History of Present Illness
The patient is a 3-year 6-month-old male who was referred to the pediatric orthopaedic clinic for evaluation of a leg deformity. The patient's mother has noticed an increasing genu valgus (knock-knee) deformity in the right leg over the past 6 months. He did sustain a right proximal tibia fracture 6 months ago when he fell from a slide (see Figure 1). He was treated in a long leg walking cast for 5 weeks for the fracture. The deformity in the leg was noticed a few weeks after the cast was removed and it seems to have increased over the last 2-3 months. He does not appear to have any pain with activity, although the genu valgus appears worse when he is running or walking. He is otherwise extremely healthy; developmental milestones were all normal.
Physical Examination
On examination the patient is a well-appearing, alert, 3-year-old male in no acute distress. His height was 37 inches and weight was 44 pounds. HEENT: Atraumatic, normocephalic, nondysmorphic. Neck was supple with full motion. Chest was clear to auscultation. Heart: Regular rate and rhythm. Examination of the patient's spine: The spine was straight without asymmetry, step-off, or defect. No scoliosis, no kyphosis. Examination of the patient's hips demonstrates equal symmetric hip abduction, internal/external rotation. No instability. Examination of the patient's lower extremities demonstrates an asymmetric genu valgum deformity on the right side coming through the proximal tibia. He is nontender to palpation. He has full range of motion of the hip and knee and ankle on that side. The knee demonstrates full range of motion and is ligamentously stable. When walking, he goes into a knock-knee or genu valgum alignment on the right side. He has bilateral flexible pes planus. He is neurologically intact in bilateral upper and lower extremity. No joint contractures present; a lower extremity joint survey x-ray was obtained (see Figure 2).
Brief Discussion/Plan
Fractures involving the proximal tibia metaphysis are relatively uncommon in children; however, they are clinically important because of the posttraumatic development of progressive valgus deformity. The knock-knee or genu valgus deformity following these fractures was initially described by S. E. Cozen, MD, in 1953; therefore, it is often referred to as a Cozen fracture. Although the exact cause of the genu valgus is unknown, many reports and hypotheses have been written and presented. The most common etiologies discussed include initial inadequate fracture reduction, early weight bearing, tethering by the fibula, and posttraumatic asymmetric overgrowth. It is imperative for providers to inform parents early that this posttraumatic knock-knee deformity is extremely common (occurs in approximately 50%-70% patients) and often unpredictable. The majority of young patients with a genu valgus deformity will have spontaneous correction, so the initial treatment is generally observation. Although the deformity will often correct completely, it may take up to 3-4 years. Various options for treatment include observation (no treatment), bracing (with a varus mold to correct deformity), and rarely surgery if the deformity persists. Surgical options include a partial or hemiepiphysiodesis or a corrective osteotomy.