EC Orthopaedics

Introduction: Anterior cruciate ligament (ACL) injuries are prevalent in sports, with revision surgeries often required due to graft failure. While several factors contribute to these failures, the role of the posterior tibial slope (PTS) in both functional outcomes and tunnel widening following ACL reconstruction has gained increasing attention. This study investigates the influence of the PTS on these outcomes in patients who underwent revision ACL reconstruction.

Methods: A retrospective cohort study was conducted with 96 patients who received revision ACL reconstructions between 2010 and 2022. Patients were categorized based on their PTS into two groups: those with a PTS greater than 10 degrees and those with a PTS less than 10 degrees. Functional outcomes were assessed using the Lysholm score, while tunnel widening was evaluated through radiographic measurements of the femoral and tibial tunnels. Statistical analysis was performed using unpaired t-tests to compare both functional outcomes and tunnel widening between the two groups.

Results: The Lysholm score in patients with a PTS greater than 10 degrees was significantly lower (mean: 79) compared to those with a PTS less than 10 degrees (mean: 89), with a p-value of <0.0001. However, no significant difference was observed in tunnel widening between the two groups across femoral and tibial measurements. The mean difference in tunnel widening was similar for both groups, suggesting that PTS has limited influence on tunnel widening after revision ACL reconstruction.

Discussion: While a steeper PTS is associated with poorer functional outcomes, particularly as measured by the Lysholm score, it does not appear to significantly affect tunnel widening in revision ACL surgeries. This suggests that the influence of PTS on functional outcomes may be more biomechanical than structural. Future research should explore the interplay between PTS and graft stability to further optimize surgical outcomes.

 Keywords: Anterior Cruciate Ligament (ACL); Posterior Tibial Slope (PTS); Medial Posterior Tibial Slope (MPTS); Patient-Reported Outcome Measures (PROMs)

1. Mall NA., et al. “Incidence and trends of anterior cruciate ligament reconstruction in the United States”. American Journal of Sports Medicine10 (2014): 2363-2370.
2. Butler DL., et al. “Ligamentous restraints to anterior-posterior drawer in the human knee. A biomechanical study”. Journal of Bone and Joint Surgery - Series A2 (1980): 259-270.
3. Kalawadia JV. “Anatomy and biomechanics of the anterior cruciate ligament”. In Prodromos C (2e), The Anterior Cruciate Ligament Reconstruction and Basic Science, Elsevier (2018): 1-7.
4. van Eck CF., et al. “Prospective analysis of failure rate and predictors of failure after anatomic anterior cruciate ligament reconstruction with allograft”. American Journal of Sports Medicine4 (2012): 800-807.
5. Duffee AR. “Patient-related risk factors for ACL graft failure”. In Marx R.G. (1e), Revision ACL Reconstruction: Indications and Technique. Springer (2014): 1-9.
6. Bayer S., et al. “Knee morphological risk factors for anterior cruciate ligament injury: a systematic review”. Journal of Bone and Joint Surgery - American Volume 8 (2020): 703-718.
7. Webb JM., et al. “Posterior tibial slope and further anterior cruciate ligament injuries in the anterior cruciate ligament-reconstructed patient”. American Journal of Sports Medicine12 (2013): 2800-2804.
8. Song GY., et al. “Slope-reducing tibial osteotomy combined with primary anterior cruciate ligament reconstruction produces improved knee stability in patients with steep posterior tibial slope, excessive anterior tibial subluxation in extension, and chronic meniscal posterior horn tears”. American Journal of Sports Medicine14 (2020): 3486-3494.
9. Dejour D., et al. “Tibial slope correction combined with second revision ACL produces good knee stability and prevents graft rupture”. Knee Surgery, Sports Traumatology, Arthroscopy10 (2015): 2846-2852.
10. Sonnery-Cottet B., et al. “Proximal tibial anterior closing wedge osteotomy in repeat revision of anterior cruciate ligament reconstruction”. American Journal of Sports Medicine8 (2014): 1873-1880.
11. Ni QK., et al. “Posterior tibial slope measurements based on the full-length tibial anatomic axis are significantly increased compared to those based on the half-length tibial anatomic axis”. Knee Surgery, Sports Traumatology, Arthroscopy 4 (2022): 1362-1368.
12. de Sousa Filho PGT., et al. “Analysis of posterior tibial slope as risk factor to anterior cruciate ligament tear”. Revista Brasileira de Ortopedia1 (2021): 47-52.
13. Fares A., et al. “Posterior tibial slope (PTS) ≥ 10 degrees is a risk factor for further anterior cruciate ligament (ACL) injury; BMI is not”. European Journal of Orthopaedic Surgery and Traumatology 5 (2022): 2091-2099.
14. Dracic A., et al. “Determining the cut-off value of the posterior tibial slope as an indication for slope reducing proximal tibial osteotomies in the setting of revision anterior cruciate ligament reconstruction [Paper presentation]”. DKGOU 2023: Berlin, Germany (2023).
15. Fauno P and Kaalund S. “Tunnel widening after anterior cruciate ligament reconstruction is influenced by the type of graft”. Knee Surgery, Sports Traumatology, Arthroscopy5 (2005): 389-393.
16. Sabat D., et al. “Tunnel widening after anterior cruciate ligament reconstruction: A prospective randomized study comparing hamstring and patellar tendon autografts”. Journal of Orthopaedic Surgery3 (2011): 288-293.
17. Buelow JU., et al. “Tunnel widening after ACL reconstruction with hamstring tendons: A randomized clinical study comparing 3 different fixation methods”. Arthroscopy: The Journal of Arthroscopic and Related Surgery1 (2002): 56-63.
18. Morgan JA., et al. “Femoral and tibial tunnel changes after ACL reconstruction: A prospective 2-year longitudinal MRI study”. The American Journal of Sports Medicine5 (2016): 1147-1153.
19. Faul F., et al. “G*Power 3: A flexible statistical power analysis program for the social, behavioral, and biomedical sciences”. Behavior Research Methods2 (2007): 175-191.
20. Faul F., et al. “Statistical power analyses using G*Power 3.1: Tests for correlation and regression analyses”. Behavior Research Methods 4 (2009): 1149-1160.
21. Grassi A. “Common Scales and Checklists in Sports Medicine Research”. In Musahl V. (1e), Basic Methods Handbook for Clinical Orthopaedic Research. Springer (2019): 417-444.
22. Hinz M., et al. “The posterior tibial slope is not associated with graft failure and functional outcomes after anatomic primary isolated anterior cruciate ligament reconstruction”. American Journal of Sports Medicine 14 (2023): 3670-3676.
23. Mabrouk A., et al. “Outcomes of slope-reducing proximal tibial osteotomy combined with a third anterior cruciate ligament reconstruction procedure with a focus on return to impact sports”. American Journal of Sports Medicine 13 (2023): 3454-3463.
24. Plancher KD., et al. “Relevance of the tibial slope on functional outcomes in acl-deficient and acl intact fixed-bearing medial unicompartmental knee arthroplasty”. Journal of Arthroplasty 9 (2021): 3123-3130.
25. Miralles-Muñoz FA., et al. “No influence of posterior tibial slope change on outcomes after cruciate-retaining total knee arthroplasty: a prospective cohort study”. Archives of Orthopaedic and Trauma Surgery 6 (2023): 3431-3437.
26. Morgan JA., et al. “Femoral and tibial tunnel changes after ACL reconstruction: A prospective 2-year longitudinal MRI study”. The American Journal of Sports Medicine5 (2016): 1147-1153.
27. de Beus A., et al. “How to evaluate bone tunnel widening after acl reconstruction - a critical review”. Muscles, Ligaments and Tendons Journal 2 (2017): 230-239.
28. Peyrache MD., et al. “Tibial tunnel enlargement after anterior cruciate ligament reconstruction by autogenous bone-patellar tendon-bone graft”. Knee Surgery, Sports Traumatology, Arthroscopy1 (1996): 2-8.
29. L’Insalata JC., et al. “Tunnel expansion following anterior cruciate ligament reconstruction: a comparison of hamstring and patellar tendon autografts”. Knee Surgery, Sports Traumatology, Arthroscopy4 (1997): 234-238.
30. Murty AN., et al. “Tibial tunnel enlargement following anterior cruciate reconstruction: does post-operative immobilisation make a difference?” Knee1 (2001): 39-43.
31. Clatworthy MG., et al. “Tunnel widening in anterior cruciate ligament reconstruction: a prospective evaluation of hamstring and patella tendon grafts”. Knee Surgery, Sports Traumatology, Arthroscopy3 (1999): 138-145.
32. Nebelung W., et al. “Bone tunnel enlargement after anterior cruciate ligament reconstruction with semitendinosus tendon using endobutton fixation on the femoral side”. Arthroscopy8 (1998): 810-815.
33. Kawaguchi Y., et al. “Comparisons of femoral tunnel enlargement in 169 patients between single-bundle and anatomic double-bundle anterior cruciate ligament reconstructions with hamstring tendon grafts”. Knee Surgery, Sports Traumatology, Arthroscopy 8 (2011): 1249-1257.
34. Surer L., et al. “Fibrin clot prevents bone tunnel enlargement after acl reconstruction with allograft”. Knee Surgery, Sports Traumatology, Arthroscopy5 (2017): 1555-1560.