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Spectrum of injuries associated with paediatric ACL tears: an MRI pictorial review.

Jaremko JL, Guenther ZD, Jans LB, Macmahon PJ - Insights Imaging (2013)

Bottom Line: ACL injury usually occurs with axial rotation in the valgus near full extension.Paediatric-specific issues of note include tibial spine avulsion, normal difficulty visualising a thin ACL and posterolateral corner structures, and differentiation between incompletely closed physis and impaction fracture.Awareness of the spectrum of secondary findings illustrated here and the features distinguishing them from normal variation can aid in accurate assessment of ACL tears and related injuries, enabling effective treatment planning and assessment of prognosis. • The ACL in children normally appears thin or attenuated, while thickening and oedema suggest tear. • Displaced medial meniscal tears are significantly more common later post-injury than immediately. • The meniscofemoral ligaments merge with the posterior lateral meniscus, complicating tear assessment. • Tibial plateau impaction fractures can be difficult to distinguish from a partially closed physis. • Axial MR sequences are more sensitive/specific than coronal for diagnosis of medial collateral ligament (MCL) injury.

View Article: PubMed Central - PubMed

Affiliation: Department of Radiology and Diagnostic Imaging, 2A2.42 Walter Mackenzie Health Sciences Centre, University of Alberta, Edmonton, Alberta, Canada, T6G 2B7, jjaremko@ualberta.ca.

ABSTRACT

Objective: Magnetic resonance imaging (MRI) findings in anterior cruciate ligament (ACL) injury are well known, but most published reviews show obvious examples of associated injuries and give little focus to paediatric patients. Here, we demonstrate the spectrum of MRI appearances at common sites of associated injury in adolescents with ACL tears, emphasising age-specific issues.

Methods: Pictorial review using images from children with surgically confirmed ACL tears after athletic injury.

Results: ACL injury usually occurs with axial rotation in the valgus near full extension. The MRI findings can be obvious and important to management (ACL rupture), subtle but clinically important (lateral meniscus posterior attachment avulsion), obvious and unimportant to management (femoral condyle impaction injury), or subtle and possibly important (medial meniscocapsular junction tear). Paediatric-specific issues of note include tibial spine avulsion, normal difficulty visualising a thin ACL and posterolateral corner structures, and differentiation between incompletely closed physis and impaction fracture.

Conclusion: ACL tear is only the most obvious sign of a complex injury involving multiple structures. Awareness of the spectrum of secondary findings illustrated here and the features distinguishing them from normal variation can aid in accurate assessment of ACL tears and related injuries, enabling effective treatment planning and assessment of prognosis.

Teaching points: • The ACL in children normally appears thin or attenuated, while thickening and oedema suggest tear. • Displaced medial meniscal tears are significantly more common later post-injury than immediately. • The meniscofemoral ligaments merge with the posterior lateral meniscus, complicating tear assessment. • Tibial plateau impaction fractures can be difficult to distinguish from a partially closed physis. • Axial MR sequences are more sensitive/specific than coronal for diagnosis of medial collateral ligament (MCL) injury.

No MeSH data available.


Related in: MedlinePlus

Tibial spine avulsion and Segond fracture. The arrow points to Segond fracture in each image. a Plain radiograph of a 16-year-old boy with a combination of injuries suggesting a pivot-shift impact mechanism. ACL was intact at surgery. b Coronal T1-weighted MRI in a different child also showing a tibial spine avulsion. c Segond fracture on coronal proton density (PD) MRI of a 15-year-old boy with ACL rupture. Note the lack of adjacent oedema, which is typical; these fractures are often subtle on MRI. Note also the fragment’s capsular attachment to the anterior oblique band of the lateral collateral ligament complex
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Fig1: Tibial spine avulsion and Segond fracture. The arrow points to Segond fracture in each image. a Plain radiograph of a 16-year-old boy with a combination of injuries suggesting a pivot-shift impact mechanism. ACL was intact at surgery. b Coronal T1-weighted MRI in a different child also showing a tibial spine avulsion. c Segond fracture on coronal proton density (PD) MRI of a 15-year-old boy with ACL rupture. Note the lack of adjacent oedema, which is typical; these fractures are often subtle on MRI. Note also the fragment’s capsular attachment to the anterior oblique band of the lateral collateral ligament complex

Mentions: Young children have weaker physes than ligaments, which can result in epiphyseal avulsion fractures at the anterior tibial spine near the ACL attachment rather than tearing of the ligament itself, for the same pivot-shift injury mechanism (Fig. 1) [3]. This review is limited to patients with ACL tears, but the search for associated injuries in a younger child with a tibial spine avulsion should follow the same pattern. The spectrum of ACL appearance from normal to completely torn is seen in Figs. 2 and 3. The normal ACL is composed of two bundles named for tibial attachment locations, anteromedial (dominant in knee flexion) and posterolateral (most active in extension) [17]. Partial tears can involve one or both bundles. In children the normal ACL can appear quite attenuated (Fig. 2b); in our experience a recently torn ACL is usually visibly thickened and oedematous, and a thin and appropriately oriented ligament without oedema is likely intact. In the last 110 cases at our institution, 7/48 (15 %) read by musculoskeletal radiologists and 26/62 (42 %) read by paediatric radiologists were initially reported as high-grade partial thickness ACL tears, while at later surgery all but one of these tears (99 %) was described as complete (Fig. 2c). Given the time delay between injury and surgery, it is possible that partial tears evolved to complete tears at surgery; however, the distinction between complete and partial tears is well known to be limited in reliability on MRI [18]. One challenge is that the torn ACL may form scar tissue that can mimic a partially intact ligament. A tear that appears to involve most of the ACL fibres is likely to be functionally complete, and we encourage reporting the tear in this fashion.Fig. 1


Spectrum of injuries associated with paediatric ACL tears: an MRI pictorial review.

Jaremko JL, Guenther ZD, Jans LB, Macmahon PJ - Insights Imaging (2013)

Tibial spine avulsion and Segond fracture. The arrow points to Segond fracture in each image. a Plain radiograph of a 16-year-old boy with a combination of injuries suggesting a pivot-shift impact mechanism. ACL was intact at surgery. b Coronal T1-weighted MRI in a different child also showing a tibial spine avulsion. c Segond fracture on coronal proton density (PD) MRI of a 15-year-old boy with ACL rupture. Note the lack of adjacent oedema, which is typical; these fractures are often subtle on MRI. Note also the fragment’s capsular attachment to the anterior oblique band of the lateral collateral ligament complex
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3675256&req=5

Fig1: Tibial spine avulsion and Segond fracture. The arrow points to Segond fracture in each image. a Plain radiograph of a 16-year-old boy with a combination of injuries suggesting a pivot-shift impact mechanism. ACL was intact at surgery. b Coronal T1-weighted MRI in a different child also showing a tibial spine avulsion. c Segond fracture on coronal proton density (PD) MRI of a 15-year-old boy with ACL rupture. Note the lack of adjacent oedema, which is typical; these fractures are often subtle on MRI. Note also the fragment’s capsular attachment to the anterior oblique band of the lateral collateral ligament complex
Mentions: Young children have weaker physes than ligaments, which can result in epiphyseal avulsion fractures at the anterior tibial spine near the ACL attachment rather than tearing of the ligament itself, for the same pivot-shift injury mechanism (Fig. 1) [3]. This review is limited to patients with ACL tears, but the search for associated injuries in a younger child with a tibial spine avulsion should follow the same pattern. The spectrum of ACL appearance from normal to completely torn is seen in Figs. 2 and 3. The normal ACL is composed of two bundles named for tibial attachment locations, anteromedial (dominant in knee flexion) and posterolateral (most active in extension) [17]. Partial tears can involve one or both bundles. In children the normal ACL can appear quite attenuated (Fig. 2b); in our experience a recently torn ACL is usually visibly thickened and oedematous, and a thin and appropriately oriented ligament without oedema is likely intact. In the last 110 cases at our institution, 7/48 (15 %) read by musculoskeletal radiologists and 26/62 (42 %) read by paediatric radiologists were initially reported as high-grade partial thickness ACL tears, while at later surgery all but one of these tears (99 %) was described as complete (Fig. 2c). Given the time delay between injury and surgery, it is possible that partial tears evolved to complete tears at surgery; however, the distinction between complete and partial tears is well known to be limited in reliability on MRI [18]. One challenge is that the torn ACL may form scar tissue that can mimic a partially intact ligament. A tear that appears to involve most of the ACL fibres is likely to be functionally complete, and we encourage reporting the tear in this fashion.Fig. 1

Bottom Line: ACL injury usually occurs with axial rotation in the valgus near full extension.Paediatric-specific issues of note include tibial spine avulsion, normal difficulty visualising a thin ACL and posterolateral corner structures, and differentiation between incompletely closed physis and impaction fracture.Awareness of the spectrum of secondary findings illustrated here and the features distinguishing them from normal variation can aid in accurate assessment of ACL tears and related injuries, enabling effective treatment planning and assessment of prognosis. • The ACL in children normally appears thin or attenuated, while thickening and oedema suggest tear. • Displaced medial meniscal tears are significantly more common later post-injury than immediately. • The meniscofemoral ligaments merge with the posterior lateral meniscus, complicating tear assessment. • Tibial plateau impaction fractures can be difficult to distinguish from a partially closed physis. • Axial MR sequences are more sensitive/specific than coronal for diagnosis of medial collateral ligament (MCL) injury.

View Article: PubMed Central - PubMed

Affiliation: Department of Radiology and Diagnostic Imaging, 2A2.42 Walter Mackenzie Health Sciences Centre, University of Alberta, Edmonton, Alberta, Canada, T6G 2B7, jjaremko@ualberta.ca.

ABSTRACT

Objective: Magnetic resonance imaging (MRI) findings in anterior cruciate ligament (ACL) injury are well known, but most published reviews show obvious examples of associated injuries and give little focus to paediatric patients. Here, we demonstrate the spectrum of MRI appearances at common sites of associated injury in adolescents with ACL tears, emphasising age-specific issues.

Methods: Pictorial review using images from children with surgically confirmed ACL tears after athletic injury.

Results: ACL injury usually occurs with axial rotation in the valgus near full extension. The MRI findings can be obvious and important to management (ACL rupture), subtle but clinically important (lateral meniscus posterior attachment avulsion), obvious and unimportant to management (femoral condyle impaction injury), or subtle and possibly important (medial meniscocapsular junction tear). Paediatric-specific issues of note include tibial spine avulsion, normal difficulty visualising a thin ACL and posterolateral corner structures, and differentiation between incompletely closed physis and impaction fracture.

Conclusion: ACL tear is only the most obvious sign of a complex injury involving multiple structures. Awareness of the spectrum of secondary findings illustrated here and the features distinguishing them from normal variation can aid in accurate assessment of ACL tears and related injuries, enabling effective treatment planning and assessment of prognosis.

Teaching points: • The ACL in children normally appears thin or attenuated, while thickening and oedema suggest tear. • Displaced medial meniscal tears are significantly more common later post-injury than immediately. • The meniscofemoral ligaments merge with the posterior lateral meniscus, complicating tear assessment. • Tibial plateau impaction fractures can be difficult to distinguish from a partially closed physis. • Axial MR sequences are more sensitive/specific than coronal for diagnosis of medial collateral ligament (MCL) injury.

No MeSH data available.


Related in: MedlinePlus