Residual passive anterior tibial subluxation following anterior cruciate ligament reconstruction using hamstring tendon autografts: A longitudinal magnetic resonance imaging study with a minimum 2-year follow-up.

PURPOSE: To track the 24-month longitudinal changes in tibiofemoral alignment characterised by passive anterior tibial subluxation (PATS) following anterior cruciate ligament reconstruction (ACLR), and to investigate associated factors.

METHODS

Fifty-one patients who underwent primary ACLR using hamstring tendon autografts between March 2021 and February 2022 were enrolled. Clinical and magnetic resonance imaging (MRI) evaluations were performed at baseline (within 3 days preoperatively) and at 6-, 12- and 24-month follow-ups to examine the graft integrity and tibiofemoral alignment. Lateral PATS (L-PATS), medial PATS (M-PATS), global PATS (G-PATS) and rotational PATS (R-PATS) were measured on serial MRI. The repeated-measures one-way analysis of variance was applied to test the longitudinal changes in PATS. Univariable and multivariable linear regression analyses were performed to identify associations between preoperative and postoperative PATS, adjusting for a priori-defined covariates including time from injury to surgery, tibial slopes, meniscal injuries and anterolateral ligament (ALL) abnormality.

RESULTS

The graft integrity was clinically and radiographically confirmed in all patients at the 24-month follow-up. However, serial MRI revealed significant increases in L-PATS, M-PATS and G-PATS (all p < 0.001) following the primary ACLR. The increases in L-PATS (1.5 mm, 95%CI [0.6,2.5], p < 0.001), M-PATS (1.2 mm, 95%CI [0.5,1.9], p < 0.001) and G-PATS (1.4 mm, 95%CI [0.6,2.1], p < 0.001) from baseline became the most prominent at 12 months and remained stable thereafter. Strong correlations were identified between preoperative and 24-month postoperative values for L-PATS (β = 0.60, p < 0.001), M-PATS (β = 0.43, p < 0.001), G-PATS (β = 0.48, p < 0.001) and R-PATS (β = 0.70, p < 0.001). ALL abnormality was associated with increased L-PATS (β = 1.85, p = 0.008) and G-PATS (β = 1.31, p = 0.009), while medial meniscal injury was associated with increased M-PATS (β = 1.12, p = 0.036) and G-PATS (β = 0.96, p = 0.048) measured at 24 months postoperatively.

CONCLUSIONS

Residual tibiofemoral malalignment characterised by increased L-PATS, M-PATS and G-PATS persists following ACLR using hamstring tendon autografts. Excessive preoperative PATS, ALL abnormality and medial meniscal injury are associated with increased postoperative PATS.

LEVEL OF EVIDENCE: Level IV.