Meniscus Injuries Ian Rice MD

How far we haven’t come “…It is, however, a clinical fact that one of the semilunar cartilage, usually the internal one, does occasionally become loosened from its attachments; and, in consequence, this body is liable to be displaced either forwards or backwards, and so to interfere with the proper movements of the knee-joint…” 1838 - 1907

Epidemiology Among most common injuries seen in orthopedic practice 61 cases per 100,000 per year Arthroscopic partial menisectomy one of the most common orthopedic procedures

Pathoanatomy Overview Crescent shaped and have triangular cross section Fibers have circumferential orientation Anterior and posterior root attachments prevent extrusion Lateral covers 84% of the condylar surface, 12mm wide, 3-5mm thick Medial covers 64%, 10mm wide, 3-5mm thick

Pathoanatomy Vascularity Genicular arteries 50% vascularized at birth 10-25% in adults Makes healing very difficult 3 vascular zones Red-red Red-white White-white

Collagen Organization Pathoanatomy Collagen Organization Circumferential fibers Radial Fibers Fine superficial layer around outside O’Connor’s textbook of arthroscopic surgery, Philadelphia, 1984.

Meniscal function Load Sharing Increases congruity Provides stability Increases contact area between femur and tibia Decreases contact stress on articular cartilage Increases congruity Provides stability Aids in lubrication

Biomechanics In extension, 50% of the load is absorbed At 90 flexion, 90% load-sharing Beyond 90, forces predominate through posterior horns

Meniscal excursion with knee flexion 11.2 mm excursion of lateral meniscus 5.1 mm excursion of medial meniscus Capsule Deep MCL Coronary ligament Thompson (1991) studied meniscal motion with 3-dimensional MRI and cinematic MRI. Medial meniscal excursion was approximately 5.1 mm, and lateral meniscal excursion, 11.2 mm. The posterior horn excursion has been noted to be less than that of the anterior horn, both medially and laterally. The posterior oblique ligament is firmly attached to the posterior medial meniscus, thereby limiting its displacement and rotation. Thompson WO, Thaete FL, Fu FH, Dye FF. Tibial meniscal dynamics using three dimensional reconstruction of magnetic resonance images. Am J Sports Med. 1991;19:210-216. http://www.kneejointsurgery.com/html/meniscus/anatomy.html

Biomechanics Complete removal of meniscus results in 2-3X increase in contact stress Removal of inner 1/3 = 10% reduction in contact area and 65% increase in stress Increase loss of meniscal tissue = increase contact stress Medial meniscal root tears have pressures similar to complete meniscectomy

Evaluation History Twisting injury with change in direction in younger patients Squatting or falling in older patients Acute tear usually has insidious swelling Joint line location Mechanical complaints

Physical Exam Small effusion Joint Line Tenderness McMurray Apley Thessaly ROM generally normal Bucket handle block Tight due to effusion

McMurray

McMurray

Apley’s Compression Test

Thessaly Test

Imaging Plain films to assess for bony injury and OA MRI is the gold standard of diagnosis

Longitudinal Vertical Tears Typically seen in younger patients High association with ACL tears 90% of LVT in MM and 83% in LM are associated with ACL tears

Bucket Handle Tears This is a LVT with central margination Most frequent type of displaced tear Double PCL Double Anterior Horn Absent Bow

Horizontal Tears Involves the free edge and propagates peripherally Usually degenerative Older patients

Radial Tears Also involve free edge, but path is perpendicular to long axis Drastically affect ability to resist hoop stresses Deeper the tear, the more drastic the biomechanical consequences

Radial Tears

Radial Tear

Parrot Beak Tears AKA vertical flap tear Starts as a radial tear Propagates as a longitudinal

Parrot Beak Tear

Root Tears

Treatment Non-surgical Stable, longitudinal <10mm with <3-5mm displacement Degenerative tears with concomitant OA <3mm radial tears Stable partial tears

Meniscectomy Indications Radial Flap Horizontal Complex White-white tears

Meniscectomy Goal is to debride tear and leave stable rim Preservation is ideal 80% satisfactory function at 5 yrs Lateral debridement = faster degeneration

Meniscectomy Predictors of Positive Result < 40yo Normal alignment Minimal arthritis at initial scope Single fragment tear

Surgical Repair Relative Contraindications Advanced OA Complex tears Poor tissue quality ACL deficiency

Open Repair Rarely used Numerous studies have proven reduced surgical morbidity with arthroscopic repair Reserved for peripheral tears in the posterior horn

Inside-out Repair Suture passed on either side of tear with needle cannula Suture is brought out of capsule A small skin incision is made Suture is tied down to capsule Posterior Horn Repairs

Outside-In Repair Sutures passed through the meniscus from the outside Eliminates need for larger incision Generally suited for anterior repair Studies have shown similar results with both techniques

All Inside All-inside repair devices were developed to reduce surgical time, prevent complications resulting from external approaches, and allow access to tears of the posterior horn Fourth-generation repair devices allow placement of sutures in the meniscus without the aid of an external incision or a suture fixator system

All Inside Self-adjusting, with the anchor located behind the capsule and with a sliding knot that can be tensioned appropriately by the surgeon Mechanical studies show comparable strength to outside-in sutures

Outcomes Success rates for all techniques reported 70-95% Second-look scopes show lower success rates of 45-91% Ligamentous laxity decreases success rate to 30-70% 90% success reported in conjunction with ACL repair

Complications Failure to heal Stiffness Articular surface damage NV structure damage

Transplantation Indications: Contraindications: Recurrent pain after partial or total debridement symptomatic with ADLs <50yo Contraindications: Malalignment Laxity Inflammatory arthritis Advanced OA

Outcomes Widely varying reports of success (Country differences) Subjective improvement in tibiofemoral pain No clear long-term benefit in preventing OA has been established Grafts seem to do better when placed with a bone block Preserving some peripheral rim helps to avoid extrusion Variety of meniscal scaffold options being investigated in animals

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