Imaging diagnosis
Case 160
【Progress】
He was directed to stop running and jumping for a while. He was given non-steroid anti-inflammatory drugs for pain relief.
【Discussion】
There are three major bone lesions of the lower extremity in an adolescent age: Osgood Schlatter (OS) disease, Sinding Larsen Johansson (SLJ) disease and fibrous cortical defect ( 2cm or less) or non ossifying fibroma (> 2cm).
Fibrous cortical defect or non ossifying fibroma is osteo-lucent or osteolytic and occurs in the metaphysis and extends into diaphysis with age, becoming radiopaque and eventually leading to normal bone (1-5).
OS disease and SLJ disease which cause the knee pain, occur in growing adolescents who conduct repetitive quadriceps contraction. The quadriceps (Rectus femoris, Vastus lateralis, Vastus Medialis, Vastus Intermedius) tendon attaches to the patella. The patella tendon attaches to the quadriceps by the quadriceps tendon and connects the patella and the tibia. Working together, the quadriceps muscles, the quadriceps tendon and the patella tendon straighten the knee. The repetitive tension of the quadriceps by excessive sports in adolescent ages injures the patella tendon and the growth plate (hyaline cartilage). The injuries of the lower edge of the patella tendon and the growth plate of the tibia tubercle induce OS disease, while the injuries of the upper edge of the patella tendon and the growth plate of the inferior patella induce SLJ disease. The both growth plate injuries of OS and SLJ diseases make one or several ossification in the growth plate separate, mimicking avulsion fracture or bone tumor (1-3). In our case, the knee radiograph showed the separation of one ossification mimicking bone tumor and the knee MRI showed the high signal intensity at the lower part of the patella, upper part of the patella tendon and Hoffa fat tissue, indicating diagnosis of SLJ disease. Irrespective of OS disease or SLJ disease, they eventually lead to normal bone following the cease of excessive athletic movement and a while of rest.
There are three types of cartilage in human: hyaline cartilage, fibrous cartilage and elastic cartilage. Hyaline cartilage is glassy full of extracellular matrix (ECM) with fine collagen (Type II collagen) and is found in the edge cartilage of long bone. Hyaline cartilage is the weakest of the three. Fibrous cartilage includes much of collagen (Type I + II collagen) and less of ECM and is found in the vertebra disc and knee meniscus. Fibrous cartilage is also found in connected and/or adjacent to the ligaments (Type I collagen) and becomes to accompany with calcification as time flow. Elastic cartilage is similar to hyaline cartilage microscopically but it contains elastic fiber, inducing more flexibility than hyaline cartilage and fibrous cartilage and it is found in larynx and ear. It is hypothesized that type I collagen content would be high throughout the tendon and ligament, type II collagen content would be high in the regions of compressive loading and type III collage content would be high in regions associated with damage (6). Where tendons and ligaments are susceptible to compression, they commonly become fibrocartilaginous with the increase volume of type II collagen (7).
New bone formation originated from hyaline cartilage irrespective of adolescent age or aged adult progresses with almost the same stage; Zone of hyaline cartilage; Zone of chondrocytes proliferation; Zone of chondrocytes hypertrophy containing glycogen and secrete alkaline phosphatase essential for mineral deposition; Zone of calcification inducing chondrocytes die: Zone of ossification by osteoblasts making calcification on the surface of calcified cartilage. Although excessive traction of patella induces the disorder to create new bone formation, resting for a while is considered to return to this normal new bone formation process.
【Summary】
We present an eleven-year-old boy suffering from the left knee pain and his knee radiograph showed a new bone formation beneath the patella, mimicking a bone tumor. The left knee MRI showed high signal intensity at the lower part of the patella, patella tendon and Hoffa space adipose tissue, indicative of diagnosis of Sinding Larsen Johansson (SLJ) disease. It is borne in mind that there are three major knee diseases in adolescent age: Osgood Schlatter (OS) disease and SLJ disease and fibrous cortical defect ( 2cm or less) or non ossifying fibroma (> 2cm). OS and SLJ arise from repetitive and excessive athletic movement by quadriceps traction to make knee straight since quadriceps, quadriceps tendon and patella tendon work together. The growth plate injury of tibia tubercle in OS and that of lower part of patella in SLJ diseases make one or several ossification in the growth plate (hyaline cartilage) separate, mimicking avulsion fracture or bone tumor. Non ossifying fibroma extending metaphysis to diaphysis also resembles to a bone tumor. They eventually lead to normal bone following the cease of excessive athletic movement and a while of rest. Further, type I collagen content would be high throughout the tendon and ligament, type II collagen content would be high in the regions of compressive loading such as vertebral disk, knee meniscus and fibrocartilage. Irrespective of adolescent bone or aged bone, new bone formation arises from hyaline cartilage with chondrocyte proliferation secreting alkaline phosphatase secretion, mineral deposit and eventually making bone formation by osteoblasts migration.
【References】
1.Carr JC, Hanly S, Griffin J et al. Sonography of the patellar tendon and adjacent structures in pediatric and adult patients. AJR Am J Roentgenol. 2001;176 (6): 1535-9.
2.Dupuis CS, et al. Injuries and conditions of the extensor mechanism of the pediatric knee. Radiographics. 29 (3): 877-86.
3.Kaya DO, et al. Long-term functional and sonographic outcomes in Osgood-Schlatter disease. Knee Surg Sports Traumatol Arthrosc. 2013; 21:1131-9.
4.Ritschl P, et al. Fibrous metaphyseal defects--determination of their origin and natural history using a radiomorphological study. Skeletal Radiol. 1988;17(1):8–15.
5.Ritschl P, et al. Fibrous metaphyseal defects. Orthopade. 1995;24(1):44–9.
6.Mark R Buckley,, et al. Distributions of Types I, II and III Collagen by Region in the Human Supraspinatus Tendon. Connect Tissue Res. 2013; 54(6): 374–379
7.Benjamin M, et al. Fibrocartilage in tendons and ligaments — an adaptation to compressive load. J Anat. 1998 Nov; 193(Pt 4): 481–494.
2019.9.4