Tibial Slope and Its Effect on Force in Anterior Cruciate Ligament Grafts: Anterior Cruciate Ligament Force Increases Linearly as Posterior Tibial Slope Increases

Abstract

Background: Previous work has reported that increased tibial slope is directly correlated with increased anterior tibial translation, possibly predisposing patients to higher rates of anterior cruciate ligament (ACL) tears and causing higher rates of ACL graft failures over the long term. However, the effect of changes in sagittal plane tibial slope on ACL reconstruction (ACLR) graft force has not been well defined. Purpose/Hypothesis: The purpose of this study was to quantify the effect of changes in sagittal plane tibial slope on ACLR graft force at varying knee flexion angles. Our null hypothesis was that changing the sagittal plane tibial slope would not affect force on the ACL graft. Study Design: Controlled laboratory study. Methods: Ten male fresh-frozen cadaveric knees had a posterior tibial osteotomy performed and an external fixator placed for testing and accurate slope adjustment. Following ACLR, specimens were compressed with a 200-N axial load at flexion angles of 0°, 15°, 30°, 45°, and 60°, and the graft loads were recorded through a force transducer clamped to the graft. Tibial slope was varied between −2° and 20° of posterior slope at 2° increments under these test conditions. Results: ACL graft force in the loaded testing state increased linearly as slope increased. This effect was independent of flexion angle. The final model utilized a 2-factor linear mixed-effects regression model and noted a significant, highly positive, and linear relationship between tibial slope and ACL graft force in axially loaded knees at all flexion angles tested (slope coefficient = 0.92, SE = 0.08, P < .001). Significantly higher graft force was also observed at 0° of flexion as compared with all other flexion angles for the loaded condition (all P < .001). Conclusion: The authors found that tibial slope had a strong linear relationship to the amount of graft force experienced by an ACL graft in axially loaded knees. Thus, a flatter tibial slope had significantly less loading of ACL grafts, while steeper slopes increased ACL graft loading. Our biomechanical findings support recent clinical evidence of increased ACL graft failure with steeper tibial slope secondary to increased graft loading. Clinical Relevance: Evaluation of the effect of increasing tibial slope on ACL graft force can guide surgeons when deciding if a slope-decreasing proximal tibial osteotomy should be performed before a revision ACLR. Overall, as slope increases, ACL graft force increases, and in our study, flatter slopes had lower ACL graft forces and were protective of the ACLR graft.

A decreased ratio of height of lateral femoral condyle to anteroposterior diameter is a risk factor for anterior cruciate ligament rupture

“…Many studies, including this one, have confirmed that the steeper the tibial slope, the greater the risk of ACL injury, and some studies have calculated the threshold [14,18,19]. In this study, we found that the HAPR has better diagnostic and predictive value than the PTS.…”

Treatment for Symptomatic Genu Recurvatum: A Systematic Review

“…3 This same study reported only 1 case of a postoperative ACL tear; however, such a large increase in posterior tibial slope compared with normal ranges increases the risk of future ACL tears and must be considered when surgically correcting genu recurvatum using a tibial osteotomy. 3,12,34 The reviewed studies that entailed osteotomies reported similar degrees of preoperative genu recurvatum in patients treated using either PTO alone or the Ilizarov method. Both corrective techniques also demonstrated similar subjective postoperative outcomes.…”

“… 33 Although this study reported improved subjective outcome scores according to the Hospital for Special Surgery scoring system (mean, 90.3 ± 9.0) and a high rate (83%) of patient satisfaction, such a significant degree of postoperative tibial slope may increase the risk of ACL instability at later follow-up. 3 This same study reported only 1 case of a postoperative ACL tear; however, such a large increase in posterior tibial slope compared with normal ranges increases the risk of future ACL tears and must be considered when surgically correcting genu recurvatum using a tibial osteotomy. 3 , 12 , 34 …”

“… 3 This same study reported only 1 case of a postoperative ACL tear; however, such a large increase in posterior tibial slope compared with normal ranges increases the risk of future ACL tears and must be considered when surgically correcting genu recurvatum using a tibial osteotomy. 3 , 12 , 34 …”

A influência do \"slope\" tibial no risco de falha da reconstrução do ligamento cruzado anterior

“…Outros pesquisadores conseguiram provar que há aumento nas forças atuantes no LCA porém sua intensidade é muito pequena (BERNHARDSON et al, 2019;MAROUANE et al, 2014b). Neste último trabalho houve um acréscimo de cerca de 30 Newtons (N), durante a aplicação de uma força de compressão axial de 200 N, em um planalto com 20 graus de "slope".…”