No Difference in Posterior Tibial Slope Comparing Patients With and Without Delayed Anterior Cruciate Ligament Tear
Roan Willson1, Sierra R Thomsen2, Morgan Swanson3
1University of Washington School of Medicine, Seattle, WA, USA.
Background:
Tibial spine fractures (TSFs) increase the risk of late ipsilateral anterior cruciate ligament (ACL) tears. The posterior tibial slope (PTS) is a recognized factor for graft failure after ACL reconstruction but has not yet been studied as a potential risk factor for a subsequent ACL tears following TSF.
Methods:
This was a multicenter, Institutional Review Board (IRB)-approved case-control and reliability study of patients who underwent TSF care. Medial PTS was measured on radiographs by three researchers blinded to whether patients had subsequent ACL tears; inter-observer reliabilities were assessed. Nonparametric tests compared PTS and ages at TSF and the duration of follow-up between patients with and without subsequent ACL tears. A 4:1 matched cohort by age and TSF grade was evaluated similarly.
Results:
One hundred 96 patients with TSFs and lateral knee radiographs were reviewed. The radiographic analysis showed an interobserver reliability of 0.734, with a 95% confidence interval of [0.627, 0.807], indicating moderate-to-substantial reliability for PTS. The average age of patients was 11.4 years (range, 5-19 years). Of these, 59 were female and 137 were male. Nine patients experienced delayed ACL tears. There was no difference in mean PTS between patients without ACL tears (PTS = 9.4, range 4-15, n = 187) and those with (PTS = 9.1, range 6-13, n = 9) (H(1, N = 196) = 0.17, P = .68). Kruskal-Wallis testing in a 4:1 matched case-control analysis showed similar results (PTS = 9.7, range 6-15, n = 36) (H(1, N = 45) = 0.39, P = .53). Patients with a delayed ACL tear were significantly older at the time of TSF (14.1 years) compared to those without (12.0 years, P = 0.015).
Conclusions:
In this multicenter cohort, patients who experienced a delayed ACL tear after TSF treatment did not have a different PTS compared to those who did not. Prospectively tracking patients with TSF will improve our understanding of modifiable risk factors for delayed ACL tears.
Key Concepts:
(1)Ipsilateral ACL tear is a common complication of tibial spine fractures.(2)An increased posterior tibial slope is associated with an increased risk of primary and secondary ACL tears.(3)We found no association between PTS and delayed ACL tear in patients who had sustained a tibial spine fracture.
Level Of Evidence:
Level III, Case-controlled study or retrospective cohort study.
