A Novel Assessment of Infratubercle Sagittal Proximal Tibial Morphology and Relationship to Full Length Posterior...

Slope-reducing high tibial osteotomy (SRO-HTO) surgically corrects elevated posterior tibial slope (PTS) and is often performed in the setting of failed anterior cruciate ligament (ACL) reconstruction. Lateral supratubercle angle (LSTA) quantifies the supratubercle component of elevated PTS, but the infratubercle component of elevated PTS has not been quantified.

The purpose of this study was to describe and establish mean values for lateral infratubercle angle (LITA) within non-ACL tear, primary ACL tear, and ACL graft tear cohorts. It was hypothesized that LITA would differ between non-ACL tear and ACL graft tear cohorts, would positively correlate with PTS elevation, and, when used with LSTA, would localize the deformity leading to PTS elevation.

Cross-sectional study; Level of evidence, 3.

Patients seen for a knee complaint were categorized into non-ACL tear, primary ACL tear, or ACL graft tear cohorts. PTS, LSTA, and LITA were measured on full-length lateral (FLL) tibia radiographs. Descriptive statistics were calculated for each measurement and cohort, and comparisons were performed using a 1-way analysis of variance with a Bonferroni correction (P < .01 indicating statistical significance). The non-ACL tear cohort's mean LITA value served as the cutoff. Pearson's correlation determined the relationship between elevated PTS with LITA and LSTA. P < .05 indicated statistical significance.

A total of 300 patients were included, 100 per cohort. The mean LITA in the non-ACL tear, primary ACL tear, and ACL graft tear cohorts were 89°± 4.6°, 90.7°± 5.8°, and 92°± 5°, respectively. Significant differences existed in LITA between the non-ACL tear and ACL graft tear cohorts (P < .001). Within the ACL graft tear cohort, 74.4% (64/86) of patients with elevated medial or lateral PTS (PTS-M/L) had elevated LITA, regardless of LSTA elevation status. Significant positive correlations existed between PTS-M/L and LITA in the non-ACL tear (P = .011/P = .004), primary ACL tear (P = .002/P = .029), and ACL graft tear cohorts (P < .001/P < .001/P < .001).

LITA is a novel measurement, with distinct anatomic landmarks, that quantifies infratubercle deformity and can be easily incorporated into FLL radiographic assessment. Elevated LITA was present in most patients with elevated PTS in both the primary ACL tear and ACL graft tear cohorts, indicating a contribution from infratubercle deformity. We recommend utilizing LITA and LSTA with PTS to quantify region-specific proximal sagittal deformity. Future studies should determine whether this quantification can help surgeons select the SRO-HTO technique and influence outcomes.