ORIGINAL ARTICLE
Normal Parameters of the Skeletally Immature Knee: Developmental Changes on Magnetic Resonance Imaging Eric W. Edmonds, MD,*w Mary Bathen, MD,z and Tracey P. Bastrom, MA*
Background: A child’s knee undergoes significant morphologic changes during development. Age-specific normal parameters have not been previously described. The purpose of this study was to delineate knee morphology changes that occur with maturation utilizing magnetic resonance imaging (MRI). Methods: A retrospective review of knee MRIs, ages 4 to 18 years, was performed using “normal” diagnosis codes, including: knee pain, plicae, septic arthritis, jumper’s knee, growing pains, benign neoplasm, and osteomyelitis. Seventeen osseous parameters were measured, plus their cartilaginous counterparts, if different. Spearman r correlations were calculated between age and MRI measures. Results: A total of 132 MR images were reviewed. Significant correlation with age was observed in all osseous measurements, except medial patellofemoral ligament (MPFL) insertion (P < 0.05). Similarly, the cartilage measures demonstrated significant correlation with age, except the notch width index, MPFL insertion, and trochlear morphology. The magnitude of correlation was significantly different between the osseous and cartilage measures for all but 4 of the variables: anterior cruciate ligament (ACL) length and width, intercondylar width and tibial tubercle-trochlear groove (TT-TG) interval. Sex seems to affect ACL length, Insall-Salvati ratio, intercondylar width, and sulcus angle. The MPFL origin starts distal to the physis and moves proximal with age (r = 0.33, P < 0.001), when at age 7 years, it is located at or above the femoral physis. The mean ACL diameter grows from 6.5 to 9.8 mm. Cartilage sulcus angle remains consistently 150 degrees, and the TT-TG interval shifts from 6 to 12 mm with maturity. Conclusions: The normative data presented here demonstrates that maturity correlates well with the morphologic changes seen in most of the studied parameters. These data not only aid in the identification of the abnormal findings by sex and age, but also provides normal sizes of the ACL and location of insertion for the MPFL which can benefit surgical planning. Level of Evidence: Level III—diagnostic study. Key Words: knee development, magnetic resonance imaging, normal knee
From the *Department of Orthopedic Surgery, Rady Children’s Hospital; Departments of wOrthopedic Surgery; and zGeneral Surgery, University of California, San Diego, San Diego, CA. The authors declare no conflicts of interest. Reprints: Eric W. Edmonds, MD, Department of Orthopedic Surgery, Rady Children’s Hospital, 3030 Children’s Way, Suite 410, San Diego, CA 92123. E-mail: [email protected]. Copyright r 2014 Wolters Kluwer Health, Inc. All rights reserved.
712 | www.pedorthopaedics.com
(J Pediatr Orthop 2015;35:712–720)
F
rom birth to physeal closure, the knee undergoes significant morphologic changes related to growth that can be highlighted by a discrepancy in the accuracy of reading magnetic resonance imaging (MRI).1 In fact, the accuracy of knee MRI interpretations may be as low as 70%.2 Understanding normal developmental changes in children may be important to understanding pathology in the skeletally immature knee, so that direct comparisons between normal and abnormal can be rendered based on age. To the best of our knowledge, no previous study has described a normative database of longitudinal morphologic changes from throughout skeletal immaturity to maturity of the knee by MR images. The purpose of this study was to describe the morphology of the pediatric knee by measuring numerous, reproducible parameters of “normal” knee MR images from children.
METHODS A retrospective review of an MRI database (housed within the radiology department of our institution) was performed with institutional review board approval by searching for otherwise “normal” knee ICD-9 codes: 719.46 (knee pain), 732.4 (Osgood-Schlatter), 727.83 (symptomatic plicae), 727.2 (jumper’s knee), 781.99 (growing pains), 213.xx (benign neoplasm), 711.0 (septic arthritis), and 730.xx (osteomyelitis). These diagnoses were selected to represent normal population as they do not disrupt the normal anatomy being evaluated in this study. After confirming the presence of an MRI study for the patients, they were divided into 15 different cohorts based on age from 4 to 18 years old. The 0- to
Normal Parameters of the Skeletally Immature Knee: Developmental Changes on Magnetic Resonance Imaging Eric W. Edmonds, MD,*w Mary Bathen, MD,z and Tracey P. Bastrom, MA*
Background: A child’s knee undergoes significant morphologic changes during development. Age-specific normal parameters have not been previously described. The purpose of this study was to delineate knee morphology changes that occur with maturation utilizing magnetic resonance imaging (MRI). Methods: A retrospective review of knee MRIs, ages 4 to 18 years, was performed using “normal” diagnosis codes, including: knee pain, plicae, septic arthritis, jumper’s knee, growing pains, benign neoplasm, and osteomyelitis. Seventeen osseous parameters were measured, plus their cartilaginous counterparts, if different. Spearman r correlations were calculated between age and MRI measures. Results: A total of 132 MR images were reviewed. Significant correlation with age was observed in all osseous measurements, except medial patellofemoral ligament (MPFL) insertion (P < 0.05). Similarly, the cartilage measures demonstrated significant correlation with age, except the notch width index, MPFL insertion, and trochlear morphology. The magnitude of correlation was significantly different between the osseous and cartilage measures for all but 4 of the variables: anterior cruciate ligament (ACL) length and width, intercondylar width and tibial tubercle-trochlear groove (TT-TG) interval. Sex seems to affect ACL length, Insall-Salvati ratio, intercondylar width, and sulcus angle. The MPFL origin starts distal to the physis and moves proximal with age (r = 0.33, P < 0.001), when at age 7 years, it is located at or above the femoral physis. The mean ACL diameter grows from 6.5 to 9.8 mm. Cartilage sulcus angle remains consistently 150 degrees, and the TT-TG interval shifts from 6 to 12 mm with maturity. Conclusions: The normative data presented here demonstrates that maturity correlates well with the morphologic changes seen in most of the studied parameters. These data not only aid in the identification of the abnormal findings by sex and age, but also provides normal sizes of the ACL and location of insertion for the MPFL which can benefit surgical planning. Level of Evidence: Level III—diagnostic study. Key Words: knee development, magnetic resonance imaging, normal knee
From the *Department of Orthopedic Surgery, Rady Children’s Hospital; Departments of wOrthopedic Surgery; and zGeneral Surgery, University of California, San Diego, San Diego, CA. The authors declare no conflicts of interest. Reprints: Eric W. Edmonds, MD, Department of Orthopedic Surgery, Rady Children’s Hospital, 3030 Children’s Way, Suite 410, San Diego, CA 92123. E-mail: [email protected]. Copyright r 2014 Wolters Kluwer Health, Inc. All rights reserved.
712 | www.pedorthopaedics.com
(J Pediatr Orthop 2015;35:712–720)
F
rom birth to physeal closure, the knee undergoes significant morphologic changes related to growth that can be highlighted by a discrepancy in the accuracy of reading magnetic resonance imaging (MRI).1 In fact, the accuracy of knee MRI interpretations may be as low as 70%.2 Understanding normal developmental changes in children may be important to understanding pathology in the skeletally immature knee, so that direct comparisons between normal and abnormal can be rendered based on age. To the best of our knowledge, no previous study has described a normative database of longitudinal morphologic changes from throughout skeletal immaturity to maturity of the knee by MR images. The purpose of this study was to describe the morphology of the pediatric knee by measuring numerous, reproducible parameters of “normal” knee MR images from children.
METHODS A retrospective review of an MRI database (housed within the radiology department of our institution) was performed with institutional review board approval by searching for otherwise “normal” knee ICD-9 codes: 719.46 (knee pain), 732.4 (Osgood-Schlatter), 727.83 (symptomatic plicae), 727.2 (jumper’s knee), 781.99 (growing pains), 213.xx (benign neoplasm), 711.0 (septic arthritis), and 730.xx (osteomyelitis). These diagnoses were selected to represent normal population as they do not disrupt the normal anatomy being evaluated in this study. After confirming the presence of an MRI study for the patients, they were divided into 15 different cohorts based on age from 4 to 18 years old. The 0- to
