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Age / Sex : 17 / M
Age/Sex: 17/M
C.C.: Lt. knee joint pain (onset: 2~3 years ago)
1) What is your impression?
* Two weeks later, you can see the final diagnosis with a brief discussion of this case
** Send Application Answers to Ja-Young Choi, MD (drchoi01@radiol.snu.ac.kr).
Courtesy : Suk-Joo Hong, MD., Korea University Guro Hospital
Diagnosis: Bosch-Bock bump (healed segond Fx)
Discussion
Findings:
Plain radiograph reveals bone excrescence inferior to far-lateral portion of lateral tibial plateau. No degenerative changes are seen On PDWI coronal MR image, the bone excrescence arising from the lateral aspect of the tibia demonstrates continuity with the medullary bone.
Differential Diagnosis:
1. Bosch-Bock bump (Healed Segond fracture)
2. Osteophyte in degenerative change.
3. osteochondroma
Discussion:
A Segond fracture initially was described prior to the discovery of X-rays by Paul Segond in 1879 in a series of cadaveric experiments. Segond demonstrated that an internal rotation and varus stress applied to the knee causes tension on the lateral joint capsule at its midpoint. The location of the Segond fracture is posterior and slightly proximal to Gerdy’s tubercle. The site of bony avulsion is corresponds to the attachment site of not only the meniscotibial ligament of deep lateral capsular ligament but also some of posterior fiber of ITB, anterior oblique band of FCL, and anterior arm of short head of biceps femoris. Thus, the precise structure that produces the Segond fracture is not entirely clear. A Segond fracture is most typical of anterolateral rotatory instability of the knee. It is highly associated with ACL tears (75-100%) and meniscal pathology (67%). In this patient, chronic ACL tear, which is implicated by empty notch sign, suggestive torn ligamentous fragment with scar on MR scan, was observed. Conversely, a Segond fracture is reported to occur in approximately 10% of ACL injuries. This fracture is highly associated with injuries to one or more of the lateral ligaments. When the avulsion relates to the anterior arm of short head of biceps femoris muscle, additional injuries in the posterolateral corner of knee are common. With time, a bone excrescence develops at the site of the injury, known as Bosch-Bock bump, resembles an osteophyte but is located several millimeters below the joint line. It is not clear if this bone outgrowth represents fusion of the original bone fragment with tibial margin or a reaction to the avulsive injury, but its presence is clear and certain evidence that a Segond fracture has occurred. It should not be mistaken for degenerative change as the location and morphology of the resulting excrescence are characteristic. It also should not be mistaken for an osteochondroma as the location and orientation of the bony excrescence are not typical of this tumor. The finding of a bony excrescence in the proximal and lateral portion of the tibia, 3-6 mm distal to the tibial plateau, implies significant internal derangement of the knee.
References:
1. GW Bock, E Bosch, DK Mishra, DM Daniel, D Resnick. The healed Segond fracture: a characteristic residual bone excrescence. Skeletal Radiol 1994;23:555-556
2. JC Campos, CB Chung, N Lektrakul, R Pedowitz, D Trudell, RA Joseph Yu, D Resnick. Pathogenesis of the Segond Fracture: Anatomic and MR Imaging Evidence of an Iliotibial Tract or Anterior Oblique Band Avulsion. Radiology 2001;219:381–386
3. Resnick D, Kang HS, Pretterklieber ML. Internal Derangement of Joints. Suanders 2nd ed. P1786-1788
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