Background

Post-traumatic knee osteoarthritis (PTOA) is the main long-term outcome of anterior cruciate ligament deficiency (ACLD). The development of PTOA has been reported in cases of knee instability even after ACL reconstruction (ACLR). The development of PTOA in ACLD knees and ACL reconstructed knees can ultimately lead to knee disability and decreased quality of life, making this an increasingly critical concern for patients. For patients with ACLD and PTOA, combining ACLR with around the knee osteotomy (AKO) is a common approach. However, detailed characteristics of knee instability in patients with ACLD and PTOA have not been reported, and the decision to perform ACLR alone, ACLR with AKO, or AKO alone is dependent on criteria set by individual surgeons. Understanding the characteristics of knee instability in ACLD knees with PTOA may be helpful in selecting a surgical procedure. Therefore, the purpose of this study is to investigate the characteristics of preoperative knee instability in patients who underwent ACLR with AKO.

Methods

Seventeen patients who underwent both ACLR with AKO were included in this study. Of these, 14 patients were performed medial opening wedge high tibial osteotomy (MOWHTO) for medial knee OA and 3 were performed medial closing wedge distal femoral osteotomy (MCWDFO). Three revision ACLR cases were included. Patients with contralateral ACL injuries or complex ligament injuries were excluded. Preoperative measurements were taken under anesthesia using KT2000 and an electromagnetic measurement system to assess posterior tibial translation and posterior tibial acceleration during the pivot shift test. These measurements (side-to-side difference of KT-2000, posterior tibial translation and posterior tibial acceleration during the pivot shift test) were then correlated with radiographic parameters, including Kellgren-Lawrence (KL) grade, %mechanical axis, posterior tibial slope, and the difference in anterior tibial translation between the affected and unaffected legs in a single-leg stance lateral view.

Results

A moderate negative correlation was observed between KT2000 measurements and both KL grade and the side-to-side difference of KT-2000 between the affected and unaffected legs in a single-leg stance lateral view (r=-0.48, -0.49). Similarly, a moderate negative correlation was found between posterior tibial translation and posterior tibial acceleration during the pivot shift test and the difference in anterior tibial translation between the affected and unaffected legs in a single-leg stance lateral view (r=-0.67, -0.51).

Discussion

In cases of ACLD with PTOA, the more anteriorly the tibia was displaced on a single-leg stance lateral X-ray image, the less anterior and rotational knee instability. Therefore, it is suggested that for patients with ACLD with PTOA, ACLR combined with AKO should be considered if the patient has knee instability with small anterior tibial translation, and, but AKO alone may be sufficient if anterior tibial translation is large.