No correlation between coronal alignment of total knee arthroplasty and clinical outcomes: a prospective clinical study using 3D-CT

Purpose: The aim of this study was to evaluate femoral and tibial as well as whole leg coronal TKA alignment using 3D-reconstructed CTs and to assess the relationship of coronal TKA alignment and clinical outcome in a large prospective series of patients. It was hypothesized that a coronal deviation of TKA position and leg alignment from the mechanical axis is correlated with poorer patients' outcome after TKA.

Methods: A total of 81 consecutive patients who underwent primary TKA were prospectively included. The patient's demographics such as age, gender and time from primary TKA were noted. All patients underwent clinical and radiological examination including standardized radiographs (anteroposterior and lateral weight-bearing, patellar skyline view) and CT as part of their postoperative follow-up. For assessment of TKA component position and orientation 3D-reconstructed CT was used. For clinical outcome scoring the Knee Society Score (KSS) was used at 1 and 2 years postoperatively. Linear and quadratic regression models were used to test for correlations between alignment variables and KSS (p < .05).

Results: The mean Knee Society Score was 181 ± 28 (range 52-200) 2 years postoperatively, while 78% of the patients were completely pain free and 22% had some persisting pain interfering with their daily activities. The mean mechanical whole limb alignment (HKA angle), femoral component alignment and tibial component alignment were 0°, 0.1° and -0.7°, respectively. The component position parameters, as well as the whole limb alignment measurements, did not show any statistically significant correlation with the KSS, after 1 and 2 years postoperatively.

Conclusion: In this prospective study, using 3D-CT to measure the component position, the postoperative outcome was not influenced by coronal TKA component position as well as the whole leg alignment. The findings challenge the current target of neutral coronal alignment and point towards a more individualized mechanical alignment target.

Level of evidence: Prognostic study, Level I.