Absence of the anterior cruciate ligament on preoperative magnetic resonance imaging is associated with lower Knee Society Score function score at mid-term follow up after cruciate-retaining total knee arthroplasty.

BACKGROUND: The clinical significance of anterior cruciate ligament (ACL) integrity in surgical planning for cruciate-retaining total knee arthroplasty (CR TKA) remains unclear. Although magnetic resonance imaging (MRI) allows assessment of the ACL status, its clinical relevance on postoperative outcomes has not been established.

METHODS: This retrospective cohort study included 164 knees that underwent primary CR TKA for knee osteoarthritis with a minimum follow up of 5 years. All cases during the study period underwent MRI scans preoperatively. The ACL was classified as intact, indeterminate, or absent based on sagittal MRI. Clinical outcomes were assessed using the Knee Society Score (KSS) 1989, Knee injury and Osteoarthritis Outcome Score (KOOS), and Forgotten Joint Score (FJS). A multivariable regression analysis was performed to determine whether the ACL status was associated with functional outcomes.

RESULTS: Inter-observer agreement for MRI-based ACL classification was excellent (Cohen's κ = 0.872). The KSS function score (FS) at 5 years was significantly lower in the ACL-absent group than in the -intact and -indeterminate groups. In the absent group, the KSS FS decreased significantly between 2 and 5 years. A multivariable regression analysis demonstrated that the ACL absence was independently associated with lower KSS FS at 5 years postoperatively (β =  -8.9, 95% confidence interval: -16.0 to -1.9, P = 0.014).

CONCLUSION: Absence of the ACL on preoperative MRI was associated with lower KSS FS at mid-term follow up after CR TKA, although KOOS, FJS and range of motion were not significantly affected.