Anterior cruciate ligament (ACL) tear Flashcards
What is the mechanism of injury in ACL tears?
acute non-contact deceleration injury,
forceful hyperextension,
or excessive rotational forces about the knee
What are the clinical features of ACL tear?
- Audible pop
- Rapid knee swelling
- Inability to return to sports
- Sensation of knee instability or buckling
- Pain
- Tenderness at lateral femoral condyle, lateral tibial plateau
- Positive Lachman’s test
- Positive pivot shift maneouvre
What are the risk factors for ACL injury?
- Acute trauma - hyperextension, valgus stress
- Female sex
- Hx of previous ACL injury
- Use of cleats or spikes - on grassy surfaces, increases risk of planting foot and twisting body without release
- Rough/uneven playing surface
- Poor weather conditions
- Fatigue
- Adolescent-middle aged atheletes
What investigations are used to assess for ACL injury?
Usually diagnosed based on clinical findings alone.
XR - based on Ottawa guidelines for the knee incl any of: 1) inability to weight bear, 2) tenderness at patelalr or fibular head, 3) active flexion of knee <90, 4) age >55. Usuallly negative unless avulsion tear within capsule is present.
MRI - ACL fibres appear disrupted, blurry on T1-weighted images, with abnormal high signal on T2-weighted images
Arthroscopy - usually performed as part of reconstruction procedure
What is the most accurate maneouvre for detecting acute ACL tear?
Lachman’s test is the most SENSITIVE test
What is Segond’s fracture?
Sign on XR showing lateral capsular sign/Segond’s fracture = a small capsular avulsion off the lateral aspect of the proximal tibia.This is uncommon but virtually pathognomonic for ACL tear.
What is the management of ACL tears?
Conservative
- PRICEM +
- Physiotherapy - to relieve pain and swelling, then to strengthen muscles and regain dynamic stability. May be done at home in those who are usually sedentary.
Medical
- NSAIDs
Surgical
- ACL reconstruction - only in some patients or those who are athletes; usually done 1-2 weeks after injury. Usually allows return to high-demand activities
- PRICEM acronym for initial management of ACL tear:*
- P = Protected weight-bearing exercise with crutches or crutch assisted with a knee immobiliser or similar brace. Avoid prolonged immobiliser use, as severe stiffness and discomfort can develop
- R = Relative rest
- I = Ice: useful for initial few days as helps minimise pain and swelling
- C = Compression
- E = Elevation
- M = Medicines (analgesics, NSAIDs as needed).
What are the complications of ACL injury?
Short term:
- Bone bruising
- MCL injury
- Meniscal tear - occurs in up to 80% of ACL injuries
- Articular cartilage injury
Long term:
- Post traumatic arthrosis
What is the prognosis with ACL tears?
No longer considered a career-ending injury for athletes and up to 90% can return to sports
What is the ‘unhappy triad’?
- MCL injury
- Meniscal tear
- ACL injury
= often present together