Western Michigan University Homer Stryker School of Medicine 2. Steadman Philippon Research Institute 3. The Steadman Clinic

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1 Biomechanical Consequences of Lateral Meniscal Posterior Root Avulsions Influence of the Meniscofemoral Ligaments and ACL on Tibiofemoral Contact Mechanics Andrew G. Geeslin, MD 1 ; David Civitarese, BA 2 ; Travis Turnbull, PhD 2 ; Grant J. Dornan, MSc 2 ; Fernando Fuso, MD 2 ; Robert F. LaPrade MD, PhD 2,3 1 Western Michigan University Homer Stryker School of Medicine 2 Steadman Philippon Research Institute 3 The Steadman Clinic

2 Disclosure No personal financial conflicts to report. Reviewer o Arthroscopy, The Journal of Arthroscopic and Related Surgery o Journal of Investigative Surgery The study was funded through internal sources. No biomedical device company was involved in funding, study design, execution, or manuscript preparation.

3 Background: Lateral Meniscal Root Tears Combined injury with up to 12% of ACL tears Function of MFL not well understood Abnormal contact mechanics with unstable LM root Brody et al. (2006) Radiology

4 Background Meniscofemoral Ligaments Gupte, JBJS Br 2002 Anderson paper, others Humphrey (anterior) in 74% Wrisberg (posterior) in 69% Both were present in 50% Anderson, JBJS % of knees had at least one MFL LaPrade et al. (2014) AJSM

5 Background Contact Mechanics Amadi, KSSTA % peak pressure with MFL sectioning LaPrade, JBJS % contact area for combined root avulsion, MFL tear. Forkel, Arthroscopy 2010 No change in pressure for root tear with intact MFLs. Musahl, AJSM 2010 Simulated pivot shift in the ACL deficient knee o Lateral meniscus secondary restraint to anterior tibial translation

6 Objectives Investigate the biomechanical effects of lateral meniscal posterior root avulsions with and without intact meniscofemoral ligaments (MFLs), and with concurrent ACL tears, on lateral compartment contact mechanics.

7 Materials Mean age 57 ACL/PCL/menisci intact Outerbridge 0/1 MFL present in all knees 6: Both Wrisberg and Humphrey ligaments 1: Isolated ligament of Wrisberg 3: Isolated ligament of Humphrey Anderson et al. (2012) JBJS

8 Methods Preparation, Testing Dissected to collaterals/capsule Tekscan pressure sensor 1000-N compressive load 0, 30, 45, 60, and 90 degrees Testing Conditions 1. Intact 2. Root avulsion, MFL intact 3. Root and MFL avulsion 4. Root, MFL, ACL tear 5. ACLR without root repair 6. ACLR and root repair

9 Methods Surgical Technique ACLR with BPTB autograft Root avulsion repaired anatomically 2 simple sutures (#2 Fiberwire), pulled through tibia, tied over metal button LaPrade et al. (2014) JBJS

10 Results Contact Pressure Map Condition 1. Intact 2. Root avulsion, MFL intact 3. Root and MFL avulsion 4. Root, MFL, ACL tear 5. ACLR without root repair 6. ACLR and root repair

11 Results Contact Area -No significant difference between (1) intact state and (2) root avulsion with intact MFL -No significant difference between (1) intact state and (6) root repair with ACL Recon

12 Results Mean Contact Pressure -No significant difference between (1) intact state and (2) root avulsion with intact MFL -No significant difference between (1) intact state and (6) root repair with ACL Recon

13 Results Peak Contact Pressure -No significant difference between (1) intact state and (2) root avulsion with intact MFL -No significant difference between (1) intact state and (6) root repair with ACL Recon

14 Discussion MFLs protect the lateral compartment from changes in contact mechanics in the setting of a lateral meniscal posterior root avulsion Combined lateral meniscal root avulsion and deficient meniscofemoral ligaments leads to substantial contact area and pressure changes Concurrent ACL reconstruction and root repair restores contact area and mean pressure to the intact state

15 Limitations Static testing scenario unable to account for shear, and dynamic or rotational loads may reveal a difference between conditions 1 and 2 that was not appreciated in our model Unable to make comment on whether a root tear can be left in situ if the MFLs are intact.

16 Conclusion Substantial contact area and pressure changes in setting of lateral meniscal root avulsion with deficient MFLs Root repair restores contact area and mean contact pressure to the intact state and is recommended in the setting of a root tear with deficient MFLs

17 Acknowledgments Funding Source: Steadman Philippon Research Institute. Co-Authors: David Civitarese, BA Travis Turnbull, PhD Grant J. Dornan, MSc Fernando Fuso, MD Robert F. LaPrade MD, PhD