A Recess Is Observed Between the Posterior Knee Capsule and the Meniscotibial Ligament Complex in Pediatric Specimens.

Purpose: To define the surgical anatomy of the meniscotibial ligament complex of the pediatric medial and lateral menisci and their relation to the proximal tibial physis and posterior joint capsule. Methods: Fourteen pediatric cadaveric knee specimens (aged 3 months to 11 years) were dissected to clarify the relation of the posterior knee capsule, the meniscus, and the meniscotibial ligament complex. Metallic markers were placed marking the meniscotibial ligament capsular attachment on the proximal tibia. Specimens underwent computed tomography scanning to evaluate pin placement and relation to the physis. A digital measurement tool was used to measure the distances between the proximal tibial physis and the pins (placed at 5 points on both the lateral and medial menisci). Results: In each specimen, clear separation was noted between the posterior joint capsule from the meniscus and meniscotibial ligament complex in the medial and lateral compartments. There was an increase in the distance between the proximal tibial physis and the insertion points of the meniscotibial ligament complex with increasing specimen age. For both the medical and lateral menisci in group 1, the median meniscotibial ligament insertion points were often less than 7 mm (interquartile range, 0.00-7.8 mm) away from the physis. The median meniscotibial ligament insertion points in group 2 tended to be farther from the physis but always less than 20 mm (interquartile range, 2.5-17.5 mm)-and as close as less than 5 mm (lateral posterior root). Conclusions: In this anatomic study of pediatric knees, we observed a distinct recess/cul-de-sac space between the posterior knee capsule and meniscal attachments in all specimens. This defines a distinct plane between the posterior knee capsule and the meniscotibial ligament complex, with a distance between the physis and meniscotibial ligament capsular attachments that increases with age. Clinical Relevance: The anatomic parameters evaluated in our study should be considered as future meniscal repair and transplantation techniques aim to restore the meniscal anatomy, stability, and mobility provided by the meniscotibial ligament complex and capsule structures.

Medial and Lateral Posterior Tibial Slope in the Skeletally Immature: A Cadaveric Study.

Background: An increased posterior tibial slope (PTS) results in greater force on the anterior cruciate ligament (ACL) and is a risk factor for ACL injuries. Biomechanical studies have suggested that a reduction in the PTS angle may lower the risk of ACL injuries. However, the majority of these investigations have been in the adult population. Purpose: To assess the mean medial and lateral PTS on pediatric cadaveric specimens without known knee injuries. Study Design: Cross-sectional study; Level of evidence, 3. Methods: A total of 39 pediatric knee specimens with computed tomography scans were analyzed. Specimens analyzed were between the ages of 2 and 12 years. The PTS of each specimen was measured on sagittal computed tomography slices at 2 locations for the medial and lateral angles. The measurements were plotted graphically by age to account for the variability in development within age groups. The anterior medial and lateral tibial plateau widths were measured. The distance between the top of the tibial plateau and the physis was measured. The independent-samples t test and analysis of variance were used to analyze the measurements. Results: The mean PTS angle for the medial and lateral tibial plateaus was 5.53° ± 4.17° and 5.95° ± 3.96°, respectively. The difference between the PTS angles of the medial and lateral tibial plateaus was not statistically significant (P > .05). When plotted graphically by age, no trend between age and PTS was identified. Conclusion: This data set offers values for the PTS in skeletally immature specimens without a history of ACL injury and suggests that age may not be an accurate predictive factor for PTS.

The Axillary Nerve Danger Zone in Percutaneous Fixation in the Pediatric Shoulder: The "1-Mountain-3-Valleys" Principle.

BACKGROUND: Adult literature cites an axillary nerve danger zone of 5 to 7 cm distal to the acromion tip for open or percutaneous shoulder surgery, but that may not be valid for younger patients. This study sought to quantify the course of the axillary nerve in adolescent patients with reference to easily identifiable intraoperative anatomic and radiographic parameters. METHODS: A single-institution hospital database was reviewed for shoulder magnetic resonance images (MRIs) in patients 10 to 17 years old. One hundred and one MRIs from patients with a mean age of 15.6 ± 1.2 years (range, 10 to 17 years) were included. Axillary nerve branches were identified in the coronal plane as they passed lateral to the proximal humerus and were measured in relation to identifiable intraoperative surface and radiographic landmarks, including the acromion tip, apex of the humeral head, lateral physis, and central apex of the physis. The physeal apex height (i.e., 1 "mountain") was defined as the vertical distance between the most lateral point of the humeral physis (LPHP) and the central intraosseous apex of the physis. RESULTS: Axillary nerve branches were found in all specimens, adjacent to the lateral cortex of the proximal humerus. A mean of 3.7 branches (range, 2 to 6) were found. The mean distance from the most proximal branch (BR1) to the most distal branch (BR2) was 11.7 mm. The pediatric danger zone for the axillary nerve branches ranged from 6.6 mm proximal to 33.1 mm distal to the LPHP. The danger zone in relation to percent of physeal apex height included from 62% proximal to 242% distal to the LPHP. CONCLUSIONS: All branches were found distal to the apex of the physis (1 "mountain" height proximal to the LPHP). Distal to the LPHP, no branches were found beyond a distance of 3 times the physeal apex height (3 "valleys"). In children and adolescents, percutaneous fixation of the proximal humerus should be performed with cortical penetration outside of this range. These parameters serve as readily identifiable intraoperative radiographic landmarks to minimize iatrogenic nerve injury. CLINICAL RELEVANCE: This study provides valuable landmarks for percutaneous approaches to the proximal humerus. The surgical approach for the placement of percutaneous implants should be adjusted accordingly (i.e., performed at least 1 mountain proximal or 3 valleys distal to the LPHP) in order to prevent iatrogenic injury to the axillary nerve.

Anterior Cruciate Ligament Length in Pediatric Populations: An MRI Study.

BACKGROUND: As regards anterior cruciate ligament (ACL) reconstruction (ACLR), graft diameter has been identified as a major predictor of failure in skeletally mature patients; however, this topic has not been well-studied in the higher risk pediatric population. Hamstring tendon autograft configuration can be adjusted to increase graft diameter, but tendon length must be adequate for ACLR. Historical parameters of expected tendon length have been variable, and no study has quantified pediatric ACL morphology with other osseous parameters. PURPOSE: To develop magnetic resonance imaging (MRI)-derived predictors of native ACL graft length in pediatric patients so as to enhance preoperative planning for graft preparation in this skeletally immature patient population. STUDY DESIGN: Cross-sectional study; Level of evidence, 3. METHODS: MRI scans of 110 patients were included (64 girls, 46 boys; median age, 10 years; range, 1-13 years). Patients with musculoskeletal diseases or prior knee injuries were excluded. The following measurements were taken on MRI: ACL length; sagittal and coronal ACL inclination; intercondylar notch width and inclination; and femoral condyle depth and width. Associations between these measurements and patient sex and age were investigated. Univariate linear regression and multivariable regression models were created for each radiographic ACL measure to compare R 2. RESULTS: Female ACL length was most strongly associated with the depth of the lateral femoral condyle as viewed in the sagittal plane (R 2 = 0.65; P < .001). Other statistically significant covariates of interest included distal femoral condylar width, age, and coronal notch width (P < .05). For males, the ACL length was most strongly associated with the distal femoral condyle width as viewed in the coronal plane (R 2 = 0.70; P < .001). Other statistically significant covariates of interest for male ACL lengths were lateral femoral condyle depth, age, and coronal notch width (P < .05). CONCLUSION: In pediatric populations, femoral condylar depth/width and patient age may be valuable in assessing ACL size and determining appropriate graft dimensions and configuration for ACLRs. The use of this information to optimize graft diameter may lower the rates of ACL graft failure in this high-risk group.

Anatomic Dissection and CT Imaging of the Anterior Cruciate and Medial Collateral Ligament Footprint Anatomy in Skeletally Immature Cadaver Knees.

BACKGROUND: Anterior cruciate ligament (ACL) and medial collateral ligament (MCL) injuries in skeletally immature patients are increasingly recognized and surgically treated. However, the relationship between the footprint anatomy and the physes are not clearly defined. The purpose of this study was to identify the origin and insertion of the ACL and MCL, and define the footprint anatomy in relation to the physes in skeletally immature knees. METHODS: Twenty-nine skeletally immature knees from 16 human cadaver specimens were dissected and divided into 2 groups: group A (aged 2 to 5 y), and group B (aged 7 to 11 y). Metallic markers were placed to mark the femoral and tibial attachments of the ACL and MCL. Computed tomography scans were obtained for each specimen used to measure the distance from the center of the ligament footprints to the respective distal femoral and proximal tibial physes. RESULTS: The median distance from the ACL femoral epiphyseal origin to the distal femoral physis was 0.30 cm (interquartile range, 0.20 to 0.50 cm) and 0.70 cm (interquartile range, 0.45 to 0.90 cm) for groups A and B, respectively. The median distance from the ACL epiphyseal tibial insertion to the proximal tibial physis for groups A and B were 1.50 cm (interquartile range, 1.40 to 1.60 cm) and 1.80 cm (interquartile range, 1.60 to 1.85 cm), respectively. The median distance from the MCL femoral origin on the epiphysis to the distal femoral physis was 1.20 cm (interquartile range, 1.00 to 1.20 cm) and 0.85 cm (interquartile range, 0.63 to 1.00 cm) for groups A and B, respectively. The median distance from the MCL insertion on the tibial metaphysis to the tibial physis was 3.05 cm (interquartile range, 2.63 to 3.30 cm) and 4.80 cm (interquartile range, 3.90 to 5.10 cm) for groups A and B, respectively. CONCLUSION: Surgical reconstruction is a common treatment for ACL injury. Computed tomography scanning of pediatric tissue clearly defines the location of the ACL and MCL with respect to the femoral and tibial physes, and may guide surgeons for physeal respecting procedures. CLINICAL RELEVANCE: In addition to ACL reconstruction, recent basic science and clinical research suggest that ACL repair may be more commonly performed in the future. MCL repair and reconstruction is also occasionally required in skeletally immature patients. This information may be useful to help surgeons avoid or minimize physeal injury during ACL/MCL reconstructions and/or repair in skeletally immature patients.

Quadriceps Tendon Graft Anatomy in the Skeletally Immature Patient.

BACKGROUND: The quadriceps tendon (QT) is increasingly considered for primary and revision anterior cruciate ligament reconstruction in skeletally immature patients, as it may be harvested as a purely soft tissue graft with considerable tissue volume. Because of distinct rectus tendon (RT) separation from the QT complex, the potential for RT retraction exists and could lead to QT weakness after QT graft harvest. PURPOSE: To describe the anatomy of the pediatric QT and clarify decussation of the RT and QT to avoid the risk of delayed RT retraction and QT weakness after QT graft harvest. STUDY DESIGN: Descriptive epidemiology study. METHODS: Nine cadaveric knee specimens (aged 4-11 years) underwent gross dissection. Coronal-plane width and depth of the QT were measured at intervals proximal to the superior pole of the patella at distances of 0.0, 0.5, 1.0, and 1.5 times the length of the patella. The distance was measured from the superior patellar pole to the point of RT separation from the remainder of the deeper/posterior QT. RESULTS: The median patellar length was 28 mm (interquartile range, 26-37 mm). The coronal-plane width of the QT was larger superficially/anteriorly when closest to the patella but wider when measured deeper/posteriorly as the tendon extended proximally. The median distance between the superior pole of the patella and RT separation from the QT was 0.95 times the patellar length. The distance to widening of the deeper/posterior aspect of the QT was 1.14 times the patellar length proximal to the patella. CONCLUSION: The RT begins a distinct separation from the QT above the superior pole of the patella at a median of 0.95 times the patellar length in skeletally immature specimens. The deeper/posterior aspect of the QT begins to increase in coronal-plane width proximally after a distance of 1.14 times the patellar length above the knee, while the superficial/anterior aspect of the tendon continues to narrow. Awareness of the separation of the RT from the QT, and the coronal-plane width variation aspects of the QT proximally, is important for surgeons utilizing the QT as a graft to avoid inadvertent release of the RT from the rest of the QT complex.

The Position of the Popliteal Artery and Peroneal Nerve Relative to the Menisci in Children: A Cadaveric Study.

BACKGROUND: Meniscal injury in skeletally immature patients is increasingly reported. During meniscal repair, all-inside devices may protrude beyond the posterior limits of the meniscus, putting the neurovascular structures at risk. PURPOSE: The purposes of this study were (1) to examine the relationship between the popliteal artery and the posterolateral and posteromedial aspects of the menisci, (2) to examine the relationship of the peroneal nerve to the posterolateral meniscus, and (3) to develop recommendations for avoiding neurovascular injury during posterior meniscal repair in pediatric patients. STUDY DESIGN: Descriptive laboratory study. METHODS: A total of 26 skeletally immature knee cadaveric specimens (7 females and 19 males) were included. Specimens were divided into age groups: 2-4, 5-8, and 9-11 years. The most posterior extent of the lateral and medial menisci was identified via sagittal and axial views on computed tomography (CT) scans. The shortest distance from the most posterior aspect of the lateral and medial menisci to the popliteal artery and the shortest distance from the posterior aspect of the lateral menisci to the anterior rim of the peroneal nerve were measured, and 3-dimensional models of representative specimens were re-created through use of CT scans. RESULTS: For the age groups 2-4, 5-8, and 9-11 years, the mean minimum distance from the posterolateral meniscus to the popliteal artery was 5.2, 6.7, and 8.2 mm, respectively, and the mean minimum distance from the posteromedial meniscus to the popliteal artery was 12.7, 15.4, and 20.3 mm, respectively. In all groups, the distance between the posteromedial meniscus and the popliteal artery was greater than that between the posterolateral meniscus and the popliteal artery. The mean distance from the peroneal nerve to the lateral meniscus was 13.3, 15.0, and 17.9 mm for the respective groups. CONCLUSION: Many all-inside meniscal repair devices have sharp tips that penetrate posterior to the meniscus and capsule. This study demonstrated that the distance between the posterior meniscus and popliteal artery is relatively small in pediatric patients, especially for the lateral meniscus region. CLINICAL RELEVANCE: Because of the higher potential for meniscal healing, meniscal repair is more likely to be performed in pediatric patients. The data in this study regarding the proximity of the lateral meniscus and neurovascular structures may be used to guide safe surgical repair of posterior meniscal tears during the use of all-inside meniscal repair devices in these patients.

Pediatric ACL Tears: Natural History.

BACKGROUND: Increased participation in youth sports is associated with increased rates of anterior cruciate ligament (ACL) tears in the skeletally immature. Historically, ACL reconstruction was avoided in the skeletally immature, or delayed until skeletal maturity, to avoid physeal injury and growth disturbance. Current practices and meta-analyses support early ACL reconstruction in some groups, to allow for return to activities and to avoid delayed cartilage/meniscus injury. PURPOSE: The purpose of this article was to report on the natural history of ACL injuries in the skeletally immature. METHODS: A review of published literature on pediatric, skeletally immature ACL tears and conservative, nonoperative treatment was conducted via Pubmed articles published from 1970 to 2018. The search criteria included the key terms "anterior cruciate ligament," "pediatric" and/or "adolescent," and "conservative" and/or "nonoperative treatment." A PRISMA workflow was used to narrow down the articles to those relevant to our analysis and available in full text format. RESULTS: Multiple articles on the nonoperative treatment of the ACL showed secondary meniscal and cartilage damage at the time of follow-up. Some articles showed no difference between the rates of secondary injuries between the surgical and nonsurgical treatment groups; however, the nonsurgical treatment groups were often on significant activity modification. Some articles concluded that nonoperative treatment of the ACL tear may be appropriate in low risk, lower level activity patients, and those that will comply with activity restrictions. Even with bracing and PT programs, active athletes treated without surgery appear to have a concerning rate of secondary meniscus injury after the primary ACL injury event. CONCLUSIONS: The natural history of the ACL tear shows nonoperative treatment for the skeletally immature may be a viable treatment pathway for those who are able to comply with the physical activity restrictions. For the general population of young, active adolescents, an ACL injury treated nonoperatively often leads to secondary meniscal and/or cartilage damage, which may lead to knee degeneration and functional instability.

Proximity of the neurovascular structures during all-inside lateral meniscal repair in children: a cadaveric study.

PURPOSE: Meniscal repair has become increasingly common in a pediatric and adolescent population. All-inside repair techniques are utilized more often given their ease of insertion and decreased operative time required. However, there are possible risks including damage to adjacent neurovascular structures. The purpose of this study to was examine the proximity of the neurovascular structures during lateral meniscus repairs in pediatric specimens simulating a worst-case scenario. METHODS: Ten pediatric cadaveric knees (age 4-11) were utilized and simulated lateral meniscal repair through the posterior horn of the lateral meniscus and both medial and lateral to the popliteal hiatus through the body of the lateral meniscus was performed with an all-inside meniscal repair device. The distance to the popliteal artery or peroneal nerve was measured. RESULTS: During posterior horn repair, the average distance from the all-inside device to the popliteal artery was 1.9 mm ± 1.1 mm. There was penetration of the artery in one specimen. During repair on the medial side of popliteal hiatus, the average distance from the all-inside device to the peroneal nerve was 3.2 mm ± 2.0 mm. During repair on the lateral side of popliteal hiatus, the average distance from the all-inside device to the peroneal nerve was 12.4 mm ± 3.7 mm. CONCLUSIONS: This study demonstrates that the proximity of the neurovascular structures to the lateral meniscus in children is extremely close and at high risk during meniscal repair with all-inside devices. This study gives important data for the proximity of these structures during these repair techniques. LEVEL OF EVIDENCE: Level 5 Cadaveric Study.