Anterior Cruciate Ligament
RupturePT ChiaHsiung Lin
Functional AnatomyAnterior tibial plateau to the posterior femoral intercondylar notchThe tibial attachment is to a facet, in front of, and lateral to the anterior tibial spine. The femoral attachment is high on the posterior aspect of the lateral wall of the intercondylar notch.The biomechanical function of the ACL in its stabilizing role it has four (main) functions: 1. Restrains anterior translation of the tibia; 2. Prevents hyperextension of the knee; 3. Acts as a secondary stabilizer to valgus stress, reinforcing the medial collateral ligament; 4. Controls rotation of the tibia on the femur in femoral extensions of 0-30.
Causes of ACL Rupture~ A traumatic force being applied to the knee in a twisting moment. ~ With either a direct or an indirect force. i.e., while side-stepping, pivoting or landing from a jump. ~ associated with some type of contact, whether it be on the football field, on the snow fields or in a motor vehicle accident.
# Hyperextension knee is straightened more than 10 degrees beyond its normal fully straightened position
# Pivoting injuries of the knee with excessive inward turning of the lower leg can also damage the ACL.
*About 40% of all individuals experience a "popping" sensation at the time of the injury,which may also produce a tearing sensation.
* Most ACL injuries occur during athletic activity. Often those are non-contact activities with the mechanism of injury usually involving: Planting and cutting : turning one direction or the other. Example: Football or baseball player making a fast cut and changing direction. - Straight-knee landing : results when the foot strikes the ground with the knee straight. Example: Basketball player coming down after a jump shot or the gymnast landing on a dismount. - One-step-stop landing with the knee hyperextended : results when the leg abruptly stops while in an over-straightened position. Example: Baseball player sliding into a base with the knee hyperextended with additional force upon hyperextension. - Pivoting and sudden deceleration resulting from a combination of rapid slowing down and a plant and twist of the foot placing extreme rotation at the knee. Example: Football or soccer player quickly slowing down followed by a quick turn in direction.
Mechanism of injury * Approximately 80% of injuries occur in non-contact situations when landing from a jump or during deceleration and change of direction on a fixed foot. * If no other player is involved, this means the athlete is placing his or her own leg in a vulnerable position. * The Position of No Return is the movement combination that most often leads to ACL rupture.
Suspicious of ACL Rupture?The following signs and symptoms are often associated with ACL rupture a bad landing from a jump or decelerating and twisting injury.Immediate pain and swelling. Usually, when the ACL is torn, it bleeds and fills the knee with blood.A sensation of giving way or instability
Examination* Palpating (feeling) the knee allows an assessment of swelling and inflammation - an inflamed knee may be very hot and tender as well as swollen. * The examiner will ask you to bend and straighten the knee as far as you can, he may then add some overpressure at the limits of your movement to check the full range. Any block to movement or pain will be noted as significant. * Typically your doctor or physiotherapist will test for cruciate ligament damage by assessing how far the tibia will glide forwards and backwards on the femur. * Usually he will test both legs and compare them - this is because there is a natural difference in normal movement between different people, the examiner will use your uninjured leg to represent what is normal for you.
Clinical AssessmentStanding leg alignment and varus thrust in gaitAssess hyperextension of opposite kneeLachman TestTip- feel the end point whilst performing the Lachman test.Pivot Shift Test Tip - Start the pivot shift test from full extension and apply slight axial force in addition to valgus and internal rotation. * Check Posterior sag tibia (PCL) as it can lead to a wrong diagnosis of ACL injury. * Check collateral stability- missed lateral ligament injury can be a reason of ACL reconstruction failure. (MRI scans or Arthroscopy are not needed for routine diagnosis of ACL rupture).
Testing for the ACL is done with your knee bent approximately 20-30 from the horizontal. This test is called the Lachman test and is very sensitive and specific for the ACL.Testing for the PCL (posterior cruciate ligament) is done with the knee bent at 90 and is called the 'Drawer test'.Lateral pivot shift test. This involves applying a sideways pressure on the joint while rotating and bending it however, it can be difficult to perform in an acute situation or if a patient is very tense. It is more likely to be tried when examining a more chronic injury, or if assessing a joint under anaesthetic.
Further diagnostic tests
Other investigations may prove necessary. Further diagnostic tests may be indicated to confirm a questionable diagnosis or to check if any other structures have also been injured - this could affect the treatment required. A Standard X-ray This will only show bone but it may be important to rule out any fractures (breaks) and also to see how the bones are positioned in relation to each other. Sometimes a 'stress X-ray' is done to assess the integrity of the collateral ligaments - the X-ray is taken while sideways pressure is applied to the knee.
An MRI Scan This will show all the structures in the knee and enables a reliable diagnosis to be made however, scans are very expensive and are not always available or if they are, there may be an unacceptably long wait.B. The second image demonstrates a torn ACL. The first image demonstrates an intact cruciate ligament.
Findings: Anterior drawer sign (lateral tibial plateau > 5 mm relative to retrofemoral line); Buckled PCL sign (tangential line along posterior margin of PCL doesn't intersect distal femur); LCL seen almost entirely on a single coronal image (due to anterior subluxation of tibia).
Management of the Ruptured ACL Once the diagnosis of ruptured ACL is made, management can be divided into conservative and surgical. Correct choice of treatment depends on assessment of three patient factors: Age Functional disability Functional requirementsTreatment for an Anterior Cruciate Rupture
What can the athlete do?Immediately stop play or competitionApply RICE (Rest, Ice, Compression, Elevation) to the knee immediatelySeek medical attention as soon as possible.
Timing of surgery can affect postoperative recovery of range of movements dueto arthrofibrosis. Too delayed a reconstruction (>12 months) can result in higher meniscal injuries and degenerative changes (Keating 2005).
Factors affecting timing of surgery are 1. Associated ligamentous and/or meniscal injuries 2. Preoperative condition of the knee- minimal or no swelling, minimal warmth, good strength, leg control and range of movements and preferably symmetrical extension 3. Mental preparation of the patient/school/ work/holidays.Operative Treatment TimingThe main choices for graft for current day ACL reconstruction are Autologous- Hamstring, Patellar tendon, quadriceps tendonAllograft- Patellar tendon, Hamstring, Achilles tendon
Decision on SurgeryThe fundamental reason for surgical treatment is to stop symptomatic instability which can produce recurrent injury- especially meniscal tears. Not all patients with ACL rupture have this instability pattern.This is because poor results from ACL reconstruction can often be due to presence of significant meniscal and chondral injuries from chronic instability. Hence it is important to know that a trial of rehabilitation is not a routine for all ACL injuries.Left: Normal knee MRI ACL and PCL . Right: ruptured ACLTibial avulsion
Tunnel position and the isometric pointSuccess of ACL reconstructions depend primarily on achieving proper tunnel position and graft fixation followed by appropriate rehabilitation. Malposition of tunnels can produce restricted movements, increased laxity or graft failure secondary to impingement. There is no isometric point for the tibial tunnel. Both tunnels have to be made within the anatomical foot print of the ACL.
* Landmarks for tibial tunnel1.Posterior aspect of the tibial ACL footprint2.About 7mm anterior to the PCL with the knee flexed 90 degrees3.Between the tibial eminences4.Just posterior to the posterior edge of the anterior horn attachment of the lateral meniscus5.About 43% posterior to the anterior edge of the tibia along the length on the sagital plane of the tibia6.The oblique orientation of the tibial tunnel in the coronal plane (about 60-70 degrees) is important for transtibial drilling of femoral tunnel. This means that the entry point on the tibia is close to or sometimes through superficial MCL.
Landmarks for femoral tunnel 1.The ACL femoral insertion has a length of 18mm width of 10mm and is 4 mm from the posterior articular cartilage. The tunnel has to be within the lower part of this footprint2.With the knee flexed 90 degrees and imagining the femoral tunnel position as the face of a clock, the aperture should be at 10-11 oclock for the