Overview
Definition:
Blount disease, also known as tibia vara, is a developmental disorder characterized by progressive posteromedial bowing of the tibia
It results from abnormal growth at the medial aspect of the proximal tibial physis, leading to a varus deformity of the knee and tibia.
Epidemiology:
It is more common in obese children and those who walk at an early age
Early-onset Blount disease typically presents before age 4 and is often bilateral
Late-onset Blount disease usually affects adolescents and is often unilateral.
Clinical Significance:
Untreated Blount disease can lead to significant pain, gait abnormalities, osteoarthritis, and functional limitations, impacting a child's quality of life and long-term skeletal health
Early diagnosis and appropriate management are crucial.
Clinical Presentation
Symptoms:
Progressive bowing of the legs or inward bowing of the knees
Gait disturbance, often described as a waddling or antalgic gait
Pain in the knee or leg, particularly with activity
Difficulty with prolonged standing or walking
Unequal leg lengths may develop over time.
Signs:
Visible varus deformity of the knee and tibia
Medial joint line opening on examination
Palpable tenderness over the medial proximal tibia
Increased femorotibial angle
Overweight or obese child
Associated internal tibial torsion may be present.
Diagnostic Criteria:
Diagnosis is primarily based on clinical examination and radiographic findings
Radiographic criteria include the metaphyseal-diaphyseal angle (MDT angle) and the medial proximal tibial angle (MPTA)
An MDT angle > 11 degrees and an MPTA > 8 degrees in infants/young children, or > 3 degrees in older children, are highly suggestive of Blount disease.
Diagnostic Approach
History Taking:
Age of onset of bowing
Progression of deformity
Presence of pain and its character
Gait abnormalities
Family history of limb deformities
Associated medical conditions, especially obesity
Age of ambulation
Activity level.
Physical Examination:
Assess the overall alignment of the lower extremities
Measure the degree of varus deformity at the knee
Evaluate for internal tibial torsion
Assess for leg length discrepancy
Palpate for tenderness over the medial proximal tibia
Assess range of motion of the knee and ankle joints.
Investigations:
Weight-bearing anteroposterior (AP) and lateral radiographs of the entire tibia and femur
Standing AP radiographs of the lower extremities are essential for assessing true alignment
Obtain oblique views if needed to visualize the physis
MRI may be useful in equivocal cases or to assess physeal integrity
Measuring the femorotibial angle and the proximal tibial angle on X-rays is key.
Differential Diagnosis:
Physiological bow legs (common in toddlers)
Rickets (metabolic bone disease)
Trauma to the proximal tibial physis
Other congenital or genetic syndromes causing limb malformation
Osteochondroma of the proximal tibia
Fibrous dysplasia.
Management
Initial Management:
Conservative management is typically the first line of treatment for early-onset Blount disease in younger children with mild deformities
Weight loss is paramount for obese children
Bracing may be considered for mild to moderate deformities.
Medical Management:
Primarily focused on weight management and addressing any underlying metabolic issues (e.g., rickets, though rare as a cause of Blount disease)
No specific pharmacotherapy for Blount disease itself.
Surgical Management:
Indications for surgery include progressive deformity, significant pain, failure of conservative management, and functional impairment
Options include: Hemiepiphysiodesis of the medial proximal tibia for younger children with remaining growth potential
Osteotomy procedures, such as a lateral opening wedge osteotomy of the proximal tibia or a valgus osteotomy of the distal femur, for older children or those with severe deformities.
Supportive Care:
Physical therapy to improve gait and strength
Pain management with NSAIDs if necessary
Orthotics or bracing may be used as adjuncts
Close monitoring of weight and growth is essential.
Complications
Early Complications:
Wound infection
Nerve or vascular injury during surgery
Non-union or malunion of osteotomy
Compartment syndrome.
Late Complications:
Progression of deformity despite treatment
Osteoarthritis of the knee due to abnormal joint loading
Leg length discrepancy
Recurrence of Blount disease
Persistent pain and functional limitation.
Prevention Strategies:
Early identification and intervention
Aggressive weight management in at-risk children
Appropriate surgical timing and technique
Close follow-up to monitor for recurrence or progression.
Prognosis
Factors Affecting Prognosis:
Age at diagnosis and treatment
Severity of the deformity
Degree of physeal involvement
Compliance with weight management and post-operative care
Type of treatment employed.
Outcomes:
With early and appropriate management, outcomes can be excellent, leading to normalized leg alignment and resolution of symptoms
Late diagnosis or aggressive forms can lead to long-term functional deficits and early-onset osteoarthritis.
Follow Up:
Regular clinical and radiographic follow-up is crucial, especially after surgical intervention
This monitoring continues until skeletal maturity to ensure deformity correction is maintained and no complications arise
Long-term follow-up may be needed for degenerative changes.
Key Points
Exam Focus:
Blount disease is a progressive posteromedial bowing of the tibia due to abnormal physeal growth
Differentiate early-onset vs
late-onset
Key radiographic markers: MDT angle and MPTA
Management depends on age and severity: conservative for mild/early, surgical for severe/late.
Clinical Pearls:
Always suspect Blount disease in obese children presenting with progressive bow legs
Weight loss is a cornerstone of non-operative management
Consider early surgical intervention in young children with significant or rapidly progressing deformity
Accurate radiographic assessment with standing films is essential.
Common Mistakes:
Confusing Blount disease with physiological bow legs in young children
Delaying surgical intervention in cases of progressive deformity
Inadequate radiographic assessment (e.g., not using standing films)
Neglecting weight management as a critical component of treatment.