Coronal and sagittal malalignment of the knee are well-recognized intrinsic risk factors for failure after anterior cruciate ligament reconstruction (ACLR). However, the influence of the axial malalignment, particularly the tibiofemoral rotational malalignment, on ACLR graft survival is still unknown. The aim of this pilot study was therefore to evaluate whether increased tibiofemoral rotational malalignment is associated with ACLR graft failure.
In this review of prospectively collected data, we analyzed data from 20 patients who underwent revision or primary ACLR with a minimum of 2 years follow-up between June 2018 and January 2019. Ten patients who required revision of ACLR due to graft failure (ACLR revision group) were compared to a matched-control group of patients who underwent primary ACLR and had no evidence of graft failure (primary ACLR group). The patients were matched by age, gender, body mass index (BMI), presence of medial and/or lateral meniscus tear, and posterior tibial slope. Axial malalignment was assessed on magnetic resonance imaging (MRI) through the tibiofemoral rotation angle and the tibial tuberosity-trochlear groove (TT-TG) distance by two independent examiners. Tibiofemoral rotation angle was measured using the angle between the posterior condylar lines of the distal femur and the proximal tibia. TT-TG distance was calculated according to established landmarks. Data were analyzed using descriptive statistics, Shapiro-Wilk test of normality, independent t test or Mann-Whitney U test, as appropriate.
Overall, the mean age was 30.1 ± 8.0 years, and the mean BMI was 24.96 ± 3.01 kg/m2. Medial and lateral posterior tibial slope were 9.6o ± 2.6o and 10o ± 3o, respectively. The mean tibiofemoral rotation angle was significantly higher in the ACLR revision group (7.1o ± 2.9o) compared to the primary ACLR group (3.8o ± 2.7o), (p= 0.02). However, TT-TG distance was similar between the groups (revision ACLR: 12.7 ± 4 vs primary ACLR: 13.4 ± 3.7 mm; p= 0.66).
Our matched-control study demonstrated that patients who required revision of ACLR due to graft failure have a higher tibiofemoral rotation angle than patients with no evidence of ACLR graft failure. We believe that increased knee rotational malalignment provides more stress on the ACLR graft and therefore might jeopardize the success of ACLR.