Summary ACL tears are common athletic injuries leading to anterior and lateral rotatory instability of the knee. Diagnosis can be suspected clinically with presence of a traumatic knee effusion with increased laxity on Lachman's test but requires MRI studies to confirm diagnosis. Treatment involves ligamentous reconstruction utilizing a variety of techniques and graft choices depending patient age and activity levels. Epidemiology Incidence common ~400,000 ACL reconstructions / year account for half of all knee injuries Demographics more common among female athlete (4.5:1 ratio) females sustain ACL injuries at a younger age than males females get more ACL injuries on the supporting leg (males get more ACL injuries on the kicking leg) table of differences Risk factors female participation in soccer, male participation in basketball valgus moment at knee and adduction moment at hip upon landing previous concussion Etiology Pathophysiology pathoantomy non-contact pivoting injury login to view 1 more bullet blow to the lateral aspect of the knee common activities are soccer, basketball, skiing, and football pre-ponderance for females due to landing biomechanics and neuromuscular activation patterns (quadriceps dominant) play the biggest role Associated conditions meniscal tears lateral meniscal tears in 54% of acute ACL tears, medial in chronic cases PCL, LCL/PLC injuries chronic ACL deficient knees associated with chondral injuries complex, unrepairable meniscal tears and bucket handle medial meniscus tears Anatomy Anatomy two bundles measuring combined 32mm length x 7-12mm width bundles named for tibial attachment anteromedial bundle login to view 3 more bullets posterolateral bundle login to view 3 more bullets femoral attachment login to view 2 more bullets tibial attachment login to view 1 more bullet Composition 90% Type I collagen 10% Type III collagen Blood supply middle geniculate artery Innervation posterior articular nerve (branch of tibial nerve) Biomechanics and Function provides 85% of the stability to prevent anterior translation of the tibia relative to the femur acts as a secondary restraint to tibial rotation and varus/valgus rotation 2200 N strength (anterior) Presentation History felt a "pop" pain deep in the knee immediate swelling (70%) / hemarthrosis Symptoms generalized knee pain feelings of instability preventing return to sport difficulty weightbearing Physical exam inspection effusion quadricep avoidance gait (does not actively extend knee) coronal or sagittal plane deformity login to view 1 more bullet motion lack of full extension secondary to meniscal injury or arthrofibrosis evaluate for meniscal or concomitant ligamentous injuries (McMurray, Dial test, varus/valgus stress) Neurovascular evaluate peroneal function following high energy mechanisms and suspicion for multi-ligamentous injury pattern Provocative tests Lachman's test most sensitive exam test grading login to view 4 more bullets PCL tear may give "false" Lachman due to posterior subluxation Pivot shift knee brought from extension (anteriorly subluxated) to flexion (reduced) with valgus and internal rotation of tibia login to view 1 more bullet patient must be completely relaxed (easier to elicit under anesthesia) mimics the actual giving way event (see pathoanatomy section) KT-1000 useful to quantify anterior laxity measured with the knee in slight flexion and externally rotated 10-30° Imaging Radiographs recommended views AP, lateral, sunrise/merchant/skyline view findings often normal Segond fracture (avulsion fracture of the proximal lateral tibia) is pathognomonic for an ACL tear login to view 2 more bullets deep sulcus (terminalis) sign login to view 1 more bullet MRI indications to confirm clinical diagnosis of ACL rupture and evaluate for concomitant pathology findings of torn ACL sagittal view login to view 12 more bullets coronal view login to view 2 more bullets sensitivity and specificity 97% and 100% respectively CT scan indications revision setting to evaluate for bone loss sensitivity and specificity most sensitive and specific test for bone loss associated with osteolysis and tunnel widening Treatment Treatment individualized to patient based on activity level, age, demands, and concomitant pathology Nonoperative physical therapy, lifestyle modifications indications login to view 2 more bullets outcomes login to view 2 more bullets Operative ACL reconstruction indications login to view 7 more bullets outcomes login to view 1 more bullet ACL repair indications login to view 3 more bullets outcomes login to view 3 more bullets ACL revision reconstruction indications login to view 1 more bullet Concurrent pathology MCL injury indications login to view 2 more bullets outcomes login to view 1 more bullet meniscal tears indications login to view 1 more bullet outcomes login to view 1 more bullet chondral injuries indications login to view 1 more bullet outcomes login to view 1 more bullet posterior cruciate ligament and posterolateral corner injuries indications login to view 1 more bullet outcomes login to view 1 more bullet high tibial osteotomy or distal femoral osteotomy indications login to view 2 more bullets outcomes login to view 1 more bullet Techniques Physical therapy, lifestyle modifications technique early symptomatic treatment followed by 3 months of supervised physical therapy physical therapy focusing on range of motion and progressing to quad, hamstring, hip abductor and core strengthening re-evaluation at conclusion to assess progress functional braces demonstrate no added functional stability ACL reconstruction goal is to anatomically reconstruct ligament to restore anterior and rotational stability approach arthroscopic assisted technique clear out remnant ACL fibers to visualize native bone landmarks login to view 1 more bullet no patient-reported differences between single or double-bundle reconstructions login to view 2 more bullets femoral tunnel placement login to view 10 more bullets tibial tunnel placement login to view 6 more bullets graft placement login to view 3 more bullets graft fixation login to view 6 more bullets Revision ACL reconstruction approach considerations cause for prior ACL failure concomittant pathology prior graft selection careful assessment of the underlying cause of re-rupture technique high strength grafts (quad tendon, hamstring, allograft) login to view 1 more bullet dual or back-up fixation (suspension + interference screws) bone grafting and reconstruction in cases of previous tunnel dilation (15mm) or if interfering with anatomic tunnel creation addition of anterolateral ligament/ALL reconstruction (lateral extra-articular tenodesis) controversial login to view 1 more bullet re-harvesting BPTB is contraindicated postoperative conservative rehab Graft Selection Bone-patellar tendon-bone (BPTB) autograft advantages of all autografts using patient's own tissue most common source of graft faster incorporation less immune reaction no chance of acquiring someone else's infection pros and cons of bone-patella-bone the longest history of use and considered the "gold standard" bone to bone healing leads to faster incorporation time ability to rigidly fix the joint line (screws) the highest incidence of anterior knee pain (up to 10-30%) and kneeling pain maximum load to failure is 2600 Newtons (intact ACL is 1725 Newtons) complications patella fracture (usually postop during rehab), patellar tendon rupture re-rupture login to view 1 more bullet Quadrupled hamstring autograft technique may be taken from contralateral side in revision situation when allograft is not desirable or available pros and cons smaller incision, less perioperative pain, less anterior knee pain maximum load to failure is approximately 4000 Newtons decreased peak flexion strength at 3 years compared to BPTB concern about hamstring weakness in female athletes leading to increased risk of re-rupture complications "windshield wiper" effect (suspensory fixation away from joint line causes tunnel abrasion and expansion with flexion/extension of knee) residual hamstring weakness parasthesias due to injury to saphenous nerve branches during harvest login to view 1 more bullet Quadriceps tendon autograft pros & cons small incision in area that does not see pressure during kneeling does not involve physis maximum load to failure 2185 Newtons similar patient-reported and functional outcomes as other autografts may include bone block or completely soft tissue less commonly used so is often available in revision setting same disadvantages as hamstring autograft with suspensory fixation Allograft pros & cons useful in revisions no harvest site morbidity longer incorporation time more expensive than autograft risk of disease transmission (HIV is < 1:1.6 million, hepatitis is even greater) increased risk of re-rupture in young athletes login to view 1 more bullet graft processing fresh-frozen grafts lower re-rupture rates compared with chemically treated or irradiated login to view 6 more bullets Pediatric Considerations Physis < 14 yrs with open physis the onset of menarche is the best determinant of skeletal maturity in females Treatment Nonoperative indications login to view 2 more bullets Surgery indications login to view 1 more bullet Operative Techniques intra-articular physis-sparing (all intra-epiphyseal) trans-physeal partial trans-physeal login to view 1 more bullet no significant difference in growth disturbances between techniques combined intra- and extra-articular (males ≤12, females ≤ 11) autogenous ITB harvested free proximally, left attached distally to Gerdy tubercle looped through the knee in over the top position passed through the notch and under intermeniscal ligament anteriorly sutured to lateral femoral condyle and proximal tibia adult type reconstruction (males >=16, females >=14) Bone-patellar tendon-bone autograft Quadriceps tendon or hamstring autograft Graft Selection trans-physeal soft tissue grafts rarely lead to growth disturbances Instrumentation Factors found to increase physeal injury include: large tunnel diameter (>12mm) is most important login to view 2 more bullets oblique tunnel position interference screw fixation high-speed tunnel reaming lateral extra-articular tenodesis dissection close to the perichondral ring of LaCroix suturing near tibial tubercle Complications physeal disruption without growth disturbance (10%) Rehabilitation Early post-operative immediate aggressive cryotherapy (ice) immediate weight bearing (shown to reduce patellofemoral pain) emphasize early full passive extension (especially if associated with MCL injury or patella dislocation) no long-term differences found between accelerated and non-accelerated protocols early rehab focus rehab on exercises that do not place excess stress on graft login to view 12 more bullets Return to play no widely accepted criteria supporting clearance or timing to return to sport previously held consensus is no sooner than 9 months following surgery patient should pass series of functional tests that replictae sport-specific activities login to view 3 more bullets clearance for return to play should be made between surgeon and patient psychological factors play large role in timing of return and should not be overlooked Injury prevention female athlete neuromuscular training/plyometrics (jump training) land from jumping in less valgus and more knee flexion increasing hamstring strength to decrease quadriceps dominance ratio skier training teach skiers how to fall ACL bracing no proven efficacy except for ACL-deficient skiers Complications Intra-operative complications graft-tunnel mismatch BPTB graft total length greater than combined length of femoral tunnel, tibial tunnel, and intra-articular distance connecting them login to view 1 more bullet risk factors login to view 3 more bullets treatment login to view 2 more bullets posterior wall blowout cortical breach of posterolateral cortical wall of lateral femoral condyle risk factors login to view 3 more bullets treatment login to view 5 more bullets Graft failure due to tunnel malposition incidence graft failure for any cause approximates 5% is the most common cause of ACL failure, attributed to 70% of failures femoral tunnel malposition coronal plane login to view 4 more bullets sagittal plane login to view 5 more bullets tibial tunnel malposition sagittal plane login to view 2 more bullets posterior misplacement login to view 1 more bullet Graft failure due to other causes inadequate graft fixation or hardware failure can be caused by graft-screw divergence >30 degrees attritional graft failure graft less then 8mm in width intra-articular femoral bone plug dislodgement treatment login to view 1 more bullet missed diagnosis of concomitant ligamentous injuries or bony malalignment in combined ACL and PLC injuries, failure to treat the PLC will overload graft lead to failure over-aggressive or improper rehab open-chain exercises preoperative factors young age hyperextension higher level of activity posterior tibial slope >12 deg Infection and septic arthritis incidence less than 1% of all ACL reconstructions most commonly superficial login to view 3 more bullets risk factors graft contamination during routine intra-operative handling graft dropped on floor presentation pain, swelling, erythema, and increased WBC at 2-14 days postop diagnosis joint aspiration with gram stain and cultures treatment intra-operative login to view 2 more bullets post-operative login to view 3 more bullets Loss of motion & arthrofibrosis incidence most common complication following ACL reconstruction risk factors lack of pre-operative motion presentation loss of patellar translation treatment pre-operative prevention login to view 2 more bullets operative prevention login to view 1 more bullet post-operative prevention login to view 1 more bullet < 12 weeks, aggressive PT and serial splinting > 12 weeks, lysis of adhesions/manipulation under anesthesia Infrapatellar contracture syndrome incidence an uncommon complication which results in knee stiffness physical exam will show decreased patellar translation Patella Tendon Rupture will see patella alta on the lateral radiograph RSD (complex regional pain syndrome) Patella fracture BPTP and quadriceps grafts w bone block implicated most fractures occur 8-12 weeks post-op Tunnel osteolysis treatment observation unless graft laxity and knee instability Late osteoarthritis related to meniscal integrity increased rates noted in patients > age 50 at the time of ACL reconstruction Local nerve irritation incidence saphenous nerve due to hamstring autograft harvest Cyclops lesion fibroproliferative tissue blocks extension "click" heard at terminal extension Prognosis Natural history ACL deficient knees believed to lead to an accelerated progression of arthritis Survival with treatment near complete restoration of native kinematics following reconstruction high level of return to sport at all levels of competition