ACUTE KNEE LIGAMENT INJURIESDr Milind Merchant

INTRODUCTION

• Knee ligaments often are injured in athletic activities, especially those involving contact, such as football, Skiing, ice hockey, gymnastics which produce enough sudden stress to disrupt knee ligaments.

• Motor vehicle accidents, especially those involving motorcycles, are common causes of knee ligament disruptions.

• Ligament disruption can occur without a fall or direct contact when sudden, severe loading or tension is placed on the ligaments, such as when a running athlete plants a foot to suddenly decelerate or change directions.

MECHANISM -

• four mechanisms capable of disrupting the ligamentous structures about the knee:

• (1) abduction, flexion, and internal rotation of the femur on the tibia,

• (2) adduction, flexion, and external rotation of the femur on the tibia,

• (3) hyperextension, • (4) anteroposterior displacement

• most common mechanism is abduction, flexion, and internal rotation of the femur on the tibia when the weight-bearing leg of an athlete is struck from the lateral aspect by an opponent.

• This mechanism results in an abduction and flexion force on the knee, and the femur is rotated internally by the shift of the body weight on the fixed tibia.

• This mechanism produces injury on the medial side of the knee, the severity of which depends on the magnitude and dissipation of the applied force.

• When abduction, flexion, and internal rotation of the femur on the tibia occur, the medial supporting structures—the tibial collateral ligament and the medial capsular ligament—are the initial structures injured. If the force is of sufficient magnitude, the anterior cruciate ligament also can be torn.

• The medial meniscus may be trapped between the condyles of the femur and the tibia, and it may be torn at its periphery as the medial structures tear, thus producing "the unhappy triad" of O'Donoghue .

• Mechanisms reported as possibly able to disrupt the anterior cruciate ligament with minimal injury of other supporting structures are hyperextension, marked internal rotation of the tibia on the femur, and pure deceleration.

• Isolated posterior cruciate disruption can result from a direct blow to the front of the tibia with the knee flexed.

CLASSIFICATION -• Sprains are classified into three degrees of

severity. • A first-degree sprain of a ligament is defined as a

tear of a minimal number of fibers of the ligament with localized tenderness but no instability;

• a second-degree sprain as a disruption of more ligamentous fibers with more loss of function and more joint reaction with mild to moderate instability;

• third-degree sprain as a complete disruption of the ligament with resultant marked instability.

• These often are classified as mild, moderate, and severe for first-, second-, and third-degree sprains, respectively.

• Third-degree sprains, that is, those demonstrating marked instability, can be further graded depending on the degree of instability demonstrated during stress testing.

• With 1+ instability the joint surfaces separate 5 mm or less;

• with 2+ instability they separate 5 to 10 mm; and

• with 3+ instability they separate 10 mm or more

ACUTE ACL INJURY -• The exact incidence of anterior cruciate ligament injuries

is unknown;• The classic history of an anterior cruciate ligament injury

begins with a noncontact deceleration, jumping, or cutting action. Obviously, other mechanisms of injury include external forces applied to the knee.

• The patient often describes the knee as having been hyperextended or popping out of joint and then reducing. A pop is frequently heard or felt.

• The patient usually has fallen to the ground and is not immediately able to get up. Resumption of activity usually is not possible, and walking is often difficult. Within a few hours, the knee swells, and aspiration of the joint reveals hemarthrosis. In this scenario, the likelihood of an anterior cruciate ligament injury is greater than 70%.

Investigations• Plain Xrays often are normal; however, a tibial eminence

fracture indicates an avulsion of the tibial attachment of the anterior cruciate ligament.

• The Segond fracture, or avulsion fracture of the lateral capsule, is pathognomonic of an anterior cruciate ligament tear .

• MRI - diagnostic technique. The reported accuracy for detecting tears of the anterior cruciate ligament has ranged from 70% to 100%. Because the anterior cruciate ligament crosses the knee joint at a slightly oblique angle, the complete ligament rarely is captured in its entirety by a single MRI scan in the true sagittal plane.

• More recent investigators reported that the accuracy for MRI in evaluating injuries to the anterior cruciate ligament approaches 95% to 100%. With the availability and accuracy of MRI.

Management-• The treatment options available include

nonoperative management,

• repair of the anterior cruciate ligament, either isolated or with augmentation,

• reconstruction with either autograft or allograft tissues or synthetics .

Repair of Bony Tibial Avulsions of ACL

• AFTERTREATMENT.• At 3 weeks, flexion from 0

to 90 degrees is allowed in the brace, and isometric quadriceps and hamstring exercises are begun.

• Crutches are discontinued at 6 weeks, and full active and passive range of motion should be obtained by 8 weeks.

• Progressive resistance exercises are continued for at least 3 months

ACUTE PCL INJURY -• As with the anterior cruciate ligament, "isolated" tears of the

posterior cruciate ligament are relatively rare; as a rule, ruptures of this ligament are associated with medial or lateral compartment disruptions, especially the latter.

• Clinically, however, isolated tears of the posterior cruciate ligament can be caused by a fall on the flexed knee or striking of the flexed tibia on the dashboard in a motor vehicle accident.

• Such a mechanism (the upper tibia driven posteriorly with the knee flexed) may produce posterior cruciate ligament disruption as the only clinically detectable instability.

• These "isolated" posterior cruciate ligament disruptions can be difficult to diagnose acutely unless a fragment of bone is avulsed from the posterior tibial insertion and is noted on roentgenograms .

Rx -• The commonly quoted criteria for nonoperative

treatment include • (1) a posterior drawer of less than 10 mm with

the tibia in neutral rotation (posterior drawer excursion decreases with internal rotation of the tibia on the femur),

• (2) less than 5 degrees of abnormal rotary laxity (specifically, abnormal external rotation of the tibia with the knee flexed 30 degrees, indicating posterolateral instability), and

• (3) no significant valgus-varus abnormal laxity (no associated significant ligamentous injury).

MCL REPAIR -• If surgical repair of the torn medial support of the knee is

planned, arthroscopic examination of the knee to rule out other intraarticular pathological conditions is done before open surgical exploration .

• The surgeon must be aware of the capsular disruption that may allow significant extravasation of irrigation fluid during arthroscopy of an acutely unstable knee.

• Ordinarily a synovial or capsular rent will seal sufficiently to prevent dangerous extravasation of irrigation fluid if the arthroscopic examination is delayed for 5 to 7 days and the surgeon is skilled and expedites the examination. A lengthy examination of an acutely injured knee is not justified, and massive extravasation of irrigation fluid may occur in such instances.

MCL REPAIR -

POPLITEUS REPAIR -

LCL REPAIR -

AFTER Rx -• The repair can be protected by applying a

long leg cast with the knee flexed 30 degrees, but we prefer to allow immediate protected motion by placing the knee in a controlled motion brace, which initially is locked in full extension. • The leg is removed from the brace several

times each day for range-of-motion exercises.