34. acl injuries

Muhammad Abdelghani

ANTERIOR CRUCIATE LIGAMENT INJURIES

Functions of the ACL

Primary restraint to anterior tibial displacement, accounting for ~ 85% of the resistance to anterior drawer test when the knee is at 90° of flexion and neutral rotation.

Secondary restraint to tibial rotation and varus-valgus angulation at full extension.

Proprioceptive function: evidenced by presence of mechanoreceptors in the ligament.

Mechanism of injury The classic history of an

ACL injury begins with a noncontact deceleration, jumping, or cutting action.

Other mechanisms of injury include external forces applied to the knee.

Symptoms

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 (haemarthrosis).

Symptoms

There are no pain receptors in the ACL, therefore pain is not an immediate feature in isolated ACL tears, but develops with hemarthrosis.

70% of acute knee hemarthrosis are associated with ACL tears.

Locking in ACL-deficient knees denotes associated meniscal tears either from the original injury, or from repeated giving way .

Signs

Aspiration of the joint reveals hemarthrosis. In this scenario, the likelihood of an ACL injury is >70%. Before the development of a hemarthrosis, the

physical examination is easier and more revealing; conversely, the examination is more difficult once pain and muscle guarding appear.

Signs

Lachman test is the most sensitive test for anterior tibial displacement (95% sensitivity).

The patient’s knee is flexed 20°; with one hand grasping the lower thigh and the other the upper

part of the leg, the joint surfaces are shifted backwards and forwards upon each other.

If the knee is stable, there should be no gliding. The test is difficult if the patient has big thighs (or

the examiner has small hands).

Signs

Anterior drawer test: Have the patient lie supine on the examination table with

his knees flexed to 90°and his feet flat on the table. Position yourself on the edge of the table so that you can

stabilize his foot by sitting on it. Cup your hands around the patient’s knee, with your

fingers on the area of insertion of medial & lateral hamstrings and your thumbs on the medial & lateral joint lines.

Draw the tibia toward you; if it slides forward from under the femur (+ve anterior drawer test), the ACL may be torn.

Signs

In both the drawer and Lachman test, note whether the end-point of

abnormal movement is ‘soft’ or ‘hard’.

Signs

Pivot shift test requires a relaxed patient and an intact MCL.

When the result is positive, this test reproduces the pathological motion in an ACL–deficient knee and is easier to elicit in a chronic ACL disruption or in an anesthetized patient with an acute ACL

injury.

Radiographic evaluationPlain x-ray

Plain radiographs often are normal; however, a tibial eminence fracture indicates an avulsion of the tibial attachment of ACL.

Segond fracture (avulsion fracture of the lateral capsule), is pathognomonic of an ACL tear.

Radiographic evaluation

MRI MRI is the most helpful diagnostic

radiographic technique.


MRIPrimary signs: Absent ACL Fuzzy ACL Bony avulsion


MRISecondary signs: Those alert attention to ACL tear

Lateral femoral condyle contusionAnterior translation of the tibiaSigond fractureLateral femoral condyle impression fractureContusion of the posteromedial corner of tibiaSigmoid PCL

Lateral femoral condyle contusion

Anterior translation of the tibia

Sigond fracture

Lateral femoral condyle impression fracture

Contusion of the posteromedial corner of

tibia

Sigmoid PCL

Natural history

As a result of abnormal loading and shear stresses in the ACL–deficient knee, the risk of late meniscal injury is high and appears to increase with time from the initial injury. Most late meniscal tears occur in the medial

meniscus because of its firm attachment to the capsule.

Osteochondral damage also influences prognosis and may be precursors of osteoarthritis.

Treatment

Treatment options available include 1. Nonoperative management

2. Repair of the ACL (± augmentation)

3. Reconstruction with either autograft or allograft tissues or synthetics.

Non-operative Treatment

Non-operative treatment is a viable option for a patient who is willing to make lifestyle changes and avoid the activities that cause recurrent instability.

If a nonoperative approach is chosen, it should include an aggressive rehabilitation program and counseling about activity level.

Non-operative Treatment

The use of a functional knee brace is controversial and has not been shown to reduce the incidence of re-injury significantly if a patient returns to high-level sports.

Primary repair (±Augmentation)

Primary repair of the ACL is no longer practised; reconstruction several weeks after the acute injury is the preferred choice.

Acute repair is appropriate when a bony avulsion occurs with the ACL attached.

The avulsed bone fragment often can be replaced and fixed with sutures or passed through transosseous drill holes or screws placed through the fragment into the bed.

ACL avulsions usually occur from the tibial insertion.

Primary repair

Repair of acute tear with avulsed bone fragment is rarely satisfactory (poor healing potential, interrupted blood supply, complex geometry of ACL), therefore, its better to go directly into primary reconstruction.

ACL Reconstruction

As evidence mounted that primary repair of midsubstance ACL tears routinely failed,

interest turned to reconstruction of the ligament.

The advances made in arthroscopy have led to the development of arthroscopic

techniques for ACL reconstruction.

Proper selection of patients.

Appropriate graft.

Meticulous technique.

Adequate rehabilitation.

Pre-requisites for successful reconstruction

Graft selectionAutograft tissues

Autograft tissue is used most commonly. Advantages:

○ Low risk of adverse inflammatory reaction ○ No risk of disease transmission.

As a biological graft, an autograft undergoes revascularization and recollagenization, but initially a 50% loss of graft strength occurs after implantation. ○ Therefore, it is desirable to begin with a graft

stronger than the tissue to be replaced.


The most common current graft choices are:

Bone–patellar tendon–bone graft Quadrupled hamstring tendon graft.


Bone–patellar tendon–bone (BPTB) graft Taken from the central third of patellar tendon,

with its adjacent patella and tibial bone blocks.


Hamstring tendon graft The use of hamstring tendon graft has increased in

recent years because of its relatively low donor site morbidity.

• Use of a single strand of the semitendinosus or gracilis tendon is inadequate because the

semitendinosus tendon has only 75% and the gracilis tendon only 49% the strength of the ACL.

• Now, surgeons are using either a triple- or quadruple-stranded semitendinosus graft or a

quadruple-stranded semitendinosus-gracilis tendon graft with both ends folded in half and combined.


Quadriceps tendon graft • The quadriceps tendon graft also has attracted

interest recently. • It can be harvested with a portion of patellar bone

or entirely as a soft-tissue graft. • This has become an alternative replacement graft,

especially for revision ACL surgeries and for knees with multiple ligament injuries

Graft selectionAllograft ligament

replacement Although autogenous tissues currently are

the most commonly used grafts for ACL reconstruction, these transfers sacrifice a normal musculotendinous structure in an already deficient knee, adding to the functional disturbance.

Extensive surgical exposure, long tourniquet times, and prolonged rehabilitation are other disadvantages of these techniques.


replacement Because collagen allografts appear capable

of fulfilling many of the requirements for an ideal ligament substitute, free allografts for ligament reconstruction have received growing attention during the past 15 years.


replacement Bone-patellar tendon-bone Achilles’ tendon Hamstrings Quadriceps tendon Fascia lata

Graft selectionAutograft vs. allograft

Viral disease transmission (1:1million) Graft incorporation & remodeling is faster

with autografts. Donor site morbidity with autografts

Graft selectionSynthetic materials for ligament

reconstruction Theoretical advantages compared with

autogenous tissues No autogenous tissues are sacrificed Avoidance of the increased morbidity associated

with the harvest of autogenous tissues.

However, many materials have failed, because they do not have the functional, physiological, and biomechanical characteristics of the normal ACL.


reconstruction The artificial ligaments are subjected to

tension, bending, and abrasion against bony structures and to interfiber friction.

With time, these stresses can result in ligament wear, fiber failure, and generation of artificial ligament wear particles.


reconstruction Artificial ligaments that serve as

augmentation devices to biological grafts may provide temporary protection for autogenous tissues, allowing earlier motion of the joint during the necrosis-revascularization-remodeling of the graft.

Ligament loading is shared by the graft tissue and the artificial device, allowing the autogenous tissue graft to remodel.

Graft placement

Although both tibial and femoral attachment sites are important, errors in the femoral site are more critical because of the proximity to the center of axis of knee motion.

Graft placement

A femoral tunnel that is too anterior will result in lengthening of the intraarticular distance between tunnels with knee flexion.

The practical implications of this anterior location are “capturing” of the knee and loss of flexion or stretching and perhaps clinical failure of the graft as flexion is achieved.

Graft placement

Posterior placement of the femoral tunnel or placement of the graft over the top of lateral femoral condyle produces a graft that is taut in extension but loosens with flexion.

This location produces an acceptable result, since the instability from an ACL deficiency occurs near terminal extension. ○ Clinical examination yields a negative Lachman test result and

a 1+ posterior drawer. If this location is chosen, secure the graft with the knee in

extension, since securing the posteriorly located graft with the knee in flexion may result in loss of extension.

If an over-the-top position is chosen, the route may be deeply grooved to approximate the “isometric” femoral position.

Graft placement The preferred location has been isometric

placement of the graft that limits changes in graft length and tension during knee flexion and extension, which possibly may lead to overstretching or failure of the graft.

Now, however, the concept of isometry is considered oversimplified, since it has been shown that the normal ACL is not isometric.

ACL bundles are under variable stress during knee motion. ○ Anteromedial bundle: higher stress during flexion.○ Posterolateral bundle: higher stress during extension.

Graft placement

Currently, most surgeons advocate placement of the graft at the posterior portion of the ACL tibial insertion site near the posterolateral bundle position for best reproduction of the function of the intact ACL.

This location also decreases graft impingement against the roof of the intercondylar notch with knee extension that can occur with anterior placement.

Graft placement

Various tools have been developed to assist the surgeon with placement of the tunnels.

These include devices in which the key point of reference is the over-the-top position, the roof of the intercondylar notch, or the anterior surface of the PCL.

Tibial drill guide for ACL referencing off PCL. ACL femoral guide.

Graft placement

Earlier techniques often included widening of the intercondylar notch or notchplasty to prevent impingement, which is more likely with anterior placement of the graft.

The posterior tibial location requires a minimal notchplasty, if at all, unless the ACL deficiency is chronic and the intercondylar notch has become stenotic with osteophytes.

Graft placement

On occasion, the surgeon encounters a narrow intercondylar notch, which has been shown to contribute to ACL injury, and notchplasty will protect the graft.

Graft placement

A vertical tunnel position high in the intercondylar notch near the 12-o'clock position has been shown to provide stability in the anteroposterior plane but does not restore stability in the rotational direction.

With this tunnel placement, the Lachman test result is normal but the pivot shift test result is positive.

Consequently, surgeons are beginning to place the femoral tunnel lower on the lateral wall toward the 10:30- or 1:30-o'clock position, which more accurately reproduces the femoral attachment site of ACL and provides rotational stability.

Graft tension The application of tension to the graft at the

time of initial fixation can significantly alter joint kinematics and in situ forces in the graft during knee motion.

Theoretically, the desired tension in the graft should be sufficient to obliterate the instability (Lachman test).

Graft tension

Too much tension may: “Capture” the joint, resulting in difficulty in

regaining motion, or lead to articular degeneration from altered joint

kinematics.

Graft fixation

In the early weeks after surgery, the weakest links in reconstruction are the fixation sites, not graft tissue itself.

Fixation of replacement grafts can be classified into direct and indirect methods.

Graft fixation

Direct fixation devices include

Interference screws○ Bioabsorbable screws

have been introduced as an alternative to metal screws

Staples Washers Cross pins

Graft fixation

Indirect fixation devices include Polyester tape–titanium button Suture-post.

Two bundles vs one Bundle

The single-bundle technique traditionally used recreates the anteromedial bundle and ignores the posterolateral bundle.

Considering the two-bundle anatomy of the native ACL, some investigators are experimenting with a two-tunnel ACL reconstruction.

The technique usually involves making 2 femoral tunnels with one tibial tunnel, but some are also using 2 tibial tunnels.

Two bundles vs one Bundle

Disadvantage of 2 Bundles:Numbers of femoral tunnelsOperative timeFemoral condyle osteonecrosis, chondrolysisMore technically demanding

Present Present recommendation for 2 recommendation for 2

bundlesbundles Only for hands of the most experienced ACL

surgeon Standard for patients who performs

demanding pivoting sports

Rehabilitation after ACL Reconstruction

Goal of rehabilitation after ACL surgery: to restore normal joint motion and strength while protecting the ligament graft.


Appropriate rehabilitation is crucial to the success of ACL reconstruction.

Some stress to the graft is desirable for healing and remodeling but should not be excessive and disruptive.

Current evidence indicates that intensive rehabilitation can help prevent early arthrofibrosis and restore strength and function earlier.


Perhaps the most important step is the early Perhaps the most important step is the early restoration of full extension. restoration of full extension.

Knee immobilization in a fully extended Knee immobilization in a fully extended brace is started immediately after surgery to brace is started immediately after surgery to prevent development of a flexion prevent development of a flexion contracture. contracture.


After surgery, the thigh muscles atrophy After surgery, the thigh muscles atrophy quickly. quickly.

Early quadriceps strengthening concentrates Early quadriceps strengthening concentrates on quadriceps sets and straight leg raises. on quadriceps sets and straight leg raises.


After isolated ACL reconstruction, partial After isolated ACL reconstruction, partial weight bearing with crutches is allowed weight bearing with crutches is allowed immediately. immediately.

A straight-leg brace is worn to support the A straight-leg brace is worn to support the weakened quadriceps. weakened quadriceps.

Certain types of concurrent meniscal repairs Certain types of concurrent meniscal repairs or articular cartilage procedures may dictate or articular cartilage procedures may dictate a different weight bearing status. a different weight bearing status.

Crutches usually are discontinued by 3-4 Crutches usually are discontinued by 3-4 weeks postoperativelyweeks postoperatively


Proprioceptive training also is instituted in Proprioceptive training also is instituted in the first 2 weeks. the first 2 weeks.

Return to sports should be delayed for at Return to sports should be delayed for at least 6 months after surgery to allow least 6 months after surgery to allow maturation of the graftmaturation of the graft

Results of ACL Reconstruction

The results reported with use of patellar The results reported with use of patellar tendon and hamstring tendons are tendon and hamstring tendons are comparablecomparable.

Complications of ACL SurgeryIntraoperative

Patellar fracture Inadequate graft length Mismatch between bone plug & tunnel sizes Graft fracture Suture laceration Violation of posterior femoral cortex Incorrect femoral or tibial tunnel placement

Complications of ACL SurgeryPostoperative

Motion (primarily extension) deficit This can result from

Preoperative factors: incl. preoperative effusion, limited ROM, & concomitant knee ligament injuries. Those make poor postoperative motion more likely.

Intraoperative factors: incl. incorrect tunnel position and inadequate notchplasty, which can result in overtightening or impingement of the graft, leading to loss of extension.

Postoperative factors: incl. prolonged immobilization and inadequate or inappropriate rehabilitation.

Complications of ACL SurgeryPostoperative

Persistent anterior knee pain Anterior knee pain probably is the most

common and most persistent complication after ACL reconstruction.

Several studies have suggested a relationship between patellofemoral pain and persistent flexion contracture or quadriceps weakness .

Failure of ACL Reconstruction

Factors potentially involved in the failure of ACL reconstruction include

surgical technique, selection of graft material, problems with graft incorporation, integrity of the secondary restraints, condition of articular & meniscal cartilage, postoperative rehabilitation, motivation and expectations of the patient.


Selection of patients and timing of surgery are crucial aspects of the preoperative plan.


Early failure, usually within the first 6 months, most often is the result of

Technical errors: This is the most avoidable and most common cause. Errors in surgical technique can include improper tunnel placement, inadequate notchplasty, and errors in graft selection, size, physiometry, or tensioning.

Incorrect or overly aggressive rehabilitation Premature return to sport Failure of graft incorporation.


Later failure, usually after 1 year, more typically is caused by recurrent injury.

Health & Medicine

34. acl injuries