Vamsi Maturi

Introduction: ACL injuries are the most common knee injury with an incidence of over 200,000 cases and 100,000 repairs each year.^6,7 ACL tears typically present as a non-contact pivot injury with joint swelling, pain, tenderness knee instability, and restricted range of motion.^1,2,3 Indication for surgery depends on injury severity, patient age, level of physical activity, lifestyle, and desired outcomes. If surgery is chosen, tunnels are drilled through the center of the proximal and distal native ACL footprints through a transtibial or anteromedial tunneling approach.⁸ A graft is then fixated from these two tunnels. ACL repair has a 16% complication rate and 83% return to sport, with 60-79% of failures attributable to tunnel placement. ^2,3,4 Identifying the optimal tunnel positions and predicting progressions is crucial to improving surgical outcomes.^5,8,9,11  Methods: A study to assess tunnel placement accuracy took 12 orthopedic surgeons and compared ACL footprint identification in-vivo vs a model with no soft tissue.¹⁰ In attempt to better define ACL failure conditions, another study ran cadaveric models through physiological movements while measuring knee forces and kinematics.¹³ Similar studies attempted to estimate in-vivo ACL forces by developing an MRI or patient measurement-based models and coupled them with in-vivo kinematic data from physiological movements. Both models were built on OpenSim using the patient specific structures from MRI or a generic model fit to the patient measurement respectively.^14,15 Model accuracy was then compared to cadaveric models.^14,15 Results: Intraoperative surgical deviation from optimal ACL placement was 3.72mm and completely inaccurate in purely osseus models.¹⁰ Cadaveric models were able to define failure forces and tensions during physiological movements, but dissimilarity to in-vivo tissue remains a concern.^12,13 Both the patient measurement and MRI based models were effective in predicting forces with an r² of .96 and p<.001 and less variation and greater reliability than cadaveric models respectively.^14,15 Conclusion: ACL footprint identification and tunnel placements are crucial to reconstruction outcomes and can be improved significantly. The cadaveric model would allow for a fine tuning the inverse kinematics used in the other models so that psychological movement-force relationship is better defined. The MRI based model can serve as a research tool to better define the optimal tunnel placement; identifying optimal placement based on patient groupings would improve outcomes. Patient-specific measurement models are computationally light and may be improved to identify optimal patient-specific ACL placement and predict graft progression to mitigate future injury.

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2. Getgood AMJ, Bryant DM, Litchfield R, Heard M, McCormack RG, Rezansoff A, Peterson D, Bardana D, MacDonald PB, Verdonk PCM, Spalding T; STABILITY Study Group, Willits K, Birmingham T, Hewison C, Wanlin S, Firth A, Pinto R, Martindale A, O’Neill L, Jennings M, Daniluk M, Boyer D, Zomar M, Moon K, Pritchett R, Payne K, Fan B, Mohan B, Buchko GM, Hiemstra LA, Kerslake S, Tynedal J, Stranges G, Mcrae S, Gullett L, Brown H, Legary A, Longo A, Christian M, Ferguson C, Mohtadi N, Barber R, Chan D, Campbell C, Garven A, Pulsifer K, Mayer M, Simunovic N, Duong A, Robinson D, Levy D, Skelly M, Shanmugaraj A, Howells F, Tough M, Spalding T, Thompson P, Metcalfe A, Asplin L, Dube A, Clarkson L, Brown J, Bolsover A, Bradshaw C, Belgrove L, Millan F, Turner S, Verdugo S, Lowe J, Dunne D, McGowan K, Suddens CM, Declercq G, Vuylsteke K, Van Haver M. Lateral Extra-articular Tenodesis Reduces Failure of Hamstring Tendon Autograft Anterior Cruciate Ligament Reconstruction: 2-Year Outcomes From the STABILITY Study Randomized Clinical Trial. Am J Sports Med. 2020 Feb;48(2):285-297. doi: 10.1177/0363546519896333. Epub 2020 Jan 15. PMID: 31940222.
3. Lai, Courtney C, et al. “Eighty-Three per Cent of Elite Athletes Return to Preinjury Sport after Anterior Cruciate Ligament Reconstruction: a Systematic Review with Meta-Analysis of Return to Sport Rates, Graft Rupture Rates and Performance Outcomes .” British Journal of Sports Medicine, vol. 52, no. 2, 2018, pp. 128–138.
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10. Laverdiere C, Schupbach D, Schupbach J, Harvey E, Boily M, Burman M, Martineau PA. Can Surgeons Identify ACL Femoral Ridges Landmark and Optimal Tunnel Position? A 3D Model Study. Arthrosc Sports Med Rehabil. 2020 Jul 29;2(4):e361-e368. doi: 10.1016/j.asmr.2020.05.008. PMID: 32875301; PMCID: PMC7451917.
11. Burnham JM, Malempati CS, Carpiaux A, Ireland ML, Johnson DL. Anatomic Femoral and Tibial Tunnel Placement During Anterior Cruciate Ligament Reconstruction: Anteromedial Portal All-Inside and Outside-In Techniques. Arthrosc Tech. 2017;6(2):e275-e282. Published 2017 Mar 6. doi:10.1016/j.eats.2016.09.035
12. Bates NA, Schilaty ND, Nagelli CV, Krych AJ, Hewett TE. Multiplanar Loading of the Knee and Its Influence on Anterior Cruciate Ligament and Medial Collateral Ligament Strain During Simulated Landings and Noncontact Tears. Am J Sports Med. 2019 Jul;47(8):1844-1853. doi: 10.1177/0363546519850165. Epub 2019 May 31. PMID: 31150273; PMCID: PMC6988507.
13. Bates NA, Schilaty ND, Nagelli CV, Krych AJ, Hewett TE. Multiplanar Loading of the Knee and Its Influence on Anterior Cruciate Ligament and Medial Collateral Ligament Strain During Simulated Landings and Noncontact Tears. Am J Sports Med. 2019 Jul;47(8):1844-1853. doi: 10.1177/0363546519850165. Epub 2019 May 31. PMID: 31150273; PMCID: PMC6988507.
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