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Vertical Tears of the Lateral Meniscus: Effects on In Vitro Tibiofemoral Joint Mechanics.

Goyal KS, Pan TJ, Tran D, Dumpe SC, Zhang X, Harner CD - Orthop J Sports Med (2014)

Bottom Line: Controlled laboratory study.Kinematic data were acquired through digitization of fiducial markers.Vertical tears of the lateral meniscus during a simulated 2-legged squat did not significantly change contact pressures and areas compared with an intact meniscus.

View Article: PubMed Central - PubMed

Affiliation: Department of Orthopaedic Surgery, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.

ABSTRACT

Background: Lateral meniscal tears are often seen with acute anterior cruciate ligament (ACL) injury and may be left in situ, repaired, or treated with meniscectomy. Clinical studies have shown good outcomes with vertical tears left in situ and poor outcomes following meniscectomy. However, clinically relevant studies are needed to establish a biomechanical foundation for treatment of these tears, particularly regarding the effects of meniscectomy.

Purpose: To compare tibiofemoral joint mechanics following vertical lateral meniscal tears and meniscectomies. We hypothesized that a peripheral vertical tear of the lateral meniscus would alter joint mechanics, increasing contact pressure and area, and that more drastic effects would be seen following meniscectomy, at higher knee flexion angles, and with increased loads.

Study design: Controlled laboratory study.

Methods: Ten fresh-frozen cadaveric knees (average age, 55 ± 12 years) were tested with 5 lateral meniscus states: intact, short vertical tear, extended vertical tear, posterior horn partial meniscectomy (rim intact), and posterior horn subtotal meniscectomy (rim excised). The specimens were loaded axially at knee flexion angles of 0°, 30°, and 60°, and musculotendinous forces were applied, simulating a 2-legged squat. Intra-articular contact pressures were measured using pressure-sensitive Fuji film. Kinematic data were acquired through digitization of fiducial markers.

Results: Vertical tears did not cause a significant change in contact pressure or area. Partial meniscectomy increased maximum contact pressures in the lateral compartment at 30° and 60° from 5.3 MPa to 7.2 MPa and 7.6 MPa, respectively (P = .02, P = .007). Subtotal meniscectomy (8.4 MPa) significantly increased contact pressure compared with partial meniscectomy (7.6 MPa) at 60° (P = .04). Both meniscectomy states significantly increased contact pressures with increasing flexion from 0° to 60° (P < .001, P < .001).

Conclusion: Vertical tears of the lateral meniscus during a simulated 2-legged squat did not significantly change contact pressures and areas compared with an intact meniscus. However, treating these tears with partial and complete meniscectomy significantly increased maximum contact pressures.

Clinical relevance: Biomechanical evidence supports treating vertical lateral meniscus tears with meniscal-sparing techniques as opposed to meniscectomy, which may lead to progressive degenerative joint disease from altered joint biomechanics.

No MeSH data available.


Related in: MedlinePlus

Flow diagram of testing protocol. The knee was mounted in a materials testing machine where an axial load and functional muscle loads were applied. Fuji film was inserted via submeniscal arthrotomies to obtain submeniscal contact pressure and area, and the fiducial markers were digitized to obtain tibiofemoral kinematics. Five knee states were studied in this manner.
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fig2-2325967114541237: Flow diagram of testing protocol. The knee was mounted in a materials testing machine where an axial load and functional muscle loads were applied. Fuji film was inserted via submeniscal arthrotomies to obtain submeniscal contact pressure and area, and the fiducial markers were digitized to obtain tibiofemoral kinematics. Five knee states were studied in this manner.

Mentions: Figure 2 summarizes our testing protocol. The specimens underwent biomechanical testing on a materials testing machine (Instron Model 8874; Instron Corp) after each of the 5 meniscal states was created. The testing configuration simulated a single lower extremity during a 2-legged squat by a person of approximately 70 kg body weight. Three knee flexion angles were included: 0°, 30°, and 60°. The femur was constrained in all 6 degrees of freedom. The distal end of the tibia was constrained in anterior-posterior and superior-inferior translations but allowed medial-lateral translation, abduction-adduction, flexion-extension, and internal-external rotation. Fuji film (Fujifilm Corp) in the shape of the tibial plateau was inserted through the anterior arthrotomies underneath both menisci using a technique previously described.4,31 Simulated muscle forces were applied by pulling the quadriceps and hamstring along the shaft of the femur via a pulley-weight system mounted on a loading frame. We used a 2:1 ratio of quadriceps versus hamstring forces, as was done in previous studies.8,27 The 2-legged knee squat was simulated such that a constant ground reaction force equal to half the weight of a 70-kg man, or 350 N, was maintained. To determine the quadriceps and hamstring forces needed to maintain equilibrium at each of the knee flexion angles, we applied a series of muscle loads to the cadaveric knee until 350 N was recorded by the load cell placed at the bottom of the specimen. With increasing squat, greater muscle forces are required to maintain force and moment equilibrium. We estimated, based on simple equilibrium equations and convenience of weight application, the forces that needed to be applied. The quadriceps and hamstring forces applied were determined to be, respectively: 30 and 15 lb (133 and 67 N) at 0° of flexion; 50 and 25 lb (222 and 111 N) at 30° of flexion; and 70 and 35 lb (311 and 156 N) at 60° of flexion. Thus, at 0° of knee flexion, a total of 550 N of force was applied, at 30° of flexion a total of 683 N was applied, and at 60° of flexion a total of 817 N was applied.


Vertical Tears of the Lateral Meniscus: Effects on In Vitro Tibiofemoral Joint Mechanics.

Goyal KS, Pan TJ, Tran D, Dumpe SC, Zhang X, Harner CD - Orthop J Sports Med (2014)

Flow diagram of testing protocol. The knee was mounted in a materials testing machine where an axial load and functional muscle loads were applied. Fuji film was inserted via submeniscal arthrotomies to obtain submeniscal contact pressure and area, and the fiducial markers were digitized to obtain tibiofemoral kinematics. Five knee states were studied in this manner.
© Copyright Policy - creative-commons
Related In: Results  -  Collection

License 1 - License 2 - License 3
Show All Figures
getmorefigures.php?uid=PMC4555575&req=5

fig2-2325967114541237: Flow diagram of testing protocol. The knee was mounted in a materials testing machine where an axial load and functional muscle loads were applied. Fuji film was inserted via submeniscal arthrotomies to obtain submeniscal contact pressure and area, and the fiducial markers were digitized to obtain tibiofemoral kinematics. Five knee states were studied in this manner.
Mentions: Figure 2 summarizes our testing protocol. The specimens underwent biomechanical testing on a materials testing machine (Instron Model 8874; Instron Corp) after each of the 5 meniscal states was created. The testing configuration simulated a single lower extremity during a 2-legged squat by a person of approximately 70 kg body weight. Three knee flexion angles were included: 0°, 30°, and 60°. The femur was constrained in all 6 degrees of freedom. The distal end of the tibia was constrained in anterior-posterior and superior-inferior translations but allowed medial-lateral translation, abduction-adduction, flexion-extension, and internal-external rotation. Fuji film (Fujifilm Corp) in the shape of the tibial plateau was inserted through the anterior arthrotomies underneath both menisci using a technique previously described.4,31 Simulated muscle forces were applied by pulling the quadriceps and hamstring along the shaft of the femur via a pulley-weight system mounted on a loading frame. We used a 2:1 ratio of quadriceps versus hamstring forces, as was done in previous studies.8,27 The 2-legged knee squat was simulated such that a constant ground reaction force equal to half the weight of a 70-kg man, or 350 N, was maintained. To determine the quadriceps and hamstring forces needed to maintain equilibrium at each of the knee flexion angles, we applied a series of muscle loads to the cadaveric knee until 350 N was recorded by the load cell placed at the bottom of the specimen. With increasing squat, greater muscle forces are required to maintain force and moment equilibrium. We estimated, based on simple equilibrium equations and convenience of weight application, the forces that needed to be applied. The quadriceps and hamstring forces applied were determined to be, respectively: 30 and 15 lb (133 and 67 N) at 0° of flexion; 50 and 25 lb (222 and 111 N) at 30° of flexion; and 70 and 35 lb (311 and 156 N) at 60° of flexion. Thus, at 0° of knee flexion, a total of 550 N of force was applied, at 30° of flexion a total of 683 N was applied, and at 60° of flexion a total of 817 N was applied.

Bottom Line: Controlled laboratory study.Kinematic data were acquired through digitization of fiducial markers.Vertical tears of the lateral meniscus during a simulated 2-legged squat did not significantly change contact pressures and areas compared with an intact meniscus.

View Article: PubMed Central - PubMed

Affiliation: Department of Orthopaedic Surgery, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.

ABSTRACT

Background: Lateral meniscal tears are often seen with acute anterior cruciate ligament (ACL) injury and may be left in situ, repaired, or treated with meniscectomy. Clinical studies have shown good outcomes with vertical tears left in situ and poor outcomes following meniscectomy. However, clinically relevant studies are needed to establish a biomechanical foundation for treatment of these tears, particularly regarding the effects of meniscectomy.

Purpose: To compare tibiofemoral joint mechanics following vertical lateral meniscal tears and meniscectomies. We hypothesized that a peripheral vertical tear of the lateral meniscus would alter joint mechanics, increasing contact pressure and area, and that more drastic effects would be seen following meniscectomy, at higher knee flexion angles, and with increased loads.

Study design: Controlled laboratory study.

Methods: Ten fresh-frozen cadaveric knees (average age, 55 ± 12 years) were tested with 5 lateral meniscus states: intact, short vertical tear, extended vertical tear, posterior horn partial meniscectomy (rim intact), and posterior horn subtotal meniscectomy (rim excised). The specimens were loaded axially at knee flexion angles of 0°, 30°, and 60°, and musculotendinous forces were applied, simulating a 2-legged squat. Intra-articular contact pressures were measured using pressure-sensitive Fuji film. Kinematic data were acquired through digitization of fiducial markers.

Results: Vertical tears did not cause a significant change in contact pressure or area. Partial meniscectomy increased maximum contact pressures in the lateral compartment at 30° and 60° from 5.3 MPa to 7.2 MPa and 7.6 MPa, respectively (P = .02, P = .007). Subtotal meniscectomy (8.4 MPa) significantly increased contact pressure compared with partial meniscectomy (7.6 MPa) at 60° (P = .04). Both meniscectomy states significantly increased contact pressures with increasing flexion from 0° to 60° (P < .001, P < .001).

Conclusion: Vertical tears of the lateral meniscus during a simulated 2-legged squat did not significantly change contact pressures and areas compared with an intact meniscus. However, treating these tears with partial and complete meniscectomy significantly increased maximum contact pressures.

Clinical relevance: Biomechanical evidence supports treating vertical lateral meniscus tears with meniscal-sparing techniques as opposed to meniscectomy, which may lead to progressive degenerative joint disease from altered joint biomechanics.

No MeSH data available.


Related in: MedlinePlus