKA)-TKA; and (ii) compare the short-term outcomes between rKA-TKA and MA-TKA.


METHODS
We retrospectively included 41 patients diagnosed with osteoarthritis who received MA-TKA between April 2019 and January 2021 and 43 patients diagnosed with osteoarthritis who received rKA-TKA were included in the prospective cohort from January 2021 to September 2021. Demographical, peri-operative, and radiological data were collected and compared. Unpaired two-sample t-test for continuous variables and χ2 test for categorical variables were used to compare various measurements in two groups. The patient-reported outcome measures at baseline, 10 days (T1), and 6 months (T6) after surgery were statistically analyzed by generalized estimating equation (GEE) models.


RESULTS
Fourty-one patients (45 knees) and 43 patients (48 knees) were included in the MA and the rKA group respectively. Three constitutional knee phenotypes (II, I, IV) were the commonest in our population. Navigation improved the surgical accuracy (1.5° vs 3.5°, p < 0.001) and precision (interquartile range 4.0 vs 2.0, p < 0.001) in the rKA group than the MA group. The changes in Knee Injury and Osteoarthritis Outcome Score 12 (KOOS12), EuroQol five-dimension questionnaire (EQ5D) from baseline to T1 and T6 for patients with on-target rKA were larger than on-target MA counterparts (26.053 vs 18.607, P < 0.001(KOOS12, T1) , 0.457 vs 0.367 p < 0.001(EQ5D, T1) ; 51.017 vs 46.896, P = 0.023(KOOS12, T6) , 0.606 vs 0.565, P = 0.01(EQ5D, T6) ). Patients with on-target rKA had better Forgotten Joint Score (FJS) at T1 (54.126 vs 40.965, P = 0.002) compared with on-target MA counterparts.


CONCLUSIONS
Computer assisted navigation achieved the level of accuracy required by rKA-TKA. rKA-TKA offered significantly better short-term outcomes than MA-TKA.