Blount Disease Workup

  • Author: Matthew J DeOrio, MD; Chief Editor: Carlos J Lavernia, MD, FAAOS   more...
 
Updated: Sep 25, 2010
 

Laboratory Studies

Lab studies have not been shown to aid in the diagnosis of Blount disease. The diagnosis of both forms of Blount disease is based on history, physical examination, and, most important, radiographs of the knee.

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Imaging Studies

Anteroposterior radiograph of the knee demonstratiAnteroposterior radiograph of the knee demonstrating the medial plateau depression and prominent metaphyseal beaking (Langenskiöld stage II-III) typical of infantile genu varum regardless of age of presentation. Anteroposterior radiograph representing important Anteroposterior radiograph representing important angles for staging typical for the adolescent form. Obvious varus deformity in the proximal tibia with no sloping or bar formation is present (bars do not occur in the adolescent form). A: Tibiofemoral angle. B: Metaphyseal-diaphyseal angle. C: Metaphyseal-epiphyseal angle.
  • Radiographs of the knee are critical in assessing and staging the severity of the deformity. An anteroposterior standing radiograph of both lower extremities and a lateral radiograph of the involved extremity are used (see the top image above).
    • Fragmentation with a protuberant step deformity and beaking of the proximal medial tibial metaphysis are the major features of the infantile group. The lateral cortical wall of the upper tibial metaphysis is nearly straight.
    • Differentiating between severe physiologic bowing and infantile-type Blount disease is difficult in early childhood. Thus, corrective intervention is not recommended when the patient is younger than 2 years.
    • Early changes of infantile Blount disease can be assessed by measuring the metaphyseal-diaphyseal angle of the proximal tibia; that is, the angle formed by the intersection of a line through the transverse plane of the proximal tibial metaphysis with a line perpendicular to the long axis of the tibial diaphysis (see the lower image above).
    • The severity of the varus deformity is based on the tibiofemoral angle as measured on standing anteroposterior radiographs that include the ankle, knee, and most of the femur; the metaphyseal-diaphyseal angle; and the metaphyseal-epiphyseal angle, that is, the angle formed by the intersection of a line through the transverse plane of the proximal tibia epiphysis with a line through the transverse plane of the metaphysis (see the lower image above).
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Histologic Findings

In the infantile form, bone changes include delayed ossification of the medial epiphysis and metaphysis of the proximal tibia.[7] In all stages of the disease, histologic specimens from the zone of resting cartilage in the medial part of the proximal tibial physis have well-defined pathologic changes, as described in Pathophysiology. These consist of (1) islands of densely packed cells exhibiting more hypertrophy than expected on the basis of their position in the growth plate, (2) islands of fibrocartilage that are nearly acellular, and (3) abnormal groups of capillary vessels. No avascular necrosis of bone or inflammation has been demonstrated.[6, 14, 19, 23]

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Staging

Langenskiöld classified infantile tibia vara into 6 progressive stages, based on the degree of metaphyseal-epiphyseal changes observed on the radiograph. Severity of disease is based on the Langenskiöld stage and the age of the child.[18, 23, 24]

Anteroposterior radiograph representing important Anteroposterior radiograph representing important angles for staging typical for the adolescent form. Obvious varus deformity in the proximal tibia with no sloping or bar formation is present (bars do not occur in the adolescent form). A: Tibiofemoral angle. B: Metaphyseal-diaphyseal angle. C: Metaphyseal-epiphyseal angle.
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Contributor Information and Disclosures
Author

Matthew J DeOrio, MD  Staff Physician, Department of Orthopedic Surgery, Mayo Clinic of Rochester

Matthew J DeOrio, MD is a member of the following medical societies: American Medical Association and Florida Medical Association

Disclosure: Nothing to disclose.

Coauthor(s)

James K DeOrio, MD  Director of Foot and Ankle Fellowship Program, Assistant Professor of Orthopedic Surgery, Orthopedic Surgery, St Lukes Hospital, Jacksonville, Florida

James K DeOrio, MD is a member of the following medical societies: American Academy of Orthopaedic Surgeons, American Orthopaedic Foot and Ankle Society, Florida Medical Association, and German Society of Neurology

Disclosure: Nothing to disclose.

Specialty Editor Board

Francisco Talavera, PharmD, PhD  Senior Pharmacy Editor, eMedicine

Disclosure: eMedicine Salary Employment

Thomas M DeBerardino, MD  Associate Professor, Department of Orthopedic Surgery, Consulting Surgeon, Sports Medicine, Arthroscopy and Reconstruction of the Knee, Hip and Shoulder, Team Physician, Orthopedic Consultant to UConn Department of Athletics, University of Connecticut Health Center

Thomas M DeBerardino, MD is a member of the following medical societies: American Academy of Orthopaedic Surgeons, American Orthopaedic Association, and American Orthopaedic Society for Sports Medicine

Disclosure: Arthrex, Inc. Grant/research funds Other; Arthrex, Inc. Consulting fee Speaking and teaching; Genzyme Biosurgery. Inc. Grant/research funds Other; Musculoskeletal Transplant Foundation Grant/research funds Other; Histogenics Grant/research funds None

Dinesh Patel, MD, FACS  Associate Clinical Professor of Orthopedic Surgery, Harvard Medical School; Chief of Arthroscopic Surgery, Department of Orthopedic Surgery, Massachusetts General Hospital

Dinesh Patel, MD, FACS is a member of the following medical societies: American Academy of Orthopaedic Surgeons

Disclosure: Nothing to disclose.

Chief Editor

Carlos J Lavernia, MD, FAAOS  Adjunct Clinical Professor, Department of Orthopedic Surgery, University of Miami School of Medicine; Medical Director, Orthopedic Institute at Mercy Hospital

Carlos J Lavernia, MD, FAAOS is a member of the following medical societies: American Academy of Orthopaedic Surgeons, American Association of Hip and Knee Surgeons, Arthritis Foundation, Biomedical Engineering Society, Florida Orthopaedic Society, and Orthopaedic Research Society

Disclosure: Zimmer Stock Implant Designer

References

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A 10-year-old boy with Blount disease. Marked obesity and bilateral genu varum is present. Courtesy of S. Standard, MD.
Anteroposterior radiograph of the knee demonstrating the medial plateau depression and prominent metaphyseal beaking (Langenskiöld stage II-III) typical of infantile genu varum regardless of age of presentation.
Anteroposterior radiograph representing important angles for staging typical for the adolescent form. Obvious varus deformity in the proximal tibia with no sloping or bar formation is present (bars do not occur in the adolescent form). A: Tibiofemoral angle. B: Metaphyseal-diaphyseal angle. C: Metaphyseal-epiphyseal angle.
Diagram depicting the radiographic changes observed in the infantile form of Blount disease and their development with increasing age.
A: Anteroposterior radiograph of the knee in a 10-year-old boy demonstrating use of an external fixator (Taylor Spatial Frame; Smith & Nephew) in correction of tibia vara. B: 6-month postoperative anteroposterior radiograph of correction. Contributed by S. Standard, MD.
 
 
 
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