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Medial Capsule Knee -

Update04.07.17

David Crane MD

Declarations Consultant for Arthrex

Discussing off-label use of technology

Balloon, Boing-Boing, Bioreactor I. Static and Dynamic Stabilization of the Joint Capsule and

Supporting Ligament, Tendon, and Myofascial structures.

II. Mechanotransduction of the Articular cartilage and

Meniscus

III. Nutrition, Lubrication, and Regeneration Function of the

Synovium and Peri-articular vasculature and Surrounding

Marrow.

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Scope of the problem

Meniscal injuries may be the most common knee

injury. The prevalence of acute meniscal tears is 61

cases per 100,000 persons.

The overall male-to-female incidence is

approximately 2.5:1.

Peak incidence of meniscal injury for males is in

those aged 31-40 years. For females, the peak

incidence is in those aged 11-20 years.

Bin SI, Kim JM, Shin SJ. Radial tears of the posterior horn of the medial meniscus. Arthroscopy. 2004

Apr. 20(4):373-8.

Arendt EA, ed. Orthopaedic Knowledge Update: Sports Medicine 2. Rosemont, Ill: American Academy of

Orthopaedic Surgeons; 1999.

Scope of the problem

In patients older than 65 years, the rate of

degenerative meniscal tears is 60%.

Root tears are observed in 28% of medial meniscal

tears.

Surgical procedures of the meniscus are performed

on an estimated 850,000 patients each year.

Bin SI, Kim JM, Shin SJ. Radial tears of the posterior horn of the medial meniscus. Arthroscopy. 2004

Apr. 20(4):373-8.

Arendt EA, ed. Orthopaedic Knowledge Update: Sports Medicine 2. Rosemont, Ill: American Academy of

Orthopaedic Surgeons; 1999.

Meniscus Anatomy

The microanatomy of the meniscus is dense

fibrocartilage composed of cells and an extracellular

matrix of collagen fibers in network. The cells are

termed fibrochondrocytes because they appear to be

a mixture of fibroblasts and chondrocytes. These

cells are responsible for the synthesis and

maintenance of the extracellular fibrocartilaginous

matrix.

Rodkey WG. Basic biology of the meniscus and response to injury. Instr Course Lect.

2000. 49:189-93.

Fu FH, Harner CD, Vince KG, eds. Knee Surgery. Philadelphia, Pa: Lippincott Williams &

Wilkins; 1994.

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Meniscus Anatomy The most abundant component of the menisci is

collagen (75%)—mainly type I collagen (>90%) but it

also contains types II, III, V, and VI. Collagen fibers

are arranged mostly along a longitudinal or

circumferential direction, with some interwoven radial

and oblique fibers. The circumferential fibers are

related directly to the menisci's functional ability to

dissipate compressive loads. The other fibers act

primarily as ties to enhance structural rigidity and to

help prevent longitudinal splitting. The extracellular

matrix also includes proteoglycans, glycoproteins,

and elastin.

Rodkey WG. Basic biology of the meniscus and response to injury. Instr Course Lect.

2000. 49:189-93.

Fu FH, Harner CD, Vince KG, eds. Knee Surgery. Philadelphia, Pa: Lippincott Williams &

Wilkins; 1994.

Meniscus Anatomy

Arnoczky and Warren demonstrated the important

vascular anatomy of the menisci. The limited

peripheral blood supply originates from the medial

and lateral inferior and superior geniculate arteries.

Branches from these vessels give rise to a

perimeniscal capillary plexus within the synovium

and joint capsule, which, in turn, supplies the

meniscus periphery.

Arnoczky SP, Warren RF. The microvasculature of the meniscus and its response to injury. An

experimental study in the dog. Am J Sports Med. 1983 May-Jun. 11(3):131-41.

Arnoczky SP, Warren RF. Microvasculature of the human meniscus. Am J Sports Med. 1982

Mar-Apr. 10(2):90-5.

Meniscus Anatomy

Studies have shown that 10-30% of the periphery of

the medial meniscus and 10-25% of the lateral

meniscus receives a vascular supply

the remainder receives its nutrition from the synovial

fluid from passive diffusion and mechanical pumping.

A few terminal branches of these vessels, along with

the middle geniculate artery through the synovial

covering of the anterior and posterior horn

attachments, supply increased vascularity to the

meniscal horns

Arnoczky SP, Warren RF. The microvasculature of the meniscus and its response to injury. An

experimental study in the dog. Am J Sports Med. 1983 May-Jun. 11(3):131-41.

Arnoczky SP, Warren RF. Microvasculature of the human meniscus. Am J Sports Med. 1982

Mar-Apr. 10(2):90-5.

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Meniscus Anatomy important functions, which include load bearing, load

and force distribution, joint stability, joint lubrication,

and proprioception.

One of the primary functions is to provide load

bearing across the knee joint.

Fifty percent of the compressive load in the knee is

transferred by the menisci in extension, whereas up

to 85% of the load is transferred at 90° of flexion. The

collagen orientation makes this load bearing possible

by converting the compressive forces to tensile

forces.

Insall JN, Scott WN, eds. Surgery of the Knee. 3rd ed. Philadelphia, Pa: WB Saunders Co; 2001.

Rodkey WG. Basic biology of the meniscus and response to injury. Instr Course Lect. 2000. 49:189-93.

Vaziri A, Nayeb-Hashemi H, Singh A, Tafti BA. Influence of meniscectomy and meniscus replacement on the

stress distribution in human knee joint. Ann Biomed Eng. 2008 May 22. epub ahead of print.

Meniscus Anatomy

Load and forces are distributed across a much larger

surface area because of the menisci, which:

(1) decrease focal contact pressure by increasing the

contact area

(2) protect the underlying articular cartilage.

Resection of 15-34% of a meniscus may increase

contact pressure by more than 350%. Normal knees

have 20% better shock-absorbing capacity than

meniscectomized knees.

Insall JN, Scott WN, eds. Surgery of the Knee. 3rd ed. Philadelphia, Pa: WB Saunders Co; 2001.

Rodkey WG. Basic biology of the meniscus and response to injury. Instr Course Lect. 2000. 49:189-93.

Vaziri A, Nayeb-Hashemi H, Singh A, Tafti BA. Influence of meniscectomy and meniscus replacement on the

stress distribution in human knee joint. Ann Biomed Eng. 2008 May 22. epub ahead of print.

Scope of the problem

Osteoartritis

Most common form of arthritis.

Classified as: Idiopathic (localized or generalized) or

Secondary (traumatic, congenital,

metabolic/endocrine/neuropathic and other medical

causes).

Characterized by focal and progressive loss of the

hyaline cartilage of joints, underlying bony changes.

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Scope of the problem

Osteoartritis

OA affects 13.9% of adults aged 25 years and older and

33.6% (12.4 million) of those 65+ in 2005

26.9 million US adults in 2005 up from 21 million in 1990

(believed to be conservative estimate).

CDC data 2015

Anatomy

Capsular Anatomy

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Capsular Anatomy

Capsular Anatomy

Three layers of the

medial capsule:

I. Crural fascia

II. Superficial portion

of the MCL

III. Deep portion of

the MCL including

the

meniscofemoral

and meniscotibial

extensions of the

deep MCL.

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Capsular Anatomy

Coronal proton-density-weighted

MR image (3,000/15) obtained

along the middle third of the

medial knee joint shows the fascia

(layer 1 [I], arrowheads) and the

sartorius (straight arrow), gracilis

(gr), and semitendinosus (st)

tendons. Note the superficial

portion of the MCL (layer 2 [II],

curved arrows).

Note the area where a split (S)

occurs in layer 2. Both the vertical

(V) and oblique (O) portions of the

MCL are shown.

Transverse section of the

medial joint capsule above

the level of the joint line:

Layers I and II are fused

anteriorly

Layers II and III are fused

posteriorly

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Cadaver Study

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Instron Data 19% increase in meniscal extrusion can be expected from

baseline to lesion conditions

13% decrease is expected between lesion and repair

There was a 6% difference between baseline and repaired

values

Clinical Cases 8 Patients to date

2 had failed to improve w prior arthroscopic partial medial

meniscectomy > 9 mos prior

All had pain > 1 year

Case 1

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Case 2

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Clinical Update All patients to date have shown improved pain and function

at three mos.

All pts with repair have shown a change in mechanics for 8 –

12 weeks

Most within 2-4 cm range

Most MCL to posterior horn in location

Outliers and decision tree change…

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