Overview
Definition:
Anterior Cruciate Ligament (ACL) injuries in adolescents are particularly complex due to the presence of open physes (growth plates), which are crucial for bone growth
Physeal-sparing techniques aim to reconstruct the ACL while minimizing disruption to these growth plates, thereby reducing the risk of premature physeal closure and subsequent limb length discrepancy or angular deformities.
Epidemiology:
ACL injuries are increasingly common in adolescent athletes, with a rising incidence in pediatric populations
While overall ACL injury rates are lower in younger children compared to adults, the proportion of growth plate fractures associated with ACL injuries can be higher in skeletally immature individuals
These injuries occur most frequently during high-impact sports involving pivoting, cutting, and sudden deceleration.
Clinical Significance:
Improper management of ACL injuries in adolescents can lead to significant long-term morbidity
Premature physeal closure can result in limb length inequality and angular deformities (e.g., genu valgum or varum), necessitating further corrective surgeries
Physeal-sparing techniques are therefore paramount to preserve growth potential while restoring knee stability and function, allowing adolescents to return to their desired activity levels.
Clinical Presentation
Symptoms:
A distinct "pop" sensation at the time of injury
Immediate onset of severe knee pain
Significant hemarthrosis (swelling) within hours
Inability to bear weight on the affected limb
Feeling of instability or giving way in the knee
Stiffness and limited range of motion.
Signs:
Gross joint effusion
Tenderness along the joint line and to palpation of collateral ligaments
Positive Lachman test indicating ACL laxity
Positive anterior drawer test
Positive pivot shift test indicating rotational instability
Palpable or visible deformity may be present in cases of associated fractures.
Diagnostic Criteria:
Diagnosis is primarily clinical, supported by imaging
Clinical diagnosis relies on a consistent history and positive findings on physical examination, particularly the Lachman test and anterior drawer test
Radiographic evidence of associated physeal fractures (avulsion fractures, especially of the tibial spine) is critical to assess skeletal maturity and guide management
MRI can confirm the ACL tear and evaluate associated intra-articular pathology.
Diagnostic Approach
History Taking:
Detailed mechanism of injury is crucial (non-contact pivoting, landing from a jump)
Ask about any previous knee injuries or pain
Assess the adolescent's level of activity and sport participation
Inquire about any reports of a "pop" at the time of injury
Document presence and progression of pain and swelling
Assess functional limitations like difficulty with stairs or walking.
Physical Examination:
Begin with inspection for swelling, ecchymosis, and deformity
Palpate for tenderness over the joint line, collateral ligaments, and tibial eminences
Perform a systematic assessment of knee range of motion (active and passive)
Evaluate ligamentous stability using Lachman, anterior drawer, posterior drawer, varus stress, and valgus stress tests
Assess for the pivot shift phenomenon
Assess neurovascular status distally.
Investigations:
Plain radiographs (AP, lateral, notch views) are essential to assess skeletal maturity (Risser sign, Salter-Harris classification) and identify associated avulsion fractures, particularly tibial spine avulsions
MRI of the knee is highly sensitive and specific for confirming the ACL tear, assessing its severity, and identifying associated injuries such as meniscal tears, collateral ligament injuries, and bone bruises
Ultrasound may be used for effusion assessment but is not primary for ACL diagnosis.
Differential Diagnosis:
Tibial spine avulsion fracture (often mimics ACL tear in children, but is a bony avulsion)
Meniscal tears
Collateral ligament injuries
Patellar dislocation
Osteochondral fractures
Referred pain from hip or other sources
Other causes of hemarthrosis in children (e.g., bleeding disorders, although rare in trauma context).
Management
Initial Management:
RICE protocol (Rest, Ice, Compression, Elevation) to control pain and swelling
Crutch ambulation with non-weight bearing or partial weight bearing
Analgesia with NSAIDs or acetaminophen
Referral to pediatric orthopedics for definitive management planning.
Surgical Management:
The choice of surgical technique depends on the adolescent's skeletal maturity, the presence of associated injuries, and the degree of instability
Physeal-sparing techniques are preferred to avoid growth plate injury
These include: Transphyseal (traditional) ACL reconstruction (less preferred due to growth plate risk)
Physeal-sparing techniques using all-epiphyseal tunnels or suspensory fixation devices that bypass or minimize disruption of the physis
Spica casting for tibial spine avulsions in very young children
Arthroscopic techniques often used to minimize soft tissue disruption.
Supportive Care:
Postoperative management includes pain control, wound care, and progressive rehabilitation
Physical therapy is critical for regaining range of motion, strength, proprioception, and neuromuscular control
Gradual return to sports is guided by functional milestones and physician assessment
Emotional support for the adolescent athlete and their family is also important.
Age Specific Dosing:
Pain management in pediatric patients requires age and weight-appropriate dosing
Acetaminophen: 10-15 mg/kg/dose PO q4-6h prn
Ibuprofen: 5-10 mg/kg/dose PO q6-8h prn
Opioids (e.g., Tramadol, Morphine) may be used judiciously for severe acute pain, with careful monitoring for respiratory depression
Doses must be calculated based on current weight and renal function.
Complications
Early Complications:
Infection (superficial or deep)
Hemarthrosis and persistent effusion
Stiffness and limited range of motion
Neurovascular injury (rare)
Gout or pseudogout flares (rare).
Late Complications:
Premature physeal closure leading to limb length discrepancy or angular deformity (valgus/varus)
Persistent knee instability
Osteoarthritis
Hardware-related issues (irritation, loosening)
Graft failure or rerupture
Stiffness and arthrofibrosis
Chronic pain.
Prevention Strategies:
Meticulous surgical technique to avoid unnecessary physeal trauma
Appropriate graft selection and fixation
Aggressive postoperative rehabilitation to prevent stiffness
Patient and family education on activity modification and return-to-sport criteria
Regular follow-up to monitor for growth disturbances and long-term outcomes.
Prognosis
Factors Affecting Prognosis:
Skeletal maturity at time of injury and surgery
Adherence to rehabilitation protocols
Presence and management of associated injuries
Quality of surgical reconstruction
Return-to-sport decisions
Patient's motivation and expectations.
Outcomes:
With appropriate physeal-sparing techniques and comprehensive rehabilitation, many adolescents can achieve good functional outcomes, return to high levels of sport, and have a reduced risk of long-term complications
However, the risk of developing osteoarthritis later in life remains higher compared to uninjured individuals
Physeal arrest complications can significantly impact long-term limb alignment and length.
Follow Up:
Regular clinical and radiographic follow-up is essential, particularly during periods of rapid skeletal growth
Monitoring for signs of premature physeal closure, limb length discrepancy, or angular deformities is crucial
Long-term follow-up (10+ years) may be warranted to assess for the development of osteoarthritis and functional status.
Key Points
Exam Focus:
Differentiate ACL tears from tibial spine avulsions in children
Recognize the importance of skeletal maturity (e.g., Risser sign) in surgical planning
Understand the principles of physeal-sparing techniques vs
transphyseal techniques
Identify common complications like physeal arrest
Recall RICE protocol and initial management steps.
Clinical Pearls:
Always obtain weight-bearing AP/lateral and notch views of the knee in adolescents with suspected ACL injury
Consider physeal injury even with a seemingly "soft tissue" mechanism
Use arthroscopy to assess intra-articular pathology and guide surgical approach
Early aggressive physical therapy is key to restoring function and preventing stiffness.
Common Mistakes:
Performing transphyseal reconstruction without considering the risks of growth plate injury
Inadequate assessment of skeletal maturity
Delaying surgical intervention for unstable injuries
Insufficient or inappropriate postoperative rehabilitation
Premature return to sport without adequate recovery and strength
Failing to adequately address associated meniscal or collateral ligament injuries.