Direct measurement of three-dimensional forces at the medial meniscal root: A validation study

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Background: Meniscal extrusion often persists after a medial meniscus root repair. If the meniscus is extruded, the function of the meniscus as a load-sharing device and secondary knee stabilizer is compromised. Hypothesis: It was hypothesized that repairing the meniscotibial ligament (MTL) would decrease meniscal extrusion in the settings of both an isolated MTL tear and a repaired medial meniscus root while also improving medial compartment contact mechanics. Study Design: Controlled laboratory study. Methods: Ten fresh-frozen cadaveric knees (mean age, 50.5 years) were tested in 5 conditions: intact, MTL deficiency, MTL deficiency + posterior medial meniscus root deficiency, MTL deficiency + posterior medial meniscus root repair, and MTL tenodesis + posterior medial meniscus root repair. Specimens were mounted to a load frame that applied a 1000-N axial load. Joint contact pressures were measured using thin pressure sensors, and the peak and mean pressures were analyzed. Ultrasound was used to measure meniscal extrusion. Results: The MTL tear in isolation resulted in significant meniscal extrusion compared with the intact state ( P = 0.035) without a detectable difference in medial compartment pressures. The addition of a root tear to the MTL tear state resulted in significantly more extrusion ( P = 0.001) and significant increases in medial compartment pressure ( P = .030) compared to the MTL tear state. Root repair alone restored extrusion, mean contact pressure, and peak contact pressure back to the intact state ( P > .05). Conclusion: This study showed that MTL disruption led to increased meniscal extrusion in a cadaveric model. Unlike the root tear state, MTL disruption did not change contact mechanics. Furthermore, root repair alone was sufficient in restoring intact biomechanics and extrusion. Clinical Relevance: This study may help clinicians understand the origin of medial meniscus root tears and aid in the decision-making process for whether to add an MTL tenodesis in the setting of root repair.

Section: Methodsmentioning

confidence: 99%

“…After testing, we removed the medial femoral condyle while maintaining surrounding ligaments. 2 The medial meniscal length was measured using digital calipers in the same way as illustrated by Paletta et al 24…”

Section: Methodsmentioning

confidence: 99%

Biomechanical Analysis of Meniscotibial Ligament Tenodesis to Treat Meniscal Extrusion in the Setting of Posterior Medial Meniscus Root Repair

Doan,

Dey Hazra,

Brown

et al. 2023

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“…For the MTL cut, the data from this study were acquired at time zero and can only be directly compared with MTL tears of this size, as referenced in LaPrade et al 15 and Paletta et al 23 The femoral condylar osteotomy has been used in previous studies and has proven its rigidity but remains a limitation, as it is an additional surgery performed on the specimen. 4 Finally, the femoral and tibial osteotomies needed to install the sensor and perform the surgery may alter bony deformation under high joint loads.…”

Section: Discussionmentioning

confidence: 99%

“…After this, an oblique medial femoral condylar osteotomy was performed using a sagittal saw on each specimen to facilitate access to the medial compartment for complete visualization per a protocol that has been previously established. 4,19,22 The osteotomy was secured using both a removable steel plate and bicortical screws to ensure its rigidity. The specimen setup is shown in Figures 1 and 2.…”

Section: Specimen Preparationmentioning

confidence: 99%

Meniscotibial Ligament Insufficiency Increases Force on the Posterior Medial Meniscus Root

Melugin,

Brown,

Hollenbeck

et al. 2023

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Background: Posterior medial meniscus root (PMMR) tears are a challenge to assess and treat. However, the forces sustained at the PMMR are yet to be fully characterized. In addition, it has been shown that meniscotibial ligament (MTL) injuries happen before PMMR tears, suggesting that insufficiency of the MTL results in a change of forces acting on the PMMR. Purpose/Hypothesis: The purpose of this study was to evaluate the 3-dimensional forces acting on the PMMR in the intact, MTL cut, and MTL tenodesis states. It was hypothesized that the MTL cut state would increase medial shear forces seen at the PMMR, whereas the medial shear force in the MTL tenodesis state would return PMMR forces to that of the intact state. Study Design: Controlled laboratory study. Methods: Ten fresh-frozen cadaveric knees were tested in 3 states (intact, MTL cut, and tenodesis). A 3-axis load cell was installed below the posterior tibial plateau and attached to the enthesis of the PMMR. The specimen was mounted to a load frame that applied an axial load, an internal torque, and an external torque. The amount of compression-tension, mediolateral shear force, and anteroposterior shear force acting on the PMMR was measured. Results: When the joint was loaded in compression, the MTL cut state significantly increased compression of the PMMR ( P = .0368). The tenodesis state did not significantly restore forces of the PMMR ( P = .008). When the joint was loaded in external torque, the MTL cut state significantly increased compression ( P < .0001) and significantly decreased anterior shear on the PMMR ( P = .0003). The tenodesis state did not significantly restore forces on the PMMR to the intact state ( P < .0001). Increased flexion angle significantly increased medial shear forces of the PMMR when the joint was loaded in compression ( P < .007 at every angle). Conclusion: When evaluated biomechanically, MTL insufficiency resulted in increased compressive force at the PMMR. A single-anchor centralization procedure did not restore PMMR forces to that of the intact state. Increased knee flexion angle resulted in increased medial shear force on the PMMR. Clinical Relevance: The findings in this study provide clinicians information on PMMR forces when the MTL is disrupted. These data can aid in the decision-making for adding an MTL repair to augment PMMR repairs.

“…After this, a medial femoral condylar osteotomy was performed using a sagittal saw to access the medial tibial plateau for complete visualization per a protocol that has been previously established. 7,23 The osteotomy was rigidly secured with a removable steel plate and bicortical screws.…”

Section: Specimen Preparationmentioning

confidence: 99%

Increased Posterior Tibial Slope Increases Force on the Posterior Medial Meniscus Root

Melugin,

Brown,

Hollenbeck

et al. 2023

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Background: Posterior medial meniscus root (PMMR) tears have been associated with increased posterior tibial slope, but this has not been fully evaluated biomechanically. In addition, the effects of knee flexion and rotation on the PMMR are not well understood biomechanically because of technological testing limitations. A novel multiaxial force sensor has made it possible to elucidate answers to these questions. Purpose: (1) To determine if increased posterior tibial slope results in increased posterior shear force and compression on the PMMR, (2) to evaluate how knee flexion angle affects PMMR forces, and (3) to assess how internal and external rotation affects force at the PMMR. Study Design: Controlled laboratory study. Methods: Ten fresh-frozen cadaveric knees were tested in all combinations of 3 posterior tibial slopes and 4 flexion angles. A multiaxial force sensor was connected to the PMMR and installed below the posterior tibial plateau maintaining anatomic position. The specimen underwent a 500-N compression load followed by a 5-N·m internal torque and a 5-N·m external torque. The magnitude and direction of the forces acting on the PMMR were measured. Results: Under joint compression, an increased tibial slope significantly reduced the tension on the PMMR between 5° and 10° (from 13.5 N to 6.4 N), after which it transitioned to a significant increase in PMMR compression, reaching 7.6 N at 15°. Under internal torque, increased tibial slope resulted in 4.7 N of posterior shear at 5° significantly changed to 2.0 N of anterior shear at 10° and then 8.2 N of anterior shear at 15°. Under external torque, increased tibial slope significantly decreased PMMR compression (5°: 8.9 N; 10°: 4.3 N; 15°: 1.1 N). Under joint compression, increased flexion angle significantly increased medial shear forces of the PMMR (0°, 3.8 N; 30°, 6.2 N; 60°, 7.3 N; 90°, 8.4 N). Under internal torque, 90° of flexion significantly increased PMMR tension from 2.3 N to 7.5 N. Under external torque, 30° of flexion significantly increased PMMR compression from 4.7 N to 12.2 N. Conclusion: An increased posterior tibial slope affects compression and anterior shear forces at the PMMR. An increased flexion angle affects compression, tension, and medial shear forces at the PMMR. Clinical Relevance: The increase in compression and posterior shear force when the knee is loaded in compression may place the PMMR under increased stress and risk potential failure after repair. This study provides clinicians with information to create safer protocols and improve repair techniques to minimize the forces experienced at the PMMR.