MR Imaging of ACL Injuries in Pediatric and Adolescent Patients

A small notch width index, steeper medial and lateral tibial slope and higher lateral/medial tibial slope ratio are relevant knee morphological factors for ACL injuries in skeletally immature patients-A systematic review

Purpose

The incidence of anterior cruciate ligament (ACL) injuries in skeletally immature patients has drastically increased over the last decades. Morphology of the knee might play an important role. This literature review provides a systematic overview of knee morphological factors relevant to ACL injury in skeletally immature patients. The hypothesis of the present study is that multiple knee morphological parameters-such as a steep medial and lateral tibial slope (MTS and LTS) and a narrow intercondylar notch-can be identified as potentially relevant factors for ACL injury in this population.

Methods

Systematic review according to PRISMA guidelines. MEDLINE, Embase and Cochrane were searched in December 2023 for studies reporting on knee morphology and ACL injury in skeletally immatures. The following inclusion criteria were used: English/Dutch studies, full-text available, human studies and skeletally immature patients. Parameters with clinical homogeneity and presented in two or more studies as means with standard deviation were included in a meta-analysis using RevMan. Parameters that could not be included in the meta-analyses were presented in a descriptive manner.

Results

After screening 1825 studies, a total of 18 studies were included, of which 16 studies had parameters included in the meta-analyses. These studies investigated 31 knee morphological factors for ACL injury in skeletally immatures. Meta-analyses identified a smaller notch width index (NWI) (0.25 vs. 0.26, mean difference: -0.02 95% confidence interval [CI]: -0.03 to -0.01, p ≤ 0.00001) steeper MTS and LTS (4.8° vs. 3.6° (mean difference: 0.55° 95% CI: 0.09-1.01, p = 0.02) and 4.3° vs 2.8° (mean difference: 2.04° 95% CI: 0.75-3.32, p = 0.0003), respectively) and higher LTS/MTS ratio as risk factors for ACL injury in skeletally immature patients.

Conclusions

A small NWI, steeper MTS and LTS and higher LTS/MTS ratios were identified as relevant knee morphological factors for ACL injuries in skeletally immature patients.

Level of Evidence

Level III.

Anatomic Differences in the Sagittal Knee Joint Are Associated With ACL Injury: Results From a Skeletally Immature Korean Population

Background:

Differences in tibiofemoral articular morphology are associated with risks of anterior cruciate ligament (ACL) injury.

Purpose:

To determine whether bony and cartilaginous morphological characteristics are related to ACL injury in pediatric patients and to investigate any differences according to sex.

Study Design:

Cohort study; Level of evidence, 3.

Methods:

A total of 200 skeletally immature Korean patients from a single institution were included in this study; 100 patients had an ACL injury, and 100 had an intact ACL. Condylar morphology and tibial slopes were evaluated and compared between the groups, and differences between sexes were evaluated in the ACL-injured group.

Results:

The lateral femoral curvature was significantly greater and the lateral and medial tibial curvatures were significantly smaller in the ACL-injured group than in the intact group (P < .01 for all). In addition, the lateral and medial femoral curvatures as well as the lateral tibial curvature were significantly smaller in female than in male patients (P < .01 for all). Both the medial and lateral tibial slopes were greater in the ACL-injured versus intact group (medial slope, 5.5° vs 5.0°; lateral slope, 3.0° vs 1.3°, respectively); this difference was statistically significant for lateral tibial slope (P = .026). No sex-based differences were found for medial or lateral tibial slope.

Conclusion:

Femoral and tibial curvatures as well as lateral tibial slope were significantly different between the ACL-injured and ACL-intact patients, and the lateral tibial curvature was significantly smaller in female than in male patients. Medial and lateral tibial slopes were not associated with a significant difference in ACL injury between male and female patients.

Knee Pathology in Young Adults After Pediatric Anterior Cruciate Ligament Injury: A Prospective Case Series of 47 Patients With a Mean 9.5-Year Follow-up

BACKGROUND

The rate of secondary knee injuries after pediatric anterior cruciate ligament (ACL) injury is uncertain, and previous studies are limited because of poor methodology.

PURPOSE

To evaluate the incidence of new meniscal injuries since the initial diagnostic magnetic resonance imaging (MRI) of young adults who sustained a pediatric ACL injury. In addition, to evaluate meniscal and cartilage injuries in the index knee and contralateral knee injuries on MRI at final follow-up (9.5 years). Furthermore, to assess leg length and alignment based on long-leg radiographs.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

Study population at final follow-up included 47 young adults who sustained a pediatric ACL injury before age 13 years. They were followed prospectively since the time of injury for a mean 9.5 years at final follow-up. Imaging included diagnostic MRI of the index knee and 3.0-T MRI of both knees at 1-, 2-, and 9.5-year follow-up, in addition to long-leg radiographs at final follow-up. Forty-three patients underwent active rehabilitation without ACL reconstruction initially; 4 were treated with initial ACL reconstruction. At final follow-up, 27 (57%) had undergone ACL reconstruction.

RESULTS

Fourteen patients had meniscal tears in the index knee at final follow-up (prevalence, 30%). The majority of these were in the same location as previously repaired tears (n = 9). Between diagnostic MRI and final follow-up, 16 patients had sustained new meniscal tears to a healthy meniscus (incidence, 34%). At final follow-up, meniscal injuries recorded at baseline or during follow-up were no longer visible and appeared healed in 17 patients (20 tears). MRI at final follow-up showed cartilage injuries in the index knee of 13 patients (28%) and contralateral injuries in 8 patients (meniscus, n = 2; cartilage, n = 5; subchondral fracture, n = 1). Two patients had a leg-length difference >15 mm, and 3 had side-to-side difference in knee alignment >5°.

CONCLUSION

The incidence of new meniscal tears after pediatric ACL injury was 34% during a mean follow-up period of 9.5 years. At final follow-up, 27 patients (57%) had normal menisci, and none had developed knee osteoarthritis. Primary active rehabilitation, close follow-up, and delayed surgery if needed may be a viable and safe treatment option for some pediatric ACL injuries.

Prevalence and incidence of new meniscus and cartilage injuries after a nonoperative treatment algorithm for ACL tears in skeletally immature children: a prospective MRI study

BACKGROUND

The increased risk of long-term osteoarthritis from concomitant injuries to the menisci or cartilage after an anterior cruciate ligament (ACL) injury in adults is well established. In skeletally immature children, ACL reconstruction is often recommended to reduce the risk of new intra-articular injuries. However, the prevalence and incidence of new injuries after nonoperative treatment of ACL injuries in children are unknown.

PURPOSE

To prospectively investigate the incidence of new injuries to the menisci and joint cartilage in nonoperatively treated, skeletally immature children with a known ACL injury by use of bilateral 3.0-T MRI.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

Forty skeletally immature children with a ruptured ACL (41 knees) followed a nonoperative treatment algorithm and were evaluated with bilateral 3.0-T MRI on 2 occasions (MRI1 and MRI2). The intra-articular structures were analyzed by 2 independent MRI radiologists. Monitoring of participation in physical activities was accomplished through a monthly online activity survey. Descriptive statistics and frequencies were extracted from the scoring forms and compared using the Fisher exact test.

RESULTS

Fourteen girls (35%) and 26 boys (65%) with a mean age of 11.0 ± 1.4 years at the time of injury were included. Time from injury to the final follow-up was 3.8 ± 1.4 years. Eighty-eight percent of the ACL-deficient children confirmed monthly participation in pivoting sports and/or in physical education classes in school. The prevalence of meniscus injuries in the 28 nonreconstructed knees was 28.5% at MRI1 and MRI2, and the incidence of new meniscus and cartilage injuries in the nonreconstructed knees from MRI1 to MRI2 was 3.6%. Thirteen children underwent ACL reconstruction, with a prevalence of meniscus procedures of 46.2%. The incidence of new meniscus injuries from diagnostic MRI to final follow-up was 19.5%. Surgical treatments for meniscus injuries were performed in 8 of the 41 knees.

CONCLUSION

The incidence of new injuries to menisci and joint cartilage was low between MRI1 and MRI2 in the 28 nonreconstructed knees. Thirty-two percent of the knees required ACL reconstruction, and 19.5% required meniscus surgeries during the 3.8 ± 1.4 years of follow-up from injury. Further follow-up is needed to evaluate the long-term knee health in these children.

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

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.