CM Gupte, PhD, FRCS (Tr&Orth), Consultant Orthopaedic Surgeon/Senior Lecturer Spyros Masouros, PhD, Lecturer Departments of Bioengineering, Mechanical Engineering and Musculoskeletal Surgery Imperial College London, UK Anatomy and Biomechanics of the Meniscus
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Anatomy and Biomechanics of the Meniscus€¦ · Anatomy and Biomechanics of the Meniscus ! ... Intraarticular knee structures ! Semi-lunar (axial) ! Wedge-shaped (coronal/saggital)
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CM Gupte, PhD, FRCS (Tr&Orth), Consultant Orthopaedic Surgeon/Senior Lecturer
Spyros Masouros, PhD, Lecturer
Departments of Bioengineering, Mechanical Engineering and Musculoskeletal Surgery
Imperial College London, UK
Anatomy and Biomechanics of the Meniscus
! Anatomy ! Structure – Function ! Load transmission – Meniscal motion ! Meniscal ligaments ! Tears – Tear management ! Summary – The importance of the meniscus
! Fluid phase – compression ! Water content ~75% ! Low permeability ! Low compressive and shear
moduli
! Hence the meniscus ! traps the fluid allowing
fluid-pressure to build up ! is very deformable ! can accommodate high loads
Structure – Function
! Axial load transferred through the joint is converted into meniscal hoop stresses
Load transmission
Tibia
Femur
! The meniscus ! conforms to the
femoral condyles ! increases its circumference ! translates outwards ! spreads the load over
a large contact area ! hence reduces the stresses
on the underlying cartilage
! Insertional ligaments are key
70-99% of the joint load is carried by the menisci1
1Seedhom & Hargreaves, 1979, Eng Med
Load spreaders
! Increase contact surface area
! Reduce contact stresses
10 Baratz ME, et al. Meniscal tears: the effect of meniscectomy and of repair on intraarticular contact areas and stress in the human knee. A preliminary report. Am J Sports Med. 1986;14:270-275. Lee SJ, et al. Tibiofemoral contact mechanics after serial medial meniscectomies in the human cadaveric knee. Am J Sports Med. 2006;34(8):1334-1344.
! Meniscectomy results in1-3 ! Cartilage to cartilage
contact ! Less conformity ! Decreased contact area ! Increased contact stresses
(up to 200%)1
! Increased shear stresses
Loss of a meniscus
Intact Meniscectomised 1Baratz et al, 1986, AJSM 2Seedhom & Hargreaves, 1979, Eng Med 3McDermott et al, 2008 in press, KSSTA (Taken from: McDermott et al, 2008 , KSSTA)
Shock absorbers
! Compressive modulus varies according to: location (anterior>posterior) strain rate (increases) species
! Modulus at 12%strain: Equilibrium: 83KPa axial 76kPa radial 32%/sec (physiological): 718 kpa and 605kPa
! Fluid film lubrication also contributes to shock absorption.
12 Helena et al: Compressive moduli of the human medial meniscus in the axial and radial directions at equilibrium and at a physiological strain rate. J Orth Res 2008
! New prostheses ! Suture techniques ! ?location of repairable tears
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! Main function of the menisci is load bearing ! This relates directly to the meniscal structure ! The insertional ligaments are key in meniscal function
! The meniscus-meniscal ligament construct works harmoniously under load to protect the cartilage
! Clinical management should aim at preserving the function of the meniscus-meniscal ligament construct
Summary
Spyros Masouros
A. Amis, A. Bull, U. Hansen, H. Amadi, C. Gupte, I. McDermott
Departments of Bioengineering, Mechanical Engineering and Musculoskeletal Surgery